Pyrolysis Activation Energy

Decomposition. Acetaldehyde decomposes at temperatures above 400°C, forming principally methane and carbon monoxide [630-08-0]. The activation energy of the pyrolysis reaction is 97.7 kj/mol (408.8 kcal/mol) (27). There have been many investigations of the photolytic and radical-induced decomposition of acetaldehyde and deuterated acetaldehyde (28—30). 

Step 4 of the thermal treatment process (see Fig. 2) involves desorption, pyrolysis, and char formation. Much Hterature exists on the pyrolysis of coal (qv) and on different pyrolysis models for coal. These models are useful starting points for describing pyrolysis in kilns. For example, the devolatilization of coal is frequently modeled as competing chemical reactions (24). Another approach for modeling devolatilization uses a set of independent, first-order parallel reactions represented by a Gaussian distribution of activation energies (25). 

A model for coal fluidity based on a macromolecular network pyrolysis model has been developed (33). In that model, bond breaking is described as a first-order reaction having a range of activation energies. A variety of lattices have also been used to describe the bonding in coal. In turn these stmctures... 

PTFE decomposes to TFE with first-order kinetics and a 347.4-kJ/mol activation energy under vacuum pyrolysis conditions It is extremely flame resistant and does not bum in air Its limiting oxygen mdex (LOR, the muumum oxygen content of an atmosphere under ambient conditions that sustams combustion, is 96%, which means that it requires almost pure oxygen for combustion... 

Because the activation energy and preexponential factor for the fuel and oxidizer pyrolysis reactions are not identical, the only way for Eq. (30) to be valid is for Ta t Tf. 

The two methods of incorporating A1 into MCM-41 provided HDPE pyrolysis products of the similar quality. A1-MCM-41-P, however, demonstrated higher catalytic activity con jared to A1-MCM-41-D, as indicated by its lower activation energies. The higher catalytic activity of A1-MCM-41-P could be attributed to the fact that it has more acid sites compared to A1-MCM-41-D. Thus, the use of Al-MCM-41-P is expected to be more effective than the use of A1-MCM-41-D in the pyrolysis of HDPE. 

Thermogravimetric analysis (TGA) has often been used to determine pyrolysis rates and activation energies (Ea). The technique is relatively fast, simple and convenient, and many experimental variables can be quickly examined. However for cellulose, as with most polymers, the kinetics of mass loss can be extremely complex (8 ) and isothermal experiments are often needed to separate and identify temperature effects (9. Also, the rate of mass loss should not be assumed to be related to the pyrolysis kinetic rate ( 6 ) since multiple competing reactions which result in different mass losses occur. Finally, kinetic rate values obtained from TGA can be dependent on the technique used to analyze the data. 

Tests were performed on pyrolysis of an oil in a heated tubular reactor. The reaction is pseudo first order with an activation energy of 56630 cal/gmol, so the specific rate is represented by... 

The thermal decomposition of dimethyl mercury in the presence of radical scavengers has been thoroughly investigated61-65. The basic mechanism, the preexponential factor and the activation energy are all well established. There is still considerable doubt about the mechanism of the pyrolysis in the absence of chemically active additives. Consequently, the quantitative interpretation of rate data from such systems is of doubtful value. Systems using effective scavengers will be discussed first. The quantitative results from these systems will be used in assessing the data obtained in the absence of additives. 

Following the conceptual idea introduced by Milliken [68], Takahashi and Glassman [53] have shown, with appropriate assumptions, that, at a fixed temperature, i/c could correlate with the number of C—C bonds in the fuel and that a plot of the log ipc versus number of C—C bonds should give a straight line. This parameter, number of C—C bonds, serves as a measure of both the size of the fuel molecule and the C/H ratio. In pyrolysis, since the activation energies of hydrocarbon fuels vary only slightly, molecular size increases the radical pool size. This increase can be regarded as an increase in the Arrhenius pre-exponential factor for the overall rate coefficient and hence in the pyrolysis and precursor formation rates so that the C/H ratio determines the OH concentration [12]. The 4>c versus C—C bond plot is shown in Fig. 8.14. When these... 

An ab initio study of the unimolecular pyrolysis mechanisms of monothioformic acid (363) has yielded activation energies for dehydrogenation and dehydrosulfidation. ... 

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