Tesis sobre el tema "Heterogeneous catalysis"

The practical importance of heterogeneous redox catalysis to many industrial processes has been well-documented over the past decade. Although there has been much technological progress in fields such as mineralogy, electrodeless plating, chlor-alkali production, photographic development, hydrometallurgy and many artificial solar to chemical energy conversion systems, the fundamental processes involved are not always fully understood. There is a need, therefore, to investigate these processes further. Chapter 3 investigates the abilities of different carbon black materials to act as catalysts for the oxidation of brine to chlorine by ceric ions. The kinetics are studied as a function of various experimental parameters, a reaction mechanism is proposed and these results are readily interpreted using an electrochemical model. Chapter 4 follows on from Chapter 3 by extending the investigation to include a study of all the three forms of crystalline carbon (graphite, diamond and C₆₀) as chlorine catalysts. This chapter reports the first example of C₆₀ acting as a redox catalyst. Chapter 5 reports the kinetics and mechanism of a rare example of reversible heterogeneous redox catalysis, in which the oxidation of ruthenium (II) tris (2,2'-bipyridine) ions by thallic ions in nitric acid is catalysed by a dispersion of ruthenium dioxide hydrate. The reaction kinetics fit an electrochemical model of reversible heterogeneous redox catalysis, assuming the kinetics are diffusion-controlled. Chapter 6 similarly investigates the use of a variety of platinum powder dispersions to act as catalysts for the reaction studied in Chapter 5. It also includes a study to show that inert metal oxides can be used as antiflocculants to enhance the rate of heterogeneous catalysis by platinum group metals of this reaction, as well as irreversible redox reactions, such as water and brine oxidation. Chapter 7 describes a novel route for the removal of harmful bromate ions from drinking water. The reaction kinetics are studied both in water and in the presence of organic pollutants and an electrochemical model, in which the two participating redox couples are both electrochemically irreversible, is used to interpret the observed kinetics.

There have been many applications of cerium oxide in oxidation catalysis but the understanding of its role in catalysis is rather limited. This research is concerned with the use of nano-size cerium oxide in methane steam reforming reaction. It is found that addition of cerium oxide to the commercial supported Ni catalysts can dramatically reduce the undesirable carbon deposition (through surface oxidation), which is thermodynamically favorable under low steam conditions. In order to understanding the fundamental role of oxidation activity of the cerium oxide, different sizes of nano-crystallined cerium oxides have been carefully prepared by micro-emulsion technique. Their reactivity is clearly shown to be size dependent. We found that ceria particle sizes of lower than 5.1 nm are able to activate molecular oxygen, which accounts for the unprecedentedly reported critical size effect on oxidation. Characterizations by EPR, XPS, TPR suggest that a substantially large quantity of adsorbed oxygen species (O₂ ^-) is preferentially formed in the small size ceria from air. Also, it is found that the oxygen vacancies are formed in the interface of metal and oxide, and the strength of the metal oxide interaction may influence the formation of the efficient oxygen vacancies, which are responsible for the adsorbed surface oxygen.

Abstract Cobalt-based complexes are widely used in industry and organic synthesis as catalysts for the oxidation of hydrocarbons. The Co/Mn/Br (known as "CAB system") catalyst system is effective for the oxidation of toluene. The Co/Mn/Br/Zr catalyst system is powerful for the oxidation of p-xylene, but not for the oxidation of toluene. [Co3O(OAc)5(OH)(py)3][PF6] (Co 3+ trimer 5) is more effective than [Co3O(OAc)6(py)3][PF6] (Co 3+ trimer 6) as a catalyst in the CAB catalyst system. Higher temperatures favour the oxidation of toluene. Zr 4+ does not enhance the oxidation of toluene. Zr 4+ could inhibit the oxidation of toluene in the combination of Co/Br/Zr, Co/Mn/Zr or Co/Zr. NHPI enhances the formation of benzyl alcohol, but the formation of other by-products is a problem for industrial processes. Complex(es) between cobalt, manganese and zirconium might be formed during the catalytic reaction. However, attempts at the preparation of complexes consisting of Co/Zr or Mn/Zr or Co3ZrP or Co8Zr4 clusters failed. The oxidation of cyclohexane to cyclohexanone and cyclohexanol is of great industrial significance. For the homogeneous catalysis at 50 o C and 3 bar N2 pressure, the activity order is: Mn(OAc)3 �2H2O > Mn12O12 cluster > Co 3+ trimer 6 > [Co3O(OAc)3(OH)2(py)5][PF6]2 (Co 3+ trimer 3) > Co 3+ trimer 5 > Co(OAc)2 �4H2O > [Co2(OAc)3(OH)2(py)4][PF6]-asym (Co dimerasym) > [Co2(OAc)3(OH)2(py)4][PF6]-sym (Co dimersym); whereas [Mn2CoO(OAc)6(py)3]�HOAc (Mn2Co complex) and zirconium(IV) acetate hydroxide showed almost no activity under these conditions. But at 120 o C and 3 bar N2 pressure, the activity order is changed to: Co dimerasym > Co(OAc)2 �4H2O > Co trimer 3 and Mn(OAc)3 �2H2O > Co 3+ trimer 6 > Mn2Co complex > Co 3+ trimer 5 > Co dimersym > Mn12O12 cluster. The molar ratio of the products was close to cyclohexanol/cyclohexanone=2/1. Mn(II) acetate and zirconium(IV) acetate hydroxide showed almost no activity under these conditions. Among those cobalt dimers and trimers, only the cobalt dimerasym survived after the stability tests, this means that [Co2(OAc)3(OH)2(py)4][PF6]-asym might be the active form for cobalt(II) acetate in the CAB system. Metal-substituted (silico)aluminophosphate-5 molecular sieves (MeAPO-5 and MeSAPO-5) are important heterogeneous catalysts for the oxidation of cyclohexane. The preparation of MeAPO-5 and MeSAPO-5 and their catalytic activities were studied. Pure MeAPO-5 and MeSAPO-5 are obtained and characterised. Four new pairs of bimetal-substituted MeAPO-5 and MeSAPO-5(CoZr, MnZr, CrZr and MnCo) were prepared successfully. Two novel trimetal-subtituted MeAPO-5 and MeSAPO-5 (MnCoZr) are reported here. Improved methods for the preparation of four monometal-substituted MeAPO-5 (Cr, Co, Mn and Zr) and for CoCe(S)APO-5 and CrCe(S)APO-5 are reported. Novel combinational mixing conditions for the formation of gel mixtures for Me(S)APO-5 syntheses have been developed. For the oxidation of cyclohexane by TBHP catalysed by MeAPO-5 and MeSAPO-5 materials, CrZrSAPO-5 is the only active MeSAPO-5 catalyst among those materials tested under conditions of refluxing in cyclohexane. Of the MeAPO-5 materials tested, whereas CrCeSAPO-5 has very little activity, CrZrAPO-5 and CrCeAPO-5 are very active catalysts under conditions of refluxing in cyclohexane. MnCoAPO-5, MnZrAPO-5 and CrAPO-5 are also active. When Cr is in the catalyst system, the product distribution is always cyclohexanone/cyclohexanol equals 2-3)/1, compared with 1/2 for other catalysts. For MeAPO-5, the activity at 150 o C and 10 bar N2 pressure is: CrZrAPO-5 > CrCeAPO-5 > CoZrAPO-5. For MeAPO-5 and MeSAPO-5, at 150 o C and 13 bar N2 pressure, the selectivity towards cyclohexanone is: CrZrAPO-5 > CrZrSAPO-5 > CrCeAPO-5 > CrAPO-5 > MnCoAPO-5 > MnZrAPO-5; and the selectivity towards cyclohexanol is: MnZrAPO-5 > CrZrAPO-5 > MnCoAPO-5 > CrZrSAPO-5 > CrCeAPO-5 > CrAPO-5. Overall the selectivity towards the oxidation of cyclohexane is: CrZrAPO-5 > CrZrSAPO-5 > CrCeAPO-5 > CrAPO-5 > MnCoAPO-5 > MnZrAPO-5. The amount of water in the system can affect the performance of CrCeAPO-5, but has almost no effect on CrZrAPO-5. Metal leaching is another concern in potential industrial applications of MeAPO-5 and MeSAPO-5 catalysts. The heterogeneous catalysts prepared in the present work showed very little metal leaching. This feature, coupled with the good selectivities and effectivities, makes them potentially very useful.

