Study On Hydrolyzation Of Cellulose By Solid Acid

Cellulose is the most abundant carbohydrate in nature.It can be degraded into glucose or dehydrated to form other important platform compounds,such as5-hydroxymethylfurfural and levulinic acid.The traditional hydrolysis methods of cellulose are mainly liquid acid hydrolysis and enzymatic hydrolysis,but there are defects such as environmental pollution and high cost.Solid acid catalysts have attracted wide attention due to their environmental protection and high efficiency.Common solid acid catalysts include ion exchange resins,zeolites,metal oxides,etc.However,these solid acids also have disadvantages such as high cost,poor activity,and low catalytic efficiency.Therefore,it is important to study the novel solid acid catalyzed hydrolysis of cellulose.In this paper,a carbon-based solid acid with a large specific surface area and a polystyrene solid acid with a graded pore structure were developed,and the catalytic performance of its application to cellulose hydrolysis reaction was investigated.Large specific surface area carbon-based solid acid(CSALA)was prepared by using peanut shell as carbon source and phosphoric acid as activator.It was studied by a series of characterizations such as nitrogen isothermal adsorption-desorption,SEM,XRD,FT-IR and XPS.The specific surface area of CSALA was found to be as high as 237.9 m²/g,which is much higher than that of solid acid CSA(5.6 m²/g)obtained without activation,and the density of three acidic functional groups of-SO₃H,-COOH and Ph-OH linked by CSALA.They were 0.53 mmol/g,1.49 mmol/g and 0.29 mmol/g,respectively.It is applied to cellulose hydrolysis reaction,when the amount of CSALA is 60%of the mass of cellulose,the amount of water added is 1%of the mass of[BMIM][Cl],the reaction was carried out at 110?for 2.5 h,the yield of reducing sugar was 60.5%.The catalyst was deactivated severely after one cycle of circulation,which was considered to be due to the dissolution of the sulfonic acid group in the ionic liquid[BMIM][Cl]and the decrease in the mass of the catalyst in the centrifugal washing step.The hierarchical macro-mesoporous cross-linked polystyrene solid acid(HP CLPS-SO₃H)was prepared by introducing a sulfonic acid group by sulfonation with the hierarchical macro-mesoporous cross-linked polystyrene as a raw material.It was characterized by FT-IR,nitrogen isothermal adsorption-desorption,elemental analysis,SEM,XPS.The specific surface area of HP CLPS-SO₃H was 109 m²/g,surface-linked sulfonic acid group density as high as 2.31 mmol/g,and the 3DOM structure remains intact.It is applied to catalyze cellulose hydrolysis reaction and optimized reaction conditions.When the amount of HP CLPS-SO₃H is 80%of the mass of cellulose,the amount of water added is 1%of the mass of[BMIM][Cl],and the reaction is carried out at 90?for 1.5 h,the yield of reducing sugar was 64.2%.When the catalyst was repeatedly used once,it was found that the deactivation was severe,and it was considered that this was due to the dissolution of the-SO₃H group in the ionic liquid[BMIM][Cl]and the partial-SO₃H conversion to SO₄^2-during the reaction,resulting in structural reforming.