Zeitschriftenartikel zum Thema „Homogenous catalysts“
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1
Testa, Maria Luisa, und Valeria La Parola. „Sulfonic Acid-Functionalized Inorganic Materials as Efficient Catalysts in Various Applications: A Minireview“. Catalysts 11, Nr. 10 (23.09.2021): 1143. http://dx.doi.org/10.3390/catal11101143.
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Acid catalysis is widely used in the chemical industry, and nowadays many efforts are being focused on replacing the more common homogeneous catalysts with heterogeneous ones in order to make greener the industrial processes. In this perspective, sulfonic solid acid materials represent a valid alternative to the homogenous mineral acid in several acid catalyzed reactions. In this minireview, an overview of the recent advances on the preparation, stability and application of these materials is reported. Special attention is addressed to the sustainability of the considered processes, starting from the catalyst’s preparation, the use of green solvents and reducing the possible reaction steps. Ways to tackle the main drawback represented by easy leaching of acid groups are described. For an easy catalyst recovery, the use of a magnetic core in a catalyst particle, with the related synthetic approaches, is also illustrated. Finally, a section is dedicated to the principal characterization techniques to identify the structural properties of the catalysts.
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Guerrero Fajardo, Carlos Alberto, Yvonne N’Guyen, Claire Courson und Anne Cécile Roger. „Fe/SiO2 catalysts for the selective oxidation of methane to formaldehyde“. Ingeniería e Investigación 26, Nr. 2 (01.05.2006): 37–44. http://dx.doi.org/10.15446/ing.investig.v26n2.14735.
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Selective oxidation of methane to formaldehyde was analysed with iron catalysts supported on silica prepared by the sol-gel method, leading to obtaining a large support surface area facilitating high dispersion of iron on silica’s amorphous surface. Seven catalysts were prepared; one of them corresponded to the silica support and another five having an iron load 0.1-0.5% in weight. Catalyst 7 (0.5% Fe in weight) was prepared with neutral pH control and had the most homogeneous characteristics since it did not present isolated iron species, corroborated by SEM and TEM analysis. The highest BET areas were 1,757 and 993 m2.g-1 for 0.5% Fe catalysts, having an average 36% microporosity and 43% mesoporosity. X-ray diffraction confirmed the catalyst’s amorphous structure. Catalytic activity was carried out with catalyser 7 at atmospheric pressure in a quartz reactor using a CH4/O2/N2=7.5/1/4 reaction mixture at 400-750°C temperature range. Reaction products were analysed by gas chromatography with TCD. The heterogeneous catalysts displayed greater methane conversion (but with methanol selectivity) whereas homogenous catalyst 7 gave better results regarding formaldehyde. The highest conversion percentage (8.60% mol) for catalyser 7 was presented at 650°C. Formaldehyde selectivity was 50% mol in the 600-650°C range and maximum yield (0.31g HCHO/Kg catalyst) was found in this range; it was thus considered that 650°C for the reaction was thereby the best operating temperature.
3
García-Álvarez, Joaquín. „Special Issue: “Advances in Homogeneous Catalysis”“. Molecules 25, Nr. 7 (25.03.2020): 1493. http://dx.doi.org/10.3390/molecules25071493.
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The use of enzymes, organo-catalysts or transition metal catalysts, as opposed to the employment of stoichiometric quantities of other traditional promoters of different organic synthetic processes (like, inorganic/organic bases, Brønsted acids, radicals, etc.) has allowed the discovery of a great number of new synthetic protocols within the toolbox of organic chemists. Moreover, the employment of the aforementioned catalysts in organic synthesis permits: (i) the diminution of the global energy demand and production cost; (ii) the enhancement of both the chemoselectivity and stereoselectivity of the global process; and (iii) the reduction of metal-, organo- or bio-catalyst consumption, thanks to the possible recycling of the catalysts; all these being synthetic concepts closely related with the principles of so-called Green Chemistry. Thus, this Special Issue on “Advances in Homogenous Catalysis” has been aimed to showcase a series of stimulating contributions from international experts within different sub-areas of catalysis in organic synthesis (ranging from metal-, organo-, or bio-catalyzed organic reactions).
4
Zhao, Da, Roland Petzold, Jiyao Yan, Dieter Muri und Tobias Ritter. „Tritiation of aryl thianthrenium salts with a molecular palladium catalyst“. Nature 600, Nr. 7889 (15.12.2021): 444–49. http://dx.doi.org/10.1038/s41586-021-04007-y.
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AbstractTritium labelling is a critical tool for investigating the pharmacokinetic and pharmacodynamic properties of drugs, autoradiography, receptor binding and receptor occupancy studies1. Tritium gas is the preferred source of tritium for the preparation of labelled molecules because it is available in high isotopic purity2. The introduction of tritium labels from tritium gas is commonly achieved by heterogeneous transition-metal-catalysed tritiation of aryl (pseudo)halides. However, heterogeneous catalysts such as palladium supported on carbon operate through a reaction mechanism that also results in the reduction of other functional groups that are prominently featured in pharmaceuticals3. Homogeneous palladium catalysts can react chemoselectively with aryl (pseudo)halides but have not been used for hydrogenolysis reactions because, after required oxidative addition, they cannot split dihydrogen4. Here we report a homogenous hydrogenolysis reaction with a well defined, molecular palladium catalyst. We show how the thianthrene leaving group—which can be introduced selectively into pharmaceuticals by late-stage C–H functionalization5—differs in its coordinating ability to relevant palladium(II) catalysts from conventional leaving groups to enable the previously unrealized catalysis with dihydrogen. This distinct reactivity combined with the chemoselectivity of a well defined molecular palladium catalyst enables the tritiation of small-molecule pharmaceuticals that contain functionality that may otherwise not be tolerated by heterogeneous catalysts. The tritiation reaction does not require an inert atmosphere or dry conditions and is therefore practical and robust to execute, and could have an immediate impact in the discovery and development of pharmaceuticals.
5
Russell, M. J. H. „Water Soluble Rhodium Catalysts“. Platinum Metals Review 32, Nr. 4 (01.10.1988): 179–86. http://dx.doi.org/10.1595/003214088x324179186.
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The rhodium catalysed hydroformylation reaction is one of the most widely used industrial applications of homogenous catalysis to employ platinum group metals. Potential limitations in the application of this technology to molecules which are heat sensitive or have high boiling points are the stability of the catalyst and the ability to separate the catalyst from the products. A means of circumventing these limitations is described. This involves locating the catalyst in an aqueous liquid phase, and it enables viable reaction rates to be achieved at moderate temperatures and pressures.
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Lowe, Brandon, Jabbar Gardy und Ali Hassanpour. „The Role of Sulfated Materials for Biodiesel Production from Cheap Raw Materials“. Catalysts 12, Nr. 2 (16.02.2022): 223. http://dx.doi.org/10.3390/catal12020223.
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There is an urgent need to reduce global greenhouse gas emissions, yet to date the decarbonization of the transportation industry has been slow and of particular difficulty. While fossil fuel replacements such as biodiesel may aid the transition to a less polluting society, production at the industrial scales required is currently heavily dependent on chemical catalysis. Conventional two-step homogenous routes require the challenging separation of catalyst from the obtained product; however, heterogenous solid catalysts bring new considerations such as material stability, surface area, porosity, deactivation effects, and reduced reactivities under mild conditions. Nanomaterials present an attractive solution, offering the high reactivity of homogenous catalysts without complex recyclability issues. Slightly less reactive, acidic sulfated nanomaterials may also demonstrate greater stability to feedstock impurity, extending lifetime and improved versatility to a range of starting feeds. There remains, however, much work to be done in demonstrating the full-scale feasibility of such catalysts. This review explores recent developments over time in acidic sulfated nanocatalysis for biodiesel production, with particular focus on metal oxides, magnetic nanoparticles, silica-supported nanomaterials, and acidic carbon nanocatalysts. Included are various summaries of current progress in the literature, as well as recommendations for future research.
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Latos, Piotr, Anna Wolny und Anna Chrobok. „Supported Ionic Liquid Phase Catalysts Dedicated for Continuous Flow Synthesis“. Materials 16, Nr. 5 (05.03.2023): 2106. http://dx.doi.org/10.3390/ma16052106.
