Study on the Influence of Furfural on the Analysis of SARA Fractions

Elution chromatography was used to analyze the content of SARA (saturate, aromatic, resin, and asphaltene) fractions in simulated raffinate and extract phases containing furfural (FUL), and the influence mechanism of furfural on the content analysis of SARA in the two phases was explored by molecular simulation. The experimental results show that the analysis of SARA fractions was more affected by the presence of a higher content of furfural in the sample. During the process of sample loading, some chromatographic bands of resins and aromatics significantly shifted downward: some aromatics were eluted earlier when saturates were eluted with n-heptane, and some resins were eluted earlier when aromatics were eluted with toluene. In addition, the molecular simulation results indicate that the ability of the model molecules and FUL to adsorb onto the surface of FCP-Al2O3 followed the order: saturates < aromatics < FUL < resins. Additionally, the interaction strength among the saturate, aromatic, resin model molecules and FUL was ranked as follows: saturates < aromatics < resins. The molecular simulation results reveal the mechanism by which furfural influences the analysis of SARA fractions: unadsorbed furfural promotes the desorption of some aromatics and resins, resulting in the downward movement of the chromatographic bands and affecting the elution effect, thereby affecting the accuracy of SARA fraction analysis data. Furthermore, the improved vacuum distillation method, namely, the vacuum-oven method, not only has good precision (RSD < 1%) and accuracy (recovery: 99.7–100.5%) in the determination of furfural content in simulated raffinate- and extract-phase samples but also has good precision (RSD < 1%) on real raffinate- and extract-phase samples under optimized conditions.