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 method of producing lower olefins and monocyclic aromatic hydrocarbons having 6 to 8 carbon atoms from stock oils selected from at least two or more kinds of oils, the method comprising:

• a first catalytic cracking step of bringing one stock oil A among the stock oils into contact with a catalytic cracking catalyst;
• a second catalytic cracking step of bringing one stock oil B into contact with the catalytic cracking catalyst;
• and
• a separation and collection step of 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 the first catalytic cracking step and the second catalytic cracking step are conducted in a single reaction tank,
• wherein the stock oil A contains 59% by mass or greater of an aromatic component,
• wherein the stock oil B contains 15% by mass or greater of a non-aromatic component and 50% by mass or greater of an aromatic component, provided that the content of the aromatic component contained in the stock oil B is 90% or less with respect to the total amount of the aromatic components contained in the stock oil A,
• wherein a contact time A during which the stock oil A is in contact with the catalytic cracking catalyst in the first catalytic cracking step is in a range of 15 seconds to 300 seconds, and
• wherein a contact time B during which the stock oil B is in contact with the catalytic cracking catalyst in the second catalytic cracking step is in a range of 0.1 seconds to 5.0 seconds.