ANTIOXIDANT MATERIAL AND ITS USE

MATERIAU ANTIOXYDANT ET UTILISATIONS CONNEXES

English Abstract

ABSTRACT OF THE DISCLOSURE
The present invention is directed to antioxidant
materials and their use in petroleum and petrochemical processes to
reduce and/or control fouling problems. The inventive antioxidant
materials are composed of non-hindered or partially hindered phenols
in combination with a strongly basic material such as an organo
amine.

Claims

-13-
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of controlling fouling on heat
transfer surfaces in a petroleum or petrochemical processing system which
comprises adding to the petroleum or petrochemical being processed a
sufficient amount for the purpose of an antioxidant composition comprising
(a) an unhindered or partially hindered phenol which possesses the
following formula:
<IMG>
wherein R and R1 are selected from the group consisting of hydrogen and
carbon groupings, with the proviso that not more than one of the R and
R1 be a secondary or tertiary grouping and R2 is alkyl, alkoxy or an
amine group; (b) at least one oil soluble strongly basic alkyl
substituted amine compound; and (c) having a pH of at least 10.5.

-14-
2. A method according to Claim 1 wherein the
composition is added to said system in an amount of from 0.1 to 2000
ppm of the petroleum or petrochemical being processed.
3. A method according to Claim 2 wherein the phenol
is selected from the group consisting of butylated hydroxy anisole,
p-cresol, p-methoxyphenol, and [p(p-methoxy
benzylideneamino)phenol].
4. A method according to Claim 3 wherein the amine
is monoethanolamine, cyclohexylamine, N(2-aminoethyl) piperazine and
1,3 cyclohexane bis (methylamine).
5. A method according to Claim 4 wherein the
composition is in an organic solvent.
6. A method according to Claim 5 wherein the phenol
and the amine are present in a percentage weight ratio of 2 to 98 to
98 to 2.
7. A method according to Claim 6 wherein the
composition comprises 60% amine and 40% phenol.
8. A method according to Claim 7 wherein the
composition is further contained in an organic solvent.

-15-
9. A method according to Claim 8 wherein the
solvent is a heavy aromatic naphtha, dimethylformamide or mixtures
thereof.
10. A composition for use as an antioxidant for
controlling fouling on heat transfer surfaces in petroleum or
petrochemical processing system comprising
(a) an unhindered or partially hindered phenol possessing the
formula
<IMG>
wherein R and R1 are selected from the group consisting of hydrogen and
a carbon containing group, with the proviso that not more than one of R or
R1 be a secondary or tertiary carbon grouping and R2 is alkyl, alkoxy
or an amino group;
(b) at least one strongly basic oil soluble alkyl substituted
amine compound; and
(c) having a pH of at least 10.5.
11. A composition according to Claim 10 wherein the
composition is contained in an organic medium.
12. A composition according to Claim 11 wherein the
amine is in sufficient amount to assure the solubility of said
phenol in said medium.

-16-
13. A composition according to Claim 10 or 12
where the amine and phenol are present in said composition in a
percentage by weight phenol to amine of 98:2 to 2:98.
14. A composition according to Claim 13 wherein the
percentage by weight of phenol and amine is 40% and 60%,
respectively.
15. A composition according to Claim 10 wherein
said phenol is selected from the group consisting of butylated
hydroxy anisole, p-cresol, p-methoxyphenol, and
[p(p-methoxy benzylideneamino)phenol].
16. A composition according to Claim 15 wherein the
amine is monoethanolamine, cyclohexylamine, N(2-aminoethyl)
piperazine and 1,3 cyclohexane bis (methylamine).
17. A composition according to Claim 16 wherein the
amine and phenol are present in said composition in a percentage by
weight ratio of 98:2 to 2:98.
18. A composition according to Claim 17 which is
contained in an organic solvent for such.
19. A composition according to Claim 18 wherein
said solvent is a heavy aromatic naphtha, dimethyl formamide or
mixtures thereof.
20. A composition according to claim 18 wherein the
amine and phenol are present in percentage by weight of about 60% and
about 40%, respectively.

