单分散SiO2的焙烧温度对Rh基催化剂上CO加氢反应性能的影响

摘要

在比较了分别以商业SiO2和采用St(o)ber法制备的单分散SiO2为载体的Rh-Mn-Li/SiO2催化剂催化CO加氢反应性能的基础上,进一步调变了St(o)ber法制备SiO2时的焙烧温度,并考察了其对Rh-Mn-Li/SiO2催化CO加氧性能的影响.利用N2吸附-脱附、傅里叶变换红外(FTIR)光谱、H2程序升温还原(H2-TPR)、程序升温表面反应(TPSR)等方法对载体及催化剂的物理化学性能进行了表征.结果表明:不同温度焙烧的载体表面具有不同的Si-OH数量,从而影响金属的分散状态及Rh和Mn之间的相互作用.载体表面较多的羟基有利于Rh的分散和CO的吸附,从而增强催化剂的反应活性.载体表面适当数量的羟基能够得到适中的Rh与Mn之间的相互作用,使催化剂具有合适的CO解离能力,有利于CHx的CO插入反应,从而提高了C2含氧化合物的选择性.%Based on a comparison of catalytic performances of Rh-Mn-Li/SiO2 catalysts, in which commercial SiO2 and monodispersed SiO2 synthesized by the Stober method were used as the support, respectively, the effect of the calcination temperature of the synthesized SiO2 on the catalytic performance of Rh-Mn-Li/SiOj for CO hydrogenation to C2 oxygenates was investigated. Fourier transform infrared spectroscopy, N2 adsorption-desorption, temperature-programmed reduction with hydrogen (H2-TPR), and temperature-programmed surface reaction (TPSR) were used to characterize the physico-chemical properties of the SiO2 supports and the corresponding catalysts. The results showed that the number of surface Si - OH groups on the SiO2 supports affected the dispersion of metal and the interaction between Rh and Mn. Large amount of surface Si -OH groups was favorable for the dispersion of Rh particles and CO adsorption, and enhanced the activity of the catalyst. An appropriate amount of Si - OH groups can gain moderate interaction between the Rh and Mn. This interaction is conducive to achieve the right CO dissociation ability, which is favorable for the insertion of CO to CH,, and ultimately increases the selectivity of C2 oxygenates.