The study of the dehydration and dehydroxylation of smectites by emanation thermal analysis

The dehydration and dehydroxylation of the smectites, beidellite and montmorillonite (dioctahedral) and saponite and laponite (trioctahedral), were investigated by ETA, DTA, TG and X-ray diffractions. There are differences between the behaviors of di- and trioctahedral clays which are due to the differences in the ability of the exchangeable cations to migrate into hexagonal holes of the SiO₄ network and due to the fact that the dehydroxylation and recrystallization of dehydroxylated trioctahedral smectites occur simultaneously, whereas there is a temperature gap of about 300°C between the dehydroxylation and the recrystallization of dioctahedral smectites.Dedicated to Dr. Robert Mackenzie on the occasion of his 75th birthdayThe authors wish to thank Laporte Industries, Inc. UK for the laponite sample.This research was supported under Project No. C12-219, Grant No. HRN5544 G002069, U.S.-IsraelCooperative Development Research Program, Office of the Science Advisor, U.S. Agency for International Development.     

Mechanochemical Adsorption of Phenol by Tot Swelling Clay Minerals

The mechanochemical adsorption of phenol by laponite, saponite, montmorillonite, beidellite and vermiculite was studied by IR and X-ray spectroscopy. Mixtures containing phenol and clay in the ratio of 6:10 were manually ground by a mortar and pestle for 1,3,5 and 10 min and the ground mixtures were investigated. Depending on the basicity of the clay mineral and the time of grinding, two different associations between interlay er cations, water and phenol were identified. In these associations phenol can act either as a proton acceptor or donor (Configurations I and II, respectively). The phenol is more acidic than water and in most cases phenol acts as a proton donor. With montmorillonite and beidellite phenol acts as a proton acceptor. In this association the aromatic ring forms π bonds with atoms of the oxygen planes of the tetrahedral sheets which donate electrons to the anti-bonding π orbitals of the phenol.     

Investigation of structure and thermal stability of surfactant-modified Al-pillared montmorillonite

For combining the properties of organoclays and pillared clays, inorganic–organic clays have attracted much attention in recent years. In this study, Al Keggin cation pillared montmorillonites (Al-Mts) were first prepared and parts of Al-Mts were calcined at different temperatures (C-Al-Mts). The inorganic–organic montmorillonites were synthesized by intercalating Al-Mts and C-Al-Mts with the cationic surfactant, hexadecyltrimethyl ammonium bromide (HDTMAB). The products were characterized by X-ray diffraction, X-ray fluorescence, and simultaneous thermogravimetric analysis. For HDTMAB-modified uncalcined Al Keggin cation pillared montmorillonites (H-Al-Mts), the basal spacing increased with the increment of surfactant loading level, but the Al content of H-Al-Mts decreased simultaneously, indicating that the intercalated surfactant replaced some Al Keggin cations in the interlayer space. However, in the case of C-Al-Mts, the interlayer spaces could not be further expanded after surfactant modification, implying that the neighboring montmorillonite layers were “locked” by the aluminum pillars which were formed by dehydroxylation of Al Keggin cation pillars during thermal treatment. The thermal stability of HDTMAB-modified C-Al-Mts (H-C-Al-Mts) was much better than that of H-Al-Mts. The major mass loss of H-C-Al-Mts occurred at ca. 410 °C, corresponding to decomposition of intercalated surfactant cations. In contrast, H-Al-Mts displayed two mass loss temperatures at ca. 270 and 410 °C, corresponding to the evaporation of surfactant molecules and the decomposition of surfactant cations in the interlayer space, respectively.     

