Добірка наукової літератури з теми "Copper-ceria catalyst"

Despite of the huge number of papers about the catalytic preferential oxidation of CO (CO-PROX) for the purification of H2 streams, there is still a need for more effective catalysts in order to reduce the large required catalyst volume of CO-PROX unity. In this work, large surface area nanometric ceria was used as support for CuO/CeO2 catalysts with CuO load up to 10 wt % easily dispersed by wet impregnation. Catalysts were characterized by ICP-MS, XRD, SEM/EDS, N2 physisorption, H2 temperature programmed reduction (TPR), and CO2 temperature programmed desorption (TPD) and tested under different reaction conditions (including under feed containing inhibiting species such as CO2 and H2O). Catalytic tests revealed that our samples show high activity and selectivity even under stringent reaction conditions; moreover, they result among the most active catalysts when compared to those reported in the scientific literature. The high activity can be related to the enhanced amount of highly dispersed copper sites in strong interaction with ceria related to the nature of the nanometric support, as evidenced by the characterization techniques. Despite the high concentration of active copper sites, catalytic performance is limited by CO2 desorption from ceria in the neighborhood of copper sites, which prevents a further improvement. This suggests that new catalyst formulations should also provide a lower affinity towards CO2.

Formic acid decomposition to H2-rich gas was investigated over a CuO-CeO2/γ-Al2O3 catalyst. The catalyst was characterized by XRD, HR TEM and EDX methods. A 100% conversion of formic acid was observed over the copper-ceria catalyst under ambient pressure, at 200–300 °C, N2:HCOOH = 75:25 vol.% and flow rate 3500–35,000 h−1 with H2 yield of 98%, wherein outlet CO concentration is below the equilibrium data (<0.5 vol.%). The copper-ceria catalyst proved to be promising for multifuel processor application, and the H2 generation from dimethoxymethane, methanol, dimethyl ether and formic acid on the same catalyst for fuel cell supply.

ABSTRACTNanosized CeO2-CuO (CeCu, 2:1) and CeO2-CoO (CeCo, 2:1) were synthesized by co-precipitation from nitrate precursors using 25% ammonia solution (NH4OH) as the precipitating agent. The catalysts were calcined in air at 800°C for 4h to evaluate the thermal stability. Powder x-ray diffraction (XRD) and Dynamic Light Scattering (DLS) techniques were used for catalyst characterization. A Thermo Gravimetric/Differential Thermal Analyzer (TG/DTA) was used to determine the catalytic efficiency and soot oxidation activity. Ce-composite nanoparticles heightens the redox properties of the catalyst relative to undoped ceria. The Ce-composite samples exhibited excellent soot catalytic combustion performance by decreasing activation energy of soot oxidation.

A copper/ceria-zirconia catalyst was incorporated onto a DPF following an environmentally-friendly impregnation procedure. Its catalytic activity was studied for diesel exhaust NO oxidation and soot combustion reactions.

The present work concerns the characterization of trimetallic nickel catalysts, NiMoRe (Nickel/Molybdenum/Rhenium), NiMoCu (Nickel/Molybdenum/Copper) and NiMoCo (Nickel/Molybdenum/Cobalt), supported on gadolinia-doped ceria and the evaluation of their catalytic performance in the auto-thermal reforming of ethanol to hydrogen. Catalysts have been prepared by wet impregnation and characterized by XRD, SEM-EDX, TG-DSC, TEM, CHNS, H2-TPR and micro-Raman spectroscopy. The resistance of Ni-alloy catalysts to the carbon deposition and sulfur poisoning has been studied. All catalysts show a similar behavior in the auto-thermal reforming reaction: 100% of ethanol conversion and high selectivity to syngas products, up to 77 vol.%. At 800 °C the coke deposition is very low (less than 0.34 wt%). Sulfur content affects the selectivity and the activity of the catalysts, especially towards the coke formation: high sulfur content promotes the ethylene formation, therefore the amount of coke deposited on spent catalyst increases. NiMoCu seems to be the trimetallic catalyst less sensitive to this aspect.

