Catalytic deoxygenation of triglycerides and fatty acids to hydrocarbons over Ni–Al layered double hydroxide

• Lipids are efficiently converted to fuel-like hydrocarbons over Ni-based catalysts.
• H2 concentration during reaction determines hydrocarbon yields and catalyst fouling.
• The Ni-specific surface area also affects catalyst productivity.
• Spent oxide-supported Ni catalysts can be regenerated via calcination in air.
• Aldehydes and fatty acid esters are proposed as reaction intermediates.

The conversion of fatty acids and triglycerides to fuel-like hydrocarbons was investigated over a Ni–Al layered double hydroxide catalyst and over 20% Ni/Al2O3 for comparison purposes. Both catalytic performance and the extent of catalyst fouling were found to show a marked dependence on the hydrogen partial pressure used during reaction and on the Ni-specific surface area of the catalyst employed. The amenability of a representative spent catalyst to regeneration via calcination in air was also demonstrated. The regenerated catalyst was observed to outperform the fresh formulation when tested for activity in the conversion of lipids to fuel-like hydrocarbons. This is attributed to the formation of strong basic sites – which are capable of catalyzing the deoxygenation of lipids – during the regeneration process. The fact that inexpensive Ni-based catalysts capable of affording good yields of fuel-like hydrocarbons can be regenerated by treatment in hot air makes these formulations interesting from an industrial standpoint. Results suggest that the conversion of triglycerides to fuel-like hydrocarbons is intermediated by fatty acids and that the conversion of fatty acids – either as the reaction feed or as reaction intermediates – to hydrocarbons proceeds via aldehyde and/or fatty acid ester intermediates.

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