Diacetylenic alcohol corrosion inhibitors

The corrosion of ferrous metals by corrosive acids at elevated temperatures is inhibited by adding to environments containing the acids an effective amount of a novel .alpha., .OMEGA. (hereinafter "alpha", "omega", respectively) diacetylenic diol (e.g., with two acetylenic functionalities) having the structural formula: ##STR1## where R is an aliphatic, alicyclic or aromatic residue containing from 1 to about 12 carbon atoms and may include one or more functional groups such as halogen atoms, carbonyl, carboxyl, carbamyl, amino, formyl or nitroso radicals or other functional groups without impaired performance. The diacetylenic diols may be employed in combination with other corrosion inhibitors.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to corrosion inhibitor compositions useful for 
retarding the corrosion of ferrous metals by corrosive acids especially 
for metals in an underground oil field location, and is particularly 
concerned with novel diacetylenic alcohols which are especially effective 
corrosion inhibitors. 
2. Description of the Prior Art 
The use of acetylenic alcohols for inhibiting the corrosion of ferrous 
metals has been proposed in the past. Although compounds such as propargyl 
alcohol which contain one acetylenic linkage and one hydroxyl group have 
been found effective, studies have shown that certain acetylenic diols 
perform very poorly. These materials have the following structures: 
##STR2## 
It has been postulated that one reason for this may be that the diols 
undergo an acid catalyzed cyclization to form a dihydrofuran as indicated 
by Formula III below or undergo water elimination to produce the 
conjugated ENE-YNE structure indicated by formula IV below. 
##STR3## 
It may also be that the ethynyl hydrogen group, -- C .tbd. C -- H, and a 
carbinol group attached directly to the acetylenic linkage, 
##STR4## 
are important if the acetylenic compound is to be an effective acid 
corrosion inhibitor. Any compound employed for this purpose should not be 
sterically hindered. 
SUMMARY OF THE INVENTION 
The present invention provides a novel class of acetylenic diol 
compositions which are surprisingly effective as corrosion inhibitors for 
ferrous metals. The improved inhibitors of the invention have the general 
formula: 
##STR5## 
where R is an aliphatic, alicyclic or aromatic residue containing from 1 
to about 12 carbon atoms and may include one or more functional groups 
such as halogen atoms, carbonyl, carboxyl, carbamyl, amino, formyl or 
nitroso radicals or other functional groups without impaired performance. 
The preferred diacetylenic diols of the invention are those prepared from 
alkyl residues and have the following structural formula: 
##STR6## 
where n is an integer from 1 to 12, preferably from 4 to 8. Examples of 
such compounds include 3,5-dihydroxy-1,6-heptadiyne, 
3,6-dihydroxy-1,7-octadiyne, 3,7-dihydroxy-1, 8-nonadiyne, 
3,8-dihydroxy-1,9-decadiyne, 3,10 -dihydroxy-1,11-dodecadiyne, 
3,12-dihydroxy-1,13-tetradecadiyne, 3,14-dihydroxy-1,15-hexadecadiyne, and 
the like. Such compounds have excellent corrosion inhibiting properties 
and do not readily undergo dehydrocyclization and other reactions which 
destroy their effectiveness. 
These diacetylenic diols are used to inhibit the corrosion of ferrous 
metals such as steel by hydrochloric acid, sulfuric acid, nitric acid and 
other corrosive acid solutions by adding them to the solutions containing 
these acids in effective concentrations. The materials of the invention 
are particularly effective for combatting corrosion at elevated 
temperatures and below ground in an oil field environment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The alpha, omega diacetylenic diol compositions of the invention may be 
prepared in a number of different ways. Suitable starting materials 
include, the alpha, omega dialdehydes such as succinic dialdehyde, malonic 
dialdehyde, adipaldehyde, sebacic aldehyde and the like. They also may be 
made from alpha, omega dialdehyde precursors such as alpha, omega 
dinitriles, cyclic olefins such as cyclohexene and cycloheptene, and 1,2 
cyclohexane diol. 
The dialdehydes can be prepared by the partial reduction of the dinitriles, 
by the reductive ozonization of cyclic olefins as described by F. G. 
Fisher and K. Lowcubert, Chem. Ber. 66, 666 (1933), or by oxidation of 1,2 
cyclohexane diol or similar dihydroxy alicyclic compounds in the presence 
of lead acetate as described in Stanley R. Sandler and Wolf Karo, "Organic 
Functional Group Preparations," page 149, Academic Press, New York, N.Y. 
(1968), and by J. English and E. W. Barber, General American Chemical 
Society, 71 3310 (1949). Certain of the dialdehydes are used as chemical 
intermediates in the manufacture of nylon and related products and are 
available from commercial sources. The use of adipaldehyde and similar 
dialdehydes containing a total of from about 6 to about 14 carbon atoms 
per molecule as starting materials is generally preferred. 
