Environmentally Friendly Chemistry Using Supported Reagent Catalysts: Chemically-Modified Mesoporous Solid Catalysts

Abstract

Chemically-modiÐed mesoporous materials can be prepared as robust catalysts suitable for application in liquid phase processes such as FriedelÈCrafts reactions, selective oxidations, nucleophilic substitutions and aromatic brominations.

Design and Preparation of Organic−Inorganic Hybrid Catalysts

“…Catalysts for use in triphasic reactions have also been prepared by immobilizing phase transfer catalysts (PTC) onto silica . The immobilization of P + R 4 X - or N + R 4 X - onto a solid allows the quaternary site to act at the phase boundary between an organic and aqueous phase .…”

Catalysis of liquid phase organic reactions using chemically modified mesoporous inorganic solids

“…We have recently reported a series of supported tetraarylphosphonium PTCs which show particularly high thermal stabilities and useful activities in nucleophilic substitution reactions and aromatic oxidative brominations. 9,53,54 The catalysts are often reusable and are effective in non-polar solvents such as hydrocarbons even when the unsupported phosphonium salt is inactive (owing to poor solubility, the supported catalysts are believed to operate at the aqueous-organic interface). The catalysts can be prepared by a variety of methods as shown in Scheme 8.…”

Solid acid-catalyzed dehydration/Beckmann rearrangement of aldoximes: towards high atom efficiency green processes

“…Low bio-degradability is a serious problem in these environmentally conscious days. The work-up of products from nitrations, sulphonations, cyanation, and many other acid-catalyzed reactions involves neutralization and the concomitant generation of inorganic wastes such as NaCl, Na 2 SO 4 and (NH 4 ) 2 SO 4 [1,2,11,12]. Green chemistry demands the replacement of these highly corrosive, hazardous and polluting acid catalysts with ecofriendly solid acid catalysts.…”