The isomerization process is the transformation of light n-alkanes into the corresponding isomeric alkanes. Isomerization process can be used for the production of isomerized oils, which are high-octane gasoline components, because isomerized alkanes with a branching structure have good anti-explosive properties and high octane values.
There are many types of catalysts used in alkane isomerization process, currently the two main types are acidic Friedel-Crafts (Friedel-Crafts) type catalysts and bifunctional catalysts.
The Friedel-Crafts catalysts mainly consist of AlX3 such as AlCl3 and AlBr3, and HX such as HCI as co-catalyst. These catalysts have high activity at low temperatures of 20~120℃, and are favorable for the formation of isomeric alkanes in chemical equilibrium. However, AlCI3 is very easy to sublimate at the reaction temperature and has a large solubility in liquid hydrocarbons, thus it is easily carried out of the reactor, solidifies in the cooler and corrodes the equipment. In industrial applications, effective measures should be taken to immobilize AlCl3.
The bifunctional catalysts are the metal with hydrogenation activity such as Ni, Pt, Pd, etc. loaded on the solid acidic carrier such as Al2O3, SiO2-Al2O3, Al2O3-B2O3 or Zeolite, forming the acidic center and the metal center with hydrogenation activity. Currently, bifunctional catalysts are widely used in the pro-hydrogen isomerization method for alkane isomerization under hydrogen pressure. The C5/C6 alkane isomerization catalysts commonly used abroad are all noble metal bifunctional catalysts. They can be divided into medium temperature type (reaction temperature is 210~280℃ ) and low temperature type (reaction temperature is below 150℃) according to the operation temperature. The isomerization reaction is exothermic, and the higher the temperature is the more unfavorable to the reaction.