Rapeseed oil transesterification reaction with ethanol under supercritical fluid conditions was performed either in the presence of catalysts or without them. The catalysts were Al2O3 and AlOOH, obtained after Al2O3 hydrothermal processing, and CaO/Al2O3 and CaO/AlOOH, obtained after permeation. The obtained product was measured for dynamic viscosity and density. Based on these data, kinematic viscosity was calculated. Biodiesel fuel was separated via centrifugation to extract more viscous ethyl esters of saturated fatty acids and unreacted triglycerides in order to comply with the standards for biodiesel fuel. Analyses have found that the maximum content of obtained ethyl esters of fatty acids in a reaction product before separation is reached, in the case of using the CaO/AlOOH catalyst, is in the amount of 93.34% by mass; and none of the samples’ kinematic viscosity values comply with the standards for biodiesel fuel. Performing centrifugation allowed us to reduce viscosity and increase biodiesel fuel concentration to reach the EN14214 standard requirements. Also, a significant deterioration of the initial catalysts’ strength after the singular experiment has been observed: Al2O3 by 22.4%, AlOOH by 13.89%, CaO/Al2O3 by 25.13%, and CaO/AlOOH by 17.27%.

This paper presents the results of an experimental study on the phase equilibrium diagram of the binary system “Freon R404A–acetone” at a temperature of T = 356 K. These results are crucial for selecting optimal thermodynamic conditions for the supercritical fluid extraction of acetone from aqueous solutions using R404A freon as an extractant. This process is particularly relevant for addressing wastewater disposal challenges at the Bisphenol-A production facility at PJSC Kazanorgsintez (Russian Federation), which manufactures phenol and acetone. The studied binary mixture exhibits type I–II phase behavior, characterized by the termination of the two-phase “liquid–vapor” equilibrium at critical points corresponding to various temperatures, a continuous critical curve, and a gas-phase region of complete miscibility beyond the binodal. The ability to approach the critical point-where the mixture displays anomalous changes in properties- may significantly enhance the efficiency of the supercritical fluid extraction process compared to systems exhibiting type V phase behavior. At the studied temperature, the critical pressure was determined to be Pkр = 4.14 MPa.

An analysis of the phase behavior of binary systems is presented, including one of the representatives of aromatic alcohols (phenyl ethanol) and two potential extractants intended for use in the supercritical fluid (SCF) state. The study of the phase state of the thermodynamic systems “CO2–benzyl alcohol” and “propane–benzyl alcohol” in the near-critical region of the state has been carried out using a high-pressure optical cell. For the first time, data on phase equilibria of the “propane–benzyl alcohol” system have been obtained. The states of different phases are fixed.

The hydrolysis of rapeseed oil in sub- and supercritical water (T = 573–653 K, p = 30 MPa) has been studied using a batch setup. Unlike traditional hydrolysis, the hydrothermal process involves in situ change of the fatty acid composition as a result of the transformation of linoleic acid to oleic acid, and there is the possibility of selective isolation of the latter with a purity sufficient for its use for technical purposes without special purification. A stepwise mechanism of the hydrothermal process has been proposed on the basis of analysis of transformation products of individual linoleic acid.

The issue of recycling polymers and their waste is quite acute. Basically, polymers are processed and blended by mechanically mixing them in a melt. However, the use of supercritical fluid in the processing and dispersion of polymers and their mixtures has shown its prospects. Previous research has found that polymer mixtures obtained by mixing in solution and then precipitating using supercritical carbon dioxide have increased structural order, and therefore an increased crystallinity degree. In this regard, research has been carried out on the application of the supercritical fluid antisolvent method for the processing of secondary raw materials. It should also be noted that dispersing polymers using the supercritical fluid antisolvent method helps remove impurities and low-molecular-weight thermal degradation products from the polymer. This article presents the results of recycling recycled polycarbonate and polyethylene terephthalate, as well as the possibilities of their joint mixing and dispersion using the supercritical fluid antisolvent method, namely the SEDS method. The kinetics of melting and crystallization of these polymers, as well as their mixtures obtained in the melt and using the SEDS method, were studied. As a result of calorimetric studies, it was established that for all mixtures of waste PET - PC obtained using the SEDS method, the specific heat of fusion exceeds the values for similar mixtures obtained in the melt. SEDS conditions create the best conditions for the crystallization process, up to the crystallization of amorphous polycarbonate and polyethylene terephthalate. The results of a study of the physical and mechanical characteristics of the mixtures under study are presented.

The oxidation of the “water-phenol-acetone” system, simulating the organic component of the concentrated water runoff from the Bisphenol-A plant of PJSC Kazanorgsintez, was experimentally studied in the temperature range of 523÷873 K, pressure 25 MPa, duration 2÷4 min in continuous mode. Air oxygen taken with excess coefficients equal to 10÷30 was used as an oxidizing agent. The composition of the oxidation reaction product, the indicator of chemical oxygen demand, the pH of the initial sample and reaction products, and the conversion were determined. A decrease in the initial organic compounds in the model runoff has been established.

