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Zn- and Mn-doped Cerium-oxide based catalyst textured as a solid solutional as well as interfacial form was compared in CO2 hydrogenation reaction to understand the role of texture as well as dopant type. Ce0.9M0.1O2 (M = Zn, Mn) solid solution was prepared by hydrothermal method and CeO2 supported 10 mol% metal oxide (Metal = Zn, Mn) were prepared by wet impregnation method, where the catalysts were characterized by XRD, N2 adsorption/desorption isotherm, TEM, Raman spectra, HAADF-STEM and H2-TPR. During the CO2 activation reaction, CO was the major product with minor amounts of methane, ethane, methanol and ethanol. In the case of the Zn-doped CeO2 catalyst, the presence of Zn improved catalytic activity in both solid solutional and interfacial form due to the synergetic effect of Zn-Ce-based oxide. However, for MnOx/CeO2 catalysts, the CO2 consumption rate significantly decreased for 10 mol% MnOx/CeO2, Ce0.9Mn0.1O2 and Mn3O4, where the MnOx addition inhibits the reduction of CeO2. In the case of the pure CeO2, DRIFTS spectra show that formate intermediate formed by reaction between activated CO2 and OH transformed into methoxy species through formaldehyde intermediates, which leads to the formation of small amount of methanol and ethanol. [ABSTRACT FROM AUTHOR]

Thermo-catalytic bio-SNG (CH 4) production is one of the useful tools for converting waste to gaseous fuels through CO 2 conversion. To abundant properly, however, efficient, robust and cost-effective catalysts would be required. Bimetallic systems based on transition metals seem to be promising candidates for this task. The CoCu bimetallic system with in-situ generated interfaces was synthesized and used as a catalyst for CO 2 methanation. The in-depth analysis of the structure-activity-selectivity relationships involving XRD, (NAP-)XPS, EXAFS and TEM-EDX revealed that the co-existence of Co0, CoO, and Cu0 in the proper distribution on the surface can ensure the selective production of methane. To fine-tune the surface composition of the bimetallic systems, a systematic alteration of the Cu:Co ratio in the precursor spinel structures must be performed. Cu 0.4 Co 2.6 O 4 derivative, stabilizing subsurface Cu(I)–O specimen, showed the best performance with high activity (12,800 nmol g–1 s–1) and a remarkable selectivity of 65–85% for methane in a wide temperature range (250–425 °C). In studying the mechanistic aspects of methanation, it has been shown that the hydrogenation of active carbon at the surface or below the surface is the key step for the production of methane. So far, this cobalt-catalyzed sub-step has been proposed in catalytic Fischer-Tropsch syntheses. [Display omitted] • Copper cobaltites are useful precursors for the construction of efficient Cu/Co bimetallic catalysts for CO 2 methanation. • The copper-to-cobalt ratios in the octahedral lattice positions of the spinels determined the catalytic performance. • The Cu 0.4 Co 2.6 O 4 derivative with a Co-enriched surface shows high performance producing CH 4 over a wide temperature range. • The hydrogenation of active carbon at the surface or below the surface is the key step for the production of methane. [ABSTRACT FROM AUTHOR]

Series of Co x M 1-x Al 4 layered triple hydroxides, LTHs were prepared as catalyst precursors for hydrogenation of biomass compound cinnamaldehyde under flow and batch reaction conditions. To this end, we have successfully extended the eco-friendly family of Al-rich layered double hydroxides (LDHs) by synthesizing MnAl 4 -LDHs, furthermore Co 3 Al-, Co 2 Al-LDHs were also exploited. Both the magnetic Co-rich and Al-rich reduced forms behaved as robust, efficient and reusable catalysts with significantly different selectivities correlated with their acid-base properties. Al-rich solids showed increased acidity and lower basicity resulting in high hydrocinnamaldehyde selectivity (∼75 %), while the Co-rich catalysts attested enhanced hydrocinnamyl alcohol production (∼80 % selectivity) due to their low acidity and high basicity (mapped by NH 3 /CO 2 temperature programmed desorption tests). Incorporation of Mn, Ni, Cu and Zn ions generally decreased the total acidity of Al-rich catalysts, while their Lewis basicity largely increased: the highest was found for Mn, resulting in activity similar to that of Co-rich catalysts. [Display omitted] • Synthesis of the new cobalt-aluminum-based LDH and LTH catalyst precursors. • Incorporation of Mn (not yet published), Ni, Cu and Zn ions into the rare CoAl 4 -LDH. • Use of Co-rich/Al-poor and Co-poor/Al-rich catalysts for cinnamaldehyde reduction. • Detailed comparative application between the catalysts in flow and batch conditions. • Effect of solid composition and acid-base properties on the selectivity of products. [ABSTRACT FROM AUTHOR]

Abstract: The formation and stability of surface species generated in the interaction of ethanol and ethanol–water mixture with Al2O3 and CeO2-supported noble metal catalysts were studied by FT-IR, TPD and TPR methods. It was found that water enhanced the stability of ethoxide surface species formed in the dissociation of ethanol. Dehydrogenation of molecularly adsorbed ethanol was proposed as a key reaction step. The TPD spectra of ethanol adsorbed on supported noble metals exhibited a high temperature desorption stage which was explained by the formation and decomposition of surface acetate species. Ethylene (product of the dehydration of ethanol) was mainly formed on Al2O3-supported noble metals, while on CeO2-supported noble metals significant amount of acetaldehyde (originated from the dehydrogenation of ethanol) was also formed. In the steam reforming of ethanol the selectivity of H2 formation decreased but that of C2H4 increased in time, while the conversions were stable on alumina-supported noble metals. These observations were explained by the inhibiting effect of surface acetate species. [Copyright &y& Elsevier]