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Industrial preparation of Demulsifiers

Chandran Udumbasseri, Technical consultant cudumbasseri@yahoo.co.in.

Theory and applications Demulsifier is a chemical used to break emulsions and separate into two phases.

Water is separated from crude oil by dozing demulsifier and breaking the emulsion.

The emulsion of water in crude oil is thermodynamically unstable but kinetically very stable. Natural surfactants, wax and solids (inorganic salts, zinc, iron, aluminum sulfate, calcium carbonate, silica and iron sulfide) stabilize such

emulsions. Asphaltene compounds were found to be one of the contributing materials to the

stability of crude oil. Asphaltenes are condensed aromatic rings containing saturated carbon chains and naphthenic rings as substituents along with hetero

atoms and metals. Asphaltenes are capable of cross linking at the water drop oil interface and preventing water droplets from coalescence. They are surface active agents present in the oil water interface.

Emulsifiers:

When two liquids are Immiscible then mixing and making visibly homogenous

pseudo phase formation is difficult. If water and vegetable oil are mixed after

sometime it can be seen that oil floats on the water surface. If mixed and

allowed to stand, the oil droplets entrapped in the water body slowly moves

upwards and join to form floating oil layer. The substance used to stop the

separation into two layers is called emulsifiers

An emulsifier molecule has two ends: one side water loving (hydrophilic end)

and the other end water hating (hydrophobic), the water loving part bonds with

water using hydrogen bonds while water hating part bonds with oil molecule

using Vander Waals forces.

Emulsifier molecules

The hydrophilic 'head' dissolves in the water and the hydrophobic 'tail' dissolves

in the oil. The water and oil droplets become unable to separate out and the

mixture formed is called an emulsion. There are two types of emulsion, water in

oil emulsion and oil in water emulsion.

Demulsifiers Demulsifiers are surfactants similar to emulsifiers but functions in the reverse

direction, they break the emulsion formed by emulsifiers. As explained above an emulsifier that formed oil in water can function in the reverse direction. Such

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emulsifiers can break the emulsion of water in oil type. If the surfactants can make oil in water emulsion, maybe they can remove water from water in oil

emulsions. So any emulsifier with definite structural properties can be considered as emulsification and demulsification agent.

Demulsifiers reduce surface tension at the water-oil interface. Demulsifiers are polymers that act as surfactants. The polymers have both hydrophilic and

hydrophobic groups. The polymeric surfactant, when added to the crude emulsion locates itself in the interface between water and oil molecules. The

hydrophilic groups orient themselves towards water while the hydrophobic ones orient themselves towards the oil. At the interface the demulsifier either replaces the emulsifying surfactant or it provides additional steric forces within the film

interface. In either case, this absorption causes a random film thickness fluctuation. This random film thickness fluctuation results in an increase in the

film surface area and also results in a localized decrease in the absorbed stabilizing emulsifier. Hence causing a local increase in interfacial surface tension and thinning of the film.

The following process takes place during the absorption of the demulsifier at the interface:

1. The demulsifier absorbs the stabilizing emulsifier at the water liquid interface and decreases the film forming capability of the emulsifying additives.

2. The demulsifier may render the additives soluble in the water phase and hence less surface active. 3. The demulsifier may mix with the emulsifying additive and reduce the

interfacial tension at the water oil interface, there by creating less stable water dispersion.

The demulsifiers used for water separation from crude oil are a combination of compounds having demulsifying activity and compounds that assist

demulsification but without demulsifying activity.

1. Compounds with demulsifying activity. 1.1. Polyethylene imine alkoxylate. 1.2. Mono or oligo-amine alkoxylate.

1.3. Alkoxylated alkylphenol formaldehyde resin. 1.4. Alkoxylated amine modified alkyl phenol formaldehyde resin.

1.5. Co or ter polymers of alkoxylated acrylates or methacrylates with vinyl compounds.

1.6. Condesates of mono- or oligo- amine alkoxylates, dicarboxylic acids

and alkylene oxide block polymers (may be quaternized at nitrogen). 1.7. Cros linked products of 1 to 6.

2. Compounds acting as demulsifying assistant.

2.1. Poly alkylene glycol ethers 2.1.1. General Formula, [R’(OA1)a ..OH]n , R’ = C7 to C20 alkyl group, phenyl

group, alkyl phenyl group: A1,A2,A3 = 1,2 alkylene group with 2 to 4 carbon atoms, phenyl ethyl group ( there should be one 1,2 alkylene group with 4 carbon atoms); a = 1 to 50; n = 1 to 10.

2.1.2. General Formula H-(OA1)b-(OA2) c-(OA3) d-OH (where b, c and d each has value from 0 to 50 and b+c+d is >3).

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Demulsifier functioning The demulsifier tend to act on the emulsion by:

Flocculation of oil droplets. Dropping of water.

