Pyrolysis of methane in the presence of hydrogen

Abstract

The kinetics of methane pyrolysis were studied in a tubular flow reactor in the temperature range 1200 to 1500°C at atmospheric pressure. To avoid excessive carbon formation the reaction time was short and the methane feed was diluted with hydrogen. Ethene, ethyne, benzene and hydrogen were the main gaseous products. Ethane was observed as a product at very low conversions of methane. More than 90% selectivity was obtained for C2 products. The ratio of ethyne to ethene increased with increasing temperature. The yield of C2 products is limited by gas-phase equilibrium at lower temperatures. Formation of carbon was strongly depressed by hydrogen at higher temperatures. The maximum yield of ethyne was found to increase from about 10% to about 50% when the temperature was increased from 1200 to 1500°C, with hydrogen dilution HZ: CH, = 2: 1. A mechanistic reaction model was used to simulate the pyrolysis of methane at the actual conditions. A sensitivity analysis was performed to evaluate the elementary reactions which influence the formation and consumption of the species in the model system.

In-situ investigation of gas phase radical chemistry in the catalytic partial oxidation of methane on Pt

“…As CH 2 ⋅ or CH⋅ radicals are not observed in the gas phase the formation of ethylene and acetylene does not occur by coupling of the aforementioned species but rather by dehydrogenation or oxidative dehydrogenation of ethane. This is also the common interpretation in the literature [42,43] [25], also the data in this work are in favor of an exclusive homogeneous generation of CH 3 radicals during m tion without CH 3 desorption from the Pt surface. It is not plausible that an increase in temperature by 50 °C from 1100 to 1150 °C leads suddenly to a production and desorption of CH 3 ⋅ radicals from the surface.…”

Pyrolysis of Natural Gas: Effects of Process Variables and Reactor Materials on the Product Gas Composition

“…Decreasing CH 4 conversion with increasing H 2 dilution has been observed previously [15,23,24] and results, in part, from the suppression of methyl radical formation, the first step in the pyrolysis of CH 4 , by H 2 (Eq. S1, and F B T 1673 R 3000 , Tab.…”

The modeling of realistic chemical vapor infiltration/deposition reactors

“…In the experiments, an effective temperature difference was determined to be between 40-50 K in [200,201]. Its is worth noting that the GRIMech3.0 mechanism [173] produces very similar results to our simulation.…”

“…Usually an effective temperature is considered [200]. Numerical validation is done by simulating the experiments of Olsvik et al [200,201] using integration Procedure I. In these experiments, a plug flow reactor with inner diameter 9 mm and length 1200 mm was used.…”