Abstract
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 °C, 30 bar of H2 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 C11-C20 hydrocarbons (>60%) than their Ni-based counterpart catalysts. Specifically, Co/Zr-SBA-15(17) sample showed remarkable behavior, favoring the HDO pathway (n-C18/(n-C18 + n-C17) > 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.
Highlights
Vegetable oils are one of the most interesting resources for the production of biofuels
In a previous work, we reported the good performance of catalysts based on Ni and Co deposited over ordered mesoporous SBA-15 and Al-SBA-15 in the methyl oleate hydrodeoxygenation, showing the benefits of using bifunctional systems for this reaction [29]
Catalysts are named M/Zr-SBA-15(x), where M corresponds to Ni or Co and x to the Si/Zr molar ratio
Summary
Vegetable oils are one of the most interesting resources for the production of biofuels. These types of catalytic systems have been generally applied to the hydrodeoxygenation of vegetable oils These materials present a very significant limitation, since the addition of hydrogen sulfide, carbonyl disulfide or dimethyl disulfide is required to keep the catalysts in their active forms. Due to their singular properties, both SBA-15 and Al-SBA-15 have been widely investigated to disperse a large variety of catalytic active phases This is the case when supporting a number of metals, such as Ni, Co, Fe, Pt, Pd, Ru, Cu and Mo to obtain catalysts with hydrodeoxygenation properties that have been applied in the hydrotreating of vegetable oils derived compounds [23,30,31,32,33]. Zr-SBA-15 samples were prepared with different Si/Zr ratios, loaded with Ni and Co species and investigated as catalysts in the hydrotreating of methyl esters
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