Abstract Cobalt-based complexes are widely used in industry and organic synthesis as catalysts for the oxidation of hydrocarbons. The Co/Mn/Br (known as "CAB system") catalyst system is effective for the oxidation of toluene. The Co/Mn/Br/Zr catalyst system is powerful for the oxidation of p-xylene, but not for the oxidation of toluene. [Co3O(OAc)5(OH)(py)3][PF6] (Co 3+ trimer 5) is more effective than [Co3O(OAc)6(py)3][PF6] (Co 3+ trimer 6) as a catalyst in the CAB catalyst system. Higher temperatures favour the oxidation of toluene. Zr 4+ does not enhance the oxidation of toluene. Zr 4+ could inhibit the oxidation of toluene in the combination of Co/Br/Zr, Co/Mn/Zr or Co/Zr. NHPI enhances the formation of benzyl alcohol, but the formation of other by-products is a problem for industrial processes. Complex(es) between cobalt, manganese and zirconium might be formed during the catalytic reaction. However, attempts at the preparation of complexes consisting of Co/Zr or Mn/Zr or Co3ZrP or Co8Zr4 clusters failed. The oxidation of cyclohexane to cyclohexanone and cyclohexanol is of great industrial significance. For the homogeneous catalysis at 50 o C and 3 bar N2 pressure, the activity order is: Mn(OAc)3 �2H2O > Mn12O12 cluster > Co 3+ trimer 6 > [Co3O(OAc)3(OH)2(py)5][PF6]2 (Co 3+ trimer 3) > Co 3+ trimer 5 > Co(OAc)2 �4H2O > [Co2(OAc)3(OH)2(py)4][PF6]-asym (Co dimerasym) > [Co2(OAc)3(OH)2(py)4][PF6]-sym (Co dimersym); whereas [Mn2CoO(OAc)6(py)3]�HOAc (Mn2Co complex) and zirconium(IV) acetate hydroxide showed almost no activity under these conditions. But at 120 o C and 3 bar N2 pressure, the activity order is changed to: Co dimerasym > Co(OAc)2 �4H2O > Co trimer 3 and Mn(OAc)3 �2H2O > Co 3+ trimer 6 > Mn2Co complex > Co 3+ trimer 5 > Co dimersym > Mn12O12 cluster. The molar ratio of the products was close to cyclohexanol/cyclohexanone=2/1. Mn(II) acetate and zirconium(IV) acetate hydroxide showed almost no activity under these conditions. Among those cobalt dimers and trimers, only the cobalt dimerasym survived after the stability tests, this means that [Co2(OAc)3(OH)2(py)4][PF6]-asym might be the active form for cobalt(II) acetate in the CAB system. Metal-substituted (silico)aluminophosphate-5 molecular sieves (MeAPO-5 and MeSAPO-5) are important heterogeneous catalysts for the oxidation of cyclohexane. The preparation of MeAPO-5 and MeSAPO-5 and their catalytic activities were studied. Pure MeAPO-5 and MeSAPO-5 are obtained and characterised. Four new pairs of bimetal-substituted MeAPO-5 and MeSAPO-5(CoZr, MnZr, CrZr and MnCo) were prepared successfully. Two novel trimetal-subtituted MeAPO-5 and MeSAPO-5 (MnCoZr) are reported here. Improved methods for the preparation of four monometal-substituted MeAPO-5 (Cr, Co, Mn and Zr) and for CoCe(S)APO-5 and CrCe(S)APO-5 are reported. Novel combinational mixing conditions for the formation of gel mixtures for Me(S)APO-5 syntheses have been developed. For the oxidation of cyclohexane by TBHP catalysed by MeAPO-5 and MeSAPO-5 materials, CrZrSAPO-5 is the only active MeSAPO-5 catalyst among those materials tested under conditions of refluxing in cyclohexane. Of the MeAPO-5 materials tested, whereas CrCeSAPO-5 has very little activity, CrZrAPO-5 and CrCeAPO-5 are very active catalysts under conditions of refluxing in cyclohexane. MnCoAPO-5, MnZrAPO-5 and CrAPO-5 are also active. When Cr is in the catalyst system, the product distribution is always cyclohexanone/cyclohexanol equals 2-3)/1, compared with 1/2 for other catalysts. For MeAPO-5, the activity at 150 o C and 10 bar N2 pressure is: CrZrAPO-5 > CrCeAPO-5 > CoZrAPO-5. For MeAPO-5 and MeSAPO-5, at 150 o C and 13 bar N2 pressure, the selectivity towards cyclohexanone is: CrZrAPO-5 > CrZrSAPO-5 > CrCeAPO-5 > CrAPO-5 > MnCoAPO-5 > MnZrAPO-5; and the selectivity towards cyclohexanol is: MnZrAPO-5 > CrZrAPO-5 > MnCoAPO-5 > CrZrSAPO-5 > CrCeAPO-5 > CrAPO-5. Overall the selectivity towards the oxidation of cyclohexane is: CrZrAPO-5 > CrZrSAPO-5 > CrCeAPO-5 > CrAPO-5 > MnCoAPO-5 > MnZrAPO-5. The amount of water in the system can affect the performance of CrCeAPO-5, but has almost no effect on CrZrAPO-5. Metal leaching is another concern in potential industrial applications of MeAPO-5 and MeSAPO-5 catalysts. The heterogeneous catalysts prepared in the present work showed very little metal leaching. This feature, coupled with the good selectivities and effectivities, makes them potentially very useful.

This work focuses on understanding the heterogeneous/homogeneous nature of the catalytic species for a variety of immobilized metal precatalysts used for C-C coupling reactions. These precatalysts include: (i) tethered organometallic palladium pincer complexes, (ii) an encapsulated small molecule palladium complex in a polymer matrix, (iii) mercapto-modified mesoporous silica metalated with palladium acetate, and (iv) amino-functionalized mesoporous silicas metalated with Ni(II). As part of this investigation, the use of metal scavengers as selective poisons of homogeneous catalysis is introduced and investigated as a test for distinguishing heterogeneous from homogeneous catalysis. The premise of this test is that insoluble materials functionalized with metal binding sites can be used to selectively remove soluble metal, but will not interfere with catalysis from immobilized metal. In this way the test can definitely distinguish between surface and solution catalysis of immobilized metal precatalysts. This work investigates three different C-C coupling reactions catalyzed by the immobilized metal precatalysts mentioned above. These reactions include the Heck, Suzuki, and Kumada reactions. In all cases it is found that catalysis is solely from leached metal. Three different metal scavenging materials are presented as selective poisons that can be used to determine solution vs. surface catalysis. These selective poisons include poly(vinylpyridine), QuadrapureTM TU, and thiol-functionalized mesoporous silica. The results are contrasted against the current understanding of this field of research and subtleties of tests for distinguishing homogeneous from heterogeneous catalysis are presented and discussed.

A sustainable solution for meeting the energy demands at our planet is by utilizing wind-, solar-, wave-, thermal-, biomass- and hydroelectric power. These renewable and CO2 emission-free energy sources are highly variable in terms of spatial and temporal availability over the Earth, introducing the need for an appropriate method of storing and carrying energy. Hydrogen has gained significant attention as an energy storage- and carrier media because of the high energy density that is exploited within the ‘power-to-gas’ process chain. A robust way of producing sustainable hydrogen is via electrochemical water splitting. In this work the search for new heterogeneous catalyst materials with the aim of increasing energy efficiency in water splitting has involved methods of both electrochemical water splitting and chemical water oxidation. Some 21 compounds including metal- oxides, oxofluorides, oxochlorides, hydroxide and metals have been evaluated as catalysts. Two of these were synthesized directly onto conductive backbones by hydrothermal methods. Dedicated electrochemical cells were constructed for appropriate analysis of reactions, with one cell simulating an upscale unit accounting for realistic large scale applications; in this cell gaseous products are quantified by use of mass spectrometry. Parameters such as real time faradaic efficiency, production of H2 and O2 in relation to power input or overpotentials, Tafel slopes, exchange current density and electrochemical active surface area as well as turnover numbers and turnover frequencies have been evaluated. Solubility, possible side reactions, the role of the oxidation state of catalytically active elements and the nature of the outermost active surface layer of the catalyst are discussed. It was concluded that metal oxides are less efficient than metal based catalysts, both in terms of energy efficiency and in terms of electrode preparation methods intended for long time operation. The most efficient material was Ni-Fe hydroxide electrodeposited onto Ni metal foam as conductive backbone. Among the other catalysts, Co3Sb4O6F6 was of particular interest because the compound incorporate a metalloid (Sb) and redox inert F and yet show pronounced catalytic performance. In addition, performance of materials in water splitting catalysis has been discussed on the basis of results from electron microscopy, solubility experiments and X-ray diffraction data.

Thesis (Master)--İzmir Institute of Technology, İzmir, 2006.
Keywords:Suzuki reactions, palladium, NaYzeolite, heterogeneous catalyst, C-C coupling. Includes bibliographical references (leaves. 71-81).

The targets of this thesis were the selective oxidation of hydrocarbons under mild conditions, using cheap and environmentally friendly oxidants and initiators. Three projects are treated; the oxidation of an alkane using O2 and a co-oxidant, the oxidation of toluene using TBHP (tert-butyl hydroperoxide) and finally the oxidation of propane using hydrogen peroxide. C-H bond activation, O2 activation and high conversion with high selectivity were essential points to investigate. In the first project, alkane oxidation was studied in presence of a co-oxidant. The co-oxidant has for purpose to initiate the activation of the alkane and O2, as well as prevent the over-oxidation of the alkane. The co-oxidation of octane using benzaldehyde has been investigated using 1 wt. % AuPd/ C catalyst; the hypothesis is that benzaldehyde oxidation would use a radical mechanism able to activate octane to octanol. Also, the coupling of octanol with activated benzaldehyde would prevent the over-oxidation of octanol by the formation of an ester; octylbenzoate. The aim of the second study was to investigate the selective oxidation of toluene using TBHP at 80 °C with supported noble metal nanoparticle catalysts prepared by sol-immobilisation techniques. Au, Pd and Pt have been use to form mono, bi and trimetallic catalysts of different morphology supported on C and TiO2. These catalysts have been tested for toluene oxidation. The catalyst showing the best activity has been used for further investigation such as reuse test, using H2O2 as oxidant or O2 activation. The third project target was to oxidise propane using H2O2 in mild conditions. 2.5 wt. % Fe/ ZSM-5 (30) has been used to investigate reaction conditions in order to optimise the system. This catalyst has been acid treated; standard and treated catalysts were characterised and analysed to identify the structure and active sites. Role of supports and metals (mono and bimetallic) has been explored in order to improve this system.

