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Open AccessArticle

Effect of Hydrazine Pretreatment on the Activity, Stability and Active Sites of Cobalt Species for Preferential Oxidation (PROX) of CO in H2-Rich Stream

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Faculty of Science and Agriculture, School of Physical and Mineral Science, Department of Chemistry, University of Limpopo, Private Bag x1106, Sovenga 0727, South Africa
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Faculty of Science and Agriculture, School of Physical and Mineral Science, Department of Physics, University of Limpopo, Private Bag x1106, Sovenga 0727, South Africa
*
Author to whom correspondence should be addressed.
Chemistry 2019, 1(1), 164-179; https://doi.org/10.3390/chemistry1010011
Received: 8 August 2019 / Revised: 10 October 2019 / Accepted: 15 October 2019 / Published: 22 October 2019
(This article belongs to the Section Catalysis)
The as-prepared (Co3O4) and hydrazine-treated (Co3O4(H)) cobalt catalysts were prepared using the precipitation method and evaluated at a temperature range of 40–220 °C for preferential oxidation (PROX) of CO in excess hydrogen. An improved surface reducibility with smaller crystallite size was noted on hydrazine-treated cobalt species (i.e., Co3O4(H) catalyst), which indicates some surface transformation. This finding correlates with the surface roughness formation (as depicted by scanning electron microscope (SEM) and transmission electron microscope (TEM) data), which was further confirmed by an increase in the Brunauer–Emmett–Teller (BET) surface area. The mesoporous structure of the Co3O4(H) catalyst remained intact, as compared to that of the Co3O4 catalyst. Interestingly, the in situ treatment of the standalone Co3O4(H) catalyst decreased the maximum CO conversion temperature (T100%) from 160 °C (over Co3O4) to 100 °C, with good selectivity. The Co3O4(H) catalyst showed good stability, with approximately 85% CO conversion at 100 °C for 21 h, as compared to a faster deactivation of the Co3O4 catalyst. However, the Co3O4(H) catalyst was unstable in both CO2 and the moisture environment. Based on the evaluation of spent hydrazine-treated (CoO(H)) cobalt catalyst, the high PROX activity is associated with the formation of Co3+ species as confirmed by X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), and temperature-programmed reduction (TPR) data. View Full-Text
Keywords: PROX; Co3O4; CoO(H); Co3O4(H); catalyst; CO conversion and selectivity PROX; Co3O4; CoO(H); Co3O4(H); catalyst; CO conversion and selectivity
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Mhlaba, R.; Mosuang, T.; Magadzu, T. Effect of Hydrazine Pretreatment on the Activity, Stability and Active Sites of Cobalt Species for Preferential Oxidation (PROX) of CO in H2-Rich Stream. Chemistry 2019, 1, 164-179.

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