In the present work, deactivation behaviour of a Pt/gamma-Al2O3 catalyst used for converting glycerin/water mixture into hydrogen was investigated. It was shown that main reason for the catalyst activity drop is due to the carbon deposition over the catalyst surface. Interestingly, the catalyst suffered from faster deactivation in the case of nitrogen presence in the inlet stream. However, the catalytic stability of the catalyst could be greatly enhanced when nitrogen was phase out from the reaction atmosphere. In the reaction mixture containing 10 wt% glycerol, the deactivation constant of the catalyst decreased from d(A) = -0.0516 mL/(min g(cat) h) under a condition with nitrogen to d(B) = -0.0051 mL/(min g(cat) h) without nitrogen in the reaction bed. Catalytic evaluation and thermogravimetric analysis revealed that nitrogen was not only an inert carrier gas served as but also an accelerator for coking. A speculation model was proposed for explanation of the coking process over the catalyst with the nitrogen effect. (C) 2010 Elsevier B. V. All rights reserved.