In situ generation of Pd nanoparticles in MCM-41 and catalytic applications in liquid-phase alkyne hydrogenations

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Abstract

Pd-MCM-41 materials were synthetized by using the cationic surfactant tetradecyltrimethylammonium bromide (C14TABr) for both the stabilization of the Pd particles and the construction of the mesoporous structure of MCM-41. Two Pd-MCM-41 samples, for which the Pd particles were generated before and after formation of the MCM-41 framework (Pd-A and Pd-B, respectively), were investigated. Structural characterization of the samples was carried out by ICP-AES, N2 sorption, XRD and TEM measurements. It was established that the highly ordered structure of MCM-41 was not appreciably affected by the formation of the Pd particles. Further, a similar particle size control was achieved for both Pd-MCM samples. However, both the location and the size distribution of the Pd particles were found to depend strongly on the preparation procedure. For Pd-A, the Pd nanoparticles were essentially situated on the external surface of MCM-41, whereas for Pd-B, the particles were found to be encapsulated inside the mesopores. For the liquid-phase hydrogenations of alkynes, the catalytic activity of Pd-A clearly surpassed that of Pd-B, indicating that the external Pd crystallites were more readily accessible for the reactants than those incorporated in the MCM-41 framework. The limited activity observed for Pd-B was attributed to mass transport limitations due to diffusion of the reactants into the mesopores of the MCM-41 host.

Original languageEnglish
Pages (from-to)170-178
Number of pages9
JournalJournal of Molecular Catalysis A: Chemical
Volume264
Issue number1-2
DOIs
Publication statusPublished - Mar 1 2007

Keywords

  • Alkyne hydrogenation
  • Cationic surfactant
  • Encapsulation
  • MCM-41
  • N sorption
  • Palladium
  • Selectivity
  • Transmission electron microscopy
  • Turnover frequency
  • X-ray diffraction

ASJC Scopus subject areas

  • Catalysis
  • Process Chemistry and Technology
  • Physical and Theoretical Chemistry

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