Preparation Of Catalysts And Process Study On Deep Hydrodesulfurization Of Inferior Diesel

With the increasingly stringent environmental protection regulations,it is particularly important to reduce the sulfur content in diesel to meet the requirements of clean diesel.At present,hydrodesulfurization(HDS)technology is one of the most critical technologies to achieve ultra-deep desulfurization of inferior diesel in industry.Its core is the design and development of highly active HDS catalysts.Generally,the HDS catalyst uses Al₂O₃ as a carrier,and its surface has only L acid sites and no B acid sites.Moreover,Ni Mo based catalyst shows low sulfidation degree due to its strong metal-support interaction.Therefore,in this study,the research ideas and synthesis methods of deep HDS catalysts for inferior diesel were established from the perspective of acid regulation and hydrogenation activity regulation.In order to control the acidity of the HDS catalyst,the paper studied the effects of the way and content of metal Fe modification on chemical properties of Y zeolite and catalyst.Fe-modified Y zeolites were prepared by three methods:impregnation modification,ion-exchange modification and in-situ modification.The results showed that Fe could be effectively introduced into the framework of Y zeolite by in-situ method.Compared with impregnation modification and ion-exchange modification,the in-situ modification had less damage to the framework structure.The surface of the catalyst had an higher amount of weak acid and B/L acid ratio,The catalyst had the higher HDS rate and hydrodenitrogenation(HDN).When Fe content was about 3.2 wt.%,the modification effectively improved the pore structure of the zeolite.The surface of the catalyst had an appropriate amount of weak B acid and the most appropriate B/L acid ratio.The catalyst had the highest HDS rate and HDN rate on inferior diesel,reaching 98.7%and 99.0%,respectively.In order to improve the hydrogenation activity of the HDS catalyst,the paper studied the effects of transition metal and complexing agent modification on the properties of Al₂O₃catalysts.The results showed that Zr and Ti modified Al₂O₃ support could weaken the interaction between the active metal and the support,and promote the sulfidation degree.These catalysts had promoted the conversion of DBT,and the Zr modified Al₂O₃ catalyst had the better HDS performance,the higher selectivity of HYD route,and the higher HDS rate and HDN rate on inferior diesel.EDTA was further added in the impregnation solution of active metal could effectively improve the dispersibility of the active metal and promote the sulfidation degree.The conversion of DBT and the selectivity of HYD route were further improved.The catalyst had the highest HDS rate and HDN rate on inferior diesel,reaching 99.1%and 99.4%,respectively.Based on the results of acid regulation and hydrogenation activity regulation,two catalysts with different functions were selected:CAT1 and CAT2.CAT1 had higher hydrogenolysis activity,which promoted the removal of BTs and DBT in diesel;CAT2had higher hydrogenation activity,which promoted the removal of alkyl-substitued DBTs in diesel.The two preferred catalysts were graded loading.The results showed that the HDS performance of a 2:1 packing order with the downstream of CAT2+CAT1catalysts was the best,reaching 99.4%.When the LHSV was further reduced to 1.5 h^-1,the sulfur content in the product could be further reduced to 10?g·g^-1,which could meet the sulfur content required by the national-? and national-? standards.