铑基CO加氢制乙醇催化剂的FTIR研究

STUDY OF RhBASED CATALYSTS FOR SYNTHESIS OF ETHANOL BY FTIR

用ＦＴＩＲ对Ｒｈ／ＣｅＯ２／ＳｉＯ２系列ＣＯ加氢制乙醇催化剂进行了研究。在Ｈ２流中升温处理时，吸附ＣＯ的脱附温度低于Ｎ２气流中ＣＯ的脱附温度，ＣｅＯ２的加入进一步降低了Ｎ２和Ｈ２气流中ＣＯ的脱附温度。在Ｈ２气流中升温处理时，相邻双羰基峰的低波数峰迅速消失，而高波数峰变得不对称。ＦＴＩＲ结果表明，在ＣＯ加氢反应中，催化剂表面上生成了Ｒｈ（Ｈ）ＣＯ物种，反应的速度决定步骤很可能是这一物种的进一步反应。ＣｅＯ２促进ＣＯ加氢反应的作用很可能是与Ｒｈ产生了电子效应。

A series of Rh/CeO 2/SiO 2 catalysts for the synthesis of ethanol in CO hydrogenation were studied by FTIR On SiO 2supported catalysts, CO was mainly adsorbed in the form of geminal dicarbonyl twin bands, indicating that Rh was dispersed at atomic level While on 2Rh/CeO 2(Ⅰ), CO was mainly adsorbed in linear and bridge forms Twin bands were also detected but very weak in intensity A peak at 1705cm 1 is assigned to a tilted CO species in which the carbon end of the molecule is bonded to Rh and the oxygen end to the cerium oxide In the presence of hydrogen with progressively increasing temperature, CO from high wavenumber peak of twin bands on SiO 2supported catalysts was removed rapidly, while the low wavenumber peak decreased slowly and became an asymmetric band On 2Rh/CeO 2(Ⅰ), a new peak evolved from the linear CO peak These results indicates that Rh(H)CO species in CO hydrogenation were formed and the ratedetermining step might be the migration and insertion of CO into Rh-H bond The addition of CeO 2 promoted the removal of adsorbed CO in both N 2 and H 2, and this promotional effect is explained electronically, i e CeO 2 denotes electrons to Rh