Study On The Catalyst Of Methane Non-oxidative Dehydroaromatization Reaction

At present,the demand for aromatics is increasing.Due to the limitation of crude oil resources,it is urgent to replace the production of aromatics by catalytic reforming of crude oil.Methane is the main component of natural gas and shale gas with abundant reserves.Therefore,converting CH4 to high value-added aromatics is a research topic of many scholars.Methane non-oxidative dehydroaromatization(MDA)is one of the most valuable research topics.Although the supported Mo/HZSM-5 catalyst is widely studied,it is not stable and is not conducive to industrialization.The Fe based catalyst has great potential for industrial application and research value due to its best stability.A new type of zeolite catalyst was designed by hydrothermal synthesis technology and the template was TPABr.The embedded zeolite Fe@HZSM-5 was prepared by inserting Fe2O3 particles into HZSM-5.It could be demonstrated that the problem of deactivation of conventional catalyst was solved.First of all,we explored the preparation method of Fe based catalysts.Through the reaction evaluation of supported and embedded catalysts,we found that the supported 5%Fe/HZSM-5 catalyst was more inclined to produce heavy aromatic-naphthalene and had poor stability.However,the embedded catalyst was prone to produce light aromatic-benzene,which has better stability and higher benzene selectivity.TG and XRD analysis showed that the embedded 5%Fe@HZSM-5 catalyst had less carbon deposition.The embedded catalyst has good anti-carbon deposition performance.The problems of a large amount of carbon deposition and serious deactivation of supported 5%Fe/HZSM-5 catalyst were solved.Based on the best preparation conditions,the catalysts prepared by different synthesis conditions were evaluated for MDA reaction and characterized by XRD,N2 adsorption desorption and NH3-TPD.It can be found that the optimum loading of Fe was 5%.Ander the condition of TPABr as template with crystallization temperature of 180℃ and crystallization time of 72 h,the optimum Si/Al ratio was 40.Then the embedded 5%Fe@HZSM-5 catalyst with optimal performance can be prepared under conditions mentioned forehead.Benzene was the main aromatic product with selectivity of 54.61%.Based on the best preparation and synthesis conditions mentioned.We explored the structure and performance of the embedded catalyst synthesized with ammonium ferric citrate,ferric chloride and ferric nitrate as different iron sources for MDA reaction and found that the embedded catalyst synthesized with ferric nitrate as iron source had the best crystallinity,morphology and stability.We adjusted carbonization temperature and reaction temperature and found that the best carbonization temperature was 650℃ and the optimal reaction temperature was 700℃,in which the reaction stability could maintain for 20 hours.The main product is benzene with selectivity of 54.92%.