CoMoS/modified-kaolin bi-functional hydrodesulfurization-olefin skeletal isomerization catalyst for FCC naphtha hydro-upgrading

Abstract

Aiming at developing a bifunctional selective hydrodesulfurization (HDS) - olefin skeletal isomerization catalyst for fluid catalytic cracking (FCC) naphtha hydro-upgrading, in this article we present an acid-assisted dealumination method, the acid-modified kaolin (AMK-850-27) with tailored porosity and acidity and CoMoS bi-functional catalysts CoMo/AMK-850-27 was obtained. The catalytic performance was assessed with model FCC naphtha that is composed of thiophene (300 mg/kg) and 1-hexene (20%) in heptane. Compared with two catalysts used γ-Al2O3 and HZSM-5 as supports, CoMoS catalyst prepared with AMK-850-27 displayed compromise catalytic performance: balanced HDS activity and selectivity, high skeletal isomerization activity and low cracking activity, and excellent octane number preservation performance. This can be attributed to the following reasons: (i) AMK-850-27 possesses micro-meso-macro porosities and appropriate Brönsted acidity that can benefit skeletal isomerization activity but depress cracking activity; and (ii) The olefin isomers are more difficult to be hydrogenated than the corresponding linear terminal ones due to the steric effect of the branched olefins. This investigation providesa novel route to achieving deep desulfurization, appropriate olefin reduction and octane number preservation for FCC naphtha upgrading, acidic support with meso-macro-porosity can benefit olefin skeletal isomerization and the HDS selectivity but lower hydrocarbon cracking activity.