Hydrocarbon processing, zeolite hydrocracking

The basic concept underlying alkylation reactions of aromatics is the formation of a stabilized carbocation able to attack nucleophilic substrates. Hydrocarbon cracking and hydrocracking, alkane isomerization, and olefin alkylation are important processes based on related alkane carbocation chemistry in the production of various types of hydrocarbons such as the branched ones for high octane gasolines. Zeolites and metal oxides are the preferred catalysts. 

Bifunctional zeolite catalysts such as platinum loaded acid zeolite catalysts are applied in several petroleum refinery operations, designated as hydroconversion processes isomerisation of light n htha, iso-dewaxing and hydrocracking of heavy fractions [4]. Most experimental investigations in academic laboratories are typically performed with pure model components or simple mixtures thereof as feedstock, and using reaction conditions under which the hydrocarbon compounds are in the vapor phase. Industrial hydroconversion processes are mostly run under three phase, or even in some cases under liquid phase conditions and with feedstocks that are extremely complex mixtures of large numbers of different hydrocarbon compounds [4]. 

Most crystalline aluminosilicates have little intrinsic catalytic activity for hydrogenation reactions. However, a considerable amount of data has recently accumulated on the use of zero-valent metal-containing zeolites in many hydrocarbon transformations. Thus noble and transition metal molecular sieve catalysts active in hydrogenation (7,256-760), hydroisomerization (161-165), hydrodealkylation (157, 158,165-167), hydrocracking (168,169), and related processes have been prepared. Since a detailed discussion of this class of reactions is beyond the scope of this review, only a few comments on preparation and molecular-shape selectivity will be made. 

---