Study On Preparation Of Aromatics From Methanol/yunnan Huaning Coal Pyrolysis Component Reforming By Metal Modified ZSM-5 Molecular Sieve

Coal,as the main energy reserve in China,is abundant and widely distributed,with low rank coal represented by brown coal and sub bituminous coal accounting for55%.Low rank coal has the characteristics of high moisture,oxygen content,volatile matter,low carbon content,and low calorific value.The pyrolysis and upgrading of low rank coal is a key direction for the utilization of low rank coal,and the hydropyrolysis or catalytic hydropyrolysis of coal can to some extent improve tar yield and light component content.Due to the low content of high added value aromatic hydrocarbons obtained through the conversion of coal pyrolysis components,the addition of hydrogen sources during the upgrading process of coal pyrolysis components can effectively improve the preparation of light aromatic hydrocarbons through reforming of coal pyrolysis components.Methanol has a high hydrogen to carbon ratio(H/C=2)and can be used as a good hydrogen donor reagent.The HZSM-5 molecular sieve catalyst has high selectivity for light aromatic hydrocarbons and is widely used in the catalytic conversion of coal and biomass.This experiment attempts to use methanol in the catalytic upgrading process of the pyrolysis components of Yunnan Huaning lignite.HZSM-5 molecular sieve and metal modified HZSM-5molecular sieve are used as catalysts,which is expected to improve the selectivity of directional conversion of light aromatics in the pyrolysis process of low rank coal.This article uses Yunnan Huaning lignite as the research object.Firstly,different loading amounts of Zr modified catalysts were investigated for the reforming reaction of methanol/Yunnan Huaning lignite pyrolysis components.The results show that Zr/ZSM-5 catalyst can improve the selectivity of light aromatics in the product while reducing the content of oxygen-containing compounds.Attributed to Zr improving the acidity and surface oxygen vacancies of the catalyst.The introduction of the second metal Zn further reduced the content of oxygen-containing compounds,and the results showed that the Zn Zr bimetallic catalyst achieved the highest yield of aromatic hydrocarbons,which can be attributed to the Zr oxygen vacancy aiding in deoxidation and Zn aiding in hydrogenation.The two synergistically contribute to the hydrogenation and deoxidation of oxygen-containing compounds.Given the catalytic role provided by Zn Zr bimetallic materials in their respective reactions,we further investigated the modification of HZSM-5 molecular sieves with other bimetallic materials and investigated the effects of Ni Cu and Fe Ti bimetallic catalysts on the reaction system.The bimetallic modified catalysts can significantly increase the yield of aromatic hydrocarbons and reduce the content of oxygencontaining compounds.The Ni Cu catalyst has abundant strong acid sites,achieving the highest yield of aromatic hydrocarbons.The Zn Zr catalyst effectively improves the selectivity of monocyclic aromatic hydrocarbons,while the Fe Ti catalyst effectively reduces the content of phenolic compounds,improves the selectivity of BTX,and has good resistance to carbon deposition.In order to further investigate the hydrogen supply behavior of methanol,2,6-dimethylphenol and benzophenone were used as model compounds for coal pyrolysis.The catalytic conversion of 2,6-dimethylphenol and benzophenone model compounds using Zn-Zr/ZSM-5 bimetallic catalysts was studied.The results showed that bimetallic catalysts could effectively convert the two model compounds into xylene,with benzophenone accompanied by a small amount of benzyl alcohol and styrene,Attributed to methanol providing hydrogen and methyl to the reaction system.