Alternative Route for Biodiesel Synthesis with Co-Production of Glycerol Carbonate

As an alternative route from the conventional alkali-catalyzed biodiesel production, the supercritical dimethyl carbonate method had been proven to successfully produce biodiesel with the co-production of glycerol carbonate in a one-step and two-step non-catalytic methods. Biodiesel or fatty acid methyl esters (FAME) obtained were high in yield, comparable with supercritical methanol method and satisfy the international standards for use as biodiesel in engines. In this paper, key parameters for the processes such as reaction temperature, pressure, time, molar ratio of dimethyl carbonate to oil, the FAME yield, thermal decomposition, degree of denaturation, tocopherol content, oxidation stability and fuel properties were discussed. The optimized condition for supercritical dimethyl carbonate method is at 300°C/20MPa/20min/42:1 molar ratio of dimethyl carbonate to oil with a satisfactory yield of FAME at 97.4wt%. The extensive approach in this study is very important to complement mathematical model for optimization in the literatures, and to ensure that only high-quality biodiesel could be produced by supercritical dimethyl carbonate method under an optimized condition.

Biodiesel from fish waste oil: synthesis via supercritical methanol and thermodynamic optimization

This study evaluates the potential of local fish waste oil as a feedstock for biodiesel via supercritical methanol transesterification (SCMT). Hexane was used as a cosolvent and the transesterification reaction was carried out in a continuous reactor under supercritical conditions. The response surface methodology (RSM) method was applied to analyse the effect of four independent variables, including the weight ratio of methanol to fish-waste oil (W), the reaction temperature (T), the pressure (P) and the feed flow rate (F), on the yield of the biodiesel production in supercritical methanol. According to the calculated optimal operating condition for the RSM, the values of W (22.3 weight ratio of methanol to fish waste oil), T (270°C), P (112.7 bar) and F (2.0 mL min–1) were achieved. Under the optimum conditions, the highest yield was estimated to be 94.6% (g/g). The obtained yield was found to be close to the theoretical yield (95.2%). This value suggests that the proposed strategy has a promising potential in the production of biodiesel fuel.