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Continuous regime of chemical-looping combustion (CLC) and chemical-looping with oxygen uncoupling (CLOU) reactivity of CuO oxygen carriers

Paper ID Volume ID Publish Year Pages File Format Full-Text
45705 46421 2015 13 PDF Available
Title
Continuous regime of chemical-looping combustion (CLC) and chemical-looping with oxygen uncoupling (CLOU) reactivity of CuO oxygen carriers
Abstract

•CLOU, CLC and Cu-catalyzed reactions are all significant even at high temperatures.•A sequential CuO reduction scheme is shown, with Cu2O as the intermediate phase.•A kinetic scheme is proposed applicable to the entire regime of CLC and CLOU of CuO.

Chemical-looping with CuO and CH4 presents an interesting reaction system, in which CuO participates in heterogeneous reduction reactions with the gaseous fuel, as well as oxygen uncoupling and catalytic reactions. Therefore, there exists a temperature dependent competition between the processes typically termed as chemical-looping combustion (CLC) and chemical-looping with oxygen uncoupling (CLOU). The objective of this work is to carry out an assessment of the rates of all the relevant reactions involved at various temperatures and thus to show a continuous regime, where the CLC reactions domination proceeds to CuO oxygen uncoupling dominance, as temperature increases. The possible reactions occurring in CuO-based chemical-looping include heterogeneous reactions with Cu oxides, CuO oxygen uncoupling and Cu-catalyzed reactions. The significance of each individual reaction and the corresponding kinetic parameters are experimentally examined in a bench-scale fixed-bed, alternating-flow chemical-looping reactor at conditions relevant to both CLC and CLOU. In situ XRD characterization is used to determine the phases in which Cu exists during reduction and oxidation and possible interactions with the SiO2 oxygen carrier support. A kinetic scheme is proposed, applicable to the entire regime of CLC and CLOU, which is validated with in-house experiments and experimental data from the literature, at conditions where heterogeneous reduction, oxygen uncoupling, Cu-catalyzed, and gas phase oxidation reactions present significant contributions.

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Keywords
Chemical-looping; Chemical-looping with oxygen uncoupling; Cu catalyzed reactions; CuO reduction
First Page Preview
Continuous regime of chemical-looping combustion (CLC) and chemical-looping with oxygen uncoupling (CLOU) reactivity of CuO oxygen carriers
Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volumes 166–167, May 2015, Pages 132–144
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis