Tin-modified SBA-15, MCM-41 Catalysts:Preparation And Catalytic Performance For Esterification Of Maleic Anhydride

Dibutyl maleate (DBM) is commonly used as an intermediate in organic synthesis industry, which is often synthesized via the esterification of maleic anhydride and n-butyl alcohol with sulfuric acid as catalysts. The sulfuric acid is corrosive to the equipment, and likely to cause environmental pollution. In order to meet the requirements of environment-friendly, researching solid acid catalysts become more important.Tin-based solid acid catalyst is a new class of solid acid, including supported SnCl4 catalyst, sulfuric acid-promoted tin oxide super acid catalyst and tin-modified molecular sieves, ect. Tin and silicon belong to the same family, and the tin can be easily incorporated into the framework of silica molecular sieves to form stable tin-modified zeolites with high acidic density, and the catalysts show high activity. Thus the tin-modified zeolite for DBM synthesis is an important research.In this paper, two kinds of modified mesoporous molecular sieves were prepared:SnClx-SBA-15 and SnClx-MCM-41 were prepared by "Grafting"; and Sn-SBA-15, Sn-MCM-41 were prepared by "One-pot synthesis". Firstly, their performances on catalytic esterification of maleic anhydride with n-butanol were studied. Secondly, the water resistance and lifetime of the catalysts were evaluated. And the structure and properties of the materials were characterized by X-ray diffraction (XRD), N2 physical adsorption (BET), Fourier infrared (FTIR), Ultraviolet-Visible diffuse reflection (DRUV-vis) and other techniques. The main conclusions are as follows:1) It was found that SnClx-SBA-15 (nSn/nsi=1:10) showed the better performance than the SnCl4 supported on SiO2 aerogel in the catalytic esterification of maleic anhydride and n-butanol. The characterization showed that SnClx-SBA-15 and SnClx-MCM-41 had larger surface area, pore volume and pore size than SiO2 aerogel, which made the reactants enter the pores more easily to involve the efficient reaction. However, the active components of SnClx-SBA-15 and SnClx-MCM-41 were usually loading on the surface of molecular sieves so that they losed seriously after several cycles.2) The catalytic performance of Sn-SBA-15 was better than that of Sn-MCM-41. And the Sn-SBA-15, still had catalytic activity after 10 times used. The characterization showed that Sn-SBA-15 had larger surface area, pore volume, pore size and stronger acidity than Sn-MCM-41, which might result in the catalytic performance of Sn-SBA-15 differing from that of Sn-MCM-41.3) The SnClx-SBA-15, SnClx-MCM-41, Sn-SBA-15, Sn-MCM-41 and Sn-Beta’s performances on catalytic esterification of maleic anhydride with n-butanol in the presence of water were studied. The results showed that: SnClx-SBA-15 and SnClx-MCM-41 lost their activity after 5 times used. Sn-SBA-15 and Sn-MCM-41 still had activity after used 7 times because of its high waterproof capability.