Appraisal of microwave-assisted ion-exchange in mordenite by crystal structure analysis

摘要

Transition metal-containing mordenite have been prepared by solid state ion exchange with microwave irradiation of mechanical mixtures of CoCl_2·6H_2O, NiCl_2·6H_2O and CuCl_2·2H_2O with mordenite at 750 W microwave power and for 10-20 min treatment time. The prepared transition metal-mordenite were characterized by X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FT-IR), simultaneous TG and DTA thermal analyses (TG/DTA), surface area measurement (BET), and diffuse reflectance spectroscopy (DRS). The results show that Co~(2+), Ni~(2+), and Cu~(2+) metal ions are actually incorporated into mordenite pores. The extra-framework locations of metal cations were determined Rietveld refinement of XRD data, performed in the Cmcm space group for all three samples. Three metal sites were located: the first site is in an almost perfect boat-shaped coordination with framework oxygen's, the second site is poorly coordinated while the third metal cation site was found at the center of mordenite cage in six-fold coordination to water molecules.