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Dobrosz-Gómez, Izabela, Miguel-Ángel Gómez-García i Jacek Michał Rynkowski. "The Origin of Au/Ce1-xZrxO2 Catalyst’s Active Sites in Low-Temperature CO Oxidation". Catalysts 10, nr 11 (13.11.2020): 1312. http://dx.doi.org/10.3390/catal10111312.
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Gold catalysts have found applications in many reactions of both industrial and environmental importance. Great interest has been paid to the development of new processes that reduce energy consumption and minimize pollution. Among these reactions, the catalytic oxidation of carbon monoxide (CO) is an important one, considering that a high concentration of CO in the atmosphere creates serious health and environmental problems. This paper examines the most important achievements and conclusions arising from the own authorship contributions concerning (2 wt. % Au)/Ce1−xZrxO2 catalyst’s active sites in low-temperature CO oxidation. The main findings of the present review are: (1) The effect of preparing conditions on Au crystallite size, highlighting some of the fundamental underpinnings of gold catalysis: the Au surface composition and the poisoning effect of residual chloride on the catalytic activity of (2 wt. % Au)/Ce1−xZrxO2 catalysts in CO oxidation; (2) The identification of ion clusters related to gold and their effect on catalyst’ surface composition; (3) The importance of physicochemical properties of oxide support (e.g., its particle size, oxygen mobility at low temperature and redox properties) in the creation of catalytic performance of Au catalysts; (4) The importance of oxygen vacancies, on the support surface, as the centers for oxygen molecule activation in CO reaction; (5) The role of moisture (200–1000 ppm) in the generation of enhanced CO conversion; (6) The Au-assisted Mars-van Krevelen (MvK) adsorption–reaction model was pertinent to describe CO oxidation mechanism. The principal role of Au in CO oxidation over (2 wt. % Au)/Ce1−xZrxO2 catalysts was related to the promotion in the transformation process of reversibly adsorbed or inactive surface oxygen into irreversibly adsorbed active species; (7) Combination of metallic gold (Au0) and Au-OH species was proposed as active sites for CO adsorption. These findings can help in the optimization of Au-containing catalysts.
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Griffith, William P., i Maria Suriaatmaja. "Studies on transition-metal nitrido and oxo complexes. Part 20. Oxoruthenates and oxo-osmates in oxidation catalysis; cis-[Os(OH)2O4]2- as a catalytic oxidant for primary amines and for alcohols". Canadian Journal of Chemistry 79, nr 5-6 (1.05.2001): 598–606. http://dx.doi.org/10.1139/v00-181.
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cis-[Os(OH)2O4]2 with [Fe(CN)6]3 and other co-oxidants has been studied as a catalytic reagent for the oxidative dehydrogenation of primary aromatic and aliphatic amines to nitriles, the oxidation of primary alcohols to carboxylic acids and of secondary alcohols to ketones. Electronic and Raman spectroscopy have been used to elucidate the nature of the oxoruthenates and oxo-osmates present in a number of reported organic oxidations catalyzed by ruthenium and osmium species.Key words: oxidation catalysis, ruthenium, osmium, amine dehydrogenation, alcohol oxidation.
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Al Soubaihi, Rola, Khaled Saoud i Joydeep Dutta. "Critical Review of Low-Temperature CO Oxidation and Hysteresis Phenomenon on Heterogeneous Catalysts". Catalysts 8, nr 12 (14.12.2018): 660. http://dx.doi.org/10.3390/catal8120660.
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There is a growing demand for new heterogeneous catalysts for cost-effective catalysis. Currently, the hysteresis phenomenon during low-temperature CO oxidation is an important topic in heterogeneous catalysis. Hysteresis provides important information about fluctuating reaction conditions that affect the regeneration of active sites and indicate the restoration of catalyst activity. Understanding its dynamic behavior, such as hysteresis and self-sustained kinetic oscillations, during CO oxidation, is crucial for the development of cost-effective, stable and long-lasting catalysts. Hysteresis during CO oxidation has a direct influence on many industrial processes and its understanding can be beneficial to a broad range of applications, including long-life CO2 lasers, gas masks, catalytic converters, sensors, indoor air quality, etc. This review considers the most recent reported advancements in the field of hysteresis behavior during CO oxidation which shed light on the origin of this phenomenon and the parameters that influence the type, shape, and width of the conversion of the hysteresis curves.
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Al Soubaihi, Rola Mohammad, Khaled Mohammad Saoud, Myo Tay Zar Myint, Mats A. Göthelid i Joydeep Dutta. "CO Oxidation Efficiency and Hysteresis Behavior over Mesoporous Pd/SiO2 Catalyst". Catalysts 11, nr 1 (16.01.2021): 131. http://dx.doi.org/10.3390/catal11010131.
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Carbon monoxide (CO) oxidation is considered an important reaction in heterogeneous industrial catalysis and has been extensively studied. Pd supported on SiO2 aerogel catalysts exhibit good catalytic activity toward this reaction owing to their CO bond activation capability and thermal stability. Pd/SiO2 catalysts were investigated using carbon monoxide (CO) oxidation as a model reaction. The catalyst becomes active, and the conversion increases after the temperature reaches the ignition temperature (Tig). A normal hysteresis in carbon monoxide (CO) oxidation has been observed, where the catalysts continue to exhibit high catalytic activity (CO conversion remains at 100%) during the extinction even at temperatures lower than Tig. The catalyst was characterized using BET, TEM, XPS, TGA-DSC, and FTIR. In this work, the influence of pretreatment conditions and stability of the active sites on the catalytic activity and hysteresis is presented. The CO oxidation on the Pd/SiO2 catalyst has been attributed to the dissociative adsorption of molecular oxygen and the activation of the C-O bond, followed by diffusion of adsorbates at Tig to form CO2. Whereas, the hysteresis has been explained by the enhanced stability of the active site caused by thermal effects, pretreatment conditions, Pd-SiO2 support interaction, and PdO formation and decomposition.
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Xanthopouloua, G. G., V. A. Novikova, Yu A. Knysha i A. P. Amosova. "Nanocatalysts for Low-Temperature Oxidation of CO: Review". Eurasian Chemico-Technological Journal 17, nr 1 (19.12.2014): 17. http://dx.doi.org/10.18321/ectj190.
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<p>The oxidation of CO covers a wide range of applications from gas masks, gas sensors, indoor air quality control to hydrogen purification for polymer electrolyte fuel cells. The reaction attracts renewed interest both in fundamental and applied research of catalysis and electrochemistry. Recent developments and trends in catalysis towards the synthesis of nanocatalysts for CO oxidation are discussed in this review. Different modifications made to conventional catalysts synthesis approaches for preparation of nanocatalysts are critically analyzed. Nanocatalysts developed on the basis of noble metals completely convert CO at temperatures below 0 °C. The development of active and stable catalysts without noble metals for low-temperature CO oxidation is a significant challenge. It was found that Co<sub>3</sub>O<sub>4</sub> nanorods can be steadily active for CO oxidation at a temperature as low as –77 °C. High activity of catalysts at low temperatures connected with nanosize particles and high surface area. This review summarized main directions of nanocatalysts development for CO low temperature oxidation.</p>
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Šmíd, Bretislav, Toshiyuki Mori, M. Takahashi, Ding Rong Ou, V. Matolín i Iva Matolínova. "Fabrication and Microanalysis of Nano-Structured CuOX-CeO2 Catalysts for CO Oxidation Reaction". Advanced Materials Research 15-17 (luty 2006): 261–66. http://dx.doi.org/10.4028/www.scientific.net/amr.15-17.261.
