Methanation of CO2-Rich Gases. Final Report.

摘要

The conversion of carbon dioxide and hydrogen was investigated using nickel catalysts developed for the methanation of CO/H2-mixtures. The pressure range varied from 15 up to 76 bar and the temperature was in between 400 and 520 C. The catalysts showed less deactivation when contacted with a synthesis gas containing CO2 instead of CO. On the fresh catalyst CO/H2 was converted faster than CO2/H2, but after a time on stream of 80 hours the reverse was detected. For two selected catalysts, at a stable activity, kinetic data have been measured for the conversion of CO2/H2-mixtures. The results were fitted to a power rate law giving reaction orders of 0.7 and 0.9 for carbon dioxide and 0 for hydrogen. The shape of CO-selectivity versus modified residence time indicated, that the CO2-methanation can be described as a consecutive reaction. According to this model CO2 first is converted to CO. The intermediate carbon monoxide then forms methane with hydrogen. Integral kinetic data, that means yield versus gas/catalyst contact time could be described sufficiently using rate equations in which the inhibiting effect of carbon monoxide on the reverse water gas shift reaction was taken into account. These studies were performed to get design data for the methanation of coke oven gases. It could be proved that the surplus of hydrogen in coke oven gas can be converted to methane by adding carbon dioxide. (orig.) with 146 refs., 13 tabs., 81 figs. (ERA citation 14:004105)