Demulsification of water-in-oil emulsions using ionic liquids: Effects of counterion and water type

Abstract

Demulsification of crude oil emulsions is of significant interest in the petroleum industry. This study aims to investigate the effect of ionic liquid (IL) counterions and water type (distilled water (DW) and laboratory formulated seawater (SW)) on the demulsification of water-in-oil (W/O) emulsions. Three ILs belonging to the phosphonium compounds with different counterions were used. These ILs were designated as THPC (contains chloride ion), THPD (contains decanoate ion), and THPDc (contains dicyanamide ion). Emulsions were formed using DW and SW while demulsification tests were conducted at temperatures of 60 °C and 80 °C. According to the demulsification outcomes at 60 °C, THPC was the best candidate for breaking W/O emulsions produced from DW while THPD and THPDc were excellent candidates for destabilizing emulsions produced from SW. The optimal percentage demulsification efficiency (DE) achieved for emulsions from DW was 99% with just 1000 ppm THPC while 1000 ppm THPD and 700 ppm THPDc are adequate to bring about excellent water separation in emulsions formulated from SW. THPD and THPDc also attained the maximum percentage DE of 99%.On the other hand, at elevated temperature (80 °C), THPC, THPD, and THPDc attained nearly the same water separation in the W/O emulsions produced from DW and SW with a demulsifying capacity of 99%. However, demulsification activities at this temperature (80 °C) in the W/O emulsions formed using SW were very fast as compared to what was observed in the case of emulsions obtained from DW. Thus, salts present in SW have propensities to accelerate the destabilization of crude oil emulsions. Viscosity and elastic modulus time sweep measurements reveal that the tested ILs can collapse the natural emulsifiers (asphaltenes and resins) existing at the water-oil interfaces.