(A) study on the characteristics of thiophene hydrodesulfurization over mesoporous silica and mesoporous carbon supported CoMo catalysts

Abstract

Hydrodesulfurization (HDS) is the process through which sulfur is removed from petroleum and other fossil fuel feedstocks by reaction with hydrogen in the presence of catalysts. In this work, potential of two different mesoporous materials, MCM-41 (one-dimensional channel) and MCM-48 (three-dimensional channel) supported sulfided CoMo bimetallic catalysts for hydrodesulfurization of thiophene at specific conditions was explored to investigate the effect of channel connectivity on HDS activity. The hydrothermal stability of MCM-41 and MCM-48 was improved remarkably by a post­salt treatment technique. Aluminum incorporation to mesoporous material frameworks improved acidity and hydrothermal stability. Mesoporous material supported CoMo catalysts with different Co/Mo atomic ratios were prepared by co­impregnation of $Co{({NO_3})_2}6{H_2 O}$ and ${({NH_4})_6}{Mo_7}{O_24}4{H_2 O}$ followed by calcination and sulfidation. The characterization of the catalysts was carried out by X­ray diffraction (XRD), ${N_2}­$ adsorption/desorption, ${NH_3}$ ­temperature programmed desorption $({NH_3-TPD})$, transmission electron microscopy (TEM), CO­chemisorption, elemental analysis (EA), and ${^{13}}C-­NMR$. The effects of Co addition on the thiophene hydrodesulfurization (HDS) reaction were investigated over MCM-41 and MCM-48 supported catalysts. MCM-41 supported catalysts showed a small decrease in activity compared to MCM-48 supported catalysts, because three-dimensional MCM-48 reduced the risk of deactivation in catalysts and facilitated the transport of reactant and product molecules. The optimal Co/Mo atomic ratio for MCM-41 and MCM-48 supported series of catalysts was 3/7. The aluminosilicate supported CoMo catalysts showed higher activity than their siliceous counterparts. The acidity of the aluminosilicate supports as measured by {NH_3-­TPD}, might help to crack thiophene, improving HDS activity. The effectiveness of Al-incorporation improved HDS activity was attributed...