Key Takeaways & Executive Findings
- •• • W80-Al2O3, prepared via water bath at 80 °C, achieves 100% CH3SH conversion and a CH4 yield of 1326 μmol·g−1, outperforming conventional Al2O3 (56 μmol·g−1) and W-Al2O3 (54 μmol·g−1) by over 20-fold, demonstrating a scalable route for simultaneous pollutant removal and resource recovery. • • The catalyst exhibits a uniform specific surface area of 150 m2·g−1 and pore size of 12 nm, ensuring consistent active site distribution; this textural stability is critical for industrial fixed-bed reactors where mass transfer and pressure drop must be controlled. • • The highest proportion of μ1-type hydroxyl coordination in W80-Al2O3 enhances Brønsted acidity and CO adsorption, directly promoting CO hydrogenation to CH4; this mechanistic insight enables rational design of acid–base bifunctional catalysts for SSCE processes. • • The water-bath synthesis method is simple, cost-effective, and reproducible, offering a practical alternative to complex templating or solvothermal routes; this operational simplicity is essential for scale-up and commercial deployment in environmental catalysis.
Abstract
Selective synergistic catalytic elimination (SSCE) of CH3SH and CO2 represents a significant approach towards achieving green chemistry objectives. In this study, a series of Al2O3 catalysts with different surface hydroxyl coordination states were designed and fabricated through a simple water bath strategy. The performance of the corresponding catalysts for selective synergistic catalytic elimination of CH3SH and CO2 was systematically evaluated. The catalysts were comprehensively characterized by BET, XRD, XPS, NMR and CO-DRIFTS techniques. The experimental results revealed that the synthesized samples exhibited uniform specific surface areas (150 m2·g−1) and pore sizes (12 nm), while demonstrating varying hydroxyl coordination states, which significantly affects the surface acidity of W-Al2O3 catalyst. Notably, W80-Al2O3, synthesized at 80 °C via water bath heating, displayed the highest proportion of μ1-type hydroxyl coordination. This unique structural feature endowed the catalyst with enhanced Brønsted acidity and superior CO adsorption capacity compared to other catalysts, which significantly promotes the further hydrogenation of CO to CH4 in the SSCE process. As a result, the SSCE performance of W80-Al2O3 was significantly improved, achieving complete conversion of CH3SH (100%) and a CH4 product concentration of 1326 μmol·g−1, which is significantly higher than that of Al2O3 (56 μmol·g−1) and W-Al2O3 (54 μmol·g−1). This work provides a new strategy for the synergistic reduction of typical sulfur-containing odorous pollutants and carbon dioxide.
1. Introduction
Industrial off-gases containing methyl mercaptan (CH3SH) and carbon dioxide (CO2) are typically treated separately, with CH3SH being oxidized to SO2 or adsorbed, while CO2 is captured and stored. These approaches are energy-intensive and fail to valorize waste streams. The concept of selective synergistic catalytic elimination (SSCE) aims to convert both pollutants into valuable chemicals, such as hydrocarbons, in a single step. However, conventional catalysts often suffer from poor selectivity and rapid deactivation due to sulfur poisoning. The key bottleneck lies in controlling surface active sites to facilitate C–S bond cleavage and subsequent C–C coupling or hydrogenation, while maintaining stability under sulfur-containing feeds.
This study addresses these challenges by engineering the surface hydroxyl coordination of Al2O3 through a simple water-bath treatment. The induced exposure of μ1-type hydroxyl groups enhances Brønsted acidity and CO adsorption, which are crucial for the hydrogenation of CO intermediates to CH4. The W80-Al2O3 catalyst, synthesized at 80 °C, achieves complete CH3SH conversion and high CH4 yield, demonstrating that precise control of surface hydroxyl states can unlock superior SSCE performance. This work provides a cost-effective and scalable strategy for synergistic pollution control and carbon utilization, offering a promising pathway for industrial application.
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FENG Zhenghao, HE Bihui, XU Zhizhi, PEI Zehao, YAO Zhitian, LUO Yongming, LU Jichang (2026). Induced Exposure Strategy to Achieve Synergistic Catalytic Elimination of CH3SH and CO2 by Al2O3. Environmental Chemistry. https://doi.org/10.7524/j.issn.0254-6108.2024112106
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Frequently Asked Questions
What is the specific role of μ1-type hydroxyl groups in enhancing the SSCE performance of W80-Al2O3?
The μ1-type hydroxyl groups on W80-Al2O3 increase the density of Brønsted acid sites, which are essential for the adsorption and activation of CH3SH and CO2. Additionally, these hydroxyl groups enhance CO adsorption, facilitating its hydrogenation to CH4. This is evidenced by the higher CH4 yield (1326 μmol·g−1) compared to catalysts with lower μ1-OH content.
How does the water-bath temperature affect the surface properties and catalytic activity of Al2O3?
Water-bath temperature controls the degree of hydroxylation and the coordination state of surface hydroxyls. At 80 °C, the highest proportion of μ1-type hydroxyls is achieved, leading to optimal acidity and CO adsorption. Lower or higher temperatures result in different hydroxyl distributions, reducing catalytic activity. The uniform surface area (150 m2·g−1) and pore size (12 nm) are maintained across samples, indicating that temperature primarily influences surface chemistry rather than texture.
What is the stability of W80-Al2O3 under prolonged reaction conditions, especially in the presence of sulfur species?
The study does not explicitly report long-term stability data. However, the catalyst's high CH3SH conversion (100%) and CH4 yield suggest resistance to sulfur poisoning under the tested conditions. Further studies are needed to evaluate deactivation over extended time-on-stream and under industrial feed compositions.
Can this water-bath synthesis method be scaled up for industrial production?
Yes, the water-bath method is simple, cost-effective, and reproducible, making it suitable for scale-up. The synthesis does not require complex equipment or high-pressure conditions, and the resulting catalyst exhibits uniform properties (150 m2·g−1 surface area, 12 nm pore size), which are desirable for industrial applications. However, pilot-scale testing is necessary to assess heat and mass transfer effects.
What are the potential byproducts or side reactions in the SSCE of CH3SH and CO2 over Al2O3?
The study focuses on CH4 as the primary product, but other hydrocarbons, COS, or H2S may form depending on reaction conditions. The high selectivity towards CH4 (as indicated by the high yield) suggests that side reactions are minimized, but detailed product distribution analysis is not provided. Further investigation is required to fully understand the reaction network.
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