Carbonization

For the chemical process that produces the bubbles in fizzy drinks, see carbonation. For the porting of Macintosh software, see Carbon (API).

Carbonization or carbonisation is the term for the conversion of an organic substance into carbon or a carbon-containing residue through pyrolysis or destructive distillation. It is often used in organic chemistry with reference to the generation of coal gas and coal tar from raw coal. Fossil fuels in general are the products of the carbonization of vegetable matter. The term carbonization is also applied to the pyrolysis of coal to produce coke. Carbonization is also a stage in the charcoal making process, and is considered the most important step of all since it has such power to influence the whole process from the growing tree to the final distribution of charcoal to various sources.

Since carbonization is a pyrolytic reaction, it is considered a complex process in which many reactions take place concurrently such as dehydrogenation, condensation, hydrogen transfer and isomerization.

Carbonization differs from coalification in that it occurs much faster, due to its reaction rate being faster by many orders of magnitude.

For the final pyrolysis temperature, the amount of heat applied controls the degree of carbonization and the residual content of foreign elements. For example, at the carbon content of the residue exceeds a mass fraction of 90 wt.%, whereas at more than 99 wt.% carbon is found .

Carbonization is often exothermic, which means that it could in principle be made self-sustaining and be used as a source of energy that does not produce carbon dioxide. (See.) In the case of glucose, the reaction releases about 237 calories per gram.

When biomaterial is exposed to sudden searing heat (as in the case of an atomic bomb explosion or pyroclastic flow from a volcano, for instance), it can be carbonized extremely quickly, turning it into solid carbon. In the destruction of Herculaneum by a volcano, many organic objects such as furniture were carbonized by the intense heat.

In one study, carbonization was used to create a new catalyst for the generation of biodiesel from ethanol and fatty acids. The catalyst was created by carbonization of simple sugars such as glucose and sucrose. The sugars were processed for 15 hours at 400 °C under a nitrogen flow to a black carbon residue consisting of a complex mixture of polycyclic aromatic carbon sheets. This material was then treated with sulfuric acid, which functionalized the sheets with sulfonite, carboxyl, and hydroxyl catalytic sites.

References

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External links

• carbonization processes at Herculaneum site