Study On Preparation And Catalytic Performance Of Biochars-derived Solid Acid By Restructuring Strategy

With the advancement of industrial technology,the contradiction between human energy demands and the gradual exhaustion of fossil energy has gradually become a major obstacle to economic and social development.With its renewable characteristics,biomass resources are gradually replacing coal and crude oil,and become an important source of downstream chemical products and fuels.From the traditional homogeneous liquid acid catalyst to the heterogeneous solid acid catalyst,solid acid significantly reduces the discharge of acid-containing wastewater in the biomass conversion process,but the complex preparation process and its expensive manufacturing cost are not conducive to the large-scale industrialization of solid acid application.The biomass carbon-based solid acid catalyst has great potential in the field of biomass conversion due to its advantages of simple preparation,low price and easy availability.However,traditional biomass carbon-based solid acid catalysts have the problems of unstable structure,easy loss of acidic sites,and dense accumulation of material sheets caused by a large number of surface functional groups forming hydrogen bonds,which is not conducive to the mass transfer of low polarity and large steric hindered substrates.Therefore,in this paper,the phenolic resin oligomer intercalation cross-linking method and silica gel supported method are conducted to prepare restructuring biochar sulfonic acid to improve the existing problems.The specific content is as follows:（1）Using phenol and formaldehyde as raw materials to prepare phenolic resin oligomers（PFO）under the catalysis of Na OH,and conducts research on PFO intercalation and cross-linking biomass carbon-based solid sulfonic acid（PFBC-SO₃H）.The effects of the amount of PFO,the amount of ferric chloride,and the carbonization temperature on the density of functional groups on the surface of the material and the efficiency of the catalytic alcoholysis of furfuryl alcohol were investigated.The catalyst PFBC-SO₃H prepared under optimized conditions had good structural stability with a sulfonic acid density of 1.3 mmol/g,showing a layered structure under a transmission electron microscope.In the furfuryl alcoholysis reaction,under the optimal conditions（catalyst dosage,20mol%;reaction temperature,110 ^oC;reaction time,14 h）,the yield of butyl levulinate reached 76%.（2）On the basis of the previous system,the synthesis of biodiesel from waste oil was studied by using the catalyst PFBC-SO₃H and using oleic acid and triglyceride oleate as model compounds.The performance of the catalyst was evaluated by esterification reaction of oleic acid with methanol and transesterification reaction of triglyceride oleate with methanol.Under the optimal conditions of oleic acid esterification（catalyst dosage was 7.5 mol%;reaction time,120 min）,the oleic acid esterification rate reached 98%.In the transesterification reaction of triglyceride oleate（reaction temperature,130 ^oC;reaction time,120 min;catalyst dosage,4mol%）,the biodiesel yield could reach up to 78%,and the catalyst recyclability kept good.（3）The preparation of 3-chloropropyltrimethoxysilane grafted silica gel supported catalyst（CL-SBCD-SO₃H）was studied using alkaline bamboo charcoal point（BCD）prepared by hydrothermal carbonization of bamboo powder with sodium hydroxide and alkaline solution of sodium silicate as precursor.The influence of sodium hydroxide dosage on the liquefaction efficiency of bamboo powder and the influence of chloropropylsilane grafting amount and carbonization temperature on the structural stability of the material and the density of surface functional groups were investigated.From the FT-IR results,it could be seen that as the dehydration temperature increased,the characteristic absorption of the C-Cl bond decreases,which indicates that the chloropropyl group was immobilized on the carbon dots.Besides,the carbon dots are immobilized on the surface of the silica gel under the transmission electron microscope.The thermogravimetric analysis results showed that the stability of the sulfonic acid group was improved after silica gel was immobilized.Under the optimal preparation conditions,the catalyst has good structural stability,and the sulfonic acid density reached 0.47 mmol/g.The nitrogen adsorption analysis showed that the specific surface area of the mesoporous catalyst reached 276 m²/g.Using oleic acid and triglyceride oleate as model compounds,the catalyst was used to catalyze the synthesis of biodiesel from waste oil.Under the optimal reaction conditions,the oleic acid esterification rate reached 98%,and the performance of the catalyst was not significantly decreased after use of the catalyst was repeated for 4 times.In addition,the yield of biodiesel could reach 75%in the transesterification reaction of triglyceride oleate,and the catalyst recyclability kept good...