Propriedades termodinâmicas: querosene, bioquerosene, aditivos e mecanismos de detecção de explosivos

Abstract

In this work we perform the characterization of thermodynamic potentials, obtaining predictions based on Density Functional Theory and statistical thermodynamics, through the canonical ensemble model. The study compared two theoretical methods, B3lyp/6-311 ++ g(d, p) and the semi-empirical method PM3, with the experimental values of the thermodynamic property of CP with the objective of validating the method with better precission. All simulations were performed conformation of the global minimums and optimizations of the molecules in thermal equilibrium and for a temperature range of 0.5 - 1500 K. We will analyze the thermal properties, such as energy, enthalpy, Gibbs free energy, entropy, heat capacity at constant pressure with respect to temperature. In the combustion enthalpy the following methods were used: B3lyp/6-311 ++ g(d, p), B3lyp/6- 31+g(d), CBS-QB3, G3, G4 and the G3 / G4 mean, obtaining results that show a good agreement with the experimental values, and verifying which of the methods best predicts the thermodynamic properties for reactions of combustion of the kerosene and bioquerosene. Also, a theoretical analysis was performed in DFT to calculate the thermodynamic properties of three molecules of additives. We simulated a composition of JP-8 with mixtures of the three additives together and separated in order to observe its efficiency over other existing methods. Then, the thermodynamic properties of the gasoline with additives were predicted under the same conditions already described. These calculated amounts included standard gasoline mixed with the following oxygenated additives: methyl tert-butyl ether, ethyl tert-butyl ether, diisopropyl ether, ethanol and methanol. It is possible to estimate some relevant fuel properties in the injection and combustion stage, showing substantial agreement with the experimental data, presenting relative errors of less than 2%, thus establishing an excellent method to calculate and predict the thermodynamic properties of the combustion reactions for with additives. In the last stage of this work, we present a theory of a simulated sensor device to identify explosive molecules that is of extreme interest for the area of public security in the fight against terrorism. For this, an armchair-type carbon nanotube (CNT) was modeled under the action of an external, longitudinal and uniform electric field, causing the molecules of the explosives: 2,4,6 trinitrotoluenes, triacetin triperoxide, hexogen, hexamethylene triperoxide diamine, octogen and pentaerythritol tetranitrate. Turn around the CNT, behaving as a sensor depending on the temperature and the radius of rotation of the molecules. In this way, we study the physico-chemical properties of the interactions of the molecules with the CNT.