Frédéric Vogel

Autothermal methanol reforming for hydrogen production in fuel cell applications

Fuel cell powered electric cars using on-board methanol reforming to produce a hydrogen-rich gas represent a low-emissions alternative to gasoline internal combustion engines (ICE). In order to exceed the well-to-wheel efficiencies of 17% for the gasoline ICE, high-efficiency fuel cells and methanol reformers must be developed. Catalytic autothermal reforming of methanol offers advantages over endothermic steam-reforming and exothermic partial oxidation. Microreactor testing of copper-containing catalysts was carried out in the temperature range between 250 and 330°C showing nearly complete methanol conversion at 85% hydrogen yield. For the overall process a simplified model of the reaction network, consisting of the total oxidation of methanol, the reverse water-gas shift reaction, and the steam-reforming of methanol, is proposed. Individual kinetic measurements for the latter two reactions on a commercial Cu/ZnO/Al2O3 catalyst are presented.

Design of a continuous-flow reactor for in situ x-ray absorption spectroscopy of solids in supercritical fluids

This paper presents the design and performance of a novel high-temperature and high-pressure continuous-flow reactor, which allows for x-ray absorption spectroscopy or diffraction in supercritical water and other fluids under high pressure and temperature. The in situ cell consists of a tube of sintered, polycrystalline aluminum nitride, which is tolerant to corrosive chemical media, and was designed to be stable at temperatures up to 500 °C and pressures up to 30 MPa. The performance of the reactor is demonstrated by the measurement of extended x-ray absorption fine structure spectra of a carbon-supported ruthenium catalyst during the continuous hydrothermal gasification of ethanol in supercritical water at 400 °C and 24 MPa.

High pressure differential scanning calorimetry of the hydrothermal salt solutions K2SO4–Na2SO4–H2O and K2HPO4–H2O

Aqueous salt solutions under hydrothermal conditions play an important role in geochemistry as well as in processes using hot compressed water as the process medium such as supercritical water oxidation (SCWO) and supercritical water gasification (SCWG). Isochoric high pressure differential scanning calorimetry (HP-DSC) was used as an accurate technique to investigate the phase behavior of such solutions under hydrothermal conditions. New data in the low concentration range (0.14–15.0 mass%) has been collected for the binary systems K2SO4–H2O, Na2SO4–H2O and K2HPO4–H2O. Furthermore we have discovered a liquid–liquid immiscibility in the ternary system K2SO4–Na2SO4–H2O, which has not been reported before.

On‐Stream Regeneration of a Sulfur‐Poisoned Ruthenium–Carbon Catalyst Under Hydrothermal Gasification Conditions

Catalytic processes that employ Ru catalysts in supercritical water are capable of converting organics, such as wood waste or biosolids, into synthetic natural gas (CH4) with high efficiencies at relatively moderate temperatures of around 400 °C. However, Ru catalysts are prone to S poisoning and are quickly deactivated. As S is ubiquitous in raw biomass and technologies to remove S from hydrothermal biomass feeds are lacking, regeneration protocols that efficiently reactivate S‐poisoned catalysts are required to realize efficient conversion processes and long catalyst lifetimes. In this work, we developed a method to remove S from a S‐poisoned Ru catalyst under hydrothermal conditions through an oxidative treatment in the aqueous phase. By using in situ X‐ray absorption spectroscopy under the reaction conditions, we show that Ru is oxidized by dilute H2O2 at low temperatures, which leads to the removal of adsorbed S species from the catalyst surface. By optimizing the regeneration conditions, it was possible to prevent oxidation of the catalyst carbon support, as revealed by ex situ TEM. This treatment led to a reactivation of the Ru catalyst with a significant increase in carbon‐to‐gas conversion and methane selectivity.