Study of the relationship between framework cation levels of y zeolites and behavior during calcination, steaming, and n-heptane cracking processes

The synthesis process and production of forms of the Y zeolite (i.e., NaY, NH 4Y, HY, and USY) have been studied in depth, in order to investigate the thermal stability of the Y structure throughout calcination, steaming, and cracking processes. The results indicate that an increase in the cation content within the Y framework during calcination and/or steaming processes led to an increase in the catalyst stability and a reduction in the rate of any associated dehydroxylation reactions. It was also found that the presence of sodium ions hindered the extraction of Al atoms from the crystal lattice structure during the steaming treatment, which minimized partial and/or entire structural collapse at high temperatures. Finally, enhancements in the distribution of the acid sites, and an increase in the activity and selectivity of the produced USY catalysts during n-C 7 cracking reactions, have also been observed. © 2012 American Chemical Society.