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Carbon monoxide (CO) is a significant air pollutant produced in incomplete oxidation of carbon in combustion. From the viewpoint of environmental protection, it is important that the concentration of CO gas is lowered in air. Catalysis is proving to be an effective route for removing this pollutant. Therefore, a design of nano-structured catalysts with high efficiency is required. In the present work, we focus on a development of nano-size CuOx-CeO2 catalysts for CO oxidation reaction. To prepare nano-structured Cu loaded CeO2 catalysts, a combined method of the conventional impregnation and ammonium carbonate co-precipitation was examined. Morphology, crystal phase and surface structure of prepared catalysts were characterized using High-Resolution Transmission Electron Microscopy (HRTEM), Scanning Electron Microscopy (SEM) and Powder X-ray Diffraction (XRD). Catalytic properties of CuOx-CeO2 for CO oxidation were investigated in gas flow reactor system under atmospheric pressure and compared with copper oxide loaded zinc oxide. We expected that nano-structured CuOx-CeO2 catalysts could be used for removing CO produced in a wet reforming reaction of fuel cell applications.
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Liu, Jin-Xun, Zhiling Liu, Ivo A. W. Filot, Yaqiong Su, Ionut Tranca i Emiel J. M. Hensen. "CO oxidation on Rh-doped hexadecagold clusters". Catalysis Science & Technology 7, nr 1 (2017): 75–83. http://dx.doi.org/10.1039/c6cy02277d.
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Dosa, Melodj, Miguel Jose Marin-Figueredo, Enrico Sartoretti, Chiara Novara, Fabrizio Giorgis, Samir Bensaid, Debora Fino, Nunzio Russo i Marco Piumetti. "Cerium-Copper Oxides Synthesized in a Multi-Inlet Vortex Reactor as Effective Nanocatalysts for CO and Ethene Oxidation Reactions". Catalysts 12, nr 4 (23.03.2022): 364. http://dx.doi.org/10.3390/catal12040364.
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In this study, a set of CuCeOx catalysts was prepared via the coprecipitation method using a Multi-Inlet Vortex Reactor: the Cu wt.% content is 5, 10, 20, 30 and 60. Moreover, pure CeO2 and CuO were synthesized for comparison purposes. The physico-chemical properties of this set of samples were investigated by complementary techniques, e.g., XRD, N2 physisorption at −196 °C, Scanning Electron Microscopy, XPS, FT-IR, Raman spectroscopy and H2-TPR. Then, the CuCeOx catalysts were tested for the CO and ethene oxidation reactions. As a whole, all the prepared samples presented good catalytic performances towards the CO oxidation reaction (1000 ppm CO, 10 vol.% O2/N2): the most promising catalyst was the 20%CuCeOx (complete CO conversion at 125 °C), which exhibited a long-term thermal stability. Similarly, the oxidative activity of the catalysts were evaluated using a gaseous mixture containing 500 ppm C2H4, 10 vol.% O2/N2. Accordingly, for the ethene oxidation reaction, the 20%CuCeOx catalyst evidenced the best catalytic properties. The elevated catalytic activity towards CO and ethene oxidation was mainly ascribed to synergistic interactions between CeO2 and CuO phases, as well as to the high amount of surface-chemisorbed oxygen species and structural defects.
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Chenouf, Meriem, Cristina Megías-Sayago, Fatima Ammari, Svetlana Ivanova, Miguel Centeno i José Odriozola. "Immobilization of Stabilized Gold Nanoparticles on Various Ceria-Based Oxides: Influence of the Protecting Agent on the Glucose Oxidation Reaction". Catalysts 9, nr 2 (31.01.2019): 125. http://dx.doi.org/10.3390/catal9020125.
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The influence of the protecting agent’s nature on gold particle size and dispersion was studied in this work over a series of gold-based catalysts. CO and glucose oxidation were chosen as catalytic reactions to determine the catalyst’s structure–activity relationship. The nature of the support appeared to be the predominant factor for the increase in activity, as the oxygen mobility was decisive for the CO oxidation in the same way that the Lewis acidity was decisive for the glucose oxidation. For the same catalyst composition, the use of montmorillonite as the stabilizing agent resulted in better catalytic performance.
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Kappis, Konstantinos, Christos Papadopoulos, Joan Papavasiliou, John Vakros, Yiannis Georgiou, Yiannis Deligiannakis i George Avgouropoulos. "Tuning the Catalytic Properties of Copper-Promoted Nanoceria via a Hydrothermal Method". Catalysts 9, nr 2 (1.02.2019): 138. http://dx.doi.org/10.3390/catal9020138.
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Copper-cerium mixed oxide catalysts have gained ground over the years in the field of heterogeneous catalysis and especially in CO oxidation reaction due to their remarkable performance. In this study, a series of highly active, atomically dispersed copper-ceria nanocatalysts were synthesized via appropriate tuning of a novel hydrothermal method. Various physicochemical techniques including electron paramagnetic resonance (EPR) spectroscopy, X-ray diffraction (XRD), N2 adsorption, scanning electron microscopy (SEM), Raman spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) were employed in the characterization of the synthesized materials, while all the catalysts were evaluated in the CO oxidation reaction. Moreover, discussion of the employed mechanism during hydrothermal route was provided. The observed catalytic activity in CO oxidation reaction was strongly dependent on the nanostructured morphology, oxygen vacancy concentration, and nature of atomically dispersed Cu2+ clusters.
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Maksimchuk, Nataliya V., Olga V. Zalomaeva, Igor Y. Skobelev, Konstantin A. Kovalenko, Vladimir P. Fedin i Oxana A. Kholdeeva. "Metal–organic frameworks of the MIL-101 family as heterogeneous single-site catalysts". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 468, nr 2143 (14.03.2012): 2017–34. http://dx.doi.org/10.1098/rspa.2012.0072.
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In this short review paper, we survey our recent findings in the catalytic applications of mesoporous metal–organic frameworks of the MIL-101 family (Fe- and Cr-MIL-101) and demonstrate their potential in two types of liquid-phase processes: (i) selective oxidation of hydrocarbons with green oxidants—O 2 and tert -butyl hydroperoxide—and (ii) coupling reaction of organic oxides with CO 2 . A comparison with conventional single-site catalysts is made with special attention to issues of the catalyst's resistance to metal leaching and the nature of catalysis.
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Saikia, Pranjal, Abu Taleb Miah, Banajit Malakar i Ankur Bordoloi. "Enhanced Catalytic Activity of Supported Gold Catalysts for Oxidation of Noxious Environmental Pollutant CO". Indian Journal of Materials Science 2015 (27.08.2015): 1–10. http://dx.doi.org/10.1155/2015/658346.
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Noble metal nanomaterials have attracted mounting research attention for applications in diverse fields of catalysis, biology, and nanotechnology. In the present study, we have undertaken a detailed investigation on synthesis, characterization, and catalytic activity studies for CO oxidation by nanogold catalysts supported over CeO2 and CeO2-ZrO2 (1 : 1 mole ratio). The support systems were prepared by modified, simple precipitation technique and the Au supported samples were synthesized using deposition-precipitation with urea method. The physicochemical characterization was performed by XRD, ICP-AES, BET surface area, FT-IR, UV-Vis DRS, Raman Spectroscopy, TEM, and XPS techniques. Au/CeO2 catalyst showed more than 80% CO conversions at 30°C, whereas Au/CeO2-ZrO2 exhibited ~100% CO conversion at that temperature. The catalytic performance of Au catalysts is highly dependent on the nature of the support.
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Mohamed, Ziyaad, Venkata D. B. C. Dasireddy, Sooboo Singh i Holger B. Friedrich. "The Mitigation of CO Present in the Water–Gas Shift Reformate Gas over IR-TiO2 and IR-ZrO2 Catalysts". Catalysts 11, nr 11 (15.11.2021): 1378. http://dx.doi.org/10.3390/catal11111378.
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CO hydrogenation and oxidation were conducted over Ir supported on TiO2 and ZrO2 catalysts using a feed mimicking the water–gas shift reformate stream. The influence of the support interaction with Ir and the catalysts’ redox and CO chemisorption properties on activity and selectivity were evaluated. Both catalysts oxidised CO to CO2 in the absence of H2, and a conversion of 70% was obtained at 200 °C. For the CO oxidation in the presence of H2 over these catalysts, the oxidation of H2 was favoured over CO due to H2 spillover occurring at the active metal and support interface, resulting in the formation of interstitials catalysed by Ir. However, both catalysts showed promising activity for CO hydrogenation. Ir-ZrO2 was more active, giving 99.9% CO conversions from 350 to 370 °C, with high selectivity towards CH4 using minimal H2 from the feed. Furthermore, results for the Ir-ZrO2 catalyst showed that the superior activity compared to the Ir-TiO2 catalyst was mainly due to the reducibility of the support and its interaction with the active metal. Controlling the isoelectric point during the synthesis allowed for a stronger interaction between Ir and the ZrO2 support, which resulted in higher catalytic activity due to better metal dispersions, and higher CO chemisorption capacities than obtained for the Ir-TiO2 catalyst.
