Breaking Reverse Emulsions




Many different methods are employed to breaking oil in water emulsions. One such method patented by Jacques et al which involving the use of a “dispersible terpolymer that consists of acrylamide, acrylic acid (or its salt derivatives) and alkylacrylamide or alkylacrylate or alkylmethacrylate; or copolymers consisting of acrylamide and alkylacrylamide or alkylacrylate or alkylmethacrylate alone or in combination with a cationic species” (Jacques et al) will be investigated.

This method of breaking reverse emulsions consists of the following steps:

a) Treating the emulsion with an ionic chemical to neutralize the charge of the oil droplets dispersed in the water. This ionic chemical is a cationic polymer (positive in charge) which can be selected from the following:
  1. melamine-formaldehyde resin
  2. polyepichlorohydrins
  3. poly-3-methacrylamidopropyltrimethylammonium chloride and copolymers with acrylamide
  4. poly-2-methacrylatoethyltrimethylammonium chloride and copolymers with acrylamide,
  5. diallyl dimethylammonium chloride and copolymers with acrylamide

b) The addition of a water soluble copolymer (a water dispersible hydrophobic ally functionalized copolymer), consisting of a water soluble and oil soluble (hydrophobic) portion. This copolymer is made of the following two monomers:
  1. One monomer (this is the hydrophobic monomer) consisting of 0.1-10 molar percentage of alkylacrylamide and alkyl(meth) acrylate with an akyl group with 4-20 carbon atoms
  2. The other monomer (this is the water soluble monomer) consisting 90-99.9 molar percentage of either acrylic acid or salts of acrylic acid

c) Allowing for the particles to separate by gravity

Alternatively, a terpolymer can be used in place of a copolymer.

a) Treating the emulsion with an ionic chemical to neutralize the charge of the oil droplets dispersed in the water. This ionic chemical is a cationic polymer (positive in charge) which can be selected from the following:
  1. melamine-formaldehyde resin
  2. polyepichlorohydrins
  3. poly-3-methacrylamidopropyltrimethylammonium chloride and copolymers with acrylamide
  4. diallyl dimethylammonium chloride and copolymers with acrylamide
b) The addition of a water soluble terpolymer (a polymer derived from three monomers), consisting of a water soluble portion an anionic water soluble portion, an an oil soluble (hydrophobic) portion. This terpolymer is made of the following three monomers:
  1. 0.1-10 molar percentage of one monomer (this is a hydrophobic monomer) consisting of alkylacrylamide or alkyl(meth) acrylate with an akyl group with 4-20 carbon atoms
  2. 5-40 molar percentage of one monomer (this is the water soluble monomer) consisting of either acrylic acid or methacrylic acid
  3. 50-94.9 molar percentage of the last monomer (the other water soluble monomer), an acrylamide monomer.
c) Allowing for the particles to separate by gravity.

These steps are discussed in greater detail below

1.Treatment with a cationic polymer for negative charge reduction





The first step involves the use of the treatment of the emulsion with a cationic polymer. The suitable cationic additives are mentioned above. In reverse emulsions, the oil droplets and other contaminants that cause fouling in various equipments carry a negative charge. The addition of cationic polymers will effectively neutralize the charge on these oil droplets or contaminants. To ensure complete neutralization of this negative charge, an amount of cationic polymer that is sufficient to neutralize all the negative charges on the droplets with perhaps even a low level of residual cationic charge is desired. The final state of this step results in oil droplets that are neutral or with a slight cationic surface charge for the next step of this process.

2.Treatment with an effective amount of hydrophobically functionalized water soluble polymer





The alkyacrylamide or akylacrylate used in this step have limited solubility in water and show a tendency to react very strongly with oil droplets in the waste water. The chain length on the alkyl group of these hydrophobic monomers is related to its insolubility and a carbon chain length of ranging from 6-20 is preferably used. Additionally the amount of hydrophobic group in the polymer necessary for oil water treatment decreases with increasing chain length, for example less octylacrylamide is needed for the same function as alkyacrylamide.
Terpolymers that consist of an acrylamide, a hydrophobic monomer (as descrbied earlier) and salts of acrylic acid can also be used. The desired characteristic is to have a hydrophobic monomer that decreases the solubility of the polymer which will enable the rapid interaction with the dispersed oil droplets in the water. The amount of this hydrophobic will need to be increased for example, if say there is a high presence of charged groups (such as carboxylic acids).

The function of these hydrophobic groups greatly improves the breaking of oil water emulsions with respect to polymers without hydrophobic groups. The emulsified oil droplets in water generally carry a negative surface charge, this is the basis of stabilization of emulsions, that is, emulsions are stabilized by the electrostatic charge repulsion between the oil droplets, keeping them dispersed in the water. The first step of application (adding cationic polymer) of breaking reverse emulsions effectively reduced the charge on these oil droplets, eliminating the electrostatic repulsion (ie. decreasing the emulsion stability greatly). As such, the oil droplets will start to approach each other and coalesce, eventually the large agglomeration (otherwise known as flocculation) of oil occurs and this floc of oil (and other contaminants) will begin to float to the top of the emulsion. The larger the flocculation, the faster the rate at which they will rise to the top of the water. The addition of the hydrophobically functionalized polymer then attaches to the oil droplets and the resulting polymer bridging accelerates the floc formation. The hydrophobically functionalized polymers can attach to the oil by means of coulombic attraction (attraction of opposite charges), hydrogen bonding and by hydrophobic attraction to the oil droplets. After a prescribed amount of time, the oil droplets and polymer separate into distinct layers from the water and can then be skimmed off in a skim tank.

The use of a hydrophobically functionalized polymer as opposed to conventional polymers without hydrophobic monomer groups has been proven in laboratory tests to greatly improve the breaking of reverse emulsions. Results indicated an improved ability in oil breaking with significantly less concentration of remaining oil as opposed to treatment with a polymer without a hydrophobic group. As well, the formed floc particles were more difficult to redisperse back into the water with additional agitation.