Tailoring micropore dimensions in pillared clays for enhanced gas adsorption

A systematic investigation has been undertaken for tailoring the micropore structure of the pillared clay. Besides the type of metal oxide (e.g. Al₂O₃ vs. ZrO₂) being used as the pillars, the important factors for determining the micropore structure are OH/Al ratio (for Al₂O₃-pillared clay), calcination temperature and the starting clay. The effect of the cation exchange capacity (CEC) of the clay on the microporous structure (and consequently the adsorption properties) is reported for the first time. Two clays with widely different CECs are used: Arizona montmorillonite (CEC = 1.40 mequiv./g) and Wyoming montmorillonite (CEC = 0.76 mequiv./g). The interlayer spacings of the pillared clays from these different clays are essentially the same, since the interlayer spacing is controlled by the sizes of the oligomers that intercalate between the clay layers. However, the pillar density in the pillared clay is substantially higher with a high CEC in the starting clay, and is shown to be approximately proportional to the CEC. Consequently, the interpillar spacing is substantially lower resulting from the higher CEC. The CH₄ adsorption on the pillared clay is nearly doubled by the smaller interpillar spacing, due to the back-to-back overlapping potential in the micropores. The N₂ adsorption was not significantly influenced because of its low polarizability (hence low inductive potential). Increasing the calcination temperature of the Al₂O₃-pillared clay from 400°C to 600°C can decrease the interlayer spacing, but only by 1 (from 8.7 to 7.7 ). The CH₄/N₂ adsorption ratio of 2.35 is reached on the Al₂O₃-pillared Arizona clay that is calcined at 600°C. Finally, the surface and pore volume are influenced by the OH/Al ratio (or pH) during pillaring, since this ratio determines the size and charge of the oligomers. A peak surface area is reached at OH/Al = 2.2.     

Minerological studies on five plastic fire clays

Mineralogical studies on five plastic fire clays of India have been carried out by DTA, TG and electron microscopy. Studies were done on both as received and <1 fraction of clays. Results indicated that all the clays were predominantly kaolinite in nature and showed the main endothermic peak between 540° and 590°C and the exothermic peak between 920° and 985°C. A large exothermic peak at 810°C and a weight loss of 5.35% between 700° and 900°C in case of Barachatarma clay indicated the presence of graphitic carbon in the same. Both Neyveli and Badampahar clays contained illite and goethite. Electron micrographs of Mohuamilan and Neyveli clays showed hexagonal flakes of well-ordered kaolinite. Some tubular particles were seen in Chittorpur, Neyveli and Badampahar clays in addition to the kaolinite particles.The authors are thankful to Dr. B. K. Sarkar, director of the Institute for his kind permission to publish this paper.     

Three‐Component Langmuir–Blodgett Films Consisting of Surfactant,Clay Mineral,and Lysozyme: Construction and Characterization

The Langmuir–Blodgett (L–B) technique has been employed for the construction of hybrid films consisting of three components: surfactant, clay, and lysozyme (Lys). The surfactants are octadecylammonium chloride (ODAH) and octadecyl ester of rhodamine B (RhB18). The clays include saponite and laponite. Surface pressure versus area isotherms indicate that lysozyme is adsorbed by the surfactant–clay L–B film at the air–water interface without phase transition. The UV‐visible spectra of the hybrid film ODAH–saponite–Lys show that the amount of immobilized lysozyme in the hybrid film is (1.3±0.2) ng mm^?2. The average surface area (Ω) per molecule of lysozyme is approximately 18.2 nm² in the saponite layer. For the multilayer film (ODAH–saponite–Lys)_n, the average amount of lysozyme per layer is (1.0±0.1) ng mm^?2. The amount of lysozyme found in the hybrid films of ODAH–laponite–Lys is at the detection limit of about 0.4 ng mm^?2. Attenuated total reflectance (ATR) FTIR spectra give evidence for clay layers, ODAH, lysozyme, and water in the hybrid film. The octadecylammonium cations are partially oxidized to the corresponding carbamate. A weak 1620 cm^?1 band of lysozyme in the hybrid films is reminiscent of the presence of lysozyme aggregates. AFM reveals evidence of randomly oriented saponite layers of various sizes and shapes. Individual lysozyme molecules are not resolved, but aggregates of about 20 nm in diameter are clearly seen. Some aggregates are in contact with the clay mineral layers, others are not. These aggregates are aligned in films deposited at a surface pressure of 20 mN m^?1.     

