The Application Of A Carbon-based Solid Acid Catalyst In The Esterification

Acid catalytic reaction is one of the important reaction type of the modern chemicalindustry, homogeneous acid catalysts have the advantages of low cost, high catalyticefficiency, strong acid are used widely in the reactions, but there are many shortcomingssuchas easily cause equipment corrosion, catalyst and reaction system inseparable,environmental pollution caused by a lot of waste liquid. In the current background of greenchemistry and sustainable development, environmental friendly solid acid catalyst instead ofliquid acid is the trend, the solid acid catalyst of carbon loaded sulfonic acid group becomecurrent research hot spot of acid catalytic reaction. In order to further improve the catalyticperformance of carbon-based catalyst, understanding the catalytic activity in the variousestreifications with carbon-based catalysts of different source. In this work, carbon-basedcatalysts were synthesized by sulfonating activated carbon in the diazonium salt reductionprocess using three kinds of commercial activated carbons, coconut shell, wood power, andcoal, respectively, their physicochemical properties were characterized by using surface areaanalyzer and inverse titration, the their catalytic properties were determinated by using theesterification of oleic acid as the catalytic model so as to screen the best carbon-based catalystwhich has the highest conversion rate. Then they were used in different length of carbonchain of fatty acids and aromatic acids with ethanol in esterification reactions, and availablecommercial acid catalysts were applied to all of the esterifications as contols, respectively,which were Amberlyst-15, of Nafion SAC-13, Nafion NR50and concentrated sulfuric acid.To further improve the catalytic activity, the pine powder is used the material, it was preparedto the activated carbon by the activation and sulfonation of carbonized, then the carbon-basedsolid acid catalyst was synthesized by sulfonating activated carbon in the diazonium saltreduction process. The esterification of acetic acid with ethanol of catalytic model was set upto investigate catalytic properties by examining conversion rate, and available commercialacid catalysts, Amberlyst-15, of Nafion SAC-13, Nafion NR50and concentrated sulfuric acidare used as contols. The research results are as follows:（1） The raw material of activated carbon has significant effect on the physicochemicalproperties and catalytic activity of catalyst, the sulfonic acid density of coal-based catalyst（AC-SO₃H）was0.64mmol·g^-1, which is the highest, and the the catalytic activity of AC-SO₃H also is the best, with the coal-based catalyst, the conversion rate of oleic acid was69.7%under the esterification conditions of80°C, reaction time6h.（2） The sulfonic acid density of AC-SO₃H is declined with the times of the catalyst used,AC-SO3H can repeat three times stabily.（3） In the esterification of amylose fatty acid with ethanol, under the reaction time is10h, AC-SO3H for conversion rate of capric acid is49.20%, the conversion rate of tetradecanoicacid is74.83%,; the conversion rate of oleic acid is58.31%, they are all higher than that ofAmberlyst-15, Nafion SAC-13and Nafion NR50. All datas indicate that AC-SO3H had thegood catalytic activity in the esterification reaction of the long chain fatty acids comparedwith the available commercial solid catalysts.（4） The AC-SO₃H was used in the esterification of aromatic acid with ethanol, the resultsshow that: as for the esterification, the conversion of benzoic acid of10h was only19.37%,which is much lower than that of concentrated sulfuric acid as catalyst （82.12%）; as for thethe esterification of phenylacetic acid and3-phenylpropionate, the conversion rate of themare89.42%and91.33%, respectively; they are slightly lower than that of concentratedsulfuric acid as catalyst. The results show that: with the increase in carbon chain length onthebenzene ring, catalytic effect of AC-SO3H enhanced.（5）The forestry wasted pine powder is used as raw material, the activation and sulfonation,the best conditions are under the best quality scores ZnCl260%, the best carbonizationtemperature500°C; and then the catalyst are prepared by the sulfonic acid diazonium saltprocess, its surface area reached364m².g^-1and sulfonic acid density reached1.36mmol g^-1.In the esterification of acetic acid, under the conditions of80°C, reaction time10h, with thecarbon-based catalyst, the conversion rate is78.50%, which is slightly lower than that ofAmberlyst-15, higher than that of Nafion NR50and Nafion SAC-13. The results indicate that:the homemade carbon-based catalyst could compete with the commercial catalysts, showing agood advantage.