Journal articles: 'Heterogeneous catalysts modification'

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Mazaheri, Hoora, Hwai Chyuan Ong, Zeynab Amini, Haji Hassan Masjuki, M. Mofijur, Chia Hung Su, Irfan Anjum Badruddin, and T. M. Yunus Khan. "An Overview of Biodiesel Production via Calcium Oxide Based Catalysts: Current State and Perspective." Energies 14, no. 13 (July 1, 2021): 3950. http://dx.doi.org/10.3390/en14133950.

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Biodiesel is a clean, renewable, liquid fuel that can be used in existing diesel engines without modification as pure or blend. Transesterification (the primary process for biodiesel generation) via heterogeneous catalysis using low-cost waste feedstocks for catalyst synthesis improves the economics of biodiesel production. Heterogeneous catalysts are preferred for the industrial generation of biodiesel due to their robustness and low costs due to the easy separation and relatively higher reusability. Calcium oxides found in abundance in nature, e.g., in seashells and eggshells, are promising candidates for the synthesis of heterogeneous catalysts. However, process improvements are required to design productive calcium oxide-based catalysts at an industrial scale. The current work presents an overview of the biodiesel production advancements using calcium oxide-based catalysts (e.g., pure, supported, and mixed with metal oxides). The review discusses different factors involved in the synthesis of calcium oxide-based catalysts, and the effect of reaction parameters on the biodiesel yield of calcium oxide-based catalysis are studied. Further, the common reactor designs used for the heterogeneous catalysis using calcium oxide-based catalysts are explained. Moreover, the catalytic activity mechanism, challenges and prospects of the application of calcium oxide-based catalysts in biodiesel generation are discussed. The study of calcium oxide-based catalyst should continue to be evaluated for the potential of their application in the commercial sector as they remain the pivotal goal of these studies.

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Lemaire, Marc. "Heterogeneous asymmetric catalysis." Pure and Applied Chemistry 76, no. 3 (January 1, 2004): 679–88. http://dx.doi.org/10.1351/pac200476030679.

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Examples of enantioselective catalysts, including homogeneous supported catalysts and biphasic liquid/liquid, are described and compared. In the case of asymmetric hydride transfer, polythiourea was proven to be more efficient for ruthenium-catalyzed reduction of arylketones, although the iridium complexes gave rise to higher ee when using amino sulfonamide bound to a polystyrene matrix. In the case of asymmetric reduction, the modification of the binap allows the formation of a polymer that could be used as a catalyst precursor and exhibits enantioselectivities as high as observed in solution, but easier to separate and recycle. Bisoxazoline bound to silica particules could also be used in copper-catalyzed asymmetric Diels-Alder reaction and cyclopropanation with selectivities similar to that obtained in solution.

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Lokteva, Ekaterina S., Elena V. Golubina, Stanislav A. Kachevsky, Anara O. Turakulova, Valery V. Lunin, and Pietro Tundo. "Heterogeneous catalysts and process for reductive dechlorination of polychlorinated hydrocarbons." Pure and Applied Chemistry 79, no. 11 (January 1, 2007): 1905–14. http://dx.doi.org/10.1351/pac200779111905.

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The utilization and decomposition of chlorinated wastes without formation of dioxins are challenges of great environmental importance. In this work, the catalytic reductive methods of chlorinated organics processing are described, focusing on catalyst development. Pd-containing catalysts are improved by modification of supports [use of ultra dispersed diamond (UDD) or double oxides] or by dilution of Pd by not-noble metals (Fe, Ni, Cu). Both ways are effective for the processing of 1,3,5-trichlorobenzene (TCB) as a model of polychlorinated organics. The reasons for improvement of catalysts are discussed. The best catalysts were effectively used for hydrodechlorination (HDC) of hexachlorobenzene (HCB).

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Dobrescu, Gianina, Florica Papa, Razvan State, Monica Raciulete, Daniela Berger, Ioan Balint, and Niculae I. Ionescu. "Modified Catalysts and Their Fractal Properties." Catalysts 11, no. 12 (December 14, 2021): 1518. http://dx.doi.org/10.3390/catal11121518.

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Obtaining high-area catalysts is in demand in heterogeneous catalysis as it influences the ratio between the number of active surface sites and the number of total surface sites of the catalysts. From this point of view, fractal theory seems to be a suitable instrument to characterize catalysts’ surfaces. Moreover, catalysts with higher fractal dimensions will perform better in catalytic reactions. Modifying catalysts to increase their fractal dimension is a constant concern in heterogeneous catalysis. In this paper, scientific results related to oxide catalysts, such as lanthanum cobaltites and ferrites with perovskite structure, and nanoparticle catalysts (such as Pt, Rh, Pt-Cu, etc.) will be reviewed, emphasizing their fractal properties and the influence of their modification on both fractal and catalytic properties. Some of the methods used to compute the fractal dimension of the catalysts (micrograph fractal analysis and the adsorption isotherm method) and the computed fractal dimensions will be presented and discussed.

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Feng, Xuefeng, Zhi Gao, Longhui Xiao, Zhenqin Lai, and Feng Luo. "A Ni/Fe complex incorporated into a covalent organic framework as a single-site heterogeneous catalyst for efficient oxygen evolution reaction." Inorganic Chemistry Frontiers 7, no. 20 (2020): 3925–31. http://dx.doi.org/10.1039/d0qi00620c.

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Padmanaban, Sudakar, and Sungho Yoon. "Surface Modification of a MOF-based Catalyst with Lewis Metal Salts for Improved Catalytic Activity in the Fixation of CO2 into Polymers." Catalysts 9, no. 11 (October 26, 2019): 892. http://dx.doi.org/10.3390/catal9110892.

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The catalyst zinc glutarate (ZnGA) is widely used in the industry for the alternating copolymerization of CO2 with epoxides. However, the activity of this heterogeneous catalyst is restricted to the outer surface of its particles. Consequently, in the current study, to increase the number of active surface metal centers, ZnGA was treated with diverse metal salts to form heterogeneous, surface-modified ZnGA-Metal chloride (ZnGA-M) composite catalysts. These catalysts were found to be highly active for the copolymerization of CO2 and propylene oxide. Among the different metal salts, the catalysts treated with ZnCl2 (ZnGA-Zn) and FeCl3 (ZnGA-Fe) exhibited ~38% and ~25% increased productivities, respectively, compared to untreated ZnGA catalysts. In addition, these surface-modified catalysts are capable of producing high-molecular-weight polymers; thus, this simple and industrially viable surface modification method is beneficial from an environmental and industrial perspective.

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Trifan, Bianca, Javier Lasobras, Jaime Soler, Javier Herguido, and Miguel Menéndez. "Modifications in the Composition of CuO/ZnO/Al2O3 Catalyst for the Synthesis of Methanol by CO2 Hydrogenation." Catalysts 11, no. 7 (June 25, 2021): 774. http://dx.doi.org/10.3390/catal11070774.

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Renewable methanol, obtained from CO2 and hydrogen provided from renewable energy, was proposed to close the CO2 loop. In industry, methanol synthesis using the catalyst CuO/ZnO/Al2O3 occurs at a high pressure. We intend to make certain modification on the traditional catalyst to work at lower pressure, maintaining high selectivity. Therefore, three heterogeneous catalysts were synthesized by coprecipitation to improve the activity and the selectivity to methanol under mild conditions of temperature and pressure. Certain modifications on the traditional catalyst Cu/Zn/Al2O3 were employed such as the modification of the synthesis time and the addition of Pd as a dopant agent. The most efficient catalyst among those tested was a palladium-doped catalyst, 5% Pd/Cu/Zn/Al2O3. This had a selectivity of 64% at 210 °C and 5 bar.

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Duan, Haonan, Zanyao Niu, and Xiaoqi Yang. "Physical Properties of Cyclic Esters and its Application in Heterogeneous Electrocatalysis." Journal of Physics: Conference Series 2083, no. 2 (November 1, 2021): 022083. http://dx.doi.org/10.1088/1742-6596/2083/2/022083.

