Basic Zeolites-Framework Composition

Taking into account the electronegativity of the framework one could increase the basicity of a zeolite by substituting framework oxygens by nitrogens. Then, two different types of strong basic sites could be developed [28] 

Alkali-exchanged zeolites can be used for selective condensation reactions [32-37], double bond isomerization, alkylation of toluene by methanol, mono-methylation of phenylacetonitrile with methanol and dimethyl carbonate (DMC) [38], and selective N-alkylation with methanol, ethanol, and 2-propanol as alkylating agents [39-44]. However, the basicity of alkaline exchanged zeolites is rather low. 

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Introductory Chapter 1 provides a historical overview of molecular sieve materials. Chapter 2 covers the definition of a zeolite and describes their basic and composite building units and how they are linked in zeolite frameworks. It defines pores, channels, cages and cavities and it gives references for finding detailed... 

Aluminium can be isomorphously substituted for silicon in the framework of zeolite Y by hydrothermal treatment of the dealuminated (ultrastabilised) zeolite with aqueous solutions of strong bases at elevated temperatures. The extent and efficiency of the reaction depend on the temperature, duration of treatment and especially on the kind and concentration of the basic solution. The degree of crystallinity and the thermal stability of the products are primarily controlled by the composition of the parent material. 29Si and 27A1 magic-angle-spinning NMR (MAS NMR) indicates that the extent of realumination is determined by the number of available tetrahedral Si(OAl) sites. 

The state and capabilities of quantum chemical modeling of silicon dioxide framework structures (silica, aluminosilicates, zeolites) are discussed by Zhido-mirov and Kazansky. Here are basic theoretical approaches to a class of catalytic compositions which contribute the probably most massive quantities of catalysts used by man s (petroleum and chemical) industries. 

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