@article { ISI:000253740900005, title = {Synthesis and characterization of novel organo-montmorillonites}, journal = {Applied Clay Science}, volume = {38}, number = {3-4}, year = {2008}, month = {FEB}, pages = {203-208}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Sodium Montmorillonite (NaMMT) has been modified via cation exchange reaction using three different organic cations. Basal spacings, interlamellar structure and thermal stability of these organo-montmorillonites (OMMT) clays have been characterized using wide angle X-ray diffraction (WARD) and thermogravimetric analysis (TGA) techniques. Increase in the basal spacing due to organic modification is in good agreement with simple theoretical calculations based on van der Waals volume of the cationic ammonium ions. TGA characterization and analysis show that the amount of organic modifier in the OMMT{\textquoteright}s is in good agreement with theoretically calculated stoichiometric content expected for almost complete exchange of Na+ ions by organic cations. The OMMT{\textquoteright}s shows stepwise decomposition corresponding to initial weight loss from residual water desorption, followed by decomposition of the organic surfactant and the dehydroxylation of structural water of the montmorillonite layers. (C) 2007 Elsevier B.V. All rights reserved.

}, keywords = {Montmorillonite, organo-clays, organo-montmorillonite, surfactant}, issn = {0169-1317}, doi = {10.1016/j.clay.2007.05.008}, author = {Tiwari, Rajkiran R. and Khilar, Kartic C. and Natarajan, Upendra} } @article { ISI:000271982400003, title = {Characterization of clay intercalated cobalt-salen catalysts for the oxidation of p-cresol}, journal = {Applied Catalysis A-General}, volume = {370}, number = {1-2}, year = {2009}, month = {NOV}, pages = {16-23}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

The intercalation of cobalt-salen complexes into the interlamelar spaces of montmorillonite clay was investigated by various characterization studies. The {\textquoteleft}{\textquoteleft}neat{\textquoteright}{\textquoteright} cobalt-salen complex showed a weight loss at 368 degrees C while the weight loss for the corresponding intercalated complex was observed at much higher temperature of 492 degrees C due to decomposition of the complex. The thermal stabilization observed was due to the host-guest interaction of clay and metal complex and thus confirmed the intercalation. The XANES spectrum of Co(salen)-mont sample revealed the change of symmetry from the tetrahedral in plane to the octahedral structure having an axial bonding of oxygen to the cobalt, indicating that cobalt atoms in Co(salen)-mont were coordinated axially with the lattice oxygen of montmorillonite. Both XANES and EXAFS results indicated that cobalt atoms in Co(salen)-mont form two additional Co-O bonds with a bond length of 0.199 nm by the intercalation while retaining the Co-salen structure. Co-salen intercalated into the montmorillonite clay showed the highest activity for the air oxidation of p-cresol, giving 88\% selectivity to the oxidation products. Effects of NaOH concentration and various solvents on the conversion and selectivity patterns also have been studied. (C) 2009 Elsevier B.V. All rights reserved.

}, keywords = {Cobalt-oxygen bond, Cobalt-salen, Extended X-ray absorption fine structure, Intercalation, Lattice oxygen, Montmorillonite, X-ray absorption near edge structure}, issn = {0926-860X}, doi = {10.1016/j.apcata.2009.09.003}, author = {Kshirsagar, V. S. and Garade, Ajit C. and Mane, R. B. and Patil, K. R. and Yamaguchi, A. and Shirai, M. and Rode, C. V.} } @article { ISI:000262658000018, title = {Montmorillonite for selective hydroxyalkylation of p-cresol}, journal = {Applied Clay Science}, volume = {43}, number = {1}, year = {2009}, month = {JAN}, pages = {113-117}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Performances of montmorillonite titanium silicate (TS-1) and dodecatungstophosphoric acid (DTP) were compared for the hydroxyalkylation of p-cresol into dihydroxydiarylmethane (DAM). Ammonia TPD studies of various catalysts showed that an appropriate combination of both strong and weak acid sites of montmorillonite was mainly responsible rather than only the stronger acidity of bulk DTP for its highest catalytic activity for selective hydroxyalkylation of p-cresol to DAM. The selectivity to DAM could be enhanced by adjusting reaction conditions like mole ratio of p-cresol to formaldehyde, reaction temperature, catalyst concentration, solvent and reaction time. (C) 2008 Elsevier B.V. All rights reserved.

}, keywords = {Ammonia TPD, Dihydroxydiarylmethane, Hydroxyalkylation, Montmorillonite, Solid acids}, issn = {0169-1317}, doi = {10.1016/j.clay.2008.07.015}, author = {Garade, Ajit C. and Mate, Vivek R. and Rode, C. V.} } @article { ISI:000291182100026, title = {Efficiency and recycling capability of montmorillonite supported Fe-Ni bimetallic nanocomposites towards hexavalent chromium remediation}, journal = {Applied Catalysis B-Environmental}, volume = {104}, number = {3-4}, year = {2011}, month = {MAY}, pages = {407-414}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

The remediation of Cr(VI) from simulated water streams is investigated using Fe-Ni bimetallic nanoparticles (Fe-Ni NPs) and their nanocomposites prepared with montmorillonite (MMT) clay. These nanocomposites are characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) surface area analyses. XRD analysis revealed proper dispersion as well as intercalation of Fe-Ni NPs in the clay matrix. TEM of nanocomposites showed the presence of spherical particles having a size of 20-40 nm. Batch experiments with a 25 mg L(-1) Cr(VI) solution and 2 g L-1 Fe-Ni NPs exhibited complete reduction of Cr(VI) within 10 min that follows first order reaction kinetics. Amongst 25\%, 50\%, 75\% in situ and loaded nanocomposites, 75\% compositions possess better activity with enhanced reduction capacity below pH 4 due to generation of reactive H center dot species. XPS analysis of nanocomposites after Cr(VI) treatment suggested that reduction process occurs through Cr(111) formation followed by its subsequent reduction to Cr(0). Their potentiality towards reusage is established from the recycling experiments that revealed the order of efficiency as 75\% in situ \> Fe-Ni NPs \> 75\% loaded nanocomposites. (C) 2011 Elsevier B.V. All rights reserved.

}, keywords = {Cr(VI) remediation, Iron-nickel bimetallics, Montmorillonite, Nanocomposites, Recycling}, issn = {0926-3373}, doi = {10.1016/j.apcatb.2011.02.011}, author = {Kadu, Brijesh S. and Sathe, Yogesh D. and Ingle, Abhijit B. and Chikate, Rajeev C. and Patil, Kashinath R. and Rode, Chandrashekhar V.} } @article { ISI:000317945100020, title = {Metal cation-exchanged montmorillonite clay as catalysts for hydroxyalkylation reaction}, journal = {Applied Clay Science}, volume = {74}, number = {SI}, year = {2013}, month = {APR}, pages = {141-146}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Several solid acid catalysts were prepared by exchanging metal cations such as Zn2+, Fe3+ and Al3+ with montmorillonite clay. Among these, Al-montmorillonite showed the highest acidity determined by the pyridine-IR as well as NH3-TPD methods. A systematic comparison of the performance of these catalysts along with parent montmorillonite was carried out for the hydroxyalkylation of p-cresol with formaldehyde to give 2, 2{\textquoteright}-methylenebis (4-methyl phenol) (DAM). It was found that the activity of these catalysts was in accordance with the increase in acidity of parent montmorillonite after the exchange of cations in the order of Zn2+, Fe3+ and Al3+. The selectivity pattern was also influenced by the exchanged cations. Since Al-montmorillonite showed the highest conversion of 51\% with 98\% selectivity to DAM, the effects of various reaction parameters, namely, mole ratio, catalyst concentration, temperature, reaction time on conversion and selectivity pattern were also studied using the same catalyst This catalyst also showed an excellent stability as evidenced by its eight times reuse. (C) 2012 Published by Elsevier B.V.

}, keywords = {Cations-exchanged clay, Montmorillonite, NH3-TPD, Pyridine-IR}, issn = {0169-1317}, doi = {10.1016/j.clay.2012.10.005}, author = {Jha, Ajay and Garade, Ajit C. and Shirai, M. and Rode, C. V.} } @article {46859, title = {Critical organic modifier aliphatic tail length for the formation of poly(methyl methacrylate)-montmorillonite nanocomposites}, journal = {Polymer Engineering and Science}, volume = {60}, year = {2020}, month = {JUL}, pages = {1604-1617}, type = {Article}, abstract = {

In this article, we report the influence of organic modifier structure (alkyl chain length C8-C20, single vs ditallow) and thereby, the effect of hydrophobicity on the structure, thermal and mechanical properties of poly(methyl methacrylate) (PMMA)-clay hybrids. Melt processed PMMA-clay hybrids were characterized using wide-angle X-ray diffraction, transmission electron microscopy, and differential scanning calorimetry. The organoclays having an alkyl chain length of more than 12 CH2 groups resulted in the formation of nanocomposites. The glass transition temperature (T-g) of PMMA increased in the presence of clay. The mean-field lattice model was used to predict the free energy for nanocomposite formation, which showed a reasonable match with the experimental results and provided a general guideline for the proper selection of polymer and organoclay (ie, organic modifier) to obtain nanocomposite. Tensile modulus showed maximum improvement of 58\% for the nanocomposites compared to 9\% improvement for the composites. Tensile modulus increased with increases in the alkyl chain length of the organic modifier and clay loading. The level of improvement for the tensile properties of nanocomposites prepared from primary and secondary ammonium-modified clay is the same as that obtained with the commercial organoclays.

}, keywords = {hybrid, mechanical properties, Montmorillonite, Nanocomposites, organoclay, poly(methyl methacrylate)}, issn = {0032-3888}, doi = {10.1002/pen.25405, Early Access Date = MAY 2020}, author = {Tiwari, Rajkiran R. and Natarajan, Upendra} }