Real-time monitoring and quantification of organic by-products and mechanism study of acetone decomposition in a dielectric barrier discharge reactor

A review of non-thermal plasma -catalysis: The mutual influence and sources of synergetic effect for boosting volatile organic compounds removal

This review is aimed at researchers in air pollution control seeking to understand the latest advancements in volatile organic compound (VOC) removal. Implementing of plasma-catalysis technology for the removal of volatile organic compounds (VOCs) led to a significant boost in terms of degradation yield and mineralization rate with low by-product formation. The plasma-catalysis combination can be used in two distinct ways: (I) the catalyst is positioned downstream of the plasma discharge, known as the "post plasma catalysis configuration" (PPC), and (II) the catalyst is located in the plasma zone and exposed directly to the discharge, called "in plasma catalysis configuration" (IPC). Coupling these two technologies, especially for VOCs elimination has attracted the interest of many researchers in recent years. The term "synergy" is widely reported in their works and associated with the positive effect of the plasma catalysis combination. This review paper investigates the state of the art of newly published papers about catalysis, photocatalysis, non-thermal plasma, and their combination for VOC removal application. The focus is on understanding different synergy sources operating mutually between plasma and catalysis discussed and classified into two main parts: the effect of the plasma discharge on the catalyst and the effect of the catalyst on plasma discharge. This approach has the potential for application in air purification systems for industrial processes or indoor environments.

Low Temperature Ozonation of Acetone by Transition Metals Derived Catalysts: Activity and Sulfur/Water Resistance

Different transition metals (Cr/Fe/Mn/Co) derived catalysts supported on γ-Al2O3 were prepared by the isovolumetric impregnation method for catalytic ozonation of acetone (C3H6O), and their catalytic activities under industrial complex conditions were investigated. Among them, CrOx/γ-Al2O3 catalyst with Cr loading of 1.5%, abbreviated as Cr1.5%, achieved the best activity, benefitting from its larger surface area, larger proportion of Cr6+/Cr, more chemically desorbed oxygen species Oβ, appropriate acidity, and superiority of low-temperature reducibility. Simulated industrial conditions were used to investigate the applicability of Cr1.5% catalysts for catalytic ozonation of acetone. Results illustrated that the optimum temperature range was 120–140 °C, with molar ratio O3/C3H6O > 6. Different C3H6O initial concentrations had less effect over the activity of Cr1.5% catalysts, with little residual ozone, confirming the applicability of Cr1.5% catalysts in industrial application. The effects of sulfur/water vapor on catalytic activity were also investigated, and satisfactory resistance to sulfur or water vapor individually was obtained. Finally, in-situ DRIFTS measurement was carried out, to explore and illustrate mechanisms of acetone catalytic ozonation pathways and sulfur/water poisoning.

A critical review on plasma-catalytic removal of VOCs: Catalyst development, process parameters and synergetic reaction mechanism

It is urgent to control the emission of volatile organic compounds (VOCs) due to their harmful effects on the environment and human health. A hybrid system integrating non-thermal-plasma and catalysis is regarded as one of the most promising technologies for VOCs removal due to their high VOCs removal efficiency, product selectivity and energy efficiency. This review systematically documents the main findings and improvements of VOCs removal using plasma-catalysis technology in recent 10 years. To better understand the fundamental relation between different aspects of this research field, this review mainly addresses the catalyst development, key influential factors, generation of by-products and reaction mechanism of VOCs decomposition in the plasma-catalysis process. Also, a comparison of the performance in various VOCs removal processes is provided. Particular emphasis is given to the importance of the selected catalyst and the synergy of plasma and catalyst in the VOCs removal in the hybrid system, which can be used as a reference point for future studies in this field.

Reaction kinetic study of nonthermal plasma continuous degradation of acetone in a closed-loop reactor

Nonthermal plasma (NTP) degradation has been shown to be a promising method for volatile organic compounds (VOCs) removal from air. However, there have been few studies on the degradation of indoor VOCs using NTP, and even less on their reaction kinetics. In this study, NTP degradation of acetone, a representative of oxygenated VOCs, in a closed-loop reactor operating in recirculation mode was investigated. Acetone and organic by-products were characterized in real-time by proton transfer reaction time-of-flight mass spectrometry. The results showed that approximately 85.7% of the acetone degraded within 7.5 h with dielectric barrier discharge treatment at 4.3 W. Methanol, acetaldehyde, formic acid, and acetic acid were observed to be the main organic byproducts with concentrations time-dependent on the order of ppb/ppm. The concentrations of the inorganic by-products O₃ and NO₂ are also time-dependent and can decrease to nearly 0 after a sufficient degradation time. Based on the concentration measurement in real-time, several rate laws were used to fit the concentration variations of acetone and the organic by-products, and it was observed that they strictly followed the simple kinetic reaction rate laws: acetone followed the first-order rate law, and formic acid formation followed the one-half-order rate law, etc. This study provides a good example of characterizing NTP removal of VOCs in airtight spaces and has important theoretical and practical significance in designing a better NTP device, predicting NTP degradation reaction rate, and accelerating the practical application of NTP technology for indoor air treatment.