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Heterogeneous catalysis, although known for over a century, is constantly improved and plays a key role in solving the present problems in chemical technology. Thanks to the development of modern materials engineering, solid supports for catalytic phases having a highly developed surface are available. Recently, continuous-flow synthesis started to be a key technology in the synthesis of high added value chemicals. These processes are more efficient, sustainable, safer and cheaper to operate. The most promising is the use of heterogeneous catalyst with column-type fixed-bed reactors. The advantages of the use of heterogeneous catalyst in continuous flow reactors are the physical separation of product and catalyst, as well as the reduction in inactivation and loss of the catalyst. However, the state-of-the-art use of heterogeneous catalysts in flow systems compared to homogenous ones remains still open. The lifetime of heterogeneous catalysts remains a significant hurdle to realise sustainable flow synthesis. The goal of this review article was to present a state of knowledge concerning the application of Supported Ionic Liquid Phase (SILP) catalysts dedicated for continuous flow synthesis.
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Nishchakova, Alina D., Lyubov G. Bulusheva und Dmitri A. Bulushev. „Supported Ni Single-Atom Catalysts: Synthesis, Structure, and Applications in Thermocatalytic Reactions“. Catalysts 13, Nr. 5 (06.05.2023): 845. http://dx.doi.org/10.3390/catal13050845.
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Nickel is a well-known catalyst in hydrogenation and dehydrogenation reactions. It is currently used in industrial processes as a homogenous and heterogeneous catalyst. However, to reduce the cost and increase the efficiency of catalytic processes, the development of single-atom catalysts (SACs) seems promising. Some SACs have already shown increased activity and stability as compared to nanoparticle catalysts. From year to year, the number of reports devoted to nickel SACs is growing rapidly. Among them, there are very few articles devoted to thermal catalysis, but at the same time, this subject is important. Thus, this review discusses recent advances in the synthesis, structure, and application of nickel SACs, mainly in catalytic hydrogenation/dehydrogenation reactions and in the dry reforming of methane. The collected and analyzed data can be useful in the development of novel nickel SACs for various processes.
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Ali, Syed Danish, Isma Noreen Javed, Usman Ali Rana, Muhammad Faizan Nazar, Waqas Ahmed, Asifa Junaid, Mahmood Pasha, Rumana Nazir und Rizwana Nazir. „Novel SrO-CaO Mixed Metal Oxides Catalyst for Ultrasonic-Assisted Transesterification of Jatropha Oil into Biodiesel“. Australian Journal of Chemistry 70, Nr. 3 (2017): 258. http://dx.doi.org/10.1071/ch16236.
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The transesterification of edible and non-edible oils to produce biodiesel is traditionally carried out using homogeneous catalysts (such as NaOH, KOH, and H2SO4). However, these homogenous catalysts often suffer from multiple drawbacks including their corrosive nature and solubility in the reaction mixture, and high costs associated with their recovery. Recent studies have shown that heterogeneous catalysts based on mixed metal oxides have the potential to address the issues associated with conventional homogeneous catalysts, thereby emerging as an efficient class of catalyst materials for biodiesel production. In this study, we describe a heterogeneous strontium oxide/calcium oxide (SrO-CaO) mixed metal oxides catalyst, which displays remarkable efficiency towards the ultrasonic-assisted transesterification of Jatropha oil into biodiesel. The SrO-CaO heterogeneous catalyst was prepared by the wet impregnation method, and the structural morphology of the as-synthesized catalyst was revealed by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and nitrogen sorption technique coupled with the Brunauer–Emmett–Teller and Barrett–Joyner–Halenda methods. The X-ray diffraction analysis confirmed the cubic structure of the SrO-CaO catalyst. The catalytic activity of this newly developed catalyst showed a high percentage conversion of triglyceride into the corresponding fatty acid methyl esters (98.19 %) as confirmed by 1H NMR spectroscopy. The chemical composition of the prepared biodiesel by this ultrasonic-assisted transesterification process was determined by the gas chromatography–mass spectrometry. Five major fatty acid methyl esters were identified, of which 9-octadecenoic acid methyl ester was obtained with the highest percentage ~38.22 %. Hence, the study reveals that the SrO-CaO catalyst exhibits high efficiency towards converting Jatropha oil into biodiesel by ultrasonic-assisted transesterification.
10
Balcer, Sylwia. „Homogeneous catalytic systems for selective oxidation of methane: state of the art“. Polish Journal of Chemical Technology 17, Nr. 3 (01.09.2015): 52–61. http://dx.doi.org/10.1515/pjct-2015-0050.
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AbstractHomogeneous catalysts for methane oxidation are of a particular interest from scientific and economic points of view. The results show a great potential for activation and functionalization of CH bonds of unreactive methane. There are still gaps in the knowledge of how to rationally design catalysts for this process. In this paper state-of-the-art. in methane oxidation homogenous catalysis is presented.
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Shakorfow, Abdelmalik M., und Abdulaziz H. Mohamed. „Homogenous Acidic and Basic Catalysts in Biodiesel Synthesis: A Review“. Acta Chemica Malaysia 4, Nr. 2 (01.12.2020): 76–85. http://dx.doi.org/10.2478/acmy-2020-0013.
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AbstractSeveral techniques, in which different homogenous catalysts and procedures, that are in use for transesterification of a vegetable oil or an animal fat have been successful in synthesizing biodiesel, although with some certain limitations. For such a purpose, among the catalysts employed are acidic as well as basic catalysts. It has been found that acidic catalysts can be tolerant with a high content of free fatty acids found in those low value feedstock oils/fats to be transesterified, although some sort of pretreatment by means of esterification might be required in order to synthesize biodiesel. Moreover, with employing homogenous acidic catalysts, it seems that biodiesel purification procedures are simplified; thus, reducing synthesis cost. In fact, these features of homogenous acidic catalysts render them advantageous over basic ones. With basic homogenous catalysts this; however, has not been possible due to the development of saponification reaction. To effectively perform, such catalysts require that the content of free fatty acids in the feedstock oil/fat is minimal. This requirement is also applicable to the moisture level in the feedstock. In terms of corrosive effects; nevertheless, acidic catalysts are disadvantageous compared to basic ones.
12
Hidayati, Nur, Titik Pujiati, Elfrida B. Prihandini und Herry Purnama. „Synthesis of Solid Acid Catalyst from Fly Ash for Eugenol Esterification“. Bulletin of Chemical Reaction Engineering & Catalysis 14, Nr. 3 (01.12.2019): 683. http://dx.doi.org/10.9767/bcrec.14.3.4254.683-688.
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A series of fly ash-based heterogeneous acid catalysts were prepared by chemical and thermal treatment. Fly ash was chemically activated using sulfuric acid and followed by thermal activation. Characterization methods of XRD, BET, SEM-EDX, and the performance in esterification of eugenyl acetate production was carried out to reveal the physical and chemical characteristics of prepared catalysts. Activated catalyst showed high silica content (96.5%) and high BET surface area of 70 m2.g-1. The catalyst was proven to be highly active solid acid catalyst for liquid phase esterification of eugenol with acetic acid yielding eugenyl acetate. A yield of 43-48% was obtained with activated fly ash catalysts for 90 minutes reaction. These catalysts may replace beneficially the conventional homogenous liquid acid to the eco-friendly heterogeneous one. Copyright © 2019 BCREC Group. All rights reserved
13
Faßbach, Thiemo A., Robin Kirchmann, Arno Behr und Andreas J. Vorholt. „Recycling of homogeneous catalysts in reactive ionic liquid – solvent-free aminofunctionalizations of alkenes“. Green Chem. 19, Nr. 21 (2017): 5243–49. http://dx.doi.org/10.1039/c7gc02272g.
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Turning down the bed for homogenous catalysts: the use of dimcarb as a reactive ionic liquid, offers the opportunity to carry out different homogeneously transition metal catalyzed aminations without using any solvent, while at the same time efficient catalyst recycling is possible.
