Dynamic hydrogen production from ethanol steam-reforming reaction on NixMoy/SBA-15 catalytic system

Summary This study examined the effects of advanced bimetallic catalytic species of Ni and Mo on hydrogen production from ethanol steam reforming. NixMoy/SBA‐15 exhibited significantly higher ethanol steam‐reforming activity at mild temperatures than monometallic Ni/SBA‐15; the highest activity was achieved using the Ni0.95Mo0.05/SBA‐15 catalyst. H2 production and ethanol conversion were maximized at 70–87% and 90–92%, respectively, over the temperature range of 500 to 800 °C with an EtOH : H2O ratio of 1:3 and a gas hourly space velocity of 3000 h−1. This highlights the synergy between the Ni and Mo loading on SBA‐15 during ethanol steam reforming through the inhibition of Ni particle agglomeration and the consequent decrease in catalytic deactivation. In the proposed mechanism for ethanol steam reforming, Mo oxide promotes CH4‐steam reforming at lower temperatures and depresses the CO‐water gas shift reaction. Overall, hydrogen production is significantly higher over NixMoy/SBA‐15 than over monometallic Ni/SBA‐15 despite the evolution of CO gas. Copyright © 2014 John Wiley & Sons, Ltd. The bottomed figure compares the hydrogen selectivity over four reduced catalysts, Ni/SBA‐15, Ni0.975Mo0.025/SBA‐15, Ni0.95Mo0.05/SBA‐15, and Ni0.925Mo0.075/SBA‐15 catalysts. The reforming temperature was remarkably lower for the bimetallic NiMo/SBA‐15 catalysts than that over Ni/SBA‐15. Hydrogen evolution was maximized over Ni0.95Mo0.05/SBA‐15 to reach 92% at 800 °C. In particular, the reforming temperature was reduced significantly, by at least 200 °C, over the Ni0.925Mo0.075/SBA‐15 catalyst compared with that of Ni/SBA‐15. To determine the amounts and shapes of carbon deposited on the used catalysts, the surfaces of Ni/SBA‐15 and Ni0.95Mo0.05/SBA‐15 were examined by transmission electron microscopy. Transmission electron microscopy images confirmed that after the ethanol steam reforming, many carbon nanofibers were generated on the Ni particles of the Ni/SBA‐15 catalyst; otherwise, the carbon deposits were relatively small. The carbon lumps, however, were deposited over the used NiMo/SBA‐15 catalyst. In particular, there are carbon donuts that surround the nickel particles with increasing amount of MoOx.