Highly Dispersed in Porous Silica for CO Hydrogenation

A facile method has been developed to prepare highly dispersed in porous silica. By utilizing C atoms in methyl modified silica supports, was obtained via insitu carburization. The obtained samples exhibited high activity for CO hydrogenation. 1. Introduction The development of new heterogeneous catalysts is a highly attractive topic in current chemical research [1, 2]. Molybdenum carbides have been found to show high catalytic activities as noble metals and may be an inexpensive alternative to noble metal catalysts [3, 4]. In recent years, molybdenum carbides highly dispersed in mesoporous silica molecular sieves have been synthesized [5] however, to insert molybdenum species during the synthesis of mesoporous silica supports, the routes are somewhat complicated and difficult. Molybdenum source, MoO3 or polymolybdates, needs to be treated into low-nuclearity molybdenum peroxo complexes via the peroxo route at the initial synthesis of mesoporous silica supports [6]. Furthermore, to carburize molybdenum species into its carbides, one of the most widely used methods is the temperature-programmed reduction (TPR) of the transition metal oxide by gaseous hydrocarbons, such as CH4 [7], C2H6 [8], C3H8 [9], and C4H10 [10], as pioneered by Levy and Boudart [3]. Few studies have been carried out on the utilization of other carbon sources. Herein, we report a facile synthesis of highly dispersed in porous silica through insitu carburization of molybdenum species on methyl modified silica (Mo-M-silica) in Ar gas. Mo-M-silica was synthesized via sol-gel route using Si(OC2H5)4 (TEOS) and polymethylhydrosiloxane (PMHS) as silica sources without using any surfactants. (NH4)6Mo7O24 4H2O (AHM) as molybdenum source was introduced without peroxo treatment. CO hydrogenation reaction was used as a probe reaction: the obtained /SiO2 exhibited high catalytic activity and selectivity to alcohols in CO hydrogenation. 2. Experimental 2.1. Synthesis of Samples The typical synthesis method is as follows. (NH4)6Mo7O24 4H2O was dispersed into 80？mL ethanol to obtain a white suspension. Then, 1.5？mL PMHS was added under vigorous stirring. Si–H bonds in PMHS interacted with transitionmetal (Mo), and the suspension turned from white to gray. Ethylene diamine (EDA) was added as catalyst to allow residual Si–H bonds to react with part of the C2H5OH and release H2. After being stirred for 12？h at room temperature, 5？mL TEOS and determined deionized water were added under vigorous stirring. The resulting gray solid was dried at 100°C in a vacuum oven to remove the EtOH and EDA. The