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1
Zhao, Xiaodan, e Lihao Liao. "Modern Organoselenium Catalysis: Opportunities and Challenges". Synlett 32, n. 13 (11 maggio 2021): 1262–68. http://dx.doi.org/10.1055/a-1506-5532.
Testo completoAbstract (sommario):
AbstractOrganoselenium catalysis has attracted increasing interest in recent years. This Cluster highlights recent key advances in this area regarding the functionalization of alkenes, alkynes, and arenes by electrophilic selenium catalysis, selenonium salt catalysis, selenium-based chalcogen-bonding catalysis, and Lewis basic selenium catalysis. These achievements might inspire and help future research.1 Introduction2 Electrophilic Selenium Catalysis3 Selenonium Salt Catalysis4 Selenium-Based Chalcogen-Bond Catalysis5 Lewis Basic Selenide Catalysis6 Conclusion
2
Dagorne, Samuel. "Recent Developments on N-Heterocyclic Carbene Supported Zinc Complexes: Synthesis and Use in Catalysis". Synthesis 50, n. 18 (28 giugno 2018): 3662–70. http://dx.doi.org/10.1055/s-0037-1610088.
Testo completoAbstract (sommario):
The present contribution reviews the synthesis, reactivity, and use in catalysis of NHC–Zn complexes reported since 2013. NHC-stabilized Zn(II) species typically display enhanced stability relative to common organozinc species (such as Zn dialkyls), a feature of interest for the mediation of various chemical processes and the stabilization of reactive Zn-based species. Their use in catalysis is essentially dominated by reduction reactions of various unsaturated small molecules (including CO2), thus primarily involving Zn–H and Zn–alkyl derivatives as catalysts. Simple NHC adducts of Zn(II) dihalides also appear as effective catalysts for the reduction amination of CO2 and borylation of alkyl/aryl halides. Stable and well-defined Zn alkoxides have also been prepared and behave as effective catalysts in the polymerization of cyclic esters/carbonates for the production of well-defined biodegradable materials. Overall, the attractive features of NHC-based Zn(II) species include ready access, a reasonable stability/reactivity balance, and steric/electronic tunability (through the NHC source), which should promote their further development.1 Introduction2 NHC-Supported Zinc Alkyl/Aryl Species2.1 Synthesis2.2 Reactivity and Use in Catalysis3 NHC-Supported Zinc Hydride Species3.1 Synthesis3.2 Reactivity and Use in Catalysis4 NHC-Supported Zinc Amido/Alkoxide Species4.1 Synthesis4.2 Use in Catalysis5 NHC-Supported Zinc Dihalide Species5.1 Synthesis5.2 Use in Catalysis6 Other NHC-Stabilized Zn Species7 Conclusion
3
Ding, Bo, Qilin Xue, Hong-Gang Cheng, Qianghui Zhou e Shihu Jia. "Recent Advances in Catalytic Nonenzymatic Kinetic Resolution of Tertiary Alcohols". Synthesis 54, n. 07 (2 dicembre 2021): 1721–32. http://dx.doi.org/10.1055/a-1712-0912.
Testo completoAbstract (sommario):
AbstractThe kinetic resolution (KR) of racemates is one of the most widely used approaches to access enantiomerically pure compounds. Over the past two decades, catalytic nonenzymatic KR has gained popularity in the field of asymmetric synthesis due to the rapid development of chiral catalysts and ligands in asymmetric catalysis. Chiral tertiary alcohols are prevalent in a variety of natural products, pharmaceuticals, and biologically active chiral compounds. The catalytic nonenzymatic KR of racemic tertiary alcohols is a straightforward strategy to access enantioenriched tertiary alcohols. This short review describes recent advances in catalytic nonenzymatic KR of tertiary alcohols, including organocatalysis and metal catalysis.1 Introduction2 Organocatalysis2.1 Peptide Catalyst2.2 Chiral Phosphoric Acid Catalyst2.3 Chiral Lewis Base Catalyst2.4 Chiral Quaternary Ammonium Salt Catalyst3 Metal Catalysis3.1 Mixed La-Li Heterobimetallic Catalyst3.2 Rh Catalyst3.3 Hf Catalyst3.4 Pd Catalyst3.5 Cu Catalyst3.6 Ag Catalyst4 Conclusion and Outlook
4
Li, Feng, e Hao Li. "Spatial compartmentalisation effects for multifunctionality catalysis: From dual sites to cascade reactions". Innovation & Technology Advances 2, n. 1 (12 marzo 2024): 1–13. http://dx.doi.org/10.61187/ita.v2i1.54.
Testo completoAbstract (sommario):
Catalysis plays a key role in the production of fuels, industrial chemicals and the chemical transformation of fine chemicals. As society faces increasing environmental pollution and energy crises, tandem catalysis has attracted increasing attention as an outstanding model due to its sustainability and environmental friendliness. Compared with traditional stepwise synthesis methods, tandem catalysis not only can couple several different reactions together, but also does not require the separation of intermediates, which provides new ideas for improving reaction activity, regulating product selectivity and developing new methods for catalysis. In order to catalyse cascade reactions efficiently, it is crucial to design suitable multifunctional catalysts, which should contain at least two active sites and achieve spatial separation. Here, we introduce the realisation and application of spatial segregation of metal, acidic and basic sites with examples to provide further insight into the indispensable role of active site compartmentalisation effects in tandem catalysis. In addition, this study highlights the challenges and issues associated with such catalysts, emphasising the importance of effective catalyst enhancement and environmentally sustainable catalytic transformations. The results of the study are intended to provide guidance for the development of rational and efficient catalysts.
5
Shi, Chunjie, Xiaofeng Yu, Wei Wang, Haibing Wu, Ai Zhang e Shengjin Liu. "The Activity and Cyclic Catalysis of Synthesized Iron-Supported Zr/Ti Solid Acid Catalysts in Methyl Benzoate Compounds". Catalysts 13, n. 6 (2 giugno 2023): 971. http://dx.doi.org/10.3390/catal13060971.
Testo completoAbstract (sommario):
The catalytic activity and cyclic catalysis of different methyl benzoates were studied by using a series of Lewis solid acid catalysts. The iron-supported zirconium/titanium solid acid catalysts were characterized using FTIR, SEM, XRD, and BET. The details of catalytic activity and cyclic catalysis verified that the catalyst catalyzed the reactions of 31 benzoic acids with different substituents and methanol. In addition, the mechanism was revealed according to the microstructure, acid strength, and specific surface area of the catalysts, and the yields of methyl benzoates by the GC-MS. Zr ions had significant effects on the catalytic activity of the catalyst. A certain proportion of Fe and Ti ions additionally enhanced the catalytic activity of the catalyst, with the catalyst-specific composition of Fe:Zr: Ti = 2:1: 1 showing optimal catalytic activity. A variety of substituents in the benzene ring, such as the electron-withdrawing group, the electron-donating group, large steric hindrance, and the position of the group on the benzene ring, had regular effects on the catalytic activity of the methyl benzoates. An increase in the catalyst activity occurred owing to the increases in the catalyst surface and the number of acid sites after the Fe ion was added. The catalytic activity remained unchanged after the facile recycling method was performed.
6
Clerici, Mario G. "Zeolites for Fine Chemical Production State of Art and Perspectives". Eurasian Chemico-Technological Journal 3, n. 4 (10 luglio 2017): 231. http://dx.doi.org/10.18321/ectj573.
Testo completoAbstract (sommario):
The paper analyses the role of catalysis and that of renewable resources in the frame of a sustainable development. The possible uses of natural feedstocks for chemical production and the application of catalytic<br />methods to their transformations are reviewed, with emphasis on carbohydrates and vegetable oils and on zeolite catalysts, respectively. The problems arising from the embedment of active sites on the catalyst<br />surface are discussed, with the aid of specific examples taken from oxidation and acid catalysed reactions.
7
Zhang, Meng. "A Novel Energy Band Match Method and a Highly Efficient CuO–Co3O4@SiO2 Catalyst for Dimethyl Carbonate Synthesis from CO2". Science of Advanced Materials 13, n. 1 (1 gennaio 2021): 115–22. http://dx.doi.org/10.1166/sam.2021.3848.
