Titania-supported 12-phosphomolybdic acid (HPMo/T) and their Ni-and Co-salts (NiPMo/T and CoPMo/T) have been prepared by impregnation and their acid properties tested by means of pyridine adsorption and by the heterogeneous partial oxidation of methanol with oxygen at atmospheric pressure. For sample HPMo/T, calcination at temperatures 523-723 K altered both methanol conversion and product distributions. At 523 K activity was high and reaction appeared to be dominated by acidity as CH3OCH3 was the major reaction product, however selectivity to CH3OCH3 decreased with the simultaneous increase of HCHO selectivity at 623 K indicating participation of redox properties of the catalyst. These changes have been interpreted as being due to the destruction of the supported heteropoly compound and the parallel change of the acid properties of the resulting catalyst.