Macrokinetics of transesterification of castor oil with methanol was studied in the presence of NaHSO ₄·H ₂O catalyst using method of excessive concentration. The relationship between castor oil conversion and reaction time and the relationship between methanol conversion and reaction time were investigated at different temperature.Methyl ester contents in the system at different reaction time were determined by high-performance liquid chromatography.The experimental data were dealt with linear regression method. The results show that reaction order is 1.5 for castor oil and is 0.5 for methanol,and that under the conditions of reaction temperature 303,313,323,333 K,mass ratio of catalyst to oil 5%,agitation speed 600 r/min, the apparent rate constant is 0.003 934,0.005 271,0.006 656,and 0.008 237 dm ³/(mol·min) ,respectively, the apparent activation energy is 20.627 kJ/mol and the apparent frequency factor is 14.2806 dm ³/(mol·min).The results predicted by the kinetic equition are in good agreement with the experimental results.

The solid base catalyst CaO was prepared and characterized by XRD technique and low temperature nitrogen adsorption-desorption technique respectively. Transesterification of castor oil to biodiesel using CaO as a solid base catalyst was studied. The separate effects of reaction temperature, molar ratio of methanol to oil, catalyst dosage and reaction time on methyl ester yield were investigated.Under the optimal conditions of reaction temperature 65 ℃, molar ratio of alcohol to oil 9∶1, mass fraction of catalyst 1.5% and reaction time 2.5 h, the methyl ester average yield is 92%. The product was analyzed by gas chromatographic technique and mass fraction of methyl ester is 97.6%.The products after reaction is dealt with easily and the environment is not polluted and the catalyst can be activated and reused.