Alcohol composition stabilized against corrosion by the use of an amino tetrazole

Alcohols may be inhibited against corrosion by addition there to of an amide reaction product of (i) ##STR1## (preferably in the form of the acid, acid chloride or ester) and (ii) an amino tetrazole.

FIELD OF THE INVENTION 
This invention relates to alcohol products particularly characterized by 
decreased ability to corrode metal surfaces with which they come into 
contact. 
BACKGROUND OF THE INVENTION 
As is well known to those skilled in the art, alcohols such as ethanol may 
corrode metal surfaces with which they come into contact. This is 
particularly true of crude or commercially available ethanols which 
undesirably contain acidic components commonly acetic acid. In the case of 
fermentation alcohols, acetic acid may be present in amount of 0.003 w 
%-0.005 w % of the alcohol; and this may be responsible for the fact that 
the alcohol causes serious corrosion problems. 
It is an object of this invention to provide a novel process for decreasing 
the corrosion of alcohol compositions. Other objects will be apparent to 
those skilled in the art. 
STATEMENT OF THE INVENTION 
In accordance with certain of its aspects, the novel composition of this 
invention may comprise (i) a water-soluble alcohol preferably selected 
from the group consisting of ethanol and methanol; and (ii) an effective 
corrosion-inhibiting amount of 
##STR2## 
wherein R is a C.sub.10 -C.sub.20 alkyl, alkenyl, alkaryl, aralkyl, aryl, 
or cycloalkyl hydrocarbon group, R' is a divalent hydrocarbon group 
selected from the same group as R and having one less hydrogen, R"' is 
alkyl, aryl, alkaryl, or aralkyl, and NH--R" is an amino tetrazole group. 
DESCRIPTION OF THE INVENTION 
The alcohol compositions which may be treated by the process of this 
invention may include C.sub.1 -C.sub.12 alkanols such as water-soluble 
alkanols including C.sub.1 -C.sub.4 alcohols. Preferably the alcohols 
include methanol, ethanol, propanols, etc. The alcohols may include 
mixtures of alcohols with each other and/or with other compositions 
including lactones, esters, hydrocarbons, etc. The alcohol may be in the 
form of gasohol--a mixture commonly containing 80 v %-95 v %, say 90 v % 
gasoline and 5 v %-20 v %, say 10 v % alcohol. The alcohol may contain 
water, for example up to 10 w %-20 w %, typically 5 w %; but preferably it 
will be anhydrous. Anhydrous compositions commonly contain less than about 
0.3 v % water, typically 0.001 v %-0.005 v %, say about 0.004 v % water. 
One preferred charge may be 100% anhydrous ethanol. Another preferred 
charge may be 100% anhydrous methanol. 
Commercially available mixtures may be employed. Illustrative of one such 
commercially available mixture may be that having the following analysis: 
TABLE I 
______________________________________ 
Component Parts 
______________________________________ 
ethanol 3157.2 
methyl isobutyl ketone 
126.3 
acetic acid 0.256 
methyl alcohol 0.24 
isopropyl alcohol 0.2 
n-propyl alcohol 0.162 
ethyl acetate 0.2 
______________________________________ 
It is a particular feature of the process of this invention that it may be 
used to treat such compositions when they are to be used as fuels, whether 
the fuel be 100% alcohol or mixtures thereof with one another or with 
other components. The fuels which may be treated by the process of this 
invention include gasohols which may be formed by mixing 90-95 volumes of 
gasoline with 5-10 volumes of ethanol or methanol. A typical gasohol may 
contain 90 volumes of gasoline and 10 volumes of absolute ethanol. 
The fuels to be treated by the process of this invention may be 
substantially anhydrous, i.e. they contain less than about 0.3 v % water; 
typically they may contain 0.001 v %-0.005 v %, say about 004 v % water. 
It is a feature of these fuels that they may undesirably contain acidic 
contaminants which may cause serious corrosion problems. These 
contaminants are particularly in evidence when the alcohol is a 
commercially available alcohol which contains therein inter alia acids 
concurrently produced as by fermentation processes for producing ethanol 
or acids which have been picked up during handling. Acetic acid is a 
common acid present in the commercially available alcohols produced by 
fermentation; and it may be present in amount of 0.003 w %-0.005 w % of 
the total of the alcohol. 
In accordance with practice of the process of this invention, there may be 
added to the alcohol a minor effective corrosion-inhibiting amount of, as 
a corrosion inhibiting agent, 
##STR3## 
wherein R is a C.sub.10 -C.sub.20 alkyl, alkenyl, alkaryl, aralkyl, aryl, 
or cycloalkyl hydrocarbon group, R' is a divalent hydrocarbon group 
selected from the same group as R and having one less hydrogen, R"' is 
alkyl, aryl, alkaryl, or aralkyl, and NH--R" is an amino tetrazole group. 
