Separation and Characterization of Petroleum Hydrocarbons and Surfactant in Orimulsion Dispersion Samples

Abstract

Orimulsion is an oil-in-water emulsion into which a nonionic surfactant has been added in order to stabilize the emulsion. Many countries have shown great interest in this new bitumen-based fuel because of its competitive price, guaranteed long-term supply, and no need for major infrastructure changes for use in existing power stations. In view of the increasing importance of Orimulsion as an alternative fuel, it becomes necessary to have a better understanding of its physical properties, chemical composition, and toxicity to aquatic organisms. This paper reports detailed separation and characterization results of petroleum hydrocarbons and surfactant in Orimulsion dispersions. A reliable and effective combined method of using membrane filtration, capillary GC, and HPLC techniques has been developed and applied for separation, characterization, and quantitation of petroleum hydrocarbons and nonionic surfactant in complicated oil-in-water dispersion samples used for fish toxicity tests. The GC analysis results demonstrate that (1) the saturates in Orimulsion are dominantly composed of GC-unresolvable aliphatic hydrocarbons; (2) Orimulsion does not contain BTEX (the collective name of benzene, toluene, ethylbenzene, and the xylene isomers) and lighter alkylbenzenes, and concentrations of alkylated PAHs are low relative to most crudes; (3) the concentrations of biomarker compounds are significantly higher than most oils. Identification of the surfactant in Orimulsion was achieved by (1) narrowing the searching range based on theoretical considerations and analysis and (2) comparing the chromatographic profiles, oligomer distribution patterns, and retention times of oligomer peaks with the known surfactants. The surfactant in Orimulsion was identified as polyethoxylated nonylphenol with oligomers having EO numbers ranging from 8 to 24 (average EO units around 20). The concentration of polyethoxylated nonylphenol in the source Orimulsion was estimated to be around 0.5.