Modification On Catalyst In Gas-phase Epoxidation Of Propylene

In this work, the effect of treatment by TPAOH-Na2SO3solution on TS-1was investigated, and the influences of calcination conditions and ion exchange on treated TS-1catalyst were also studied. The comparative studies about the catalytic performance of all TS-1samples before and after treatment in gas-phase epoxidation of propylene were carried out. Meanwhile, all TS-1samples were characterized by SEM, XRD, UV-Vis, FT-IR, UV-Raman and N2physical adsorption technologies.1. TS-1treated by TPAOH-Na2SO3solution with0.020mol/L Na2SO3and0.100mol/L TPAOH for24h had the best catalytic performance in gas-phase propylene epoxidation. TS-1after treatment still kept the original MFI structure, but the distribution of Ti species had been changed, as well as the pore structure.2. Took TS-1samples after TPAOH-Na2SO3solution hydrothermal treatment as catalysts in gas-phase epoxidation of propylene, the conversion of propylene first increased, and then decreased, as the calcination temperature was increased. When the calcination temperature was350℃, the conversion rate of propylene was highest. Once the calcination temperature was higher than350℃, the conversion rate of propylene decreased; the selectivity of propylene oxide remained unchanged. However, with the increase of calcination temperature, the crystal morphologies, the crystallinity, the distribution of Ti species and the coordination environment of TiO4have been changed.3. Modified TS-1(after TPAOH-Na2SO3solution hydrothermal treatment) calcinated under540℃in N2(TS-1-M-N2) has better catalytic performance in gas-phase epoxidation of propylene than that calcinated under540℃in air (TS-1-M). Compared with TS-1-M, reunion phenomenon of TS-1-M-N2is relatively serious, the crystallinity is higher, and the non-framework titanium content is less.4. The modified TS-1(after TPAOH-Na2SO3solution hydrothermal treatment) after ion exchange treatment does not have catalytic activity in gas-phase epoxidation of propylene. Therefore, the ion exchange method cannot solve the problem that the modified TS-1cannot be calcinated under high temperature.