Spectroscopy and decomposition kinetics of dimethoxymethane and 1,2-dimethoxyethane at high temperatures

Abstract

This work focuses on measuring the temperature dependent absorption spectra and decomposition rates of two small diethers, dimethoxymethane (DMM) and 1,2-dimethoxyethane (12DME). The experiments were conducted using a broadband, rapid-tuning laser combined with a shock tube and a newly developed high-temperature optical gas cell. Broadband spectral measurements were performed at various temperatures, reaching up to 822 K, and pressures close to 1.01 bar. These measurements spanned the wavelength range of 8.4–10.5 µm (950–1190 cm⁻¹), which corresponds to the strongest infrared absorption bands of these diethers. These spectra were used to develop a fixed-wavelength high-temperature diagnostic for transient reactive systems. Based on our analysis, we proposed a probe wavelength of 1120.5 cm⁻¹ for the decomposition study of these diethers. Mole fraction time-histories of their consumption were measured in shock tube experiments at temperatures ranging from 1116 to 1413 K, and pressures ranging 0.9–2 bar. Our experimental concentration profiles for DMM showed excellent agreement with simulation results based on a recent model proposed by Jacobs et al. [1]. For 12DME, our measured decomposition rates are approximately 70 % lower than those reported in the only available literature model by Sun et al. [2]. Our measured unimolecular decomposition rates are described by the following modified Arrhenius rate expressions (unit s⁻¹): k_DMM(T) = 2.184 × 10⁴⁶×(K/T)^9.183 × exp(−42730 K/T) and k_12DME(T) = 2.576 × 10¹³ × exp(−28670 K/T).