Infrared Spectroscopy Study of CO Adsorption on Rh-Mn/SiO(2) Catalyst for C(2)-Oxygenates Synthesis from Syngas
Hua, Weiqi（Yantai Wanhua Polyurethanes Co Ltd）
- 化学化工－已发表论文 
The Rh-xMn/SiO(2)(x is Mn/Rh atomic ratio = 0-3) catalyst samples were prepared by conventional co-impregnation. The samples were characterized by transmission electron microscopy, X-ray diffraction and catalytic performance evaluation using CO hydrogenation to C(2)-oxygenates. CO adsorption behavior over Rh-xMn/SiO(2) catalyst under CO and syngas atmosphere at 50 and 280 degrees C, temperature-programmed reaction of CO with H(2) on the Rh/SiO(2)and Rh-0.5Mn/SiO(2)catalyst samples between 50 and 280 degrees C, and the change of the gem-dicarbonyl species with increasing temperature under CO atmosphere and vacuum were also studied by infrared spectroscopy. The results showed that, when the temperature was higher than 200 degrees C, the gem-dicarbonyl species was undetectable on the catalyst in the presence of CO, implying that Rh(+) site is unlikely the active site for CO insertion. The addition of Mn promoter resulted in the formation of tilted CO. The addition of Mn could be also in favor of weakening the Rh-C bond in the linear CO adspecies, which facilitated the linear CO migration on the catalyst surface and enhanced the rate of CO insertion into CH(x). This is consistent with the results from the experiment to improve C(2)-oxygenates selectivity with addition of Mn into Rh/SiO(2) catalyst. The formyl adspecies was detected by infrared spectroscopy in the experiment of temperature-programmed reaction of syngas over Rh-0.5Mn/SiO(2) catalyst. This result suggests that addition of Mn to Rh/SiO(2) is helpful to stabilize formyl species and this will be favorable to enhance the rate of hydrogen-assisted CO dissociation during the hydrogenation of CO to C(2)-oxygenates.
出处CHINESE JOURNAL OF CATALYSIS，2011,32（4）：672-691