Our society has a problem with the use of fossil fuels, due to the vast and exceeding emissions derived from human activities. Two ways could be consider to mitigate these harmful effects. On the one hand, the capture, activation, and conversion of these hazardous gases towards valuable compounds, and on the other hand, the substitution of fossil fuels for renewable energies. This thesis encompasses the study of two different green chemistry reactions to convert the most abundant greenhouse gas in Earth's atmosphere and the production of a new environmental friendly fuel, the hydrogen. In the current search for new catalysts, Transition Metal Carbides (TMCs) have arisen as an appealing alternative, because their exhibit broad and amazing physical and chemical properties and their low cost. In particular, titanium carbide (001) was proposed from experimental and theoretical points of view as active catalyst and support of small metal particles for CO2 hydrogenation to methanol and water gas shift reaction. However, given that titanium carbide is a cumbersome support to be used in applications due to the difficulty of obtaining nanoparticles on working conditions, we have carried out these reactions on cubic δ-MoC (001) and orthorhombic β-Mo2C (001) surfaces. The adsorption and activation of a CO2 molecule on cubic δ-MoC (001) and orthorhombic β-Mo2C (001) surfaces have been investigated by means of periodic density functional theory based calculations using the Perdew-Burke-Ernzerhof exchange-correlation functional showing that both surface are promising catalyst for CO2 conversion because they are able to activate and bend the CO2 molecule. The β- Mo2C (001) surface is able to dissociate the CO2 molecule easily, with a low energy barrier, whereas δ-MoC (001) surface activates CO2 but it does not promote its direct dissociation. Experiments accomplished by the group of Dr. Jose Rodriguez revealed that CO and methane are the main products of the CO2 hydrogenation using β-Mo2C (001) as catalyst, and the amount of methanol is lower. On the other hand, only CO and methanol are produced using δ-MoC (001). Experiments revealed that the deposition of small copper particles on the carbide surfaces increase drastically the catalysts' activity and selectivity, which was demonstrated by theoretical calculations. On β-Mo2C, the amount of CO and methanol increase whilst the amount of methane decrease, since copper blocks reactive sites on surface. This is a positive fact since copper avoid the excessive oxygen deposition, which deactivated the catalysts. On the other hand, the deposition of copper on δ-MoC (001) increases a lot the amount of CO and methanol. In summary, our combining DFT- experimental study proposed the Cu/δ-MoC as promising catalyst for CO2 hydrogenation due to its activity (the amount of products is superior than other TMCS, metals, and the model of commercial catalysts), selectivity (only CO and methanol are produced), and stability ( this catalysts is not deactivated by the oxygen deposition). The results obtained in the first part of the thesis were used to study the water gas shift reaction. Given that the excellent features, experiments proposed Au supported on δ-MoC (001) as catalysts. Our theoretical calculations demonstrated that clean δ-MoC (001) is not a good catalysts for WGS, due to the fact that the reverse reactions are favorable respect the direct ones, which implies that the amount of products is lower. Nevertheless, the deposition of Au clusters change the reaction mechanism, favoring the direct barriers instead of reverse ones, and increasing the amount of produced H2. In summary, this thesis has displayed the prominent role of molybdenum carbides as support of small metal particles to catalyze green chemistry reactions.
En aquesta tesi es mostra un treball computacional sobre l'ús de catalitzadors econòmics per a la conversió de CO2, un perillós gas d'efecte hivernacle i també per a la producció d'hidrogen, el combustible del futur. En la recerca actual de nous catalitzadors, els carburs de metalls de transició (TMC) han sorgit com una alternativa atractiva pel el seu baix cost i per exhibir excel·lents propietats físiques i químiques. En aquest treball utilitzarem com a catalitzadors les superfícies cúbica δ-MoC (001) i ortoròmbica β-Mo2C (001). L'adsorció de la molècula de CO2 mostra que ambdues superfícies són capaces d'activar i doblegar la molècula. La superfície β-Mo2C (001) és capaç de dissociar fàcilment la molècula de CO2, mentre que la superfície δ-MoC (001) activa CO2 però no la dissocia. Els experiments realitzats pel grup del Dr. Jose Rodriguez van revelar que el CO i el metà són els principals productes de la hidrogenació de CO2 utilitzant β-Mo2C (001) com a catalitzador, i la quantitat de metanol és menor. D'altra banda, només es produeixen CO i metanol utilitzant δ-MoC (001). La deposició de partícules de coure a les superfícies del carbur augmenta dràsticament l'activitat dels catalitzadors, cosa que es va demostrar mitjançant càlculs teòrics. A la superfície β-Mo2C, la quantitat de CO i metanol augmenten mentre que la quantitat de metà disminueix. D'altra banda, la deposició de coure a δ-MoC (001) augmenta molt la quantitat de CO i metanol. En resum, el nostre estudi proposa el Cu/δ-MoC com a prometedor catalitzador de la hidrogenació de CO2 a causa de la seva activitat (la quantitat de productes és superior a la resta de TMCS, metalls i el model de catalitzadors comercials), selectivitat (només el CO i el metanol es produeixen) i l'estabilitat (aquests catalitzadors no es desactiven per la deposició d'oxigen). Tenint en compte els resultats previs, es va proposar la deposició d'or en la superfície δ-MoC per a la producció d'hidrogen. Els càlculs teòrics demostren que la superfície δ-MoC (001) no és un bon catalitzador per WGS, però la deposició dels clústers d'or canvia el mecanisme de reacció i augmenta la quantitat d'H2 produïda.

Catalytic deactivation caused by coking was studied in ZSM5 and zeolite Y catalysts during the isomerisation of 1-hexene under sub and supercritical conditions. The effects of varying temperature and pressure, from 220–250 °C and 10-70 bar respectively, on conversion and coke deposition were studied in both zeolites. TGA, DRIFTS, nitrogen sorption isotherms for fresh and coked catalysts and catalyst acidity measurements were compared. In ZSM5 the catalyst was stable for 96 hours. TGA and DRIFTS results show coke deposits were mainly polyolefinic and the amount decreases considerably from 18.8 wt% in the subcritical region to 10 wt% in the supercritical region. In zeolite Y, decay in conversion was observed with the rate of deactivation being slower at supercritical conditions at 235 °C and 40 bar. Naphthalene hydrogenation on NiMo/γ-Al2O3 catalyst was also studied. The effect of temperature, pressure, varying naphthalene feed concentration and operating in sub and supercritical conditions were studied. Coke deposit decreased by 38 wt% in the supercritical region. SC CO2 (Tc 31.04 °C, Pc 73.8 bar) was also used to re-activate the coked catalysts. This resulted in recovering 93% of the catalytic activity and 37% of the coke was effectively extracted by SC CO2.

Thesis (Ph. D.)--University of Maryland, College Park, 2007.
Thesis research directed by: Chemistry. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

Biodiesel is a re-emerging biofuel as an alternative to the traditional petroleum derived diesel. There are however, several factors that currently hinder the widespread uptake. Majority of the biodiesel are currently produced from edible oils thereby sparking the food versus fuel debate, the cost of feedstock is significantly high, there are problems experienced in the traditional production process and the resulting fuel is of inadequate quality. This work focused on addressing the issue of poor cold flow properties to improve the overall quality of biodiesel. The skeletal isomerisation of linear fatty acid methyl esters (FAMEs) into branched chain isomers, using solid acid catalysts, appears to be the most comprehensive solution in enhancing the cold flow properties of biodiesel. However, obtaining high branched chain yields, mitigation of undesired side reactions, achieving shorter reaction times, using fewer processing steps and lower operating conditions have still not been achieved to a large extent. Moreover, no studies were found to date investigating isomerisation of FAMEs as a continuous process. A trickle bed reactor (TBR) system has been identified to be an effective continuous reactor. Its key features of being a three phase system and allowing a high degree of contact between the reactant and the catalyst offering a high conversion per unit volume provides an encouraging opportunity to lower reaction times, reaction steps and conditions whilst increasing branched chain yields. This thesis explores the use of the TBR system, for the first time, to enhance the cold flow properties of biodiesel through molecular modification using zeolite beta catalyst with Si/Al ratios of 180 and 12.5. A range of reactions have been investigated including isomerisation, dewaxing (hydroisomerisation and hydrocracking) and decarboxylation on biodiesels derived from camelina, palm and coconut oils. Significant progress has been made in this research area with a 7 °C drop in MP being achieved upon the dewaxing of the coconut biodiesel at 250 °C, 1.01 bar pressure, 0.2 ml/min LF and 37.5 ml/min GF. To achieve greater drops in melting points it has been suggested to investigate mesoporous catalysts as they will ensure greater facilitated molecular access to the active sites, resulting in a higher conversion by preventing pore blockages. All in all, a series of key findings and serendipitous discoveries have brought to surface an array of new challenges as well as paving the way for a host of exciting opportunities for future research. The ability to continuously produce high quality renewable fuel offers a fascinating prospective for various industrial associates such as Argent Energy, Olleco, Neste Oil and ConocoPhillips.

Process options to minimise the environmental impact and improve the efficiency of biodiesel production have been investigated. The process options considered include the use of heterogeneous catalysts and used cooking oil (UCO). An esterification pre-treatment reaction was investigated using an ion-exchange resin (Purolite D5082) and an immobilised enzyme (Novozyme 435). Another immobilised enzyme (Amano Lipase PS-IM) was investigated for transesterification. The fresh and used catalysts have been characterised. The catalytic activity of Purolite D5082, Novozyme 435 and Amano Lipase PS-IM have been investigated using a jacketed batch reactor with a reflux condenser. Purolite D5082 has been developed for the esterification pre-treatment process and is not commercially available. Novozyme 435 has been shown to be an effective esterification catalyst for materials with high concentrations of free fatty acid but it has not been investigated for the esterification pre-treatment reaction. It was found that a high conversion was possible with both catalysts. The optimum reaction conditions identified for Purolite D5081 were a temperature of 60 C, a methanol to free fatty acid (FFA) mole ratio of 62:1, a catalyst loading of 5 wt% resulting in a FFAs conversion of 88% after 8 h of reaction time. The optimum conditions identified for Novozyme 435 were a temperature of 50 C, a methanol to FFA mole ratio of 6.2:1 and a catalyst loading of 1 wt% resulting in a conversion of 90% after 8 h of reaction time. These catalysts were compared to previously investigated Purolite D5081 and it was found that the highest conversion of 97% was achieved using Purolite D5081, however there were benefits to using Novozyme 435 because the reaction could be carried out using a much lower mole ratio, at a lower temperature and in much shorter reaction time. During the Novozyme 435 catalysed esterification pre-treatment reactions it was found that the amount of free fatty acid methyl esters (FAME) formed during the reaction was greater than the amount of FFAs consumed. In order to investigate further an ultra-performance liquid chromatography mass spectrometry (UPLC-MS) method was developed to monitor the monogclyeride (MG), diglyceride (DG) and triglyceride (TG) concentrations. This analytical method was used to show that Novozyme 435 would catalyse the esterification of FFAs as well as the transesterification of MGs and DGs typically found in UCO. With the UPLC-MS method it was possible to separate the 1, 2 and 1, 3 DG positional isomers and from this it could be seen that the 1, 3 isomer reacted more readily than the 1, 2 isomer. The results from the UPLC-MS method were combined with a kinetic model to investigate the reaction mechanism. The kinetic model indicated that the reaction progressed with the sequential hydrolysis esterification reactions in parallel with transesterification. Commercially available Amano Lipase PS-IM was investigated for the transesterification reaction. Enzymes are not affected by FFAs and as a result the optimisation was carried out with UCO as the raw material. An optimisation study for the transesterification of UCO with Amano Lipase PS-IM has not previously been reported. The conditions identified for the Amano Lipase PS-IM catalysed transesterification step are addition of 5 vol% water, a temperature of 30 C, a methanol to UCO mole ratio of 3:1 and a catalyst loading of 0.789 wt% resulting in a TG conversion of 43%. An overall enzyme catalysed process was proposed consisting of Amano Lipase PS-IM catalysed transesterification (stage 1) followed by Novozyme 435 catalysed esterification (stage 2). The previously identified optimum conditions identified for each catalyst were used for above stages. It was found that when the oil layer from stage 1 was dried the final TG conversion was 55%.

A combination of Temporal Analysis of Products, Temperature Programmed Reduction, and Density Functional theory techniques have been used to perform kinetic analysis on data from heterogeneous catalysis experiments. A new method of data filtering has been developed for Temporal Analysis of Products, and has been applied to a system of 4 Pt−Mo2C, and the current methodology has been expanded upon to calculate rate coefficients for the oxidation of CO to CO2 via the Boudard reaction. From the kinetic constants it appears that a phase change occurs in the material at approximately 200�C. The current theory for analysing Temperature Programmed Reduction has been applied in a new methodology which is able to perform the deconvolution of thermograms with high accuracy, while also calculating the kinetic parameters related to the reduction processes. This new methodology has been applied to a system of CeO2 calcined at 400, 500 and 600�C and the strengths and limitations of the methodology are explored. From the deconvolution procedure it was found that there are three distinct reduction processes occurring on the CeO2 and that a phase change occurs between 400 and 500�C. Finally Density Functional Theory combined with classical dynamics has been used to explore the mechanism of the hydrogenation of Levulinic Acid to gamma-Valerolactone over a CuZrO2 catalyst. It was found that the Levulinic Acid is more likely to hydrogenate then cyclise, and from using molecular dynamics simulations it was shown that the solvent H2O plays a very important role in the cyclisation of the hydrogenated intermediate.

