Experimental and kinetic studies of the ethanol steam reforming reaction equipped with ultrathin Pd and Pd-Cu membranes for improved conversion and hydrogen yield

Abstract

The ethanol steam reforming (EtOH SR) reaction was carried out over a Co-Na/ZnO catalyst both in a packed bed reactor (PBR) and in membrane reactors (MRs) equipped with ultrathin Pd or Pd-Cu membranes to evaluate the benefits of employing membranes. For all conditions, ethanol conversion and hydrogen production were significantly higher in the MRs than in the PBR. Average ethanol conversion enhancement and hydrogen production enhancement were measured to be 12% and 11% in the Pd MR and 22% and 19% in the Pd-Cu MR, respectively. These enhancements of the conversion and product yield can be attributed to the shift in equilibrium by continuous hydrogen removal by the Pd based membranes. A significant contamination of the Pd layer by CO or carbon compounds during the reaction can be the reason for the comparatively low enhancement in the Pd MR compared to the Pd-Cu MR in spite of the high H-2 permeability of the original Pd membrane. A one-dimensional modeling study of the MRs and the PBR was conducted and their predicted results were compared to those obtained from the experimental study. The model was developed using a simplified power law expression but the predicted values fit the experimental data with only minor deviations. Enhancements of ethanol conversion and hydrogen yield with space velocity (SV) could be explained by the increased H-2 flux through the membranes with SV in the MRs.