Xl30 environmental

Powder X-ray diffraction (PXRD) patterns of the Cu- and Zn-zeolite samples were collected on Bruker D8 powder X-ray diffractometer with Cu Kα radiation with a wavelength of 1.5406 Å, and the PXRD patterns of Fe-zeolites were collected on Siemens D5000 powder diffractometer with Co Kα radiation with a wavelength of 1.7902 Å at a scan speed of 2.0° min⁻¹ and a step size of 0.04°. Scanning electron microscopy (SEM) images of powdered samples were collected using an XL30 environmental FEG (FEI) microscope operating at 15 kV acceleration voltage. Brunauer–Emmett–Teller (BET) surface areas were estimated with a Micrometrics ASAP 2020 volumetric adsorption analyzer with nitrogen as the adsorbate at 77 K. Prior to the analysis, samples (300 mg) were degassed at 300 °C for 10 h under vacuum until a residual pressure of ≤10 μm Hg was reached. Specific surface areas were determined from the BET equation. The t-plot method was used to distinguish the micropores from the mesopores in the samples and to calculate the external surface areas. The mesopore volumes were calculated by subtracting the micropore volume from the total pore volume. Mesopore size distributions were obtained using the Barrett–Joyner–Halenda (BJH) method assuming a cylindrical pore model.^{39 (link)}