U.S. patent application number 14/451787 was filed with the patent office on 2015-03-05 for heavy oils having reduced total acid number and olefin content.
The applicant listed for this patent is Michel Chornet, Christos Chronopoulos, Soumaine Dehkissia, Jean Frechette. Invention is credited to Michel Chornet, Christos Chronopoulos, Soumaine Dehkissia, Jean Frechette.
Application Number | 20150065766 14/451787 |
Document ID | / |
Family ID | 52460456 |
Filed Date | 2015-03-05 |
United States Patent
Application |
20150065766 |
Kind Code |
A1 |
Dehkissia; Soumaine ; et
al. |
March 5, 2015 |
Heavy Oils Having Reduced Total Acid Number and Olefin Content
Abstract
A process for treating a heavy oil by heating a feedstock
comprising a heavy oil in order to separate from the heavy oil a
first fraction. The first fraction contains no more than 25% of the
total number of acid groups of the heavy oil. A second fraction
contains at least 75% of the total number of acid groups of the
heavy oil. The second fraction then is treated under conditions
that provide a heavy oil that has a total acid number, or TAN, that
does not exceed 1.0 mg KOH/g, or is at least 50% lower than the
total acid number prior to treatment, an olefin content that does
not exceed 1.0 wt. %, and a p-value of at least 50% of the p-value
of the heavy oil prior to treatment, or a p-value that is at least
1.5.
Inventors: |
Dehkissia; Soumaine;
(Sherbrooke, CA) ; Chronopoulos; Christos;
(Sherbrooke, CA) ; Chornet; Michel; (Sherwood
Park, CA) ; Frechette; Jean; (Sherbrooke,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dehkissia; Soumaine
Chronopoulos; Christos
Chornet; Michel
Frechette; Jean |
Sherbrooke
Sherbrooke
Sherwood Park
Sherbrooke |
|
CA
CA
CA
CA |
|
|
Family ID: |
52460456 |
Appl. No.: |
14/451787 |
Filed: |
August 5, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61864118 |
Aug 9, 2013 |
|
|
|
Current U.S.
Class: |
585/264 ;
208/263; 208/88; 585/310; 585/800 |
Current CPC
Class: |
Y02P 30/20 20151101;
C10G 31/06 20130101; C10G 55/04 20130101; C10G 53/02 20130101; C10G
67/14 20130101; C10G 9/007 20130101; C10G 2300/203 20130101; C10G
67/02 20130101; C10G 2300/308 20130101; C10G 3/40 20130101 |
Class at
Publication: |
585/264 ;
208/263; 208/88; 585/800; 585/310 |
International
Class: |
C10G 31/06 20060101
C10G031/06; C10G 55/04 20060101 C10G055/04; C10G 67/02 20060101
C10G067/02 |
Claims
1. A process for treating a heavy oil, comprising: (a) heating a
feedstock comprising a heavy oil to remove from said heavy oil a
first fraction, wherein said first fraction contains no more than
25% of the total number of acid groups of the heavy oil, and
thereby providing a second fraction, wherein said second fraction
contains at least 75% of the total number of acid groups of the
heavy oil; and (b) treating said second fraction under conditions
that provide a treated heavy oil that has a total acid number (TAN)
that does not exceed 1.0 mg KOH/g, or is at least 50% lower than
the total acid number (TAN) of said heavy oil prior to step (a), an
olefin content that does not exceed 1.0 wt. %, and a p-value which
is at least 50% of the p-value of said heavy oil prior to step (a),
or a p-value of at least 1.5.
2. The process of claim 1 wherein step (a) comprises heating said
feedstock comprising a heavy oil to a temperature that does not
exceed 350.degree. C. atmospheric equivalent temperature and
subjecting said feedstock comprising a heavy oil a pressure that
does not exceed 3 atm.
3. The process of claim 1 wherein step (b) comprises heating said
second fraction to a temperature that does not exceed 400.degree.
C. atmospheric equivalent temperature and subjecting said second
fraction to a pressure that does not exceed 1 atm.
4. The process of claim 3 wherein step (b) comprises heating said
second fraction to a temperature that does not exceed 385.degree.
C. atmospheric equivalent temperature and subjecting said second
fraction to a pressure that does not exceed 1 atm.
5. The process of claim 4 where step (b) comprises heating said
second fraction to a temperature that does not exceed 380.degree.