14
Cerón Ferrusca, Montserrat, Rubi Romero, Sandra Luz Martínez, Armando Ramírez-Serrano und Reyna Natividad. „Biodiesel Production from Waste Cooking Oil: A Perspective on Catalytic Processes“. Processes 11, Nr. 7 (28.06.2023): 1952. http://dx.doi.org/10.3390/pr11071952.
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Presently, the use of fossil fuels is not ecologically sustainable, which results in the need for new alternative energies such as biodiesel. This work presents a review of the classification of the lipidic feedstocks and the catalysts for biodiesel production. It also presents the pros and cons of the different processes and feedstocks through which biodiesel is obtained. In this context, cooking oil (WCO) has emerged as an alternative with a high potential for making the process sustainable. A detected limitation to achieving this is the high content of free fatty acids (FFA) and existing problems related to homogeneous and heterogeneous catalysts. To overcome this, the use of bifunctional catalysts is being evaluated by the scientific community. Thus, this work also explores the advances in the study of bifunctional catalysts, which are capable of simultaneously carrying out the esterification of free fatty acids (FFA) and the triglycerides present in the WCO. For the sake of an improved understanding of biodiesel production, flow diagrams and the mechanisms implied by each type of process (enzymatic, homogenous, and heterogeneous) are provided. This article also highlights some of the challenges in catalyst development for sustainable biodiesel production from low-grade raw materials.
15
Brook, Michael A., Shigui Zhao, Lihua Liu und Yang Chen. „Surface etching of silicone elastomers by depolymerization“. Canadian Journal of Chemistry 90, Nr. 1 (Januar 2012): 153–60. http://dx.doi.org/10.1139/v11-145.
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Silicone elastomer surfaces that are rough at the nanometer to micron scales could be useful for biomaterials, but there are few efficient routes for their preparation. Silicones undergo depolymerization under equilibrating conditions. We demonstrate that surface roughness can be induced by depolymerizing silicone elastomers using triflic acid, tetrabutylammonium fluoride or KOH as catalysts. The efficiency of depolymerization, however, is decoupled from the roughness that develops. When the catalysts are dissolved in solvents that do not effectively swell silicones, the etching reaction can be mostly directed to the elastomer surface. Acid catalysis leads to slow, nearly homogenous surface erosion with surface roughnesses only increasing from 15 to about 125 nm root mean squared roughness. By contrast, once KOH partitions into the elastomer, the rate of erosion is more efficient than return of the catalyst to the solvent, leading to deep channels and roughnesses of up to ∼850 nm. The use of fluoride requires good solvents for silicone, and leads to surfaces of intermediate roughness. Thus, judicious choice of catalyst and solvent permits independent control over depolymerization and the induction of surface roughness.
16
Liu, Hui, Mengyuan Huang, Wenling Tao, Liangliang Han, Jinqiang Zhang und Qingshan Zhao. „A Palladium Catalyst Supported on Boron-Doped Porous Carbon for Efficient Dehydrogenation of Formic Acid“. Nanomaterials 14, Nr. 6 (20.03.2024): 549. http://dx.doi.org/10.3390/nano14060549.
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Formic acid has emerged as a highly promising hydrogen storage material, and the development of efficient catalysts to facilitate its dehydrogenation remains imperative. In this study, a novel catalyst consisting of palladium nanoparticles supported on boron-doped porous carbon (Pd/BPC) was successfully synthesized to enable efficient hydrogen production through the dehydrogenation of formic acid. The impacts of the boron doping ratio, doping temperature, and palladium reduction temperature on the catalyst’s performance were systemically investigated. The results demonstrated the Pd/BPC catalyst synthesized with a carbon-to-boron ratio of 1:5 by calcination at 900 °C and subsequent reduction at 60 °C exhibited superior formic acid dehydrogenation performance, being 2.9 and 3.8 times greater than that of the Pd/PC catalysts without boron doping and commercial Pd/C, respectively. Additionally, the catalyst showed excellent cycle stability with no significant activity reduction after five consecutive cycles. Experimental and theoretical results reveal that boron doping not only facilitates the homogenous distribution of Pd nanoparticles but also induces a stronger support–metal interaction, thereby reinforcing the catalytic performance. This research is expected to provide valuable insights into the economically viable and efficient production of environmentally friendly hydrogen energy.
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José da Silva, Márcio, und Abiney Lemos Cardoso. „Heterogeneous Tin Catalysts Applied to the Esterification and Transesterification Reactions“. Journal of Catalysts 2013 (20.11.2013): 1–11. http://dx.doi.org/10.1155/2013/510509.
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The interest in the development of efficient and environmentally benign catalysts for esters synthesis has increased exponentially, mainly due to the demand for biodiesel. In general, fatty esters are used as bioadditive, cosmetic ingredients, polymers, and, more recently, biofuel. Nevertheless, most of the production processes use nonrecyclable and homogenous alkaline catalysts, which results in the reactors corrosion, large generation of effluents, and residues on the steps of separation and catalyst neutralization. Heterogeneous acid catalysts can answer these demands and are an environmentally benign alternative extensively explored. Remarkably, solid acid catalysts based on tin have been shown highly attractive for the biodiesel production, mainly via FFA esterification reactions. This review describes important features related to be the synthesis, stability to, and activity of heterogeneous tin catalysts in biodiesel production reactions.
18
Kaminsky, W., A. Bark und M. Arndt. „New polymers by homogenous zirconocene/aluminoxane catalysts“. Makromolekulare Chemie. Macromolecular Symposia 47, Nr. 1 (Juli 1991): 83–93. http://dx.doi.org/10.1002/masy.19910470108.
19
Kim, Jae Hyuk, Se Jung Kim, Chung Hak Lee und Sang Ho Lee. „Control of Organic Micropollutants Using Dual Functional Adsorbent/Catalyst System“. Materials Science Forum 544-545 (Mai 2007): 35–38. http://dx.doi.org/10.4028/www.scientific.net/msf.544-545.35.
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This study focuses on the development of novel catalysts for simultaneous adsorption and oxidation of micropollutants in aqueous phase. Molecular catalysts were physically immobilized on the surface or pore of amberlite IRA-400 or powdered activated carbon (PAC). Comparison of different combinations of catalysts and adsorbents showed that the Fe(III)-TsPc combined with amberlite had the highest removal efficiency for target compounds. Although the catalyst was immobilized by electrical attraction, no dissociation of catalyst from adsorbent occurred during the tests. Amberlite-supported Fe(III)-TsPc shows more than 98% removal efficiency in 40 min. In homogenous system (suspension of Fe(III)-TsPc in aqueous solution), the oxidation reaction occurred only in acidic conditions (pH ~ 4.5) and the catalyst deactivation rate was fast. On the contrary, the reaction was fast in neutral pH and catalytic deactivation was negligible using the amberlite-supported Fe(III)-TsPc.
20
Rizkin, Benjamin A., und Ryan L. Hartman. „Activation of homogenous polyolefin catalysis with a machine-assisted reactor laboratory-in-a-box (μAIR-LAB)“. Reaction Chemistry & Engineering 5, Nr. 8 (2020): 1450–60. http://dx.doi.org/10.1039/d0re00139b.
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Catalysis discovery is typically limited to specialized labs – this work demonstrates an Artificially Intelligent Microreactor Lab in a Box applied to investigate the chemistry of different co-catalysts for zirconocene-catalyzed olefin polymerization.
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Chethan, S. G., M. H. Moinuddin Khan und L. K. Sreepathi. „An Approach for Biodiesel Production from Blends of Azadirachta indica and Simarouba glauca Triglycerides by Graphene-Doped Calcium Oxide Catalyst and Its Comparative Studies“. Nature Environment and Pollution Technology 22, Nr. 3 (01.09.2023): 1607–14. http://dx.doi.org/10.46488/nept.2023.v22i03.047.
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Over the past several decades, people from many nations have adopted and supported using biodiesel energy sources due to their accessibility and advantages in reducing CO2 and H.C. emissions to the environment. Today, biodiesel is recognized as a sustainable alternative energy source. Commercially, biodiesel was produced by converting homogenous oil treated with a catalyst like NaOH or KOH in Alcohol. These homogeneous catalysts are hazardous to the environment and cannot be recycled. As an alternative, this research article focuses on biodiesel production from a 1:1 blend of Simarubha glauca (Laxmitharu in Kannada) and Azadirachta indica (Neem) triglyceride via acid-base catalyzed transesterification reaction. The heterogeneous-based graphene-doped CaO was used as a catalyst obtained through the calcination method by doping it with graphene oxide by the hummers’ method. SEM, FTIR, and XRD were used to characterize the GaO-CaO catalyst. The results predict that the prepared catalyst yielded a high percentage of ASFAME (94.0%) and meets the quality as per ASTM standards 6751D.
