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Size-dependent microwave heating and catalytic activity of fine iron particles in the deep dehydrogenation of hexadecane

Jie, Xiangyu, Chen, Roujia, Biddle, Tara, Slocombe, Daniel R., Dilworth, Jonathan Robin, Xiao, Tiancun and Edwards, Peter P. 2022. Size-dependent microwave heating and catalytic activity of fine iron particles in the deep dehydrogenation of hexadecane. Chemistry of Materials 34 (10) , pp. 4682-4693. 10.1021/acs.chemmater.2c00630

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Abstract

Knowledge of the electromagnetic microwave radiation–solid matter interaction and ensuing mechanisms at active catalytic sites will enable a deeper understanding of microwave-initiated chemical interactions and processes, and will lead to further optimization of this class of heterogeneous catalysis. Here, we study the fundamental mechanism of the interaction between microwave radiation and solid Fe catalysts and the deep dehydrogenation of a model hydrocarbon, hexadecane. We find that the size-dependent electronic transition of particulate Fe metal from a microwave “reflector” to a microwave “absorber” lies at the heart of efficient metal catalysis in these heterogeneous processes. In this regard, the optimal particle size of a Fe metal catalyst for highly effective microwave-initiated dehydrogenation reactions is approximately 80–120 nm, and the catalytic performance is strongly dependent on the ratio of the mean radius of Fe particles to the microwave skin depth (r/δ) at the operating frequency. Importantly, the particle size of selected Fe catalysts will ultimately affect the basic heating properties of the catalysts and decisively influence their catalytic performance under microwave initiation. In addition, we have found that when two or more materials─present as a mechanical mixture─are simultaneously exposed to microwave irradiation, each constituent material will respond to the microwaves independently. Thus, the interaction between the two materials has been found to have synergistic effects, subsequently contributing to heating and improving the overall catalytic performance.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Engineering
Additional Information: CC-BY
Publisher: American Chemical Society
ISSN: 0897-4756
Funders: EPSRC
Date of First Compliant Deposit: 23 May 2022
Date of Acceptance: 4 May 2022
Last Modified: 22 Jun 2022 13:14
URI: https://orca.cardiff.ac.uk/id/eprint/149816

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