Effect of Cu promotion on cracking and methanation during the Ni-catalyzed deoxygenation of waste lipids and hemp seed oil to fuel like hydrocarbons

Deoxygenation of yellow grease and hemp seed oil was studied over 20% Ni/Al2O3 and 20% Ni-5% Cu/Al2O3 catalysts in the presence of H-2. In the deoxygenation of 25 wt% yellow grease (dissolved in dodecane) both catalysts afforded a liquid product consisting of mainly linear C10-C17 alkanes; however, the Cu-promoted catalyst showed improved selectivity to long chain (C15-C17) hydrocarbons as a result of its lower cracking activity. Analysis of the light hydrocarbon products (C10-C16) showed that cracking mainly occurred via the removal of terminal carbons (with methane formation), although a small amount of internal cracking also occurs based on the presence of C6-C11 in the product mixtures. Similar improvements were also observed in the deoxygenation of 25 wt% hemp seed oil, showing that Cu was able to curb cracking even when a highly unsaturated feed was employed. The Cu promotion effect was more pronounced in the deoxygenation of 75 wt% yellow grease in which the 20% Ni/Al2O3 catalyst did not yield any liquid products, whereas the 20% Ni-5% Cu/Al2O3 catalyst afforded liquid products consisting of >90% diesel-like hydrocarbons. (C) 2017 Elsevier B.V. All rights reserved.