Mechanistic investigation into water tolerance of non-catalytic biodiesel conversion

• Non-catalytic biodiesel conversion via a continuous flow system.
• Non-catalytic biodiesel conversion under ambient pressure.
• Utilizing porous materials and CO2.
• High tolerance of the content of free fatty acid.
• Enhanced water tolerance under the presence of hydrophobic porous material.

This study provides a systematic approach to understand the water tolerance of a newly developed non-catalytic biodiesel conversion process. The influence of water on the non-catalytic biodiesel conversion process was compared directly with the conventional transesterification reaction, which uses homogenous catalysts, such as KOH and H2SO4. This study demonstrated that water had no significant impact on non-catalytic biodiesel conversion and the conversion efficiency reached approximately ∼98 ± 0.5% at a water content of 5 wt.% in the biodiesel lipid feedstock (i.e., corn oil). However, this work showed that the non-catalytic biodiesel conversion using porous hydrophobic materials (i.e., charcoal) exhibited better biodiesel conversion performance compared to non-catalytic biodiesel conversion in the presence of activated alumina. This can be explained by the mechanism of the reaction between gas-phase MeOH and liquid-phase triglycerides.