Selectively synthesis of fatty alcohols over mild reaction conditions via non-catalytic liquid-phase fatty acid methyl esters reduction

Abstract: The upgrading of fatty alcohols synthesis from natural fatty acid methyl esters reduction using alumina-supported NaBH4 without H2 supply was investigated. It was possible to synthesize fatty alcohols with high yields. Pure NaBH4 or alumina‐supported NaBH4 and methanol were used as co‐reactants and 100% fatty alcohols selectivities were achieved. The aim of supporting the metal hydride was to increase its stability and achieve the full recovery of the solid at the end of reaction. When alumina‐supported NaBH4 was used, final fatty alcohol high yields were achieved. The use of methanol and NaBH4 in amounts higher than stoichiometric is important to generate alkoxy-borohydride anions which act as better reducing species than NaBH4. The reaction conditions effect was investigated and the role of short carbon chain alcohol structure was elucidated. The effect of fatty acid methyl ester structure was also studied. Fatty acid methyl esters with shorter carbon chain length and without unsaturation (methyl laurate, methyl myristate) were easily reduced using NaBH4/Al2O3 and methanol reaching high conversions and fatty alcohol selectivities. Unsaturated fatty acid methyl ester with longer carbon chain (methyl oleate) introduced steric hindrance which disfavoured interaction between ester and reducing solid surface and fatty acid methyl ester con-version was noticeably lower.
Keywords: fatty alcohols; reduction reaction; fatty acid methyl esters