等离子体还原催化剂在CO2甲烷化反应中的活性

摘要

Ni-Ce/γ-Al2 O3 and Ni-Ce-LDHs/γ-Al2 O3 catalyst precursors were synthesized by impregnation and in situ chemical-growing methods, respectively. These precursors were reduced by Ar-H2 cold plasma jet and conventional H2 thermal reduction. The evaluation of these catalysts were carried out in a CO2 methanation reaction system. The results showed that the catalysts reduced by plasma had better catalytic activity, the reaction start-temperature with catalysts reduced by plasma was 20—30 ℃ lower than that with catalysts by conventional method. The catalysts were characterized by X-ray diffraction ( XRD ) , transmission electron microscopy( TEM) , CO2-temperature programmed desorption ( CO2-TPD ) , as well as X-ray photoelectron spectrum( XPS) . The results showed that plasma reduction could remarkably improve the dispersion of active components, the alkalinity of support and the size of crystal metal particles. It was these improvements that enhanced the activity of catalysts in methanation reaction.%采用浸渍法和原位生长水滑石法制备了Ni-Ce/γ-Al2 O3和Ni-Ce-LDHs/γ-Al2 O32种不同类型的催化剂前驱体，考察了2种前驱体分别经氩-氢等离子体和常规氢热方法还原所得催化剂在CO2甲烷化反应中的活性.结果表明，等离子体还原催化剂的低温活性明显高于常规氢热还原催化剂，主要表现为前者反应启动的临界温度点比后者低20~30℃.采用X射线衍射( XRD)分析、透射电子显微镜( TEM)、 CO2程序升温脱附( CO2-TPD)以及X射线光电子能谱( XPS)对所得催化剂的形貌和结构进行了表征.结果表明，等离子体还原催化剂具有较小的活性组分粒径、较高的活性组分分散度以及较高的表面碱性，这些特性有利于催化剂活性位对CO2的化学吸附，使其在甲烷化反应中表现出较好的低温活性.