Effect of a second metal (Y, K, Ca, Mn or Cu) addition on the carbon dioxide reforming of methane over nanostructured palladium catalysts

摘要: Abstract The CO2 reforming of CH4 to synthesis gas was investigated over nanostructured Pd/Al2O3 catalysts promoted by various additives (K, Ca, Y, Mn and Cu) using a stoichiometric feedstock mixture. In order understand the effect on surface properties catalytic performance catalysts, fresh spent samples were characterized number techniques, such as N2 adsorption-desorption isotherms, XRD, CO-chemisorption, H2-TPR, TPO, Raman TEM. Additives strongly modified reduction Pd species metal dispersion. results showed that addition Y or Ca slightly increased initial activity expressed conversions, which is attributed decreased reducibility enhanced contrast, while K, Cu similarly reduced species, their dispersions apparently owing decoration alloy formation. This leads lower activities for than Pd/Al2O3. On other hand, stability during long-term tests associated with sintering resistance well carbon deposition. ceased after around 4.5 h reaction due catalyst bed blockage caused large amount formation accelerated sintering. Among all Y-modified best almost no loss in 20 h reaction. probably because notably suppresses maintains particle size below 10 nm. crucial, can be completely avoided under present conditions. For different degrees tests,