High Temperature Thermal Decomposition of Diethyl Carbonate by Pool Film Boiling

Abstract

We use the configuration of film boiling on a horizontal tube positioned in a stagnant pool of saturated diethyl carbonate (DEC, (C2H5O)2CO) to study DEC decomposition at temperatures up to 1500 K. The composition of bubbles that percolate through the liquid pool is measured and the results are used to infer the decomposition reactions. The results show that below tube temperatures of about 1100 K, the decomposition products are ethylene (C2H4), carbon dioxide (CO2), and ethanol (EtOH, C2H5OH) with a molar ratio nC2H4/nCO2∼1, which is consistent with a first-order decomposition process. At higher temperatures, nC2H4/nCO2 > 1 which is explained by an additional route to forming C2H4 from radicals in the system (created by EtOH decomposition) attacking DEC. The presence of H2, CO, CH4, and C2H6 in the product stream was noted at all temperatures examined with concentrations that increased from trace values at low temperatures to values comparable to the DEC unimolecular process at the highest temperatures. Formation of a carbon layer on the tube was observed but did not appear to influence the decomposition process. A scale analysis shows that the rate constant controls decomposition compared to the residence time, which has a weaker dependence on temperature.