CuO–CeO2/SiO2 catalysts with Ce loading of 24% and above keep high activity after calcination at 700 °C. Therefore, a catalyst with high thermal stability of CuO–CeO2 interface can be obtained able to work in a higher range of temperatures.

Recently, the interest in ethanol production from renewable natural sources in Thailand has been receiving much attention as an alternative form of energy. The low-cost accessibility of ethanol has been seen as an interesting topic, leading to the extensive study of the formation of distinct chemicals, such as ethylene, diethyl ether, acetaldehyde, and ethyl acetate, starting from ethanol as a raw material. In this paper, ethanol dehydrogenation to acetaldehyde in a one-step reaction was investigated by using commercial activated carbon with four different metal-doped catalysts. The reaction was conducted in a packed-bed micro-tubular reactor under a temperature range of 250–400 °C. The best results were found by using the copper doped on an activated carbon catalyst. Under this specified condition, ethanol conversion of 65.3% with acetaldehyde selectivity of 96.3% at 350 °C was achieved. This was probably due to the optimal acidity of copper doped on the activated carbon catalyst, as proven by the temperature-programmed desorption of ammonia (NH3-TPD). In addition, the other three catalyst samples (activated carbon, ceria, and cobalt doped on activated carbon) also favored high selectivity to acetaldehyde (>90%). In contrast, the nickel-doped catalyst was found to be suitable for ethylene production at an operating temperature of 350 °C.

CeO2, Cu0.05Ce0.95O2-δ, Ni0.04Ce0.96O2-δ, Cu0.05Ni0.05Ce0.90O2-δ, catalysts were synthesised via solution combustion technique using urea as a fuel. The as pre-preared catalysts were characterised via X-ray powder diffraction, Brunauer-Emmett-Teller surface area analysis, transmission and scanning electron microscopy analysis. The characterisation techniques strongly suggested that all the catalysts were prepared successfully, and that copper and nickel were successfully incorporated into the lattice structure of ceria. The effect of the reaction conditions on the catalytic properties of the synthesised material were studied in detail using Cu0.05Ni0.05Ce0.90O2-δ as the model catalyst. The effect of temperature, solvents and co-oxidants was investigated in optimisation studies. A combination of acetonitrile, tert-butyl hydroperoxide and a temperature of 60 °C were found to be optimal after 24 hours and used for all catalysts. All catalysts were found to be active in styrene oxidation under these conditions, with styrene conversion as high as 69% over Ni0.04Ce0.96O2-δ, and selectivity to benzaldehyde and styrene oxide 38 and 26% respectively.

CuNi nanoparticles were synthesized using a new polyol synthesis method. Three different CuxNi1-x catalysts were synthesized where x = 20, 50 and 80. The nanoparticles were deposited on carbon, C, gamma-alumina, γ-Al2O3, yttria-stabilized zirconia, YSZ, and samariumdoped ceria, SDC. Each set of catalysts was tested using the Reverse Water Gas Shift, RWGS, reaction under atmospheric pressure and at temperatures ranging from 400°C-700°C. The experiments were repeated 3 times to ensure stability and reproducibility. Platinum nanoparticles were also deposited on the same supports and tested for the RWGS reaction at the same conditions. The CuNi nanoparticles were characterized using a variety of different techniques. Xray diffraction, XRD, measurements demonstrate the resence of two CuNi solid solutions: one Cu rich solid solution, and the other a Ni rich solid solution. X-ray photo electron spectroscopy, XPS, measurements show Cu enrichment on all catalytic surfaces. Scanning electron microscopy, SEM, measurements show CuNi nanoparticles ranging in size from 4 nm to 100 nm. Some agglomeration was observed. SDC showed the best yield with all catalysts. Furthermore, high oxygen vacancy content was shown to increase yield of CO for the RWGS reaction. Cu50Ni50/SDC shows the combination of highest yield of CO and the best stability among CuNi catalysts. It also has similar yields (39.8%) as Pt/SDC at 700°C, which achieved the equilibrium yield at that temperature (43.9%). The catalyst was stable for 48 hours when exposed to high temperatures (600-700°C). There was no CH4 observed during any of the experiments when the partial pressure of the reactant gases was fed stoichiometrically. Partial pressure variation experiments demonstrated the presence of CH4 when the partial pressure of hydrogen was increased to twice the value of the partial pressure of CO2.

