Methanol steam reforming using Ce and La modified low-Cu catalysts for On-board hydrogen production

• Cu-CL-Al catalysts suitable for on-board hydrogen production via MSR . • Higher H 2 yield of Cu-Cl-Al due to low R-WGS rate. • Strong Cu-CeO 2 interaction & CO 2 adsorption inhibit R-WGS. • Oxygen introduction maintains optimal Cu 0 /Cu + ratio for long-term activity. Methanol steam reforming (MSR) combined with simultaneous hydrogen purification using palladium membranes offers an advanced method for on-board hydrogen utilization in fuel cell vehicles. However, commercial Cu-Zn-Al catalysts typically operate around 300 °C, significantly lower than palladium membranes. In this study, a series of γ-Al 2 O 3 supported and CeO 2 and La 2 O 3 modified low-copper catalysts (n%Cu-CL-Al, n% = 2∼6 wt.%) were synthesized and compared with a commercial 45 %Cu-Zn-Al catalyst at 1.1 MPa. The Cu-CL-Al catalysts exhibited higher hydrogen yields (Y [H 2 ]) at temperatures above 400 °C. This performance is attributed to a limited reverse water-gas shift (R-WGS) reaction, facilitated by the strong CO 2 absorption properties of rare earth oxides. During long-term stability tests, the activity of the 4 %Cu-CL-Al catalyst significantly decreased after 50 h but rapidly recovered upon oxygen introduction. As no significant carbon deposition was observed on the catalyst surface, and nearly all Cu species in the used catalyst were reduced to Cu 0 , suggesting that deactivation was due to the over-reduction of Cu species by the generated H 2 . The presence of O 2 accelerated the oxidation rate of Cu 0 , maintaining an appropriate Cu 0 /Cu + ratio for MSR reaction. At 450 °C, Y [H 2 ] was constrained only by the equilibrium of R-WGS reaction, independent of the Cu loading and contact time. This indicates that for on-board hydrogen production using Cu-based catalysts, it is crucial to regulate Cu loading and catalyst quantity to achieve Y [H 2 ] that surpass the equilibrium limit of the chemical reaction.