Selective Hydrocracking Polyaromatics into Light Aromatics: the Separation of Hydrogenation Center and Cracking Center

Abstract

Serial combined catalysts with separated hydrogenation centers and cracking centers, which were composed of CoMo/Al2O3 and Ni/B, were synthesized and compared with the normal bifunctional catalysts of NiMo/Al2O3–Beta and CoMo/Al2O3–Beta. The properties of different catalysts were characterized by various methods. H2-TPR results demonstrated the existence of hydrogen spillover between a Co or Ni promoter, and Mo metals could facilitate the reducibility of oxide Mo species and hydrogenation of aromatics. The naphthalene hydrocracking performances were also evaluated and compared with different catalysts. The combined catalysts showed relatively high yields of light aromatics with high-octane values (<C10 aromatics) and low yields of cyclanes. The reason should be correlated to the synergistic effect of CoMo/Al2O3 (hydrogenation center) with a high selectivity of converting naphthalene into C10 aromatics and the Ni/B (cracking center) with high activity of cracking C10 aromatics into light aromatics. The kinetic and thermodynamic analyses confirmed that the naphthalene hydrocracking activity of the CoMo/Al2O3–Beta catalyst was the highest, and the combined catalysts showed higher selectivity of converting naphthalene into light aromatics than NiMo/Al2O3–Beta and CoMo/Al2O3–Beta catalysts.