Method of producing lower olefin and monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms and device for producing lower olefin and monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms

A device for producing a lower olefin and a monocyclic aromatic hydrocarbon having 6 to 8 carbon atoms from stock oils selected from at least two or more kinds of oils, the device comprising:

• first catalytic cracking means for bringing one stock oil A among the stock oils into contact with a catalytic cracking catalyst;
• second catalytic cracking means for bringing one stock oil B, having an aromatic component content smaller than that of the stock oil A, among the stock oils into contact with the catalytic cracking catalyst;
• and
• separation and collection means for collecting the lower olefins and the monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms from a product generated in the first and second catalytic cracking steps,
• wherein a contact time A during which the aromatic component is in contact with the catalytic cracking catalyst in the first catalytic cracking step is longer than a contact time B during which a non-aromatic component is in contact with the catalytic cracking catalyst in the second catalytic cracking step.