Because of the adsorption selectivity of different molecules from gaseous and liquid media, boron nitride (BN) nanostructures with large specific surface area are considered as useful materials in environmental protection, e.g., in water treatment for removal of organic pollutants. Here, we propose a theoretical model explaining the selectivity of boron nitride surfaces to adsorb different molecules. The weakness of interaction between BN hexagonal layers gives the possibility for such kind of reconstruction of the surface layer when B and N atoms are displaced in opposite directions from the surface plane. Bonding in BN is partially ionic, i.e., B and N atoms possess non-zero effective electrical charges of opposite signs. Thus, BN surfaces should be polarized and interact with ions, and induce and/or attract the electrical dipoles of molecules. The adsorption depends on the relation between electrical attraction and Pauli repulsion forces between BN hexagonal surface and molecules, i.e., their characteristics, such as size, charge, dipole moment, and polarizability.
The new possibilities of preparing the ethyl 4-nitrobenzoate by esterification of 4-nitrobenzoic acid (4-NBA) with ethanol under argon at 80˚C are shown; particularly, over catalysts: on micrometric (4.8 -7.0 μm) or ultradispersed crystallites (290 -480 nm) of hydrogen forms of nanoporous natural zeolites H-CL, H-MOR, H-HEU-M, H-PHI and under irradiation of the reaction mixture with ultrasound (US, 37 kHz, 330 W, 2 h) or microwaves (MW, 2450 MHz, 300 W, 2 h). Ultradispersed crystallites of zeolite catalysts were prepared from hydrogen forms of parent natural zeolites by their treatment with US or MW. In the esterification, the synergism of the actions of catalysts and MW or US was revealed; wherein on the ultradispersed best catalysts H-HEU-M and H-MOR conversion of 4-NBA and yield of ethyl 4-nitrobenzoate reached up to 70% and 67%, respectively. GC/MS, FTIR, NMR methods were used in the study.
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