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

•Cyclohexyl phenyl sulfide is considered as a model compound in aquathermolysis.•Initial reaction steps that determine the kinetics were examined by ab initio methods.•Reaction with H+ is most favorable for the thiophenyl-sec(tert)-alkyl radicals.•The water involvement process in reactions with radicals became more favorable.

Aquathermolysis is often proposed as a method to reduce the viscosity of heavy oils. In the present work we have investigated the aquathermolysis reaction of cyclohexyl phenyl sulfide in water medium by means of density functional theory. The water molecule was considered as a reagent and as a catalyst. We have shown that ab initio quantum chemistry methods could be applicable for comparative analysis of chemical reaction pathways in aquathermolysis processes. The obtained results could be useful for the systems like tert-alkyl (secondary-alkyl) thiophenyl ethers, which could be formed in heavy oils at harsh conditions. The scheme of different reaction directions with corresponding calculated values of reaction barriers, which are correlated with experimental data, is presented and could be used for comparison with other reaction mechanisms.

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