Novel porous CaO-MgO-promoting γ-Al2O3-catalyzed selective hydrogenation of oleic acid to green hydrocarbon fuels in biogasoline range with methanol as an internal hydrogen source

An efficient and highly selective CaO-MgO-promoting γ-Al2O3 decarboxylation catalyst was fabricated with different CaO to MgO ratios via a ball-milling method for regulating product distribution and production of gasoline-kerosene-diesel hydrocarbons via the catalytic copyrolysis of oleic acid (OA) and methanol under hydrogen-generating conditions. In addition, influencing factors, reaction mechanisms, possible reaction pathways and deactivation mechanisms were probed. The results showed that combining Ca, Mg and AlOx was vital for boosting oleic acid conversion, and synergy between metal and acid active sites via strong metal-support interactions enhanced deoxygenation-cracking activity. High-alkalinity CaO boosted C-C/CC bond cleavage, and MgO provided medium-strength Lewis acid sites; additionally, a large BET surface area and mesopore volume suppressed excessive hydrocracking reactions, improving biogasoline yield. Methanol addition provided active hydrogen atoms to enhance biogasoline selectivity at the expense of diesel and heavy oil production via olefinic cycles and aromatic cycle mechanisms and reduced coke deposition. The maximum hydrocarbon and biogasoline yields of 94.53% and 57.59% were achieved at OA/methanol= 5:1 and pyrolysis/catalytic temperature= 450/500 °C with1 g catalyst at a feedstock input rate of 0.1 ml/min.