Oxidation of alcohols in supercritical CO2 fluid
Whether in the actual industrial production process or in the field of basic research, the selective oxidation of alcohols has very important significance. The traditional alcohol oxidation research is mainly based on heterogeneous catalytic oxidation reaction. The reaction needs to be carried out in a certain organic reaction solvent. Therefore, there are many environmental pollution problems in the reaction process, and a large number of precious metal catalysts are required. Therefore, from the perspective of environmental protection and economics of industrial production, the development of a clean alcohol oxidation process is also one of the hotspots of chemical workers.
In supercritical carbon dioxide medium, the reaction mechanism of the supported metal catalyst is similar to the selective oxidation process in traditional solvents, which is mainly divided into two steps
① Alcohol dehydrogenation process on the catalyst surface;
②Oxidize and remove the reduced substances formed on the surface of the catalyst
The catalysts commonly used for alcohol oxidation in supercritical carbon dioxide are mainly Pd/Pt based catalyst systems and Au based catalyst systems. Table 7-1 summarizes the alcohol oxidation reactions based on Pd catalysts.
Compared with traditional solvents, supercritical carbon dioxide has a good effect on some catalytic reactions. For alcohol-catalyzed oxidation in supercritical carbon dioxide system, when the system is in homogeneous phase, it is beneficial to the reaction process. In addition, it was also found that the presence of supercritical carbon dioxide also has an effect on the rate of adsorption and desorption of substances on the surface of the catalyst, which is also conducive to the improvement of the reaction rate