C. atmospheric equivalent temperature and subjecting said second
fraction to a pressure that does not exceed 1 atm.
6. The process of claim 1 wherein, prior to step (a), said
feedstock comprising a heavy oil is heated to a temperature that
does not exceed 100.degree. C. atmospheric equivalent temperature,
thereby removing components having a boiling point of 100.degree.
C. atmospheric equivalent temperature or less from said heavy
oil.
7. The process of claim 1 wherein, in step (a), said feedstock
comprising a heavy oil is subjected to a pressure that does not
exceed 500 mmHg.
8. The process of claim 3 wherein, in step (b), said second
fraction is subjected to a pressure of about 500 mmHg.
9. The process of claim 3 wherein, in step (b), said second
fraction is heated to a temperature of from about 350.degree. C.
atmospheric equivalent temperature to a temperature that does not
exceed 400.degree. C. atmospheric equivalent temperature.
10. The process of claim 3 wherein, in step (b), said second
fraction is heated to a temperature that does not exceed
400.degree. C. atmospheric equivalent temperature and subjected to
a pressure that does not exceed 1 atm for a period of time of from
about 1 minute to about 60 minutes.
11. The process of claim 10 wherein, in step (b), said second
fraction is heated to a temperature that does not exceed
400.degree. C. atmospheric equivalent temperature and subjected to
a pressure that does not exceed 1 atm for a period of time of from
about 20 minutes to about 35 minutes.
12. The process of claim 1 wherein said treated heavy oil has a
p-value that is at least 75% of the p-value of the heavy oil prior
to step (a), or has a p-value of at least 2.0.
13. The process of claim 1 wherein said first fraction contains no
more than 10% of the total number of acid groups of the heavy oil,
and said second fraction contains at least 90% of the total number
of acid groups of the heavy oil.
14. The process of claim 13 wherein said first fraction contains no
more than 5% of the total number of acid groups of the heavy oil,
and said second fraction contains at least 95% of the total number
of acid groups of the heavy oil.
15. The process of claim 14 wherein said first fraction contains no
more than 3% of the total number of acid groups of the heavy oil,
and said second fraction contains at least 97% of the total number
of acid groups of the heavy oil.
16. The process of claim 1 wherein said treated heavy oil has an
API gravity which is no more than 0.5.degree. greater than that of
said heavy oil prior to step (a).
17. The process of claim 16 wherein said treated heavy oil has an
API gravity which is no more than 0.2.degree. greater than that of
said heavy oil prior to step (a).
18. The process of claim 17 wherein said treated heavy oil has an
API gravity which is no more than 0.1.degree. greater than that of
said heavy oil prior to step (a).
19. The process of claim 1 wherein step (b) is performed in the
absence of a stripping gas.
20. The process of claim 1, and further comprising: recombining at
least a portion of said first fraction with said treated heavy oil
of step (b).
21. The process of claim 1, and further comprising: subjecting said
treated heavy oil to cavitation.
22. The process of claim 21 wherein said cavitation is hydrodynamic
cavitation.
23. The process of claim 1, and further comprising: subjecting said
treated heavy oil to visbreaking.
24. The process of claim 1, and further comprising: subjecting said
treated heavy oil to a hydrogen addition process.
Description
[0001] This application claims priority based on provisional
Application Ser. No. 61/864,118, filed Aug. 9, 2013, the contents
of which are incorporated by reference in their entirety.
[0002] This invention relates to the treatment of heavy oils. More
particularly, this invention relates to treating heavy oils to
provide a stable treated heavy oil having a total acid number (TAN)
that does not exceed 1.0 mg KOH/g, or is at least 50% lower than
the total acid number (TAN) prior to treatment, while having an
olefin content that does not exceed 1.0 wt. %, and a p-value which
is at least 50% of the p-value of the heavy oil prior to treatment,
or is at least 1.5. The treated heavy oil also may have an API
gravity which is no more than 0.5.degree. greater than the API
gravity of the heavy oil prior to treatment. The treatment may be
performed in the absence of a stripping gas. Such treatment also
may be performed without adding hydrogen to the heavy oil.
[0003] The term "heavy oil", as used herein, includes oils which
are classified by the American Petroleum Institute (API), as heavy
oils or extra heavy oils, as well as blended oils such as dilbit (a
diluent-bitumen blend) or synbit (a synthetic oil-bitumen blend).
