427019 Self-Activation and Improved Stability Investigation of a Novel Plate-Type Al2O3/Al Monolith Supported Cu-Based Catalyst in Steam Reforming of Dimethyl Ether

Thursday, November 12, 2015: 10:10 AM
255F (Salt Palace Convention Center)
Feiyue Fan, Qi Zhang, Xing Wang and Zibin Zhu, Department of Chemical Engineering, East China University of Science and Technology, Shanghai, China

Hydrogen is considered as a clean source of energy and steam reforming of dimethyl ether (DME) is regarded as a promising method to produce hydrogen for fuel cell applications. Unlike many other fuels (e.g. methanol methane and bio-ethanol), DME is non-toxic and provides high H/C ratio and high energy density. Generally, steam reforming of dimethyl ether (DME SR) (Eq. (1)) consists of two moderate endothermic reactions: DME hydrolysis (Eq. (2)) to methanol over a solid acid catalyst, followed by steam reforming of methanol (MSR, Eq. (3)) over a steam reforming catalyst. Therefore, a bi-functional catalyst consisting of acid sites and MSR sites is required for overall DME SR process.

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)

For DME hydrolysis system, a novel plate-type anodic γ-Al2O3 as monolithic support was prepared through the anodization technology, and its catalytic performance for hydrolysis of dimethyl ether (DME) was compared with that of the commercial γ-Al2O3. The results show that the anodic Al2O3/Al monolith exhibited higher catalytic activity than the commercial γ-Al2O3 due to its stronger acidity, better hydrophilicity and lower activation energy. Moreover, a 120h stability evolution was carried out and the results show that the plate-type anodic alumina has an excellent ability for coke suppression, which demonstrated that the novel anodic γ-Al2O3/Al monolith was an excellent acidic catalyst and support for DME SR.

  For DME SR system, a series of Cu/γ-Al2O3/Al bi-functional catalysts were prepared by impregnation method. The catalytic performance of Cu/γ-Al2O3/Al catalysts both with and without H2 pre-reduction was compared. It was found that these two composite catalysts exhibited the similar catalytic activity. Meanwhile, according to XRD and XPS results, copper species over un-reduced catalyst was reduced to metallic Cu after DME SR reaction, indicating the in situ reduction of CuO in the reaction condition of DME SR. However, Cu-based catalysts have poor thermal stability and can easily lose catalytic activity due to the sintering of metallic Cu above 300°C. To improve the thermal stability of Cu, several components (e.g. Mn, Cr, Ni) were added to the Cu-based catalyst and their catalytic performance for DME SR was studied. It was found that Ni-doped catalyst had excellent catalytic activity. Moreover, the durability test of Cu/Ni/γ-Al2O3/Al was carried out under critical conditions (400°C) and the results show that it has an excellent stability for 100h with a 100% DME conversion, which demonstrated that the novel plate anodic 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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