Dealumination and the Preparation of Ultrastable Zeolite

The largest use of a zeolite as a catalyst is the acid form of zeolite Y in catalytic cracking of the heavier fraction of crude oil to more valuable hydrocarbon 

Nickel K-edge k -weighted EXAFS spectra, with fitted curves according to chemical model (top row) and the associated Fourier transforms (bottom row) for (a) Ni(diethylenetriamine)2-Al6P6024F2 (Ni(deta)2-UT-6) (b) Ni(deta)2-UT-6 calcined in oxygen at 600 °C (c) bulk NiO, which has the rocksalt structure. The similarity between (b) and (c) indicates that NiO particles are produced upon calcination of the as-prepared complex-templated AlPO. 

Microporous silicates synthesised with isomorphous substitution of elements such as boron and gallium for silicon show similar demetallation behaviour, where the heteroatoms leave the structure more readily than aluminium atoms. In particular, the behaviour upon calcination of boron-containing solids has been examined by and Si MAS NMR. Boron is observed to move from tetrahedral to trigonal coordination upon the formation of the protonic boro-silicate form, and studies on the protonated form of zeolite B-Beta have shown that the boron may be removed from the framework stepwise by hydrolysis of Si-O-B bonds, ultimately giving boric acid. This is lost from the structure if put into contact with aqueous solution. 

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