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Soares Dias, Ana Paula, Igor Pedra, Érica Salvador, Bruna Rijo, Manuel Francisco Costa Pereira, Fátima Serralha und Isabel Nogueira. „Biodiesel Production over Banana Peel Biochar as a Sustainable Catalyst“. Catalysts 14, Nr. 4 (16.04.2024): 266. http://dx.doi.org/10.3390/catal14040266.
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Biodiesel from waste frying oil was produced via methanolysis using biochar-based catalysts prepared by carbonizing banana peels (350 °C and 400 °C) mixed with 20% (wt.) of alkali carbonates (Na, Li, or K). The catalysts exhibited a bi-functional character: acidic and basic. Raman spectroscopy confirmed the alkali’s role in char graphitization, influencing morphology and oxygen content. Oxygenated surface sites acted as acidic sites for free fatty acid esterification, while alkali sites facilitated triglyceride transesterification. The best catalyst obtained by carbonization at 350 °C, without alkali modifier, led to 97.5% FAME by processing a waste frying oil with 1.2 mg KOH/g oil acidity. Most of the studied catalysts yielded high-quality glycerin, allowing the significance of homogenous catalyzed processes to be discarded.
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Corma, Avelino, und Hermenegildo Garcia. „Silica-Bound Homogenous Catalysts as Recoverable and Reusable Catalysts in Organic Synthesis“. Advanced Synthesis & Catalysis 348, Nr. 12-13 (August 2006): 1391–412. http://dx.doi.org/10.1002/adsc.200606192.
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Nabae, Yuta, und Masa-aki Kakimoto. „Design and Synthesis of Hyperbranched Aromatic Polymers for Catalysis“. Polymers 10, Nr. 12 (05.12.2018): 1344. http://dx.doi.org/10.3390/polym10121344.
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Aromatic polymers such as poly(ether sulfone), poly(ether ketone), and polyimide have been widely used in industry due to their thermal, mechanical, and chemical stabilities. Although their application to catalysis has been limited, the introduction of a hyperbranched architecture to such aromatic polymers is effective in developing catalytic materials that combine the advantages of homogenous and heterogeneous catalysts. This review article overviews the recent progress on the design and synthesis of hyperbranched aromatic polymers. Several acid catalyzed reactions and the aerobic oxidation of alcohols have been demonstrated using hyperbranched aromatic polymers as catalysts. The advantage of hyperbranched polymers against linear polymers is also discussed.
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Ribeiro, Ana P. C., Inês A. S. Matias, Sónia A. C. Carabineiro und Luísa M. D. R. S. Martins. „Commercial Gold Complexes Supported on Functionalised Carbon Materials as Efficient Catalysts for the Direct Oxidation of Ethane to Acetic Acid“. Catalysts 12, Nr. 2 (28.01.2022): 165. http://dx.doi.org/10.3390/catal12020165.
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The single-pot efficient oxidation of ethane to acetic acid catalysed by Au(I) or Au(III) compounds, chlorotriphenylphosphinegold(I) (1), chlorotrimethylphosphinegold(I) (2), 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidenegold(I) chloride (3), dichloro(2-pyridinecarboxylato)gold(III) (4), homogenous and supported on different carbon materials: activated carbon (AC), multi-walled carbon nanotubes (CNT) and carbon xerogel (CX), oxidised with nitric acid followed by treatment with NaOH (-ox-Na), is reported. The reactions were performed in water/acetonitrile. The materials were selective for the production of acetic acid, with no trace of by-products being detected. The best homogenous catalysts were complexes 2 and 3 which showed the highest ethane conversion and an acetic acid yield of ca. 21%, followed by 4 and 1. The heterogenised materials showed much better activity than the homogenous counterparts, with acetic acid yields up to 41.4% for 4@CNT-ox-Na, and remarkable selectivity (with acetic acid being the only product detected). The heterogenised catalysts with the best results were reused up to five cycles, with no significant loss of activity, and maintaining high selectivity for acetic acid. 4@CNT-ox-Na showed not only the best catalytic activity but also the best stability during the recycling runs.
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Abdul Kudus, Muhammad Helmi, Md Akil Hazizan und Mohamad Hasmaliza. „Synthesis of MWCNT-Alumina Hybrid as Composite Reinforcement Using Nickel Catalyst“. Key Engineering Materials 471-472 (Februar 2011): 596–600. http://dx.doi.org/10.4028/www.scientific.net/kem.471-472.596.
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This work focuses on synthesis of MWCNT-alumina hybrid compound via methane decomposition process using nickel catalyst. The catalysts prepared through in situ process by using nickel salt and aluminium powder which then calcined at 900oC followed by methane decomposition process to grow MWCNT on alumina surface. The Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HRTEM) images confirmed the formation of MWCNT with homogenous dispersion on alumina particles.
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Hanif, Maryam, Ijaz Ahmad Bhatti, Muhammad Asif Hanif, Umer Rashid, Bryan R. Moser, Asma Hanif und Fahad A. Alharthi. „Nano-Magnetic CaO/Fe2O3/Feldspar Catalysts for the Production of Biodiesel from Waste Oils“. Catalysts 13, Nr. 6 (13.06.2023): 998. http://dx.doi.org/10.3390/catal13060998.
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Production of biodiesel from edible vegetable oils using homogenous catalysts negatively impacts food availability and cost while generating significant amounts of caustic wastewater during purification. Thus, there is an urgent need to utilize low-cost, non-food feedstocks for the production of biodiesel using sustainable heterogeneous catalysis. The objective of this study was to synthesize a novel supported nano-magnetic catalyst (CaO/Fe2O3/feldspar) for the production of biodiesel (fatty acid methyl esters) from waste and low-cost plant seed oils, including Sinapis arvensis (wild mustard), Carthamus oxyacantha (wild safflower) and Pongamia pinnata (karanja). The structure, morphology, surface area, porosity, crystallinity, and magnetization of the nano-magnetic catalyst was confirmed using XRD, FESEM/EDX, BET, and VSM. The maximum biodiesel yield (93.6–99.9%) was achieved at 1.0 or 1.5 wt.% catalyst with methanol-to-oil molar ratios of 5:1 or 10:1 at 40 °C for 2 h. The CaO/Fe2O3/feldspar catalyst retained high activity for four consecutive cycles for conversion of karanja, wild mustard, and wild safflower oils. The effective separation of the catalyst from biodiesel was achieved using an external magnet. Various different physico-chemical parameters, such as pour point, density, cloud point, iodine value, acid value, and cetane number, were also determined for the optimized fuels and found to be within the ranges specified in ASTM D6751 and EN 14214, where applicable.
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Bury, Gabriel, und Yulia Pushkar. „Computational Analysis of Structure–Activity Relationships in Highly Active Homogeneous Ruthenium−Based Water Oxidation Catalysts“. Catalysts 12, Nr. 8 (05.08.2022): 863. http://dx.doi.org/10.3390/catal12080863.
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Linear free−energy scaling relationships (LFESRs) and regression analysis may predict the catalytic performance of heterogeneous and recently, homogenous water oxidation catalysts (WOCs). This study analyses thirteen homogeneous Ru−based catalysts—some, the most active catalysts studied: the Ru(tpy−R)(QC) and Ru(tpy−R)(4−pic)2 complexes, where tpy is 2,2’;6’,2”terpyridine, QC is 8−quinolinecarboxylate and 4−pic is 4−picoline. Typical relationships studied among heterogenous catalysts cannot be applied to homogeneous catalysts. The selected group of structurally similar catalysts with impressive catalytic activity deserves closer computational and statistical analysis of multiple reaction step energetics correlating with measured catalytic activity. We report general methods of LFESR analysis yield insufficiently robust relationships between descriptor variables. However, volcano−plot−based analysis grounded in Sabatier’s principle reveals ideal relative energies of the RuIV = O and RuIV−OH intermediates and optimal changes in free energies of water nucleophilic attack on RuV = O. A narrow range of RuIV−OH to RuV = O redox potentials corresponding with the highest catalytic activities suggests facile access to the catalytically competent high−valent RuV = O state, often inaccessible from RuIV = O. Our work incorporates experimental oxygen evolution rates into approaches of LFESR and Sabatier−principle−based analysis, identifying a narrow yet fertile energetic landscape to bountiful oxygen evolution activity, leading to future rational design.
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Sawisai, Rotcharin, Ratchaneekorn Wanchanthuek, Widchaya Radchatawedchakoon und Uthai Sakee. „Synthesis, Characterization, and Catalytic Activity of Pd(II) Salen-Functionalized Mesoporous Silica“. Journal of Chemistry 2017 (2017): 1–12. http://dx.doi.org/10.1155/2017/6208132.
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Salen ligand synthesized from 2-hydroxybenzaldehyde and 2-hydroxy-1-naphthaldehyde was used as a palladium chelating ligand for the immobilization of the catalytic site. Mesoporous silica supported palladium catalysts were prepared by immobilizing Pd(OAc)2 onto a mesoporous silica gel through the coordination of the imine-functionalized mesoporous silica gel. The prepared catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), inductivity couple plasma (ICP), nitrogen adsorption-desorption, and Fourier transform infrared (FT-IR) spectroscopy. The solid catalysts showed higher activity for the hydroamination of C-(tetra-O-acetyl-β-D-galactopyranosyl)allene with aromatic amines compared with the corresponding homogenous catalyst. The heterogeneous catalytic system can be easily recovered by simple filtration and reused for up to five cycles with no significant loss of catalytic activity.
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L. Simakova, Irina, Andrey V. Simakov und Dmitry Yu. Murzin. „Valorization of Biomass Derived Terpene Compounds by Catalytic Amination“. Catalysts 8, Nr. 9 (29.08.2018): 365. http://dx.doi.org/10.3390/catal8090365.
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This review fills an apparent gap existing in the literature by providing an overview of the readily available terpenes and existing catalytic protocols for preparation of terpene-derived amines. To address the role of solid catalysts in amination of terpenes the same reactions with homogeneous counterparts are also discussed. Such catalysts can be considered as a benchmark, which solid catalysts should match. Although catalytic systems based on transition metal complexes have been developed for synthesis of amines to a larger extent, there is an apparent need to reduce the production costs. Subsequently, homogenous systems based on cheaper metals operating by nucleophilic substitution (e.g., Ni, Co, Cu, Fe) with a possibility of easy recycling, as well as metal nanoparticles (e.g., Pd, Au) supported on amphoteric oxides should be developed. These catalysts will allow synthesis of amine derivatives of terpenes which have a broad range of applications as specialty chemicals (e.g., pesticides, surfactants, etc.) and pharmaceuticals. The review will be useful in selection and design of appropriate solid materials with tailored properties as efficient catalysts for amination of terpenes.
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Singh, Rajesh K., Ashima Dhiman, Shallu Chaudhary, Deo Nandan Prasad und Sahil Kumar. „Current Progress in the Multicomponent Catalytic Synthesis of Amidoalkyl- Naphthols: An Update“. Current Organic Chemistry 24, Nr. 5 (17.05.2020): 487–515. http://dx.doi.org/10.2174/1385272822666200217100344.
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Amidoalkyl-2-naphthol is one of the vital synthetic intermediates which occupy an imperative position in medicinal chemistry due to its amazing biological, pharmacological as well as industrial and synthetic applications. Owing to its diverse pharmaceutical activities, hundreds of scientific literature are available, signifying the efficient synthesis of this intermediate using various catalysts. Most of these literature methods suffer from low yield and harsh reaction conditions that further ignited the researcher to explore for another green catalyst and fresh methodologies. This review summarizes the last five years progress in the catalytic synthesis of 1-amidoalkyl-2-naphthols using various heterogenous, homogenous and nanocatalysts along with their mechanism of action. Various advantages like green synthesis, atom economy, clean reaction profile and catalyst recovery are discussed which facilitate the scientist to probe and stimulate the study on this scaffold. In the end, the catalysts and reactions condition are organized into the tables for swift at a glance understanding of different catalysts used with their yield and time taken for the synthesis.
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Deka, Juti Rani, Diganta Saikia, Kuo-Shu Hsia, Hsien-Ming Kao, Yung-Chin Yang und Ching-Shiun Chen. „Ru Nanoparticles Embedded in Cubic Mesoporous Silica SBA-1 as Highly Efficient Catalysts for Hydrogen Generation from Ammonia Borane“. Catalysts 10, Nr. 3 (26.02.2020): 267. http://dx.doi.org/10.3390/catal10030267.
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Cubic mesoporous silica SBA-1 functionalized with carboxylic acid (-COOH), namely S1B-C10, is used as a support to fabricate and confine Ru nanoparticles (NPs). The uniformly dispersed organic functional groups in SBA-1 are beneficial in attracting Ru cations, and as a result, homogenously distributed small sized Ru NPs are formed within the mesopores. The prepared Ru@S1B-C10 is utilized as a catalyst for H2 generation from the hydrolysis of ammonia borane (AB). The Ru@S1B-C10 catalyst demonstrates high catalytic activity for H2 generation (202 mol H2 molRu min−1) and lower activation energy (24.13 kJ mol−1) due to the small sized Ru NPs with high dispersion and the support’s interconnected mesoporous structure. The nanosized Ru particles provide abundant active sites for the catalytic reaction to take place, while the interconnected porous support facilitates homogenous transference and easy dispersal of AB molecules to the active sites. The catalyst demonstrates good recycle ability since the accumulation and leaking of NPs throughout catalysis can be effectively prevented by the support.
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Keşir, Melek Koç, Münevver Sökmen und Zekeriya Bıyıklıoğlu. „Photocatalytic Efficiency of Metallo Phthalocyanine Sensitized TiO2 (MPc/TiO2) Nanocomposites for Cr(VI) and Antibiotic Amoxicillin“. Water 13, Nr. 16 (08.08.2021): 2174. http://dx.doi.org/10.3390/w13162174.
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Dye sensitization on semiconductor catalyst TiO2 was performed with four different metallophthalocyanine (MPc) derivates (M: Zn, Cu, Co, and Si) using a modified sol-gel method. MPc derivatives were loaded on TiO2 at 1% mass ratio aiming to increase its photocatalytic action and to shift the light absorption to higher UV region (365 nm). Non-ionic surfactant Triton X-100 (TX-100) was used to obtain a homogenous and mesa pore catalyst structure. The prepared catalysts were characterized by FT-IR, XRD, and SEM to determine the crystal and surface structural properties of nanocomposites. The nanocomposites were used for photocatalytic removal and degradation of Cr(VI) and amoxicillin (AMX) as model pollutants. Photocatalytic reduction capacities of the catalysts were tested for Cr(VI) (10 mg/L) and AMX (20 mg/L) aqueous solutions. ZnPc-TiO2 catalyst was successful for Cr(VI) photoreduction since all Cr(VI) ions in the solution were successfully removed. Presence of TX-100 in the sol-gel synthesis of ZnPc-TiO2 had a positive effect by increasing the Cr(VI) removal rate to 97.93% after 150 min exposure period. Prepared catalysts were also tested for photodegradation of AMX, applying similar procedures. In general, all catalysts exhibited low degradation rates under the studied condition but more effective with 254 nm UV light (50.38%). Neither surface modification with TX-100 nor MPc sensitization provided significant degradation of AMX.
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Yu, Pei, Can Chen, Guangci Li, Zhong Wang und Xuebing Li. „Active, Selective, and Recyclable Zr(SO4)2/SiO2 and Zr(SO4)2/Activated Carbon Solid Acid Catalysts for Esterification of Malic Acid to Dimethyl Malate“. Catalysts 10, Nr. 4 (01.04.2020): 384. http://dx.doi.org/10.3390/catal10040384.
