A heterogeneous reactor model was developed describing kinetic experiments on the heterogeneously catalyzed oxidative coupling of methane in a laboratory fixed-bed reactor. The catalyst produces radicals which react further through gas-phase reactions in the pores of the catalyst and in the interstitial phase. The reactor model accounts for the irreducible mass-transport limitations for the reactive radicals, which occur even at conditions where no mass-transport limitations occur for the molecules, both reactants and reaction products. The effects of these irreducible mass-transport limitations on the conversion and selectivity of the process were investigated and were found to be essential for an adequate description of experimental data.

A kinetic model was developed for the heterogeneously catalyzed oxidative coupling of methane for temperatures between 923 and 1023 K, inlet methane-to-oxygen ratios of 2 to 12, and oxygen conversions between 10 and 100%. This model features 10 catalytic reactions coupled to 39 gas-phase chain reactions and accounts for irreducible mass-transport limitations for reactive intermediates. The observed conversions and selectivities are adequately described up to 200 kPa total pressure. The observed strong increase of the conversions between 200 and 1000 kPa is described qualitatively. The catalyst not only produces radicals but also acts as an important radical quencher. Regeneration of the active sites through water desorption was found to be a kinetically significant step in the catalytic sequence producing methyl radicals. At atmospheric pressure approximately 90% of the methane and oxygen is converted on the surface of Sn/Li/MgO, the balance being converted through branched-chain reactions in the pores of the catalyst and in the interstitial phase. For Li/MgO only one-third of the methane is converted on the catalyst surface. For Sn/Li/MgO the catalytic oxidation of methyl radicals, rather than gas-phase reactions, limits the selectivity toward C2 products.

The oxidative coupling of methane with cofeeding of ethane was investigated experimentally both in the absence and in the presence of a Sn/Li/MgO catalyst. Cofeeding ethane in the absence of catalyst results in a higher total radical concentration, explaining the strong increase of the observed feed conversions. The hydrogen-peroxy radical-concentration increase is more pronounced than the corresponding methyl radical concentration increase, resulting in a lower selectivity. The combined effect of feed conversion and selectivity is beneficial for inlet ethane-to-methane ratios lower than 4 mol%. Ethane cofeeding results in a slight increase of the oxygen conversion in the presence of a Sn/Li/ MgO catalyst. This can be accounted for by a mechanism in which both the hydrogen abstraction from the hydrocarbon and the regeneration of the active sites are kinetically significant. The corresponding decrease of methane conversion results from competition between methane and the more reactive ethane for these sites. The addition of ethane does not result in a beneficial effect on conversions to ethane or C2.

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For contemporary applications, CL-20’s energy density is the highest of any explosive, but it has a very high susceptibility and very low stability. Eutectic techniques can successfully lower CL-20’s susceptibility. However, the eutectic susceptibility can be significantly impacted by the high temperature and many flaws found in its manufacture. By removing CL-20 molecules in Materials Studio (MS) using a molecular dynamics approach, a CL-20/TNT eutectic model with various vacancy concentrations was created in this study. Equilibrium state simulations of the model were run at various temperatures to determine the corresponding kinetic parameters. The susceptibility of CL-20/TNT eutectic-containing vacancy defects is found to increase with the increase in defect concentration and with the increase in temperature, which guides the study of CL-20’s stability and the reduction of susceptibility methods in engineering preparation. Cohesive energy density and binding energy are used at the molecular level as the evaluation criteria of the susceptibility at the macroscopic level.