A water soluble heteropolyoxotungstate as a selective, efficient and environment friendly oxidation catalyst

A series of water soluble Keggin type heteropolyoxotungstates have been tested as oxidation catalysts in aqueous-biphasic media with dilute H2O2 (30%) as the oxygen atom donor, without using any phase transfer agent. The Zn substituted polyoxoanion {(NH4)7Zn0.5[α-ZnO4W11O30ZnO5(OH2)]·nH2O} has been found to be the most efficient catalyst, which oxidizes a wide range of organic functionalities with good turnovers and high selectivities. The functionalities that undergo oxidations are: organic sulfides, pyridines, anilines, benzyl alcohols and benzyl halides. The oxidations of sulfides to sulfoxides and/or sulfones have been studied in detail, and a simple kinetic model consisting of two consecutive reactions, is shown to give good fit with the experimental data. In the catalytic system described here product isolation is easy, and the aqueous catalyst solution can be re-used several times with little loss in its efficiency

Polyethersulfone supported titanium complexes as ethylene polymerization catalysts

Polyethersulfone has been used as the support to anchor TiCl4 or Cp2TiCl2 through dative 'O-Ti' bond. The supported complexes in combination with methylaluminoxane are effective ethylene polymerization catalysts. The polyethylene made by the supported catalysts, especially the titanocene-derived catalyst, has low polydispersity indicating single site character

Effect of cross-linking on catalytic performance of polystyrene supported platinum carbonyl clusters

2392-2397Commercial chlormethylated divinylbenzene cross- linked polystyrene resins (5.5% and 8%) have been functionalized by the reaction with triethylamine. The Clinicl uster [Pt15(CO)30]2- has been anchored onto the resultant materials by anion exchange. The degrees of functonalization in terms of chloromethyl and benzyltriethyl ammonium functionalities are found to be very high and high (>85% and >60%) respectively for both the polymers. The total platinum content of the 8% crosslinked polystyrene is a little (~13%) more than that of 5.5% cross-linked polymer. The catalytic activities of the resultant materials after mild thermal activation have been studied for the hydrogenation of a variety of unsaturated compounds. The substrates studied are: cyclohexanone, acetophenone, methyl pyruvate, ethyl acetoacetate and nitrobenzene. For most of the substrates the activity of the 5.5% cross- linked material is found to be a little more than that of the 8.8% cross-linked material. This is despite the fact that the latter has more platinum both in the bulk and on the surface as measured by atomic absorption and EDAX (SEM) techniques respectively. After functionalization with cinchonine and [Pt15(CO)30] 2-, both the polymers have been tested as possible asymmetric catalysts for the hydrogenation of methyl pyruvate. No enantioselection is observed and a tentative explanation is offered for the lack of enantioselection

Effect of cross-linking on catalytic performance of polystyrene supported platinum carbonyl clusters

Commercial chlormethylated divinylbenzene cross-linked polystyrene resins (5.5% and 8%) have been functionalized by the reaction with triethylamine. The Chini cluster [Pt15(CO)30]2- has been anchored onto the resultant materials by anion exchange. The degrees of functonalization in terms of chloromethyl and benzyltriethyl ammonium functionalities are found to be very high and high (> 85% and > 60%) respectively for both the polymers. The total platinum content of the 8% cross-linked polystyrene is a little (~13%) more than that of 5.5% cross-linked polymer. The catalytic activities of the resultant materials after mild thermal activation have been studied for the hydrogenation of a variety of unsaturated compounds. The substrates studied are: cyclohexanone, acetophenone, methyl pyruvate, ethyl acetoacetate and nitrobenzene. For most of the substrates the activity of the 5.5% cross-linked material is found to be a little more than that of the 8.8% cross-linked material. This is despite the fact that the latter has more platinum both in the bulk and on the surface as measured by atomic absorption and EDAX (SEM) techniques respectively. After functionalization with cinchonine and [Pt15(CO)30]2- , both the polymers have been tested as possible asymmetric catalysts for the hydrogenation of methyl pyruvate. No enantioselection is observed and a tentative explanation is offered for the lack of enantioselection

A water soluble nanostructured platinum (0) metal catalyst from platinum carbonyl molecular clusters: synthesis, characterization and application in the selective hydrogenations of olefins, ketones and aldehydes

High nuclearity platinum carbonyl cluster anions (Chini's clusters) have been used as precursors to prepare a platinum nanocatalyst. The ionic polyelectrolyte poly(diallyldimethylammonium chloride) has been used as the support material for anchoring [Pt30(CO)60]2− via ion-pairing and subsequent stabilization of the nanoparticles. The polymer-supported material has been studied by spectroscopy (NIR, 13C NMR, and IR) and TEM before and after its use as a water soluble hydrogenation catalyst. The nanocatalyst is found to be effective for the chemoselective hydrogenation of olefinic, aldehydic and ketonic double bonds. For most of the substrates isolation of the product and reuse of the catalyst are extremely easy due to the automatic phase separation of the products from the catalyst. The spectral features of the fresh catalyst show retention of the carbonyl ligands and molecular identity of the parent cluster, but after use the carbonyl ligands appear to be lost. TEM of the supported material before and after use as a catalyst shows the presence of platinum nanoparticles with majority (≥70%) of the particles in the range of 2–6 nm. Smaller particles are dominant in the used catalyst and this observation is rationalized on the basis of the known reactivity of Chini's clusters with dihydrogen.© Elsevie

Platinum carbonyl derived catalysts on inorganic and organic supports: a comparative study

Fumed silica, silica gel, silica–alumina and cross-linked (5.5%) polystyrene have been functionalized with quaternary ammonium groups and the Chini cluster [Pt12(CO)24]2− has been anchored onto these functionalized materials by ion pairing. A catalyst has also been prepared by the adsorption of Na2[Pt12(CO)24] on unfunctionalized fumed silica. The catalytic activities of the resultant materials, and that of commercially purchased 5% platinum on alumina have been studied for the hydrogenation of a variety of unsaturated compounds. The substrates studied are: α-acetamidocinnamic acid, cyclohexanone, acetophenone, methyl pyruvate, ethyl acetoacetate, nitrobenzene and benzonitrile. Compared to the polystyrene supported catalyst, the inorganic oxide supported catalysts have higher surface areas and for most of the substrates have notably higher activities. The functionalized fumed silica-based catalyst gives higher conversions than functionalized silica gel and silica–alumina-based catalysts. In the hydrogenation of acetophenone and ethyl acetoacetate, the functionalized fumed silica-based catalyst show superior activity compared to the commercial platinum catalyst, and the catalyst made by conventional adsorption method. In benzonitrile hydrogenation with all the cluster-derived catalysts a hydrazine derivative is selectively formed, but when the commercial platinum catalyst is used benzyl amine is the main product.© Elsevie

Huge congenital teratoma containing tooth in a three-day-old neonate

Congenital teratoma is a rare cause of congenital proptosis. A full term three-day-old male child was presented with massive unilateral swelling in the left orbit, which was noted since birth. Diagnosis of orbital teratoma without intracranial extension was made based on clinical examination and imaging. Lid-sparing exenteration of the left orbit was done. Histopathological examination confirmed the diagnosis of cystic teratoma. Congenital orbital teratoma with a tooth and mature elements of all the three germ cell layers is reported due to its extreme rarity

Pareto optimization of electro discharge machining of titanium nitride-aluminium oxide composite material using Genetic algorithm

Titanium nitride-aluminium oxide (TiN-Al 2O 3) is a new generation ceramic composite material having potential for many industrial applications as it possesses high resistance to thermal degradation, anti-wear and anti-abrasion properties. In the present research the characteristic features of EDM process are explored through Taguchi methodology based experimental studies with various process parametric combinations. Finally the process has been optimized using Genetic algorithm based Pareto optimization search. From Pareto optimal search the technology guideline for optimal parameter settings have been selected. The present research approach is extremely useful for maximizing the productivity while maintaining the geometrical accuracy within desired limit