Extraction method

Covers a method of separating a nonionic surfactant from an anionic surfactant by use of methylal.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a method of extracting out certain sulfonated 
organic compounds from alcohols used to prepare said compounds. 
2. Description of the Prior Art 
Organic sulfonic acids and organic sulfonates are becoming increasingly 
important due to their use in the preparation of liquid detergents, as 
surfactants for enhanced oil recovery processes and for other uses. A 
number of general schemes are available to sulfonate organic compounds. 
For example, sulfonated materials may be prepared by sulfonation processes 
employing concentrated sulfuric acid or oleum. Another method of preparing 
organic sulfonates involves reacting an organic alcohol containing at 
least one hydroxyl group with a hydroxy-containing alkyl sulfonic acid or 
salt thereof. Under appropriate conditions the two compounds are condensed 
with formation of by-product water to produce an ether sulfonate. This 
reaction can be termed a sulfoalkylation reaction. A typical sulfonating 
reagent here used to react with a wide variety of organic alcohols is 
sodium isethionate, also named as the sodium salt of 2-hydroxy ethane 
sulfonic acid. 
In most instances it is necessary to separate out the sulfonate produced or 
anionic surfactant from the reaction mixture which normally contains 
unreacted starting materials such as the alcohol reactant. In the above 
case wherein an alcohol is reacted with a sulfonating agent such as sodium 
isethionate usually an excess of alcohol is employed to assist in driving 
the reaction to completion. Thus, it is necessary to resolve the mixture 
of starting alcohol material and final ether sulfonate, one from the 
other. 
There are a number of ways available to effect such separation. However, 
with respect to surfactants of relatively high molecular weight usually an 
extraction technique is devised. The use of such extractants in the usual 
situation is at best an emperical type of science faced with much 
unpredictability. For example, a class of extractant materials useful in 
separating one group of nonionic surfactants from anionic surfactants 
derived therefrom may be entirely useless in making a similar resolution, 
though of only a slightly different class of surfactants. 
In other situations while a solvent may be found useful as an extractant in 
certain situations, such solvent while displaying proper selectivity may 
have other drawbacks such as itself being unstable, or having a tendency 
to convert the materials being separated to other derivatives by chemical 
reaction, which derivatives may be corrosive or have other undesirable 
properties. In still further instances, the extraction may require heat, 
causing formation of emulsions or gels. Lastly, while a solvent may be 
useful as an extractant, in many instances the solvent itself is difficult 
to separate out from the material it has extracted, and in some cases is 
impossible to do so. 
It is therefore a principle object of this invention to provide a method 
for separating out ether sulfonates from organic alcohols from which ether 
sulfonates were derived through reaction with hydroxy-containing alkyl 
sulfonic acids or salts by means of a unique extraction technique, which 
process is free from the just-mentioned disadvantages of prior art 
processes. 
The above-mentioned object and advantages of the present invention will 
become apparent as the invention is more thoroughly discussed hereinafter. 
SUMMARY OF THE INVENTION 
In its broadest aspects the present invention comprises a method of 
resolving a mixture of a nonionic surfactant and an anionic surfactant 
existing in an aqueous medium, said nonionic surfactant having a 
structural formula as follows: 
EQU R.sub.2 OH 
where R.sub.2 is a radical selected group consisting C.sub.1 -C.sub.22 
alkyl, C.sub.1 -C.sub.22 alkenyl, C.sub.1 -C.sub.22 hydroxy alkyl, C.sub.1 
-C.sub.22 hydroxy alkenyl, alkaryl containing one or more C.sub.1 
-C.sub.22 groups substituted on said aryl group, aralkyl containing 7-22 
carbon atoms, and polyether derivatives of any of the foregoing, with said 
anionic surfactant having a structural formula as follows: 
EQU R.sub.2 --O--R.sub.3)SO.sub.3 A 
where R.sub.2 has a significance as above, R.sub.3 is alkylene or arylene 
and A represents an cation; which comprises the step of treating said 
aqueous media with at least an effective amount of methylal sufficient to 
dissolve said nonionic surfactant in said methylal and separating out said 
solution or nonionic surfactant in methylal from a remaining solution or 
anionic surfactant in water.

A DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In more detail the practice of the present invention relates to a method of 
separating out nonionic surfactant alcohols of the above type from anionic 
sulfonate surfactants prepared therefrom. The ether sulfonates which are 
derived from the alcohol surfactants are prepared by reacting said alcohol 
compound with a hydroxy-containing alkyl sulfonic acid or salt thereof. 
