Meso-porogen-assistant Synthesis Of Hierarchical Titanium Silicalite-1

Titanium silicalite-1 (TS-1) possesses 2-dimensional microporous structure with MFI type topology. The catalytic oxidation system, consisted of TS-1 and H2O2 solution, shows excellent catalytic oxidation performance under mild conditions, and has attracted much attention of researchers both in domestic and aboard. However, the intrinsic microporous structure of TS-1 zeolite shows great diffusion resistance for the macromolecular reactants and products, which may lead to a decrease of the catalytic performance and the deactivation of TS-1. In this thesis, cetyltrimethylammonium bromide (CTAB) and soluble starch were introduced as meso-porogens, combined with tetrapropylammonium hydroxide (TPAOH) as microporous template. TS-1 molecular sieves with hierarchical structure were synthesized by hydrothermal crystallization process. The effects of different meso-porogen on structures and catalytic performances of the molecular sieves were studied. The main conclusions are shown as follows:1. Hierarchical TS-1 molecular sieve was synthesized with CTAB and TPAOH. A competitive relationship between meso-porogen CTAB and microporous template TPAOH was existed. Hierarchical TS-1 with specific mesopore/micropore ratio could be obtained by tuning the CTAB/TPAOH molar ratio.2. Hierarchical TS-1 possessed wormlike mesopores was synthesized by adding CTAB before aging at room temperature when using H2O as solvent. When employing different alcohols as the solvent of CTAB, the morphology and pore diameter of the hierarchical TS-1 could be controllably synthesized. The pore diameter can be adjusted from 2nm to 14 nm.3. Hierarchical TS-1 molecular sieve with intercrystalline mesopores and macropores were synthesized by using soluble starch and TPAOH. The intercrystalline pores will transform from mesopores to macropores by increasing the addition of soluble starch. Moreover, the presents of soluble starch during synthesis process could inhibit the formation of anatase TiO2, significantly. The extra-framework Ti species could also be suppressed at an appropriate amount of soluble starch addition.4. The hierarchical TS-1 molecular sieve showed different catalytic performances for the reactants with different size. Due to the improvement of diffusion and the elimination of extra-framework Ti species, the hierarchical TS-1 performed excellent catalytic performance in epoxidation of 1-butylene.