Zero emissions hydrogen production by fluidized bed catalytic decomposition of methane

Abstract

The present paper deals with the strategic field of production of clean fuels with very low to zero emissions. A two stage fluidized bed process for catalytic decomposition of methane has been investigated. Firstly, the fluidized bed has been operated for the thermo-catalytic decomposition (TCD) of methane to produce hydrogen and solid carbon, which deposited on the catalyst. Secondly, the carbon oxy-combustion has been carried out to regenerate the catalyst producing a separated CO2 stream candidate to be directly fed to a sequestration unit. Experiments have been carried out in a laboratory scale bubbling fluidized bed reactor (26mm ID) using a home-made copper dispersed on γ-alumina as catalyst operated at 800°C. The carbon oxy-combustion regeneration strategy have been compared to the carbon combustion one on the basis of the efficiency of carbon removal and the performance of regenerated catalyst with respect to the TCD process. The effect of multiple cycles of decomposition and regeneration steps has been also quantified. A reasonable cyclic process has been simulated switching between two different feeds, the first containing CH4 and the second containing the regeneration stream. Experimental activity confirmed the possibility of producing a CO 2 stream that can be finalized to a sequestration unit but also indicated some drawbacks related to the oxy-combustion regeneration strategy which affect the production of COx species during the methane decomposition stage.