Shock Tube/Laser Absorption and Kinetic Modeling Study of Triethyl Phosphate Combustion

Abstract

Pyrolysis and oxidation of triethyl phosphate (TEP) were performed in the reflected shock region at temperatures of 1462-1673 K and 1213-1508 K, respectively, and at pressures near 1.3 atm. CO concentration time histories during the experiments were measured using laser absorption spectroscopy at 4580.4 nm. Experimental CO yields were compared with model predictions using the detailed organophosphorus compounds (OPC) incineration mechanism from the Lawrence Livermore National Lab (LLNL). The mechanism significantly underpredicts CO yield in TEP pyrolysis. During TEP oxidation, predicted rate of CO formation was significantly slower than the experimental results. Therefore, a new improved kinetic model for TEP combustion was developed, which was built upon the AramcoMech2.0 mechanism for C-C chemistry and the existing LLNL submechanism for phosphorus chemistry. Thermochemical data of 40 phosphorus (P)-containing species were reevaluated, either using recently published group values for P-containing species or by quantum chemical calculations (CBS-QB3). The new improved model is in better agreement with the experimental CO time histories within the temperature and pressure conditions tested in this study. Sensitivity analysis was used to identify important reactions affecting CO formation, and future experimental/theoretical studies on kinetic parameters of these reactions were suggested to further improve the model. To the best of our knowledge, this is the first study of TEP kinetics in a shock tube under these conditions and the first time-resolved laser-based species time history data during its pyrolysis and oxidation.

The decisive role of pericyclic reactions in the thermal decomposition of organophosphorus compounds

“…6a-c) and oxidation (Fig. 6d-g) respectively, by Neupane et al [15] and simulations carried out with the model from these authors [16] and our model. Experimental uncertainty in the measured CO mole fraction was estimated to be 7.2% or ±123…”

“…P=1.42-1.32 atm, (f, g) X TEP = 0.038%, =0.078, P=1.27-1.17 atm. Symbols, experimental results [15]; simulations, this work (solid curve), literature model [16] (dashed curve).…”

“…They pointed out the important role of molecular elimination reactions even in highly reactive combustion conditions and showed that DMMP, which cannot react through a six-membered elimination, was not a suitable surrogate for sarin, contrary to DIMP. In shock tube, Mathieu et al [14] investigated the influence of DMMP on hydrogen, methane, and ethylene ignition in shock tube and Neupane et al studied experimentally [15] and modelled [16] the decomposition of TEP.…”

Decomposition of Chemical Warfare Agent Simulants Utilizing Pyrolyzed Cotton Balls as Wicks

“…The formation of this vapor, which was more pronounced in smaller pans, was attributed to a pericyclic reaction that results in the fragmentation of TEP, a retro-ene reaction, as proposed in Figure 7 . 39 , 40 , 46 , 47 , 49 While the literature differs on if the pericyclic reaction proceeds in a six-centered 47 or four-centered 46 pericyclic reaction, the expected byproducts are consistently ethylene, ethanol, and phosphoric acid. While the exact mechanism of decomposition has not been confirmed, the proposed mechanism suggests that the energy from the burning napalm causes the pericyclic reaction, resulting in the expulsion of highly flammable ethylene.…”

An Optical Measurement System to Measure Velocity and Provide Shock Wave Pressure Diagrams

“…The first group of sensors are time detectors with laser [9], cinematography [10], X-ray flash [11], electromagnetic sensors, shadowgraph, high-speed cameras, Schlieren [12,13], and other innovative techniques [14], which are also visible in some of these methods such as the high-speed cameras, Schlieren, and some laser methods, as well as the shape of the wavefront. In all of these methods, the need for an external supply is to receive changes from the sensor.…”