Catalytic Fast Pyrolysis Of Different Biomass Feedstocks To Produce Aromatics And Olefins

Aromatic hydrocarbons and olefins are important base materials and platform compounds in organic chemistry.Their production has long been highly dependent on traditional fossil fuels.Developing technologies for the production of aromatics and olefins from renewable biomass resources is of great importance for alleviating oil shortages and ensuring national energy security.Biomass catalytic pyrolysis can convert biomass into high value-added products such as aromatic hydrocarbons and olefins in one step in a single reactor.However,a wide range of biomass exist,and the specific relationship between biomass composition,aromatic hydrocarbons,and olefin production efficiency is still not clear enough.In view of the above problems,this paper selected ten typical biomass to explore the inherent relationship between the composition of raw materials and pyrolysis characteristics,product distribution;investigated the impact of biomass inherent inorganic components on the generation of aromatic hydrocarbons.olefins;and through the raw and treated naterials and catalysts.The catalytic products distribution was studied.The compositional improvements have led to a substantial increase in the hydrocarbon production efficiency.Thermogravimetric analysis was used to study the pyrolysis kinetic characteristics of the three major components of biomass and ten typical biomass.The results showed that pyrolysis characteristics of the three components were significantly different.The pyrolysis temperature range of hemicellulose,cellulose and lignin were between 180-320 ?.220-420 ? and 180-600 ?,respectively.The pyrolytic behavior of different kinds of biomass also showed significant differences.The pyrolysis temperature ranges of herbaceous biomass and woody biomass appeared at 180-380 ? and 190-420 ?.respectively.The kinetic properties of different biomass depend largely on the content of each component,but due to the strong interaction between the components during pyrolysis,the pyrolysis characteristics of raw materials can not be quantitatively predicted directly by the component content.The activation energy of biomass pyrolysis reaction increases with increasing heating rate.At lower heating rate,the reaction order and diffusion mechanism play a leading role.At higher heating rate.the reaction process is partly controlled by diffusion and power law model.The aromatic hydrocarbons and olefins were produced by fast pyrolysis of ten typical biomass under non-cataly tic and catalytic pyrolysis conditions were studied on a continuous feed fluidized bed.Under the non-catalytic conditions,the yields of aromatics and olefins are very low(up to 5%),and most of the products are oxygenates.However,under the catalytic conditions,the HZSM-5 catalyst can effectively deoxygenate pyrolysis voprs to form high yields of target products.The highest caxbon yields of pinewood,corncob and poplar were 12.12%.12.52%and 12.58%respectively,while pinewood,corn cob and poplar were most suitable for the production of olefins with yields of 10.19%,10.69%and 9.89%.respectively.Aromatic hydrocarbons,olefin yields,and biomass feedstock content of the three components showed a high degree of correlation.cellulose-rich biomass to produce more aromatic hydrocarbons and liquid products,rich in hemicellulose biomass more olefins and gas products are produced,w hile lignin-rich biomass is easier to form pyroytic carbon.Therefore,the pyrolysis products distribution can be predicted based on the biomass composition,which is of great significance for the screening of raw materials.At different reaction temperatures(RT)and sweeping gas flow rates(SGFR),the effect of inorganics matters was investigated,by comparing the catalytic pyrolysis products of raw and pretreated sugarcane bagasse over HZSM-5 catalyst.At various RT and SGFR,the pretreated bagasse yielded higher yields of aromatics and olefins than the raw bagasse.When the pyrolysis temperature was 500 ? and the SGFR was 2.5 L/min,the yield of aromatic hydrocarbons and olefins reached the maximum of 12.41%and 10.89%,respectively.The results showed that the inherent inorganic components of biomass had an inhibitory effect on the formation of hydrocarbons and could deactivate the catalyst by clogging the catalyst pores.The pretreatment can effectively remove inorganic components and increase the yield of hydrocarbons.From the perspectives of raw material optimization and catalyst performance optimization,the co-pyrolysis pyrolysis of biomass/hydrogen-rich feedstock and the USY/HZSM-5 dual catalytic approach were respectively used to achieve an effective increase of hydrocarbon yield.The bioplastic(chicken feather)hydrogen-rich material was added to the bagasse to increase the effective hydrogen-carbon ratio of the raw material.The results showed that the yield of the aromatics hydrocarbon increased obviously with the increase in the bioplastic content,and the synergistic effect between the two raw materials was remarkable.The larger pore size USY catalyst and shape-selective catalyst HZSM-5 are arranged in sequence to form a cascade conversion method of pyrolyzing vapor through macroporous and micropore deoxygenation simultaneouly.The results showed that the yield of hydrocarbons in the dual catalyst design catalysis of USY/HZSM-5 is greatly increased,which is 2.66 times that of the single-stage catalysis when using HZSM-5 catalyst.