Steam-stabilized Y zeolites

Figure 16.2 Transmission electron microscopy image of steam-stabilized Y zeolite showing mesopore network.

Operationally, the basic difference between the Type X and Type Y structures was largely a matter of thermal stability, although acid strength-related differences in selectivity were also found. While the Type Y zeolite was much more stable, it was also much more expensive. Davison initially marketed their XZ-15 catalyst, containing steam-stabilized Y zeolite admixed with low-alumina silica-alumina, at a price of 800 per ton. This was quite a high price at the time, but despite that, about 15 refiners tried it. At the same time, Filtrol introduced their Grade 800 catalyst, and although they didn t officially claim that it contained molecular sieves, the product distributions clearly pointed to their presence (67). 

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