Dielectric Barrier Discharge Plasma Reactor Research Articles

Oxygen atom activated ZIF-67/carbon cloth in plasma system for CO2 reduction

ZIF-67 was grown in situ on carbon cloth (CC) using a simple one-step method. The prepared ZIF-67/CC electrodes exhibited excellent CO2 reduction reaction (CO2RR) performance in a dielectric barrier discharge plasma reactor. The highest concentrations of produced formic acid and formaldehyde were 9.16 and 0.068 mmol L−1 at a reaction time of 1 h, respectively. The high performance is related to the unique high aspect ratio structure and pad-like cavity of ZIF-67, which results not only in an increase in the specific surface area for CO2 adsorption but also in the hydrophobicity of the electrode. Unexpectedly, the superoxide radical (·O2−) greatly affects the reduction performance of the electrode. In addition, the ZIF-67/CC electrode maintained good CO2RR performance in the presence of different pollutants, and the production of formic acid and formaldehyde increased to 10.81 and 0.11 mmol L−1 at 1 h with the addition of 10 mg L−1 phenol. This research provides new directions in the field of plasma catalysis.

Enhancing CO2 conversion in a temperature-controlled DBD plasma reactor with HKUST-1 catalyst: Water removal and CuO/Cu2O-derived approach

Due to a synergy effect, using dielectric barrier discharge (DBD) plasma technology combined with catalysts for CO2 decomposition, a major contributor to global warming, is recognized as an effective approach to transforming CO2 into valuable products such as CO, which is a crucial feedstock for chemical synthesis. Herein, HKUST-1 was synthesized using the hydrothermal method for CO2 conversion in the DBD reactor. To enhance catalyst performance in the plasma region, HKUST-1 was treated with O2 plasma to increase its specific surface area. Additionally, HKUST-1 was calcined at 300 °C to produce the CuO/Cu2O catalyst. Since the recombination reaction in the CO2 conversion is increased at higher temperatures, the reactor heat is removed using fan cooling and a water circulation system. In the presence of the HKUST-1 catalyst, the CO2 conversion rate significantly increased by 132 %, 82 %, and 12 % in reactors operating without cooling, with fan cooling, and with water cooling circulation, respectively compared to the reactors without catalyst, at a flow rate of 50 ml/min and maximum input power. The catalysts have been characterized using a comprehensive suite of analytical techniques, including FTIR, XRD,TEM, SEM, EDS, and BET analysis. The BET analysis indicates that the specific surface area of HKUST-1 after O2 plasma treatment is increased by 52 %, which causes an increasing conversion rate of up to 18 %. The CuO/Cu2O catalyst demonstrated maximum CO2 conversion of 21 % at an input power of 140 W and achieved energy efficiency of 8.6 % at 40 W. The presence of oxygen vacancies within this catalyst enhances the process of CO2 decomposition.

Studies of dynamic spatio-temporal processes of electrons in a 50 kHz/5 MHz dual-frequency dielectric barrier discharge plasma at atmospheric pressure

Dual-frequency excitation of dielectric barrier discharge (DBD) plasma reactors, where the plasma is generated by a low-frequency (LF) source and modulated by a radio-frequency (RF) source, have been widely adopted in the low-pressure regime. However, the impacts of the RF voltage and LF voltage amplitudes on the plasma parameters, including the spatiotemporal distributions of ion and electron densities, electron dynamics, and gas temperatures, remain poorly understood in the atmospheric pressure regime. The present work addresses this issue by conducting joint experimental and simulation studies for an atmospheric-pressure 50 kHz/5 MHz dual-frequency driven DBD plasma reactor based on phase-resolved optical emission spectra and a drift–diffusion model. The results demonstrate that the dynamic spatiotemporal behaviors of electrons change dramatically as the voltage of the RF component increases from 50 V to 300 V with the voltage of the LF component fixed at 1 kV. Moreover, the RF component is further demonstrated to modulate other plasma characteristics, such as particle densities, gas temperature, and argon emissions. These results contribute toward the tailoring of the non-equilibrium and nonlinear plasma parameters obtained under atmospheric pressure conditions.