Synthesis,characterization, and thermal stability of poly (lactic acid)/zinc oxide pillared organic saponite nanocomposites via ring‐opening polymerization of d,l‐lactide

Poly (lactic acid) (PLA) was synthesized using d , l ‐lactide monomer and zinc oxide (ZnO) pillared organic saponite as the green catalyst, through ring‐opening polymerization. The effects of stoichiometry of catalyst and polymerization conditions on molecular weight of PLA were evaluated by orthogonal experiment. The optimum polymerization parameters were: 0.5 wt% ZnO pillared organic saponite and reaction conditions of 170°C for 20 hr. Fourier transform infrared spectroscopy and ¹H nuclear magnetic resonance spectroscopy confirmed the PLA structure. Gel permeation chromatography showed that the average molecular weight of PLA was 48,442 g/mol, and its polydispersity index was 1.875. Differential scanning calorimetry, X‐ray diffraction, and polarized optical microscopy showed that ZnO pillared organic saponite improved the crystallinity of PLA. Thermal gravimetric analysis showed improved thermal stability of PLA because of ZnO pillared organic saponite. Thermal decomposition kinetics of PLA/ZnO pillared organic saponite nanocomposites was also studied. The activation energies (E_a) for thermal degradation of PLA and PLA/ZnO pillared organic saponite nanocomposites were evaluated by the Kissinger and Ozawa methods, which demonstrated that ZnO pillared organic saponite enhanced E_a of thermal degradation of PLA and significantly improved its thermal stability. Copyright © 2015 John Wiley & Sons, Ltd.     

The synthesis of pillared nickel-substituted saponite and its hydroisomerization activity

Nickel-substituted saponite clays (NiS) were synthesized. The pillared clays notedPNiS were prepared from the NiS intercalated with large inorganic cations such as [Al_(13)O_4(OH)_(24).(H_2O)_(12)]~(7+). It is found that the pillar density is correlative with aluminium content in the tetra-hedral sheet of NiS. The results from TPR indicate that the palladium loaded on samples promotesthe reduction of the nickel ion in the octahedral sheet. The pillared clays impregnated with Pd~(2+)noted PdPNiS show excellent hydroisomerization property which is much better than that of nickelsubstituted mica-montmorillonite pillared with silicon oxide oligomer noted PdPSMM. The hexaneconversion increases with the content of aluminium ion in the tetrahedral sheet, whereas the changeof the selectivity of isomerization is not obvious.     

PLS vs zeolites as sorbents and catalysts. Part 7. The role of oxide pillars and aluminosilicate sheets in alcohol dehydration on PILCs

Reactions of primary aliphatic C2-C8 alcohols on alumina and iron-aluminium-oxides pillared montmorillonite and beidellite indicate that dehydration reaction occurs on Lewis sites of pillars, while clays are responsible of cracking. This revised version was published online in June 2006 with corrections to the Cover Date.     

Characterisation of pillared clays by contrast-matching small-angle neutron scattering

The contrast-matching SANS technique has been utilised to determine inter-pillar distances (and surface texture) in montmorillonite and beidellite pillared smectite clays; they lie in the range 1.40-1.80 nm, reflecting different inter-pillar orderings.     

层柱人工水热合成皂石的制备与表征(英)

利用具有理想皂石结构的人工水热合成蒙皂石为层原料，通过与羟基聚合铝离子（[Al₁₃O₄(OH)₂₄(H₂O)₁₂]⁷⁺）交换反应合成得到了一种层柱粘土。实验对于该铝柱皂石进行了粉末XRD，FT-IR和TG-DTA表征。氮气吸附实验说明其高温活化（773K，2 h）产物具有很高的BET比表面（360 m²·g^-1）。相对于层柱蒙脱土，层柱皂石显示了更高的催化裂解性能和热稳定性。层柱皂石的异丙苯裂解转化率达到了65%；而层柱蒙脱土的转化率只有4%。这说明层材料的四面体取代对于层柱粘土Br?nsted酸位的形成具有重要的决定作用。氨程序升温脱附实验发现铝柱皂石在350～650 ℃区间具有较强的氨脱附量，表明层柱皂石具有层柱蒙脱土所没有的强酸中心。     

