Achieving strong thermal stability in catalytic reforming of methanol over in-situ self-activated nano Cu2O/ZnO catalyst with dual-sites of Cu species

Abstract

Copper based catalysts with excellent catalytic activity and hydrogen selectivity are widely used in methanol steam reforming (MSR). Yet, the hydrogen pre-reduction step results in hydrogen consumption and energy loss. In addition, the copper nanoparticles are extremely sintered (≥ 300 ℃) to render deactivation caused by the low Taman temperature of 407 ℃. To solve these specific problems, a nano Cu2O/ZnO catalyst with double copper active sites (Cu+ and Cu0) was designed. Cu+ with high reducibility could lessen the catalyst's self-activation time using methanol as the hydrogen carrier. Nano ZnO could support and scatter the active components, effectively prevent the sintering and aggregation of copper nanoclusters. Furthermore, the synergy between the carrier and the active components existed according to H2-TPR. In order to maximize the hydrogen yield and reduce undesirable CO, the quadratic polynomial functions were established to investigate the effects of temperature (T = 450–550 °C), molar ratio of steam to carbon (SCMR=1.5–2.5 mol/mol), and weight-hour space velocity (WHSV=4–6 h−1) on H2 yield (HY) and potential H2 yield (PHY) based on the response surface methodology (RSM) in conjunction with the Box-Behnken design (BBD). The HY (92.1%) and PHY (97.2%) were obtained under T = 550 °C, SCMR= 2.0 mol/mol, and WHSV= 4.7 h−1. Within 36 h, stable 99% hydrogen selectivity was attained at 550 °C. The activity is induced by a new double copper active reaction path substituting the conventional Cu0-determined path. These discoveries provide a basis for the development of efficient catalysts with commercial potential.