Description

~2~63~
ANTIOXIDANT MATERIAL AND ITS USE
BACKGROUND OF THE INVENTION
Fouling can be defined as the accumulation of unwanted
matter on heat transfer surfaces. This depos~tion can be very
costly in refinery and petrochemical plants since it increases fuel
usage, results in interrupted operations and production losses and
increases maintenance costs.
Deposits are found in a variety of equipment: preheat
exchangers, overhead condensers, furnaces, fractionating towers,
reboilers, compressors and reactor beds. These deposits are
complex; broadly, they can be characterized as organic and
inorganic. They consist of metal oxides and sulfides, soluble
organic metals, organic polymers J coke, salt and various other
particulate matter. Chemlca1 antifoulants have been developed that
effectively combat fouling.
The chemical composition of organic foulants is rarely
identified completely. Organic fouling is caused by insoluble
polymers which sometimes are degraded to coke. The polymers are
usually formed by reactions o~ unsaturated hydrocarbons, although
any hydrocarbon can polymerize. Generally, oleflns tend to
polymerize more readily than aromatics, which in turn polymerize
.~

lZ9~;37
more readily than paraffins. Trace organic materials containing
hetero atoms such as nitrogen, oxygen and sulfur also contribute to
polymerization.
Polymers are formed by free radical chain reactions.
These reactions, shown below, consist of two phases, an initiation
phase and a propagation phase. In reaction 1~ the chain initiation
reaction, a free radical represented by R, is formed (the symbol R
can be any hydrocarbon). These free radicals, which have an odd
electronJ act as chain carriers. During chain propagation,
additional free radicals are formed and the hydrocarbon molecules
(R) grow larger and larger (see reaction 4), forming the unwanted
polymers which accumulate on heat transfer surfaces.
Chain reactions can be triggered in several ways. In
reaction 1, heat starts the chain. Example: when a reactive
molecule such as an olefin or a diolefin is heated, a free radical
is produced. Another way a chain reaction starts is shown in
reaction 3. Here metal ions initiate free radical formation.
Accelerating polymerization by oxygen and metals can be seen by
reviewing reactions 2 and 3.
Coke formation is the result of polymerization initially,
but as ~he polymer sticks to a heat transfer surface, more and more
hydrogen is driven off until the polymer is eventually converted to
coke.
1. Chain Initiation
R-H ~R- + H+

~291637
2. Chain Propagation
a. R- + 2 ~ R-0-0
b. R-0-0 + R' - H -~ R' + R-0-0-H
3. Chain Initiation
a. Me++ + RH ~ Me+ + R- + H+
b. Me++ + R-0-0-H -- ~ Me~ + R-0-0- + H+
4. Chain Termination
a. R- + R' -- - > R-R'
b. R- + R-0-0 -----~ R-0-0-R
In some cases, foul~ng and corrosion may be related
problems. In that case, solving the corrosion problem which exists
upstream may well eliminate the fouling problem.
In refineries, deposits usually contain both organic and
inorganic compounds. This makes the identification of the exact
cause of fouling extremely difficult. Even if it were possible to
preclsely identify every single deposit constituent, this would not
guarantee uncovering the cause of the problem. Assumptions are
often erroneously made that if a deposit is predomlnantly a certain
compound, that campound is the cause of the foul~ng, In reallty, a
mlnor constltuent in the deposit could be actlng as a binder, a
catalyst, or in some role that influences actual deposlt formation.
The final form of the deposit as viewed by analytical
chemists may not always indicate its origin or cause. Before
openings, equiplnent is steamed, waterwashed, or otherwise readied
for inspection. During this preparation, fouling matter can be
changed both physically and chemically. For example, water-soluble

~29~637
--4--
salts can be washed away or certain deposit constituents oxidized to
another form.
In petrochemical plants, fouling matter is often organic.
Fouling can be severe when monomers convert to polymers before they
leave the plant. This can occur in streams high in ethylene,
propylene, butadiene, sytrene and other unsaturates. Probable
locations for such reactions include units where the unsaturates are
being handled or purified, or in streams which contain these
reactive materials only as contaminants.
Even though some petrochem~cal fouling problems seem
similar, subtle differences in feedstock, processing schemes,
equipment and contaminants can lead to variations in fouling
severity. For example, ethylene plant depropanizer reboilers
experience fouling that appears to be primarily polybutadiene in
nature. The severity of thls problem varies significantly from
plant to plant, however. Average reboiler run length may vary frcm
one to two weeks up to four to six months (without chemical
treatment).
Although it is usually ~mpractical to ident~fy the fouling
problem by analytlcal techniques alone, this information, alony with
knowledge of the process, processing condit~ons and the factors that
contribute to fouling, are all essential to understanding the
problem.
There are many ways, mechanical as well as chemical, to
reduce fouling. Chemical additives offer an effective means;
however, processing changes, mechanical modifications equipment and
other methods available to the plant should not be overlooked.

