Catalytic cracking of light hydrocarbons to produce hydrogen and solid carbon

A reactor system, comprising:

• a riser operatively connected to a bottom portion of a reactor, the riser being configured to receive a first spent catalyst stream comprising catalyst particles and solid carbon flowing downwards from a reaction zone in a top portion of the reactor and to combust the first spent catalyst to produce a mixture of a heated catalyst solid stream and a heated gas effluent;
• and
• a separator operatively connected to the top portion of the reactor and a top portion of the riser, the separator being configured to separate the heated catalyst solid stream from the heated gas effluent, wherein the heated catalyst solid stream flows downwards to the reaction zone in the reactor at a temperature sufficient to crack a light hydrocarbon feed stream flowing upwards in the presence of fresh catalyst to produce a product effluent comprising hydrogen and a second spent catalyst stream comprising catalyst particles and solid carbon.