Study On The New Procedure For Synthesizing Titanosilicate TS-1

Titanosilicate TS-1has been paid much attention by academia and enterprise because of its excellent performance in selective oxidation of hydrocarbons. Synthesis of high-performance TS-1and influence of heteroatoms on the catalytic activity of TS-1are the most important research in catalytic field. In this dissertation, we systematically studied the influence factors on synthesis and catalytic oxidation performance of TS-1, including matching the hydrolysis of organic silicon source with organic titanium source and insertion of heteroatom Al into TS-1framework. The main results are as following:1. he synthesis of TS-1by hydrolyzing mixture of TEOS and TBOT in acidic system and crystallizing in basic system was studied. It showed that Ti species can be well dispersed in acidic hydrolysis system, but the acid could neutralize part of TPAOH (template), further leading to increase the particle size of TS-1. The results of epoxidation of1-hexene indicated that the catalytic activity of as-synthesized TS-1in acidic system was similar to that synthesized by conventionally hydrothermal synthesis. Perhaps, that’s because the enlarged particle size of TS-1weakened the positive effect of well-dispersed Ti species.2. The synthesis of TS-1by hydrolyzing TEOS and TBOT with the parallel flow was investigated. The results showed that this method could eliminate the concentration gradient of alkali in the hydrolysis process. The catalytic oxidation performance of the obtained TS-1enhanced obviously when the structure-directing capability and the nucleation are the same as that in conventionally hydrothermal synthesis. We conjectured that Ti species in TS-1could be well-dispersed and the particle size was silimar to that in hydrothermal synthesis.3. The preparation of titanium silicalite-1(TS-1) containing Al (Al-TS-1) and its catalytic oxidation properties were also investigated systematically. The results showed that incorporation of Al into the TS-1framework during the synthesis process influenced the amount of framework Ti (IV) in Al-TS-1. However, when the Al/Si ratio is lower than0.005, the amount of framework Ti in Al-TS-1is hardly affected. Meanwhile, neither the Al centers nor the Ti centers in the Al-TS-1framework influence the acidic catalytic and catalytic oxidation performances. Al in the Al-TS-1framework suppressed desilication of silica species adjacent to framework Ti species in Al-TS-1in a basic catalytic system, so Ti active sites in the Al-TS-1framework could be protected. The existence of Al atoms in TS-1framework also has great influence on morphology of TS-1which is related to the content of Al in the framework and different adding sequence of Al species.