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Abstract Oxygen reduction is a key reaction in many energy conversion devices. Phosphorus-containing porous organic polymers not only have developed pores and surface structure, but also have strong adjustable modification and modification, so they have a wide application prospect in heterogeneous catalysis. At present, the preparation of phosphorus-containing porous organic polymers and their applications in heterogeneous catalysis have not been reviewed. in this paper, the research progress in this field in the past decade is summarized and reviewed. The synthetic methods of phosphorus-containing porous organic polymers are developing rapidly, including coupling Polycondensation, lithium salt-mediated Polycondensation, Friedel-Crafts Polycondensation, solvothermal olefin polymerization, Scholl Polycondensation, phenolic polymerization, aldehyde-amine condensation, phosphorization of polypyran salts and multistage polymerization. At the same time of briefly describing the mechanism of oxygen reduction reaction, combined with the research results of my own team, this paper focuses on the application of new porous materials (metal-organic framework MOF, conjugated microporous polymer CMP, etc.) in electrocatalysis. In view of the problems existing in the current electrocatalysts, the future research ideas are pointed out, including the use of advanced technical means to characterize the active sites of the catalysts in situ, based on the fact that there are a large number of phosphine ligands in the framework, phosphorus-containing porous organic polymers can be loaded with a series of metal compounds to make supported metal nanoparticles catalysts, or even monoatomic or unit point metal catalysts. The optimal structure of the catalyst was inversely calculated from the high active sites, and the preparation conditions of the materials were optimized. Under the guidance of theory and practice, a new type of electrocatalyst with high efficiency, stability, economy and environmental protection was developed on the premise of in-depth understanding of the mechanism of oxygen reduction reaction. Then an example is given to introduce the use of POPs to solve the basic scientific problems related to biomimetic catalysis, and show its great application potential. Finally, the challenges and opportunities in this emerging field are summarized and put forward.

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Kumar, Vijyendra, Titikshya Mohapatra, Sandeep Dharmadhikari, and Prabir Ghosh. "A Review Paper on Heterogeneous Fenton Catalyst: Types of Preparation, Modification Techniques, Factors Affecting the Synthesis, Characterization, and Application in the Wastewater Treatment." Bulletin of Chemical Reaction Engineering & Catalysis 15, no. 1 (September 10, 2019): 1–34. http://dx.doi.org/10.9767/bcrec.15.1.4374.1-34.

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This comprehensive review focuses on the different factors, modification in the synthesis method, characterization and application of heterogeneous catalyst in the wastewater treatment based on the Fenton process. The present review highlights the different catalyst preparation methods like wet impregnation method, hydrothermal method, sol-gel method, precipitation method and their application to treat different recalcitrant organic chemicals. Major heterogeneous catalyst synthesis methods were discussed with their excellent workability. The importance of modification through physical and chemical method was also reported. Different catalyst, pollutants and optimum parametric conditions available in the literature along with some relevant studies are summarized. The effect of factors like pH, calcination and some other modifiers on the synthesis and their efficiency in the wastewater treatment has been described. The important characterization of synthesized catalysts explaining their working efficiency has also been discussed. In the final section, the application of heterogeneous catalyst synthesized by different methods in the wastewater/effluent treatment has been investigated. The main aim of this review is to find out the influence of process parameters and catalytic method on degradation/decolorization of organic compounds present in industrial or synthetic wastewater. Copyright © 2020 BCREC Group. All rights reserved

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Wu, Bowen, Jian Chen, and Linping Qian. "Recent Advances in Heterogeneous Electroreduction of CO2 on Copper-Based Catalysts." Catalysts 12, no. 8 (August 4, 2022): 860. http://dx.doi.org/10.3390/catal12080860.

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Facing greenhouse effects and the rapid exhaustion of fossil fuel, CO2 electrochemical reduction presents a promising method of environmental protection and energy transformation. Low onset potential, large current density, high faradaic efficiency (FE), and long-time stability are required for industrial production, due to economic costs and energy consumption. This minireview showcases the recent progress in catalyst design and engineering technology in CO2 reduction reaction (CO2RR) on copper based-catalysts. We focus on strategies optimizing the performance of copper-based catalysts, such as single-atom catalysts, doping, surface modification, crystal facet engineering, etc., and reactor design including gas diffusion layer, membrane electrode assembly, etc., in enhancing target electroreduction products including methane, methanol, ethylene, and C2+ oxygenates. The determination of the correlation and the developed technology might be helpful for future applications in the industry.

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Long, Shanghai, Li Xu, and Guoji Liu. "Preparation and Modification of Heterogeneous Vanadium-Titanium-Based Catalysts." Russian Journal of General Chemistry 91, no. 3 (March 2021): 464–87. http://dx.doi.org/10.1134/s1070363221030166.

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Wolny, Anna, and Anna Chrobok. "Silica-Based Supported Ionic Liquid-like Phases as Heterogeneous Catalysts." Molecules 27, no. 18 (September 11, 2022): 5900. http://dx.doi.org/10.3390/molecules27185900.

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Supported ionic liquid phases offer several advantages related with catalysis. Immobilization of ionic liquid on the solid support provides catalytic activity or efficient matrix for active phases, as enzymes or metal compounds. Ionic liquid can be physically adsorbed on the carrier (supported ionic liquid phase) or chemically grafted to the material surface (supported ionic liquid-like phase). The use of supported ionic liquid phases improves mass transport, reduces ionic amount in the process and, most importantly, enables effortless catalyst separation and recycling. Moreover, chemical modification of the surface material with ionic liquid prevents its leaching, enhancing length of catalyst life. Silica-based materials have become an effective and powerful matrix for supported ionic liquid-like phase due to its cost-efficiency, presence of hydroxyl groups on the surface enabling its functionalization, and specific material properties, such as the size and shapes of the pores. For these reasons, supported ionic liquid-like phase silica-based materials are successfully used in the organic catalysis.

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Caliman, Anca Florentina, and Ion Balasanian. "CATALYSTS FOR HETEROGENEOUS PHOTOCATALYSIS. PART I. POSSIBILITIES TO IMPROVE PHOTOEFFICIENCY THROUGH CATALYST MODIFICATION." Environmental Engineering and Management Journal 2, no. 3 (2003): 175–83. http://dx.doi.org/10.30638/eemj.2003.017.

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Ayare, Pooja, Shawn Gregory, Typher Yom, Mark D. Losego, and Aaron Vannucci. "Using Atomic Layer Deposition (ALD) to Immobilize Molecular Catalysts on Solid Powder Supports." ECS Meeting Abstracts MA2022-02, no. 31 (October 9, 2022): 1151. http://dx.doi.org/10.1149/ma2022-02311151mtgabs.

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While homogeneous molecular catalysts are valued for their high reaction specificity, they are not as easily recoverable at industrial scales as heterogeneous catalyst powders that can be rapidly separated from the reaction solution. Here, we will discuss a new approach using atomic layer deposition (ALD) to immobilize molecular catalysts onto heterogeneous powder supports to achieve this combination of selectivity and recoverability. In this presentation, we demonstrate applicability using a non-noble metal (nickel) molecular catalyst to do Suzuki carbon-carbon cross-coupling reactions. Due to extremely short catalyst lifetimes caused by dimerization, this catalyst exhibits limited catalytic reactivity under homogeneous conditions. However, when heterogenized and immobilized, product yields of over 90% can be achieved in aqueous conditions, and the catalytic activity is preserved through over five hundred recovery and wash cycles. Following this work, we will also report on how modification of the ALD surface chemistry and number of ALD cycles affect catalytic performance.

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He, Qianfeng, Jie Zhao, Ming Xu, Jing Tao, Peipei Zhang, and Shihui Si. "The modification and application of Sewage Sludge based in heterogeneous Fenton-like system." E3S Web of Conferences 136 (2019): 07026. http://dx.doi.org/10.1051/e3sconf/201913607026.

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In this study, dewatered domestic sewage sludge of moisture content of 65.6% was used as a pore-forming agent to sinter Ceramics with kaolin clay, coal ash and sodium silicate at 1050-1100 oC for 20 min. The weight percentage of sludge of total dried solids was 60% with pore rate >45% and compressive >20 MPa. The Ceramics could be used as catalysts in heterogeneous Fenton-like system to treat phenol wastewater through modification by FeSO4 solution. After reaction with ceramics catalyst for 2.5 h, phenol removal of the wastewater could reach 99.87% from 100 mg/L to 0.13 mg/L and the COD removal is 85.75%. The performance of this catalyst was stable and had no significant in 30d repeat experiments.

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Gao, Xingyuan, Xinyi Lin, Xiangjuan Xie, Jinyu Li, Xinyi Wu, Yuyan Li, and Sibudjing Kawi. "Modification strategies of heterogeneous catalysts for water–gas shift reactions." Reaction Chemistry & Engineering 7, no. 3 (2022): 551–65. http://dx.doi.org/10.1039/d1re00537e.

