Experimental and DFT study of (sorption-enhanced) steam methane reforming over bimetallic Ni-Cu catalysts

• Bimetallic Ni-Cu catalysts tested for (sorption-enhanced) steam methane reforming. • The addition of Cu promoted the activity and coke resistance of the catalysts. • Medium Cu loading (50 wt%) sufficient for achieving high CH 4 conversion for SMR. • Highest methane conversion of 97 % achieved by Ni and Ni 3 Cu 1 at 700 °C for SESMR. • Promoting effect of Cu explained by DFT calculations and microkinetic modelling. The catalytic performance of a monometallic Ni/Al 2 O 3 and three bimetallic Ni-Cu catalysts (with Cu loading of 2.5, 5, and 7.5 mol%, respectively) for the (sorption-enhanced) steam methane reforming reaction was evaluated. Physico-chemical characterization of the materials confirmed the formation of Ni-Cu alloy and the even distribution of active metals within the porous high-surface area support. All three bimetallic catalysts showed enhanced methane conversion compared to the conventional Ni/Al 2 O 3 catalyst at higher temperatures (800 °C), which was attributed to the promotion of the water–gas shift reaction by the addition of Cu. The experimental observations were supported by the Density Functional Theory calculations of carbon and oxygen adsorption on the mono and bimetallic surfaces. Ni 3 Cu 1 and Ni 1 Cu 1 were calculated to have a similar level of catalytic activity as Ni, based on results from a microkinetic model of the steam methane reforming reaction. Ni 1 Cu 3 showed slightly lower activity, potentially due to its low carbon adsorption ability which impedes the rate-determining methane decomposition process. The SMR reaction was further improved by adding calcium oxide as the CO 2 sorbent, which increased both methane conversion and hydrogen yield. Ni 3 Cu 1 /Al 2 O 3 and Ni 1 Cu 1 /Al 2 O 3 were identified as promising SMR catalysts with a high methane conversion of approximately 90 % at 800 °C and 97 % at 700 °C, without and with the sorbent, respectively.