On-line extraction of polymers, oligomers, additives and monomers by multiple solvents on packed HPLC columns

Extn. of monomers, additives, oligomers, and polymers from a blend is very time-consuming and labor intensive. Using a special guard column and multi-solvent gradient liq. chromatog. (HPLC), the extn. and anal. can be performed in one ste

Novel composites of TiO2 (anatase) and silicate nanoparticles

Thermally stable composite nanostructures of titanium dioxide (anatase) and silicate nanoparticles were prepared from Laponite clay and a sol of titanium hydrate in the presence of poly(ethylene oxide) (PEO) surfactants. Laponite is a synthetic clay that readily disperses in water and exists as exfoliated silicate layers of about 1-nm thick in transparent dispersions of high pH. The acidic sol solution reacts with the clay platelets and leaches out most of the magnesium in the clay, while the sol particles hydrolyze further due to the high pH of the clay dispersion. As a result, larger precursors of TiO2 nanoparticles form and condense on the fragmentized pieces of the leached silicate. Introducing PEO surfactants into the synthesis can significantly increase the porosity and surface area of the composite solids. The TiO2 exists as anatase nanoparticles that are separated by silicate fragments and voids such that they are accessible to organic molecules. The size of the anatase particle can be tailored by manipulating the experimental parameters at various synthesis stages. Therefore, we can design and engineer composite nanostructures to achieve better performance. The composite solids exhibit superior properties as photocatalysts for the degradation of Rhodamine 6G in aqueous solution

On the synthesis of vanadium containing molecular sieves by experimental design from a VOSO4.5H2O.Al(iPrO)3.Pr2NH.H2O gel: occurrence of VAPO-41 as a secondary structure in the synthesis of VAPO-11

An experimental design was applied to the hydrothermal synthesis of VAPO-11 molecular sieve (AEL structure)from a VOSO4.5H2O.Al(iPrO)3.Pr2NH.H2O gel. The influence of five synthesis parameters (synthesis temperature, synthesis time, vanadium content, water content and template content) on the crystallinity and physicochemical properties of the as-synthesized materials was studied. The obtained materials were characterized by electron spin resonance (ESR), diffuse reflectance spectroscopy (DRS), X-ray diffraction, thermal analysis measurements, scanning electron microscopy and in situ Fourier transform infrared (FTIR) spectroscopy. The AEL structure appears either as a single phase or as a physical mixture together with the AFO structure (VAPO-41). A statistical model is proposed, which relates the synthesis variables with the crystallinity allowing to indicate the optimal synthesis conditions for VAPO-11. Highly crystalline single-phase VAPO-11 can be best prepared at 170°C from a synthesis gel with a low vanadium content (0.02 mol) and a high water content (25 mol). The co-ordination of vanadium in these materials is discussed on the basis of the ESR and DRS spectra. The spectroscopic data are explained by the presence of a vanadium species in distorted octahedral co-ordination, composed of two V-O-T bonds with the framework, one bond with the vanadyl oxygen and three water molecules as ligands

AlOx Coating of Ultrastable Zeolite Y: A Possible Method for Vanadium Passivation of FCC Catalysts

AlOx coating is proposed as a possible method for vanadium passivation of the ultrastable zeolite Y (USY). Two coating methods are discussed: (i) the deposition of the [Al13O4(OH)24(H2O)12]7+ ([Al13]) complex from aqueous solutions and (ii) the anchoring of alumoxane by in situ triisobutylaluminum hydrolysis followed by calcination. The properties and the efficiency in vanadium passivation of the coated materials have been investigated with DRS, ESR, XPS, FTIR, and sorption measurements. XPS revealed for all the coated samples an enrichment in the Al content in the near-surface region and differences in Al coordination geometry. Vanadyl(IV) etioporphyrin, the major contaminant in crude oil, was used to probe the trapping efficiency of the external AlOx layer. The [Al13]-derived layer is homogeneously distributed and covers the external surface of the USY zeolite, following its topology, but without blocking its pores. About 80% of the offered vanadyl species have been preferentially trapped in this layer. The alumoxane-based method is less efficient in vanadium passivation, most probably because after calcination the aluminum species are heterogeneously distributed, both on the external surface and in the channels of USY zeolite

AlOx Coating of Ultrastable Zeolite Y: A Possible Method for Vanadium Passivation of FCC Catalysts

AlOx coating is proposed as a possible method for vanadium passivation of the ultrastable zeolite Y (USY). Two coating methods are discussed: (i) the deposition of the [Al13O4(OH)24(H2O)12]7+ ([Al13]) complex from aqueous solutions and (ii) the anchoring of alumoxane by in situ triisobutylaluminum hydrolysis followed by calcination. The properties and the efficiency in vanadium passivation of the coated materials have been investigated with DRS, ESR, XPS, FTIR, and sorption measurements. XPS revealed for all the coated samples an enrichment in the Al content in the near-surface region and differences in Al coordination geometry. Vanadyl(IV) etioporphyrin, the major contaminant in crude oil, was used to probe the trapping efficiency of the external AlOx layer. The [Al13]-derived layer is homogeneously distributed and covers the external surface of the USY zeolite, following its topology, but without blocking its pores. About 80% of the offered vanadyl species have been preferentially trapped in this layer. The alumoxane-based method is less efficient in vanadium passivation, most probably because after calcination the aluminum species are heterogeneously distributed, both on the external surface and in the channels of USY zeolite