Niobium nitride was synthesized on a Si(400) substrate and a gamma-alumina pellet using a CVD method with a stream of NbCl5/Ar, NH3, and H-2 gases at 723-973 K under reduced pressure. The composition and surface properties of the deposited niobium nitride were analyzed using XRD and XPS measurements. The activity of alumina-supported niobium nitrides for the hydrodesulfurization (HDS) of thiophene at 673 K and atmospheric pressure was determined. The alumina had a surface area of 177 m(2) g(-1) and the alumina-supported niobium nitride catalyst had surface areas of 179-190 m(2) g(-1). Although the catalysts had low activity in the initial stages, the activity increased after 200-300 min started to about three times the initial activities. XPS analysis indicated that the activity of the niobium nitride catalysts was decreased by sulfur accumulation on the surface and nitrogen released from niobium nitride. The relationship between the surface properties of the niobium nitride catalysts and the activities for thiophene HDS is discussed. (C)2000 Elsevier Science B.V. All rights reserved.