Hydrodeoxygenation (HDO) Of Multi-stage Bio-oil To Produce Hydrocarbons Based On Hydrogen/Hydrogen Donor

Biomass is the only renewable resource and can be converted to biofuels through tiiermo-chemical and bio-chemical methods.Liquid biofuels are promising alternatives in fixture application since they can replace traditional petroleum fuels.Crude bio-oil derived from biomass pyrolysis has several inferior properties such as high water,oxygen content and viscosity,low heating value and strong acidity.Therefore it should be upgraded to be high quality biofuel.In the paper,the main components of the multi-stage condensation bio-oils were analyzed.Phenols,acids and ketones were selected as the model compounds.The research on the effects of different catalysts and process parameters on the HDO of model compounds was carried out,and the excellent catalysts and process routes were screened for the HDO of bio-oil model compounds.Based on the above,the HDO of real multi-stage bio-oils was further studied.Meanwhile,the surface morphology,physicochemical properties and stability of the catalysts were characterized and analyzed,and the mechanism of HDO of bio-oils was explored.Reference data for the application of multi-stage bio-oil,the relevant research results are as follows.?1?The composite support nickel-phosphorus catalyst,nickel-based catalyst and nickel-copper catalyst were prepared by impregnation method.The catalysts were characterized by BET,XRD,TGA,NH₃-TPD,H₂-TPR,FT-IR,SEM and XPS.The results show that the composite carrier contributes to the increase of the specific surface area,the improvement of the pore structure,the dispersion of the active material and the increase of the surface acidity of the catalyst.?2?The multi-stage bio-oils were prepared by multi-stage condensation of biomass pyrolysis.The approximate separation of different boiling points was achieved,and the three main oxy-compound in the multi-stage bio-oils were phenols,acids and ketones.?3?The effect of different catalysts on the HDO of a single model compound was investigated.The results of HDO of guaiacol showed that the catalysts NiCu/HZSM-5-La₂O₃,Ni/HZSM-5-?-Al₂O₃,Ni/HBeta-La₂O₃ and Ni/HBeta-Ga₂O₃ had better effects on guaiacol.The conversion rate was above 96%,the hydrocarbon content was over 70%,and the cyclic hydrocarbons and aromatic hydrocarbons were the main components in the upgraded liquid.The results of HDO of acetic acid and hydroxyacetone showed that the catalyst Ni/HZSM-5-?-Al₂O₃ had good HDO effect on both substances,and the conversion rates of acetic acid and hydroxyacetone were both 100.00%.The contents of these compounds were 88.62%and 80.30%,respectively,and they were mainly long chain alkanes.?4?The effect of catalyst Ni/HZSM-5-?-Al₂O₃ on the HDO of mixed model compounds was studied.The results showed that when the content of acetic acid was higher than 44%,the conversion rate of guaiacol and acetic acid decreased;when the proportion of acetic acid was lower than 25%,the catalyst was Ni/HZSM-5-?-Al₂O₃ has good catalytic activity,and the liquid products are mainly cyclic hydrocarbons and aromatic hydrocarbons.?5?HDO of the multi-stage bio-oils was studied using mixed supports Ni/HZSM-5-?-Al₂O₃.The results show that the effects of temperature,pressure,flow rate and WHSV are not a simple linear relationship.This may be due to the complexity of bio-oil components resulting in complex reactions.When the reaction temperature is 380?,the pressure is 2MPa,the flow rate is 380mL/min,and the WHSV is 0.75h^-1,the hydrocarbon content can reach 85.03%.After 5 hours of reaction,the relative gas content remained stable,indicating that the catalyst had better anti-coking performance.The contents of hydrocarbons in the upgraded oils are as follows:3th?water phase?>4th>2th>1th>3th?oil phase?,with the highest and lowest hydrocarbon content was89.47%and 54.48%,respectively.?6?The effects of catalyst Ni/HZSM-5-?-Al₂O₃ on the HDO of phenolic model compounds and multi-stage bio-oils under different hydrogen donor conditions were studied.The results show that when the molar ratio of hydrogen donor isopropanol to guaiacol is 30.96:1,the conversion rate and hydrocarbon content of guaiacol can reach100%and 88.15%,respectively.When the mass ratio of isopropanol to real bio-oil is 15:1,the content of hydrocarbons in upgraded oil can reach 81.38%?3th?water phase??and82.17%?3th?oil phase??.?7?The mechanism of HDO of guaiacol has many parallel reactions such as demethylation,demethoxylation,dehydroxylation,transmethylation,and saturated hydrogenation.The intermediate products will undergo condensation,hydrogenation,isomerization,and alkylation at the surface active center of the catalyst.After several cycle,the final product get out.Acetic acid and hydroxyacetone mainly undergoes hydrogenation,self-condensation,aldol condensation,saturated hydrogenation,and isomerization reactions,resulting in the formation of long-chain alkanes.