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Evdokimenko, Nikolay D., Alexander L. Kustov, Konstantin O. Kim, Igor V. Mishin, Vera D. Nissenbaum, Genadiy I. Kapustin, Timur R. Aymaletdinov, and Leonid M. Kustov. "Ce–Zr materials with a high surface area as catalyst supports for hydrogenation of CO2." Functional Materials Letters 13, no. 04 (April 14, 2020): 2040004. http://dx.doi.org/10.1142/s1793604720400044.

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The most promising way of CO2 utilization is its catalytic conversion into valuable products, in particular, the direct hydrogenation of CO2 on heterogeneous catalysts to obtain such products as synthesis gas, hydrocarbons, alcohols, esters, carboxylic acids, and some other organic molecules. Heterogeneous iron-based catalysts possess a special position among the promising candidates for the synthesis of CO2-based hydrocarbons. However, individual iron oxide catalysts have a fairly low surface area, which requires their deposition on the support or modification. CeO2 is rather attractive in catalysis because of its high oxygen storage capacity. The most effective thermal stabilizer of CeO2 is ZrO2. In this work, cerium–zirconium systems with various Ce to Zr ratios were synthesized by the method of coprecipitation in the absence and presence of the hexadecyltrimethylammonium bromide template. These systems were characterized by adsorption of N2, XRD, and DTA-TG-DTG and used as supports for 5% Fe catalysts. The activity of synthesized Fe-containing catalysts was investigated in the reaction of CO2 hydrogenation. The developed surface and the presence of cerium in the supports are the possible reasons for the high activity of Fe-containing catalysts in the hydrogenation reaction of CO2.

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Nengah Simpen, I., I. Made Sutha Negara, and Ni Made Puspawati. "The Characterization of Heterogeneous Nanocatalyst of Biohydroxyapatite-Lithium and its Application for Converting Malapari Seed Oil (Milletia pinnata L.) to Biodiesel." Oriental Journal of Chemistry 34, no. 4 (August 27, 2018): 1817–23. http://dx.doi.org/10.13005/ojc/3404015.

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Heterogeneous nanocatalyst of biohydroxyapatite-lithium (HA-Li) has been prepared through modification of HA extracted from bovine bone waste with Li at various calcination temperatures (400-700oC). Characterizations of the heterogeneous catalysts were including surface acidity-basicity, functional groups, BET surface area, particle size, and surface morphology. Optimization of catalyst ratios (1-7%) with the best characterization was applied for converting Malapari seed oil (Milletia pinnata L.) to biodiesel. The characterization results showed that HA-Li catalyst calcinated at 600oChad the highest surface basicity and Lewis acid sites revealing specific functional group of O-Li at wavenumber of 1612.49 cm-1. BET surface area of HA-Li catalyst decreased with increased average particle size. SEM analysis suggested that morfology of catalysts formed stack of agglomerates. The highest yield of biodiesel obtained on a catalyst ratio of 5% was 88.16%. GC-MS analysis showed 10 peaks, and 5 of the peaks exhibiting the highest percentage area were identified as methyl oleic, methyl palmitic, methyl erusic, methyl stearic, and methyl linoleic.

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Kholdeeva, Oxana, and Nataliya Maksimchuk. "Metal-Organic Frameworks in Oxidation Catalysis with Hydrogen Peroxide." Catalysts 11, no. 2 (February 21, 2021): 283. http://dx.doi.org/10.3390/catal11020283.

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In recent years, metal–organic frameworks (MOFs) have received increasing attention as selective oxidation catalysts and supports for their construction. In this short review paper, we survey recent findings concerning use of MOFs in heterogeneous liquid-phase selective oxidation catalysis with the green oxidant–aqueous hydrogen peroxide. MOFs having outstanding thermal and chemical stability, such as Cr(III)-based MIL-101, Ti(IV)-based MIL-125, Zr(IV)-based UiO-66(67), Zn(II)-based ZIF-8, and some others, will be in the main focus of this work. The effects of the metal nature and MOF structure on catalytic activity and oxidation selectivity are analyzed and the mechanisms of hydrogen peroxide activation are discussed. In some cases, we also make an attempt to analyze relationships between liquid-phase adsorption properties of MOFs and peculiarities of their catalytic performance. Attempts of using MOFs as supports for construction of single-site catalysts through their modification with heterometals will be also addressed in relation to the use of such catalysts for activation of H2O2. Special attention is given to the critical issues of catalyst stability and reusability. The scope and limitations of MOF catalysts in H2O2-based selective oxidation are discussed.

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Ghafuri, Hossein, Ghazaleh Jafari, Nahal Goodarzi, and Afsaneh Rashidizadeh. "ZrO2/g-C3N4 Hybrid Nanocomposite: An Efficient and Eco-Friendly Recyclable Catalyst for the Trimethylsilyl Protection of Hydroxyl Groups and Synthesis of α-Aminophosphonates." Proceedings 9, no. 1 (November 14, 2018): 51. http://dx.doi.org/10.3390/ecsoc-22-05652.

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Recently, considerable attention has been devoted to heterogeneous catalysts. Generally, heterogeneous catalysts offer several advantages, such as mild reaction conditions, high throughput, and ease of work-up procedures. Among the heterogeneous catalysts investigated, polymeric mesoporous graphitic carbon nitrides (g-C3N4) have attracted much attention recently due to strong van der Waals interactions between the layers. g-C3N4 is chemically stable against acidic, basic, and organic solvents, and thermogravimetric analysis (TGA) also reveals that g-C3N4 is thermally stable even in air up to 600 °C, which can be attributed to its aromatic C-N heterocycles. More importantly, g-C3N4 is only composed of two earth-abundant elements: carbon and nitrogen. This not only suggests that it can be easily prepared at low cost, but also that its properties can be tuned by simple strategies without significant alteration of the overall composition. The last approach is considered to be the most efficient way to design high-performance heterogeneous catalysts utilizing g-C3N4 as a catalyst support. An interesting phenomenon is that the modification is mainly focused on metal oxides. Zirconia (ZrO2) is a physically rigid material with chemical inertness. It has high resistance against attacks by acids, alkalis, oxidants, and reductants. In this study, a ZrO2/g-C3N4 hybrid nanocomposite was shown to be an excellent catalyst for the conversion of alcohols and phenols into their corresponding trimethylsilyl ethers with hexamethyldisilazane (HMDS) under solvent-free conditions and for the synthesis of α-aminophosphonates. In addition, ZrO2/g-C3N4 could easily be recycled after separation from the reaction mixture without considerable loss in catalytic activity.

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Jain, Deepti, Renu Hada, and Ashu Rani. "Surface Modification of Fly Ash for Active Catalysis." Journal of Catalysts 2013 (July 1, 2013): 1–9. http://dx.doi.org/10.1155/2013/723957.

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Fly ash based effective solid base catalyst (KF/Al2O3/fly ash473, KF/Al2O3/fly ash673, and KF/Al2O3/fly ash873) was synthesized by loading KF over chemically and thermally activated fly ash. The chemical activation was done by treating fly ash with aluminum nitrate via precipitation method followed by thermal activation at 650°C to increase the alumina content in fly ash. The increased alumina content was confirmed by SEM-EDX analysis. The alumina enriched fly ash was then loaded with KF (10 wt%) and calcined at three different temperatures 473 K, 673 K and 873 K. The amount of loaded KF was monitored by XRD, FTIR spectroscopy, SEM-EDX, TEM and Flame Atomic Absorption Spectrophotometer. The catalytic activities of the catalysts were tested in the Claisen-Schmidt condensation of benzaldehyde and 4-methoxybenzaldehyde with 2′-hydroxyacetophenone to produce 2′-hydroxychalcone and 4-methoxy-2′-hydroxychalcone respectively. Higher conversion (83%) of benzaldehyde and (89%) of 4-methoxybenzaldehyde reveals that among these heterogeneous catalysts KF/Al2O3/fly ash673 is very active.

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Panurin, Nikita A., Natalya Yu Isaeva, Ekaterina B. Markova, Tatiana F. Sheshko, Alexander G. Cherednechenko, Alena S. Savchenko, Yulia Samoilenko, and Garry Z. Kaziev. "Efficiency of using heteropoly compounds of the type (NH4)2[Co(H2O)4]2[Mo8O27]∙6H2O as catalysts for the production of ethylene." Butlerov Communications 60, no. 11 (November 30, 2019): 85–92. http://dx.doi.org/10.37952/roi-jbc-01/19-60-11-85.

