Biodiesel Prepared By Solid-base Catalyst

As a clean energy, biodiesel has become more and more attractive recently because of its environmental concerns. However, when biodiesel prepared by traditional homogeneous acid/base catalyst, some problems could be unavoidable. Separating transesterification products with used catalyst is very difficult. Discharge of waste catalyst may induce environmental problems. In this paper, biodiesel preparation has been studied in a heterogeneous catalytic system, which can make production procedure continuous, enhance the yield of biodiesel. Researches on heterogeneous catalytic transesterification are meaningful for both the production and application of biodiesel.A solid base catalyst, using Al₂O₃ loaded with NaKHC₄H₄O₆·4H₂O, was prepared by impregnation method. Effects of various factors on the catalytic activity of catalyst, such as carries, load, preparation conditions were investigated. The optimal conditions for the catalyst preparation were confirmed: the carrier of Al₂O₃, the load of NaKHC₄H₄O₆·4H₂O, load quantity of 35%, impregnation time of 2 hours, impregnation temperature of 70℃, agitation speed of 350 rpm, baking temperature of 460℃, baking time of 3 hours.The catalysts were characterized by IR,TG-DTA,SEM and BET. The IR and TG-DTA patterns show that the new compounds of Al-OK,Al-ONa,or Al-OKNa, generated by NaKHC₄H₄O₆·4H₂O with Al₂O₃, induce the catalytic activity. The TG-DTA curves demostrate the catalysts loss its weight in two steps before 460℃. The SEM patterns exhibit that too high temperature may lead to sintering warpage of catalyst. BET results show that too high temperature may cause sharp reduction of specific surface of catalyst.The reaction conditions of synthesizing biodiesel by solid base catalyst were investigated. The optimized reaction conditions are as follow: the methanol/oil mole ratio of 9:1, the catalyst dosage of 3.0%, reaction temperature of 65℃, reaction time of 3h, agitation speed of 350rpm. Under the above-mentioned conditions, the conversion of biodiesel reached 95.8%.The mechanics of transesterification catalyzed by solid base was studied in the paper and the kinetics equation is presented as follow: r_A=k₁c_Aⁿ=0.06913c_A^0.5。...