Qualitative and Quantitative Evaluation of Sulfur-Containing Compound Types in Heavy Crude Oil and Its Fractions

Alessandro Vetere,Daniel Pröfrock,Wolfgang Schrader

doi:10.1021/acs.energyfuels.1c00491

Abstract

Detailed molecular analysis of complex mixtures such as crude oil and its fractions has been successfully covered by a number of groups during the past two decades. On the other side, the most glaring need is some type of method that allows quantitative analysis of a single class, compound species, or even individual compounds. Here, the problem is being complicated by the complexity of the sample and the need for individual response factors necessary for the analysis of single compounds in almost all analytical methods. This can be circumvented by using a method with uniform response like inductively coupled plasma-mass spectrometry. Sulfur is one of the most important heteroelements present in crude oil and its products due to stringent regulations. Quantification of sulfur by means of mass spectrometry has always been a challenging task. Here, we present the combination of a sulfur-selective chromatographic separation of crude oil and its fractions on a Pd-coated stationary phase with two-dimensional detection. Qualitative analysis by ultrahigh-resolution Orbitrap mass spectrometry allows a detailed understanding of individual compositions after chromatographic separation, while the quantitative data from inductively coupled plasma tandem mass spectrometry details the quantities of each part of the chromatogram. The combination of the results from both methods allows assigning three different types of sulfur species and their quantitative determination in extremely complex heavy crude oil fractions.

Highlights

Quantification of compounds is routinely done in numerous labs throughout the world on a daily basis
We recently introduced a new approach that profits from the combination of HPLC separation with qualitative Fourier transform mass spectrometry (FTMS) as well as with quantitative inductively coupled plasma tandem mass spectrometry (ICP-mass spectrometric detection (MS)/MS) for the quantification of three different groups of sulfur-containing compounds within a light crude oil.[1]
The results presented here show the first application of an online HPLC-FTMS analysis for the detailed analysis of sulfur species in heavy crude oil and its fractions

Summary

INTRODUCTION

Quantification of compounds is routinely done in numerous labs throughout the world on a daily basis. This problem has recently been tackled by employing a triple quadrupole system where the second analyzer stage is a collision/reaction cell with an octopole ion guide rather than a conventional quadrupole, as shown in Figure S3 in the Supporting Information.[37−39] We previously introduced this approach by means of a proof-of-principle study using a relatively light full crude oil.[1] Here, we investigate the possibilities and the limits of the method by using it for a very heavy crude oil and its SARA (saturates, aromatics, resins, and asphaltenes) fractions.

EXPERIMENTAL SECTION

RESULTS AND DISCUSSION

CONCLUSIONS

■ REFERENCES