The emergence of unique or enhanced physical, chemical and optical material properties at the nanoscale underlies the swift rise of nanomaterials science over recent decades. Within this interdisciplinary field, catalysis performed by nanomaterials (i.e. nanocatalysis) is one area where differences between nanoscale and bulk material properties offer particularly attractive opportunities for application. The consequent pursuit of viable nanomaterials with unprecedented catalytic activity has inevitably expanded across the periodic table, whereby a number of highly efficient precious metal, metal oxide and composite nanostructured catalysts have been developed for a wide range of synthetic organic and inorganic transformations. The lanthanide series has not been excluded from this search, but is still underrepresented in catalysis despite some rich chemistry and reactivity which sets these elements apart from many other metals. More recently however, the necessary paradigm shift away from commonly utilized but expensive, potentially toxic precious metal catalysts, and toward more sustainable alternatives, has seen an upsurge in the development of novel nanomaterials for heterogeneous catalysis: the general topic of this doctoral thesis. Heterogeneous nanocatalysis offers distinct advantages over homogeneous catalysis. Catalyst recyclability, ease of separation from reaction mixtures, and minimal product contamination all contribute to the higher overall effectiveness of heterogeneous catalysts relative to their homogeneous counterparts. The use of light as an abundant reagent, both in nanomaterial fabrication and for photocatalysis, is another attractive prospect. This dissertation addresses both points, describing the iterative development and application of photochemically-prepared samarium oxide based nanomaterials for heterogeneous catalysis and photocatalysis. Through a series of related peer-reviewed publications and associated commentary, the evolution of the application-driven design of a nanomaterial which is both efficient and effective for a diversity of heterogeneous catalytic and photocatalytic transformations is presented. Major findings include 1) both colloidal and supported samarium oxide nanoparticles can be prepared photochemically and comprise primarily Sm2O3 but may contain localized mixed valences or dynamic surface oxidation states; 2) colloidal samarium oxide nanoparticles possess high activity for Brønsted acid and oxidative catalysis, but recyclability and overall effectiveness is less than optimal due to a combination of polydispersity and size-dependent catalytic activity; 3) a similarly-prepared “second generation” samarium oxide/titanium dioxide nanocomposite presented several advantages over its predecessor, performing highly efficient and effective pure heterogeneous, dual photoredox-Lewis acid catalysis in two different types of synthetically relevant photocyclizations. Effects of different nanoparticle supports, rare insights into the catalytic mechanisms and behaviour of these nanomaterials‒obtained at the single molecule level by innovative application of Total Internal Reflection Fluorescence Microscopy (TIRFM) to catalysis research‒as well as advances in TIRFM data analysis protocols, are also discussed.

Includes bibliographical references.
Despite the nobleness of bulk gold metal in air, small supported gold particles have been shown experimentally to be active in a wide range of chemical reactions. The objective of this work was to study, theoretically, some of the fundamental aspects of the reactivity of gold catalysts. Using activation of CO, CO2 and H2 as a test case, periodic and cluster density functional theory (DFT) calculations, within the generalized-gradient approximation (GGA), were performed to investigate the change in nobility of gold from the extended surface to small clusters. Potential methanol synthesis intermediates were optimized on the Au(111) surface. It was found that the molecules that are stable as gasphase species generally adsorbed weakly on the surface. Surface hydrogenation of CO-derived species appeared to be easier than surface hydrogenation of CO2- derived species. On an AU13 cluster, the energetics of CO2 adsorption and hydrogenation remain unfavourable. The cluster-size dependency of hydrogen and carbon monoxide adsorption was investigated. It was found that small gold clusters (1 to 13 atoms in size) can bind both H and CO strongly. Due to the changes in the orbital spatial symmetries and the energies of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) with cluster size in this small size range, the adsorption energies depend very strongly on the number of gold atoms present, i.e. each atom makes a difference. For H adsorption, there is a very marked oscillation in adsorption energies, with the clusters with an odd number of gold atoms (with lower LUMO energies) being generally more reactive than the even clusters, up to about 10 atoms when the HOMO-LUMO gap ceases to fluctuate strongly. The role of the support material in activating gold atoms was studied. A hybrid quantum mechanics/molecular mechanics (QMlMM) electronic embedding technique was employed to model the ZnO(000l) surface of zincite. The QM region of the surface, treated by density functional theory, consisted of a total of 13 zinc and oxygen atoms for the zinc-vacant site, and 14 atoms for the bulk-terminated island site. It was found that Au0 and Au+ could be stabilized at the zinc vacant site of this surface. The higher oxidation states are unstable with respect to auto-reduction by the ZnO surface (i.e. their LUMO energies were below the HOMO of a bare ZnO surface. However, gold hydroxyls, where gold has + 1 to +3 oxidation states, can be stabilized at the vacancy. As zinc-substitutional impurities on the bulk-terminated island site, Au+, Au2+ and Au3+ oxidation states can be stabilized. CO was used as a test molecule to probe the chemical reactivity of the gold atoms in different adsorption sites and oxidation states. It was found that supported Au+ was more reactive than Au0, Au2+, or Au3+. Furthermore, CO binds more strongly to supported Au0 than the free Au0 atom. This implies that the support does not simply disperse gold particles, but it also modifies their electronic properties. It was also found that the nucleation of gold atoms to clusters can be affected by the support. Supported charges Au clusters have shorter Au-Au distances than their gas-phase counterparts.

Dottorato di Ricerca in Chimica Industriale (XXVII Ciclo) Report finale Dottorando: Dott. Matteo Mariani Tutor: Dott.ssa Laura Santagostini Co-Tutor: Dott. ssa Nicoletta Ravasio Heterogeneous catalysis for the synthesis of bioproducts Before the discovery of crude oil, in 19th century, society was dependent only on biomass to answer to its energy request. Petroleum discovery provided a source of inexpensive material for energy production, that helped to industrialize the world and improved the standards of living. Unfortunately petroleum sources are waning, due to the growing request especially from the emerging countries, like India, China and Brazil. Moreover the crude oil usage creates very burdensome pollution problems, related to the emission of greenhouse gases. One possible answer to this important challenge could be the exploitation of biomass resources to produce not only energy, but also chemicals and liquid fuels in a sustainable way. In fact biomass is a renewable feedstock, that can be also obtained from agricultural and forest wastes. BIOLUBRICANTS Lubricants cover a large part of the worldwide chemicals market, and their consumption is estimated to be around 40 million metric tonnes per year. Automotive and hydraulics are the largest group of sold and used lubricant in the world. Unfortunately about 50% of all sold lubricants are loss in environment, resulting in severe contamination of soil, groundwater and air [1]. As a result, there has been an increasing demand of biolubricants, derived from vegetable oils. This kind of materials are biodegradable, and permit to limit the environmental pollution [2]. Vegetable oils have technical properties suitable for their use in lubricants formulation, but one significant problem is their low thermal stability, that depends on the presence of H atoms located in the beta position of ester groups, thus making the glycerol esters susceptible to elimination reaction and subsequent degradation of the native molecule. That is why so called hindered esters, that is esters of fatty acids with alcohols without H atoms in beta position, are preferred for lubricants that have to withstand high temperature and pressures [3]. The synthesis of these esters is based on the esterification reaction between an acid, derived from vegetable oils, and a polyol, like trimethylolpropane (TMP) or pentaerithrol (PE). The reaction is usually carried out with a homogeneous acidic catalyst (e.g., p-toluenesulfonic acid, mineral acids) that requires neutralization and washing steps:. In order to make the reaction greener it would be better to use heterogeneous catalysis and to avoid in particular the use of huge amounts of water. Heterogeneous catalysts provide simpler and cheaper separation processes, reduced wastes production, in this case inorganic salts, and in some cases can be recycled. Scheme 1: Esterification reaction between TMP and a carboxylic acid I tested in the esterification of fatty acids with polyols a series of amorphous mixed oxides, namely Silica zirconia silica alumina and silica titania, with surface area ranging from 300 to 500 m2/g and porosity in the range of mesoporousity. Results are summed up in Table 1 Polyol Fatty Acid Cat (%) Exp. Cond. t (h) Conv (%) TMP Nonanoic SiO2-ZrO2 (2,5%) 5% exc TMP 6 99 TMP Nonanoic SiO2-TiO2 (2,5%) 5% exc TMP 6 94 TMP Nonanoic SiO2-Al2O3 (2,5%) 5% exc TMP 6 94 TMP Caprilic SiO2-ZrO2 (2,5%) 5% exc TMP 6 98 TMP Caprilic SiO2-TiO2 (2,5%) 5% exc TMP 6 92 TMP Caprilic SiO2-Al2O3 (2,5%) 5% exc TMP 6 92 TMP Oleic SiO2-ZrO2 (2,5%) 5% exc TMP 6 98 TMP Oleic SiO2-TiO2 (2,5%) 5% exc TMP 6 95 TMP Oleic SiO2-Al2O3 (2,5%) 5% exc TMP 6 89 TMP Oleic SiO2-TiO2 (2,5%) stoichiometric 6 87 NPG Oleic SiO2-ZrO2 (2,5%) 5% exc fatty acid 6 92 PE Oleic SiO2-ZrO2 (2,5%) 5% exc fatty acid 6 99 TMP Oleic SiO2-ZrO2 (10%) 5% exc fatty acid 6 >99 TMP Oleic SiO2-ZrO2 (5%) 5% exc fatty acid 6 >99 TMP Oleic SiO2-ZrO2 (2,5%) 5% exc fatty acid 6 99 TMP Oleic Sn ossalate (0,04%) 5% exc TMP 6 89 Table 1: Esterification reactions Reactions were carried out at 200°C without any solvent under a weak nitrogen flow and a Claisen condenser, to remove the water produced in the esterification reaction. Not only activity was comparable with that obtained under the same exp condition in the presence of SnO, but selectivity was higher, giving oils with excellent physical properties. The catalyst could be removed very easily and reused up to 6 times without any re-activation treatment. MONOGLYCERIDES Monoglycerides are a very important class of compound for industry; in fact a lot of products of daily use contain monoglycerides. The long chain fatty acid monoesters of glycerol are valuable compounds with wide applications as emulsifier in food, pharmaceutics, cosmetics, and detergent industries [4]. While short chain fatty acids monoglycerides are used as antibacterial and antibiotic agents in feed. Therefore production of biocompatible monoglycerides gain great importance. Also the synthesis of these compounds starting from renewable raw materials (glycerol from biodiesel production and vegetable oils) is much more important and greener. The industrial synthesis foresee the transesterification of glycerol with triglycerides or fatty acid methyl esters (FAMEs) or, alternatively, the direct esterification of glycerol with free fatty acids (FFAs). Transesterification is usually catalyzed by homogeneous basic catalyst (e.g., KOH, NaOH, Ca(OH)2), but this route has the drawback to produce large amount of soaps that do not permit an easy separation of products. Heterogeneous basic catalysts offer many advantages, like catalyst separation and recycling; the most used ones being MgO and hydrotalcites [5]. On the other hand, esterification needs acidic catalysts, such as mineral or organic ones, but, once again, heterogeneous catalysis offers much more advantages. Acidic oxides and zeolites are the most used catalysts to perform this kind of reaction. In this part of my work, I focused my attention on esterification of glycerol with oleic (table 2) and valeric acid (table 3) in molar ratio 1:1 with glycerol, using different types of silicas as heterogeneous catalysts (2.5 % or 5% by weight with respect to the acid). The reaction temperature was 150°C with valeric acid and 200 °C with oleic acid, in a three necked flask, equipped with Claisen condenser and a bubbler for nitrogen flux. The reaction time was 6 hours, and the catalysts were not activated. Residual acidity was determined by titration with NaOH 0.1M in diethyl ether:ethanol solution 2:1, with phenolphthalein as indicator. Selectivity was determined by GC analysis using an Agilent 6890N GC equipped with a CP-Sil 8 CB column. ENTRY CATALYST ACIDITY CONVERSION SELECTIVITY MG 1 SiO2-TiO2 2.3% 0.9% 99.1% 49% 2 SiO2-Al2O3 135 3.6% 96.4% 77.8% 3 SiO2-ZrO2 4.7% 3.4% 96.6% 76.9% 4 SiO2-Al2O3 0.6% 2.9% 97.1% 37.1% Table 2: Esterification of glycerol with oleic acid with different solid catalysts Conversion of these reaction are excellent, and selectivity in monoglycerides are high for entries 2 and 3, that represent a good compromise between conversion and selectivity. ENTRY CATALYST ACIDITY CONVERSION SELECTIVITY MG 1a Mesoporous silica 8.2% 91.8% 31.35% 2 a SiO2-TiO2 2.3% 6.6% 93.4% 0.4% 3 SiO2-Al2O3 135 19% 81% 72.2% 4 SiO2-TiO2 2.3% 15% 85% 74.3% 5 SiO2-Al2O3 0.6% 16.5% 83.5% 64.5% 6 Mesoporous silica 19% 81% 64.1% a 170°C and 5% by weight of catalyst with respect to acid Table 3: Esterification of glycerol with valeric acid with different solid catalysts As you can see from the table 3 temperature have a dramatic effect on both conversion and selectivity of these reactions. The two reactions performed at 170°C (entry 1 and 2) give good conversion, but a scarce selectivity in monoglycerides. The other reaction shows a little bit lower conversion, but the selectivity is much improved. The catalyst amount don’t have a significant effect on the reaction, so we decided to lower it. CELLULOSE Cellulose consist of a linear polysaccharide with -1,4 linkages of D-glucopyranose monomers. Cellulose is a crystalline material, with a very large amount of hydrogen bonds that reinforce the structure. Since cellulose is the principal constituent of the terrestrial biomass, the attention of chemists fell on this molecule. In fact from cellulose we can extract a lot of interesting molecules, that can be used like biofuels (levulinic esters and methyl-tetrahydrofuran), chemicals (HMF, organic acids, glycols) and sugars [6]. Many method can be used to depolimerize cellulose and to obtain the searched products: two of them are hydrolysis and hydrogenation. The first reaction requests acidic catalysts to broken the glycoside linkages, the latter needs the presence of hydrogen and a transition metal to perform hydrogenation and give reduced products (xylitol, sorbitol and sorbitan). For hydrolysis homogeneous catalysts, like sulphuric acid, can be used but heterogeneous acid catalysts permit to perform a greener process, while in hydrolysis-hydrogenation a solid catalyst are needed. Our research group set up the preparation of a copper oxide catalyst with very interesting characteristics for cellulose hydrolysis and hydrogenation [7]. This CuO/SiO2 catalyst, produced by chemisorption-hydrolysis, present a unexpected acidity, that unsupported copper oxide doesn’t show. This fact was confirmed by pyridine absorption spectra, that shows typical bands of Lewis sites (1453 and 1611 cm-1) also at 200°C. The acidity can be ascribed to the very high dispersion of copper oxide over the support, confirmed by HRTEM analysis (Fig 1). Figure 1: HRTEM and particle distribution of CuO/silica This copper catalyst permits to perform hydrolysis, but also the hydrogenation in an one pot reaction. Testing different supports and the relative copper catalysts, we found some interesting features. For example: the catalyzed reaction was much more selective than the non-catalyzed. Also the copper catalysts, especially CuO/Si, CuO/SiTi and CuO/SiZr shows a sharp increase in glucose and levulinic acid formation. Figure 2: conversion and selectivity for cellulose hydrolisys (A) bare supports and (B) copper catalysts CuO/SiAl represent a singular case, because it shows the higher conversion and selectivity in lactic acid. This is due to the strong Lewis acidity of the support, leading to the formation of ionic copper species with a marked Lewis acidity. This trend is confirmed by a series of catalytic tests with different CuO/SiAl catalysts, with a different copper loading. The lactic acid selectivity grows linearly with the copper content, reaching a maximum at 8% of Cu. This trend is confirmed by the pyridine absorption spectra, that shows a progressive growth of the band ascribed to the pyridinium ion bonded to Lewis acid sites [8]. Figure 3: Conversion and selectivity with CuO/SiAl with different Cu loading We carried out this kind of reactions in a hastelloy Parr autoclave, with 1,5 g of -cellulose and 0.8 g of catalyst in 30 ml of distilled water. The temperature was 180°C, and we used an overpressure of 4 atm of nitrogen. In the case of hydrogenation we tried different hydrogen pressures. The reaction time is 24 hours. The products analysis were performed with an Agilent 1200 Series HPLC equipped with UV and RID detectors and a MetaCarb H Plus column (eluent H2SO4 0.0085 N in MQ water). To determine the conversion in water soluble product I used a Shimadzu TOC-L total organic carbon analyzer. LACTOSE Lactose is a disaccharide formed by one D-glucose unit, linked by a -1,4 bond, to one D-galactose unit. Milk whey is constituted by about 70% of its dry weight by lactose. Whey is the principal waste of dairy industry and constituted a big environmental problem. In fact its disposal is very exigent concerning the chemical and biochemical demand [9]. Its recovering and reuse became newsworthy for countries with huge cheeses production. There are some reaction for exploit lactose and obtain important industrial products, the principal are oxidation, to lactobionic acid, reduction, to obtain lactitol and hydrolysis to obtain glucose and fructose. We think to hydrolyse lactose to obtain the two sugars and then to reduce them to sorbitol and dulcitol. Sorbitol in particular is very interesting for food industry, in fact it is used widely in sugar-free candy and chewingum. Other uses can be in pharmaceutical as excipients. With our catalyst Cu/SiO2 is possible to hydrolyse and reduce, in one-pot reaction, the lactose to obtain sorbitol and dulcitol. All the reaction were carried on in a hastelloy Parr autoclave, with 1 g of -lactose and different loading of catalyst in 40 ml of distilled water. The temperature was 180°C, and we used an overpressure of 30 atm of hydrogen. The reaction time is 8 hours. The products analysis were performed with an Agilent 1200 Series HPLC equipped with UV and RID detectors and a MetaCarb H Plus column (eluent H2SO4 0.0085 N in MQ water). We tried 2 different copper loading: 8% and 16%, and the best one is the latter. Also influence of the support was investigated, using different kind of silica and mixed oxides. The mixed oxides (SiAl and SiZr) results inactive in hydrogenation, but active in hydrolysis. Between silicas the most active are MP04300, Trysil 300 and SiO2 from FLUKA. These 3 catalysts gives selectivity in hydrogenated compounds up to 90%. Surprisingly Trysil gives bad results. Regard to the amount of catalyst we started with 40% by weight by respect to the lactose, but we obtained same results with only 20% by weight. Oxide Surface area (m2/g) PV (mL/g) DP (Å) SiO2 480 0,75 60 SiO2-Al2O3 135 485 0,79 33 SiO2-TiO2 297 1,26 84 SiO2-Al2O3 0,6% 488 1,43 117 SiO2-ZrO2 421 2,38 181 SiO2 MP04300 723 0,66 38 CuO/ SiO2 (8% Cu) 363 0,68 78 CuO/SiO2-Al2O3 135(8% Cu) 412 0,75 37 CuO/SiO2-TiO2(8% Cu) 318 1,01 64 CuO/ SiO2 MP04300 ((% Cu) 299 0,55 73 Table 4: porosimetric data for the used supports and relative copper catalysts In the table there are listed the porosimetric data for the supports used in the reactions.

Several heterogeneously catalysed reactions have been studied at pressures above and below the critical pressure of carbon dioxide in both carbon dioxide and nitrogen. The purpose of this study was to ascertain if carbon dioxide above its critical pressure and temperature would have a beneficial effect on the active life time of the catalysts When the Beckmann rearrangement of cyclohexanone oxime was studied it was discovered that using carbon dioxide above its critical pressure and temperature was beneficial to catalyst lifetime at both 250°C and 300°C, however the beneficial effect was also observed in nitrogen under the same conditions. It is proposed that the benefits at higher pressures are due to an increased residence time in the reactor or increased competition for active sites. When the process was performed at 380°C, a previously unreported impurity was observed in the collected samples. This was shown to be N-ethyl caprolactam, it is proposed that this is formed by a Ritter style reaction with 5-cyanopent-1-ene known to be formed during the reaction When the Fries rearrangement of phenyl acetate was studied it was discovered that increasing reactor pressure appeared to have little or no effect on the catalyst; it is thought this is because the reaction temperature of 150°C is below the boiling point of phenyl acetate, and that the reaction being observed occurs purely in the liquid phase. When the Diels-Alder addition of isoprene to methyl acrylate was studied, it was discovered that using carbon dioxide above its critical pressure had the effect of improving catalyst lifetime and conversion to desired product, with the greatest effect being at 50 bar. It was discovered that using nitrogen under the same conditions led to a greater improvement in conversion and catalyst lifetime. It is thought that the reactions in carbon dioxide are in a near critical state at 50 bar leading to the maximum effect at this pressure, and at higher pressures the reactions are bi- or multi-phasic, leading to the decrease in the effect. In the process of studying the above reactions an effective rig for the study of high pressure heterogeneously catalysed reactions was built.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 182-188).
The steam methane reforming (SMR) reaction is the primary industrial means for producing hydrogen gas. As such, it is a critical support process for applications including petrochemical processing and ammonia synthesis. In addition, SMR could be an important component of future energy infrastructures as a means for producing hydrogen as an energy carrier for applications including fuel cells in automobiles and direct combustion for electricity generation. Nickel is the preferred SMR catalyst; however, the efficiency of SMR over nickel can be severely hindered by carbon formation, which leads to the deactivation or even destruction of the catalyst particles. Thus, there is significant interest in catalysts that inhibit carbon formation yet retain activity to SMR. In order to develop improved catalysts for SMR, a thorough understanding of the processes occurring on the nickel surface is needed. In this thesis, computational heterogeneous catalysis is applied to investigate steam methane reforming over nickel (Ni) and silver-alloyed nickel (Ni/Ag) catalysts. Electronic structure calculations using density functional theory (DFT) are employed to develop thermochemical landscapes describing the relative stabilities of SMR intermediates on the catalyst surfaces. In addition, DFT calculations are used to obtain kinetic parameters that describe elementary surface reactions taking place during SMR. A detailed statistical thermodynamics framework is developed to allow for the calculation of enthalpies, entropies, and free energies of the surface species at the temperatures and pressures relevant to industrial SMR. The data from the DFT calculations are used to build detailed ab inito microkinetic models of SMR over the multi-faceted nickel catalyst. The resulting microkinetic models are used to provide insight into the processes occurring on the catalyst surface through identifying the most important intermediate species and reactions occurring on the catalyst. The effects of alloying the nickel catalyst with silver are predicted through modeling the dissociative methane adsorption reaction on multiple facets of the Ni/Ag surface with varying concentrations of silver. In addition, DFT calculations are used to investigate carbon formation on the Ni and Ni/Ag catalyst surfaces, including relative stabilities of various carbon-containing intermediates and the effects of alloying the nickel surface with silver on carbon formation.
by Donnie Wayne Blaylock.
Ph.D.

El tema central de la Tesis es el estudio de procesos selectivos en catálisis heterogénea. Los catalizadores considerados son superficies monometálicas y bimetálicas compuestas por metales de transición, básicamente Pd y Au. Se utilizan teorías y herramientas fundamentales dentro del campo de la simulación: Teoría del Funcional de la Densidad, DFT, Termodinámica Estadística, reactividad superficial, etc.
Las principales líneas de investigación son: caracterización de superficies, oxidación de CO, síntesis directa del peróxido de hidrógeno, justificación de la fuerte dependencia con la estructura superficial de la síntesis del acetato de vinilo, análisis de la hidrogenación selectiva de alquinos sobre Pd y estudio de las diferencias entre catálisis homogénea y heterogénea en el acoplamiento de alquinos y alquenos con catalizadores de Au. Los cálculos se han realizado mediante los códigos VASP (modelos periódicos) y Gaussian (modelos finitos).
Los resultados teóricos se han validado, siempre que ha sido posible, con datos experimentales.
The topic of the Thesis is theoretical studies of selective processes in heterogeneous catalysis. The most relevant theories and tools in the computational field are used: Density Functional Theory, DFT, Statistical Thermodynamics, surface reactivity, etc.
The catalysts employed are monometallic and bimetallic surfaces of transition metals. The main points dealt are: surface characterization, CO oxidation, direct hydrogen peroxide synthesis, study of the dependence on the local structure of the ensemble for the VA synthesis, study of the effect of the catalyst state on the reaction network and analysis of the link between homogenous and heterogeneous gold catalysis in the selective activation of alkynes. The theoretical calculations were performed using the VASP (periodic models) and Gaussian (finite models) codes. The results were compared with experimental evidences when it was possible.

En la present tesi s’han emprat tècniques computacionals per investigar la utilització de materials basats en òxids de metalls de transició amb estructura de rutil com a catalitzadors per a compostos halogenats. Els estudis exploren la interacció entre l’estructura i composició de la superfície, l’activitat catalítica i la selectivitat de formació de productes. El treball se centra en diòxids de ruteni i titani com catalitzadors per les reaccions d’oxidació d’halurs d’hidrogen i oxicloració d’etilè. Els càlculs amb la teoria del funcional de la densitat demostren com pot tindre lloc la substitució d’oxígens superficials, sota condicions de reacció per la oxidació d’halurs d’hidrogen. Particularment, una important absorció de brom va ser determinada en òxid de ruteni, amb la substitució de brom extenent-se des de la superfície fins les capes sub-superficials, i introduint una gran reorganització estructural de la superfície. Per tant, es proposa que el mecanisme de reacció estigui estretament vinculat al grau de substitució a la superfície. Les investigacions també examinen sistemes basats en diòxids de titani dopats. Ha estat explorada la relació entre els defectes a l’estructura electrònica induïts pel dopant, i l’activitat catalítica cap a processos elementals associats a l’oxidació d’halurs d’hidrogen. Particularment, ha estat determinat que es pot realitzar una elecció racional del dopant per optimitzar el nombre de defectes, i les seves energies associades, amb la finalitat de modificar de forma acurada l’estructura electrònica de la superfície, i així, obtenir una activitat òptima. Finalment, el diòxid de ruteni es investigat com un potencial catalitzador per a la oxicloració d’etilè. Es va determinar que la competició entre els processos de combustió i oxicloració es millorada pel confinament dimensional dels adsorbats sobre la superfície del catalitzador, i que el recobriment superficial és un factor essencial per determinar la viabilitat de certs processos elementals, i així, la selectivitat dels productes. La tesi proporciona una clara visió general dels rutils com catalitzadors per la química dels halògens. A més, també proporciona coneixements detallats que poden ser utilitzats per al desenvolupament de millors catalitzadors al futur.
En la presente tesis se han empleado técnicas computacionales para investigar el uso de materiales basados en óxidos de metales de transición con estructura de rutilo como catalizadores para la química de halógenos. Los estudios exploran la interacción entre la estructura y composición de la superficie, la actividad catalítica y la selectividad de los productos. El trabajo se enfoca en sistemas basados en dióxidos de rutenio y titanio como catalizadores para las reacciones de oxidación de haluros de hidrógeno y oxicloración de etileno. Los cálculos con métodos de la teoría del funcional de la densidad muestran como, bajo condiciones de reacción para la oxidación de haluros de hidrógeno, la sustitución de oxígenos superficiales puede tener lugar. Particularmente, una importante absorción de bromo fue encontrada en dióxido de rutenio, con la sustitución de bromo extendiéndose desde la superficie hacia las capas subsuperficiales, e induciendo una gran reorganización estructural de la superficie. Por lo tanto, se propone que el mecanismo de reacción está estrechamente vinculado al grado de sustitución en la superficie. Las investigaciones también examinan sistemas basados en dióxidos de titanio dopados. La relación entre los defectos en la estructura electrónica inducidos por el dopante, y la actividad catalítica hacia procesos elementales asociados con la oxidación de haluros de hidrógeno, es explorada. Particularmente, se encontró que una elección racional del dopante puede ser realizada para optimizar el número de defectos, y sus energías asociadas, con la finalidad de modificar de forma precisa la estructura electrónica de la superficie y, así, obtener una actividad óptima. Finalmente, se investigó el dióxido de rutenio como un potencial catalizador para la oxicloración de etileno. Se encontró que la competición entre los procesos combustión y oxicloración es mejorada por el confinamiento dimensional de adsorbatos sobre la superficie del catalizador, y que la recubrimiento superficial es un factor esencial para determinar la viabilidad de ciertos procesos elementales y, así, la selectividad de los productos. La tesis proporciona una clara visión general de los rutilos como catalizadores para la química de los halógenos. Además, también proporciona conocimientos detallados que pueden ser usados para el desar
Computational techniques are applied to investigate the utility of rutile transition metal oxide based systems as catalysts for halogen chemistry. The studies explore the interplay between surface structure and composition, catalytic activity and product selectivity. The work focuses on ruthenium dioxide and titanium dioxide based systems as catalysts for hydrogen halide oxidation and ethylene oxychlorination reactions. DFT calculations show that under hydrogen halide oxidation conditions, replacement of surface oxygen atoms in the rutile catalyst can occur. In particular, significant bromine uptake was found to occur in ruthenium dioxide, with bromine replacement extending beyond the surface to the subsurface layers and inducing a major structural rearrangement at the surface. It is thus proposed that the reaction mechanism is closely linked to the extent of surface replacement. The investigations also examine doped titanium dioxide based systems. The relationship between dopant-induced electronic structure defect states, and the catalyst activity towards elementary processes associated with hydrogen halide oxidation, is explored. In particular, it was found that a judicious choice of dopant atom can be made to optimise the number of defect states, and their associated energies, in order to fine-tune the electronic structure of the system for optimal activity. Finally, ruthenium dioxide is investigated as a potential catalyst for ethylene oxychlorination. It was found that competition between combustion and oxychlorination processes is enhanced by dimensional confinement of adsorbates on the catalyst surface, and that surface coverage is an essential factor in determining the feasibility of certain elementary processes, and thus product selectivity. The thesis provides a clear overview of rutile catalysts for halogen chemistry and provides detailed insights which can inform the future development of superior catalysts.

The development of new methods to prepare Pd-containing nanomaterials for catalysis are reported. Monodisperse, catalytically active Pd0 nanoparticles were prepared using a one-pot procedure, and new insights into the mechanism of the formation of these catalytically active Pd0 nanoparticles were obtained. A number of key intermediates and byproducts were determined using NMR and IR spectroscopies. Furthermore, addition of Lewis bases such as TOPO and DMSO to the reaction mixture greatly reduced the temperature at which highly monodisperse nanoparticles were formed. This effect was shown to be applicable to other Pd precursors in preparing Pd0 nanoparticles. Spherical Pd0@m-SiO2 core-shell nanoparticles were prepared and characterized by a number of techniques, including TEM, PXRD, TGA, and XPS. These nanoparticles consist of a Pd0 core enclosed by a mesoporous silica shell and are prepared using a simple, scalable one-pot procedure. The reaction conditions were crucial in controlling the morphology and pore diameter of the nanoparticles synthesized. Acid treatment of the Pd0@m-SiO2 nanoparticles was found to be the most suitable method in removing CTAB. The morphology, surface area, and pore diameter of the core-shell nanoparticles remained intact after removal of CTAB. A new ceria-containing core-shell material, PdO@m-CeO2, was prepared via templating from Pd0@m-SiO2 and PdO@m-SiO2 nanoparticles. The absence of Pd0 and presence of Pd2+ was explained by the possible formation of a solid solution composed of Ce1-xPdxO2-δ when Pd0 was the core. The catalytic activity of the nanoparticles was examined by performing the catalytic oxidation of methane. As well, the silica channels of the Pd0@m-SiO2 nanoparticles were used as selector to separate molecules based on their size. Size-selective hydrogenation was investigated using the porous silica shell of the Pd0@m-SiO2 nanoparticles as a selector, where the porous shell controlled the selectivity by the size of the substrates. Hydrogenation of a small molecule, 1-hexene, in CDCl3 using acid-treated Pd0@m-SiO2 nanoparticles occurred quickly, while the hydrogenation of a larger substrate, O-allyl cholesterol proceeded more slowly. However, similar results were observed using commercially available Pd/C as the catalyst. Narrowing the pore diameter of Pd0@m-SiO2 nanoparticles showed drastic difference in reaction rates between 1-hexene and O-allyl cholesterol.
Science, Faculty of
Chemistry, Department of
Graduate

This thesis summarizes studies which focus on addressing, using both theoretical and experimental methods, fundamental questions about surface phenomena, such as chemical reactions and bonding, related to processes in heterogeneous catalysis. The main focus is on the theoretical approach and this aspect of the results. The included articles are collected into three categories of which the first contains detailed studies of model systems in heterogeneous catalysis. For example, the trimerization of acetylene adsorbed on Cu(110) is measured using vibrational spectroscopy and modeled within the framework of Density Functional Theory (DFT) and quantitative agreement of the reaction barriers is obtained. In the second category, aspects of fuel cell catalysis are discussed. O2 dissociation is rate-limiting for the reduction of oxygen (ORR) under certain conditions and we find that adsorbate-adsorbate interactions are decisive when modeling this reaction step. Oxidation of Pt(111) (Pt is the electrocatalyst), which may alter the overall activity of the catalyst, is found to start via a PtO-like surface oxide while formation of α-PtO2 trilayers precedes bulk oxidation. When considering alternative catalyst materials for the ORR, their stability needs to be investigated in detail under realistic conditions. The Pt/Cu(111) skin alloy offers a promising candidate but segregation of Cu atoms to the surface is induced by O adsorption. This is confirmed by modeling oxygen x-ray emission (XES) and absorption spectra of the segregated system and near-perfect agreement with experiment is obtained when vibrational interference effects are included in the computed XES. The last category shows results from femtosecond laser measurements of processes involving CO on Ru(0001). Using free-electron x-ray laser experiments a precursor state to desorption is detected and also found in simulations if van der Waals effects are included. Resonant XES can be used to distinguish two different species of CO on the surface; vibrationally hot, chemisorbed CO and CO in the precursor state. Laser-induced CO oxidation on Ru(0001) is modeled and three competing mechanisms are found. Kinetic modeling reproduces the experiment qualitatively.

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 8: Manuscript.

The development of sustainable methods with applications in synthetic organic chemistry has been investigated widely in recent years. Catalytic processes often provide sustainable strategies with high efficiency, high selectivity and low environmental impact in terms of energy consumption and waste production. In this project, heterogeneous catalysis and biocatalysis have been investigated separately and combined into a two-step process. Gold nanoparticle catalysts supported on inert bulk materials have been applied in the oxidation of alcohol feedstocks as an alternative to stoichiometric oxidation techniques. Synthesis of a range of gold nanoparticle catalysts has been undertaken with variation in support materials and preparation methods. These catalysts have been tested in the oxidation of the benchmark substrate benzyl alcohol, and the substrate scope also extended to include secondary alcohols. The low gold loading and reusability of these heterogeneous catalysts coupled with the use of water as the solvent has provided a sustainable oxidation method for primary and secondary alcohols. Transaminases are enzymes which catalyse the transfer of an amino group to the carbonyl group of an aldehyde or ketone. Screening of transaminases from the UCL transaminase library was undertaken to identify enzymes for application in this project. These enzymes have been applied in the synthesis of furfurylamines from furfurals, in a one-step biocatalytic reaction under mild conditions on a preparative scale. The transaminases were also applied in the synthesis of chiral amines from ketone precursors, with high yields and stereoselectivities achieved. Heterogeneous catalysis and biocatalysis have been coupled together into a novel two-step cascade to produce chiral amines from secondary alcohol feedstocks. The oxidation of secondary alcohols using gold nanoparticle catalysts was followed by the transamination of the ketone intermediates. This process was conducted in one pot, with water as the solvent and no isolation or purification of the ketone intermediate.

Biodiesel has emerged as a promising renewable and clean energy alternative to petrodiesel. While biodiesel has traditionally been prepared through homogeneous basic catalysis, heterogeneous acid catalysis has been investigated recently due to its ability to convert cheaper but high free fatty acid content oils such as waste vegetable oil while decreasing production cost. In this work, the esterification of free fatty acid over sulfated zirconia and activated acidic alumina in a batch reactor was considered. The models of the reaction over the catalysts were developed in two parts. First, a kinetic study was performed using a deterministic model to develop a suitable kinetic expression; the related parameters were subsequently estimated by numerical techniques. Second, a stochastic model was developed to further confirm the nature of the reaction at the molecular level. The esterification of palmitic acid obeyed the Eley-Rideal mechanism in which palmitic acid and methanol are adsorbed on the surface for SO?/ZrO?-550°C and AcAl?O? respectively. The coefficients of determination of the deterministic model were 0.98, 0.99 and 0.99 for SO?/ZrO?-550°C at 40, 60 and 80°C respectively and 0.99, 0.98 and 0.96 for AcAl?O? at the same temperature. The deterministic and stochastic models were in good agreement.
Master of Science

In this thesis, by means of different case studies, we explore the design from the micro to the atomic scale of different nanostructured heterogeneous catalysts that can be applied in the field of energy conversion and chemicals synthesis. We highlight the importance of the rational design of the materials to improve significantly the efficiency and performances of novel heterogeneous catalysts. The chemical nature and the morphology of the catalysts are correlated with their catalytic activities in order to tailor their physicochemical properties for each specific application. To do this, we have employed a large set of tools offered by Materials Science, exploring advanced synthetic methods and operando and in situ characterization techniques.
In questa tesi, attraverso diversi casi di studio, abbiamo studiato il design dalla scala micrometrica a quella atomica di diversi catalizzatori eterogenei nanostrutturati che possono essere applicati nel campo della conversione energetica e della sintesi chimica. In questo lavoro, abbiamo sottolineato l'importanza della progettazione razionale dei materiali per migliorare significativamente l'efficienza e le prestazioni di nuovi catalizzatori eterogenei. La natura chimica e la morfologia dei catalizzatori sono state correlate con le loro attività catalitiche al fine di adattare le loro proprietà fisico-chimiche per ogni specifica applicazione. Per fare questo, abbiamo impiegato un ampio set di strumenti offerti dalla Scienza dei Materiali, esplorando metodi sintetici avanzati e tecniche di caratterizzazione operando e in situ.

Thesis (Master)--İzmir Institute of Technology, İzmir, 2005.
Keywords: Palladium, Immobilization, Heck Reaction, Palladium-N-Heterocyclic Carbene, Carbon-Carbon Coupling. Includes bibliographical references (leaves. 89-104).

Copper is an inexpensive, earth-abundant, non-toxic metal that is found to have widespread applications in catalysis. Ullmann and Ullmann-type reactions and Glaser-Hay oxidative coupling of terminal alkynes are some of the well-established copper catalyzed coupling reactions used for the construction of important organic molecules, including pharmaceuticals, commodity chemicals and polymers. Those reactions have been mainly performed homogeneously, where the removal of residual copper from the reaction mixture is a challenge. Therefore, many researchers tried supporting copper precatalysts in order to help recover, and thus reduce final product contamination. Some studies showed that copper leached significantly from the support, with others showing that leached copper has a role in the catalysis. Nevertheless, many studies reported that the used supported catalysts were recyclable and claimed catalyst's heterogeneity. In most cases, the nature of the truly active copper species is still not clear. The objectives of this thesis were (1) to assess the heterogeneity/homogeneity of active copper species in popular catalytic C-N coupling reactions with already studied catalysts, mainly a copper exchanged zeolite and copper oxide nanoparticles, and (2) to use the collected information in designing a truly heterogeneous (stable and recyclable) catalyst. Initially, and because of its shape selectivity characteristics, copper-exchanged NaY zeolite, Cu(II)Y, was chosen to study the heterogeneity of copper catalyzed amination of aryl iodide with imidazole. The collected results from conducted shape selectivity tests indicated that Cu(II)Y might be heterogeneous catalyst, but because of the used base, that is crucial for this C-N coupling reaction, the crystallinity of the zeolite structure was diminished. Therefore, it was important to support copper on a framework that is stable under the basic conditions required for this type of reaction if a heterogeneous, recyclable catalyst were to be achieved. For this purpose, cerium oxide was chosen, and copper oxide supported on cerium oxide, CuO-CeO₂, was investigated as a potential heterogeneous catalyst for C-N coupling reaction. This investigation included the role of each reaction reagent in facilitating copper leaching into solution. It was found that copper leached from the support and it was demonstrated through hot filtration tests that the leached copper species was the main active catalyst. Leaching was caused by the solvent (DMSO) as well as the used reactants and the base. Similar conclusions were drawn when this CuO-CeO₂ catalyst was used for the direct synthesis of imines from amines under aerobic conditions. Although this CuO-CeO₂ catalyst has the advantages of being more recoverable and active than unsupported CuO nanoparticles at similar copper loadings, it is not fully recyclable, as the copper catalysis occurs in solution. These findings meant that designing a truly heterogeneous catalyst for this reaction is a challenging task. Understanding the effect of each individual factor of this complicated system might help in achieving the second goal - designing a truly heterogeneous catalyst. Therefore, further studies were carried out to understand the effect of reaction conditions, including temperature, base, support, and solvent, on copper leaching. Homocoupling of terminal alkynes was chosen as a model reaction for this study, and CuO was supported on TiO₂ (10CuO-TiO₂) and on γ-Al₂O₃ (10CuO-Al₂O₃). It was found that copper interaction with the support affects the extent of leaching as well as the nature and activity of leached species. High temperature also facilitates copper leaching especially when a ligating amine, like piperidine, is present in the system.

