Optical and Mass Spectrometric Measurements of the CH-CO Dry Reforming Process in a Low Pressure, Very High Density, and Purely Inductive Plasma.

This paper presents a study of a CH-CO plasma-reforming process carried out in a high power density (5-50 W/cm), using toroidal transformer-coupled plasma, and operated at low pressure (0.2-0.7 Torr). Using the intermediate between a thermal and nonthermal plasma (electron density, ≈ 3 × 10 cm and a maximum gas temperature of ∼4000-6000 K along the center line), the low-pressure study provides a unique set of conditions to investigate reaction mechanisms, where three-body reactions can be ignored. Reactive species in the plasma were identified by optical emission spectroscopy. End products of the reforming process were measured by mass spectrometry. Quite high conversions of CO and CH were found (90%), with selectivities for CO and H of 80% at 300 sccm feed gas flow rate in a 0.5 Torr plasma, with a mole ratio CO-CH of 1:1. A detailed reaction mechanism is presented, taking into account the combined detection of reactive intermediates in the plasma (H, O, CH, and C) and stable product downstream.