Preparation Of Levulinic Acid By Magnetic Bifunctional Solid Acid Catalyst

In recent years,the rise of sustainable development has provided a lot of opportunities for the production of chemicals and fuels from renewable raw materials.As an important renewable energy,the utilization of biomass waste plays an important role in realizing emission peak,carbon neutrality and promoting economic development in China.Among them,lignocellulosic biomass has the excellent characteristics of pollution-free and renewable.And it can be transformed into high value-added fuels,biological products and chemicals.Among them,levulinic acid(LA)can be obtained by direct hydrolysis of lignocellulosic biomass.Levulinic acid contains a carbonyl group,a carboxyl group and α-hydrogen,which has good stability and broad application prospects.In this paper,a carbon-based carrier with binding sites(-Cl,-OH,-COOH)was prepared by hydrothermal reaction with sucralose as raw material.The carbon based carrier was then grafted(grafting-oxidization)to prepare a bifunctional solid acid catalyst(HTC-Cl-SO3H)containing both binding sites(-Cl,-OH,-COOH)and catalytic sites(-SO3H).Using glucose as raw material,the catalytic performance of the catalyst was investigated.The results showed that the acid sites of the catalyst can catalyze glucose hydrolysis well.Under the conditions of y-valerolactone/aqueous solvent system(9:1),2 g of catalyst dosage(raw material 3 g),180℃of reaction temperature,150 min of reaction time,the highest yield of LA was 85.31%.The catalytic activity of the bifunctional solid acid catalyst with binding and catalytic sites for the hydrolysis of furfural residue to levulinic acid was investigated.Firstly,the effect of binding site on hydrolysis of furfural residue was studied.The results showed that the yield of LA was 70.02%when the solid acid containing binding site of-Cl,which was nearly 15%higher than that without-Cl.Secondly,the effect of acidic sites on the hydrolysis of furfural residue was studied.The results showed that the yield of LA first increased and then decreased with the increase of acidic sites;At the same time,the effects of different hydrolysis temperature,time and solvent ratio on the hydrolysis of furfural residue were investigated.The results showed that a highest LA yield of 74.81%was obtained in the reaction system ofγ-valerolactone/water(1:1)under 190℃ for 180 min.γ-valerolactone in the solvent contributed to the dissolution of cellulose,while cellulose binded to the catalyst through the binding site.At the same time,by the effect of the catalytic site(-SO3H),cellulose was hydrolyzed to levulinic acid.Considering the catalyst is difficult to separate from the hydrolysis residue,a magnetic bifunctional solid acid catalyst(HTC-Cl-SO3H-Fe3O4)was prepared by coprecipitation method.New Lewis acid catalytic site(Fe3O4)was added on the basis of the original active site.The introduction of Lewis acid promoted the hydrolysis of cellulose.An LA yield of 70.18%was obtained using a 15%dosage magnetic catalyst,which decreased for about 5%comparing to non-magnetic catalyst.For the reusability of the catalyst,the yield of LA decreased by about 9%after 5 cycles used of magnetic solid acid bifunctional catalyst,and the acidity of the catalyst did not decrease significantly during the recycle reactions.