The HDS activities of zeolite supported Mo catalysts were equivalent to those of alumina supported Mo catalysts. MCM-41 supported Mo catalysts showed the stable 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.
The hydrothermal stability of MCM-41 and MCM-48 was improved significantly with the post salt treatment due to increase in the pore wall thickness during the restructuring process. This was confirmed by the XRD results. Physical properties of the supported CoMo catalysts showed that due to this post salt treatment, there was only a small decrease in BET surface area and pore volume of the catalysts.
The effect of different mode of pore blockage on the catalyst deactivation was demonstrated by measuring the amount and aromaticity of coke deposit, molybdenum dispersion, and acidity of (Al-)MCM’s, together with the activity of thiophene HDS over the (Al-)MCM-41 and (Al-)MCM-48 based Mo catalysts. The coke deposits resulted in different deactivation obviously due to the difference in channel connectivity between MCM-41 and MCM-48. MCM-48 supported molybdenum catalysts with biporous channels showed a better stability than MCM-41 supported catalysts with unidimensional channels.
MCM-41 and MCM-48 supported Mo and CoMo catalysts showed higher acidity than Co supported catalysts as measured by $NH_3-TPD$. Accordingly this Mo and CoMo supported catalysts showed higher activity for thiophene HDS than Co supported catalysts. Mesoporous materials supported CoMo (3:7) catalysts showed the highest and CoMo (9:1) showed the lowest conversion. The highest thiophene HDS conversion was obtained at CoMo ratio of 3:7. This is attributed to higher amount of the active CoMoS species on supported CoMo (3:7) catalysts.
A series of La-modified Al-MCM-41 mesoporous material...