Note: Descriptions are shown in the official language in which they were submitted.
2 ~ ~
Proces_ for_thQ Se~aration_of 0~ water Emulsions
The present invention relates to a process for the
separation of oil-water emulsions.
OfW emulsions frequently turn up as contaminated prod-
uct streams which, in addition to organic substances,
such as mineral oils, vegetable oil, animal oils or
fats in emulsified form, also contain non-emulsified
substances as well as solid matter.
For exampls~ these mixtures arise in the production of
crude oil, when it is transported in oil tankers or
pipelines, and during the processing in refineries.
Waste water contaminated with oil and fat also turn up
in the metal-working industry, the motorcar industry,
in foodstuff manufacturing. workshops and gas sta-
tions. Said sewage is heavily loaded and poses great
problems for sewage purification plants. It is there-
fore absolutely necessary to subject said waste water
to special preliminary purification methods before it
is introduced into the drainage ditch or the sewage
treatment D lant.
Known separation techniques, for example, include flo-
tation, filtration, adsorption and sedimentation. In
all thesa ~rocesses the organic phase which is present
in the water in emulsified form must at first be con-
verted into the "free" form. This process is referred
to as "cracking of emulsions or demulsification".
The emulsions may be very stable depending on the kind
of emulsion and the sort of accompanying substances or
ingredients. In order to carry out a physical liquid-
2 ~ ~ 3 3 ~ ?~ ~
liquld-phase-separation the emulsion must be cracked
in any case. If instable emulsions are concerned, a
phase separation may be effected by allowing them to
stand for a longer period of time and/or by heating.
To break emulsions stabili~ed with emulsifiers they
must be treated with chemical substances to substan-
tially discharge the very fine organic, liquid parti-
cles which are electrostatically charged in the aque-
ous phase. In this case the mutually repelling forces
between the organic particles emulsified in water are
neutrali~ed, and an agglomeration of the fine droplets
takes place which finally results in demulsification
by an enlar-gement of the drops.
In general, oil particles in an aqueous emulsion are
negatively charged. To reach the isoelectric point
cations are added to the emulsion. In addition to the
inorganic salts. such as iron (III)- or aluminum
salts, and acids, organic water-soluble cationic poly-
mers of different chain lengths or molecular weights,
respectively, are also used for the same purpose as
demulsifiers.
For the purification of oil-containing sewage both
cationic and anionic water-soluble Dolymers are fre-
quently used irl combination with iron- or aluminum
salts. Corresponding purification processes are gen-
erally carried out in practice in i-lotations plants af
various types, e.g., flash flotation, rnechallical flo-
tation, etc.
~ process for the separation of oil from stable O/W-
emulsions is described by DE-O~ 19 26 623. The emul-
sion is mixed with an iron salt and caustic soda lye
and subseque--,tly subjected to a secondary treatment
2~2~
with a high-molecular, water-soluble polymer on the
basis of polyacrylic acid, polyacrylamide, polyvinyl
alcohol, and polyethylene oxide.
DE-OS 28 41 122 describes the application of cationic,
anionic, or non-ionogenic polymers alone or in combi-
nation with metal salts for the purification of waste
water. Polyamides, polyamines, and copolymers of ac-
rylamide with quaternary ammonium polyacrylamides are
mentioned as cationic polymer types.
A process employing cationic polymers for the oil-wa-
ter-separation is described by U.S. Patent No. 3,691,
086. The polymers are preferably used in combination
with silica sol and a multivalent metal salt. Polymers
according to this U.S.-Patent 3,691,086 are compared
with the polymers according to the present invention
in the comparison examples A to F, to demonstrate the
qualitatively and quantitatively superior separation
achieved by the products according to the present in-
vention.
Copolymers of the monomers acrylamide and acryloyl
oxiethylenedimethylbenzyl ammonium salts and the use
thereof as retention agents in papermaking are de-
scribed in ''Chemical Abstracts, vol. 105 (1986) Ref-
erence No. 116866c and 116867d.
