助剂促进的Rh-Fe/Al_2O_3催化剂上CO加氢制乙醇反应性能

Performance of Promoted Rh-Fe/Al_2O_3 Catalysts for CO Hydrogenation to Ethanol

考察了Fe,Rh载量以及助剂对Rh-Fe/Al2O3催化剂上合成气制乙醇反应性能的影响.结果表明,随着Fe载量的增加,甲醇选择性持续上升伴随着甲烷选择性的持续下降,而乙醇选择性有最优值.助剂的添加或多或少促进了甲醇耦合、CO插入和解离的活性,或抑制了催化剂加氢能力,使得乙醇选择性有所上升,甲醇选择性有所下降,而烃类选择性变化不大.随着CO加氢反应的进行,Rh-Fe/Al2O3催化剂上烃类选择性逐渐下降,但甲醇的生成活性逐渐上升,而乙醇选择性和生成活性逐渐下降;然而,助剂的添加并未提高催化剂的稳定性.这可能是由于在反应过程中Fe物种逐渐被合成气还原使得乙醇生成活性位数量逐渐减少所致.

The effects of Rh and Fe loading,and promoters on CO hydrogenation performance over Rh-Fe/Al2O3 catalysts were investigated,as well as the stability of the catalysts.The results showed that with the increasing of Fe loading,methanol selectivity produced from syngas increased continuously accompanying by the decrease in methane selectivity,but the ethanol selectivity had a maximum value.The addition of alkaline or alkaline earth metals promoted methanol coupling or CO dissociation and insertion,or suppressed hydrogenation ability more or less,as a result,ethanol selectivity enhanced,and methanol selectivity decreased,but hydrocarbon selectivity remained almost unchanged.With CO hydrogenation reaction proceeding,hydrocarbon selectivity decreased,but methanol selectivity increased gradually,unfortunately,ethanol selectivity decreased,and the additions of promoters had little effect on it,probably due to the reduction of Fe species by syngas or decreasing of Rh-Fe interface areas during reaction.