Abstract
Thiophene hydrodesulfurization (HDS) activity was measured for a series of Mo/TiO{sub 2} catalysts having Mo loadings of 0.5-13.5 wt% MoO{sub 3}. Raman data and thiophene HDS activity measurements suggest that three molybdenum species are present on oxidic Mo/TiO{sub 2} catalysts. A surface Mo interaction species is formed up to Mo loadings of 2.5 wt% MoO{sub 3} and is the oxidic precursor to the most active species for thiophene HDS (intrinsic thiophene HDS activity of 816 cm{sup 3} of C{sub 4} product/(h g of MoO{sub 3})). For higher Mo loadings, a second surface Mo interaction species is formed, which contributes to the background on the low-frequency side of the broad 950-960-cm{sup {minus}1} Raman peak and is less active for thiophene HDS (intrinsic activity of 250 cm{sup 3} of C{sub 4} product/(h g of MoO{sub 3})). X-ray photoelectron spectroscopic data show that both Mo surface species have similar dispersions. Catalysts with Mo loadings of > 8-9 wt % MoO{sub 3} also contain bulk MoO{sub 3}. The distribution of the three Mo species for the oxidic Mo/TiO{sub 2} catalysts is derived from Raman and HDS measurements.
Published Version
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