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Determination of the total content of aromatic hydrocarbons by Fourier-transform IR spectroscopy in the products of diesel hydrofining

A comparative analysis of current methods for determination of aromatic hydrocarbons in the components of diesel fuel revealed that IR spectrometry appeared to be the most optimal method for operational control of the content of aromatic hydrocarbons in medium distillate products of the hydrogenation process. We developed a procedure for quantitative determination of aromatic hydrocarbons in the components of diesel fuel using IR Fourier spectroscopy. The analysis of absorption spectra of the components of diesel fuel revealed that the optical density of the stretching vibration band of the aromatic ring is proportional to the quantitative content of aromatic hydrocarbons (AHC) in the components of diesel fuel. One of the components for compounding diesel fuels obtained at JSC «ANKhK» during hydrotreating of raw materials under severe conditions (30 MPa, 380 – 400°C) was selected as an object of the study. Conditions of IR spectrometric analysis (wave number — 1606.5 cm–1, cell material — NaCl, absorbing layer thickness — 0.1 cm) were specified after recording of the absorption spectrum of the purified component. To construct a calibration dependence the total AHC content and corresponding optical density of the sample were determined by the methods of HPLC and IR spectrometry, respectively. The samples of hydrogenate under study (taken at different timepoints) contained 1 – 8% AHC on average depending on the parameters of a continuously operating unit. The characteristics of the proposed procedure were evaluated in accordance with the requirements of RMG 76–2014. The correctness of the obtained results of AHC determination was confirmed in comparison with the data of independent (tetrimetric) analysis. The use of the developed method in analysis of other components of diesel fuel, requires additional studies to determine the interfering substances and assess their impact on the accuracy of AHC determination.