The effect of controlled catalyst hydrothermal deactivation on morphology, structural and activity of K-decorated ZnO/ZnAl2O4 catalysts for HT-WGS

Abstract

The effect of hydrothermal treatment on activity of Fe-based and Zn-Al-based HT-WGS catalysts has been studied. The catalysts were investigated by XRF, XRD, low-temperature N2 sorption, Hg‑porosimetry, CO2- and NH3-TPD, FT-IR, SEM, STEM-EDS, HR-TEM with FFT and HT-WGS rates in the range of 330–400 °C were measured. The temperature of thermal treatment which causes processes corresponding to the textural changes resulted from long-term performance in an industrial reactor was estimated and a methodology for the simulation of deactivation in hydrothermal process conditions for both conventional and novel K-ZnO-ZnAl2O4 catalysts was proposed. It has been shown that the promotion by potassium is both structural, electronc and inhibits the growth of ZnAl2O4 crystallites.The K-decorated ZnO-ZnAl2O4 catalyst for HT-WGS shows significantly lower tendency to sintering than Fe-based catalysts, which results in higher resistance to hydrothermal deactivation under typical conditions of the HT-WGS process and also under lower steam/gas ratios. Finally, it was concluded that non-stoichiometric Zn-Al catalyst promoted with K can be regarded as an attractive next generation catalyst for more efficient and cheaper technologies of generating hydrogen for industry.