(118a) Dimethyl Ether and Methanol Steam Reforming to Hydrogen-Rich Gas Over СuO-CeO2/Al2O3 Catalysts

         Currently, fuel cells are considered as an alternative environmentally sound source of electric power. The most of fuel cells are fed by pure hydrogen or hydrogen-rich gas mixtures produced by catalytic conversion of hydrocarbons. Dimethyl ether (DME) and methanol are among the most promising primary sources of hydrogen. DME as well as methanol can be easily and selectively converted to hydrogen-rich gas by steam reforming (SR) reaction at relatively low temperatures (250-350^oC) compared to other fuels such as natural gas, gasoline and LPG.

Overall DME and methanol SR are expressed by the equations:

CH₃OН + Н₂O= 3H₂ + CO₂   

(CH₃)₂O + 3H₂O = 6H₂ + 2CO₂  

 It is generally assumed that DME SR proceeds via consecutive two-step reaction mechanism. The first step is hydration of DME to methanol and the second step is methanol SR to the hydrogen-rich gas:              

A design of active and selective catalysts for the DME SR requires knowledge on the properties of both Cu-containing catalysts for methanol SR and solid acids for the DME hydration to methanol.

The present work reports the studies of methanol and DME SR to hydrogen rich gas over bifunctionalСuO-CeO₂/g-Al₂O₃ catalysts. The СuO-CeO₂/g-Al₂O₃ catalysts were synthesized by treating γ-alumina (S_BET = 200 m²/g, V_pore= 0.7 cm³/g, diameter of granules is 0.25–0.5 mm) with solutions of copper and cerium salts. All catalytic experiments were performed in a fixed bed flow reactor at atmospheric pressure with gas analysis on line. Reaction conditions: CH₃OCH₃/H₂O/N₂=20/60/20 vol.% (CH₃OH/H₂O/N₂=40/40/20 vol.%), GHSV=10000 h^-1, temperature 200-370^oC. Prior experiments, the catalysts were reduced in a flow of 5 vol % H₂ + 95 vol % N₂ at 350 ^oC for 1h.

The results obtained prove СuO-CeO₂/g-Al₂O₃ to be efficient catalyst for DME and methanol SR to hydrogen-rich gas with a low CO content. With this catalysts, the hydrogen production rate reaches 600 mmol H₂/(g_cat · h). Besides, the catalyst shows good stability in the temperature range of 200-350^oC. Note that the presence of both copper oxide and ceria is of key importance for getting the active and stable catalysts for DME and methanol SR;

 The catalysts were characterized by XRD, HRTEM, EDX and FTIR spectroscopy. Activity and stability of СuO-CeO₂/g-Al₂O₃ catalyst for DME SR are most likely associated with the g-Al₂O₃ acidic centers and with the formation of an oxide copper–cerium solid solution, which are responsible for, respectively, DME hydration reaction and methanol SR reaction.

 

 Acknowledgements

The work was partially supported by Government Contract № P960 of  27.05.10 in the framework of Federal Targeted Program «Scientific and Research-Educational Staff for Innovative Russia 2009-2013».