Research On Depolymerization Of Lignin Catalyzed By Solid Acid

Biomass is a resource which is renewable over time,and is also the only renewable organic carbon resource in nature,this gives biomass the unique value.Lignin is one of the main components of biomass.It is only 20%of biomass from the quality point of view,but it reached above 40%from the energy point of view,and it has unique aromatic ring unit structure.The preparation of high value-added chemicals and bio-oil from lignin has attracted much attention of researchers.Lignin is composed of aromatic ring units which are linked by C-O bonds and C-C bond,and the acid catalyst can break the ether bond(a-and ?-aryl ether bonds)effectively.Therefore,a solid super acid catalyst S2O82-/ZrO2-TiO2-SiO2 which both with Bronsted acid and Lewis acid was prepared and used for lignin depolymerization.The yield of ethyl acetate solution was 91%at 310? for 1 hours,which means that solid acid catalyst is effective catalyst for lignin depolymerization as lignin is almost insoluble in ethyl acetate.We also investigated the effect of hydrogenation catalysts Pt/C as co-catalyst on lignin depolymerization in our research.The yield of petroleum ether soluble fraction(which represents the monomeric and dimeric products)can be improved with the addition of hydrogenation catalyst.The solid acid catalyst S2O82-/ZrO2-TiO2-SiO2 and hydrogenation catalyst Pt/C were mixed as the ratio of 1:1,and reacted at 310? for 24 hours.The yield of petroleum ether soluble and the yield of aromatic compound were 46%and 14.8%,respectively.The recycle of solid acid S2O82-/ZrO2-TiO2-SiO2 was also studied in this experiment,the activity of the catalyst was still better after three cycles,this shown that the solid acid catalyst S2O82-/ZrO2-TiO2-SiO2 has excellent stability.It is can be found that the addition of hydrogenation catalyst can improve the yield of petroleum ether solution and the yield of aromatic compound,obviously.Therefore,we further studied the effect of a noble metal-supported acid catalyst for lignin depolymerization.Since Ru has a good hydrogenation effect and can inhibit the self-condensation of lignin product,W-Sn-AlOx has strong ability to absore electrons,and has a certain degree of acidity.Ru was supported on the catalyst W-Sn-AlOx,and it is desirable to achieve a better catalytic effect of hydrodeoxygenation.The activity of catalyst was investigated in this experiment,the result was shown when the section of Sn-AlOx was modification by phosphptungstic acid.When the temperature was increased to 310?,and the reaction time was 1 hour,the yield of petroleum ether soluble was increased to 32%.When the reaction time was extended to 24 hours at 310?,the yield of liquid product was 85%,and the yield of petroleum ether soluble was 67%,the result shown that most of liquid product were oligomers composed of monomers and dimers.The oxygen content in the liquid product,after reacting at 310° C for 1 hour,decreased by 10.12%compared with the initial lignin,the result show that the catalyst can effectively reduce the oxygen content in the depolymerization product.In addition,the catalyst Ru/W-Sn-AlOx has good stability and can maintain good catalytic activity even after three cycles.Overall,this is a promising catalyst for the depolymerization of lignin.