Ce and Al pillared clays were prepared by (i) pillaring Ce3+-exchanged montmorillonite with Al13 polycation (Ce-Al-PILC) and (ii) by pillaring Na-montmorillonite with an oligomer obtained from cohydrolysis of Ce3+ and Al3+ salts (Al-Ce-PILC). Cohydrolyzed oligomer gives larger intercalating species with Ce3+ incorporated in it. The UV-DRS spectrum of clay sample intercalated with this species shows four distinct absorption bands at 224, 263, 294 and 342 nm, which are attributed to the 4f-5d interconfigurational transitions of Ce3+ ions associated with alumina pillars.

Gangavarapu Ranga Rao

Department Of Chemistry

Aluminum Compounds

CERIUM COMPOUNDS

Electron transitions

Hydrolysis

Ion Exchange

Oligomers

Ultraviolet spectroscopy

X ray diffraction analysis

ABSORPTION BANDS

ALUMINA PILLARS

COHYDROLYSIS

INTERCONFIGURATIONAL TRANSITIONS

Montmorillonite

ULTRAVIOLET-VIS DIFFUSE REFLECTANCE STUDY

Clay

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

Mixed Al/Ce oxide pillaring of montmorillonite: XRD and UV-VIS diffuse reflectance study

Reaction Kinetics and Catalysis Letters

The environment, location and interaction of the Ce3+ ions in the micropores of Al- and Zr-pillared clays have been studied by UV-vis-diffuse reflectance spectroscopy (UV-vis-DRS). The DRS spectra show that the chemical environment of the Ce3+ ions in cerium exchanged clay is different from that of the Al- and Zr-pillared clays. The Al-Ce pillared clays (Al-Ce-PM) show four distinct absorption bands at 224, 263, 294 and 342 nm in the UV region which are attributed to 4f → 5d interconfigurational transitions of Ce3+ ions associated with alumina pillars. The O2- → Ce3+ charge transfer band observed at 263 nm for Ce-exchanged and Al-Ce-PM clays is blue shifted by 10 nm for Ce-Zr-pillared clays (Ce-Zr-PM) due to fully hydrated Ce3+ ions. The Ce3+ ions are incorporated in the Al- and Zr-pillars possibly as AlCeO3 and Ce xZr1-xC2 particles upon heat treatment. © 2004 Elsevier B.V. All rights reserved.

Materials Chemistry and Physics

A comparative UV-vis-diffuse reflectance study on the location and interaction of cerium ions in Al- And Zr-pillared montmorillonite clays

Zr-pillared clays were prepared from ZrOCl2 pillaring solutions by adopting different preparative conditions. Ce3+ ions are introduced to Zr-pillared clays by co-intercalation method. The resulting samples were characterized by XRD, TGA, N2 sorption and UV-VIS-Diffuse reflectance spectroscopy techniques. Basal spacings in the range of 18-21 Å were observed depending upon the preparative condition. TG analysis shows three weight loss regions corresponding to removal of various types of water molecules. All pillared clays show Type-I sorption isotherm typical of microporous materials. Pillaring under refluxing condition is found to have beneficial effect on the surface area and pore volume of the Zr-pillared clay. The chemical environment and location of Ce3+ ions is studied by UV-VIS-DRS. The Ce3+ ions are found to be present in the micropores of the Zr-pillared clays. However heat treatment at higher temperature may result in peripheral interaction between Ce3+ ions and Zr-pillars. Catalytic activity of these pillared clays was evaluated for cyclohexanol dehydration which correlates well with the Brønsted acidity of these materials. The Zr-Pillared clay containing Ce3+ ions show good catalytic activity and stability with reaction time which has been ascribed to the stabilazition of the Brønsted acidic centers.

Journal of Porous Materials

Influence of Synthesis Conditions and Cerium Incorporation on the Properties of Zr-Pillared Clays

Reduction of NO by CO catalysed by Rh/CeO2-ZrO2 solid solutions is investigated with the aim to elucidate the role of the CeO2-ZrO2 supports in modifying the activity of supported Rh. Two distinct kinetic regimes, characterised by different activation energies are observed below and above 500 K. It is proposed that below 500 K the reduction of NO occurs at the expenses of a concomitant oxidation of Ce3+ sites. In this model, the supported metal activates the reducing agent favouring the efficiency of Ce4+/Ce3+ redox couple. The influence of a high temperature reduction (H2, 1073 K) is also investigated. Such a treatment, which increases the reducibility at low temperatures of the CeO2-ZrO2 solid solution, promotes the efficiency of the catalysts at low temperatures, confirming the important role of the Ce4+/Ce3+ redox couple in determining the activity of the catalyst. © 1998 Academic Press.

Journal of Catalysis

Reduction of NO by CO over Rh/CeO2-ZrO2 catalysts: Evidence for a support-promoted catalytic activity

Industrial & Engineering Chemistry Research

Ce−Al-Pillared Clays: Synthesis, Characterization, and Catalytic Performance

Catalysis Reviews

Recent Advances in the Synthesis and Catalytic Applications of Pillared Clays

Applied Clay Science

Clays and catalysis: a promising future

Journal of Materials Chemistry

Porosity and thermal stability of PILCs prepared with clays from different origins and different metal–polyhydroxycationic species ofAl and Al/Ce

Journal	Reaction Kinetics and Catalysis Letters
ISSN	01331736
Open Access	No