Study On Separation Efficiency Of Wheat Straw Based On Catalytic Reinforced Ethanol-based Organosolv Process

China is a large agricultural country with abundant agricultural straw resources.Statistically,China's annual straw production is 9.84×10⁸ t.Therefore,the development of biorefinery with straw is necessary,and greatly alleviate the environmental problems caused by straw burning as well.Currently,there is a lack of efficient and clean straw biomass separation technology.Ethanol-based organosolv process has broad prospects for the clean separation of straw resources.In this work,wheat straw was used as raw materials.In order to overcome the problem of lower separation efficiency,the catalysts and selective separation were introduced to accelerate the separation efficiency of each component and achieve efficient separation of wheat straw.The effect of non-catalytic,catalyst CH₃COOH,MgCl₂,H₃PO₄ and H₂SO₄on component separation of wheat straw was discussed.The morphology and structure of the crude cellulose and ethanol lignin were characterized.And the dissolution route and mechanism of lignin in the separation process were analyzed by SEM and CRM.The results showed that the separation effect of 0.02 mol/L H₃PO₄ was the best that the yield of crude cellulose was 40.53%,and the removal rate of lignin and hemicellulose were 80.99%and 69.90%,respectively.During the separation processes,the lignin exuded out through the surface and cross section of straw.The fiber surface had enrichment phenomenon of the lignin particles.Concentration of cell corner and middle lamella were significantly decreased under the action of ethanol-based organosolv processes.The addition of different catalysts had no significant effect on its lignin functional groups.The crystal form of crude cellulose did not change under different catalytic conditions,and the crystallinity of the crude cellulose catalyzed by H₃PO₄ was the largest,which was 61.50%.On the basis of previous research,H₂O₂ was introduced to form two component catalytic system.The effect of CH₃COOH/H₂O₂,MgCl₂/H₂O₂ and H₃PO₄/H₂O₂ on the component separation of wheat straw was discussed.It can be obtained that the catalytic effect of H₃PO₄/H₂O₂ was best that the yield of crude cellulose was 44.73%,and the removal rate of lignin and hemicellulose were 88.64%and 68.99%,respectively.Compared to single H₃PO₄,the lignin removal rate was increased by 9.45%and the removal of hemicellulose was maintained at a higher level.The lignin separation effect of H₃PO₄/H₂O₂ was optimized by response surface methodology.When the temperature was 190°C,and the time was 70 min,and the ethanol concentration was 60%,and the solid-liquid ratio was 1:12,the maximum removal rate of lignin was 97.33%.The study on the hydrothermal-ethanol coupling selective separation process of wheat straw was carried out.The hemicellulose of wheat straw was removal by clean hydrothermal method,and then cellulose and lignin were separated by CH₃COOH catalyzed ethanol-based organosolv process.The separation effect,the lignin migration and adhesion on fibers law,the morphology and structure of the separation components were compared by single ethanol-based organosolv process and hydrothermal-ethanol coupling separation process.It can be obtained that both two treatments can dissociate the wheat straw.Although the hydrothermal-ethanol coupling separation significantly improved the hemicellulose removal rate,from 49.10%to 92.20%,the removal rate of lignin decreased significantly from 83.30%to 37.10%?SEM and AFM analysis of crude fiber showed that the surface lignin of crude fiber by single ethanol process was enriched in the form of particles,while the surface lignin of crude fiber by hydrothermal-ethanol process was sheet.This is because,lignin,which was enriched on the surface during the hydrothermal process,cannot be effectively separation by the ethanol-based organosolv process.Instead,it was melted and coated on the surface of the fiber in a sheet form,resulting in the lower yield of ethanol lignin.The sheet deposition of lignin on the surface also caused clogging of the pores on the fibers surface,resulting in making the surface area decreased.However,the crystal form of the crude fiber by two separation methods did not change,and all of them were type I.The different separation methods had no significant effect on lignin functional groups.In summary,the introduction of catalyst can significantly improve the removal rate of lignin and hemicellulose,which is beneficial to dissociation of wheat straw biomass and effectively solves the problem of low efficiency of ethanol-based organosolv process.It is very significant for the high value utilization of lignocellulosic biomass.