Rh基催化剂上CO加氢制C2含氧化物的原位红外光谱研究

 用原位红外光谱考察了Rh-Mn-Li-Fe/SiO2和Rh/SiO2催化剂表面上CO的吸附态及CO加氢反应过程中吸附物种的变化. 结果表明,CO在Rh/SiO2催化剂上仅有线式吸附态存在,而CO在Rh-Mn-Li-Fe/SiO2催化剂上既有线式吸附态存在,又有孪生吸附态存在. 这说明Rh-Mn-Li-Fe/SiO2催化剂中Rh的分散度较高. 经CO加氢反应(3.0 MPa,593 K)后,在Rh-Mn-Li-Fe/SiO2催化剂上可观测到C2含氧化物前驱物种的吸收谱带,而在Rh/SiO2催化剂上未观测到相应的谱带; CO在这两种催化剂上主要以线式吸附态存在,孪生吸附态基本消失. 结合催化剂对CO加氢的催化性能,可以认为线式吸附的CO对生成C2含氧化物有贡献. Rh-Mn-Li-Fe/SiO2催化剂的高活性是由于助剂的存在削弱了其表面吸附CO的 C-O键,促进了CO的活化,从而有利于C2含氧化物前驱物的生成.

In-Situ FT-IR Study of CO Hydrogenation to C2 Oxygenates over Rh-Based Catalysts

In situ FT IR technique was employed to investigate CO adsorption and the changes of adsorbed species on the surface of Rh based catalysts during CO hydrogenation. The result showed that only the linear CO was observed on Rh/SiO 2, while linear CO and twin CO appeared on Rh Mn Li Fe/SiO 2, indicating that Rh dispersion on Rh Mn Li Fe/SiO 2 was higher than that on Rh/SiO 2. In the IR spectra of CO hydrogenation under the conditions of 593 K and 3 0 MPa, the bands at 1?716 , 1?566 , 1?442 , and 1?343 cm -1 , which were attributed to C 2 oxygenate precursors, were observed for Rh Mn Li Fe/SiO 2, while no band was detected for Rh/SiO 2. CO was adsorbed mainly as linear CO on both the catalysts during CO hydrogenation. Correlating the FT IR results with the CO hydrogenation performance suggested that the linear CO might be mainly responsible for the formation of C 2 oxygenates. The high activity of Rh Mn Li Fe/SiO 2 was due to the fact that the existence of promoters weakened the C O bond of adsorbed CO on the catalyst, promoted CO activation and favored the formation of C 2 oxygenate intermediates under the reaction conditions.