Core-Shell Redox Catalyst for Chemical Looping Reforming of Methane

Conversion of methane into syngas, a gaseous mixture composed primarily of carbon monoxide and hydrogen, is a topic of practical relevance for many synthetic fuel and chemical production processes. At present, methane-derived syngas is produced primarily through reforming in the presence of gaseous oxidants such as steam, oxygen, and/or carbon dioxide. Although the reforming based approaches have been successfully utilized at a commercial scale, the efficiencies of the state-of-the-art reforming processes are limited due to the high steam to methane ratio required by the reforming catalysts and/or the needs for energy intensive air separation operations.

Chemical Looping Reforming (CLR) represents an alternative approach for methane reforming. In the CLR scheme, a solid oxygen carrier or “redox catalyst” is used to partially oxidize methane into syngas. The reduced oxygen carrier is then transferred to a subsequent reactor for regeneration with steam and/or air. The cyclic redox operation avoids the needs for air separation. Compared to oxygen carriers in other cyclic redox processes such as chemical looping combustion (CLC), the redox catalyst/oxygen carrier in CLR should exhibit high selectivity towards partial oxidation products.

The current study investigates the performance of a novel “core-shell” redox catalyst in CLR reactions. A number of oxygen carriers composed of a primary metal oxide and mixed ionic-electronic conductor (MIEC), are synthesized, characterized, and tested under redox conditions. Results indicate that the newly developed core-shell redox catalyst is significantly more selective than conventional oxygen carriers for syngas production. It also showed better carbon formation resistance and maintained structural/phase integrity.