Research On Preparation Of Biodiesel From Waste Cooking Oil Catalyzed By Modified Graphene Oxide Solid Acid

Fossil energy is depleting and the world is facing a serious energy crisis.As a clean and renewable energy,biodiesel has a good development prospects.But at present,biodiesel mainly uses edible oil as raw material,which limits its development.It is a good solution to use waste cooking oil as biodiesel raw material.However,the acid value and impurity content of waste cooking oil are high,so traditional alkali catalysis can not be used.Homogeneous acid catalysis will pollute the environment,and the by-product glycerol is also difficult to recycle.Therefore,it is necessary to develop solid acid catalysts for simultaneous esterification and transesterification of waste cooking oil with methanol.Graphene oxide as a good catalyst carrier has been extensively studied in recent years.Two kind of Metal Oxide modified Graphene Oxide solid acids(MxOy-GO-SO3H)were prepared and characterized by XRD,FT-IR,XPS and SEM.It was used in the simultaneous esterification and transesterification of low-quality waste cooking oil with methanol prepared in the laboratory.The yield of fatty acid methyl ester in the esterification and transesterification reaction was used as the evaluation index of the catalytic performance of the catalyst.The effects of the ratio of MxOy to GO on the catalytic performance of catalysts were studied.The reaction temperature,molar ratio of alcohol to oil,catalyst dosage and reaction time were optimized for the simultaneous esterification and transesterification of different catalysts.The reusability and regeneration methods of catalysts were preliminarily studied.Finally,the biodiesel production from waste cooking oil catalyzed by different catalysts was studied.The quality of the product was analyzed and all met the national BD100 biodiesel standard.The main results are as follows:(1)The acid value and unsaponifiable substance content of the low-quality waste cooking oil prepared in the laboratory are higher than those of edible oil,but the carbon chain of fatty acid has not changed significantly,so it can be used as raw material of biodiesel.(2)Modification of GO with MxOy can effectively enhance its catalytic activity.Moreover,the ratio of MxOy to GO has a great influence on the catalytic performance of the catalysts,while the optimum mass ratio of MxOy to GO-SO3H varies with different MxOy:GO.The optimum mass ratios of Al2O3:GO and Fe2O3:GO are 1:3 and 3:1 respectively.(3)The optimum reaction conditions of Al2O3-GO-SO3H are as follows:reaction temperature was 60?,molar ratio of methanol to oil was 9:1,catalyst dosage was 3%,reaction time was 5h.Under these conditions,the yield of fatty acid methyl ester in Al2O3-GO-SO3H catalytic reaction can reach 91.23%.The optimum reaction conditions of Fe2O3-GO-SO3H are as follows:reaction temperature was 90?,molar ratio of methanol to oil was 12:1,catalyst dosage was 6%,reaction time was 4h.Under the optimum reaction conditions,the yield of fatty acid methyl ester catalyzed by Fe2O3-GO-SO3H was up to 89.09%.The catalytic conditions of Al2O3-GO-SO3H are relatively mild,and the yield of fatty acid methyl ester is higher,but the reaction time of Fe2O3-GO-SO3H to reach the optimal yield is shorter.(4)The reusability of the two catalysts is relatively general.After five reuses,the catalytic activity decreases by about 50%.The used catalysts will be washed,dried and impregnated with second concentrated sulfuric acid to recover their catalytic activity to a certain extent.