Copper catalysts Cu – (Zr + Ce)O2 – Al2O3 as carrier in the process of ethanol conversion: effect of catalyst composition and ethanol concentration

Abstract

The impregnation technique was used to produce a range of copper catalysts with different concentrations of copper and with a complex-oxide ceramic carrier 50% (Zr + Ce)O2 – 50% Al2O3. The characterization was done based on X-ray phase analysis and electron paramagnetic resonance (EPR). BET method was used to measure the specific surface area. The catalysts were tested in aqueous solutions of ethanol of different concentrations. The EPR method helped establish that copper(II) oxide only is present on the surface of the catalyst after it has been heat treated in inert atmosphere, while copper ions form during catalysis. Copper was found to change its forms during catalysis and interact with the Ce3+ ions of the carrier in the case of the specimen with a high concentration of copper. The results showed that the activity of the catalysts is governed by the concentration of copper in the specimen and their prior processing. To obtain a high-performance dehydrogenation catalyst, the optimum amount of deposited copper phase is 5–10%. The resultant catalysts can be effectively used for the dehydrogenation of aqueous solutions of ethanol in the temperature range of 320 to 360 oC. The highest amount of acetaldehyde was observed on the specimen with 5 wt % copper without prior reduction treatment: 76% at Т = 380 oC with a 98% selectivity. Hydrogen flow reduction of the catalyst affects its catalytic activity bringing it down by 10–15%. The presence of water in ethanol does not impact the catalytic acti vity of the catalysts. The output of acetaldehyde in ethanol conversions with 50 wt % is higher than in ethanol conversions with 96.6 wt %.The EPR study was carried out at the Nanochemistry and Nanomaterials Shared Knowledge Centre at the Lomonosov Moscow State University as part of the University’s Development Plan. The authors thank senior researcher A. V. Fionov, PhD (Chemistry), for his support.This research was funded by the Russian Science Foundation under Research Project No. 22-29-01135.