Abstract: A CO2 conversion system includes at least a first reactor including a gas mixing tube, a spark ignition system for generating sparks in the gas mixing tube coupled to a catalyst chamber having a catalyst therein coupled to a reaction chamber. Inlet tubes each with gas flow control valves are for injecting process gases including O2, H2 and CO2 into the gas mixing tube, wherein the process gases react in the reaction chamber in at least one chemical reaction to form reaction products including output gases including CH4 and reaction heat. A process controller utilizes at a process temperature setpoint or a criteria for an output gas to control a temperature in the catalyst chamber to maintain the process temperature setpoint or output gas criteria by adjusting gas flow control valves for changing the mass flow of at least one process gas to reduce a heat from the chemical reaction.