Effect of cobalt supported on the hierarchical Ni/HZSM-5 catalyst in hydrocracking of Sunan candlenut oil (Reutealis trisperma (Blanco) airy shaw)

Abstract

The effect of cobalt supported on the hierarchical Ni/HZSM-5 on conversion, n-paraffin/aromatic selectivity, the degree of hydrocracking and polymerization in hydrocracking of Sunan candlenut oil was investigated. The hierarchical HZSM-5 was obtained through desilication with 0.2 M NaOH solution. The cobalt (Co), nickel (Ni) and Co-Ni supported on hierarchical HZSM-5 catalysts were prepared by incipient wetness impregnation. Desilication and metal impregnation did not change the crystalline structure of HZSM-5 catalyst. Hydrocracking of Sunan candlenut oil into gasoil-range hydrocarbon was tested with the catalysts at a temperature of 400 °C, and a reactor pressure of 15 bar for 2 h under initial hydrogen pressure in a pressured batch reactor. All catalysts reached conversion almost 100 %. Non-catalytic hydrocracking contained large amounts of undesired compounds (50 %), N-containing compounds around 1 area% and a small amount of compound containing oxygen including ketone (2-heptadecanone) and alcohol (<1%). The addition of cobalt supported on the hierarchical Ni/HZSM-5 improved C15/C16 ratio up to 11, the n-paraffin selectivity up to 78% and decreased polycyclic aromatic hydrocarbons (2-3.7 %). Then, N-containing compounds were not detected. The degree of hydrocracking decreased from 0.28 to 0.23. These results indicated that cobalt could control hydrogenation ability of nickel. The presence of cobalt in the hierarchical Co-Ni/HZSM-5 catalyst increased catalytic activity in decarboxylation route to produce the most abundant n-paraffin, i.e. pentadecane (n-C15) and heptadecane (n-C17). Overall, the monocyclic aromatic hydrocarbons selectivity produced for hierarchical pore structure based HZSM-5 catalyst were 15-18 %.