A key reaction in petrochemical processes is the isomerization of light hydrocarbons into high-octane naphtha feedstock for gasoline and other products.isomerization catalyst During this process the isomerization reaction takes place in the presence of an isomerization catalyst to select the desired enantiomers. To achieve the best possible isomerization selectivity a dual-function catalyst is required that carries both an acid function and a noble metal function. This is particularly true for acid catalyzed alkane isomerization. In this reaction the acid functional is incorporated into a porous material that supports the reaction under catalytic conditions. The isomerization of alkanes is a complicated reaction that involves many parallel and consecutive reactions. As such, the equilibrium of the isomerized alkanes is difficult to reach due to competing side reactions like cracking or alkylation. Consequently, a large number of isomerized alkenes are produced and the selectivity to the desired product decreases. In addition, the isomerization catalyst itself is vulnerable to degradation and poisoning by coke deposits and other unwanted reactions.
To overcome these problems a new type of isomerization catalyst was developed by the Hull group in the University of Hull.isomerization catalyst This is a Rh-catalyzed auto-tandem system that is able to selectively isomerize alkanes and also catalyze the subsequent reaction of enamine exchange and Rh-catalyzed 1,4-addition of a secondary amine to give chiral b-branched isopropenyl amides (see Scheme 11.1).
These new compounds are suitable for further use in the synthesis of menthol, an essential natural substance used in many pharmaceutics and cosmetics as well as flavors and fragrances.isomerization catalyst Unlike the conventional isomerization process, which uses a tertiary amine and requires the complex preparation of a chiral reagent, the enamine in the Hull process is readily obtainable through the Rh-catalyzed isomerization of allyl amines.
This simple but elegant process is a unique example of how the coordination chemistry of a noble metal can be combined with a Lewis acid catalyzed reaction to produce a new chemical entity.
A series of Pt loaded on MCM-48 silica and composites with HZSM-5 zeolite, HY zeolite and TiO2 have been studied for n-heptane isomerization. The characterization of the catalysts, including X-ray diffraction, Fourier transform infrared, scanning electron microscopy, temperature-programmed desorption and nitrogen adsorption-desorption, shows that these materials have excellent activity, isomerization selectivity, stability and low coke deposition. They are capable of converting a low octane naphtha stream into an isomerate with high octane number at temperatures in the range 200-350 degC.
As stringent environmental protection regulations are introduced worldwide for gasoline octane numbers, it becomes increasingly important to improve the isomerization process to reduce the proportion of aromatic hydrocarbons in gasoline. To meet this demand, the isomerization of C4-C7 naphtha feedstocks is becoming a major upgrading process at oil refineries and petrochemical plants. The octane-boosting isomerization of light naphtha in a gas processing plant is achieved by utilizing a high-octane n-heptane isomerization catalyst based on chlorinated aluminum oxide. However, the catalysts based on this material loose chlorine during the isomerization reaction and require frequent injection of chlorinated compounds to maintain the desired high activity.
Tags:butene isomerization catalyst | cu catalyst
