Acidic-treated TS-1 zeolites with high titanium for cyclohexanone efficient oximation

Successful preparation of acidic-treated TS-1 zeolites with high titanium by hydrothermal synthesis in the presence of cetyltrimethylammonium bromide and tetrapropylammonium hydroxide as templates and followed by treatment with 1 M hydrochloric acid were reported in this paper. Many characterization techniques, including XRD, N2 adsorption-desorption, ICP, UV-vis, FT-IR, SEM, Raman, XPS and TEM, were applied to characterize their physical and chemical properties, and the cyclohexanone oximation was also conducted to investigate the catalytic performance. The results showed that although the crystalline TS-1 zeolite with high titanium can be obtained with double templates, the extra-framework TiOx would be formed based on the SEM images and UV-vis spectra. The MFI topological structure with the acidic treatment can be kept and all the titanium species can be almost incorporated into the framework of TS-1 zeolite, whose relative content for S-0.2-CTS-0.04-160 sample was about 96%. The S-0.2-CTS-0.04-160 sample with the skeleton titanium species as high as 3.38 mol.% resulting in more defects showed higher catalytic performance than other catalysts, whose cyclohexanone conversion of 97.6 % and caprolactam yield of 94.6 % can be obtained. Compared to classical TS-1 zeolite, the S-0.2-CTS-0.04-160 catalyst showed good stability with 89.8 % of cyclohexanone conversion and 84.9 % of caprolactam yield even though after repeated use for 5 times.