~2~163~
Antifoulan~s are formulated from several materials: some
prevent foulan~s from forming, others prevent foulants from
depositing on heat transfer equipment. Materials that prevent
deposit formation include antioxidants, metal coordinators and
corrosion inhibitors. Compounds that prevent deposition are
surfactants which act as detergents or dispersants. Different
combinations of these properties are blended to provide maximum
results for different applications. These "polyfunctional"
antifoulants are generally more versatile and effective since they
are designed to combat various types of fouling that can be present
in any given system.
Research indicates that even very small amounts of oxygen
can cause or accelerate polymerization. Accordingly, antioxidant-
type antifoulants have been developed to prevent oxygen from
initiating polymerization. Antioxldants act as chain-stoppers by
forminy inert molecules with the oxidized free radical hydrocarbons,
in accordance with the following reaction:
Chaln Termination
ROO Antioxidant - ~ ROOH ~ Antioxidant (H)
Surface mod~f1ers or detergents change metal surface
characteristics to prevent foulants from depositing. Dispersants or
stabilizers prevent insoluble polymers, coke and other particulate
matter from agglomerating into large particles which can settle out
of the process stream and adhere to metal surfaces of process
equipment. They also modify the part~cle surface so that
polymerizatlon cannot readily take place.
Antifoulants are designed to prevent equipment surfaces
from fouling. They are not designed for clean up. Therefore, an

129~63
--6--
antifoulant should be started immediately after equipment is
cleaned. It is usually good to pretreat the system at double the
recommended dosage for two or three weeks to reduce the initial high
rate of fouling immediately after startup.
The increased profit possible with antifoulants varies
from application to application. It can include an increase in
production, fuel savings, maintenance savings and other savings from
greater operating efficiency.
There are many areas in the hydrocarbon processing
~ndustry where antifoulants have been used successfully; the main
treatment areas are discussed below.
.
In a refinery, the crude unit has been the focus of
attention, especially because of the recen~ tremendous increases in
fuel cost. Antifoulants have been successfully applied at the
exchangers; downstream and upstream of the desalter, on the product
side of the preheat train, on both sides of the desalter makeup
water exchanger, and at the sour water stripper.
Hydrodesulfurization units of all types experience preheat
fouliny problems. Among those that have been successfully treated
are reformer pretreaters processing both straight run and coker
naphtha, desulfurizers processing catalytically cracked and coker
gas 0;1SJ and distillate hydrotreaters. In one case, fouling of a
Unif~ner stripper column was solved by applying a corrosion
~nhibitor upstream of the problem source.
Unsaturated and saturated gas plants [refinery vapor
recovery units) experience fouling in the various fractionation
columns, rebo~lers and compressors. In some cases~ a corrosion

~291637
control program along with the antifoulant program gave the best
results. In other cases, antifoulants alone were enough to solve
the problem.
Cat cracker preheat exchanger fouling, both at the vacuum
column and at the cat cracker itself, has also been corrected by the
use of antifoulants.
In petrochemical plants, the two most prevalent areas for
fouling problems are ethylene and styrene plants. In an ethylene
plant, the furnace gas compressors, the various fractionating
columns and reboilers are subject to fouling. Polyfunctional
antifoulants, for the most part, have provided good results in these
areas. Fouling can also be a problem at the butadiene extraction
area. Both antioxidants and polyfunctional antifoulants have been
used with good results.
In the different design butadiene plants, absorption oil
16 fouling and distillation column and reboiler fouling have been
corrected with various types of antifoulants.
Chlor~nated hydrocarbon plants, such as VCM, EDC and
perchloroethane and trlchloroethane have all experienced various
types of fouling problems. The metal-coordinating/antioxidant-type
antifoulants give excellent service in these areas. The present
invention ~s directed to antioxidant compositions and their use in
controlling fouling in petroleum and petrochemical processing
systems as above exemplified.