Testo completoAbstract (sommario):
The present research on dimethyl carbonate (DMC) synthesis from CO2 was short of effective theoretical guidance and catalyst design was also blind. A kind of regular relationship was found from catalyst structure calculation and activity experiments. Therefore, a novel energy band matching method was proposed. After substantial verification experiments, it was proved to be correct. Whether one certain catalyst has catalytic activity can be judged predictably according to this novel method. Novel and efficient catalysts can be designed or selected on the basis of designer's wishes. Based on this method, three efficient catalysts were prepared and CuO–Co3O4@SiO2 catalyst had the best catalytic performance. In a word, once it is applied in catalysts research, there will be a huge progress in catalysis and materials science fields.
8
Jankovič, Ľuboš, e Peter Komadel. "Catalytic Properties of a Heated Ammonium-Saturated Dioctahedral Smectite". Collection of Czechoslovak Chemical Communications 65, n. 9 (2000): 1527–36. http://dx.doi.org/10.1135/cccc20001527.
Testo completoAbstract (sommario):
A series of acid catalysts was prepared by heating of NH4-saturated montmorillonite at 200-600 °C for 24 h. Their catalytic activity was tested in acetylation of 3,4,5-trimethoxybenzaldehyde with acetic anhydride. This reaction is sufficiently sensitive to modification of the catalyst and thus suitable for testing catalytic activity of modified montmorillonites. Most of the prepared catalysts were able to catalyse the test reaction and produce diacetate in higher than 50% yields. The most active catalyst was obtained after heating at 300 °C. It was slightly less effective than commercially available acid-activated K10 catalyst.
9
Zhuang, Huimin, Bili Chen, Wenjin Cai, Yanyan Xi, Tianxu Ye, Chuangye Wang e Xufeng Lin. "UiO-66-supported Fe catalyst: a vapour deposition preparation method and its superior catalytic performance for removal of organic pollutants in water". Royal Society Open Science 6, n. 4 (aprile 2019): 182047. http://dx.doi.org/10.1098/rsos.182047.
Testo completoAbstract (sommario):
A vapour deposition (VD) method was established for preparation of the UiO-66-supported Fe (Fe/UiO-66) catalyst, which provided the first case of the metal-organic framework (MOF)-supported Fe catalyst prepared by using the vapour-based method. The Fe loading was around 7.0–8.5 wt% under the present preparation conditions. The crystal structure of UiO-66 was not obviously influenced by the Fe loading, while the surface area significantly decreased, implicating most of the Fe components resided in the pores on UiO-66. The results for the methyl orange (MO) removal tests showed that MO in aqueous solution can be removed by UiO-66 by adsorption, and in contrast, it can be oxidized by H 2 O 2 with the catalysis of Fe/UiO-66. Further catalytic tests showed that Fe/UiO-66 was rather effective to catalyse the oxidation of benzene derivatives like aniline in water in terms of chemical oxygen demand (COD) removal efficiency. The catalytic test results for Fe/UiO-66 were compared to those of Fe/Al 2 O 3 with the same Fe loading and to the catalysts reported in the literature. This paper provides a general strategy for VD preparation of MOF-supported Fe catalyst on the one hand, and new catalysts for removing organic pollutants from water, on the other hand.
10
Motokura, Ken, e Kyogo Maeda. "Recent Advances in Heterogeneous Ir Complex Catalysts for Aromatic C–H Borylation". Synthesis 53, n. 18 (9 aprile 2021): 3227–34. http://dx.doi.org/10.1055/a-1478-6118.
Testo completoAbstract (sommario):
AbstractAromatic C–H borylation catalyzed by an Ir complex is among the most powerful methods for activating inert bonds. The products, i.e., arylboronic acids and their esters, are usable chemicals for the Suzuki–Miyaura cross-coupling reaction, and significant effort has been directed toward the development of homogeneous catalysis chemistry. In this short review, we present a recent overview of current heterogeneous Ir-complex catalyst developments for aromatic C–H borylation. Not only have Ir complexes been immobilized on support surfaces with phosphine and bipyridine ligands, but Ir complexes incorporated within solid materials have also been developed as highly active and reusable heterogeneous Ir catalysts. Their catalytic activities and stabilities strongly depend on their surface structures, including linker length and ligand structure.1 Introduction and Homogeneous Ir Catalysis2 Heterogeneous Ir Complex Catalysts for C–H Borylation Reactions3 Other Heterogeneous Metal Complex Catalysts for C–H Borylation Reactions4 Summary and Outlook
11
Lukey, CA, MA Long e JL Garnett. "Aromatic Hydrogen Isotope Exchange Reactions Catalyzed by Iridium Complexes in Aqueous Solution". Australian Journal of Chemistry 48, n. 1 (1995): 79. http://dx.doi.org/10.1071/ch9950079.
Testo completoAbstract (sommario):
Sodium hexachloroiridate (III) and sodium hexachloroiridate (IV) have been used as homogeneous catalysts for hydrogen isotope exchange between benzenoid compounds and water. The ideal solvent consisted of 50 mole % acetic acid/water, and the optimum temperature was found to be 160°C. Under these conditions the rate of incorporation of deuterium into benzene was significant (typically 15% D in 6 h), and reduction to iridium metal was minimized. The active catalytic species was identified as a solvated iridium(III) species, which is also postulated to be the active catalyst in solutions containing hexachloroiridate (IV). The kinetics of exchange in benzene catalysed by sodium hexachloroiridate (III) were elucidated, and found to be more complex than for the corresponding sodium tetrachloroplatinate (II) catalysed exchange, in that a two-term rate dependence was found for catalyst concentration and the reaction was inversely dependent on hydrogen ion concentration. The reaction was found to be independent of chloride ion concentration, this confirming that the active catalyst is a solvated species. Isotopic labelling in all compounds was confined to the aromatic ring, and most substituted benzenes exhibited deactivation of the ortho positions, indicating that a dissociative π-complex exchange mechanism was operating. This was confirmed by exchange into naphthalene, where it was found that labelling was predominantly in the β position. Facile exchange into nitrobenzene provided good evidence of homogeneous catalysis, and not catalysis by precipitated metal.
12
Holzwarth, Arnold, e Wilhelm F. Maier. "Catalytic Phenomena in Combinatorial Libraries of Heterogeneous Catalysts". Platinum Metals Review 44, n. 1 (1 gennaio 2000): 16–21. http://dx.doi.org/10.1595/003214000x4411621.
Testo completoAbstract (sommario):
Combinatorial catalysis is becoming a significant method for investigating the activities of large numbers of potential catalysts. A very important prerequisite for making use of combinatorial catalysis research is a reliable, fast and efficient technique for monitoring the catalytic activities. Emissivity-corrected infrared thermography, which monitors the heat changes resulting from the heat of reaction on catalyst surfaces, is such a technique. In this article we describe emissivity-corrected infrared thermography and demonstrate its performance, over time, in monitoring the catalytic activities of catalyst libraries. It is shown that not only can static relative activity be displayed, but also that catalyst-specific time-dependent properties, such as activation and deactivation phenomena can be demonstrated.
13
Zhou, Wen-Jun, Da-Gang Yu, Yi-Han Zhang, Yong-Yuan Gui e Liang Sun. "Merging Transition-Metal Catalysis with Photoredox Catalysis: An Environmentally Friendly Strategy for C–H Functionalization". Synthesis 50, n. 17 (8 agosto 2018): 3359–78. http://dx.doi.org/10.1055/s-0037-1610222.
Testo completoAbstract (sommario):
Transition-metal-catalyzed C–H functionalization is already a useful tool in organic synthesis, whilst the rapid development of photoredox catalysis provides new pathways for C–H functionalization with high selectivity and efficiency under mild reaction conditions. In this review, recent advances in C–H functionalization through merging transition-metal catalysis with photoredox catalysis are discussed.1 Introduction2 Merging Nickel Catalysis with Photoredox Catalysis3 Merging Palladium Catalysis with Photoredox Catalysis4 Merging Cobalt Catalysis with Photoredox Catalysis5 Merging Photoredox Catalysis with Other Transition-Metal Catalysis6 Conclusions
14
Miceli, Mariachiara, Patrizia Frontera, Anastasia Macario e Angela Malara. "Recovery/Reuse of Heterogeneous Supported Spent Catalysts". Catalysts 11, n. 5 (1 maggio 2021): 591. http://dx.doi.org/10.3390/catal11050591.
