Molecular beam mass spectrometry and kinetic modelling of CH4–CO2–H2O plasmas for syngas production

The overall purpose of the present work is the feasibility study of syngas production from biogas in a microwave plasma discharge. Concentrations of both stable and labile species are presented from molecular beam mass spectrometry (MBMS) measurements in the case of a 50%CH4–16.7%CO2–33.3%H2O mixture. This mixture was chosen as it leads to constant amounts of CO and H2 (respectively 1/3:2/3) in the syngas produced if a complete conversion of the reactants is assumed. Practically, this initial mixture could be produced by any biogas provided that its composition is analyzed and completed to reach the required values. In our study, special attention is paid to the effect of microwave power (600–1600 W) and pressure (10–50 Torr). A complete modelling initially developed and validated (using several experimental characterization techniques such as Optical Emission Spectroscopy, Microwave Interferometry, Langmuir Probing, MBMS) for diamond deposition purposes is here used to simulate syngas production. This model takes into account the coupled hydrodynamics of the gaseous species and the gas-phase chemistry (including reactions between neutral species and dissociation by electron impact). The surface recombination of radicals at the reactor wall is also modelled. The influence of both power and pressure on syngas production is discussed as well as the transfer of the process to industry.

► We study the syngas production from biogas in a microwave plasma discharge. ► We measure concentrations of stable species by molecular beam mass spectrometry. ► We choose a 50%CH4–16.7%CO2–33.3%H2O mixture as it leads to constant amounts of CO and H2. ► The model includes the coupled hydrodynamics of the gaseous species and the gas-phase chemistry. ► We discuss the influence of both power and pressure on syngas production.