Hydrotreating of Methyl Esters to Produce Green Diesel over Co- and Ni-Containing Zr-SBA-15 Catalysts

This work explores the performance of Zr-SBA-15 as a support for the conversion of methyl esters into green diesel. Thereby, a series of SBA-15 samples incorporating different amounts of Zr into the walls have been synthesized and impregnated with Ni and Co as hydrogenating species. All materials have been characterized, pelletized and tested in the hydrotreating of methyl esters using a fixed-bed tubular reactor at 300 degrees C, 30 bar of H-2 and a continuous flow of 0.1 mL/min for 6 h. Co and Ni phases are present both over the surface and within the pores of the support. Interactions between the metals and the Zr species are more pronounced for Co-containing samples, leading to smaller Co particles at low Si/Zr ratios. Materials having higher Zr contents resulted in more methyl ester conversion, although an adequate metal-support combination was required to promote the hydrodeoxygenation (HDO) route. Co/Zr-SBA-15 materials exhibited more conversion (>90%) and higher yields of C-11-C-20 hydrocarbons (>60%) than their Ni-based counterpart catalysts. Specifically, Co/Zr-SBA-15(17) sample showed remarkable behavior, favoring the HDO pathway (n-C-18/(n-C-18 + n-C-17) > 0.5), while keeping the methyl esters' conversion close to 100% along the time on stream. These results evidence a synergistic effect between Co and Zr.