A microwave discharge inside of a methane bubble in boiling water is modeled in a 0D approximation taking into account the change in the size of the plasma bubble. The process of quenching the reaction products after the bubble detaches from the electrode surface is also simulated. The working pressure is 1 atm. It is shown that the main reaction products are H2, CO2, and CO. The ratio of CO2 and CO concentrations depends on the ratio of the initial flows of water vapor and methane. The calculated concentrations of the main decomposition products of methane and water are in good agreement with experimental data.

Gas chromatography was used to study the products of an atmospheric pressure microwave discharge in water with methane bubbling at incident microwave power ranging between 500 and 650 W and methane flow rate ranging between 25 and 75 mL/min. The main components of products are H2, CO, CO2, and CH4. The concentration of H2 reaches 75% with the energy consumption for hydrogen formation of 25 L/kWh. A zero-dimensional self-consistent nonstationary discharge model, which takes into account the process of quenching of reaction products, was developed to analyze experimental results and study mechanisms of the formation of hydrogen and carbon oxides. Taking into account the quenching of reaction products is an important and necessary part of modeling discharges in liquids. Microwave plasma in liquid hydrocarbons is the new area of plasma physics and plasma processing. In this article, we focus on the study of hydrogen production in microwave discharge in water with methane bubbling. This process is similar to so-called methane steam reforming. The process is studied using gas chromatography and optical emission methods and a specially designed zero-dimensional self-consistent model. This model includes the stage of quenching the products of reactions. Mechanisms of main gas products (H2, CO, and CO2) were determined. image

The physical and chemical characteristics of the microwave discharge in petroleum solvent during hydrogen production processes involving Ar, He, and CO2 barbotage were studied. Gas chromatography, emission spectroscopy, high-speed photography, and shadow photography were used for diagnosis. The results demonstrated the dependence of hydrogen yield on the flow rates of Ar, He, and CO2. The maximum yield values of hydrogen were 791 mL/min and 811 mL/min, while the maximum energy efficiency reached 135.6 NL/kWh and 162.2 NL/kWh in Nefras with Ar and He barbotage, respectively. The dynamics of discharge structure and the rotational and vibrational temperatures of C2 molecules were studied.

Gas chromatography, optical emission spectroscope, high speed video camera were used to study the microwave discharge ignited near the end of the microwave antenna in aqueous solution of ethanol at different ethanol content and different incident microwave power. The pressure above the surface of liquid was close to atmospheric pressure. The main gas products were H-2, CO, C2H2, CH4, C2H4. H-2 (approximate to 60 vol%) and CO (approximate to 30 vol%) are predominated. The composition of the reaction products in a microwave discharge is practically independent of incident power and ethanol content in the solution, but the total flow rate of gas products at the system output increases with an increase in the incident power and the ethanol content in solution. Best obtained characteristics of process of hydrogen production were: flow rate of hydrogen was of 3240 mL/min, concentration of hydrogen in gas mixture on the discharge outlet was of 59 vol%, maximum energy efficiency of hydrogen production was of 324 NL/kWh.

A number of catalysts based on cerium oxide have been synthesized to study the process of plasma-catalytic decomposition of CO 2 in a barrier discharge. For the first time, an oxide catalyst MgCe-Al has been compared with samples containing in the composition only cerium oxide or magnesium oxide. It has been established that, in the presence of the MgCe-Al sample, the highest degree of the CO 2 decomposition and highest energy efficiency get achieved. Keywords: barrier discharge, cerium oxide, low temperature plasma, catalyst, CO 2 decomposition.

A number of catalysts based on cerium oxide have been synthesized to study the process of plasma-catalytic decomposition of CO2 in a barrier discharge. For the first time, an oxide catalyst MgCe–Al has been compared with samples containing only cerium oxide or magnesium oxide in the composition. It has been established that in the presence of the MgCe–Al sample, the highest degree of CO2 decomposition and energy efficiency are achieved.

