330
The Chemistry and Technology of Petroleum
weight loss is recorded after prolonged exposure of the material to a high vacuum. The net result is
the formation of a product with an atomic (H + I)/C ratio of 1.24 after an 8 h reaction; a more prolonged reaction period affords a product with a (H + I)/C ratio of 1.17. This latter may be the result
of iodination of the alkyl or naphthenic moieties of the asphaltenes with subsequent elimination of
hydrogen iodide. Alternatively, dehydrogenation of naphthene rings to aromatic systems or coupling
of aromatic nuclei would also account for lower (H + I)/C ratios. In fact, this latter phenomenon
could account, in part, for the insolubility of the products in solvents that are normally excellent for
dissolving the unchanged asphaltenes. However, it will be appreciated that these aforementioned
reactions are only a few of many possible reactions that can occur, and, undoubtedly, halogenation
of the asphaltenes is much more complex than would appear from the product data.
Halogenation of the asphaltenes can also be achieved by use of sulfonyl chloride, iodine monochloride, and N-bromusuccinimide, or, indirectly, via the Gomberg reaction.
Attempts to introduce hydrophilic groups into asphaltenes by hydrolysis of the halo derivatives
with either aqueous sodium hydroxide or aqueous sodium sulfite are not feasible. The products
from the reaction of halogenated Athabasca asphaltenes with these aqueous solutions are insoluble
in strong aqueous alkali. Partial reaction does occur and is evident from the decreased atomic
(H + Cl)/C ratios and the increased oxygen-to-carbon atomic ratios of the products relative to those
of the untreated halo-asphaltenes (Moschopedis and Speight, 1971). However, it was not possible to
establish conclusively the presence of sulfonic acid group(s) in the product from the sodium sulfite
reaction by assignment of infrared absorption bands to this particular group.
It is also conceivable that the decreased atomic (H + Cl)/C ratios may be due, in part, to elimination of the elements of hydrogen chloride during the reactions, not solely, as intended, to substitution
of chlorine by –OH and by –SO 3 H. Olefin formation by elimination of hydrogen halide from alkyl
or aralkyl halides in strongly basic media is well known, and the elimination of hydrogen chloride
from β-phenylethyl chloride in the presence of aqueous sodium sulfite to yield styrene has also been
recorded. On the other hand, α-phenylpropyl and α-phenylbutylbromides react normally with aqueous sodium sulfite to afford the corresponding sulfonic acids:
Interactions of asphaltenes with metal chlorides yield products containing organically bound
chlorine, but the analytic data indicate that dehydrogenation processes occur simultaneously. There
is, of course, no clear way that the extent of the dehydrogenation can be estimated, but it is presumed
to be a dehydrogenation condensation rather than olefin formation.
Inter- or intramolecular condensations are the preferred reaction route, insofar as the solubility
and apparent complexity of the products vary markedly from those of the starting materials, and
these differences cannot be attributed wholly to the incorporation of chlorine atoms into the constituents of the asphaltenes or heavy oil. Indeed, the data accumulated are indicative of a condensation
dehydrogenation or, in part, loss of alkyl substituents (e.g., lower molecular weight hydrocarbons)
during the reactions. As an illustration of the former, the cokes produced during the thermal cracking (450°C, 840°F) of the asphaltenes or heavy oil have H/C ratios in the range of 0.59–0.77.
The majority of the insoluble materials produced in the asphaltene–metal chloride reactions have
only slightly higher (H + Cl)/C ratios (0.88–1.10).
The facile reactions of asphaltenes with metal chlorides have also been applied as a possible
means of petroleum deasphalting. The results indicate that, without exception, the asphaltenes react
more rapidly than the heavy oil to produce insoluble organic material. It is also worthy of note here
that, in the case of the heavy oil, the soluble organic material contains only traces (<1%, usually of
the order of 0.5%) of organically bound chlorine. This is in contrast to the results described when
higher ratios of metal chloride to heavy oil are employed and the reaction is presumed to go to
completion over 24 h.
Thus, application of the process to a heavy feedstock shows that maximum yields of asphaltene
materials are removed from the feedstock–solvent mix at low concentrations of metal chloride. The
resulting deasphalted heavy oil contains only traces (<0.5% w/w) of organically bound chlorine and
little or no (<0.1% w/w) mineral matter.
