铁系稀土CO中温变换催化剂的吸附性能及反应机理研究

A Study on the Adsorptivity and Water—Gas—Shift Reactive Behaviors of Rare—Earth Promoted Fe_2O_3 Catalysts

本文采用原位红外技术,程序升温脱附技术及脉冲反应法,对比研究了铁系稀土 CO 中温变换催化剂(FeCrCeK)和主剂 Fe_2O_3的吸附性能和反应性能。从原位红外研究发现两种催化剂还原表面都能被 H_2O 和 CO_2氧化,从而导致表面结构的变化,在红外谱图中看到了结构变化峰。程序升温脱附结果证实了上述结论,并根据催化剂脉冲反应研究结果归纳出了催化剂的交换反应机理。

In this paper,the adsorptivity and reactive behaviors of Fe_2O_3 and promoted Fe_2O_3 catalysts have been investigated by temperature— programmed desorption (TPD),pulsed surface reaction (PSR) and in situ Fourier—transform infrared (FT—IR) techniques.The promoted Fe_2O_3 water—gas—shift catalyst containing Ce,Cr and K elements shows much ??higher reactivity and selectivity than pure Fe_2O_3.H_2 is always evolved from the initial pulse of H_2O on the pre—reduced catalyst,and also from the initial pulse of CO on the H Opreheated catalyst,It is suggested that H_2 formation on the promoted Fe_2O_3 catalyst proceed via both the direcr reaction of H_2O with the reduced catalyst and the reaction of CO with the surface hydroxyls.The catalyst experiences a rapid redox process accompanying the two reaction routes.The redox property of the catalyst is further confirmed by IR results which reveal that the surface structure of the reduced catalyst is very sensitive to the adsorption of H_2O and CO_2.The TPD and IR results demonstrate that the adsorbed CO_2 on the catalyst is more easily desorbed than that on pure Fe_2O_3 and the surface concentration of hydroxyls on the catalyst seems to be higher than that on pure Fe_2O_3.This is one of the reasons why the promoted Fe O has much better catalytic performance than pure Fe_2O_3.