The effect of nitrilotriacetic acid (NTA) as a complexing agent on the sulf
idation mechanisms of Co-Mo catalysts supported on activated carbon and alu
mina was examined by the XAFS technique. The XAFS results revealed that NTA
interacted with Co atoms and formed the Co-NTA interaction, while it showe
d almost no influence on the local structures around Mo atoms. The Co-NTA i
nteraction suppressed the aggregation of cobalt atoms and the interaction b
etween cobalt and alumina during sulfiding, and consequently promoted the f
ormation of the Co-Mo-S phase.