Hydroprocessing of waste cooking oil to produce liquid fuels over Ni-Mo and Co-Mo supported on carbon nanotubes

Abstract

New fuel production alternatives are becoming increasingly necessary to replace fossil energy sources and reduce the environmental implications of carbon emissions. In this context, renewable sources, such as waste cooking oil (WCO), are an excellent choice for producing bio-based fuels. However, to use WCO as fuel, the oxygen content in its triglyceride structures must be removed. To this end, bimetallic Co-Mo and Ni-Mo supported on pristine carbon nanotubes (CNT) and oxidized carbon nanotubes (CNTox) were synthesized to investigate the hydroprocessing of WCO in a batch reactor operating at 350 degrees C, 70 bar of H2 (evaluated at ambient temperature) for 3 h. The results showed that Ni-Mo/CNTox exhibited superior catalytic performance, mainly producing n-alkanes in the range of C14-C22 with a carbon conversion of about 67 mol.% and being selective for light alkanes (6.6 mol.% of C5-C7), jet fuel (11.4 mol.% of C8-C16) and diesel fuel (81.2 mol.% of C17-C22). On the other hand, a residence time of 5 h was necessary to achieve the same results with the carbon-supported Co-Mo catalysts. Hydrodeoxygenation was the main deoxygenation route followed using CNT based catalysts.