Octanoic acid (OA) deoxygenation was investigated over silica- and carbon-supported palladium catalysts (each containing 5 wt.% Pd) at 235-300 degrees C and 1 atm in a continuous flow reactor. A commercial Pd/SiO2 (A) catalyst was active for OA decarbonylation (DCN) and hydrodeoxygenation (HDO) at 260 degrees C under 10% H-2; subsequent hydrogenation (HY) and DCN of the primary products, 1-heptene and octanal, respectively, produced n-heptane. Under equivalent conditions, a Pd/SiO2 (B) catalyst prepared using Pd(NO3)(2) and Aerosil 300 produced n-heptane with very high selectivity (>99%) via DCN/HY. In contrast, a commercial Pd/C (A) catalyst was highly active and selective to n-heptane (>98%) and CO2 (65%) under these conditions. Moreover, CO2 selectivity and n-heptane yield increased with reaction temperature consistent with direct decarboxylation (DCX). Increasing H-2 partial pressure resulted in markedly lower activity and CO2 selectivity; however, Pd/C (A) had negligible activity under He. Pd/C (A) exhibited greater water-gas shift (WGS) activity than Pd/SiO2 (A); however, differences in WGS activity alone cannot explain the observed support effect. A more highly dispersed Pd/C (B) catalyst was more active at 260 degrees C under H-2 than Pd/C (A); however, under 10% H-2, it had lower activity, CO2 selectivity (55%), and stability. Pd/C (A) and Pd/C (B) have very similar textural properties, but Pd/C (A) has a much higher Na content. By comparison, Pd supported on high-purity acetylene carbon black exhibited only DCN activity. These results indicate that carbon surface properties (e.g., polar functional groups, alkali metal content) influence the fatty acid deoxygenation performance of Pd/C catalysts. (C) 2016 Elsevier B.V. All rights reserved.