Atmospheric‐pressure nonthermal plasma was used to synthesize ammonia from nitrogen and hydrogen over ruthenium catalysts. Formation of NH3 in a N2‐H2 mixture altered the plasma characteristics due ...to the low ionization potential of NH3 (10.15 eV). The optimum gas ratio was found at N2:H2 = 4:1 by volume (i.e., N2‐rich conditions). When plasma was operated at a temperature below 250 °C, the NH3 concentration increased linearly with increasing specific input energy (SIE). For the Ru(2)‐Mg(5)/γ‐Al2O3 catalyst at 250 °C, pulse energization was four times more efficient than the AC energization case. The presence of RuO2 was found to be beneficial for the NH3 synthesis via plasma‐catalysis. The addition of a small amount of O2 was found to be effective for the in situ regeneration of the deactivated catalyst. The effect of metal promoters was in the order of Mg > K > Cs > no promoter.
Plasma‐catalysis was studied to synthesis ammonia (NH3) at atmospheric pressure and temperatures near light‐off of Ru‐based catalysts. We found that the interaction of plasma and catalyst become significant when plasma‐catalyst reactor is operated at light‐off temperature of catalyst. Energy yield of NH3 synthesis was reached up to 36 g‐NH3/kWh in this study, while it was less than about 2 g‐NH3/kWh.
As the coronavirus disease 2019 (COVID-19) pandemic continues to progress, awareness about its long-term impacts has been growing. To date, studies on the long-term course of symptoms, factors ...associated with persistent symptoms, and quality of life after 12 months since recovery from acute COVID-19 have been limited.
A prospective online survey (First: September 8, 2020-September 10, 2020; Second: May 26, 2021-June 1, 2021) was conducted on recovered patients who were previously diagnosed with COVID-19 between February 13, 2020 and March 13, 2020 at Kyungpook National University Hospital. Responders aged between 17 and 70 years were included in the study. Overall, 900 and 241 responders were followed up at 6 and 12 months after recovery from COVID-19 in the first and second surveys, respectively. Clinical characteristics, self-reported persistent symptoms, and EuroQol-5-dimension (EQ5D) index score were investigated for evaluating quality of life.
The median period from the date of the first symptom onset or COVID-19 diagnosis to the time of the survey was 454 (interquartile range IQR 451-458) days. The median age of the responders was 37 (IQR 26.0-51.0) years, and 164 (68.0%) responders were women. Altogether, 11 (4.6%) responders were asymptomatic, and 194 (80.5%), 30 (12.4%), and 6 (2.5%) responders had mild, moderate, and severe illness, respectively. Overall, 127 (52.7%) responders still experienced COVID-19-related persistent symptoms and 12 (5.0%) were receiving outpatient treatment for such symptoms. The main symptoms were difficulty in concentration, cognitive dysfunction, amnesia, depression, fatigue, and anxiety. Considering the EQ5D index scores, only 59.3% of the responders did not have anxiety or depression. Older age, female sex, and disease severity were identified as risk factors for persistent neuropsychiatric symptoms.
COVID-19-related persistent symptoms improved over time; however, neurological symptoms can last longer than other symptoms. Continuous careful observation of symptom improvement and multidisciplinary integrated research on recovered COVID-19 patients are required.
•Literature review of the current status of the plasma-catalysis.•Electrical factor and equivalent circuit analysis of plasma-catalysis.•Relation between surface streamer and catalytic ...activity.•Dimensionless parameter Λ for the criteria for the interaction between NTP and catalyst.
Low temperature catalytic reactions induced by nonthermal plasma (NTP) have been of great interest in plasma chemistry for application to pollution control and energy-related issues. Current progress in the experimental observations and the understanding of interactions between NTP and catalyst are reviewed herein. Considering the diffusion length and lifetime of reactive species, we introduced a dimensionless parameter Λ that describes the criteria for a direct interaction between NTP and catalysts. Several lines of experimental evidences on the interaction were introduced: discharge mode, formation of metal cluster ions, and plasma-induced fluorescence from the catalyst. For faujasite zeolites, the Si/Al ratio was found to be an important parameter that determines the propagation of surface streamers and catalytic performance. The oxidation status of metals is closely correlated with the Si/Al ratio, which is related to substantial changes in electrical resistivity.
The current status of plasma-catalysis research and the associated possible applications are outlined. A basic explanation of plasma chemistry is given, which is then used as a foundation to indicate ...the research vector for the ongoing development of various applications. As an example of an environmental application, volatile organic compound decomposition using plasma-catalysis is discussed in depth, from the fundamental concept to the current industrial application status. As a potential application of plasma-catalysis towards the realization of a future “hydrogen society”, ammonia synthesis is discussed in terms of current social attitudes and regulations, along with historical developments. Additionally, up-to-date information on the fundamentals of the nonthermal plasma interaction with a catalyst is provided.
