QUESTIONS AND ANSWERS

I.FLUID CATALYTIC CRACKING:               www.wissenschaftler-avh.in

B.CATALYST/ADDITIVES(Contd.):

Q-39: What's the difference between a high Al2O3 FCC catalyst and a low Al2O3 one?

A-39:

High and low alumina are generally applied to older style amorphous catalysts. The first synthetic FCC catalyst contained about 12% alumina. High alumina catalysts were introduced in 1955 and were the dominant catalyst until the introduction of zeolite catalysts in 1964. Today, virtually all FCC's run on zeolite catalysts.

Some of these catalysts do, however, contain an active alumina in addition to the zeolite. These may be what you are referring to as high Al2O3 catalysts. The added alumina is intended to improve the conversion of the highest boiling fraction of the FCC feed. For this reason, these catalysts are often referred to as "bottoms cracking" catalysts.

In addition to increasing the bottoms conversion, the addition of active alumina to zeolite based catalysts also tends to increase the catalsyt delta coke (and thus the regenerator temperature). The alumina can also increase the dispersion of nickel deposited on the catalyst and thus, increase its dehydrogenation activity.