Location and relative orientation of methanol adsorbate molecules in A, X, and Y zeolites from electron spin-echo studies

Hydroxymethyl radicals have been generated by γ-radiolysis at 77 K from specifically deuterated methanols, CD3OH and CH3OD, adsorbed on NaA, Ca4Na4A, NaX, KX, NaY, and KY zeolites. These radicals have been studied by electron spin-echo spectrometry and the deuterium modulation patterns analyzed. In A zeolites, the hydroxymethyl radical is located in the α-cage above a hexagonal interior face, with the molecular radical's electric dipole oriented along the threefold axis of the hexagonal face. Since a majority of the cations are in or near the hexagonal faces this orientation is consistent with a cation charge-molecular dipole interaction controlling the adsorbate geometry. The radical interacts with three equivalent closest methanol molecules in the α-cage, with their methyl groups 0.38 nm from the α-carbon of the radical. The radical location and orientation in X and Y xeolites is similar, except that both square and hexagonal faces are involved and the free nearest interacting methanol molecules lie slightly further away