FCC reactors are among the largest processing units used in the petroleum industry. Figure P1.3 shows an example of such units. A typical unit is 4-10 m ID and 10-20 m high and contains about 50 tons of p = 800 kg/m³ porous catalyst. It is fed about 38 000 barrels of crude oil per day (6000 m³/day at a density p = 900 kg/m³), and it cracks these long chain hydrocarbons into shorter molecules.

To get an idea of the rate of reaction in these giant units, let us simplify and suppose that the feed consists of just C₂₀ hydrocarbon, or

If 60% of the vaporized feed is cracked in the unit, what is the rate of reaction, expressed as -r' (mols reacted/kg cat · s) and as-r' (mols reacted/m³ cat · s)?

C20H42 -C12 Cg C5 C3 CH4