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The esterification of malic acid using traditional homogenous catalysts suffers from the difficulty in reuse of the catalyst and undesirable side reactions. In this work, Zr(SO4)2/SiO2 and Zr(SO4)2/activated carbon (AC) as solid acid catalysts were prepared for malic acid esterification with methanol. The conversion of malic acid over these two catalysts is comparable to that over H2SO4 and unsupported Zr(SO4)2∙4H2O catalysts; however; a 99% selectivity of dimethyl malate can be realized on these two supported catalysts, which is much higher than that of conventional H2SO4 (75%) and unsupported Zr(SO4)2∙4H2O (80%) catalysts, highlighting the critical role of AC and SiO2 supports in tuning the selectivity. We suggest that the surface hydroxyls of AC or lattice O2− ions from SiO2 donate electrons to Zr4+ in Zr(SO4)2/AC and Zr(SO4)2/SiO2 catalysts, which results in the increase in electron density on Zr4+. The enhanced electron density on Zr4+ reduces the degree of H delocalization from crystal water and then decreases the Brønsted acid strength. Consequently, the reduced Brønsted acid strength of Zr(SO4)2/AC and Zr(SO4)2/SiO2 catalysts suppresses the intermolecular dehydration side reaction. In addition, these two supported catalysts can be easily separated from the reaction system by simple filtration with almost no loss of activity.
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Lashanizadegan, Maryam, Sahar Shayegan und Marzieh Sarkheil. „Copper(II) complex of (±)trans-1,2-cyclohexanediamine azo-linked Schiff base ligand encapsulated in nanocavity of zeolite-Y for the catalytic oxidation of olefins“. Journal of the Serbian Chemical Society 81, Nr. 2 (2016): 153–62. http://dx.doi.org/10.2298/jsc150708085l.
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A Schiff base ligand derived from 4-(benzeneazo) salicylaldehyde and (?)trans-1,2-cyclohexanediamine (H2L) and its corresponding Cu(II) complex (CuL) has been synthesized and characterized by FT-IR, UV-VIS and 1H NMR. The copper Schiff base complex encapsulated in the nanopores of zeolite-Y (CuL-Y) by flexible ligand method and its encapsulation have been ensured by different studies. The homogeneous and its corresponding heterogeneous catalysts have been used for oxidation of different alkenes with tert-butyl hydroperoxide. Under the optimized reaction conditions, the oxidation of cyclooctene, cyclohexene, styrene and norbornene catalyzed by CuL gave 89, 63, 46 and 13% conversion, respectively. These olefins were oxidized efficiently with 50, 96, 96 and 92% conversion in the presence of CuL-Y, respectively. Comparison of the catalytic behavior of CuL and CuL-Y showed the higher catalytic activity and selectivity of the heterogeneous catalyst with respect to the homogenous one.
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Hejazi, Seyedsina, Manuela S. Killian, Anca Mazare und Shiva Mohajernia. „Single-Atom-Based Catalysts for Photocatalytic Water Splitting on TiO2 Nanostructures“. Catalysts 12, Nr. 8 (17.08.2022): 905. http://dx.doi.org/10.3390/catal12080905.
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H2 generation from photocatalytic water splitting is one of the most promising approaches to producing cost-effective and sustainable fuel. Nanostructured TiO2 is a highly stable and efficient semiconductor photocatalyst for this purpose. The main drawback of TiO2 as a photocatalyst is the sluggish charge transfer on the surface of TiO2 that can be tackled to a great extent by the use of platinum group materials (PGM) as co-catalysts. However, the scarcity and high cost of the PGMs is one of the issues that prevent the widespread use of TiO2/PGM systems for photocatalytic H2 generation. Single-atom catalysts which are currently the frontline in the catalysis field can be a favorable path to overcome the scarcity and further advance the use of noble metals. More importantly, single-atom (SA) catalysts simultaneously have the advantage of homogenous and heterogeneous catalysts. This mini-review specifically focuses on the single atom decoration of TiO2 nanostructures for photocatalytic water splitting. The latest progress in fabrication, characterization, and application of single-atoms in photocatalytic H2 generation on TiO2 is reviewed.
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Vlnieska, Vitor, Aline Muniz, Angelo Oliveira, Maria César-Oliveira und Danays Kunka. „Oligocat: Oligoesters as Pseudo-Homogenous Catalysts for Biodiesel Synthesis“. Polymers 14, Nr. 1 (05.01.2022): 210. http://dx.doi.org/10.3390/polym14010210.
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Biodiesel production from first-generation feedstock has shown a strong correlation with the increase in deforestation and the necessity of larger areas for land farming. Recent estimation from the European Federation for Transport and Environment evidenced that since the 2000s decade, an area equal to the Netherlands was deforested to supply global biodiesel demand, mainly originating from first-generation feedstock. Nevertheless, biodiesel is renewable, and it can be a greener source of energy than petroleum. A promising approach to make biodiesel independent from large areas of farming is to shift as much as possible the biodiesel production chain to second and third generations of feedstock. The second generation presents three main advantages, where it does not compete with the food industry, its commercial value is negligible, or none, and its usage as feedstock for biodiesel production reduces the overall waste disposal. In this manuscript, we present an oligomeric catalyst designed to be multi-functional for second-generation feedstock transesterification reactions, mainly focusing our efforts to optimize the conversion of tallow fat and sauteing oil to FAME and FAEE, applying our innovative catalyst. Named as Oligocat, our catalyst acts as a Brønsted-Lowry acid catalyst, providing protons to the reaction medium, and at the same time, with the course of the reaction, it sequesters glycerol molecules from the medium and changes its physical phase during the transesterification reaction. With this set of properties, Oligocat presents a pseudo-homogenous behavior, reducing the purification and separation steps of the biodiesel process production. Reaction conditions were optimized applying a 42 factorial planning. The output parameter evaluated was the conversion rate of triacylglycerol to mono alkyl esters, measured through gel permeation chromatography (GPC). After the optimization studies, a conversion yield of 96.7 (±1.9) wt% was achieved, which allows classifying the obtained mono alkyl esters as biodiesel by ASTM D6751 or EN 14214:2003. After applying the catalyst in three reaction cycles, Oligocat still presented a conversion rate above 96.5 wt% and as well an excellent recovery rate.
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Maitlis, Peter. „“Ruthenium Oxidation Complexes: Their Uses as Homogenous Organic Catalysts”“. Platinum Metals Review 55, Nr. 3 (01.07.2011): 193–95. http://dx.doi.org/10.1595/147106711x580072.
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Anxolabéhère-Mallart, Elodie, und Frédéric Banse. „Bioinspired molecular catalysts for homogenous electrochemical activation of dioxygen“. Current Opinion in Electrochemistry 15 (Juni 2019): 118–24. http://dx.doi.org/10.1016/j.coelec.2019.05.002.
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Hoque, Md Abdul, Chaminda P. Nawarathne und Noe T. Alvarez. „Synthesis of Vertically Aligned Carbon Nanotube Arrays from Premade Bimetallic Aluminum-Iron Oxide Nanoparticles Monolayer“. ECS Meeting Abstracts MA2023-01, Nr. 10 (28.08.2023): 1215. http://dx.doi.org/10.1149/ma2023-01101215mtgabs.
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Abstract: Carbon Nanotubes (CNTs) are excellent materials because of their unique physical and chemical properties. Though catalyst nanoparticles preparation from thin film catalysts are common but premade catalysts nanoparticles in liquid phase has control over the size and composition which control the diameter and length of CNTs. Here, we report the synthesis of vertically aligned (VA) CNTs on metal oxide substrates including silicon oxide and stainless-steel using aluminum-iron oxides Al2O3-Fe2O3 nanoparticles monolayer. Oleic acid functionalized Al2O3-Fe2O3 nanoparticles were assembled onto metal oxide substrate as a monolayer using 11-phousnoundecanoic acid (PNDA) linker molecule where phosphonate group bind to the substrate and terminal carboxylic group of PNDA bind to the surface of bimetallic oxide catalysts. Homogenous catalyst nanoparticles distribution from monolayer assembly can reduce the aggregation of catalyst particles which can increases the catalyst lifetime during CNTs growth. Synthesis of VA-CNTs require Al2O3 catalyst support on substrate surface, but our bimetallic Al2O3-Fe2O3 nanoparticles contain both catalyst support (Al2O3) and catalyst (Fe) in the same particle. The successful VA-CNTs synthesis were achieved by chemical vapor deposition (CVD) process using acetylene as carbon precursor in atmospheric pressure. We envision that our catalyst preparation for VA-CNTs growth can be a cost-efficient method for large scale synthesis of CNTs. Further, the VA-CNTs growth on conductive stainless-steel substrate can facilitate the electrochemical application of this hybrid materials for biomolecule sensing and heavy metals detection.
