Study On Catalytic Cleavage Of Organosilane High Boiling Residues Into Monosilanes By Aminopropylated Mesoporous Silica

In this master thesis, organic amine was selected as the cracking catalyst of conversion high boiling residues from organosilicone industry into valuable products, for example, dimethyldichlorosilane, and the APTES was selected as the catalyst active component because of its being immobilized easily. It was reported by literature that with the organic amine as the catalysts of conversion HBS into useful product, the cracking reaction can proceed under mild reaction conditions and get high yield of target products, but also resulting in difficult separation and recycle of catalysts due to the homogeneous catalysts. In order to solve the aforementioned problem, we designed a new catalyst of mesoporous materials which was functioned by APTES, and realized the heterogeneous catalysis of organic amine. In this thesis, the selected mesoporous materials were MCM type and SBA-16, and the methods of co-condensation and grafting were adopted for the synthesis of NH₂-MCM and NH₂-SBA-16. Mesoporous MCM-type catalysts containing amine were synthesized via co-condensation and characterized by means of XRD, N₂ adsorption-desorption, FT-IR and TGA. The characterization results indicated that the aminopropyl-incorporation was successful, but the excess incorporation of aminopropyl may destroy mesoporous structure, resulting in bad order of meso-pore and decline of specific surface area and pore volume. The catalyst of NH₂-SBA-16 was synthesized by different methods, such as co-condensation and grafting, and also characterized by means of N₂ adsorption-desorption, FT-IR and TGA. The characterization results indicated that the better physicochemical properties were obtained, and the physicochemical properties became worse gradually with the increase of APTES content in catalysts, however, the physicochemical properties of catalysts synthesized by grafting method degenerated fast. In this thesis, the reaction conditions for APTES, NH₂-MCM and NH₂-SBA-16 were investigated and the optimal reaction conditions for them were obtained. The optimal reaction conditions were , for APTES: the volume ratio between catalyst and HBS was 4:5, the reaction proceeded under 120℃for 2 hours , and the yields of methylchlorosilanes and conversions of HBS were 71% and 93% respectively. For NH₂-MCM, the molar ratio of APTES and TEOS was 3:7, the catalyst dosage employed was 5%, the reaction proceeded under 140℃for 6 hours , and the yields of methylchlorosilanes and conversions of HBS were 63.3% and 76.6% respectively. For NH₂-SBA-16 synthesized by co-condensation, the molar ratio of APTES and TEOS was 4:36, the catalyst dosage employed was 5%, the reaction proceeded under 120℃for 4 hours, and the yields of methylchlorosilanes and conversions of HBS were 72.5% and 90.1% respectively.