助催化剂对Fe_(1-x)O基氨合成催化剂热稳定性的影响

Effects of promoters on thermal stability of Fe_(1-x)O based ammonia synthesis catalysts

采用梯级升温耐热和层叠添加助催化剂技术,运用XRD、BET和SEM表征方法,研究助催化剂对Fe_(1-x)O基氨合成催化剂热稳定性的影响。结果表明,多助剂的Fe_(1-x)O基氨合成催化剂晶粒随温度升高而长大,比Fe_3O_4基催化剂晶粒小且长大缓慢;孔径和孔容随温度升高而减小。K_2O和CaO能提高催化剂活性,但不利于热稳定性,CaO和Al_2O_3能均匀分散催化剂晶粒,M既能提高催化剂活性,又能增强其耐热性。

Effects of promoters on the thermal stability of Fe_(1-x) 0 based catalysts were studied by SEM, XRD and BET,after step-wise heating and adding different promoters in a layer-by-layer way.The results showed that for Fe_(1-x)0 based catalysts with multi-promoters,the crystallites gradually grew up and the pore volume and pore size decreased with increasing temperature,with smaller crystallites and slower grow-up speed than Fe_3O_4 based catalysts.For Fe_(1-x)0 based catalysts,K_20 and CaO improve the activity but impair the thermal stability.CaO and A1_20_3 uniformly disperse the crystallites.M improve both the activity and thermal stability.