Intensification On Hydrolysis And Esterification Precess By Hydrodynamic Cavitation Technology In Biodiesel Preparation

As a kind of new energy, biodiesel had attracted a lot of attention with its excellent properties, such as environment friendly and raw materials renewability. It was obtained by transesterification of vegetable oils and animal fats with alcohol (methanol or ethanol).In this paper, we studied hydrolysis of glyceride and esterification of fatty acids, and intensification of hydrodynamic cavitation on the reaction processes.For hydrolysis reactions, the influence of different catalysts and dosage, emulsifier's dosage, reaction temperature, stirring speed, raw materials'acid value on hydrolysis were investigated, and the optimal reaction conditions were obtained. Based on the results, the hydrolysis kinetics under hydrodynamic cavitation was studied. Compared with the mechanic stirring, hydrolysis under hydrodynamic cavitation had longer induction period and lower reaction rate. The experimental data showed that the acid catalytic hydrolysis was a pseudo-second-order reaction. And the apparent activation energy are 143.49 KJ/mol, and the former factor is 5.01 x 10¹⁹ g/(mmol·min). Furthermore, the theoretical calculation showed that the mass transfer outside the droplet had more important influence on the apparent hydrolysis rate.The hydrolysis-esterification process and the esterification- transesterification process were compared. The results showed that the hydrolysis-esterification process could be more effective in reducing phosphorus content in biodiesel and enhancing biodiesel saturation.To study esterification of fatty acid, Palm oil with high acid value, Jatropha oil and their mixtures were used as raw material, H2SO4 was used as catalyst. The effect of the dosage of methanol and H2SO4, the acid value of raw material, hydrodynamic cavitation and its operation models on the esterification was investigated. The results showed that the mass diffusion effects obviously on the esterification reaction, The optimum amount of methanol depends on the acid value of raw material. And the relationship is y=3.488x0.174(y: molar ratio of methanol to free fatty acid, x: the acid value of raw material). Compared to the single-stage operation, the esterification rate was increased, the conversion was improved under the multistage hydrodynamic cavitation. The main reason was that generated water could be removed in time during the multistage process.The intensification of hydrodynamic cavitation on two-phase solvent dispersion was studied by investigating the effect of temperature, flow rate, inlet pressure and structure of cavitation device, and different liquid-liquid systems on the droplet diameter. The droplet diameter of the soybean oil-methanol-oleic system was between 150nm and 400nm under hydrodynamic cavitation. Micromixing by hydrodynamic cavitation was better than traditional mechanical agitation. The results showed that hydrodynamic cavitation can emulsify the glyceride-methanol system, increase greatly the contact area between glyceride and methanol, and thus strengthen the mass transfer process and increase reaction rate.