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Universidade Federal de Sao Carlos
Particle size effect and Ce addition on the catalytic properties of Cu/Al2O3catalysts were investigated for the water gas shift reaction (WGS). The catalysts were prepared by dry impregnation of an aqueous solution of nitrates of the respective metals on alumina, synthesized by sol-gel method. Samples were prepared with 5, 10 and 15% w/w of metallic copper and 12% w/w of CeO2. The catalysts were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR) spectroscopy, X-ray absorption (XAS). The WGS reaction was performed with reagents ratio of H2O:CO = 1:3 with temperature range from 200 to 350° C. The crystallites CuO were not detected by XRD. As the Cu content increased, the crystallite size of CeO2 decreased with a fluorite type structure from 7.4 to 3.4 nm. The results of TPR showed that the interaction Cu-O-Al was crucial to reduce temperature and ceria addition on the catalysts did not affect the temperature reduction of the CuO. The XANES in situ results along the WGS reaction showed that metallic Cu predominated and ceria was partially reduced. EXAFS results showed that the Cu particle size increased from 0.65 to 0.91 nm with an increased load of copper from 5 to 15%, respectively. After the reduction, step prior to reaction, the catalysts were not completely reduced. The degree of reduction increased with the Cu particle size and it was also dependent on the temperature and the oxidation potential of mixing of the reactants. The addition of ceria did not change the degree of reduction of samples Cu/Al2O3. The results suggest that the Cu particles have a reduced Cu core covered with an oxide layer. The catalytic activity increased as the Cu particle size decreased, which can be associated with the presence of the redox couple Cu+/Cu0. This provides a possibility of CO oxidation and its reoxidation due to water activation. The ceria addition also increased catalytic activity and it is probably attributed to activation of the water on the surface of ceria, followed by transfer of oxygen from its structure to the oxidation of CO in an interface Cu-CeO2.
O efeito do tamanho da partícula de Cu e a adição de céria nas propriedades catalíticas dos catalisadores de Cu/Al2O3 foram investigados para a reação de deslocamento gás água (WGS). Os catalisadores foram preparados por impregnação da solução alcoólica dos respectivos nitratos dos metais em alumina, sintetizada pelo método sol-gel. As amostras foram preparadas com teores de Cu de 5, 10 e 15% m/m e 12% m/m de CeO2. Os catalisadores foram caracterizados por difração de raios X (DRX), redução a temperatura programada (TPR) e espectroscopia de absorção de raios X (XAS). A reação de WGS foi realizada com a razão de reagentes H2O:CO = 3:1 em temperaturas entre 200 e 350ºC . Os cristalitos de CuO não foram detectados por DRX. Com o aumento do teor de Cu de 5 para 15% m/m verificou-se um decréscimo no tamanho de cristalitos de CeO2 com uma estrutura do tipo fluorita de 7,4 para 3,4 nm. A interação Cu-O-Al foi determinante na temperatura de redução dos catalisadores e a adição da céria não afetou a temperatura da redução do CuO. Os resultados de XANES in situ mostraram que ao longo da reação de WGS o Cu na forma metálica foi predominante e a céria encontrava-se parcialmente reduzida. Os resultados de EXAFS mostraram que o tamanho das partículas de Cu aumentou de 0,65 para 0,91nm com o aumento do teor do cobre de 5 para 15%, respectivamente. Após a etapa de redução que antecede a reação, os catalisadores não se encontraram completamente reduzidos. O grau de redução aumentou com o tamanho da partícula de Cu e mostrou-se dependente também da temperatura e do potencial de oxidação da mistura dos reagentes. A adição da céria não modificou o grau de redução das amostras de Cu/Al2O3. Tais resultados sugerem que as partículas de cobre apresentam um núcleo reduzido com óxido de cobre na superfície. A atividade catalítica aumentou com a diminuição do tamanho de partícula de Cu, o que pode estar associado à maior presença do par redox Cu+/Cu0 nas menores partículas. Este possivelmente proporciona a oxidação do CO, reduzindo o Cu+ ao Cu0 e a reoxidação ocorre devido à ativação da água. A adição da céria também aumentou a atividade catalítica, a qual foi atribuída provavelmente à ativação da água nas vacâncias de oxigênio da céria, seguida da transferência de oxigênio de sua estrutura para a oxidação do CO em uma interface Cu-CeO2.

