taining 65% ethylene to produce diethylbenzene (DEB). Alkylation over the RE-Si-ZSM-5 catalysts yielded 95～98% P-DEB. The high para-setec-tivity is due to the reduction in acid strength within the pores and the reduction in acid sites on the crystal's external surface. These catalysts have good performance in the industrial application.

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, 13C 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 200h of reaction, both the conversion and the utilization of H2O2 is about 95%, the selectivity of PO is about 90%.

The propylene epoxidation using supported titanium silicalite TS-1 catalyst was systematically investigated in a fixed bed reactor. Different supports such as SiO2 and Al2O3 were used and two molding methods were adopted to prepare the catalyst. Strip TS-1 catalyst of 1mm

The direct synthesis of para-diethylbenzene (PDEB) was achieved commercially via ethylation of ethylbenzene over EA catalysts (modified ZSM-5 zeolites). The preparations of EA catalysts by modifying micron-sized ZSM-5 zeolites and the performances of EA catalysts in industrial units are discussed. It is observed, that the PDEB selectivity of HZSM-5 can be enhanced by strengthening the channels' geometric constraints, decreasing the amount of strong acid sites and eliminating the external surface acid sites of H-type zeolites. And that with combined modifications, an all-sided adjustment of said parameters of HZSM-5 zeolites could be reached, which favors the preparation of commercial catalyst by allowing good activity and durability. Combined modifications also works well in elevating the PDEB selectivity ofnano-sized ZSM-5 zeolite, the promising candidate for a new generation ofpara-selective catalyst.

The synthesis of titanium silicalite by two methods (gas-solid isomorphous substitution of Ti4+ for Si4+ and hydrothermal crystallization synthesis), aiming at decreasing its cost, and the characterization of the prepared catalyst are presented. In the hydrothermal crystallization synthesis method of titanium silicalite-1 (TS-1), TPABr can be used to replace TPAOH and the amount of TPABr can be decreased to 0.05 (TPA+/SiO2). Organic amine cannot act as a template in the presence of TPA+. It can only regulate the basicity of the gel. The order of the template effect of different templates is as follows: TPA+>TBA+>TEA+>>organic amine. In the preparation of titanium-containing zeolite by secondary synthesis, the nature of the precursor and the preparation conditions have great influence on the incorporation of titanium into the framework. The mechanism of gas-solid isomorphous substitution is proposed, and under its guidance, we have successfully prepared Ti-ZSM-5, Ti-ZSM-11, Ti-β, and Ti-mordenite. The synthesized titanium-containing zeolites have been evaluated through catalytic hydroxylation of phenol, oxidation of styrene and epoxidation of propylene with aqueous H2O2. Results show that the Ti-containing zeolites possess high activity both in hydroxylation, styrene oxidation and in epoxidation.