The Chemistry and Technology of Petroleum
weight loss is recorded after prolonged exposure of the material to a high vacuum. The net result is
the formation of a product with an atomic (H + I)/C ratio of 1.24 after an 8 h reaction; a more prolonged reaction period affords a product with a (H + I)/C ratio of 1.17. This latter may be the result
of iodination of the alkyl or naphthenic moieties of the asphaltenes with subsequent elimination of
hydrogen iodide. Alternatively, dehydrogenation of naphthene rings to aromatic systems or coupling
of aromatic nuclei would also account for lower (H + I)/C ratios. In fact, this latter phenomenon
could account, in part, for the insolubility of the products in solvents that are normally excellent for
dissolving the unchanged asphaltenes. However, it will be appreciated that these aforementioned
reactions are only a few of many possible reactions that can occur, and, undoubtedly, halogenation
of the asphaltenes is much more complex than would appear from the product data.
Halogenation of the asphaltenes can also be achieved by use of sulfonyl chloride, iodine monochloride, and N-bromusuccinimide, or, indirectly, via the Gomberg reaction.
Attempts to introduce hydrophilic groups into asphaltenes by hydrolysis of the halo derivatives
with either aqueous sodium hydroxide or aqueous sodium sulfite are not feasible. The products
from the reaction of halogenated Athabasca asphaltenes with these aqueous solutions are insoluble
in strong aqueous alkali. Partial reaction does occur and is evident from the decreased atomic
(H + Cl)/C ratios and the increased oxygen-to-carbon atomic ratios of the products relative to those
of the untreated halo-asphaltenes (Moschopedis and Speight, 1971). However, it was not possible to
establish conclusively the presence of sulfonic acid group(s) in the product from the sodium sulfite
reaction by assignment of infrared absorption bands to this particular group.
It is also conceivable that the decreased atomic (H + Cl)/C ratios may be due, in part, to elimination of the elements of hydrogen chloride during the reactions, not solely, as intended, to substitution
of chlorine by –OH and by –SO 3 H. Olefin formation by elimination of hydrogen halide from alkyl
or aralkyl halides in strongly basic media is well known, and the elimination of hydrogen chloride
from β-phenylethyl chloride in the presence of aqueous sodium sulfite to yield styrene has also been
recorded. On the other hand, α-phenylpropyl and α-phenylbutylbromides react normally with aqueous sodium sulfite to afford the corresponding sulfonic acids:
Interactions of asphaltenes with metal chlorides yield products containing organically bound
chlorine, but the analytic data indicate that dehydrogenation processes occur simultaneously. There
is, of course, no clear way that the extent of the dehydrogenation can be estimated, but it is presumed
to be a dehydrogenation condensation rather than olefin formation.
Inter- or intramolecular condensations are the preferred reaction route, insofar as the solubility
and apparent complexity of the products vary markedly from those of the starting materials, and
these differences cannot be attributed wholly to the incorporation of chlorine atoms into the constituents of the asphaltenes or heavy oil. Indeed, the data accumulated are indicative of a condensation
dehydrogenation or, in part, loss of alkyl substituents (e.g., lower molecular weight hydrocarbons)
during the reactions. As an illustration of the former, the cokes produced during the thermal cracking (450°C, 840°F) of the asphaltenes or heavy oil have H/C ratios in the range of 0.59–0.77.
The majority of the insoluble materials produced in the asphaltene–metal chloride reactions have
only slightly higher (H + Cl)/C ratios (0.88–1.10).
The facile reactions of asphaltenes with metal chlorides have also been applied as a possible
means of petroleum deasphalting. The results indicate that, without exception, the asphaltenes react
more rapidly than the heavy oil to produce insoluble organic material. It is also worthy of note here
that, in the case of the heavy oil, the soluble organic material contains only traces (<1%, usually of
the order of 0.5%) of organically bound chlorine. This is in contrast to the results described when
higher ratios of metal chloride to heavy oil are employed and the reaction is presumed to go to
completion over 24 h.
Thus, application of the process to a heavy feedstock shows that maximum yields of asphaltene
materials are removed from the feedstock–solvent mix at low concentrations of metal chloride. The
resulting deasphalted heavy oil contains only traces (<0.5% w/w) of organically bound chlorine and
little or no (<0.1% w/w) mineral matter.