A fuel tank inerting system is disclosed. In addition to a fuel tank, the system includes a catalytic reactor with an inlet, an outlet, a reactive flow path between the inlet and the outlet, and a catalyst on the reactive flow path. The catalytic reactor is arranged to receive fuel from the fuel tank and air from an air source, and to react the fuel and air along the reactive flow path to generate an inert gas. The system also includes an inert gas flow path from the catalytic reactor to the fuel tank. The system also includes a non-uniform catalyst composition along the reactive flow path.