publications

2023

1. Use of the UNIFAC model in the calculation of physicochemical properties of ecotoxicants for technological and ecoanalytical purposes

   Vladimir G Povarov , and Ignaty Efimov

   Journal of Mining Institute, 2023
2. Fuel

   UNIFAC residual marine fuels stability prediction from NMR and elemental analysis of SARA components

   Ignaty Efimov, Ksenia I. Smyshlyaeva , Vladimir G. Povarov , and 4 more authors

   Fuel, 2023

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   This paper focuses on the development of theoretical approaches to predict the stability of very low-sulfur residual marine fuel (VLSFO) and is based on molecular weight, CHNS-, SARA-, NMR analysis, and the UNIFAC model. The main issue of using the UNIFAC model is to determine the group composition of marine fuel components in the UNIFAC representation. According to the data obtained, we developed a method for calculating UNIFAC pseudo-components group composition for residual and distillate petroleum products. The hyperparameters used in this model were the asphaltenes’ heat of fusion and melting point. The melting point was successfully estimated using a regression formula that took into account the molecular weight and C/H ratio. The heat of fusion was calculated using the optimization method. The resulting model makes it possible to estimate the influence of the VLSFO component’s parameters on the shape and position of the metastability line in ternary systems. The reliability of the developed model was confirmed by comparing the calculated and experimental data on the example of the VLSFO sedimentation stability diagram in the system of hydrotreated diesel fuel - catalytic cracking light gasoil - visbreaking residue. Based on the developed model it is possible to predict the stability of the residual marine fuel of a given composition. The application of this model is intended to greatly simplify the development of the stable VLSFO composition that meets the requirements of ISO 8217:2017.

2022

1. I&EC

   Comparison of UNIFAC and LSER models for calculating partition coefficients in the hexane–acetonitrile system using middle distillate petroleum products as an example

   Ignaty Efimov, Vladimir G Povarov , and Viacheslav A Rudko

   Industrial & Engineering Chemistry Research, 2022

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   In this work, the possibility of using the two-phase hexane–acetonitrile system in gas chromatography analysis for the effective identification of middle distillate petroleum products containing polar organic compounds based on the example of diesel fractions variable in composition and delayed coking distillates is studied. The partition coefficient was calculated using the multiple internal standards based on petroleum products’ compounds, which are primary representatives of different homologous series. Partition coefficients for 21 individual substances were calculated using this method. In addition, average partition coefficients were calculated for 23 different homologic groups of polyaromatic and heterocyclic compounds. The experimentally determined partition coefficients were compared with the coefficients calculated by group models─UNIFAC and the group version of the linear solvation energy relationship model. In the case of UNIFAC, different sets of parameters of both the classical model and the modified model were used. Based on a comparison of the results obtained, the optimal method for predicting the partition coefficients of petroleum products in the hexane–acetonitrile system was selected.

2. JMSE

   Application of the UNIFAC Model for the Low-Sulfur Residue Marine Fuel Asphaltenes Solubility Calculation

   Vladimir G. Povarov , Ignaty Efimov, Ksenia I. Smyshlyaeva , and 1 more author

   Journal of Marine Science and Engineering, 2022

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   Since 2020, 0.5% limits on the sulfur content of marine fuels have been in effect worldwide. One way to achieve this value is to mix the residual sulfur and distillate low sulfur components. The main problem with this method is the possibility of sedimentation instability of the compounded residual marine fuel due to sedimentation of asphaltenes. In this paper, the application of the UNIFAC group solution model for calculating the solubility of asphaltenes in hydrocarbons is considered. This model makes it possible to represent organic compounds as a set of functional groups (ACH, AC, CH2, CH3), the qualitative and quantitative composition of which determines the thermodynamic properties of the solution. According to the asphaltene composition, average molecular weight (450–2500 mol/L) and group theories of solutions, a method for predicting the sedimentation stability of compounded residual marine fuels was proposed. The effect of the heat of fusion, temperature of fusion, molecular weight, and group composition on the solubility of asphaltenes in marine fuel has been evaluated. The comparison of the model approach with the data obtained experimentally is carried out. The results obtained make it possible to predict the sedimentation stability of the fuel system depending on the structure and composition of asphaltenes.

2021

1. ACS Omega

   Use of partition coefficients in a hexane–acetonitrile system in the GC–MS analysis of polyaromatic hydrocarbons in the example of delayed coking gas oils

   Ignaty Efimov, Vladimir Glebovich Povarov , and Viacheslav A Rudko

   ACS Omega, 2021

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   The partition coefficients’ application in the hexane–acetonitrile system as an additional identification feature of polyaromatic hydrocarbons in the review gas chromatography–mass spectrometry analysis of delayed coking gas oils has been considered. The UNIFAC model was used to calculate the partition coefficients of polycyclic aromatic hydrocarbons. It is shown that methyl derivatives of naphthalene, fluorene, anthracene, and pyrene can be identified with an accuracy up to several methyl groups by the position of the figurative point on the partition coefficient–retention index plane. The experimental values of partition coefficients for naphthalene, anthracene, and pyrene are 0.82, 0.78, and 0.77, respectively. The appearance of one methyl group increases the partition coefficient by 0.15–0.2 on average. A total of 53 polyaromatic hydrocarbons were identified in this way.

2. JMSE

   Influence of Asphaltenes on the Low-Sulphur Residual Marine Fuels’ Stability

   Ksenia I. Smyshlyaeva , Viacheslav A. Rudko , Vladimir G. Povarov , and 5 more authors

   Journal of Marine Science and Engineering, 2021

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   The effects of asphaltenes from two heavy oil residues on the sedimentation stability of residual marine fuels were assessed and compared. As base components of residual marine fuels, the vacuum residue (VacRes) and visbreaking residue (VisRes) were taken. The heptane-insoluble fractions (HI-fractions), including asphaltenes, isolated from vacuum residue and visbreaking residue, were analyzed to determine the elemental composition (XRF) and cluster parameters (XRD). The results of the analysis of the parameters of the asphaltene cluster (HI-fraction) for vacuum residue and visbreaking residue showed that dγ – 6.1 and 5.9 Å, Lc – 26.72 and 20.78 Å, and La – 7.68 and 7.20 Å. The sedimentation stability of residual marine fuel was determined according to the ISO 10307-1-2009 (TSA) method and described using ternary phase diagrams. The ratio of stable compositions to the total number of possible compositions (with a step of 10 wt%) was 65/66 or 98.5% for residual marine fuel comprising a mixture VacRes/ULSD/LCGO (vacuum residue/ultra-low sulphur diesel/light catalytic gas oil). Meanwhile, the ratio of stable compositions to the total number of possible compositions was 38/66 or 57.6% for residual marine fuel comprising a mixture VisRes/ULSD/LCGO (visbreaking residue/ultra-low sulphur diesel/light catalytic gas oil).