Studying demulsification mechanisms of water-in-crude oil emulsions using a modified thin liquid film technique

The thin liquid film (TLF) technique equipped with Scheludko-Exerowa cell has been demonstrated to be a valuable tool for studying stability of dispersed systems of soft matter such as emulsions and foams. Many industrial applications involve the addition of various chemical aids to obtain desired properties or resolve technical problems. One of the examples is the use of chemical demulsifiers to remove emulsified water from petroleum emulsions. To study the role of chemicals in this process, a TLF technique with a dosing system is required to add demulsifiers into already formed thin liquid films stabilized by interfacial layers formed from indigenous surface active molecules. Herein, we present a modified design of the Scheludko-Exerowa cell with a dosing mechanism which allows for addition of desired chemicals to the intervening organic liquid film that is already formed. The stability of the water-in-oil emulsions and the mechanisms of their chemical destabilization were studied by determining the thinning process of intervening thin oil films before and after dosing a controlled amount of demulsifiers into the film. Dosing of a biodegradable polymer demulsifier (EC300) into the intervening oil film converted a stable film formed by asphaltene-in-heptol solutions into an unstable film with lifetimes of less than 20 s. The observed change in the film drainage rate and stability is related to the disruption of asphaltene network formed at the oil-water interface by EC300 demulsifiers. The experiments with the modified TLF cell also revealed the overdosing effect of EC300 demulsifier, forming more stable films at high EC300 concentrations. A comparison of the experimental results between a dosed system and a premixed system confirmed the value of the modification in the current TLF technique to study the stabilization/destabilization processes of water-in-oil emulsions that mimic more closely the real petroleum emulsions. The modified TLF technique allows for a better understanding of the underlying demulsification mechanisms.