Hopcalite

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Hopcalite (also Hopcalite or Germanized Hopcalite ) is the name for mixed catalysts , which mainly consist of manganese dioxide and copper (II) oxide . In addition, they can contain other metal oxides , for example cobalt oxides and silver (I) oxide . The name Hopcalite is derived from Johns Hopkins University ( "Hop" ) and the University of California ( "Cal" ), where these catalysts were discovered in the course of fundamental studies on carbon monoxide oxidation during the First World War and in the 1920s were.

Hopcalites catalyze the oxidation of toxic carbon monoxide (CO) to the relatively harmless carbon dioxide (CO 2 ) by (air) oxygen (O 2 ) at room temperature. That is why they are used in the filters of gas masks and other breathing apparatus . To be on the safe side, this also applies to diving air compressors, if they are driven by internal combustion engines, as on ships. In addition, hopcalites catalyze the oxidation of various organic compounds at elevated temperatures (200–500 ° C).

Various methods are known for the production of hopcalites in the laboratory and on an industrial scale, as listed here by way of example:

  • Physical mixing of the (finely divided) metal oxides
  • Joint precipitation of the metal oxides from metal salt solutions (see salts )
  • Thermal decomposition of mixtures of metal nitrates (see nitrate ) and metal carbonates (see carbonate )
  • One-step synthesis via flame spray pyrolysis from organic and inorganic precursor systems

Compositions are for example 60% MnO 2 /40% CuO or 50% MnO 2 /30% CuO / 15% CoO and 5% Ag 2 O.

Although hopcalite-based catalysts have been used in practice for decades, many questions regarding their mode of action remain open. This is due to their complex structures, which make it difficult to obtain information about the active centers and the mechanisms of catalysis and deactivation.

See also: catalysis , catalyst , heterogeneous catalysis

Individual evidence

  1. ↑ T. Biemelt, K. Wegner: Microemulsion flame pyrolysis for hopcalite nanoparticle synthesis: a new concept for catalyst preparation . In: National Center for Biotechnology Information (Ed.): PubMed . April 7, 2015. doi : 10.1039 / c5cc00481k . PMID 25726946 .