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3.2. Effects of the thermal pre-treatment
on the activation energies of a viscous flow
The phase transition, involving asphaltenes, is accompanied
by an increase of the apparent Arrhenius activation energy U
app
,
determined for the entire range of the measurement (flow) tem-
peratures T
m
=8–30°C.
Fig. 2. Effects of the thermal
pre-treatment of the crude oil on the
apparent activation energy at 8–30°C.
Fig. 3. Variations of the activation
energy of the viscous flow in the
thermally pretreated oil samples.
Fig. 2 shows that in the oil samples, pre-treated at “moder-
ately warm conditions” (T
pt
=18–26°C) U
app
remains fairly constant
and close to 16–17 kcal/mol (67–72 kJ/mol), which is within the
range of 14–20 kcal/mol, reported by other authors for asphaltene
activation/association energies (cf. [3]). After the assumed phase
transition in the pre-treated crude oil, U
app
increases up to a
maximum of to 43–46 kcal/mol (181–193 kJ/mol) at T
pt
=36–38°C.
In the samples, preheated to temperatures, exceeding the WAT
(T
pt
>39–40°C), U
app
is again decreased to 10–11 kcal/mol
(42–46 kJ/mol). The observed variations of U
app
are indicative of
the formation/destruction of interparticle bonds in the disperse
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