Rh基催化剂上CO加氢制C2含氧化合物的红外光谱研究

 用红外光谱法考察了Rh-Mn-Li-Ti/SiO2催化剂在CO加氢反应过程中表面吸附物种随压力、温度和H2/CO比的改变而变化的规律. 结果表明,高压有利于提高催化剂表面吸附的CO浓度和活性,高温有利于CO解离; 而高温、高压条件不但促进了CO吸附,而且提高并平衡了CO的解离和插入之间的相对活性,促进了C2含氧化合物的生成. H2/CO比的增大有利于CO在催化剂表面的吸附,从而促进了CO插入,尤其是CO的解离和加氢活性,但是过高的H2/CO比将导致过高的CO解离和加氢活性,引起CO插入活性的削弱而最终导致C2含氧化合物生成活性的下降. 同时,考察了助剂(Mn, Li和Ti)对Rh基催化剂表面吸附物种的影响. 结果表明,助剂的加入可提高C2含氧化合物的生成活性.

FT-IR Study on CO Hydrogenation to C2-Oxygenates over Rh-Based Catalyst

In-situ FT-IR technique was employed to investigate the evolution of surface species adsorbed on the Rh-Mn-Li-Ti/SiO_2 catalyst under the reaction conditions including pressure, temperature, and H_2/CO ratio during CO hydrogenation to C_2-oxygenates. The results showed that high pressure favored the adsorption and the activation of CO, while high temperature favored the dissociation of adsorbed CO. The employment of high pressure and nigh temperature conditions not only promoted CO adsorption on the catalyst surface but also remained proper activity of CO dissociation. Thus CO insertion activity was enhanced, resulting in good performance for C_2-oxygenate formation. The increase in H_2/CO ratio promoted the adsorption of CO, and hence CO insertion, especially CO dissociation and hydrogenation, were enhanced. However, the high activities for CO dissociation and hydrogenation resulted from too high H_2/CO ratio might suppress CO insertion, and thus the activity for the formation of C_2-oxygenates decreased. Compared with the Rh/SiO_2 catalyst, the addition of promoters (Mn, Li, and Ti) favored the formation of C_2-oxygenates.