Coalescence of the water droplets. The speed and efficiency at which this occurs can be improved by process

equipment design and operating condition (e.g.: Increasing the

temperature, separator design, etc.).

The components of the demulsifier formulation are characterized according to their primary function. But components can provide multipurpose function in a particular crude oil. Also inclusion of surface wetters can assist in the treating of

emulsion problem.

Function of different demulsifiers Oxyalkylated Phenolic Resins

High molecular weight phenolic resin oxyalkylates have been found to be highly effective as crude oil emulsion breakers. Resins are used on emulsions of the

water-in-oil type and work by counteracting the stabilizing influence of naturally present emulsifying agents.

They are classified as nonionic surface-active organic chemicals that will not interact with ionic type chemicals.

Applications phenolic resin oxyalkylates are generally used in dilute form in aromatic solvent

or blended with chemicals of different generic structures to give synergistic formulas which may have greater efficiency.

Polyalkylene Glycols Polyalkylene glycols are non-ionic in character. Polyols work by counteracting

naturally occurring emulsifiers. Polyols have been found to be particularly effective when used in low salt water brine or in fresh water emulsions. In these cases, polyols are often formulated with sulfonates or used as is.

Polyols are stable to hydrolysis. Polyols exhibit exceptional ability to lower interfacial tension and, as a result, have a high degree of wetting activity. For

this reason, polyols can effectively disperse or deflocculate solids. Applications

Polyalkylene glycols can be used with effectiveness in synergistic blends with oxyalkylated phenolic resins or with sulfonic acid salts, or in blends of all three,

to break crude oil emulsions of the water in oil type. Polymeric Elastomers

Polymeric elastomers are used in a variety of geographical locations in standard emulsion breakers. Rapid penetration through the oil phase to finely emulsified

water droplets has made them indispensable in many areas. This penetration is vividly demonstrated by the rapid blackening of cream colored emulsions and the quick brightening of water-hazed emulsions. Being extremely oil soluble in

nature, polymeric elastomers exhibit great tenacity for finishing the dehydration of crudes where more water-soluble compounds can “wash out” with the water

phase of a partially resolved emulsion.

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Applications

Polymeric elastomers may require blending with other emulsion breaker intermediates to achieve complete treatment of water-in-oil emulsion. Polymeric

elastomers can be formulated in toluene, xylene, or heavy aromatic solvent, and are compatible with other emulsion breaker intermediates. If necessary, alcohols can be used as brightening or stabilizing agents in these field strength blends.

Polymerized Polyols

Polymerized polyol intermediates are used in a variety of geographical locations in standard emulsion breakers. Rapid penetration through the oil phase to finely emulsified water droplets has made them indispensable in many areas. This

penetration is vividly demonstrated by the rapid blackening of cream-colored emulsions and the quick brightening of water-hazed emulsions.

They are extremely oil soluble in nature and exhibit great tenacity for finishing the dehydration of crudes where more water-soluble compounds can “wash out” with the water phase of a partially resolved emulsion.

Applications

Polymerized polyols typically require blending with other emulsion breaker intermediates to achieve complete treatment of water-in-oil emulsion.

Polymerized polyols can be formulated in toluene, xylene, or heavy aromatic solvent, and are compatible with other emulsion breaker intermediates. If necessary, alcohols can be used as brightening or stabilizing agents in these field

strength blends.

Polyol Esters Polyol esters are a reaction product of a polyalkylene oxide block polymer and a polyfunctional organic acid. Polyol esters are particularly effective on fresh-water

emulsions and tend not to cause emulsion inversion or oil-in-water emulsions. Polyol esters act, as do most emulsion breakers, by counteracting the effect of

naturally occurring emulsifiers. Applications

Polyol esters are an effective emulsion breaker when used separately or in blends with oxyalkylated phenolic resins. This high molecular weight chemical is

non-ionic in character. Resin Esters

Resin ester intermediates are reaction products of an oxyalkylated phenolic resin and an organic carboxylic acid. Resin esters are unusually effective when used

as a detergent or as a wetting agent in emulsion breaker formulations. Applications

Despite resin ester’s high detergency, they do not cause inversion to oil-in-water emulsion. Resin esters have also been used in limited applications as a desalting

chemical and in treating slop oils.

Sulfonates Sulfonates have outstanding characteristics that include low cost and a

resistance to “burning” or “overtreating” when used in formulations to treat

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crude oil emulsions of the water-in oil type. Sulfonates aid in emulsion breaking by counteracting naturally occurring emulsifiers and are extremely effective in

resolving loose water emulsions stabilized by solids. Sulfonates are often used in treating refinery “slop” emulsions as well as tank bottoms.

