Bio-ethanol steam reforming and autothermal reforming in 3-μm channels coated with RhPd/CeO2 for hydrogen generation

A silicon micromonolith of 7 mm diameter and 0.2 mm length containing 1.5 million regular channels with a diameter of 3.3 μm was used for obtaining hydrogen through ethanol or bio-ethanol steam reforming (ESR) and oxidative steam reforming (OSR). The microchannels were coated with RhPd/CeO2 catalyst by a two-step method. First a CeO2 layer of ca. 100 nm thickness was deposited from cerium methoxyethoxide over a SiO2 layer, which was previously grown over the silicon microchannels by oxidation. Then, noble metals were grafted over the CeO2 support from chloride precursors. The unit was successfully tested for hydrogen production, achieving hydrogen rates of 180 LH2 cmR−3180 LH2 cmR−3 for the steam reforming of bio-ethanol at 873 K, S/C = 2 and 0.009 s contact time. Reaction yields of 3.8 and 3.7 mol hydrogen generated per mol ethanol in feed were measured for ESR and OSR, respectively. A performance comparison was performed with a conventional cordierite monolith with the same catalyst formulation. Results show for the silicon microreactor an outstanding improvement of the specific hydrogen production rate, operating at considerably reduced residence times, due to the increase in contact area per unit volume.

► Silicon microchannels of 3 μm diameter have been coated with RhPd/CeO2 catalyst.
► The microreactor performs well to generate H2 by bio-ethanol reforming.
► Activity amounts to 2 orders of magnitude higher than conventional microreactors.