An Eco-Friendly Ultrasonic-Assisted Method for Efficient Asphaltene Separation from Crude Oil: Optimization and Analytical Evaluation

This study introduces an ultrasonic-assisted method for asphaltene separation from crude oils as a safer, faster, and greener alternative to the conventional ASTM D۶۵۶۰ procedure. Ultrasonic waves enhance mass transfer, accelerating solvent penetration and dispersion without heating, thereby reducing time, solvent use, and safety risks. Method optimization was achieved through the design of experiments, enabling systematic evaluation of factors and identification of robust conditions. In this method, the crude oil was first dispersed in an organic solvent (n-pentane) using ultrasonic waves to obtain a suspended asphaltene. The resulting suspension is then centrifuged, after which the supernatant is decanted and the asphaltenes are collected. The effects of experimental parameters on separation efficiency—defined as the purity of the recovered asphaltenes (%)—were investigated using a fractional factorial design and response surface methodology, to obtain the optimal linear model. Under the optimal condition (۵.۰ mL n-pentane, ۵-minute ultrasonication, and four elutions), the method was applied to various crude oil samples for asphaltene quantification. The recovered asphaltenes were subsequently characterized using Fourier-transform infrared spectroscopy and Iatroscan analysis to determine structural properties and evaluate purity. In the following stage, the remaining supernatant was further fractionated using column chromatography. Biomarkers and polycyclic aromatic hydrocarbons were then analyzed via gas chromatography–mass spectrometry, and the results were compared to those obtained from the conventional standard method using star diagram visualization. The results showed that the optimized method separated asphaltene with a purity of over ۹۷%, demonstrating strong consistency with the outcomes obtained using the standard ASTM procedure. Statistical analysis via the t-test revealed no significant difference between the mean values from the two approaches (t-statistic ≤ t-critical), confirming their equivalence. Moreover, the optimized method offers notable advantages, including simplicity, high precision and accuracy (relative standard deviation < ۱.۵), and improved environmental compatibility.

کلیدواژه ها:

Asphaltene separation ، Ultrasonic Dispersion ، Biomarkers ، PAHs ، Gas chromatography- mass spectrometry ، fractional factorial design ، Response surface methodology ، Environmental friendly methods.