1~9~6~7
DESCRIPTION OF THE INVENTION
The present invention relates to the formulation of
specific phenolic antioxidants in a non-aqueous medium which
incorporates a sufficient amount of an oil soluble base such that
the antioxidant material l~ould experience a basic environment (pH~
10.5) and would at the same time become soluble in a hydrocarbon
medium. The specific phenolic antioxidants encompassed by the
invention include any unhindered or partially hindered phenol.
Unhindered phenols with strong electron donating groups such as an
alkyl or alkoxy group (OX) where the alkyl (X) contains from 1 to 10
carbon atoms, amine group (-NH2) or an alkyl substituted amine, in
the para position.
The phenols utilizable are those that have the structural
formula OH
R1 ~ R
R2
wherein R and Rl are hydrogen and a carbon gr~uping (1 to 8 carbon
atoms), with the proviso that not more than one of R and Rl be a
secondary or tertiary carbon grouping, and R2 is alkylJ alkoxy or
an amine grouplng.
Specific examples of the phenols include, but are not
limited to, p-cresol, p-methoxyphenol, p amino-phenol, p (p-methoxy
benzylideneamino) phenol, and 2-tert-butyl-4-methoxyphenol
(butylated hydroxy anisole).

~ 3~L6;3~
The oil soluble strong bases which are used in conjunction
with the phenol may be exemplified by monoethanolamine,
N(2-aminoethyl) piperazine, cyclohexylamine, and 1,3-cyclohexane bis
(methylamine). However, any amine which has the NR5R6R7 where
R5, R6 and R7 are hydrogen, alkyl, aryl, or subs~ituted alkyl
or aryl or in any combination thereof. The amine functions, it is
D believed, in a dual capacity. It generally is included in su&h 5
amount that the pH of the composition increases to a pH of-~3-or
above, thereby solubilizing the phenol in any hydrocarbon solvent
which might be used to enhance the solubility of the phenol in the
petroleum or petrochemical being processed. It has also been
unexpectedly determined that the presence of the amine,~in small
percentages by weight (active) of the phenol to amine of 98:2 to
2:98 and preferrably 40 to 60 enhances the antioxidant capabilities
of the phenol. The test data recorded hereinafter will in fact
illustrate this conclusively.
The treatment range for the composition, i.e.,
amine/phenol, clearly is dependent upon the severity of the fouling
problem due to free radical polymerization encountered as well as
the activity and constituency of the combinat~on util~zed. For this
reason, the success of the treatment is totally dependent upon the
use of a sufficlent amount for the purpose of whatever the
composition of choice is. Broadly speaking, the treatment
recommendation could be in the range of 0.1 to 2000 parts per
million of petroleum or petrochemical being processed with perhaps
10 to 200 ppm being applicable in most cases.
Specific Embodiments
,. ~ The ASTM test method D-525 ~*~e4y-~neortor~e~

~2gl6~7
-10-
e$~r~Y~ was carried out under accelerated conditions (high 2
content) that would normally not be experienced in an actual field
environment. Nevertheless, when examining potential antioxidant
candidates, the test provides reliable data on the effectiveness of
a given antioxidant material to inhibit the polymerization of
certain petroleum feedstocks.
The method (ASTM D-525) covers the determination of the
stability of gasoline under accelerated oxidation conditions.
According to the procedure the sample is ox~dized in a
bomb initially filled with oxygen. The pressure ~s read at stated
intervals or recorded continuously until the break point is
reached. The time required for the sample to reach this point is
the observed induction period at the temperature of the test, from
which the induction period at lOO~C may be calculated.
The induction period may be used as an indication of the
tendency of ~otor gasoline to form gum in storage. In accordance
with the test, an increase in induction time indicates that the
candidate antioxidant material is performing its Function. Further
difunctional aspects and the actual procedure can be determined from
an actual reYiew of the test procedures described in ASTM D-525.
The results of the testing were as follows:

~16~37
TABLE 1
Active Induction
Conc. Solvent Time
Sample Additive (ppm) System (min.)
WITHOUT AMINE
1 pyro1ysis None - N.A. 10
gasoline
2 " P-[p-methoxy-
benzylidine
amino] phenol 200 DMF or HAN 55
3 " p-methoxy
phenol 200 HAN 55
4 " butylated
hydroxy
anisole 200 HAN 105
" p-cresol 200 " 10
WITH AMINE 300 ppm N-(2-Amino-ethyl) Piperazine (AEP)
2 " p-[p-methoxy-
benzy1idine
amino] phenol 200 - 160
3 " p-methoxy
phenol 200 - lOS
4 " butylated 200 - 160
hydroxy
anisole
" p-cresol 200 - 20
6 " AEP 300 -- 10

1~9~637
-12-
While this invention has been described with respect
to particular embodiments thereof, it is apparent that numerous
other forms and modifications of this invention will be obvious to
those skilled in the art. The appended claims and this invention
generally should be construed to cover all such obvious forms and
modifications which are within the true spirit and scope of the
present invention.