The effect of triethylene glycol on phosphate-doped Co(Zn)Mo catalysts supported on gamma-Al2O3 was studied by means of P-31 magic angle spinning nuclear magnetic resonance (MAS NMR) and Raman spectroscopy. P-31 MAS NMR experiments, carried out on ZnMo/gamma-Al2O3 doped with phosphate and triethylene glycol, suggested that the P2Mo5O236- species that formed in the impregnation solution decomposed to monophosphate and an Anderson-type aluminum molybdate species on contact with the support. The presence of triethylene glycol favored the formation of polyphosphate and PMo12O403- heteropolymolybdate species, but no P2Mo5O236- was detected. The use of paramagnetic cobalt instead of zinc cations had a paramagnetic effect on the P-31-NMR signal of the PMo12O403-,indicating that the PMo12O403- species are bound to the promoter atoms. The close proximity of the promoter and Mo allows a better decoration of MoS2 and improves the catalytic activity. (c) 2005 Elsevier Inc. All rights reserved.