Dimethyl ether (DME), which is an excellent green diesel-fuel alternate with excellent clean burning properties, is synthesized by dehydration of methanol over novel solid acid catalysts, which are synthesized following a direct hydrothermal route and using silicotungstic acid (STA) as the active compound. These mesoporous silicate structured catalysts have surface area values of 108-393 m(2)/g, depending upon their W/Si ratio. These catalysts showed very high methanol dehydration activity and also very high DME selectivity values, approaching 100%. The STA-SiO2 mesoporous nanocomposite catalyst having a W/Si atomic ratio of 0.33 showed the highest activity, with a DME selectivity over 99% and a methanol conversion over 60%, at 250 degrees C and at a space time of 0.27 s.g.cm(-3). Effects of W/Si atomic ratio, calcination temperature and the synthesis procedure on the catalytic performance of these novel mesoporous catalytic materials were investigated.