Comparison of column chromatography and solid-phase extraction on virgin and aged bituminous maltene phases

Abstract

Bitumen is a complex mixture consisting of different hydrocarbons, which can be categorised into substance classes called SARA (saturates, aromatics, resins and asphaltenes) fractions. The saturates, aromatics and resins are further referred to as maltenes or maltene phase. To determine the SARA fractions the asphaltenes were separated from the maltenes in a first step. A standard method to further separate the maltenes is column chromatography (CC). Since column chromatography is a time-consuming and solvent-intensive process, an alternative method for separating maltenes using solid-phase extraction (SPE) was investigated. A total of nine bitumen samples of the same type in different ageing states but from different manufacturers were separated with both methods to determine the mass percentages of the fractions for investigating their comparability. The results show that both methods led to different mass percentages of the fractions. However, with the SPE, separating smaller amounts of maltenes is possible while saving a large amount of material, costs, and workload. Linear regression analyses between the colloidal indices with conventional and rheological parameters revealed that the fractions obtained from SPE led to higher coefficients of determination of the linear regression model. The obtained fractions were further structurally compared with FTIR spectroscopy, whereby the spectra of the SPE fractions and the CC fractions did not show any significant differences. The overall consideration of the results concludes that the SPE can replace the CC.