Hydrodeoxygenation of aliphatic esters on sulphided NiMo/γ-Al2O3 and CoMo/γ-Al2O3 catalyst: The effect of water

Water formed during hydrotreating of oxygen-containing feeds has been found to affect the performance of sulphided catalysts in different ways. The effect of water on the activity of sulphided NiMo/γ-Al2O3 and CoMo/γ-Al2O3 catalysts in hydrodeoxygenation (HDO) of aliphatic esters was investigated in a tubular reactor by varying the amount of water in the feed. In additional experiments, H2S was added to the feed, alone and simultaneously with water. Under the same conditions, the NiMo catalyst exhibited a higher activity than the CoMo catalyst. The ester conversions decreased with increase in the amount of added water. When H2S and water were added simultaneously, the conversion increased to the same level as without water addition on the NiMo catalyst and reached a higher value on the CoMo catalyst. The conversions were highest, however, when only H2S was added. Unfortunately, the conversions decreased with time under all conditions. On both catalysts, the total yield of the C7 and C6 hydrocarbons decreased with the amount of added water, while the concentrations of the oxygen-containing intermediates increased. The presence of H2S improved the total hydrocarbon yield and shifted the main products towards the C6 hydrocarbons. Thus, the addition of H2S effectively compensated the inhibition by water.