Thermal-stable Pd@mesoporous silica core-shell nanocatalysts for dry reforming of methane with good coke-resistant performance

Dry reforming of methane (DRM) reaction is an environment-friendly process to convert greenhouse gases, methane (CH4) and carbon dioxide (CO2) into synthesis gases for industrial application. However, the catalysts used for DRM reaction always deactivate at high temperatures due to the sintering of metal nanoparticles and coking on the active surface. Core-shell structures composed of metal cores surrounded by oxide shells (core-shell structures) have been confirmed to be thermal-stable by solving the two problems. Pd@SiO2 core-shell nanocatalyst has been prepared by using a sol-gel process, along with two supported catalysts prepared by using impregnation method in this work. The catalysts were characterized by using transmission electron microscopy (TEM), X-ray diffraction (XRD), N-2 adsorption-desorption isotherms, CO chemisorption, inductively coupled plasma optical emission spectrometry (ICP-OES). The Pd@SiO2 after thermal treatment at 700 degrees C for 6 h exhibits no obvious sintering. For DRM reaction catalyzed by Pd@SiO2 core-shell nanocatalyst, the conversions of CO2 and CH4 are 89% and 83% respectively, which show no significant decrease for > 10 h. However, two supported Pd catalysts (Pd cub/SiO2 and Pd/SiO2) deactivate to a very low activity (conversion lower than 20%). The results suggest that the Pd@SiO2 nanocatalyst is excellent for DRM reaction, which also can be used for other heterogeneous catalysis reaction at high temperatures.