Pyrolysis of Alkanes

Pyrolysis is derived from the Greek components pyro, which means “fire,” and lysis, which means “separating.” Normally, it is employed in the production of organic materials.

As opposed to combustion reactions, it occurs in the absence of air, which distinguishes it from them. The oxidation of chemicals is prevented as a result of this. Cracking is a word that is commonly used to describe the pyrolysis of alkanes.

In contrast to combustion, the rate of pyrolysis increases with the increase in the molecular weight and branching of an alkane, whereas the rate of combustion decreases.

The fission of C-C bonds results in the formation of alkanes and alkenes, whereas the fission of C-H bonds results in the formation of alkenes and hydrogen.

C-H bond fission happens as a result of the catalytic action of Cr₂O₃, V₂O₃, and MoO₃, while C-C bond fission occurs as a result of the presence of SiO₂, Al₂O₃, and ZnO in the presence of the catalysts Cr₂O₃, V₂O₃, and MoO₃.

The cracking of alkanes is caused by the action of free radicals.

It is critical in the petroleum industry’s development and growth. Cracking is the process by which higher-molecular alkanes are converted into lower-molecular alkanes (petrol C₆ to C₁₁).

Using dodecane as an example, which is a component of kerosene oil, pyrolysis produces a combination of heptane and pentane as a result of the reaction.

A temperature of 973K is reached by heating the material under the catalytic action of platinum, palladium, or nickel.

The physical properties of alkanes and the changes in these properties

The following are some of the most important physical features of alkanes:

• Alkanes are colourless and odourless, and they have no flammability.

• They have weak Van der Waals forces of attraction, which makes them attractive to others.

• At 298 degrees Celsius, alkanes containing 1-4 carbon atoms are gases, alkanes containing 5-17 carbon atoms are liquids, and alkanes containing 18 or more carbon atoms are solids.

Temperatures of melting and boiling

When it comes to alkanes, the melting and boiling temperatures of shorter chain alkanes are lower, but as the number of carbon atoms in the chain rises, the melting and boiling points rise.

Because of the Van der Waals effect, the boiling point increases with increasing molecular weight.

Straight chain alkanes have a greater boiling point than their structural isomers because they have a shorter carbon chain.

In addition, the melting point of heavier alkanes increases with increasing molecular weight since it is difficult to break the intermolecular forces of attraction that exist between them because they are solids in their natural state.

Even-numbered alkanes have better packing in the solid phase than odd-numbered alkanes because they form a well-organised structure that is difficult to break.

As a result, even-numbered alkanes have a higher melting point than odd-numbered alkanes because they have better packing in the solid phase.

Cracking of alkanes

Cracking is a chemical reaction in which larger saturated hydrocarbon molecules are broken down into smaller, more valuable hydrocarbon molecules, some of which are unsaturated.

The original starting hydrocarbons are alkanes.The product is a smaller, more useful hydrocarbon molecule.

Alkanes and alkenes are among the results of cracking, each of which belongs to a different homologous family.

When huge hydrocarbon molecules are cracked, they can be broken down into smaller, more usable hydrocarbon molecules, which is called cracking.

Heat is applied to fractions containing big hydrocarbon molecules in order to get them to vaporise.

Watch this video to see a hands-on demonstration of alkane cracking in the lab. Cracking results in the formation of a mixture of smaller alkanes and alkenes.

Conclusion

Kerosene is a flammable liquid mixture of chemicals that is formed during the distillation of crude oil.

It is used in the production of gasoline.

Kerosene is produced by distilling crude oil in a distillation tower, in a process that is quite similar to that used in the production of diesel and gasoline.

The distillate is a medium-weight distillate in the refining process, and it can be created by distilling crude oil (in which case it is referred to as straight run kerosene) or by hydrocarbon cracking heavier petroleum products (here it is known as cracked kerosene).

Kérosene has a complicated chemical makeup that includes paraffins (55.2 percent), naphthene (40.9 percent), and aromatic hydrocarbons, among other things (3.9 percent ).

Kerosene often contains hydrocarbons with 11 to 13 carbons in their chains, which indicates that it is a light fuel.

Liquid kerosene fuels contain potentially toxic chemicals such as hexane and benzene, which are found in gasoline.