Study On Catalytic Pyrolysis Of Shendong Coal By Ni-ZSM-5 Zeolite

Coal pyrolysis technology is the core of the coal grading utilization,which can realize the clean conversion of coal and the effective utilization of resources and energy.The introduction of catalysts can promote or inhibit the occurrence of some reactions in pyrolysis process and regulate distribution and quality of pyrolysis products.In this paper,ZSM-5 zeolites with different Si/Al ratios?all-silicon,Si/Al=120,Si/Al=60?were used as carriers,transition metal Ni was introduced into the carriers by in-situ synthesis and isovolumetric impregnation,respectively.Then the pyrolysis evaluation of prepared catalysts was carried out in the powder-particle fluidized bed,the effects of metal modification methods and Si/Al ratio on the products of catalytic pyrolysis of Shendong coal by Ni-ZSM-5 zeolite were investigated as follow,?1?Ni-ZSM-5 zeolites with different metal modification methods and different Si/Al ratios have different acidity and specific surface area,but the pore structure has little change.It was found that compared with the unmodified ZSM-5 catalyst,Ni-ZSM-5modified by in-situ synthesis have larger total acidity and specific surface area,while Ni-ZSM-5 modified by impregnation have smaller specific surface area,and the influence on the acid distribution is related to the acid content of the carrier.When Ni-ZSM-5 with different Si/Al ratios was investigated,it was found that the acid content,acid strength and total specific surface area of zeolites prepared by the two methods increased with the decrease of Si/Al ratios.?2?Distribution and composition of catalytic pyrolysis products of Ni-ZSM-5 zeolite vary with different metal modification methods.Compared with the unmodified ZSM-5catalysts,the impregnated Ni-ZSM-5 catalysts have significant effect on the distribution of pyrolysis products.The tar yield is significantly reduced,the coke deposition of catalyst and pyrolysis gas yield are increased,the production of H₂ and CO in the gas product are increased obviously,the proportion of total aromatic hydrocarbons and the content of phenols and oxides in the tar is reduced,the thermal weight loss of pyrolysis tar at 300?are less.Compared with the unmodified ZSM-5 catalyst,the in-situ synthesis of Ni-ZSM-5catalysts increase the amount of H₂ in gas product,increase the proportion of total aromatic hydrocarbons in tar,increase the content of aromatic hydrocarbons with an aromatic ring number of 1-2,reduce the content of phenolic substances and aliphatic hydrocarbons,and the thermal weight loss rate of the pyrolysis tar at 300?are increased.?3?Compared with non-catalytic pyrolysis,Ni-ZSM-5 prepared by the two methods reduced the amount of phenols and oxygenates in pyrolysis tar.The content of monocyclic aromatic hydrocarbons in the pyrolysis tar of Ni-ZSM-5 synthesized in situ by Si/Al=120is the largest,which is 75.6%higher than that of non-catalytic pyrolysis.Ni-ZSM-5catalysts prepared by two different metal introduction methods,with the decrease of Si/Al ratio,increase the proportion of total aromatic hydrocarbons and the amount of aromatic hydrocarbons with 2-4 ring in catalytic pyrolysis tar gradually,the thermal weightlessness of the pyrolysis tar are increased at 300?,and increase the production of several main components in pyrolysis gas products.