Influences of cation and anion substitutions on oxidative coupling of methane over hydroxyapatite catalysts

FUEL

卷:167

Article

Oh, Su Cheun¹  Wu, Yiqing¹  Tran, Dat T.²  Lee, Ivan C.²  Lei, Yu³  Liu, Dongxia¹ 

[1] Univ Maryland, Dept Chem & Biomol Engn, College Pk, MD 20742 USA

[2] US Army, Res Lab, RDRL SED E, Adelphi, MD 20783 USA

[3] Univ Alabama, Chem & Mat Engn, Huntsville, AL 35899 USA

关键词: Hydroxyapatite;    Membrane reactor;    Anion and cation substitution;    Methane;    Oxidative coupling;   

DOI  :  10.1016/j.fuel.2015.11.058

来源: Elsevier

【 摘 要 】

Lead substituted hydroxyapatite (Pb-HAP) has been an active catalyst for oxidative coupling of methane (OCM) reactions. CO32- substituted HAP (HAP-CO3) has showed enhanced oxide ion conductivity than bare HAP in high temperature solid oxide fuel cells. Substitutions for both cations and anions in HAP structure (Pb-HAP-CO3) are promising to integrate the catalytic property of Pb-HAP and oxide ion conductive property of HAP-CO3 into one apatite-based ceramic material that can be manufactured into membrane reactors for possessing CH4 activation and O-2 permeation capabilities for efficient OCM reactions. In this work, the effects of substitutions for both cation (Pb2+) and anion (CO32-) in HAP structure on OCM reactions were studied. The composition and physicochemical properties of HAP catalysts were changed by the cation and anion substitutions, respectively, and as consequences, they influenced the catalytic performances of HAP structure in OCM reactions. The selectivity to C-2 (ethylene and ethane) products increased in the order of HAP-CO3 < HAP < Pb-HAP-CO3 < Pb-HAP, while Pb-HAP-CO3 showed the best stability and comparable C-2 yield (under optimized reaction conditions) to Pb-HAP catalyst. Under different reaction temperature and/or CH4/O-2 ratio in the OCM reactions, the CH4 conversion and C-2 or COx (CO and CO2) selectivity showed a strong dependence on the composition of HAP-based catalysts. The present study forms a basis for understanding of the correlations between the composition, structure, and catalytic performance of HAP and other apatite structured catalysts, which are potential membrane materials for OCM reactions in membrane reactors. (C) 2015 Elsevier Ltd. All rights reserved.

【 授权许可】

Free