In general, a heavy hydrocarbon oil has an API gravity between
22.3.degree. (density of 920 kg/m.sup.3 or 0.920 g/cm.sup.3) and
10.0.degree. (density of 1,000 kg/m.sup.3 or 1 g/cm.sup.3). An
extra heavy oil in general has an API gravity of less than
10.0.degree. (density greater than 1,000 kg/m.sup.3 or greater than
1 g/cm.sup.3). For example, heavy oils may be extracted from oil
sands, atmospheric tar bottoms products, vacuum tar bottoms
products, shale oils, coal-derived liquids, crude oil residues, and
topped crude oils.
[0004] Heavy oils contain high molecular weight compounds known as
asphaltenes, as well as organic compounds containing acidic groups
(e.g., carboxylic acid or --COOH groups), such as naphthenic acids,
and metals such as nickel and vanadium.
[0005] The carboxylic acid groups in acidic organic molecules cause
corrosion, and heavy oil refineries discount the value of heavy
oils having high acidity levels. The asphaltenes may cause fouling
in visbreaking, and may cause fouling in refinery heat exchangers
and burners.
[0006] The total acid number, or TAN, is an indicator of the
acidity, mainly in the form of naphthenic acids, present in heavy
oils. Naphthenic acids include a cyclic core with no double bonds
between the carbon atoms, and one or more alkyl groups attached to
the cyclic naphthenic core. One or more of the alkyl groups
attached to the naphthenic core has a terminal carboxylic acid
(--COOH) group. A typical naphthenic acid group has a carbon
backbone of 9 to 20 carbon atoms. The backbone contains at least
one naphthenic ring (Cyclopentane is the most common.) to which are
attached alkyl groups. One or two of the alkyl groups have a
terminal carboxylic acid group. These terminal carboxylic acid
group(s) are responsible primarily for the corrosion that may be
caused by heavy oils.
[0007] The total acid number, or TAN, is determined by a
neutralization test using potassium hydroxide, or KOH. The TAN is
measured, in general, as the number of milligrams of KOH needed to
neutralize 1 gram of oil following an established standardized
methodology known as ASTM-D664. It is desirable that the TAN for
heavy oil does not exceed 1.0 mg KOH/g. In general, the values of
heavy oils having a TAN that is greater than 1.0 mg KOH/g are
discounted.
[0008] Although heavy oils can be treated, such as by heating, for
example, in order to reduce the TAN, such treatments result in the
production of other undesirable components, such as olefins, and an
increase in the tendency of the asphaltenes to precipitate. For
example, such treatments may reduce the TAN of the heavy oil, but
increase the olefin content of the heavy oil to unacceptable
levels, and increase the tendency of the asphaltenes to
precipitate, as shown by decreased peptization values, or p-values,
whereby such heavy oils are less than stable.
[0009] Olefin content can be measured by the bromine number test or
by the proton Nuclear Magnetic Resonance Spectroscopy (HNMR) test.
The bromine number is the amount of bromine (in grams) absorbed by
100 grams of a sample. The bromine number is measured according to
the ASTM-D1159 procedure. The number indicates the degree of
unsaturation, which is related to olefin content. A bromine number
under 10 is considered acceptable for normal crude oil handling.
The HNMR test measures olefin content on the full crude by mass as
1-decene equivalent. A test result that is greater than 1.0% olefin
by mass as 1-decene equivalent indicates the presence of an
unacceptable amount of olefins. A bromine number of 10 corresponds
generally to an olefin content of 1.0% by weight. With respect to
the transportation of heavy oils, the olefin content of the heavy
oil should not exceed 1.0% by weight, as measured by the HNMR test
or the bromine number test, for example.
[0010] The p-value of a heavy oil is a measure of the flocculation
potential of asphaltenes and their tendency to form solid deposits.
The p-value is a stability indicator and also is a measure of
asphaltene solubility. The p-value is determined by testing the
heavy oil according to the ASTM-D7157 method or a method similar to
ASTM D-7157, and ranges from 1 (unstable) to 5 (very stable). The
method consists of solubilizing three samples of the heavy oil
using different amounts of toluene or xylenes. These three
different mixtures of heavy oil samples and aromatic solvent (i.e.,
toluene or xylene) then are titrated with a paraffinic solvent,
such as n-heptane, to precipitate the asphaltenes. The amounts of
heavy oil and solvents added, including the titration solvent, up
to the onset of the peptization of the asphaltenes, are used to
calculate the stability parameters and their intrinsic stability. A
p-value which is at least 1.5 indicates that the heavy oil is
stable, while a heavy oil having a p-value of less than 1.5
generally is considered unstable.
