RESEARCH OF THE KINETICS OF PYROLYSIS OF CROSS-LINKED POLYETHYLENE AND HDPE

В данной работе представлено исследование кинетики процесса термодеструкции полимеров. Процесс пиролиза полиэтилена высокого давления и сшитого полиэтилена изучался методом термогравиметрии. Для определения кинетической модели деструкции и параметров Аррениуса разложение образцов проводилось с различной скоростью нагрева (2,5; 5 и 10 К/мин). В ходе моделирования процесса пиролиза была определена наиболее адекватная модель: термодеструкция включает две последовательные стадии с автокатализом на первой стадии. Энергии активации деструкции полиэтилена составили 111 и 91 кДж/моль для первой и второй стадии соответственно. В случае сшитого полиэтилена - 175 и 308 кДж/моль. This paper presents a study of the kinetics of the process of thermal degradation of polymers. The pyrolysis process of high-pressure polyethylene and cross-linked polyethylene was studied by thermogravimetry. To determine the kinetic model of destruction and Arrhenius parameters, the samples were decomposed at different heating rates (2.5, 5, and 10 K / min). During the simulation of the pyrolysis process, the most adequate model was determined: thermal degradation includes two consecutive stages with autocatalysis at the first stage. The activation energies of polyethylene degradation were 111 and 91 kJ/mol for the first and second stages, respectively. In the case of cross-linked polyethylene - 175 and 308 kJ/mol.

Kinetics of Formic Acid Decomposition in Subcritical and Supercritical Water - A Raman Spectroscopic Study

The decomposition of formic acid is studied in a continuous sub- or supercritical water reactor at temperatures between 300 and 430°C, a pressure of 25 MPa, residence times between 4 and 65 s, and a feedstock concentration of 3.6 wt%. <i>In-situ </i>Raman spectroscopy is used to produce real-time data and accurately quantify decomposition product yields of H₂, CO₂, and CO. Collected spectra are used to determine global decomposition rates and kinetic rates for individual reaction pathways. First-order global Arrhenius parameters are determined as log <i>A</i> (s^-1) = 1.6 ± 0.20 and <i>E_A</i>= 9.5 ± 0.55 kcal/mol for subcritical decomposition, and log <i>A</i> (s^-1) = 12.56 ± 1.96 and <i>E_A</i>= 41.90 ± 6.08 kcal/mol for supercritical decomposition. Subcritical and supercritical Arrhenius parameters for individual pathways are proposed. The variance in rate parameters is likely due to changing thermophysical properties of water across the critical point. There is strong evidence for a surface catalyzed free-radical mechanism responsible for rapid decomposition above the critical point, facilitated by low density at supercritical conditions.

Kinetics of Formic Acid Decomposition in Subcritical and Supercritical Water - A Raman Spectroscopic Study

The decomposition of formic acid is studied in a continuous sub- or supercritical water reactor at temperatures between 300 and 430°C, a pressure of 25 MPa, residence times between 4 and 65 s, and a feedstock concentration of 3.6 wt%. <i>In-situ </i>Raman spectroscopy is used to produce real-time data and accurately quantify decomposition product yields of H₂, CO₂, and CO. Collected spectra are used to determine global decomposition rates and kinetic rates for individual reaction pathways. First-order global Arrhenius parameters are determined as log <i>A</i> (s^-1) = 1.6 ± 0.20 and <i>E_A</i>= 9.5 ± 0.55 kcal/mol for subcritical decomposition, and log <i>A</i> (s^-1) = 12.56 ± 1.96 and <i>E_A</i>= 41.90 ± 6.08 kcal/mol for supercritical decomposition. Subcritical and supercritical Arrhenius parameters for individual pathways are proposed. The variance in rate parameters is likely due to changing thermophysical properties of water across the critical point. There is strong evidence for a surface catalyzed free-radical mechanism responsible for rapid decomposition above the critical point, facilitated by low density at supercritical conditions.

From n-butyl acrylate Arrhenius parameters for backbiting and tertiary propagation to β-scission via stepwise pulsed laser polymerization

A stepwise method to estimate the Arrhenius parameters for backbiting, tertiary propagation, and β-scission in acrylate radical polymerization.