Effect of emulsified water on the wax appearance temperature of water-in-waxy-crude-oil emulsions

•A new wax formation mechanism for water-in-waxy-crude-oil emulsions is proposed.•The mechanism relies on the variations in Gibbs free energy upon emulsification.•Emulsified water thermally change and accelerates the crystallization process.•Effect of emulsified water on the wax appearance temperature should be considered.

The article concentrates on the effect of emulsified water on the wax appearance temperatures (WATs) of water-in-waxy-crude-oil emulsions. Water-in-oil (w/o) emulsion samples with various water volume fractions (WVFs) were prepared by mixing a waxy crude oil with deionized water at three different stirring speeds. The WAT of each sample was attained via differential scanning calorimetry and was compared with that of the dehydrated crude. In addition, the effects of the WVF and the mean droplet size on the WAT of the emulsions were theoretically evaluated based on the relationship between the wax solubility in the crude oil and the Gibbs free energy concept. The results indicate a sharp increase in the WAT with the presence of water in the system, regardless of the volume of water. Greater deviations became apparent at higher WVFs and rotational speeds, which resulted in the formation of a larger number of droplets.

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