The phase behavior of binary systems containing organic components (phenol and acetone) and potential extractants (carbon dioxide and propane–butane mixture), which were proposed to be used in the supercritical state to treat the industrial wastewater from PAO Kazanorgsintez, is analyzed. The phase behavior of the CO2–acetone thermodynamic system in the near-critical region (313 K) is studied using a high-pressure optical cell. In this binary system, various phase states are detected, including areas of critical opalescence and complete miscibility. Supercritical fluid extraction (SFE) is investigated in treating a model aqueous solution of phenol and acetone with the concentration corresponding to industrial wastewater.

The isobaric heat capacities of acetone and its binary aqueous solutions were measured using a heat capacity meter (IT-s-400). The measurements were performed at temperatures from 323.15 to 453.15 K and pressures below 19.6 MPa for acetone and at temperatures from 348.15 to 473.15 K and the same pressures for its solutions, at concentrations of 2.5, 3.5, and 5 wt

This paper reports new results from studies of the isobaric heat capacities of OMEGA-3 “950” fish oil provided by SOLGAR INC (USA) at high temperatures and high pressures. The measurements were carried out on a differential scanning calorimeter (ITs-400) with an automatic data acquisition system in the temperature range from 298.15 to 473.15 K and at pressures from 0.098 to 39.2 MPa. The coverage factor for the 95% confidence level for a two-way coverage interval is assumed to be 2. The expanded measurement uncertainty of heat capacity is estimated to be 2.4%, pressure is estimated to be 0.05% and temperature is estimated to be 15 mK. Experimental data on the fish oil isobaric heat capacity as a function of temperature and pressure are approximated by the correlation equation proposed in the work. At atmospheric pressure, the deviations between those calculated by the correlation equation and the current measured data on isobaric heat capacity are within the range of average absolute deviations (AAD) = 0.22% (standard deviation St. Dev = 0.28% and maximum deviation Max. Dev = 0.39%). Additionally, a comparison was made of the state parameters obtained during the experiment and the literature data at the studied parameters.

С использованием оптической ячейки высокого давления в интервале температур 403-443 К и давлений 5,3-24,5 МПа исследовано фазовое равновесие системы сера-пропан/бутан и установлен V-й тип фазового поведения. Растворимость серы в сверхкритической пропан-бутановой смеси оценена на основе характеристик паровой ветви фазового равновесия системы сера-пропан/бутан и описана с использованием уравнения состояния Пенга-Робинсона в сочетании с правилом комбинирования Мухопадхъяи и Рао. Установлено, что пропан-бутановая смесь в сверхкритическом флюидном состоянии, наряду с хорошими экстракционными свойствами, позволяет осуществить процесс обессеривания товарных углеводоро­дов. Например, снижение давления с 25 до 7 МПа позволяет уменьшить содержание серы в продукте на изотерме 413 К в два раза, а на изотерме 443 К - в 10 раз. The results of an experimental study of the phase equilibrium of the sulfur-propane/butane system carried out in the temperature range 403-443 K and pressure range 5.3-24.5 MРa using a high-pressure optical cell are presented. The V type of phase behavior is established. The solubility of sulfur in a supercritical propane-butane mixture under the above mentioned thermodynamic conditions is estimated based on the characteristics of the vapor branch of the phase equilibrium of the sulfur-propane/butane system and described using the Рeng-Robinson equation of state in combination with the rule of combining Mukhopadhyay and Rao. It has been established that the propane-butane mixture in the SCF state, along with good extraction properties, allows for the desulfurization of commercial hydrocarbons. Reducing the pressure from 25 to 7 MРa makes it possible to reduce the sulfur content at the 413 K isotherm by two times, at the 443 K isotherm by 10 times.

Type II phase behavior is determined in the study of the phase equilibrium of the decalin–carbon dioxide binary system in the 313 and 333 K isotherms in the pressure range of 2–15 MPa using a high-pressure optical cell. The experimental results are described using the Peng–Robinson equation of state.

Представлен анализ фазового поведения бинарных систем, включающих органические компоненты (фенол и ацетон) и потенциальные экстрагенты (диоксид углерода и пропан-бутановая смесь), которые предполагаются использовать в сверхкритическом состоянии для очистки промышленного водного стока ПАО «Казаньоргсинтез». Проведено исследование фазового поведения термодинамической системы «CO2—ацетон» в околокритической области состояния (313 K) с использованием оптической ячейки высокого давления. Зафиксированы различные фазовые состояния, включая области критической опалесценции и безграничного смешивания для этой бинарной системы. Приведены результаты использования метода сверхкритической флюидной экстракции для очистки модельного водного раствора фенола и ацетона с концентрацией, соответствующей промышленному стоку. An analysis of the phase behavior of binary systems that include organic components (phenol and acetone) and potential extractants (carbon dioxide and propane-butane mixture), which are supposed to be used in the supercritical state to treat the industrialwastewater runoff of «Êazanorgsintez» PJSC, is presented. The study of the phase behavior of the thermodynamic system «CO2—acetone» in the near-critical region of the state (313 K) was carried out using a high-pressure optical cell. Various phase states are fixed, including areas of critical opalescence and boundless miscibility for this binary system. The results of using the supercritical fluid extraction method for purification of a model aqueous solution of phenol and acetone with concentrations corresponding to industrial waste are presented.

The experimental solubility data of polyvinyl chloride (PVC) and high-pressure polyethylene (HPPE) in organic solvents (toluene, dichloromethane, and chloroform) at temperatures ranging from 308.15 to 373.15 K at atmospheric pressure are reported in the present paper. The solubility of the polymers (PVC and HPPE) in organic solvents (toluene, dichloromethane, and chloroform) was studied at temperatures between 298 and 373 K. The supercritical SEDS dispersion of PVC and HPPE polymer blends at pressures between 8.0 and 25 MPa and at temperatures from 313 to 333 K are reported in the present work. The kinetics of crystallization and phase transformation in polymer blends obtained by blending in a melt, and using the supercritical SEDS method, have been studied. The effect of the HPPE/PVC ratio on the thermal and mechanical characteristics of the polymer blends has been studied. For all studied polymer blends and pure polymers obtained using the SEDS method, the heat of fusion ΔfusH exceeds the values obtained by blending in the melt by 1.5 to 5) times. The heat of fusion of the obtained polymer blends is higher than the additive value; therefore, the degree of crystallinity is higher, and this effect persists after heat treatment. The relative elongation decreases for all polymer blends, but their tensile strength increases significantly.

The paper presents the results of impregnation of dried common pine (Pinus sylvestris) specimens with propiconazole using a supercritical fluid CO2 impregnation process carried out at a temperature of 338 K in the pressure range of 10–30 MPa. Within the framework of the formation of a database on the properties of the impregnation material required for the stages of modeling, optimization, and scaling of the impregnation process, an investigation was conducted of some thermodynamic properties of a propiconazole–carbon dioxide mixture in the supercritical fluid region of the state. The isomeric composition of propiconazole has been investigated, and it has been established that it represents a mixture of two isomers. The methods of thermogravimetric analysis and differential scanning calorimetry have been used to study the thermal characteristics of propiconazole. The paper presents the results of an experimental investigation of propiconazole solubility in supercritical carbon dioxide on the isotherms T = 338, 358, and 378 K in the pressure range of 10–30 MPa. The experimental data on solubility have been described using the Peng–Robinson equation of state and providing the pressure of saturated propiconazole vapors with the status of the second adjustable parameter in the calculation algorithm. The paper presents the results of an experimental investigation of the isobaric heat capacity of propiconazole at atmospheric pressure in the temperature interval of 313–573 K and of propiconazole–carbon dioxide mixture in the timperature interval of 313–473 K and the pressure range of 0.098–25.0 MPa.

This work reports supercritical water oxidation (SCWO) of organic pollutants in industrial wastewater in the absence and presence of catalysts. To increase the efficiency of the oxidation process, the SCWO of organic compounds in industrial wastewater was performed in the presence of various iron- and manganese-containing heterogeneous catalysts (Fe-Ac, Fe-OH, and Mn-Al). The catalytic and non-catalytic SCWO of organic compounds in wastewater from PJSC “Nizhnekamskneftekhim”, generated from the epoxidation of propylene with ethylbenzene hydroperoxide in the process of producing propylene oxide and styrene (PO/SM), was performed. The effect of operational parameters (temperature, pressure, residence time, type of catalysts, oxygen excess ratio, etc.) on the efficiency of the process of oxidation of organic compounds in the wastewater was studied. SCWO was studied in a flow reactor with induction heating under different temperatures (between 673.15 and 873.15 K) and at a pressure of 22.5 MPa. The reaction time ranged from 1.8 to 4.83 min. Compressed air was used as an oxidizing agent (oxidant) with an oxidant ratio of two to four. A pseudo-first-order model expressed the kinetics of the SCWO processes, and the rate constants were evaluated. In the present work, in order to optimize the operation parameters of the SCWO process, we used the thermodynamic properties of near- and supercritical water by taking into account the asymmetric behavior of the liquid–vapor coexistence curve.

