An inelastic neutron scattering and NIR-FT Raman spectroscopy study of chloroform and trichloroethylene in faujasites

Molecular information about the nature and the strength of the interactions between chloroform and trichloroethylene (TCE) sorbates and siliceous FAU, NaY, and NaX zeolites was obtained by inelastic neutron scattering (INS) a nd Raman spectroscopies. The spectral features of the two sorbates differ i n terms of their frequencies, splittings, and line widths from the ones of chloroform and TCE molecules in the gas phase. In conjunction with our simu lation results, these differences are rationalized by assuming that, in sil iceous FAU, the two sorbates undergo a nondissociative adsorption involving the formation of an H-sorbate... O-framework hydrogen bond and Cl-sorbate. .. O-framework van der Waals interactions, whereas in NaY and NaX, addition al Cl-sorbate... Na+ electrostatic interactions are involved. Interestingly , no pi/Na+ interaction takes place for TCE. These findings, which are in a greement with previous calorimetric and simulation results, confirm that th e strength of the sorbate/zeolite interactions is correlated to the basicit y of the zeolite and therefore increases in the sequence siliceous FAU < Na Y < NaX, following the sequence of the heats of adsorption.