Dehydration of 1,4-butanediol (14BDO) was investigated over indium oxide. Over the indium oxide prepared by precipitation, both conversion of 14BDO and selectivity to unsaturated alcohol, 3-buten-1-ol (3B1ol), increase with the increase in calcination temperature of indium oxide irrespective of the decrease in the specific surface area. The maximum values of 79.6% conversion and 79.0% selectivity to 3B1ol are obtained over indium oxide calcined at 900 degrees C. The values are much higher than the activities of commercial indium oxide. The activities of indium oxide depend on the shape of particles. Indium oxides prepared by the precipitation are composed of particles with diameter of 10-70 nm. The size and shape of particles change by calcination: spherical shape at low temperature of <800 degrees C varies to angular one at >800 degrees C with a slight growth of particle size. The change in the shape of the particles means that indium oxide crystallites calcined at >800 degrees C mainly expose 222 facets. The dehydration reaction of 14BDO to 3B1ol is preferentially promoted over 222 surface of bixbyite structure. (C) 2010 Elsevier B.V. All rights reserved.