Methods for pore size engineering in ZSM-5 zeolite Original Research Article

Pore size of ZSM-5 zeolite can be engineered by two different methods: (a) the desilication–stabilization (DS) method allows the enlargement of the size of the ZSM-5 zeolite micropores from the average value of 0.53 nm to that of 0.59 nm. (b) The desilication–reinsertion–stabilization (DRS) method results in the narrowing of the size of the zeolite micropores down to 0.46 nm. The DRS method has recently been improved by using the ammonium form of the desilicated zeolite in the reinsertion step. This is probably due to an easier reaction between the zeolite silanol groups and the orthosilicate species, which occurs during the thermal treatment. Such a reaction leads to the zeolite structure stabilization and the formation of smaller pores.Selective adsorption tests with BTX aromatics and catalytic runs performed with methanol at various reaction temperatures, confirm the pore enlargement due to the DS treatment, and the pore narrowing as the result of the DRS treatment.