The sulfonation reaction may be carried out via a number of prior art 
techniques, which will not described in any detail since their description 
forms no part of the invention. 
A number of alcohols, R.sub.2 OH, may be resolved via the process here from 
ether sulfonates formed therefrom. Such alcohols may include methanol, 
ethanol, isopropanol, n-propanol, t-butanol, isobutanol, n-butanol, heptyl 
alcohol, hexyl alcohol, fatty alcohols containing from about 8 to about 20 
carbon atoms such as octyl alcohol, decyl alcohol, lauryl alcohol, 
tridecyl alcohol, tetradecyl alcohol, cetyl alcohol, tallow alcohol, 
octadecyl alcohol, and eicosyl alcohol. 
Other alcohols which may be treated here include the so-called Oxo alcohols 
from the Oxo process, vinylidene alcohols, Ziegler-type primary linear 
alcohols prepared from trialkylaluminum mixtures made by way of ethylene 
polymerization, subsequent oxidation, and hydrolysis of the resultant 
aluminum alkoxides as set out in U.S. Pat. No. 3,598,747, and other 
alcohols of this type. Typical vinylidene alcohols are set out in U.S. 
Pat. No. 3,952,068 and have the general structure 
##STR1## 
wherein individually, x and y are numbers from 1 to 15 and the sum of x 
and y is in the range of 6 to 16. 
Polyhydric alcohols may also be included in the process of the invention, 
including such polyhydric alcohols as aliphatic polyhydric alcohols 
including the aliphatic glycols, such as, for example, ethylene glycol, 
propylene glycol, butanediol-1, 4 etc.; and the glycol ethers such as 
diethylene glycol, dipropylene glycol and the like. Higher functionality 
polyhydric materials which may be treated include such as glycerol, 
sorbitol, trimethylolpropane, 1,2,6-hexanetriol, pentaerythritol and the 
like. Also, suitable are dihydric aromatic materials such as bisphenol-A 
and hydrogenated bisphenol-A. Preferred polyhydric alcohols are the 
aliphatic glycols having from 2 to 10 carbon atoms and the aliphatic 
glycol ethers having from 4 to 20 carbon atoms. 
Still other alcohols which may be separated from their ether sulfonates 
include alkylene glycol mono-lower alkyl ether compounds such as ethylene 
glycol monomethyl ether, ethylene glycol monobutyl ether (Butyl 
Cellosolve), propylene glycol monomethyl ether, propylene glycol monoethyl 
ether, diethylene glycol monobutyl ether (Butyl Carbitol), and the like. 
Phenols and alkyl substituted phenols may also be employed here. Thus, for 
example, exemplary phenolic reactants include phenol, nonylphenol, 
bromophenol, iodophenol, chlorophenol, hydroxyanisole, dinonylphenol, 
dichlorophenol, cresol, and the like. Particularly preferred are alkyl 
substituted phenolic compounds falling within the following structural 
formula 
##STR2## 
where R is an alkyl group containing from 6 to 20 carbon atoms or a halo, 
nitro, or hydroxy alkyl substituted group of the same chain length, and n 
is an integer of 1, 2 or 3. Typically R in the above formula is a 
C.sub.8-12 alkyl group. 
Another useful class of reactant alcohols from which ether sulfonates are 
prepared and which can be treated here are those prepared by alkoxylating 
any of the above class of alcohols or others. Thus, the above compounds 
may be reacted with ethylene oxide, propylene oxide, butylene oxide or 
higher alkylene oxides having up to 18 carbon atoms or mixtures thereof. 
When mixed oxides are used, they may be added to the hydroxy or 
polyhydroxy compound either sequentially to form block polyether polyol 
compounds, or may be mixed and reacted simultaneously to form a random, or 
heteric oxyalkylene chain. The reaction of an alkylene oxide and hydroxy 
or polyhydroxy compound is well-known to those skilled in the art, and the 
base-catalyzed reaction is particularly described in U.S. Pat. Nos. 
3,655,590; 3,535,307 and 3,194,773. If diols, triols, tetrols and mixtures 
thereof are alkoxylated polyether polyols may be obtained which have a 
molecular weight of from about 500 to about 10,000. These polyether 
polyols are well-known and may be prepared by any known process such as, 
for example, the processes described in Encyclopedia of Chemical 
Technology, Vol. 7, pages 257-262, published by Interscience Publishers, 
Inc. 
