Al-MCM-48 as a potential hydrotreating catalyst support: II – Diffusion property study

Mesoporous alumina MCM-48 materials (denoted as Al-MCM-48) were synthesized as a potential hydrotreating catalyst supports for light-cycle oil (LCO). Diffusion phenomenon of typical large di-aromatic in LCO (i.e., 1-methylnaphthalene) in MCM-48, Al-MCM-48 samples and reference H-USY zeolite, and small aromatic (i.e., toluene) in one Al-MCM-48 sample were studied with the aid of standard zero length column (ZLC) technique. The influences of Si/Al ratio, dimension of aromatic molecule and the post-synthesis hydrothermal restructuring treatment on the diffusion behaviors have been investigated. Compared with conventional catalyst support like H-USY zeolite, Al-MCM-48 samples showed faster diffusion for 1-methylnaphthalen, demonstrating its advantage as a promising catalyst support. The diffusion results revealed that Si/Al ratio was an important factor for the transport process, which should be optimized. Post-synthesis treatment enhanced the diffusion of 1-methylnaphthalene but with limitation. The results also indicated that the overall diffusion of aromatic compounds in LCO was controlled by the mobility of di-aromatic molecules (i.e., 1-methylnaphthalene). Therefore, it is critical to select a catalyst support with improved diffusion of large di-aromatic molecules.