A Kinetic Study of the Nonisothermal Decomposition of Palladium Acetylacetonate Investigated by Thermogravimetric and X-Ray Diffraction Analysis Determination of Distributed Reactivity Model

Abstract

The nonisothermal decomposition process of the powder sample of palladium acetylacetonate [Pd(acac) 2 ] was investigated by thermogravimetric (TG) and X-ray diffraction (XRD) techniques. The experimental TG and differential thermogravimetric (DTG) curves were obtained at different heating rates (b = 2°C min À1 , 5°C min À1 , 10°C min À1 , 20°C min À1 , and 30°C min À1 ) under a pure nitrogen (N 2 ) atmosphere. The kinetic triplet (A, E a , and model function f(a)) was determined using different kinetic methods. It was found that the apparent activation energy was not really changed and was almost independent with respect to the level of conversion (a). This result suggests that the nonisothermal decomposition process of palladium acetylacetonate follows a single-step reaction. Practically constant E a values approximating 140.1 ± 1.5 kJ mol À1 were found. It was concluded that the reaction model R3, for the integral composite method I, is the model with the best regression and with kinetic parameters that are both unique and very similar to those obtained by the Friedman isoconversional method. In addition, it was found that the results obtained from both the Master-plot and Ma´lek methods confirm the results obtained from the multiple-rate isotemperature method, specifically, that the R3 (contracting volume) reaction mechanism can best describe the investigated decomposition process. By applying the Miura procedure, a distributed reactivity model (DRM) for the investigated decomposition process was established. From the a = a(E a ) dependence, the experimental distribution curve of E a was estimated. Using the nonlinear (NL) least-squares analysis, it was found that the Gaussian distribution model (with distribution parameters: E 0 = 138.4 kJ mol À1 and r = 0.71 kJ mol À1 ) represents the best reactivity model for describing the investigated process. Also, it was concluded that the E a values calculated by the Friedman isoconversional method and the estimated distribution curve (f(E a )), are correct, even in the case in which the investigated decomposition process occurs through a single-step reaction mechanism.

Nitrogen-Doped Anatase Nanofibers Decorated with Noble Metal Nanoparticles for Photocatalytic Production of Hydrogen

“…The particle size is determined by several factors as decomposition of the noble metal source compounds, seed formation rates, and diffusion properties. While both platinum acetylacetonate and palladium acetylacetonate decompose around 200 °C, 31,32 the activation energy of the diffusion of platinum is 1.4À1.5 times higher than that in the case of palladium 33 which leads to a slower surface diffusion of platinum and results in nanoparticle formation from a smaller area around the seed.…”

In Situ Small-Angle X-ray Scattering from Pd Nanoparticles Formed by Thermal Decomposition of Organo-Pd Catalyst Precursors Dissolved in Hydrocarbons

“…One interesting observation is that the primary particle size seems to stop growing or grow very slow in the case of Pd(acetate) 2 , whereas for Pd(acac) 2 , the particles detected by SAXS continue to grow. It is reported that the thermal decomposition of Pd(acac) 2 is a single-step process that forms Pd and acac . For Pd(acetate) 2 , in the inert atmosphere, the major decomposition product is Pd, whereas in air, the thermal decomposition of Pd(acetate) 2 is more complicated, and other Pd-containing species are also formed .…”

“…It is reported that the thermal decomposition of Pd(acac) 2 is a single-step process that forms Pd and acac. 43 For Pd(acetate) 2 , in the inert atmosphere, the major decomposition product is Pd, whereas in air, the thermal decomposition of Pd(acetate) 2 is more complicated, and other Pd-containing species are also formed. 32 In our experiment, the Pd(acac) 2 and Pd(acetate) 2 are heated in solution.…”

Preparation of Bi2Sr2CaCu2O8+δ(Bi2212) superconductor by Pechini sol–gel method: thermal decomposition and phase formation kinetics of the precursors

“…Thus, the reaction model can be numerically reconstructed by the values of the pre-exponential factor A and the activation energy E. The dependence of time and temperature on the reaction rate can be also obtained. At present, thermal analysis kinetics has been applied in the fields of ceramics, complexes, polymers, biopolymers, and energetic materials [30][31][32][33][34][35], determining reaction mechanism during materials decomposition and synthesis. In this work, the nonisothermal method was used to investigate the thermal decomposition and phase formation mechanism of Bi2212 precursors with different heating rates.…”