Imogolite is a tubular clay mineral with a typical chemical composition of (OH)₃Al₂O₃SiOH. This material has been expected as a shape selective catalyst, however, because of its chemical stability, an incorporation of another element is necessary to generate a chemical function. Thus Fe containing imogolite was prepared using NaSiO₄, FeCl₃ and AlCl₃. In the case of the ratio of Fe/(Al+Fe) =0.1 in the starting solution, the product was amorphous. In the case of the sample with the ratio of Fe/(Al+Fe) =0.05 named “Fe-imo”, we obtained the XRD profile and the IR spectrum which were similar to those of the imogolite. The state of iron was found to be octahedral Fe³⁺ ion in the sample from the UV-VIS diffuse reflectance spectrum and X-ray absorption spectrum. The EXAFS function of Fe-imo is different from that of Fe³⁺ ion adsorbed on the imogolite (abbrev. Fe/imo). In the catalytic oxidation of cyclohexene, it was found that the catalytic properties were different for Fe-imo and Fe/imo. It is an interesting finding that Fe-imo catalyzed the oxidation of benzene to yield phenol. It is considered that state of Fe³⁺ in Fe-imo is different from that of Fe/imo and has higher potential toward oxidation reaction.

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Three LDHs (Layered Double Hydroxides) with hydrotalcite type structure were synthesized by a modified coprecipitation method, and the corresponding oxides LDOs were prepared by calcinating LDHs in air. The as-synthesized LDHs and LDOs were characterized by XRD and elemental analysis. Dilute nitric acid was employed for the selective extraction of LDHs and LDOs to obtain porous ferrihydrites, which were further characterized by XRD, TEM, TG-DTA, IR, and BET gas sorptometry measurement for specific surface area and pore volume.

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Zr-pillared clays with different pillar density are prepared from Ni₂₊ exchanged clays by heat treatment in the range 160-400°C and subsequent exchange with Zr-polycations. These materials are characterized by XRD, FTIR, TGA and sorptometric techniques. Migration of Ni²⁺ ions from interlayer position to vacant octahedral sties in clay structure is inferred from FTIR analysis. The Zr-pillared clays with different pillar densities are used as catalysts for alkylation of phenol with methanol. Pillared materials with lesser pillar density are found to be more selective towards anisole which is attributed to the control of acidic properties. Al-pillared clays are studied as supports for PdCu bimetallic particles. Well dispersed nanometer size metallic particles are observed in pillared clay matrix by TEM analysis. EDAX analysis indicates a homogeneous distribution of metallic components in the clay and pillared clay surfaces. Nitrate ion reduction carried out over these samples reveals that the bimetallic catalysts are more active and selective to the product N₂ compared to monometallic particles. Pillared clays as supports are found to be beneficial in terms of greater dispersion and higher catalytic activity compared to parent clays.

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For the first time, we have used the intercalated montmorillonite with aluminium polyoxocations (Al₁₃) as precursor for the synthesis of porous clay heterostructures (Al-PCHs) materials. They are obtained by simple addition of tetraethylorthosilicate (TEOS) and neutral amines with different lengths (C8 to C12) at a molar ratio of Al₁₃-clay/amine/TEOS close to 1/20/150. The obtained Al-PCHs exhibited higher surface area of 880m²/g and pore volume of 0.85mL/g. The X-ray diffraction, and ²⁹Si MAS NMR indicated the polymerization of silica species in the interlayer gallery, and two different octahedral aluminium conformations detected by ²⁷Al MAS NMR, compared to the starting raw clay. Infrared spectroscopy of adsorbed pyridine suggests the presence of both Brönsted and Lewis acid sites up to 300°C. The thermal desorption of cyclohexylamine was used as further probe to monitor the acidity of the different materials.

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For the first time, we report the use of zirconyl nitrate solution as a pillaring agent. Ca-montmorillonite was exchanged with zirconium species at different conditions and Zr (mmole)/clay ratios, then calcined at different temperatures to obtain stable Zr-pillared clays. These materials have been investigated by X-ray diffraction, nitrogen adsorption, and pyridine desorption. The catalytic performance towards the isomerization of n-heptane was tested in a temperature range of 250-350°C. The results show that the properties of the Zr pillared clays were affected by the aging temperature of the starting Zr solution after exchange reaction. Sample prepared at room temperature exhibited lower surface areas and smaller interlayer distance compared to that prepared at 80°C. These differences are attributed to the nature of zirconium species polymerized in the pillaring solution. The obtained pillared clays exhibited both Brönsted and Lewis acid sites, however Lewis acid sites were mainly detected at temperatures above 200°C. This Lewis acidic character influenced the n-heptane conversion, and mainly cracking products were obtained, with yield of about 10% at 300°C for some isomers.

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Bentonite from Kutch district, Gujarat State, India was activated using sulfuric acid as the activating agent. Investigations on acid activation optimization indicate that the main factors affecting the decolorizing capacity of the activated products are acid concentration (1N to 15N), temperature (65-85°C) and time of activation (1-15hrs). Optimum conditions were obtained by a variety of combination of these three factors. Surface area increased from 45m²/g (raw bentonite) to a maximum of 417m²/g surface area with acid treatment and optimum decolorizing capacity for Soya bean oil was generally found below this maximum. Studies were also carried out to correlate decolorizing capacity of the activated product with surface area, crystallinity and the removal of octahedral cations.

