Determination of the [formula omitted] and [formula omitted] ratios of two specimens of zeolite A by proton inelastic scattering

Abstract

The silicon/aluminum and sodium/aluminum ratios of two bulk samples of zeolite A were measured by the nondestructive technique of proton inelastic scattering using two NBS standard reference materials. For the first sample of single crystals made by the Charnell method (Mobil Corp.), the measured atomic ratio of Si Al = 1.04 ± 0.01 agrees with values from electron microprobe analysis (1.03), X-ray diffraction intensities (>1.00), and magic-angle-spinning nuclear magnetic resonance of 29Si (1.03 ± 0.01). Measurements of Na Al (1.01 ± 0.02; 1.02 ± 0.01) are consistent with the value of unity expected for tetrahedrally-bonded Al in the zeolite framework. For the second sample of bulk powder (MD224, Union Carbide Corporation), the measured values of Si Al = 0.96 ± 0.01 and Na Al = 0.99 ± 0.02 and 1.00 ± 0.01 are consistent with a published bulk chemical analysis ( Si Al = 0.94 ); these indications of excess aluminum over Si Al = 1 are consistent with evidence for a non-crystalline component observed in a neutron scattering experiment on the same sample, and with ion-exchange properties of other commercial samples of zeolite A.