高稳定性Ni/SBA-15催化剂的结构特征及其对二氧化碳重整甲烷反应的催化性能

Structural Characterization of Highly Stable Ni/SBA-15 Catalyst and Its Catalytic Performance for Methane Reforming with CO_2

采用浸渍法制备了Ni含量为2.5%～20%的系列Ni/SBA-15催化剂,在常压连续流动固定床反应器上考察了催化剂对二氧化碳重整甲烷制合成气的催化性能,并用X射线衍射和N2吸附法研究了Ni/SBA-15催化剂的结构特征.结果表明,Ni/SBA-15催化剂具有很高的CH4和CO2转化率,12.5%Ni/SBA-15催化剂在800℃反应600h后活性没有明显下降,但反应710h后CH4的转化率下降了约50%,CO2的转化率下降了约25%.其活性下降的主要原因是催化剂积炭.在高温条件下反应时,SBA-15的介孔结构也没有遭到破坏,分子筛的孔壁能有效阻止活性组分Ni的团聚.SBA-15孔中组装一定量的Ni活性组分后,除了SBA-15的介孔外,还会形成另外一种较小的孔,但这不影响SBA-15的有序介孔结构,只是其孔径、孔容和BET比表面积降低.

A series of Ni/SBA-15 catalysts with different Ni contents （2.5% to 20% ） were prepared by an incipient wetness impregnation method. The catalytic properties of the catalysts for the methane reforming with carbon dioxide were tested with a continuous-flow fixed-bed quartz reactor. The structure of the catalysts was characterized using X-ray diffraction and N2 adsorption. The results indicated that Ni/SBA-15 catalysts had a higher conversion of CH4 and CO2 under the reaction conditions. The 12.5 % Ni/SBA-15 catalyst showed highly stable activity at 800℃ for 600 h. However, after reaction of 710 h, the conversion of CH4 and CO2 decreased about 50% and 25% , respectively. Coking was the main reason for the deactivation of Ni/SBA-15 catalysts. At high reaction temperatures, the mesoporous structure of SBA-15 was not destroyed and the pore walls of SBA-15 could prevent the aggregation of the nickel species. Upon insertion of nickel into SBA-15, small pores were formed besides the mesopores of SBA-15. The mesoporous structure of SBA-15 was not affected by the nickel species, however, the pore diameter, pore volume, and BET surface area were decreased.