Effect of sulphiding agents on the hydrodeoxygenation of aliphatic esters on sulphided catalysts

The effects of H 2S and CS 2 on the hydrodeoxygenation (HDO) of aliphatic oxygenates were investigated on sulphided NiMo/γ-Al 2O 3 and CoMo/γ-Al 2O 3 catalysts. Unlike CS 2, H 2S had a promoting effect on the HDO. The use of H 2S as sulphiding agent in the HDO of aliphatic oxygenates was concluded to be more beneficial than the use of CS 2. ▪ In hydrodeoxygenation (HDO) on sulphided hydrotreating catalysts, addition of a sulphiding agent is typically required to maintain the catalyst activity. The effects of H 2S and CS 2 on the HDO of aliphatic esters on sulphided NiMo/γ-Al 2O 3 and CoMo/γ-Al 2O 3 catalysts were investigated in a fixed-bed flow reactor. The model compounds studied were methyl heptanoate, ethyl heptanoate, heptanol and heptanoic acid. The HDO produced C 7 and C 6 hydrocarbons in reactions where oxygen- and sulphur-containing compounds were formed as intermediates. Unlike CS 2, H 2S had a promoting effect on the HDO of the aliphatic oxygenates. The addition of H 2S stabilised the selectivities as a function of time, and shifted the main products from C 7 to C 6 hydrocarbons, but did not prevent catalyst deactivation. The promoting effect of H 2S was attributed to the increased catalyst acidity, which enhanced the acid-catalysed reactions (hydrolysis, esterification, dehydration, E 2 elimination and S N2 nucleophilic substitution). Both H 2S and CS 2 suppressed the hydrogenation reactions on the NiMo catalyst but did not affect them significantly on the CoMo catalyst. H 2S induced less hydrogen consumption and coke formation than CS 2, but the carbon efficiency suffered in the presence of H 2S. Thus, the use of H 2S as sulphiding agent in the HDO of the aliphatic oxygenates was concluded to be more beneficial than the use of CS 2.