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Boudjema, S., E. Vispe, A. Choukchou-Braham, J. A. Mayoral, R. Bachir und J. M. Fraile. „Preparation and characterization of activated montmorillonite clay supported 11-molybdo-vanado-phosphoric acid for cyclohexene oxidation“. RSC Advances 5, Nr. 9 (2015): 6853–63. http://dx.doi.org/10.1039/c4ra13604g.
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Singhanatkaisi, Natthakit, Mathi Kandiah, Alvin Lim Teik Zheng, Yoshito Ando und Supakorn Boonyuen. „Biodiesel production from used palm oil using magnetic solid base catalyst“. Journal of Physics: Conference Series 2175, Nr. 1 (01.01.2022): 012025. http://dx.doi.org/10.1088/1742-6596/2175/1/012025.
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Abstract In this research the biodiesel from palm oil were synthesized by using magnetic solid base catalyst. The magnetic solid base catalyst was prepared by using co-precipitation method and followed by modified Stober’s method and wet impregnation method. CaO-ferrite nanometre magnetic solid base catalysts (CaO@Fe3O4/SiO2) were synthesized by loading CaO on the surface of Fe3O4 core-shell using the polymeric binder, TEOS. Under the optimized condition reactions, the catalysts were synthesized by co-precipitation and incipient wetness impregnation followed by calcination at 700 °C for 5 h. The calcined catalyst was fully characterized. The basic strength of the catalysts (H_) was first assessed using Hammett indicators, which are in range 9.8–15.0. The calcined Ca/ferrite-TEOS showed homogenous spherical shape with an apparent thickness of 92 nm. The FT-IR of CaO observed at 520 cm-1 is attributed to the Ca-O vibrations. The EDX analysis confirmed the presence of Fe, Si and Ca on the catalyst. The optimization conditions for biodiesel production have been measured. The catalyst was used 5.0 % wt. The methanol to oil ratio is 5:1, reaction time is 180 minutes and reaction was produced at 80°C. The catalyst achieved a biodiesel conversion of used palm oil (acid value 1.2) above 92 %. The catalytic activity and recovery rate of CaO@Fe3O4/SiO2 are better as compared to CaO catalyst. The properties of synthesized biodiesel have been studied and meet standard the Department of Energy Business.
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Cornejo, Alfonso, Fernando Bimbela, Rui Moreira, Karina Hablich, Íñigo García-Yoldi, Maitane Maisterra, António Portugal, Luis M. Gandía und Víctor Martínez-Merino. „Production of Aromatic Compounds by Catalytic Depolymerization of Technical and Downstream Biorefinery Lignins“. Biomolecules 10, Nr. 9 (18.09.2020): 1338. http://dx.doi.org/10.3390/biom10091338.
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Lignocellulosic materials are promising alternatives to non-renewable fossil sources when producing aromatic compounds. Lignins from Populus salicaceae. Pinus radiata and Pinus pinaster from industrial wastes and biorefinery effluents were isolated and characterized. Lignin was depolymerized using homogenous (NaOH) and heterogeneous (Ni-, Cu- or Ni-Cu-hydrotalcites) base catalysis and catalytic hydrogenolysis using Ru/C. When homogeneous base catalyzed depolymerization (BCD) and Ru/C hydrogenolysis were combined on poplar lignin, the aromatics amount was ca. 11 wt.%. Monomer distributions changed depending on the feedstock and the reaction conditions. Aqueous NaOH produced cleavage of the alkyl side chain that was preserved when using modified hydrotalcite catalysts or Ru/C-catalyzed hydrogenolysis in ethanol. Depolymerization using hydrotalcite catalysts in ethanol produced monomers bearing carbonyl groups on the alkyl side chain. The analysis of the reaction mixtures was done by size exclusion chromatography (SEC) and diffusion ordered nuclear magnetic resonance spectroscopy (DOSY NMR). 31P NMR and heteronuclear single quantum coherence spectroscopy (HSQC) were also used in this study. The content in poly-(hydroxy)-aromatic ethers in the reaction mixtures decreased upon thermal treatments in ethanol. It was concluded that thermo-solvolysis is key in lignin depolymerization, and that the synergistic effect of Ni and Cu provided monomers with oxidized alkyl side chains.
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Soongprasit, Chakrit, Duangdao Aht-Ong und Duangduen Atong. „Bimetallic LaNi1-xCoxO3 (x=0, 0.3, 0.5, 0.7, and 1) Perovskite Catalysts for Tar Reforming to Syngas“. Advanced Materials Research 747 (August 2013): 690–93. http://dx.doi.org/10.4028/www.scientific.net/amr.747.690.
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Perovskite-type oxide with transition metal as active site presented a promising potential catalyst for tar elimination in gasification process. LaNi1-xCoxO3 (x= 0, 0.3, 0.5, 0.7, and 1) were prepared by sol-gel method. The XRD profiles of the calcined catalysts revealed the mixed metal oxide forms including LaNiO3 and LaCoO3 rhombohedral structures. Good dispersion of La, Ni, and Co with homogenous structure was observed in synthesized catalyst. The particle size and surface area were in the range of 12.64-21.86 μm and 3.89-11.69 m2 /g, respectively. Activity of prepared catalysts on tar elimination was carried out using steam reforming of toluene as tar model compound at 500, 600, 700, and 800°C. Product distributions obtained from reforming reaction with LaNi1-xCoxO3 were between 40.24-88.84% of gas, 10.99-59.59% of liquid, and 0.15-0.17% of solid. Conversion to CO and H2 were found to increase with the reaction temperature. The maximum carbon and hydrogen conversion to syngas, CO and H2, of approximately 78.42% and 83.49% with acceptable heating value were occurred at 800oC using LaNiO3 as catalyst. Crystal structure of used catalysts clearly showed destruction of perovskite structure and transformation to metallic Ni and Co at effective temperature.
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da Silva, Márcio José, Cláudio Júnior Andrade Ribeiro, Eduardo Nery de Araújo und Isadora Merighi Torteloti. „Acetalization of Alkyl Alcohols with Benzaldehyde over Cesium Phosphomolybdovanadate Salts“. Processes 11, Nr. 7 (24.07.2023): 2220. http://dx.doi.org/10.3390/pr11072220.
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In this work, vanadium-substituted cesium phosphomolybdate salts with general formulae Cs3+nPMo12−nVnO40 (n = 0, 1, 2, and 3) were synthesized and evaluated in the acetalization of benzaldehyde with alkyl alcohols. All the catalysts were characterized through Raman, infrared, and ultraviolet–visible spectroscopies, powder X-ray diffraction patterns, isotherms of N2 desorption/adsorption, and measurements of acidity strength. The catalytic activity of cesium phosphomolybdovanadate salts was evaluated in the acetalization reactions of benzaldehyde with alkyl alcohols. Among the salts tested, the Cs4PMo11V1O40 was the most active and selective catalyst in the conversion of benzaldehyde to methyl benzyl acetal and benzoic acid, which was obtained without the use of an oxidant agent. The impact of the main reaction parameters on the conversion and selectivity was evaluated by varying the content of vanadium per heteropolyanion, catalyst load, temperature, and alkyl alcohols. The greatest activity of the Cs4PMo11V1O40 salt was assigned to the highest Brønsted acidity strength, as demonstrated by the acidity measurements and analysis of their surface properties. This solid catalyst has advantages over traditional liquid homogenous catalysts, such as low corrosiveness, a minimum generation of residues and effluents, and easy recovery/reuse. In addition, its synthesis route is easier and quicker than solid-supported catalysts and comprises a potential alternative route to synthesize acetals.