The amides of this invention may be formed by various routes from the acid 
(or its equivalent, for this purpose, the ester, anhydride or halide) 
##STR4## 
In the above compound, R may be a hydrocarbon group, including inertly 
substituted hydrocarbon groups, selected from the group consisting of 
alkyl, aralkyl, cycloalkyl, aryl, alkaryl, and alkenyl including such 
radicals when inertly substituted. When R is alkyl, it may typically be 
methyl, ethyl, n-propyl, iso-propyl, n-butyl, i-butyl, sec-butyl, amyl, 
octyl, decyl, octadecyl, etc. When R is aralkyl, it may typically be 
benzyl, beta-phenylethyl, etc. When R is cycloalkyl, it may typically be 
cyclohexyl, cycloheptyl, cyclooctyl, 2-methylcycloheptyl, 
3-butylcyclohexyl, 3-methylcyclohexyl, etc. When R is aryl, it may 
typically be phenyl, naphthyl, etc. When R is alkaryl, it may typically be 
tolyl, xylyl, etc. When R is alkenyl, it may typically be vinyl, allyl, 
1-butenyl, etc. R may be inertly substituted, ie.e. it may bear a 
non-reactive substituent such as alkyl, aryl, cycloalkyl, ether, etc. 
Typically inertly substituted R groups may include 3-chloropropyl, 
2-ethoxyethyl, carboethoxymethyl, 4-methyl cyclohexyl, etc. The preferred 
R groups may be alkyl groups containing 10-20 carbon atoms including e.g. 
stearyl (18 carbons), decyl, (10 carbons), and cocoyl (12-18 carbons). 
R' may be selected from the same group and have one less hydrogen. 
Preferably R' is a straight chain lower alkyl group containing 1-5, more 
preferably 1-3, say 1 carbon atom. 
R"' may be an alkyl, aryl, alkaryl, or aralkyl group--which may be selected 
from the same groups as that from which R is selected. The preferred R"' 
group is methyl. 
Although the amide may be prepared from the acid, the anhydride, or the 
ester, it is preferred to prepare it from the halide--most preferably the 
chloride. 
The preferred "acids" include acid chlorides wherein R is stearyl, oleyl, 
or cocoyl and R' is methylene. Typical compounds which may be employed 
include: 
TABLE 
______________________________________ 
##STR5## 
##STR6## 
##STR7## 
##STR8## 
______________________________________ 
The preferred composition is the compound wherein R is cocoyl, i.e. the 
commercial mixture of fatty acid residues corresponding to 12-18 carbon 
atoms. 
The amino tetrazoles which may be employed include 1-amino tetrazoles (I), 
2-amino tetrazoles (II), 3-amino tetrazoles (III), 4-amino tetrazoles 
(IV), and 5-amino tetrazoles (V), including those bearing inert 
substituents which do not interfere with or react in the instant 
reaction--typified by hydrocarbon or alkoxy groups. 
##STR9## 
The preferred amino tetrazole may be 5-amino tetrazole. 
It will be apparent to those skilled in the art that the several reactants 
may bear inert substituents typified by alkyl, alkoxy, etc. It will also 
be apparent that the preferred compounds to be employed will be those 
which are soluble in the solvents employed during the reaction and which 
produce products which are soluble in or compatible with the system in 
which the product is to be employed. 
Typical solvents which may be employed may include alcohols as methanol, 
ethanol, butanols, cyclohexanol, etc. or hydrocarbons including heptane, 
octane, toluene, xylene, gasoline, etc. It is preferred that the solvent 
system include alcohol and hydrocarbon. A particularly preferred system 
may include equal volumes of methanol and xylene. 
Formation of the desired additive may preferably be effected by placing the 
amino tetrazole in a reaction vessel in an excess of solvent. A typical 
solvent (e.g. equal volumes of methanol and xylene) may be present in an 
excess amount of typically 50-200 volumes, say 120 volumes per volume of 
the total of the other reactants. The acid (in preferably equimolar 
amount) may be added slowly with agitation to the reaction mixture. It is 
not necessary to add catalyst. 
As the acid is added, the following typical reaction occurs (in the case of 
5-amino-1-H-tetrazole). 
##STR10## 
wherein R may preferably be a C.sub.12 -C.sub.18 alkyl such as oleoyl or 
tallowyl or cocoyl. 
During and after addition of the acid or acid chloride, the reaction 
mixture may be refluxed at 50.degree. C.-80.degree. C., say 76.degree. C. 
for 1-10 hours, say 3 hours. At the end of the reaction period the 
reaction mixture may be cooled to ambient temperature of 20.degree. 
C.-27.degree. C., say 25.degree. C. and filtered and then stripped (as by 
distillation at 80.degree. C.-100.degree. C., say 76.degree. C.) of 
solvent. When the acid chloride is used, a base (hydrogen halide acceptor) 
such as puridine, triethylamine, sodium hydroxide, potassium hydroxide, 
etc. is used to remove the hydrogen chloride which is produced as 
by-product. 
The residue which is generally a waxy solid or viscous liquid is recovered 
in yield approaching stoichiometric. 
The so-prepared rust and corrosion inhibitors may be added to alcohols or 
to antifreeze. These compositions may be particularly found to be 
effective as rust and corrosion inhibitors when added to alcohols typified 
by those available commercially containing compounds including ethers, 
esters, acids, etc. and also including absolute alcohols, alcohols 
containing water such as 95 w % ethanol, gasohols, etc. 
