Identification of representative compounds for saturate, aromatic, resin, and asphaltene (SARA) fractions using the SARA-HPLC technique

Abstract

Petroleum is a complex mixture comprising a diverse range of hydrocarbons. Due to this complexity and the limited knowledge of their chemical structures, identifying representative compounds for their compositional group analysis remains unexplored. In this work, we identified and introduced standard hydrocarbon compounds with characteristics of petroleum fractions—saturates, aromatics, resins, and asphaltenes (SARA)—using the SARA-HPLC analytical technique. The proposed standard SARA compounds exhibit similar behavior to their respective fractions. The proposed saturate standard is a mixture of 67% n-C₆ and 33% n-C₃₆ (wt%), while the aromatic standard includes 65% nitrobenzene and 35% phenanthrene (wt%). The resin standard is composed of 71% anthrone and 29% 9-anthracenemethanol (wt%), and the asphaltene standard contains 62% salicylic acid and 38% bathophenanthroline (wt%). These compounds are adsorbed exclusively onto their corresponding columns in the SARA-HPLC system without any interaction or affinity with other columns, which is highly favorable for SARA fractionation. These proposed standard compounds align with the characteristics of the actual petroleum mixture SARA fractions, demonstrating their accuracy and reliability as representative standards. Additionally, the proposed SARA standards eliminate the need for time-consuming and laborious calibration procedures and references currently used in the petroleum industry while reducing the repeatability and uncertainty challenges caused by current practices in SARA fraction determination.