Hydrogen production with carbon dioxide capture by dual-phase ceramic-carbonate membrane reactor via steam reforming of methane

The existing process for hydrogen production from methane through steam-reforming requires multiple reactors and separators and is thus costly and energy-intensive. This paper reports a new concept of CO₂-permselective membrane reactor for promoting hydrogen production via steam reforming of methane (SRM) with CO₂ capture. The membrane reactor is made of a ceramic-carbonate dual-phase membrane with a two-layered asymmetric wall structure. Bismuth-yttrium-samarium oxide (Bi_1.5Y_0.3Sm_0.2O_3-δ, BYS) was added to the support layer to make it non-wettable by molten carbonate, leaving the samarium-doped ceria (Sm_0.2Ce_0.8O_2-δ, SDC) layer to form a thin (~150 μm) CO₂-permselective SDC/molten-carbonate dual-phase layer after molten carbonate infiltration. The output product composition from the membrane reactor confirms that in situ CO₂ removal effectively promotes water-gas shift conversion in SRM and thus enhances hydrogen yield. At 900 °C with feed pressure at 1 atm, the membrane reactor achieves 90% hydrogen yield with 84% CO₂ recovery, which poses significant improvement when compared with conventional fixed-bed reactor under similar conditions. Analysis of CO₂ permeation activation energy suggests that surface reaction rate might have an effect on CO₂ permeation flux for the thin SDC/molten-carbonate membranes. Under atmospheric conditions the CO₂ permeation with reactive feed for SRM is lower than with non-reactive feed due to lower driving force under reactive conditions in the feed.