Modification And Scale-up Synthesis Of Nano-sized Titanium Silicalite-1

Nano-sized titanium silicalite-1(TS-1) was synthesized using tetrapropyl ammonium hydroxide (TPAOH) as template. The nano-sized TS-1was extruded with different supports. The obtained TS-1extrudates were then treated with TPAOH and characterized. The influences of size, amount and types of seeds on the physical and chemical properties of TS-1were studied. The synthesis of TS-1was further scaled up to investigate the effects of scale on the performance of TS-1. The main results are as follows:1. TS-1was extruded with Al2O3and SiO2as supports. The extrudates were then treated with TPAOH. For extrusion with Al2O3followed by TPAOH treatment mainly aluminum dissolution occurs, whereas extrusion with SiO2leads to secondary crystallization together with silicon dissolution. The acid amount in TS-1/Al2O3is more than that in TS-1/SiO2, making the TS-1/Al2O3more susceptible to deactivation. After TPAOH treatment, the silica in TS-1/SiO2crystallized, resulting in the unblocking of TS-1channels and forming of new framework Ti-O-Si with catalytic activity, which induced a higher activity and stability than TS-1/Al2O3.2. The effects of seeds on the physical and chemical properties and catalytic performance of TS-1synthesized with the TPAOH template were investigated. The size and amount of seed play a more important role than the types of seeds. The smaller the seed size and the more seed are added, the smaller the resulting TS-1crystal size. Seed properties rarely affect the coordination of Ti. The catalytic activity of TS-1decreases with the increasing crystal size.3. TS-1was synthesized in autoclaves of different scales. When the scale of autoclave increased, a higher crystallinity, a lower proportion anatase TiO2and a smaller crystal size were obtained, so that the TS-1synthesized at a larger scale exhibited a better catalytic performance for epoxidation of propylene than that synthesized at a smaller scale.