Size exclusion chromatography of aromatic compounds in high-boiling petroleum samples

A B S T R A C T Knowledge of aromatic compounds in petroleum samples is of paramount interest from processing and environmental viewpoints. Considering the complexity of such samples, a selective analytical strategy viz. aromatic specific size exclusion chromatographic methodology using amino-bonded silica phase, was adopted to obtain the average molecular weights of distilled cuts, residue and the corresponding crude oil. The method was found to be suitable from middle distillates up to the residue. It was found that the increase in boiling temperature of distilled cuts was reflected in an increase in high molecular weight aromatic species. The increase in the molecular weight of aromatic species is linked to the increase in alkylation as verified by studying the elution pattern of alkylated aromatic compounds. The accuracy of the molecular weights obtained from the size exclusion chromatographic method depends on the elution profile of aromatic species in petroleum samples. It was found that the size and shape of the parent aromatic compounds negatively influence the size exclusion elution profile. However, such influence can be assumed to be negligible as all the aromatic species of each distilled cut, residue, and crude oil eluted in the permeation zone of the chromatogram. This method has the potential to be used in the second dimension of a 2D-LC method where the aromatic compounds are separated based on the size (or alkylation). The first dimension will separate compounds based on the number of aromatic rings, thereby eliminating the interference of parent aromatic compounds of different sizes in the total elution profile. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study employed an aromatic specific size exclusion chromatographic method to analyze aromatic compounds in petroleum samples. The findings suggest that an increase in alkylation is linked to an increase in the molecular weight of aromatic species, as observed in the elution pattern of alkylated aromatic compounds. The size exclusion elution profile of aromatic species in petroleum samples is influenced by the size and shape of the parent aromatic compounds, but all aromatic species eluted in the permeation zone of the chromatogram, indicating negligible interference.