[ES] Dado su tamaño subnanométrico, los clusters metálicos están regidos por el confinamiento cuántico, lo que les hace más "moleculares" y menos "metálicos". En consecuencia, manifiestan propiedades que difieren con respecto a las de partículas más grandes del mismo elemento, y que a menudo son ventajosas para la catálisis de reacciones específicas. Además, su menor tamaño los hace más económicos, con una mayor superficie expuesta. Todo ello hace que los clusters sean opciones muy interesantes en catálisis, y su estudio, síntesis y aplicación ha crecido continuamente desde su descubrimiento en los años 90. Esta tesis se ha centrado principalmente en el cobre, del que se presenta, en primer lugar, un estudio fundamental sobre la disociación de oxígeno por clusters de diferentes tamaños. Después, se explora computacionalmente la catálisis de las oxidaciones de CO y propeno, confirmando que los clusters de Cu5 (o inferior) son prometedores para reacciones de oxidación. Las dos reacciones utilizadas son buenos ejemplos de la aplicación potencial en industria, sea para reducir emisiones de CO o para producir epóxido de propeno, que es un intermedio importante en la producción de plásticos y adhesivos, entre otros. Además, también se estudió la influencia de dos soportes en los clusters de cobre y su capacidad de oxidación: N-grafeno como un sistema más inerte y ceria como uno que puede participar activamente en reacciones de oxidación. Finalmente, se incluyen otros dos estudios más específicos, sobre la capacidad de los clusters de Pt3 y Pd3 para catalizar reaciones de acoplamiento C-C como la reacción de Heck, importante para la síntesis de productos de la química fina, y sobre la reacción CO + NO en clusters de Pt, motivado por su uso potencial como catalizadores para la conversión de esas especies en los menos perjudiciales CO2 y N2 en motores de combustión interna.
[CAT] Atès que són de grandària subnanomètrica, els clusters metàl·lics estan regits pel confinament quàntic, el qual els fa més "moleculars" i menys "metàl·lics". En conseqüència, manifesten propietats que són diferents a les de partícules més grans del mateix element, i que sovint són avantatjoses per a la catàlisi de reaccions específiques. A més a més, la seua menor grandària fa que siguen més econòmics, amb una major superfície exposada. Així, els clusters són una opció molt interesant en catàlisi, i el seu estudi, síntesi i aplicació ha cres-cut contínuament des del seu descobriment als anys 90. Aquesta tesi s'ha centrat principalment en el coure, del qual es presenta, en primer lloc, un estudi fonamental sobre la dissociació de l'oxígen per clusters de diferents grandàries. Després, s'explora computacionalment la catàlisi de les oxidacions de CO i de propè, confirmant que els clusters de Cu5 (o inferior) són prometedors per a reaccions d'oxidació. Les dues reaccions utilitzades són bons exemples de l'aplicació potencial en indústria, siga per reduir emissions de CO o per produir epòxid de propè, que és un intermedi important en la producció de plàstics i adhesius, entre altres. A més, també es va estudiar la influència de dos suports en els clusters de coure i la seua capacitat d'oxidació: N-grafè com a un sistema més inert i cèria com a un que pot participar activament en reaccions d'oxidació. Finalment, s'inclouen altres dos estudis més específics, sobre la capacitat dels clusters de Pt3 y Pd3 per catalitzar reaccions d'acoblament C-C com la reacció de Heck, important per a la síntesi de productes de la química fina, i sobre la reacció CO + NO als clusters de Pt, motivat pel seu ús potencial com a catalitzadors per a la conversió d'eixes espècies en els menys perjudicials CO2 i N2 als motors de combustió interna.
[EN] Due to their subnanometric size, metal clusters belong to the regime affected by quantum confinement, which makes them more "molecular" and less "metallic". As a result, they exhibit properties that differ with respect to those of larger particles of the same element, and which are often advantageous in the catalysis of specific reactions. Besides, their smaller size makes them more economic and with a higher surface exposed. All of this renders metal clusters very interesting options for catalysis, and their study, synthesis and application has steadily increased since their discovery in the 90s. In this work we have largely focused on copper, of which a fundamental study on the oxygen dissociation by clusters of different sizes is first presented. Then, the catalysis of the CO and propene oxidation reactions is theoretically explored, confirming that Cu5 (or smaller) clusters are promising systems for oxidation reactions. The two reactions used are good examples of the potential application in industry, either to reduce CO emissions or to produce propene epoxide, an important intermediate in the production of plastics and adhesives, among others. In addition, the influence of two supports in the copper clusters and their oxidation capability is explored: on N-graphene as a more inert system and on ceria as one that can actively participate in oxidation reactions. Finally, two other more specific studies are included, regarding the capability of Pt3 and Pd3 clusters to undergo C-C coupling reactions such as the Heck reaction, important for the synthesis of many products of fine chemistry, and regarding the CO + NO reaction on Pt clusters, motivated by their potential use as catalysts for the conversion of those species in less harmful CO2 and N2 in internal combustion engines.
En primer lugar me gustaría agradecer al Ministerio de Economía y Competitividad de España (MINECO) por la financiación de esta tesis mediante el programa Severo Ochoa (SVP-2013-068146), incluyendo los costes adicionales de mi estancia de investigación (EEBB-I-17-12057).
Fernández Villanueva, E. (2019). Theoretical Study of the Geometrical, Electronic and Catalytic properties of Metal Clusters and Nanoparticles [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/135277
TESIS

