Pyrolysis: Reaction of Wood, Oil, Biomass and Alkanes

The pyrolysis It consists of a thermal decomposition process where the substances -of organic origin in its great majority- are subjected to high temperatures in an inert medium (without the presence of oxygen). When organic matter is treated by means of pyrolysis, products that are used in the industrial field are obtained.

One of the elements that can be obtained in coke, which is used as a type of industrial characteristics fuel. You can also obtain biochar (known as biochar), which is used to modify or improve soils.

Pyrolysis Pyrolysis converts organic matter into the substances that compose it in a gaseous state, a solid residual species formed by carbon and ash, and a liquid substance known as bio-oil.

This reaction causes other compounds, such as non-condensable gases or liquids that can be condensed, while transforming matter irreversibly. Although this technique is very important and has many applications, it can generate elements harmful to the environment and present a risk of toxicity to living beings.

Index

  • 1 Chemical reaction of pyrolysis
  • 2 Reaction of wood
  • 3 Oil reaction
  • 4 Biomass reaction
  • 5 Reaction of alkanes
  • 6 References

Chemical reaction of pyrolysis

The pyrolysis reaction, as mentioned previously, involves the application of very high temperatures in an atmosphere without oxygen, to induce changes in the physical and chemical properties of the substances through their thermal decomposition.

In this sense, this process converts organic matter into the substances that compose it in the gas phase, a solid phase residual species formed by carbon and ash, and a liquid substance with oily characteristics known as bio-oil.

This reaction is used to eliminate polluting substances from organic matter, and fulfills that purpose through two means:

- The fragmentation of contaminating molecules through a break in the bonds to form species with a smaller molecular weight (known as destruction).

- The separation of these harmful compounds from the material without destroying them.

So the technique of pyrolysis is widely used in the treatment of organic substances that undergo fracture or decomposition when exposed to heat, such as polycyclic aromatic hydrocarbons.

On the contrary, this reaction is unsuccessful if it is used to eliminate inorganic species such as metal compounds; however, it is possible to use it in processes that convert these metals into inert ones.

Reaction of wood

In the case of the pyrolysis reaction in wood, this process involves the application of very high temperatures (approximately 1000 ° C) in an environment lacking air. Depending on the products that you wish to obtain, there are several processes that are regularly used.

One of the techniques is carbonization, in which conical wooden columns are erected and covered with earth to heat it in metal ovens; This originates different products, such as activated carbon, drugs, pyrotechnic games, among others.

On the other hand, destructive distillation causes acetic acid, tar and other substances through the heating of the wood gradually, increasing the temperature gradually in the enclosures used for this purpose.

Liquefaction is also used, which is a procedure commonly used in the production of a liquid phase fuel known as pyrolytic oil, which is produced in tanks designed for this purpose.

Oil reaction

When referring to oil pyrolysis, reference is made to the process of decomposition or fractionation of the high molecular weight hydrocarbons contained in the mixtures that make up this substance.

So, when some products derived from crude oil are subjected to certain conditions of pressure and temperature, the molecules of greater weight contained in these undergo a process of cracking or"cracking"that fragments them into lighter hydrocarbons (with lower boiling point and lower weight).

This process, which uses mostly the heavier fractions of petroleum, transforms large quantities of aliphatic hydrocarbons into aromatic molecules and helps in the production and improvement of fuels such as gasoline, diesel, aviation fuel, among others.

In this sense, molecules such as alkanes, alkenes and other low molecular weight species produced by this reaction can be separated and purified in order to obtain raw material of great relevance for other procedures, such as the synthesis of certain organic compounds.

Biomass reaction

The biomass pyrolysis reaction (organic material deposited from living beings) involves the breaking of chemical bonds in compounds of high molecular weight, such as hemicellulose or cellulose, which are considered macromolecules.

These substances are fragmented into smaller gaseous species through complex reactions of cleavage, ring opening and depolymerization, for the transformation of biomass into potentially usable material in terms of energy.

According to the state of aggregation in which they are in normal environmental conditions, the pyrolysis of biomass can originate three types of substances: coal, tar and gas; These can result in valuable products such as biofuel.

Reaction of alkanes

As previously stated, pyrolysis consists of the decomposition of organic substances by the application of heat and, in the case of alkanes, a closed room is used at high temperatures similar to the types of pyrolysis that have been explained.

However, since these are large alkenes, the carbon-carbon bonds are broken - in a random manner - along the molecule and different radical species are produced.

So, when the alkyl chain of these compounds is fragmented, smaller alkanes, some alkenes (mainly ethylene) and other smaller species such as alkyl radicals are produced, in addition to lesser amounts of hydrogen.

References

  1. Wikipedia. (s.f.) Pyrolysis. Retrieved from en.wikipedia.org
  2. Britannica, E. (s.f.). Pyrolysis. Recovered from britannica.com
  3. Wang, S., and Luo, Z. (2017). Pyrolysis of Biomass. Retrieved from books.google.co.ve
  4. Berlin, A. A. (2005). Chemical Physics of Pyrolysis, Combustion, and Oxidation. Recovered from books.google.co.ve
  5. Moldoveanu, S.C. (2009). Pyrolysis of Organic Molecules: Applications to Health and Environmental Issues. Retrieved from google.co.ve


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