Influence of Polymorphic ZrO₂Phases and the Silver Electronic State on the Activity of Ag/ZrO₂Catalysts in the Hydrogenation of CO₂to Methanol

Abstract

Ag/ZrO 2 and Ag/ZrO 2 /ZnO catalysts obtained by the coprecipitation method were studied in the CO 2 hydrogenation to methanol. The catalyst structure was determined using X-ray diffraction (XRD) and Thermo-Programmed Reduction (TPR). The X-ray Photoelectron Spectroscopy (XPS) and Auger spectroscopies were used to determine the silver electronic state. It was found that selection of the appropriate conditions of the catalyst preparation influences silver dispersion degree, its electronic state, and contents of the zirconia polymorphic phases (tetragonal and monoclinic). The presence of oxygen vacancies stabilizes both the thermodynamically unstable t-ZrO 2 phase and the Ag þ cations, which are present in the vicinity of oxygen vacancies. The catalytic activity to methanol increases with increasing t-ZrO 2 content but RWGS reaction is accelerated by dispersed metallic silver. The implications of the obtained results for the mechanism of the catalytic hydrogenation of CO 2 are discussed.

Spectroscopic characterization of gold supported on tungstated zirconia

“…The Zr 3d photoelectron line for all Au catalysts exhibits peak for Zr 3d 5/2 at 182.0-182.9 eV, close to that observed for Zr 4+ ions [25,30,34,36,[39][40][41]. Fig.…”

Recent development in catalytic technologies for methanol synthesis from renewable sources: A critical review

“…However, there are few studies that indicate the opposite [46]. In the work done by Grabowski [47], Ag/ZrO 2 catalyst showed good performance in methanol synthesis. It was found that both selectivity and activity did not have any correlation with Ag 0 dispersion and content.…”

Influence of niobium on carbon nanofibres based Cu/ZrO 2 catalysts for liquid phase hydrogenation of CO 2 to methanol

“…The presence of two different XPS peaks with 2.4 eV energy gap indicates the existence of two different types of zirconium ions. Lower binding energy peak at 182.2 eV ratifies the existence of Zr 4+ as ZrO 2 whereas higher binding energy peak at 184.6 eV represents Zr 2+ species [41]. Cu 2p 3/2 peak of each catalyst was resolved into different peaks to identify the different Cu species and is displayed in Fig.…”