The germanium catalyst refers to an elemental germanium or germanium compound which has a catalytic function. Germanium is a rare metal, located in the fourth periodic period of the chemical periodic table, Group IVA. The germanium enamel is a grayish white metal that is shiny. It is chemically stable and does not interact with air or water vapor at room temperature. However, at 600 to 700℃, germanium reacts quickly with oxygen to form germanium oxide. The common valences of germanium are +2 and +4.
Figure 1. Germanium Catalysts
Compared to other rare metal catalysts, germanium catalysts are easier to prepare. In addition, some germanium catalysts are unique in structure and have specific catalytic functions. Therefore, germanium catalysts are applied in both organic synthesis and environmental protection.
- Organic synthesis: In the polyester production process, the catalyst is the most important additive, which has a great influence on the process, product quality and post-processing. Of the many catalyst series, the GeO2 catalyst has good catalytic and stability properties, causing little pollution to the polyester reaction system. Therefore, GeO2 catalysts have extremely important applications in the polyester process. Decomposition of acetylene is one of the effective methods for preparing carbon nanomaterials. The germanium catalyst can be used in this process in combination with other catalysts. For example, different carbon nanostructures can be synthesized by decomposing acetylene with an Al2O3 supported germanium/palladium composite catalyst. In organic synthesis, a,β-unsaturated aldehydes can be converted to saturated aldehydes by hydrogenation. The germanium catalyst exhibits a good catalytic effect on the reaction, which not only cuts the time required for the reaction, but also significantly increases the yield. Therefore, germanium catalysts can be used in catalytic hydrogenation of a,β-unsaturated aldehydes to give saturated aldehydes.
- Environmental protection: GeO4 comes with a tetrahedral structure, and the tetrahedral distortion causes a dipole moment inside the molecule. Light can promote the separation of photogenerated electrons from holes, and GeO4 thus becomes a good photogenerated electron acceptor. Therefore, GeO4 can act as a catalyst for photocatalytic oxidation technology. Up to now, GeO4 catalysts have been applied to the degradation of pollutants in water, carbon dioxide reduction,and photolysis of hydrogen in water.
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