The dialdehydes which are employed as the preferred starting materials for 
the preparation of the diacetylenic alcohols can be converted into the 
corresponding alcohols by a variety of different methods. Several such 
methods are described by Thomas F. Rutledge in "Acetylenic Compounds," 
Reinhold Book Corporation, New York, N.Y. (1968). One such method involves 
treatment of the dialdehyde with ethynyl magnesium bromide in 
tetrahydrofuran as described by Lars Skatterbol, E. R. H. Jones and Mark 
C. Whiting in Org. Syn. Coll. Vol. IV, pp. 792-795 (1963). Other methods 
which may be used for production of the diacetylenic alcohols will be 
familiar to those skilled in the art. 
The diacetylenic alcohols which are prepared as described above have the 
general formula 
##STR7## 
where R is an aliphatic, alicyclic or aromatic residue containing from 1 
to about 12 carbon atoms and may include one or more other functional 
groups such as halogen atoms, carbonyl, carboxyl, carbamyl, amino, formyl 
or nitroso radicals or other functional groups without impaired 
performance. 
The alpha, omega diacetylenic alcohols which have been prepared from alkyl 
residues are preferred for purposes of the invention. These diols have the 
following structural formula: 
##STR8## 
where n is a small number from 1 to 12, preferably from about 4 to 8. 
Compounds of this type which are corrosion inhibitors in accordance with 
the invention include 3,5-dihydroxy-1,6-hepadiyne, 
2,6-dihydroxy-1,7-octadiyne, 3,7-dihydroxy-1,8-nonadiyne, 
3,8-dihydroxy-1,9-decadiyne, 3,7-dihydroxy-5-methyl-1,8-nonadiyne, 
3,8-dihydroxy-6-dimethyl-1,9-decadiyne, 
3,10-dihydroxy-5-methyl-7-ethyl-1,11-dodecadiyne, 3, 
12-dihydroxy-7,8-dimethyl-1,13-tetradecadiyne, 
3,12-dihydroxy-1,13-tetradecadiyne, 
3,14-dihydroxy-7,8,9-trimethyl-1,15-hexadecadiyne, 
3,14-dihydroxy-1,15-hexadecadiyne and the like. 
The alpha, omega diacetylenic alcohols are useful for inhibiting the 
corrosion of iron, steel, stainless steel and other ferrous metals by 
nonoxidizing acids such as hydrochloric acid, sulfuric acid, phosphoric 
acid, acetic acid and the like. They are useful at atmospheric 
temperatures as well as at elevated temperatures up to about 200.degree. F 
and in some cases even higher. They are effective with both dilute and 
concentrated acids, including commercial concentrated hydrochloric acid of 
37% strength. Applications in which they are particularly useful include 
oil well acidizing, metal pickling, cleaning and polishing baths, boiler 
cleaning compositions and the like. 
The novel diols of the invention are generally utilized by dissolving or 
dispersing them, alone or in combination with other materials, in the acid 
solution which is to be inhibited. Other standard inhibitor constituents 
can be employed in conjunction with the diols such as surface active 
agents, wetting compounds, long chain aliphatic amines, alkaryl, 
polyethylene oxyethanol, quaternary derivatives of heterocyclic nitrogen 
compounds and halomethylated aromatic compounds, 
perfluoroalkylimidazolines and the like. The diols are normally employed 
in concentrations between about 0.005% and about 2.0%, preferably 0.05% to 
1.0%, based on the volume of the aqueous acid solutions to which they are 
added, and are particularly effective when used in concentrations between 
about 0.1 and about 1.0% by volume. 
The nature and objects of the invention are further illustrated by the 
following examples. 
EXAMPLE 1 
Adipaldehyde was prepared by the oxidation of cyclohexane diol with lead 
acetate using the procedure described by Sandler and Karo in "Organic 
Functional Group Preparation," page 149, Academic Press, New York, N.Y. 
(1968) The adipaldehyde was then converted to 3,8-dihydroxy-1,9-decadiyne 
by treatment with ethynyl magnesium bromide in tetrahydrofuran by first 
fitting a 1000 ml three-neck flask with a stirrer, addition funnel, 
nitrogen tube and condenser. 
Into this were placed 24 g. of magnesium turnings and 300 ml of anhydrous 
tetrahydrofuran. A solution of 100 g. of ethylbromide in anhydrous 
tetrahydrofuran was then slowly added to the magnesium turnings until the 
formation of ethyl magensium bromide was complete. This step and the 
subsequent reaction steps were carried out under dry nitrogen gas. 
The ethyl magnesium-bromide solution was then transferred to a large 
pressure equalizing addition funnel by means of a bent glass tube and 
nitrogen pressure. 400 ml of tetrahydrofuran was then placed in a dry 
glass 200 ml reaction kettle equipped with a gas inlet tube, a 
thermometer, a stirrer, and the pressure equalizing addition funnel. 
Acetylene was added to the gas dispersion tube with slow addition of the 
ethyl magnesium bromide. This was continued until the formation of ethynyl 
magnesium bromide was complete. 
The ethynyl magnesium bromide prepared as described above was cooled in an 
ice-methanol bath. A solution of 39.0 g of adipaldehyde in 50 ml of 
anhydrous tetrahydrofuran was added to the stirred ethynyl magnesium 
bromide solution. After addition had been completed, the mixture was 
allowed to warm to room temperature with stirring over a period of 10 
hours 
The reaction mixture was then added to a 4-liter separatory funnel 
containing 1.5 liters of saturated aqueous ammonium chloride solution. The 
resulting mixture was shaken and then allowed to separate into an organic 
top phase and aqueous lower phase. The organic phase was removed and the 
lower phase was then extracted three times with ether to recover any 
organic materials present. 
Following this, the organic phase and ether solutions were combined, dried 
over magnesium sulfate, and filtered. The ther and tetrahydrofuran were 
removed from the filtrate by distillation. Vacuum distillation of the 
product, which had a boiling point between 130.degree. and 141.degree. C 
at 9 mm of mercury, yielded a clear viscous liquid that slowly solidified 
after several days. The yield was 39.2 g., 69% of the theoretical yield of 
3,8-dihydroxy-1,9-decadiyne. Analysis showed an empirical formula of 
C.sub.10 H.sub.14 O.sub.2. Infrared spectrum analysis and proton magnetic 
resonance spectrum analysis confirmed that the product obtained was 
3,8-dihydroxy-1,9-decadiyne. 
EXAMPLE 2 
Corrosion tests were carried out using propargyl alcohol and 
3,8-dihydroxy-1,9-decadiyne prepared as described in Example 1 above. 
These tests were conducted by preparing 100 ml samples of 15% hydrochloric 
acid in separate sample bottles. Test coupons of steel cut from J-55 oil 
well tubing were placed in the sample bottles and 0.5% by volume of the 
selected inhibitors were added to the bottles. The bottles were then held 
at a temperature of 200.degree. F and at ambient pressure for a period of 
4 hours. Following this, the samples were moved from the acid solution, 
washed repeatedly to remove any remaining acid, and then dried. The dried 
samples were weighed to determine the weight loss and permit calculation 
of the corrosion rate. The results obtained are shown in Table I below. 
TABLE I 
______________________________________ 
Corrosion Tests 
Weight Corrosion 
Loss, Rate, 
Inhibitor grams lb/ft.sup.2 
______________________________________ 
##STR9## 0.3050 0.0216 
##STR10## 0.0412 0.00292 
______________________________________ 
It is noted from the above table that the corrosion rate with the 
3,8-dihydroxy-1,9-decadiyne was nearly an order of magnitude lower than 
that with the propargyl alcohol. This low corrosion rate under the 
relatively severe conditions of the test demonstrates that the alpha, 
omega diacetylenic alcohols are surprisingly more effective as corrosion 
inhibitors than propargyl alcohol and similar materials employed in the 
past. 
EXAMPLE 3 
Following the work repeated above, additional corrosion tests were carried 
out with three different grades of steel used in oil well tubing and three 
acetylenic alcohols. One of the alcohols was 3,8-dihydroxy-1,9-decadiyne 
prepared as described in Example 1 above and the other two were acetylenic 
alcohols outside the scope of this invention. One of these was 
2,5-dimethyl-3-yn3-2,5-diol and the other was 
2,7-dimethyl-3,5-octadiyne-2,7 diol. Sample bottles containing 100 ml of 
15% hydrochloric acid and weighed steel corrosion coupons were prepared as 
described in Example 2. 
To each of these bottles was added one of the acetylenic alcohols in a 
concentration of 0.25 or 0.5% by volume. The bottles were then held at 
200.degree. F and ambient pressure for a period of 4 hours. Following 
this, the samples were removed, washed and dried, and weighed to permit 
determination of the weight loss and corrosion rate. Results are shown in 
Table II. 
TABLE II 
__________________________________________________________________________ 
Comparative Corrosion Tests 
Inhibitor 
Concentration, 
Steel Weight 
Corrosion Rate, 
Inhibitor Vol. % Coupon 
Loss, g. 
lb/ft.sup.2 
__________________________________________________________________________ 
3,8-Dihydroxy-1,9-decadiyne 
0.25 P 105 0.5916 
0.0420 
" 0.2 N 80 0.6110 
0.0434 
" 0.25 J 55 0.1437 
0.0102 
" 0.50 P 105 0.0809 
0.00574 
" 0.50 N 80 0.0432 
0.00307 
" 0.50 J 55 0.0350 
0.00248 
2,5-Dimethyl-3-yne-2,5-diol 
0.25 P 105 12.2687 
0.942 
" 0.25 N 80 13.3726 
0.950 
" 0.25 J 55 10.2762 
0.730 
" 0.50 P 105 13.3492 
0.948 
" 0.50 N 80 13.3404 
0.947 
" 0.50 J 55 11.8972 
0.845 
2,7-Dimethyl-3,5-octadiyne-2,7-diol 
0.25 P 105 13.1646 
0.935 
" 0.25 N 80 11.8172 
0.839 
" 0.25 J 55 12.3035 
0.874 
" 0.50 P 105 12.9889 
0.922 
" 0.50 J 55 10.8834 
0.708 
__________________________________________________________________________ 
Again, it can be seen that the alpha, omega diacetylenic alcohols of the 
invention are surprisingly more effective than closely related acetylenic 
alcohols which lack the structure of the materials of the invention.