The abstract is the summary of three different projects all centered around the generalidea of catalysis which is the general theme of research in the Michaelis laboratory. The firstproject focuses on development of a new heterogeneous catalyst for selective catalysis. In theMichaelis lab, we were interested in the potential of nanoparticle catalysts for regioselectivetransformations. We showed that polymer supported ruthenium nanoparticles performed as areliable catalyst for regioselective reduction of azide to amine. In our study of regioselectivereduction of multiple azide containing substrates, we observed that in presence of ourruthenium nanoparticle catalysts, the least sterically hindered azide group reduced to aminefunctional group. The results were complementary to the conventional methods that employtriphenyl phosphine (Staudinger reaction) as the reductant and target the most electronicallyactive azide group.In the second project, we were looking to develop a new class of hetero-bimetallicNickel-Titanium complexes as an efficient catalyst for organic transformations. We designedand synthesized numerous bidentate ligands including NHC-Phosphine ligand. Our kineticstudies on the Suzuki cross coupling of allylic alcohols and phenyl boronic esters showed thatthe bidentate nature of the ligand was necessary for the success of the catalytic process. Theligand was proved to stabilize the catalyst in the solution by increasing the lifetime of thenickel (0) in the reaction medium. We also discovered a new cooperative titanium-nickelsystem for mild allylic amination of allyl alcohols. The system also represents an idealcatalyst for tandem cyclization amination process.In the Michaelis lab, we were also interested to explore the ability of bimetalliccomplexes in C-H functionalization process. Our efforts in this project led to the discovery ofnew Pallladium dimer complexes with two palladium centers in oxidation state of (I). Thecatalyst showed unique reactivity in C-C bond activation/functionalization. We have alsodiscovered that in presence of catalytic amount of triflic acid and stoichiometric amount ofphenyl boronic acid, cinnamyl alcohol undergoes a boron template dimerization/cyclization.The reaction represents a great synthetic pathway for the synthsis of bis homoallylic alcohols.

The development of sustainable, environmentally benign oxidation processes of organic compounds is an important task for chemical industry. This challenge can be addressed by designing catalysts that enable the utilisation of molecular oxygen as an oxidant. The work in this thesis is focused on the development of heterogeneous catalysts for the selective aerobic oxidation of various organic compounds. The first part of the thesis (Chapters 3 and 4) covers the study of bifunctional gold catalysts for the solvent-free aerobic oxidation of cyclohexene, with a particular focus on tuning the selectivity of the catalyst. Various characterisation techniques (such as TEM, diffuse-reflectance UV-Vis spectroscopy, XPS), catalytic experiments and kinetic studies were used to investigate the nature of catalyst functionality and establish the optimal structure of a gold catalyst. The second part of the thesis (Chapter 5) covers the study of the photocatalytic activity of hydrous ruthenium oxide deposited on TiO₂ in the aerobic oxidation of amines to nitriles under irradiation with visible light. The effect of the wavelength of the utilised light, applicability of the Sun as light source and water as a solvent were investigated. High catalytic activity of ruthenium-based catalyst was demonstrated for various benzylic and aliphatic amines. Various mechanistic studies were performed, based on which the mechanism of photocatalysis was suggested.

The chemical industry of today is under increased pressure to develop novel green materials, bio-fuels as well as sustainable chemicals for the chemical industry. Indeed, the endeavour is to move towards more eco-friendly cost efficient production processes and technologies and chemical transformation of renewables has a central role considering the future sustainable supply of chemicals and energy needed for societies. In the Nordic countries, the importance of pulping and paper industry has been particularly pronounced and the declining European demand on these products as a result of our digitalizing world has forced the industry to look at alternative sources of revenue and profitability. In this thesis, the production of levulinic and formic acid from biomass and macromolecules has been studied. Further, the optimum reaction conditions as well as the influence of the catalyst and biomass type were also discussed. Nordic sulphite and sulphate (Kraft) cellulose originating from two Nordic pulp mills were used as raw materials in the catalytic synthesis of green platform chemicals, levulinic and formic acids, respectively. The catalyst of choice used in this study was a macro-porous, cationic ion-exchange resin, Amberlyst 70, for which the optimal reaction conditions leading to best yields were determined. Cellulose from Nordic pulp mills were used as raw materials in the catalytic one-pot synthesis of ‘green’ levulinic and formic acid. The kinetic experiments were performed in a temperature range of 150–200 °C and an initial substrate concentration regime ranging from 0.7 to 6.0 wt %. It was concluded that the most important parameters in the one-pot hydrolysis of biomass were the reaction temperature, initial reactant concentration, acid type as well as the raw material applied. The reaction route includes dehydration of glucose to hydroxymethylfurfural as well as its further rehydration to formic and levulinic acids. The theoretical maximum yield can hardly be obtained due to formation of humins. For this system, maximum yields of 59 mol % and 68 mol % were obtained for formic and levulinic acid, respectively. The maximum yields were separately obtained in a straight-forward conversion system only containing cellulose, water and the heterogeneous catalyst. These yields were achieved at a reaction temperature of 180 °C and an initial cellulose intake of 0.7 wt % and belong to the upper range for solid catalysts so far presented in the literature. The reaction network of the various chemical species involved was investigated and a simple mechanistic approach involving first order reaction kinetics was developed. The concept introduces a one-pot procedure providing a feasible route to green platform chemicals obtained via conversion of coniferous soft wood pulp to levulinic and formic acids, respectively. The model was able to describe the behaviour of the system in a satisfactory manner (degree of explanation 97.8 %). Since the solid catalyst proved to exhibit good mechanical strength under the experimental conditions applied here and a one-pot procedure providing a route to green platform chemicals was developed. A simplified reaction network of the various chemical species involved was investigated and a mechanistic approach involving first order reaction kinetics was developed.

The preparation, testing and characterisation of catalysts for the total oxidation of two volatile organic compounds (VOCs) have been studied. These two VOCs were naphthalene and propane. Naphthalene was the main focus of this study. CeZrC>2 with varied Ce:Zr ratios and preparation methods was investigated for the total oxidation of naphthalene. These preparation methods were all precipitation methods using different precipitating agents (urea, sodium carbonate and supercritical CO₂). Zr contents as low as 1 molar percent enhanced activity for both urea and sodium carbonate precipitated catalysts compared to CeC>2. A supercritical analogue was found to be less active. Pt/SiC>2 as a catalyst for naphthalene total oxidation was studied with a view to optimise an existing impregnation technique. A Pt loading of 2.5wt% with a calcination regime of 550 °C for 12h in static air with a ramp rate of 5 °C/min was found to be optimal. These preparation conditions were found to increase the proportion of metallic Pt which was found to exist as large crystallites with low dispersion. Other catalyst features were probed in this study. The type of silica used as a support was changed to novel hollow sphere silica then nanopore silica but no improvement in activity was found. Pt was then substituted for Pd which again did not improve activity. It was found that the Pd existed as Pd oxide hence Pd oxide is not as active for naphthalene oxidation as metallic Pt. The preparation of impregnated catalysts using non-aqueous solvents on so-called 'hydrophobic' materials was also investigated. These were tested for both naphthalene and propane total oxidation. It was found that Pt and Pd based catalysts afforded the most active catalysts. Several supports were studied which interacted with the impregnated metals in different ways. This affected the nature of the impregnated metals and therefore the activities of these catalysts. Some of the more active catalysts used supports that were of a low surface area. A high surface area SnO₂ support was produced and impregnated with Pd. The high surface area SnO₂ was found to be more active than the original Pd/SnO₂ catalyst for propane total oxidation.

Ceria is well known for its unique properties in fast oxygen mobility and formation of oxygen vacancies which makes ceria an excellent catalyst support for metal nanoparticles. Promotional effect of ceria has been well established in a number of reactions including three-way catalyst and CO oxidation. These unique properties of ceria are dependent on the surface facets it exposes, where they can be enhanced by the exposure of high energy surfaces such as (100) and (110). The work presented in this thesis involves controlling the surface exposed by the ceria support by making them into cube and rod morphology, which predominantly expose the (100) and (110) surface, respectively. Hence, the effect of these surfaces on the ceria support can be investigated. The ceria morphologies were deposited with Pd nanoparticles and their catalytic properties were tested on methane combustion and gas-phase formic acid decomposition reactions. In both of the catalyst test reactions, the Pd deposited on the ceria cubes support had shown superior catalytic properties compared to the Pd deposited on the ceria rods support, indicated by the former's higher activity, TOF and resistance to poisoning. Based on the characterisation techniques performed in this study such as TPR, ambient pressure XPS, STEM-EELS and pulse isotopic oxygen exchange, the enhanced catalytic properties of Pd/ceria cubes were attributed to the high energy ceria (100) surface which led to more favourable formation of oxygen vacancies and faster oxygen mobility.

Metalloenzymes catalyse the most fundamental reactions in organic chemistry from oxidation of hydrocarbons to complex C-C bond forming reactions with exceptional selectivity. Mimicking the active site of a metalloenzyme by immobilising well-defined amino acids containing catalytically active transition metal centres based on transitionmetals on a robust inorganic framework, affords powerful catalysts that can be utilised in oxidation reactions. Porous aluminosilicates, mesoporous silicas and polymers offer suitable supports for single-site bio-derived catalysts. Dispersion of catalytically active centers within porous solids with high surface area improves site-isolation which is essential in catalytic processes. These materials can be created from a range of methodologies and the different strategies used for immobilisation can greatly affect the nature of the active catalyst. The routes by which these catalysts are immobilised have given the potential to derivatize inorganic porous hosts and organic polymer structures with amino acids for complexation to metal centres. These bio-derivatized frameworks offer advantages over the homogeneous counterparts in terms of easy separation, recover and recyclability and can carry out selective oxidation reactions with great effectiveness. Herein, heterogenous bioinspired complexes of two amino acids; proline and valine with a series of transition metals (Fe, Cu) were synthesised and immobilised within zeolite cages, mesoporous silica MCM-41 and polystyrene. The preparation methods allowed the synthesis of materials with varying loadings of immobilized active sites. The structural information obtained by spectral and elemental analysis suggested tetrahedral geometry for iron complexes and distorted square planar geometry for copper complexes. Both amino acids coordinated to metal ions through the nitrogen atom of amino group and oxygen atom of carboxylate group via dissociation of the acidic proton as bidentate N,O-donors. The resulting biomimetic complexes were employed as catalysts for oxidation of cyclohexane, cyclohexene, benzyl alcohol and dimethyl sulfide, using molecular dioxygen (O2), tert-butyl hydroperoxide (TBHP) and acetylperoxyborate (APB) as oxidants. The observed trends in catalytic activity showed that the metal loading and separation of the active sites played key role in the selective oxidation reactions. By decreasing the loading of metal active centres, their spatial separation increased which strongly enhanced the activity of catalysts. The decrease in metal active site content resulted in significant increase in TON and TOF. The product selectivity was dependent on the nature of oxidant, hydrophobicity/hydrophilicity of the support, loading of metal active centres and the metal/substrate ratio.