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CuO/ceria and CuO/Y-doped ceria catalysts were synthesized. The Y-modified supports (1.0, 2.5 and 5.0 wt% Y2O3) were prepared by coprecipitation. CuO (3 wt% Cu) was loaded by deposition-precipitation. Having in mind the known effect of Y3+ modification for the generation of oxygen vacancies in ceria, its positive role on the water-gas shift (WGS) performance was expected. However, the catalytic test showed a trend of decreased WGS activity by increasing the Y-dopant amount, nevertheless that the differences were not very substantial. On the basis of XRD, XPS, EPR, Raman spectroscopy and H2-TPR results the explanation related to the key role of the oxygen mobility influenced by Y-doping could be proposed. The reason of the inferior WGS performance with increasing Y-content would be the higher amount of surface oxygen vacancies around Y3+ ions which disturbed the Cu-Ovac-Ce active sites for WGS reaction. Though, during the long run catalytic tests in WGS reaction a positive effect of Y-doping for improved stability of CuO/ceria catalysts was evidenced.

Gold catalysts on CeO2/Al2O3 and Y-doped CeO2/Al2O3 supports prepared by mechanical mixing were tested in the preferential CO oxidation in hydrogen rich stream (PROX). The samples were characterized by XRD, HRTEM/HAADF, XPS and TPR measurements and the effect of preparation method on the textural, structural, reductive and catalytic properties was commented. The difference in the catalytic behaviour at the temperatures of interest for fuel cells application (80–120 °C) was not very substantial showing a degree of CO conversion in the range of 60 and 70%. An exception was the highest CO conversion at 80 °C observed over the gold catalyst on CeO2/Al2O3 with 20 wt.% ceria loading. The explanation of the lower activity of gold catalyst on Y-doped CeO2/ Al2O3 with the same ceria amount was related to gold dispersion as a key factor for CO oxidation. The positive effect of yttrium was evidenced during long run tests in PROX with CO2 and water addition to gas stream. The better stability caused by the Y-presence was in agreement with the CO2-TPD results showing lower surface basicity.

Using periodic density functional calculations, we studied the local structure and preferred locations of yttrium cations and oxygen vacancies in Y-doped cerium dioxide. We employed three kinds of models - a slab of the CeO2(111) surface and two ceria nanoparticles of different sizes and shapes. In the slab models, which represent the (111) surface of ceria and the corresponding extended terraces on the facets of its nanoparticles, Y3+ cation dopants were calculated to be preferentially located close to each other. They tend to surround a subsurface oxygen vacancy that forms to maintain the charge balance. Such general behavior was not found for the nanoparticle models, in which structural flexibility and the presence of various low-coordinated surface centers seem to be crucial and suppress most of the trends. Configurations with four Y3+ cations were calculated to be particularly stable when they combined two of the most stable configurations with two Y3+ cations. However, no clear trend was found regarding the preferential spatial distribution of the Y3+ pairs - they can be stable both in isolation and close to each other. In general, doping by yttrium does not notably change the reducibility of ceria systems but selectively facilitates the formation of oxygen vacancies at the ceria surface in comparison with pristine ceria. Yttrium cations also slightly increase the basicity of the nearby oxygen centers with respect to a stoichiometric ceria surface.

