Novel Pt/Mg(In)(Al)O catalysts for ethane and propane dehydrogenation

Pingping Sun, Georges Siddiqi, William C. Vining, Miaofang Chi, Alexis T. Bell

Research output: Contribution to journalArticlepeer-review

223 Scopus citations

Abstract

Catalysts for the dehydrogenation of light alkanes were prepared by dispersing Pt on the surface of a calcined hydrotalcite-like support containing indium, Mg(In)(Al)O. Upon reduction in H2 at temperatures above 673 K, bimetallic particles of PtIn are observed by TEM, which have an average diameter of 1 nm. Analysis of Pt LIII-edge extended X-ray absorption fine structure (EXAFS) data shows that the In content of the bimetallic particles increases with increasing bulk In/Pt ratio and reduction temperature. Pt LIII-edge X-ray absorption near edge structure (XANES) indicates that an increasing donation of electronic charge from In to Pt occurs with increasing In content in the PtIn particles. The activity and selectivity of the Pt/Mg(In)(Al)O catalysts for ethane and propane dehydrogenation reactions are strongly dependent on the bulk In/Pt ratio. For both reactants, maximum activity was achieved for a bulk In/Pt ratio of 0.48, and at this In/Pt ratio, the selectivity to alkene was nearly 100%. Coke deposition was observed after catalyst use for either ethane or propane dehydrogenation, and it was observed that the alloying of Pt with In greatly reduced the amount of coke deposited. Characterization of the deposit by Raman spectroscopy indicates that the coke is present as highly disordered graphite particles <30 nm in diameter. While the amount of coke deposited during ethane and propane dehydrogenation are comparable, the effects on activity are dependent on reactant composition. Coke deposition had no effect on ethane dehydrogenation activity, but caused a loss in propane dehydrogenation activity. This difference is attributed to the greater ease with which coke produced on the surface of PtIn nanoparticles migrates to the support during ethane dehydrogenation versus propane dehydrogenation.

Original languageEnglish
Pages (from-to)165-174
Number of pages10
JournalJournal of Catalysis
Volume282
Issue number1
DOIs
StatePublished - Aug 15 2011

Funding

This work was supported by Chevron Energy and Technology Company . A portion of this research was conducted at the SHaRE User Facility, which is sponsored by the Division of Scientific User Facilities , Office of Basic Energy Sciences, US Department of Energy.

Keywords

  • Dehydrogenation
  • Mg(In)(Al)O
  • Pt bimetallic catalyst
  • STEM
  • XAFS

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