Comprehensive study of plasma polymerization parameters on thiol-coated LDPE films for effective fibronectin adsorption targeting biomedical applications

In the realm of biomedical applications, biocompatible materials with optimized surface properties are crucial for facilitating cellular interactions. To attain the perfect balance of these properties, surface modification of non-toxic and stable bulk materials is often required. Within this context, this research aimed to improve the physiochemical and cell-responsive properties of a low-density polyethylene film. This was achieved by depositing thiol-rich coatings using a dielectric barrier discharge plasma reactor operating at medium pressures, with 1-propanethiol serving as polymerization precursor. The study systematically investigated the impact of key plasma polymerization parameters, including DBD chamber pressure, treatment time, and the combination of precursor flow rate and discharge power represented by the Yasuda parameter, to identify optimal plasma processing conditions for the formation of thiol-rich coatings. To characterize the coating thickness, hydrophilicity and surface chemical composition, atomic force microscopy, water contact angle measurements, and X-ray photoelectron spectroscopy were employed. The findings indicated that reducing the chamber pressure to 10 kPa led to more hydrophilic and thicker deposits possessing a higher sulphur content. Deposition time (5 to 15 min) also significantly impacted coating thickness and surface chemistry, where long times increased thickness, but also led to a reduced sulphur and increased oxygen content because of more pronounced etching. The optimal deposition time was therefore set at 10 min resulting in the deposition of dense coatings possessing a high number of sulphur-containing functionalities. The Yasuda parameter (W/FM) analysis demonstrated optimal thiol incorporation in combination with high coating stability at an intermediate W/FM value of 72 MJ/kg. Following the determination of the optimal plasma polymerization parameters, the effectiveness of thiol plasma polymerization and subsequent fibronectin immobilization for enhancing cell adhesion and proliferation was investigated. The thiol-coated substrates were found to exhibit superior protein immobilization, because of the high affinity for protein binding of the available thiol groups. To assess cellular responses, Schwann cells were cultured on uncoated and coated samples before and after fibronectin immobilization. The results revealed a superior cellular response of the thiol-coated samples after fibronectin immobilization, showing the highest cell viability and significantly enhanced cell adhesion and proliferation. Collectively, these results underscore the synergistic effect of thiol plasma polymerization and fibronectin immobilization in promoting the cellular response of LDPE substrates, thus highlighting their potential as a surface modification strategy of biomaterials.

Novel multineedle-to-cylinder plasma coupled with bimetallic catalysts for efficient removal of sulfides and ammonia in odor gases

Dielectric barrier discharge (DBD) plasma is a promising technology for treating odor gases. This study developed an innovative multineedle-to-cylinder (MC) configuration DBD plasma reactor and investigated its synergistic effect with bimetallic catalysts. The results demonstrated that MC-DBD plasma achieved complete elimination of ammonia and organic sulfides, while the removal efficiencies of inorganic H2S and CS2 reached 44.0 % and 53.0 % respectively. Compared with conventional plasma, the specific energy input (SEI) of MC-DBD was significantly reduced to 4.44 J/L. Furthermore, with the incorporation of Mn-Ce/ZSM-5 catalyst, optimal removal efficiencies of H2S and CS2 were significantly improved to 82.6 % and 90.7 %, and the SEI was reduced by 18 %. The electrical performance revealed that the low energy consumption was mainly attributed to stable fast-pulse micro-discharge channels and significantly enhanced inhomogeneous electric fields achieved by the filament discharge mode. Catalyst characterization (X-ray photoelectron spectroscopy and O2-temperature programming desorption) confirmed that surface catalytic reaction mainly follows the Mars-van Krevelen mechanism, where increased lattice oxygen content and the electron transfer between Mn and Ce play crucial roles in enhancing malodor degradation performance. This work proposes an efficient solution for degrading mixed malodors and provides an experimental and theoretical basis for optimizing plasma structure as well as researching treatment of mixed pollutants.

