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Reduction of Vegetable Oil‐Derived Fatty Acid Methyl Esters toward Fatty Alcohols without the Supply of Gaseous H 2
Author(s) -
Vallejo Orrego Alejandro,
Ferretti Cristián A.,
Díez Verónica K.
Publication year - 2020
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1002/aocs.12375
Subject(s) - chemistry , alcohol , methanol , fatty acid , fatty alcohol , organic chemistry , methyl group , fatty acid methyl ester , degree of unsaturation , hydride , ethanol , catalysis , hydrogen , alkyl , biodiesel
An alternative route to the conventional one for fatty alcohol synthesis was investigated. It was possible to synthesize lauryl alcohol from methyl laurate via reduction by transfer of hydrogen and hydride in liquid phase, in noncatalytic reactions and without the supply of H 2 gaseous. Pure NaBH 4 or alumina‐supported NaBH 4 and methanol were used as co‐reactants and 100% fatty alcohol 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 NaBH 4 was used, a final fatty alcohol yield of 93% was achieved. The use of methanol and NaBH 4 in amounts higher than stoichiometric is important to generate alkoxyborohydride anions which act as better reducing species than NaBH 4 . 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 NaBH 4 /Al 2 O 3 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 conversion was noticeably lower. A reaction mechanism based on alkoxyborohydride anions as the actual reducing species was proposed. This mechanism fully interprets results obtained during fatty acid methyl ester reduction using short carbon chain alcohols and metal hydride.