Quantitative Analysis of Sulfur in Diesel by Enzymatic Oxidation, Steady-State Fluorescence, and Linear Regression Analysis

Abstract

International environmental regulations have created the need for sensitive, accurate, and reproducible analytical tools to measure ultralow sulfur concentrations in fuels, such as diesel and gasoline. In this work, a sensitive, accurate, and reproducible analytical methodology to measure ultralow sulfur concentrations in desulfurized diesels (<0.01 ppb) is presented. The spectroscopic technique used here overcomes the lack of selectivity or signal overlapping that is present in other techniques used nowadays. The methodology consists first of an enzymatic partial oxidation of sulfur compounds of diesel, followed by the selective determination of the sulfur content from the emission spectra of the oxidized diesel using simple regression analysis. As a result of the enzymatic oxidation, we report here that the oxidized diesel exhibits different spectroscopic behaviors, where the oxidized organic sulfur compounds present a characteristic emission band at higher wavelengths. This fact is taken in this study for a selective quantification of sulfur from diesel. Our study is focused on 4,6-dimethyldibenzothiophene (DMDBT) as a model and standard compound for predicting the sulfur content in desulfurized diesel. The correlation coefficient (R 2 ) between predicted and real sulfur contents was 0.95.

Prediction of sulfur content in diesel fuel using fluorescence spectroscopy and a hybrid ant colony - Tabu Search algorithm with polynomial bases expansion

“…To implement advanced controlling techniques to the HDS, it is of utmost importance to be able to predict in real-time the sulfur concentration of the desulfurized product. As can be seen in works as [11,[59][60][61], EEM fluorescence spectroscopy can be used as a non-invasive, fast, and sensitive technique to capture information about total sulfur content in diesel fuel. After HDS, most of the oil's sulfur is contained in stable polycyclic aromatic molecules as benzothiophenes and dibenzothiophenes, being the latter the hardest sulfur to remove in diesel oil [62,63].…”

Sulfur and Total Carboxylic Acid Number Determination in Vacuum Gas Oil by Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy

“…Vibration spectroscopic techniques (infrared and near-infrared spectroscopy) with partial least-squares (PLS) chemometric statistical modeling has been attracting researchers for its wide applicability in quantitative measurement. − Recent advances involves the use of Fourier transform infrared spectroscopy (FTIR) with the quantification of carbonyl (−C=O) group of organic acids after dissolution of petroleum oil in a suitable solvent with or without pretreatment of samples. Several published articles in literature suggest the use of mid-IR and NIR techniques for the petroleum products evaluation such as density, octane number of gasoline, and complete diesel properties. ,,− FTIR and NIR spectroscopic methods have been used in the past for the measurement of total acid number and total sulfur content of crude oils and their fractions.…”

Classification of Diesel Fuel Using Two-Dimensional Fluorescence Spectroscopy

“…Conventional hydrodesulfurization (HDS) is a catalytic chemical process used in refineries for efficient elimination of sulfur compounds, particularly for light compounds, such as thiophenes and benzothiophenes . Evolving side by side with the technology for desulfurization is the capability to measure sulfur content in process streams.…”

“…This method shows excellent sensitivity and better limits of detection, up to three orders higher than the ones presented by absorption spectroscopies. Because many sulfur compounds on diesel emit fluorescence, it seems natural to apply the fluorescence principle to develop an optical sensor …”