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In the absence of artifacts, the above “specific points” may be
expected to form well-defined phase boundaries on a T–C graph.
The T–C area of possible practical importance is wide: from pour
point temperatures to those of asphaltene decomposition/coking
and from “infinitely diluted petroleum solutions” to solid asphalte-
nes. Over the past decades, a number of experimental groups have
published a large volume of experimental data, which show a pres-
ence of “specific points” in various parts of the above T–C area for
asphaltenes. E. g., our research group investigated concentration
effects in dilute solutions with asphaltene contents from ~1 mg/l to
~1 g/l, mostly close to room temperatures.
32-34
Fig. 4. Identification of specific/critical points for asphaltene phase
diagram in experimental data sets (adapted from Ref. 31).
On the other hand, detailed studies of temperature effects in
the range from –50°C to ~400°C have been performed
35-37
with bi-
tumen and precipitated asphaltenes, i.e. for asphaltene concentra-
tions from ~140 g/l to ~1200 g/l. Some specific concentra-
tions/temperatures were neither noticed, nor discussed in original
publications, but the corresponding “specific points” are clearly
seen in the published data plots. E. g., SANS study of asphaltene
aggregation
38
provided detailed concentration dependencies of the
radii of gyration R
G
in solutions of asphaltenes with concentrations
3.4–117 mg/l, at temperatures from 8 to 73°C. The authors made a
qualitative discussion of concentration/temperature effects, but did
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