Testo completoAbstract (sommario):
The rapid separation and efficient recycling of catalysts after a catalytic reaction are considered important requirements along with the high catalytic performances. In this view, although heterogeneous catalysis is generally less efficient if compared to the homogeneous type, it is generally preferred since it benefits from the easy recovery of the catalyst. Recycling of heterogeneous catalysts using traditional methods of separation such as extraction, filtration, vacuum distillation, or centrifugation is tedious and time-consuming. They are uneconomic processes and, hence, they cannot be carried out in the industrial scale. For these limitations, today, the research is devoted to the development of new methods that allow a good separation and recycling of catalysts. The separation process should follow a procedure economically and technically feasible with a minimal loss of the solid catalyst. The aim of this work is to provide an overview about the current trends in the methods of separation/recycling used in the heterogeneous catalysis.
15
Zhai, Peng, Geng Sun, Qingjun Zhu e Ding Ma. "Fischer-Tropsch synthesis nanostructured catalysts: understanding structural characteristics and catalytic reaction". Nanotechnology Reviews 2, n. 5 (1 ottobre 2013): 547–76. http://dx.doi.org/10.1515/ntrev-2013-0025.
Testo completoAbstract (sommario):
AbstractOne key goal of heterogeneous catalysis study is to understand the correlation between the catalyst structure and its corresponding catalytic activity. In this review, we focus on recent strategies to synthesize well-defined Fischer-Tropsch synthesis (FTS) nanostructured catalysts and their catalytic performance in FTS. The development of those promising catalysts highlights the potentials of nanostructured materials to unravel the complex and dynamic reaction mechanism, particularly under the in situ reaction conditions. The crucial factors associated with the catalyst compositions and structures and their effects on the FTS activities are discussed with an emphasis on the role of theoretical modeling and experimental results.
16
Cottone, Grazia, Sergio Giuffrida, Stefano Bettati, Stefano Bruno, Barbara Campanini, Marialaura Marchetti, Stefania Abbruzzetti et al. "More than a Confinement: “Soft” and “Hard” Enzyme Entrapment Modulates Biological Catalyst Function". Catalysts 9, n. 12 (4 dicembre 2019): 1024. http://dx.doi.org/10.3390/catal9121024.
Testo completoAbstract (sommario):
Catalysis makes chemical and biochemical reactions kinetically accessible. From a technological point of view, organic, inorganic, and biochemical catalysis is relevant for several applications, from industrial synthesis to biomedical, material, and food sciences. A heterogeneous catalyst, i.e., a catalyst confined in a different phase with respect to the reagents’ phase, requires either its physical confinement in an immobilization matrix or its physical adsorption on a surface. In this review, we will focus on the immobilization of biological catalysts, i.e., enzymes, by comparing hard and soft immobilization matrices and their effect on the modulation of the catalysts’ function. Indeed, unlike smaller molecules, the catalytic activity of protein catalysts depends on their structure, conformation, local environment, and dynamics, properties that can be strongly affected by the immobilization matrices, which, therefore, not only provide physical confinement, but also modulate catalysis.
17
Patil, Siddappa A., Shivaputra A. Patil e Renukadevi Patil. "Magnetic Nanoparticles Supported Carbene and Amine Based Metal Complexes in Catalysis". Journal of Nano Research 42 (luglio 2016): 112–35. http://dx.doi.org/10.4028/www.scientific.net/jnanor.42.112.
Testo completoAbstract (sommario):
Catalysis is one of the hottest research topics in chemistry. In recent years, metal complexes attracted great interest as catalysts towards various types of organic reactions. However, these catalysts, in most cases, suffer from the deficits during their recovery, recycling and the difficulty in separation of catalysts from the products. Therefore, the design and synthesis of recoverable and recyclable catalyst is very important aspect in catalysis. The aim of this review article is to highlight the speedy growth in the synthesis and catalytic applications of magnetic nanoparticles (Fe3O4, MNPs) supported N-heterocyclic carbene (NHC) and amine based metal complexes in various organic reactions. Furthermore, these catalysts can be easily separated from the reaction media with the external magnet and reused various times without a substantial loss of catalytic activity.
18
Tang, Xiaolong, Xianmang Xu, Honghong Yi, Chen Chen e Chuan Wang. "Recent Developments of Electrochemical Promotion of Catalysis in the Techniques of DeNOx". Scientific World Journal 2013 (2013): 1–13. http://dx.doi.org/10.1155/2013/463160.
Testo completoAbstract (sommario):
Electrochemical promotion of catalysis reactions (EPOC) is one of the most significant discoveries in the field of catalytic and environmental protection. The work presented in this paper focuses on the aspects of reaction mechanism, influencing factors, and recent positive results. It has been shown with more than 80 different catalytic systems that the catalytic activity and selectivity of conductive catalysts deposited on solid electrolytes can be altered in the last 30 years. The active ingredient of catalyst can be activated by applying constant voltage or constant current to the catalysts/electrolyte interface. The effect of EPOC can improve greatly the conversion rate of NOx. And it can also improve the lifetime of catalyst by inhibiting its poisoning.
19
Gao, Yan, Wenchao Jiang, Tao Luan, Hui Li, Wenke Zhang, Wenchen Feng e Haolin Jiang. "High-Efficiency Catalytic Conversion of NOx by the Synergy of Nanocatalyst and Plasma: Effect of Mn-Based Bimetallic Active Species". Catalysts 9, n. 1 (18 gennaio 2019): 103. http://dx.doi.org/10.3390/catal9010103.
Testo completoAbstract (sommario):
Three typical Mn-based bimetallic nanocatalysts of Mn−Fe/TiO2, Mn−Co/TiO2, Mn−Ce/TiO2 were synthesized via the hydrothermal method to reveal the synergistic effects of dielectric barrier discharge (DBD) plasma and bimetallic nanocatalysts on NOx catalytic conversion. The plasma-catalyst hybrid catalysis was investigated compared with the catalytic effects of plasma alone and nanocatalyst alone. During the catalytic process of catalyst alone, the catalytic activities of all tested catalysts were lower than 20% at ambient temperature. While in the plasma-catalyst hybrid catalytic process, NOx conversion significantly improved with discharge energy enlarging. The maximum NOx conversion of about 99.5% achieved over Mn−Ce/TiO2 under discharge energy of 15 W·h/m3 at ambient temperature. The reaction temperature had an inhibiting effect on plasma-catalyst hybrid catalysis. Among these three Mn-based bimetallic nanocatalysts, Mn−Ce/TiO2 displayed the optimal catalytic property with higher catalytic activity and superior selectivity in the plasma-catalyst hybrid catalytic process. Furthermore, the physicochemical properties of these three typical Mn-based bimetallic nanocatalysts were analyzed by N2 adsorption, Transmission Electron Microscope (TEM), X-ray diffraction (XRD), H2-temperature-programmed reduction (TPR), NH3-temperature-programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS). The multiple characterizations demonstrated that the plasma-catalyst hybrid catalytic performance was highly dependent on the phase compositions. Mn−Ce/TiO2 nanocatalyst presented the optimal structure characteristic among all tested samples, with the largest surface area, the minished particle sizes, the reduced crystallinity, and the increased active components distributions. In the meantime, the ratios of Mn4+/(Mn2+ + Mn3+ + Mn4+) in the Mn−Ce/TiO2 sample was the highest, which was beneficial to plasma-catalyst hybrid catalysis. Generally, it was verified that the plasma-catalyst hybrid catalytic process with the Mn-based bimetallic nanocatalysts was an effective approach for high-efficiency catalytic conversion of NOx, especially at ambient temperature.
20
Liu, Jingyue. "Advanced Electron Microscopy Characterization of Nanostructured Heterogeneous Catalysts". Microscopy and Microanalysis 10, n. 1 (22 gennaio 2004): 55–76. http://dx.doi.org/10.1017/s1431927604040310.
Testo completoAbstract (sommario):
Heterogeneous catalysis is one of the oldest nanosciences. Although model catalysts can be designed, synthesized, and, to a certain degree, characterized, industrial heterogeneous catalysts are often chemically and physically complex systems that have been developed through many years of catalytic art, technology, and science. The preparation of commercial catalysts is generally not well controlled and is often based on accumulated experiences. Catalyst characterization is thus critical to developing new catalysts with better activity, selectivity, and/or stability. Advanced electron microscopy, among many characterization techniques, can provide useful information for the fundamental understanding of heterogeneous catalysis and for guiding the development of industrial catalysts. In this article, we discuss the recent developments in applying advanced electron microscopy techniques to characterizing model and industrial heterogeneous catalysts. The importance of understanding the catalyst nanostructure and the challenges and opportunities of advanced electron microscopy in developing nanostructured catalysts are also discussed.