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Schmal, Martin, i Hans-Joachim Freund. "Towards an atomic level understanding of niobia based catalysts and catalysis by combining the science of catalysis with surface science". Anais da Academia Brasileira de Ciências 81, nr 2 (czerwiec 2009): 297–318. http://dx.doi.org/10.1590/s0001-37652009000200016.
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The science of catalysis and surface science have developed, independently, key information for understanding catalytic processes. One might argue: is there anything fundamental to be discovered through the interplay between catalysis and surface science? Real catalysts of monometallic and bimetallic Co/Nb2O5 and Pd-Co/Nb2O5 catalysts showed interesting selectivity results on the Fischer-Tropsch synthesis (Noronha et al. 1996, Rosenir et al. 1993). The presence of a noble metal increased the C+5 selectivity and decreased the methane formation depending of the reduction temperature. Model catalyst of Co-Pd supported on niobia and alumina were prepared and characterized at the atomic level, thus forming the basis for a comparison with "real" support materials. Growth, morphology and structure of both pure metal and alloy particles were studied. It is possible to support the strong metal support interaction suggested by studies on real catalysts via the investigation of model systems for niobia in comparison to alumina support in which this effect does not occur. Formation of Co2+ penetration into the niobia lattice was suggested on the basis of powder studies and can be fully supported on the basis of model studies. It is shown for both real catalysts and model systems that oxidation state of Co plays a key role in controlling the reactivity in Fischer-Tropsch reactions systems and that the addition of Pd is a determining factor for the stability of the catalyst. It is demonstrated that the interaction with unsaturated hydrocarbons depends strongly on the state of oxidation.
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Li, Wei-Jing, Shu Tsai i Ming-Yen Wey. "Positive effects of a halloysite-supported Cu/Co catalyst fabricated by a urea-driven deposition precipitation method on the CO-SCR reaction and SO2 poisoning". Catalysis Science & Technology 11, nr 10 (2021): 3456–65. http://dx.doi.org/10.1039/d0cy02261f.
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Mardwita, Mardwita, Eka Sri Yusmartini i Nidya Wisudawati. "Effects of Cobalt and Chromium Loadings to The Catalytic Activities of Supported Metal Catalysts in Methane Oxidation". Bulletin of Chemical Reaction Engineering & Catalysis 15, nr 1 (15.01.2020): 213–20. http://dx.doi.org/10.9767/bcrec.15.1.6320.213-220.
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A series of alumina supported cobalt and chromium catalysts with different metal loadings were prepared by impregnation method. Six types of alumina supported cobalt and chromium catalysts contained 5 wt%, 10 wt%, and 15 wt% loadings were produced and tested in methane oxidation. The catalysts were characterized by using x-ray diffraction (XRD) and carbon monoxide chemisorption (CO chemisorption). The XRD results do not confirmed any features of cobalt and chromium metal. The metal sizes for both catalysts were larger in high loading as shown by CO chemisorption results. Methane conversion results showed that the conversion increases with increasing the metal loading, however supported chromium catalysts were higher in activities compared to supported cobalt catalysts. Thermal stability tests on 15 wt% Co/Al and 15 wt% Cr/Al catalyst showed that supported chromium catalyst is more stable and maintain the particle size due to its strong interaction with support, while supported cobalt catalyst decrease in methane conversion due to deactivation of the catalyst. Copyright © 2020 BCREC Group. All rights reserved
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Cui, Yan, Leilei Xu, Mindong Chen, Chufei Lv, Xinbo Lian, Cai-e. Wu, Bo Yang, Zhichao Miao, Fagen Wang i Xun Hu. "CO Oxidation over Metal Oxide (La2O3, Fe2O3, PrO2, Sm2O3, and MnO2) Doped CuO-Based Catalysts Supported on Mesoporous Ce0.8Zr0.2O2 with Intensified Low-Temperature Activity". Catalysts 9, nr 9 (28.08.2019): 724. http://dx.doi.org/10.3390/catal9090724.
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CuO-based catalysts are usually used for CO oxidation owing to their low cost and excellent catalytic activities. In this study, a series of metal oxide (La2O3, Fe2O3, PrO2, Sm2O3, and MnO2)-doped CuO-based catalysts with mesoporous Ce0.8Zr0.2O2 support were simply prepared by the incipient impregnation method and used directly as catalysts for CO catalytic oxidation. These mesoporous catalysts were systematically characterized by X-ray powder diffraction (XRD), N2 physisorption, transmission electron microscopy (TEM), energy-dispersed spectroscopy (EDS) mapping, X-ray photoelectron spectroscopy (XPS), and H2 temperature programmed reduction (H2-TPR). It was found that the CuO and the dopants were highly dispersed among the mesoporous framework via the incipient impregnation method, and the strong metal framework interaction had been formed. The effects of the types of the dopants and the loading amounts of the dopants on the low-temperature catalytic performances were carefully studied. It was concluded that doped transition metal oxides could regulate the oxygen mobility and reduction ability of catalysts, further improving the catalytic activity. It was also found that the high dispersion of rare earth metal oxides (PrO2, Sm2O3) was able to prevent the thermal sintering and aggregation of CuO-based catalysts during the process of calcination. In addition, their presence also evidently improved the reducibility and significantly reduced the particle size of the CuO active sites for CO oxidation. The results demonstrated that the 15CuO-3Fe2O3/M-Ce80Zr20 catalyst with 3 wt. % of Fe2O3 showed the best low-temperature catalytic activity toward CO oxidation. Overall, the present Fe2O3-doped CuO-based catalysts with mesoporous nanocrystalline Ce0.8Zr0.2O2 solid solution as support were considered a promising series of catalysts for low-temperature CO oxidation.
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Konsolakis, Michalis, i Maria Lykaki. "Facet-Dependent Reactivity of Ceria Nanoparticles Exemplified by CeO2-Based Transition Metal Catalysts: A Critical Review". Catalysts 11, nr 4 (31.03.2021): 452. http://dx.doi.org/10.3390/catal11040452.
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The rational design and fabrication of highly-active and cost-efficient catalytic materials constitutes the main research pillar in catalysis field. In this context, the fine-tuning of size and shape at the nanometer scale can exert an intense impact not only on the inherent reactivity of catalyst’s counterparts but also on their interfacial interactions; it can also opening up new horizons for the development of highly active and robust materials. The present critical review, focusing mainly on our recent advances on the topic, aims to highlight the pivotal role of shape engineering in catalysis, exemplified by noble metal-free, CeO2-based transition metal catalysts (TMs/CeO2). The underlying mechanism of facet-dependent reactivity is initially discussed. The main implications of ceria nanoparticles’ shape engineering (rods, cubes, and polyhedra) in catalysis are next discussed, on the ground of some of the most pertinent heterogeneous reactions, such as CO2 hydrogenation, CO oxidation, and N2O decomposition. It is clearly revealed that shape functionalization can remarkably affect the intrinsic features and in turn the reactivity of ceria nanoparticles. More importantly, by combining ceria nanoparticles (CeO2 NPs) of specific architecture with various transition metals (e.g., Cu, Fe, Co, and Ni) remarkably active multifunctional composites can be obtained due mainly to the synergistic metalceria interactions. From the practical point of view, novel catalyst formulations with similar or even superior reactivity to that of noble metals can be obtained by co-adjusting the shape and composition of mixed oxides, such as Cu/ceria nanorods for CO oxidation and Ni/ceria nanorods for CO2 hydrogenation. The conclusions derived could provide the design principles of earth-abundant metal oxide catalysts for various real-life environmental and energy applications.