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Carrying out heterogeneous acid catalysis with the use of heteropoly compounds has received considerable attention due to the great economic and environmental benefits. In spite of this, its industrial application is limited as there are difficulties in catalyst regeneration (settling) caused by its relatively low thermal stability. The aim of present work was to search and select catalysts related to the class of heteropoly compounds for propane cracking, to test the selectivity of the prosses as well as to discuss possible approaches for solving the problem of catalyst deactivation, that can contribute to achieve stable characteristics of solid heteropoly catalysts. Among these approaches are: the development of new catalysts with high thermal stability, the modification of catalysts to promote coke combustion, the inhibition of coke formation on heteropoly compound catalysts during the process, carrying out the reactions in supercritical media and also the cascade reactions using a multifunctional heteropoly catalyst. The obtained catalyst was also studied by physicochemical methods to get deep knowledge about which features of these compounds influence on the catalytic activity. A highly active and selective catalyst for ammonium octomolybdenocobaltate(II) ammonium (NH4)2[Co(H2O)4]2[Mo8O27]∙6H2O was synthesized for cracking associated petroleum gases. The qualitative, quantitative, and structural composition as well as the specific surface area of the obtained catalyst was established by the methods of X-ray diffraction, X-ray phase and fluorescence analysis. It was revealed that ammonium octomolybdenocobaltate(II) crystallizes in a triclinic syngony with cell parameters: а = 8.6292(9) Å b = 9.4795(10) Å c = 12.2071(13) Å α = 104.326(2)° β = 109.910(2)° γ = 100.820(2)°.

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Astuti, N. K. D., I. N. Simpen, and I. W. Suarsa. "TRANSESTERIFIKASI MINYAK BIJI KARET (Hevea brasiliensis) MENGGUNAKAN KATALIS HETEROGEN CANGKANG KEPITING LIMBAH SEAFOOD TERMODIFIKASI K2O." Jurnal Kimia 13, no. 1 (January 16, 2019): 1. http://dx.doi.org/10.24843/jchem.2019.v13.i01.p01.

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The CaO heterogeneous catalysts can be prepared by CaCO3 calcination process, with one source of CaCO3 being a crab shell from seafood waste. The preparation of the heterogeneous catalyst was successfully carried out by modification with KOH using a wet impregnation method at 800oC for 5 hours. The purpose of this research is to determine the physical and chemical characteristics of heterogeneous catalyst of K2O-modified crab shell and to examine the heterogeneous catalyst of K2O-modified shells in converting rubber seed oil into biodiesel. The results showed that the lowest basic alkalinity possessed without modified catalyst (1.0428 mmol g-1) and the highest alkali possessed potassium-modified catalyst (1.8314 mmol g-1). Characterization of specific surface area of ??crab shells without and with modified K2O were relatively the same. The surface morphology of the catalyst without and K2O modified was uniform. The catalyst examination results for conversion of rubber seed oil (Hevea brasiliensis) to biodiesel, the optimum catalyst concentration of 3% and the molar ratio of oil:methanol of 1:9 capable converting to biodiesel with the yield of 91.05%. The content of biodiesel were stearic methyl ester, linoleic methyl ester, linolenic methyl ester, and palmitic methyl ester.

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Taslim, Sri Zahrani Dwi Mauliyah Parinduri, and Putri Retno Wahyu Ningsih. "PEMBUATAN BIODIESEL DARI MINYAK DEDAK PADI DENGAN REAKSI TRANSESTERIFIKASI MENGGUNAKAN KATALIS HETEROGEN ZEOLIT ALAM YANG DIMODIFIKASI DENGAN KOH." Jurnal Teknik Kimia USU 6, no. 1 (May 19, 2017): 12–18. http://dx.doi.org/10.32734/jtk.v6i1.1559.

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Biodiesel was usually produced from transesterification using alchohol. In this research rice bran oil was used as feedstock and methanol was used as reagent. The transesterification of rice bran oil had studied using KOH/natural zeolite as a solid heterogeneous catalyst. The objective of this study was to discover the effectivess of using natural zeolite modified by KOH as heterogeneous catalysts in the production of biodiesel from rice bran oil (RBO). KOH/natural zeolite catalyst was prepared by modification through impregnation method which was conducted on various KOH concentration (75 gram/100 ml – 175 gram/100 ml). Transesterification reaction was conducted at 60 ºC, 500 rpm, and various amount of catalyst (2-4%), reaction time (1,5-3,5 hour) and molar ratio alcohol/oil (8:1-12:1). The highest yield of biodiesel was 98,71%, which was obtained by using 2% catalyst, reaction time 2 hour, molar ratio alcohol/oil 10:1. Natural zeolite as heterogeneous catalyst which modified by KOH could get the higher yield biodiesel on transesterification.

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Yahya, Amri, Dwiarso Rubiyanto, and Is Fatimah. "Heterogeneous Catalytic Conversion of Citronellal into Isopulegol and Menthol: Literature Review." Science and Technology Indonesia 6, no. 3 (July 22, 2021): 166–80. http://dx.doi.org/10.26554/sti.2021.6.3.166-180.

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The conversion of citronellal into isopulegol is a key route in the production of a number of important chemicals. In the perspective of green conversion, the use of a heterogeneous catalyst is superior due to its ease in separation and reusability, so it facilitates a highly economical conversion. In this review, we examine the use of some transition metals in cyclization reactions, which are suitable for citronellal conversion into isopulegol, and consider the potential progress in clay-based catalysts. The structure of clay which potentially provides the porosity by modification and supporting active metal is proposed to be the low-cost catalyst for the conversion. As other mechanism by porous materials-supported metal, the porosity of clay support contributes to conduct thesurface adsorption mechanism and the Broensted acid supply, meanwhile the metal acts as active site for cyclization, and in the one-pot conversion into menthol, as both cyclization and hydrogenation.

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Михайлов, Степан Петрович, Валентин Юрьевич Долуда, Михаил Геннадьевич Сульман, and Валентина Геннадьевна Матвеева. "MODIFICATION OF NICKEL CATALYSTS FOR REDUCTIVE AMINATION BASED ON POLYMER SUPPORTS." Вестник Тверского государственного университета. Серия: Химия, no. 2(48) (July 7, 2022): 32–38. http://dx.doi.org/10.26456/vtchem2022.2.4.

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Процесс каталитической гидроконденсации является основным для синтеза огромного количества химических соединений. Примером таких соединений могут являться N-содержащие функциональные соединения, которые можно использовать в качестве исходного продукта для получения фармацевтических препаратов и агрохимикатов. За последние годы было проделано не мало исследований по поиску наиболее активного и селективного гетерогенного катализатора реакции восстановительного аминирования. Настоящая статья посвящена изучению Ni - содержащих катализаторов на основе полимерных носителей и результатам их модификации. The process of catalytic hydrocondensation is the main one for the synthesis of a huge number of chemical compounds. An example of such compounds can be N-containing functional compounds that can be used as a starting product for the production of pharmaceuticals and agrochemicals. In recent years, a lot of research has been done to find the most active and selective heterogeneous catalyst for the reductive amination reaction. This article is devoted to the study of Ni-containing polymer-supported catalysts and the results of their modification.

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Yarmo, Mohd Ambar, Raja Saadiah Raja Shariff, Siti Rohaya Omar, Juan Joon Ching, and Roziana Haron. "New Perspective in Recent Solid Acid Catalyst." Materials Science Forum 517 (June 2006): 117–22. http://dx.doi.org/10.4028/www.scientific.net/msf.517.117.

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This paper will review on the latest development on solid acid catalysts used in industries as well in research activities. Application of heterogeneous acid catalysis becomes current trend for many industries due to world wide environmental concern. Conventional synthetic or natural zeolites widely used for petrochemical processing, has some limitation because its pore size is normally smaller than reactant molecules. To overcome this challenge new delaminated zeolite process was introduced. In this process specific synthetic zeolite (i.e. ferrierite) was swelled up using specific surfactant followed by sonification to produce the delaminated zeolite. Further modification of this material such as sulfonification reaction to its surface has been found to improve the catalytic activity and selectivity for esterification reaction. Other acid catalyst systems based on mesoporous molecular sieves and Keggin heteropolyacids (HPA) are also discussed in this paper.