21
Zhang, Xiaolong, Shilei Jin, Yuhan Zhang, Liyuan Wang, Yang Liu e Qian Duan. "One-Pot Facile Synthesis of Noble Metal Nanoparticles Supported on rGO with Enhanced Catalytic Performance for 4-Nitrophenol Reduction". Molecules 26, n. 23 (30 novembre 2021): 7261. http://dx.doi.org/10.3390/molecules26237261.
Testo completoAbstract (sommario):
In this study, reduced graphene oxide (rGO)-supported noble metal (gold, silver, and platinum) nanoparticle catalysts were prepared via the one-pot facile co-reduction technique. Various measurement techniques were used to investigate the structures and properties of the catalysts. The relative intensity ratios of ID/IG in rGO/Au, rGO/Ag, rGO/Pt, and GO were 1.106, 1.078, 1.047, and 0.863, respectively. The results showed the formation of rGO and that noble metal nanoparticles were decorated on rGO. Furthermore, the catalytic activities of the designed nanocomposites were investigated via 4-nitrophenol. The catalysts were used in 4-nitrophenol reduction. The catalytic performance of the catalysts was evaluated using the apparent rate constant k values. The k value of rGO/Au was 0.618 min−1, which was higher than those of rGO/Ag (0.55 min−1) and rGO/Pt (0.038 min−1). The result proved that the rGO/Au catalyst exhibited a higher catalytic performance than the rGO/Ag catalyst and the rGO/Pt catalyst. The results provide a facile method for the synthesis of rGO-supported nanomaterials in catalysis.
22
BOUSBA, DALILA, CHAFIA SOBHI, AMNA ZOUAOUI e SOUAD BOUASLA. "Synthesis of activated carbon sand their application in the synthesis of monometallic and bimetallic supported catalysts". Algerian Journal of Signals and Systems 5, n. 4 (15 dicembre 2020): 190–96. http://dx.doi.org/10.51485/ajss.v5i4.116.
Testo completoAbstract (sommario):
Biomass-derived porous carbons are attractive materials for the synthesis of carbon-supported catalysts, carbonaceous catalysts are environmentally benign and could provide an important competitive advantage as compared to existing heterogeneous catalysts, however the surface properties of carbon materials and excellent physical and chemical properties are compatible with diverse catalysis reactions including organic transformations. Currently, activated carbons are one of well known carbonaceous materials for their catalytic properties and for use as support in heterogeneous catalysis. The supported catalysts have been successfully used in the chemical industries for a long time, in which carbon supported catalysts have allowed to a new chemical catalytic process, on the other hand Heterogeneous catalysis plays a key role in the manufacture of essential products in different fields. In this paper, we present a comparative study, between two main different methods for activated carbons (ACs) preparation namely, physical and chemical activations. Latter was prepared from agro-industrial biomass and used as a support to prepare monometallic (dry impregnation and excess impregnation) and bimetallic catalyst (successive impregnation and co impregnation).
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Xu, Jun Qiang, Fang Guo, Shu Shu Zou e Xue Jun Quan. "Optimization of the Catalytic Wet Peroxide Oxidation of Phenol over the Fe/NH4Y Catalyst". Materials Science Forum 694 (luglio 2011): 640–44. http://dx.doi.org/10.4028/www.scientific.net/msf.694.640.
Testo completoAbstract (sommario):
The heterogeneous NH4Y zeolite-supported iron catalysts were prepared by incipient wetness impregnation. The catalysis oxidation degradation of phenol was carried over the heterogeneous catalyst in the peroxide catalytic oxidation process. Compared with the homogeneous Fenton process, the Fe/ NH4Y-acid catalyst can effectively degrade contaminants with high catalytic activity and easy catalyst separation from the solution. The phenol removal efficiency could reach 96% in the optimum experimental conditions. These process conditions were as follows: iron content is 5%, reaction time was 60 min, reaction temperature was 70 oC, the catalyst dosage was 1g/L, the H2O2 concentration was 1.65g/L.
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Chen, Jianfeng, Xing Gong, Jianyu Li, Yingkun Li, Jiguo Ma, Chengkang Hou, Guoqing Zhao, Weicheng Yuan e Baoguo Zhao. "Carbonyl catalysis enables a biomimetic asymmetric Mannich reaction". Science 360, n. 6396 (28 giugno 2018): 1438–42. http://dx.doi.org/10.1126/science.aat4210.
Testo completoAbstract (sommario):
Chiral amines are widely used as catalysts in asymmetric synthesis to activate carbonyl groups for α-functionalization. Carbonyl catalysis reverses that strategy by using a carbonyl group to activate a primary amine. Inspired by biological carbonyl catalysis, which is exemplified by reactions of pyridoxal-dependent enzymes, we developed an N-quaternized pyridoxal catalyst for the asymmetric Mannich reaction of glycinate with aryl N-diphenylphosphinyl imines. The catalyst exhibits high activity and stereoselectivity, likely enabled by enzyme-like cooperative bifunctional activation of the substrates. Our work demonstrates the catalytic utility of the pyridoxal moiety in asymmetric catalysis.
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Galiwango, Emmanuel, James Butler e Samira Lotfi. "A Review of Catalyst Integration in Hydrothermal Gasification". Fuels 5, n. 3 (23 agosto 2024): 375–93. http://dx.doi.org/10.3390/fuels5030022.
Testo completoAbstract (sommario):
Industrial scale-up of hydrothermal supercritical water gasification process requires catalytic integration to reduce the high operational temperatures and pressures to enhance controlled chemical reaction pathways, product yields, and overall process economics. There is greater literature disparity in consensus on what is the best catalyst and reactor design for hydrothermal gasification. This arises from the limited research on catalysis in continuous flow hydrothermal systems and rudimentary lab-scale experimentation on simple biomasses. This review summarizes the literature status of catalytic hydrothermal processing, especially for continuous gasification and in situ catalyst handling. The rationale for using low and high temperatures during catalytic hydrothermal processing is highlighted. The role of homogeneous and heterogeneous catalysts in hydrothermal gasification is presented. In addition, the rationale behind certain designs and component selection for catalytic investigations in continuous hydrothermal conversion is highlighted. Furthermore, the effect of different classes of catalysts on the reactor and reactions are elaborated. Overall, design and infrastructural challenges such as plugging, corrosion, agglomeration of the catalysts, catalyst metal leaching, and practical assessment of catalyst integration towards enhancement of process economics still present open questions. Therefore, strategies for catalytic configuration in continuous hydrothermal process must be evaluated on a system-by-system basis depending on the feedstock and experimental goals.
26
Li, Siyi, Shuo Cheng e Jeffrey S. Cross. "Homogeneous and Heterogeneous Catalysis Impact on Pyrolyzed Cellulose to Produce Bio-Oil". Catalysts 10, n. 2 (3 febbraio 2020): 178. http://dx.doi.org/10.3390/catal10020178.
Testo completoAbstract (sommario):
Effectively utilizing catalytic pyrolysis to upgrade bio-oil products prepared from biomass has many potential benefits for the environment. In this paper, cellulose (a major component of plants and a biomass model compound) is pyrolyzed and catalyzed with different catalysts: Ni2Fe3, ZSM-5, and Ni2Fe3/ZSM-5. Two different pyrolysis processes are investigated to compare homogeneous and heterogeneous catalysis influence on the products. The results indicate that the Ni2Fe3 cluster catalyst shows the best activity as a homogeneous catalysis. It can also be recycled repeatedly, increases the yield of bio-oil, and improves the quality of the bio-oil by decreasing the sugar concentration. Furthermore, it also catalyzes the formation of a small amount of hydrocarbon compounds. In the case of Ni2Fe3/ZSM-5 catalyst, it shows a lower yield of bio-oil but also decreases the sugar concentration significantly. Ni2Fe3, not only can it be used as homogeneous catalysis mixed with cellulose but also shows catalytic activity as a supported catalyst on ZSM-5, with higher catalytic activity than ZSM-5. These results indicate that the Ni2Fe3 catalyst has significant activity for potential use in industry to produce high quality bio-oil from biomass.
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Md Ali, Siti Aminah, Ku Halim Ku Hamid e Kamariah Noor Ismail. "Effect of Ni/Co Ratio on Bimetallic Oxide Supported Silica Catalyst in CO2 Methanation". Applied Mechanics and Materials 802 (ottobre 2015): 431–36. http://dx.doi.org/10.4028/www.scientific.net/amm.802.431.
