Highly Engineered Cr-In/H-SSZ-39 Catalyst for Enhanced Performance in CH<sub>4</sub>-SCR of NO<i><sub>x</sub></i>
The selective catalytic reduction of NO<i><sub>x</sub></i> with CH<sub>4</sub> (CH<sub>4</sub>-SCR) holds the potential to simultaneously abate harmful NO<i><sub>x</sub></i> and CH<sub>4</sub> greenhouse gases. In th...
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| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-06-01
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| Series: | Molecules |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1420-3049/30/13/2691 |
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| Summary: | The selective catalytic reduction of NO<i><sub>x</sub></i> with CH<sub>4</sub> (CH<sub>4</sub>-SCR) holds the potential to simultaneously abate harmful NO<i><sub>x</sub></i> and CH<sub>4</sub> greenhouse gases. In this study, a series of bimetallic M-In/H-SSZ-39 catalysts (where M represents Cr, Co, Ce, and Fe) were prepared via an ion exchange method and subsequently evaluated for their CH<sub>4</sub>-SCR activity. The influences of the preparation parameters, including the metal ion concentration and calcination temperature, as well as the operating conditions, such as the CH<sub>4</sub>/NO ratio, O<sub>2</sub> concentration, water vapor content, and gas hourly space velocity (GHSV), on the catalytic activity of the optimal Cr-In/H-SSZ-39 catalyst were meticulously examined. The results revealed that the Cr-In/H-SSZ-39 catalyst exhibited peak CH<sub>4</sub>-SCR catalytic performance when the Cr(NO<sub>3</sub>)<sub>3</sub> concentration was 0.0075 M, the In(NO<sub>3</sub>)<sub>3</sub> concentration was 0.066 M, and the calcination temperature was 500 °C. Under optimal operating conditions, namely GHSV of 10,000 h<sup>−1</sup>, 400 ppm NO, 800 ppm CH<sub>4</sub>, 15 vol% O<sub>2</sub>, and 6 vol% H<sub>2</sub>O, the NO<i><sub>x</sub></i> conversion rate reached 93.4%. To shed light on the excellent performance of Cr-In/H-SSZ-39 under humid conditions, a comparative analysis of the crystalline phase, chemical composition, pore structure, surface chemical state, surface acidity, and redox properties of Cr-In/H-SSZ-39 and In/H-SSZ-39 was conducted. The characterization results indicated that the incorporation of Cr into In/H-SSZ-39 enhanced its acidity and also facilitated the generation of InO<sup>+</sup> active species, which promoted the oxidation of NO and the activation of CH<sub>4</sub>, respectively. A synergistic effect was observed between Cr and In species, which significantly improved the redox properties of the catalyst. Consequently, the activated CH<sub>4</sub> could further interact with InO<sup>+</sup> to produce carbon-containing intermediates such as HCOO<sup>−</sup>, which ultimately reacted with nitrate-based intermediates to yield N<sub>2</sub>, CO<sub>2</sub>, and H<sub>2</sub>O. |
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| ISSN: | 1420-3049 |