Adsorption Kinetics of Demulsifiers to an Expanded Oil—Water Interface

Abstract

Relaxation of interfacial tension was recorded for the sudden expansion of a water droplet in the presence of a heptane or toluene solution of a number of demulsifier polymers prototypical of products used in industry to demulsify crude oil. Adsorption kinetics were found in all cases to be non-diffusion controlled. Increasing the polyoxyethylene content within the demulsifiers resulted in slower relaxation rates. This effect was much stronger in heptane than in toluene suggesting that polyoxypropylene-type polymers would be better candidates for demulsifying light, waxy crude oil emulsions.Much has been written concerning the specific chemical mechanisms involved in demulsification 1 " 7 . Much of this work addresses the behavior of polymers at an oil-brine interface or in thin films. What has generally been ascertained is that the demulsification process involves the displacement of emulsifying entities such as asphaltenes, natural surfactants or solids at the interface by a surface-active demulsifier which then also causes changes in the rheological properties of the interface. Such changes favor rapid coalescence between converging droplets of dispersed aqueous phase by increasing the rate at which the continuous oil phase can drain.More specifically, as dispersed phase water droplets approach each other and flatten to form a thin film of continuous oil phase between them, the outward drainage flow of the film can create gradients in interfacial tension which then oppose and slow such drainage (Marangoni-Gibbs effect) 8,9 . The presence of a demulsifier in the continuous phase, which rapidly adsorbs to prevent the formation of gradients at the interface, speeds drainage and coalescence 4 . In effect, the demulsifier serves to impart a lower elasticity, or dynamic film modulus, to the interface by minimizing changes in 0097-6156/95/0615-0268$12.00/0

Emulsion Characteristics and Novel Demulsifiers for Treating Chemical Induced Emulsions

“…The treated samples, however, produced a much faster phase separation and better water and oil quality than the untreated. Interfacial tension measurements: Interfacial tension measurements have been investigated by several authors to give insights into the mechanisms of demulsifier adsorption at the oil-water interface [23,24]. Figure 9 shows results from equilibrium interfacial tension measurements on C6TAB, C12TAB, C16TAB, and the untreated samples in an ASP emulsions at 22 o C and 60 o C. The appearance of the bottles of these samples after 1 day was also shown in Figure 9.…”

Properties of Langmuir Surface and Interfacial Films Built up by Asphaltenes and Resins: Influence of Chemical Demulsifiers

“…Breen (11) analyzed the overall relaxation kinetics of an expanded oil-water interface in the presence of various potential demulsifiers. These tests showed that the interfacial tension relaxation process is nondiffusion controlled, but it is dependent on structural factors such as molecular weight and hydrophobicity.…”

Study of Dynamic Interfacial Tension for Demulsification of Crude Oil Emulsions

“…5 It was pointed out in his study that kinetic comparisons should be made based on an equimolar basis, not an equal mass or ppm basis. 5 It was pointed out in his study that kinetic comparisons should be made based on an equimolar basis, not an equal mass or ppm basis.…”

“…It is interesting to raise the question about interfacial effects for a polymer that has molecular weight between 400 and 15000 MW, such as 2000 MW glycol , which has both a relaxation lifetime and thermodynamic adsorption just between the 400 and 15000 MW glycol according to Breen's results 5 . It is unable quantitatively to compare the interfacial activity of 2000 MW glycol with its counterparts based on an equal mass (ppm) basis if using Breen's data 5 .…”