Study On The Catalysts For Hydrorefining Of Crude Benzene At Low Temperature

Crude benzene is one of the byproducts produced in coking process, and its composition is complex. Benzene, toluene and xylene could be obtained by the refining of crude benzene. The refining methods of crude benzene include sulfur acid washing method and hydrorefining method. Taking environmental protection and economic benefit into consideration, hydrorefining method now dominates the field. It's significant for us to research the corresponding catalysts.This paper mainly focuses on the study of the catalysts for main reaction. The target is removing thiophene from benzene, at the same time raising the retention rate of benzene, toluene and xylene as high as possible. The catalysts were characterized with BET and XRD.This paper consists of four parts:(1) Choosing the carrier for the catalyst. (2) Researching the impregnation methods. (3) Researching the influence of the metal load, atomic ratio of cobalt and molybdenum and the calcination temperature on the activity of the catalyst and the retention rate of BTX. (4) Researching the optimum prepararing conditions of the catalyst.By comparing the reaction result of the catalysts prepared under same conditions, spherical aluminum oxide was choosed as the carrier of the catalyst.Various impregnation methods, including co-impregnation method and multi-step impregnation method, were choosed to prepare the catalysts. Multi-step impregnation method could be divided into two ways, for example impregnating Co at first or impregnating Mo firstly. The results of the experiments showed that hydrodesulphurization (HDS) activity of the catalyst prepared by co-impregnation method was better than that of the catalyst prepared by multi-step impregnation method.Results of experiments on the metal load showed that the HDS activity of the catalyst firstly increased with the increasement of metal load, then got down. It reached the maximum value when the metal load was 20%.Results of experiments on atomic ratio of cobalt and molybdenum showed that the HDS activity of the catalyst firstly increased with the increasement of atomic ratio of cobalt and molybdenum, then got down The activity was bighest when p (Co)/n (Co+Mo) was 0.3.Results of experiments on the calcination temperature showed that the HDS activity of the catalysts firstly increased with the increasement of calcination temperature, then decreased. The best calcination temperature was 540℃.Orthogonal experiments showed that when the metal load was 20%, atomic ratio of cobalt and molybdenum was 0.2 and at the calcination temperature of 580℃, the HDS activity reached the maximum value under low condition: the concentration of thiophene 1.2 ppm and the retention rate of BTX 95.9%. The concentration of thiophene was 0.5 ppm and the retention rate of BTX was 91.6% when the reaction was carried under high condition.