U.S. patent number 3,766,053 [Application Number 05/267,333] was granted by the patent office on 1973-10-16 for corrosion inhibitors for refining & petrochemical processing equipment.
This patent grant is currently assigned to Nalco Chemical Company. Invention is credited to William E. Seffens.
United States Patent |
3,766,053 |
Seffens |
October 16, 1973 |
CORROSION INHIBITORS FOR REFINING & PETROCHEMICAL PROCESSING
EQUIPMENT
Abstract
A process for the prevention of corrosion in refinery systems by
the injection of an imidazoline compound into the overhead vapor
line. The imidazoline compound is formed from the reaction of a
naphthenic acid and dipropylene triamine.
Inventors: |
Seffens; William E. (Houston,
TX) |
Assignee: |
Nalco Chemical Company
(Chicago, IL)
|
Family
ID: |
23018354 |
Appl.
No.: |
05/267,333 |
Filed: |
June 29, 1972 |
Current U.S.
Class: |
208/47; 208/187;
208/350; 422/11; 203/7; 208/188; 422/9 |
Current CPC
Class: |
C23F
11/149 (20130101) |
Current International
Class: |
C23F
11/10 (20060101); C23F 11/14 (20060101); C23f
011/10 (); C07d 049/34 (); C10g 009/16 () |
Field of
Search: |
;208/47,350 ;21/2.7
;203/7 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gantz; Delbert E.
Assistant Examiner: Schmitkons; G. E.
Claims
I claim:
1. A process for the prevention of corrosion in refinery systems
comprising the step of injecting into the overhead vapor line of
the refinery system a composition consisting of:
A. from 10-40 percent by weight of an organic solvent; and
B. from 50-90 percent by weight of an imidazoline compound having
corrosion inhibition properties, said compound formed by the
reaction of dipropylene triamine and a naphthenic acid in the
ratios of 1:2 to 2:1.
2. The process for the prevention of corrosion in refinery systems
as in claim 1 wherein the ratio of dipropylene triamine to
naphthenic acid is 1:2.
3. A process for the prevention of corrosion in refinery systems in
refinery processing comprising the step of injecting into the
overhead vapor line of the refinery system a composition consisting
of:
A. 20 percent by weight of an organic solvent; and
B. 80 percent by weight of an imidazoline surfactant having
corrosion inhibition properties, said surfactant formed by the
reaction of dipropylene triamine and a naphthenic acid in the ratio
of 1:2.
4. A process for the prevention of corrosion in refinery systems as
in claim 1 wherein from 2-5 ppm of the composition is injected into
the overhead vapor line.
Description
INTRODUCTION
This invention relates to a process for the prevention of corrosion
in refinery systems by injecting an imidazoline compound into the
overhead vapor line. More specifically, this invention relates to
the addition of an imidazoline compound having corrosion inhibition
properties to the refinery system, the imidazoline being capable of
preventing corrosion inside the refinery system. The preferred
imidazolines are formed by the reaction of dipropylene triamine and
naphthenic acid.
The imidazoline surfactant is known to the art as a corrosion
inhibitor. The composition and its use as a corrosion inhibitor in
motor fuel and on metal surfaces is disclosed in U. S. Pat. No.
2,466,517 and U. S. Pat. No. 3,510,282, the specifications of which
are to be incorporated by reference in its entirety. In particular,
the imidazoline surfactant formed by the reaction of dipropylene
triamine and a naphthenic acid is disclosed as a corrosion
inhibitor.
In refinery processing there is usually a significant amount of
water present with the crude petroleum. Water is present with the
crude petroleum when it is extracted from the ground. In addition,
substantial amounts of water are present from condensation
resulting from the use of steam in the distilling stage. In
refinery processing due to the presence of both water and crude
petroleum, it has been found that the water and crude petroleum
easily mix, the result being the formation of an emulsion. When
such an emulsion is formed it is often quite time consuming and
expensive to break the emulsion to rid the system of the water. It,
therefore, would be desirable to inject into the system a chemical
which would prevent or reduce this emulsion formation.
It has been found that when the imidazoline compound is injected
into a refinery system, in addition to its corrosion inhibition
properties, it also exhibits the ability to reduce formation of an
emulsion of water and crude petroleum.
