In order to investigate HDS(hydrodesulfurization) characteristics of thiophene, several Mo catalysts supported on zeolite USY, HZSM-5 and MCM-41 were prepared by using incipient wetness impregnation method. Also CoMo and NiMo catalysts supported on MCM-41 were prepared by using the same method in order to investigate the promoting effect of Co or Ni. All catalysts were activated under two different conditions(sulfidation and nitridation followed by sulfidation, respectively). The characteristics of Mo containing zeolite catalysts and of pretreatment on them were investigated by HDS reaction of thiophene, XRD, NH$_3$ TPD, BET, and TGA.
The HDS activities of zeolite supported Mo catalysts were equivalent to those of alumina supported Mo catalysts. MCM-41 supported Mo catalysts showed the highest HDS activity among zeolite supported Mo catalysts due to its higher surface area, larger pore channel and mild acidity. However, USY or ZSM-5 supported Mo catalysts were deactivated rapidly owing to the coke developed by the acidity of zeolites.
Introduction of Co or Ni to Mo/MCM-41 resulted in a synergistic activity for HDS reaction. This synergistic effect is well known on the CoMo/$Al_2O_3$ catalyst and has become the key issue on this catalytic system. The present result showed that the synergistic effect was also conserved for MCM-41 support and the optimum atomic ratio(Co/Mo) was 1.
Metal oxide was found to be converted into nitride or oxynitride through the temperature programmed nitridation. The nitride catalysts showed a lower HDS activity than metal sulfide catalyst.