Heavy Naphtha Desulfurization by Ozone Generated via the DBD Plasma Reactor

This work presents an investigation into the ultra-desulfurization of heavy naphtha fuel (model using BT and DBT) using oxidation and solvent extraction techniques. Ozone produced by the DBD (Dielectric barrier discharge) plasma generator was employed in the oxidation process as an oxidant, and acetonitrile was used as a solvent extraction. Box-Behnken experimental design was adopted in the current study to examine oxidation desulfurization by non-thermal plasma for the various operation conditions including time, flow rate, and temperature on sulfur removal efficiency. Acetonitrile with an oxidized oil/solvent ratio of 1:1(v/v ratio) was utilized as the extraction solvent. The results showed that the maximum sulfur removal of about 91% was obtained with a temperature of 50°C, flow rate of 75 ml/min, and time of 4 hours.

Nanosized curing catalyst via nano-templated plasma PVD for attaining superior low-cure powder coating films

The addition of curing catalysts into powder coating is a key method to fabricate low-temperature curing powder coating for reducing energy consumption and expanding its applications to heat-sensitive substrates. However, the heterogeneous dispersion of the unmodified catalysts in powder coatings results in inconsistent catalysis of resin crosslinking, thus leading to compromised surface smoothness and gloss. Utilizing nanosized catalysts is an efficient solution to such problems. In this paper, we propose a nano-templated dielectric barrier discharge (DBD) plasma-assisted physical vapor deposition (PVD) strategy to fabricate the nanosized catalysts. The curing catalyst, 2-ethylimidazole (2-elm), is successfully vaporized and deposited on nano-carrier SiO2 (SiO2-NPs) in the DBD plasma reactor at atmospheric pressure, producing 2-elm@SiO2-NPs. The mechanical strength and chemical resistance of finishes of powder coating incorporated with the 2-elm@SiO2-NPs remained at low curing temperature (170 °C for 15 min) and fast curing condition (190 °C for 8 min). In addition, their surface qualities are comparable to that of the original powder coating, with up to 100 % gloss retention, successfully eliminating the issue of more than 25 % gloss attenuation of the powder coating with unmodified 2-elm. This study provides an effective, solvent-free strategy for fabricating nanosized curing catalysts and achieving high-quality film finishes.

Importance of plasma discharge characteristics in plasma catalysis: Dry reforming of methane vs. ammonia synthesis

Plasma catalysis is a rapidly growing field, often employing a packed-bed dielectric barrier discharge plasma reactor. Such dielectric barrier discharges are complex, especially when a packing material (e.g., a catalyst) is introduced in the discharge volume. Catalysts are known to affect the plasma discharge, though the underlying mechanisms influencing the plasma physics are not fully understood. Moreover, the effect of the catalysts on the plasma discharge and its subsequent effect on the overall performance is often overlooked. In this work, we deliberately design and synthesize catalysts to affect the plasma discharge in different ways. These Ni or Co alumina-based catalysts are used in plasma-catalytic dry reforming of methane and ammonia synthesis. Our work shows that introducing a metal to the dielectric packing can affect the plasma discharge, and that the distribution of the metal is crucial in this regard. Further, the altered discharge can greatly influence the overall performance. In an atmospheric pressure dielectric barrier discharge reactor, this apparently more uniform plasma yields a significantly better performance for ammonia synthesis compared to the more conventional filamentary discharge, while it underperforms in dry reforming of methane. This study stresses the importance of analyzing the plasma discharge in plasma catalysis experiments. We hope this work encourages a more critical view on the plasma discharge characteristics when studying various catalysts in a plasma reactor.

