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[Display omitted] • Removal of toluene examines with honeycomb catalyst for industrial application. • Uniform corona plasma with a high flowrate with negligible pressure drop. • The surface resistance of dielectric monolith reduces by the water vapor coat. • Plasma strength largely depends on the humidity of the inlet gas. • Metal clusters on the honeycomb surface can act as floating grounds. Efficiently processing volatile organic compounds (VOCs) with nonthermal plasma and honeycomb catalyst for practical industrial applications presents a sizable challenge. An attempt has been made to generate a large volume of uniform plasma at atmospheric pressure in a practical-scale honeycomb catalyst. H-ZSM-5, a type of zeolite, was washcoated on a commercial bare honeycomb monolith as the catalyst-supporting material, after which the monolith was impregnated with Pd. The plasma discharge power can be controlled by controlling the humidity in the feed gas, metal content, applied voltage, and total flow rate of the feed gas. The plasma was characterized by the voltage and current waveforms, and optical emission spectroscopy (OES). In this study, 85% of dilute toluene (15 ppm) was successfully removed from an airstream at a large flow rate of 60 L/min with an energy density of 84 J/L. Under this condition, the selectivity of CO 2 was 76%. This investigation demonstrated the practical applicability of the plasma-honeycomb catalytic reactor to process a fast-flowing feed gas without resulting in a significant large pressure drop, which can hardly be achieved with typical packed-bed plasma reactors. [ABSTRACT FROM AUTHOR]

This work focused on the factors affecting the effective generation of corona discharge plasma in a honeycomb catalyst reactor. Pd, Co, and Ag were used as the active metal catalysts to investigate the plasma formation and decomposition of ethylene. Unlike the Ag-coated honeycomb catalyst, which resulted in excessive arcing, the Co-coated honeycomb monolith was able to generate stable plasma, but the discharge power was insufficient to decompose ethylene at an acceptable level. The incorporation of a small amount of Pd with Co significantly enhanced the discharge power and the ethylene removal performance. The catalytic activity of the prepared catalyst for the removal of ethylene was evaluated using plasma catalytic oxidation and thermal catalytic oxidation. ANOVA was used to assess the effect of single process factors and their relationships in the plasma process. All the process factors such as specific energy input (SEI), ethylene concentration, and flow rate were found to affect the ethylene conversion, CO 2 selectivity, and energy efficiency (EE). Under the optimal conditions, i.e., an SEI of 80 J/L, an ethylene concentration of 20 ppm, and a flow rate of 20 L/min, the ethylene conversion was 85 %, CO 2 selectivity was 70 %, and EE was 0.86 g/kW h. [Display omitted] • Stable corona plasma formation using Co/ZSM-5/monolith and Co-Pd/ZSM-5/monolith. • Bimetallic catalyst shows better catalytic activity than monometallic catalyst. • Ag/ZSM-5/monolith creates numerous arcing and poor plasma formations. • ANOVA with F-test investigates the relationship between the influential factors and NTP reaction activity. [ABSTRACT FROM AUTHOR]

This study focused on the removal of styrene using a metal-coated monolith (MCM) catalyst integrated with non-thermal plasma. The MCM catalyst was prepared by depositing a ZSM-5 support impregnated with a combination of three metals (Co, Pd, La) on a practical-scale honeycomb monolith. A comparative study with a commercial metal-coated monolith (CMCM) of the same dimensions was conducted to evaluate the effectiveness of the MCM with respect to styrene removal. The plasma discharge in the monolith was characterized by measuring the voltage and current waveforms and optical emission spectroscopy (OES). The electric power of the plasma discharge largely depended on the metal loading, flow rate, and humidity of the feed gas. The removal efficiency of styrene (inlet concentration: 20 parts per million, volumetric (ppm)) was examined using both plasma catalytic oxidation (PCO) and thermal catalytic oxidation (TCO), to enable the effect of plasma to be clearly assessed. PCO with the MCM catalyst achieved styrene removal efficiency of nearly 100% at a specific energy input (SEI) of 40 J/L, whereas the CMCM catalyst achieved 92% removal for identical SEI. In comparison, TCO with the MCM and CMCM catalysts required high temperatures of 420 °C and 480 °C, respectively, for the complete removal of styrene. In addition, the CO 2 selectivity of the MCM catalyst was higher at 83% compared with 75% for the CMCM at SEI of 40 J/L. The optimal silica binder content for the deposition of a robust washcoat layer was found to be approximately 5%. [Display omitted] • Uniform robust coating layer of ZSM-5 was obtained using the washcoating method. • Uniform honeycomb plasma was generated using the MCM/CMCM catalysts. • Styrene was removed at room temperature using plasma catalytic oxidation. [ABSTRACT FROM AUTHOR]

Nonthermal plasma combined with a practical-scale honeycomb catalyst of 5.0 cm in height and 9.3 cm in diameter was investigated for the removal of toluene. The creation of plasma in the honeycomb catalyst greatly depended on the humidity of the feed gas and the presence of metals on the honeycomb surface. Compared to the bare ceramic honeycomb, the metal-loaded one gave higher toluene removal efficiency because the decomposition of toluene by the plasma-generated reactive species occurred not only homogeneously in the gas phase but also heterogeneously on the catalyst surface. The present plasma-catalytic reactor was able to successfully remove about 80% of dilute toluene (15 ppm in air) at a large flow rate of 60 L/min with a specific energy input of 58 J/L. The honeycomb-based plasma-catalytic reactor system is promising for practical applications since it can overcome such problems as high-pressure drop and difficulty in scale-up encountered in packed-bed reactors. ga1 • The removal of toluene investigates on a practical-scale honeycomb catalyst. • A large flow rate without significant pressure drop is used to generate plasma. • Plasma intensity largely depends on the humidity of the feed gas. • The metal clusters dotted on the honeycomb surface can act as floating grounds. [ABSTRACT FROM AUTHOR]