[0011] It therefore is an object of the present invention to
provide a treated heavy oil having a reduced total acid number, as
well as an acceptable olefin content and p-value. Such treated
heavy oil also may have a small increase or no increase in density,
as compared to the heavy oil prior to treatment.
[0012] In accordance with an aspect of the present invention, there
is provided a process for treating a heavy oil. The process
comprises, in a first step, heating a feedstock comprising a heavy
oil to remove a first, or light, fraction from the heavy oil. The
first fraction contains no more than 25% of the total number of
acid groups of the heavy oil. The first, or light, fraction, in
general contains TAN reduction inhibitors such as water vapor or
other incondensable gases, and thus the first step removes those
inhibitors. Thus, there also is provided a second fraction. The
second fraction contains at least 75% of the total number of acid
groups of the heavy oil. The second fraction then is treated, in a
second step, under conditions that provide a treated heavy oil that
has a total acid number (TAN) that does not exceed 1.0 mg KOH/g, or
is at least 50% lower than the total acid number (TAN) of the heavy
oil prior to the treatment of the heavy oil. The treated heavy oil
also has an olefin content that does not exceed 1.0 wt. %, and a
p-value that is at least 50% of the p-value of the heavy oil prior
to the treatment of the heavy oil, or a p-value of at least
1.5.
[0013] In a non-limiting embodiment, the treated heavy oil has a
p-value that is at least 75% of the p-value of the heavy oil prior
to the treatment of the heavy oil, or a p-value of at least
2.0.
[0014] In a non-limiting embodiment, the treated heavy oil has a
density, as measured by API gravity, that is slightly greater or no
greater than that of the heavy oil prior to treatment. In one
non-limiting embodiment, the treated heavy oil has an API gravity
which is no more than 0.5.degree. greater than the heavy oil prior
to treatment. In another non-limiting embodiment, the treated heavy
oil has an API gravity which is no more than 0.2.degree. greater
than the heavy oil prior to treatment. In yet another non-limiting
embodiment, the treated heavy oil has an API gravity which is no
more than 0.1.degree. greater than the heavy oil prior to
treatment.
[0015] In a non-limiting embodiment, a total acid number, or TAN,
profile of the heavy oil is determined first by measuring the TAN
of the heavy oil prior to treating the heavy oil. A sample of the
heavy oil then is distilled at various temperatures, and the TAN of
each distilled fraction is determined. From the TAN values of each
distilled fraction of the heavy oil, one can determine the
temperature of the heavy oil at which components that boil below
such temperature will contain no more than 25% of the total number
of acid groups of such heavy oil, and at which components that boil
at or above such temperature contain at least 75% of the total
number of acid groups of the heavy oil.
[0016] In many cases, the first fraction, which contains no more
than 25% of the total number of acid groups of the heavy oil,
includes components which boil at a temperature no greater than
250.degree. C. to 300.degree. C. atmospheric equivalent temperature
(AET), while the second fraction, which contains at least 75% of
the total number of acid groups of the heavy oil, includes
components which boil at a temperature at least 250.degree. C. to
300.degree. C. atmospheric equivalent temperature (AET).
[0017] In a non-limiting embodiment, the first fraction contains no
more than 10% of the total acid groups of the heavy oil, and the
second fraction contains at least 90% of the total acid groups of
the heavy oil. In another non-limiting embodiment, the first
fraction contains no more than 5% of the total acid groups of the
heavy oil, and the second fraction contains at least 95% of the
total acid groups of the heavy oil. In yet another non-limiting
embodiment, the first fraction contains no more than 3% of the
total acid groups of the heavy oil, and the second fraction
contains at least 97% of the total acid groups of the heavy
oil.
[0018] Although the scope of the present invention is not intended
to be limited to any theoretical reasoning, it is believed that,
when a heavy oil is treated, such as by heating the heavy oil, in
order to reduce the total acid number (TAN) of the heavy oil, that
the lower-boiling components, i.e., components that in general
contain small amounts of acid groups, can contain water vapor or
other compounds which could inhibit or reduce the rate of
decarboxylation of acidic components, such as the naphthenic acids.
