An alternating-current (AC) gliding arc reactor has been developed offering a new route for the co-generation of syngas and value-added carbon nanomaterials by plasma dry reforming of methane. ...Different carbon nanostructures including spherical carbon nanoparticles, multi-wall carbon nanotubes and amorphous carbon have been obtained as by-products of syngas generation in the plasma system. Optical emission spectra of the discharge demonstrate the formation of different reactive species (Al, CO, CH, C2, Hα, Hβ and O) in the plasma dry reforming reaction. The effect of different operating parameters (feed flow rate, input power and CH4/CO2 molar ratio) on the performance of the plasma process has been evaluated in terms of the conversion of feed gas, product selectivity and energy conversion efficiency. It is interesting to note that gliding arc plasma can be used to generate much cleaner gas products of which syngas is the main one. The results also show that the energy efficiency of dry reforming using gliding arc plasma is an order of magnitude higher than that for processing using dielectric barrier or corona discharges. Both of these can be attributed to the higher electron density in the order of 1023 m−3 generated in the gliding arc plasma.
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•Gliding arc offers a new route to co-generate syngas and carbon nanomaterials.•Three different carbon nanomaterials are generated as by-products of syngas.•Gliding arc dry reforming process generates much cleaner gas products.•High electron density of the order of 1023 m−3 is generated in the gliding arc.•The energy efficiency of the gliding arc dry reforming is much higher than for other cold plasmas.
The combination of a nonthermal, atmospheric plasma with a catalyst is investigated as a means of destroying pollutants in waste gas streams. Using the examples of dichloromethane (DCM) and toluene ...in air streams, it is shown that the destruction of the pollutant can be increased whilst lowering the operating temperature, giving increasing energy efficiency. Unwanted by-products can also be reduced selectively by appropriate choice of catalyst and of the plasma–catalyst configuration. By studying the temperature dependence of plasma catalysis, some ideas can be obtained about the nature of the interaction between plasma and catalyst in the processing.
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.
The issues of describing and understanding the changes in performance that result when a catalyst is placed into plasma are discussed. The different chemical and physical interactions that result and ...how their combination might produce beneficial results for the plasma-catalytic processing of different gas streams are outlined with particular emphasis being placed on the different range of spatial and temporal scales that must be considered both in experiment and modelling. The focus is on non-thermal plasma where the lack of thermal equilibrium creates a range of temperature scales that must be considered. This contributes in part to a wide range of inhomogeneity in different properties such as species concentrations and electric fields that must be determined experimentally by
in situ
methods and be incorporated into modelling. It is concluded that plasma-catalysis is best regarded as conventional catalysis perturbed by the presence of a discharge, which modifies its operating conditions, properties and outcomes often in a very localised way. The sometimes used description “plasma-activated catalysis” is an apt one.
Large prospective studies to establish the prevalence of non-alcoholic fatty liver disease (NAFLD) and steatohepatitis (NASH), are lacking. We prospectively assessed the prevalence and severity of ...NAFLD/NASH in a cohort of asymptomatic middle-aged Americans attending a colonoscopy class at a gastroenterology clinic.
Screening for NAFLD was performed using magnetic resonance (MR)-based LiverMultiScan® proton density fat fraction (LMS-PDFF). MR exams also included corrected T1 and elastography for liver stiffness measurement (LSM). FibroScan® was also used to measure LSM. Participants with predetermined abnormal imaging parameters were offered a liver biopsy. Biopsies were read in a blinded fashion with results based on the consensus by 2 expert pathologists. The prevalence of NAFLD was determined by PDFF ≥5% or by histological diagnosis of NAFLD (if biopsy data were available). The prevalence of NASH was defined by biopsy.
Of 835 participants, 664 met the inclusion and exclusion criteria. The mean age was 56 ± 6.4 years, 50% were male, the mean BMI was 30.48 ± 5.46 kg/m2, and 52% were obese. The prevalence of NAFLD was 38% (95% CI 34–41%) and the prevalence of NASH was 14% (95% CI 12–17%). While no patient had cirrhosis on biopsy, significant fibrosis (F ≥2) was present in 5.9% (95% CI 4–8%) and bridging fibrosis in 1.6% (95% CI 1-3%). In a multivariable analysis, factors associated with the presence of NASH were race, obesity, and diabetes.
Using state-of-the-art liver imaging modalities and reference biopsy, this study establishes an overall prevalence of NAFLD of 38% and NASH by biopsy of 14% in this cohort of asymptomatic middle-aged US adults.
There are no prospective studies to determine how common is nonalcoholic steatohepatitis (NASH), the severe form of non-alcoholic fatty liver disease (NAFLD). In a large number of asymptomatic middle-aged Americans, we used a combination of state-of-the-art liver imaging methods and liver biopsy to prospectively determine the prevalence of NAFLD and NASH. NAFLD was diagnosed in 38%, NASH in 14%, and significant liver fibrosis in 6% of asymptomatic middle-aged Americans.
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•In a prospective large cohort of middle-aged Americans living in Texas, the prevalence of NAFLD was estimated to be 38%.•Based on liver histology data, NASH was diagnosed in 14% of the entire cohort and 37% of those with NAFLD.•NASH was more common in Hispanics and those with obesity or type 2 diabetes.
Non‐thermal plasma has been investigated for CO2 reforming of CH4 in a coaxial DBD reactor with different reactor packing materials placed into the discharge gap. Both the chemical and physical ...effects on reaction performance have been examined for the addition of quartz wool, γ‐Al2O3 and zeolite 3A, in order to gain a better understanding of plasma interactions with materials during CH4 reforming reactions. Quartz wool was found to enhance the conversion of CH4 and improve H2 yields as a result of changes in the physical properties of the discharge; electrical measurements showed an increase in the intensity of microdischarge filaments over quartz wool. In the presence of Al2O3 and zeolite 3A, the discharge intensity was reduced and consequently CH4 and CO2 conversions were lower for these materials. However, in the presence of zeolite 3A improved selectivities towards H2 and light hydrocarbons acetylene/ethylene were obtained and formation of liquid hydrocarbons was inhibited due to shape‐selectivity determined by the zeolite pore size.
Both the physical and chemical interactions between plasma and packing materials play an important role in improving the reaction performance in a plasma‐catalysis system. The presence of zeolite 3A in the discharge significantly improves the selectivities towards H2 and light hydrocarbon (C2H2/C2H4) production due to shape‐selectivity determined by the zeolite pore diameter.
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