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The study of thermal decomposition mechanism of sulfates and the thermal stability of catalysts during heat treatments constitute a good approach for determination of sulfate mode bonds in sulfated zirconium pillared clay (ZrS-PILC) catalysts. The thermal stability of solids prepared with different SO42-/Zr have been investigated by means of TGA/DTG techniques, mass spectrometry (MS), 29Si MAS NMR, nitrogen adsorption-desorption at 77K and chemical analysis. The results indicate the presence of two modes of sulfate bonds. The first one, called Σ1, decomposes at low temperature to give SO2 and lets oxygen atoms to the matrix. This sulfate group probably links two tetrameric Zr entities present in the intercalation solution. Decomposition of the second type (referred as Σ2) which is probably low coordinated occurs with SO2 and O2 release. The coordination of sulfates Σ2 is equal to 2 and each one links most likely two zirconium octamers. For SO42-/Zr<0.125, the sulfates are linked with Σ1 mode bond and for higher ratio, the Σ2 mode takes place. However, the decomposition of each type of sulfates in two stages in the sample prepared with SO42-/Zr=0.175 could be explained by the presence of a high polymeric phase.

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Pillared clays are excellent candidates for adsorption of transition metal ions because of the presence of an ultra dispersed oxyhydroxide phase between the clay layers. On the basis of both macroic (adsorption at variable pHs and the speciation of Cu (II) complexes) and microscopic (ESR of Cu (II) data, we propose a model of adsorption of Cu (II))([Cu (NO₃)₂] =10^-2 mol L^-1) from aqueous ammoniacal solution ([NH₃]-1-[NH₄⁺] =1mol L^-1) on a pillared saponite by hydroxyalum polycations. When the concentration of NH₄⁺ is high, it seems that the Cu (OH) _2aq, Cu (OH) ⁺ and Cu₂ (OH) ₂²⁺ complexes have more affinity for adsorption than [Cu (NH₃) ⁿ (H₂O) _6-n] ²⁺. On the other hand when the pH is above 9 the concentrations of NH₄⁺ and of the hydroxo copper complexes are very low and the majority adsorbed form becomes [Cu (NH₃) ₄ (H₂O)₂] ²⁺.

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A comparative study on the intercalation of the hexadecyltrimethylammonium (C16TMA) cations into two montmorillonites with different cation exchange capacity (CEC) values, is reported. The effect of selected counterions (Br^-, Cl^- and OH^-) on the adsorption of C16TMA was investigated. The aim of this study is to gain further insight into the influence of the type of surfactant solutions and the physicochemical properties of raw clays on their intercalation behaviors. The intercalated amounts depended on the CEC values of the starting clays and the type of C16TMA solutions. The content of surfactants was higher in the raw clay with higher CEC, and followed the trend C16TMABr>C16TMACl>C16TMAOH. The expansion of the basal distance in the range of 1.8nm to 3.7 nm, was related to the starting raw clay and to the starting concentrations of bromide and chloride surfactant solutions. However, the interlayer spacing was almost independent of the starting raw clay-and the concentrations of C16TMA hydroxide solution, related to a difficult swelling behavior of clay sheets in basic solutions.

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Ion-exchange reaction of various protonated layer compounds with Bi³⁺ ion was carried out in order to investigate ion-exchange property of protonated layer compounds for a high valence cation. 14 kinds of protonated layer compounds were used such as HBiNb₂O₇·1.10H₂O (HB), HNb₃O₈·0.97H₂O (HN), H_0.7Ti_1.825O₄·0.93H₂O (HT), HLaNb₂O₇·0.17H₂O (HLN), HCa₂Nb₃O₁₀·1.2H₂O (HCN), HFe_0.5Nb_1.5O₅·0.63H₂O (HFN), HTiNbO₅·0.16H₂O (HTN), H₂Ti₃O₇·0.17H₂O (HT237), H₂Ti₄O₉·1.27H₂O (HT249), H₂K₂Nb₆O₁₇·2.0H₂O (HKN), HNbWO₆·1.50H₂O (HNW), H_1.8 [Bi_0.2Ca_0.8NaNb₃O₁₀]·1.55H₂O (HBCNN), H₂W₂O₇·1.40H₂O (HW) and α-Zr (HPO₄) ₂·H₂O (α-ZrP). The ion-exchange reaction for each compound came to equilibrium longer than 36h. The highest uptake amount of Bi³⁺ ion was observed for HBCNN in which 87% of proton was exchanged. The uptake amount of Bi³⁺ ion decreased in order; HBCNN (87%)>HT (75%)>HT249 (72%)>HT237 (61%)>HW (60%)>HNW (48%)>HCN (33%)>HTN (27%)>HKN (21%)>HN (18%)>HLN (12%)>α-ZrP (9%) =HFN (9%)>HB (0%). This tendency of the uptake amount of Bi³⁺ ion was discussed by the charge density of protonated layer compounds.

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