Aqueous suspensions of natural swelling clay minerals. 1. Structure and electrostatic interactions

In this article, we present a general overview of the organization of colloidal charged clay particles in aqueous suspension by studying different natural samples with different structural charges and charge locations. Small-angle X-ray scattering experiments (SAXS) are first used to derive swelling laws that demonstrate the almost perfect exfoliation of clay sheets in suspension. Using a simple approach based on geometrical constraints, we show that these swelling laws can be fully modeled on the basis of morphological parameters only. The validity of this approach was further extended to other clay data from the literature, in particular, synthetic Laponite. For all of the investigated samples, experimental osmotic pressures can be properly described by a Poisson-Boltzmann approach for ionic strength up to 10(-3) M, which reveals that these systems are dominated by repulsive electrostatic interactions. However, a detailed analysis of the Poisson-Boltzmann treatment shows differences in the repulsive potential strength that are not directly linked to the structural charge of the minerals but rather to the charge location in the structure for tetrahedrally charged clays (beidellite and nontronites) undergoing stronger electrostatic repulsions than octahedrally charged samples (montmorillonites, laponite). Only minerals subjected to the strongest electrostatic repulsions present a true isotropic to nematic phase transition in their phase diagrams. The influence of ionic repulsions on the local order of clay platelets was then analyzed through a detailed investigation of the structure factors of the various clay samples. It appears that stronger electrostatic repulsions improve the liquidlike positional local order.     

Development of Composite Adsorbents of Carbon and Intercalated Clay for N2and O2Adsorption: A Preliminary Study

Composite adsorbents of carbon and alumina intercalated montmorillonite were prepared and characterized by adsorption of N₂and O₂at various temperatures. The effects of pyrolysis, temperature, heating rate, subsequent degassing, and doping of cations and anions were investigated. The adsorption capacities of the composite adsorbents developed at higher temperatures (0 and −79°C) are found to be larger than those of normal alumina pillared clays. The experimental results showed that the framework of these adsorbents is made of alumina particles and clay sheets while the pyrolyzed carbon distributes in the space of interlayers and interpillars. The pores between the carbon particles, clay sheets, and alumina pillars are very narrow with very strong adsorption forces, leading to enhanced adsorption capacities at 0 and −79°C. The composite adsorbents exhibit features similar to those of carbonaceous adsorbents. Their pore structures, adsorption capacities, and selectivities to oxygen can be tailored by a controlled degassing procedure. Meanwhile, ions can be doped into the adsorbents to modify their adsorption properties, as usually observed for oxide adsorbents like zeolite and pillared clays. Such flexibility in pore structure tailoring is a potential advantage of the composite adsorbents developed for their adsorption and separation applications.     

Stereochemie von Metallocenen, 20. Mitt.: Die Ermittlung der optischen Reinheit der Methylferrocen-α-carbonsäure (40. Mitt. über Ferrocenderivate)

Zusammenfassung Die optische Reinheit der Methylferrocen--carbonsäure (1) wurde mit Hilfe zweier Methoden ermittelt. Die Isotopenverdünnung unter Verwendung von (²H₁-Methyl)ferrocen--carbonsäure sowie ein Verfahren, das auf der Auswertung der Intensitätsverhältnisse diastereotoper Protonen in denNMR-Spektren der -Phenäthylamide von1 (verschiedener Drehung) beruht, lieferten übereinstimmende Ergebnisse: [] _d für optisch reines1 beträgt 55,6±1,0° bzw. 54±3°. Der durch Racematspaltung von1 gefundene Wert beträgt 51,5±0,8° (bzw. 53±2°)³. Damit sind die Drehungen aller 90, mit1 bereits früher chemisch korrelierten Ferrocenderivate, wenn überhaupt, nur geringfügig zu korrigieren.

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The optical purity of methylferrocene--carboxylic acid (1) was determined by two methods: isotope dilution, employing (²H₁-methyl)ferrocene--carboxylic acid, and a procedure based on the evaluation of the relative intensities of diastereotopic protons in theNMR-spectra of the -phenethylamides of1 having different rotations. By both methods corresponding results were obtained: optically pure1 has an []d of 55.6±1.0° and 54±3°, resp. The value for1 as found by optical resolution is 51.5±0.8° and 53±2°, resp.³. Hence, the rotations of all 90 ferrocene derivatives previously correlated with1 by unambiguous chemical methods have—if at all—to be corrected only slightly.

