Effect of tungsten deposition method on K-modified NiW/γ-Al2O3 as sulphur-tolerant water–gas shift reaction catalyst

• EDF ensures higher dispersion of W-oxo species in comparison with WI.
• Wet impregnation of W(VI) favors the formation of WO3 crystals.
• Modification by potassium increases the dispersion of the NiW phase.
• Nickel and potassium incorporation in tungsten is higher with the EDF sample due to its higher dispersion.
• The EDF method and potassium enhance the sulphability and activity of (K)NiW catalysts.

A specific preparation method for depositing W oxo-species and modification with potassium have been applied to study physicochemical features and activity behaviour of a NiW/Al2O3 system as a sulphur-tolerant water–gas shift catalyst.Equilibrium deposition filtration and conventional wet impregnation were used for W loading on alumina surface. Nickel and potassium deposition was carried out following incipient wetness impregnation. Catalytic measurements were performed in a fixed bed reactor at atmospheric pressure in the range of 250–400 °C. Samples were characterised by means of N2 physisorption, X-ray diffraction, Raman, diffuse reflectance UV–vis-NIR, and XP spectroscopies.A combination between the equilibrium deposition-filtration method for tungsten deposition and potassium modification of NiW catalysts gives rise to increased tungsten dispersion of calcined and tested samples. This has led to enhanced reducibility/sulphidability, improved stability of the metal–sulphur bond at the surface, and a higher activity of the KNiW catalysts for the water–gas shift reaction in sulphur-containing gas mixtures.

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