Catalytic consequences of cation and anion substitutions on rate and mechanism of oxidative coupling of methane over hydroxyapatite catalysts

FUEL

卷:191

Article

Oh, Su Cheun¹  Lei, Yu²  Chen, Huiyong³  Liu, Dongxia¹ 

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

[2] Univ Alabama, Dept Chem & Mat Engn, 301 Sparkman Dr, Huntsville, AL 35899 USA

[3] Northwest Univ, Sch Chem Engn, Xian 710069, Shaanxi, Peoples R China

关键词: Hydroxyapatite;    Anion and cation substitution;    Oxidative coupling of methane;    Pb-hydroxyapatite;    Kinetics;   

DOI  :  10.1016/j.fuel.2016.11.106

来源: Elsevier

【 摘 要 】

The identity and rate constants of elementary steps in primary reactions of oxidative coupling of methane (OCM) over Pb2+ and/or F- substituted hydroxyapatite (HAP, Pb-HAP, HAP-F, and Pb-HAP-F) catalysts have been studied. The rigorous kinetics analysis suggests that HAP and HAP-F initiated the reaction between adsorbed methane and O-2 following Langmuir-Hinshelwood behavior. The Pb-HAP and Pb-HAP-F, however, enabled the reaction between gaseous methane and adsorbed O-2 in the Eley-Rideal mechanism. The F- substitution of OH- weakened both O-2 adsorption and C-H bond activation, leading to low methane conversion and slightly higher C2H6 selectivity. The substitution of Ca2+ by Pb2+ weakened both methane and oxygen adsorptions, but maintained C-H bond activation and raised C2H6 selectivity. The present analysis explored for the first time the effects of cation and/or anion in HAP on OCM reactions in which the analysis has been detailed and quantified in the nature of the mechanism-based kinetic models. (C) 2016 Elsevier Ltd. All rights reserved.

【 授权许可】

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