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Liu, Yuxi, Guofeng Zhao, Dingsheng Wang i Yadong Li. "Heterogeneous catalysis for green chemistry based on nanocrystals". National Science Review 2, nr 2 (30.04.2015): 150–66. http://dx.doi.org/10.1093/nsr/nwv014.
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Abstract Modern society has an ever-increasing demand for environmentally friendly catalytic processes. Catalysis research is working towards a solution through the development of effective heterogeneous catalysts for environment-related applications. Nanotechnologies have provided effective strategies for the preparation of nanocrystals (NCs) with well-defined sizes, shapes and compositions. Precise control of these NCs provides an important foundation for the studies of structure-performance relationships in catalysis, which is critical to the design of NCs with optimized catalytic performances for practical applications. We focus on recent advances in the development of bottom-up strategies to control NCs structures for some key catalytic applications, including CO oxidation, selective oxidation of alcohols, semihydrogenation of alkynes, and selective hydrogenation of unsaturated aldehydes and nitrobenzene. These key applications have been a popular research focus because of their significance in green chemistry. Herein we also discuss the scientific understandings of the active species and active structures of these systems to gain an insight for rational design of efficient catalytic systems for these catalytic reactions.
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Popovic, Ksenija, i Jelena Lovic. "Formic acid oxidation at platinum-bismuth catalysts". Journal of the Serbian Chemical Society 80, nr 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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Iqbal, Zahoor, Muhammad Sufaid Khan, Rozina Khattak, Tausif Iqbal, Ivar Zekker, Muhammad Zahoor, Helal F. Hetta, Gaber El-Saber Batiha i Eida M. Alshammari. "Selective Oxidation of Cinnamyl Alcohol to Cinnamaldehyde over Functionalized Multi-Walled Carbon Nanotubes Supported Silver-Cobalt Nanoparticles". Catalysts 11, nr 7 (19.07.2021): 863. http://dx.doi.org/10.3390/catal11070863.
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The selective oxidation of alcohols to aldehydes has attracted a lot of attention because of its potential use in agrochemicals, fragrances, and fine chemicals. However, due to homogenous catalysis, low yield, low selectivity, and hazardous oxidants, traditional approaches have lost their efficiency. The co-precipitation method was used to synthesize the silver-cobalt bimetallic catalyst supported on functionalized multi-walled carbon nanotubes (Ag-Co/S). Brunauer Emmet Teller (BET), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and X-ray diffraction (XRD) were used to characterize the catalyst. For the oxidation of cinnamyl alcohol (CA) with O2 as an oxidant, the catalyst’s selectivity and activity were investigated. The impacts of several parameters on catalyst’s selectivity and activity, such as time, temperature, solvents, catalyst dosage, and stirring speed, were comprehensively studied. The results revealed that in the presence of Ag-Co/S as a catalyst, O2 could be employed as an effective oxidant for the catalytic oxidation of cinnamyl alcohol to cinnamaldehyde (CD) with 99% selectivity and 90% conversion. In terms of cost effectiveness, catalytic activity, selectivity, and recyclability, Ag-Co/S outperforms the competition. As a result, under the green chemistry methodology, it can be utilized as an effective catalyst for the conversion of CA to CD.
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Dreyer, Maik, Moritz Krebs, Sharif Najafishirtari, Anna Rabe, Klaus Friedel Ortega i Malte Behrens. "The Effect of Co Incorporation on the CO Oxidation Activity of LaFe1−xCoxO3 Perovskites". Catalysts 11, nr 5 (27.04.2021): 550. http://dx.doi.org/10.3390/catal11050550.
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Perovskite oxides are versatile materials due to their wide variety of compositions offering promising catalytic properties, especially in oxidation reactions. In the presented study, LaFe1−xCoxO3 perovskites were synthesized by hydroxycarbonate precursor co-precipitation and thermal decomposition thereof. Precursor and calcined materials were studied by scanning electron microscopy (SEM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TG), and X-ray powder diffraction (XRD). The calcined catalysts were in addition studied by transmission electron microscopy (TEM) and N2 physisorption. The obtained perovskites were applied as catalysts in transient CO oxidation, and in operando studies of CO oxidation in diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). A pronounced increase in activity was already observed by incorporating 5% cobalt into the structure, which continued, though not linearly, at higher loadings. This could be most likely due to the enhanced redox properties as inferred by H2-temperature programmed reduction (H2-TPR). Catalysts with higher Co contents showing higher activities suffered less from surface deactivation related to carbonate poisoning. Despite the similarity in the crystalline structures upon Co incorporation, we observed a different promotion or suppression of various carbonate-related bands, which could indicate different surface properties of the catalysts, subsequently resulting in the observed non-linear CO oxidation activity trend at higher Co contents.
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KAZUSAKA, A. "Catalysis on Mo(CO)6-derived supported molybdenum catalysts: CO oxidation with N2O". Journal of Catalysis 111, nr 1 (maj 1988): 50–58. http://dx.doi.org/10.1016/0021-9517(88)90064-4.
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Li, Jing-Jing, Bao-Lin Zhu, Gui-Chang Wang, Zun-Feng Liu, Wei-Ping Huang i Shou-Min Zhang. "Enhanced CO catalytic oxidation over an Au–Pt alloy supported on TiO2 nanotubes: investigation of the hydroxyl and Au/Pt ratio influences". Catalysis Science & Technology 8, nr 23 (2018): 6109–22. http://dx.doi.org/10.1039/c8cy01642a.
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Dey, Subhashish, Ganesh Chandra Dhal, Devendra Mohan i Ram Prasad. "Effect of Preparation Conditions on the Catalytic Activity of CuMnOx Catalysts for CO Oxidation". Bulletin of Chemical Reaction Engineering & Catalysis 12, nr 3 (28.10.2017): 437. http://dx.doi.org/10.9767/bcrec.12.3.900.437-451.
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The hopcalite (CuMnOx) catalyst is a well-known catalyst for oxidation of CO at ambient temperature. It has prepared by co-precipitation method and the preparation parameters were like Copper/Manganese (Cu:Mn) molar ratios, drying temperature, drying time, calcination temperature and calcination time has an influence on activity of the resultant catalyst. The activity of the catalyst was measured in flowing air calcinations (FAC) conditions. The reaction temperature was increased from ambient to a higher value at which complete oxidation of CO was achieved. The particle size, weight of catalyst and CO flow rate in the air were also influenced by the activity of the catalyst for CO oxidation. The characterizations of the catalysts were done by several techniques like XRD, FTIR, BET, SEM-EDX and XPS. These results were interpreted in terms of the structure of the active catalyst. The main aim of this paper was to identify the optimum preparation conditions of CuMnOx catalyst with respect to the performance of catalyst for CO oxidation. Copyright © 2017 BCREC Group. All rights reservedReceived: 9th January 2017; Revised: 24th May 2017; Accepted: 25th May 2017; Available online: 27th October 2017; Published regularly: December 2017How to Cite: Dey, S., Dhal, G.C., Mohan, D., Prasad, R. (2017). Effect of Preparation Conditions on the Catalytic Activity of CuMnOx Catalysts for CO Oxidation. Bulletin of Chemical Reaction Engineering & Catalysis, 12 (3): 431-451 (doi:10.9767/bcrec.12.3.900.437-451)
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Mouanni, Sihem, Tassadit Mazari, Sihem Benadji, Leila Dermeche, Catherine Marchal-Roch i Cherifa Rabia. "Simple and Green Adipic Acid Synthesis from Cyclohexanone and/or Cyclohexanol Oxidation with Efficient (NH4)xHyMzPMo12O40 (M: Fe, Co, Ni) Catalysts". Bulletin of Chemical Reaction Engineering & Catalysis 13, nr 2 (11.06.2018): 386. http://dx.doi.org/10.9767/bcrec.13.2.1749.386-392.
