Study On Pyrolysis Characteristics Of Shendong Coal By Modified ZSM-5 Under Hydrogen-Rich Atmosphere

High-definition clean utilization of coal is an important part of China's energy demand,and the coal pyrolysis process is an important means for upgrading low-grade coal.The pyrolysis process and volatile matter are modified by changing the pyrolysis process conditions and catalytic pyrolysis to improve the high value-added products of tar.In this paper,Shendong coal is used as a raw material.The powder-particle fluidized bed was used to analyze the coal pyrolysis products under different atmospheres and the metal(Zn,Ni,Fe,Ga)impregnation modification and alkali treatment modified ZSM-5 catalyst.Conclusions as follow :(1)Compared with the nitrogen atmosphere,the conversion rate of Shendong coal increased and the yield of char decreased by 2.33% under the hydrogen atmosphere.The methane production in the gas increased greatly,from 1.14mmol/g of nitrogen to 1.75mmol/g.Meantime,hydrogen has a certain effect on the improvement of tar quality,the content of H in the tar under hydrogen conditions has increased to 8.44%.In addition,the introduction of hydrogen improves the performance of deoxidation,denitrification,and desulfurization,reduces the content of heavy components(the number of aromatic rings is greater than 3),and the content of light components in tar increases significantly at 300 ° C(2)After the metal modification,the distribution of strong and weak acids changed,the specific surface area and the total pore volume tended to decrease,and the catalyst structure did not change.The addition of the catalyst did not affect the yield of solid products,but modified the pyrolysis volatiles and mainly manifested as the conversion of liquid phase products into part of gas phase products and part of coke.Under the condition of hydrogen,the catalyst promoted the deoxygenation reaction,and the CO and CO2 in the gas phase increased.The oxygencontaining component in the pyrolysis tar catalyzed by ZSM-5 was reduced from 31.88% to 12.68% in nitrogen.The yield of total aromatics reached 70.83%,of which the content of PAHs decreased.After the introduction of metal,PAHs increased slightly,and the thermal weight loss rate decreased compared to the ZSM-5.(3)The structure of ATZSM-5 modified by alkali treatment has not changed,and the SEM image shows that the surface of the zeolite is etched and roughened,the specific surface area and pore volume are increased,the total acid content is increased,and the strong acid peak is 439.4 ? from the parent ZSM-5 Migrate to 430 ?.The mesoporous structure improves the mass transfer efficiency,avoids the deep molecular reaction in the pores to form coke,and promotes further volatile reactions.The gas phase products of ATZSM-5 increased by 27.39%,and the liquid phase products decreased,but the Aromatics yield of ATZSM-5 increased to 84.43%,in which the content of naphthalenes was greatly increased,and the lower hydrogen partial pressure was beneficial to the production of substances of molecular size such as naphthalene and its alkyl substituents.After treatment,the thermal weight loss of tar is slightly reduced.The proton acidic sites of the zeolite are reduced after the metal is loaded,the cracking of heavy components is suppressed and the content of light components is reduced.