Preparation, characterization and reactivity of NI-CE/SBA-15 catalysts in dry reforming of methane

Abstract

Dry reforming of methane (DRM) is a promising option for the production of hydrogen and syngas. CH4 (g) + CO2 (g) → 2 CO (g) + 2 H2 (g) This process consumes two greenhouse gases, namely methane (CH4) and carbon dioxide (CO2). Thus, it contributes to reducing CO2 emissions and adjusting H2:CO ratio in a suitable ratio (1:1) that is readily utilized in Fischer-Tropsch synthesis for the production of hydrocarbons. Consequently, this process is gaining more interest from an environmental, economic and energetic point of view. The challenge in this application is the design of a catalyst that can maintain its activity and stability under severe conditions like high temperature and rapid coke deposition. Although noble metals demonstrated great catalytic activity and stability, for accessibility and economic reasons, nickel-based catalysts arose as a promising alternative. In this study, two series of Nix/SBA-15 and NixCe6/SBA-15 (x = 2.5, 5 or 7.5 wt%) catalysts are prepared and tested in the dry reforming of methane. The mesoporous supports are used to prevent sintering while the addition of cerium is for the reduction of coking. Both Ni and Ce are impregnated using the "two solvents" method. The calcined samples are first characterized by N2 sorption, XRD, TEM, TPR and UV-visible NIR. The results suggest a well dispersion of the NiO and CeO2 nanoparticles that fill the pores. Catalytic activities are measured at atmospheric pressure and temperatures from 200 to 800oC. Stability measurements are conducted at 500oC for 12 hours. As the percentage of Ni increases, the promotional effect of Ce is more important. The catalysts show high activity and selectivity toward DRM. No significant deactivation is observed throughout the stability test. The characterizations after the reaction indicate that no sintering takes place. Coke quantification is not possible due to Ni reoxidation under air.