Chemical looping reforming (CLR) utilizes redox properties of transition metal oxides, a.k.a. redox catalysts, to partially oxidize (POx) methane into syngas with its lattice oxygen. The lattice oxygen removed in the methane POx step is subsequently replenished with air in a separate regeneration step. Utilization of lattice oxygen avoids typical efficiency losses seen in endothermic steam/dry reforming reactions or oxygen generation. With the redox catalyst being critical to CLR, high methane conversion and syngas selectivity are desired from the redox catalyst. We reported Rh promoted CaMnO3 as effective redox catalysts for methane partial oxidation at relatively low temperatures (600oC). However, the methane conversion in our previous study was relatively low. In the present work, methane partial oxidation using Rh promoted CaMnO3 is enhanced through A/B site dopants and a secondary reforming bed. The dopant investigated included Sr (for A-site) and Fe (for B-site). Both Sr and Fe doping increased oxygen donation. The largest increase in oxygen extraction was 35% for Fe-doped CaMnO3. It was also determined that incorporation of a secondary reforming bed (Rh supported on alumina) significantly increased the overall methane conversion. The methane conversion was further improved by controlling reduction (POx) duration and space velocity in CaMn0.75Fe0.25O3 + Rh, demonstrating 80% methane conversion. In addition to high methane conversion, high CO and H2 selectivity was achieved by the combination of doping and a secondary reforming bed. 90% CO selectivity and 100% H2 selectivity was achieved. These results demonstrate a potentially effective strategy for converting methane into syngas in a relatively simple, packed-bed reactor system.

Rh promoted perovskites as effective redox catalysts for chemical looping reforming of methane

255th National Meeting (2018)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.