The Influence of Active Phase Loading on the Hydrodeoxygenation (HDO) of Ethylene Glycol over Promoted MoS₂/MgAl₂O₄ Catalysts

The hydrodeoxygenation (HDO) of ethylene glycol over MgAl₂O₄ supported NiMo and CoMo catalysts with around 0.8 and 3 wt% Mo loading was studied in a continuous flow reactor setup operated at 27 bar H₂ and 400 °C. A co-feed of H₂S of typically 550 ppm was beneficial for both deoxygenation and hydrogenation and for enhancing catalyst stability. With 2.8–3.3 wt% Mo, a total carbon based gas yield of 80–100% was obtained with an ethane yield of 36–50% at up to 118 h on stream. No ethylene was detected. A moderate selectivity towards HDO was obtained, but cracking and HDO were generally catalyzed to the same extent by the active phase. Thus, the C₂/C₁ ratio of gaseous products was 1.1–1.5 for all prepared catalysts independent on Mo loading (0.8–3.3 wt%), but higher yields of C₁–C₃ gas products were obtained with higher loading catalysts. Similar activities were obtained from Ni and Co promoted catalysts. For the low loading catalysts (0.83–0.88 wt% Mo), a slightly higher hydrogenation activity was observed over NiMo compared to CoMo, giving a relatively higher yield of ethane compared to ethylene. Addition of 30 wt% water to the ethylene glycol feed did not result in significant deactivation. Instead, the main source of deactivation was carbon deposition, which was favored at limited hydrogenation activity and thus, was more severe for the low loading catalysts.