Effect of alcohol solvents treated ZrO(OH)2 hydrogel on properties of ZrO2 and its catalytic performance in isosynthesis

Abstract

A series of ZrO₂ catalysts were prepared by treating ZrO(OH)₂ hydrogel with different alcohol solvents (C₂-C₄ alcohols) and calcining under N₂ flow at 773 K for 3 h. The obtained ZrO₂ catalysts were systematically characterized by the methods of N₂ adsorption-desorption, powder X-ray diffraction, NH₃ temperature-programmed desorption, and CO₂ temperature-programmed desorption. The catalytic performance of each catalyst was evaluated in the selective synthesis of iso-C₄ (isobutene and isobutane) and light olefins ( ${\text{C}}_2^{=}\sim {\text{C}}_4^{=}$) from CO hydrogenation. The specific surface area increased for the ZrO₂ catalysts obtained by treating ZrO(OH)₂ hydrogel with different alcohol solvents. The amounts of both acidic and basic sites on the catalyst surface increased obviously. The catalytic activity (CO conversion) of ZrO₂ catalysts also increased after the treatment with different alcohol solvents. The highest activity was obtained over the catalyst which was pretreated with isopropanol. However, alcohol solvent treatment retarded the transformation of ZrO₂ crystal structure from tetragonal phase to monoclinic phase, and subsequently resulted in the decrease of monoclinic phase in ZrO₂, which led to the decrease of olefin selectivity in corresponding hydrocarbon products ( ${\text{C}}_2^{=}\sim {\text{C}}_4^{=}/\text{CH}$).