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Coking and decoking during methanation and methane decomposition on Ni-Cu suppo...

The effect of the composition of silica supported Ni-Cu alloy catalysts on the process of coking and decoking during methane decomposition and during methanation was considered. The kinetics of methanation was studied and compared to those of carbon deposition and of strong adsorption of hydrogen. Initiation of the formation of filamentous carbon formation on mono-metallic surfaces may take place if the ratio o...

Carbon formation on nickel and nickel-copper alloy catalysts

Equilibrium, kinetic and morphological studies of carbon formation in CH4+H2, CO, and CO+H2 gases on silica supported nickel and nickel-copper catalysts are reviewed. The equilibrium deviates in all cases from graphite equilibrium and more so in CO+CO2 than in CH4+H2. A kinetic model based on information from surface science results with chemisorption of CH4 and possibly also the first dehydrogenation step as r...

Carbon formation and CO methanation on silica-supported nickel and nickel–coppe...

The steady-state rates of simultaneous carbon formation and methanation on silica-supported nickel and nickel-copper catalysts in CO + H 2 gas mixtures have been measured in the partial pressure range 10-30 kPa and the temperature range 583-873 K. The steady-state kinetic results for carbon formation can be explained by a model previously used for carbon formation in pure CO gas, but modified to take into accou...

CO disproportionation on silica-supported Nickel and nickel-copper catalysts

The carbon formation/gasification equilibrium on silica-supported nickel and nickel-copper catalysts in CO + CO2 gas mixtures and the steady state kinetics of carbon formation from CO on the same catalysts were studied in a thermogravimetric flow system. The equilibrium gas composition was found to be the same for the nickel and the nickel-copper catalysts except at the highest copper concentrations (≥25 at.%),...

Kinetics of carbon formation from CH4 + H2 on silica-supported nickel and Ni-Cu...

Steady-state rates of carbon formation on a silica-supported nickel catalyst exposed to CH4 + H2 gas mixtures have been measured for a range of gas compositions (partial pressure of methane, 20-80 kPa, and of hydrogen, 5-15 kPa) and temperatures in the range 723-863 K. The data are used to test various kinetic models suggested previously in the literature. It is shown that the data are in conflict with previous...

The kinetics of carbon formation from CH4+H2 on a silica-supported nickel catalyst

A microkinetic model for the formation of carbon on a nickel surface exposed to CH4 + H2 gas mixtures is constructed and compared with measured carbon formation rates for a Ni/SiO2 catalyst. Most of the parameters of the model are determined independently from single-crystal experiments or from ab initio calculations. Two rate constants and two chemisorption bond energies are determined by least-squares minimiz...

Actividade e desactivação de catalisadores Ni-Cu/SiO2 : avaliação da estabilida...

O presente trabalho relata o estudo da deposição de carbono em catalisadores de niquel-cobre suportados em sílica, a partir de misturas de CH4+H2 e CO+CO2 com diferentes composições e a diferentes temperaturas. Verifica-se que a diminuição da velocidade de deposição de carbono nas ligas (normalizada pela velocidade de deposição no niquel puro) não é significativamente afectada nem pela natureza, nem pela concen...

Reactivity of carbon deposited on nickel-copper alloy catalysts from the decomp...