Evaluation of different dielectric barrier discharge plasma configurations as an alternative technology for green C1 chemistry in the carbon dioxide reforming of methane and the direct decomposition of methanol

Plasma-assisted removal of methanol in N2, dry and humidified air using a dielectric barrier discharge (DBD) reactor

In this work, a non-thermal plasma dielectric barrier discharge (DBD) was used to remove methanol from ambient air. The effects of carrier gases (N2, dry and humidified air), power (2-10 W), inlet concentration (260-350 ppm), and residence time (1.2-3.3 s) were investigated to evaluate the performance of the plasma DBD reactor in terms of removal efficiency, product selectivity and reduction of unwanted by-products at ambient temperature and atmospheric pressure. It was found that the conversion of methanol increased with power and residence time regardless of the carrier gas used. However, the removal efficiency decreased with the increasing concentration of CH3OH. Almost complete removal of methanol (96.7%) was achieved at 10 W and a residence time of 3.3 s in dry air. The removal efficiency of methanol followed a sequence of dry air > humidified air > N2 carrier gas. This was due to the action of the O radical in dry air, which dominates the decomposition process of the plasma system. The introduction of water vapour into the DBD system decreased the removal efficiency but had a number of significant advantages: increased CO2 selectivity and yield of H2, it significantly reduced the formation of O3, CO and higher hydrocarbons. These influences are probably due to the presence of potent OH radicals, and the conversion pathways for the various effects are proposed. It is important to note that no solid residue was formed in the DBD reactor in any carrier gas. Overall, this research indicates that methanol can be almost completely removed with the correct operating parameters (96.7% removal; 10 W; 3.3 s) and shows that humidification of the gas stream is beneficial.

Acetic acid formation from methane and carbon dioxide via non-thermal plasma reactions towards an effective carbon fixation

A non-thermal plasma reaction with CO2 and isotopic CH4 revealed that the primly produced CH3COOH could comprise both CH4-derived carbons, indicating the importance of a particular CO2 activation control for an effective carbon fixation.

Recent Developments in Dielectric Barrier Discharge Plasma-Assisted Catalytic Dry Reforming of Methane over Ni-Based Catalysts

The greenhouse effect is leading to global warming and destruction of the ecological environment. The conversion of carbon dioxide and methane greenhouse gases into valuable substances has attracted scientists’ attentions. Dry reforming of methane (DRM) alleviates environmental problems and converts CO2 and CH4 into valuable chemical substances; however, due to the high energy input to break the strong chemical bonds in CO2 and CH4, non-thermal plasma (NTP) catalyzed DRM has been promising in activating CO2 at ambient conditions, thus greatly lowering the energy input; moreover, the synergistic effect of the catalyst and plasma improves the reaction efficiency. In this review, the recent developments of catalytic DRM in a dielectric barrier discharge (DBD) plasma reactor on Ni-based catalysts are summarized, including the concept, characteristics, generation, and types of NTP used for catalytic DRM and corresponding mechanisms, the synergy and performance of Ni-based catalysts with DBD plasma, the design of DBD reactor and process parameter optimization, and finally current challenges and future prospects are provided.

Electrocatalysts for direct methanol fuel cells to demonstrate China's renewable energy renewable portfolio standards within the framework of the 13th five-year plan

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Methanol synthesis via carbon dioxide hydrogenation is reviewed.

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Up to date review on high yield catalysts for methanol synthesis are discussed.

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Catalytic performance parameters (temperature, Pressure, Support) are reviewed.

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Policy framework towards renewable energy for China is extensively reviewed.

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The catalytic mechanism and the role of promoters, bi-metallic catalyst is also discussed.

