Mechanism investigation on the formation of olefins and paraffin from the thermochemical catalytic conversion of triglycerides catalyzed by alkali metal catalysts

Triglycerides are a promising biomass feedstock that can be used for production of organic hydrocarbons including long-chain olefins and paraffin. The challenge for this production process lies on the lack of a clear mechanism of the conversion process. In this work, the conversion mechanism from triglycerides to olefins and paraffin using alkali metal catalysts was investigated adopting both computational calculations using density functional theory and experimental studies. The bond dissociation energies of the main bonds were calculated, especially for the α carbon‑carbon bond, which leads to effective removal of carboxyl groups during the thermochemical conversion process. The dynamic behavior of triglycerides catalyzed by alkali metal catalysts was also investigated using thermogravimetric analysis, which found that Li ion has lowest activation energy below 200 kJ/mol when compared with the other alkali ions studied. The catalytic conversion mechanism was proposed in this work based on the results obtained from TG-IR, GC, GC–MS and XRD analyses. The O atoms are removed in the form of CO, CO2 and H2O, product M + O and M+, which generates M2CO3. A more detailed mechanism has been proposed in this paper, which has significance toward guiding the cleavage of triglycerides to produce long‑carbon-chain terminal olefins and normal paraffin.