OBJECTS
It is an object of this invention to provide a process for the
prevention of corrosion in refinery systems by injecting into the
overhead vapor line an imidazoline compound.
It is an object of this invention to provide an imidazoline
compound to prevent emulsion formation between water and the crude
petroleum in refinery processing.
It is also an object of this invention to provide an imidazoline
compound useful in preventing emulsion formation between water and
crude petroleum in refinery processing, said surfactant having
corrosion inhibition properties.
It is a further object of this invention to provide an imidazoline
compound formed by the reaction of dipropylene triamine and
naphthenic acid, said compound preventing emulsion formation of
water and crude petroleum in refinery processing.
Further objects will appear hereinafter.
THE INVENTION
This invention relates to a process for the prevention of corrosion
in refinery systems comprising the step of injecting into the
refinery system a composition consisting of:
A. from 10-40 percent by weight of an organic solvent; and
B. from 60-90 percent by weight of an imidazoline compound having
corrosion inhibition properties, said compound formed by the
reaction of dipropylene triamine and a naphthenic acid in the
ratios of 1:2 to 2:1.
The preferred composition consists of:
A. 20 percent by weight of an organic solvent; and
B. 80 percent by weight of an imidazoline surfactant having
corrosion inhibition properties, said surfactant formed by the
reaction of dipropylene triamine and a naphthenic acid in the ratio
of 1:2.
ORGANIC SOLVENT
The organic solvent of the composition acts merely as a solvent or
carrier for the imidazoline surfactant. The organic solvent may be
aliphatic or non-aliphatic liquid. Generally, the organic solvent
is a hydrocarbon liquid having from 3 to 22 carbon atoms.
Typically, high boiling aromatic organics are used in the practice
of this invention. For example, kerosene is a preferred organic
solvent. Other solvents which may be used are propane, butane, and
heptane. The organic solvents used in this invention are not
limited to those mentioned above but include a large type and
variety of organic solvents in which the imidazoline surfactant is
soluble.
IMIDAZOLINE SURFACTANT
The imidazoline surfactant of this invention is formed by the
reaction of dipropylene triamine and a naphthenic acid in a ratio
of 1:2 to 2:1. The preferred ratio of dipropylene triamine to
naphthenic acid is 1:2. It has been found that when ratios of the
dipropylene triamine to naphthenic acid outside the above mentioned
range are used, an inferior imidazoline surfactant is obtained
which is not as efficient in preventing the formation of an
emulsion between water and the fuel.
The naphthenic acid used in this invention is defined in U.S. Pat.
No. 3,510,282 as being a petroleum refining by-product obtained
when the alkali liquor from the caustic treatment of gas oil is
acidified with sulfuric acid. This treatment produces a dark brown
about 12 on the Gardner color scale (when cut 1 to 9 with mineral
spirits) oily liquid which separates to the top of the aqueous
liquor. The mixed acids can be divided roughly into three groups
having the general formulas: C.sub.n H.sub.2n O.sub.2, C.sub.n
H.sub.2n.sub.-2 O.sub.2, and C.sub.n H.sub.2n.sub.-4 O.sub.2. The
first group occurs largely in the lower boiling fraction of the
mixture. They usually contain 6 or 7 carbon atoms and are
colorless.
The second group, usually the largest, contains acids of 8 to 12
carbon atoms having the structure: ##SPC1##
The third group contains the heaviest molecules which are
polycyclic and have from 12 to 23 carbon atoms. All fractions from
a carefully distilled naphthenic acid (24) contain some color
which, so far, has proved impossible to remove. Tarry residues
account for the dark color of the crude, but these are largely
removed by distillation. Since naphthenic acids are saturated and
primarily cyclic, their soaps have much greater stability than
those of other common liquid acids. The crude acid as delivered has
a density of 8.04 to 8.44 pounds per gallon and a viscosity of 1.25
poises at 77.degree. F. The acid values range from 160 to 270, but
naphthenic acid used for soap manufacture usually has an acid value
between 220 and 230. pH of the water extract is about 5.5 and the
iodine value between 8 and 11. Unsaponoifiables are held below 12
percent. The initial boiling points vary widely from shipment to
shipment. Individual batches have boiled below 200.degree. F. and
up to almost 400.degree. F. at 3.5 inches of mercury.
A typical formula in connection with some of the commercially
available naphthenic acids is the following: ##SPC2##
These particular acids are available in at least three different
grades; Grade 1 having an average molecular weight of 290-300.
Generally speaking, there is present about 6 percent of
non-saponifiables and this type is perhaps characteristic of the
most common commercially available naphthenic acid.
Grade 2 has a somewhat higher molecular weight, for instance
320-330 and contains about 8 percent of non-saponifiable matter.
Grade 3, which finds considerable utility, has a molecular weight
range of 410-420 and contains about 10 percent nonsaponifiable
matter.
Any naphthenic acid may be used but preference is to use the
commercial grades above described, or in some instances, mixtures
of two different grades so as to give, for example, an average
molecular weight of 360 to 370 in some instance, and in others, a
molecular weight of about 310, or thereabouts.
In examining the formula immediately preceding, with the formula
preceding the above formula, and ignoring difference in the cyclic
structure of the naphthenic acids, it is apparent that in at least
some naphthenic acids which are available commercially the cyclic
structure is part of the beta carbon atom. On the other hand, as
far as is known, and referring to the formula ##SPC3##
there are available naphthenic acids in which apparently x in the
formula represents a small whole number, for instance, 3 or 4 or
the like.
In practicing the present invention preference is given to the
higher molecular weight naphthenic acids, for example those having
an average molecular weight of at least about 2,000 such as about
250 to 500, or greater, for example from about 290 to 420 but
preferably from about 325-375.
Since commercial grades of naphthenic acids are employed, these
contain many individual species over a molecular weight range.
The most preferred naphthenic acid those known as "Sunaptic" acids
which are high-molecular-weight naphthenic acids prepared by the
caustic extraction of selected base stocks. They range in acid
number from 120 to 180, in molecular weight from 300 to 415, and
are available in three grades, A, B, and C.
Specifications and typical analyses for the three Sunaptic acids
are given in the table below. They are mono-carboxylic acids and,
having no olefinic unsaturation, are highly resistant to oxidative
rancidity. They have low pour points and contain relatively low
amounts of unsaponifiable matter. Sunaptic acids are soluble in
most hydrocarbons. ##SPC4##
THE DIPROPYLENE TRIAMINE
The amine that reacts with the naphthenic acid to form the
imidazoline surfactant of this invention is dipropylene triamine.
One molecule of dipropylene triamine reacts with two molecules of
naphthenic acid to form two isomers: ##SPC5##
One molecule of dipropylene triamine reacts with one molecule of
naphthenic acid to form two isomers: ##SPC6##
Thus, there are four possible imidazoline surfactant isomers which
may be formed from the reaction of dipropylene triamine and
naphthenic acid.
APPLICATION
As mentioned above, water is usually present in the refinery
system. Water is present with the crude petroleum when extracted
from the ground and, in addition, substantial amounts of water are
present from condensation resulting from the use of steam in the
distilling stage. In order to prevent the formation of an emulsion
between the water and the crude petroleum, the imidazoline
surfactant is injected into the refinery system. The imidazoline
surfactant is generally diluted by an organic solvent. The
preferred concentration of the imidazoline surfactant is 20 percent
by weight.
The diluted imidazoline surfactant can be injected at numerous
stages of the refinery system. The preferred points of injection
are at the overhead vapor line and at the reflux line. Generally,
the composition is injected as a spray. The imidazoline surfactant
will distribute throughout the system preventing formation of an
emulsion as well as preventing corrosion on the metal surfaces
inside the refinery unit. Generally from 2-5ppm of the composition
is injected.
To further illustrate the invention, the following examples are
presented:
EXAMPLE 1
At a petroleum refinery in Southern California, an imidazoline
surfactant dissolved in kerosene was injected into the overhead
vapor line as a fine spray. The composition consisted of 80 percent
kerosene and 20 percent imidazoline surfactant.
