Ion exchange of zeolites

It is well known that Rh(I) complexes can catalyze the carbonylation of methanol. A heterogenized catalyst was prepared by ion exchange of zeolite X or Y with Rh cations.126 The same catalytic cycle takes place in zeolites and in solution because the activation energy is nearly the same. The specific activity in zeolites, however, is less by an order of magnitude, suggesting that the Rh sites in the zeolite are not uniformly accessible. The oxidation of camphene was performed over zeolites exchanged with different metals (Mn, Co, Cu, Ni, and Zn).127 Cu-loaded zeolites have attracted considerable attention because of their unique properties applied in catalytic redox reactions.128-130 Four different Cu sites with defined coordinations have been found.131 It was found that the zeolitic media affects strongly the catalytic activity of the Cd2+ ion sites in Cd zeolites used to catalyze the hydration of acetylene.132... 

The high temperature XRPD technique can be used to investigate the dynamics of solid-state ion exchange of zeolites. Data suggest that the rate of Cd2+ ion transport in the zeolite Y micropores controls the rate of the solid-state ion exchange. 

In recent years the necessity of controlling the heavy metal content of waste water has become more apparent. This need has prompted us to study Pb2+ and Cd2+ ion exchange in the synthetic zeolite Na-A. There has been no work published on Pb2+ ion exchange in this zeolite and we are only aware of the work of Gal and coworkers on Cd2+ ion exchange of Na-A (1). Gal and Radovanov (2) and Maes and Cremers (3 4) have also reported work on Cd2+ ion exchange of zeolites Na-X and Na-Y. 

Lead and cadmium ion exchange of zeolite Na-A has been studied as a function of coion and temperature. It is found that the zeolite is very selective for these ions and that this selectivity is greater in nitrate solutions than in acetate solutions. The temperature dependence of the ion exchange reaction is small but distinguishable in the case of Pb + and too small to observe in the case of Cd +. 

Pertinent results for solid state ion exchange of zeolites Rho, ZK-5 and SAPO-42 with noble metal chlorides. 

The addition of binder to the H-EMT leads to a drop in activity which is higher than expected fi-om the binder proportion alone. Enhancement of the activity upon ion-exchange of zeolite-containing binder is rather high. 

The selectivity is also affected by the pretreatinent ion-exchange of zeolite with binder leads to a greater selectivity the ratio of the para -isomer (3) to the meta -isomer (4) is 17 for H-EMT, 20 for H-EMT with binder and 30 for H-(H-EMT -i-binder). The selectivity of the latter is 25% higher than the reported selectivity of a CuY-catalyst for the same reaction [3]. 

CuNaY zeolites were prepared by ion exchange of zeolite NaY with an aqueous 0.03 M solution of Cu(N03)2 ( Merck, pro analysi) at 300 K. After washing and drying at ambient temperature, the composition determined by AAS was CUj, i,Na2j jY. The samples were pressed into self-supporting wafers of about 8 or 80 mg cm thickness for IR and X-Ray measurements, respectively. They were dehydrated in vacuo up to 12 h at temperatures between 625 and 575... 

Alkaline Earth Ion Exchange of Zeolites X and Y. In recent years, alkaline earth ion exchange in zeolites X and Y has been studied thoroughly. In 1966, Barrer, Rees, and Shamsuzzoha reported on alkaline earth ion exchange in zeolite X at 25°C (12), and in 1968, Barrer, Davies, and Rees reported on exchange in zeolite Y at 25°C (6). In 1968, Sherry reported on alkaline earth ion exchange in zeolites X and Y over the temperature range of 5° to 50°C (54). 

Combined detemplation FedID ion-exchange of zeolites It combines several steps of the preparation of metal-exchanged zeolites in a single process. Application for Co(II) and Cu(n) can also be applied by modifying the original protocol. 

On the basis of ion exchange of zeolites, it is also possible to modify the characteristics of the cavities of the sieves leading to potential applications in purification and separation processes as well as in catalytic reactions. However, the sorption capacities of R-exchanged zeolites depend on the nature and content of R. 

How is it possible to distinguish radical cation reactions from genuine transformations catalyzed by the zeolite, and what types of processes tend to intrade on the identification of products of catalysis To answer the first question, we rely on the ion-exchangeability of zeolites. Zeolites are crystalline aluminosilicates, natural or man-made, that can adopt a remarkable range of channel-type and cage-type lattice architectures, depending on the... 

Cr/Zeolite catalysts have been prepared both by ion exchange and by impregnation. Ion-exchange of zeolite was performed by using aqueous solutions of Cr(N03)3 in the concentration range of 0.8M to 0.0 IM. The suspension of the zeolite in the Cr aqueous solution was stirred at room temperature for 2 hours. Then the solution was filtered and the solid calcined at 480 °C for 8 hours. 

Decomposition of Organometallic Cluster Compounds Ion Exchange of Zeolites. 

Catalyst preparation Cu(II)-NaY zeolite was prepared by ion exchange of zeolite NaY (10 g) with a solution of copper(II) acetate (2.86 g, 15.75 mmol in deionized water 150 mL) for 24 h at room temperature. The material was recovered... 

The formation of intrazeolitic zinc or cadmium oxide particles was also achieved by ion exchange of zeolites X, Y or EMT with the corresponding acetate solutions followed by precipitation of zeoHte-encaged hydroxides in a sodium hydroxide solution [148-151]. After calcination at 400°C, the formation of CdO particles was confirmed by XPS measurements [151]. The zeoHte-encapsulated... 

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