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

• Published in: Applied catalysis. A, General General, 2015-10, Vol.506, p.14-24
• Main Authors: Nikolova, D., Vakros, J., Grozeva, T., Lycourghiotis, A., Tyuliev, G., Edreva-Kardjieva, R., Kordulis, Ch
• Format: Article
• Language: English
• Subjects: Diffuse reflectance spectra; Equilibrium deposition filtration; KNiW catalyst; Raman spectroscopy; Sulphur-tolerant water–gas shift reaction; XPS
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2015.08.030

[Display omitted] •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.