Experimental activities in view of hydrogen- deuterium equilibrium reaction in dielectric barrier discharge reactor: Effects of plasma treatment parameters and reactor design

Cryogenic distillation (CD) is a crucial process for separating and concentrating tritium in the tritium fuel cycle of fusion reactors. The equilibrator plays a vital role in decomposing HD, DT, and HT to improve the separation efficiency of hydrogen isotopes in CD. As the equilibrium reaction temperature decreases, a larger proportion of HD, HT, and DT decomposes into H2, D2, and T2, which enhances the performance of the equilibrator. While Pt/Al2O3 catalyst exhibits high activity at 303 K in the H2-D2 equilibrium reaction, it is almost inactive at 77 K. Non-thermal plasma (NTP) technology offers a promising and attractive alternative to conventional catalytic technology. In this study, H2-D2 equilibrium reaction was carried out without catalysts in a dielectric barrier discharge (DBD) reactor, achieving efficient conversion of HD even at 77 K. In the single-electrode DBD plasma reactor (S-P-Reactor), with an input power of 50 W, the conversion efficiency of HD was found to be 99.5% at 303 K, 99.5% at 273 K, and 99.2% at 77 K. To further optimize the energy efficiency of the S-P-Reactor, the reactor structure was enhanced, leading to the development of a multi-high-voltage DBD reactor (M-P-Reactor). The input power of the M-P-Reactor was reduced by approximately 10 W compared to the S-P-Reactor, while maintaining a conversion efficiency of over 95% for HD. The energy density of the reactor was calculated using the Q-V Lissajous graphic method, demonstrating that the M-P-Reactor exhibited superior energy conversion efficiency compared to the S-P-Reactor. Furthermore, the yield of HD was solely determined by the energy density and temperature. At a specific energy density, the yield of HD remained consistent for the same temperature. However, generating HD at lower temperatures required more energy due to the lower reactant activity. These results illustrate the potential application of NTP technology in improving hydrogen isotope separation performance in the cryogenic distillation process for fusion applications.

Non-thermal plasma mitigation of low concentration of air pollutants: removal of isopropyl alcohol using transition metal-oxide integration.

The present work studied the decomposition of isopropyl alcohol (IPA), widely used in chemical industries and households, in a packed-bed dielectric barrier discharge (DBD) plasma reactor. Metal oxide (MOx) coated on γ-Al2O3 (M = Cu, Mn, Co) was utilized for packing. The plasma-packed mode was a likely alternative to the conventional removal techniques, as it aids the conversion of dilute concentrations of IPA to CO and CO2 at ambient conditions (room temperature and atmospheric pressure). The mean electron energy calculations suggest that electrons with higher energy are generated when the discharge zone is packed with catalysts. When comparing IPA conversion (input concentration of 25ppm) for no packing mode and MOx/γ-Al2O3 coupled plasma mode, the latter method enhances conversion to greater than 90% at an applied voltage of 18kV. Also, MOx/γ-Al2O3 showed the highest selectivity to CO2 (70%) compared to plasma-only mode (45%). The metal-oxide layer provides the necessary catalytic surface facilitating the oxidation of IPA to COx through active oxygen species or the interaction of surface hydroxyl groups. The use of MOx/γ-Al2O3 resulted in about 90% carbon balance and reduced ozone generation, demonstrating the significance of integrating metal oxide to achieve efficient conversion and maximal selectivity towards the desired products.

Tailoring the surface acidity of catalyst to enhance nonthermal plasma-assisted ammonia synthesis rates

We report nonthermal plasma-assisted catalytic ammonia synthesis from N2 and H2 molecules at near ambient conditions in a custom-built coaxial dielectric barrier discharge plasma reactor. Here, we strategically designed catalysts to facilitate dissociation of strong nitrogen bond and desorption of NH3 molecules. This work demonstrates the use of empty orbitals of boron doped in graphitic carbon nitride (BCN) to activate nitrogen molecules, by creating electron-deficient sites, under nonthermal plasma conditions. Transition metals (Co and Fe) further contribute to the ammonia generation by altering the amount of weak acid sites of the BCN catalyst. As a result, at 20.16 kJ L−1, the maximum ammonia synthesis rate of ∼2.48mmolg−1h−1 was achieved by Co-BCN that corresponds to energy efficiency of 2.09 g-NH3 kWh−1, which was ca. 2.89-folds higher than that of plasma only. Evidently, dual mechanisms at play, leading to enhanced ammonia synthesis rates. Our strategy of tailoring catalyst structure provides a roadmap for engineering synergy with nonthermal plasma towards targeted applications.

