Abstract
The effect of the basic (KOH) or acid (H3PO4) treatment of the MFI (HZSM-5) zeolite has been studied comparing the structural and acidic features with the catalytic performance and deactivation of a set of unmodified and modified zeolites (SiO2/Al2O3 =30-280, 0-3 wt% of K or P). The properties of the catalysts have been elucidated using XRD, (27)AI and Si-29 NMR, N-2 adsorption-desorption, and adsorption-TPD of tert-butylamine. The catalytic performance has been evaluated in the cracking of 1-butene by means of initial, 5 h on-stream activity and coke formation. Our results point to the fact that using zeolites with high SiO2/Al2O3 ratio or neutralizing the strongest acid sites with KOH or H3PO4 increases propylene selectivity while decreases 1-butene conversion. The overall pathway of reaction involves propylene and other olefins as primary products that condensate in further steps to aromatics and ultimately to coke. This pathway can be controlled with less severe acidic features and by desilication with KOH or H3PO4 (particularly with the former). (C) 2015 The Authors. Published by Elsevier B.V.