| In the present work, the small-crystal titanium silicalite-1extrudates were modified with dilute organic base solution. The modification procedure was as follows:10g extruded small-crystal TS-1was added to100mL organic base solution-(the concentration of base was0.06mol/L),in a Teflon lined autoclave, and modified at170°C for48h. The obtained solid was washed and dried, then calcined at540°C for6h. The small-crystal TS-1extrudates treated with dilute TMAOH, TEAOH, TPAOH, EA and DEA solution was evaluated in the epoxidation of propylene in a fixed-bed reactor. The catalytic performance for propylene epoxidation in different conditions (different H2O2concentration) over the TS-1modified with TPAOH solution was studied and lasted for1000h in the optimal condition TEOS and magnesium acetate were adopted to modify the small-crystal TS-1extrudates by impregnation. Finally, the influences of conditions, including pH, temperature and the amount of TS-1, on the alcoholysis of PO were carried out in a stainless batch reactor.The conclusions were shown as follows:1The framework of the extruded small-crystal TS-1was not destroyed by modification with dilute organic base solution, but the framework titanium was transformed to octahedrally coordinated titanium species and anatase TiO2.The modification with TPAOH solution led to a larger pore volume and surface area, due to the formation of mesopore in the crystals;2The catalytic properties of the samples modified with organic bases were improved significantly in the epoxidation of propylene. The sample modified with dilute TPAOH solution, showing the highest catalytic activity, was evaluated in the long-term running, the reaction conditions of which were:40°C,3.0MPa, WHSV of propylene was0.74h-1, concentration of H2O2was1.6mol/L, and concentration of NH3? H2O was1.2mmol/L. The sample showed high catalytic performance after1000h running, when the conversion of H2O2and the selectivity of PO were both more than95%;3The catalytic activity of the small-crystal TS-1modified with TEOS and magnesium acetate were improved slightly, but the stability of the catalyst decreased. The conversion of H2O2decreased from97%to91%after120h running; 4In the range of the settled factors, the alcoholysis of PO was affected most serious by the pH of reaction liquid, when the temperature was low; however, when the temperature was higher than110°C, temperature affected much more serious than pH of reaction liquid on the PO alcoholysis. |
