Hydrogen-free deoxygenation of oleic acid on acidic and basic ZSM-5 and Y-zeolites: Products for biofuel and reaction pathways

A large volume of highly acidic vegetable oils generated as waste could be utilized to produce low-cost biofuels without competing with food production. This study investigated the conversion of oleic acid (OA), used as a model fatty compound, in a micropyrolysis apparatus under conditions similar to those employed in fluidized catalytic cracking (FCC) of petroleum feedstocks. The influence of small-micropore size zeolites (ZSM-5) and large-micropore size zeolites (Y), in both their acidic H- and basic Na-forms, on the product distribution was evaluated. Oleic acid was pre-adsorbed onto the zeolites at a mass ratio Catalyst:OA = 10:1. Thermal cracking of pure oleic acid was limited, predominantly producing linear 1-alkenes and carboxylic acids. Conversion in the presence of catalysts was enhanced, resulting in the formation of a greater variety of hydrocarbons. Branched and cyclic alkanes, as well as polyaromatics hydrocarbons, were produced in greater quantities on Y zeolites compared to ZSM-5, due to the larger micropore diameter of the Y zeolite. Among the catalysts, Na-Y produced the highest number of hydrocarbons, predominantly within the gasoline range. These results are promising for the co-processing of fatty residues in the FCC, promoting the production of second-generation drop-in biofuels and bio-based chemicals, and contributing to industrial decarbonization.