Metal-promoted sulfated zirconia catalysts redox and acidic characteristics and their impact on n-butane isomerization

The catalytic efficiency of palladium supported sulfated zirconia catalysts in the isomerization of n-butane to isobutane has been studied in relation to the effects of the active site features (redox and acidic). By using the XRD, UV-DRS, and N-2 adsorption methods, the structural and textural changes in the synthesized catalyst were investigated. H-2-TPR was used to assess the sulfate species' type and distribution on the surface of the catalysts as well as their redox behavior. The n-butylamine titration method, NH3-TPD, and Py-FT-IR spectroscopy were used to characterize the nature/strength and kinds of acid sites. The CO-TPD was used to determine the kind of active sites. The outcomes showed that the Fe promoter in a sulfated catalyst has a major impact on the activity of n-butane isomerization. Comparing Fe-Mn and Fe alone promoted catalysts to a combination of Fe-Cr and Fe-V promoters, the activity was further increased. The findings of the characterization showed that the nature of the metal dopants influences the surface characteristics of the catalysts (their redox nature and the strength of their surface adsorption), which may be related to their ionic charge or electron density. The metal-metal synergy between the metal dopant and the zirconia matrix, which helped to improve the catalysts performance for n-butane isomerization, is primarily responsible for the active sites' adsorption capacity and reducibility. The findings of the characterization showed that the nature of metal dopants governs the surface properties of the catalysts (redox nature and surface adsorption strength), which could be related to the electron density or ionic charge. The metal-metal synergy between the metal dopant and the zirconia matrix is primarily responsible for the active sites' adsorption capacity and reducibility, which contributed to improve the catalysts' performance for n-butane isomerization. In addition, for the purpose of optimizing the Fe-V promoted sulfated zirconia catalyst, catalyst characteristics (acidity) can be adjusted by the catalyst synthesis conditions.