A unified treatment of the renewable portfolio standards is given concerning direct methanol fuel. The current mechanism of electrocatalysis of methanol oxidation on platinum and non-platinum-containing alloys is summarized for the systematic improvement of the rate of electro-oxidation of methanol are discussed. Policy realignment under the five-year plan is discussed in length to demonstrate how policy, markets, and engineering designs contribute towards the development of model direct methanol fuel cells operational enhancement, and factors that affect critical performance parameters for commercial exploitation are summarized for catalytic formulations and cell design within the context of why this investment in technology, education, and finances is required within the global context of sustainable energy and energy independence as exposed by thirteenth the five-year plan. The prolog focuses on the way, whereas the section on methanol fuel cells on the how and the post log on what is expected post-COVID-19 era in science and technology as China pivots to a post-fossil fuel economy.

China's industrial growth has been through internal market reforms and supplies side economics from the Chinese markets for fossil fuels except for petroleum. The latest renewable portfolio standards adopted have common elements as adopted from North American and the United Kingdom in terms of adaptation of obligation in terms of renewable portfolio standards as well as a realization that the necessity for renewables standards for the thirteen five year plan (from 2016 to 2020) need to less rigorously implemented due to performance targets that were met during the eleventh (06–10) and twelfth five-year plans (11–15) in terms of utilization of small coal-ire power plants, development of newer standards, led to an improvement of energy efficiency of 15 %, reduction of SO_x/NO_x by an average of 90 % and PM2.5 by 96 % over the last two five-year plans.

The current phase of the plan has a focus on energy generation from coal and a slowing down of renewables or Renewable energy curtailment of approximately 400 T Wh renewables including 300 T Wh of non-hydro power, principally from Guangdong, and Jiangsu for transfer of hydropower and Zhejiang, Tianjin, Henan for non-hydro power transfer with Beijing and Shanghai playing important roles in renewables energy curtailment and realignment using an integrated approach to optimize each provinces energy portfolio. The realignment of the renewable energy portfolio indicates that the newly installed capacity in Sichuan, Yunnan, Inner Mongolia, and Zhejiang will account for less than 20 % of the current renewable energy portfolio but with the NO_x SO_x and PM_2.5 savings already accrued.

The catalytic reduction of carbon dioxide to methanol (70 / 110 million metric tons from all sources in 2019 for China/world) is one technological approach to reduce global carbon dioxide emissions and suggests that catalytic methanol synthesis by CO₂ hydrogenation may be a plausible approach, even if it is more expensive economically than methanol synthesis by the syngas approach. This is because the CO₂ emissions of the synthesis are lower than other synthesis methodologies. The Chinese government has placed a premium on cleaner air and water and may view such an approach as solving the dual issues of fuel substitution and reduction of CO₂. Thus, the coupling of hydrogen generation from sustainable energies sources (Solar 175 / 509 GW) or wind (211/591.5 GW in 2019) may be an attractive approach, as this requires slightly less water than coal gasification. Due to the thermodynamic requirement of lower operating pressure and higher operating pressure, currently, there is no single operational approach, although some practice approaches (220 °C at 48 atm using copper) and zinc oxide/alumina are suggested for optimal performance.

Enhanced hydrogen generation efficiency of methanol using dielectric barrier discharge plasma methodology and conducting sea water as an electrode

In this work, methanol decomposition method has been discussed for the production of hydrogen gas with the application of plasma. A simple dielectric barrier discharge (DBD) plasma reactor was designed for this purpose with two types of electrode. The DBD plasma reactor was experimented by substituting one of the metal electrodes with feebly conducting sea water which yielded better efficiency in producing hydrogen gas. Experimental parameters such as; discharge voltage and time were varied by maintaining a discharge gap of 1.5 mm and the plasma discharge characteristics were studied. Filamentary type micro-discharges were found to be formed which was observed as numerous streamer clusters in the current waveform. Gas chromatographic study confirmed the production of hydrogen gas with residence time around 3.6 min. Although, the concentration (%) of H₂ was high (98.1 %) and consistent with copper electrode assembly, the rate of formation and concentration was found to be the highest (98.7 %) for water electrode for specific discharge voltage. The energy efficiency was found to be 0.5 mol H₂/kWh and 1.2 mol H₂/kWh for metal (Cu) and water electrodes respectively. The electrode material significantly affects the plasma condition and hence the rate of hydrogen production. Compositional analysis of the water used as electrode showed a minimal change in the composition even after the completion of the experiment as compared to the untreated water. Methanol degradation study shows the presence of untreated methanol in the residue of the plasma reactor which has been confirmed from the absorption spectra.

