Optimization of biodiesel production from transesterification of triolein using zeolite LTA catalysts synthesized from kaolin clay

Biodiesel was produced from transesterification of triolein with excess methanol using NaOH-treated kaolin clay as an active catalyst. The natural kaolin was first transformed into an efficacious catalyst under the conditions as (1) calcined kaolin/NaOH_(aq) = 1/2 (w/w), and (2) hydrothermal aging for 24 h at 90 °C prior to calcination at 400 °C for 6 h. Coincidently, these NaOH-treated kaolin catalysts possess characteristics of zeolite LTA. Subsequently, the Box–Behnken experimental design was applied to optimize the transesterification process of triolein in methanol. The optimal conditions are found as follows: (1) 36.6 as the mass ratio of methanol-to-triolein in the initial feed, (2) at 62.9 °C as the reaction temperature, (3) 146 min for reaction time, and (4) a catalyst loading at 72 wt. % of triolein used. Under this optimal condition, the conversion efficiency of triolein to biodiesel is (92.8 ± 4.0)%. Furthermore, these as-synthesized zeolite LTA-kaolin catalysts could be reused at least for three consecutive reaction cycles.