Hydrocarbons production through hydrotreating of methyl esters over Ni and Co supported on SBA-15 and Al-SBA-15

Hydrodeoxygenation (HDO) is a suitable process to eliminate the oxygen content in vegetable oils and to produce a renewable fuel with characteristics similar to petroleum derived diesel. In this investigation, ordered mesoporous materials based on SBA-15 and Al-SBA-15 were synthesized and impregnated by incipient wetness impregnation with Ni or Co nitrate, being subsequently calcined and reduced with hydrogen. All the samples were characterized by means of XRD, N2 adsorption–desorption analysis at 77 K, ICP-OES, H2-TPR and TPD-NH3. Hydrotreating of a methyl esters mixture, used as convenient surrogate of triglycerides, was studied in the present work. Catalytic tests were carried out in a fixed-bed tubular reactor at 340–300 °C and 30 bar of H2 for 6 h, obtaining n-paraffins as main products. The results revealed that the presence of aluminum in the supports favors HDO processes, specifically at low temperatures, achieving higher selectivities and yields to C18 hydrocarbons than SBA-15 based materials. Besides, acid sites promote the formation of non-linear hydrocarbons in addition to n-paraffins, which are mainly produced with pure silica based catalysts. Regarding active phases, Co proved to be more active than Ni under the reaction conditions used in this study. On the basis of these results, Co/Al-SBA-15 can be considered as a very promising catalyst for the production of biofuels in diesel range from vegetable oils with a remarkable HDO activity.

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► Utilization of mesostructured silica (SBA-15) to disperse Ni and Co metallic particles as efficient catalysts for the hydrodeoxygenation of methyl esters.
► Bifunctional catalysts (with metallic and acidic sites) presented a very high yield to hydrocarbons in diesel range, as well as a higher contribution of HDO versus HDC processes under suitable conditions.
► An adequate selection of the catalyst characteristics (type of metal, acidity) and operation conditions (temperature) must be taken into account to enhance hydrodeoxygenation processes.