Density functional theory (DFT) calculations indicate that boron atoms are thermodynamically stable at step, p4g clock, and subsurface sites of a Co catalyst under Fischer-Tropsch synthesis (FTS) conditions. Moreover, the presence of boron at step and clock sites is calculated to destabilize the adsorption of carbon atoms at neighboring sites by +160 and +108 kJ/mol, respectively. The calculations hence suggest that boron promotion can selectively block the deposition, nucleation, and growth of resilient carbon species. To experimentally evaluate this concept, the deactivation of a 20 wt.% Co/gamma-Al(2)O(3) catalyst promoted with 0.5 wt.% boron was studied for 200 h during FTS at 240 degrees C and 20 bar. Boron promotion was found to reduce the deactivation rate more than six-fold, without affecting the initial activity or selectivity. Characterization with X-ray photoelectron spectroscopy (XPS) and temperature-programmed hydrogenation (TPH) confirms that boron promotion reduces the deposition of resilient carbon species. (C) 2011 Elsevier Inc. All rights reserved.