Catalytic Deoxygenation of Octanoic Acid over Supported Palladium: Effects of Particle Size and Alloying with Gold

Abstract

Catalytic deoxygenation of octanoic acid (OA) to n-heptane was investigated over silica-supported Pd and PdAu catalysts at 260 °C and 1 atm in a fixed-bed microreactor. Pd/SiO2 catalysts were prepared by incipient wetness (IW) and ion exchange (IE). Bimetallic catalysts were prepared using an IE procedure that is known to produce supported PdAu nanoparticles. The Pd nanoparticles (7.5 nm average size) in the Pd/SiO2 (IW) catalyst exhibit well-defined (100) and (111) facets, as evidenced by high-resolution electron microscopy (HREM) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) of adsorbed CO. As expected, the smaller nanoparticles (1.5 nm average size) in the Pd/SiO2 (IE) catalyst display strong linear and bridging CO DRIFTS bands. The PdAu/SiO2 (1/1 atomic ratio) catalyst contains 5 nm alloy nanoparticles with Pd-rich surfaces, as evidenced by HREM with energy-dispersive X-ray (EDX) analysis and in situ EXAFS spectroscopy. DRIFTS thermal desorption experiments demonstrated that...