Plasma kinetics in ethanol/water/air mixture in a ‘tornado’-type electrical discharge

Abstract

This paper presents the results of a theoretical and experimental study of plasma-assisted reforming of ethanol into molecular hydrogen in a new modification of the "tornado" type electrical discharge.Numerical modeling clarifies the nature of the non-thermal conversion and explains the kinetic mechanism of nonequilibrium plasma-chemical transformations in the gas-liquid system and the evolution of hydrogen during the reforming as a function of discharge parameters and ethanol-to-water ratio in the mixture. We also propose a scheme of chemical reactions for plasma kinetics description. It is shown that some characteristics of the investigated reactor are at least not inferior to characteristics of other plasma chemical reactors. PACS: 52.65.-y, 52.80.-s IntroductionThe interest to alternative fuels research in the last two decades is increased by the depletion of the traditional fossil fuels. Today, ethanol is considered the most perspective fuel for internal-combustion engines [1]. First, it could be produced from renewable sources (biomass, industrial waste, etc). Second, its combustion produces relatively small amount of pollutants. However, the low velocity of the ethanol combustion wave propagation does not allow its use in its pure form as an engine fuel [2]. In order to increase this velocity, one needs to enrich С 2 Н 5 ОН by molecular hydrogen [3], since the latter has higher flame speed than alcohol. Unfortunately, there is another problem of storing H 2 on a vehicle. Recently, several methods were proposed to obtain hydrogen from hydrocarbon fuels before its entering to the engine [1]. The methods are partial oxidation, steam reforming, dry CO 2 reforming, thermal decomposition and plasma-assisted reforming.The use of non-equilibrium plasma looks more attractive as a result of its lower energy consumption. Plasma acts as a catalyst and initiates fast chain reactions that do not progress under normal conditions. Today different plasma chemical reactors are used (for example [1], [4][5][6]) for molecular hydrogen generation from different hydrocarbons (ethanol, methane, etc) in non-equilibrium plasma. In [7][8], a new plasma chemical reactor for ethanol-to-hydrogen conversion was proposed. It was shown

Effect of Catalyst Deactivation on Kinetics of Plasma-Catalysis for Methanol Decomposition

“…As already mentioned, the plasma effect induced by electron collisions mainly contributes to the generation of primary radicals in the initial reaction step. At this point, the reaction pathway is determined by the energy levels of the electrons participating in collisions; the threshold energy levels for Equation – are shown below …”

“…At this point, the reaction pathway is determined by the energy levels of the electrons participating in collisions; the threshold energy levels for Equation (13)- (15) are shown below. [26,27] CH 3 OH þ e ! CH 3 O þ H E th ¼ 7:95 eV ð13Þ…”

“…This process finally results in lowered activities of collision-induced reaction pathways. [26] The relative proportions of primary radicals induced by direct collisions with electrons (P1-P3) therefore change. The above discussion suggests that modification of the catalyst surface through reactions can be a passive parameter that controls the selectivities among P1-P3, and gives a clue to the possible control of the reaction pathway by active modification of the discharge surface.…”

Hydrogen Conversion in DC and Impulse Plasma-Liquid Systems

“…The full mechanism developed for this experimental work is composed of 30 components and 130 chemical reactions between them and its closed to [11]. The charged particles (electrons and ions) are ignored in the mechanism, because of low degree of ionization of the gas (~ 10 −6 -10 −5 ).…”

Theoretical studies on the mechanism and kinetic for CH3CH2O + HO2 and CH3CHOH + HO2 reactions

“…[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] As highly reactive transient intermediates, HO 2 radical plays an important role in the atmospheric oxidation, [16] hydrocarbon fuel combustion reaction, [17] atmospheric photo-chemical reaction, [18] and some very important biochemical reactions. [19] As an important reaction with HO 2 radical and C 2 H 5 O radical, [20,21] it is of great significance to the study of atmospheric chemistry. It has been suggested that the further oxidation of CH 3 O and CH 2 OH radicals by HO 2 produces more stable species like formaldehyde, formic acid, or hydrogen peroxide Equations 3 to 5.…”