磷前驱体对金属磷化物甲烷化催化性能的影响

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

采用氢气程序升温还原方法制备了系列金属磷化物催化剂,研究了磷前驱体和H_(2)/CO比对其甲烷化催化性能的影响。结果表明,与磷酸氢二铵相比,由植酸制备的金属磷化物催化剂具有较高的甲烷化活性;植酸作为螯合剂可以有效地分散金属前驱体,降低还原温度,使催化剂具有较高的比表面积和较小的晶粒尺寸,并更好地还原为纯磷化物晶相。不同金属磷化物催化剂的活性顺序为MoP>WP>CoP>NiP。高H_(2)/CO比有利于甲烷化反应进行,随着反应物H_(2)/CO比的增加,所有磷化物催化剂的甲烷选择性都增加。

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 H_(2)/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 H_(2)/CO ratio in the feed is favorable for the methanation over the phosphide catalysts;the selectivity to methane increases with an increase in the H_(2)/CO ratio.