Research On Upgrading Of Rice Husk Bio-oil By Solid Acid Catalyst

The consumption of a large number of fossil resources causes energy shortage and environmental pollution.As an ideal clean energy,biomass energy is one of the main direction of energy development in the future.Bio-oil is a brown-black liquid fuel obtained by biomass pyrolysis technology.Compared with traditional fossil fuels,it has disadvantages such as high acidity,high water content,high viscosity,strong corrosivity,and extremely unstable.In order to improve the performance of bio-oil,this paper mainly focused on the defects of bio-oil by catalytic esterification,acid reduction and dehydration.The main contents of this paper are as follows:A variety of carbon-based solid acid catalysts and supported solid acid catalysts were prepared and their acetic acid conversion and surface acidity were determined.The results showed that the acetic acid conversion rate of the solid acid catalysts was 75.4-93.01%and the surface acidity was 1.024-1.962 mmol/g.Among the carbon-based solid acid catalysts,starch-TsOH is better in acetic acid conversion rate andsurface acidity,and TsOH/HZSM-5 catalyst is better in acetic acid conversion rate andsurface acidity in supported solid acid catalyst.FTIR analysis of solid acid catalysts showed that p-toluenesulfonic acid was uniformly loaded into carbohydrates in the carbon-based solid acid catalysts prepared by incomplete carbonization.Supported solid acid catalysts prepared by impregnation were loaded on HZSM-5 zeolite with toluene sulfonic acid,zirconium oxychloride and phosphotungstic acid.The starch-TsOH and TsOH/HZSM-5 catalysts were analyzed by SEM,XRD and TG.The results showed that the starch-TsOH catalysts were massive particles with porous structure on the surface.The size of TsOH/HZSM-5 catalysts was uniform,and they were massive particles with a small amount of flake solids.Starch-TsOH catalyst has amorphous structure,and TsOH/HZSM-5 catalyst has zeolite crystal structure.Starch-TsOH and TsOH/HZSM-5 catalysts have good thermal stability at room temperature to 200?.Single factor and response surface methodology were used to optimize the conditions of catalytic esterification of bio-oil model compounds.The optimum technological parameters were as follows:alkyd-acid ratio 3,reaction time 2.5h,catalyst dosage 5%.Three verification experiments were carried out under these conditions.The experimental values were in good agreement with the predicted values,with a relative deviation of 0.83%.The results showed that the model was reliable in analyzing and predicting the optimum esterification conditions.Azeotropic dehydration and re-esterification,esterification under azeotropic water removal,dehydration after esterification were used to improve the quality of bio-oil.The properties of bio-oil before and after upgrading were determined.The results showed that the acidity and water content of bio-oil were significantly reduced by three schemes,and the calorific value of bio-oil increased after upgrading.Considering the effects of three schemes on bio-oil upgrading,the esterification under azeotropic water removal is best.In the upgrading oil,the water content decreases to 1.52%,the pH value increases to 3.27s the acid value decreases to 24.70 mg/g,the density and viscosity also decreases and the calorific value increases to 36.945 MJ/kg.The quality of the upgrading oil was obviously improved.FTIR and GC-MS analysis of bio-oil and upgrading oil showed that the composition of refined oil changed and carboxylic acids were converted into esters to achieve the purpose of esterification.In order to solve the instability of bio-oil,the bio-oil was treated by water extraction.The bio-oil was divided into water-soluble fraction and water-insoluble fraction.After upgrading the water-soluble fraction of bio-oil,the quality of the bio-oil was obviously improved,the calorific value was increased to 35.081 MJ/kg,the acid value was reduced to 6.002 mg/g,and the water content was reduced to 2.60%.The bio-oil water-insoluble fraction was diluted with glycerol and distilled to obtain phenolic-rich substances.The yield of distillate was 31.22%,and the content of phenolic-rich substances was 50.78%.The method is feasible for the extraction of phenolic compounds from bio-oil.