碩士
國立臺灣科技大學
工程技術研究所
98
This research aims to study the absorption and conversion of ethanol on catalyst supported on SiO2- and CeO2- in order to understand ethanol reforming reaction. The CeO2 was loaded on the SiO2 via incipient wetness impregnation, and its properties was compared with the CeO2 prepared by homogeneous precipitation method. The catalysts were characterized and examined by N2 physisorption, X-ray powder diffraction, temperature programmed reduction, ethanol pulse chemisorption, temperature programmed desorption and ethanol pulse reaction. Higher ethanol absorption of CeO2(HSA) was achieved by loading 0.2wt% Cu. During the process of temperature programmed reduction, the incorporation of the Cu promoted the decomposition of the surface species of catalyst. The loading of Cu also enhanced the ethanol conversion as indicated in the ethanol pulse chemisorption experiments suggesting that the catalyst system is feasible to operate with lower temperature.

碩士
逢甲大學
化學工程學所
93
This study is focused to optimize the selective oxidation of carbon monoxide reaction process over three types of the lab-prepared catalysts to remove CO or convert into CO2 in the presence of excess hydrogen.The proposed catalysts, Cu/Ce/γ-Al2O3 and Cu/Ce-MCM-41 were prepared by incipient wetness method, and CuO-CeO2 was made by co-precipitation. These catalysts were characterized by XRD, BET, and ICP. The activity of catalysts was tested in an environment of 1vol% CO, 2vol%O2 50vol% H2, 15vol% CO2, and 3vol%H2O. The experimental results showed that the CO conversion achieved 100% at 170 oC ~230oC when the CuO-CeO2 catalyst with Cu to Ce molar ratio is 3:7. At the same molar ratio, the CO conversion of Cu/Ce/γ-Al2O3 was higher than those by CuO-CeO2 catalysts.The CO conversion achieved 99.5% at 230°C when the Cu/Ce/γ-Al2O3 catalyst with Cu to Ce molar ratio was 6:4. According to the BET and ICP results showed that surface area of Cu/Ce-MCM-41 decrease significantly.The active centers decreased and the ceria content was insuffucuent as well.