Applications Sulfonate intermediates are generally used in conjunction with oxyalkylated

phenolic resins and with polyglycols. The solubility characteristics of sulfonates enable them to work at the oil/water interface where they are extremely

effective in resolving loose water emulsion stabilized by solids. Classification

Water droppers

Water droppers coalesce water droplets in the crude oil and release free water. Predominant type is based on alkyl phenol formaldehyde resins with low levels of addition of ethylene oxide or propylene oxide. These demulsifiers also show

excellent desalting properties.

Treaters The primary function of these compounds is to flocculate the large number of

sub-micron water droplets dispersed in the crude oil. Water droplets are thus concentrated at the base of the oil column prior to coalescence and the crude is dehydrated above the settling level of the flocs. This can be noticed by the

brightening of the top oil in contrast to its dull appearance when the water dispersion existed.

The predominant type is based on high molecular poly propylene glycol molecules with hydrophilic ‘tips’ which solvate into the water droplets and facilitate gathering.

Hybrids

These compounds incorporate a balance of molecular design features such that both ‘dropping’ and ‘treating’ characteristics are exhibited. Hybrids are more cost effective than blends of droppers and treaters.

Desalters

The emulsions coming along the crude to the desalting stage have low amounts of water and are less stable. Some of the naturally occurring emulsion stabilizers have been removed at the 1st stage demulsification process. The droplet size is

not very small. High potential electric field applied coalesce these polar salt water droplets. A good desalter demulsifier would achieve rapid water separation

at low level addition rates. Preparation of demulsifier bases

The methods of preparation of demulsifiers are taken from various U.S. Patents

that were developed in their laboratories. Initially the intermediate product, resin (alkyl phenol formaldehyde resin,

Polyalkylene poly imine resin, Polyalkylene resin, intermediate amine, polyoxyalkylene glycol, polyoxyalkylene glycol-diglycidyl ether condensate,

polyamidoamine, vinyl polymers) is prepared. This product is then condensed

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with ethylene oxide, propylene oxide or butylenes oxide or their mixture to make oxyalkylate. As the number of molecules of ethylene oxide increases the

solubility of the resin in water increases. By increasing other oxides of propylene and butylenes the solubility of the resin in water is reduced. Depending on the

requirement of degree of solubility in oil/water the ratio of resin to alkylene oxide is varied.

Most important process in demulsifier preparation is alkoxylation – ethoxylation and propoxylation.

Etherified resin polypropylene glycol alkoxylate Procedure for the preparation of a new type of demulsifier is given below. More products will be added now and then.

Product A- Condensation of Phenol and Formaldehyde 1. Phenol …………………….94.1g (1mole)

NaOH (50%) ………… 03.1g

2. Place above materials in a flask which can be fitted with stirrer, thermometer,

distillation, etc

3. Heat the flask with contents to 55-60oC

4. Formaldehyde (35% )……………..171g (2mole)

5. Add formaldehyde slowly to keep the temperature at 55-60 oC

6. When the formaldehyde was added completely heat to 70 oC until free from

formaldehyde is < 2%

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Product B- Alkoxylation of polypropylene glycol

7. Polypropylene glycol (Mol Weight 2000)…. 400g (0.2Mole)

KOH (85%)……………………………………… 2.5g

8. Dry the PPG with KOH at 110 oC for 2hrs

9. Ethylene oxide (EO) 240g (240x100/400 =60% of PPG) (5.45mole)

10. Meter EO at 130 oC -140 oC

Condensation of product A &B- Etherification

11. A……………………..80g (0.3mole)

B……………………640g (0.2mole)

12. Mix A and B with stirring

13. Neutralize with DDBSA

14. Mole ratio A to B is 1.5:1

15. Reduce vacuum to 2000mPa (0.015mmHg) at 80-85 oC

16. Distill out water under vacuum.

17. The mixture is etherified by increasing the temperature to 140 oC

18. Remove water

Oxypropylation of etherified condensate

19. Condensate (etherified product)……………..325g

KOH (85%) ……………………………………………3.8g

20. Heat the mixture to 100-120 oC

21. Dry the mixture at a vacuum of 2000mPa (0.05mmHg) for 2hrs

22. PO…………………630g (194g epoxide per 100g condensate)

23. Meter PO at 120-130 oC and pressure 50-500kPa (7-72psi) for 3hrs

24. Final product is dark liquid

25. Dilute to 50% by Xylene

Require raw materials:

1. Phenol 2. NaOH/KOH 3. Formaldehyde (35%) 4. Polypropylene glycol (mol weight: 2000) 5. Dodecyl benzene sulfonic acid 6. Ethylene oxide 7. Propylene oxide