Probing the Thermochemistry Properties and Rate Kinetics of Trimethyl Phosphate (TMP): An H-Atom Abstraction (HAA) Reactions Perspective

Trimethyl Phosphate (TMP), an organophosphorus liquid compound, is valued for its versatile qualities and applications in various fields. In modern chemical research and industry, processes involving Trimethyl Phosphate are optimized for minimal negative environmental impact, and scientific advancement is driven by adherence to stringent regulations to provide sustainable solutions and resource preservation. Thermochemical insights enhance our understanding of monomer incorporation, initiation, and propagation energetics. This study comprehensively investigates the thermochemistry and rate kinetics that govern H-atom abstractions in TMP through advanced computational techniques. The theoretical framework encompasses methodologies for conducting conformer searches, exploring transition states, and performing energy calculations. This study calculates rate constants for eight H-atom abstraction reactions involving TMP with stable species, O2 (oxygen), H (hydrogen), and radicals [ȮH (hydroxyl), ĊH3 (methyl), CH3Ȯ (methoxy), HȮ2 (hydroperoxyl), ṄH2 (amino), and ĊN (cyano)], and further analogies are related to barrier heights. Bond dissociation energies are also determined, highlighting TMP's susceptibility to various reaction pathways. The discussion and findings elucidate the need for further experimental validation for practical applications of TMP in chemical synthesis, combustion, flame-retardant technologies, environmental processes, and pharmaceutical research.

Numerical study of gas-phase interactions of phosphorus compounds with co-flow diffusion flames

The effects of phosphorus-containing compounds (PCCs) on the extinguishment and structure of methane-air coflow diffusion flames, in the cup-burner configuration, is studied computationally. Dimethyl methylphosphonate (DMMP), trimethyl phosphate (TMP), or phosphoric acid is added to either the air or fuel flow. Time-dependent axisymmetric computation is performed with full gas-phase chemistry and transport to reveal the flame structure and inhibition process. A detailed chemical-kinetics model (77 species and 886 reactions) is constructed by combining the methane-oxygen combustion and phosphorus inhibition chemistry. A simple model for radiation from CH4, CO, CO2, H2O, and soot based on the optically thin-media assumption is incorporated into the energy equation. The inhibitor effectiveness is calculated as the minimum extinguishing concentrations (MECs) of CO2 (added to the oxidizer) as a function of the PCC loading (added to the oxidizer or fuel stream). The calculated MEC of CO2 without an inhibitor is in good agreement with the measured value. For moderate DMMP loading to the air (<1 %), the measured value becomes significantly smaller, presumably due to particle formation in the experiment. An inhibitor in the oxidizer flow is an order of magnitude more effective compared to that in the fuel flow in gas-phase inhibition of co-flow diffusion flames. The three PCCs studied behave similarly with regard to flame inhibition, lowering radical concentrations and the heat-release rate at the flame-stabilizing peak reactivity spot (i.e., reaction kernel) in the base, promoting flame blow-off. The three compounds behave differently, however, with regard to the trailing flame. While all three raise the maximum temperature in the trailing flame, DMMP and TMP, which contain three methyl groups, result in higher maximum flame temperature and combustion enhancement there, with a unique two-zone flame structure, whereas phosphoric acid does not.

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

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 C₀-C₂ 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.