Decarboxylation/decarbonylation (deCOx) represents a hydrogen-efficient alternative to hydrotreating for the conversion of triglycerides and fatty acids to fuel-like hydrocarbons. We have demonstrated that inexpensive nickel catalysts comprising oxidic supports display near comparable performance to the costly carbon-supported precious metal formulations commonly used to catalyze this reaction. Given that deCOx catalysts are susceptible to deactivation by the accumulation of carbonaceous deposits on their surface, the use of oxides as the support has facilitated the study of spent Ni catalysts via thermogravimetric analysis (TGA) and allowed for their regeneration through the combustion of these deposits. Figure 1 shows the TGA of Ni-Al layered double hydroxide (LDH) and 20% Ni/Al2O3 spent in the deoxygenation of tristearin under H2, 10%H2/N2 and N2.   Tellingly, the trends followed by these TGA plots and the yields of fuel-like hydrocarbons obtained show a marked correspondence. Indeed, yields increased monotonically with increasing H2 partial pressure and consistently higher yields were obtained over Ni-Al LDH than over 20% Ni/Al2O3 regardless of the reaction atmosphere. This indicates that the influence of hydrogen partial pressure and catalyst acidity on catalyst performance can be explained in terms of the effect of these variables on catalyst fouling. Finally, recycling studies have shown that the activity and selectivity of the Ni-Al LDH catalyst can be restored by calcination in hot air, which makes this formulation interesting from an industrial standpoint.

Conversion of triglycerides and fatty acids to fuel-like hydrocarbons over supported nickel catalysts

246th National Meeting (2013)

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