Hydrodesulfurization , Hydrodenitrogenation and Hydrodearomatization over CoMo / SAPO-11-Al 2 O 3 Catalysts

The fluidized catalytic cracking (FCC) process is a method for the catalytic conversion of heavy oil into lighter products, and is very important in the petroleum refinery. The main product of the FCC process is FCC gasoline and the by-product is light cycle oil (LCO), which mainly consists of bicyclic or polycyclic aromatic compounds and small amounts of sulfur and nitrogen compounds. Conversion of large content of polyaromatic compounds in LCO to mono-aromatic compounds would yield high added value products for p roduc ing Benzene-Toluene-Xylene (BTXs) . However, conventional hydrotreating catalysts, as well as catalysts for the removal of sulfur compounds and nitrogen compounds cause the hydrogenation of polyaromatic compounds, so no mono-aromatic compounds are obtained. Therefore, a specific catalyst is needed for desulfurization and denitrogenation, and selective hydrogenation of bicyclic or tricyclic aromatic compounds to monocyclic aromatic compounds1). Several models for the structure of the active phase2)~4) of cobalt promoted MoS2 catalysts have been proposed, but the CoMoS phase consisting of cobalt atoms on the edge of MoS2 slabs is widely accepted5)~7). The RimEdge model with two types of active sites, the Rim site and the Edge site, can explain the differences in the hydrogenation (HYD) and hydrodesulfurization (HDS) active sites8). The Rim sites are located only on the top and bottom of the MoS2 slabs, and have both hydrogenation and desulfurization activities. In contrast, the Edge site located on the edge of each layer of the slabs only has desulfurization activity. Based on this model, a catalyst for selective hydrogenation, i.e. higher HDS and/or hydrodenitrogenation (HDN) but lower hydrodearomatization (HDA), could be developed by controlling the proportions of the Rim and Edge sites. The acidity of the support is expected to affect the hydrogenation activity9),10). Higher support acidity enhanced hydrogenation activity of catalyst9). Low acidity zeolite materials such as the SAPO series or SBA series could be used mixed with Al2O3 to decrease support acidity and control hydrogenation catalytic activity. Evaluation of various zeolite types and alumina for hydrocracking catalysts concluded that zeolite with both small crystal size and mesoporous alumina 301 Journal of the Japan Petroleum Institute, 60, (6), 301-310 (2017)