Hydrodeoxygenation of oleic acid in hexane containing pressurized CO2 using Fe/SBA-15 as catalyst

The hydrotreatment of oleic acid in a green reaction media to produce the major hydrodeoxygenation product octadecane using a 6 wt% nano Fe loaded Fe/SBA-15 as catalyst was demonstrated in this study. The data show that hexane containing pressurized CO2 could dictate the selectivity of the hydrotreatment of oleic acid with high selectivity for hydrodeoxygenation over decarboxylation/decarbonylation. In addition, hexane containing pressurized CO2 could offer beneficial effects including reduction of viscosity of the solution and increase of H2 solubility. As a result, uniform dispersion of the catalyst occurred in the solution and the diffusion resistances were reduced as well due to the increase in mass transfer. At the best operating condition of 290 °C, 6 h, 30 bars H2 and 40 bars CO2, an octadecane yield of 83.3% and a heptadecane yield of 8.7% were observed when compared to 65% and 15%, which were the yields in the absence of CO2. The effects of three independent operation variables namely, temperature, CO2 pressure and time and their interactions on the hydrotreatment of oleic acid were studied using a central composite design and response surface methodology. The results showed that all these three variables were significant factors for increasing the yield of octadecane while CO2 pressure was the most significant variable in decreasing the yield of heptadecane, the major decarboxylation/decarbonylation product.