A series of metal phosphates (Al, Fe, Ni, Ca and Mn) and stoichiometric (Al/Fe = Al/Ca = 1) mixed systems: FeAl(PO4)(2) and Ca3Al3(PO4)(5), were prepared by an ammonia gelation method. Their amorphous character was determined through several physical methods: nitrogen adsorption, DRIFT and XRD patterns. Gas-phase competitive dehydration/dehydrogenation reaction of cyclohexanol was carried out as a probe reaction and cyclohexene was usually the main reaction product, but different amounts of 1- and 3-methylcyclopentenes as well as cyclohexanone were always obtained. These results were compared to those obtained with 17 commercial inorganic solids (several metal oxides, sulfates and phosphates). A main unexpected conclusion was that cyclohexanol dehydration is obtained not only in acid sites but also in basic sites.