The task of CO2 decomposition is one of the components of the problem associated with global warming. One of the promising directions of its solution is the use of low-temperature plasma. For these purposes, different types of discharges are used. Microwave discharge in liquid hydrocarbons has not been studied before for this problem. This paper presents the results of a study of microwave discharge products in liquid Nefras C2 80/120 (petroleum solvent, a mixture of light hydrocarbons with a boiling point from 33 to 205 °C) when CO2 is introduced into the discharge zone, as well as the results of a study of the discharge by optical emission spectroscopy and shadow photography methods. The main gas products are H2, C2H2, C2H4, CH4, CO2, and CO. No oxygen was found in the products. The mechanisms of CO2 decomposition in the discharge are considered. The formation of H2 occurs simultaneously with the decomposition of CO2 in the discharge, with a volumetric rate of up to 475 mL/min and energy consumption of up to 81.4 NL/kWh.

Results of the study of acoustic phenomena and changes in the structure of the microwave (2.45 GHz) discharge in liquid hydrocarbons in time are presented. Discharge was ignited at the tip of microwave antennas with conical or rounded ends. Petroleum solvent Nefras was chosen as representative of liquid hydrocarbons. Electret microphone and high-speed video cameras were used to study the discharge. It is shown that the discharge is always attached to the top of the cone in the case of the conical end of the antenna whereas ignition of the discharge generates in the gas part of the reactor a set of acoustic oscillations with frequencies corresponding to the characteristic oscillations of the reactor.

The methods of emission spectroscopy, shadow photography, and integral radiation of a discharge with time resolution are used to study the initial stages of the development of a microwave discharge in liquid hydrocarbons when argon is supplied to the discharge region. As a representative of a wide range of hydrocarbons, the petroleum solvent Nefras C2 80/120 is used. With the help of shadow photographs, the change in the structure of the discharge with time was studied, and the sizes and growth rates of the gas bubble with plasma are determined. The emission spectra of the discharge, obtained at an exposure time of 1 ms, shows that, in addition to the usual Swan and CH bands, the spectrum contains atomic emission lines of Hα and of a carbon ion. The presence of these lines is associated with the big role of electron impact in the kinetics of processes in plasma at short times.

Time-resolved optical techniques (spectrograph, high-speed camera, photodiode) were used for scrutinizing the initial stages of the microwave discharge (2.45 GHz, 200-500 W) achieved in liquid alkanes (CnH2n + 2). Petroleum solvent Nefras S2 80/120 (a mixture of light hydrocarbons with boiling temperatures ranging between 33 degrees C and 205 degrees C) was considered to be representative of alkanes. The discharge was ignited in the liquid, at the end of a molybdenum antenna located under ambient conditions above the liquid. The discharge displaced sequences of light pulses of different shapes and amplitudes, randomly distributed in time. The minimum pulse duration is 0.5 ms. At times close to 1 ms, the spectrum comprises emission bands of the C-2 molecule, lines of hydrogen, and the C+ ion, but there is no continuum associated with the emission of the formed solid carbon-containing particles. In a number of cases, an anomalous spectrum of the C-2 molecule was recorded, with no such sequences having been observed before.

In this work solution enthalpies of aromatic compounds and their halogen derivatives in 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4], 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide [BMIM][NTf2], 1-butyl-3-methylimidazolium trifluoromethanesulfonate [BMIM][TfO] were measured by solution calorimetry method. The solvation enthalpies of aromatic compounds and their halogen derivatives in ionic liquids were calculated. Based on experimentally measured solvation enthalpies and calculated non-specific solvation enthalpy the contribution of the solvophobic effect on the solvation enthalpy of dissolved molecules in ionic liquids was demonstrated to be negligible. The correlation between solvation enthalpies of the aromatic compounds and their halogen derivatives in ionic liquids and solute molecules polarizability parameter was found. Also, a comparison of relationships between solvation enthalpy and molar refractions in ionic liquids and molecular solvents was made.