(143e) MgO-CuO-CeOx Sorbent Bead for a Trace Carbon Monoxide Removal for Fuel-Cell Grade Hydrogen Production

Hydrogen is noted as a clean energy source for fuel cells and power generation. Various techniques to separate and purify hydrogen mixtures have been developed to produce high-purity hydrogen (99.99+% level) ^[1]. Many studies have reported performance degradation of fuel cells due to trace amounts of CO in hydrogen, let alone H₂ purity. Adsorptive cyclic processes such as P(V)SA and TSA can produce high purity H₂ from various H₂ mixture off-gases, but the steep decrease of recovery is expected to produce H₂ with less than 3 ppm CO for fuel-cell grade ^[2]. Currently, selective catalytic oxidation is mainly studied as CO removal for fuel-cell grade hydrogen production, but this reaction is accompanied by other gases, which has the disadvantage of requiring an additional separation process. Therefore, the removal of trace CO in H₂ is still a great challenge in producing H₂ with ppb level of CO.

Herein, we present the MgO-CuO-CeO_x sorbent beads with very strong adsorption affinity at an extremely low pressure of CO. The adsorbents were synthesized by a combustion-assisted method. The spherical composite beads with hundreds of micrometers in diameter were highly porous, and the metals were homogeneously dispersed in the bead. The morphological characterization of spherical MgO-CuO-CeO_x sorbent bead was conducted via SEM, HR-TEM, XRD, and a gas sorption analyzer. In addition, the ratio of the surface copper to bulk copper in the beads was measured through a dissociative H₂ TPR method, and the adsorption capacity and mechanism were also analyzed by adding XPS analysis.

Adsorption isotherms of CO on the as-prepared composites with various metal ratios were measured by a volumetric method. The high and strong adsorption capacity was observed, especially up to 100 ppm CO. The regeneration conditions and cyclic stability were evaluated by cyclic thermogravimetric tests. Based on the analysis results, the direction of developing metal composites for various physisorption-chemisorption mechanisms accompanied by CO adsorption as well as CO removal is suggested.

^[1] G Bang, DK Moon, JH Kang, YJ Han, KM Kim, CH Lee, Chem. Eng. J., 411 (2021)

^[2] YW You, DG Lee, KY Yoon, DK Moon, SM Kim, CH Lee, Int. J. Hydrogen Energy, 37 (2012)