Adsorption of CO on Zn-Cu(I)/HMCM-41

摘要

Using mesoporous acidic HMCM-41 as parent, the Zn-Cu(I)/HMCM-41 catalysts, which can reversibly adsorb and release CO, were successfully prepared in laboratory scale by means of the solid-state ion exchange together with introducing Zn as an assistant to improve the dispersion degree of the active component Cu(I) on the surface. With increase of the loading amounts of Zn and CuCl from 0% to 9.0% and 25.0% respectively, its CO adsorption amounts increased from 10.6 μmol/g to 183.0 umol/g correspondingly. The FT-IR in situ characterization for CO adsorption demonstrated that there existed two dynamic equilibriums between surface carbonyl complexes: Cu(CO)_3~+<=> Cu(CO)_2~++ CO and Cu(CO)_2~+<=> Cu(CO)~+ + CO. The equilibriums can be shifted reversibly by changing the temperature and pressure. At the same time, adsorption and release of CO is accompanied, which is the possible CO source for carbonylation reactions. Our recent research reveals that a starting alcohol was protonated at the acid sites of modified microporous Y, β or ZSM-5 and transformed into carbonium ions, from which the carboxylic acids (≤C_5) were produced by cooperative catalysis of the adjacent metallic carbonyl centers under mild conditions (～ 523K, atmospheric pressure). Due to the modified MCM-41 mesoporous materials possess both of the acidic and metallic carbonyl centers, it could be predicted that there are wide prospects for exploration in developing such a kind of 1.6-3.2 nm mesoporous bifunctional catalysts for carbonylation reactions, in which larger molecules are involved.