Pyridine sorption into

Fig. 11 FTIR spectra of the ring deformation region after pyridine sorption into H-ZSM-5 (sample No. 3), Li-ZSM-5 (sample No. 5), and Na-ZSM-5 (sample No. 6) monitored through the changes in the absorbance of the band at 1443 cm ...

The assumption that the strong interaction between the strongly acidic adsorbent and the strongly basic adsorbate under our experimental conditions was the reason for the failure to achieve reversibility was confirmed when adsorbents with the same structure but lower (Li-ZSM-5 or Na-ZSM-5) or zero acidity (silicalite-1) were employed [26]. Figure 12 demonstrates the perfect reversibility of pyridine sorption into the slightly acidic Li-ZSM-5 zeolite. 

Reduction of sugars into alditols is effected by treatment with sodium borohydride, and acetylation by treatment with acetic anhydride containing sulphuric acid (2%) at 80°C for 15 h [436] or for 4 h by refluxing with a mixture of acetic anhydride and pyridine (1 1) [437]. The excess of reducing agent is usually decomposed prior to the acylation by treatment with an acid. The boric acid so produced should be removed, as it forms a complex with alditols and retards the acylation. Polar stationary phases (e.g., Carbowax 20M), on which strong sorption and decomposition of the derivatives occur, are not very suitable for the GC separation of acetates. Carbowax 20M modified with terephthalic acid and XE-60 provides good results, but some derivatives do not separate. 

Fig. 12 Curves obtained upon reversible uptake sorption (left side) and desorption (right side) of pyridine into and out of Li-ZSM-5...

LB films of tetra-4-tert-butyl- and tetra-(3-nitro-5-tcrt-butyl)-substituted CoPcs were used to detect pyridine, primary aliphatic amines, and benzylamine, by means of microgravimetry, UV-Vis spectroscopy, and optic microscopy [59], The sorption occurs as stepwise intercalation of the sorbate molecules into the supramolecular 3D structure of the phthalocyanine assembly followed by formation of the donor-acceptor complexes. Both intercalation depth and stoichiometry of the complexes are determined by the molecular structure of amines. The supramolecular factor allows discrimination between amines in air but not in aqueous solutions because of concurrent intercalation of water. 

The polyamide obtained by polycondensation of 2,6-diaminopyridine and 2,6-pyridine dicarboxylic acid was the first polymer to assemble itself into a double helix (DNA-type) in solution. The synthesis and physicochemical characterization of some polymer-supported rhodium catalysts based on polyamides containing 2,6- and 2,5-pyridine units were reported by Michalska and Strzelec (2000) these catalysts were used for the hydrosilylation of vinyl compounds such as phenylacetylene. Chevallier et al. (2002) prepared polyamide-esters from 2,6-pyridine dicarboxylic acid and thanolamine derivatives and investigated their polymer sorption behavior towards heavy metal ions. Finally, Scorlanu et al. (2006) also prepared a polymer with improved performance based on polyureas containing 2,6-pyridine moiety and polyparabanic acids, and polymethane-ureas containing 2,6-pyridine rings. 

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