Using niobium(V) chloride and F127 in a water-ethanol system, this work reports the effect of aging of niobium-surfactant gel at 40 and 110 degrees C on the final product properties. The aging at low temperature of 40 degrees C showed small modification of the textural properties of the mesoporous niobium oxide. On the other hand, the hydrothermal aging at 110 degrees C showed significant increase in BET surface area, pore volume, pore size and microporosity with additional thermal and structural properties deviation. The process of hydrothermal aging at 110 degrees C is believed to lock chlorides in the niobium structure and cause the structural modification of the niobium skeleton leading to distinct developed crystalline structure and phase transformation behavior. The result also showed that hydrothermal aging at 110 degrees C could also enhance Lewis acidity of the product after calcination at 500 degrees C. (C) 2008 Elsevier B.V. All rights reserved.