Metal/bromide autoxidation of triglycerides for the preparation of FAMES to improve the cold-flow characteristics of biodiesel

• Autoxidation/esterification process of tallow, canola and soy bean oil.
• Biodiesel with significant improved cold temperature properties.
• Co/Mn/Zr/bromide catalyst relatively non-hazardous and inexpensive.
• Air as oxidant.

Triglyceride autoxidation using a homogeneous Co/Mn/Zr/bromide catalyst in acetic acid (93%) of low grade tallow, canola oil or soy bean oil in a batch reactor at 150 °C for 2 h, produced lower molecular weight products relative to the fatty acids of the starting triglycerides. For the autoxidation of tallow the main products after esterification were monoesters Me(CH2)mC(O)OMe (m = 5–12) and diesters MeOC(O)(CH2)nC(O)OMe, (n = 7–12). Oxidation of the saturated fatty acids in triglycerides was confirmed and modelled using methyl palmitate. Post-treatment esterification of tallow autoxidation products to produce biodiesel (BD) esters resulted in improved cold temperature properties by a mean of 13.0 °C, i.e. a mean cloud point (CP) 1.0 °C (cf. unmodified tallow biodiesel: CP 14 °C).

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