In at least one embodiment of the present invention, a method of heating a FCC unit having a regenerator and a reactor for over CO.sub.2 reduction is provided. The method comprises compressing syngas to define compressed syngas. CO.sub.2 is separated from the compressed syngas to provide a first stream of gas comprising CO.sub.2. The first stream of gas is expanded with a second stream of gas comprising O.sub.2 to define a feed gas. The feed gas and an injected hydrocarbon feed are introduced to the regenerator having spent catalyst from the reactor. The regenerator is at gasification conditions to burn the injected hydrocarbon feed and coke from the spent catalyst producing the syngas and heat for operating the reactor at reaction temperatures.