A greatly preferred class of hydroxy compounds from which ether sulfonates 
may be prepared include the compounds falling within the following 
##STR3## 
where R is a C.sub.1 -C.sub.22 radical and n is an integer of 1-3, R.sub.1 
is hydrogen or an alkyl group of 1-18 carbon atoms, and z is a number 
ranging from 1 to 40. Preferably R.sub.1 is hydrogen or methyl and z is 
1--10. 
Still other alcohols are aralkanols containing a total of from about 7 to 
about 28 carbon atoms. These may be represented by the following formula 
##STR4## 
where R.sub.2 is an alkylene group containing 1-22 carbon atoms, and R and 
n are as just noted. Polyether derivatives of these compounds may also be 
made by appropriate alkoxylation techniques. 
Thus, preferred alcohols which may be employed as reactants in preparing 
ether sulfonates and thus must be separated therefrom via the process here 
are those having the general formula ROH, where R is a radical selected 
from the group consisting of C.sub.1 -C.sub.22 alkyl, C.sub.1 -C.sub.22 
alkenyl, hydroxy or polyhydroxy derivatives of these alkyl or alkenyl 
compounds, alkaryl radicals containing one or more C.sub.1 -C.sub.18 alkyl 
groups substituted on said aryl group, and aralkyl radicals containing 
7-22 carbon atoms, and polyether derivatives of any of the foregoing. 
Ether sulfonates are then prepared from the above alcohols. The sulfonating 
agent (sulfoalkylating agent) preferably used is a hydroxyalkyl sulfonic 
acid or salt thereof. Preferably, the sulfonating agent is an alkali or 
alkaline earth metal hydroxy-terminated straight chain alkyl sulfonic acid 
or salt. Thus, the sulfonating agent employed here has the following 
structural formula 
EQU OHR.sub.3 SO.sub.3 A 
where R.sub.3 is a straight or branched alkylene group or an arylene group 
such as phenylene, which optionally may contain other non-interfering 
groups such as halo, nitro, nitrile, etc. groups. More preferably, R.sub.3 
is a straight or branched chain unsubstituted alkylene group such as 
methylene, ethylene, propylene, butylene, pentylene, hexylene and higher 
alkylene groups. Most preferably, R.sub.3 contains 1-4 carbon atoms, and 
in a greatly preferred embodiment is ethylene or propylene. A represents 
hydrogen or a cation, preferably an alkali or alkaline earth metal cation 
such as sodium, lithium, potassium, calcium, magnesium, cesium, etc. 
In the most preferred embodiment of the invention, a process of separating 
ether sulfonates of the formula 
##STR5## 
from alcohols formed therefrom is carried out. Here R is a C.sub.1 
-C.sub.22 alkyl group, n is an integer of 1-3, R.sub.1 is hydrogen or 
methyl, z is an integer of 1-40, R.sub.3 is ethylene or propylene and A is 
hydrogen or an alkali or alkaline earth metal cation. More preferably A is 
an alkali or an alkaline earth cation, and most preferably is an alkali 
metal cation as sodium or potassium. In this instance an alcoholic 
compound of the formula 
##STR6## 
when R, n, R.sub.1 and z have a significance as just discussed is reacted 
with a compound of the formula 
EQU OHR.sub.3 SO.sub.3 A 
where R.sub.3 and A are as just mentioned. The product ether sulfonate is 
then separated from the reactant alcohol by the extraction technique used 
here. 
The extraction practice here itself utilizing methylal (dimethoxymethane) 
is carried conventionally. One or more extractions may be effected. 
Moreover, the extraction may be carried at room temperature or even below 
as it may likewise be done at temperatures of say 40-80.degree. C. The 
methylal extractant will selectively remove the alcohol ether sulfonate at 
temperatures up to the boiling point of the extraction mixture. Again, the 
extraction method may be employed at atmospheric, sub-atmospheric or 
super-atmospheric pressures. By contact of the mixture of alcohol and 
ether sulfonate with methylal, the methylal selectively acts as a solvent 
for the nonionic surfactant alcohol while the anionic sulfonate stays 
behind in the aqueous media. The methylal may be then distilled from the 
alcohol while the ether sulfonate may be recovered from the aqueous phase 
by a number of techniques including distillation off of water, 
precipitation, crystallation or through other means. 
