462795 Steam Reforming of Dimethyl Ether over a Novel Plate-Type γ-Al2O3/Al Monolith Supported Cu-Based Bi-Functional Catalyst
DME steam reforming: CH3OCH3 + 3H2O ↔ 6H2 + 2CO2 △Hr = +135kJ/mol (1)
DME hydrolysis: CH3OCH3 + H2O ↔ 2CH3OH △Hr = +37kJ/mol (2)
MeOH steam reforming: CH3OH + H2O ↔ 3H2 + CO2 △Hr = +49kJ/mol (3)
In our previous works,1-3 a plate-type γ-Al2O3/Al monolith was prepared through anodization technology. The structured monolith was proven to have an excellent activity in DME hydrolysis. Moreover, the anodic alumina supported Cu composite catalyst exhibited a satisfied performance in DME SR system.
In this study, the self-reduction behavior of fresh Cu/γ-Al2O3/Al catalyst during DME SR was further studied and the self-activation mechanism was proposed based on XRD and XPS analysis. However, the Cu/γ-Al2O3/Al catalyst showed a poor thermal stability at 350 °C due to the sintering of copper. As an approach, nickel was added to the Cu-based catalyst, and then the effect of nickel loading and chemical state on the activity of Cu/Ni/γ-Al2O3/Al catalyst was investigated. It was found that the proper amount of nickel could improve the dispersion of copper species, and thus enhancing the catalytic activity. For catalysts with lower nickel loadings, the thermal stability of Cu-based catalyst could not be improved. While, for catalysts with higher nickel loadings, part of nickel species would aggregate and block the active sites of copper. Moreover, a small amount of metallic Ni appeared, which resulted in the occurrence of side-reaction of CO methanation. Finally, the durability evaluation of optimized Cu/Ni/γ-Al2O3/Al was carried out under critical conditions (400 °C) and the results showed that it has an excellent stability during a 120 h test, which demonstrated that the novel plate-type γ-Al2O3/Al monolith supported Cu and Ni composite catalyst was an excellent catalyst for DME SR. Furthermore, it would be very promising for the application of micro-channel reformer for the domestic fuel cell system as for its outstanding shape flexibility and catalytic performance.
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