12-Tungstophosphoric acid supported on montmorillonite K10 (PWA/mont-K10) catalysed Pechmann condensation reaction was reported. The catalyst was characterized by XRD, FTIR, UV-Vis DRS, surface area and pore size analysis, TGA and acidity by DRIFTS using pyridine. The morphology of the catalyst was studied by SEM. The activity of mont-K10, mont-KSF, SO 2- 4/ZrO 2, 12-tungstophosphoric acid, and PWA/mont-K10 was investigated by condensation reaction of resorcinol with ethyl acetoacetate in the absence of solvent. Effect of molar ratio, amount of catalyst, reaction temperature and time on the yield of 7-hydroxy-4-methylcoumarin had been investigated on PWA/mont-K10. PWA/mont-K10 catalysed condensation of ethyl acetoacetate with phenol and a few substituted phenols had also been carried out to yield corresponding coumarins. The recycled catalyst showed reduced activity after single use. 15 wt% PWA on mont- K10 was found to be effective for synthesis of coumarin derivatives without employing any solvent. © Springer Science+Business Media, LLC 2011.

Gangavarapu Ranga Rao

Department Of Chemistry

12-TUNGSTOPHOSPHORIC ACID

7-HYDROXY-4-METHYLCOUMARIN

COUMARIN

COUMARIN DERIVATIVES

Ethylacetoacetate

FTIR

Molar ratio

MONTMORILLONITE K10

PECHMANN CONDENSATION

PORE-SIZE ANALYSIS

PWA/MONT-K10

Reaction temperature

Solvent free

Solvent free conditions

SUBSTITUTED PHENOL

surface area

UV-VIS-DRS

catalysis

Clay Minerals

Condensation

Condensation reactions

Phenols

Solvents

Catalyst activity

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Journal of Porous Materials

The nature of the Keggin ions of tungstophosphoric acid interacting with Ce0.5Zr0.5O2 solid solution has been investigated. The vibrational study shows additional IR features at 1051 and 957 cm-1 which are correlated to the primary Keggin anions interacting with Lewis sites involving Ce4+ and Zr4+ ions, and thus affecting the P-O and W=Oterminal bonds. The IR study indicates the formation of interfacial Ce4+-O-W and Zr4+-O-W bonds. The chemisorbed Keggin molecular layers on Ce0.5Zr0.5O 2 show activity towards conversion of acetophenone to styrene by Meerwein-Ponndorf-Verley reduction followed by dehydration. The activity is correlated with the relative intensities of IR peaks at 1051 and 957 cm -1 of the perturbed Keggin molecular layers. © 2007 Springer Science+Business Media, LLC.

Catalysis Letters

Investigation of 12-tungstophosphoric acid supported on Ce 0.5Zr0.5O2 solid solution

12-Phosphotungstic acid supported on porous hydrous zirconia was prepared and characterized by N2 adsorption isotherm, powder XRD, FTIR, 31P MAS NMR, H2-TPR, NH3-TPD, SEM and TEM. It is found that the chemical interaction of Keggin anions with hydrous zirconia is different compared to the interaction with ZrO2 and Ce0.5Zr0.5O2 supports. The phosphotungstic acid clusters dispersed on porous hydrous zirconia did not show any split of IR bands at 1080 cm-1 (νP-O) and 983 cm-1 (νW{double bond, long}O,ter) while those dispersed on ZrO2 and Ce0.5Zr0.5O2 showed a split in these two bands due to the lowering of symmetry of the central PO4 tetrahedron and direct interaction of W{double bond, long}Oter with oxide support. The dispersion of phosphotungstic acid on porous hydrous zirconia led to the growth of crystallites which showed catalytic activity for liquid-phase esterification of 2-ethyl-1-hexanol with acetic acid. Both conversion of 2-ethyl-1-hexanol and selectivity for 2-ethyl-1-hexyl acetate can be achieved at 100%. © 2008 Elsevier B.V. All rights reserved.

Journal of Molecular Catalysis A: Chemical

Porous hydrous zirconia supported 12-tungstophosphoric acid catalysts for liquid-phase esterification of 2-ethyl-1-hexanol

The interaction of 20 wt% 12-tungstophosphoric acid with Cex Zr1 - x O2 solid solutions has been studied by PXRD, FTIR, FT-Raman, H2-TPR, NH3-TPD, diffuse reflectance UV-vis-NIR, and 31P MAS NMR techniques. The study indicates that the Keggin anions are attached to Lewis metal ion centres and anion vacancies on Cex Zr1 - x O2 supports through W{double bond, long}O terminal bonds. The Keggin units at the interface are chemically perturbed as indicated by non-intrinsic IR bands observed at 958 cm-1 (W{double bond, long}Oter bond), and 1052, 1102 cm-1 (P{single bond}O bond). NH3-TPD shows that the Keggin anions fixed to Lewis sites and/or oxygen ion vacancies decrease the ammonia uptake on Cex Zr1 - x O2 solid solutions. H2-TPR shows modified redox behaviour of Cex Zr1 - x O2 solid solutions due to the simultaneous reduction of ceria, decomposition of Keggin anions and the reduction of WO3. The broadening of 31P MAS NMR and DR-UV-vis-NIR spectra demonstrate the existence of chemical interactions between the Keggin anions and Cex Zr1 - x O2 supports. © 2008 Elsevier Inc. All rights reserved.

Journal of Colloid and Interface Science

Interaction of Keggin anions of 12-tungstophosphoric acid with Cex Zr1 - x O2 solid solutions

A solid hybrid molecular material containing 1-butyl 3-methyl imidazolium cations and Keggin anions of phosphotungstic acid has been synthesized. It is fully characterized by CHN analysis, FTIR, XRD, UV-Vis-NIR DRS, 31P MAS NMR, TGA and SEM. The FTIR spectrum of the compound shows the fingerprint vibrational bands of both Keggin molecular anions and imidazolium cations. The aromatic C-H stretch region (2700-3250 cm-1) of imidazolium cation is split due to the interaction between the ring C-H and bulky Keggin anion. The red-shift in the UV-Vis spectra and the downfield 31P MAS NMR chemical shift also confirm the electrostatic interaction between the ions in the compound. Near IR spectral region (1000-2500 nm) shows the elimination of water in the compound which is hydrophobic. © Indian Academy of Sciences.

Fulltext

Journal of Chemical Sciences

Investigation of hybrid molecular material prepared by ionic liquid and polyoxometalate anion

Optics Express

Focus detection criterion for refocusing in multi-wavelength digital holography

PWA/montmorillonite K10 catalyst for synthesis of coumarins under solvent-free conditions

Journal	Journal of Porous Materials
ISSN	13802224
Open Access	No