Fixed-bed reactors for exothermic reactions: A qualitative relation between start-up time and traveling waves velocity

•New data for a methanation reactor using novel, microstructed interdiffused catalyst.•Quantitative analysis determined for transient reactor performance.•Reaction front backward velocity is a linear function of the temperature.•The characteristic time of the forward movement is maximum for a setpoint of ~410 °C.•410 °C marks the predominance between reactant depletion and thermal self-acceleration. An experimental investigation of the reaction front movements upon reacting gas injection in a pre-heated non-adiabatic fixed-bed methanation reactor is conducted. The relocation starts with a backward movement of the front, whose maximal velocity turns out to be a linear function of the temperature setpoint. The front then moves forward in response to the fact that the injected cold gas cools down the bed in the upstream zone. The front stabilizes asymptotically in the downstream (upstream, resp.) zone of the reactor after a characteristic time that is an increasing (decreasing, resp.) function of the temperature setpoint, if the setpoint is below (above, resp.) a certain threshold. This behavior is interpreted in terms of reaction wave velocity.