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experimental data, along with the starting temperature and the content of
exotherms. To reach adiabatic conditions, an oil sample is usually put in a
“close” ARC system. But a “flowing” type of ARC testing system is also
possible with the oil sample under a high air purge and at a quasiadiabatic
operation (Yannimaras and Tiffin, 1995). ARC is similar to DSC or TG
except that reactions can be performed at a high pressure in ARC.

13.3 Kinetic parameters

Oxidation reaction rates are described commonly using the Arrhenius
type of equation which includes several kinetic parameters: activation energy,
frequency factor and reaction order. These kinetic parameters are obtained
through thermogravimetry (TG) and Differential scanning calorimetry
(DSC), accelerating rate calorimeter (ARC), and small batch reactor (SBR).
Example methods to obtain kinetic parameters using TG and DSC are
presented next.

13.3.1 Thermogravimetric analysis (TGA)
Oxidation is a thermal decomposition process which needs kinetic parameters
to describe it. One of the classic methods is based on the Arrhenius method to
estimate the kinetic parameters from thermogravimetric tests or thermo-
gravimetric analysis (TGA) (Coats and Redfern, 1964). The time-derivative
thermogravimetric (DTG) data are readily available in TG equipment and
sometimes used together with TG data. A TG test is used to measure the
mass loss of a substance as the temperature is increased. It is described by
the following equation:

dm t
(13.1)
dt ¼ kf ðm; C o ; .Þ
where f(m,C o , .) is a function of the mass m t remaining at time t, oxidation
concentration, etc., k is the temperature-dependent rate constant, (m/t),
which is described by the Arrhenius equation:

E
RT
k ¼ Ae (13.2)
1 1
where A is the preexponential or frequency factor, [t ], (s ). E is the
2
2
activation energy of the decomposition reaction, [L /t ], (kJ/mol). R is the
2
2
universal gas constant, [L /Tt ], (kJ/mol K). T is the absolute temperature,
[T], (K).