Supported catalysts copper-exchanged zeolites

Dimerizations of aryldiazomethanes to 1,2-diarylethylenes were reported to be catalyzed by cerium(IV) ammonium nitrate (4J), lithium bromide (42), copper(II) salts (43), and rhodium(II) acetate (44) and to be induced by photolysis (45). Catalysis of copper ion-exchanged zeolite (CuNaY) was compared with reactions of copper salts supported on AI2O3 and a homogeneous catalyst, Cu(C104)2, for the dimerization [Eq. (11)] of aryldiazomethane (Table XIII) (-/6). 

Catalytic activity depends more on the nature and pre-treatment of the catalyst than on the content of copper. Thus, Cu(II)-exchanged KlO-montmorillonite displays an activity similar to the other clays and CuCl2-supported catalysts in spite of the very low amount of copper contained in that clay. Zeolite Y is less active than clays and does not promote the reaction at room temperature. Finally, calcination under dry air reduces the catalytic activity. 

Cobalt, copper and nickel metal ions were deposited by two different methods, ionic exchange and impregnation, on an amorphous silica-alumina and a ZSM-5 zeolite. The adsorption properties towards NH3 and NO were determined at 353 and 313 K, respectively, by coupled calorimetric-volumetric measurements. The average acid strength of the catalysts supported on silica-alumina was stronger than that of the parent support, while the zeolite-based catalysts had (with the exception of the nickel sample) weaker acid sites than the parent ZSM-5. The oxide materials used as supports adsorbed NO in very small amounts only, and the presence of metal cations improved the NO adsorption [70]. 

Hutchings and coworkers have extensively studied the zeolites supported heterogenous catalyst for aziridination of alkene [57-58]. The catalyst was synthesized using ion exchange of NaY zeolite and CuCOAc). This zeolite supported copper acetate is then premixed with chiral bis(oxazoline) in acetonitrile. The catalysis further promoted by addition of nitrene donor PHI=NNs or PhI=NTs and the desired alkene (Scheme 11.5). 

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