Research On Preparation Of Biodiesel Intensified By Microwave Irradiation

With the development of China’s economy, the demand for diesel has increased rapidly over the last few years. Because of the limited oil production and reserves, our country has been constrained to international crude oil supply and price fluctuation. As biodiesel has good combustion performance, renewable and other advantages, the research on the preparation of this clean alternative energy resource has vital significance for energy security. Waste oil is suitable for our country as the raw materials for the production of biodiesel. In this paper, the preparation of methyl esters from high-acid fish oil catalyzed by solid catalysts was investigated. We also studied the intensification of microwave irradiation on the production of biodiesel.(1) The physicochemical properties of high acid value fish oil and palm oil were measured. The average molar mass and the fatty acid composition of materials were analyzed. The method for the calculation of the biodiesel yield was also determined, which laid the foundation for the subsequent experimental data acquisition and analysis.(2) The esterification reaction of high-acid fish oil was catalyzed by Amberlyst15 to reduce the acid value, and then fatty acid methyl esters were produced by CaO-catalyzed transesterification reaction. The optimum process conditions were obtained by orthogonal experiments. For esterification, the acid value was dropped to 3.35 mg KOH/g, which could be reduced to 1.24 mg KOH/g after the second pre-esterification. For transesterification, the yield of fatty acid methyl esters was 93.7%. Amberlyst15 and CaO used several times could still maintain high catalytic activity. The process can be used for the preparation of biodiesel from other raw materials with high acid value.(3) For the preparation of biodiesel catalysted by CaO from palm oil intensified by microwave, the effects of microwave power, ratio of methanol to oil and CaO content on fatty acid methyl ester yield were investigated. The microwave irradiation improved the reaction significantly, and reduced the reaction time and the amount of catalyst. The reaction kinetics of transesterification showed that the total reaction order under microwave heating was 3, which was 1 under conventional heating. The intensification of microwave on transesterification was mainly reflected in the effect on methanol. The yield of fatty acid methyl esters under microwave irradiation in 60 min was 82.9%, and under the conventional heating was only 27.3%.(4) In order to study microwave reactive distillation process for biodiesel production, we tried several solid catalysts, which could be filled in the distillation tower. CaO particles formed by powders had poor tolerant performance of methanol erosion in distillation. A solid base catalyst was prepared by columnar activated carbon loading K2CO3. The methyl ester yield under conventional heating decreased from 77.3% to 13.3% after the K2CO3/C being used six times. D261, a macroporous strongly basic ion exchange resin catalyst, had poor thermal stability. When the reaction temperature exceeds the maximum service temperature of D261, the yield of fatty acid methyl ester decreased sharply. All the catalysts mentioned above were not suitable for reactive distillation operation.