The catalytic oxidation of CO and volatile organic compounds (VOCs) is considered as one of the most efficient ways to reduce harmful emissions from various chemical industries. The effectiveness of gold-based catalysts for many reactions of environmental significance was proven during the past three decades. The aim of this work was to combine the favorable features of Au and Cu-Ce mixed oxides in the design of new catalytic materials of improved efficiency and economic viability for removal of air pollutants in waste gases from formaldehyde production. Supported oxides of copper and cerium with Cu: Ce molar ratio 2:1 and 1:5 were prepared by wet impregnation of g-alumina. Gold (2 wt.%) catalysts were synthesized by a deposition-precipitation method. Catalysts characterization was carried out by texture measurements, powder X-ray diffraction, temperature programmed reduction and electron paramagnetic resonance spectroscopy. The catalytic activity in the oxidation of CO, CH3OH and (CH3)2O was measured using continuous flow equipment with fixed bed reactor. Both Cu-Ce/alumina samples demonstrated similar catalytic behavior. The addition of gold caused significant enhancement of CO and methanol oxidation activity (100 % degree of CO and CH3OH conversion at about 60 and 140 oC, respectively). The composition of Cu-Ce mixed oxides affected the performance of gold-based samples considerably. Gold catalyst on Cu-Ce/γ-Al2O3 1:5 exhibited higher activity for CO and CH3OH oxidation in comparison with Au on Cu-Ce/γ-Al2O3 2:1. The better performance of Au/Cu-Ce 1:5 was related to the availability of highly dispersed gold particles and copper oxide clusters in close contact with ceria., {"references":["J. Li, H. Liu, Y. Deng, G. Liu, Y. Chen, and J. Yang, \"Emerging nanostructured materials for the catalytic removal of volatile organic compounds,\" Nanotechnology Reviews, vol. 5, no 1, pp. 147–181, 2016.","M. S. Kamal, S. A. Razzak, and M. M. Hossain, \"Catalytic oxidation of volatile organic compounds (VOCs): A review,\" Atmospheric Environment, vol. 140, pp. 117-134, 2016.","Z. Zhang, Z. Jiang, and W. Shangguan, \"Low-temperature catalysis for VOCs removal in technology and application: A state-of-the-art review,\" Catalysis Today, vol. 264, pp. 270-278, 2016.","L. F. Liotta, \"Catalytic oxidation of volatile organic compounds on supported noble metals,\" Applied Catalysis B, vol. 100, pp. 403-412, 2010.","G. Avgouropoulos, and T. Tabakova, Environmental Catalysis over Gold-Based Materials, RSC Catalysis Series, no 13, RSC Publishing, Thomas Graham House, Cambridge, 2013.","S. Scire, and L. F. Liotta, \"Supported gold catalysts for the total oxidation of volatile organic compounds,\" Applied Catalysis B, vol. 125, pp. 222–246, 2012.","M. Stoyanova, D. Petrov, D. Dimitrov, K. Ivanov, and S. Christoskova, \"Nanocomposite oxide systems for oxidation of CO and VOCs in gaseous phase, Journal of International Scientific Publications: Ecology and Safety, vol. 8, pp. 479-486, 2014.","L. F. Liotta, H. Wu, G. Pantaleo, and A. M. Venezia, \"Co3O4 nanocrystals and Co3O4-MOx binary oxides for CO, CH4 and VOC oxidation at low temperatures: A review,\" Catalysis Science & Technology, vol. 3, pp. 3085–3102, 2013.","P.-O. Larsson, and A. Andersson, \"Oxides of copper, ceria promoted copper, manganese and copper manganese on Al2O3 for the combustion of CO, ethyl acetate and ethanol,\" Applied Catalysis B, vol. 24, pp. 175–192, 2000.\n[10]\tH. Wan, D. Li, Y. Dai, Y. Hu, Y. Zhang, L. Liu, et al., \"Effect of CO pretreatment on the performance of CuO/CeO2/-Al2O3 catalysts in CO + O2 reactions,\" Applied Catalysis A, vol. 360, pp. 26–32, 2009.\n[11]\tM. Konsolakis, \"The role of copper–ceria interactions in catalysis science: Recent theoretical and experimental advances,\" Applied Catalysis B, vol. 198, pp. 49–66, 2016.\n[12]\tD. Delimaris, and T. Ioannides, \"VOC oxidation over CuO–CeO2 catalysts prepared by a combustion method,\" Applied Catalysis B, vol. 89, pp. 295–302, 2009.\n[13]\tM. Piumetti, S. Bensaid, T. Andana, N. Russo, R. Pirone, and D. Fino, \"Cerium-copper oxides prepared by solution combustion synthesis for total oxidation reactions: From powder catalysts to structured reactors,\" Applied Catalysis B, vol. 205, pp. 455–468, 2017. \n[14]\tA. Trovarelli, and P. Fornasiero, \"Catalysis by Ceria and Related Materials – 2nd Edition,\" Imperial College Press, London, 2013.\n[15]\tE. Kolentsova, D. Dimitrov, K. Ivanov, T. Tabakova, Y. Karakirova, K. Tenchev, G. Avdeev, \"CO and VOCs oxidation over alumina supported Cu-Mn catalysts modified by cerium,\" Bulgarian Chemical Communications, to be published.\n[16]\tM. Gonzalez Castaño, T. R. Reina, S. Ivanova, M. A. Centeno, and J. A. Odriozola, \"Pt vs. Au in water–gas shift reaction,\" Journal of Catalysis, vol. 314, pp. 1–9, 2014.\n[17]\tH. C. Yao and Y. F. Yu Yao, \"Ceria in automotive exhaust catalysts: I. Oxygen storage,\" Journal of Catalysis, vol. 86, pp. 254-256, 1984.\n[18]\tA. Ishikawa, M. Neurock, and E. Iglesia, \"Structural Requirements and Reaction Pathways in Dimethyl Ether Combustion Catalyzed by Supported Pt Clusters,\" J. Am. Chem. Soc., vol. 129, pp. 13201-13212, 2007.\n[19]\tA. Ishikawa and E. Iglesia, \"Bifunctional pathways mediated by Pt clusters and Al2O3 in the catalytic combustion of dimethyl ether,\" Chemical Communications, pp. 2992- 2993, 2007."]}

