Vapour phase deep oxidation of chlorinated hydrocarbons catalyzed by pillared bentonites

doi:10.1016/1381-1169(94)00083-2

Journal of Molecular Catalysis A: Chemical

Volume 97, Issue 3, 16 April 1995, Pages 139-143

https://doi.org/10.1016/1381-1169(94)00083-2 Get rights and content

Abstract

A natural sodium bentonite was pillared with aluminum, aluminum-iron, aluminum-ruthenium and aluminum-chromium polyoxocations. The clays were characterized by X-ray diffraction, ESCA and nitrogen adsorption. All the clays resulted to varying degrees in active catalyst for the deep oxidation of volatile chlorinated hydrocarbons (CVOCs) in the 300–400°C temperature range. The chromium pillared clay was by far the most active and stable catalyst, with more than 99% hydrocarbon conversion at 300°C. The catalytic activity trend is discussed as a function of the Brønsted acidity and of the oxidizing power of the metallic couple.

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One of the most promising emergent technologies for the elimination of CVOCs is catalytic oxidation, which can operate at lower temperature [7] and has a higher efficiency [8] than competing technologies [9]. Deep oxidation means total oxidation of chlorinated hydrocarbons, results in the final products such as carbon dioxide and hydrochloric acid [10]. The key factor in this technology is the development of more efficient catalysts for the oxidation of CVOCs, and the creation of a system of suitable catalysts which can realize the deep oxidation of CVOCs to CO2 and H2O without the formation of harmful byproducts [11,12].
Core-shell structured Co₃O₄@ZSM-5 catalysts were successfully synthesized by a simple two-step microwave hydrothermal method and used for the catalytic oxidation of dichloromethane (DCM). Co₃O₄@ZSM-5 catalysts exhibited better CO₂ yield and lower byproduct yield than pristine Co₃O₄ and ZSM-5. For pure ZSM-5 and Co₃O₄, dechlorinated byproducts CH₃Cl formed more readily over ZSM-5 due to its higher acidity and lower redox property, while polychlorinated byproducts (CHCl₃ and CCl₄) formed more readily over Co₃O₄ due to its lower acidity and higher redox property. Thanks to its core-shell structure, Co₃O₄@ZSM-5 exhibited appropriate redox ability and a suitable distribution of acid sites, possibly explaining its lower byproduct yields and more efficient formation and desorption of HCl and Cl₂. In situ Fourier transform infrared (FTIR) spectra analysis indicated that formaldehyde, formate and methoxy species were the main intermediates of the catalytic oxidation reaction. A pathway for the catalytic oxidation of DCM on 1.5-Co₃O₄@ZSM-5 was proposed based on the DCM degradation performance and physicochemical property analysis. The addition of water vapor to the DCM degradation process on core-shell structure Co₃O₄@ZSM-5 was shown to promote DCM conversion and CO₂ yield. In addition, we concluded that core-shell catalysts exhibited good thermal stability and durability for DCM oxidation.
Active, selective and robust Pd and/or Cr catalysts supported on Ti-, Zr- or [Ti,Zr]-pillared montmorillonites for destruction of chlorinated volatile organic compounds
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There are several reports in the open literature on the application of catalysts based on pillared clays to the destruction of CVOCs [11,14,21,36,46–51]. Most of them describe the use of Al-, Cr- or Fe-pillared montmorillonites as CVOCs oxidation catalysts or catalyst supports [11,14,46–51]. Those stemming from our group show results obtained for Ti-PILC-based systems, and demonstrate that such catalysts are much more efficient than the commercial alumina-supported noble metal reference [21,36].
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Active, selective and robust Pd and/or Cr catalysts supported on Ti-, Zr- or [Ti,Zr]-pillared montmorillonites for destruction of chlorinated volatile organic compounds
2015, Applied Catalysis B: Environmental
Citation Excerpt :
There are several reports in the open literature on the application of catalysts based on pillared clays to the destruction of CVOCs [11,14,21,36,46–51]. Most of them describe the use of Al-, Cr- or Fe-pillared montmorillonites as CVOCs oxidation catalysts or catalyst supports [11,14,46–51]. Those stemming from our group show results obtained for Ti-PILC-based systems, and demonstrate that such catalysts are much more efficient than the commercial alumina-supported noble metal reference [21,36].
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Al- and Fe-pillared montmorillonite (Al- and Fe-PILCs) were prepared and examined as catalysts in the deep oxidation of toluene and chlorobenzene. The catalysts before and after reaction were characterized by X-ray powder diffraction, N₂ adsorption, scanning electron microscopy, and energy dispersive X-ray spectrometer. Results show that Al- and Fe-PILCs with layer structures increase the surface area. For the catalytic oxidation of volatile organic compounds (VOCs), Fe-PILCs exhibit higher performance than fresh montmorillonite and Al-PILCs. Higher concentration of Fe also resulted in higher catalytic activity. Fe-PILCs also exhibited higher stability than Al-PILCs. Even at a low temperature (100 °C), Fe-PILCs still exhibited certain activity. Lifetime evaluation results show that the activity of Fe-PILC (3) did not vary after a 96-hour reaction. BET and XRD results indicate that these pillared catalysts have very stable structures even after prolonged reaction. Hence, Fe-PILCs are potential materials for VOC decontamination.
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Citation Excerpt :
mixed Al–Cr: Carrado et al. (1986a,b), Skoularikis et al. (1988), Zhao et al. (1995), Storaro et al. (1997), Toranzo et al. (1997), and Mata et al. (2007); mixed Al–Fe: Barrault et al. (1988, 1992), Lee et al. (1989), Bergaya and Barrault (1990), Rightor et al. (1991), Bergaya et al. (1991, 1993b), Zhao et al. (1993a), Bakas et al. (1994), Lenarda et al. (1994), Storaro et al. (1995, 1996), Ladavos et al. (1996), Mandalia et al. (1998), Belver et al. (2004a,b), Yuan et al. (2006, 2008), Aouad et al., 2010, and Galeano et al. (2010, 2011, 2012); mixed Al–Cu: Frini et al. (1997), Barrault et al. (1998), Abdelaoui et al. (1999), and Galeano et al. (2010);
This chapter makes a general overview of pillared clay minerals. First, the general concepts of the process and the terminology recommended by the IUPAC are summarized, followed by the analysis of the host clay minerals and of the pillaring species, with special attention to the Al₁₃ polycation, mixed species, and new species. The main experimental pillaring methods are summarized, and also the main characteristics of the pillared solids, with special attention to the linking between the clay mineral layers and the polycations. Also, an overview of the mathematical modelling of pillaring processes is given. The chapter does not give exhaustive information in each item, available in review articles and books, but the general concepts needed for a general knowledge of the pillaring process and of the pillared solids.

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Vapour phase deep oxidation of chlorinated hydrocarbons catalyzed by pillared bentonites

Abstract

J. Chem. Soc., Chem. Commun.

Science

Ind. Eng., Chem. Prod. Res. Dev.

Geol. Carpath.-Ser. Clays

Ind. Eng. Chem. Res.

J. Chem. Eng. Jpn.

Clays Clay Miner.

Chem. Eng. News

Chem. Eng. News

Chem. Eng. News

Chem. Eng. News

Environ. Sci. Technol.

Environ. Sci. Technol.