Zeolites large pore size

POMs can he immobilized onto anion-exchange resins and surface-modified metal oxides with quaternary ammonium cation- or amino-functional groups via anion-exchange. Jacobs and coworkers tethered Venturello s catalyst [P04(W0(02)2)4]3-on a commercially available nitrate-form resin with alkylammonium cations and have carried out the epoxidation of allylic alcohols and terpenes with this supported catalyst [166, 167]. The regio- and diastereoselectivity of the parent homogeneous catalysts were preserved in the supported catalyst. For bulky alkenes, the reactivity of the POM catalyst was superior to that of Ti- 3 zeolite with a large pore size. The catalytic activity of the recycled catalyst was maintained completely after several cycles. 

Note that the coke formation itself is not deactivated. This is probably due to the growth of coke, which is not hampered yet in this zeolite with its relatively large pore size, unlike that observed on ZSM-48 [Froment et al, 1990]. 

A specially formulated catalyst for maximizing the yield of light olefins can be tailored in the light of the feed properties and target products by optimizing the composition of a mixture of different natural zeolites. The pore size distribution of the matrix should be sueh as to allow access to the large molecules of the feedstock, whilst incorporation of large pore Y zeolite favors intermediate molecule formation and mesoporous ZSM-5 favors production... 

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