Kinetic Study of the Oxidative Degradation of Brazilian Fuel Oils

Abstract

Complex materials as fuel oils are characterized by physical and chemical parameters. This paper deals with the determination of the activation energy of three kinds of Brazilian fuel oils. As it is possible to establish a direct relation between ignition delay and activation energy, these kinetic parameters can be used to characterize these oils regarding the combustion quality of the fuel. Activation energies were determined as a function of conversion degree (R) and temperature by model-free kinetics. The samples, here named A, B, and C, were supplied by Petrobras-Cenpes, and they were characterized by thermogravimetry (TG) and differential thermal analysis (DTA). Transient experiments were performed from room temperature up to 600 °C at five heating rates (2.5, 5.0, 10.0, 15.0, and 20.0 °C min -1 ) in an atmosphere of synthetic air and samples of about 20.0 mg were used. In all experiments, three distinct decomposition regions were observed and identified as lowtemperature oxidation (LTO), fuel deposition (FD), and high-temperature oxidation (HTO). In order to compare these oils, we considered the medium value of the activation energy obtained between conversions of 1% and 90% only for the LTO region. The results are as follows: sample A ) 43.8 kJ mol -1 , sample B ) 57.2 kJ mol -1 , and sample C ) 61.8 kJ mol -1 , showing that the sample A is the best option among the samples studied in this work and that the activation energy is a suitable parameter for this purpose.

Determination of the activation energies of beef tallow and crude glycerin combustion using thermogravimetry

“…LTO is the process in which there occurs firstly the vaporization of volatile hydrocarbons and their decomposition into lighter molecular weight compounds followed by combustion [30] and [31]. This LTO region is responsible for the intermediate species formation, which in a critical concentration are responsible for the propagation of exothermic chemical reactions [32].…”

Correlation Between Nox and Co Emissions and Activation Energy of Renewable Fuels

“…Where, t is the time, T the temperature, f (α) the model of the reaction and k (T) is the coefficient of Arrhenius reaction rate. After the necessary adjustments and considerations, as shown in several prior studies [9] e [10] the model Model-free kinetics is represented by "Equation (2)".…”

Characterization of Thermal Stability of Synthetic and Semi-Synthetic Engine Oils

“…Engine oil ageing can be characterized by different markers like apparent activation energy of decomposition, oxidation, sulfation and nitration indices, antiwear breakdown, viscosity index, total acid number (TAN), total base number (TBN), dielectric constant and soot deposition. Different analytical techniques like infrared and nuclear magnetic resonance (NMR) spectroscopy [4][5][6][7][8][9][10][11], thermal analysis [12][13][14][15][16], rheological measurements [13,17,18] and chromatographic analyses [9,16,19] have been utilized to evaluate the above properties. Thermo(oxidative) degradation of engine oils in conventional thermogravimetric analyzer (TGA) and differential scanning calorimeter (DSC) are fundamental techniques to evaluate the stability of engine oils under isothermal and dynamic heating conditions [10,[13][14][15].…”