CO_2 methanation combined with NH_3 decomposition by in situ H_2 separation using a Pd membrane reactor

摘要

Combination of the reactions by means of membrane separation techniques are of interest. The CO_2 methanation was combined with NH_3 decomposition by in situ H_2 separation through a Pd membrane. The CO_2 methanation reaction in the permeate side was found to significantly enhance the H_2 removal rate of Pd membrane compared to the use of sweep gas. The reaction rate of CO_2 methanation was not influenced by H_2 supply through the Pd membrane in contrast to NH_3 decomposition in the retentate side. However, the CH_4 selectivity could be improved by using a membrane separation technique. This would be caused by the active dissociated H species which might immediately react with adsorbed CO species on the catalysts to CH_4 before those CO species desorbed. From the reactor configuration tests, the countercurrent mode showed higher H_2 removal rate in the combined reaction at 673 K compared to the cocurrent mode but the reaction rate in CO_2 methanation should be improved to maximize the perfomance of membrane reactor.