Study On Lipase-Catalyzed Production Of Biodiesel From High Acid Value Waste Edible Oil

Biodiesel consists of fatty acid alkyl esters produced by esterification or transesterif-ication of vegetable oils, animal fats or waste oils with short chain alcohols and is a biod-egradable, nontoxic, cleaning and renewable fuel, which is expected as a part of substitutefor conventional fossil diesel. At present, Biodiesel can be produced by chemical methods,enzymatic methods and Supercritical Method. Synthesis of biodiesel by enzymatic catal-ysis has some advantages of mild condition, broad source of stock, no saponification rea-ction, separating the reactants easily and low requirement of equipments. Furthermore,some lipase could be seasoned with the high content of fatty acid in some high acid valuewaste oil and have particular advantage in enzyme-catalyzed synthesis of biodiesel fromhigh acid value waste oil. In this study, high acid value waste edible oil was chosed as rawmaterial and various commercial lipases were screened out as biocatalyzer. For the sake ofimprovement in lipase-catlyzed production of biodiesel, the enzyme-catalyzedesterification and transesterification of high acid value waste edible oil were investigatedwith ultrasonic assistant or using diesel as organic solvent. Through the studies above,conclusions were made as follows:1. Study on lipase-catalyzed production of biodiesel from high acid value waste edibleoil with ultrasonic assistantBiodiesel produced with the enzyme-catalyzed esterification and transesterificationof high acid value waste edible oil through ultrasonic assistant was explored. Propyloleate, biodiesel, converted from high acid value waste oil and 1-proponal catalyzed withimmobilized lipases from Candida Antarctica and Aspergillus oryzae in conditions ofultrasonic assistant. Commercial immobilized lipase Novozym 435 from C. antarcticawas utilized as biocatalyst catalyzing high acid value waste oil and 1-proponalesterification and transesterification to propyl oleate under the ultrasonic assistantconditions and different conditions such as lipases amounts, initiatory molar ratio of propanol to oil, frequency of ultrasonic and power of ultrasonic were investigated andoptimized.It is revealed that the enzymatic activity of Novozym435 is enhanced and, inparticular, enzyme-catalyzed transesterification activity is enhanced obviously under theultrasonic assistant conditions. Low frequency and mild energy ultrasonic is key factorfor enhancing enzymatic activity, emulsifying oil-propanol system and accelerating thespeed of produce diffusing in the system.Under the optimal ultrasonic assistant reaction conditions, such as Novozym435amounts 8% by oil quantity, initiatory molar ratio of propanol to oil 3:1, frequency ofultrasonic 28 KHz, power of ultrasonic 100W and temperature of water batch 40～45℃,the conversion ratio to propyl oleate is achieved 94.86% in 50min in comparison with thehighest conversion ratio 84.43% under the conventional mechanical agitation conditions.Furthermore, it is demonstrated that various short chain linear and branchedalcohols (C₁～C₅) showed high conversion ratio to fatty acid alkyl esters (biodiesel) underthe optimal ultrasonic assistant reaction conditions.On the other hand, ultrasonic energy is propitious to reduce the adsorption ofproduct propyl oleate, by-product glycerol and other emplastics in system on the surfaceof immobilized lipase Novzym435 and recyclable Novozym435 possess cleanappearances, well decentralizations, no agglomeration and easy washing and welloperational stability.2. Study on lipase-catalyzed production of biodiesel from high acid value waste edibleoil using diesel as organic solvent.Lipase-catalyzed estefification of high acid value waste edible oil for biodieselproduction was investigated using diesel as organic solvent. Commercial immobilizedlipase Novozym435 from Candida antarctica was utilized as biocatalyst catalyzing highacid value waste edible oil, whose acid value is 157 mgKOH/g, and methanolesterification to fatty acid methyl ester in the 0^# diesel reaction medium.The optimum conditions of esterification of high acid value waste edible oil were asfollow: 10%Novozyme435 based on oil weight, initiatory molar ratio of methanol to oil 2:1, quantity ratio of diesel to oil 5:1, shaking rate 170 r/min and reaction temperature 50℃and the conversion ratio is achieved 95.10% in 2h.The stability of Novozyme435 is improved in respect that the viscosity of wasteedible oil is decreased and the negative effects caused by excessive methanol iseliminated in the 0^# diesel reaction medium, which would dissolve high acid value wasteedible oil and methanol effectively.Furthermore, it is demonstrated that the key factor of high acid value waste edibleoil using as raw material for biodiesel production and maintenance of stability ofNovozyme435 is degumming treatment of waste edible oil and the method ofdegumming treatment in spite of that diesel would dilute the rudimental phospholipids inwaste edible oil slightly, which would inhibit the enzyme-catalyzing esterificationreaction.Use of diesel as solvent in the biodiesel production from high acid value wasteedible oil simplifies the process and produces the fuel mixture of biodiesel and dieseldirectly avoiding the cockamamie operation of distillation and reclaim of organic solvent.