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The oxidation of cyclohexanone and/or cyclohexanol to adipic acid (AA) was performed at 90 °C with a reaction time of 20 h, in the presence of H2O2 as oxidant and transition metal substituted ammonia polyoxometalates of formula, (NH4)xHyMzPMo12O40 (M: Fe, Co, or Ni, and x = 2.5 or 2.28) as catalysts. The catalytic results showed that the AA yield is sensitive to the transition metal nature and to the reaction conditions (sample weight and substrate amount). The (NH4)2.29H0.39Co0.16PMo12O40 was found to be the better catalytic system toward AA synthesis from cyclohexanone oxidation, with 40% of AA yield Copyright © 2018 BCREC Group. All rights reservedReceived: 12nd November 2017; Revised: 18th February 2018; Accepted: 19th February 2018; Available online: 11st June 2018; Published regularly: 1st August 2018How to Cite: Mouanni, S., Mazari, T., Benadji, S., Dermeche, L., Marchal-Roch, C., Rabia, C. (2018). Simple and Green Adipic Acid Synthesis from Cyclohexanone and/or Cyclohexanol Oxidation with Efficient (NH4)xHyMzPMo12O40 (M: Fe, Co, Ni) Catalysts. Bulletin of Chemical Reaction Engineering & Catalysis, 13 (2): 386-392 (doi:10.9767/bcrec.13.2.1749.386-392)
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Dang, Shuailin. "Oxidation of CO in three-way catalytic converter through single-atom catalysis". Applied and Computational Engineering 7, nr 1 (21.07.2023): 125–30. http://dx.doi.org/10.54254/2755-2721/7/20230383.
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Automobile exhaust emissions are the main source of pollution at present, and Three-Way catalytic converter (TWC), as the main mean of automobile exhaust purification, can effectively control the negative impact posed by automobile exhaust. However, there are still some problems that can be improved in the current TWC, such as catalyst sintering and low temperature catalytic efficiency. As an advanced catalytic field, it has a good effect on CO governance in TWC. This paper mainly studies how single-atom catalysis catalyzes CO in TWC based on related literature researches and analyzes the mechanisms and experimental data from other teams. The preparation method of SAC will also be introduced. It is concluded that SAC has a good effect on CO catalysis in TWC, and it can also improve the existing problems in TWC. Different supports also have different mechanisms for CO oxidation. In the future, if SAC can be applied in TWC, all aspects will be significantly improved.
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Liu, Xin, Xin Zhang i Changgong Meng. "Coadsorption Interfered CO Oxidation over Atomically Dispersed Au on h-BN". Molecules 27, nr 11 (5.06.2022): 3627. http://dx.doi.org/10.3390/molecules27113627.
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Similar to the metal centers in biocatalysis and homogeneous catalysis, the metal species in single atom catalysts (SACs) are charged, atomically dispersed and stabilized by support and substrate. The reaction condition dependent catalytic performance of SACs has long been realized, but seldom investigated before. We investigated CO oxidation pathways over SACs in reaction conditions using atomically dispersed Au on h-BN (AuBN) as a model with extensive first-principles-based calculations. We demonstrated that the adsorption of reactants, namely CO, O2 and CO2, and their coadsorption with reaction species on AuBN would be condition dependent, leading to various reaction species with different reactivity and impact the CO conversion. Specifically, the revised Langmuir–Hinshelwood pathway with the CO-mediated activation of O2 and dissociation of cyclic peroxide intermediate followed by the Eley–Rideal type reduction is dominant at high temperatures, while the coadsorbed CO-mediated dissociation of peroxide intermediate becomes plausible at low temperatures and high CO partial pressures. Carbonate species would also form in existence of CO2, react with coadsorbed CO and benefit the conversion. The findings highlight the origin of the condition-dependent CO oxidation performance of SACs in detailed conditions and may help to rationalize the current understanding of the superior catalytic performance of SACs.
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Wang, Nan, Shan Wang, Jie Yang, Ping Xiao i Junjiang Zhu. "Promotion Effect of Ce Doping on Catalytic Performance of LaMnO3 for CO Oxidation". Catalysts 12, nr 11 (10.11.2022): 1409. http://dx.doi.org/10.3390/catal12111409.
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In this paper, Ce-doped La1-xCexMnO3 perovskite catalysts are prepared by the sol–gel method, and the promotion effect of Ce doping on LaMnO3 catalysts for CO oxidation is investigated. The catalysts are characterized by X-ray diffractograms, Raman, N2 physisorption isotherms, temperature-programed reduction with H2, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results show that the Ce doping greatly improves the catalytic activity of LaMnO3 for CO oxidation. Among the La1-xCexMnO3 catalysts, La0.8Ce0.2MnO3 shows the best CO catalytic activity, with 100% CO conversion obtained at 180 °C. The characteristic results show that the LaMnO3 perovskite phase exists in all Ce-doped catalysts, and the CeO2 crystalline phase begins to appear at x ≥ 0.1. The high activity of La0.8Ce0.2MnO3 for CO oxidation could be that: (1) it possesses large surface area (25.8 m2/g) to contact with reactants; (2) it has a high surface Ce3+/(Ce3+ + Ce4+) ratio of 0.27, which means high content of oxygen vacancies used for O2 adsorption and activation; and (3) it exhibits strong reducibility that is beneficial to CO activation.
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Yang, Hao, Fusheng Li, Shaoqi Zhan, Yawen Liu, Wenlong Li, Qijun Meng, Alexander Kravchenko i in. "Intramolecular hydroxyl nucleophilic attack pathway by a polymeric water oxidation catalyst with single cobalt sites". Nature Catalysis 5, nr 5 (maj 2022): 414–29. http://dx.doi.org/10.1038/s41929-022-00783-6.
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AbstractExploration of efficient water oxidation catalysts (WOCs) is the primary challenge in conversion of renewable energy into fuels. Here we report a molecularly well-defined heterogeneous WOC with Aza-fused, π-conjugated, microporous polymer (Aza-CMP) coordinated single cobalt sites (Aza-CMP-Co). The single cobalt sites in Aza-CMP-Co exhibited superior activity under alkaline and near-neutral conditions. Moreover, the molecular nature of the isolated catalytic sites makes Aza-CMP-Co a reliable model for studying the heterogeneous water oxidation mechanism. By a combination of experimental and theoretical results, a pH-dependent nucleophilic attack pathway for O-O bond formation was proposed. Under alkaline conditions, the intramolecular hydroxyl nucleophilic attack (IHNA) process with which the adjacent -OH group nucleophilically attacks Co4+=O was identified as the rate-determining step. This process leads to lower activation energy and accelerated kinetics than those of the intermolecular water nucleophilic attack (WNA) pathway. This study provides significant insights into the crucial function of electrolyte pH in water oxidation catalysis and enhancement of water oxidation activity by regulation of the IHNA pathway.
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Roy, Mouni, Somjyoti Basak i Milan Kanti Naskar. "Bi-template assisted synthesis of mesoporous manganese oxide nanostructures: Tuning properties for efficient CO oxidation". Physical Chemistry Chemical Physics 18, nr 7 (2016): 5253–63. http://dx.doi.org/10.1039/c5cp07295f.
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Saoud, Khaled Mohammad, i Mohamed Samy El-Shall. "Physical and Chemical Synthesis of Au/CeO2 Nanoparticle Catalysts for Room Temperature CO Oxidation: A Comparative Study". Catalysts 10, nr 11 (20.11.2020): 1351. http://dx.doi.org/10.3390/catal10111351.
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In many heterogeneous catalytic reactions, such as low-temperature CO oxidation, the preparation conditions, and the role of the CeO2 support (oxygen vacancies and redox properties) in the dispersion and the chemical state of Au, are considered critical factors for obtaining gold nanoparticle catalysts with high catalytic performance. In this work, the physical and chemical preparation methods were compared, aiming at understanding how the preparation method influences the catalytic activity. The Au/CeO2 nanoparticle catalysts with 5% Au loading were prepared via the Physical Laser Vaporization Controlled Condensation method (LVCC), and the chemical Deposition-Precipitation method (DP) was used to investigate the effect of synthesis methods on the structure and the catalytic activity toward the CO oxidation. In this manuscript, we compare the activity of nanostructured Au/CeO2 catalysts. The structure and the redox properties of the catalysts were investigated by the XRD, SEM, TEM, TPR, and XPS. The catalytic activity for low-temperature CO oxidation was studied using a custom-built quartz tube flow reactor coupled with an infrared detector system at atmospheric pressure. The study reveals that the prepared CeO2-supported Au nanoparticles’ catalytic activity was highly dependent on the preparation methods. It showed that the sample prepared by the DP method exhibits higher catalytic efficiency toward CO oxidation when compared with the sample prepared by the LVCC method. The high catalytic activity could be attributed to the small particle size and shape, slightly higher Au concentration at the surface, surface-active Au species such as Au1+, along with the large interface between Au and CeO2. This study suggests that the stability, dispersion of Au nanoparticles on CeO2, and strong interaction between Au and CeO2 lead to strong oxidation ability even below room temperature. Considering the universal character of different physical and chemical methods for Au/CeO2 preparation, this study may also provide a base for supported Au-based catalysts for many oxidation reactions in energy and environmental applications.
