The effects of plasma inhomogeneity on the nanoparticle coating in a low pressure plasma reactor

Modelling excited species and their role on kinetic pathways in the non-oxidative coupling of methane by dielectric barrier discharge

“…For the long time-scale flow reactor simulations (Section 4.2) use of these sticking coefficient values resulted in unrealistically high carbon losses to the walls, which is in line with observations of similar studies under equivalent assumptions (De Bie et al, 2011). For such long time scales, for a fully consistent model to be developed, a carbon deposition model should be incorporated, along the lines of previous works (Bera et al, 2001, Farouk et al, 2008, Pourali and Foroutan, 2015, Yarin et al, 2006, however this was out of the scope of the present study. Results are presented primarily from simulations where the sticking coefficients of the least mobile radicals (carbon number of 2 and higher) were set to zero, while keeping the rest (ions, smaller radicals) at their literature values, however in the Supplementary material the impact of these sticking coefficients on carbon balance closure is further investigated (part 7).…”

“…The reactivity of the excited species has not been considered in the majority of previous modelling work on the upgrading of pure methane by dielectric barrier discharges (De Bie et al, 2011, Indarto et al, 2008, Khadir et al, 2017, Yang, 2003b. Of all published modelling studies on low temperature methane plasmas (Agiral et al, 2008, Bera et al, 1999, Bleecker et al, 2003, De Bie et al, 2011, Efremov et al, 2015, Fan et al, 1999, Ferrara et al, 2012, Gogolides et al, 1994, Herrebout et al, 2001, Indarto et al, 2008, Khadir et al, 2017, Kraus et al, 2002, Kudryashov et al, 2018, Liu et al, 1998, Luche et al, 2009, Masi et al, 1998, Naidis, 2007, 2018, Pintassilgo et al, 2007, Pourali and Foroutan, 2015, Qian et al, 2018, Snoeckx et al, 2013, Sun and Chen, 2019, Tachibana et al, 1984, Yang, 2003b, Yarin et al, 2006, Yoon et al, 2001, the reactivity of vibrationally excited states was accounted for by Sun and Chen (2019), who performed zero-dimensional modelling of methane upgrading via radio-frequency plasma. The results indicated that, indeed, a significant amount of vibrationally excited states is produced, with around 40% of the conversion of methane proceeding via vibrationally excited methane.…”

Plasma-enhanced catalysis for the upgrading of methane: a review of modelling and simulation methods

“…In 2015, Pourali and Foroutan presented results of a space charge sheath fluid model coupled to a surface deposition model for a collection of nano particles at various locations in a sheath. 56 It was found that the variation of the growth of nano particle size is based on the inhomogeneity of the plasma found in the space charge sheath, particularly of the concentration of the ions, as depicted in Figure 11. Finally, in 2018, Naidis demonstrated through one dimensional fluid modelling of streamer propagation, in various methane, nitrogen, and oxygen mixtures, that the streamer propagation velocity increases with heightened photon production.…”

“…A variety of works, as presented in the previous sections, have indeed implemented surface chemistry models, coupled to gasphase fluid models of methane plasmas, however all concerned film deposition and etching applications related to semiconductors processing or particle coating. 51,56,61,98 As such, the set of surface reactions considered aimed at describing the deposition rate of carbon on non-catalytic surfaces via the adsorption/desorption of radicals, ion-induced incorporation of these radicals in the growing film, direct ion incorporation in the film, etching and carbon sputtering. In plasma-catalysis, the adsorption of neutral molecules and their numerous follow-up surface reactions leading to the desorption of products, as encountered in thermal catalysis, is accompanied and potentially dominated by the interaction of the plasmagenerated radicals and excited species with the surface.…”

“…Using this type of detailed schemes has been employed for different gas discharges and different methane upgrading applications, ranging from oxidative [28][29][30][31][32][33][34][35] to non-oxidative 5,[36][37][38][39][40][41][42][43][44][45][46] and methane conversion in the presence of nitrogen. [47][48][49][50] Besides upgrading, methane plasma kinetic schemes have been employed for other purposes too, with the oldest occurrences being related to plasma-enhanced chemical vapour deposition, [51][52][53][54][55][56][57][58][59][60][61][62][63][64] and combustion and pyrolysis studies. When reviewing these sources, it is clear that within each field similar techniques have been used but in different ways e.g.…”