Influence of oxygen-containing surface groups on the activity and selectivity of carbon nanofiber-supported ruthenium catalysts in the hydrogenation of cinnamaldehyde

Carbon-nanofiber-supported ruthenium catalysts were employed to study the influence of oxygen-containing surface groups on catalytic performance in the liquid-phase hydrogenation of cinnamaldehyde. The carbon nanofibers were oxidized to introduce oxygen-containing groups and the metal precursor was applied using homogeneous deposition precipitation. After reduction the catalysts were heat-treated in nitrogen at different temperatures to tune the number of surface oxygen functional groups. TEM and chemisorption studies showed the presence of a narrow and stable particle-size distribution (1–2 nm) even after heat treatment at 973 K. The overall specific activity increased by a factor of 22 after treatment at 973 K, which is related to the decreasing number of oxygen-containing groups. The cinnamyl alcohol selectivity decreases from 48 to 8% due to enhanced rate of hydrocinnamaldehyde production with increasing heat treatment. This unambiguously demonstrates the metal–support interaction, which involves support surface-oxygen functionalities that affect the metal activity and selectivity. The precise nature of this interaction has yet to be elucidated.