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Magnesium aluminophosphate-36 (MAPO-36) molecular sieve was synthesised hydrothermally and subjected to wet ion-exchange with Fe 3+ , Zn 2+ , La 3+ or Ce 3+ . They were characterised by using XRD, SEM, temperature programmed desorption (TPD) of ammonia and thermogravimetric analysis (TGA). The XRD patterns of ion-exchanged MAPO-36 exhibit similar features to that of MAPO-36, which revealed no structural degradation during ion-exchange. TPD (ammonia) showed selective ion-exchange of strong acid sites for Fe 3+ , La 3+ and Ce 3+ but not for Zn 2+ . Based on the results of TGA the actual species involved in the ion-exchange is suggested to be M(OH) 2 + , which upon calcination converted to MO + where M is Fe 3+ , La 3+ or Ce 3+ . tert- Butylation of phenol was carried out in the vapour phase as a probe reaction to examine the catalytic activity of MAPO-36 and ion-exchanged MAPO-36 molecular sieves. The ion-exchanged catalysts were found to be more active than the parent MAPO-36 and also showed higher selectivity to 4- tert- butylphenol. |
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