Europium -exchanged zeolites

Two main components were used in the model catalysts described in this paper. One component was a europium exchanged ammonium Y zeolite (EuNH-Y). The other component was an amorphous aluminosilicate containing about 75% Si 0 and 25% Al203 (AAA-alumina). All materials were artificially V-contaminated by impregnation with vanadyl naphthenate solutions in benzene. Tetraphenyl tin (in hot toluene) was the passivating agent used. It was added either before or after loading vanadium on the zeolite (EuNH-Y), on the gel or on a gel-zeolite mixture. 

Europium(III) exchanged zeolites have been studied by a number of research groups. Arakawa and coworkers (20, 21 ) report the luminescence properties of europium(III)-exchanged zeolite Y. Emission spectra were measured under a variety of conditions and bands for europium(II) were observed after thermal treatment of the europium(III) Y zeolites. A mechanism was proposed for the thermal splitting of water which involved the cycling of europium between the two different oxidation states. Europium MSssbauer experiments (22 ) also show that on thermal treatment of europium-(III) zeolites that europium(II) is formed. Stucky and coworkers (23, 24) studied the phosphorescence lifetime of these europium-(lll) zeolites and showed that the inverse of the lifetime (the decay constant) was linearly related to the number of water molecules surrounding the europium(III) ion in the zeolite supercages. These studies involved zeolites A, X, Y and ZSM-5. 

Michael reaction of cyclopent-2-enone with dimethyl malonate has been studied on europium-containing Y zeolite at 30°C (Baba et al. 1995). In this case, europium was introduced into K+-exchanged zeolite by impregnation from a solution of the metal on... 

Alkali and alkaline-earth exchanged zeolites or zeotypes (c.g. MCM-41) [15, 39, 130, 141-155] have been extensively used as base catalysts. However, they are w eak bases. Alternatively, either alkali metal or alkali and alkaline-metal oxides can be occluded into zeolites and zeotypes in order to increase their basicity [18,63, 154, 156-161]. This is usually referred to as the introduction of a basic guest into a zeolite host. Moreover, the loading of Yterbium or Europium metal on zeolites, thus yielding strong bases, has been reported [17]. 

Europium and ytterbium (R/zeolite) introduced into K+-exchanged Y-zeolite by impregnation from liquid ammonia solutions similarly show various catalytic reactivities with changes in evacuation temperatures (Baba et al. 1992). The changes in the chemical state of rare earths with the evacuation temperature are studied by IR and X-ray absorption... 

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