ABSTRACT:The synthesis and characterization of poly(4-hydroxystyrene) (PHS) and poly(4-vinylphenol) (PVPh) by the polymer modification route are reported. Polystyrene prepared by free-radical and anionic polymerization was acetylated quantitatively to poly(4-acetylstyrene) (ACPS) with acetyl chloride and anhydrous aluminum trichloride in carbon disulfide. The acetylation worked equally well in a mixture of 1,2-dichloroethane (DCE) and nitrobenzene containing largely DCE. The extent of the acetylation was estimated by 1 H NMR. The oxidation of ACPS was carried out with various oxidizing agents and reaction conditions. The peracetic acid oxidation in chloroform resulted in quantitative oxidation to poly(4-acetoxystyrene) (APS) as estimated by 1 H NMR spectroscopy. The treatment of APS with hydrazine hydrate in dioxane resulted in the formation of PVPh. Deacetylation occurred with equal versatility in a mixture of aqueous sodium hydroxide and tetrahydrofuran. All the polymers were characterized via gel permeation chromatography, IR, UV, 1 H NMR, and 13 C NMR spectroscopic techniques. This is the first report on the synthesis of ACPS, APS, and PHS of reasonably narrow molecular weight distributions or otherwise by the polymer modification route.

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A series of Sb containing CNTs based MnOx/TiO2 catalysts were prepared by the incipient wetness co-impregnation method and tested for the selective catalytic reduction (SCR) of NOx with NH3. The Sb loaded MnOx/TiO2-CNTs catalyst showed better performance than the other catalysts tested and presented the highest activity in the temperature regime of 100–400 oC. Interestingly, Sb loaded catalyst exhibited SO2 and H2O resistance with better thermal stability. Physico-chemical characterizations such as SEM, XRD, BET, XPS, NH3-TPD, and H2-TPR were employed to investigate the influence of Sb loading on NOx removal over MnOx/TiO2-CNTs catalysts. A step-wise addition of SO2 into the gas stream disclosed that MnOx-Sb/TiO2-CNTs catalyst has better SO2 resistance by avoiding the sulphur poisoning than the base catalyst MnOx/TiO2. Moreover, the results of SEM and XRD revealed that the dispersion of MnOx on TiO2/CNT surface was more uniform after Sb loading. We evidenced that the decrease in SCR activity of MnOx based catalyst is due to the formation of MnSO4. Indeed, in Sb loaded catalysts, the SOx species react more preferably with SbOx than that of MnOx. This strong interaction of SO2 with SbOx successfully prevents the poisoning of active sites on MnOx from being sulphated. This significantly improved the SO2 tolerance of Sb-loaded catalysts.