On the influence of sorbent-filler on the temperature of thermal destruction of composite sorbent-active materials based on zeolite and fluorine derivatives of ethylene
Authors:   Roskhimzashchita, Ferapontova Lyudmila L. , Ferapontov Yury А. ,   Roskhimzashchita, Sergunin Alexander S. ,   Roskhimzashchita, Posternak Nikolai V. ,   Roskhimzashchita, Zakharov Innokentiy V. ,   Tekhnodinamika
Published: November 2024

The work is a continuation of research on the study of the physico-chemical properties of composite sorption–active materials (CSAM) based on polymers of fluorinated ethylene derivatives (fluoroplastics) and various adsorbent fillers and is aimed at identifying patterns of influence of the amount of adsorbent filler in CSAM on the temperature of their thermal destruction in order to find optimal parameters of thermal regeneration. Based on studies using thermogravimetric and differential thermal analysis, the relationship has been established between the temperature of thermal degradation of composite sorption-active materials based on ethylene fluorinated polymers and the content of zeolite NaX in them. During the experiments, it was found that at a temperature of 112,7 ± 1,5 0C, the process of desorption of water vapor from the CSAM begins, passing through a maximum at 172,8 ± 1.2 0C and ending at 305,8± 1,9 0C. The decrease in the mass of the studied CSAM samples was 26,0± 0.2%, which confirms the almost complete desorption of water from the studied samples under experimental conditions. To confirm this conclusion, the analysis of substances released in the temperature range of 90 ÷ 310 0C was carried out by gas chromatography. Only water molecules and a small amount of dimethyl ketone, which was used as a solvent at the synthesis stage, were recorded in the sample. The presence of only one endothermic effect on the DTA curves in the temperature range from 105 0C to 320 0C indicates that in the desorption process, energy is spent on only one stage - the separation of sorbate molecules from the sorbent surface. The validity of this hypothesis is confirmed by the fact that the curves of DTG desorption of water from CSAM and NaX crystallite (acting as an adsorbent filler) are practically identical. This confirms the absence of the influence of the matrix and the diffusion of sorbate in the secondary porous structure of the CSAM on the value of the activation energy of the desorption process. It has been experimentally shown that the thermal degradation of the polymer matrix begins in the temperature range 390 ÷ 450 0C, depending on the composition of the sample. The fact of increasing the heat resistance of the polymer matrix made of fluoroplast of the F - 42B brand by 45 ÷ 90 0C with the introduction of more than 6% by weight of NaX zeolite into it has been established. It is shown that thermal desorption at temperatures up to 390 0C occurs without destruction of the material. To confirm this conclusion, 25 cycles of water vapor sorption – desorption of the studied materials were carried out and these parameters were compared with similar indicators of commercially available granular zeolite NaX-B-1G registered under identical conditions. The sorbent samples had the same geometric configuration. Sorption was carried out under static conditions at relative humidity ω = 44 and temperature (20±2)°C for 120 minutes. Desorption of the samples was carried out at a temperature of 340,8 ± 1,5 0C for 4 hours. After each sorption–desorption stage, a change in the mass of the sample was recorded. The study of the processes of mass transfer of water vapor in 25 consecutive sorption – desorption cycles confirmed the possibility of complete thermal regeneration of the obtained CSAM. The results obtained made it possible to recommend optimal technological parameters of CSAM regeneration with minimal resource consumption.