Nitrogen-containing carbon nanotubes were prepared, characterized and used as catalysts for two reactions of interest in the biomass upgrading processes: acetone aldol and acetic acid decarboxylative condensations. N-CNT were synthesized in a fluidized bed reactor by catalytic chemical vapor decomposition of acetonitrile on iron-, cobalt- and nickel-supported catalysts. Ni-N-CNT catalyst exhibits the highest activity, attributed to the surface concentration of basic sites, particularly the pyridinic species detected by X-ray photoelectron spectra (XPS). Likewise, the selectivity toward the final products of the reaction pathway is related both to the strength of basic sites (Ni-N-CNT) and to the morphology and chemical environment of the active sites (Fe-N-CNT). Synthesized catalysts show high stability for acetone condensation, whereas for ketonic condensation the catalyst stability decreases, mainly due to acic-base interactions with the active sites. (c) 2013 Elsevier B.V. All rights reserved.