Effect of phosphorus on the surface state of alumina-supported nickelmolybdenum catalysts for hydrodesulphurization

Support effect on the properties of iron–molybdenum hydrodesulfurization catalysts

“…MoO 3 phase was not identified in the spectra of the TiO 2 -supported catalysts [24] and instead, a new band at 674 cm )1 appeared. Presence of the new band in the 400-700 cm )1 region is observed [25] when Mo (W) is substituted for transition metal ion in the heteroatom surroundings. Therefore, we can suppose formation of Fe substituted heteropolyanion as well as substitution of Mo for Ti in the loaded HPMo heteropolyanion.…”

“…In the spectrum of the initial HPMo acid, the characteristic bands of the Keggin-type heteropolyacids at and a band in the region 880-950 cm )1 (terminal Mo=O group [18,25]) are visible in the spectra of the catalysts. Appearance of the intense band at $445 cm )1 also points out the presence of aluminum molybdate and aluminum heteropolymolybdate [26] in the catalysts.…”

Phosphorus Promotion of Ni(Co)-Containing Mo-Free Catalysts in Quinoline Hydrodenitrogenation

“…36) gave rise to an even higher activity when tested under the same (DMDS-free) conditions as No. 35. Upon addition of DMDS to the feed (at 603 K and 24 h run time), the activity of catalyst No.…”

The Phenomena of Proton Transfer from Catalytic Oxides

“…Other more conventional techniques such as temperatureprogrammed reduction (TPR), X-ray photoelectron spectroscopy (XPS), and laser Raman spectroscopy (LRS) were used to support the findings cited above (65). TPR data confirmed that, above a certain weight loading of Co, when the catalysts contain about 15% Mo, an amount of Co cannot be accommodated intimately with Mo and undergoes a type of phase separation.…”

“…A surface Co-Mo interaction species may thus be formed and it was proposed to be a heteropolymolybdate-like structure in the oxidic state. The existence of nickel heteropolymolybdate on Ni/Mo/Al 2 O 3 catalysts (in oxidic form) was suggested in the literature (65). The feature at pK of approximately 6 might be the hydrolysis of such a species.…”