Why should the use of CO-containing gases as a hydrogen source for high-hydrogen reduction be avoided as much as possible during the reduction of copper-based bifunctional alcohol catalysts?
Thread Content
Why is it advisable to avoid using gases containing CO as the source for high-hydrogen reduction during the temperature increase and reduction process of the bifunctional alcohol catalyst?
Because CO causes the grains of the reduced active component to grow larger (compared to pure hydrogen).
Using carbon monoxide for reduction – it seems difficult to determine the end point of this reduction as well
When copper-based methanol synthesis catalysts are reduced, if reduction is carried out using a gas containing high levels of CO2, basic copper carbonate is formed, resulting in a decrease in the catalyst’s activity after reduction.
Reduction reactions of copper oxide: CuO + H2 = Cu + H2O + 86.6 KJ/mol; CuO + CO = Cu + CO2 + 125.7 KJ/mol. As can be seen from these equations, CO can also be used to reduce CuO, and its heat generation is one-third higher than that when using H2, which makes temperature control more difficult. Practice has shown that CO reduces CuO more easily than H2, at lower starting temperatures as well, which complicates the catalyst reduction process; as the temperature rises, errors are more likely to occur, leading to uncontrolled reduction and overheating. Worse still, the presence of CO tends to form carbonyl compounds that are toxic to the catalyst, resulting in poor activity of the catalyst after reduction. Moreover, the reduction product of CO is CO2, which accumulates within the system; at temperatures of 150–160°C, when the catalyst has a certain level of activity, the methanol synthesis reaction between CO2 and H2 further complicates the reduction process.