Organic catalysis over zeolites: A perspective on reaction paths within micropores

Zeolites have proved to be valuable technical catalysts in petrochemistry and in oil processing. The characteristic properties of zeolites, such as acidity, shape-selectivity and thermal stability also enable them to be used for highly selective synthesis in the fields of chemical intermediates and fine chemicals. This interesting area of application has grown continuously in recent years. The present article summarizes the various standard types of reaction involved in organic syntheses which can be catalyzed by zeolites; these include, inter alia, electrophilic and nucleophilic substitution reactions, isomerization of double bonds and carbon skeletons, as well as addition, elimination and hydrogenation reactions.

Zeolites: Catalysts for Organic Syntheses

Recent advances in the industrial alkylation of aromatics: new catalysts and new processes

This review describes mechanisms of catalytic reactions leading to mono- and dialkyl benzenes over zeolites, which represent an important part of petrochemical products. The emphasis is given to the effect of the type of acid sites, zeolite structure, and reaction conditions on the activity and selectivity of these complex reactions, and particularly to the individual products with respect to their iso- vs. n- and ortho-, meta-, and para-isomers. The first part of the paper deals with the description and analysis of the structure and properties of the acid sites, and zeolite pore inner structure applied in synthesis of alkyl benzenes. Individual reactions leading to the synthesis of propyl benzene, xylenes, ethyl toluenes, diethyl benzenes, and transformation of trimethyl benzenes to xylenes from the view point of the reaction mechanism, function of the acid sites, and inner pore geometry of zeolites are described in the second part.

Acid-catalyzed synthesis of mono- and dialkyl benzenes over zeolites: active sites, zeolite topology, and reaction mechanisms

Disproportionation and transalkylation are important processes for the interconversion of mono-, di-, and tri-alkylbenzenes. In this review, we discuss the recent advances in process technology with special focus on improvements of para-isomer selectivity and catalyst stability. Extensive patent search and discussion on technology development are presented. The key criteria for process development are identified. The working principles of para-isomer selectivity improvements involve the reduction of diffusivity and the inactivation of external surface. In conjunction with the fundamental research, various practical modification aspects particularly the pre-coking and the silica deposition techniques, are extensively reviewed. The impact of para-isomer selective technology on process economics and product recovery strategy is discussed. Furthermore, perspective trends in related research and development are provided.

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Warren W. Kaeding

Papers

Shape-selective reactions with zeolite catalysts. IV: Alkylation of toluene with ethylene to produce p-ethyltoluene

Shape-selective reactions with zeolite catalysts: V. Alkylation or disproportionation of ethylbenzene to produce ϱ-diethylbenzene

Shape-selective reactions with zeolite catalysts: VI. Alkylation of benzene with propylene to produce cumene

Shape-selective reactions with zeolite catalysts: VII. Alkylation and disproportionation of cumene to produce diisopropylbenzene

Conversion of methanol to hydrocarbons: III. Methylation, ethylation, and propylation of benzene with methanol