Testo completoAbstract (sommario):
Five series of silica supported bimetallic oxide (NiCo/SiO2) catalysts have been synthesized through successive reverse co-precipitation and wet impregnation methods at different metal loadings (i.e. 80Ni20Co/SiO2,, 60Ni40Co/SiO2,50Ni50Co/SiO2,40Ni60Co/SiO2,20Ni80Co/SiO2). The catalytic performance of these catalysts were tested for the CO2methanation catalysis using microactivity fixed bed reactor. Nickel rich catalyst (80Ni20Co/SiO2) exhibited the highest catalytic activity in the CO2methanation with 47.1% of CO2conversion. Meanwhile, the CH4selectivity and yield was found to be at 99.9% and 27%, respectively.
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Chen, Huihui, Zhenhua Dong e Jun Yue. "Advances in Microfluidic Synthesis of Solid Catalysts". Powders 1, n. 3 (4 agosto 2022): 155–83. http://dx.doi.org/10.3390/powders1030011.
Testo completoAbstract (sommario):
Heterogeneous catalysis plays a central role in the chemical and energy fields, owing to the high and tunable activities of solid catalysts that are essential to achieve the favorable reaction process efficiency, and their ease of recycle and reuse. Numerous research efforts have been focused on the synthesis of solid catalysts towards obtaining the desired structure, property and catalytic performance. The emergence and development of microfluidic reactor technology provide a new and attractive platform for the controllable synthesis of solid catalysts, primarily because of its superior mixing performance and high heat/mass transfer efficiency. In this review, the recent research progress on the synthesis of solid catalysts based on microfluidic reactor technology is summarized. The first section deals with the synthesis strategies for solid catalysts, including conventional methods in batch reactors and microfluidic alternatives (based on single- and two-phase flow processing). Then, different kinds of solid catalysts synthesized in microflow are discussed, especially with regard to the catalyst type, synthetic process, structure and property, and catalytic performance. Finally, challenges in the microreactor operation and scale-up, as well as future perspectives in terms of the synthesis of more types of catalysts, catalyst performance improvement, and the combination of catalyst synthesis process and catalytic reaction in microreactors, are provided.
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Ma, Yubo, Zhixian Gao, Tao Yuan e Tianfu Wang. "Kinetics of Dicyclopentadiene Hydroformylation over Rh–SiO2 Catalysts". Progress in Reaction Kinetics and Mechanism 42, n. 2 (maggio 2017): 191–99. http://dx.doi.org/10.3184/146867817x14821527549013.
Testo completoAbstract (sommario):
The hydroformylation of dicyclopentadiene (DCPD) to monoformyltricyclodecenes (MFTD) represents a key intermediate step in the conversion of the C5 fraction derived from the petrochemical process to value-added fine chemicals, for example, diformyltricyclodecanes and tricyclodecanedimethylol. Although both heterogeneous and homogeneous catalysts can catalyse this reaction, the heterogeneously catalysed pathway has received significantly less attention due to its lower catalytic activities. We demonstrate in this work that a low Rh loaded heterogeneous 0.1% Rh–SiO2 catalyst can present a similar performance relative to the homogeneous Rh(PPh3)Cl, a reference catalyst for this reaction. Furthermore, an extensive kinetic study of DCPD hydroformylation to MFTD using heterogeneous 0.1% Rh–SiO2 catalysts has been performed. A series of kinetic experiments was carried out over a broad range of conditions (temperature: 100–120 °C; pressure: 1.5–5 MPa; catalyst-to-reactant mass ratio: 0.02–0.05; PPh3 concentration: 5–12.5 g L−1). A kinetic analysis was carried out, indicating the activation energy for the reaction to be 84.7 kJ mol−1. DCPD conversion and MFTD yield could be optimised to be as high as 99% at 0.1% Rh loading, a DCPD/catalyst mass ratio of 25, a PPh3 concentration of 10 g L−1, a reaction time of 4 h and a reaction pressure of 4 MPa.
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Gamaliia, Vira, Artem Zabuga e Gennadii Zabuga. "On the History of Developing Catalysis in Ukraine (1850s–1980s)". Acta Baltica Historiae et Philosophiae Scientiarum 11, n. 2 (15 dicembre 2023): 76–92. http://dx.doi.org/10.11590/abhps.2023.2.04.
Testo completoAbstract (sommario):
The article is dedicated to the history of developing highly effective catalysts in the leading scientific institutions of Ukraine and explores the prerequisites for developing theories in physical chemistry, in particular those related to kinetics and catalysis. It highlights the significance of scientific discoveries at the turn of the 19th and 20th century and their application by native scientists to advance theoretical development in the field of chemistry. Special attention is paid to the works of Lev Pisarzhevskii, focusing on his advancements in electronic chemistry and, in particular, the electronic theory of catalysis. The article also outlines current challenges in creating highly efficient catalysts for the chemical and light industry, emphasizing the importance of such indicators of catalysts as activity and selectivity. Drawing on historical, scientific and patent data, the study investigates the process of creating a highly efficient catalyst for obtaining acrylic acid from acrolein. This catalyst holds a great ractical importance for the production of various polymers in industrial conditions. It is shown that, as a result of research conducted by native scientists of the Institute of Physical Chemistry of the Academy of Sciences of the Ukrainian SSR and the Chemistry Department of Kyiv State University, the catalyst K-2-5 was developed. The catalyst has good indicators for the industrial production of acrylic acid from acrolein. The authors also highlight works studying the properties of the obtained catalyst, specifically its porous structure, which is an important factor in catalytic processes. They extensively focus on the kinetic indicators of catalytic reactions that occur when using this catalyst. The article also emphasizes the relevance of these developments for advancing research in catalysis and chemical industrial production.
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Chen, Qi, Zhigang Qi, Zhaoxuan Wang, Ziqi Song e Weimin Wang. "Recent Advances in and Challenges with Fe-Based Metallic Glasses for Catalytic Efficiency: Environment and Energy Fields". Materials 17, n. 12 (14 giugno 2024): 2922. http://dx.doi.org/10.3390/ma17122922.
Testo completoAbstract (sommario):
Metallic glass is being gradually recognized for its unique disordered atomic configuration and excellent catalytic activity, so is of great significance in the field of catalysis. Recent reports have demonstrated that Fe-based metallic glass, as a competitive new catalyst, has good catalytic activity for the fields of environment and energy, including high catalytic efficiency and stability. This review introduces the latest developments in metallic glasses with various atomic components and their excellent catalytic properties as catalysts. In this article, the influence of Fe-based metallic glass catalysts on the catalytic activity of dye wastewater treatment and water-splitting is discussed. The catalytic performance in different atomic composition systems and different water environment systems, and the preparation parameters to improve the surface activity of catalysts, are reviewed. This review also describes several prospects in the future development and practical application of Fe-based metallic glass catalysts and provides a new reference for the synthesis of novel catalysts.
32
Lu, Dongsheng, Yufa Feng, Zitian Ding, Jinyun Liao, Xibin Zhang, Hui-Ru Liu e Hao Li. "MoO3-Doped MnCo2O4 Microspheres Consisting of Nanosheets: An Inexpensive Nanostructured Catalyst to Hydrolyze Ammonia Borane for Hydrogen Generation". Nanomaterials 9, n. 1 (24 dicembre 2018): 21. http://dx.doi.org/10.3390/nano9010021.
Testo completoAbstract (sommario):
Production of hydrogen by catalytically hydrolyzing ammonia borane (AB) has attracted extensive attention in the field of catalysis and energy. However, it is still a challenge to develop a both inexpensive and active catalyst for AB hydrolysis. In this work, we designed a series of MoO3-doped MnCo2O4 (x) catalysts, which were fabricated by a hydrothermal process. The morphology, crystalline structure, and chemical components of the catalysts were systematically analyzed. The catalytic behavior of the catalyst in AB hydrolysis was investigated. Among these catalysts, MoO3-doped MnCo2O4 (0.10) microspheres composed of nanosheets exhibited the highest catalytic activity. The apparent activation energy is 34.24 kJ mol−1 and the corresponding turnover frequency is 26.4 molhydrogen min−1 molcat−1. Taking into consideration the low cost and high performance, the MoO3-doped MnCo2O4 (0.10) microspheres composed of nanosheets represent a promising catalyst to hydrolyze AB for hydrogen production.
