(515d) Hydrogen Production By Catalytic Steam Reforming of Dimethoxymethane

Hydrogen Production by Catalytic Steam Reforming of Dimethoxymethane

S.D. Badmaev^1,2, A.A. Pechenkin^1,2, V.D. Belyaev^1,2, V.A. Sobyanin ¹

¹ Boreskov Institute of Catalysis, 630090, Novosibirsk, Russia

² Novosibirsk State University, 630090, Novosibirsk, Russia

sukhe@catalysis.ru

At present time, low- and high-temperature proton exchange membrane fuel cells (PEMFC) are considered to be alternative and environmentally safe pure sources of electric power. The fuel for PEMFC is hydrogen, which can be produced via steam reforming (SR) of hydrocarbons or oxygen containing organic compounds to synthesis gas and its subsequent conditioning to obtain hydrogen-rich gas with an insignificant content of carbon monoxide.

In particular, hydrogen rich gas production from synthetic oxygen containing organic compounds, such as methanol and dimethyl ether (DME), for PEMFC feeding application has long attracted considerable attention from researchers and engineers. It has been shown that methanol and DME, as distinct from hydrocarbons, can be easily and selectively converted to hydrogen rich gas at relatively low temperature (250–350°C). Efficient catalysts for methanol and DME SR have been suggested and then used to develop fuel processors - hydrogen rich gas generators.

Dimethoxymethane (DMM), like methanol and DME is a promising feedstock for producing hydrogen rich gas for PEMFC feeding application. Only few papers on DMM SR have been published. Overall DMM SR to hydrogen-rich gas is expressed by equation:

CH₃OCH₂OCH₃ + 4H₂O = 8H₂ + 3CO₂                    (1)

The reaction proceeds via a consecutive two-step mechanism including DMM hydration to methanol and formaldehyde (2), followed by steam reforming of the formed methanol (3) and formaldehyde (4) to hydrogen-rich gas:

CH₃OCH₂OCH₃ + Н₂О = 2СН₃ОН + СН₂О             (2)

СН₃ОН + Н₂О = 3Н₂ +СО₂                                  (3)

СН₂О + Н₂О = 2Н₂ + СО₂                                          (4)

A design of active and selective catalysts for the DMM 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 DMM SR to hydrogen rich gas over bifunctionalСuO-ZnO/g-Al₂O₃ andСuO-CeO₂/g-Al₂O₃ catalysts. The 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: CH₃OCH₂OCH₃/H₂O/N₂=14/70/20 vol.%, GHSV=10000 h^-1, temperature 200-300^oC.

The bifunctional СuO-ZnO/g-Al₂O₃ andСuO-CeO₂/g-Al₂O₃ catalysts contains both the acid sites on g-Al₂O₃ surface for DMM hydration to methanol/formaldehyde and copper-zinc-based oxide species for steam reforming of the formed methanol/formaldehyde to hydrogen-rich gas. The developed catalysts are active and selective for DMM SR to hydrogen-rich gas with low CO content (≤ 1 vol.%). In particular, it provides 100% DMM conversion with hydrogen production rate of ca. 16 L H₂/(g_cat·h) at T = 300°C and GHSV = 10000 h^-1. Based on these results and on the fact that DMM, in contrast to methanol, is environmentally benign chemical, we expect DMM to become a promising feedstock for the production of hydrogen for household and portable PEM FC feeding.