02141nas a2200181 4500008004100000022001400041245008800055210006900143260006900212300001200281490000700293520143400300653003401734653001601768653002701784100002501811856012301836 2005 eng d a0255-270100aModeling a continuous multistage liquid phase cyclohexane oxidation reactor network0 aModeling a continuous multistage liquid phase cyclohexane oxidat aPO BOX 564, 1001 LAUSANNE, SWITZERLANDbELSEVIER SCIENCE SAcMAY a567-5790 v443 a

A model is presented for a continuous multistage liquid phase cyclohexane oxidation reactors-in-series network, which uses, unlike previous efforts, a closed form rate model derived on the basis of the well-known free-radical kinetic mechanism of the oxidation reaction leading to a more generalized representation of the oxygen dependence of the rate. The model calculates the required transport and hydrodynamic parameters by one of the best available set of correlations shown earlier to be successfully used in cyclohexane oxidation in a well-designed laboratory reactor. Process sensitivities with regard to variables such as air rate, residence time, head pressure, inlet air composition and sparger configuration have been predicted. Some of these trends compared very well with the limited published experimental data in a three (351) agitated and sparged tank-in-series reactor system, thus partially validating the model. The model has highlighted a fairly generalized way of correlating performance data from a given reactor, namely in terms of a yield-conversion characteristic which can change depending on the mass transfer efficiency and the effective kinetics. Hence, it can aid in plant monitoring and optimization. It has also been shown how to use the same as an aid in preliminary scale-up studies based on laboratory or pilot plant reactor performance data. (C) 2004 Elsevier B.V. All rights reserved.

10acontinuous multistage reactor10aCyclohexane10aLiquid phase oxidation1 aBhattacharya, Arijit uhttps://library.ncl.res.in/content/modeling-continuous-multistage-liquid-phase-cyclohexane-oxidation-reactor-network-002407nas a2200217 4500008004100000022001400041245015100055210006900206260007300275300001200348490000800360520156700368653001301935653001601948653001401964653002301978100001602001700002402017700001802041856013002059 2007 eng d a0926-860X00aChromium-containing small pore mesoporous silicas: synthesis, characterization and catalytic behavior in the liquid phase oxidation of cyclohexane0 aChromiumcontaining small pore mesoporous silicas synthesis chara aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcFEB a128-1360 v3183 a

Organic-inorganic hybrid mesoporous silica materials containing chromium and various organo trialkoxysilanes (chloropropyl, vinyl, methyl) were prepared by the co-condensation method, in the presence of cetyl trimethyl ammonium surfactants. The hybrid material, containing chromium, retains one X-ray diffractogram (XRD) peak up to a molar ratio of 1: 1 between tetra ethyl orthosilicate (TEOS) and organosilane in the synthesis gel. Small pore mesoporous chromium-silica samples can be prepared from the large pore hybrid mesoporous chromium samples by calcination. By this method, the pore size of the material can be tailored into the supermicroporous region, without changing the chain length of the surfactant used in the assembly process, as judged from the XRD and N-2 sorption isotherms. The shrinkage in pore size is dependent on the nature and percentage of the organic pendant groups, such that the chloro propyl and vinyl pendant mesoporous material show more pore size shrinkage than the smaller methyl pendant units. Because of the tailorable pore size and with better textural characteristics, the chromium samples show better catalytic activity in the aerial oxidation reaction of cyclohexane than the conventional chromium-containing mesoporous material, like Cr-MCM-41, under a solvent free system. Among the porous chromium catalysts, the samples prepared using chloro propyl silane show higher cyclohexane conversion and cyclohexanone selectivity and behave as a true heterogeneous catalyst. (c) 2006 Elsevier B.V. All rights reserved.

10achromium10aCyclohexane10aOxidation10asmall pore silicas1 aShylesh, S.1 aSamuel, Prinson, P.1 aSingh, A., P. uhttps://library.ncl.res.in/content/chromium-containing-small-pore-mesoporous-silicas-synthesis-characterization-and-catalytic02373nas a2200241 4500008004100000022001400041245014100055210006900196260007300265300001200338490000700350520148000357653001401837653001101851653001601862653003201878653001401910100001601924700002001940700001801960700002101978856013201999 2007 eng d a1387-181100aOne step synthesis of chromium-containing periodic mesoporous organosilicas and their catalytic activity in the oxidation of cyclohexane0 aOne step synthesis of chromiumcontaining periodic mesoporous org aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcFEB a334-3440 v993 a

Chromium-containing ethane-bridged hybrid mesoporous materials (Cr-PMO) with uniform hexagonal arrangement were synthesized by two different synthesis routes using 1,2-bis(triethoxysilyl)ethane (BTEE) and tetraethyl orthosilicate (TEOS) as silica sources and alkyltrimethyl ammonium salts (ATMA) as surfactants. Powder X-ray diffraction, TEM, N-2 adsorption-desorption, FT-IR, in situ FT-Raman, UV-ViS, XPS, Si-29 MAS NMR and C-13 CP MAS NMR were used to probe the mesoporous structure and the nature of chromium sites in the hybrid catalyst matrix. PXRD, TEM and N-2 adsorption-desorption analysis showed that the original hexagonal structure of the materials is maintained after chromium substitution, while FT-Raman, UV-Vis and XPS analysis showed that chromium atoms exist in a highly dispersed state. The catalytic performance of the chromium-containing hybrid samples was tested in the liquid-phase oxidation of cyclohexane with aqueous hydrogen peroxide (H2O2) and non-aqueous tert-butylhydroperoxide (TBHP) as oxidants. The hybrid materials exhibited better catalytic activities and were more stable than the conventional Cr-MCM-41 catalyst. The higher catalytic activity of the new chromium-containing molecular sieves is attributed to the improved hydrophobicity of the materials and to the complementary structural features that facilitates the accessibility of cyclohexane to the active framework chromium sites. (c) 2006 Elsevier Inc. All rights reserved.

10aCr-MCM-4110aCr-PMO10aCyclohexane10ahybrid mesoporous materials10aOxidation1 aShylesh, S.1 aSrilakshmi, Ch.1 aSingh, A., P.1 aAnderson, B., G. uhttps://library.ncl.res.in/content/one-step-synthesis-chromium-containing-periodic-mesoporous-organosilicas-and-their-catalytic02664nas a2200241 4500008004100000022001400041245013100055210006900186260007300255300001000328490000800338520179500346653002502141653001302166653001602179653001102195653001402206100001602220700002102236700001802257700002102275856012602296 2008 eng d a1387-181100aBridging the gap between micropores and mesopores by the controlled transformation of bifunctional periodic mesoporous silicas0 aBridging the gap between micropores and mesopores by the control aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcFEB a29-400 v1083 a

Novel bifunctional periodic mesoporous silicas having high content of organic groups in the pore channels and chromium in the frame wall has been synthesized by direct co-condensation method, using organo trialkoxysilanes (chloro propyl, vinyl, methyl), chromium nitrate and tetraethyl orthosilicate, in presence of cetyltrimethyl ammonium surfactants. The obtained materials show one main peak in the XRD patterns up to a molar ratio of 1: 1 between TEOS and organosilane in the synthesis gel and N-2 adsorption-desorption analysis shows that the mesopore structure remains intact after the surfactant removal process. Among the organosilanes, chloro propyl and vinyl pendant chromium samples shows a shift in the main peak to higher 2-theta values with a corresponding decrease in pore volume and pore diameter, with the percentage of organosilane functionalization. Small-pore silicas and chromium silicas can be prepared from the large pore mesoporous MCM-41, by effectively removing the organic groups by calcination. By this method, the pore size of the material can be tailored into the super-microporous region, without changing the chain length of the surfactant used in the assembly process. The shrinkage in pore size is dependent on the nature and percentage of the organic pendant groups that the chloro propyl and vinyl pendant mesoporous materials show the maximum pore size shrinkage than the small chain length methyl units. Because of the tailorable pore size and with better textural characteristics, chromium-silica materials find applications in the field of shape selective heterogeneous catalysis, as demonstrated in the oxidation reaction of cyclohexane, than the conventional metal-containing mesoporous materials. (c) 2007 Elsevier Inc. All rights reserved.

