Abstract
TS-1/SiO2 extrudate was post-treated with mixed solution of tetrapropyl ammonium hydroxide (TPAOH) and various ammonium salts solution (NH4F, (NH4)3PO4, (NH4)2CO3, (NH4)2SO4, NH4CH3CO2, NH4NO3, NH4Cl and (NH4)2TiF6). The obtained hierarchical TS-1 catalysts were characterized by many techniques and tested for propylene epoxidation using hydrogen peroxide as an oxidant in a fixed-bed reactor. It was shown that the physicochemical and catalytic properties of the treated TS-1/SiO2 extrudate depended on the types of ammonium salts added. Compared to the treatment with TPAOH alone, the treatment with a mixed solution of TPAOH and some ammonium salts can greatly improve the catalytic properties of the treated TS-1/SiO2 extrudate. Some of these ammonium salts were favorable for the incorporation of titanium in the framework, and the beneficial effect depended on the types of ammonium salt. TS-1/SiO2 extrudate treated with a mixed solution of TPAOH and (NH4)3PO4 exhibited the highest catalyst stability in propylene epoxidation. Such catalytic property can be correlated to high crystallinity, more framework titanium, large specific surface area and large external surface area.
Published Version
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