ACTIVE-SITE STRUCTURE OF CU ZSM-5 - COMPUTATIONAL STUDY/

The coordination structures of Cu ionic species in ZSM-5 zeolite were investigated by molecular dynamics (MD) simulations and molecular orbi tal (MO) calculations. Al sites were first sought seas to reproduce th e square-planar coordination of Cu(II), which is well characterized by the ESR spectra. When two Al's occupy T8 sites in the six-membered ri ng, the calculated coordination of Cu(II) agreed well with the experim ental data. For this Al siting, Cu(II)-O-Cu(II) and two Cu(I)'s were r espectively simulated, and the coordination of the former species was found to be consistent with the EXAFS results. Furthermore, from the M O calculation Cu-O-Cu was anticipated to be very reactive and thus mig ht be the active site. The function of zeolite would therefore be the stabilization of this species. On the other hand, Cu dimer was found u nstable, and the reaction mechanism based on it was supposed unlikely.