Составители:
14
not specify obvious RG maxima at concentrations ~5, ~20–22 and
~70 g/l. Moreover, their original data, being re-plotted on R
G
vs T
graph clearly indicate the presence of “specific temperatures” of
about 28–32°C. In a single journal paper it is impossible to make a
complete list of all relevant references; other sources of “specific
points” used for constructing the T–C phase diagram will be listed
in a forthcoming publication.
T-C Phase Diagram of Asphaltenes in Petroleum –
Current Version
To our knowledge, there have been no attempts to make a com-
parative analysis of all available information on “specific points” in
asphaltene-containing media. In Fig. 5 we present a first cumula-
tive T–C plot of all “specific points” obtained as described in the
previous section. As can be seen from the figure, currently avail-
able experimental evidence already is sufficient for revealing some
fairly well-defined phase boundaries in the T–C phase diagram.
However, the still limited amount of data does not allow any statis-
tical analysis; hence all below discussed numerical values of “criti-
cal” parameters should be regarded as approximate and will be
subjected to further investigation.
Concentration-Defined Phase Boundaries
Primary aggregation boundary (line 1 in Fig. 5). The first
experimental evidence for this primary aggregation stage at ca.
7–10 mg/l (at 20°C) was obtained by measuring UV/vis absorption,
viscosity and NMR relaxation in toluene solutions of solid asphal-
tenes and of heavy crude oils.
32-34
Attribution of this boundary to
primary association of asphaltenes monomers recently was also
confirmed by fluorescence technique.
39
Liquid-liquid demixing boundary (line 2 in Fig. 5). This
boundary (ca. 100–150 mg/l at 20°C) has been revealed for solu-
tions of solid asphaltenes and of heavy crudes by measurements of
optical absorption,
32-34
of NMR relaxation,
33,34
of viscosity,
33,34,40
of
ultrasonic velocity,
41
etc. A well-known feature of demixing sys-
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