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Zhanaidarova, Almagul, Curtis E. Moore, Milan Gembicky, and Clifford P. Kubiak. "Covalent attachment of [Ni(alkynyl-cyclam)]2+ catalysts to glassy carbon electrodes." Chemical Communications 54, no. 33 (2018): 4116–19. http://dx.doi.org/10.1039/c8cc00718g.

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Wu, Suntao, Liyu Chen, Biaolin Yin, and Yingwei Li. "“Click” post-functionalization of a metal–organic framework for engineering active single-site heterogeneous Ru(iii) catalysts." Chemical Communications 51, no. 48 (2015): 9884–87. http://dx.doi.org/10.1039/c5cc02741a.

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A terpyridyl NNN-chelator has been successfully incorporated into MIL-101(Cr) by using a click post-synthetic modification method, offering a useful platform for metalation to prepare highly active and stable single-site heterogeneous catalysts.

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Zhang, Shuai, and Liang-Nian He. "Capture and Fixation of CO2 Promoted by Guanidine Derivatives." Australian Journal of Chemistry 67, no. 7 (2014): 980. http://dx.doi.org/10.1071/ch14125.

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Guanidine compounds and their derivatives can be developed as catalysts, additives, or promoters in organic synthesis due to their unique chemical properties, which have attracted much attention in the chemistry and catalysis communities. Particularly, the strong basicity and ease of structural modification allow them to offer wide applications in the field of CO2 capture and conversion. Guanidine compounds modified as ionic liquids or heterogeneous catalysts have also been developed for CO2 capture and conversion. In this context, the latest progress on CO2 capture using guanidine and their derivatives as absorbents with high capacity will be summarized. Furthermore, guanidine-catalyzed transformation of CO2 to a series of value-added chemicals with mechanistic consideration on a molecular level will be particularly elaborated in this article.

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Liao, Peisen, Guangmei Cai, Jianying Shi, and Jianyong Zhang. "Post-modified porphyrin imine gels with improved chemical stability and efficient heterogeneous activity in CO2 transformation." New Journal of Chemistry 43, no. 25 (2019): 10017–24. http://dx.doi.org/10.1039/c9nj00570f.

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Konsolakis, Michalis, and Maria Lykaki. "Recent Advances on the Rational Design of Non-Precious Metal Oxide Catalysts Exemplified by CuOx/CeO2 Binary System: Implications of Size, Shape and Electronic Effects on Intrinsic Reactivity and Metal-Support Interactions." Catalysts 10, no. 2 (February 1, 2020): 160. http://dx.doi.org/10.3390/catal10020160.

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Catalysis is an indispensable part of our society, massively involved in numerous energy and environmental applications. Although, noble metals (NMs)-based catalysts are routinely employed in catalysis, their limited resources and high cost hinder the widespread practical application. In this regard, the development of NMs-free metal oxides (MOs) with improved catalytic activity, selectivity and durability is currently one of the main research pillars in the area of heterogeneous catalysis. The present review, involving our recent efforts in the field, aims to provide the latest advances—mainly in the last 10 years—on the rational design of MOs, i.e., the general optimization framework followed to fine-tune non-precious metal oxide sites and their surrounding environment by means of appropriate synthetic and promotional/modification routes, exemplified by CuOx/CeO2 binary system. The fine-tuning of size, shape and electronic/chemical state (e.g., through advanced synthetic routes, special pretreatment protocols, alkali promotion, chemical/structural modification by reduced graphene oxide (rGO)) can exert a profound influence not only to the reactivity of metal sites in its own right, but also to metal-support interfacial activity, offering highly active and stable materials for real-life energy and environmental applications. The main implications of size-, shape- and electronic/chemical-adjustment on the catalytic performance of CuOx/CeO2 binary system during some of the most relevant applications in heterogeneous catalysis, such as CO oxidation, N2O decomposition, preferential oxidation of CO (CO-PROX), water gas shift reaction (WGSR), and CO2 hydrogenation to value-added products, are thoroughly discussed. It is clearly revealed that the rational design and tailoring of NMs-free metal oxides can lead to extremely active composites, with comparable or even superior reactivity than that of NMs-based catalysts. The obtained conclusions could provide rationales and design principles towards the development of cost-effective, highly active NMs-free MOs, paving also the way for the decrease of noble metals content in NMs-based catalysts.

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Zhang, Ruixue, Yanping Liu, Xinke Jiang, and Bo Meng. "Vital Role of Synthesis Temperature in Co–Cu Layered Hydroxides and Their Fenton-like Activity for RhB Degradation." Catalysts 12, no. 6 (June 13, 2022): 646. http://dx.doi.org/10.3390/catal12060646.

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Cu and Co have shown superior catalytic performance to other transitional elements, and layered double hydroxides (LDHs) have presented advantages over other heterogeneous Fenton catalysts. However, there have been few studies about Co–Cu LDHs as catalysts for organic degradation via the Fenton reaction. Here, we prepared a series of Co–Cu LDH catalysts by a co-precipitation method under different synthesis temperatures and set Rhodamine B (RhB) as the target compound. The structure-performance relationship and the influence of reaction parameters were explored. A study of the Fenton-like reaction was conducted over Co–Cu layered hydroxide catalysts, and the variation of synthesis temperature greatly influenced their Fenton-like catalytic performance. The Co–Cut=65°C catalyst with the strongest LDH structure showed the highest RhB removal efficiency (99.3% within 30 min). The change of synthesis temperature induced bulk-phase transformation, structural distortion, and metal–oxygen (M–O) modification. An appropriate temperature improved LDH formation with defect sites and lengthened M–O bonds. Co–Cu LDH catalysts with a higher concentration of defect sites promoted surface hydroxide formation for H2O2 adsorption. These oxygen vacancies (Ovs) promoted electron transfer and H2O2 dissociation. Thus, the Co–Cu LDH catalyst is an attractive alternative organic pollutants treatment.

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Dai, Zhifeng, Yang Long, Jianliang Liu, Yuanfei Bao, Liping Zheng, Jiacong Ma, Jiayi Liu, Fei Zhang, Yubing Xiong, and Ji-Qing Lu. "Functional Porous Ionic Polymers as Efficient Heterogeneous Catalysts for the Chemical Fixation of CO2 under Mild Conditions." Polymers 14, no. 13 (June 29, 2022): 2658. http://dx.doi.org/10.3390/polym14132658.

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The development of efficient and metal-free heterogeneous catalysts for the chemical fixation of CO2 into value-added products is still a challenge. Herein, we reported two kinds of polar group (−COOH, −OH)-functionalized porous ionic polymers (PIPs) that were constructed from the corresponding phosphonium salt monomers (v-PBC and v-PBH) using a solvothermal radical polymerization method. The resulting PIPs (POP-PBC and POP-PBH) can be used as efficient bifunctional heterogeneous catalysts in the cycloaddition reaction of CO2 with epoxides under relatively low temperature, ambient pressure, and metal-free conditions without any additives. It was found that the catalytic activities of the POP-PBC and POP-PBH were comparable with the homogeneous catalysts of Me-PBC and PBH and were higher than that of the POP-PPh3-COOH that was synthesized through a post-modification method, indicating the importance of the high concentration catalytic active sites in the heterogeneous catalysts. Reaction under low CO2 concentration conditions showed that the activity of the POP-PBC (with a conversion of 53.8% and a selectivity of 99.0%) was higher than that of the POP-PBH (with a conversion of 32.3% and a selectivity of 99.0%), verifying the promoting effect of the polar group (−COOH group) in the porous framework. The POP-PBC can also be recycled at least five times without a significant loss of catalytic activity, indicating the high stability and robustness of the PIPs-based heterogeneous catalysts.

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Modak, Arindam, Akshay R. Mankar, Kamal Kishore Pant, and Asim Bhaumik. "Mesoporous Porphyrin-Silica Nanocomposite as Solid Acid Catalyst for High Yield Synthesis of HMF in Water." Molecules 26, no. 9 (April 26, 2021): 2519. http://dx.doi.org/10.3390/molecules26092519.

