Green Catalytic Degradation of Ethyl Acetate Incurred by Strong Interaction Between PdO and Ce0.5Co0.5 Support at Low Temperature

Strong metal-support interaction (SMSI) in environmental catalysis: Mechanisms, application, regulation strategies, and breakthroughs

The strong metal-support interaction (SMSI) in supported catalysts plays a dominant role in catalytic degradation, upgrading, and remanufacturing of environmental pollutants. Previous studies have shown that SMSI is crucial in supported catalysts' activity and stability. However, for redox reactions catalyzed in environmental catalysis, the enhancement mechanism of SMSI-induced oxygen vacancy and electron transfer needs to be clarified. Additionally, the precise control of SMSI interface sites remains to be fully understood. Here we provide a systematic review of SMSI's catalytic mechanisms and control strategies in purifying gaseous pollutants, treating organic wastewater, and valorizing biomass solid waste. We explore the adsorption and activation mechanisms of SMSI in redox reactions by examining interfacial electron transfer, interfacial oxygen vacancy, and interfacial acidic sites. Furthermore, we develop a precise regulation strategy of SMSI from systematical perspectives of interface effect, crystal facet effect, size effect, guest ion doping, and modification effect. Importantly, we point out the drawbacks and breakthrough directions for SMSI regulation in environmental catalysis, including partial encapsulation strategy, size optimization strategy, interface oxygen vacancy strategy, and multi-component strategy. This review article provides the potential applications of SMSI and offers guidance for its controlled regulation in environmental catalysis.

Strong metal-support interactions between atomically dispersed Ru and CrO x for improved durability of chlorobenzene oxidation

In this work, two single-atom catalysts (SACs) with atomically dispersed RuO₂ supported on CrO _x were successfully synthesized with a simple reduction strategy for the efficient catalytic oxidation of chlorobenzene (CB). With characterizations like Cs-corrected STEM, XPS, H₂-TPR, and O₂-TPD, the structure-activity relationship is addressed. The noble metal precursor Ru³⁺ was anchored with different oxygen species and exposed facets based on the physicochemical properties of catalyst supports. Based on the analysis results, the Ru³⁺ precursor could be mainly anchored into the surface lattice oxygen of Cr₂O₃-M over high-index facets (223) and adsorbed oxygen of Cr₂O₃-P over low-index facets (104), where the precursor Ru³⁺ was all oxidized to RuO₂ when being anchored with the oxygen species of Cr₂O₃-M and Cr₂O₃-P, respectively according to XPS analysis. There is a stronger metal-support interaction (SMSI) between Ru ions and the surface lattice oxygen of Cr₂O₃-M, according to H₂-TPR and O₂-TPD characterizations. Further, the catalytic performance for CB combustion at a high space velocity of 120 000 mL (g^-1 h^-1) was tested, and 1RuCr₂O₃-M performed better than 1RuCr₂O₃-P in both durability and activity. This could be attributed to the SMSI between single-atom Ru and the lattice oxygen of the 1RuCr₂O₃-M catalyst and the abundant active sites from the exposed high-index facets. The study provided a novel synthesis strategy for Ru-based SACs with SMSI effect, and the good durability of the catalyst (1RuCr₂O₃-M) extended the great potential for practical application.

Removal of ethyl acetate in air by using different types of corona discharges generated in a honeycomb monolith structure coated with Pd/γ-alumina

A method based on the corona discharge produced by high voltage alternating current (AC) and direct current (DC) over a Pd/γ-Al₂O₃ catalyst supported on a honeycomb structure monolith was developed to eliminate ethyl acetate (EA) from the air at atmospheric pressure. The characteristics of the AC and DC corona discharge generated inside the honeycomb structure monolith were investigated by varying the humidity, gas hourly space velocity (GHSV), and temperature. The results showed that the DC corona discharge is more stable and easily operated at different operating conditions such as humidity, GHSV, and gas temperature compared to the AC discharge. At a given applied voltage, the EA conversion in the DC honeycomb catalyst discharge is, therefore, higher compared with that in the AC honeycomb catalyst discharge (e.g., 96% of EA conversion compared with approximately 68%, respectively, at 11.2 kV). These new results can open opportunities for wide applications of DC corona discharge combined with honeycomb catalysts to VOC treatment.

Effect of impregnation sequence of Pd/Ce/γ-Al2O3 sorbents on Hg0 removal from coal derived fuel gas

This study attempted to investigate the effect of impregnation sequence of the Pd/Ce/γ-Al₂O₃ sorbents on Hg⁰ removal. To this end, five kinds of sorbents were prepared and tested in simulated coal derived fuel gas (N₂-H₂-CO-H₂S-Hg), including Pd/γ-Al₂O₃, Ce/γ-Al₂O₃ and three kinds of Pd-based sorbents with Ce impregnation on γ-Al₂O₃ substrate. The tests were conducted at 250 and 300 °C respectively. According to the results, bimetallic Ce-Pd/γ-Al₂O₃ sorbent prepared by simultaneously impregnating Pd and Ce showed much higher and more stable removal efficiency of Hg⁰ than the other three kinds of sorbents. The Hg⁰ removal efficiency of Ce-Pd/γ-Al₂O₃ sorbent reached above 98% within 480 min at 250 °C and 91% within 200 min at 300 °C. Characterization results indicated that the sorbent Ce-Pd/γ-Al₂O₃ prepared by the co-impregnation method had bigger specific surface area (216.6 m²/g) than the other three kinds of Pd-based sorbents. The content Pd and Ce on the sorbent Ce-Pd/γ-Al₂O₃ surface is 0.21% and 0.61%, which proved higher than that of the other three kinds of Pd-based sorbents, and observation from STEM-XEDS maps showed it demonstrated the highest dispersion. It is found that Ce is likely to promote the dispersion of Pd on the support surface during the preparation of the sorbent under the co-impregnation method. Meanwhile, Ce enhanced the H₂S resistance of the sorbent. Thereby, Ce-Pd/γ-Al₂O₃ sorbent is found to have the optimal performance of mercury removal. In this study, the Hg⁰ removal mechanism of the Pd/Ce/γ-Al₂O₃ sorbents in the simulated coal derived fuel gas was also elaborated.

Catalytic oxidation of ethyl acetate over LaBO3 (B = Co, Mn, Ni, Fe) perovskites supported silver catalysts

A series of silver catalysts supported on lanthanum based perovskites LaBO₃ (B = Co, Mn, Ni, Fe) were synthesized and evaluated in the catalytic oxidation of ethyl acetate. XRD, BET, TEM/HRTEM, HAADF-STEM, XPS and H₂-TPR were conducted, and the results indicate that redox activity of the catalysts is of great importance to the oxidation reaction. Activity tests demonstrated that Ag/LaCoO₃ was more active than the other samples in ethyl acetate oxidation. Moreover, the CO₂ selectivity, CO_x yields and byproduct distributions for all catalysts were studied, and Ag/LaCoO₃ showed the best catalytic performance. Besides, Ag/LaCoO₃ also showed excellent catalytic activity for other OVOCs.

Ag/LaBO₃ (B = Co, Mn, Ni, Fe) were investigated for the catalytic oxidation of ethyl acetate, and Ag/LaCoO₃ showed the best catalytic performance.