Catalysts for Metal-Oxide Reactions

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Catalysts for Metal-Oxide Reactions

Copper oxide is a valuable catalyst material able to convert different feedstock such as methanol into fuels. In order to achieve an optimal result, understanding the mechanisms of the catalytic reaction started by an oxide catalyst is of great importance. This enables scientists to steer the reaction by controlling the amount of oxygen and the number of electrons involved and thus achieve a smooth and efficient reaction.Get more news about Oxide Deoxidizing Catalyst,you can vist our website!

Now (2023), scientists at Brookhaven Laboratory have launched a project which is aimed at getting greater insight into how peroxides present on the surface of copper oxide are able to facilitate the oxidation of hydrogen and at the same time inhibit the oxidation of carbon monoxide. The knowledge gained should help them steer oxidation reactions better. Observing the mechanisms of these quick changes was made possible by employing different spectroscopy methods.

Peroxides contain two oxygen atoms linked by shared electrons and have relatively weak electron bonds. This makes them highly reactive. In this study, the scientists focused on altering the redox steps of catalytic oxidation reactions on an oxidized copper surface (CuO) through identifying the makeup of peroxide species formed with different gases: O2 (oxygen), H2 (hydrogen), and CO (carbon monoxide).

In a redox reaction, the oxidizing agent gains an electron and the reducing agent loses an electron. When the different peroxide species and how the altered redox steps would influence the reaction as a whole were analysed, it was found that a surface layer of peroxide significantly enhanced CuO reducibility in favor of H2 oxidation. Moreover, it seemed to act as an inhibitor to suppress CuO reduction against CO (carbon monoxide) oxidation. This reverse effect of the peroxide on the two oxidation reactions was found to be caused by the modification of the surface sites where the reaction takes place. The scientists were convinced that by making out the bonding sites and learning how they enhanced or inhibited oxidation, they could steer the reaction of the gases. Therefore, they had to get a clearer picture of the reaction dynamics.

The first step was to study the reaction in situ as peroxides are extremely reactive and reactions happen fast. The scientists used in-situ infrared (IR) spectroscopy to get a better understanding of the chemical properties of the material and looked at the way the radiation was absorbed or reflected under reaction conditions. In this manner, they were able to make out different forms of peroxide, with very slight variations in the oxygen they were carrying, which would not have been possible to identify on the metal oxide surface otherwise.

The second technique the team used on the samples was ambient pressure X-ray Photoelectron Spectroscopy (XPS). XPS uses lower-energy x-rays to get electrons out of the sample. The energy of these electrons makes it possible to analyse the chemical properties of atoms in the sample and thus achieve a better catalyst in the long run.

For decades, scientists have tried to improve the functioning of copper oxide catalysts. In 2019, the influence of copper content in the monometallic catalysts supported on the CeO2·Al2O3 binary oxide system was analysed with a view to their catalytic activity and physicochemical properties in the process of oxy-steam reforming of methanol. It was found that activity and selectivity was largely dependent on the content of copper and dispersion on the catalysts surface. The optimal copper content amounted to 20 wt% of Cu. Catalysts with 20 wt% of Cu showed the highest methanol conversion and reaction rate value compared to the rest of the investigated catalysts systems. The kinetic measurements performed in oxy-steam reforming of methanol on 20%Cu/CeO2·Al2O3 catalysts, showed an activation energy for this system equal Ea (OSRM) = 66.56 kJ/mol.