Abstract:

Surrogate and Deepwater Horizon (DWH) crude oils were subjected to a sulfur separation to yield fractions enriched in sulfide and thiophene functionalities. The resultant fractions (DWH sulfides, DWH thiophenes, surrogate sulfides, surrogate thiophenes) were subjected to 24h solar irradiation in a laboratory and their oil- and water-soluble photoproducts were isolated. The parent oil sulfur fractions (before irradiation) as well as the oil- and water-soluble photoproducts were analyzed by FT-ICR MS for molecular analysis.

Suggested Citation:

Niles, Sydney F., Martha L. Chacon-Patino, and Ryan P. Rodgers. 2021. Molecular composition of photooxidation products derived from sulfur-containing compounds isolated from petroleum samples. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/AXZAV70S

Purpose:

Though sulfur content is very low (<0.5%) in light sweet crude oils (such as surrogate and MC252), high concentrations of SOx species have been observed in the water-soluble fraction produced from irradiation of MC252. Furthermore, sulfur-containing polyaromatic hydrocarbons from crude oil have been demonstrated to photooxidize and become water soluble, however the role of sulfur-functionality in the formation of photogenerated water-solubles has not been extensively studied. Therefore, we analyze the oil- and water-soluble photoproducts from sulfur fractions from DWH and surrogate oils, to probe the role of sulfur functionality in petroleum photochemistry.

Data Parameters and Units:

Dataset consists of several Excel files. The name of each file consists of the analytical technique (e.g. Neg ESI, Pos ESI, PosAPPI), type of material (DWH or surrogate), time of irradiation, oil or water soluble, parent or product. Legend Number of Peaks = Number of Peaks on Full Spectrum with signal magnitude greater than six times the baseline root-mean square noise % R. A. = Percent Relative Abundance DBE = double bond equivalents - number of aromatic rings plus double bonds to carbon % R. A.(No Hits Discarded) = Percent Relative Abundance with Non Classified Peaks Removed A. M. W. average = Relative abundance weighted average molecular weight A.W. average C# = relative abundance weighted average carbon number A.W. average DBE = average number of double bond equivalents A.W. average H/C = relative abundance weighted average hydrogen-to-carbon ratio A.W. average O/C = relative abundance weighted average oxygen-to-carbon ratio A.W. average N/C = relative abundance weighted average nitrogen-to-carbon ratio Sum R. A. = Sum of Relative Abundance for all mass spectral peaks RMS Error = Root Mean Square Error PosESI = Positive Electrospray Ionization NegESI = Negative ion electrospray ionization APPI = atmospheric pressure photoionization}

Methods:

MC252 and surrogate crude oil samples were subjected to a previously-published sulfur separation (Lobodin et al. 2015) to yield fractions enriched in thiophene and sulfide functionalities. The fractions were irradiated in a solar simulator (ATLAS Suntest CPS+) for 24 hours at 25 Celsius. After irradiation, the water-soluble portion was collected by pipet and the oil layer was removed, dried under nitrogen gas and stored in the dark to prevent further oxidation. Water-soluble samples were subjected to PPL (priority pollutant) solid phase extraction to yield methanol fractions for mass spectral analysis (Dittmar et al. 2008). FT-ICR MS analysis was performed on oil-soluble (+ESI, -ESI, +APPI) and water-soluble (-ESI) samples before and after irradiation.

Instruments:

9.4 Tesla FT-ICR MS was used for mass analysis.

Provenance and Historical References:

Dittmar, Thorsten, Boris Koch, Norbert Hertkorn, Gerhard Kattner. 2008. A simple and efficient method for the solid‐phase extraction of dissolved organic matter (SPE‐DOM) from seawater. Limnology and Oceanography Methods 6(6): 230-235. DOI:10.4319/lom.2008.6.230 Lobodin Vladislav V., Winston K. Robbins, Jie Lu, and Ryan P. Rodgers. 2015. Separation and characterization of reactive and non-reactive sulfur in petroleum and its fractions. Energy Fuels 29(10):6177–6186. DOI: 10.1021/acs.energyfuels.5b00780

Individual Files: