Characteristics and mechanism of toluene removal from gas by novelty array double dielectric barrier discharge combined with TiO2/Al2O3 catalyst

doi:10.1016/j.chemosphere.2019.04.005

Chemosphere

Volume 226, July 2019, Pages 766-773

https://doi.org/10.1016/j.chemosphere.2019.04.005 Get rights and content

Highlights

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A new reactor of array DDBD combined with catalysis is founded.
•
Effects of factors on removal efficiency of toluene by DDBD with catalysis are investigated.
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DDBD combined with TiO₂/Al₂O₃ shows superior degradation capacity for toluene.
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There are five possible pathways for DDBD combined with TiO₂/Al₂O₃ to degrade toluene.

Abstract

A new reactor of array double dielectric barrier discharge (DDBD) combined with catalysis was prepared, and the effect of different factors on removal efficiency of toluene at pilot scale were investigated. The possible degradation mechanism was explored. The results indicate that the removal efficiency of toluene in the exhaust gas decreases with the increasing of the toluene initial concentration and the gas flow rate, but increases with the increasing of the specific energy density. When the air relative humidity is 55%, the removal efficiency of toluene is higher than that of the relative humidity by 85%. The results of XPS, FT-IR and GC-MS analysis show that the main intermediate products of removing toluene by DDBD combined with TiO₂/Al₂O₃ catalyst are phenol, benzaldehyde, benzyl alcohol, benzoic acid, N-benzyl formamide, dimethyl terephthalate, dimethyl isophthalate and other substances. There are five possible pathways to degrade toluene by DDBD combined with TiO₂/Al₂O₃.

Graphical abstract

Introduction

Volatile organic compounds (VOCs) are the important precursors of PM_2.5 and O₃, which not only exacerbate the occurrence of haze, but also damage people's health due to its heavy emission (Jones, 1999; Kerminen et al., 2000; Domingo et al., 2015). Toluene is a typical volatile organic compound, which is widely utilized for industry such as dyestuff, medicine, agriculture and spice industries, and has a neurotoxic effect. Therefore, it is very important to remove toluene from the exhaust gas. At present, there are some main methods for toluene removal including adsorption, absorption, incineration and condensation (Hu et al., 2015; Chen et al., 2018). However, the removal efficiencies of these methods are not very significant due to the large gas flow rate and low concentration in the industry (Ramos et al., 2010; Bai et al., 2013). Dielectric barrier discharge combined with catalysis has become a research hot spot nowadays as a promising emerging method for its advantages such as moderate operating conditions, high oxidation efficiency and low energy cost (Huang et al., 2008; Wang et al., 2017; Yao et al., 2018; Zhu et al., 2018). For gas purification, double dielectric barrier discharge (DDBD) configured reactor is more suitable as it not only isolates electrodes from the plasma reaction chamber but also to protect the inner electrode from carbon deposition and generation of by-products during chemical reaction process. However, most of the studies about this method are only in the laboratory stage and the gas flow rate is less, which cannot satisfy with the removal efficiency of toluene in the industry (Kim, 2004; Wu et al., 2006; Durme et al., 2008; Czapka, 2011; Liang et al., 2013). At the same time, the mechanism and reaction process of removing toluene by DDBD combined with catalysis are not yet clear.

The objective of this work is to investigate the effect of different factors (the toluene initial concentration, the gas flow rate, the relative humidity, the discharge plate space and the specific energy density) on removal efficiency of toluene in the large volume of exhaust gas by using self-made reactor of array DDBD combined with catalyst (TiO₂/Al₂O₃ or Co/activated carbon) and to explore possible mechanism and reaction process of removing toluene by DDBD combined with TiO₂/Al₂O₃ catalyst.

Section snippets

Experimental set-up

The schematic diagram of the experimental system is shown in Fig. 1, which was mainly composed of the gas supply system, the power supply, the reactor system of DDBD combined with catalysis and the sampling system. The gas supply system mainly consisted of the ventilator, the air pump, the mass flow controller (MFC), the toluene bubbler and the mixing tank. Toluene was evaporated by bubbling with air and mixed with air before being introduced into the reactor. The carrier gas was air. The gas

Effects of the initial concentration

As seen in Fig. 2a, when the initial concentration of toluene was 50 mg m⁻³, array DDBD with TiO₂/Al₂O₃ catalyst obtained the highest removal efficiency, up to 98.5%. The removal efficiency of toluene by DDBD combined with catalysis is higher than that of the separated DDBD. At the same time, the removal efficiency of toluene decreases with the increasing of the initial concentration of toluene. This result is in good agreement with that of previous works (Wu, 2014). The reason is that when the

Conclusions

The removal efficiency of toluene in the large volume of exhaust gas by DDBD combined with catalysis decreases with the increasing of the initial concentration of toluene and the gas flow rate, but increases with the increasing of the specific energy density. When the air relative humidity is 55%, the removal efficiency of toluene is higher than that of relative humidity by 85%. In general, the order of the toluene removal efficiency is: DDBD combined with TiO₂/Al₂O₃ catalyst ＞DDBD combined

Acknowledgements

This work was financially supported by the Zhejiang Provincial Natural Science Foundation of China (LY16E080001) and the Science and Technology Department of Zhejiang Province (2016F50G5220037).

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View full text

Characteristics and mechanism of toluene removal from gas by novelty array double dielectric barrier discharge combined with TiO2/Al2O3 catalyst

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Experimental set-up

Effects of the initial concentration

Conclusions

Acknowledgements

Adsorption of benzene and ethanol on activated carbon nanofibers prepared by electrospinning

Adsorption

Nitrogen dioxide formation in the gliding arc discharge-assisted decomposition of volatile organic compounds

J. Hazard. Mater.

Catalytic combustion of toluene over mesoporous Cr2O3-supported platinum catalysts prepared by in situ pyrolysis of MOFs

Chem. Eng. J.

Titanium dioxide photocatalysis in atmospheric chemistry

Chem. Rev.

Back-corona discharge phenomenon in the non-thermal plasma system

IEEE Trans. Plasma Sci.

Health risks for the population living in the vicinity of an Integrated Waste Management Facility: screening environmental pollutants

Sci. Total Environ.

The mechanism of enhanced visible light photocatalysis with micro-structurally optimized and graphene oxide coupled (BiO)2CO3 (in Chinese)

Chin. Sci. Bull.

Langenhove, Efficient toluene abatement in indoor air by a plasma catalytic hybrid system

Appl. Catal. B Environ.

Combining non-thermal plasma with heterogeneous catalysis in waste gas treatment: a review

Appl. Catal. B Environ.

Plasma Chemistry

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Fuel

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Chem. Eng. J.

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J. Photochem. Photobiol. A Chem.

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Chem. Eng. J.

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Langmuir

Reduction of NO by propene over supported iridium catalysts under lean-burn conditions: an in situ FTIR study

Appl. Catal. Gen.

Indoor air quality and Health

Atmos. Environ.

Characteristics and mechanism of toluene removal from gas by novelty array double dielectric barrier discharge combined with TiO₂/Al₂O₃ catalyst

The mechanism of enhanced visible light photocatalysis with micro-structurally optimized and graphene oxide coupled (BiO)₂CO₃ (in Chinese)

Benzene and toluene gas-phase photocatalytic degradation over H₂O and HCl pretreated TiO₂: by-products and mechanisms