Oxidative coupling of methane using non-stoichiometric lead hydroxyapatite catalyst mixtures

Jai Hyun Park, Dae Won Lee, Sung Woo Im, Yong Hee Lee, Dong Jin Suh, Ki Won Jun, Kwan Young Lee

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20 Citations (Scopus)

Abstract

Lead hydroxyapatite (Pb xCa 10-x(PO 4) 6(OH) 2, 0 < x ≤ 10) is one of the most active catalysts for oxidative coupling of methane (OCM) to produce ethane and ethylene from natural gas (methane). In this study, we investigated how the OCM activity of a precipitated lead hydroxyapatite is associated with its mixture and non-stoichiometric properties. Lead hydroxyapatite was prepared through aqueous precipitation in the presence of chlorine anions and calcination under helium background at 1073 K, which resulted in a mixture of non-stoichiometric lead hydroxyapatites, each having a different cationic composition (Pb xCa 10-x). The mixture could be diversified by extracting the chlorines thermally from the chloro-hydroxyapatites of various chlorine contents. The formation of an apatite structure was confirmed through Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), X-ray fluorescence (XRF) and inductively coupled plasma (ICP) analyses. The non-stoichiometric characters of the prepared hydroxyapatites were analyzed through Raman/FT-Raman spectroscopy. The C 2 selectivities of the prepared catalysts were evaluated at 1048 K with a fixed CH 4 conversion of 35%. Among the tested catalysts, lead hydroxyapatite, which was obtained by removing chlorines from Pb 2Ca 8(PO 4) 6(OH) 0.5Cl 1.5, showed a C 2 selectivity of 62%, and achieved a C 2 yield of 22% at 1048 K. The OCM activity of the catalyst was mainly associated with its surface basicity, which was investigated using CO 2-temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) analyses.

Original languageEnglish
Pages (from-to)433-439
Number of pages7
JournalFuel
Volume94
DOIs
Publication statusPublished - 2012 Apr 1

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Keywords

  • Ethylene
  • Lead hydroxyapatite
  • Natural gas
  • Oxidative coupling of methane
  • Partial oxidation

ASJC Scopus subject areas

  • Fuel Technology
  • Energy Engineering and Power Technology
  • Chemical Engineering(all)
  • Organic Chemistry

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