New vanado-silicates with a bimodal mesoporous system (V-UVM-7) and high vanadium contents (Si/V >= 7) have been prepared by a modification of the so-called atrane method. Its morphology consists of aggregation of nano-particles with V-MCM-41 structure, creating a second broader porous system in their interparticle space. Its structure allows to incorporate a high V contents into tetrahedral sites of the framework while keeping vanadium dispersion. V-UVM-7 catalysts are very active and selective for the direct transformation of isobutane to isobutene and methacrolein. Total conversion and methacrolein-to-isobutene ratio in the products increased with increasing vanadium contents. The catalytic performance comparison with homologous V-MCM-41 catalysts revealed an influence of the channel length on the products distribution. (C) 2006 Elsevier B.V. All rights reserved.