Catalytic reforming chemical reactions

1. Aromatization reactions

Any reaction that produces aromatics can be called an aromatization reaction. Under reforming conditions, aromatization reactions include the following

-Dehydrogenation of six-membered rings

-isomeric dehydrogenation of five-membered ring alkanes

-alkane cyclisation dehydrogenation reactions

The dehydrogenation of hexa-cyclic alkanes proceeds rapidly, reaches chemical equilibrium under industrial conditions and is the most important reaction for the production of aromatics. Bimetallic and polymetallic catalysts such as platinum-rhenium have shown a significant increase in aromatic conversion, mainly due to the increased reaction rate of conversion of alkanes to aromatics.

2. Isomerisation reactions

- Isomerisation of straight-chain alkanes

-Isomerisation of cycloalkanes and alkanes

3. Hydrocracking reactions

Hydrocracking is actually a combination of hydrogenation, cracking and isomerisation. Hydrocracking is an exothermic reaction of moderate intensity and can be considered irreversible, so only its reaction rate is generally studied. Increasing pressure favours hydrocracking reactions. The main reason for the low reaction rate of the hydrocracking reaction is that it takes place in the last reactor of the catalytic reforming.

4. Hydrodealkylation

The aromatic demethylation reaction is similar to the aromatic dealkylation reaction, differing only in the size of the part removed from the ring. The difference is only the size of the part removed from the ring. Demethylation generally only occurs under very demanding reforming operating conditions (high temperature and pressure). Under certain Under certain conditions, demethylation may occur after catalyst replacement or regenerative reduction during the operation of the plant.

5. Condensation coking

Under reforming conditions, hydrocarbons can also undergo molecular enlargement reactions such as stacking and condensation, eventually condensing to coke, which covers on the catalyst surface, deactivating it. Therefore, these reactions must be controlled. The mechanism of the coking reaction is not yet well understood. In general, the tendency to coke is related to the molecular size and structure of the feedstock, with heavier fractions and feedstocks containing more olefins usually being more susceptible to coking.

In production, the rate of coking decreases as the catalyst is used for a longer period of time and therefore the temperature is raised faster at the beginning of the operation and slower later. The temperature is therefore raised quickly at the beginning of the operation and slowly later.