• A plasma reactor for practical-scale environmental plasma applications. • Successful plasma generation in a commercial honeycomb monolith. • Increased volume of plasma discharge with humidified air at high flow rates. Large-volume atmospheric-pressure plasma based on corona discharge was successfully generated in a sandwich-type plasma reactor by controlling the humidity of the feed gas. The reactor comprised a 5-cm-high and 9-cm-wide commercial honeycomb monolith and two perforated stainless-steel disk electrodes with 3-mm holes, which covered up both sides of the monolith. The high-voltage applied disk electrode was placed 2 ~ 6 mm away from the monolith, whereas the counter ground electrode typically touched it. The characteristics of air plasma such as power delivery, breakdown voltage, current, and impedance were found to strongly depend on the water vapor content in the feed gas as well as in the monolith, exhibiting an exponential increase of discharge power with increasing the humidity. The discharge characteristics also depended on the gas flow rate and the electrode-monolith distance. Better discharge performance was observed as the electrode was closer to the monolith, and as the air flow rate was higher. Discharge power above 30 W was achieved under the condition of gas flow rate 75 L/min, applied voltage 25 kV, and humidity 2.1%(v/v) when the high-voltage electrode was 2 mm away from the monolith, and the ground electrode kept up against it. The air plasma produced reactive species, being demonstrated by the formation of ozone at several tens of ppm, depending on specific energy input. The plasma source has potential applications in the abatements of odor, organic compounds, and NO x with high throughputs. [ABSTRACT FROM AUTHOR]

This paper reports on the ethyl acetate (EA) removal over a honeycomb catalyst using an experimental design methodology. A mathematical model based on the response surface methodology is developed to evaluate the effect of parameters such as specific input energy (SIE), humidity, and EA concentration on the response variables (i.e., removal and energy efficiency). A set of experiments based on a statistical three-level full-factorial design of the experimental method were performed to collect the removal data. The model (R 1 2 = 0.9858 and R 2 2 = 0.9305 for removal and energy efficiency, respectively) indicates a satisfactory correlation between the experimental and predicted values. The analysis results using the model show that SIE is the principal parameter affecting the EA removal. Besides, verification of the experimental results indicates that the EA removal of 90.93% and the energy efficiency of 2.91 g. kWh − 1 at 235 J L-1, 1.5%, and 30.3 ppm were achieved under optimal conditions. [Display omitted] • High-performance EA removal was obtained in honeycomb catalyst plasma system. • Establishing relationships of input variables to output results via a model evaluation. • Optimal operating condition for EA removal efficiency was determined. • Specific input energy (SIE) is the most important factor to enhance EA removal. [ABSTRACT FROM AUTHOR]

[Display omitted] • A practice-scale sandwich-type honeycomb catalyst discharge reactor was developed. • High-throughput without significant pressure drop condition was obtained. • 94.5 % IPA was removed using the honeycomb catalyst discharge reactor. • Uniform discharge was created using Pd/Al2O3/honeycomb combined with plasma. • Byproducts formation and IPA oxidation pathways were elucidated. A practical-scale sandwich-type honeycomb catalyst reactor incorporating non-thermal plasma was developed for the high-throughput removal of isopropanol (IPA) from air. The Pd/γ-Al 2 O 3 /honeycomb catalyst was fabricated by coating a cordierite monolith with γ-alumina powder on which to support the palladium (Pd). The supported catalyst showed good activity and the combination of the honeycomb structure with plasma produced a uniform plasma inside the catalyst chamber. The influence of different parameters, including the energy density (SIE), humidity, initial concentration, and flow rate, on the plasma characteristics and IPA removal efficiency was investigated. The results showed that the SIE has the strongest effect on the IPA removal efficiency. The efficiency of IPA removal was 94.5% and the CO2 selectivity was 85% for an SIE of 180 J/L. Using optical emission spectroscopy, we found that the increased formation of atomic oxygen and reactive species plays an essential role in the oxidation of IPA by plasma catalysis. The main byproducts were identified by GC-MS, which indicated that acetone is the major liquid product. A plausible reaction mechanism for the plasma-catalytic oxidation of IPA is proposed based on the intermediates and byproducts. [ABSTRACT FROM AUTHOR]

A method based on the corona discharge produced by high voltage alternating current (AC) and direct current (DC) over a Pd/γ-Al 2 O 3 catalyst supported on a honeycomb structure monolith was developed to eliminate ethyl acetate (EA) from the air at atmospheric pressure. The characteristics of the AC and DC corona discharge generated inside the honeycomb structure monolith were investigated by varying the humidity, gas hourly space velocity (GHSV), and temperature. The results showed that the DC corona discharge is more stable and easily operated at different operating conditions such as humidity, GHSV, and gas temperature compared to the AC discharge. At a given applied voltage, the EA conversion in the DC honeycomb catalyst discharge is, therefore, higher compared with that in the AC honeycomb catalyst discharge (e.g., 96% of EA conversion compared with approximately 68%, respectively, at 11.2 kV). These new results can open opportunities for wide applications of DC corona discharge combined with honeycomb catalysts to VOC treatment. [Display omitted] • Uniform plasma generation inside honeycomb without significant pressure drop. • Positive DC discharge is more stable and easier to operate than AC discharge. • Ethylacetate removal was as high as 96% in the DC plasma/honeycomb catalyst. • Feasibility of DC plasma-in-honeycomb for practical pollution control applications. [ABSTRACT FROM AUTHOR]