| Popis: |
This chapter discusses the use of zeolites in separation of organic products, and in shifting equilibria by selective adsorption (or selective membrane passage) of products or side products. Zeolites and mesoporous molecular sieves contribute in several ways to organic synthesis. They play an important role in subtle separation and in isomerization of aromatic regio-isomers, allowing low-waste integrated reaction/separation/isomerization processes. Zeolites can in situ remove selectively small by-products by adsorption or membrane action, thus shifting equilibria to completion. A generally overlooked pitfall is that zeolites induce—by ion exchange—some ionization of hydroxylic organic solvents and reactants. Zeolites and mesoporous molecular sieves can be tuned and modified in many ways, and generally, the protocols are available. Therefore, a given reaction a zeolite catalyst can be upgraded to improved performance. By its acid functions, a zeolite or mesoporous system can act as a bifunctional catalyst and can serve in the so-called “cascade reactions.” |
