Investigation Of Nanosized Composite Catalysts Transforming Gaseous Cyclohexane Into Succinic Anhydride

In this thesis, butanedioic anhydride preparation acted as the target reaction by selectively catalytic oxidation of gaseous cyclohexane, nano-TiO2 was loaded on the general supporters of Al2O3 and ZRP-5 molecular sieves based on sol-gel method and a series of composite supporters were obtained. A series of catalysts probing into the target reaction were obtained with main active ingredient of V2O5 and doped reagent of different content such as P, Mo, Sb and K. The catalyst supporters, active ingredients and the conditions of preparation were optimized by the orthogonal test. The catalytic reactions were processed in the bed-secured micro-reactor under normal pressure. It showed that the composite supporters, the catalyst component and the reaction conditions could have great influence on the target reaction.The results showed that the content of TiO2 on the composite supporters had great effect on the performance of the supporters. The appropriate content of TiO2 was 10wt%. The catalysts containing 5.5 wt% V2O5, 1.15 wt% Mo, 0.5 wt% Sb, 3.8 wt% K and P/V atomic ratios of 3/2 exhibited high activity.Techniques, such as differential thermal analysis thermogravimetry (DTA-TG), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), transmission electron microscope (TEM) were performed to study the physicochemical change during the heat treatment process, the surface structure, the crystalline structure and surface morphology of the catalysts and supporters. The DTA-TG results showed that the transformation from anatase phase to rutile phase started at 600. The temperature scope that samples lost weight was in conformity to its transformation temperature. The nanoparticals could be dispersed on the composite supporters very well during the transformation. There was interaction between nanoparticals and the supporters. The cyclohexane was mainly adsorpted on V=O and Mo = O of the catalysts. The results of XRD and TEM showed that the composite supporters still reserved the framework Al2O3 and ZRP-5, the particle sizes of TiO2 loaded on the Al2O3 and ZRP-5 were around 35 nm and 26 nm respectively, and TiO2 of the two supporters was present in an anatase state on the supporters.The evaluation results of the catalyst activity showed that catalyst obtained by sol-gel method exhibited higher catalytic activity than by impregnation method and mixing gel method. The proper content of O2. cyclohexane and CO2 could increase the conversion rate of cyclohexane and the selectivity of butanedioic anhydride. The optimal reaction conditions in the target reaction were reaction temperature 90-310,7GHSV=1400h-1, the concentration of cyclohexane 2 vol%, and the content of O2 15-20 vol %.