An in situ XAS study of the cobalt rhenium catalyst for ammonia synthesis

Mathisen, K., Kirste, K. G., Hargreaves, J. S.J. , Laassiri, S., McAulay, K., McFarlane, A. R. and Spencer, N. A. (2018) An in situ XAS study of the cobalt rhenium catalyst for ammonia synthesis. Topics in Catalysis, 61(3-4), pp. 225-239. (doi:10.1007/s11244-018-0892-7)

[img]
Preview
Text
156969.pdf - Published Version
Available under License Creative Commons Attribution.

2MB

Abstract

A cobalt rhenium catalyst active for ammonia synthesis at 400 °C and ambient pressure was studied using in situ XAS to elucidate the reducibility and local environment of the two metals during reaction conditions. The ammonia reactivity is greatly affected by the gas mixture used in the pre-treatment step. Following H2/Ar pre-treatment, a subsequent 20 min induction period is also observed before ammonia production occurs whereas ammonia production commences immediately following comparable H2/N2 pre-treatment. In situ XAS at the Co K-edge and Re LIII-edge show that cobalt initiates reduction, undergoing reduction between 225 and 300 °C, whereas reduction of rhenium starts at 300 °C. The reduction of rhenium is near complete below 400 °C, as also confirmed by H2-TPR measurements. A synergistic co-metal effect is observed for the cobalt rhenium system, as complete reduction of both cobalt and rhenium independently requires higher temperatures. The phases present in the cobalt rhenium catalyst during ammonia production following both pre-treatments are largely bimetallic Co–Re phases, and also monometallic Co and Re phases. The presence of nitrogen during the reduction step strongly promotes mixing of the two metals, and the bimetallic Co–Re phase is believed to be a pre-requisite for activity.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Laassiri, Dr Said and Hargreaves, Professor Justin and McFarlane, Dr Andrew and McAulay, Dr Kate
Authors: Mathisen, K., Kirste, K. G., Hargreaves, J. S.J., Laassiri, S., McAulay, K., McFarlane, A. R., and Spencer, N. A.
College/School:College of Science and Engineering > School of Chemistry
Journal Name:Topics in Catalysis
Publisher:Springer
ISSN:1022-5528
ISSN (Online):1572-9028
Published Online:12 February 2018
Copyright Holders:Copyright © 2018 The Authors
First Published:First published in Topics in Catalysis 61(3-4):225-239
Publisher Policy:Reproduced under a Creative Commons License

University Staff: Request a correction | Enlighten Editors: Update this record

Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
652781First principles design of novel ammonia synthesis catalystsJustin HargreavesEngineering and Physical Sciences Research Council (EPSRC)EP/L02537X/1CHEM - CHEMISTRY
591351Controlled ensemble size and elucidation of structure-sensitivity: a new approach in nitride catalysisJustin HargreavesEngineering and Physical Sciences Research Council (EPSRC)EP/J018384/1CHEM - CHEMISTRY

Downloads per month over past year

View more statistics