Post Modification of Ti-MWW and Its Patalytic Properties in Propylene Epoxidation
|School||East China Normal University|
|Course||Physical and chemical|
|Keywords||Ti-MWW prop ylene epo xidatio n reactio n fixed bed reaction propylene oxide|
Propylene oxide (PO) is an important organic chemical raw material. In industry, the production of PO is produced mainly by chlorohydrination process or hydroperoxidation process, but the former process produces large amounts of industrial pollutants, and the latter process produces too much co-product whose effectiveness relays largely on the market demand of co-product. As it was found that the titanium silicalites (including TS-1and Ti-MWW) in the olefin epoxidation reactions have excellent performance. What’s more, Ti-MWW exhibits more effective in the olefin epoxidation reaction than TS-1, Ti-MWW is expected to be a promising catalyst in industrial applications.In order to investigate the Ti-MWW performance in catalytic reaction over propylene, this thesis has dealt with following issues:the research of ammonia treatment effect on Ti-MWW catalyst, the research of the shaping condition of Ti-MWW catalyst, the hydrothermal treatment of shaped catalyst, the propylene epoxidation on a fixed bed reactor catalyzed by shaped Ti-MWW catalysts, and the investigation on the reason of catalyst deactivation.With the treatment with ammonia atmosphere, we found that Ti-MWW’s catalytic ability could be enhanced by treating at673K, which is due to less coke was produced in the probe reaction.In the Ti-MWW molding experiments, we used two kinds of molding methods. The first one is by changing the content of the molecular sieve, the type and content of the pore-forming agent, the carrier type and content, etc., we found that when the zeolite content is80wt%, sesbania powder is5wt%, and the carrier is alkaline silica sol, the shaped catalyst exhibit relatively good catalytic activity and mechanical strength. In the second molding method, we by changing the content of phenolic resin prepolymer, we obtained a series of organic-inorganic shaped catalysts.In the hydrothermal treatment of shaped catalysts experiments, we put the shaped catalysts into the piperidine solution, and treated it24hours at a certain temperature. After that, the treated catalysts were filtered, dried, and calcined. At last, the catalytic ability and mechanical strength of the catalysts were enhanced greatly.Under the fixed bed reaction condition, through changing the propylene space velocity, the reaction temperature, feed ratios, etc, we obtained the appropriate reaction conditions, and then we examined the lifetime of shaped catalyst and regenerated the used catalyst.Finally, through analyzing and characterizing the difference between fresh catalyst and deactivation catalyst, we believe that the main reason which caused the deactivation of the catalysts is the deposition of trace amount of propylene glycol produced in and around the zeolite pores. By calcination and extraction, the catalytic activity of the deactived catalysts can be partly recovered.