Studies of the effect of pressure and hydrogen permeance on the ethanol steam reforming reaction with palladium- and silica-based membranes

The effects of hydrogen permeance and selectivity in the performance of membrane reactors for the ethanol steam reforming (EtOHSR) were studied at 1–10 atm and 623 K. The studies were performed with Pd–Cu and SiO2–Al2O3 composite membranes prepared by depositing the permselective components onto porous alumina supports with intermediate layers. The hydrogen permeances of the membranes varied from 5.2 × 10−8 to 3.9 × 10−6 mol m−2 s−1 Pa−1 and the selectivity ranged from 200 to 1000 (H2/CO2) at 623 K, which allowed a broad set of conditions to be probed. Comparison studies with packed-bed reactor (PBR) and membrane reactor (MR) operation showed that higher ethanol conversions and hydrogen molar flows were obtained in the MRs for all pressures studied. It was determined that both hydrogen permeance and selectivity had a favorable effect on the EtOHSR reaction, with the highest ethanol conversion enhancement of 44% and hydrogen molar flow enhancement of 69% obtained in a MR fitted with a membrane with the highest hydrogen permeance. A criterion for the required permeance for industrial applications is developed, which for 1 cm diameter membrane tubes is 2.5 × 10−7 mol m−2 s−1 Pa−1.