An experimental and modeling study of diethyl carbonate oxidation

Abstract

Diethyl carbonate (DEC) is an attractive biofuel that can be used to displace petroleum-derived diesel fuel, thereby reducing CO 2 and particulate emissions from diesel engines. A better understanding of DEC combustion characteristics is needed to facilitate its use in internal combustion engines. Towards this goal, ignition delay times for DEC were measured at conditions relevant to internal combustion engines using a rapid compression machine (RCM) and a shock tube. The experimental conditions investigated covered a wide range of temperatures (660-1300 K), a pressure of 30 bar, and equivalence ratios of 0.5, 1.0 and 2.0 in air.To provide further understanding of the intermediates formed in DEC oxidation, species concentrations were measured in a jet-stirred reactor at 10 atm over a temperature range of 500-1200 K and at equivalence ratios of 0.5, 1.0 and 2.0. These experimental measurements were used to aid the development and validation of a chemical kinetic model for DEC.The experimental results for ignition in the RCM showed near negative temperature coefficient (NTC) behavior. Six-membered alkylperoxy radical (R 2 ) isomerizations are conventionally thought to initiate low-temperature branching reactions responsible for NTC behavior, but DEC has no such possible 6-and 7-membered ring isomerizations. However, its molecular structure allows for 5-, 8-and 9-membered ring R 2 isomerizations. To provide accurate rate constants for these ring structures, ab initio computations for R 2 QOOH isomerization reactions were performed. These new R 2 isomerization rate constants have been implemented in a chemical kinetic model for DEC oxidation. The model simulations have been compared with ignition delay times measured in the RCM near the NTC region. Results of the 3 simulation were also compared with experimental results for ignition in the high-temperature region and for species concentrations in the jet-stirred reactor. Chemical kinetic insights into the oxidation of DEC were made using these experimental and modeling results.

Glycerol carbonate as a fuel additive for a sustainable future

“…15 The other reason being that the decomposition of alkyl and aryl carbonates is found to be almost three order of magnitude faster than that of GC below 1000 K. Consequently, even in low temperature oxidative environment (fuel/air mixtures), their unimolecular decomposition to produce alcohol, olefin and CO 2 still remains the predominant consumption pathways (see Ref. 65 for DEC low temperature oxidation). Therefore, the ignition behavior of such fuels is pretty much governed by their decomposition products.…”

Advances in rapid compression machine studies of low- and intermediate-temperature autoignition phenomena

“…Model discrepencies found in this work, and with other experimental observations highlight the need for continued study in this area. Nakamura et al [443] measured ign for diethyl carbonate (DEC) using both an RCM and a shock tube.…”

Biodiesel at the Crossroads: A Critical Review

“…A DMC and diesel blend may also have potential in the reduction of yet unregulated carcinogenic emissions such as benzene and 1,3-butadiene [250][251][252][253][254]. Similarly to these processes, the use of diethyl carbonate (DEC) instead of DMC has been much less investigate [221,227,234], although the available results in literature [255][256][257][258][259][260][261][262][263][264][265][266] allow us to conclude that they exhibit a behavior very similar to those obtained with DMC.…”