U.S. patent number 3,819,328 [Application Number 05/371,393] was granted by the patent office on 1974-06-25 for use of alkylene polyamines in distillation columns to control corrosion.
This patent grant is currently assigned to Petrolite Corporation. Invention is credited to Ting Sin Go.
United States Patent |
3,819,328 |
Go |
June 25, 1974 |
USE OF ALKYLENE POLYAMINES IN DISTILLATION COLUMNS TO CONTROL
CORROSION
Abstract
Alkylene polyamines, such as ethylene diamine (EDA), are
employed to control acid corrosion in distillation columns, such as
occurs in petroleum distillation columns; preferably where the
polyamine is employed in conjunction with a corrosion inhibitor,
for example, a non-neutralizing corrosion inhibitor such as a
film-forming corrosion inhibitor. PH control is more accurately and
easily achieved with polyamines, such as EDA, than with either
ammonia or morpholine. By employing EDA one preferably regulates
the pH between about 5.5 - 7 and preferably about 6 - 7 with
minimal deviations therefrom, thus avoiding or minimizing corrosion
on the acid side (< about pH 5.5) and fouling on the basic side
(> about pH 7). In addition, the addition of amines to the
petroleum charge prior to distillation in place of caustic
treatment reduces the amount of HCl in the distillation column
without the disadvantages resulting from the conventional caustic
treatment.
Inventors: |
Go; Ting Sin (Crestwood,
MO) |
Assignee: |
Petrolite Corporation
(Wilmington, DE)
|
Family
ID: |
26726741 |
Appl.
No.: |
05/371,393 |
Filed: |
June 19, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
48975 |
Jun 24, 1970 |
|
|
|
|
Current U.S.
Class: |
422/3; 203/7;
208/47 |
Current CPC
Class: |
C10G
7/10 (20130101) |
Current International
Class: |
C10G
7/00 (20060101); C10G 7/10 (20060101); C23f
014/02 () |
Field of
Search: |
;21/2.5R,2.5B,2.7R
;203/7 ;208/47 ;252/390 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Richman; Barry S.
Attorney, Agent or Firm: Ring; Sidney B. Glass; Hyman F.
Parent Case Text
This application is a continuation-in-part of S.N. 48,975 filed
June 24, 1970, which application only has become abandoned.
Claims
I claim:
1. A process of controlling corrosion caused by acidic components
in a petroleum system containing a petroleum medium which comprises
regulating the pH of said petroleum medium in said petroleum system
to between about 5.5 to about 7 by adding an alkylene polyamine to
said petroleum system.
2. The process of claim 1 where the alkylene polyamine is ethylene
diamine.
3. The process of claim 1 where a film-forming corrosion inhibitor
is also added to said petroleum system.
4. The process of claim 3 where the alkylene polyamine is ethylene
diamine.
5. The process of claim 1 which comprises regulating the pH of said
petroleum medium in said petroleum system to between about 5.5 to
about 7 by adding said alkylene polyamine to said petroleum system,
said petroleum system including a distillation unit through which
said petroleum medium passes.
6. The process of claim 5 where the alkylene polyamine is ethylene
diamine.
7. The process of claim 5 where a film-forming corrosion inhibitor
is also added to said petroleum system.
8. The process of claim 7 where the alkylene polyamine is ethylene
diamine.
9. The process of claim 5 wherein said petroleum system includes an
overhead vapor-condensation means and where the pH of said
petroleum medium in said petroleum system is regulated to between
about 5.5 to about 7 by adding the alkylene polyamine to the
overhead vapor-condensation means.
10. The process of claim 9 where the alkylene polyamine is ethylene
diamine.
11. The process of claim 9 where a film-forming corrosion inhibitor
is also added to said petroleum system.
12. The process of claim 11 where the alkylene polyamine is
ethylene diamine.
Description
This invention relates to the control of acid corrosion in
distillation columns such as occurs in petroleum distillation
columns.
Petroleum crudes as well as gas oils, reduced crudes, etc., are
subjected to various processes in order to form lower boiling
components such as gasoline, etc. The products obtained are
distilled to produce a gasoline fraction, a fuel oil fraction, or
lubricating oil fraction, etc. The lower boiling fractions and
particularly gasoline are recovered as an overhead fraction from
distillation zones. The intermediate components are recovered as
side cuts from the distillation zone.
