Cu/ZrO2 catalysts obtained by impregnation of ZrO2 and complexation with citric acid were studied for CO2 hydrogenation to methanol. The catalyst structure, texture, and active copper surface were determined using XRD, BET, and reactive adsorption of N2O, respectively. The XPS and Auger spectroscopies were used to determine the surface structure and copper electronic state. FT-IR pyridine adsorption was studied to determine acidity of the catalysts. The results of quantum-chemical calculations concerning the formation of oxygen vacancies in monoclinic and tetragonal ZrO2 have been also presented. It was found that selection of the appropriate conditions of the catalyst preparation influences the degree of copper dispersion, its electronic state, and contents of the zirconia polymorphic phases (tetragonal and monoclinic). The presence of oxygen vacancies stabilizes both the thermodynamically unstable t-ZrO2 phase and Cu1+ cations, which are present in the vicinity of oxygen vacancies. Complexes formed preferentially on tetragonal ZrO2 built from Cu cations and oxygen vacancies are the acid centers active in methanol synthesis reaction; therefore the catalytic activity toward methanol increases with increasing t-ZrO2 content. The implications of the obtained results for the mechanism of the catalytic hydrogenation of CO2 are discussed.

A novel route for the production of renewable aromatic chemicals, particularly substituted phthalic acid anhydrides, is presented. The classical two-step approach to furanics-derived aromatics via Diels-Alder (DA) aromatization has been modified into a three-step procedure to address the general issue of the reversible nature of the intermediate DA addition step. The new sequence involves DA addition, followed by a mild hydrogenation step to obtain a stable oxanorbornane intermediate in high yield and purity. Subsequent one-pot, liquid-phase dehydration and dehydrogenation of the hydrogenated adduct using a physical mixture of acidic zeolites or resins in combination with metal on a carbon support then allows aromatization with yields as high as 84 % of total aromatics under relatively mild conditions. The mechanism of the final aromatization reaction step unexpectedly involves a lactone as primary intermediate.

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.

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