Effects of Microwave and Additional Co–Solvents on Two–Stage Waste Cooking Oil to Biodiesel Conversion

This paper introduced a better solution to accelerating the production of biodiesel from waste cooking oil by using suitable acidic and alkaline catalysts in a two-stage catalytic reaction. Next, a co-solvent named tetrahydrofuran (THF), which significantly increased mixing level of the reactants in the mixture of vegetable oil and methanol, was added to form a single phase system. The whole system was then put into a microwave oven to support heat for the transesterification of biodiesel to shorten the reaction time. Reaction conditions of the first stage were methanol to oil molar ratio of 9:1, catalyst amount 1wt%, reaction temperature 60 oC and reaction time 7.5 minutes. In the second stage, for the transesterification, reaction conditions were methanol to oil molar ratio 12:1, catalyst loadings 1 wt%, reaction temperature 60 oC and reaction time 1.5 minutes. Finally, the conversion rate of biodiesel after the nine-minute reaction time was 97.38% which was higher than the EU EN14214 standard value of 96.5%.