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Catalytic Decomposition of N2O over Cu–Zn/ZnAl2O4 Catalysts

Catalysts 2017, 7(8), 236; https://doi.org/10.3390/catal7080236

Editorial
Heterogeneous Catalysis for Environmental Remediation
Department of Chemical Engineering, Curtin University, GPO Box U1987, Bentley, WA 6845, Australia
*
Authors to whom correspondence should be addressed.
Received: 11 August 2017 / Accepted: 15 August 2017 / Published: 16 August 2017
The intensive human activities in chemical industry and environmental purification urge the development of advanced protocols for green production and waste management. In environmental science, developing highly efficient and environmentally-friendly catalytic materials and systems are very favourable approaches to green chemical synthesis and remediation of contaminated air, soil, and wastewater. Therefore, unveiling the relationship between material structure/chemistry and performances in heterogeneous catalysis would provide valuable guidance for rational catalyst design as well as addressing the challenges in potential applications in environmental science. Here, we dedicate this special issue to showcasing the recent progress in fabrication and evaluation of state-of-the-art carbon/metal catalysts for green chemistry, photocatalysis, advanced oxidation processes (AOPs), and other applications in environmental technologies.
Advanced oxidative processes have been demonstrated as a powerful technique for activating superoxides producing oxidative species (free radicals) for complete degradation of organic pollutants in aqueous systems. Wang et al. [1] synthesized magnetic carbon supported manganese oxides (Fe3O4/C/Mn), which could effectively activate peroxymonosulfate (PMS) for phenol mineralization. The redox Mn4+/Mn3+ couple is the catalytic site for radical generation and the magnetic Fe3O4 counterpart not only serves as a support but also results in easy separation of the catalyst from the water by an external magnetic field. Zhu et al. [2] developed a Co-Fe alloy catalyst which outperformed CoFe2O4 for triggering PMS to evolve sulfate radicals, while the formation of Co-Fe nitride crystallites significantly improved the stability in the aqueous oxidative environment. Chen et al. [3] reported a Ce-Mg/Al2O3/ozone system that exhibited great oxidative efficiency for decomposition of resistant petroleum organic wastes from the petroleum refinery industry.
Chemical synthesis usually requires a green and robust catalyst to transfer hydrocarbons to target products with desired conversion efficiency, selectivity, and stability. Zhao et al. [4] synthesized a Cu-g-C3N4/activated-carbon composites to replace the toxic mercury-based catalysts for acetylene hydrochlorination which yielded a high conversion of acetylene and great selectivity of vinyl chloride. Meanwhile, the catalyst maintained superb stability in resistance to coke deposition. Lin et al. [5] discovered that sulphated tin ion-exchanged montmorillonite (SO42−/Sn-MMT), with both Brønsted and Lewis acid sites, could catalytically convert xylose and xylan into furfural. Chung et al. [6] revealed that the acid strength and porous structure of microporous zeolites could be manipulated to achieve selective glucose conversion to decyl glucoside.
Carbon monoxide (CO) and nitrogen oxides (NOx) generated from industrial production and human activities are hazardous gases that would cause severe air pollution. The nanocomposites such as mesoporous CuO-TiO nanotubes (Zedan et al. [7]) and CuO nanorods-reduced graphene oxide (Wang et al. [8]) were developed for catalytic oxidation of CO to CO2 at low temperatures. Di and co-workers [9] discovered that the thermal activation atmosphere dramatically impacted the catalytic activity of CuBTC MOF for CO oxidation. Besides, mixed metal oxides of Fe-W-Ce (Stahl et al. [10]) and V2O5-WO3/TiO2 (Qi et al. [11]) could be utilized for selectively converting NOx with NH3 into harmless N2 and water. The reduction of nitrous oxide (N2O) and oxidative dehydrogenation of ethane to ethylene could be simultaneously achieved on Cr/Al2O3 (Zhang et al. [12]). It was also discovered that N2O could be directly decomposed on Cu-Zn/ZuAl2O4 (Zeng et al. [13]) and Cu-Zn/γ-Al2O3 (Zhang et al. [14]).
Developing photocatalysts for efficient utilization of solar energy would contribute to a sustainable future for the human race. Truppi et al. [15] conducted a comprehensive review of the recent progress in novel TiO2-based nanocomposites as visible-light-driven photocatalysts for versatile environmental applications. The mesoporous TiO2/SiO2 composites from a biotemplating method (Yan et al. [16]) and TiO2-impregnated porous silica tubes (Hayashi et al. [17]) have been demonstrated as outstanding photocatalysts for dye purification under UV irradiation. Two/three-unit hybrid nanomaterials of MoS2/TiO2 nanobelts (Liu et al. [18]), three-dimensional WO3-TiO2 nanoflowers (Lee et al. [19]) and TiO2/RGO/Ag (Tian et al. [20]) were constructed for photocatalytic Cr(VI) reduction, photo-oxidation of toxic aromatic volatile compounds, and photodegradation of methylene blue, respectively. The superior photocatalytic activity of the composites compared with the single compounds was due to the enhanced light absorption, improved charge separation efficiency, and optimized band structure of the semiconductors. Photocatalysts beyond TiO2 were also explored in this special issue. Shu et al. [21] reported that immobilized ZnO/Vis could be applied for decomposition of orange G in wastewater. Meng et al. [22] prepared ZnCr layered double hydroxides (LDHs) with salen-metal complex (M = Co or Ni) intercalation which exhibited much better photocatalytic activity than traditional LDHs. Additionally, layered perovskite K2La2Ti3O10 was modified with a Cu2+ iron-exchange (Pang et al. [23]) for mineralization of chlorobenzene in the presence of CO2 under simulated solar light irradiation.
Overall, this special issue covers state-of-the-art heterogeneous catalysis for applications in environmental science which would contribute to addressing technical problems for material design as well as underpinning the mechanistic insights of environmental catalysis. The guest editors would like to express their appreciation for the professional assistance from the editorial team and for the excellent research findings from all the authors which made this issue a great success.

Author Contributions

S.W. wrote the background and aims of this special issue; X.D. briefly categorized and summarized the research findings in this issue.

Conflicts of Interest

The authors declare no conflict of interest.

References

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