Biodiesel production from non-edible high acid value phoenix seed oil using a cheap immobilized lipase

Abstract

Fatty acid methyl ester (FAME) is one kind of renewable and biodegradable biodiesel energy. In this work, in order to decrease FAME production cost, a cheap immobilized lipase Lipozyme TLIM (Thermomyces lanuginosus lipase, 100$/kg) and waste phoenix seed (Firmiana platanifolia (L. f.) Marsili) oil with high free fatty acids (FFA) content (30.1 ± 0.4%) were used as catalyst and new feedstock, respectively. The effects of reaction variables were evaluated and optimized by response surface methodology. Results showed that Lipozyme TLIM can simultaneously catalyze the esterification and transesterification of high FFA phoenix seed oil to produce FAME. The conditions were optimized as follows: 11.8% water load added, 3.1:1 molar ratio of CH3OH to oil, and 7% lipase load at 33 °C for 6.47 h. High FAME yield (93.3 ± 1.6%) was achieved under the optimized conditions. Kinetic values (Vm and K’m) of FAME production were 2.66 × 10−2 mol/(L·min) and 7.4 mol/L, respectively, and the activation energy (Ea) was 42.62 kJ/mol. Therefore, a cheap immobilized lipase Lipozyme TLIM with a noted high level of tolerance of water could be useful in the industrial FAME production from phoenix seed oil with high FFA. After purified by molecular distillation, the contents of FAME, FFA, and water content of the final biodiesel product were 97.2%, 0.3%, and 0.04%, which were in accord with the quality standard of ASTM D6751 (>96.5%, <0.4%, and < 0.05%).