A catalytic reformer assembly includes a heated medium flow path for a first medium and a reforming flow path for a second medium. A catalyst substrate is located within the reforming flow path and supports a catalyst. A heat exchanger is disposed within the heated medium flow path for transferring heat from the heated medium flow path to the catalyst substrate.
 This invention was made with government support under contract DE-EE0000478 awarded by the Department of Energy. The government has certain rights in the invention.