Gold nanoparticles (AuNPs) encapsulated in the extra-large spherical cages of ordered mesoporous silica EP-FDU-12 with controlled and narrow size distributions have been investigated for the gas-phase oxidation of cyclohexanol. The size effect of AuNPs was demonstrated that the highest TOF for oxidation of cyclohexanol was 939 h-1 at 230 degrees C when the resulting particle size was in the range of 56 nm. The smaller or larger AuNPs ranging from 3.3 to 14.2 nm led to poor catalytic performances in the cyclohexanol oxidation. Importantly, AuNPs loaded in EP-FDU-12 catalyst exhibited remarkably long lifetime (>550 h) without obvious mass-specific activity decrease and poisonous coke formation, which will light the path for the large-scale industrialization of fine chemicals over noble metal catalysts. (C) 2017 Elsevier B.V. All rights reserved.