Vacuum-ultraviolet (VUV) irradiation (kexc: 172 ± 12 nm) of polystyrene films in the presence of oxygen
produced not only oxidatively functionalized surfaces, but generated also morphological changes.
Whereas OH- and C=O-functionalized surfaces might be used for e.g. secondary functionalization,
enhanced aggregation or printing, processes leading to morphological changes open new possibilities of
microstructurization. Series of experiments made under different experimental conditions brought
evidence of two different reaction pathways: introduction of OH- and C=O-groups at the polystyrene
pathways is mainly due to the reaction of reactive oxygen species (hydroxyl radicals, atomic oxygen,
ozone) produced in the gas phase between the VUV-radiation source and the substrate. However,
oxidative fragmentation leading to morphological changes, oxidation products of low molecular weight
and eventually to mineralization of the organic substrate is initiated by electronic excitation of the
polymer leading to C–C-bond homolysis and to a complex oxidation manifold after trapping of the
C-centred radicals by molecular oxygen. The pathways of oxidative functionalization or fragmentation
could be differentiated by FTIR-ATR analysis of irradiated polystyrene surfaces before and after
washing with acetonitrile and microscopic fluorescence analysis of the surfaces secondarily
functionalized with the N,N,N-tridodecyl-triaza-triangulenium (TATA) cation. Ozonization of the
polystyrene leads to oxidative functionalization of the polymer surface but cannot initiate the
fragmentation of the polymer backbone. Oxidative fragmentation is initiated by electronic excitation of
the polymer (contact-mode AFM analysis), and evidence of the generation of intermediate C-centred
radicals is given e.g. by experiments in the absence of oxygen leading to cross-linking (solubility effects,
optical microscopy, friction-mode AFM) and disproportionation (fluorescence).
Vanadia/ceria catalysts (2–10 wt% of V2O5) were prepared by wet impregnation of ammonium metavanadate in oxalic acid solution. Structural characterization was done with energy dispersive X-ray analysis (EDX), powder X-ray diffraction (XRD), BET surface area measurements, FT-IR spectroscopy and nuclear magnetic spectral analysis (51V MASNMR). XRD and 51V MASNMR results show highly dispersed vanadia species at lower loadings and the formation of CeVO4 phase at higher V2O5 loading. The catalytic activity of catalysts was conducted in liquid phase oxidation of ethylbenzene with H2O2 as oxidant. The oxidation activity is increased with loading up to 8 wt% V2O5 and then decreased with further increase in V2O5 content to 10 wt%. Different vanadia species evidenced by various techniques were found to be selective towards ethylbenzene oxidation. The CeVO4 formation associated with increased concentration of vanadia on ceria results the production of acetophenone along with 2-hydroxyacetophenone.
Manju, Kurian; Sugunan, S(Elsevier, January , 2006)
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Abstract:
Wet peroxide oxidation (WPO) of phenol is an effective means for the production of diphenols, which are of great industrial importance. An added advantage of this method is the removal of phenol from wastewater effluents. Hydroxylation of phenol occurs efficiently over mixed iron aluminium pillared montmorillonites. An initial induction period is noticed in all cases. A thorough study on the reaction variables suggests free radical mechanism for the reaction.
Mohammed Yusuff, k K; Varsha, Gopalakrishnan; Arun, Vasudevan; Manju, Sebastian; Leeju, P; Digna, Varghese(Crystallography Journals,Acta Crystallographica Section E ,Structure Reports, March 24, 2009)
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Abstract:
The asymmetric unit of the title compound, C11H8N4, contains
two independent molecules. In the crystal structure, intermolecular
N—H.....N hydrogen bonds link molecules into
ribbons extended in the [100] direction
Xavier, K O; Chacko, J; Mohammed Yusuff, K K(Elsevier, Applied Catalysis A :General, September 4, 2003)
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Abstract:
Co(II), Ni(II) and Cu(II) complexes of dimethylglyoxime and N,N-ethylenebis(7-methylsalicylideneamine) have been synthesized in situ
in Y zeolite by the reaction of ion-exchanged metal ions with the flexible ligand molecules that had diffused into the cavities. The hybrid
materials obtained have been characterized by elemental analysis, SEM, XRD, surface area, pore volume, magnetic moment, FTIR, UV-Vis
and EPR techniques. Analysis of data indicates the formation of complexes in the pores without affecting the zeolite framework structure, the
absence of any extraneous species and the geometry of encapsulated complexes. The catalytic activities for hydrogen peroxide decomposition
and oxidation of benzyl alcohol and ethylbenzene of zeolite complexes are reported. Zeolite Cu(II) complexes were found to be more active
than the corresponding Co(II) and Ni(II) complexes for oxidation reactions. The catalytic properties of the complexes are influenced by their
geometry and by the steric environment of the active sites. Zeolite complexes are stable enough to be reused and are suitable to be utilized as
partial oxidation catalysts.