Possible formation of Cu_2~I(CO)_2(H_2O)_n complexes in a Cu-ZSM5 zeolite prepared by direct synthesis: evidence for the occurrence of Cu~I- Cu~I pairs?

摘要

Cu~I-ZSM-5 zeolite prepared by direct synthesis via the methylamine route involves Cu~I species as well defined as those in samples prepared by exchanging H-ZSM-5 with CuCl vapor. A systematic FTIR study of the reversible interaction of water with presorbed CO on Cu~I-ZSM-5 activated in various conditions shows the formation of polynuclear species of type (H_2O)_nCOCu~I(OH)Cu~ICO(H_2O)_m (n or m = 0, 1, 2), which suggests the occurrence of Cu~I species in pairs, probably in interaction with the negative charge close to the Al atoms of the structure.