Study On Synthesis And Mother Liquor Recycling Of Titanium Silicalite

In this paper, Titanium Silicalite-1(TS-1) was synthesized in hydrothermal system by using solid silica as silicon source, in which the solid silica was activated with a certain amount of alkali source. The effect of particle size and alkalinity and activation time of silicon source, ageing temperature and ageing time on the synthesis of TS-1zeolite was investigated; then the preparation of TS-1molecular sieve in cheap system with mother liquor circulation was studied, the influence of template recycle ratio, crystallization time and template cycle-index on the TS-1catalytic performance was investigated. The samples were characterized by XRD, SEM, UV-Vis, IR, NH3-TPD, Hammett indicator titration technologies, and the impurity ion in initial mother liquor was measured, the accumulation of impurity ions in circular process was analyzed. The catalytic performance was evaluated by liquid epoxidation of propylene. The following results had been obtained:1. The silicon source with small particle size, low degree of polymerization are good for the synthesis of TS-1. The silicon source after preactivation2h at room temperature can reduce the content of non-framework titanium species in TS-1, the sample with aging24h at100℃and crystallizing36h at170℃has the highest crystallinity and least non-framework titanium.2. Recycled and fresh template showed the similar structure-directing effect, mother liquid recycling experiments has obtained1-5generations TS-1products with high crystallinity and high content of framework titanium.3. Impurity ions exist in the mother liquor, the accumulation of Na+, Al3+will not affect the performance of products probably, but the accumulation of Br-would increase the content of non-framework titanium obviously in products, which result in an enhance of strong acid sites in H0=+3.3～+3.85and an decrease of the PO selectivity.