The so-prepared rust and corrosion inhibitors may be added to alcohol in 
amount of 0.25-25 PTB, preferably 1-20 PTB, more preferably 1-10 PTB, say 
10 PTB. (PTB stands for pounds of additive per thousand barrels of 
alcohol.) Alternatively expressed, the inhibitor may be added to an 
alcohol in minor corrosion-inhibiting amount of 0.0001-0.01 w % preferably 
0.0004-0.008 w %, more preferably 0.0004-0.004 w %, say 0.004 w %. Larger 
amounts may be employed but may not be necessary. 
It is a feature of this invention that the alcohol composition so prepared 
is characterized by its increased corrosion and rust inhibition, i.e. its 
decreased ability to form rust on iron surfaces in the presence of aqueous 
acid systems. 
The corrosive nature of the formulated products may be readily measured by 
the Iron Strip Corrosion Test (ISCT). In this test, an iron strip (12 
mm.times.125 mm.+-.1 mm) is prepared by washing in dilute aqueous 
hydrochloric acid to remove mill scale, then with distilled water to 
remove the acid, then with acetone followed by air drying. The strip is 
then polished with #100 emery cloth. 
The polished strip is totally immersed in 110 ml of the test liquid in a 4 
ounce bottle for 15 minutes at room temperature of 20.degree. C. 20 ml of 
the test liquid is poured off and replaced with 10 ml of distilled water. 
The bottle is shaken and the sample is maintained for 3 hours at 
90.degree. F. The percent rust on the strip is determined visually. A 
second reading may be taken after 40 hours and another after 6 days. 
The inhibited alcohols of this invention, after 6 days of ISCT, generally 
show a Rust and Corrosion rating below about 2-3% and frequently as low as 
trace-to-1%.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Practice of this invention will be apparent to those skilled in the art 
from the following examples wherein, as elsewhere in this specification, 
all parts are parts by weight unless otherwise specified. 
EXAMPLE I 
In this example which illustrates the best mode known to me of practicing 
the process of this invention, there is added to a reaction vessel 175 
parts of the Sarkosyl LC brand of cocoyl sarcosine having the formula 
##STR11## 
wherein R, the cocoyl radical, is a mixture of saturated straight chain 
alkyl group having 12-18 carbon atoms. There is also added 42.5 parts of 
5-amino tetrazole and 4 parts of crystallite, a hydrocarbon solvent having 
a boiling range of 300.degree. F.-550.degree. F. 
The mixture is refluxed for 3 hours at 175.degree. C. during which time 8 
parts of water are recovered. The reaction mixture is cooled, filtered, 
and stripped of crystallite solvent. The product is characterized by 
infra-red spectra and by NMR. 
EXAMPLE II 
In this example, the reaction product of Example I (20 PTB of additive) is 
added to 90 parts of the ethanol of Table I. 
Distilled water (10 parts) is added and the system is subjected to the ISCT 
Test. The iron strip is observed after 6 days. 
EXAMPLE III 
In this control Example, the system of Example II is tested without the 
additive. 
EXAMPLE IV 
In this control Example, the procedure of Example II is employed except 
that the additive is a prior art commercial rust and corrosion inhibitor 
(100 PTB) and only 3 parts of distilled water are added. The additive is 
the Ethomid HT/15 brand of polyoxyethylene (5) hydrogenated tallow amide. 
The results of the Iron Strip Corrosion Test were as follows: 
TABLE 
______________________________________ 
Six-Day 
Example Rust & Corrosion Rating 
______________________________________ 
II 1%-5% 
III 30% 
IV 25% 
______________________________________ 
From the above Table, it will be apparent that the system of Example II, 
prepared in accordance with practice of the process of this invention, 
showed 1%-5% rust and corrosion. Control Examples III-IV showed 25%-30% 
rust and corrosion which is unsatisfactory. 
Results comparable to those of Example I may be obtained when the acid 
reacted is: 
TABLE 
______________________________________ 
Example Acid 
______________________________________ 
##STR12## 
VI 
##STR13## 
VII 
##STR14## 
______________________________________ 
Results comparable to those of Examples I and II may be obtained when the 
amino tetrazole reactant is: 
TABLE 
______________________________________ 
Example Amino Tetrazole 
______________________________________ 
VIII 1-amino tetrazole 
IX 2-amino tetrazole 
X 3-amino tetrazole 
XI 4-amino tetrazole 
______________________________________ 
Results comparable to those of Example I and II may be obtained if the fuel 
is as follows: 
TABLE 
______________________________________ 
Example Fuel 
______________________________________ 
XII Gasoline containing 90 v % 
gasoline and 10 v % 
absolute ethanol 
XIII absolute ethanol 
XIV absolute methanol 
______________________________________ 
Although this invention has been illustrated by reference to specific 
embodiments, it will be apparent to those skilled in the art that various 
changes and modifications may be made which clearly fall within the scope 
of this invention.