Montmorillonite titania

The photocatalytic activity of Ti02-montmorillonite in the reduction of with oxidation of triethanolamine (261) and the oxidation of several aliphatic alcohols have also been reported (259). The photodegradation of dichloro-methane, which is not readily degraded or hydrolyzed in an aquatic environment, to hydrochloric acid and carbon dioxide using titanium-exchanged montmorillonite, titania-pillared montmorillonite, and titanium-aluminum polymeric cation pillared montmorillonite has been reported (261). 

Yoneyama et al. [142, 143] formed Ti02 pillars with thickness of about 1.5 nm in the galleries of montmorillonite by intercalation of titania sol followed by decom-... 

Alumina and titania in different solvents were studied in [822]. MgO and ZnO in seven organic liquids were studied in [1686]. Silica in a series of nonaqueous solvents and in acetonitrile-water and methanol-water mixtures was studied in [3139,3140]. Only positive potentials are reported, probably by mistake. Silica in decane was studied in [3141]. ZnO in absolute methanol, ethanol, and propanol was studied in [3142]. Montmorillonite in 2-propanol was studied in [3143]. Silicon in a 99% l-butanol-1% water mixture was studied in [3145]. In [3146], 11 solids (oxides and inorganic salts) in 9 solvents were studied. 

The microparticles that make up the coating can be of any desired substance composition wise which can be reduced to a colloidal state of subdivision however, they must be dispersible in a medium as a colloidal dispersion. Water is the best medium for dispersions of particles of varying ionic charges. Examples of suitable aqueous sols are amorphous silica, iron oxide, alumina, thoria, titania, zirconia, zircon, and alumina sihcates, including colloidal clays such as montmorillonite, colloidal kaolin, attapul-gite, and hectorite. Silica is preferred material because of its low order of chemical activity, its ready dispersibility, and the easy availabihty of aqueous sols of various concentrations. 

Inorganic/PVA composites have been also considered, including sulfonic or phosphonic modified silica, titania, hydroxyapatite, heteropoly acids, zirconium phosphate, and montmorillonite. Hybrid organic-inorganic PVA composite membranes, like PVA/Ti02/PSSA, PVA/SiOa/SSA/, PVA/PWA/sPEEK/PWA, PVA/Si02/PPA, etc., have been reported. 

Research efforts on filled polymer blends have been more focused on nanopartide-filled systems [42, 43]. One usual observation is the same as those with microscopic fillers - polar nanofillers localize in more polar phases [44—53]. In cases where both phases are polar or nonpolar, the filler particles have been observed to be expelled from both phases in the blend [54—56]. Selective localization of nano-sized partides has been an interesting topic of research. We discuss some of the results here. Gahleitner et al. [57] observed a preferential localization of clay particles in PA6 droplets in PA6/PP blends. Recall that day, espedally montmorillonite, is highly polar in both its pristine and various organically modified forms [58-62]. Similarly, Wang et al. [63] reported selective localization of clay particles in maleic anhydride grafted ethylene-propylene-diene (EPDM-MA) rubber droplets in poly(trimethylene terephthalate)/EPDM-MA blends. Selective localization of fillers other than clay particles has also been reported. Eor instance, Ou and Li [64] observed that toluene diisocyanate modified titania particles selectively localized in PA6 droplets in PP/ PA6/titania blends. 

Preparation, physicochemical characterization and catalytic properties of vanadium-doped alumina- and titania-pillared montmorillonites... 

Procedures leading to preparation of vanadium-doped alumina- and/or titania-pillared montmorillonites are described and physicochemical characterization (chemical analysis, XRD, BET, ESR) of the products is provided. Results show that introduction of vanadium into the pillared montmorillonites leads to a rigid association of the dopant with pillars, irrespective of the method of preparation. The mode of vanadyl attachment in alumina-pillared samples does not depend on the mode of preparation, while in titania-pillared montmorillonite it does. Certain degree of delocalization of the unpaired electron into ligands and increased in-plane 7t-covalent bonding is observed for vanadyl ions present in the co-pillared (V-Ti)-PILC samples which also show particularly high activity in catalytic ammoxidation of m-xylene to nitrile product, as monitored by IR. A hypothesis is advanced that this effect is due to the unique character of vanadyl species present in these catalysts. 

This paper describes preparation, physicochemical characterization and catalytic properties of a series of vanadium-doped alumina- and titania-pillared montmorillonites obtained by various methods The aim of this work was to investigate the influence of the preparation procedure and pretreatment on location of vanadium dopant within the PILC structure and to correlate the physicochemical characteristics of tiie samples with their catalytic activity in ammoxidation of m-xylene. 

ESR data presented in detail elsewhere [7] show that all vanadium-doped alumina-and/or titania-pillared montmorillonite samples contain immobilized vanadyl ions bound to the pillars. 

Fig. la shows typical ESR spectra of alumina-pillared samples obtained by different methods. Differences in the ESR parameters of vanadyl species introduced by exchange with uncalcined or calcined pillars are very small indicating that similar vanadium species are formed irrespective of the preparative procedure. Also in the case of titania-pillared montmorillonite the ESR parameters of vanadyl ions deposited onto uncalcined (V(Ti)-PILC) and calcined (V-(Ti-PILC)) pillars are similar In the co-pillared (V-Ti)-PILC sample, however, a vanadyl spectrum with different parameters is observed (e g. smaller value of Aj, Fig. lb) pointing to a different character of vanadyl-pillar bonding in this case Analysis of the ESR parameters [7] shows that in the co-pillared samples the unpaired electron is partially delocalized into ligands and the vanadyl species posses increased inplane 7t-covalent bonding. 

M. (2009) Montmorillonite-based porous clay heterostructures (PCHs) intercalated with silica-titania pillars synthesis and characterization./. Solid State Chem., 182, 1094-1104. 

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