碩士
大同大學
化學工程學系(所)
92
In the methanol steam-reforming reaction, there are small quantities carbon monoxides, and the water-gas shift reaction is the method which is applies recently to converse large amount of carbon monoxide. This research is to develop, Cu-series catalyst with high performance of removing carbon monoxide at low temperature (200 ℃~280 ℃). In this research, silicon dioxide (SiO2) was used as carrier, treats as the active metal by the Cu and Ce, contains the different proportion active metal impregnated on the carrier, then they were calcined at the high temperature of 500 ℃. After being reduced, the catalysts possessed the best efficiency of removing CO. The characteristic analyses of the Cu-series catalysts were performed by TGA, TPR, TPO, XRD and ICP. The water-gas shift reaction was carried out in the fixed-bed reaction: under the circumstances of the hydrogen-rich atmosphere, a gas containing small quantity of CO for simulating the trailing gas of fuel cell passed through the reactor, and before the reaction took place, the catalysts were reduced with hydrogen; besides, comparisons of the active metals of oxidization state with the active metals of reduction state were made, so as to find out the differences in efficiencies of removing CO and the optimal proportions of catalysts. The experimental result showed that the active metal Ce increased on the Cu/SiO2 carrier promoted the metal dispersion and particle diameters of active metal copper was smaller. From the reduction peak diagrams of TPR, it could be known that the higher was the active metals content in the catalyst, the easier was on the carrier surface to from large grains of oxidized copper, and the higher was the reduction temperature, showing that when the catalysts carried out WGSR, the activities were poorer. During WGSR, added ceria in Cu-series catalyst, its catalyst activity had not added the ceria in Cu-series catalyst is better than; Using SiO2 was the support, when the Cu content reached to 25 wt%, the CO removing percentage at 250 ℃ could reach 92%; When has not added the ceria the catalyst, the Cu content reached to 25 wt%, the CO removing percentage at 250 ℃ could reach 75%.

Washcoating copper catalyst in the micro-channel reactor for steam reforming of methanol (SRM) is advantageous to get high ratio of surface area to volume. Catalyst was coated using brushing method by making slurry with different metal oxides sol as binder (ceria, zirconia and yttria). In the preparation of catalyst slurry, the solid content, ratio of catalyst to binder, pH value and solvent were investigated. The adhesion of catalyst can be compared by estimating the weight loses of washcoating layer after 130W sonication for 30 min. The crystallite, morphology, reduction temperature and chemical environment of catalysts can be characterized by XRD, SEM, TPR and OTPR. The catalyst coated with various metal oxides sol mixing water/ethanol solvent with a specific solid content and catalyst/binder ratio in the neutral solution exhibits a good adherence with the substrate. The performance of fabricated micro-reformer is investigated in the temperature range 150–300 °C. In GHSV = 60,000 h−1, the conversion reaches 80% at 210 °C, and it corresponded to the generating of hydrogen for power output of 2 W assuming a 50% fuel cell operating efficiency. Furthermore, the fabrication of microchannels reactor connecting high temperature PEMFC is investigated.

<div class="section abstract"><div class="htmlview paragraph">Diesel-powered engines are used worldwide for efficient transportation and stationary power generation. The significant drawback of a diesel engine is its harmful emissions. The stringent emission norms enforced by the different organization demands effective catalyst system to control the gaseous emissions. Diesel oxidation catalysts are the extensively used technique for diesel engines to control HC and CO emissions. Currently the catalyst in the diesel oxidation system employs precious metals such as Pt/Pd/Rh to reduce the emissions and makes the DOC system expensive. This paper presents a cost-effective catalyst prepared to employ non-noble mixed oxides of copper and nickel supported on non-conventional support (i.e.) ceria doped calcium borophosphates (Ce-SCaPB). Initially, ceramic beads (5mm X 5mm) were coated with (Ce-SCaPB) support material. Secondly, the copper and nickel salts were deposited on the Ce-SCaPB coated ceramic beads and subsequently reduced and calcined. The crystallinity and phase formation was studied using XRD technique and SEM image showed particle size ranging between 40 - 50 nm. These catalyst coated beads were loaded into the fabricated DOC reactor and was retrofitted into the tailpipe of the engine exhaust. The experimental emission testing was carried out in a single-cylinder diesel engine coupled with eddy current dynamometer. In engine testing, catalytic material are tested individually to evaluate his reduction percentage. The engine test was conducted under different engine loads (0-100%) and the emission readings were taken for each load. Uncertainty analysis is calculated for the results and the results showed a higher reduction in CO, HC and smoke emissions.</div></div>