The following examples specifically illustrate the process of the 
invention. It should be understood of course, that these are merely 
illustrative and that the invention is not to be limited thereto. 
EXAMPLE I 
Here 40 grams of an aqueous slurry of approximately equal amounts of the 
alcohol 
##STR7## 
and an ethoxy sulfonate having the structure 
##STR8## 
were extracted with 240 gram portions of methylal. The aqueous layer was 
analyzed for alcohol and anionic surfactant and found to contain 0.7 grams 
of alcohol and 4.84 grams of the ethoxy sulfonate anionic surfactant. 
EXAMPLE II 
Here an aqueous mixture (20% solids) of the alcohol of Example I (7.94%) 
and the ether sulfonate of Example I (9.7%) in an amount of 2,000 grams 
was extracted sequentially with 1,500 grams of methylal followed by 6 
extractions using 500 grams of methylal. The combined organic extracts 
were distilled to yield 165.6 grams of residue which contain approximately 
16 grams of ether sulfonate. The aqueous layer was stripped of dissolved 
methylal to give 1538 grams of a solution containing 11.0% ether sulfonate 
and 0.25% alcohol. Results of this experiment are summarized below. 
TABLE I 
______________________________________ 
MIXTURE CRUDE AQUEOUS METHYLAL 
COMPONENT MIXTURE LAYER EXTRACT 
______________________________________ 
Alcohol 159 grams 3.8 grams not analyzed 
Ether Sulfonate 
189 grams 169 grams 16 grams 
______________________________________ 
EXAMPLE III 
In this run 100 grams of an aqueous slurry (48.5% water) of an alcohol 
(24.8%) having the formula 
##STR9## 
and an ether sulfonate (20.5%) having the formula 
##STR10## 
were extracted in a separatory funnel with 100 grams of water and 200 
grams of methylal followed by extraction with a second 200 gram portion of 
methylal, and finally with 100 grams of methylal. The combined extracts 
were evaporated to give 23.7 grams of residue. The aqueous layer was 
stripped to give 146 grams of solution containing 13.1% ether sulfonate 
and 1.32% alcohol. Results of this run are given below: 
TABLE II 
______________________________________ 
MIXTURE CRUDE AQUEOUS METHYLAL 
COMPONENT MIXTURE LAYER EXTRACT 
______________________________________ 
Alcohol 24.8 grams 
1.9 grams Not analyzed 
Ether Sulfonate 
20.5 grams 
19.2 grams 0.5 grams 
______________________________________ 
EXAMPLE IV 
The efficiency of the methylal as an extractant in the particular system 
here was compared with a number of other solvents by mixing 10 grams of 
crude aqueous ether sulfonate of Example I (30% solids) and 10 grams of 
solvent. Results are given in Table III below. While ethyl acetate may act 
as a solvent in the system treated by the process of the invention, use of 
ethyl acetate has a number of drawbacks. For example, such solvent has a 
higher boiling point than methylal and is not as easily recovered by 
distillation. In addition, to avoid emulsions and gels use of ethyl 
acetate requires heating, leading to the tendency therefore to convert it 
to ethanol and acetic acid causing transesterification of the alkoxylate 
being separated out. Also, the acetic acid formed is corrosive to 
equipment and the ethanol detracts from the extraction properties of ethyl 
acetate. 
As can be seen from Table III below normally methylal and ethyl acetate 
have the ability to function as an extraction solvent in removing alcohols 
from ether sulfonates formed therefrom. However, as just noted, ethyl 
acetate has a number of glaring deficiencies which make it less attractive 
than use of the methylal solvent. 
TABLE III 
______________________________________ 
SOLVENT APPEARANCE OF SOLUTION 
______________________________________ 
Ethyl Acetate 
Two layers of about equal volume 
Methylal Two layers of about equal volume 
Acetone Clear solution with trace of 
sediment. 
Methyl Ethyl Ketone 
Clear solution 
2-Propanol Clear solution 
2-Butanol Small lower layer, about 5% of 
total volume 
Butyl Acetate 
Emulsion 
Butylal Emulsion 
Hexane Gel 
Tetrahydrofuran 
Clear solution 
______________________________________ 
The terms "sulfonation" and "sulfonating agent" as herein used are meant to 
refer to and include both situations involving a convention sulfonation 
reaction and a sulfoalkylation reaction. 
The invention is hereby claimed as follows: