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 biodiesel fuel synthesis process is implemented in a batch plant by the transesterification of shea (Karite) and palm oils in an ethanol medium under supercritical fluid conditions in the temperature range 623–673 K and an alcohol-to-oil molar ratio range of 30 to 42 at a pressure of 30 MPa for 30 min. Data on the determination of the kinematic viscosity and composition of the resulting products and the feedstock conversion are obtained; and the optimal reaction conditions are found.

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.

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.