Hierarchically porous materials built of Fe–silicalite nanobeads

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 2; no. 38; pp. 16061 - 16070
• Main Authors: Sashkina, KA, Rudina, NA, Lysikov, AI, Ayupov, AB, Parkhomchuk, E V
• Format: Journal Article
• Language: English
• Published: 01.01.2014
• Subjects: Catalysis; Catalysts; Iron; Nanocrystals; Nanoparticles; Nanostructure; Porous materials; Scanning electron microscopy; Texture
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c4ta02904f

Hierarchically porous zeolite materials built of closely and randomly packed uniform Fe-silicalite nanobeads were synthesized. The desired assembly of nanobeads was achieved by the centrifugation and sedimentation of nanozeolite suspension followed by drying and calcination. A micro/meso/macroporous Fe-silicalite material with spongy texture built of closely packed nanocrystals was designed using polystyrene latex as a supramolecular template. Large Fe-silicalite microbeads were synthesized to compare their structure with the nanocrystalline materials. The synthesized samples were characterized by laser diffraction analysis, X-ray diffraction, scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy, argon and nitrogen adsorption measurements, inductively coupled plasma optical emission spectrometry, UV visible diffuse reflectance spectroscopy and temperature-programmed desorption of ammonia. Fe-silicalite nanozeolite materials have shown high crystallinity, and possess micro- and meso/macropore surface areas and high specific pore volumes. Pellets built of closely packed nanocrystals have exhibited good mechanical stability in benzene and water. Calcined Fe-silicalite materials built of nanobeads were observed to contain highly dispersed ferric clusters no more than 1 nm in size. The 3 nm ferric clusters in the zeolitic microbeads resulted in the appearance of Lewis acid sites with medium strength, which are absent in the nanobeads. Catalytic performance of hierarchically porous Fe-silicalites was studied in the total oxidation of clarithromycin lactobionate by H sub(2)O sub(2) at 323 K compared with Fe-silicalite microbeads. Hierarchical Fe-silicalites are more efficient catalysts vs.Fe-silicalite microbeads due to increased catalytic site accessibility.