The imidazoline surfactant was prepared by the reaction of
dipropylene triamine and a commerical naphthenic acid in a molar
ratio of 1:2. The naphthenic acid used in the Examples is derived
from petroleum and is an organic acid containing a substituted
naphthenic ring structure. The naphthenic acid has the following
properties:
TABLE II
Flash Point, Tag, Open Cup, .degree.F. 150+ Acid Number,
Oil-Included 189 Acid Number, Oil-Free 219 Unsaponifiable Content,
(% by wt.) 14.1 Color (ASTM) Black Water Content (% by wt.) Trace
Viscosity, at 100.degree.F., SSU Viscosity, at 210.degree.F., SSU
Specific Gravity at 60.degree.F. 0.983
the reactants were charged to reactor and heated to 170.degree.C.
for 30 minutes at which time a vacuum of about 28 inches was
applied for an additional 4 hours. The product was cooled and
dissolved in the heptane.
The composition was injected in a concentration of 12ppm. Samples
of the fuel were removed from the refinery system and the amount of
water emulsified was measured by using the test procedure ASTM D
2550. This is a measure of transmittance with the WISM values
ranging from 0-100 with the higher WISM value indicating lower
amounts of water present. The WISM value obtained was 97.
Typical WISM values obtained using other surfactants are listed in
Table III.
TABLE III
SURFACTANT PPM WISM Value Diethylene triamine + Naphthenic Acid 20
70 Diethylene triamine + Oleic Acid 20 75 Dipropylene triamine +
Naphthenic Acid 20 93 Dipropylene triamine + Linoleic Acid 20
67
It is observed from the data presented above that the imidazoline
surfactant of this invention results in substantial reduction in
the amount of water held in emulsion with the crude petroleum.
EXAMPLE II
The corrosion rate of the imidazoline surfactant as prepared in
Example I was measured as compared to the corrosion rates of the
surfactants listed in Table III. The resulting corrosion rates are
tabulated in Table IV.
The corrosion rates were determined by use of the following
procedure:
Through the scale neck of a 1000 ml round bottom, three-neck Pyrex
flask having a gas dispersion tube inserted through a cork stopper
and a coupon holder is inserted 425 cc of depolarized naphtha and
225 cc of refinery stream water.
The refinery stream water is deionized water containing 1000 ppm
hydrochloric acid and 500 ppm acetic acid. The pH of the water is
adjusted to 7.5 with ammonium hydroxide. The surfactant is also
added at this point. The gas tube holder is inserted into the flask
neck and the flow of gas started. The gas consists of 93 percent
prepurified nitrogen, 5 percent air and 3 percent hydrogen sulfide
and is fed at a rate of 40 cc/min./test through calibrated
capillary tubings. The cone drive motor is turned on as is the
heating mantle. The test is allowed to run for an hour before the
coupon is inserted to attain equilibrium. The coupon is positioned
such that the gas dispersion tube is on the downstream side of the
coupon, the gas makes a complete circuit of the flask before it
hits the coupon.
The corrosion coupon is a 0.9525 cm (3/8 inch) .times. 3.81 cm
(1-1/2 inches ) .times. 0.317 cm (1/8 inch) S.A.E. 1020 mild steel
coupon. A 0.317 cm diameter hold is drilled or punched through one
end of the coupon not less than 0.317 cm from the edge. Prior to
use, this coupon is sandblasted and weighed. Contact with skin is
avoided. The coupon remains in the system overnight at which time
it is removed from the flask, cleaned with cleansing powder to
remove loose corrosion products, dipped with agitation in an
inhibited acid bath for 30 seconds, in a saturated soda ash bath
for 20 seconds, washed in tap water to remove remaining salts,
dipped with agitation in an acetone bath and spun dry. The coupon
is then dried in a 100.degree.C. oven for 30 minutes and reweighed.
The corrosion rate is calculated on the basis of weight loss and
test duration.
The corrosion rate of the product formed in Example I was 12 mpy at
a dosage of 12 ppm and 14 mpy at a dosage of 6 ppm.
TABLE IV
Surfactant No. Dosage (PPM) Corrosion Rate (MPY) 1 12 25 1 6 35 2
12 27 2 6 38 3 12 29 3 6 37 4 12 23 4 6 39
it is observed from the data presented in Table IV that in a
refinery system the imidazoline surfactant of this invention
results in substantially improved corrosion rates.
* * * * *