Synthesis Of Biodiesel From Soybean Oil By Transesterification Using Solid Acid Catalysts

Due to the increasing depletion of petroleum and concern for the environment, biodieselas a new environmentally friendly and renewable energy has been the object attention. Thispaper studied the synthesis of biodiesel using soybean oil and methanol as raw materialsthrough transesterification catalyzed by solid acid. Preparation, screening and characterizationof solid acid catalysts and optimization of reaction conditions were researched.Three solid acid catalysts using methane, amino and P-toluene sulfonic acid as activeingredients and SiO2as carriers were prepared by impregnation. The activities of catalystswere researched by transesterification of soybean oil and methanol. The experimental resultsshowed that solid acid loaded with10%methane sulfonic acid displayed relatively highacitivity. The structure and performance of optimal catalysts were determined by IR, TG, BETand acid-base neutralization titration. The results showed that surface acidity of preparedcatalyst with-SO3H and high specific surface area was1.8mmol/g. TG indicated that thecatalyst had good stability under350℃.The reaction conditions of transesterification of soybean oil with methanol usingmethane sulfonic acid as catalysts were optimized. The effects of reaction time, reactiontemperature, amount of catalyst and molar ratio of CH3OH to soybean oil were investigated inorthogonal experiments of four factors and three levels. The conditions of the best group byrange analysis were attained as follows: reaction time5h, reaction temperature130℃, molarratio of CH3OH to soybean oil36:1, amount of catalysts8%. The yield of biodiesel under thecondition was about97%.Three carbon-based solid acid catalysts were synthesized respectively by hightemperature carbonization, hydrothermal carbonization and one-step carbonization andsulfonation. The activities of catalysts were investigated by transesterification of soybean oiland methanol. The results showed that the activity of catalysts prepared by one-stepcarbonization and sulfonation was the highest. The optimum preparation conditions ofcatalysts by single factor experiments were attained as follow:5g glucose as carbon source,carbonization and sulfonation time8h, carbonization and sulfonation temperature150℃,amount of concentrated sulfuric acid50mL. The structure and performance of optimalcatalysts were determined by IR, TG, XRD, SEM and acid-base neutralization titration. Theresults found that surface acidity of prepared catalysts with-SO3H and high specific surfacearea was2.1mmol/g. TG indicated that the catalysts had good stability under210℃. XRD andSEM indicated that the catalysts were amorphous carbon structure consisting of polycyclicaromatic carbon sheets.The reaction conditions of transesterification of soybean oil with methanol usingcarbon-based solid acid as catalysts were optimized by single factor experiments. The optimalresults were as follows: reaction temperature130℃, reaction time4h, molar ratio of CH3OHto soybean oil36:1, amount of catalysts10%. The yield of biodiesel under the condition wasabout95%.The water and acid resistance and reusability of two catalysts were researched. Theresults showed that two catalysts have good water or acid resistance, and catalysts have high acitities after six times. The two catalyst systems have a certain prospect for industrialapplication.