Some Sugar Fatty Ester Ethoxylates as Demulsifiers for Petroleum Sludge

Several ethoxylated sugar fatty ester surfactants were prepared by the reaction of glucose with three fatty acids, namely, adipic, stearic and palmitic acids to produce GA, GS and GP esters. These glucose esters were then ethoxylated by four different molecular weight polyethylene glycols, namely, 400, 1,000, 2,000 and 4,000 mol L-1. The prepared ethoxylated esters (12 compounds) were characterized by IR and H-1-NMR spectroscopy. The surface activity of the prepared compounds was thoroughly studied by measuring the surface tension of different solutions of these compounds at three temperatures, namely 298, 308 and 318 K. From the surface tension-concentration plots of these compounds some surface properties, such as CMC (critical micelle concentration), I(max) (maximum surface excess concentration) and A (min) (area occupied per molecule) were calculated. The surface properties of the prepared surfactants were correlated to their chemical structure. It was found that the CMC decreases when increasing the molecular weight of polyethylene glycols, whereas A (min) increases. Furthermore, the demulsification test was carried out and the results of demulsification efficiency were correlated to the chemical composition of the investigated compounds. Some factors that affect the demulsification efficiency were also considered. The oil phase recovered from the treated sludge was characterized and mixed with fresh crude to improve its API.