A study of 2-, 3- and 4-methoxyphenol hydrogenation and hydrodeoxygenation over Rh/silica using deuterium

Abstract

Hydrogenation and hydrodeoxygenation (HDO) of 2-, 3- and 4- methoxyphenol was studied in the liquid phase over Rh/silica at 303–343 K and 3 barg hydrogen pressure. The order of overall reactivity was 3-methoxyphenol >2-methoxyphenol >4-methoxyphenol. The route to HDO products was direct from the aromatic species, while hydrogenation and HDO take place on different sites. When 2MP was competitively hydrogenated with 3MP, 2MP inhibited hydrogenation of 3MP but allowed HDO. Using deuterium revealed that cyclohexane was not formed from cyclohexanol and that mechanistically the route to the mono-HDO products was not the same as that to cyclohexane.