Various synthetic solids were prepared by precipitation with sodium hydroxide from magnesium chloride or nitrate solutions. The materials thus obtained were characterized in structural terms by using X-ray diffraction, thermogravimetric analysis, EDAX analysis and diffuse reflectance infrared spectroscopy. Their surface properties were determined from N-2 adsorption-desorption isotherms and their chemical properties by using various titrants. Once calcined, the solids were found to consist mainly of sodium-magnesium mixed phosphates; on the other hand, those washed with water were found to contain primarily Mg-3(PO4)(2). The former exhibited a high selectivity towards the formation of hexanone from 2-hexanol; by contrasts, the latter also yielded the corresponding dehydration products (hexenes). The catalytic activity and selectivity results for the reactions leading to the different possible products are related to the structure and composition of the solids. (C) 2002 Elsevier Science B.V. All rights reserved.