Synthesis Of Cuprous Chloride Catalyst Supported On Organic-inorganic Hybrid Materials And Its Catalytic Property In The Oxidative Carbonylation Of Methanol To Dimethyl Carbonate

Homogeneous catalytic systems often have disadvantages, such as difficult separation from the products and corrosive effect on the reactor materials. Heterogeneous catalytic systems have attractive advantages over homogeneous counterparts in liquid-phase reactions, including easy removal of catalysts from reaction mixtures and recycling of catalysts. Organic-inorganic hybrid materials (OIH), in which the organic groups are covalently attached to porous inorganic solids, can be used as catalyst support. The goal in this paper is to utilize the organic moiety as the active site and the inorganic solid to provide avenues for recovering the active site. This new kind of catalyst system is expected to contribute to the development of commercialization of homogeneous catalytic reactions. The Sol-gel technology offers several advantages employed in the preparation of heterogeneous catalysts. Inorganic Sol-gel supports are indeed superior in their thermal stability, inertness towards molecules, and in their porosity and high surface areas. Thus, the Sol-gel technology is a promising method using to synthesize the supported catalyst.Firstly, OIH was prepared by Sol-gel technique usingγ-aminopropyltriethoxysilane (APTES) as spacer, 2-acetylpyridine as organic ligand, and tetraethoxysilane (TEOS) as precursor, then the OIH was reacted with CuCl to prepare heterogeneous catalyst CuCl/OIH (A).Secondly, cuprous chloride catalysts CuCl/OIH (B) anchored on silica-based support were synthesized by Sol-gel technique usingγ-chloropropyltriethoxysilane (CPTES) as spacer, 5-amino-1,10-phenanthroline as organic ligands and TEOS as precursor. The effects of reaction temperature, reaction time and other factors on the synthesis of OIH were investigated. The results show that the optimum reaction conditions for synthesis of secondary ammonia are: the solvent DMF, the concentration of NH2-Phen 10 mg/ml, molar ratio of CPTES to NH₂-Phen 1.1:1, reaction temperature 70℃,reaction time 72 h. The structure of support and heterogeneous catalyst were characterized by EA, FT-IR, TGA, DTA and NMR (¹H NMR, ²⁹Si-MAS-NMR). The copper loading of the supported catalyst were detected by atomic absorption (AAS). Thirdly, the catalytic activity of CuCl/OIH in the oxidative carbonylation of methanol to dimethyl carbonate was studied in this paper. The catalyst CuCl/OIH (B) exhibited higher activity and selectivity than the homogeneous CuCl catalysts, the yield of dimethyl carbonate improved 25.0 %. It could be separated easily and reused several times, with slight loss of the active components. After recycling 4 times, the catalyst still showed high catalytic activity and selectivity under the reaction conditions of [Cu(I)]=0.1 mol/L, 2.4 MPa (P_CO:P_O2=2:1), 2 h, 120℃.