A chemical process in the refinery used to convert refinery naptha, which is of low octane levels to high octane reformates, which are components of high octane gasoline (high octane petrol).
The process re-arranges or re-structures the hydrocarbon molecule in the naptha feedstock. In the some cases it can break the molecules up. The overall effect is that the reformate contains hydrocarbons with more complex shapes with higher octane values. In so doing hydrogen atoms are separated and hydrogen gas is produced as a by-product. Small amounts of methane, ethane, propane and butanes are produced.
The original process was developed by UOP scientist Vladimir Haensel in the 1940’s.
The chemical reaction takes place in the presence of catalyst and the high partial pressure of hydrogen. Depending on the severity of the reaction the temperature will vary from 495°C to 525°C and the pressure will vary from 5 to 45 atm.
The catalysts are usually platinum or rhenium on silica or a silica-alumina support base. However such metals are very susceptible to sulphur and nitrogen contamination as such the feedstock is treated to remove both by hydrodesulphurization. Fresh catalyst is chlorinated first. Normally the catalyst can be regenerated 3 to 4 times before it has to be returned to the manufacturer for reclamation of the metal.
The four reaction steps:
- Dehydrogenation of the napthenes to convert them to aromatics.
- Isomerization of normal paraffin to iso-paraffin.
- Dehydrogenation and aromatization of paraffin to aromatics.
- Hydrocracking of paraffin into smaller molecules.
The hydrocracking of paraffin is the only one of the four major reforming reactions that consumes hydrogen. The isomerization of normal paraffin does not consume or produce hydrogen.
The most modern version of the process utilizes continuous catalyst regeneration (CCR). They are characterized by continuous in-situ catalyst regeneration. Part of the catalyst is regenerated in a special regenerator and by continuous addition of the regenerated catalyst to the operating reactors.
There are two possible options for such a process:
- UOP CCR Platformer Process
- Axen’s Octanizing Process
The liquid feed is pumped (5 to 45atm) to reaction pressure and is joined by a stream of hydrogen rich recycle gas. The liquid gas mixture is heated by flowing through a pre-heater. The mixture is then vapourized and heated to the reaction temperature (495°C to 525°C) before entering the reactor. The feed then flows through the reactors where the respective reactions take place. The feed is reheated between reactors to keep the reaction temperature up. Only three reactors are needed to effectively continue the reaction. The products are then cooled; the hydrogen gas then goes to other plants that need it. The product is then sent to a fractionator column where the liquid will become part of the gasoline blend the gas at the top can be recycled and reprocessed to obtain more fractions usually propane or butane. Any excess gas can become part of the refinery’s fuel gas system.
