Synthesis gas production by catalytic partial oxidation of natural gas using ceramic foam catalyst

Catalytic partial oxidation (CPOX) of natural gas was investigated over granule and ceramic foam Rh/CeO₂+ZrO₂+MgO catalysts under high throughput (GHSV of 180,000–1,600,000 h⁻¹) conditions at various pressures from 0.1 to 2.1 MPaA. The application of ceramic foam as the substrate of Rh/CeO₂+ZrO₂+MgO catalyst improved the stability of the catalytic performance. It was found that the catalyst deactivation occurred when Reynolds number for flow through the catalyst bed exceeded around 20 and flow in the void of the catalyst bed changed from laminar flow regime to transitional flow regime. This change of fluid flow causes the acceleration of the mass transfer of the reactants from the gas phase to the catalyst surface and a rapid increase of the exothermic surface reaction rates over the catalyst, leading to hot spot formation. Due to larger void and smaller strut diameter of the ceramic foam, the configuration of the foam catalyst can make linear velocity lower in the catalyst bed and maintain laminar flow regime up to higher GHSV conditions than the granule catalyst, resulting in higher stability of the foam catalyst by suppression of hot spot formation. Chemical species measurements in the ceramic foam catalysts by means of a capillary sampling method revealed that the consumption rates of CH₄ and O₂ over Rh/CeO₂+ZrO₂+MgO were much lower than those over Rh/MgO and mild exothermic oxidation reaction over Rh/CeO₂+ZrO₂+MgO proceeds in wide region of the catalyst bed. High resistance to oxidation of Rh surface over CeO₂+ZrO₂+MgO even in the presence of O₂ during CPOX reaction is considered to change the rates of both complete combustion reaction and reforming reaction, and to increase a contribution of another way to produce syngas.