Stabilization of Pd3−xIn1+x polymorphs with Pd-like crystal structure and their superior performance as catalysts for semi-hydrogenation of alkynes

Johnston, Shaun K; Bryant, Thomas A; Strong, Jonathan; Lazzarini, Laura; Ibhadon, Alex O; Francesconi, M. Grazia

Abstract

Selective hydrogenation (semi-hydrogenation) reactions of alkynes rely on Pd-based catalysts to provide the correct pathway to favour formation of double bonds and avoid full hydrogenation to single bonds. Here, we present the preparation and characterisation of "Pd3In"/TiO2 nanocatalysts, which show improved activity and selectivity compared to pure Pd catalysts, towards the liquid phase semi-hydrogenation of 2-methyl-3-butyn-2-ol (MBY) to 2-methyl-3-buten-2-ol (MBE), a fundamental step in the preparation of pharmaceuticals, and other industrially produced substances, as well as a model reaction for the semi-hydrogenation of alkynes. For both the supported and unsupported "Pd3In" alloys (later redefined as Pd3-xIn1+x), we stabilised two new cubic polymorphs with a Pd-like structure, instead of the tetragonal structure as reported so far in the literature. The stabilisation of these new polymorphs was made possible by using a solution-based synthesis and, thanks to the use of different solvents, the reaction was 2 carried out at different temperatures and the Pd/In ratio could be tuned. The same synthetic approach was adapted to prepare two "Pd3In"/TiO2 catalysts by adding the TiO2 support to the reaction mixture, in a practical one-step, one-pot reaction. HREM and X-Ray maps show that the cubic crystal structure of "Pd3In" is maintained when prepared in the presence of the support, however, the support seems to influence the Pd/In ratio.

• Journal Article Type: Article
• Publication Date: Jun 19, 2019
• Journal: ChemCatChem
• Print ISSN: 1867-3880
• Electronic ISSN: 1867-3899
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 11
• Issue: 12
• Pages: 2909-2918
• APA6 Citation: Johnston, S. K., Bryant, T. A., Strong, J., Lazzarini, L., Ibhadon, A. O., & Francesconi, M. G. (2019). Stabilization of Pd3−xIn1+x polymorphs with Pd-like crystal structure and their superior performance as catalysts for semi-hydrogenation of alkynes. ChemCatChem, 11(12), 2909-2918. https://doi.org/10.1002/cctc.201900391
• DOI: https://doi.org/10.1002/cctc.201900391
• Keywords: Semi-hydrogenation; Nanoalloys; Pd3in
• Publisher URL: https://onlinelibrary.wiley.com/doi/10.1002/cctc.201900391
• Additional Information: This is the accepted manuscript of an article published in ChemCatChem, 2019. The version of record is available at the DOI link in this record.