| Using n-butyl bromide as modifier, calcium oxide was surfacely modified by chemical bonding method. The characterizations of modified calcium oxide were determined by FT-IR and XRD. Then biodiesel was prepared by transesterification of rapeseed oil and methanol with modified calcium oxide as catalyst. The results showed that the catalytic performance of modified calcium oxide improved greatly contributing to well diffusion of reactants to the surface of catalyst and the catalytic efficiency was enhanced.The optimal reaction conditions were obtained as follows: reaction temperature 65℃, dosage of n-butyl bromide 0.01% (based on the amount of substance of calcium oxide), molar ratio of methanol to rapeseed oil 15∶1, catalyst dosage 5% and reaction time 3 h. Under these conditions, the yield of biodiesel could reach 96.6%.While the yield of biodiesel was only 89.3% with calcium oxide as catalyst under the same conditions. Furthermore, the modified calcium oxide showed good water-resistance by keeping 79.1% of biodiesel yield with 2.0% water in the reaction system. The characterization results of FT-IR and XRD showed that the modifier had bonded on the surface of calcium oxide, and the phase structure and dispersion state of modified calcium oxide didnt change obviously. |
