AbstractA dual-frequency-comb spectrometer based on two quantum-cascade lasers is applied to kinetics studies of formaldehyde (HCHO) in a shock tube. Multispectral absorption measurements are carried out in a broad spectral range of 1740–1790 cm^–1 at temperatures of 800–1500 K and pressures of 2–3 bar. The formation of HCHO from thermal decomposition of 1,3,5-trioxane (C₃H₆O₃, 0.9% diluted in argon) and the subsequent oxidation of formaldehyde is monitored with a time resolution of 4 µs. The rate coefficient of the decomposition of C₃H₆O₃ (i.e., HCHO formation) is found to be k₁ = 6.0 × 10¹⁵ exp(− 205.58 kJ mol⁻¹/RT) s^–1. For the oxidation studies, mixtures of 0.36% C₃H₆O₃ and 1% O₂ in argon are used. The information of all laser lines, along with the consideration of individual signal variance of each line, is utilized for kinetic and spectral analysis. The experimental kinetic profiles of HCHO are compared with simulations based on the mechanisms of Zhou et al. (Combust Flame, 197:423–438, 2018) and Cai and Pitsch (Combust Flame, 162:1623–1637, 2015).