Coupling of CH4 to C2 Hydrocarbons in a Packed Bed DBD Plasma Reactor: The Effect of Dielectric Constant and Porosity of the Packing

The conversion of methane was investigated in a packed-bed dielectric barrier discharge (DBD) plasma reactor operated at ambient conditions. High dielectric BaTiO3 was utilized as packing in comparison with γ-alumina, α-alumina, and silica-SBA-15. Results show a considerably lower conversion of CH4 and C2 yield for the BaTiO3 packed reactor, which is even less than that obtained for the nonpacked reactor. In contrast, the low dielectric alumina (γ and α) packed reactor improved the conversion of CH4 and C2 yield. Additionally, the alumina packed reactor shifted the distribution of C2 compounds towards C2H4 higher than that obtained for the nonpacked reactor and resulted in a higher energy efficiency compared to the BaTiO3 packed reactor. This is attributed to the small pore size of BaTiO3 (10–200 nm) and its high dielectric constant, whereas the polarization inside small pores does not lead to the formation of an overall strong electric field.

DBD Plasma Combined with Different Foam Metal Electrodes for CO2 Decomposition: Experimental Results and DFT Validations

In the last few years, due to the large amount of greenhouse gas emissions causing environmental issue like global warming, methods for the full consumption and utilization of greenhouse gases such as carbon dioxide (CO₂) have attracted great attention. In this study, a packed-bed dielectric barrier discharge (DBD) coaxial reactor has been developed and applied to split CO₂ into industrial fuel carbon monoxide (CO). Different packing materials (foam Fe, Al, and Ti) were placed into the discharge gap of the DBD reactor, and then CO₂ conversion was investigated. The effects of power, flow velocity, and other discharge characteristics of CO₂ conversion were studied to understand the influence of the filling catalysts on CO₂ splitting. Experimental results showed that the filling of foam metals in the reactor caused changes in discharge characteristics and discharge patterns, from the original filamentary discharge to the current filamentary discharge as well as surface discharge. Compared with the maximum CO₂ conversion of 21.15% and energy efficiency of 3.92% in the reaction tube without the foam metal materials, a maximum CO₂ decomposition rate of 44.84%, 44.02%, and 46.61% and energy efficiency of 6.86%, 6.19%, and 8.85% were obtained in the reaction tubes packed with foam Fe, Al, and Ti, respectively. The CO₂ conversion rate for reaction tubes filled with the foam metal materials was clearly enhanced compared to the non-packed tubes. It could be seen that the foam Ti had the best CO₂ decomposition rate among the three foam metals. Furthermore, we used density functional theory to further verify the experimental results. The results indicated that CO₂ adsorption had a lower activation energy barrier on the foam Ti surface. The theoretical calculation was consistent with the experimental results, which better explain the mechanism of CO₂ decomposition.

Green chemical engineering in China

In China, the rapid development greatly promotes the national economic power and living standard but also inevitably brings a series of environmental problems. In order to resolve these problems fundamentally, Chinese scientists have been undertaking research in the area of green chemical engineering (GCE) for many years and achieved great progresses. In this paper, we reviewed the research progresses related to GCE in China and screened four typical topics related to the Chinese resources characteristics and environmental requirements, i.e. ionic liquids and their applications, biomass utilization and bio-based materials/products, green solvent-mediated extraction technologies, and cold plasmas for coal conversion. Afterwards, the perspectives and development tendencies of GCE were proposed, and the challenges which will be faced while developing available industrial technologies in China were mentioned.

