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

© 2020 American Chemical Society 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 Cu2+ 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: Cu2+ ≫ Co2+ ≈ Ni2+ > Fe2+. It is theoretically confirmed that transition-metal ions, especially Cu2+, 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

Послеоперационная диарея как осложнение хирургического лечения детей с нейрогенными опухолями забрюшинной локализации

BACKGROUND: Diarrhea as a result of skeletonization of the superior mesenteric artery (SMA) and celiac trunk after retroperitoneal lymph node dissection is a common complication in adult patients with malignant neoplasms of the pancreas, colon, and retroperitoneal tumors. The reports mentioning this complication in the treatment of neurogenic tumors in children are scarce. AIM: This study aims to improve the surgical treatment results of locally advanced retroperitoneal neuroblastomas by studying which factors influence the development of prolonged postoperative diarrhea. MATERIALS AND METHODS: An analysis of the treatment results in patients with locally advanced neurogenic retroperitoneal neoplasms at the Dmitry Rogachev national medical research center of pediatric hematology, oncology, and immunology from 2018 to 2020 was conducted. All patients from this cohort underwent SMA and celiac trunk dissection. RESULTS: During this period, surgeries with dissection of the SMA and celiac trunk were performed in 29 patients. In four (13%) cases, prolonged diarrhea was noted (median duration, 136.5 days with a frequency of up to 13 times a day). Assessment of the dependence of diarrhea frequency on complete dissection or preservation of the tumor component in the SMA and celiac trunk showed no significant differences. CONCLUSIONS: The complete removal of a neurogenic tumor improves prognosis in patients with a locally advanced form of the disease, but it is associated with the risk of long-term intractable complications. This study does not confirm the opinion that preservation of the tumor component on the SMA prevents its denervation and postoperative diarrhea.Введение. Диарея в результате скелетизации верхней брыжеечной артерии и чревного ствола при забрюшинной лимфаденэктомии распространенное осложнение у взрослых пациентов, страдающих новообразованиями поджелудочной железы, ободочной кишки и внеорганными забрюшинными опухолями. Диарея может осложнять течение послеоперационного периода у детей с нейрогенными опухолями, однако информация о данном состоянии в литературе встречается редко. Цель улучшение результатов хирургического лечения при местнораспространенных нейробластомах забрюшинной локализации за счет изучения факторов, влияющих на развитие длительной послеоперационной диареи. Материалы и методы. Проведен анализ результатов лечения пациентов с местнораспространенными нейрогенными опухолями забрюшинного пространства в НМИЦ ДГОИ им. Д. Рогачева с 2018 по 2020 гг. Всем пациентам из данной выборки в ходе хирургического вмешательства выполнялась скелетизация верхней брыжеечной артерии и чревного ствола. Результаты. В исследование включены 29 пациентов. В 4 (13 %) случаях отмечено развитие длительной диареи (медиана длительности 136,5 суток с частотой до 13 раз в день). При оценке зависимости частоты диареи от полной скелетизации или сохранения компонента опухоли на верхней брыжеечной артерии и чревном стволе значимых различий не получено. Выводы. Полное удаление нейрогенной опухоли, улучшающее прогноз пациента при местнораспространенной форме заболевания, связано с риском длительных некупируемых осложнений. В данном исследовании не удалось подтвердить тезис о превентивной роли сохранения мягкотканного компонента на верхней брыжеечной артерии с целью предотвращения послеоперационной диареи