Waxphaltene Determinator Method for Automated Precipitation and Redissolution of Wax and Asphaltene Components

Abstract

The new Waxphaltene Determinator method is based on the on-column precipitation and redissolution separation technique developed at Western Research Institute. Although high-performance liquid chromatography (HPLC) instrumentation and detectors are used, the separation does not involve chromatographic interaction between the material being separated and the stationary phase. It is based on freezing, melting, and solubility. The Waxphaltene Determinator uses methyl ethyl ketone at −24 °C to precipitate waxes and asphaltenes. The precipitated material is redissolved in four steps using a series of three solvents of increasing polarity, at different temperatures: heptane at −24 °C, heptane at 60 °C, toluene at 30 °C, and methylene chloride/methanol (98:2, v/v) at 30 °C. This approach allows for the detection of waxy, polar, and pericondensed aromatic components in minutes.