Stabilization of Pd 3−x In 1+x Polymorphs with Pd‐like Crystal Structure and their Superior Performance as Catalysts for Semi‐Hydrogenation of Alkynes

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

Research output: Contribution to journalArticle

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 “Pd 3In”/TiO 2 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 “Pd 3In” alloys (later re-defined as Pd 3−xIn 1+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 carried out at different temperatures and the Pd/In ratio could be tuned. The same synthetic approach was adapted to prepare two “Pd 3In”/TiO 2 catalysts by adding the TiO 2 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 “Pd 3In” is maintained when prepared in the presence of the support, however, the support seems to influence the Pd/In ratio.

Original languageEnglish
Pages (from-to)2909-2918
Number of pages10
JournalChemCatChem
Volume11
Issue number12
Early online date20 May 2019
DOIs
Publication statusPublished - 19 Jun 2019

Bibliographical note

Funding: FP7 Research for the Benefit of SMEs. Grant Number: FP70NMP-2012-SMALL-6

Keywords

  • alloys
  • indium
  • palladium
  • polymorphs
  • selective hydrogenation

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