Degradation of 2,4-dinitrotoluene in aqueous solution by dielectric barrier discharge plasma combined with Fe–RGO–BiVO4 nanocomposite

2,4-Dinitrotoluene (2,4-DNT) as a priority and hazardous pollutant, is widely used in industrial and military activities. In this study the synergistic effect of Fe–RGO–BiVO4 nanocomposite in a non-thermal dielectric barrier discharge plasma reactor (NTP-DBD) for degrading 2,4-DNT was evaluated. Preparation of the Fe–RGO–BiVO4 nanocomposite was done by a stepwise chemical method depositing Fe and reduced graphene oxide (RGO) on BiVO4. Field emission scanning electron microscopy (FESEM), X-ray diffraction analysis (XRD), UV–vis diffuse reflectance spectra (DRS), and energy-dispersive X-ray spectroscopy mapping (EDS-mapping) validated the satisfactory synthesis of Fe–RGO–BiVO4. To find the optimal conditions and to determine the interaction of model parameters, a central composite design (RSM-CCD) had been employed. 2,4 DNT can be completely degraded at: initial 2,4-DNT concentration of 40 mg L−1, Fe–RGO–BiVO4 dosage of 0.75 g L−1, applied voltage of 21kV, reaction time of 30 min and pH equal to 7, while the single plasma process reached a degradation efficiency of 67%. The removal efficiency of chemical oxygen demand (COD) and total organic carbon (TOC) were 90.62% and 88.02% at 30 min contact time, respectively. Results also indicated that average oxidation state (AOS) and carbon oxidation state (COS) were enhanced in the catalytic NTP-DBD process, which demonstrate the effectiveness of proposed process for facilitating biodegradability of 2,4-DNT.

Atmospheric–pressure DBD plasma modifying photoemission, optical and electrical properties of polycarbonate films

In this study, the DBD plasma reactor has been constructed, characterized, and tested to be employed in material treatment for use in different applications. A neon power source with an output of 10 kV, 30 mA, with a frequency of 20 kHz is used to drive the DBD reactor in an atmospheric-pressure environment. The investigation covered the analysis of many parameters of the dielectric barrier discharge (DBD) reactor, including its discharge voltage, current, capacitance, consumption energy, and the light emission of the produced plasma. Also, to examine the generated DBD plasma effect, the photoemission, optical, and electrical characteristics of untreated/treated polycarbonate films were investigated using photoluminescence spectroscopy, UV/Vis spectroscopy, and electrical spectroscopy. The results demonstrated the appearance of two modes in the DBD discharge: filamentary and homogeneous. Moreover, the DBD reactor's power consumption has been measured to be 20 mW at a supplied voltage of 6.5 kV peak-to-peak, operated in atmospheric–pressure. The photoluminescence emission results emphasized that the treated films are modified particularly with increasing DBD treatment time. The UV–Vis spectra demonstrated a notable displacement of the absorption edge towards higher wavelengths as the duration of DBD exposure increased. This is indicative of the reduction of the band gap energy, thus improving the electric conductivities. The optical parameters of the treated polycarbonate films were enhanced in comparison to the untreated sample. Through the used frequency range, measurements of dielectric loss, dielectric constant, as well as AC electrical conductivity, are sensitive parameters to the modifications in electrical behaviors due to DBD plasma treatment.

