Sulfur Speciation of Crude Oils by Partial Least Squares Regression Modeling of Their Infrared Spectra

Abstract

Research has been carried out to determine the feasibility of partial least-squares regression (PLS) modeling of infrared (IR) spectra of crude oils as a tool for fast sulfur speciation. The study is a continuation of a previously developed method to predict long and short residue properties of crude oils from IR and near-infrared (NIR) spectra. Retention data of two-dimensional gas chromatography (GC × GC) of 47 crude oil samples have been used as input for modeling the corresponding IR spectra. A total of 10 different PLS prediction models have been built: 1 for the total sulfur content and 9 for the sulfur compound classes (1) sulfides, thiols, disulfides, and thiophenes, (2) aryl-sulfides, (3) benzothiophenes, (4) naphthenic-benzothiophenes, (5) dibenzothiophenes, (6) naphthenic-dibenzothiophenes, (7) benzo-naphthothiophenes, (8) naphthenic-benzo-naphthothiophenes, and (9) dinaphthothiophenes. Research was carried out on a set of 47 IR spectra of which 28 were selected for calibration by means of a principal component analysis. The remaining 19 spectra were used as a test set to validate the PLS regression models. The results confirm the conclusion from previous studies that PLS modeling of IR spectra to predict the total sulfur concentration of a crude oil is a valuable alternative for the commonly applied physicochemical ASTM method D2622. Besides, the concentration of dibenzothiophenes and three different benzothiophene classes can be predicted with reasonable accuracy. The corresponding models offer a valuable tool for quick on-site screening on these compounds, which are potentially harmful for production plants. The models for the remaining sulfur compound classes are insufficiently accurate to be used as a method for detailed sulfur speciation of crude oils.

Unimolecular Pyrolysis Mechanism of Thiophene and Furan: An Ab Initio Comparative Study

“…Emission of sulfur could also lead to severe environmental problems, including acid rain, haze weather, , and respiratory and cardiovascular diseases . To minimize the negative effects, countries worldwide are adopting more rigorous regulations to achieve zero-sulfur emission. − …”

DFT Research on Benzothiophene Pyrolysis Reaction Mechanism

“…Sulfur will cause emission of SO x gases, which lead to serious air pollution. To minimize the negative effects, countries worldwide are adopting stricter regulations to reduce sulfur emissions by enforcing ultralow sulfur concentration in fuels. − …”

Roles of surface chemistry and structural defects of activated carbons in the oxidative desulfurization of benzothiophenes

“…For example, in the USA, the acceptable level of sulfur in diesel was reduced to 500 ppm in 1995 by the Clean Air Act amendments; it was then reduced to 350 ppm in 2000; 50 ppm in 2005; and finally 15 ppm since 2006 [1][2][3][4][5][6][7][8][9]. Similarly, in the European Union, maximum sulfur in the market diesel was reduced to 10 ppm since 2008 [10]. To address these strict regulatory requirements, several technologies have been developed for deep desulfurization of oil refinery fuels, which can be generally classified [11] into hydrodesulfurization (HDS) [2,[12][13][14], oxidative desulfurization (ODS) [15][16][17][18][19][20][21][22][23], biodesulfurization [24][25][26][27][28], adsorption desulfurization (ADS) [6,[29][30][31][32][33][34][35][36][37][38][39][40][41], and extractive desulfurization using organic solvent, ionic liquids [42,43]…”