Abstract: Shape selective zeolites, such as ZSM-5, are added to the equilibrium catalyst in a catalytic cracking unit in large amounts. Sufficient fresh zeolite is added to result in an unacceptable increase in production of wet gas (C.sub.3 /C.sub.4) by the catalytic cracking unit, if operated at normal charge rates and operating conditions. To compensate, conditions in the catalytic cracking unit are adjusted, such as by reducing feed rate, catalyst/oil ratio, or cracking reaction temperature, to reduce the production of "light ends" to an amount which can be tolerated by the catalytic cracking unit. Within a few days to a few weeks, excessive production of wet gas will diminish so that unit operation may be returned to normal. Resumption of normal cracking operations using a catalyst inventory containing a relatively large amount of shape selective zeolite additive results in significant increases in the octane number of the catalytically cracked gasoline.

Abstract: The invention combines two unit operations i.e. fluid catalytic cracking (FCC) and circulating fluid bed (CFB) boiler technologies. The circulating solid inventory of the CFB boiler is introduced to the bottom of a conventional FCC unit to supply the endothermic heat of reaction. A once-through FCC catalyst is introduced under high-temperature, short residence time conditions whereby improved yields are achieved through the reduction of coke made in the FCC unit.