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Solid acid catalysts occupy a special class in heterogeneous catalysis for their efficiency in eco-friendly conversion of biomass into demanding chemicals. We synthesized porphyrin containing porous organic polymers (PorPOPs) using colloidal silica as a support. Post-modification with chlorosulfonic acid enabled sulfonic acid functionalization, and the resulting material (PorPOPS) showed excellent activity and durability for the conversion of fructose to 5-hydroxymethyl furfural (HMF) in green solvent water. PorPOPS composite was characterized by N2 sorption, FTIR, TGA, CHNS, FESEM, TEM and XPS techniques, justifying the successful synthesis of organic networks and the grafting of sulfonic acid sites (5 wt%). Furthermore, a high surface area (260 m2/g) and the presence of distinct mesopores of ~15 nm were distinctly different from the porphyrin containing sulfonated porous organic polymer (FePOP-1S). Surprisingly the hybrid PorPOPS showed an excellent yield of HMF (85%) and high selectivity (>90%) in water as compared to microporous pristine-FePOP-1S (yield of HMF = 35%). This research demonstrates the requirement of organic modification on silica surfaces to tailor the activity and selectivity of the catalysts. We foresee that this research may inspire further applications of biomass conversion in water in future environmental research.

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Feng, Feng, Yaqin Deng, Zheng Cheng, Xiaoliang Xu, Qunfeng Zhang, Chunshan Lu, Lei Ma, and Xiaonian Li. "Heterogeneous Catalytic Synthesis of 2-Methylbenzimidazole from 2-Nitroaniline and Ethanol Over Mg Modified Cu-Pd/γ-Al2O3." Catalysts 9, no. 1 (December 24, 2018): 8. http://dx.doi.org/10.3390/catal9010008.

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The direct synthesis of benzimidazoles from 2-nitroaniline and ethanol over Cu-Pd/γ-Al2O3 catalysts has the advantages of requiring easily available starting materials, having high efficiency, and a simple procedure. The modification by Mg of the Cu-Pd/γ-Al2O3 catalyst could improve the catalytic activity significantly. The addition of Mg to the Cu-Pd/γ-Al2O3 catalyst could maintain and promote the formation of CuPd alloy active sites. Meanwhile, the basicity of the support was enhanced appropriately by Mg, which generated more basic sites (Al-Oδ−) to accelerate the dehydrogenation of alcohol and increased the rate of the whole coupled reaction. The 2-nitroaniline was completely converted over Cu-Pd/(Mg)γ-Al2O3 after reacting for six hours, and the yield of 2-methylbenzimidazole was 98.8%. The results of this work provide a simple method to develop a more efficient catalyst for the “alcohol-dehydrogenation, hydrogen transfer and hydrogenation” coupled reaction system.

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Pang, Xiaoyan, Xin Ge, Jianye Ji, Weijie Liang, Xunjun Chen, and Jianfang Ge. "Facile Route for Bio-Phenol Siloxane Synthesis via Heterogeneous Catalytic Method and its Autonomic Antibacterial Property." Polymers 10, no. 10 (October 16, 2018): 1151. http://dx.doi.org/10.3390/polym10101151.

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Eugenol, used as bio-phenol, was designed to replace the hydrogen atom of hydrogenterminated siloxane by hydrosilylation reaction under the presence of alumina-supported platinum catalyst (Pt-Al2O3), silica-supported platinum catalyst (Pt-SiO2) and carbon nanotube-supported platinum catalyst (Pt-CNT), respectively. The catalytic activities of these three platinum catalysts were measured by nuclear magnetic resonance hydrogen spectrometer (1H NMR). The properties of bio-phenol siloxane were characterized by Fourier transform infrared spectrometer (FT–IR), UV-visible spectrophotometer (UV) and thermogravimeter (TGA), and its antibacterial property against Escherichia coli was also studied. The results showed that the catalytic activity of the catalyst Pt-CNT was preferable. When the catalyst concentration was 100 ppm, the reaction temperature was 80 °C and reaction time was 6 h, the reactant conversion rate reached 97%. After modification with bio-phenol, the thermal stability of the obtained bio-phenol siloxane was improved. For bio-phenol siloxane, when the ratio of weight loss reached 98%, the pyrolysis temperature was raised to 663 °C which was 60 °C higher than hydrogenterminated siloxane. Meanwhile, its autonomic antibacterial property against Escherichia coli was improved significantly.

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Bečelić-Tomin, M., A. Kulić, Đ. Kerkez, D. Tomašević Pilipović, V. Pešić, and B. Dalmacija. "Synthesis of impregnated bentonite using ultrasound waves for application in the Fenton process." Clay Minerals 53, no. 2 (June 2018): 203–12. http://dx.doi.org/10.1180/clm.2018.14.

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ABSTRACTThe use of clays as industrial catalysts requires optimization of modification methods during their preparation. The objective of this paper was to improve the traditional method of bentonite impregnation using ultrasound. For this purpose, three series of samples with Fe3+/clay molar ratios of 0.6–11 mmol/g were prepared, which differed in terms of preparation procedure. The first batch of samples was subjected to the conventional method of impregnation, where total synthesis of catalysts took 4 h. The other two series of samples were prepared with impregnation improved by ultrasound: preparation of Fe-polycation (5 min) and then its incorporation with a clay suspension for 5 and 10 min. The effect of clay preparation method on the catalyst stability and efficiency in a heterogeneous Fenton process was studied on aqueous solutions of synthetic Reactive Blue 4 dye. The catalysts prepared by the conventional method and the improved ultrasound method achieved high efficacy (91–97%, respectively), but their stability was different in the Fenton process. The catalysts prepared using ultrasound for 10 min exhibited greatest stability in the Fenton process. The catalysts synthesized with different Fe loadings displayed an increase in specific surface area and mesoporosity. Samples prepared by the improved impregnation method are comparable in terms of their characteristics with their counterparts prepared by the conventional method. It is thus possible to reduce the time taken by traditional catalyst synthesis by using optimized exposure time to ultrasonic waves.

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Bakangura, Erigene, Philippe Roger, Rafaela S. B. Soares, Mohamed Mellah, Nadine Barroca-Aubry, Anne-Chantal Gouget-Laemmel, François Ozanam, Ludovic Costa, Jean-Pierre Baltaze, and Emmanuelle Schulz. "Post-Modification of Copolymers Obtained by ATRP for an Application in Heterogeneous Asymmetric Salen Catalysis." Molecules 27, no. 14 (July 21, 2022): 4654. http://dx.doi.org/10.3390/molecules27144654.

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Copolymers are valuable supports for obtaining heterogeneous catalysts that allow their recycling and therefore substantial savings, particularly in the field of asymmetric catalysis. This contribution reports the use of two comonomers: Azido-3-propylmethacrylate (AZMA) bearing a reactive azide function was associated with 2-methoxyethyl methacrylate (MEMA), used as a spacer, for the ATRP synthesis of copolymers, and then post-functionalized with a propargyl chromium salen complex. The controlled homopolymerization of MEMA by ATRP was firstly described and proved to be more controlled in molar mass than that of AZMA for conversions up to 63%. The ATRP copolymerization of both monomers made it possible to control the molar masses and the composition, with nevertheless a slight increase in the dispersity (from 1.05 to 1.3) when the incorporation ratio of AZMA increased from 10 to 50 mol%. These copolymers were post-functionalized with chromium salen units by click chemistry and their activity was evaluated in the asymmetric ring opening of cyclohexene oxide with trimethylsilyl azide. At an equal catalytic ratio, a significant increase in enantioselectivity was obtained by using the copolymer containing the largest part of salen units, probably allowing, in this case, the more favorable bimetallic activation of both the engaged nucleophile and electrophile. Moreover, the catalytic polymer was recovered by simple filtration and re-engaged in subsequent catalytic runs, up to seven times, without loss of activity or selectivity.

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Popovic, Ksenija, and Jelena Lovic. "Formic acid oxidation at platinum-bismuth catalysts." Journal of the Serbian Chemical Society 80, no. 10 (2015): 1217–49. http://dx.doi.org/10.2298/jsc150318044p.

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The field of heterogeneous catalysis, specifically catalysis on bimetallic surfaces, has seen many advances over the past few decades. Bimetallic catalysts, which often show electronic and chemical properties that are distinct from those of their parent metals, offer the opportunity to obtain new catalysts with enhanced selectivity, activity, and stability. The oxidation of formic acid is of permanent interest as a model reaction for the mechanistic understanding of the electrooxidation of small organic molecules and because of its technical relevance for fuel cell applications. Platinum is one of the most commonly used catalysts for this reaction, despite the fact that it shows a few significant disadvantages: high cost and extreme susceptibility to poisoning by CO. To solve this problem, several approaches have been used, but generally, they all consist in the modification of platinum with a second element. Especially, bismuth has received significant attention as Pt modifier. According to the results presented in this survey dealing with the effects influencing the formic acid oxidation it was found that two types of Pt-Bi bimetallic catalysts (bulk and low loading deposits on GC) showed superior catalytic activity in terms of the lower onset potential and oxidation current density, as well as exceptional stability compared to Pt. The findings in this report are important for the understanding of mechanism of formic acid electrooxidation on a bulk alloy and decorated surface, for the development of advanced anode catalysts for direct formic acid fuel cells, as well as for the synthesis of novel low-loading bimetallic catalysts. The use of bimetallic compounds as the anode catalysts is an effective solution to overcoming the problems of the formic acid oxidation current stability for long term applications. In the future, the tolerance of both CO poisoning and electrochemical leaching should be considered as the key factors in the development of electrocatalysts for the anodic reactions.

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Han, Mengyi, Xue Tang, Peng Wang, Zhiyong Zhao, Xiaohua Ba, Yu Jiang, and Xiaowei Zhang. "Metal-Organic Frameworks Decorated Cu2O Heterogeneous Catalysts for Selective Oxidation of Styrene." Catalysts 12, no. 5 (April 26, 2022): 487. http://dx.doi.org/10.3390/catal12050487.

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The selective oxidation of styrene with highly efficient, environmentally benign, and cost-effective catalysts are of great importance for sustainable chemical processes. Here, we develop an in situ self-assembly strategy to decorate Cu-based metal-organic framework (MOF) Cu-BDC-NH2 nanocrystals on Cu2O octahedra to construct a series of Cu2O@Cu-BDC-NH2 catalysts for selective oxidation of styrene. Using H2O2 as green oxidants, the optimized sample of Cu2O@Cu-BDC-NH2-8h could achieve 85% styrene conversion with 76% selectivity of benzaldehyde under a mild condition of 40 °C. The high performance of the as-prepared heterogeneous catalysts was attributed to the well-designed Cu+/Cu2+ interface between Cu2O and Cu-BDC-NH2 as well as the porous MOF shells composed of the uniformly dispersed Cu-BDC-NH2 nanocrystals. The alkaline properties of Cu2O and the –NH2 modification of MOFs enable the reaction to be carried out in a base-free condition, which simplifies the separation process and makes the catalytic system more environmentally friendly. Besides the Cu2O octahedra (od-Cu2O), the Cu2O cuboctahedrons (cod-Cu2O) were synthesized by adjusting the added polyvinyl pyrrolidone, and the obtained cod-Cu2O@Cu-BDC-NH2 composite also showed good catalytic performance. This work provides a useful strategy for developing highly efficient and environmentally benign heterogeneous catalysts for the selective oxidation of styrene.

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Shabani, Juvet Malonda, Alechine E. Ameh, Oluwaseun Oyekola, Omotola O. Babajide, and Leslie Petrik. "Fusion-Assisted Hydrothermal Synthesis and Post-Synthesis Modification of Mesoporous Hydroxy Sodalite Zeolite Prepared from Waste Coal Fly Ash for Biodiesel Production." Catalysts 12, no. 12 (December 15, 2022): 1652. http://dx.doi.org/10.3390/catal12121652.

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Increases in biodiesel prices remains a challenge, mainly due to the high cost of conventional oil feedstocks used during biodiesel production and the challenges associated with using homogeneous catalysts in the process. This study investigated the conversion of waste-derived black soldier fly (BSF) maggot oil feedstock over hydroxy sodalite (HS) zeolite synthesized from waste coal fly ash (CFA) in biodiesel production. The zeolite product prepared after fusion of CFA followed by hydrothermal synthesis (F-HS) resulted in a highly crystalline, mesoporous F-HS zeolite with a considerable surface area of 45 m2/g. The impact of post-synthesis modification of the parent HS catalyst (F-HS) by ion exchange with an alkali source (KOH) on its performance in biodiesel production was investigated. The parent F-HS zeolite catalyst resulted in a high biodiesel yield of 84.10%, with a good quality of 65% fatty acid methyl ester (FAME) content and fuel characteristics compliant with standard biodiesel specifications. After ion exchange, the modified HS zeolite catalyst (K/F-HS) decreased in crystallinity, mesoporosity and total surface area. The K/F-HS catalyst resulted in sub-standard biodiesel of 51.50% FAME content. Hence, contrary to various studies, the ion exchange modified zeolite was unfavorable as a catalyst for biodiesel production. Interestingly, the F-HS zeolite derived from waste CFA showed a favorable performance as a heterogeneous catalyst compared to the conventional sodium hydroxide (NaOH) homogeneous catalyst. The zeolite catalyst resulted in a more profitable process using BSF maggot oil and was economically comparable with NaOH for every kilogram of biodiesel produced. Furthermore, this study showed the potential to address the overall biodiesel production cost challenge via the development of waste-derived catalysts and BSF maggot oil as low-cost feedstock alternatives.

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Jia, Yihong, Asma A. Alothman, Rui Liang, Xiaoyong Li, Weiyi Ouyang, Xiangdong Wang, Yong Wu, et al. "Oligomeric (Salen)Mn(III) Complexes Featuring Tartrate Linkers Immobilized over Layered Double Hydroxide for Catalytically Asymmetric Epoxidation of Unfunctionalized Olefins." Materials 13, no. 21 (October 29, 2020): 4860. http://dx.doi.org/10.3390/ma13214860.

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A series of oligomeric (salen)Mn(III) complexes featuring tartrate linkers were prepared and immobilized over layered double hydroxide, and then used as catalysts for asymmetric epoxidation of unfunctionalized olefins. Comprehensive characterizations including 1H NMR, FT-IR, UV-Vis, elemental analysis, GPC, and ICP-AES were used to illustrate structures of oligomeric (salen)Mn(III) complexes, while powdered XRD, nitrogen physisorption, together with XPS studies provided further details to detect structures of heterogeneous catalysts. Interestingly, scanning electron microscopy found an interesting morphology change during modification of layered supporting material. Catalytic experiments indicated that configuration of major epoxide products was determined by salen chirality more than that of tartrate linker, but enantioselectivity (e.e. values) could be enhanced when tartrate and salen showed identical chiral configurations. Furthermore, the (R,R)-salen moieties linked with (R,R)-tartrate spacers usually offered higher enantioselectivity compared to other combinations. Lastly, Zn(II)/Al(III) layered double hydroxide played as a rigid supporting material in catalysis, showing positive chiral induction and high recycling potential in catalytic reactions.

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Nope, Eliana, Gabriel Sathicq, José Martinez, Hugo Rojas, Rafael Luque, and Gustavo Romanelli. "Hydrotalcites in Organic Synthesis: Multicomponent Reactions." Current Organic Synthesis 15, no. 8 (December 17, 2018): 1073–90. http://dx.doi.org/10.2174/1570179415666180815143927.

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Background: The use of solid bases as heterogeneous catalysts allows the replacement of conventional bases in Organic Chemistry, being of outmost importance. Lamellar double hydroxides or hydrotalcites are materials having excellent basic properties and high surface areas. As their surface properties have been used as bifunctional catalysts allowing the incorporation of metals and depending on the calcination temperature, these materials may exhibit Lewis or Brönsted basic sites. Additionally, they are widely used in various organic synthesis reactions. Objective: This contribution has been aimed to provide a compilation of the application of hydrotalcites as basic materials in organic synthesis, with a particular emphasis on multicomponent reactions. Conclusion: Hydrotalcites act as heterogeneous catalysts that conduct highly efficient processes in short reaction times and with the advantage of their easy recovery and reuse without significant loss of their catalytic activity. In addition, due to the modification of their structural and chemical properties, they are catalysts with multiple applications in organic synthesis such as Michael addition reactions, dehydrogenation reactions of alcohols, Knoevenagel condensations, reduction reactions, oxidations, epoxidations, multicomponent reactions, among others. Multicomponent reactions are of major interest since they allow obtaining compounds that have high biological activity and are generated through processes in a single step by combining three or more starting reagents under solvent-free conditions.

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Wang, Jingjing, Mu Yang, Wenjun Dong, Zhaokui Jin, Jia Tang, Shuang Fan, Yunfeng Lu, and Ge Wang. "Co(ii) complexes loaded into metal–organic frameworks as efficient heterogeneous catalysts for aerobic epoxidation of olefins." Catalysis Science & Technology 6, no. 1 (2016): 161–68. http://dx.doi.org/10.1039/c5cy01099c.

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An efficient cobalt(ii)-anchored Cr-MOF (Cr-MIL-101-NH₂) catalyst, Co(ii)@Cr-MIL-101-P2I, has been successfully synthesized by one-pot modification of the terminal amino group with pyridine-2-aldehyde and anchoring of Co(ii) ions into the mesoporous Cr-MOF support.

