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The kinetic modeling of high-temperature reforming of oxygen-free mixtures of methane with H2, H2O, CO, and CO2 additives into synthesis gas with strong dilution with argon under conditions of variable temperature and the formation of microheterogeneous soot particles was carried out. Such mixtures are typical for biomass gasification products, in which H2O, CO, and CO2 additives act as oxidizing agents. A direct comparison of kinetic calculations with the results of published experiments in a flow reactor at temperatures of 1100–1800 K, atmospheric pressure, and a reaction time of 0.68 s was carried out. The yields of soot were calculated for all test mixtures and conditions. A comparison of the results of kinetic calculations and experiments made it possible to evaluate the effect of soot formation on the reforming of methane with the additions of H2, H2O, CO, and CO2. The work analyzes two ways for carbon atoms to leave a reacting gas-phase system. The first way is the heterogeneous deposition of acetylene molecules from the gas phase onto the surface of the reactor with the subsequent formation of solid carbon, and the second way is the formation of microheterogeneous soot particles from nuclei in the gas phase. The paper compares the results of experiments in reflected shock waves and our kinetic calculations of the absolute concentration of CO for the process of methane oxidation in oxygen-free mixtures of methane and CO2. Mixtures with various CH4/CO2 ratios, 90/10, 75/25, and 50/50, were studied at temperatures above 2200 K and atmospheric pressure. It has been shown that the agreement between the calculated and measured CO concentrations improved with increasing temperature and CO2 fraction in the mixture. [ABSTRACT FROM AUTHOR]

Reducing carbon dioxide emissions during production is one of the main trends in modern oil and gas chemistry. One of the most realistic possibilities for achieving this is to involve carbon dioxide generated in technological processes as a feedstock for producing gas chemical products. The maximum effect can be achieved in the production of large-scale chemicals, such as syngas, hydrogen, and methanol. We consider such possibilities and present a new combined autothermal process for the joint production of hydrogen and methanol based on non-catalytic matrix conversion of natural gas into syngas, which allows one to almost avoid CO2 emissions. [ABSTRACT FROM AUTHOR]

The influence of the formation of microheterogeneous soot particles on the gas-phase conversion of rich mixtures of methane with oxygen into synthesis gas in a temperature range from 1500 to 1800 K under the conditions of an adiabatic reactor was studied by kinetic modeling. The effect of CO2 and H2O additives on this process was studied. The appearance of soot particles was observed in rich mixtures, starting from the fuel excess factor ϕ = 3.33. At relatively low temperatures of ~1500 K, a small amount of microheterogeneous soot particles was formed, which did not significantly affect other components of the reacting system. A noticeable effect of soot particles at this temperature was observed at a higher value of ϕ = 8.0. This was most clearly manifested in the temperature profile of the process, in which two maximums were observed at times of about 0.01 and 0.1 s upon the addition of water to the reacting mixture. In the case of CO2 additions, the second maximum in the temperature profile was almost not pronounced. A complex temperature profile led to the appearance of the second concentration maximum of hydroxyl radicals OH at times of ~0.1 s. The addition of H2O and CO2 made it possible to vary the H2/CO ratio in the synthesis gas over a wide range, which is necessary for the synthesis of various products. Because the added CO2 under these conditions was actually involved in the chemical process of obtaining synthesis gas, its partial recirculation from the conversion products made it possible to reduce its emission in the production of synthesis gas. [ABSTRACT FROM AUTHOR]

The paper reports the results of a kinetic and thermodynamic analysis of non-catalytic partial oxidation of methane and C2–C4 hydrocarbon/hydrogen mixtures (C/H = 1 : 4) at 1400–1700 K. The hydrocarbon conversion sequence and the time periods of the major process stages were identified for isothermal conditions. The initial stage of the oxidative conversion of C2+ hydrocarbons consists of their pyrolysis, primarily into ethylene and propylene, followed by oxidation of the pyrolysis products. In this respect, the kinetics of C2+ hydrocarbon oxidative conversion are different from those of methane conversion, marked by the almost simultaneous and significantly slower occurrence of pyrolysis and oxidation. The subsequent stages involve steam and dry reforming of the oxidation products, namely acetylene and methane; these stages continue until the main products (H2, CO, CO2, and H2O) reach an equilibrium distribution for the given temperature. The study findings are important for the optimization of various techniques for high-temperature syngas production via partial oxidation of C2+ hydrocarbons, as well as Moderate or Intense Low-Oxygen Dilution (MILD) combustion processes. [ABSTRACT FROM AUTHOR]