The development of platinum-zirconia catalysts for the CO₂ reforming of methane

A novel catalyst consisting of platinum supported on zirconia has been developed for the CO₂ reforming of methane, a process which produces a synthesis gas with a H₂:CO ratio close to 1:1. It has been found that the catalyst preparation procedure is critical in order to obtain a catalyst which is stable over time and which shows no significant deactivation as a result of coke formation. The various catalysts examined were tested in a small fixed bed reactor at temperatures up to 800°C using various ratios of CO₂:CH₄ in the feed gas. The behaviour of the Pt/ZrO₂ catalyst has been compared with Pt supported on other oxides and with the other noble metals supported on zirconia. The effect of Pt content on the catalyst behaviour has also been examined. The optimum Pt/ZrO₂ catalyst has been tested for a period of over 1000 h; for the first 300 h there was significant deactivation, after which the activity stabilised. The initial deactivation was caused by deposition of small quantities of a 'working layer' of carbon on the catalyst surface. This carbon could quickly be removed by exposure of the catalyst to CO₂ alone, restoring the activity of the catalyst to its original level. A process design using the newly-developed catalyst has been prepared to produce a feedstock for the production of acetic acid. This process has been compared with the existing commercial processes of steam reforming and partial oxidation. It is concluded that CO₂ reforming has a definite economic advantage over steam reforming. Investment costs for the partial oxidation process are lower but the operating costs are significantly higher. The economic evaluation thus confirms the potential of CO₂ reforming using this novel catalyst.