Effect of phosphorus precursor on the catalytic performance of metal phosphides in the methanation of syngas

A series of metal phosphides including MoP, WP, CoP and NiP was prepared by temperature-programmed reduction with hydrogen from different phosphorus precursors. The effect of phosphorus precursor and feed H₂/CO ratio on the catalytic performance of metal phosphides in the methanation was investigated. In comparison with diammonium hydrogen phosphate (DAP), phytic acid (PA) as a chelating agent can effectively disperse the metal precursor, reduce the reduction temperature, promote to form pure phosphide phase, and give the phosphide catalyst a higher surface area and a smaller particle size; as a result, the metal phosphides prepared with PA as a phosphorus precursor exhibit higher catalytic activity in methanation. In addition, the catalytic activity of various metal phosphides in methanation follows the sequence of MoP > WP > CoP > NiP. A high H₂/CO ratio in the feed is favorable for the methanation over the phosphide catalysts; the selectivity to methane increases with an increase in the H₂/CO ratio.