Highly Efficient Methane Reforming over the 0.15wt% Ru/y-Al2O3 Catalyst in the 5um Pd-Ag Film Membrane Reformer

Highly efficient methane reforming over the 0.15wt% Ru/y-Al₂O₃ catalyst in the 5um Pd-Ag film membrane reformer

David S. A. Simakov and Yuriy Román-Leshkov

Department of Chemical Engineering, MIT, Cambridge MA 02139, USA

Natural gas is an abundant, cheap and relatively clean source of energy and chemical feedstocks, which can be reformed to syngas (CH₄ + H₂O = CO + 3H₂), requiring however temperatures above 850°C [1]. Membrane catalytic reformers can provide high CH₄ conversions below 650°C by selective separation of H₂ (providing also a source of extra-pure H₂) [2], but highly active and stable catalysts are required. Commercial Ni-based catalysts do not have sufficient activity at these temperatures and deactivate rapidly by coking, particularly at (highly desirable) low steam/carbon ratios. In our recent work we have demonstrated that the ultra-low loading 0.15wt% Ru/y-Al₂O₃ catalyst is highly active in low temperature CH₄ reforming and has excellent stability at low steam/carbon ratios [3]. Herein, we demonstrate the implementation of this catalyst in a membrane reformer, using the supported 5um Pd-Ag film membrane for H₂ separation. Conversions well above the equilibrium were achieved (Fig. 1a), generating 3.5 mol of ultra-pure H₂ per mol of CH₄ fed at the maximum (Fig. 1b). Importantly, the maximal power density of this (6 inch length, 0.5 inch OD) unit was 0.9kW/L (if the H₂ generated is fed to a 60% efficient fuel cell). No significant deactivation was observed after 200h of operation. The feasibility of the low steam/carbon ratio (S/C=1, 2) and of dry (CO₂) reforming was also investigated.

[1] Simakov, D. S. A., Wright, M. M., Ahmed, S., Mokheimer E. M. A. & Román-Leshkov, Y. Solar thermal reforming of natural gas: a review on chemistry, catalysis and system design. Catal. Sci. Technol. 5,  1991-2016 (2015).

[2] Said S. A. M., Simakov D. S. A., Mokheimer E. M. A., Habib M. A., Ahmed, S., Waseeuddin M. & Román-Leshkov Y. Computational fluid dynamics study of hydrogen generation by low temperature methane reforming in a membrane reactor. Int. J. Hydrogen Energy. 40, 3158–3169 (2015).

[3] Simakov, D. S. A., Luo H. Y. & Román-Leshkov, Y. Ultra-low loading Ru/g-Al₂O₃: a highly active and stable catalyst for low temperature solar thermal reforming of methane. Appl. Catal. B: Environ. 169, 540–549 (2015).