Pyrolysis of diethyl carbonate: Shock-tube and flow-reactor measurements and modeling

Shock-tube and flow-reactor experiments were used to study the thermal decomposition of diethyl carbonate (C2H5OC(O)OC2H5; DEC). The formation of CO2, C2H4, and C2H5OH was measured with gas chromatography/mass spectrometry (GC/MS) and high-repetition-rate time-of-flight mass spectrometry (HRR-TOF-MS) behind reflected shock waves. The same products were also detected by GC/MS in flow reactor experiments. All experiments combined span a temperature range of 663-1203 K at pressures be-tween 1.0 and 2.0 bar. Time-resolved species concentration profiles from HRR-TOF-MS and product com-positions from GC/MS measurements were simulated applying a detailed reaction mechanism for DEC combustion. A master-equation analysis was conducted based on computed energies from G4 calcula-tions. Quantum chemical calculations confirm that DEC primarily decomposes by six-center elimination, C2H5OC(O)OC2H5 -> C2H4 + C2H5OC(O)OH (1a), followed by rapid decomposition of the alkoxy acid, C2H5OC(O)OH -> C2H5OH + CO2 (1b). Measured DEC decomposition rate constants k(T) at p approximate to 1.5 bar can be represented by the Arrhenius equation k(T) = 10(13.64 +/- 0.12) exp(-204.24 +/- 1.95 kJ/mol/RT) s(-1). Theoretical predictions for k 1a were in good agreement with experimentally derived values. The theoretical analysis also included dipropyl carbonate (C3H7OC(O)OC3H7; DPC) decomposition and the reactivities of DEC and DPC are compared and discussed in the context of reactivity of dialkyl carbonates under pyrolytic conditions. (c) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

Shock-tube and flow-reactor experiments were conducted to study the thermal decomposition of diethyl carbonate (DEC). The formation of products and reaction mechanisms were analyzed using gas chromatography/mass spectrometry (GC/MS) and theoretical calculations. Results showed that DEC primarily decomposes by six-center elimination and the decomposition rate constants align well with the Arrhenius equation. The study also compared the reactivities of dialkyl carbonates under pyrolytic conditions.