Shock-tube study of methane pyrolysis in the context of energy-storage processes

Abstract

The thermal decomposition of methane (10 mol% in inert gases) was investigated behind reflected shock waves. Product spectra were measured via GC/MS after reactions with initial temperatures between 1285 and 2400 K at pressures of 1.5 bar in a single-pulse shock tube and of 30 bar in a high-pressure shock tube with rapid gas sampling via a fast opening valve. In the 1.5-bar experiments, additional time-resolved absorption measurements in the mid-IR were carried out. The temporal variation in CH4 concentration was measured at 836–2495 K and 1.8 bar with interband-cascade lasers near 3.39 µm. Time-resolved temperatures were determined via CO two-line thermometry with two quantum-cascade lasers near 4.56 and 4.85 µm for initial post-shock temperatures of 1715–2573 K at 2.2 bar. The results were compared to simulations based on three different literature mechanisms (Cai and Pitsch, 2015; Porras et al., 2017; Wang et al., 2007) as well as with the new rate constant of methane dissociation from Wang et al. (2016).