The 2020 plasma catalysis roadmap Bogaerts, Annemie; Tu, Xin; Whitehead, J Christopher ...
Journal of physics. D, Applied physics,
10/2020, Letnik:
53, Številka:
44
Journal Article
Recenzirano
Odprti dostop
Plasma catalysis is gaining increasing interest for various gas conversion applications, such as CO2 conversion into value-added chemicals and fuels, CH4 activation into hydrogen, higher hydrocarbons ...or oxygenates, and NH3 synthesis. Other applications are already more established, such as for air pollution control, e.g. volatile organic compound remediation, particulate matter and NOx removal. In addition, plasma is also very promising for catalyst synthesis and treatment. Plasma catalysis clearly has benefits over 'conventional' catalysis, as outlined in the Introduction. However, a better insight into the underlying physical and chemical processes is crucial. This can be obtained by experiments applying diagnostics, studying both the chemical processes at the catalyst surface and the physicochemical mechanisms of plasma-catalyst interactions, as well as by computer modeling. The key challenge is to design cost-effective, highly active and stable catalysts tailored to the plasma environment. Therefore, insight from thermal catalysis as well as electro- and photocatalysis is crucial. All these aspects are covered in this Roadmap paper, written by specialists in their field, presenting the state-of-the-art, the current and future challenges, as well as the advances in science and technology needed to meet these challenges.
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•Nonthermal plasma enables mode-selective surface chemistry.•Vibrationally excited CH4 is the key to enhancing the strong C–H bond breaking.•Co-operative activation of CO2 is ...necessary to promote overall reforming performance.•Cumulative population of bending mode CH4 is highly anticipated in 100 kHz DBD.•Kinetic parameters of plasma-enabled promotion of CH4 dry reforming is clarified.
A mode-selective control of the surface reaction is expected to be a promising approach in the heterogeneous catalysis. Nonthermal plasma is a vital solution for the generation of vibrationally excited molecules, thereby enhancing mode-selective surface chemistry. Especially, plasma-enabled promotion of heterogeneous catalysis for CH4 conversion attracts keen attention because the strong C–H bond breaking is possible via vibrational excitation of CH4 at low temperature. Similarly, vibrational excitation of CO2 possesses unique reactivity in heterogeneous catalysts. Herein, we provide a rigorous determination of kinetic parameters of CH4 dry reforming to elucidate the drastic reaction promotion mechanism enabled by plasma-catalyst interaction. Lanthanum-modified Ni/Al2O3 catalyst was combined with dielectric barrier discharge (DBD) at 5 kPa and 400–700 °C without dilution gas. Reaction order for CH4 and CO2 were determined respectively as 0.68 and −0.17; these values were kept unchanged by DBD, indicating the surface coverage of CH4 and CO2 was not influenced by nonthermal plasma. The Arrhenius plot for forward CH4 rate constant revealed that 12 kHz DBD hybrid reaction is characterized as mixed catalysis where plasma and thermal catalysis are not decoupled. The apparent activation energy was influenced only slightly by the specific energy input (SEI, eV/molecules) and gaseous hourly space velocity (GHSV, h−1), because the electrical properties of streamer swarm are not influenced to a large extent by either SEI or GHSV at fixed frequency. In contrast, 100 kHz DBD yielded significant improvement of CH4 and CO2 conversion via vibrational excitation. Activation energy decreased from 91 kJ/mol to 44.7 kJ/mol which was well correlated with the state-specific gas-surface reactivity of vibrationally excited CH4 on Ni surfaces.
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•Plasma dynamics in a packed bed DBD reactor were studied by fluid modelling.•Dielectric constant of packing beads affects plasma-catalyst interaction.•Packing with most suitable ...dielectric constant depends on the application.•Higher dielectric constant may limit catalyst activation due to confined discharge.
A packed bed dielectric barrier discharge (DBD) is widely used for plasma catalysis applications, but the exact plasma characteristics in between the packing beads are far from understood. Therefore, we study here these plasma characteristics by means of fluid modelling and experimental observations using ICCD imaging, for packing materials with different dielectric constants. Our study reveals that a packed bed DBD reactor in dry air at atmospheric pressure may show three types of discharges, i.e. positive restrikes, filamentary microdischarges, which can also be localized between two packing beads, and surface discharges (so-called surface ionization waves). Restrikes between the dielectric surfaces result in the formation of filamentary microdischarges, while surface charging creates electric field components parallel to the dielectric surfaces, leading to the formation of surface discharges. A transition in discharge mode occurs from surface discharges to local filamentary discharges between the packing beads when the dielectric constant of the packing rises from 5 to 1000. This may have implications for the efficiency of plasma catalytic gas treatment, because the catalyst activation may be limited by constraining the discharge to the contact points of the beads. The production of reactive species occurs most in the positive restrikes, the surface discharges and the local microdischarges in between the beads, and is less significant in the longer filamentary microdischarges. The faster streamer propagation and discharge development with higher dielectric constant of the packing beads leads to a faster production of reactive species. This study is of great interest for plasma catalysis, where packing beads with different dielectric constants are often used as supports for the catalytic materials. It allows us to better understand how different packing materials can influence the performance of packed bed plasma reactors for environmental applications.