The study performed on the supercritical aqueous oxidation of organic compounds in the water runoff of Nizhnekamskneftekhim PJSC, which was formed at the stage of epoxidation of propylene with ethylbenzene hydroperoxide during the joint production of propylene and styrene oxide, as well as run-off at PJSC "Kazanorginsez", when obtaining phenol and acetone from "Bisphenol-A" plant. The article studies a continuous operation mode on a flow reactor with induction heating (the drain from PJSC "Nizhnekamneftekhim") and periodic on coming from PJSC "Kazanorginsez". It was identified that close to complete oxidation in the presence of heterogeneous catalysts was achieved in a continuous mode at a temperature of 823 K and an excess of oxygen equal to 4.

This paper presents a new experimental VLE property data in the binary system of carbon dioxide – n-tetradecane at three selected isotherms of 313.15 K, 333.15 K, and 353.15 K in the pressure range from (3.8 to 19.0) MPa. The measurements were made using a high-temperature and high-pressure optical cell. The standard absolute u and relativeur uncertainties of temperature, pressure, concentration measurements are: u(T)=7.5 mK; ur(P)=0.00025; ur(x)=0.015; and ur(y)=0.015. The measured VLE data were used to determine the criticalPC-TC curve data. Based on the derived values of the critical parameters of CO2+n-tetradecane mixture the value (-67.58 MPa) of the Krichevskii parameter has been determined. The predictive capabilities of the perturbed chain-statistical associating fluid theory (PC-SAFT), the critical point-based modification of PC-SAFT (CP-PC-SAFT), and the Enhanced-Predictive-Peng-Robinson-78 (E-PPR78) models were examined.

The results of an experimental study of the phase equilibrium (VLE) properties of CO2 in organic mixture of (0.564 toluene/0.436 chloroform) at three selected isotherms of 313.15 K, 333.15 K, and 353.15 K in the pressure range from (0.95 to 12.27) MPa, involved in the supercritical SEDS dispersion process of immiscible polymer blending, are reported in the present work. The compatibility of immiscible linear high-pressure polyethylene (HPPE)/polycarbonate (PC) polymer blends with organic toluene + chloroform solvent in the presence of supercritical carbon dioxide (SC CO2) was studied. The PC and LHPPE polymers blending have been carried out in the pressure range from (8 to 25) MPa at temperatures between (313.15 and 353.15) K using the supercritical SEDS method. The kinetics of crystallization and phase transformation in polymer blends obtained by the melt blending (mixed in the molten state) and the supercritical SEDS methods have been studied using DSC technique. The thermodynamic characteristics such as (temperature, $$t_{{{\text{fus}}}}$$ , and enthalpy of fusion, $$\Delta_{{{\text{fus}}}} H$$ ) of the produced LHPPE/PC polymer blends are presented. The influence of the supercritical SEDS dispersion process parameters on the heat of fusion of the obtained LHPPE/PC polymer blends has been studied. The compatibility of LHPPE/PC blends was confirmed by studying the DSC melting-crystallization curve properties and investigating the morphology. The morphology of the LHPPE/PC polymer blends was examined using a scanning electron microscope (SEM) and the particle sizes depending on the operating temperature and pressure were studied.

Представлены результаты сравнительного анализа показателей ключевых факторов механизма увеличения нефтеотдачи пластов с использованием газов в сверхкритическом флюидном состоянии, применительно к диоксиду углерода и пропану (пропан/бутановым смесям). Вышеотмеченные факторы, как предмет рассмотрения, включают: растворяющую способность сжатых газов по отношению к нефти и ее компонентам; фазовое поведение бинарных систем, включающих обозначенные вытесняющие агенты и углеводороды нефти; критические параметры бинарных систем I–II типов фазового поведения; сжимаемость диоксида углерода и пропана в условиях осуществления процесса вытеснения нефти в рамках третичной нефтедобычи; вязкость сред, участвующих в обсуждаемом процессе и наконец, набухание нефти в результате ее насыщения газом. Приведены результаты экспериментальной реализации процесса экстракционного извлечения нефти, реализованного в сверхкритических флюидных условиях с использованием в качестве экстрагента диоксида углерода в одном случае и пропана в другом. Установлено, что пропан и пропан/бутановые смеси в сопоставлении с СО 2 имеют трех и более кратное превосходство в растворяющей способности по отношению к компонентам нефти в условиях процесса вытеснения; чаще формируют с компонентами нефти предпочтительные для процесса ее извлечения системы с I–II типом фазового поведения; мощность компрессора, затрачиваемая на сжатие диоксида углерода и метана, почти в три и более раза, соответственно, превосходит ту, что необходима при сжатии пропана и, наконец, пропан в условиях вытеснения нефти обладает существенно меньшей вязкостью, что в совокупности указывает на предпочтительность пропана и пропан/бутановых смесей в процессе вытеснения нефти в рамках процесса третичной нефтедобычи.