The fractions are coolec, condensed, and sent to collecting
equipment. No matter what the source of the oil that is subject to
distillation it has been found that corrosion of the equipment
takes place. Acidic materials that are present in all crudes are
carried along from the distillation zone with the distillate
product and often cause extensive corrosion to take place on the
metal surfaces of fractionating towers such as crude towers, trays
within such towers, heat exchangers, receiving tanks, connecting
pipes, etc. The most serious corrosion occurs in condensers and in
the overhead line leading from the fractionating towers. The
overhead line is used as a connection between the distillation
tower and condensers. The distillate or stock which will be stored
or used subsequently to charge other refining processes is
condensed on the cooled surfaces of the condenser equipment and is
then caught in an overhead accumulator drum. A portion of the
distillate is recycled to the crude pot with the remainder being
transferred to other refinery units.
One of the chief points of difficulty with respect to corrosion
occurs in the area of the condensation of water that is carried
over in the overhead line. The top temperature of the fractionating
column is maintained above the boiling point of water. The
condensate formed after the vapor leaves the column contains a high
percentage of acidic materials such as hydrogen sulfide, hydrogen
cyanide, CO.sub.2, HCl, etc. Due to the high concentration of acids
dissolved in the water, the pH of the condensate is quite low. For
this reason the water is highly corrosive. It is important,
therefore, that the condensate be rendered less corrosive.
One approach to the solution of overhead distillation acid
corrosion is the use of ammonia. However, ammonia being more
volatile than water is often carried beyond the point of
condensation so that its effectiveness is diminished. In addition
ammonia tends to form NH.sub.4 Cl which is trapped in stagnant
locations causing fouling. Since NH.sub.4 Cl contains the chloride
ion, it creates a high level of corrosion in a localized area
unreachable by corrosion inhibitor treatment, thus rendering the
system virtually unprotected at that point.
Another approach to overhead corrosion comprises the use of certain
amines such as morpholine. These amines are more expensive than
ammonia but they still cause salt deposition of their HCl salts and
subsequent local corrosion. In addition since certain of these
amines and their derivatives are excellent emulsifiers, they often
cause process difficulties down stream.
In the overhead distillation column it is highly desirable to
maintain a pH with minimal deviations of between about 6 and 7,
(since an acidic pH tends to cause acid corrosion) whereas a pH
higher than 7 tends to cause fouling with the attendant deposition
of HCl salts which cause localized corrosion in the unprotected
areas of deposition.
In adding ammonia or morpholine to the column a variation in the
rate of addition causes problems. For example, where 6.5 is the
target pH, a variation of .+-. 10 percent in the addition would
yield a pH of about 2.8 or 8.8 with NH.sub.3 and 3.2 or 7.5 with
morpholine, thus causing acid corrosion in the lower pH ranges and
fouling in the higher pH ranges.
I have now discovered that in contrast to NH.sub.3 or morpholine,
when ethylene diamine (EDA) is employed to control pH, an addition
rate fluctuation of .+-. 10 percent would still give a pH between
about 6 - 7 with minimal deviation. When a pH of 6.8 is used as the
target point, such control is easily obtained. In this way
corrosion at the lower pH's and fouling at the higher pH's are
avoided.
The advantages of this invention are illustrated in the following
Figures:
FIG. 1 presents titration curves obtained by neutralizing the
Cl.sup.- ion in sour water systems by employing NH.sub.3,
morpholine and ethylene diamine as neutralizing agents. It is to be
noted that because of its greater buffering action, the curve for
ethylene diamine is not as steep as that obtained with either
ammonia or morpholine.
FIG. 2 presents a graph of pH as a percent fluctuation of the
injection or feed rate based on desired control at pH 6.5. It is
noted from this curve that, in contrast to the steep curve with
both NH.sub.3 and morpholine, EDA gives a flat curve indicating
that variation in the feed rate has less affect on pH as compared
to NH.sub.3 or morpholine.
By moving the control point to pH 6.8 in the case of EDA, a
variation .+-. 10 percent in feed will still maintain a pH of about
6 to 7 in contrast to the wide fluctuations with either NH.sub.3 or
morpholine. Stated another way, with EDA deviations from a pH of 6
to 7 are minimized.
The purpose of neutralizing corrosive systems is to maintain the pH
as close as possible to a pH of 7 with minimum temporary
deviations. However, during actual neutralization the deviation
from 7 can vary widely. This is clearly shown in FIG. 3 and Table I
which compares the use of ethylene diamine with ammonia and
morpholine as neutralizers. Even though the average pH may be close
to 7, temporary deviations cause corrosion.
In refinery practice, pH control is maintained indirectly by
measuring chloride concentration. Thus, chloride concentration is
maintained at 60 ppm .+-. 10, i.e., from 50 - 70 ppm chloride, the
.+-. standard deviation (.sigma.) being .+-. 10. Theoreticaly the
following pH's are the ranges for the neutralizer shown in the
attached tables
Neutralizer pH Range ______________________________________
NH.sub.3 2.8 to 8.2 pH Morpholine 3.0 to 7.6 pH E.D.A. 3.9 to 7.0
pH ______________________________________
Note that EDA has the narrowest theoretical pH range.
In practice close pH control is desired. This is shown in FIG. 3
and in Table I where it is demonstrated that EDA maintains the pH
within the desirable pH range of 5.5 to 7.0 and most preferably 6 -
7, more effectively than either ammonia or morpholine. Although
some deviations from this range may occur, they are minimal as
compared to NH.sub.3 or morpholine.
Refinery Example 1
Table I ______________________________________ Crude charge 100,000
B/D Overhead water condensate 30 gpm Average chloride concentration
60 ppm Range of chloride concentration 50-65 ppm NH.sub.3 EDA
Morpholine Injection Rate 11 lb/day 5 gal/day 12 gal/day pH at
different chloride levels Example Number Cl ppm NH.sub.3 EDA
Morpholine 1 60 6.5 * 6.5 * 6.5 * 2 58 7.5 6.7 * 7.0 * 3 61 4.1 6.3
* 4.7 4 56 7.9 6.9 * 7.3 5 62 3.3 6.2 * 3.7 6 54 8.1 6.9 * 7.5 7 63
3.1 5.9 * 3.3 8 52 8.1 7.0 * 7.6 9 64 3.0 5.7 * 3.3 10 50 8.3 7.0 *
7.7 11 65 2.9 5.0 3.1 12 53 8.2 7.0 * 7.6 13 64 3.0 5.7 * 3.3 14 55
8.0 6.9 * 7.4 15 63 3.1 5.9 * 3.3 16 57 7.7 6.8 * 7.2 17 62 3.3 6.2
* 3.7 18 59 7.1 6.6 * 6.8 * 19 61 4.1 6.3 * 4.7 20 60 6.5 * 6.5 *
6.5 * ______________________________________ * Within desirable pH
range
FIG. 3 is a graph of the pH at different chloride (Cl.sup.-)
concentrations of the particular examples in Table I when treated
with EDA, NH.sub.3, and morpholine, demonstrating that a more
narrow pH range is obtained with EDA than with either NH.sub.3 or
morpholine.
From the above data it is evident that the present invention
employing EDA is more effective than either NH.sub.3 or morpholine
in keeping the pH range within about 5.5 and 7.0 and preferably 6 -
7 with minor deviations where corrosion is minimal. Since corrosion
is a great problem in refining, this improvement is of high
commercial significance.
Although there are temporary deviations from the above desired and
preferred ranges, these deviations are minimal as compared to
NH.sub.3 and morpholine. This is clearly shown in FIG. 3.
I have also discovered that polyamines such as ethylene diamines
have the following additional advantages.
A. Ethylene Diamine is a volatile amine which has a vapor pressure
range very similar to water. In the overhead vapor system of the
column it will condense somewhat at the same time as the acidic
water to give instantaneous neutralization, without premature
condensation.
FIG. 4 presents the vapor pressures of water, EDA and morpholine at
various temperatures from which it is evident that EDA has a vapor
pressure closer to water than morpholine and thus in an overhead
vapor system it will condense somewhat at the same time as acidic
water to give instantaneous neutralization without premature
condensation. The vapor pressure of NH.sub.3 on the other hand is
very high and its condensate is difficult to control and condense
at the proper location.
B. Although ethylene diamine is more expensive than NH.sub.3, it is
less expensive than morpholine. Comparative properties of ammonia,
ethylene diamine and morpholine are shown in Table II.
Table II ______________________________________ PROPERTIES OF
AMMONIA, ETHYLENE DIAMINE AND MORPHOLINE Ethylene Ammonia Diamine
Morpholine ______________________________________ Molecular Weight
17 60 87 Equivalent Weight 17 30 87 Specific Gravity 0.82 0.91 1.00
Boiling Point, .degree.C. -33 117 128 Flash Point, .degree.F. -- 99
102 Pounds to Neutralize 100 Pounds of Cl.sup.- to pH 6.5 48 97 250
______________________________________
Because of the neutralization stoichiometry, a little EDA goes a
long way in neutralization with low cost performance. It has
one-fourth the cost of morpholine in neutralization.
C. Unlike NH.sub.3, ethylene diamine can be formulated with a
corrosion inhibitor in any proportion with the aid of a common
solvent. The ability of EDA to do so offers the versatility to vary
the dosage according to the need of corrosion protection. When the
overhead condensing system has a high level of acidic conditions,
more neutralizers will be used to control the desired pH and
thereby an automatically higher dosage of inhibitor is also present
to combat high corrosion condition. On the other hand, at low
acidic level, the inhibitor is automatically reduced.
D. The corrosion inhibitors employed are surface active and thereby
offer detergent action to combat fouling; and the detergency
requirement of the system will be automatically satisfied according
to thhe need of the system, by controlling the rate of addition of
the EDA corrosion inhibitor mixture.
E. EDA has excellent water tolerance.
Corrosion inhibitors are also employed in addition to EDA. The
corrosion inhibitor is generally a nitrogen compound of high
molecular weight such as amines, amides, aminoamides, imidazolines,
etc., which may be dissolved in a solvent. Since they are believed
to form a protective film on the metal surface to inhibit
corrosion, they are called film-forming corrosion inhibitors.
Since corrosion inhibitors are surface active and tend to stabilize
oil/water emulsions, when water is entrained in the oil, they can
cause difficulties in product finishing processes and pollution.
Since corrosion inhibitors vary widely in their tendency to
stabilize emulsions, the inhibitor dosage should be less than that
concentration which will create a emulsion problem.
Although the inhibitor and EDA may be added separately, it is
convenient to formulate a common solution of EDA and the corrosion
inhibitor so that a fixed ratio of corrosion inhibitor is present
per unit EDA. This solution offers the versatility of varying
dosage according to the need of corrosion protection. Thus, when
the overhead condensate system has a high level of acid, more
neutralizers will be used to control the desired pH and a higher
dosage of inhibitor will automatically be present to combat a high
corrosion condition. Conversely, at a low acidic level, the
inhibitor will also be automatically reduced.
In addition to acting as a corrosion inhibitor, the detergency of
the corrosion inhibitor is very effective in breaking up fouling
deposits which may form, thus preventing localized corrosion.
In general, the film-forming organic corrosion inhibitors which are
employed in this invention are generally heteropolar, for example,
cationic in nature. The most widely used type of film-forming
corrosion inhibitor is the cationic type, which is generally a
comparatively high molecular weight organic compound containing one
or more basic nitrogen atoms.
In general, assuming a monomolecular layer, the more effective
film-forming corrosion inhibitors are those which cover the largest
area per molecule and form the most coherent and oriented film.
Typical but non-limiting examples, of film-forming corrosion
inhibitors are presented below.
A wide variety of nitrogen bases are known to be film-forming
corrosion inhibitors. The following are a few non-limiting
examples:
1. Oxazolines (U.S. Pat. No. 2,587,955)
2. Tetrahydropyrimides (U.S. Pat. No. 2,640,029)
3. Imidazolines (Re. 23,227)
4. Pyrrolinediones (U.S. Pat. No. 2,466,530)
5. Amino amides (U.S. Pats. No. 2,550,682 and 2,598,213)
6. Quaternary amines (U.S. Pat. No. 2,659,693)
7. Monoamines, such as Rosin Amine
(OIL GAS JOURNAL 46, No. 31, 91-6 (1946)
Oxyalkylated Rosin Amine (U.S. Pat. No. 2,564,749)
Rosin Amine + solubilizing agent (U.S. Pat. Nos. 2,564,757 and
2,564,753)
The imidazolines employed in the specific examples are a member of
the cyclic amidine family of compounds and are prepared in the
manner described in Reissue 23,227, U.S. Pat. No. 2,468,163, and
elsewhere.
They may be described, for example, as follows: ##SPC1##
where ##SPC2##
are residues derived from the carboxylic acid employed in preparing
the compound wherein R is, for example, a hydrocarbon radical,
having, for example, up to about 30 carbon atoms, such as 1 - 30
carbon atoms, B is hydrogen or a hydrocarbon radical, for example,
a lower alkyl, such as methyl - for example, where CB.sub.2
##SPC3##
but preferably - CH.sub.2 - CH.sub.2 - or -CH.sub.2 -CH.sub.2 -
CH.sub.2 - , and R is the residue derived from the cyclic
amidine-forming polyamine, for example where DR is ##SPC4##
and wherein n is, for example, the numeral 1 to 6 and R' is
hydrogen or an aliphatic, cycloaliphatic hydrocarbon, etc.,
radical.
In the simplest case, the group R' may be directly attached to the
1-nitrogen atom of the ring, as follows: ##SPC5##
The particularly outstanding corrosion-preventative reagents result
when the cyclic amidine contains basic nitrogen groups in addition
to those inherently present in the imidazoline ring. In general,
compounds of this type which are effective are those in which the
basic nitrogen group is contained in the radical D in the above
formula.
In this case the products may be represented by the formula
##SPC6##
where R and R' are hydrogen or a hydrocarbon radical, and in which
at least one of the groups R and R' is an aliphatic or
cycloaliphatic hydrocarbon group containing from 8 to 32 carbon
atoms; and Y is a divalent organic radical containing amino groups.
The group R' may be, and usually is, an amino nitrogen substituent.
Examples of organic radicals which Y - R' may represent are
##SPC7##
-C.sub.2 H.sub.4 - NR' - C.sub.2 H.sub.4 - NR' - C.sub.2 H.sub.4 -
NR.sub.2 , where R' and R have their previous significance.
Of this class of corrosion inhibitors in which an amino group
occurs as a portion of the 1-nitrogen substituent, those which are
derived from the polyethylene polyamines appear to be particularly
effective as corrosion inhibitors. These have the general formula
##SPC8##
where R and R' have their previous meanings, and m is a small
number, usually less than 6. Amides of these imidazolines are also
effective.
Imidazolines have been described in Re. 23,227. A typical claim is
as follows:
"A process for preventing corrosion of metals, comprising the step
of applying to such metals a substituted imidazoline selected from
the class consisting of ##SPC9##
in which D represents a divalent, non-amino organic radical
containing less than 25 carbon atoms, composed of elements from the
group consisting of C, H, O, and N; D' represents a divalent,
organic radical containing less than 25 carbon atoms, composed of
elements from the group consisting of C, H, O and N'; D' represents
a divalent organic radical containing less than 25 carbon atoms,
composed of elements from the group consisting of C, H, O and N,
and containing at least one amino group; R is a member of the class
consisting of hydrogen and aliphatic and cycloaliphatic hydrocarbon
radicals; with the proviso that at least one occurrence of R
contains 8 to 32 carbon atoms; and B is a member of the class
consisting of hydrogen and alkyl radicals having not over 2 carbon
atoms, with the proviso that at least three occurrences of B be
hydrogen."
Tetrahydropyrimidines have been described in U.S. Pat. No.
2,640,028 where a typical claim is as follows:
"A process for preventing corrosion of metals including the step of
applying to such metals a substituted tetrahydropyrimidine of the
formula type: ##SPC10##
where D is a member of the class consisting of D' -R and R' D'
represents a divalent organic radical containing less than 25
carbon atoms, composed of elements from the group consisting of C,
H, O and N; R is a member of the class consisting of hydrogen and
hydrocarbon radicals, with the proviso that at least one occurrence
of R contains from 8 to 32 carbon atoms; B is a member of the class
consisting of hydrogen and hydrocarbon radicals containing less
than 7 carbon atoms, with the proviso that at least three
occurrences of B be hydrogen."
In general, the preferred embodiments of film-forming corrosion
inhibitors are of the type of cyclic amidines described above and
acylated alkylene polyamines of the type described in U.S. Pat. No.
2,598,213 which are by reference incorporated in the present
invention.
As is quite evident, other film-forming corrosion inhibitors are
known and new film-forming inhibitors will be constantly developed
which are useful in this invention. It is therefore not only
impossible to attempt a comprehensive catalogue of such inhibitors,
but to attempt to describe the invention in its broadest aspects in
terms of specific chemical names of film-forming corrosion
inhibitors used would be too voluminous and unnecessary, since one
skilled in the art could by following known testing procedures
select the proper film-forming inhibitor. This invention lies in
the use of suitable film-forming corrosion inhibitors in the
process and compositions of this invention and their individual
composition is important only in the sense that their properties
can effect the process.
For optimum results EDA is generally formulated with the corrosion
inhibitors in a solution suitable for controlled addition to the
system. Depending on the particular corrosion inhibitor the ratio
of EDA to corrosion inhibitor can vary widely such as from about
0.75'-0.99 or more, for example from about 0.85-0.98, such as from
about 0.90-0.97, but preferably from 0.92-0.95 exclusive of
solvent. The concentration of EDA + corrosion inhibitor in the
solvent can vary widely such as from about 5- 85 percent for
example from about 10- 60 percent, such as from 20- 50 percent, but
preferably from 30- 45 percent.
A typical formulation by weight is as follows:
Formulation A ______________________________________ EDA 40% Film
Forming Corrosion Inhibitor 2% Alcohol 5% Hydrocarbon 53% 100%
______________________________________
The corrosion inhibitor is the reaction product formed by acylating
diethylenetriamine with naphthenic acid to yield imidazolines and
amides.
The rate of addition can vary widely and will depend on the
particular formulation employed and the acidity of the system. In
general it should be sufficient to maintain the overhead pH at a
goal of about 6 to 7.
Although EDA is the preferred polyamine, other
polyalkylene-polyamines can also be employed such as those of the
formula ##SPC11##
where n is an integer such as from 1 - 10 and A is alkylene
preferably lower alkylene and most preferably ethylene and/or
propylene. Preferably the polyethylene polyamine are preferred when
n=1-5, i.e. ##SPC12##
The polyamine can be added to the distillation unit at any suitable
place. For example, the polyamine can be added to the petroleum
charge. This is a highly convenient method of carrying out the
process since it will also neutralize condensation within the tower
and recirculation lines. The polyamine can also be pumped directly
into the gaseous overhead line. The polyamine can also be passed
into the reflux line or can be added to recirculating water at the
top of the column. The particular point at which the polyamine is
added will depend largely on the design of the particular
equipment, the personal preference of the operator, the point where
corrosion is more severe, etc.
In addition to the use of polyamines in controlling acid corrosion
in the distillation column by regulation of the pH within the
general range of about pH 6-7 with minimum variations on the acid
or the basic side, the addition of amines to the petroleum charge
prior to distillation in place of a conventional caustic treatment
reduces the amount of HCl in the overhead condensate without the
disadvantages resulting from the conventional caustic
treatment.
Crude petroleum as received by the refinery generally contains
brine (0.2 to 2.0 percent) which cannot be removed in the field.
The brine solution consists primarily of sodium, calcium and
magnesium chlorides. Although the desalting process is designed to
remove these impurities, a small amount of salt solutions is
retained in the desalted crude as it is charged into the crude
unit. When the crude oil is subjected to a distillation temperature
of as high as 700.degree.F., chloride salts are hydrolyzed and
decomposed to liberate hydrogen chloride that is then carried
overhead in the fractionation towers. Caustic soda has been
employed for many years to reduce the hydrogen chloride evolution
in the distillation process. This is normally done by injecting an
aqueous solution of caustic into the desalted crude oil charge
line. It is theorized that sodium hydroxide reacts with the readily
hydrolyzable salts such as magnesium chloride to form more stable
sodium chloride and the corresponding hydroxide. However, the
introduction of caustic causes fouling in the preheat exchangers
and causes excessive coking in furnace tubes in addition to causing
an increase in sodium content of residual fuel oil.
I have discovered that when amines such as alkylene polyamines are
added to the crude instead of using the conventional caustic
treatment, one achieves a reduction of HCl in the distillation
column without the disadvantages caused by caustic injection. Thus
by adding such amines in place of caustic into the desalted crude,
I have achieved HCl reduction without the disadvantages caused by
the use of caustic.
This result is unexpected since it cannot be explained by the
general theory that NaCl is less readily hydrolyzed than MgCl since
the amines employed herein are less basic than caustic. Therefore,
the reason for this unexpected action is not understood.
Thus in addition to the injection of amines into the crude with the
resulting reduction of overhead HCl without caustic disadvantages,
the polyamine can also be injected into the distillation column as
described herein.
The following examples are presented for purposes of illustration
and not of limitation.
A two-liter pot was filled with 700 ml of crude oil or gas oil for
each distillation; 4 ml of a water solution of 3.75 g Mg Cl.sub.2
/6 H.sub.2 O/100 ml or 0.15 g of MgCl.sub.2.sup.. 6 H.sub.2 O also
was charged to each distillation. The laboratory still pot was
equipped with a 21/2 ft. stainless steel saddle packed heated
column of approximately six to eight plates.
Example A
Crude Oil Distillation.
The crude oil used for these distillations contained 2.5 ppm
chloride in addition to the chloride that was added. The density of
the crude was 0.825, therefore, the weight of crude charged was 577
g. The crude oil and the 4 ml of salt solution were heated to
130.degree. C. removing water during this period. In order to
simulate the steaming effect of a crude unit 2-5 drops of water was
added above 155.degree. because of excess foaming and for the same
reason could not be heated above 175.degree. C. which was the final
pot temperature. The condensate from the still was removed by means
of a glass tube submersed in 20 ml of water in order to collect the
chloride that distilled over. The total grams of chloride ion
contained in the crude oil distillations was as follows: 0.00175 g
(from 2.5 ppm in crude) 0.02616 g from salt solution charge
Tabulation of crude oil distillations is as follows:
pH PPM * Total Ml of con- chloride in % Chloride H.sub.2 O in
densate condensate obtained in receiver water H.sub.2 O condensate
______________________________________ Blank 23.36 4.0 17.7 1.5%
NaOH (1) 31.56 4.3 3.6 0.41% EDA (2) 28.45 5.1 3.2 0.33%
______________________________________ * Chloride content is
adjusted as if 23.36 ml of water (1) NaOH charged = .065 g (1 ml at
6.5 g/100 ml) (2) EDA charged = 0.139 g (1 mol at 13.9 g/100
ml)
Example B
Gas Oil Distillations
The only chloride present was from the 4 ml of MgCl.sub.2 solution
added to the pot (0.02616 g of Cl.sup.-). The Gas oil water mixture
was heated to 150.degree. C. before adding the additional water.
Water was added from 150.degree. to 215.degree. C. at 2-5 drops per
every 5.degree. C. The batch was then reheated to 215.degree. C.
(419.degree. F.) where gas oil started refluxing such that no
further increase in pot temperature could be obtained. Receiver
water charge for chloride absorbing in the gas oil runs was 15
ml.
Tabulation of gas oil distillations is as follows:
PPM * Total Ml pH of chloride in % Chloride H.sub.2 O in condensate
condensate obtained in receiver water H.sub.2 O condensate
______________________________________ Blank 25.40 7.7 3 (1) 0.35%
NaOH 32.38 8.5 1.4 (2) 0.17% EDA 31.05 7.7 1.7 0.2%
______________________________________ (1) diluted to 31.05 ml for
chloride + pH determinations. (2) ppm chloride corrected for 31.05
ml water in summary section.
The NaOH and EDA charges for the gas oil runs were the same as
reported in details for the crude oil distillations. The chloride
content of the water distillate layers from the laboratory still
were as follows: On (A) a crude oil, (B) gas oil using a 10 percent
excess of EDA or NaOH over the amount of chloride charged.
A. crude oil runs - pot temperature to 347.degree. F.
1. blank run Cl.sup.- = 17.7 ppm
2. NaOH run Cl.sup.-= 4.8 ppm (73 percent reduction)
3. EDA run Cl.sup.- = 3.9 ppm (78 percent reduction)
B. gas oil runs - pot temperature to 419.degree. F.
1. blank run Cl.sup.- = 3 ppm
2. NaOH run cl.sup.- = 1.4 ppm (53 percent reduction)
3. EDA run Cl.sup.- = 1.7 ppm (43 percent reduction)
The above data shows a definite effect of the ability of EDA to
reduce the amount of chloride in distillate condensates.
Refinery Example A
Formulation A is injected into the overhead system of a refinery
distillation unit so that neutralization takes place in the
vapor-condensate system as soon as water condensation occurs to
form an acid solution. The dosage is adjusted so as to maintain the
pH goal of about 6 - 7 with sufficient control so that there are
minimal deviations below about 5. In this way corrosion is
minimized.
Refinery Example B
The above example is repeated except that the petroleum feed is
pretreated with EDA instead of caustic as was done in Example A.
Formulation A is then injected into the overhead system in the
manner of Refinery Example A.
The petroleum feed in Refinery Examples A and B are crudes.
Refinery Examples C and D
Examples A and B are repeated except that the feeds are gas
oils.
From the foregoing description various modifications in this
invention will be apparent to those skilled in the art which do not
depart from the spirit of the invention.
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