Background: Double metal phosphates, such as silver- and copper-zirconium phosphates, are considered promising materials for alcohol transformation to high-value chemicals (aldehydes, esters, olefins) due to high functional properties.Objective: The work was aimed to synthesize AgZr2(PO4)3 and Zr2.25(PO4)3 and study the influence of reduction conditions on their chemical and phase composition as well as catalytic properties under aerobic and anaerobic ethanol transformation. Methods: The structure of the catalysts was characterized by the XRD and HR TEM methods. The gas-phase ethanol conversion was studied in the temperature-programmed mode with online chromatographic analysis of reaction products. Results: The treatment of silver-zirconium phosphate with hydrogen leads to formation of 5-10 nm Ag0 particles along with partial destruction of initial AgZr2(PO4)3 phase. The products of the acidic route are eliminated under oxygen-free conditions for both catalysts, while the acetaldehyde is mainly formed in the oxygen-containing reaction mixtures. The formation of acetaldehyde over zirconium phosphate involves formation of Zr4+Oads oxidized sites. The highest yield of acetaldehyde is 74% at 330 oC and 93% ethanol conversion over Ag-containing catalyst in aerobic conditions. Conclusion: The ethanol dehydration is the main reaction pathway under anaerobic conditions regardless of the presence of Ag. In contrast, the presence of oxygen in the feed favors ethanol conversion to acetaldehyde.
Keywords: Ethanol, oxidation, dehydrogenation, zirconium phosphate, silver nanoparticles.