The effects of wall defects on the molecular diffusion and hydrocracking ability of mesoporous MCM-41 materials having particulate and hierarchical tubular morphologies with various extents of structural defects have been studied. The diffusion properties of the MCM-41 materials were investigated by 1H pulsed-field-gradient NMR self-diffusion measurements of cyclohexane, whereas the catalytic performances of the aluminosilicate MCM-41 were evaluated using 1,3,5-triisopropylbenzene cracking as the test reaction. 31P MAS NMR of the adsorbed trimethylphosphine oxide probe molecules confirmed the existence of active sites in the Al-MCM-41 samples, whose acid distribution were evaluated in conjunction with elemental analyses. It was found that, the Al-MCM-41 sample with tubules-within-tubule (TWT) morphology showed superior catalytic activity and tolerance for deactivation during hydrocracking reaction compared to the particulate morphology sample having the same Al content. The TWT Al-MCM-41 sample, which has more extensive structural defects than the particulate Al-MCM-41, was also found to have higher cyclohexane diffusivity. It is conclusive that, the structural defects possessed by these unique Al-MCM-41 materials synthesized by the 'delayed neutralization method' effectively provoke interchannel connections, which facilitate transport of the adsorbate molecules, thus promote the catalytic activity of the catalysts.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials