Effect of treatment with different bases on the catalytic properties of TS-1/SiO2 extrudates in propylene epoxidation

• The catalytic properties of the TS-1/SiO2 were improved after TEAOH and TPAOH treatments.
• The distribution of Si and Ti was adjusted after TEAOH and TPAOH treatments.
• The MFI structure was destroyed and the framework Ti species decreased after EA and TMAOH treatments.
• The treatment with higher structure-directing ability is beneficial to the improvement of catalytic properties.

The effect of treatment with organic bases (ethylamine (EA), tetramethylammonium hydroxide (TMAOH), tetraethylammonium hydroxide (TEAOH) and tetrapropylammonium hydroxide (TPAOH)) on the catalytic properties of TS-1/SiO2 extrudates was investigated in the epoxidation of propylene. The morphology and MFI structure of the TS-1 were destroyed and the amount of non-framework Ti species in the catalysts increased when the TS-1/SiO2 extrudates were treated with EA and TMAOH, due to desilication. These changes are opposite to the improvement of the catalytic properties. On the contrary, treatment with TEAOH and TPAOH made the crystalline structure of the catalysts more homogeneous and adjusted the distribution of Ti and Si in the catalysts. In addition, the acidity of the samples increased appreciably, the pore openings at the surface of the catalysts were expanded as revealed by a series of characterizations. Thus, the catalytic activity and stability of the two catalysts were substantially enhanced.

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