# Alkanes: Sources and Relevance

## Alkanes: Catalytic Reforming

The transformation of long-chain hydrocarbons with low octane numbers into branched, cyclic or aromatic compounds with high octane ratings is called catalytic reforming. The goal of this process is to produce anti-knocking compounds which can be used as engine fuels.

Fig.1
Catalytic reformer
Fig.2
Distillation installation

### Reaction principle

During catalytic reforming, gasoline fractions obtained from the distillation of crude oil are being passed at ca.500 - 550$°C$ over beds of previously chlorinated platinum catalysts on fixed porous aluminum. Therefore, the process is also called plate-reforming. Three processes mainly increase the octane number.

Fig.3
Isomerisation of long-chain to branched alkanes
Fig.4
Dehydrogenation of cycloalkanes to aromatic compounds
Fig.5
Dehydrocyclization of long-chain alkanes to aromatic compounds

Fragmentation into shorter alkanes () and dehydrogenation to olefins are side reactions observed during catalytic reforming. The formation of olefins, especially of , is undesirable because they reduce the stability of fuels towards oxidation and have a tendency to polymerize. The formation of undesirable olefinic compounds is prevented by adding hydrogen to the mixture of alkanes thereby re-hydrogenating the olefins to the corresponding alkanes. The activity of the Pt-catalyst is insufficient for to the desired anti-knocking .

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