Gliding Arc Plasmatron: Providing an Alternative Method for Carbon Dioxide Conversion

Low-temperature plasmas are gaining a lot of interest for environmental and energy applications. A large research field in these applications is the conversion of CO₂ into chemicals and fuels. Since CO₂ is a very stable molecule, a key performance indicator for the research on plasma-based CO₂ conversion is the energy efficiency. Until now, the energy efficiency in atmospheric plasma reactors is quite low, and therefore we employ here a novel type of plasma reactor, the gliding arc plasmatron (GAP). This paper provides a detailed experimental and computational study of the CO₂ conversion, as well as the energy cost and efficiency in a GAP. A comparison with thermal conversion, other plasma types and other novel CO₂ conversion technologies is made to find out whether this novel plasma reactor can provide a significant contribution to the much-needed efficient conversion of CO₂ . From these comparisons it becomes evident that our results are less than a factor of two away from being cost competitive and already outperform several other new technologies. Furthermore, we indicate how the performance of the GAP can still be improved by further exploiting its non-equilibrium character. Hence, it is clear that the GAP is very promising for CO₂ conversion.

The Quest for Value-Added Products from Carbon Dioxide and Water in a Dielectric Barrier Discharge: A Chemical Kinetics Study

Recycling of carbon dioxide by its conversion into value-added products has gained significant interest owing to the role it can play for use in an anthropogenic carbon cycle. The combined conversion with H₂ O could even mimic the natural photosynthesis process. An interesting gas conversion technique currently being considered in the field of CO₂ conversion is plasma technology. To investigate whether it is also promising for this combined conversion, we performed a series of experiments and developed a chemical kinetics plasma chemistry model for a deeper understanding of the process. The main products formed were the syngas components CO and H₂ , as well as O₂ and H₂ O₂ , whereas methanol formation was only observed in the parts-per-billion to parts-per-million range. The syngas ratio, on the other hand, could easily be controlled by varying both the water content and/or energy input. On the basis of the model, which was validated with experimental results, a chemical kinetics analysis was performed, which allowed the construction and investigation of the different pathways leading to the observed experimental results and which helped to clarify these results. This approach allowed us to evaluate this technology on the basis of its underlying chemistry and to propose solutions on how to further improve the formation of value-added products by using plasma technology.

Synergistic effects of plasma–catalyst interactions for CH4 activation

Plasma-assisted catalysis populates vibrationally excited CH₄ interacting with catalyst, leading to small energy barriers and enhanced rates to activate CH₄.

Plasma technology – a novel solution for CO2 conversion?

Plasma technology as a potential breakthrough technology for the economic conversion of CO₂ into value-added chemicals and fuels.

Enhanced hydrogen production by methanol decomposition using a novel rotating gliding arc discharge plasma

Hydrogen production from methanol decomposition was performed in a novel direct current (DC) rotating gliding arc (RGA) plasma reactor.

Low temperature activation of CO removal by O3-assisted catalysis

Catalytic CO oxidation was activated at low temperature by injecting O3 as an additive. It was empirically confirmed that CO removal rate was dramatically enhanced by supplying a small amount of O3, and the reaction temperature was almost half that required for CO oxidation when using a catalyst only. By optimizing the concentration of O3, catalytic CO oxidation could be achieved within 1 min at low operational temperature. The removal rate of CO was sensitive to the concentration of O3, and a deduced reaction mechanism is discussed to explain how catalytic CO oxidation is activated but subsequently deactivated at higher O3 concentration. Moreover, the presence of C3H8 and C3H6 were considered to evaluate the effects of each gas on the enhancement of CO removal rate by O3. Finally, the rate of CO removal was evaluated with increasing O3 concentration for practical applications such as the cold-start problem in automobile engines.

Combination of plasma with a honeycomb-structured catalyst for automobile exhaust treatment

To activate a catalyst efficiently at low temperature by plasma for environmental control, we developed a hybrid reactor that combines plasma with a honeycomb-structured catalyst in a practical manner. The reactor developed generated stable cold plasma at atmospheric pressure because of the dielectric and conductive nature of the honeycomb catalyst by consuming low amounts of power. In this reactor, the applied voltage and temperature determined the balance between the oxidation and adsorption by the plasma and catalyst. The synergistic reaction of the plasma and catalyst was more effective at low temperatures, resulting in a reduction in a lowered light-off temperature.