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Genoni, Andrea, Giuseppina La Ganga, Andrea Volpe, Fausto Puntoriero, Marilena Di Valentin, Marcella Bonchio, Mirco Natali i Andrea Sartorel. "Water oxidation catalysis upon evolution of molecular Co(iii) cubanes in aqueous media". Faraday Discussions 185 (2015): 121–41. http://dx.doi.org/10.1039/c5fd00076a.
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The increasing global energy demand has stimulated great recent efforts in investigating new solutions for artificial photosynthesis, a potential source of clean and renewable solar fuel. In particular, according to the generally accepted modular approach aimed at optimising separately the different compartments of the entire process, many studies have focused on the development of catalytic systems for water oxidation to oxygen. While in recent years there have been many reports on new catalytic systems, the mechanism and the active intermediates operating the catalysis have been less investigated. Well-defined, molecular catalysts, constituted by transition metals stabilised by a suitable ligand pool, could help in solving this aspect. However, in some cases molecular species have been shown to evolve to active metal oxides that constitute the other side of this catalysis dichotomy. In this paper, we address the evolution of tetracobalt(iii) cubanes, stabilised by a pyridine/acetate ligand pool, to active species that perform water oxidation to oxygen. Primary evolution of the cubane in aqueous solution is likely initiated by removal of an acetate bridge, opening the coordination sphere of the cobalt centres. This cobalt derivative, where the pristine ligands still impact on the reactivity, shows enhanced electron transfer rates to Ru(bpy)33+(hole scavenging) within a photocatalytic cycle with Ru(bpy)32+as the photosensitiser and S2O82−as the electron sink. A more accentuated evolution occurs under continuous irradiation, where Electron Paramagnetic Resonance (EPR) spectroscopy reveals the formation of Co(ii) intermediates, likely contributing to the catalytic process that evolves oxygen. All together, these results confirm the relevant effect of molecular species, in particular in fostering the rate of the electron transfer processes involved in light activated cycles, pivotal in the design of a photoactive device.
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Saha, Subrata, Md Eaqub Ali, Azman Maamor i Wan Jeffery Basirun. "Design and Synthesis of Silica Supported Nanoporous Gold-Palladium Bimetallic Catalyst for Alkyl Benzene Oxidation". Advanced Materials Research 1109 (czerwiec 2015): 444–47. http://dx.doi.org/10.4028/www.scientific.net/amr.1109.444.
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Gold palladium (Au-Pd) bimetallic catalysts are very promising for various reactions including oxidative catalysis. Mesoporous silica supported Au-Pd catalysts have large surface area, controlled hydrophobi and file-cities and are thus highly efficient for the oxidation of alkyl benzene to selective products. Alkyl Benzene oxidation is important for the productions of drugs, perfumes, polymers, insecticides and pesticides. Unfortunately, the efficient oxidation of alkyl benzene has been remaining a challenging task due to lack of suitable catalysts. Functionalized mesoporous silica with ordered surface and uniform porosity is an exciting template for the synthesis of supported catalysts. Metal precursors could be co-impregnated on the highly ordered surface of ammine functionalized silica. This method facilitates great dispersion of the Au-Pd clusters with tiny and controlled particle size. Here, we described a two-step adsorption –reduction method along with various ratios of metal loadings for the synthesis of silica supported nanoporous Au-Pd catalyst for alkyl benzene oxidation.
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Mihailova, Irena, i Dimitar Mehandjiev. "Catalytic activity of Co-åkermanite and Co-pyroxene in oxidation reactions". Canadian Journal of Chemistry 89, nr 8 (sierpień 2011): 939–47. http://dx.doi.org/10.1139/v11-061.
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Two calcium–cobalt silicates were synthesized in which cobalt occupies different structural positions. The crystal phases belong to two main structural silicate types. In the Co-åkermanite structure (Ca2CoSi2O7), cobalt cations take tetrahedral coordination toward oxygen atoms. In the Co-pyroxene structure of CaCoSi2O6, cobalt displays octahedral coordination. Ca2CoSi2O7 was prepared by solid-phase synthesis and CaCoSi2O6 was prepared by sol–gel method. The synthesis of the phases was confirmed by XRD, FTIR, and EPR data. On the basis of the XPS analysis, it can be concluded that Co2+ cations exist in the studied silicates. Thus, it is possible to study the catalytic activity of two silicate phases containing Co2+ cations in different coordinations: tetrahedral and octahedral. It was found that cobalt silicates with crystal structures corresponding to pyroxene and åkermanite possess catalytic activity in the reactions of complete oxidation of CO and toluene. Co-pyroxene exhibits higher catalytic activity than Co-åkermanite, but the higher cobalt content on the surface of Co-pyroxene should also be taken into account. Then, it turns out that catalytically active complexes with Со2+ ions in tetrahedral coordination are more efficient than those with such ions in octahedral coordination when equal concentrations of cobalt were used on the surface of the catalysts.
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Li, Guobo, Yingying Zhang, Jie Yan, Yiwei Luo, Conghui Wang, Weiwei Feng, Shule Zhang, Wenming Liu, Zehui Zhang i Honggen Peng. "Insights into SnO2 Nanoparticles Supported on Fibrous Mesoporous Silica for CO Catalytic Oxidation". Catalysts 13, nr 8 (26.07.2023): 1156. http://dx.doi.org/10.3390/catal13081156.
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A large surface area dendritic mesoporous silica material (KCC-1) was successfully synthesized and used as a support to confine SnO2 nanoparticles (NPs). Owing to the large specific surface area and abundant mesoporous structure of dendritic KCC-1, the SnO2 NPs were highly dispersed, resulting in significantly improved CO catalytic oxidation activity. The obtained Snx/KCC-1 catalysts (x represents the mass fraction of SnO2 loading) exhibited excellent CO catalytic activity, with the Sn7@KCC-1 catalyst achieving 90% CO conversion at about 175 °C. The SnO2 NPs on the KCC-1 surface in a highly dispersed amorphous form, as well as the excellent interaction between SnO2 NPs and KCC-1, positively contributed to the catalytic removal process of CO on the catalyst surface. The CO catalytic removal pathway was established through a combination of in situ diffuse reflectance infrared transform spectroscopy and density-functional theory calculations, revealing the sequential steps: ① CO → CO32−ads, ② CO32−ads → CO2free+SnOx−1, ③ SnOx−1+O2 → SnOx+1. This study provides valuable insights into the design of high-efficiency non-precious metal catalysts for CO catalytic oxidation catalysts with high efficiency.
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Sui, Chao, LeHong Xing, Xue Cai, Yang Wang, Qi Zhou i Minghao Li. "Co-Supported CeO2Nanoparticles for CO Catalytic Oxidation: Effects of Different Synthesis Methods on Catalytic Performance". Catalysts 10, nr 2 (18.02.2020): 243. http://dx.doi.org/10.3390/catal10020243.
