Stability of CuZnOAl2O3/HZSM-5 and CuFe2O4/HZSM-5 catalysts in dimethyl ether steam reforming operating in reaction–regeneration cycles

The study focuses on the regenerability of bifunctional catalysts prepared with different metallic functions (CuZnOAl2O3 and CuFe2O4 spinel) and HZSM-5 zeolite (SiO2/Al2O3 = 30) as the acid function. These catalysts have been employed for H2 production in the steam reforming of dimethyl ether in a fluidized bed reactor, operating in reaction-regeneration cycles. The regeneration of the catalysts was carried out by combustion in air (at 315 or 500 °C) of the deposited coke, in order to establish: i) the coke combustion temperature required for recovering the activity of the metallic and acid functions; and ii) the kinetic behavior of the catalysts after removing the coke deposited on the metallic function and after the complete removal of coke. At 315 °C only the coke deposited on the metallic sites is burned, whereas 500 °C is required to remove the coke deposited on the zeolite. The catalyst with CuFe2O4 spinel metallic function exhibits higher stability and allows operating uninterruptedly under reaction–regeneration cycles, since it recovers its activity after regeneration at 500 °C. The catalyst with CuZnOAl2O3 metallic function, which is more active than the Cu-Fe spinel for the dymethyl ether steam reforming, deactivates irreversibly at 500 °C due to Cu sintering.