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Trigoura, Leslie, Yalan Xing e Bhanu P. S. Chauhan. "Recyclable Catalysts for Alkyne Functionalization". Molecules 26, n. 12 (9 giugno 2021): 3525. http://dx.doi.org/10.3390/molecules26123525.
Testo completoAbstract (sommario):
In this review, we present an assessment of recent advances in alkyne functionalization reactions, classified according to different classes of recyclable catalysts. In this work, we have incorporated and reviewed the activity and selectivity of recyclable catalytic systems such as polysiloxane-encapsulated novel metal nanoparticle-based catalysts, silica–copper-supported nanocatalysts, graphitic carbon-supported nanocatalysts, metal organic framework (MOF) catalysts, porous organic framework (POP) catalysts, bio-material-supported catalysts, and metal/solvent free recyclable catalysts. In addition, several alkyne functionalization reactions have been elucidated to demonstrate the success and efficiency of recyclable catalysts. In addition, this review also provides the fundamental knowledge required for utilization of green catalysts, which can combine the advantageous features of both homogeneous (catalyst modulation) and heterogeneous (catalyst recycling) catalysis.
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Vayenas, C. G., S. Bebelis, I. V. Yentekakis, P. Tsiakaras e H. Karasali. "Non-Faradaic Electrochemical Modification of Catalytic Activity". Platinum Metals Review 34, n. 3 (1 luglio 1990): 122–30. http://dx.doi.org/10.1595/003214090x343122130.
Testo completoAbstract (sommario):
The catalytic activity and selectivity of platinum metals can be altered dramatically and reversibly by interfacing the metal with a solid electrolyte which supplies ions onto the catalyst surface under the influence of an external potential. The induced change in catalytic rate is orders of magnitude higher than the rate of ion supply. This new effect has revealed a surprisingly simple exponential relationship between catalytic activity and catalyst work function. The effect appears to apply to all heterogeneously catalysed reactions, but is particularly pronounced for platinum. This interfacing of electrochemistry and catalysis appears to offer some exciting theoretical and technological possibilities.
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Dadashi-Silab, Sajjad, e Krzysztof Matyjaszewski. "Iron Catalysts in Atom Transfer Radical Polymerization". Molecules 25, n. 7 (3 aprile 2020): 1648. http://dx.doi.org/10.3390/molecules25071648.
Testo completoAbstract (sommario):
Catalysts are essential for mediating a controlled polymerization in atom transfer radical polymerization (ATRP). Copper-based catalysts are widely explored in ATRP and are highly efficient, leading to well-controlled polymerization of a variety of functional monomers. In addition to copper, iron-based complexes offer new opportunities in ATRP catalysis to develop environmentally friendly, less toxic, inexpensive, and abundant catalytic systems. Despite the high efficiency of iron catalysts in controlling polymerization of various monomers including methacrylates and styrene, ATRP of acrylate-based monomers by iron catalysts still remains a challenge. In this paper, we review the fundamentals and recent advances of iron-catalyzed ATRP focusing on development of ligands, catalyst design, and techniques used for iron catalysis in ATRP.
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Du, Yuan-Peng, e Jeremy S. Luterbacher. "Designing Heterogeneous Catalysts for Renewable Catalysis Applications Using Metal Oxide Deposition". CHIMIA International Journal for Chemistry 73, n. 9 (18 settembre 2019): 698–706. http://dx.doi.org/10.2533/chimia.2019.698.
Testo completoAbstract (sommario):
Heterogeneous catalysis has long been a workhorse for the chemical industry and will likely play a key role in the emerging area of renewable chemistry. However, renewable molecule streams pose unique challenges for heterogeneous catalysis due to their high oxygen content, frequent low volatility and the near constant presence of water. These constraints can often lead to the need for catalyst operation in harsh liquid phase conditions, which has compounded traditional catalyst deactivation issues. Oxygenated molecules are also frequently more reactive than petroleum-derived molecules, which creates a need for highly selective catalysts. Synthetic control over the nanostructured environment of catalytic active sites could facilitate the creation of both more stable and selective catalysts. In this review, we discuss the use of metal oxide deposition as an emerging strategy that can be used to synthesize and/or modify heterogeneous catalysts to introduce tailored nanostructures. Several important applications are reviewed, including the synthesis of high surface area mesoporous metal oxides, the enhancement of catalyst stability, and the improvement of catalyst selectivity.
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Zhou, Hong-Jie, Chun-Lei Song, Li-Ping Si, Xu-Jia Hong e Yue-Peng Cai. "The Development of Catalyst Materials for the Advanced Lithium–Sulfur Battery". Catalysts 10, n. 6 (17 giugno 2020): 682. http://dx.doi.org/10.3390/catal10060682.
Testo completoAbstract (sommario):
The lithium–sulfur battery is considered as one of the most promising next-generation energy storage systems owing to its high theoretical capacity and energy density. However, the shuttle effect in lithium–sulfur battery leads to the problems of low sulfur utilization, poor cyclability, and rate capability, which has attracted the attention of a large number of researchers in the recent years. Among them, the catalysts with efficient catalytic function for lithium polysulfides (LPSs) can effectively inhibit the shuttle effect. This review outlines the progress of catalyst materials for lithium–sulfur battery in recent years. Based on the structure and properties of the reported catalysts, the development of the reported catalyst materials for LPSs was divided into three generations. We can find that the design of highly efficient catalytic materials needs to consider not only strong chemical adsorption on polysulfides, but also good conductivity, catalysis, and mass transfer. Finally, the perspectives and outlook of reasonable design of catalyst materials for high performance lithium–sulfur battery are put forward. Catalytic materials with high conductivity and both lipophilic and thiophile sites will become the next-generation catalytic materials, such as heterosingle atom catalysis and heterometal carbide. The development of these catalytic materials will help catalyze LPSs more efficiently and improve the reaction kinetics, thus providing guarantee for lithium sulfur batteries with high load or rapid charge and discharge, which will promote the practical application of lithium–sulfur battery.
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Limlamthong, Mutjalin, Nithinart Chitpong e Bunjerd Jongsomjit. "Influence of Phosphoric Acid Modification on Catalytic Properties of γ-χ Al2O3 Catalysts for Dehydration of Ethanol to Diethyl Ether". Bulletin of Chemical Reaction Engineering & Catalysis 14, n. 1 (15 aprile 2019): 1. http://dx.doi.org/10.9767/bcrec.14.1.2436.1-8.
Testo completoAbstract (sommario):
In this present work, diethyl ether, which is currently served as promising alternative fuel for diesel engines, was produced via catalytic dehydration of ethanol over H3PO4-modified g-c Al2O3 catalysts. The impact of H3PO4 addition on catalytic performance and characteristics of catalysts was investigated. While catalytic dehydration of ethanol was performed in a fixed-bed microreactor at the temperature ranging from 200ºC to 400ºC under atmospheric pressure, catalyst characterization was conducted by inductively coupled plasma (ICP), X-ray diffraction (XRD), N2 physisorption, temperature-programmed desorption of ammonia (NH3-TPD) and thermogravimetric (TG) analysis. The results showed that although the H3PO4 addition tended to decrease surface area of catalyst resulting in the reduction of ethanol conversion, the Al2O3 containing 5 wt% of phosphorus (5P/Al2O3) was the most suitable catalyst for the catalytic dehydration of ethanol to diethyl ether since it exhibited the highest catalytic ability regarding diethyl ether yield and the quantity of coke formation as well as it had similar long-term stability to conventional Al2O3 catalyst. The NH3-TPD profiles of catalysts revealed that catalysts containing more weak acidity sites were preferred for dehydration of ethanol into diethyl ether and the adequate promotion of H3PO4 would lower the amount of medium surface acidity with increasing catalyst weak surface acidity. Nevertheless, when the excessive amount of H3PO4 was introduced, it caused the destruction of catalysts structure, which resulted in the catalyst incapability due to the decrease in active surface area and pore enlargement. Copyright © 2019 BCREC Group. All rights reservedReceived: 28th March 2018; Revised: 7th August 2018; Accepted: 15th August 2018; Available online: 25th January 2019; Published regularly: April 2019How to Cite: Limlamthong, M., Chitpong, N., Jongsomjit, B. (2019). Influence of Phosphoric Acid Modification on Catalytic Properties of g-c Al2O3 Catalysts for Dehydration of Ethanol to Diethyl Ether. Bulletin of Chemical Reaction Engineering & Catalysis, 14 (1): 1-8 (doi:10.9767/bcrec.14.1.2436.1-8)Permalink/DOI: https://doi.org/10.9767/bcrec.14.1.2436.1-8
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Liang, Wenjun, Xiujuan Shi, Qinglei Li, Sida Ren e Guobin Yin. "Effect of Pd/Ce Loading and Catalyst Components on the Catalytic Abatement of Toluene". Catalysts 12, n. 2 (16 febbraio 2022): 225. http://dx.doi.org/10.3390/catal12020225.
