Synthesis of biodiesel from waste oil by glycerol pre-esterification

The waste oil with high acid value was used as raw material, and compared the pre-esterification of methanol and glycerol. The results showed that methanol pre-esterification can reduce the acid value to below 4 mgKOH/g only by multiple chemical reactions. But glycerol can reduce the acid value to less than 2 mgKOH/g once without catalysis. Through orthogonal experiment, the optimal process was obtained: the mass ratio of glycerol pre esterified oil to methanol was 10:3, the amount of catalyst was 0.8 % of the mass of oil, the reaction temperature was 65 °C, the reaction time was 150 min, and the conversion rate was 96.7 %. The results of characteristic comparison and process analysis show that glycerin pre-esterification not only has fast reaction, good effect and better environmental protection, but also has the same quality as methanol pre-esterification, and it’s easier to realize the continuous process of biodiesel synthesis from waste oil with high acid.