Park, Jai Hyun Lee, Dae-Won Im, Sung-Woo Lee, Yong Hee Suh, Dong-Jin Jun, Ki-Won Lee, Kwan-Young 2024-01-20T15:03:36Z 2024-01-20T15:03:36Z 2021-09-05 2012-04 0016-2361 https://pubs.kist.re.kr/handle/201004/129389 Lead hydroxyapatite (PbxCa10-x(PO4)(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 (PbxCa10-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 CH4 conversion of 35%. Among the tested catalysts, lead hydroxyapatite, which was obtained by removing chlorines from Pb2Ca8(PO4)(6)(OH)(0.5)Cl-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 CO2-temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) analyses. (C) 2011 Elsevier Ltd. All rights reserved. English ELSEVIER SCI LTD SUBSTITUTED HYDROXYAPATITE CALCIUM HYDROXYAPATITE OXIDE CATALYSTS EARTH-OXIDES STRONTIUM CO2 BASICITY GAS Oxidative coupling of methane using non-stoichiometric lead hydroxyapatite catalyst mixtures Article 10.1016/j.fuel.2011.08.056 1 FUEL, v.94, no.1, pp.433 - 439 FUEL 94 1 433 439 scie scopus 000300497300052 2-s2.0-84856717701 Energy & Fuels Engineering, Chemical Energy & Fuels Engineering Article SUBSTITUTED HYDROXYAPATITE CALCIUM HYDROXYAPATITE OXIDE CATALYSTS EARTH-OXIDES STRONTIUM CO2 BASICITY GAS Natural gas Partial oxidation Oxidative coupling of methane Ethylene Lead hydroxyapatite