Methanol synthesis: Insights into the structure of an enigmatic catalyst


Date:
August 4, 2020
Source:
Ruhr-University Bochum
Summary:
To render the production process more efficient, it would be helpful
to know more about the copper/zinc oxide/aluminium oxide catalyst
deployed in methanol production. To date, however, it hasn't been
possible to analyse the structure of its surface under reaction
conditions. A team has now succeeded in gaining insights into the
structure of its active site.



FULL STORY ========================================================================== Methanol is one of the most important basic chemicals used, for example,
to produce plastics or building materials. To render the production
process even more efficient, it would be helpful to know more about
the copper/zinc oxide/ aluminium oxide catalyst deployed in methanol production. To date, however, it hasn't been possible to analyse
the structure of its surface under reaction conditions. A team from Ruhr-Universita"t Bochum (RUB) and the Max Planck Institute for Chemical
Energy Conversion (MPI CEC) has now succeeded in gaining insights into
the structure of its active site. The researchers describe their findings
in the journal Nature Communications from 4 August 2020.


==========================================================================
In a first, the team showed that the zinc component of the active site is positively charged and that the catalyst has as many as two copper-based
active sites. "The state of the zinc component at the active site has
been the subject of controversial discussion since the catalyst was
introduced in the 1960s.

Based on our findings, we can now derive numerous ideas on how to optimise
the catalyst in the future," outlines Professor Martin Muhler, Head of
the Department of Industrial Chemistry at RUB and Max Planck Fellow at
MPI CEC. For the project, he collaborated with Bochum-based researcher
Dr. Daniel Laudenschleger and Mu"lheim-based researcher Dr. Holger Ruland.

Sustainable methanol production The study was embedded in the
Carbon-2-Chem project, the aim of which is to reduce CO2 emissions by
utilising metallurgical gases produced during steel production for the manufacture of chemicals. In combination with electrolytically produced hydrogen, metallurgical gases could also serve as a starting material for sustainable methanol synthesis. As part of the Carbon-2- Chem project,
the research team recently examined how impurities in metallurgical
gases, such as are produced in coking plants or blast furnaces, affect
the catalyst. This research ultimately paved the way for insights into
the structure of the active site.

Active site deactivated for analysis The researchers had identified nitrogen-containing molecules- ammonia and amines -- as impurities
that act as catalyst poisons. They deactivated the catalyst, but not permanently: if the impurities disappear, the catalyst recovers by
itself. Using a unique research apparatus that was developed in- house,
i.e. a continuously operated flow apparatus with an integrated high-
pressure pulse unit, the researchers passed ammonia and amines over
the catalyst surface, temporarily deactivating the active site with a
zinc component. Despite the zinc component being deactivated, another
reaction still took place on the catalyst: namely the conversion of
ethene to ethane. The researchers thus detected a second active site
operating in parallel, which contains metallic copper but doesn't have
a zinc component.

Since ammonia and the amines are bound to positively charged metal ions
on the surface, it was evident that zinc, as part of the active site,
carries a positive charge.


========================================================================== Story Source: Materials provided by Ruhr-University_Bochum. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Daniel Laudenschleger, Holger Ruland, Martin Muhler. Identifying the
nature of the active sites in methanol synthesis over
Cu/ZnO/Al2O3 catalysts. Nature Communications, 2020; 11 (1) DOI:
10.1038/s41467-020- 17631-5 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200804111453.htm

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