Absence of Diffusion Control of Reaction Rate in the Thermal Decomposition of Amorphous Polymers

Nature ◽  
1965 ◽  
Vol 208 (5016) ◽  
pp. 1200-1201
Author(s):  
DEREK A. SMITH
Keyword(s):  
Thermal Decomposition ◽  
Reaction Rate ◽  
Amorphous Polymers ◽  
Diffusion Control

Thermal Decomposition Kinetics of Glyphosate (GP) and its Metabolite Aminomethylphosphonic Acid (AMPA)

2019 ◽  
Author(s):  
Milad Narimani ◽  
Gabriel da Silva
Keyword(s):  
Thermal Decomposition ◽  
Reaction Rate ◽  
Decomposition Kinetics ◽  
Rate Theory ◽  
Thermal Decomposition Mechanism ◽  
Treatment Processes ◽  
Aminomethylphosphonic Acid ◽  
Reaction Rate Theory ◽  
Decomposition Chemistry ◽  
Kinetics Of

Glyphosate (GP) is a widely used herbicide worldwide, yet accumulation of GP and its main byproduct, aminomethylphosphonic acid (AMPA), in soil and water has raised concerns about its potential effects to human health. Thermal treatment processes are one option for decontaminating material containing GP and AMPA, yet the thermal decomposition chemistry of these compounds remains poorly understood. Here, we have revealed the thermal decomposition mechanism of GP and AMPA by applying computational chemistry and reaction rate theory methods. <br>

Kinetic Study on Microwave Magnetizing Roast of Fe2O3 Powders

2020 ◽  
Vol 304 ◽  
pp. 91-97
Author(s):  
Lei Wang ◽  
Ling Bing Kong ◽  
Pei Min Guo ◽  
Jie Li
Keyword(s):  
Reaction Rate ◽  
Reaction Kinetic ◽  
Three Dimensional ◽  
Kinetic Mechanism ◽  
Electrical Heating ◽  
Diffusion Control ◽  
Weight Loss Curve ◽  
Dimensional Diffusion ◽  
Boundary Reaction ◽  
Phase Boundary Reaction

In this paper, the reaction kinetic mechanism of Fe2O3 powder containing carbon was studied by microwave magnetizing roast. Based on the temperature-rise curve and weight loss curve of Fe2O3 powder by microwave magnetizing roast, the kinetic parameters of Fe2O3 powder microwave magnetizing roast were calculated by non-isothermal methods. The controlling steps of different temperature-rising periods in microwave magnetizing roast process of Fe2O3 powder were calculated by the Achar-Brindley-Sharp-Wendworth method. The results indicated that the controlling step of microwave magnetizing roast was phase boundary reaction control of contracted cylinder in 250~450°C, and it was three-dimensional diffusion control of spherical symmetry in 450~650°C. The results showed that the starting temperature of reduction roasting of Fe2O3 powder was 250°C, which was lower than that under electrical heating, thereby, it proved in theory that microwave heating can enhance reaction rate.

Cavitation-induced Reactions in Pure Substituted Benzenes

1972 ◽  
Vol 50 (11) ◽  
pp. 1743-1750 ◽  
Author(s):  
G. K. Diedrich ◽  
P. Kruus ◽  
L. M. Rachlis
Keyword(s):  
Thermal Decomposition ◽  
Low Temperature ◽  
Bond Dissociation Energy ◽  
Dissociation Energy ◽  
Cavitation Bubble ◽  
Reaction Rate ◽  
Substituted Benzenes ◽  
Thermal Reactions ◽  
Initiation Reaction ◽  
Low Temperature Pyrolysis

The formation of polymers has been observed on exposure of pure substituted benzenes to ultrasound intense enough to cause cavitation. The products have some of the characteristics of the char obtained from low temperature pyrolysis of hydrocarbons. They are difficult to dissolve, melt above 300 °C, and give a large broad e.p.r. signal. A crude correlation between bond dissociation energy and the reaction rate suggests that the initiation reaction is a thermal decomposition in a cavitation bubble. The phenomenon is compared to radiolysis and thermal reactions.