Enhanced methanol selectivity and synthesis in a non-catalytic dielectric barrier discharge (DBD) plasma reactor

Direct utilisation of CO2 to methanol via environmentally friendly gas-to-liquid processes with plasma poses various challenges, such as low methanol selectivity. This study explores the non-catalytic hydrogenation of CO2 and CO gas mixtures in a self-cooling dielectric barrier discharge (DBD) plasma at atmospheric pressure and temperature. Small amounts of N2 and argon were input as auxiliary gases to investigate their effect on methanol production and a probable reaction mechanism was suggested. A H2 + CO2 + CO + N2 mixture minimised methanation and the reverse water–gas shift competitive reactions, thus enhancing methanol selectivity and yield to 86 % and 22.5 %, respectively. Furthermore, N2 helped reduce plasma power requirements, stabilised the discharge, and displayed suitable third-body properties able to tune up plasma reactions yielding a better methanol production rate than argon. Our findings reveal that plasma performance can be enhanced using a suitable reactant composition in combination with gas additives (in this case, N2) to improve methanol synthesis.

Experimental and kinetic modeling study of tar partial oxidative reforming by dielectric barrier discharge plasma using toluene as a model compound

In this study, partial oxidation of toluene as a biomass tar surrogate was carried out in a dielectric barrier discharge (DBD) plasma reactor. In order to understand the reaction characteristics and thus potential of the approach, the effect of reaction temperature, O2/toluene molar ratio (OTR) and discharge power on performances was investigated by experiments and kinetic modeling. The results showed that the three factors could change the E/n and hence the G-values of species, as well as alter O2 concentration in background gas and input energy, leading to the variation in active species production and thus, the performance. Appropriate high temperatures, as well as higher OTRs and discharge power obtained better performances by promoting toluene destruction and gas product production. Excited N2 species play a crucial role in the process, by means of participating in reactions directly and strongly influencing on the production of secondary active species. At 300 °C, the highest toluene conversion of 100.0 % with an energy efficiency of 25.7 g/kWh was achieved without catalysts usage, a comparable performance as compared to the steam reforming by plasma catalysis, demonstrating the potential of this method for the purification of gasification gases. Furthermore, based on the rate of production (ROP) and sensitivity analyses of the model developed, as well as experimental results, the reaction mechanism was proposed.

On the Effect of Non-Thermal Atmospheric Pressure Plasma Treatment on the Properties of PET Film.

The aim of the work was to investigate the effect of non-thermal plasma treatment of an ultra-thin polyethylene terephthalate (PET) film on changes in its physicochemical properties and biodegradability. Plasma treatment using a dielectric barrier discharge plasma reactor was carried out in air at room temperature and atmospheric pressure twice for 5 and 15 min, respectively. It has been shown that pre-treatment of the PET surface with non-thermal atmospheric plasma leads to changes in the physicochemical properties of this polymer. After plasma modification, the films showed a more developed surface compared to the control samples, which may be related to the surface etching and oxidation processes. After a 5-min plasma exposure, PET films were characterized by the highest wettability, i.e., the contact angle decreased by more than twice compared to the untreated samples. The differential scanning calorimetry analysis revealed the influence of plasma pretreatment on crystallinity content and the melt crystallization behavior of PET after soil degradation. The main novelty of the work is the fact that the combined action of two factors (i.e., physical and biological) led to a reduction in the content of the crystalline phase in the tested polymeric material.

Evaluating the carbon footprint of the integrated DBD‐plasma bi‐reforming unit via laboratory scale experiments and scaled‐up process modeling

AbstractCatalytic dielectric barrier discharge (DBD) plasma reactor experiments were performed in a tubular glass reactor with a 2 mm gap at 550°C to facilitate the reaction kinetics of steam added dry reforming or bireforming. The best specific energy input obtained was 11.2 eV/molecule feed at CO2:CH4:H2O of 4.5:1:4.5 ratio and gas hour space velocity (GHSV) = 432 h−1. This value was used to design a conceptual process and assess the environmental impact of methane steam reforming‐based H2 production 18.4 kmol/h CO2 emission processing into H2:CO = 2 syngas, with an emphasis on the carbon footprint.

Innovative Method for Water-in-Oil Emulsion Treatment Using Atmospheric Nonthermal-Plasma Technology.

