Supported Catalytically Active Metal Solutions (SCALMS) - single atom catalysis for alkane dehydrogenation
Prof. Dr. Peter Wasserscheid
Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Lehrstuhl für Chemische Reaktionstechnik (CRT), Erlangen
Efficient dehydrogenation catalysis is a key success factor in chemical energy storage technologies and for applying alkanes as feedstock for chemical transformations. Recently, our group became interested in supported liquid alloys and have published a first account of this new catalyst material technology. In this paper, we described the use of Ga-rich Ga/Pd mixtures (Ga/Pd ratio> 10) supported on porous glass in n-butane dehydrogenation. The liquid nature of the supported alloy droplet under the reaction conditions was confirmed through a combination of XRD, SEM, XPS, and ab initio dynamics calculations. The following key features of the new SCALMS materials in dehydrogenation catalysis were established:
• SCALMS showed very high precious metal-based catalytic activities.
• Molecular dynamics (MD) calculations suggested that the top-most layer of the Ga-rich Ga/Pd alloy is depleted in Pd, but the layer directly underneath is enriched. This led us to propose that single Pd atoms appear dynamically at the liquid interface to promote the catalytic reaction in the presence of reactants.
• Coking, the typical deactivation mechanism for high temperature hydrocarbon chemistry under reductive conditions, was largely suppressed.
The presentation will show new examples of Ga-Pt, Ga-Rh, and Ga-Ni SCALMS systems and their application in alkane and cycloalkane dehydrogenation. For all systems we observe a clear boost in catalytic activity at the transition temperature from supported solid intermetallic phases to the fully liquid, supported alloy system. Moreover, additional insights to the chemical nature of the active site in SCALMS that have been collected by microscopic studies, IR spectroscopy and temperature programmed oxidation studies will be discussed.