Pd Particle Stabilization on Carbon Supports Under Hydrothermal Conditions

Carbon, as a catalyst support, has been shown to provide improved hydrothermal stability relative to common metal oxide supports such as silica and alumina, making it suitable for aqueous phase biomass conversion to chemicals and fuels. However, for supported metal catalysts, not only the stability of the carbon support, but also the stability of the supported metals needs to be considered. The stability is likely dependent on the carbon surface chemistry. The current work systematically examined this premise. Three carbon coated silica supports were synthesized at different temperatures to provide a range of oxygen content and functionality followed by the deposition of Pd. Through detailed and quantitative XPS and ¹³C NMR characterization, lower temperature synthesized carbons gave a range of oxygen functional groups, while higher temperature carbons had more aromatic groups. The hydrothermal stability was tested using treatment in water at 170°C for 24 hours. Additionally, aqueous phase hydrogenation of furfural was performed in both batch and flow reactor systems to further characterize the relative stabilities of the catalysts. The low temperature carbon with more oxygen functional groups led to better Pd dispersion and improved hydrothermal stability.