Experiment one: Effect of alkali in crude oil emulsification

Kang Wanli

2011.3

Observing the phenomenon of emulsification after the mixture of alkali and oil solutions.

Learn to determine the best concentration range of alkali used for emulsifying oil by using instability coefficient method.

One. Experimental purposes

Two. Experimental principles

The alkali (such as NaOH) can react with the acidic components of crude oil and the product is surface active substance:

Crude oil can be emulsified by the surface active substances to form the oil-in-water (O/W) emulsion. The form and stability of the oil-in-water emulsion are very important for the alkali flooding and the reduction of viscosity of heavy oil by emulsifying. Such as the mechanisms of emulsified-carrying, emulsified-collection and spontaneous emulsification happening in the alkali flooding and the mechanism of dispersion of oil by emulsifying in the reduction of viscosity of heavy oil by emulsifying are all on condition that the oil-in-water emulsion is formed.

The alkali concentration is very important for the emulsification of oil caused by alkali. When the alkali concentration is low, fewer surface active substances can be formed during the reaction between alkali and oil which is bad for the stability of emulsion. When the alkali concentration is too high, for one thing, alkali can react with the weak acid with long carbochain in oil to form the oleophylic active substances that can counteract the action of hydrophilic active substances which is bad for the stability of oil-in-water emulsion, meanwhile, the superfluous alkali can act as the salt and it’s also bad for the stability of oil-in-water emulsion. So the stable oil-in-water emulsion can only be formed during the reaction between alkali and oil when the concentration range of alkali is suitable.

The stability of emulsion can be defined by the instability coefficient (USI). And the instability coefficient is defined as 4-1:

Where: USI - Instability coefficient, ml; V(t) – Function of the relationship between the volume of wa

ter separated from the emulsion system and time. t - Time of the static separation of emulsion system. It can be indicated from the defining equation that the small

er the instability coefficient is, the better the stability of the emulsion is.

Equipments and chemicals

Equipments Electronic balance (sensibility reciprocal

0.001g), 10ml graduated test tube with plug, Stopwatch, Dropper, Test tube rack.

Chemicals Sodium hydroxide, Crude oil, Distilled water.

1. Add 5ml of the sodium hydroxide solution with the mass fraction of 1.0×10-4, 2.5×10-4, 5×10-4, 4.0×10-3, 5.0×10-3, 8.0×10-3,1.0×10-2, 2.0×10-2 into eight 10ml graduated test tubes separately. And then separately add 5ml oil into the eight tubes by using dropper. Then cover the plug of tubes and shake every test tube up and down for 30 times.

2. Vertically put the test tubes on test tube rack immediately after they have been shaked, and then begin to time. Record the volume of the separated water in the test tube every 3min (The volume can be recorded every 1min if the water is separated quickly). And the total time for recording is 30min.

3. Get the test tube in which the emulsion has the best stability and then shake it for 30 times again.

Five． Experimental results processing 1. Determine the instability coefficient of emulsified oil with the dif

ferent mass fraction of alkali. (1) Draw out the curve of relationship between the volume of sep

arated water and time (V-t). Pay attention that every curve at different mass fraction of alkali should be drawed on the coordinate with same standard.

(2) Determine the instability coefficient using equation 4-2:

2. Draw out the curve of relationship between USI-ω(NaOH), and determine the best concentration range of alkali used for emulsifying oil, and explain the variation regularity of the curve.

3. Express the record of experiment, result of data processing in the form of table or picture. Write out the experiment report.