Deoxygenation of rapeseed oil into green diesel by Ni-Mo-Al solventless-catalyst

A Ni-Mo-Al catalyst was produced by solventless-synthesis (to decrease wastes and enhance scalability) and used in the catalytic deoxygenation (DO) of triglycerides to produce green diesel. Preliminary catalytic DO tests were performed at laboratory scale in a batch reactor using commercial rapeseed oil as the fatty feedstock. The experiments occurred by an unreplicated 23 factorial design of experiments with three central replications. Temperature, catalyst-to-oil mass ratio, and reaction time were investigated as factors, at respective levels 280–320 ◦C, 4–10 %w/w, 2–6 h. Catalyst characterizations were performed before and after tests and used comparatively. The catalyst effectively converted triglycerides into green diesel, achieving 100 % conversion of triglycerides and a reasonable diesel yield (64.4-71.1 %) at 320 ◦C, 10 %w/w, and 6 h. Statistical analysis of the experimental data revealed significant effects of temperature, catalyst-to-oil ratio, and reaction time on product composition and DO performance metrics. As a first step for future developments of the solventless catalysts, recycling tests were performed: a decline in catalytic performance occurred over four cycles (71.1% to 13.2% diesel yield), empirically correlated to the carbon deposition experimentally detected on spent catalyst samples. Solventless syntheses emerged as a potentially sustainable approach to produce catalysts for the DO of vegetable oils, even though further studies are needed to improve catalytic long-term stability.