In-situ Hvdrodeoxygenation Upgrading Of Bio-oil With Furfural As The Model Compound

With the decrease of fossil fuel reserves and more seirous environment problems,it is urgent to search for sustainable energy sources.The research on biomass conversion has received rapid developments since it is regarded as a kind of abundant,cheap,stable and environmental friendly resource,as well as the only renewable carbon source.Therein,fast pyrolysis technology can efficiently convert biomass into bio-oil which can be a promising alternative to supply the fuels.However,due to the undesired poor natural properties of bio-oil,it has to be upgraded to reduce water content,acidity,oxygen content etc.and increase heat value and stability.A method named in-situ hydrodeoxygenation was employed to solve this problem with respect of reducing the operation,transporation,storage and safety problems,caused by the addition of a large amount of H2 in conventional hydrodeoxygenation process.In order to understand more basic and specific reaction mechanisms,furfural was selected as the model compound in the research as it could be the representative compound of furans and aldehydes in bio-oil.The preliminary experiment indicated that obvious coke formation of furfural aqueous solution started when the reaction temperature was higher than 140?.However,by adding alcohol solvents into the system such as methanol,ethanol,isopropanol,the coke formation could be completely inhibited.Thus,methanol aqueous was selected as the solvent and hydrogen donor for this system.Two types of catalyst:metal oxide catalysts(Fe2O3,ZnO,NiO,CuO)and metal catalysts(Pd,Pt,Ru,Fe,Cu,Ni)were screened.The results showed that metal oxdie catalysts just had very low catalytic activity while the metal catalysts showed distinct performance.Pd was favorable for decarbonylation with a high 81mol%yield of furan;Pt,Ru,Ni all showed the catalytic activities for both carbonyl and furan ring with the ability ranking:Pt>Ni>Ru.Cu showed a low activity but a high selectivity for the reduction of carbonyl.Fe was hardly active in this system.Therefore,further researches were performed over Ni based catalyst to investigate the effect of support,reaction temperature,catalysts loading,feed ratio,residence time.The results indicated that the support with larger pore size and more acidities was preferable for the conversion of furfural and the formation of furan and 2-methylfuran.More decarbonylation product furan could be obtained by increasing temperature.More deep hydrogenated product tetrahydrofuran could be obtained by increasing metal loading and more 2-methylfuran could be obtained by increasing the fraction of methanol in the reaction medium.By studing the factor of reaction time,it was found that the primary reaction occurred in the first 4 hours and then the product distribution gradually turned stable.The in-situ HDO of synthetic bio-oil was also studied in this reaction system and it was found that except phenol,all the other compounds could be effectively converted for higher heat value and stability of bio-oil.When using formic acid as the hydrogen donor,the bimetallic Ni-10%Cu/Al2O3 catalyst was prepared by virtue of the high instinctive activity of Ni and high selectivity for carbonyl reduction of Cu.The characteristic results showed that the addition of Ni could change the dispersion and crystallite size of catalysts.The formation of Ni-Cu alloy was beneficial for the adsorption of carbonyl and the repulsion of furan ring.Thus,more 2-methylfuran could be generated with a highest yield 92mol%within 7 h.Moreover,the isopropanol solvent could contribute to the hydrogenation of carbonyl through transfer hydrogenation process while promoted slightly for the next hydrogenolysis,which required the participation of the stronger hydrogen donor formic acid.