Testo completoAbstract (sommario):
Monolithic catalysts are widely used in industrial catalysis. However, in the preparation of a monolithic catalyst, the traditional methods have some drawbacks such as low washcoat uploading ratio and poor uniformity. In the present work, the effects of Pd/Ce loading and catalyst components on the catalytic abatement of toluene were investigated. The acid treatment of the substrate, the particle size of the slurry and the dispersant on the uniformity of the washcoat and the catalytic performance were also explored. Characterisation was achieved via BET, SEM, zeta potential and laser grain-size analyses. The results showed that the catalytic activity of the catalyst increased with the increasing of the Ce content. It was found that the 0.2Pd-0.3Ce/γ-Al2O3 catalysts had the best toluene catalytic activity. The pretreatment of the cordierite with 20% HCl could improve the properties of the cordierite. It was also found that reducing the particle size of the washcoat and adding dispersant PAA could effectively improve the stability of the suspension and the uniformity of the washcoat. When 20% HCl pretreatment was used, the toluene catalytic activity of the monolith catalyst prepared by cordierite increased, in which T10 and T90 decreased by about 5 °C. Decreasing the particle size and dispersant also promoted the efficiency of catalytic degradation.
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Pan, Dipika, e Jhuma Ganguly. "Assessment of Chitosan Based Catalyst and their Mode of Action". Current Organocatalysis 6, n. 2 (24 giugno 2019): 106–38. http://dx.doi.org/10.2174/2213337206666190327174103.
Testo completoAbstract (sommario):
Introduction:The popularity of chitosan is increasing among the researchers due to its environment friendly nature, high activity and easy approachability. Chitosan based catalysts are not only the most active and selective in catalytic reaction, but their “green” accessibility also makes them promising in organic catalysis. Chitosan is commonly extracted from chitin by alkaline deacetylation and it is the second abundant biopolymer in nature after cellulose. Chitosan based catalysts are advantageous by means of non-metallic activation as it involves small organic molecules. The robustness, nontoxicity, the lack of metal leaching possibility, inertness towards moisture and oxygen, easy handling and storage are the main advantages of organocatalysts. Traditional drawbacks associated with the metal-based heterogeneous catalysts, like longer reaction times during any synthesis, metal-leaching after every reaction and structural instability of the catalyst for prolonged recycling experiments are also very negligible for chitosan based catalysts. Besides, these catalysts can contribute more in catalysis due to their reusability and these special features increase their demand as the functionalized and profitable catalysts.Objective:The thorough description about the preparation of organocatalysts from chitosan and their uniqueness and novel activities in various famous reactions includes as the main aim of this review. Reusable and recycle nature of chitosan based organocatalysts gain the advantages over traditional and conventional catalyst which is further discussed over here.Methods and Discussions:In this article only those reactions are discussed where chitosan has been used both as support in heterogeneous catalysts or used as a catalyst itself without any co-catalyst for some reactions. Owing to its high biodegradability, nontoxicity, and antimicrobial properties, chitosan is widely-used as a green and sustainable polymeric catalyst in vast number of the reactions. Most of the preparations of catalyst have been achieved by exploring the complexation properties of chitosan with metal ions in heterogeneous molecular catalysis. Organocatalysis with chitosan is primarily discussed for carbon-carbon bond-forming reactions, carbon dioxide fixation through cyclo- addition reaction, condensation reaction and fine chemical synthesis reactions. Furthermore, its application as an enantioselective catalyst is also considered here for the chiral, helical organization of the chitosan skeleton. Moreover, another advantage of this polymeric catalyst is its easy recovery and reusability for several times under solvent-free conditions which is also explored in the current article.Conclusion:Important organocatalyzed reactions with either native chitosan or functionalized chitosan as catalysts have attracted great attention in the recent past. Also, chitosan has been widely used as a very promising support for the immobilization of catalytic metals for many reactions. In this review, various reactions have been discussed which show the potentiality of chitosan as catalyst or catalyst support.
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Fan, Guozhi, Min Wang, Zhenxiao Duan, Minghai Wan e Tao Fang. "Synthesis of Diphenyl Carbonate from Carbon Dioxide, Phenol, and Carbon Tetrachloride Catalysed by ZnCl2 Using Trifluoromethanesulfonic Acid as Functional Co-Catalyst". Australian Journal of Chemistry 65, n. 12 (2012): 1667. http://dx.doi.org/10.1071/ch12115.
Testo completoAbstract (sommario):
Diphenyl carbonate (DPC) was synthesised from carbon dioxide, phenol, and carbon tetrachloride catalysed by the Lewis acid ZnCl2 with the addition of co-catalyst. It was found that common bases are not effective co-catalysts for the production of DPC, and only slight enhancement in the catalytic activity of ZnCl2 was observed in the presence of inorganic additives such as inorganic carbonates and quaternary ammonium salts. Although poor conversion of phenol and yield of DPC were obtained using ZnCl2 or trifluoromethanesulfonic acid (CF3SO3H) as the sole catalyst, the catalytic activity of ZnCl2 was significantly improved by the addition of a catalytic amount of CF3SO3H. CF3SO3H has been proven to be an effective co-catalyst. The conversion of phenol and the yield of DPC were dependent on the amount of ZnCl2 and CF3SO3H, the reaction temperature, and the pressure of CO2. A possible reaction mechanism for the synthesis of DPC catalysed by the co-catalytic system including ZnCl2 and CF3SO3H was also proposed.
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Chen, Haimei, Shaofei Wang, Lilan Huang, Leitao Zhang, Jin Han, Wanzheng Ren, Jian Pan e Jiao Li. "Core-Shell Hierarchical Fe/Cu Bimetallic Fenton Catalyst with Improved Adsorption and Catalytic Performance for Congo Red Degradation". Catalysts 12, n. 11 (4 novembre 2022): 1363. http://dx.doi.org/10.3390/catal12111363.
Testo completoAbstract (sommario):
The preparation of heterogeneous Fenton catalysts with both adsorption and catalytic properties has become an effective strategy for the treatment of refractory organic wastewater. In this work, 4A-Fe@Cu bimetallic Fenton catalysts with a three-dimensional core-shell structure were prepared by a simple, template-free, and surfactant-free methodology and used in the adsorption and degradation of Congo red (CR). The results showed that the open three-dimensional network structure and the positive charge of the surface of the 4A-Fe@Cu catalyst could endow a high adsorption capacity for CR, reaching 432.9 mg/g. The good adsorption property of 4A-Fe@Cu for CR not only did not inactivate the catalytic site on 4A-Fe@Cu but also could promote the contact between CR and the active sites on the catalyst surface and accelerate the degradation process. The 4A-Fe@Cu bimetallic catalyst exhibited higher catalytic activity than monometallic 4A@Cu and/or 4A-Fe catalysts due to low work function value. The effects of different pH, H2O2 dosages, and catalyst dosages on the catalytic performance of 4A-Fe@Cu were explored. In the conditions of 7.2 mM H2O2, 2 g/L 4A-Fe@Cu, and 1 g/L CR solution, the degradation ratio of CR by 4A-Fe@Cu could reach 99.2% at pH 8. This strategy provided guidance to the design of high-performance Fenton-like catalysts with both adsorption and catalysis properties for dye wastewater treatment.
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Gates, Bruce C. "Concluding remarks: progress toward the design of solid catalysts". Faraday Discussions 188 (2016): 591–602. http://dx.doi.org/10.1039/c6fd00134c.
Testo completoAbstract (sommario):
The 2016 Faraday Discussion on the topic “Designing New Heterogeneous Catalysts” brought together a group of scientists and engineers to address forefront topics in catalysis and the challenge of catalyst design—which is daunting because of the intrinsic non-uniformity of the surfaces of catalytic materials. “Catalyst design” has taken on a pragmatic meaning which implies the discovery of new and better catalysts on the basis of fundamental understanding of the catalyst structure and performance. The presentations and discussion at the meeting illustrate the rapid progress in this understanding linked with improvements in spectroscopy, microscopy, theory, and catalyst performance testing. The following text includes a statement of recurrent themes in the discussion and examples of forefront science that evidences progress toward catalyst design.
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Zhang, Yujun, Hui Teng, Junpeng Chen, Rui Xia, Yujun Zhou, Kunlin Xie e Zhiyong Chen. "Application of Palladium Single Atoms in C−C Coupling Reactions of Pharmaceutical Synthesis". Advances in Computer and Engineering Technology Research 1, n. 1 (8 dicembre 2023): 192. http://dx.doi.org/10.61935/acetr.1.1.2023.p192.
Testo completoAbstract (sommario):
Designing highly active and structurally well-defined catalysts while reducing the amount of catalyst has become a key issue in heterogeneous catalytic reactions. In this study, palladium single-atom catalysts were prepared for efficient catalysis in the Suzuki cross-coupling reaction of iodobenzene and phenylboronic acid, which was prepared by one-step high-temperature pyrolysis. The palladium single-atom catalysts have high activity as well as stability in Suzuki cross-coupling reactions and have great potential in catalyzing organic reactions.
45
Hou, Zhiquan, Mengwei Hua, Yuxi Liu, Jiguang Deng, Xin Zhou, Ying Feng, Yifan Li e Hongxing Dai. "Exploring Intermetallic Compounds: Properties and Applications in Catalysis". Catalysts 14, n. 8 (18 agosto 2024): 538. http://dx.doi.org/10.3390/catal14080538.
Testo completoAbstract (sommario):
Intermetallic compounds (IMCs) have attracted significant attention in recent years due to their unique properties and potential applications in various fields, particularly in catalysis. This review aims to provide an in-depth understanding of IMCs, including their synthesis methods, structural characteristics, and diverse catalytic applications. The review begins with an introduction to IMCs, highlighting their distinct features and advantages over traditional catalyst materials. It then delves into the synthesis techniques employed to prepare IMCs and explores their structural properties. Subsequently, catalytic applications of the IMCs are introduced, focusing on the key reactions and highlighting their superior catalytic performance compared to conventional catalysts. Future perspectives for, and challenges to, the catalysis of IMCs are then proposed.
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Ortega-Caballero, Fernando, e Mikael Bols. "Cyclodextrin derivatives with cyanohydrin and carboxylate groups as artificial glycosidases". Canadian Journal of Chemistry 84, n. 4 (1 aprile 2006): 650–58. http://dx.doi.org/10.1139/v06-039.
Testo completoAbstract (sommario):
Two cyclodextrin derivatives (1 and 2) were prepared in an attempt to create glycosidase mimics with a general acid catalyst and a nucleophilic carboxylate group. The catalysts 1 and 2 were found to catalyse the hydrolysis of 4-nitrophenyl β-D-glucopyranoside at pH 8.0, but rapidly underwent decomposition with loss of hydrogen cyanide to convert the cyanohydrin to the corresponding aldehyde. The initial rate of the catalysis shows that the cyanohydrin group in these molecules functions as a good catalyst, but that the carboxylate has no positive effect. The decomposition product aldehydes display little or no catalysis. A mechanism for the decomposition is suggested.Key words: biomimicry, enzyme model, kinetics, intramolecular reaction.
47
Xu, Jun Qiang, Fang Guo, Jun Li, Xiu Zhi Ran e Yan Tang. "Synthesis of the Cu/Flokite Catalysts and their Performances for Catalytic Wet Peroxide Oxidation of Phenol". Advanced Materials Research 560-561 (agosto 2012): 869–72. http://dx.doi.org/10.4028/www.scientific.net/amr.560-561.869.
Testo completoAbstract (sommario):
The supported Cu/Flokite catalysts were prepared by conventional incipient wetness impregnation. The catalysis oxidation degradation of phenol was carried out in heterogeneous catalyst and H2O2 process. The results indicated that the reaction system with catalyst and hydrogen peroxide was more benefit to degradation of phenol. When the phenol initial concentration was 100 mg/L, the phenol removal over the 2.5%Cu -2.5% Fe/Flokite catalyst could reach 96%. The peroxide catalytic oxidation process over the enhanced heterogeneous catalyst would be a novel technique for the treatment of phenol wastewater.
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Crozier, P. A. "In Situ Characterization of Dynamic Changes in the Microstructure and Chemistry of Catalysts". Microscopy and Microanalysis 7, S2 (agosto 2001): 1058–59. http://dx.doi.org/10.1017/s1431927600031366.
Testo completoAbstract (sommario):
Controlled atmosphere electron microscopy (CAEM) is a form of in situ microscopy in which the sample is exposed to a reactive gas during observation. This instrument essentially combines the nano-structural characterization features of a TEM with a microreactor and is ideal for studying gas/solid reactions in catalysts. Such in situ techniques can provide a link between surface studies performed under UHV conditions and catalytic reactions run in high-pressure reactors. with correctly designed experiments, CAEM is a powerful technique for correlating dynamic changes in microstructure with catalysis and can be used to provide insights on the location of active sites and mechanisms for catalysis. Baker and colleagues have worked for over thirty years on different heterogeneous catalysts using in situ electron microscopy (see [1] for example). Gai has also published many studies on the application of CAEM to oxide catalysts [2].The technique usually relies on detecting a change in the heterogeneous catalyst during a catalytic reaction.
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Dabhane, Harshal, Suresh Ghotekar, Pawan Tambade, Shreyas Pansambal, Rajeshwari Oza e Vijay Medhane. "MgO nanoparticles: Synthesis, characterization, and applications as a catalyst for organic transformations". European Journal of Chemistry 12, n. 1 (31 marzo 2021): 86–108. http://dx.doi.org/10.5155/eurjchem.12.1.86-108.2060.
Testo completoAbstract (sommario):
Currently, the size and shape selective synthesis of nanoparticles (NPs) and their varied catalytic applications are gaining significant enthusiasm in the field of nanochemistry. Homogeneous catalysis is crucial due to its inherent benefits like high selectivity and mild reaction conditions. Nevertheless, it endures with serious disadvantages of catalysts and/or product separation/recycles compared to their heterogeneous counterparts restricting their catalytic applications. The utilization of catalysts in the form of nano-size is an elective methodology for the combination of merits of homogeneous and heterogeneous catalysis. Magnesium oxide (MgO) NPs are important as they find applications for catalysis, organic transformation, and synthesis of fine chemicals and organic intermediates. The applications of MgO NPs in diverse organic transformations including oxidation, reduction, epoxidation, condensation, and C-C, C-N, C-O, C-S bond formation in a variety of notable heterocyclic reactions are also discussed. The use of MgO NPs in organic transformation is advantageous as it mitigates the use of ligands; the procurable separation of catalyst for recyclability makes the protocol heterogeneous and monetary. MgO NPs gave efficacious catalytic performance towards the desired products due to high surface area. By considering these efficient merits, scientists have focused their attentions towards stupendous applications of MgO NPs in selective organic transformation. In the current review article, we summarized the synthesis of MgO NPs and numerous characterization techniques, whereas the application section illustrates their utility as a catalyst in several organic transformations. We believe this decisive appraisal will provide imperative details to further advance the application of MgO NPs in selective catalysis.
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Jia, Wenzhi, Xia Cai, Yong Zhang, Xiaohua Zuo, Juanjuan Yuan, Xinhua Liu, Zhirong Zhu e Xiangyi Deng. "Catalytic Dehydrofluorination of Hydrofluoroalkanes to Fluorinated Olifein Over Ni/AlF3 Catalysts". MATEC Web of Conferences 238 (2018): 03004. http://dx.doi.org/10.1051/matecconf/201823803004.
Testo completoAbstract (sommario):
The hydrofluoric acid-resisting aluminum compounds (AlF3, AlPO4, AlN) supported with Ni catalyst were prepared by the wetness impregnation and tested for dehydrofluorination of hydrofluoroalkane to synthesize fluoroolefins. It is found that Ni/AlF3 catalyst has the best catalytic performance, CF3CFH2 conversion of 29.3% after the reaction at 430 °C for 30 h, CF2HCH3 conversion of 31.8% after the reaction at 250 °C for 30 h, respectively. Comparatively, dehydrofluorination temperature of CF3CFH2 is higher than CF2HCH3 over the aluminum compounds catalyst, and the activity of catalysts is related with Lewis acidity. For the aluminum compounds catalyst, addition of Ni had promoted the activity and stability of Lewis acidic catalysts, it is attributed to synergistic catalysis of Lewis acid sites and Ni.