Thermal Decomposition and Isomerization of Furfural and 2-Pyrone: A Theoretical Kinetic Study

2020 ◽  
Author(s):  
Saddam Al-Hammadi ◽  
Gabriel da Silva
Keyword(s):  
Thermal Decomposition ◽  
Kinetic Study ◽  
Gas Phase ◽  
Quantum Chemical ◽  
Reaction Rate ◽  
Rate Theory ◽  
Reaction Rate Theory ◽  
Reaction Channels

We have studied the decomposition and isomerization of furfural in the gas-phase using quantum chemical and statistical reaction rate theory techniques. This work uncovers a variety of new reaction channels...

Diffusion control of the Diels—Alder reaction rate at elevated pressures

2004 ◽  
Vol 53 (1) ◽  
pp. 45-50 ◽  
Author(s):  
V. D. Kiselev ◽  
E. A. Kashaeva ◽  
M. S. Shihab ◽  
L. N. Potapova ◽  
G. G. Iskhakova
Keyword(s):  
Reaction Rate ◽  
Alder Reaction ◽  
Diels Alder ◽  
Diffusion Control ◽  
Elevated Pressures ◽  
Diels Alder Reaction

Effect of Co-precursor Maliec Anhydride on the Thermal Decomposition of Acetyl Ferrocene: A Reaction Kinetic Analysis

2019 ◽  
Vol 9 (1) ◽  
pp. 22-35
Author(s):  
Bratati Das ◽  
Ashis Bhattacharjee
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Reaction Mechanism ◽  
Kinetic Analysis ◽  
Reaction Rate ◽  
Reaction Kinetic ◽  
Step Process ◽  
Probable Reaction Mechanism ◽  
Probable Reaction ◽  
Reaction Atmosphere

Background: Thermal decomposition of iron-bearing organometallic complex acetyl ferrocene, (C5H4COCH3)Fe(C5H5), leads to hematite (α-Fe2O3) nanoparticles. Presence of maliec anhydride, C4H2O3 as co-precursor during thermal decomposition modifies the size of the particles as well as the quantity of the reaction product significantly. Objective: Kinetic analysis of the solid-state thermal reaction of acetyl ferrocene in the presence of varying amount of co-precursor maliec anhydride under inert reaction atmosphere has been studied in order to understand the reaction mechanism involved behind the formation of hematite and the role of co-precursor in the reaction process. For this purpose, reaction kinetic analysis of three mixtures of acetyl ferrocene and maliec anhydride has been carried out. Methods: Thermogravimetry under non-isothermal protocol with multiple heating rates has been employed. The data are analyzed using model-free iso-conversional kinetic techniques to estimate the activation energy of reaction and reaction rate. The most-probable reaction mechanism has been identified by master plot method. The kinetic triplets (activation energy, reaction rate, most probable reaction mechanism function) have been employed to estimate the thermodynamic triplets (ΔS, ΔH and ΔG). Observations: Acetyl Ferrocene (AFc) undergoes thermal decomposition in a four-step process leaving certain residual mass whereas maliec anhydride (MA) undergoes complete mass loss owing to melting followed by evaporation. In contrast, the (AFc1-x-MAx) mixtures undergo thermal decomposition through a two-step process, and the decompositions are completed at much lower temperatures than that in AFc. The estimated activation energy and reaction rate values are found strongly dependent on the extent of conversion as well as on the extent of mixing. Introduction of MA in the solid reaction atmosphere of AFc in one hand reduces the activation energy required by AFc to undergo thermal decomposition and the reaction rate, while on the other hand varies the nature of reaction mechanism involved. Results: The range of reaction rate values estimated for the mixtures indicate that the activated complexes during Step-I of thermal decomposition may be treated as ‘loose’ complex whereas ‘tight’ complex for the Step-II. From the estimated entropy values, thermal process of (AFc1-x-MAx) mixture for Steps I and II may be interpreted as ‘‘slow’’ stage. Conclusion: Variation of Gibb’s free energy with the fraction of maliec anhydride in the mixtures for Step-I and II indicate that the thermal processes of changing the corresponding activated complexes are non-spontaneous at room temperature.

Sign in / Sign up

Export Citation Format

Share Document