02791nas a2200277 4500008004100000022001400041245012800055210006900183260009500252300000900347490000800356520166100364653002202025653001702047653005402064653004402118653002802162653002802190653003502218653006902253653001402322100001802336700001602354700001702370856012602387 2005 eng d a0021-951700aCO2 activation and synthesis of cyclic carbonates and alkyl/aryl carbamates over adenine-modified Ti-SBA-15 solid catalysts0 aCO2 activation and synthesis of cyclic carbonates and alkylaryl  a525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USAbACADEMIC PRESS INC ELSEVIER SCIENCEcJUL a1-150 v2333 a

Cyclic carbonates were synthesized by the cycloaddition Of CO2 to epoxides (epichlorohydrin, propene oxide, and styrene oxide), and carbamates were synthesized by reaction of alkyl or aryl amines, CO2, and n-butyl bromide. Solvents and cocatalysts/promoters, like N,N-dimethylaminopyridine (DMAP) and quaternary ammonium salts, which are usually essential with conventional catalyst systems, could be avoided with the use of adenine-modi lied Ti-SBA-15 catalysts. The catalysts were reused in several recycle experiments. The structural and textural properties of the catalysts were determined by X-ray diffraction (XRD), transmission electron microscopy (TEM), N-2 adsorption, and Fourier transform infrared (FTIR) and diffuse reflectance ultraviolet-visible (UV-vis DRS) techniques. Acid-base properties of the solid catalysts were investigated by temperature-programmed desorption (TPD) of NH3 and CO2 and DRIFTIR spectroscopy of adsorbed pyridine and CO2 techniques. The studies reveal that the Ti4+ ions increase catalytic activity by enhancing the adsorption of the epoxide and alkyl or aryl amine substrates. CO2 molecules are activated at the basic nitrogen groups of adenine. Increasing the surface concentrations of either CO2 (by anchoring basic molecules like adenine or increasing the partial pressure of CO2) or epoxides and alkyl or aryl amines (by increasing the concentration of Lewis acidic Ti4+ ions) enhances the catalytic activity. CO2 molecules activated at the covalently anchored adenine sites react with epoxide/amines adsorbed on the silica surface to form carbonates/carbamates. (c) 2005 Elsevier Inc. All rights reserved.

10aactivation of CO210aCO2 fixation10aDRIFTIR spectroscopy of adsorbed pyridine and CO210aorgano-functionalized mesoporous silica10aphosgene-free synthesis10asynthesis of carbamates10asynthesis of cyclic carbonates10atemperature-programmed desorption of NH3 and CO2 titanosilicates10aTi-SBA-151 aSrivastava, R1 aSrinivas, D1 aRatnasamy, P uhttps://library.ncl.res.in/content/co2-activation-and-synthesis-cyclic-carbonates-and-alkylaryl-carbamates-over-adenine-002573nas a2200217 4500008004100000022001400041245006900055210006700124260007600191300001400267490000800281520180600289653003202095653003302127653002002160653003602180100001702216700001202233700001702245856009302262 2005 eng d a1364-503X00aNovel, benign, solid catalysts for the oxidation of hydrocarbons0 aNovel benign solid catalysts for the oxidation of hydrocarbons a6-9 CARLTON HOUSE TERRACE, LONDON SW1Y 5AG, ENGLANDbROYAL SOCIETYcAPR a1001-10120 v3633 a

The catalytic properties of two classes of solid catalysts for the oxidation of hydrocarbons in the liquid phase are discussed: (i) microporous solids, encapsulating transition metal complexes in their cavities and (ii) titanosilicate molecular sieves. Copper acetate dimers encapsulated in molecular sieves Y, AICM-22 and VPI-5 use dioxygen to regioselectively ortho-hydroxylate L-tyrosine to L-dopa, phenol to catechol and cresols to the corresponding o-dihydroxy and o-quinone compounds. Monomeric copper phthalocyanine and salen complexes entrapped in zeolite-Y oxidize methane to methanol, toluene to cresols, naphthalene to naphthols, xylene to xylenols and phenol to diphenols. Trimeric mu(3)-oxo-bridged Co/Mn cluster complexes, encapsulated inside Y-zeolite, oxidize para-xylene, almost quantitatively, to terephthalic acid. In almost all cases, the intrinsic catalytic activity (turnover frequency) of the metal complex is enhanced very significantly, upon encapsulation in the porous solids. Spectroscopic and electrochemical studies suggest that the geometric distortions of the complex on encapsulation change the electron density at the metal ion site and its redox behaviour, thereby influencing its catalytic activity and selectivity in oxidation reactions. Titanosilieate molecular sieves can oxidize hydrocarbons using dioxygen when loaded with transition metals like Pd, An or Ag. The structure of surface Ti ions and the type of oxo-Ti species generated on contact with oxidants depend on several factors including the method of zeolite synthesis, zeolite structure, solvent, temperature and oxidant. Although, similar oxo-Ti species are present on all the titanosilicates, their relative concentrations vary among different structures and determine the product selectivity.

10abenign catalytic oxidations10aencapsulated metal complexes10aSolid catalysts10atitanosilicate molecular sieves1 aRatnasamy, P1 aRaja, R1 aSrinivasi, D uhttps://library.ncl.res.in/content/novel-benign-solid-catalysts-oxidation-hydrocarbons-001720nas a2200265 4500008004100000022001400041245010200055210006900157260008600226300001200312490000800324520073800332653004201070653003001112653002101142653001501163653002401178653002801202653002701230653002001257100001501277700001601292700001701308856012901325 2005 eng d a0942-935200aTi-oxo radicals and product selectivity in olefin oxidations over titanosilicate molecular sieves0 aTioxo radicals and product selectivity in olefin oxidations over aLEKTORAT MINT, POSTFACH 80 13 60, D-81613 MUNICH, GERMANYbOLDENBOURG VERLAGcJUL a905-9200 v2193 a

The O-O bond of Ti-oxo species (Ti-peroxo, Ti-hydroperoxo or Ti-superoxo) generated on titanosilicate molecular sieves contacted with H2O2 cleaves either heterolytically or homolytically. While the former type of O-O cleavage (generating non-radical reactive oxygen intermediates) leads to selective epoxide products, the latter (generating reactive oxygen radical intermediates, O-2(-center dot) and HOOcenter dot) results in non-sclective, allylic oxidation products in cyclohexene oxidation. These radicals were detected using EPR spin trapping techniques 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) was used as the spin trap. Radical quenchers like hydroquinone suppressed their concentration and enhanced epoxide selectivity.

10acyclic voltammetry of titanosilicates10aEPR-spin trap experiments10aMolecular sieves10aoxidations10aproduct selectivity10areactive oxygen species10atitaniunz-oxo radicals10aTitanosilicates1 aShetti, VN1 aSrinivas, D1 aRatnasamy, P uhttps://library.ncl.res.in/content/ti-oxo-radicals-and-product-selectivity-olefin-oxidations-over-titanosilicate-molecular-002099nas a2200241 4500008004100000022001400041245016700055210006900222260007300291300001200364490000800376520114000384653003001524653003101554653002101585653003401606653001801640653001701658100001801675700001601693700001701709856013101726 2005 eng d a0926-860X00aZeolite-based organic-inorganic hybrid catalysts for phosgene-free and solvent-free synthesis of cyclic carbonates and carbamates at mild conditions utilizing CO20 aZeolitebased organicinorganic hybrid catalysts for phosgenefree  aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcAUG a128-1340 v2893 a

As-synthesized zeolite-beta exhibits high catalytic activity for the synthesis of cyclic carbonates and alkyl and aryl carbarnates by a phosgene-free route, utilizing the greenhouse effect gas CO2. The reaction occurs with high yields of the desired products at mild conditions and without using any solvent or cocatalyst. Cyclic carbonates are synthesized by cycloaddition reaction Of CO2 with oxiranes (epichlorohydrin, propene oxide, styrene oxide and n-butene oxide) at 393 K and 6.9 bar. Alkyl and aryl carbarnates are synthesized by the reaction of the corresponding amines, CO2 and n-butyl bromide at 353 K and 3.4 bar. The as-synthesized zeolite-beta containing the encapsulated quaternary ammonium ions is not only reusable in several recycling experiments, but also shows superior activity to that of the corresponding homogeneous, quaternary ammonium halide salt generally used in the commercial synthetic practice. The microporous silica (inorganic) acting in concert with the encapsulated organic component constitutes an efficient, recyclable catalyst for this reaction. (c) 2005 Elsevier B.V. All rights reserved.

10aalkyl and aryl carbamates10acarbon dioxide utilization10acyclic carbonate10aphosgene-free synthetic route10aPolycarbonate10azeolite-beta1 aSrivastava, R1 aSrinivas, D1 aRatnasamy, P uhttps://library.ncl.res.in/content/zeolite-based-organic-inorganic-hybrid-catalysts-phosgene-free-and-solvent-free-synthesis-0