Study Of Technology Of Biodiesel Production Through Transesteriifcation Of Lard With Aid Of Ultrasonic

With the exhausting of fossil fuels and the growing awareness of environment protection,the development of a sustainable green energy has become a global consensus. Biodiesel,which has many advantages over the fossil diesel, is a kind of renewable green biomass fuelsand plays an important role in relieving the energy crisis and protecting environment.Compared with the traditional mechanical stirring, transesterification reaction enhanced byultrasonic has many advantages such as shorter reaction time, the lower consumption ofmethanol, energy and catalyst, simple process and so on. Preparation of biodiesel throughtransesterification of lard with methanol by ultrasonic irradiation was investigated.A low acid value of raw material is required in alkali-catalyzed transesterificationreaction and H2SO4-catalyzed esterification reaction was applied to reduce the acid value oflard. The esterification optimization of lard was carried out under mechanical agitation andultrasonic radiation. The optimal operating conditions were methanol to oil molar ratio of8:1,ultrasonic power of150W, reaction temperature of50℃, catalyst dosage of2.0wt.%, reactiontime of30min under ultrasonic radiation and methanol to oil ratio of10:1, catalyst dosage of2.5wt.%, reaction temperature of60℃, mechanical agitation of400r/min, reaction time of90min under mechanical agitation, respectively. The acid value of lard could be reduced to1.82mgKOH/g and1.96mgKOH/g under ultrasonic radiation and mechanical agitation,respectively.Response surface methodology was applied to optimize homogeneous KOH-catalyzedtransesterification. The result shows that the optimal condition was that methanol to oil ratioof5.8:1, ultrasonic power of135.91, reaction temperature of52.8℃, catalyst dosage of0.86wt%（based on oil）, in which theoretical conversion achieve99.53%. The experiment wasrepeated four times under the optimal condition，and an average conversion of99.03%wasachieved.The solid base catalyst CaO/NaY was prepared by means of the isovolumetricimpregnation and the condition for preparing the catalyst was optimized. Results of theorthogonal experiments show that the solid catalyst is of the highest performance when it isburned at700℃for4h with a CaO loading amount of15%. Effects of ultrasonic power,methanol to oil molar ratio, reaction temperature, catalyst dosage and reaction time on theconversion of methyl esters were discussed during the transesterification of lard. A conversionof95.21%was achieved under the optimal conditions: ultrasonic power of150W, methanol tooil molar ratio of9:1, reaction temperature of60℃, catalyst dosage of4wt.%and reaction time of100min. The solid base catalyst still had high catalytic activity after3-time recycling.According to the principle of reaction kinetic，kinetic equations of transesterificationunder ultrasonic radiation and mechanical agitation were obtained by linear regression ofexperimental data which were obtained at the optimal condition，and the kinetic equationswere-r_A=0.07255C_A^1.0977and-r_A=0.02899C_A^1.4721,respectively. In the condition ofultrasonic irradiation and mechanical agitation the reaction rate constant were0.07255and0.02899, respectively. In the same reaction condition, the reaction rate constant in ultrasonicirradiation is2.5times as much as that with mechanical agitation. The values of1.86×106and47.37kJ/mol of frequency factor and activation energy of transesterification catalyzed byCaO/NaY with aid of ultrasonics were obtained by the fitting of experiment data according toArrhenius equation，which shows that transesterification reaction with aid of ultrasonic ismore easy to proceed because of the low activation energy.