The plasma catalytic valorization of gases, particularly CH4 and CO2, has gained increasing attention. Value‐added chemicals, such as syngas and ethene, can be formed under mild conditions when ...temperature‐decoupled plasma activation and multistep feasible catalytic conversion are combined. In this sense, efficient plasma–catalyst interaction is of key importance, for which, however, plasma catalysis, as an emerging technology, is still poorly studied, where new catalyst design and investigation took up the most effort. In this perspective work, the challenging but equally important plasma–catalyst interaction is discussed, comparatively analyzing which type of plasma, catalyst bed, is the most promising. Representative plasma catalytic systems with their characteristic features are summarized, where the intrinsic capability of fluidized‐bed dielectric barrier discharge (FB‐DBD) reactor to maximize the plasma–catalyst interaction is highlighted. Furthermore, ongoing research on FB plasma catalysis is reviewed, based on which the superiority of FB‐DBD to other candidates, especially the most widely used packed‐bed DBD reactor, is critically evaluated. In addition, the perspectives of FB‐DBD, including challenges and development potential, are discussed.
Herein, we focused on the challenging but critically important plasma–catalyst interaction, comparatively analyzing the candidate plasma catalytic technologies in terms of both catalyst bed and plasma characteristics, by which, the intrinsic superiority of fluidized‐bed dielectric barrier discharge (FB‐DBD) reactor was clearly confirmed: the FB with extended powdered catalyst surface area, efficient plasma generation and high transfer of heat, combined with DBD with direct catalyst‐oriented coupling, highly nonthermal properties and appropriate ionization, can cooperatively contribute to a maximized plasma–catalyst interaction.
Navigation of nanoparticles to target sites of blood flow disturbance markedly upgrades the diagnostic paradigm in vascular medicine. The theranostic treatment of pre‐stenotic vessels can prevent the ...irreversible occlusion process effectively. Here, these nanotheranostic functions are established by displaying CDK9(cyclin‐dependent kinase 9)‐targeting peptide (P.) onto nanovesicles (NV) and liposomes using the navigation function and subsequent binding‐on signaling of P. as a game‐changer. When rabbit vessels are allografted with injecting contrast‐loaded P. liposomes, the case‐dependent stenotic degree after 2–6 weeks can be diagnosed accurately within 2–4 days via computed tomography imaging with cross‐validation in a mouse model of partial carotid ligation. Furthermore, the anti‐CDK9 signaling of P. NV is activated post‐targeting and effectively prevents vascular stenosis by suppressing inflammation and lipotoxicity in the vessels, serum, and/or liver. CDK9 targeting is confirmed using computer, in vitro, and in vivo models. This study demonstrates an unprecedented nanotheranostic function for future clinical applications.
The disturbed flow‐sensing peptide plays a game‐changer role in guiding diagnosis and treatment of pre‐stenotic vessels as a theranostic navigator. Displaying the peptide on nanoparticles enables accurate prediction of vascular stenosis with subsequent prevention of vascular remodeling through multi‐organ targeting. The results from rabbit, mouse, and in vitro models validates an unprecedented nanotheranostic function for the future medicine.
There has been an increasing interest in the long-term impact of long COVID. However, only a few studies have investigated the clinical manifestations of long COVID after 24 months of acute ...infection. In this study, prospective online surveys were conducted in adults previously diagnosed with coronavirus disease 2019 (COVID-19) in South Korea between February 13 and March 13, 2020, at 6, 12, and 24 months after COVID-19. We investigated self-reported symptoms and the EuroQol-5-dimension index. Among 900 individuals enrolled initially, 150 completed all 3 surveys. After excluding the cases of COVID-19 reinfection, 132 individuals were included in the final analysis. Among the 132 participants, 94 (71.2%) experienced symptoms of long COVID. The most frequently reported symptoms were fatigue (34.8%), amnesia (30.3%), concentration difficulties (24.2%), insomnia (20.5%), and depression (19.7%). Notably, no significant differences were noted in the incidence of long COVID at 24 months in terms of the number of vaccinations received. Although the neuropsychiatric quality of life improved over time, it continued to affect 32.7% of participants. Symptoms of long COVID, particularly neuropsychiatric symptoms, tend to persist over time, and COVID-19 vaccination or the number of vaccinations received may not significantly affect the incidence of long COVID.
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