The invention relates to a method for separating gases which comprises: a first step in which a gas fuel stream comprising combustible substances that produce gas products when oxidised, and an oxygen-rich inlet stream are passed through at least two modules of oxygen-separating ceramic membranes, such that the two streams come into contact through the membranes and exchange heat; a second step of selective diffusion of oxygen from the oxygen-rich stream to the fuel stream, such that the outlet streams from the membrane modules are an oxygen-depleted or completely oxygen-free stream and a partially or completely oxidised stream; and a third step of recovery of at least two separate outlet streams of at least two gases selected from oxygen, nitrogen, carbon dioxide and hydrogen.

A reactor system and methods of operating are described herein. In some approaches, the system comprises a reactor body defining an internal cavity and a three-dimensional structure disposed in the internal cavity. The three-dimensional structure comprises an ionic conductor. A power supply is coupled to the three-dimensional structure generate an ionic current in the three-dimensional structure to control a temperature of the reactor. In some embodiments, the three-dimensional structure comprises multi-layer structure with alternating layers of the ionic conductor and the electronic conductor. In some embodiments, the system comprises a controller in operative communication with the power supply. The controller may control the amount of heat energy input to the reactor by adjusting the parameters of the power supply. In some embodiments, a catalyst is disposed in the three-dimensional structure.