By removing such components prior to treating the heavy oil, the
heavy oil can be treated to reduce the total acid number (TAN) more
efficiently. Also, low boiling components in the heavy oil
generally are saturated compounds that are not miscible easily with
the asphaltenes in the heavy oil, and decrease the oil's stability.
By removing the lighter fraction, the stability of the heavy oil is
improved, and further TAN reduction is accomplished with the
maintenance of acceptable olefin levels, and such further TAN
reduction of the heavy oil is not inhibited by water vapor.
[0019] In a non-limiting embodiment, the first step comprises
separating the first fraction, which contains no more than 25% of
the total acid groups, by heating the feedstock comprising the
heavy oil to a temperature that does not exceed 350.degree. C.
atmospheric equivalent temperature (AET) to avoid thermal cracking,
which for hydrocarbons occurs generally around 370.degree. C. AET,
and subjecting the feedstock comprising a heavy oil to a pressure
that does not exceed 3 atm.
[0020] In another non-limiting embodiment, the second step
comprises heating the second fraction to a temperature that does
not exceed 400.degree. C. atmospheric equivalent temperature (AET),
and subjecting the second fraction to a pressure that does not
exceed 1 atm. In another non-limiting embodiment, the second step
comprises heating the second fraction to a temperature that does
not exceed 385.degree. C. atmospheric equivalent temperature (AET),
and subjecting the second fraction to a pressure that does not
exceed 1 atm. In yet another non-limiting embodiment, the second
step comprises heating the second fraction to a temperature that
does not exceed 380.degree. C. atmospheric equivalent temperature
(AET), and subjecting the second fraction to a pressure that does
not exceed 1 atm.
[0021] In one non-limiting embodiment, prior to removing the first
fraction from the feedstock comprising a heavy oil, the feedstock
is heated to a temperature that does not exceed 100.degree. C.
(AET), thereby removing light components having a boiling point of
less than 100.degree. C. (AET) from the heavy oil. In general, such
components having a boiling point of less than 100.degree. C. (AET)
may be solvents and/or diluents.
[0022] In another non-limiting embodiment, in the first step, the
feedstock comprising a heavy oil is heated to a temperature that
does not exceed 350.degree. C. (AET) and a pressure that does not
exceed 500 mmHg.
[0023] In another non-limiting embodiment, the second fraction, in
the second step, is heated to a temperature that does not exceed
400.degree. C. (AET) and a pressure that does not exceed 500 mmHg.
In yet another non-limiting embodiment, the second fraction, in the
second step, is heated to a temperature of from about 350.degree.
C. (AET) to a temperature that does not exceed 400.degree. C.
(AET).
[0024] In a further non-limiting embodiment, the second fraction,
in the second step, is heated to a temperature that does not exceed
400.degree. C. (AET) and is subjected to a pressure that does not
exceed 1 atm for a period of time of from about 1 minute to about
60 minutes. In yet another non-limiting embodiment, the second
fraction, in the second step, is subjected to a temperature that
does not exceed 490.degree. C. (AET) and is subjected to a pressure
that does not exceed 1 atm for a period of time of from about 20
minutes to about 35 minutes.
[0025] In another non-limiting embodiment, a stripping gas is not
employed in the second step.
[0026] In yet another non-limiting embodiment, subsequent to the
second step, the treated heavy oil is recombined with at least a
portion of the first fraction. Upon recombination of at least a
portion of the first fraction with the treated heavy oil, the
resulting heavy oil also has a TAN that does not exceed 1.0 mg
KOH/g, or is at least 50% lower than the TAN of the heavy oil prior
to the treatment of the heavy oil, has an olefin content that does
not exceed 1.0 wt. %, and a p-value that is at least 50% of the
p-value of the heavy oil prior to the treatment of the heavy oil,
or a p-value of at least 1.5.
[0027] In a non-limiting embodiment, a feedstock comprising a heavy
oil is heated to a temperature that does not exceed 100.degree. C.
(AET) in order to remove any diluents and/or solvents that may be
contained in the feedstock. The heavy oil then is passed to a
fractionator, which may be a vacuum distillation column, which is
operated at a temperature of 350.degree. C. and a pressure of about
250 mmHg. Such vacuum distillation separates the heavy oil into a
first, or light, fraction, comprised mainly of aliphatic saturates
and containing less than 25% of the total acid groups of the
original heavy oil, and a second, or heavy, fraction with higher
aromaticity, containing at least 75% of the acid groups of the
original heavy oil.
[0028] The second fraction then is passed to a decarboxylation
column, which is operated at a temperature of from about
350.degree. C. (AET) to about 380.degree. C. (AET), and a pressure
of 500 mmHg, for a period of time of from about 20 minutes to about
35 minutes. In the decarboxylation column, any naphthenic acids in
the second fraction are reduced, while the olefin content is not
increased significantly. In a non-limiting embodiment, the
decarboxylation is effected in the absence of a stripping gas.
[0029] Thus, there is produced a stable heavy oil having an
acceptable acid level and olefin content. In general, such stable
heavy oil has a total acid number (TAN) that does not exceed 1.0 mg
KOH/g or is at least 50% lower than the total acid number of the
heavy oil prior to treatment, has an olefin content that does not
exceed 1.0 wt. %, and has a p-value of at least 50% of the p-value
of the heavy oil prior to treatment, or is at least 1.5.
[0030] The stable heavy oil then can be recombined with at least a
portion of the first, or light fraction, or may be treated further
to reduce the density and viscosity of the heavy oil, thereby
making the heavy oil more pumpable and transportable. Such
treatment includes heating the heavy oil and/or subjecting the
heavy oil to cavitation, such as hydrodynamic and/or ultrasonic
cavitation and/or subjecting the oil to visbreaking, and/or other
upgrading technologies, such as thermal processes and/or hydrogen
addition processes.
[0031] In a non-limiting embodiment, after the stable heavy oil is
treated to reduce the density and viscosity of the heavy oil, such
as by heating and/or hydrodynamic and/or ultrasonic cavitation,
and/or other upgrading technologies, the stable heavy oil may be
recombined with the first fraction.
[0032] The invention now will be described with respect to the
drawing, wherein.
[0033] FIG. 1 is a schematic of an embodiment of the method for
treating a heavy oil in accordance with the present invention.
[0034] Referring now to the drawing, as shown in FIG. 1, a heavy
oil in line 10 is pumped and heated and sent to fractionator 11. In
general, fractionator 11 is operated at a temperature of about
300.degree. C. in the bottom, and in any event, the temperature
does not exceed 350.degree. C., and a pressure that does not exceed
3 atm, whereby a fraction, comprised of diluents, water vapor,
naphtha, and lighter ends in the form of gases, which have a
boiling point less than 250.degree. C. (AET), i.e., a 250.degree.
C. fraction, are withdrawn from fractionator 11 through line 12 and
passed to knock-out drum 17. The 250.degree. C. fraction contains
no more than 25% of the naphthenic acids of the heavy oil. Off
gases are withdrawn from knock-out drum 17 through line 19, while
the remainder of the 250.degree. C. fraction is withdrawn from
knock-out drum 17 through line 18. Thus, a fraction that has a
boiling point of less than 250.degree. C. at atmospheric pressure
(i.e., a 250.degree. C. fraction) is separated from the heavy oil,
whereby the resulting heavy oil contains a minimal amount of
components that decrease the stability of the heavy oil, and
further treatment to reduce the total acid number (TAN) of the
heavy oil facilities the maintenance of acceptable olefin
levels.
[0035] A heavier heavy oil fraction is withdrawn from fractionator
11 through line 13 and passed to decarboxylation column 14. In
general, decarboxylation column 14 is operated at a temperature
that does not exceed 380.degree. C. and a pressure that does not
exceed 1 atm. The heavy oil is treated in decarboxylation column 14
for a period of time such that the naphthenic acids and other
acidic components that may be present in the heavy oil are reacted,
whereby the total acid number (TAN) is reduced to an acceptable
level, i.e., not exceeding 1.0 mg KOH/g, or is at least 50% below
the total acid number prior to the treatment of the heavy oil. In
decarboxylation column 14, through the combination of heat and
residence time, weak chemical bonds are broken, and acid gases such
as CO.sub.2, NO.sub.x, and sulfur species such as H.sub.2S and COS
are liberated. In general, the heavy oil is treated in
decarboxylation column 14 for a period of time of from about 1
minute to about 60 minutes. Incondensable gases or off gases, such
as CO.sub.2, NO.sub.2, and CO, as well as steam, are withdrawn from
decarboxylation column 14 through line 15. A decarboxylated heavy
oil is withdrawn from decarboxylation column 14 through line
16.
