Preparation And Hydrothermal Treatment Of Titanium Silicalite Catalyst And Course Of Propylene Epoxidation Reaction

In the 21th century, the pollution has held back the economic development and has affected quality of life. In order to resolve the problem of environment, cleaner chemical technology and Green Chemistry have been put forward. Zeolites, especially TS-1, open a new way that can be environmentally benign. TS-1 exhibites an unique catalytic performance in oxidation reaction involving H2O2 as the oxidant. The hydroxylation of phenol and the ammoxidation of cyclohexanone using TS-1 as the catalyst, as clean manufacture methods, have been industrialized.Propylene oxide (PO) is one of industrially important bulk chemicals. At present, the conventional route for propylene epoxidation involving the use of chlorine and lime not only erodes equipments but also produces much pollution in China. The H2O2 conversion and PO selectivity above 95% are obtained in epoxidation of propylene catalyzed by TS-1 under 100℃ reaction temperature. Therefore, it is a clean manufacture route. However, there are four problems to be resolved for this new manufacture route: preparation of catalyst; feasibility of byproduct separation; reduction of the cost of the TS-1 synthesis and H2O2. As TS-1 synthesized using TPABr as template in a 5M3 autoclave decreases the cost of TS-1, the former two problems hamper industrialization.In this paper, effects of the extruding process, solvents and the size of TS-1 on propylene epoxidation were studied. The thermostability of extruded TS-1 catalyst was investigated. The hydrothermally treated extruded TS-1 catalyst exhibited very high activity and stability in propylene epoxidation. In the system of TS-1/urea/hydrogen peroxide, byproduct separation was feasible. All the above work will afford valuable information to industrialize the synthesis of propylene oxide (PO) from propylene and hydrogen peroxide using TS-1 as the catalyst.From the systematical studies in this paper, the following results have been obtained.1. The characteristics of lamina TS-1 catalyst were explored. Effects of the extruding process, solvents and the size of TS-1 on propylene epoxidation were examined. It has shown that extruded TS-1 exhibits higher activity than lamina TS-1 at 0.3h-1 of propylene in propylene epoxidation, but lower PO selectivity. The 3% polyethylene glycol as a pore-forming agent is preferred when increasing the PO selectivity. The pore (around 1.5nm) has an important effect on the PO selectivity. When the amount of acetone is 75% in co-solvent, performance of extruded TS-1 is the best. The smaller the crystalline size is, the higher activity extruded TS-1 exhibits in co-solvent.2. Effects of calcination method and calcination temperature were investigated using XRD, IR, UV-Raman. It has shown that the temperature-programmed calcination under nitrogen is preferred to obtain extruded TS-1 catalyst. The thermostability of extruded TS-1 catalyst is inferior to that of TS-1. The activities of extrudedTS-1 catalyst and TS-1 keep constant when calcination temperature is between 540 and 700 ℃, but the activity of extruded TS-1 catalyst decreases when calcination temperature is 900 ℃.3. The effect of hydrothermal treatment on extruded TS-1 catalyst in propylene epoxidation in fixed bed was examined by means of XRD, XRF, BET, UV-vis and EPR et al. The long-term stability of hydrothermally treated extruded TS-1 catalyst was investigated. The material equilibrium of the hydrothermally treated extruded TS-1 was caculated. The results show the conversion of the Ti(IV)-superoxide radical species A (gz =2.0271; gy = 2.0074; gx = 2.0010) to B (gz =2.0247; gy = 2.0074; gx = 2.0010) leading to a higher activity of the hydrothermally treated extruded TS-1 catalyst. Hydrothermal. treatment has marked effect on the performance of extruded TS-1 catalyst in propylene epoxidation. The optimal hydrothermal treatment temperature and time are 170℃ and 4h, respectively. The extruded TS-1 catalyst hydrothermally treated at 170 ℃ for 4 h exhibits very high activity and stability in propylene epoxidation. The H2O2 conversio...