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1

Correlation of kinetic parameters of sodium acetate thermal decomposition

Olszak-Humienik M., Możejko J.

Polish Journal of Chemical Technology

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2006

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Vol. 8, nr 2

22-25

EN

Thermogravimetry and differential thermal analysis were used in the study of the kinetics of non-isothermal sodium acetate's thermal decomposition under an air atmosphere. The diagrams were recorded on a sample mass of 20 mg at temperatures ranging from 20 to 600°C. Five different heating rates were used. The relations of α vs. T were estimated from the mass losses. The values of the kinetic parameters (activation energy and the pre-exponential factor) of the thermal decomposition were calculated from α(T) data in several ways: by using the integral method, applying the Coats-Redfern approximation, the modified isoconversional Coats-Redfern method, the differential method of Friedman and the Kissinger's method. A correlation was found between kinetic parameters estimated by different kinetic methods.

2

Analysis of the decomposition process of CuSO4 · 5H2O under non-isothermal conditions

Straszko J., Strzelczak A., Chrościechowska J.

Polish Journal of Chemical Technology

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2005

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Vol. 7, nr 2

54-61

EN

The results of the investigation on thermal decomposition of CuSO4 · 5H2O under the non-isothermal conditions are presented. The measurements were carried out at the following heating rates: 2, 4, 6, 8 and 10 [K/min]. The mass of the used samples was about 30mg. The process occurred in five steps. Three of them were associated with dehydration and the two of them with the decomposition of the anhydrous salt. The dependencies of the conversion degree on temperature were determined for every stage of the process. They were the basis of the presented quantitative description . The Coats and Redfern equation was applied. The g(alpha) function (kinetic model) of the best accuracy for the individual step and the kinetic parameters of the Arrhenius equation were determined. The identification of the kinetic models was carried out by means of the artificial neural networks. A and E coefficients were evaluated using statistical methods. The described conversions were assumed as stochastic processes.

3

Kinetyka termicznej dehydratacji BaCl2 x 2H20 w warunkach nieizotermicznych

Możejko J., Kotfica M.

Prace Naukowe Politechniki Szczecińskiej. Instytut Inżynierii Chemicznej i Procesów Ochrony Środowiska

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2000

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Nr 558 (36)

225-236

PL

Przeprowadzono badania dehydratacji BaCl2 x 2H2O metodą analizy termicznej (TG, DTG, DTA) w warunkach nieizotermicznych, w atmosferze powietrza. Ustalono, że odwadnianie BaCl2 x 2H2O zachodzi w dwóch etapach, w których uwalniane są kolejno pojedyncze cząsteczki wody. Analizę kinetyczną prowadzono z wykorzystaniem krzywych termograwimetrycznych TG, dotyczących poszczególnych etapów procesu. Wyznaczono parametry kinetyczne: pozorną energię aktywacji i współczynnik przedwykładniczy równania Arrheniusa oraz określono mechanizm reakcji. Stwierdzono, że obydwa etapy dehydratacji można przedstawić równaniem g(a) = -ln(1-a) odpowiadającym mechanizmowi nukleacji przypadkowej. Na podstawie równań kinetycznych opisujących oba etapy wyznaczono zależności szybkości reakcji od temperatury.

EN

The thermal dehydration of BaCl2 x 2H2O was investigated by simultaneous thermal analysis (TG, DTG, DTA) under non-isothermal condition in air atmosphere. From the thermoanalytical curves it was found that the process occurred in two steps associated with the liberation of one molecule of water. Using the thermogravimetric data the kinetic parameters: apparent activation energy, pre-exponential Arrhenius factor, and mechanism of particular dehydration stages were calculated by means of the Coats-Redferns integral method. The apparent activation energies found for dehydration processes were 124 - 168 kJ/mol for first step and 146 - 224 kJ/mol for second step. All stages of decomposition were governed by a random nucleation model: g(a) = -ln(1-a). The thermodynamic functions