Initial steps in reactions of aquathermolysis of cyclohexyl phenyl sulfide by means of ab initio calculations

Lysogorskiy, Yury; Aminova, R. M.; Tayurskiı̆, D. A.

doi:10.1016/j.comptc.2016.01.008

Cited by 10 publications

(7 citation statements)

References 32 publications

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“…Cyclohexyl phenyl sulfide is a typical model compound for simulating high-sulfur heavy oil components that are responsible for the cross-linking and high viscosity. A comprehensive ab initio study of different reaction pathways of aquathermolysis of cyclohexyl phenyl sulfide (CPS) also showed that the proton-catalyzed carbocation mechanism is a major route in the aquathermolysis of CPS in the presence of H + ions, which has the lowest energy barrier for the cleavage of the C–S bond . The major final products of the reaction chain, in this case, are 1-methylcyclopenten and thiophenol, which agrees well with the experimental data .…”

Section: Introductionsupporting

confidence: 80%

“…Previously, both the experimental and theoretical studies confirmed that the acid-catalyzed mechanism of heterolytic cleavage of CPS with the formation of methylcyclopentene and thiophenol as main products should be a major route in the aquathermolysis process. In addition, the mass spectral analysis of the reaction products of aquathermolysis of cyclohexyl phenyl sulfide shows that thiophenol is converted in significant amounts to secondary reaction products, such as the products of dimerization and reactions with intermediate cyclohexyl and methylcyclopentyl carbocations .…”

Section: Resultsmentioning

confidence: 92%

“…The major final products of the reaction chain, in this case, are 1-methylcyclopenten and thiophenol, which agrees well with the experimental data . As for other thermal aquathermal processes, such as the homolytic cleavage with formation of radical products and the hydrolysis, their thermodynamic characteristics and energy barriers in the C–S bond cleavage are significantly less favorable . However, it should be noted that the delivery of H + ions in the organic media of heavy oil components, in which the aquathermolysis processes take place, is difficult.…”

Section: Introductionmentioning

confidence: 86%

“… 13 As for other thermal aquathermal processes, such as the homolytic cleavage with formation of radical products and the hydrolysis, their thermodynamic characteristics and energy barriers in the C–S bond cleavage are significantly less favorable. 21 However, it should be noted that the delivery of H + ions in the organic media of heavy oil components, in which the aquathermolysis processes take place, is difficult. The metal-based catalyst seems to be able to catalyze this process and promote its occurrence since some of them have been tested to be effective in improving the level of in situ upgrading in aquathermolysis processes.…”

Section: Introductionmentioning

confidence: 99%

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Theoretical Insights into the Catalytic Effect of Transition-Metal Ions on the Aquathermal Degradation of Sulfur-Containing Heavy Oil: A DFT Study of Cyclohexyl Phenyl Sulfide Cleavage

et al. 2020

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Steam injection is the most widely used technique for effectively reducing the viscosity of heavy oil in heavy oil production, in which in situ upgrading of heavy oil by aquathermolysis plays an important role. Earlier, transition-metal catalysts have been used for improving the efficiency of steam injection by catalytic aquathermolysis and achieving a higher degree of in situ oil upgrading. However, the unclear mechanism of aquathermolysis makes it difficult to choose efficient catalysts for different types of heavy oil. This theoretical study is aimed at deeply understanding the mechanism of in situ upgrading of sulfur-containing heavy oil and its catalysis. For this purpose, cyclohexyl phenyl sulfide (CPS) is selected as a model compound of sulfur-containing oil components, and, for the first time, a catalytic effect of transition metals on the thermochemistry and kinetics of its aquathermolysis is investigated by the density functional theory (DFT) methods with the use of the Becke three-parameter Lee–Yang–Parr (B3LYP), ωB97X-D, and M06-2X functionals. Calculation results show that the hydrolysis of CPS is characterized by fairly high energy barriers in comparison with other possible reaction routes leading to the cleavage of C–S bonds, while the heterolysis of C–S bonds in the presence of protons has a substantially lower kinetic barrier. According to the theoretical analysis, transition-metal ions significantly reduce the kinetic barrier of heterolysis. The Cu 2+ ion outperforms the other investigated metal ions and the hydrogen ion in the calculated rate constant by 5–6 (depending on the metal) and 7 orders of magnitude, respectively. The catalytic activity of the investigated transition-metal ions is arranged in the following sequence, depending on the used DFT functional: Cu 2+ ≫ Co 2+ ≈ Ni 2+ > Fe 2+ . It is theoretically confirmed that transition-metal ions, especially Cu 2+ , can serve as effective catalysts in aquathermolysis reactions. The proposed quantum-chemical approach for studying the catalytic aquathermolysis provides a new supplementary theoretical tool that can be used in the development of catalysts for different chemical transformations of heavy oil components in reservoirs due to hydrothermal treatment.

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Section: Introductionsupporting

confidence: 80%

Section: Resultsmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Theoretical Insights into the Catalytic Effect of Transition-Metal Ions on the Aquathermal Degradation of Sulfur-Containing Heavy Oil: A DFT Study of Cyclohexyl Phenyl Sulfide Cleavage

et al. 2020

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“…It can be inferred that the water somehow participated in the reactions acting as if it is hydrogen donor. Lysogorskiy et al also indicated that the cleavage of C-heteroatom bonds in the presence of water can be an important mechanism for the viscosity reduction of heavy oils [34]. However, at 300 °C, the content of resins and asphaltenes was greatly increased instead of a continuing their reduction, which explains the increase of viscosity at 300 °C (Section 3.…”

Section: Changes In Sara Fractionsmentioning

confidence: 99%