High-purity Green Hydrogen Production by Bio-oil/ethanol Mixtures Steam Reforming in Pd-based Membrane Reactors

Abstract

The use of a membrane reactor (MR) for the reforming of biomass derived oxygenates is a promising approach to produce pure hydrogen from renewable sources. In this study, a Pd membrane supported on a porous stainless-steel (PSS) tube was fabricated by Electroless Pore Plating (ELP- PP) and tested in the steam reforming (SR) of bio-oil stabilized with 25 wt.% ethanol. All reaction tests were conducted in a reaction setup with two consecutive steps: (i) the thermal treatment for the vaporization of the bio-oil/ethanol mixture and the controlled deposition of pyrolytic lignin, and (ii) the SR reaction in an upwards-flow bed reactor with a Ni-based catalyst obtained upon reduction of a NiAl₂O₄ spinel. The Pd membrane was allocated in the middle of the SR reactor for its use as a MR. The reaction conditions were maintained at 580 °C with steam/carbon ratio of 2.5, space time of 0.15 h, feed pressure in the range of 1-3.3 bar, 0.1 bar in the permeate side, and time on stream of 4 h. The results reveal the enhancement of the hydrogen yield when using the MR at 3.3 bar and with the lowest gas velocity, allowing a hydrogen recovery of 57.74% with 99.8% purity. Consequently, the total hydrogen production in the MR operating at 3.3 bar and 0.6 cm s^-1 increased from 0.309 to 0.367 g H₂ (g C)^-1 if compared to the conventional reactor at 1 bar and 0.9 cm·s^-1