Study Of Modified ZSM-5 Catalysts For Shendong Coal Pyrolysis Characteristics

Coal pyrolysis is the first and key step to coal conversion,at this stage,how to improve energy efficiency,achieve clean and effective utilization of coal is a majorissue of China’s energy strategy,is also the hotspotsforresearchers.TG-FTIR and fixed bedreactor of self-assembly were used to research low rank coal-shendong coal hydrogenationpyrolysis and hydrogenation catalytic pyrolysis,to explore the influence of catalysts and pyrolysis atmosphere on coal pyrolysis process.Modified catalysts with elements such as N、W、P were prepared on self-made ZSM-5 carrier through incipient-wetness impregnation method and hydrothermal immersion method,and a variety of means were used to characterize catalysts.In 5%H2+95%N2 atmosphere,the pyrolysis behavior of shendong coal under different catalysts was evaluated with TG-FTIR.This study has found that compared with ZSM-5,modified ZSM-5 with single metal(Ni or W)could improve the conversion rate of coal pyrolysis,reduce the primary and secondary pyrolysis peak temperature,improve the composition and distribution of products.In all NiW/ZSM-5 catalysts prepared by incipient-wetness impregnation method and hydrothermal immersion method,the optimum ratio of Ni-W is 4-6%;when the ratio of Ni-W was same,the catalysts prepared by hydrothermal immersion method show higher catalytic activity,the characteristics of pyrolysis peak temperature of shendong coal decreased and thetotal conversion increased,4-6%NiW/ZSM-5(SR)haved maximum weightlessness.Compared with raw coal pyrolysis,over 4-6%NiW/ZSM-5(SR)coal conversion rate increased by 4.3%;over 4-6%PNiW/ZSM-5(SR)coal conversion rate increased by 7.2%compared with raw coal pyrolysis,it indicated that P modification can enhance catalyst activity,make the coal pyrolysis conditions more moderate.In general,4-6%PNiW/ZSM-5(SR)receive best catalysis efficiency.Under the fixed bed reactor,the effect of catalysts on coal pyrolysis product distribution was investigated,conclusions as follows:1.H2 atmosphere was beneficial to improve the conversion rate,increase the tar yield,enhance desulphurization and denitrification performance of coal powder,and also improve BTX and naphthalene content in tar;2.Compared with non-catalytic pyrolysis,catalytic pyrolysis could raise aromatic hydrocarbon and naphthalene compounds content in tar.In N2 atmosphere,ZSM-5 had the maximum selectivity of aromatic compounds,its content in tar increased from 19.07%to 50.28%;4-6%NiW/ZSM-5(SR)can promote naphthalene compounds content,it increased from 10.72%to 39.04%;4-6%PNiW/ZSM5(SR)could significantly promote the production of phenolic compounds,it increased from 38.65%to 50.57%.In H2 atmosphere,6%W/ZSM5 had the maximum selectivity of aromatic compounds,it increased from 22.78%to 39.34%;ZSM-5 can promote naphthalene compounds content,it increased from 18.95%to 53.95%.Catalysts(except ZSM-5)can improve the BTX content in tar,and 4-6%PNiW/ZSM-5(SR)had the maximum selectivity of BTX.