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Hydrothermal and co-precipitation methods were studied as two different methods for the synthesis of CeO2nanocatalysts. Co/CeO2 catalysts supported by 2, 4, 6, or 8wt% Co were further synthesized through impregnation and the performance of the catalytic oxidation of CO has been investigated. The highest specific surface area and the best catalytic performance was obtained by the catalyst 4wt% Co/CeO2 with the CeO2 support synthesized by the hydrothermal method (4% Co/CeO2-h), which yielded 100% CO conversion at 130 °C. The formation of CeO2 nanoparticles was confirmed by TEM analysis. XRD and SEM-EDX mapping analyses indicated that CoOx is highly dispersed on the 4% Co/CeO2-h catalyst surface. H2-TPR and O2-TPD results showed that 4% Co/CeO2-h possesses the best redox properties and the highest amount of chemically adsorbed oxygen on its surface among all tested catalysts. Raman and XPS spectra showed strong interactions between highly dispersed Co2+ active sites and exposed Ce3+ on the surface of the CeO2 support, resulting in the formation of the strong redox cycle Ce4+ + Co2+↔ Ce3+ + Co3+.This may explain that 4% Co/CeO2-h exhibited the best catalytic activity among all tested catalysts.
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Li, Yudong, Michael Hinshelwood i Gottlieb S. Oehrlein. "Investigation of Ni catalyst activation during plasma-assisted methane oxidation". Journal of Physics D: Applied Physics 55, nr 15 (19.01.2022): 155202. http://dx.doi.org/10.1088/1361-6463/ac4724.
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Abstract Atmospheric pressure plasma has shown promise in improving thermally activated catalytic reactions through a process termed plasma-catalysis synergy. In this work, we investigated atmospheric pressure plasma jet (APPJ)-assisted CH4 oxidation over a Ni/SiO2 .Al2O3 catalyst. Downstream gas-phase products from CH4 conversion were quantified by Fourier transform infrared spectroscopy. The catalyst near-surface region was characterized by in-situ diffuse reflectance infrared Fourier transform spectroscopy. The catalyst was observed to be activated at elevated temperature (500 °C) if it was exposed to the APPJ operated at large plasma power. ‘Catalyst activation’ signifies that the purely thermal conversion of CH4 using catalysts which had been pre-exposed to plasma became more intense and produced consistently CO product, even if the plasma was extinguished. Without the application of the APPJ to the Ni catalyst surface this was not observed at 500 °C. The study of different exposure conditions of the activated catalyst indicates that the reduction of the catalyst by the APPJ is likely the cause of the catalyst activation. We also observed a systematic shift of the vibrational frequency of adsorbed CO on Ni catalyst when plasma operating conditions and catalyst temperatures were varied and discussed possible explanations for the observed changes. This work provides insights into the plasma-catalyst interaction, especially catalyst modification in the plasma catalysis process, and potentially demonstrates the possibility of utilizing the surface CO as a local probe to understand the plasma-catalyst interaction and shed light on the complexity of plasma catalysis.
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Todorova, Silviya, Anton Naydenov, Maya Shopska, Hristo Kolev, Iliyana Yordanova i Krasimir Tenchev. "Pt-Modified Nano-Sized Mn2O3 Oxide Prepared from the Mn3O4 Phase with Tetragonal Symmetry for CO Oxidation". Symmetry 14, nr 12 (1.12.2022): 2543. http://dx.doi.org/10.3390/sym14122543.
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One of the current problems in the environmental catalysis is the design of an effective and less costly catalytic system for the oxidation of CO. The nano-sized α-Mn2O3 oxide has been prepared and modified with 0.5 wt.% Pt. The catalysts have been characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), temperature-programmed reduction (TPR) and diffuse-reflectance infrared spectroscopy (DRIFTS). Finely divided PtO and Pt(OH)2 are being formed on the Mn2O3 surface as a result of the strong interaction between platinum and the nano-oxide. Based on DRIFTS investigations and the model calculations, a Langmuir–Hinshelwood type of mechanism is supposed for CO oxidation on Pt/Mn2O3. The CO and oxygen are adsorbed on different types of sites. The Mars–van Krevelen mechanism is the most probable one over pure Mn2O3, thus suggesting that CO2 is adsorbed on the oxidized sites. The CO adsorption in the mixture CO + N2 or in the presence of oxygen (CO + N2 + O2) leads to a partial reduction in the Pt+ surface species and the formation of linear Pt1+−CO and Pt0−CO carbonyls. Both of them take part in the CO oxidation reaction.
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Konsolakis, Michalis, i 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, nr 2 (1.02.2020): 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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Dong, Ning, Mengyue Chen, Qing Ye, Dan Zhang i Hongxing Dai. "Catalytic Elimination of Carbon Monoxide, Ethyl Acetate, and Toluene over the Ni/OMS-2 Catalysts". Catalysts 11, nr 5 (30.04.2021): 581. http://dx.doi.org/10.3390/catal11050581.
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The Ni-loaded cryptomelane-type manganese oxide octahedral molecular sieve (OMS-2) catalysts (xNi/OMS-2: x = 1, 3, 5, and 10 wt%) were prepared by a pre-incorporation method. Physicochemical properties of the as-synthesized materials were characterized by means of various techniques, and their catalytic activities for CO, ethyl acetate, and toluene oxidation were evaluated.The loading of Ni played an important role in improving physicochemical propertiesof OMS-2. Among all of the samples, 5Ni/OMS-2 exhibited the best catalytic activity, with the T90 being 155 °C for CO oxidation at a space velocity (SV) of 60,000 mL/(g·h), 225°C for ethyl acetate oxidation at an SV of 240,000 mL/(g·h), and 300 °C for toluene oxidation at an SV of 240,000 mL/(g·h), which was due to its high Mn3+ content and Oads concentration, good low-temperature reducibility and lattice oxygen mobility, and strong interaction between the Ni species and the OMS-2 support. In addition, catalytic mechanisms of the oxidation of three pollutants over 5Ni/OMS-2 were also studied. The oxidation of CO, ethyl acetate, and toluene over the catalysts took place first via the activated adsorption, then intermediates formation, and finally complete conversion of the formed intermediates to CO2 and H2O.
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Zhang, Haiou, Yixin Zhang, Huikang Song, Yan Cui, Yingying Xue, Cai-e. Wu, Chao Pan i in. "Transition Metal (Fe2O3, Co3O4 and NiO)-Promoted CuO-Based α-MnO2 Nanowire Catalysts for Low-Temperature CO Oxidation". Catalysts 13, nr 3 (15.03.2023): 588. http://dx.doi.org/10.3390/catal13030588.
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As a toxic pollutant, carbon monoxide (CO) usually causes harmful effects on human health. Therefore, the thermally catalytic oxidation of CO has received extensive attention in recent years. The CuO-based catalysts have been widely investigated due to their availability. In this study, a series of transition metal oxides (Fe2O3, Co3O4 and NiO) promoted CuO-based catalysts supported on the α-MnO2 nanowire catalysts were prepared by the deposition precipitation method for catalytic CO oxidation reactions. The effects of the loaded transition metal type, the loading amount, and the calcination temperature on the catalytic performances were systematically investigated. Further catalyst characterization showed that the CuO/α-MnO2 catalyst modified with 3 wt% Co3O4 and calcined at 400 °C performed the highest CO catalytic activity (T90 = 75 °C) among the investigated catalysts. It was supposed that the loading of the Co3O4 dopant not only increased the content of oxygen vacancies in the catalyst but also increased the specific surface area and pore volume of the CuO/α-MnO2 nanowire catalyst, which would further enhance the catalytic activity. The CuO/α-MnO2 catalyst modified with 3 wt% NiO and calcined at 400 °C exhibited the highest surface adsorbed oxygen content and the best normalized reaction rate, but the specific surface area limited its activity. Therefore, the appropriate loading of the Co3O4 modifier could greatly enhance the activity of CuO/α-MnO2. This research could provide a reference method for constructing efficient low-temperature CO oxidation catalysts.
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Jiang, Angran, Zhibo Ren, Yaqi Qu, Yanjun Zhang i Jianwei Li. "Promotional Effect of Pt-Doping on the Catalytic Performance of Pt−CeO2 Catalyst for CO Oxidation". Catalysts 12, nr 5 (9.05.2022): 529. http://dx.doi.org/10.3390/catal12050529.
