助剂Cu、K对F-T合成铁基催化剂作用的表征研究

Effects of Cu and K promoter on Fe-based catalysts for Fischer-Tropsch synthesis

采用连续共沉淀和喷雾干燥技术相结合的方法制备了一组Cu、K助剂单独或同时加入的微球状Fischer-Tropsch(F-T)合成铁基催化剂,借助低温N2 吸附、MES、XRD、H2 -TPR、CO-TPR研究了Cu和K助剂对催化剂织构、还原性能以及还原和炭化过程中的物相变化的影响。结果表明,K助剂的加入能明显提高催化剂的比表面积和铁物相在催化剂中的分散程度,增加了Fe2O3 与SiO2 间的相互作用;当催化剂在H2 和合成气中还原时,Cu助剂的加入有利于催化剂的还原和Fe3O4 的生成,在CO中还原时,Cu助剂的加入则有利于α-Fe的生成和稳定化。在H2 和合成气中,单独K助剂的加入会抑制催化剂的还原或炭化,而Cu和K助剂的同时加入在H2、CO和合成气下均可使催化剂的还原或炭化能力明显提高,表明Cu和K助剂间存在一定的协同作用。

A series of spherical micron-scale Fe-based catalysts, in which K and Cu promoters are incorporated respectively or simultaneously, are prepared by a combination method of continuous co-precipitation and spray drying technology. The textural properties, reduction performance, phase transformation in reduction and/or carbonization process are studied by means of low temperature N2 adsorption, MES, XRD, H2-TPR, CO-TPR and constant temperature reduction in H2, CO and syngas environment. The results indicate that the addition of K promoter can increase the surface area of Fe-based catalyst and iron species dispersion in catalyst, and reinforce the interaction between Fe2O3 and silica. The addition of Cu promoter improves the reduction of catalyst and the formation of Fe3O4 phase in H2 and syngas environment, but Cu promoter favors the formation and stabilization of a-Fe phase in CO environment. The addition of K promoter only will suppress the reduction and/or carbonization of catalyst in H2-containous environment, but the simultaneous addition of K and Cu promoters can apparently enhance the reduction and/or carbonization in H2, CO and syngas environment, which shows the synergic effect of Cu and K promoters.