[0036] The 250.degree. C..sup.- fraction in line 18 is passed to
line 16, where it is recombined with the decarboxylated heavy
oil.
[0037] The 250.degree. C. fraction in line 18 may be recombined
with the decarboxylated heavy oil in line 16 either before or after
subjecting the heavy oil to further processing to reduce the
density and viscosity of the heavy oil. The decarboxylated heavy
oil in line 16 is a treated and stable heavy oil that has a total
acid number (TAN) that does not exceed 1.0 mg KOH/g, or is at least
50% below the total acid number prior to the treatment of the heavy
oil, and an olefin content that does not exceed 1.0 wt. %, and a
p-value that is at least 50% of the p-value of the heavy oil prior
to treatment, or a p-value that is at least 1.5.
[0038] The invention now will be described with respect to the
following example; however, the scope of the present invention is
not intended to be limited thereby.
Example
[0039] Four samples of a heavy oil having a TAN of 5.32 mg KOH/g, a
bromine number (a measure of olefin content wherein a bromine
number of 10 gBr2/100 g generally or approximately corresponds to
an olefin content of 1.0%) of 5.72 gBr.sub.2/100 g, a p-value of
3.48, and a density of 0.9714 g/cm.sup.3, were treated in a topping
step, to remove a fraction containing 3% of the total acid groups
of the original oil samples, and having a resulting fraction
boiling point (at atmospheric pressure) of less than 250.degree. C.
(i.e., a 250.degree. C..sup.- fraction), and then the samples were
treated in a second step to remove napthenic acid components
therefrom.
[0040] In the topping step, each of Samples 1 and 2 were heated to
350.degree. C. at a pressure of 252 mmHg. Sample 3 was heated to
257.degree. C. at a pressure of 125 mmHg, and Sample 4 was heated
to 276.degree. C. at a pressure of 125 mmHg. In the reaction step,
Sample 1 was heated to 367.degree. C. at a pressure of 500 mmHg for
32 minutes, and Sample 2 was heated to 373.degree. C. at 500 mmHg
for 20 minutes. Sample 3 was heated to 385.degree. C. at a pressure
of 760 mmHg (i.e., atmospheric pressure) for 15 minutes, and Sample
4 was heated to 385.degree. C. at a pressure of 760 mmHg for 2
minutes.
[0041] After the topping step and the second step, each of the
250.degree. C..sup.- fractions that were separated previously from
the heavy oil samples was recombined with each of the treated
residue Samples 1 through 4. After the 250.degree. C..sup.-
fractions were recombined with each of the treated Samples 1
through 4, the TAN values, bromine numbers, and p-values for each
of Samples 1 through 4 were measured. After the above measurements,
each of Samples 1 through 4 were subjected to an additional
distillation step at 300.degree. C. under vacuum (20 mmHg pressure)
to verify whether olefins were produced during the second step.
After the distillation under vacuum, the TAN values, bromine
numbers, and p-values again were measured. The increases in
density, as measured in API gravity, of each of the recombined oil
samples, also were measured. It can be seen from the results with
respect to Sample 3 that the reaction severity (combination of time
and temperature) was too high and thus the bromine number, which is
indicative of olefin content, was higher than desired.
[0042] The TAN values, bromine numbers, p-values, and increases in
density for each of Samples 1 through 4 are given in Table 1
below.
TABLE-US-00001 TABLE 1 Density Topping Bromine P- Increase Sample
Condition Reaction Conditions TAN Number Value (.degree. API) 1
350.degree. C./252 mmHg 367.degree. C./500 mmHg/32 min 1.0 9.2 3.1
0 2 350.degree. C./252 mmHg 373.degree. C./500 mmHg/20 min 0.89
10.6 3 0 3 257.degree. C./125 mmHg 385.degree. C./760 mmHg/15 min.
0.99 16.69 2.5 0.05 4 276.degree. C./125 mmHg 385.degree. C./760
mmHg/2 min. 1.90 8.72 3.15 0
[0043] The disclosures of all patents and publications, including
published patent applications, are herein incorporated by reference
to the same extent as if each patent and publication were
incorporated individually by reference.
[0044] It is to be understood, however, that the scope of the
present invention is not to be limited to the specific embodiments
described above. The invention may be practiced other than as
particularly described and still be within the scope of the
accompanying claims.
* * * * *