TY - JOUR

T1 - Base-free transfer hydrogenation of menthone by sub- and supercritical alcohols

AU - Philippov, Alexey A.

AU - Chibiryaev, Andrey M.

AU - Martyanov, Oleg N.

N1 - Publisher Copyright: © 2018 Elsevier B.V.

PY - 2019/3/1

Y1 - 2019/3/1

N2 - The base-free transfer hydrogenation (THR) of menthone with six aliphatic alcohols as hydrogen source has been developed under sub- and supercritical conditions. Under sc conditions (at 350 °C and 78–210 atm) without any catalyst, all alcohols demonstrated the similar H-donor activity, which was high enough. The menthone conversion was about 64 ± 5% for 5 h of the reaction, whereas the selectivity on menthol reached 92–99% for all alcohols except MeOH (73%). The non-catalytic THR at 250 °C was very slow and the conversion in the most active 2-PrOH was only 7.0–7.5% for 9 h of the reaction. Under subcritical conditions at 150 °C, the non-catalytic menthone reduction was negligible in all alcohols. But in secondary 2-PrOH and 2-BuOH, the base-free THR catalyzed by Raney® nickel results in excellent conversion and selectivity of menthol at 150 °C, whereas no conversion of menthone was observed in primary alcohols under the same reaction conditions. A quasi-equilibrium of isomeric menthone/isomenthone mixture reached via enolization was evaluated under sub- and supercritical conditions and the Gibbs energies of the isomerization in each alcohol were calculated.

AB - The base-free transfer hydrogenation (THR) of menthone with six aliphatic alcohols as hydrogen source has been developed under sub- and supercritical conditions. Under sc conditions (at 350 °C and 78–210 atm) without any catalyst, all alcohols demonstrated the similar H-donor activity, which was high enough. The menthone conversion was about 64 ± 5% for 5 h of the reaction, whereas the selectivity on menthol reached 92–99% for all alcohols except MeOH (73%). The non-catalytic THR at 250 °C was very slow and the conversion in the most active 2-PrOH was only 7.0–7.5% for 9 h of the reaction. Under subcritical conditions at 150 °C, the non-catalytic menthone reduction was negligible in all alcohols. But in secondary 2-PrOH and 2-BuOH, the base-free THR catalyzed by Raney® nickel results in excellent conversion and selectivity of menthol at 150 °C, whereas no conversion of menthone was observed in primary alcohols under the same reaction conditions. A quasi-equilibrium of isomeric menthone/isomenthone mixture reached via enolization was evaluated under sub- and supercritical conditions and the Gibbs energies of the isomerization in each alcohol were calculated.

KW - Base-free

KW - Enolization

KW - Menthone

KW - Raney® nickel

KW - Supercritical alcohols

KW - Transfer hydrogenation

KW - TRANSFER REDUCTION

KW - HEAVY OIL

KW - Raney (R) nickel

KW - STEREOSELECTIVE HYDROGENATION

KW - N-METHYLATION

KW - KETONES

KW - BIO-OIL

KW - KINETICS

KW - RANEY(R) NI

KW - VERLEY REDUCTION

KW - CATALYSTS

UR - http://www.scopus.com/inward/record.url?scp=85058705730&partnerID=8YFLogxK

U2 - 10.1016/j.supflu.2018.12.011

DO - 10.1016/j.supflu.2018.12.011

M3 - Article

AN - SCOPUS:85058705730

VL - 145

SP - 162

EP - 168

JO - Journal of Supercritical Fluids

JF - Journal of Supercritical Fluids

SN - 0896-8446

ER -