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Fluid Catalytic Cracking
The branched molecules help to give petrol with higher octane number, less inclined to knocking.
To find out how a fluid catalytic cracker operates click the numbered buttons on the diagram

Current designs of FCC reactors are processing anywhere from 13,000 to 125,000 barrels of feedstock per day
1 barrel = 159dm3

A Fluid Catalytic Cracker
In the 1960s synthetic zeolites started to replace silica/alumina catalysts. A big advantage of zeolites is that they are more selective, giving a higher yield of products in the more useful C5 to C10 range, and fewer in the C3 to C4 range. They also give more branched molecules which makes for a higher octane petrol

The oil industry switched to zeolites almost overnight and still uses them. The combination of higher activity and improved selectivity saves vast amounts of energy and money, making cheaper products possible.

The greater effectiveness of catalytic cracking with zeolites rather than silica-alumina saved over 200 million barrels of crude oil in 1977 in the USA alone, about 30 million tonnes.

Over 400 fluid catalytic cracking units are in operation at oil refineries around the world today. The reactions are varied. They include: