Oxidative coupling of methane using non-stoichiometric lead hydroxyapatite catalyst mixtures
Oxidative coupling of methane using non-stoichiometric lead hydroxyapatite catalyst mixtures
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DOI：
10.1016/j.fuel.2011.08.056
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发表时间：
2012-04
期刊：
影响因子：
7.4
通讯作者：
Jai Hyun Park;D. Lee;S. Im;Yong Hee Lee;D. Suh;K. Jun;Kwan-Young Lee
中科院分区：
文献类型：
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作者：
Jai Hyun Park;D. Lee;S. Im;Yong Hee Lee;D. Suh;K. Jun;Kwan-Young Lee
羟基磷灰石铅（PbxCa 10 −x（PO 4）6（OH）2，0<x <$10）是甲烷氧化偶联（OCM）反应中最活跃的催化剂之一。在这项研究中，我们研究了沉淀的铅羟基磷灰石的OCM活性是如何与其混合物和非化学计量的属性。铅羟基磷灰石是通过在氯阴离子存在下的水沉淀和在氦背景下在1073 K下煅烧来制备的，这导致非化学计量的铅羟基磷灰石的混合物，每种都具有不同的阳离子组成（PbxCa 10 −x）。混合物可以多样化，通过热提取氯从不同氯含量的氯羟基磷灰石的氯。通过傅里叶变换红外光谱（FT-IR）、X射线衍射（XRD）、X射线荧光（XRF）和电感耦合等离子体（ICP）分析证实了磷灰石结构的形成。通过拉曼/傅立叶变换拉曼光谱分析了所制备的羟基磷灰石的非化学计量比特征。在1048 K下，固定甲烷转化率为35%的条件下，考察了催化剂的C2选择性。在所测试的催化剂中，由Pb_2Ca_8（PO_4）_6（OH）_0.5Cl_1.5脱氯得到的羟基磷灰石铅在1048 K下表现出62%的C_2选择性，C_2收率为22%。采用CO2程序升温脱附（TPD）和X射线光电子能谱（XPS）对催化剂的表面碱性进行了研究，发现催化剂的OCM活性主要与其表面碱性有关。
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 1073K, 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 C2selectivities of the prepared catalysts were evaluated at 1048K with a fixed CH4conversion of 35%. Among the tested catalysts, lead hydroxyapatite, which was obtained by removing chlorines from Pb2Ca8(PO4)6(OH)0.5Cl1.5, showed a C2selectivity of 62%, and achieved a C2yield of 22% at 1048K. 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.