Study On Preparation Of Carbon-based Solid Acid From Lignin And Using As A Catalyst On Synthesis Of α-terpineol From α-pinene

A carbon-based solid acid was synthesized via carbonization and sulfonation of dry lignin gel derived from lignin and epichlorohydrin by gel method.Synthesis ofα-terpineol via hydration ofα-pinene by using carbon-based solid acid derived from lignin as a catalyst was studied.The main research contents and results were as follows:1.Lignin-based hydrogel was prepared by cross-linking of lignin with epoxychloropropane.Carbon-based solid acid derived from lignin was obtained from lignin-based hydrogel which was dried by vacuum,then followed by carbonization at 400℃and sulfonation using concentrated sulfuric acid as sulfonating agent.The carbon-based solid acids were used as catalyst to synthesizeα-terpineol through the hydration ofα-pinene.The conditions of synthesis of lignin-based hydrogel,preparation of carbon-based solid acid derived from lignin and catalytic reaction were studied,and the optimum synthesis of conditions of lignin-based hydrogel were obtained as follows:the dosage of lignin was 5.00 g,the dosage of NaOH was 1.20 g,the dosage of water was 4.00 g,the dosage of epoxychloropropane was 2.50 g,gelation temperature was 60℃,and gelation time was 6h.The appropriate conditions of preparation of carbon-based solid acid from dry lignin-based gel were as follows:the carbonization temperature was 400℃,carbonization time was 3h,the sulfonated temperature was 180℃,sulfonated time was 3h.The synthesis conditions ofα-terpineol via hydration ofα-pinene by using carbon-based solid acid as a catalyst were as follows:the dosage ofα-pinene was4.00 g,the dosage of water was 4.00 g,the dosage of catalyst was 0.40 g,the volume of isopropyl alcohol was 20.00 mL,and the reaction temperature was 80℃.Under optimum conditions,the conversion ofα-pinene was 93.07%,the yield ofα-terpineol was 40.36%,and the selectivity ofα-terpineol was 43.37%.The catalyst had a good reusability.After five reuses,the conversion ofα-pinene decreased from 93.07% to 86.67%,the yield ofα-terpinol decreased from 40.36% to 32.56%,and the selectivity ofα-terpinol decreased from 43.37% to 37.57%.2.Lignin-based aerogel was prepared by supercritical CO₂ drying.The effects of drying temperature,drying stress and aging time on the microstructure of lignin aerogel and the catalytic properties of carbon-based solid acids derived from lignin were studied,and the appropriate of drying conditions were acquired:aging temperature was 40℃,aging time was 3 days,the drying temperature was 40℃,drying stress was 10 MPa.Carbon-based solid acids were synthesized from lignin-based aerogels carbonizated and sulfonated,and be used to catalyze the hydration ofα-pinene to synthesizeα-terpineol.Under the optimum conditions,the conversion ofα-pinene was 98.27%,the yield ofα-terpineol was 48.71%,and the selectivity ofα-terpineol was 49.57%.After five reuses of the carbon-based solid acid,the conversion ofα-pinene decreased from 98.27%to 89.91%,the yield ofα-terpinol decreased from 48.71% to 39.67%,and the selectivity ofα-terpinol decreased from 49.57% to 44.12%.3.The carbon-based solid acid was characterized by FT-IR,XRD,N₂ adsorption-desorption experiment,adsorption capacity ofα-pinene,adsorption of methylene blue,and contact angle test.The results showed that sulfonic acid groups were successfully introduced onto carbon-based solid acid with oxygen-containing groups such as carboxyl and hydroxyl.Carbon-based solid acids were mainly composed of amorphous carbon.The specific surface area of the carbon-based solid acid prepared by vacuum drying was 281.3 m²/g,and the average pore diameter was 4.87nm.The adsorption capacity ofα-pinene and methylene blue on carbon-based solid acid prepared by supercritical drying were 425.16 mg/g and 97.97 mg/g,respectively.Carbon-based solid acid had good hydrophilic properties and the water contact angle was 38.36°.4.Kinetic experiments were carried out on the hydration reaction of pinene using carbon-based solid acid as a catalyst at different temperatures,and it conforms to the first-order dynamics model.The rate constant of the reaction was determined to be 0.2020 h^-1,and the activation energy was 67.501 KJ/mol.