10abifunctional silicas10achromium10aCyclohexane10aMCM-4110aOxidation1 aShylesh, S.1 aSrilakshini, Ch.1 aSingh, A., P.1 aAnderson, B., G. uhttps://library.ncl.res.in/content/bridging-gap-between-micropores-and-mesopores-controlled-transformation-bifunctional-002083nas a2200253 4500008004100000022001400041245011500055210006900170260005700239300001200296490000800308520123300316653001401549653001601563653001801579653001801597653001401615100001801629700001501647700001601662700001401678700001301692856012401705 2009 eng d a1011-372X00aCatalytic aerobic oxidation of cyclohexane and ethyl benzene over chromium-containing mesoporous organosilicas0 aCatalytic aerobic oxidation of cyclohexane and ethyl benzene ove a233 SPRING ST, NEW YORK, NY 10013 USAbSPRINGERcOCT a492-4990 v1323 a

Chromium-containing ethane-bridged hybrid periodic mesoporous organosilicas (Cr-PMO) were synthesized using 1,2-bis(triethoxysilyl) ethane (BTEE) and tetraethyl orthosilicate (TEOS) as silica sources and alkyltrimethyl ammonium salts as surfactants by two different synthesis routes. PXRD and N(2) adsorption-desorption analysis shows that the original structure of the materials is maintained after chromium substitution while spectroscopic study proves the incorporation of chromium in the frame wall positions and show the existence of Cr(2)O(3) species in the mixed silica source (BTEE-TEOS) synthesized chromium samples. The catalytic activity of the newly developed chromium samples was evaluated in the liquid phase oxidation of cyclohexane and ethylbenzene using air as an oxidant. Further, the Cr-PMO samples exhibited better cyclohexane conversion and cyclohexanone selectivity than the conventional Cr-MCM-41 and other metal-containing MCM-41 samples. The exceptional activity of the new chromium-containing molecular sieves is attributed to the hydrophobicity of the materials and to the complementary structural features that facilitates the accessibility of substrate to the active framework chromium sites.

10aCr-MCM-4110aCyclohexane10aEthyl benzene10aOrganosilicas10aOxidation1 aSingh, A., P.1 aTorita, N.1 aShylesh, S.1 aIwasa, N.1 aArai, M. uhttps://library.ncl.res.in/content/catalytic-aerobic-oxidation-cyclohexane-and-ethyl-benzene-over-chromium-containing-002009nas a2200265 4500008004100000022001400041245009700055210006900152260007300221300001200294490000800306520108900314653001501403653001601418653001601434653001301450653001201463653001801475100001901493700002101512700002401533700002901557700002601586856013101612 2010 eng d a0304-389400aReductive dechlorination of gamma-hexachlorocyclohexane using Fe-Pd bimetallic nanoparticles0 aReductive dechlorination of gammahexachlorocyclohexane using FeP aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcMAR a680-6870 v1753 a

Nanoscale Fe-Pd bimetallic particles were synthesized and used for degradation of lindane (gamma-hexachlorocyclohexane) in aqueous solution. Batch studies showed that 5 mg/Lof lindane was completely dechlorinated within 5 min at a catalyst loading of 0.5 g/L and the degradation process followed first-order kinetics. GC-MS analysis in corroboration with GC-ECD results showed the presence of cyclohexane as the final degradation product. The proposed mechanism for the reductive dechlorination of lindane involves Fe corrosion-induced hydrogen atom transfer from the Pd Surface. The enhanced degradation efficiency of Fe-Pd nanoparticles is attributed to: (1) high specific surface area of the nanoscale metal particles (60 m(2)/g), manyfold greater that of commercial grade micro- or milli-scale iron particles (similar to 1.6 m(2)/g); and, (2) increased catalytic reactivity due to the presence of I'd on the Surface. Recycling and column studies showed that these nanoparticles exhibit efficient and sustained catalytic activity. (C) 2009 Elsevier B.V. All rights reserved.

10aBimetallic10aCyclohexane10aDegradation10akinetics10aLindane10aNanoparticles1 aNagpal, Varima1 aBokare, Alok, D.1 aChikate, Rajeev, C.1 aRode, Chandrashekhar, V.1 aPaknikar, Kishore, M. uhttps://library.ncl.res.in/content/reductive-dechlorination-gamma-hexachlorocyclohexane-using-fe-pd-bimetallic-nanoparticles-0