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Fdez-Sanromán, Antía, Rocío Martinez-Treinta, Marta Pazos, Emilio Rosales und María Ángeles Sanromán. „Heterogeneous Electro-Fenton-like Designs for the Disposal of 2-Phenylphenol from Water“. Applied Sciences 11, Nr. 24 (19.12.2021): 12103. http://dx.doi.org/10.3390/app112412103.
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The hunt for efficient and environmentally friendly degradation processes has positioned the heterogeneous advanced oxidation processes as an alternative more interesting and economical rather than homogenous processes. Hence, the current study lies in investigating the efficiency of different heterogeneous catalysts using transition metals in order to prevent the generation of iron sludge and to extend the catalogue of possible catalysts to be used in advanced oxidation processes. In this study, nickel and zinc were tested and the ability for radical-generation degradation capacity of both ions as homogeneous was evaluated in the electro-Fenton-like degradation of 2-phenylphenol. In both cases, the degradation profiles followed a first-order kinetic model with the highest degradation rate for nickel (1 mM) with 2-phenylphenol removal level of 90.12% and a total organic reduction near 70% in 2 h. To synthesise the heterogeneous nickel catalyst, this transition metal was fixed on perlite by hydrothermal treatment and in a biochar or carbon nanofibers by adsorption. From the removal results using the three synthesized catalysts, it is concluded that the best catalysts were obtained by inclusion of nickel on biochar or nanofibers achieving in both with removal around 80% before 1 h. Thus, to synthetize a nickel electrocatalyst, nickel doped nanofibers were included on carbon felt. To do this, the amount of carbon black, nickel nanofibers and polytetrafluoroethylene to add on the carbon felt was optimized by Taguchi design. The obtained results revealed that under the optimised conditions, a near-complete removal was achieved after 2 h with high stability of the nickel electrocatalyst that open the applicability of this heterogeneous system to operate in flow systems.
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Hadiyanto, Hadiyanto, Sri Puji Lestari und Widayat Widayat. „Preparation and Characterization of Anadara Granosa Shells and CaCO3 as Heterogeneous Catalyst for Biodiesel Production“. Bulletin of Chemical Reaction Engineering & Catalysis 11, Nr. 1 (10.03.2016): 21. http://dx.doi.org/10.9767/bcrec.11.1.402.21-26.
Annotation:
<p>Nowadays, the use of homogenous catalyst has been gradually reduced for its operational reason. The homogenous catalyst leads in difficulty of separation after the process completed and the life cycle is shorter. Therefore, most of researches are introducing heterogenous catalyst for its substitution. This research was aimed to evaluate the use of shell of Anadara granosa and CaCO3 as source of CaO based catalyst through impregnation method. The preparation of the catalyst was started by decomposition of shells and CaCO3 at temperature of 800 oC for 3 hours, followed by impregnation at 70 oC for 4 hours and then calcined at 800 oC for 2 hours. The CaCO3 based catalyst gained high yield of biodiesel (94%) as compared to Anadara granoasa based catalyst (92%). The reusability study showed that these catalysts could be used until three times recycle with 40-60% yield of biodiesel. The CaO contents of catalyst decreased up to 90% after three times recycles. Copyright © 2016 BCREC GROUP. All rights reserved</p><p><em>Received: 10<sup>th</sup> November 2015; Revised: 6<sup>th</sup> January 2016; Accepted: 6<sup>th</sup> January 2016</em></p><p><strong>How to Cite:</strong> Hadiyanto, H., Lestari, S.P., Widayat, W. (2016). Preparation and Characterization of Anadara Granosa Shells and CaCO3 as Heterogeneous Catalyst for Biodiesel Production. <em>Bulletin of Chemical Reaction Engineering & Catalysis</em>, 11 (1): 21-26. (doi:10.9767/bcrec.11.1.402.21-26)</p><p><strong>Permalink/DOI</strong>: <a href="http://dx.doi.org/10.9767/bcrec.11.1.402.21-26">http://dx.doi.org/10.9767/bcrec.11.1.402.21-26</a></p><p> </p>
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Ali Nasr Abdulkareem und Nurul Fitriah Nasir. „Biodiesel Production from Canola Oil Using TiO2CaO as a Heterogenous Catalyst“. Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 93, Nr. 2 (09.04.2022): 125–37. http://dx.doi.org/10.37934/arfmts.93.2.125137.
Annotation:
Biodiesel is one of the renewable energy sources that is an alternative to fossil diesel that is non-toxic and produces less CO emissions. Transesterification process is a conventional mechanism to produce biodiesel from vegetable oil with a homogeneous or heterogenous catalyst. However, heterogenous catalysts are considered as more efficient than homogenous catalysts. Recently, TiO2/CaO has been used as a compound heterogenous catalyst to produce biodiesel produce from palm oil, waste cooking oils and algae. In this research, biodiesel was manufactured using canola oil as a feedstock and titanium dioxide / calcium oxide (TiO2/CaO) as a catalyst. The aim of this study is to prepare the catalyst, investigate the transesterification process and measure the chemical and physical biodiesel properties. Catalyst preparation required four stages: dry mixing, wet mixing, water separation and catalyst activation where there were two temperature phases (200 °C and 600 °C). Catalyst mixed with methanol by 1:16 ratio had different mixing time phases (30 minutes, 60 minutes, and 90 minutes). The Transesterification process was by blending the catalyst-methanol mixture with canola oil under 3 phases (4 hours, 5 hours, and 6 hours). The catalyst characterization was by analysis of X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), temperature activation effects and activation time effects. The transesterification process analysis showed that the optimization conditions to produce biodiesel are 600 °C activation catalyst temperature, 90 minutes of catalyst-methanol mixing, 1.5% wt. catalyst concentration and 5 hours of transesterification time. The biodiesel yield was 96.9%. Moreover, new parameters were applied for this research (time and temperature of activation catalyst, catalyst-methanol mixing parameters and transesterification process conditions). Biodiesel properties (kinematic viscosity, flash point and water content) were measured according to ASTM D6751 standards and similarity was 98%. Therefore, biodiesel can be produced from canola oil and TiO2/CaO, but this still needs more studies on several topics such as the blending of canola with multi feedstocks, the ethanol impact and catalyst poisoning in the case of using TiO2-CaO as a catalyst.
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Wang, Y., Y. Nie, W. Ding, S. G. Chen, K. Xiong, X. Q. Qi, Y. Zhang, J. Wang und Z. D. Wei. „Unification of catalytic oxygen reduction and hydrogen evolution reactions: highly dispersive Co nanoparticles encapsulated inside Co and nitrogen co-doped carbon“. Chemical Communications 51, Nr. 43 (2015): 8942–45. http://dx.doi.org/10.1039/c5cc02400e.
Annotation:
The elaborately synthesized Co nanoparticles encapsulated inside Co and nitrogen co-doped carbon catalysts with homogenous distribution of Co NPs exhibit evidently outstanding performances toward ORR/HER.
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Liu, Han-Yu, Hannah M. C. Lant, Jennifer L. Troiano, Gongfang Hu, Brandon Q. Mercado, Robert H. Crabtree und Gary W. Brudvig. „Electrocatalytic, Homogeneous Ammonia Oxidation in Water to Nitrate and Nitrite with a Copper Complex“. ECS Meeting Abstracts MA2023-01, Nr. 55 (28.08.2023): 2691. http://dx.doi.org/10.1149/ma2023-01552691mtgabs.
Annotation:
Electrocatalytic ammonia oxidation (AO) at room temperature and pressure allows energy-economical and environmentally-friendly production of nitrites and nitrates. Few molecular catalysts, however, have been developed for this six- or eight-electron oxidation process. We now report [Cu(bipyalk)]+, a homogenous, earth-abundant metal electrocatalyst that realizes the title reaction in water. The complex selectively catalyzes the ammonia oxidation electrochemically at 94% Faradaic efficiency without generating the less-valuable N2 product commonly seen in molecular AO catalysis. Moreover, our complex is designed to not mediate water oxidation (WO), which is beneficial for high selectivity in AO in aqueous media. Initial mechanistic studies by electrochemistry propose monometallic catalysis and water or ammonia-nucleophilic attack for N–O bond formation. Figure 1