(A) study on the characteristics of thiophene hydrodesulfurization over mesoporous materials supported sulfided CoMo bimetallic catalysts

Abstract

In this work, it was explored the 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 to investigate the effect of different channel connectivity on the HDS activity. The hydrothermal stability of MCM-41 and MCM-48 was improved remarkably by the post salt treatment technique. MCM-41 or MCM-48 supported series of CoMo catalysts with different Co/Mo atomic ratios were prepared by co-impregnation of $Co(NO_3)_2ㆍ6H_2O$ and $(NH_4)_6Mo_7O_{24}ㆍ4H_2O$ followed by calcination and sulfidation. The characterization of the catalysts was carried out by X-ray diffraction (XRD), $N_2$ -adsorption/desorption, $NH_3$ -temperature programmed desorption ($NH_3$-TPD), TEM, elemental analysis (EA), and $^{13}C-NMR$. The thiophene HDS reaction was carried out in a micro flow reactor at 400 ˚C and 20 atm with space time of 2.85 gㆍmin/cc-thiophene and $H_2/thiophene$ mole ratio of 15. CoMo supported catalysts were significantly affected via post salt treatment during the impregnation. As the metals were loaded, there was only a small decrease in the BET surface area and the pore volume of the catalysts. CoMo/MCM-41 and CoMo/MCM-48 catalysts showed a similar activity change from the start of HDS reaction to 8 h. The CoMo/MCM-41 catalysts showed a little bit more deactivation after 8 h. Slightly more deactivation in CoMo/MCM-41 catalysts is believed due to the blocking of their one-dimensional pore channels with coke deposits. On the other hand, the CoMo/MCM-48 catalysts showed a stable activity up to 10 h. The three-dimensional pore structures of these catalysts should have reduced the risk of channel blockage by coke and facilitated the transport of reactant and product molecules. The amount of coke deposit during thiophene HDS was measured by elemental analysis (EA) and their effects on the pore structure an...