Page 145 - Fluid Catalytic Cracking Handbook

120 Fluid Catalytic Cracking Handbook

* Operation of the reactor stripper be efficient. The stripper efficiency
is very important to allow the release of sulfate and the formation
of H 2S.

Since most of the regenerators operating in full combustion mode
usually operate with 1% to 3% excess oxygen, the capturing efficiency
of SO X additive is often greater in full combustion than in partial
combustion units.

ZSM-5

ZSM-5 is Mobil Oil's proprietary shape-selective zeolite that has a
different pore structure from that of Y-zeolite. The pore size of ZSM-
5 is smaller than that of Y-zeolite (5.1°A to 5.6°A versus 8°A to 9°A),
In addition, the pore arrangement of ZSM-5 is different from Y-zeolite,
as shown in Figure 3-16. The shape selectivity of ZSM-5 allows

Figure 3-16. Comparison of Y faujasite and ZSM-5 zeolites [13].