Characterization of carbon anode protected by low boron level : an attempt to understand carbon−boron inhibitor mechanism

Authors: Ishak, RamziLaroche, Gaétan; Lamonier, Jean-François; Ziegler, Donald PaulDarvishi Alamdari, Houshang
Abstract: Several chemical reactions occur during the electrolysis of alumina in the Hall–Héroult process resulting in a significant overconsumption of the carbon anode. Carbon oxidation with oxygen is one of these reactions. The inhibition of this reaction by the application of protective layers on the anode can be an effective technique to reduce carbon consumption. Boron impregnation was shown to suppress this reaction. In this study, very low boron content has been impregnated on the anode, and several characterization methods have been performed to understand the protection mechanism of such a low boron concentration during the oxidation reaction of anodes. An air reactivity test of boron-impregnated anodes has been performed at temperatures between 400 and 600 °C. The samples were characterized using XPS, Raman spectroscopy, XRD, XRF, porosimetry, and thermogravimetric analysis (TGA). TGA revealed that the total number of interactions between oxygen atoms and carbon active sites was reduced, decreasing the pre-exponential factor. Time-of-flight secondary ion mass spectroscopy (ToF-SIMS) has been employed as a highly sensitive surface characterization method to identify chemical forms of boron on the anode. It has been confirmed that boron blocks active sites of carbon by creating boron–carbon bonds, thus reducing the interaction of carbon active sites with oxygen.
Document Type: Article de recherche
Issue Date: 19 July 2017
Open Access Date: 23 July 2019
Document version: AM
This document was published in: ACS Sustainable Chemistry & Engineering, Vol 5 (8), 6700-6706 (2017)
American Chemical Society
Alternative version: 10.1021/acssuschemeng.7b00945
Collection:Articles publiés dans des revues avec comité de lecture

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