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Shen, Guo-Ping, Ruo-Yao Fan, Bin Dong, and Bo Chen. "Ferrocene Formic Acid Surface Modified Ni(OH)2 for Highly Efficient Alkaline Oxygen Evolution." Crystals 12, no. 10 (October 4, 2022): 1404. http://dx.doi.org/10.3390/cryst12101404.

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FeNi-based hybrid materials are among the most representative catalysts for alkaline oxygen evolution reaction (OER), but the modulation of their surface atoms to achieve the optimal catalytic properties is still a big challenge. Here, we report the surface modification of Ni(OH)2/nickel foam (NF)-based electrocatalyst with a trace amount of ferrocene formic acid (FFA) (FFA-Ni(OH)2/NF) for highly efficient OER. Owing to the strong electron interaction and synergistic effects of Fe-Ni heteroatoms, FFA-Ni(OH)2/NF exhibits an overpotential of 311 mV at a current density of 100 mA cm−2. Impressively, the overpotential of FFA-Ni(OH)2/NF at 100 mA cm−2 is 108 mV less than that of bulk phase doped Ni/FFA(OH)2/NF, demonstrating the surprising effect of heteroatomic surface modification. In addition, by introducing a small amount of surface modifier into the electrolyte, the weak surface reconstruction process in the electrochemical process can be fully utilized to achieve obvious modification effects. Therefore, this work fully proves the feasibility of improving catalytic activities of FeNi-based catalysts by modifying surface heterogeneous atom pairs.

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Hawa, Karfika Ainil, Zuchra Helwani, and Amun Amri. "Synthesis of Heterogeneous Catalysts NaOH/CaO/C From Eggshells for Biodiesel Production Using Off-Grade Palm Oil." Jurnal Rekayasa Kimia & Lingkungan 15, no. 1 (February 28, 2020): 31–37. http://dx.doi.org/10.23955/rkl.v15i1.14610.

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A heterogeneous catalyst, such as Calcium Oxide (CaO), is widely used in biodiesel production due to its various advantages over homogeneous ones. The optimum condition for synthesizing this catalyst is determined by calcination temperature and mass ratio. As a result, a modification is required to increase its performance in improving the biodiesel yield. In this study, eggshell waste was modified by calcination, hydration, and dehydration methods integrated with activated carbon and NaOH. It is used as a heterogeneous base catalyst for off-grade palm oil transesterification reactions. The results shows the catalyst with the highest activity is obtained at calcination temperature of 800°c and mass ratio of 7 to 3. This is achieved with transesterification reaction conditions, which include a mole ratio of methanol/oil 6 to 1, catalyst concentration of 6%-b oil, and temperature 70°c for 3 hours, yielding 79.08% of the biodiesel. Additionally, CaO, Na2CO3, and Ca (OH) 2 materials were found in the catalyst with a catalyst alkalinity value of H greater than 9.3 through X-ray diffraction (XRD) analysis. Several methyl esters, such as palmitate and oleate were also found in biodiesel through Gas Chromatography-Mass Spectrometry (GC-MS) analysis.

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Chadha, Utkarsh, Senthil Kumaran Selvaraj, Hridya Ashokan, Sai P. Hariharan, V. Mathew Paul, Vishal Venkatarangan, and Velmurugan Paramasivam. "Complex Nanomaterials in Catalysis for Chemically Significant Applications: From Synthesis and Hydrocarbon Processing to Renewable Energy Applications." Advances in Materials Science and Engineering 2022 (February 8, 2022): 1–72. http://dx.doi.org/10.1155/2022/1552334.

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The world is rapidly changing, the resources are getting depleted, and the demand for newer technologies and products is increasing. To keep up with these new advances, highly efficient catalytic routes need to be taken to be sustainable and ensure a drawn-out existence of resources for future generations. Catalysis turns out to be a significantly important field of application when it comes to the era of nanoscience, where all devices and technologies are becoming smaller and smaller in size with improved properties. When deeming the usability of a catalyst, it is of paramount importance to have a good understanding of their properties and their synergistic effect on the other reagents in the reaction. Over the last decade, the field of nanocatalysis has grown rapidly, both in homogeneous and heterogeneous catalysis. Given that nanoparticles have a high surface-to-volume ratio when compared to bulk materials, they are appealing as catalysts. Catalysts accelerate and boost thousands of different chemical reactions on a daily basis, forming the foundation of the multibillion-dollar chemical industry worldwide, a pathway leading to green chemistry, and a novel, yet crucial, environmental protection technology. As a result, in this review, the use of nanocatalysts and the application of their special features in the renewable energy, hydrocarbon processing, and fine chemical synthesis sector was explored. A detailed explanation of the working mechanism of these nanocatalysts, starting from how they are synthesized to the effect of modification of their surface, has been put together. We have tried to collect all the current progresses in these three sectors to the best of our abilities. Furthermore, it is anticipated that this paper would be useful for future researchers and academicians wishing to contribute toward this subject of interest.

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Kamalyan, Tatevik O., Petros S. Gukasyan, Samvel M. Vardapetyan, and Oleg A. Kamalyan. "NEW POSSIBILITIES OF LOW-TEMPERATURE GENERATION OF ACTIVE CENTERS DURING HETEROGENEOUS-HOMOGENEOUS ACTIVATION OF PROPANE ON SILICA GEL SURFACE, MODIFIED WITH ZnO BY THE SOL-GEL AND CHEICAL TRANSPORT REACTION METHODS." Proceedings of the YSU B: Chemical and Biological Sciences 55, no. 1 (254) (April 28, 2021): 1–6. http://dx.doi.org/10.46991/pysu:b/2021.55.1.001.

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By the example of heterogeneous catalytic oxidation of propane the process of peroxide radicals transfer from the surface of catalysts into the reactor volume is studied. For comparison ZnO/SiO2 contacts obtained by depositing the active phase on the silica surface by sol-gel and chemical transport reaction (CTR) were used. It was established that for the case both the temperature of the radicals transfer from the surface to the volume and the value of the activation energy are lower than in the case. It was shown that the modification of the silica gel surface with zinc oxide by the CTR method is more effective as compared with the sol-gel method. It is established that in both cases the active phase of the catalyst exhibits paramagnetic properties. On the basis of the given, semi-artificial kinetic method of radical detachment, the obligatory mechanism of activation failed.

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Fernandes, Simone, Daniela Flores, Daniel Silva, Isabel Santos-Vieira, Fátima Mirante, Carlos M. Granadeiro, and Salete S. Balula. "Lindqvist@Nanoporous MOF-Based Catalyst for Effective Desulfurization of Fuels." Nanomaterials 12, no. 16 (August 22, 2022): 2887. http://dx.doi.org/10.3390/nano12162887.

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An effective and sustainable oxidative desulfurization process for treating a multicomponent model fuel was successfully developed using as a heterogeneous catalyst a composite material containing as an active center the europium Lindqvist [Eu(W5O18)2]9− (abbreviated as EuW10) encapsulated into the nanoporous ZIF-8 (zeolitic imidazolate framework) support. The EuW10@ZIF-8 composite was obtained through an impregnation procedure, and its successful preparation was confirmed by various characterization techniques (FT-IR, XRD, SEM/EDS, ICP-OES). The catalytic activity of the composite and the isolated EuW10 was evaluated in the desulfurization of a multicomponent model fuel containing dibenzothiophene derivatives (DBT, 4-MDBT and 4,6-DMDBT) with a total sulfur concentration of 1500 ppm. Oxidative desulfurization was performed using an ionic liquid as extraction solvent and aqueous hydrogen peroxide as oxidant. The catalytic results showed a remarkable desulfurization performance, with 99.5 and 94.7% sulfur removal in the first 180 min, for the homogeneous active center EuW10 and the heterogeneous EuW10@ZIF-8 catalysts, respectively. Furthermore, the stability of the nanocomposite catalyst was investigated by reusing and recycling processes. A superior retention of catalyst activity in consecutive desulfurization cycles was observed in the recycling studies when compared with the reusing experiments. Nevertheless, the nanostructure of ZIF-8 incorporating the active POM (polyoxometalate) was shown to be highly suitable for guaranteeing the absence of POM leaching, although structural modification was found for ZIF-8 after catalytic use that did not influenced catalytic performance.

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Journal articles on the topic 'Heterogeneous catalysts modification'

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