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Non-thermal plasma (NTP) catalysis has attracted widespread attention in volatile organic compounds (VOCs). Combining NTP with heterogeneous catalyst has been proved to reduce the formation of unwanted by-products and improve the energy efficiency of the process. The mechanisms of interaction with plasma and catalyst and VOCs oxidation in plasma catalysis are particularly hot research topic. This paper reviewed the mechanism of non-thermal plasma catalysis on volatile organic compounds removal. In the first part, the interaction between plasma and catalyst is disscussed. And the different catalysis systems and discharge types are presented in the second part. In the third part, attention is given to the influence of critical parameters on the removal processes. Finally, based on a large number of literatures, an extended review is presented detailly on the treatment of VOCs with plasma-catalysis system including the oxidation pathways. Moreover, future works of this promising technology are discussed. [ABSTRACT FROM AUTHOR]

Naphthalene (Nap) degradation by photocatalysis of Fe 3 O 4 /Oxone/UV was studied. The system eliminated Nap in 30 min and the kinetics is described by a novel mixed order model with adsorption and decay dominant rate constants, representing non-radical and radical pathways respectively. The reaction is dominated by catalysis in acidic pHs as Oxone anions are adsorbed onto the protonated Fe 3 O 4 surface for activation; In alkaline solution, the adsorption of Nap to the deprotonated Fe 3 O 4 surface is the main removal pathway. The catalyst was reused for 5 cycles and the performance was enhanced after reuse. XPS study confirmed that the surface Fe content of Fe 3 O 4 remained stable after reusing due to the effective UV-assisted ≡FeII—≡FeIII catalytic cycle. An additional C‒O bond on Fe 3 O 4 surface was detected after reuse, which is proposed to be an OH bond on catalyst as an extra adsorption site and for radical generation. ga1 • Fe 3 O 4 /Oxone/UV for Naphthalene degradation with complete removal in 30 min. • Fe 3 O 4 performs mainly as catalyst in acidic and adsorbent in basic pH. • A mixed order kinetics model to describe both adsorption and catalysis stages. • Roles of Fe 3 O 4 in the system are distinguished. • Better performance of reused catalyst as extra OH• generated with UV irradiation. [ABSTRACT FROM AUTHOR]

• Ca-Ni/ZSM-5 sample shows the best potential for toluene conversion and CO 2 selectivity. • The introduction of Ca and Ni reduce the acidity of ZSM-5. • Ca-Ni/ZSM-5 catalyst greatly reduces the production of p-nitrotoluene. • Eleven intermediates are detected and four of them are not previously reported. • The reaction mechanism of toluene decomposition in the plasma has been proposed. The effect of Ca modification on the Ni/ZSM-5 catalyst for efficient toluene oxidation was studied in a plasma-catalytic system. The Ni/ZSM-5 and Ca-Ni/ZSM-5 catalysts were prepared by a wet impregnation method and characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Pyridine-FTIR spectroscopy and temperature programmed desorption of ammonia (NH 3 -TPD). Among the catalysts tested, the Ca-Ni/ZSM-5 sample showed the best potential for toluene conversion (90.2%) and CO 2 selectivity (70.7%). Pyridine-FTIR spectra and NH 3 -TPD results proved that the introduction of Ca and Ni onto ZSM-5 caused a decrease in the strong and weak acidic sites. In addition, gas chromatography/mass spectrometry (GC-MS) result showed that the Ca-Ni/ZSM-5 catalyst reduced the production of undesirable byproducts (such as p-nitrotoluene and methyl benzoate). Calcium in the Ni/ZSM-5 system influenced the acidity and other surface characteristic of the catalyst, as well as directly impacting the reactive plasma species and the intermediates. Finally, possible reaction mechanisms in the plasma catalysis of toluene were also proposed. [ABSTRACT FROM AUTHOR]

In this study, a series of HZSM-5 catalysts were prepared by the chemical liquid-phase deposition method, and low concentration toluene degradation was carried out in an atmospheric pressure dielectric barrier discharge (DBD) reactor. The catalysts were characterized by X-ray powder diffraction (XRD), SEM, TEM, and N2 adsorption analysis techniques. In addition, several organic contaminants were used to evaluate the adsorption performance of the prepared catalysts, and the effect of pore size on the removal efficiency of toluene and byproduct formation was also investigated. The unmodified HZSM-5 zeolite (Z0) exhibited good performance in toluene removal and CO2 selectivity due to the diffusion resistance of ozone and the amounts of active species (OH• and O•). Meanwhile, the time of flight mass spectrometry (TOF-MS) result showed that there were more byproducts of the benzene ring in the gas phase under the action of small micropore size catalysts. Moreover, the surface byproducts were detected by gas chromatography–mass spectrometry (GC-MS). [ABSTRACT FROM AUTHOR]

The destruction of low concentrations of toluene using two non-thermal plasma catalytic systems has been investigated in this study. Metals (Ag, Mn and AgMn) loaded SBA-15 catalysts were prepared by an impregnation method and further characterized by X-ray diffraction (XRD), N 2 adsorption–desorption isotherm and H 2 -temperature-programmed reduction (H 2 -TPR). In our research, two types of plasma catalytic system, including continuously introduced and adsorption-discharge plasma system, were studied. The results showed that the loaded metals retained the highly ordered mesopore structure of SBA-15. The activities of as-prepared catalysts for the toluene conversion and carbon balance in both catalytic systems decreased in the following order: AgMn/SBA-15 > Ag/SBA-15 > Mn/SBA-15 > SBA-15, which were consistent with the ozone decomposition activities. Compared to traditional continuously introduced plasma system, the adsorption-discharge plasma system slightly increased toluene conversion and significantly improved the carbon balance. The reaction intermediates and products in two plasma systems were detected by the GC–MS and in situ FT-IR analyses. The results showed that the types of organic byproducts detected in the adsorption-discharge system greatly decreased compared to continuously introduced system. Moreover, the different mechanisms of two systems were discussed. [ABSTRACT FROM AUTHOR]