Study On Modified HZSM-5 Catalysts In Methanol To Olefin

Olefins such as ethylene and propylene are the essential chemical raw materials for the development of modern industrial,mainly from traditional petroleum refining industry.But it is the international oil crisis and the ever-changing international situation in recent years that makes non-oil routes to light olefins process become necessary.The production technology of methanol from coal,natural gas or biomass which sources are very extensive,had become mature,and therefore the production technology of light olefins from methanol as an intermediate,which is a non-oil technology,is considered more significance in China.The catalyst research and development is the core part of MTO process.Due to the large pore size,strong surface acidity,HZSM-5 catalyst exhibited low yields toward olefins in the methanol-to-olefins(MTO)process.The Si/Al ratio,modified with phosphorus compounds,hydrothermal treatment and both of treatment with phosphorus and hydrothermal(cross-modified)was investigated to improve the yield of light olefins,at the same time,the microscopic nature change of modified catalysts was characterized by using modern characterization techniques,such as XRD,Py-IR,NH3-TPD and BET.The catalysts was evaluated in an fixed bed reactor,which its loading amount is 10 ml,at temperatures 480 ?,reaction pressure ranging from 0 to 0.1 MPa,methanol/ water ratios 3:2.The optimal loading of phosphorus was 2.5 wt% by changing the amount of phosphorus load ing on the catalyst(0.6 ~ 3.5 wt%)in this paper,and olefins yield was improved.The relationship between the amount of acid and acid strength on the catalyst surface and the yield of olefins was achieved.The yield of olefins was improved by the modified catalysts with hydrothermal treatment,which was the synergistic effect of catalyst surface acid strength and pore structure.The cross-modified catalysts had improved the yield of olefins,and the yield of olefins reached a level of 68 % which basically reached the German Lurgi MTP technology.This is synergy results of the modified phosphorus and hydrothermal modification.The optimal catalyst was prepared through experiments and its yield of ethylene + propylene is 68 % which it was higher than the current literature level nearly 30 %.The optimal catalyst was prepared by loading 2.5 %(wt)phosphorus content and hydrothermal treatment at 550 ? for 4 hour.