The fixed bed catalytic cracking method is described in the following diagram.

The charge is passed through a heater where it is heated to cracking level then it is goes to catalyst towers. These towers have catalyst tubes and around these tubes molten salt mixtures (mixture of sodium nitrate and sodium nitrite) are circulated to distribute heat and maintain uniform temperature in the reactor. The cracked vapors form these catalyst towers of fractionators in the fractionating column to recover gases and gasoline vapors from the top and the heavy gas/oil is removed from the bottom of the column.

Gasoline vapors are cooled and condensed in the condenser and then sent to the stabilizer. In the stabilizer certain dissolved gases are removed and the desired boiling range and vapor pressure is obtained. The main catalysts used are

1. Bauxite pellets
2. Silicon Nitrite complex of Alumina (SiN₂.Al₂O₃) of 6 mesh size