Insights into the deactivation mechanism of Zn-Cr binary catalyst for isobutanol synthesis via syngas

Abstract

The long-time stability test of Zn-Cr catalysts for isobutanol synthesis via syngas under vigorous reaction conditions was reported in this work, and the deactivation mechanism over these catalysts for isobutanol synthesis was discussed deeply. Based on the analysis of TEM, XRD, TG-DT, ICP and N2 adsorption-desorption isotherms, some traditional causes of deactivation, such as sintering, coke deposition, the formation of inactive species, and the loss of active metals, are negligible over the Zn-Cr catalyst. From the IR and XAS analysis, the spent catalyst presents a lower level of cation disorder distribution with fewer defects and oxygen vacancies on the surface, suggesting that the nanostructural change of the Zn-Cr catalyst will be the main cause of catalyst deactivation. The physico-chemical properties of the fresh and spent catalysts were investigated by XPS, CO2-TPD and NH3-TPD analyses, and the results show that the structural change would affect the oxygen state and the acidity-basicity over the surface of the catalysts. The loss of hydroxyl groups, as well as the weak synergistic effects between acidity and basicity over the spent catalyst surface, also plays a crucial role in the catalyst deactivation of the Zn-Cr catalyst.