Sulfonated Solid Acid Catalyst Performance on Esterification Reaction of Waste Cooking Oil

Carbonaceous material containing sulfonate groups as solid acid catalyst was generated by one-step mild hydrothermal carbonization of glucose. The process took place in the presence of hydroxyethylsulfonic acid at 180 °C for 4 h. The obtained sulfonated carbon (C-SO3H) was microsphere with diameter size of 50–100 micrometer. The sulfonate groups were further attached on the surface of the carbonaceous materials. The catalytic esterification of waste cooking oil (WCO) with methanol could be easily achieved by using C-SO3H. Free fatty acids (FFAs) in WCO could be decreased up to 93.4% at 60 °C for 3 h. The biodiesel yield was achieved about 87% within 1 h at 60 °C by transesterification using 1% NaOH (w/w) as catalyst. The C-SO3H was demonstrated to have good stability with only 7% decrease in FFAs conversion after 5 repeat uses. The sulfonated carbon-based solid acid catalyst was thus designed to be an active, stable and reusable solid acid as an environmentally benign replacement for homogeneous catalyst.