Synthesis of titanium silicalite (TS-1) from the TPABr system and its catalytic properties for epoxidation of propylene

Abstract

Titanium silicalite (TS-1) was successfully synthesized by using tetra-propylammonium bromide (TPABr) and n-butylamine as the template and the base, respectively. XRD, IR, SEM, 13 C CP/MAS NMR, UV–VIS, and UV-Raman techniques were used to characterize the synthesized products. The results show that TS-1 has MFI structure with high crystallinity and large crystal size, and with two kinds of titanium species. Using epoxidation of propylene as the probe, the catalytic properties of TS-1 in the present work were investigated. The crystal size of TS-1 affects much the initial reaction rate of propylene oxide (PO) formation. The effects of reaction conditions on PO reveal that the PO formation is greatly influenced by the solvent and the solution pH value. Methanol is the most preferable solvent, and a portion of water (<30%) in solution does not have much impact on the reaction. Moreover, the addition of base used to neutralize the residual acidity of the catalyst favor the reaction, the catalyst shows high activity and selectivity upon the adequate amount of base and the catalyst can be used repeatedly without regeneration. In the fixed-bed reactor, using ammonium water as the neutralizer, after 200 h of reaction, both the conversion and the utilization of H 2O 2 is about 95%, the selectivity of PO is about 90%.