Group type characterization of crude oil and bitumen. Part I: Enhanced separation and quantification of saturates, aromatics, resins and asphaltenes (SARA)
Abstract Compositional analysis of crude oils is very important along the entire value chain of the oil industry, from upstream to midstream and downstream operations. An essential step of this analysis is to separate crude oil into fractions of saturate hydrocarbon (saturates) aromatic hydrocarbon (aromatics) resins, and asphaltenes (SARA) Though a number of methods have been developed for SARA separation, traditional methods involve significant drawbacks that include, but are not limited to, inconsistent results among labs and methods, extensive cross contamination, and poor analytical precision. Here, we report on a novel automated multi dimensional high performance liquid chromatography (AMD HPLC) approach to enhance group type characterization of crude oil or bitumen. The AMD HPLC system is fully automated and developed based on a combination of adsorption and partition chromatography. It is equipped with a cyano column and a silica column. Each set of SARA columns is connected in series via multi position valves that allow a given column to be inserted "in" or to be bypassed "out" of the flow path of the mobile phase at pre set times in the process. In practice, a bitumen or oil sample of 0.02 g is dissolved in a solvent mixture of 15% methanol, 15% acetone, and 70% chloroform, and injected into the instrument. The sample is fractionated into the four groups by selective retention through interactions with the solvent mobile phases and the column substrates. The instrument then resets and is ready to start the next run. The entire analysis cycle requires about 60 min per run, including system re conditioning. Based on its wide application at our laboratory, the AMD HPLC is characterized by high efficiency, elimination of cross contamination, and high reproducibility when compared to traditional methods.