Pyrolysis as a Chemical Process

The pyrolytic reactions usually take place at temperatures higher than 250-300° C, commonly between 500° C and 800° C. The chemical transformations taking place under the influence of heat at a temperature between 100° C and 300° C are commonly called thermal degradations [4] and not pyrolysis. Mild pyrolysis is considered to take place between 300° C and 500° C and vigorous pyrolysis above 800° C. 

The term pyrolysis is not restricted to the decomposition of pure compounds. The same term is frequently used in the literature in connection with the thermal decomposition of many complex materials such as coal, oil shales, etc. or even of composite materials such as wood or whole microorganisms. 

Analytical pyrolysis is by definition the characterization of a material (or a chemical process) by chemical degradation reactions induced by thermal energy. It consists of a collection of techniques involving pyrolysis performed with the purpose of obtaining analytical information on a given sample. The type of analytical information can be 

If a physical property of a sample is measured during heating as a function of temperature, the technique is commonly named a thermoanalytical technique. 

Analytical pyrolysis is considered somehow apart from the other thermoanalytical techniques such as thermometry, calorimetry, thermogravimetry, differential thermal analysis, etc. In contrast to analytical pyrolysis, thermoanalytical techniques are not usually concerned with the chemical nature of the reaction products during heating. Certainly, some overlap exists between analytical pyrolysis and other thermoanalytical techniques. The study of the kinetics of the pyrolysis process, for example, was found to provide useful information about the samples and it is part of a series of pyrolytic studies (e.g. [6-8]). Also, during thermoanalytical measurements, analysis of the decomposition products can be done. This does not transform that particular thermoanalysis into analytical pyrolysis (e.g. [9]). A typical example is the analysis of the gases evolved during a chemical reaction as a function of temperature, known as EGA (evolved gas analysis). 

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