Recently, copper and manganese-containing systems are recognized as active and selective catalysts in many oxidation reactions. The main idea of this study is to obtain more information about γ-Al2O3 supported Cu-La catalysts and to evaluate their activity to simultaneous oxidation of CO, CH3OH and dimethyl ether (DME). The catalysts were synthesized by impregnation of support with a mixed aqueous solution of nitrates of copper, manganese and lanthanum under different conditions. XRD, HRTEM/EDS, TPR and thermal analysis were performed to investigate catalysts’ bulk and surface properties. The texture characteristics were determined by Quantachrome Instruments NOVA 1200e specific surface area and pore analyzer. The catalytic measurements of single compounds oxidation were carried out on continuous flow equipment with a four-channel isothermal stainless steel reactor in a wide temperature range. On the basis of XRD analysis and HRTEM/EDS, it was concluded that the active component of the mixed Cu-Mn-La/γ–alumina catalysts strongly depends on the Cu/Mn molar ratio and consisted of at least four compounds – CuO, La2O3, MnO2 and Cu1.5Mn1.5O4. A homogeneous distribution of the active component on the carrier surface was found. The chemical composition strongly influenced catalytic properties. This influence was quite variable with regards to the different processes., {"references":["Y. Nishihata, J. Mizuki, T. Akao, H. Tanaka, M. Uenishi, M. Kimura, N. Hamada, \"Self-regeneration of a Pd-perovskite catalyst for automotive emissions control\", Nature, 418 (6894), pp. 164-167 2002.","H. Tanaka, M. Misono, \"Advances in designing perovskite catalysts\", Current Opinion in Solid State and Materials Science, 5 (5), pp. 381-387, 2001.","M. Stoyanova ,P. Konova, P. Nikolov, A. Naydenov, St. Christoskova, D. Mehandjiev \"Alumina-supported nickel oxide for ozone decomposition and catalytic ozonation of CO and VOCs\" , Chemical Engineering Journal 122 (1-2) , pp 41-46, 2006.","S. Moreau, J. Choisnet, F. Beguin, J., \"Development of LaxMOy nanoparticles dispersed in a layered silicate matrix\", Phys. Chem. Solids, 57, pp. 1049-1056, 1996.","E. A. Lombardo, M.A. Ulla, \"Perovskite oxides in catalysis: Past, present and future\", Res. Chem. lntermed., 24 (5), pp. 581-592, 1998.","X. Chen, S.A.C. Carabineiro, P.B. Tavares, J.J.M. Orfao, M.F.R. Pereira, J.L. Figueired, \"Catalytic oxidation of ethyl acetate over La-Co and La-Cu oxides\", J. Envir. Chem. Eng., 2, pp. 344-355, 2014.","R. Prasad, P. Singh, \"A Review on CO oxidation over copper chromite catalyst\", Catal. Rev.: Sci. Eng., 54, pp. 224–279, 2012.","A. Urbutis, S. Kitrys, \"Structure and activity of CuO catalysts promoted with CeO2 and La2O3 for complete oxidation of VOCs\", Chemija., 24 (2), pp. 111–117, 2013.","S. Mentus, D. Jeli, V. Grudi, \"Lanthanum nitrate decomposition by both temperature programmed heating and citrate gel combustion. Comparative study\", J. Therm. Anal. Calorim., 90 (2), pp.393–39, 2007.\n[10]\tH.E. Runxia, H. Jiang, W.U. Fang, K. Zhi, N. Wang, C. Zhou, Q. Liu, \"Effect of doping rare earth oxide on performance of copper-manganese catalysts for water-gas shift reaction\", J. Rare Earths, 32 (4), pp. 298-305, 2014."]}

[EN] The invention relates to the synthesis and application of gold catalysts supported in mixed CuO/ZnO/Al203 oxides prepared on the basis of their corresponding solids with a hydrotalcite structure as catalysts in the displacement reaction of gas from water, for use in fuel processors coupled to fuel cells., [ES] La presente invención se refiere la síntesis y aplicación de catalizadores de oro soportado en óxidos mixtos CuO/ZnO/Al203 preparados a partir de sus correspondientes sólidos con estructura hidrotalcita como catalizadores en la reacción de despalzamiento de gas de agua, para uso en procesadores de combustible acoplados a celdas de combustibles., Universidad de Sevilla, Consejo Superior de Investigaciones Científicas (España), A1 Solicitud de patente con informe sobre el estado de la técnica