The field of plasma-liquid interactions is rapidly growing, with increasing publications across applications. While plasma's interactions with water and oil have been researched, there is a notable gap in the study of plasma-emulsion interactions and their practical applications. Investigating plasma-emulsion interactions offers a dual advantage, as demonstrated in this study, as it is applicable to both water/oil separation and emulsion stabilization processes. This study introduces a groundbreaking approach utilizing the fountain dielectric barrier discharge (FDBD) plasma reactor. The reactor exposes a model emulsion to different plasma gases, such as air, nitrogen, argon, and ammonia, along with varying parameters of plasma input voltage and treatment time. Consequently, due to demulsification, the emulsion segregates into distinct water and oil phases. Remarkably, the results demonstrate that short-term plasma treatment leads to the separation of over 99% of emulsified water. However, prolonged exposure to plasma for around 7 min reveals a decrease in the volume of free-separated water, implying the occurrence of stable emulsion formation instead of further demulsification. To optimize experimental conditions for compliance with regulatory requirements, the study employs the response surface methodology (RSM). Adapting pH and separation contours in three-dimensional (3D) RSM plots shows that achieving higher separation is likely associated with higher pH levels in air, nitrogen, and argon plasmas. Notably, the plasma treatment involving ammonia gas elevates the pH level and yields the highest degree of separation compared with air, nitrogen, or argon plasmas.

Plasma-catalytic pyrolysis of polypropylene for hydrogen and carbon nanotubes: Understanding the influence of plasma on volatiles

Plasma-catalytic pyrolysis was developed for upgrading polypropylene (PP) pyrolysis volatiles to co-produce carbon nanotubes (CNTs) and hydrogen. To uncover the role of plasma on the plastic catalytic pyrolysis process, the pyrolysis of polypropylene (PP) over Fe/γ-Al2O3 was carried out in a two-stage pyrolysis system with a coaxial dielectric barrier discharge (DBD) plasma reactor. The results showed that the plastic pyrolysis volatiles were further cleaved and activated with plasma, resulting in more active carbon species for the growth of CNTs. Compared to conventional catalytic pyrolysis, plasma addition shifted the initial formation temperature of CNTs to a lower ambient temperature by ∼100 °C, and significantly promoted the conversion of liquid and gaseous products to CNTs and hydrogen, with higher carbon and hydrogen yields of ∼322 mg/gplastic and 30 mmol/gplastic, respectively. In addition, the degree of graphitization of the CNTs in the presence of the plasma was significantly enhanced with less defectivity. The influence of catalytic temperature variation caused by plasma on CNTs growth was also discussed from the perspective of volatile evolution. This work highlights the potential of plasma-catalytic pyrolysis for the production of hydrogen and high-value carbon materials from plastic waste.

Optimization of Discharge Plasma Reactor for Dry Reforming of Methane using Response Surface Methodology

This research provides a study of the dry reforming of methane (DRM), which converts two main greenhouses gases (CO2 and CH4) to synthesis gas (H2 and CO) by a Dielectric Barrier Discharge (DBD) plasma reactor at atmospheric pressure. The Box-Behnken Design (BBD) method based on the Response Surface Methodology (RSM) was applied to determine the optimum experimental conditions on the plasma stability and the synthesis gas production. The synergistic effects of input power (P), CO2/CH4 ratio (R), and flow rate (FR) on the CO2, CH4 conversions, H2, CO yields, and the syngas ratio of H2 to CO were studied. With the desirability value of 0.97, the optimum values of 10.05 W (P), 1.03 (R), and 1.58 L.min−1 FR were identified with CO2 conversion of 48.56% and CH4 conversion of 86.67%; H2 and CO yields of 45.87% and 39.43% respectively; and syngas ratio of H2 to CO of 0.88. The study shows that both P and FR have a major significant effect on the reactant conversions and syngas ratio, followed by R. Meanwhile, the value of R has a significant impact on the H2, CO yields followed P and FR. In contrast, the synergistic effects between P-R, P-FR, and R-FR had a weak significant on the CO2 and CH4 conversions, H2 and CO yields, and H2 to CO ratio respectively. The quadratic term coefficients of P, R, and FR had a remarkable effect on all responses. Thus, the synergistic effect of the most important parameters improves the process efficiency. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).