Effect of specific surface area on oxygen storage capacity (OSC) and methane steam reforming reactivity of CeO₂

Abstract

It was found from the work that the specific surface area of ceria presents an important role on the oxygen storage capacity (OSC), the reactivity toward methane steam reforming, and the resistance toward carbon formation of this material. After calcination at 900°C, ceria prepared by surfactant-assisted method (SF) was observed from the present work to have significantly higher surface area than those prepared by templating (TP) and precipitation (PP) methods; this material showed strong OSC with good reforming reactivity in terms of thermal stability and resistance toward carbon formation compared to others. In detail, the degree of OSC was measured by the number of hydrogen uptake from the temperature programmed reduction (TPR). It was found that the value of hydrogen uptake from the TPR-1 of ceria prepared by SF was 2084 mmol g⁻¹, whereas those of ceria prepared by TP and PP were 1724 and 781 mmol g⁻¹, respectively. In addition, it was also proven in the present work that the OSC of these materials are reversible, according to the temperature programmed oxidation (TPO) and the second time temperature programmed reduction (TPR-2) results. According to the reactivity toward methane steam reforming, after purging in 3 kPa methane and 9 kPa steam at 900°C for 8 h, the methane conversion at steady state of ceria prepared by SF was approximately 38% with very low amount of carbon formed on the surface (0.16 mmol g⁻¹), whereas those of ceria prepared by TP and PP were 22% (with the amount of carbon formation of 0.30 mmol g⁻¹) and 13% (with the amount of carbon formation of 0.33 mmol g⁻¹), respectively.