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Growing interest in the development of a hydrogen economy means that CO oxidation is increasingly important for upgrading H2-rich fuel gas streams for fuel cells. CeO2-supported catalysts are the most promising candidates for the catalytic oxidation of CO because of their high activity. In the present work, DFT+U calculations were performed to investigate the stability and CO oxidation reactivity of Ptn (n = 1−4) clusters supported on CeO2(111) (Pt/CeO2) and Pt-doped CeO2(111) (Pt/(Pt−Ce)O2) surfaces. The Pt clusters showed similar nucleation behavior on both CeO2 and (Pt−Ce)O2 surfaces. Further, the formation of oxygen vacancies (Ov) was facilitated because of surface charge depletion caused by the dopant Pt. Our DFT results suggest that the interfacial OV plays an important role in the CO oxidation reaction cycle, and the calculated energy barrier for the CO oxidation reaction on the Pt/(Pt−Ce)O2 surface is approximately 0.43 eV lower than that on the surface of the undoped catalyst, suggesting enhanced CO oxidation reactivity. Therefore, the chemical modification of the CeO2 support via doping is an effective strategy for improving the catalytic performance of Pt/CeO2.
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Vedyagin, Aleksey A., Vladimir O. Stoyanovskii, Roman M. Kenzhin, Pavel E. Plyusnin, Yury V. Shubin i Alexander M. Volodin. "New Trends in Automotive Exhaust Gas Purification Materials: Improvement of the Support against Stability of the Active Components". Materials Science Forum 950 (kwiecień 2019): 185–89. http://dx.doi.org/10.4028/www.scientific.net/msf.950.185.
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Lanthanum and zirconium oxides are well known to be applied as an additive to improve the properties of the commercial alumina. Such modified aluminas are widely used in different catalytic fields including three-way catalysis. In the present research we have paid attention to the possible effects of the doping on the catalytic performance and stability of bimetallic Pd-Rh catalysts. The samples were prepared via an incipient wetness impregnation of the commercial supports, tested in CO oxidation under prompt thermal aging regime and characterized by physicochemical methods.
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Ali, Asma A., Metwally Madkour, Fakhreia Al Sagheer, Mohamed I. Zaki i Ahmed Abdel Nazeer. "Low-Temperature Catalytic CO Oxidation Over Non-Noble, Efficient Chromia in Reduced Graphene Oxide and Graphene Oxide Nanocomposites". Catalysts 10, nr 1 (11.01.2020): 105. http://dx.doi.org/10.3390/catal10010105.
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Herein, bare chromia nanoparticles (Cr2O3 NPs) and chromia supported on reduced graphene oxide (rGO) and graphene oxide (GO) hybrids were synthesized, followed by characterization by means of FESEM, Raman spectroscopy, TGA, XRD, TEM/HRTEM, XPS and N2 sorptiometry. The investigated bare Cr2O3 and the hybrids (Cr2O3/rGO and Cr2O3/GO) were employed as catalysts for low-temperature CO oxidation. Compared with the other catalysts, the results revealed efficient catalytic activity using Cr2O3/GO, which was attributed to its higher surface area together with the mixed oxidation state of chromium (Cr3+ and Cr>3+). These are important oxidation sites that facilitate the electron mobility essential for CO oxidation. Moreover, the presence of carbon vacancy defects and functional groups facilitate the stabilizing of Cr2O3 NPs on its surface, forming a thermally stable hybrid material, which assists the CO oxidation process. The Cr2O3/GO hybrid is a promising low-cost and efficient catalyst for CO oxidation at low temperatures. The higher activity of graphene oxide supported Cr2O3 NPs can provide an efficient and cost-effective solution to a prominent environmental problem.
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Del Río, José Daniel, Gustavo Andrés Durán, Álvaro Orjuela Londoño, Francisco José Sánchez Castellanos i Carlos Alberto Guerrero Fajardo. "Partial oxidation of methane to formaldehyde on MoO3, Fe2O3 and ferromolybdenum catalysts". Ingeniería e Investigación 27, nr 1 (1.01.2007): 19–24. http://dx.doi.org/10.15446/ing.investig.v27n1.14773.
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One of the main challenges for catalysis has been direct methane conversion to useful products such as methanol and formaldehyde. Formaldehyde is currently produced by a three-step industrial process with syngas and methanol as intermediate products. MoO3 Fe2O3, and Fe2(MoO4)3 catalysts were used with four different Mo/Fe molar ratios (0.5, 1, 1.5, 2) in this work. The ferromolybdenum catalyst was prepared by coprecipitation. Pure oxides are more active; however they are not formaldehyde selective, but carbon oxide (CO, CO2) selective. The ferromolybdenum catalysts showed better HCHO selectivity at low conversions; the molybdenum oxide content did not show increased in catalytic activity. Increased reaction temperature did not increase formaldehyde selectivity.
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Dyakonov, AJ, i EA Robinson. "Low-Temperature Oxidation of CO in Smoke: A Review". Beiträge zur Tabakforschung International/Contributions to Tobacco Research 22, nr 2 (1.07.2006): 89–106. http://dx.doi.org/10.2478/cttr-2013-0820.
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AbstractThe low-temperature catalytic oxidation of CO has been reviewed, targeting its possible application to cigarette smoke. The treatment of CO in smoke by using a filter-packed catalyst is extremely complicated by the presence of a variety of chemically active gaseous compounds, a particulate phase, the high velocity of pulsing smoke flow, and ambient temperature. The relevant mechanisms of catalysis and the catalyst preparation variables that could help to overcome these problems are considered. Possible contributors to the overall kinetics that must include variety of diffusion processes were briefly discussed. The chemisorption of O2, CO and CO2 on Pd, Pt and Au and on partially reducible supports, surface reactions and oscillations of the CO oxidation rate were analyzed. The effects of the surface structure and electronic properties of the catalyst support, preparation conditions and presence of a second transition metal on the projected CO oxidation activity of the catalysts in smoke are also discussed. The reviewed catalyst preparation approaches can solve the low-temperature catalyst activity problem. However, more work is required to stabilize this activity of an air-exposed catalyst to provide a necessary shelf life for a cigarette. The greatest challenge seems to be a particular phase - exclusive selectivity that would not contradict with the necessary fast diffusion of gases through the catalyst pores.
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MEUNIER, B. "Oxidation catalysis". Journal of Porphyrins and Phthalocyanines 04, nr 04 (czerwiec 2000): 353. http://dx.doi.org/10.1002/(sici)1099-1409(200006/07)4:4<353::aid-jpp258>3.0.co;2-9.
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Niu, Xiaowei, Liang Zhou, Xiaojun Hu i Wei Han. "Mesoporous CexCo1−xCr2O4 spinels: synthesis, characterization and catalytic application in simultaneous removal of soot particulate and NO". RSC Advances 5, nr 65 (2015): 52595–601. http://dx.doi.org/10.1039/c5ra04759e.
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Ma, Guoyan, Le Wang, Xiaorong Wang, Lu Li i Hongfei Ma. "CO Oxidation over Alumina-Supported Copper Catalysts". Catalysts 12, nr 9 (10.09.2022): 1030. http://dx.doi.org/10.3390/catal12091030.
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CO oxidation, one of the most important chemical reactions, has been commonly studied in both academia and the industry. It is one good probe reaction in the fields of surface science and heterogeneous catalysis, by which we can gain a better understanding and knowledge of the reaction mechanism. Herein, we studied the oxidation state of the Cu species to seek insight into the role of the copper species in the reaction activity. The catalysts were characterized by XRD, N2 adsorption-desorption, X-ray absorption spectroscopy, and temperature-programmed reduction. The obtained results suggested that adding of Fe into the Cu/Al2O3 catalyst can greatly shift the light-off curve of the CO conversion to a much lower temperature, which means the activity was significantly improved by the Fe promoter. From the transient and temperature-programmed reduction experiments, we conclude that oxygen vacancy plays an important role in influencing CO oxidation activity. Adding Fe into the Cu/Al2O3 catalyst can remove part of the oxygen from the Cu species and form more oxygen vacancy. These oxygen vacancy sites are the main active sites for CO oxidation reaction and follow a Mars-van Krevelen-type reaction mechanism.