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Inhibiting the interaction between FeO and Al<inf>2</inf>O<inf>3</inf> during chemical looping production of hydrogen

Liu, W and Ismail, M and Dunstan, MT and Hu, W and Zhang, Z and Fennell, PS and Scott, SA and Dennis, JS (2015) Inhibiting the interaction between FeO and Al<inf>2</inf>O<inf>3</inf> during chemical looping production of hydrogen. RSC Advances, 5. pp. 1759-1771.

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Abstract

© The Royal Society of Chemistry 2015. Hydrogen of high purity can be produced by chemical looping using iron oxide as an oxygen carrier and making use of the reaction between steam and either iron or FeO. However, this process is viable only if the iron oxide can be cycled between the fully-oxidised and fully-reduced states many times. This can be achieved if the iron oxide is supported on refractory oxides such as alumina. Unfortunately, the interaction between alumina and oxides of iron to form FeAl 2 O 4 hinders the kinetics of the reactions essential to the production of hydrogen, viz. the reduction of Fe(ii) to metallic iron by a mixture of CO and CO 2 prior to the oxidation by steam. Here, oxygen carriers containing Fe 2 O 3 and Al 2 O 3 were doped with Na 2 O and, or, MgO, in order to inhibit the formation of FeAl 2 O 4 by forming NaAlO 2 or MgAl 2 O 4 , respectively. The performance of the modified oxygen carriers for producing hydrogen, i.e. cyclic transitions between Fe 2 O 3 (or Fe 3 O 4 ) and metallic Fe at 1123 K were investigated. It was found that the interaction between FeO and Al 2 O 3 was successfully mitigated in an oxygen carrier containing Mg, with an Al: Mg ratio of 2, resulting in consistently stable and high capacity for producing hydrogen by chemical looping, whether or not the material was oxidised fully in air in each cycle. However, the oxygen carrier without Mg only remained active when a step to oxidise the sample in air was included in each cycle. Otherwise it progressively deactivated with cycling, showing substantial interaction between Al 2 O 3 and oxides of Fe. This journal is

Item Type: Article
Subjects: UNSPECIFIED
Divisions: Div A > Energy
Depositing User: Cron Job
Date Deposited: 17 Jul 2017 18:59
Last Modified: 14 Sep 2017 01:25
DOI: