Study On The Modification Of V-MCM-41and Its Application In Oxidation Of Toluene To Benzaldehyde

MCM-41mesoporous molecular sieves is an ideal carrier for metal and metal oxide with the advantages of ordering rules of large pores and large specific surface area. However, one of the major disadvantages of pure MCM-41mesoporous materials is its relatively small capacity of ion exchange. Besides, it is also low in acid content and acid strength so that it isn’t capable of catalytic oxidation. The performance of these materials and their themal stability can be improved by introducing metal or metal oxide with redox ability. As a result, the application prospect of the mesoporous molecular sieves will be expand in catalysis.Benzaldehyde is an important intermediates in the organic synthesis industry. As it’s difficult to gain it from the oxidation of toluene, it is urgent to select and prepare a highly active catalyst for the oxidation of toluene. While environmental pollution is increasingly serious at present, it is of great important to search for pollution-free oxidant and catalyst.In this thesis, we prepare MCM-41by the atrane method, and modify it with Mn, Co as well as V-ZSM-5/MCM-41composite molecular sieve. Then it is applied in the oxidation reaction of toluene to benzaldehyde with oxygen as the oxidant.In the first part, we apply the reformed V-MCM-41mesoporous molecular sieve to the reaction, and research on its performance. Then, we characterize on the structure of zeolite by means of XRD, BET, IR, UV-vis and so on. Experimental results show that V is added to the skeleton, while Co which added by the impregnation method is highly dispersed on the pore surface instead of getting into the skeleton. The optimum conditions of reaction conditions are:reaction temperature80℃, air velocity300mLl/min,0.1g catalyst reaction for2h. The yield on benzaldehyde is20%.In the second part, we added Mn to the V-MCM-41molecular sieves by impregnation method. Then, we investigate the catalytic activity of the Mn/V-MCM-41by the same means of characterization and study the activity of catalysis through the same process conditions as the first part. The results shows that the addition of Mn can improve the conversion rate of toluene, but no obvious benefit for the selectivity of benzaldehyde.In the third part, we synthesize V-ZSM-5/MCM-41composite molecular sieve by two-step crystallization method, and characterize their pore structure and performance. After that, we investigate the influence of the content of V on the zeolite structure.