Use of trialkanolamine polyethers as demulsifiers for oil-in-water emulsions

The present invention relates to the use of trialkanolamine polyethers obtained by condensation of one or more trialkanolamines in the presence of phosphorous acid and/or hypophosphorous acid as demulsifiers for oil-in-water emulsions.

The present invention females to the use of trialkanolamine polyethers as 
demulsifiers for oil-in-water emulsions. 
The production and subsequent processing of crude oils involves large 
quantities of oil-in-water emulsions in which the continuous phase depends 
on the ratio of water to oil, on the natural emulsifier system contained 
in the oil and on the origin of the emulsion. Most of the crude oil to be 
transported is in the form of a water-in-oil emulsion which must be broken 
by the addition of chemical demulsifiers. The separated brine contains a 
certain amount of residual oil and there is a tendency for oil-in-water 
emulsions to form. 
The tendency for oil-in-water emulsions to occur when crude oils are 
processed on the oil field or in refineries is even stronger. The amount 
of emulsified crude oil in said oil-in-water emulsions can be up to 5%. To 
remove this residual oil content, use is made of special demulsifiers, 
so-called `deoilers`, which are usually cationic polymers, as described, 
for example, in DE 3,404,538. Typical products are also described in U.S. 
Pat. Nos. 3,528,928, and 4,333,947. 
The removal of the residual oil content is necessary for clarification and 
processing of oil field waste water and for ecological and engineering 
reasons, since, for example, when said water is used for secondary 
production by water drive the presence of residual oil therein would 
increase the injection pressure. 
U.S. Pat. No. 2,407,895 describes a method of breaking oil-in-water 
emulsions with comparatively low molecular weight condensates of 
alkanolamines, prepared by condensation in the presence of basic 
catalysts. 
Further, U.S. Pat. Nos. 4,179,396 and 4,383,933 describe deoilers prepared 
from aluminum salts or titanium tetrachloride and alkanolamine 
condensates, which may have been partially acylated or quaternized. 
In addition, U.S. Pat. Nos. 4,505,839 and 4,731,481 describe the use of 
quaternized and low molecular weight alkanolamine polycondensates as 
deoilers, which have been prepared by catalytic reaction with ZnCl.sub.2 
/acetic acid or Al.sub.2 (SO.sub.4).sub.3 /acetic acid. 
Also, U.S. Pat. Nos. 4,404,362 and 4,459,220 describe block polycondensates 
prepared by the condensation of triethanolamine polycondensates and 
triisopropanolamine polycondensates separately synthesized by catalytic 
reaction with Lewis acids or mineral acids. 
However, such prior demulsifiers are not satisfactory. 
We have now found that trialkanolamine polyethers obtained by condensation 
of one or more trialkanolamines in the presence of phosphorous acid and/or 
hypophosphorous acid are highly effective demulsifiers for oil-in-water 
emulsions and are, when used for this purpose, superior to the prior art 
deoilers in respect of general usefulness and emulsion-breaking speed and 
are largely insensitive to overdosing. They contain no metal salts, in 
particular no chlorides, which could have a corrosive action. Unlike 
deoilers which have been prepared by condensation in the presence of 
carboxylic acids, the demulsifiers of the invention contain no carboxylate 
groups which could impair their efficiency. 
The preferred and particularly effective compounds are trialkanolamine 
polyethers prepared by condensation, in the presence of phosphorous acid 
and/or hypophosphorous acid, of one or more trialkanolamines of the 
formula 
##STR1## 
in which R.sup.1 to R.sup.3 denote the same or different 1,2-alkylene 
groups of from 2 to 4 carbon atoms. 
The trialkanolamine polyethers are prepared by condensing the 
trialkanolamines, preferably triethanolamine or triisopropanolamine 
N[CH.sub.2 --CH(CH.sub.3)-OH].sub.3 or mixtures of several 
trialkanolamines in the presence of phosphorous acid (H.sub.3 PO.sub.3) 
and/or hypophosphorous acid (H.sub.3 PO.sub.2). The phosphorous acid 
and/or hypophosphorous acid is advantageously used, calculated as 100% 
acid, in an amount of from 0.05 to 2% w/w and preferably from 0.1 to 1.0% 
w/w of the trialkanolamine to be condensed. Generally, the temperature 
used for the condensation ranges from 120.degree. to 280.degree. C. and is 
preferably from 150.degree. to 260.degree. C. and more preferably from 
180.degree. to 240.degree. C. The reaction is generally carried out over a 
period of from 1 to 10 hours and preferably from 4 to 8 hours. 
Advantageously, the degree of condensation is controlled by varying the 
temperature and time of reaction in such a manner that when 
triethanolamine is used as starting material, the viscosity of the 
resulting triethanolamine polyether is in the range of 10,000 to 100,000 
mPa. s, preferably 20,000 to 50,000 mPa.s, and, similarly, the viscosity 
of the triisopropanolamine polyether is in the range of 100,000 to 
1,000,000 mPa.s, preferably 200,000 to 600,000 mPa.s, and that of a mixed 
condensate from, preferably, equimolar amounts of triethanolamine and 
triisopropanolamine is in the range of 80,000 to 400,000 mPa.s, preferably 
100,000 to 300,000 mPa.s (measured, in all cases, on the undiluted product 
at 20.degree. C.). 
The trialkanolamine polyethers of the invention are advantageously added to 
the oil-in-water emulsions, for the purpose of breaking the same, in 
amounts of from 1 to 100 ppm, preferably from 1 to 30 ppm and more 
preferably from 2 to 10 ppm, by weight. 
Synthesis Example 
1,788 g of triethanolamine and 12 g of hypophosphorous acid (50% aqueous 
solution) were heated at 225.degree. to 230.degree. C. with stirring under 
a weak stream of nitrogen. The water of reaction was distilled off. After 
7 to 8 hours, at which point the viscosity was 21,000 mPa.s, condensation 
was terminated by cooling to room temperature. There were obtained 1,492 g 
of triethanolamine polyether (amine number 7.69 mmoles/g). 
Example of application 
Graduated, transparent test bottles of rectangular cross-section and having 
a capacity of 177.44 ml were filled with 100 ml of the oil-in-water 
emulsion to be tested. Various amounts of demulsifier were added to the 
oil-in-water emulsions in the test bottles to cover the range of 1 to 10 
ppm of demulsifier in the emulsion, by weight. The test bottles containing 
the test samples were shaken 50 times and then assessed for water clarity 
according to the criteria given below. This test procedure was repeated 
twice. The samples were then shaken 100 times and assessed and then shaken 
150 times for the final assessment. If the amount of oil present was 
sufficient to cause the oil to adhere to the inside of the bottle, thus 
making assessment difficult, the sample was decanted after the second 
shaking treatment and poured into a clean test bottle.

Assessment scale 
10 untreated--no change in appearance of emulsion 
9 slight change in color of emulsion 
8 emulsion shows distinct change of color 
7 water pale yellow 
6 water white--numbers or letters on the base of the bottle are legible 
5 water white--numbers or letters on the long side of the bottle are 
legible when viewed through the bottle in the direction parallel to the 
short side of the bottle 
4 water white--numbers on the long side of the bottle are legible when 
viewed through the bottle in the direction parallel to the short side of 
the bottle 
3 water white--numbers on the short side of the bottle are legible when 
viewed through the bottle in the direction parallel to the long side of 
the bottle 
2 water white--numbers on the short side of the bottle are legible when 
viewed through the bottle in the direction parallel to the long side of 
the bottle 
1 water very clear--numbers on the short side of the bottle are very 
clearly legible when viewed through the bottle in the direction parallel 
to the long side of the bottle. 
The test emulsion was an oil-in-water emulsion from a petroleum processing 
plant and had an oil content of 430 ppm by weight, It was treated with the 
demulsifier at ambient temperature. 
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Amount used 
Assessment after shaking the sample 
Demulsifier 
[ppm w/w] 
50 times 
50 times 
50 times 
100 times 
150 times 
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triethanol- 
6 8 5 2 1 1 
amine polyether 
of synthesis Ex- 
ample of present 
invention 
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The use of the triethanolamine polyether as a deoiler in accordance with 
the present invention gave good results over a wide range of 
concentrations. The deoiler was largely insensitive to overdosing. 
Furthermore, it showed no adverse interaction with other demulsifiers such 
as those used for breaking water-in-oil emulsions.