The processes alld agents for demu`lsi-Fication known
from the state cf the art do not achleve a sufficient
separation bstween organic phase and water. It is ac-
cordingly the object of -the present invention to com-
plete the demulsifying action by providing an improved
agent for demulsification purposes and to provide a
process which leads to a satisfactory separation
~3~2 ~
effect both i!l Tlotation plants and in static separa-
tion devices.
In general practice problems with respect to the sepa-
ration of oil and water frequently arise when the sep-
aration is to take place without a flotation plant by
simply allowing the emulsion to stand, e.g., in a tank
or a plate separator. These problems frequently arise
in offshore crude oil production sites where the pro-
vision of a demulsi~ier for O/W emulsions effecting a
breaking without energy input into the sewageT like in
the rnechanical flotation, and without application of
inorganic salts, has been an urgent need.
Most surprisingly it was found that the object accord-
ing to the present invention was achieved by the use
of a synthetic organic, cationic polymer of
a) 5 to 70%-wt. of a monomer of ths general formula
R1 R3
IE>
CH2 = C - COY - R2 - N - R4 X (I)
I
Rs
wherein
R1 is -H or -CH3.
Y is -O- or -NH-.
R2 is a straight--chain or branched alkylene greup
with ~ to 6 C-atorns,
R3, Ra are -CH3 or -CH2 -CH3,
Rs is an alkylene-aromatic residue,
X is Cl-,CH3 S04 -,
2 ~ r~
b) 20 ~o 95~, acrylamide, and
c) 0 to 10% of another water-soluble monomer, e.g.,
methacrylamide, (meth)acrylic acid, vinyl
pyrrolidone, dimethyldiallyl ammonium chloride,
acrylamidomethyl propane sulfonic acid, N,N-di-
methylacrylamide, vinyl actetamide, or vinyl
formamide.
The addition of a cationic polymer of the afore-men-
tioned composition in an amount of 0.1 to 50~-wt.,
preferably 1 to 20%-wt., relative to the organic por-
tion of ~he oil-water emulsion, results in demulsifi-
cation of this 0/W emulsion. The cationic polymer may
be added to the OJW emulsion to be cracked in the form
of an emulsion, a powder or of an aqueous so~lution.
The thir~ water-soluble monomer component c) may pre-
ferably be acrylic acid or N-vinyl pyrrolidone.
Basic monomers a), which may be quaternized with the
residue Rs according to the above definition, particu-
larly include:
dimethylaminoethyl acrylate, dimethylaminoethyl meth-
acrylate, dimethylaminopropyl acrylamide, dimethyl-
aminoprcDyl methacrylamide, diethylam-inoethyl acry-
late, dimethylamino-2,2-dimethylpropyl acrylamide.
With respect to the present inventiotl it was most sur-
prisingly found that the demulsifying action oF these
cationic "poly-quat-types" e~tremely depended on the
quaternizing component, i.e., on the kind of the sub-
stituent Rs of the general Formula I.
The advantageous results according to the present in-
vention are achieved, if as Rs an alkylene-aromatics-
3 ~, 2 ~
residue, such as, in particular, the benzyl group, ispresent as subs~ituent at the quaternary nitrogen
atom.
To illustrate the invention, different cationic poly-
mers were tested as to their demulsifying action. In
this connection, the sewage of a petroleum plant was
used as model emulsion and treated in two test series,
on the one hand, with known products the character-
izing structural feature of which is that Rs = CH3
(referred to as 'comparative product") and, on the
other hand, with the product according to the present
invention having the same basic structure and differ-
ing from the comparative product by the fact that the
residue Rs of the general formula I is an alkylene-
aromatic according to the definition of the main
claim. Tests with Rs = benzyl were also carried out as
examples. Homopolymers as described by U.S.-Patent
3,691,086 were used as comparison products E and F.
The following products were tested:
omparative product A: copolymer, consisting of
25%-wt. N-(dimethylamino-
propyl)acrylamide, quater-
nized with m thyl chloride
and 75%-wt. acrylamide.
Product A: copolymer, consisting o~
25%-wt. N-(dimethylamino-
propyl~acrylamide, quater-
nized with benzyl_chlor_de
and 75%-wt. acrylamide.
2 2 ~
omparative product B: cGpolymer, consisting of
70%-wt. N-(dimethylamino-
pr^opyl~acrylamide, quater-
nized with methyl,,chloride
and 30%-wt. acrylamide.
Product B: copolymer, consisting of
70%-wt. N-(dimethylamino-
ELPvl)acrYlam _ , quater-
nized with benzYl chloride
and 30%-wt. acrylamide.
omparative product C: copolymer, consisting of
5~-wt. dimethylaminoethYl
_crYlate, quaternized with
dimethyl sulf_te and 95%-wt.
acrylamide.
Product C: copolymer, consisting oF
5%-wt. dimethylaminoethyl
acrYlate, quaternized with
_enzY1 chloride and 95%-wt._
acrylamide.
omparative product D: copolymer, consisting of
50%-wt. dimethylamino-2,2-
dimethyl~ropyl acrylamlcie,quaternized with dimethyl
sulfate and 50%-wt. acryl-
amide
Product D: copolymer, consisting of
50%-wt. dimethylamino-2,2-
dimethylpropyl acrylamide,
cluaternized with be,nzyl
2~3322 i
chlorlde and 50%-wt. acryl-
annide
omparative product E: polymer, consisting of 100%-
wt. dimethylaminoet~y~l_meth-
acrYlate, quaternized with
e_hyl ch_oride.
omparative product F: polymer, consisting of 100%-
wt. dimethylaminoethYl meth-
_crYlate~ quaternized with
be_zyl chloride.
After treatment with the demulsifying cationic polymer
according to the present invention the residual oil
content in the purified water was determined as heavy
lipophilic substances according to DIN 38409, part H
13.
_ample 1_(_est serie~,,_st,,,a,tic separation)
In a beaker, the sewage was mi~ed with 50 ppm of each
of the above-mentioned comparative products and prod-
ucts. The demulsifier was added from a 0.1% aqueous
solution. The samples were stirred with a finger blade
agitator for 60 seconds at 50 rpm. The emulslon was
cracked during this period, when it was then allowed
to stand for 30 minutes, tne organic phase settled out
at the water surface. Deterrnination of the residual
oil contents as difficultly volatile lipophillc sub-
stances was carried out for the lower aqueous phase.
~ 3
Exa,m~,l,e_?_,~T,~st serie,s ?,_flo,ta,t_on)
The sewage was placed in a 2-liter-laboratory flota-
tion cell, type KHD. During stirring at 1,500 rpm and
simultaneous introduction of air through a double-
walled shaft, 5 ppm demulsifier were added from a 0.1%
aqueous solution; subsequent flotation for ~ minutes.
The organic substances discharged with the foam were
separated from the flotation cell by means of a strip-
per. The purified water was examined as described
above according to DIN 38409, part H 18.
The results of the test series according to Examples 1
and 2 are listed in the following Tables 1 and 2.
Table 1_.
Results of test series l (static separation, Example
1 )
Example Demulsifier Contents of diffi-
cultly volatile,
lipophilic sub-
stances in mg/l,
according to DIN
38409, part H 18
1 without addition 68
2 Comparative product A 36
3 Product A l3
4 Comparative product B 28
Product B l2
6 Comparative product C 32
7 Product C lO
8 Comparative product D 35
9 Product D 10
Comparative product E 28
11 Comparative procluct F 29
s~
Table ?
Results of test series 2
(Flotation Example 2)
Example Demulsifier Contents of diffi-
cultly volatile
lipophilic sub-
stances in mg/l
according to DIN
38409 part H 18
1 without addition 42
2 Comparative product A 6
3 Product A
4 Comparative product B 5
Product B 0.8
6 Comparative product C 4
7 Product C 0.5
a Comparative product D 4.5
9 Product D 0.2
Comparative product E 6
11 Comparative product F 7
The results given in Tables 1 and 2 demonstrate that
the addition of the cationic polymers used according
to the present invention as demulsifiers results in a
by far lower content of heavy lipophilic substances in
the sewage.
The results obtained in the tests with the comparative
products E and F show that quaterrlized homopolymers
both with and without benzyl group result in consider-
ably worse separation results comparsd to the copoly-
mers used according to the present invention.
