Study On Catalytic Fast Pyrolysis Of Corn Stover For Bio-oil Production And Its Upgrading Based On Hydrogenation And Deoxygenation Techniques

The development of biomass energy is beneficial for alleviating increasingly serious energy and environmental problems.A wide array of methods has been researched for the utilization of biomass energy,and one of the most attractive ways is catalytic fast pyrolysis(CFP)technology for the production of liquid fuels(termed bio-oil).However,hydrogenation and deoxygenation are needed for the generated bio-oil,and foundational research should be conducted.In order to promote the hydrocarbon production in biomass CFP process,a comprehensive systematic optimization research is carried out form the aspects of biomass feedstock,HZSM-5 catalyst,pyrolysis reactor and process,and primary bio-oil in this thesis.Catalytic fast co-pyrolysis of corn stover and high-density polyethylene(HDPE)was carried out to increase the relative content of hydrocarbons in pyrolysis vapors.The results illustrated that there was a remarkable synergistic effect between corn stover and HDPE,resulting in a promotion for hydrocarbon production.Besides,the highest yield of pyrolysis vapors was achieved at the reaction temperature of 750?.When the mass ratio of corn stover to HDPE was above 1.0,the relative content of aromatic hydrocarbons remained virtually constant,and then increased with decreasing mass ratio of corn stover to HDPE when this mass ratio was below 1.0.Fresh HZSM-5 catalyst was hydrothermally treated,and catalytic upgrading of corn stover fast pyrolysis vapors with fresh and hydrothermally treated HZSM-5 catalysts was studied.Hydrothermal treatment caused a reduction in the yield of pyrolysis vapors,and HZSM-5 catalyst with higher hydrothermal treatment temperature resulted in a higher relative content of carbon dioxide and hydrocarbons.On the other hand,the increase of hydrothermal treatment temperature was also conducive to the decrease of oxygen content in the organic pyrolysis vapors.Results also showed that pre-coking was a good method to minimize coke yield and induce the formation of target products.A novel technology of two-step microwave-assisted catalytic fast pyrolysis(MACFP)of corn stover for bio-oil production using microwave absorbent and HZSM-5 catalyst was investigated.The results showed that the optimum MACFP temperature was 500?,and the increase of catalyst-to-biomass ratio reduced the bio-oil yield and promoted the bio-oil quality.In addition,compared to one-step MACFP,two-step MACFP could reduce the use of HZSM-5 catalyst and improve the bio-oil quality.Also,SiO2-chemical vapor deposition modified HZSM-5 was applied in MACFP process,leading to the decrease in coke yield and relative content of oxygenates and increase in relative content of hydrocarbons in the bio-oil.The primary bio-oil was also upgraded in this thesis using two technical routes.In the first technical route,primary bio-oil was first extracted by ether,and then microwave-assisted catalytic esterification of ether-soluble(ES)fraction was conducted.Experimental results showed that ES had a better quality compared to crude bio-oil,and the relative content of acids in ES decreased dramatically while that of esters increased after microwave-assisted catalytic esterification.Meanwhile,microwave heating resulted in a better effect in contrast with conventional heating method.In the second technical route,primary bio-oil was upgraded using looped-oxide catalysis technique first,and after upgrading the oxygen content in bio-oil reduced significantly,and the relative contents of acids,alcohols and sugars decreased while those of esters,carbonyls and phenols increased.Then the upgraded bio-oil was further refined using electrocatalytic hydrogenation(ECH)technique,and after ECH,the relative contents of acids,esters,carbonyls,phenols and furans decreased while the relative content of alcohols increased significantly.Finally,catalytic cracking of the generated bio-oil was carried out to produce hydrocarbons,and the carbon yield of aromatics,olefins and total chemicals increased with the increase in hydrogen to carbon effective ratio.In this thesis,the definition of hydrogen to carbon effective ratio was improved,which combined the macro level element compositions and structural features in the feedstocks.