A method of producing olefins by catalytic cracking of hydrocarbons is disclosed. The method may include catalytic cracking hydrocarbons in a feed stream that includes the hydrocarbons and the dry gasdiluent. The catalytic cracking may be carried out in a process using a train of fixed bed reactors while one or more other trains of fixed bed reactors are being regenerated or are on standby afterbeing regenerated. When the train of fixed bed reactors being used needs regenerating, it is taken out of service and the one or more other trains of fixed bed reactors put in service to carry out thecatalytic cracking process. Dry gas instead of steam may be used to reduce the partial pressure of hydrocarbons.