Isomerization and disproportionation of m-xylene in a zeolite with 9-and 10-membered ring pores:Molecular dynamics and catalytic studies

摘要

The unique pore topology of zeolite ITQ-13 with 9-membered ring (MR) channels intersected by perpendicular 10-MR channels and larger void space with 10-MR cross-sections was studied for meta-xylene isomerization and disproportionation.Product distribution was interpreted on the basis of pore topology and compared with zeolites with 12-MR (beta),10-MR,and intersecting 12-MR cavities (NU-87),as well as 10-MR (ZSM-5) zeolites.The presence of cavities allows more space for bulky intermediates and/or products and also provides room for molecules to drive consecutive reactions toward thermodynamic equilibrium.Channels,on the other hand,allow diffusion without trapping if their free diameters are large enough.The 9-MR channels are not suitable for diffusion of para-xylene,ortho-xylene,meta-xylene,or 1,2,4-trimethylbenzene.Catalytic experiments and atomistic molecular dynamics are used to interpret the behavior of ITQ-13 and explain the results in comparison with other structures.