Preparation And Catalytic Properties Of Bifunctional Catalyst For Olefin Epoxditaion And Carbonation

Chemical researchers have been making efforts to develop novel materials containing multifunctional groups with the purpose to make the chemical processes environmentally benign, energy saving or low contamination to our environment. Since catalysis is an important technology in modern industry, it is extremely attractive and challenging to develop new catalytic materials. In recent years , the design of multifunctional materials capable of carrying out heterogeneous catalysis has been very active.Ti-MWW has been proved to be one of the most effective catalysts for the oxidation of alkenes. In this study, we have prepared bifunctional catalyst through combining the organic quaternary ammonium groups with titanosilicates together to expand its application. The bifunctional catalyst was prepared successfully through grafting quaternary ammonium halides onto titanosilicates. The resultant material possessed both oxidation and cycloaddition catalytic activity, never reported yet. The thesis is mainly made up of following parts:(1) The bifunctional catalysts have been characterized by XRD, FT-IR, TG, ²⁹Si and ¹³C CP/MAS NMR to investigate that the way of grafting between the titanosilicate support and organic ammonium. The loading amount of quaternary ammonium halides were investigated in detail, showing that Del-TiMWW was the best support for grafting. The maximum loading of =Si (CH₂)₃N⁺Me₃X^- was 3.0 mmol/g and 1.2 mmol/g for =Si (CH₂)₃N⁺Bu₃X^-, respectively.(2) The bifunctional catalysts were applied to the oxidation of propylene. Increasing the loading amount of quaternary ammonium halides lead to a gradual decrease of PO yield. A good activity was obtained when the loading amount was less than 1.5mmol/g.(3) The bifunctional catalysts have been tested for the cycloaddition of PO and CO2. Compared with Ti-MWW, TS-1, Ti-Beta, functionalized Del-Ti-MWW exhibited the best catalytic activity. Higher loading amount of ammonium halides made PC yield increase first and then decrease. A proper loading amount was 1-1.5 mmol/g. The most appropriate conditions for this reaction were temp, of 423 K, P_CO2 of 2 MPa, reaction time of 6 h. PC yield was maintained 90% after being used for 4 times. The key factor for the formation of by-products was the amount of water.(4) The bifuntional catalyst was applied to the one pot synthesis of PC from olefin. The PC selectivity was influenced remarkably by the concentration of H₂O₂. The highest PC yield (55%) was obtained when using 69% H₂O₂. The product yield decreased at first recycle, but remained constant till the forth run. We have confirmed that the reason for the decrease of catalytic activity during the first recycle was due to a large amount of polyethers which was formed to block the pores of Ti-MWW.