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Mit 2 Abbildungen

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19. Mitt.:H. Falk undG. Haller, Mh. Chem.99, 1103 (1968).

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39. Mitt.:K. Schlögl undHeidelore Soukup, Mh. Chem.99, 927 (1968).     

Viscosities of solutions of electrolytes and non-electrolytes in ethylene carbonate at 40°C

The viscosities of dilute solutions of a number of tetraalkylammonium and alkali metal halides, tetraphenylarsonium chloride, sodium tetraphenylborate, tetrabutylammonium tetrabutylborate, water, and 3,3-diethylpentane have been measured in the high-dielectric constant solvent, ethylene carbonate (EC) at 40°C. Crude values of the apparent molar volumes of these solutes have also been obtained. Relative viscosities were fitted to the extended Jones-Dole equation, _r=17#x002B;A c ^1/2+B C+D c ².The pattern of the B coefficients is strikingly similar to that previously observed in the high dielectric constant, linear-chain hydrogen-bonded solvent, N-methylacetamide (NMA). Ionic values for _v and B have been obtained using a variety of splitting techniques. Alkali metal ions have large B coefficients indicating strong cation solvation with the normal order Li>Na>K>Cs. Small anions have positive but much smaller B values than in NMA. The observed order does suggest, however, a small degree of anion solvation. Large organic ions do not display the sharp crossing of the Einstein law,D =2.5_v, uniquely characteristic in H₂O of hydrophobic interaction. The two non-electrolytes have negative B coefficients showing that the Einstein law is not valid at the molecular level and that hydrocarbons are not good models for their isoelectronic tetraalkylammonium ion counterparts. An empirical modification of the Einstein law to account for the finite size of the solvent molecules is discussed. As in NMA the D coefficients are roughly linear in the square of B suggesting that they arise from hydrodynamic origins.     

Catalytic wet peroxide oxidation of phenol over pillared clays containing iron or copper species

The catalytic wet oxidation of phenol by hydrogen peroxide in the presence of oxygen is catalysed, at room temperature, by copper or iron homogeneous species at pH 5 or 3.5, respectively. In such conditions phenol mild oxidation is mainly observed, the total phenol oxidation to CO₂ (TOC abatement) not exceeding 20 %. In similar experimental conditions, Fe, Al or Cu, Al pillared clays (FAZA or CAZA) are much more active, the phenol or the TOC conversion being directly related to the iron or copper content. Moreover, in the presence of iron containing pillared clay (FAZA), the TOC abatement can reach 80 % at 70 °C, with only a H₂O₂ stoichiometric excess equal to 1.5. The low iron leaching (less than 0.2 % of the total amount of iron in the catalyst) observed after a standard experiment (4 h) shows that the FAZA catalyst is highly stable in water media and could be used several consecutive times. These properties could result in the iron species stabilization in the interlamellar space of the pillared clays both by bonding with the Al pillars (60 % of the iron species) or as oxide clusters dispersed between the clay layers.     

Sorption of cobalt on organic and inorganic intercalated clays

A Mexican montmorillonite clay was intercalated on the one hand with aluminium or zirconium polyhydroxications, and on the other with two organic compounds. Radioactive cobalt was used to study the Co²⁺ sorption curves in the original and pillared clays. It was found that pillaring in general does not favour the diffusion of cobalt between the layers specially the organic pillared clays. In equilibrium, the cobalt retention reached the highest level, around 0.7 meq/g in the Zr pillared clay.     

A vibrational spectroscopic study of the adsorption of 4,4′-bipyridyl by sepiolite and smectite group clay minerals from Anatolia (Turkey)

The adsorption of 4,4-bipyridyl by natural sepiolite and smectite group clay minerals (bentonite, hectorite and saponite) from Anatolia (Turkey) has been studied using vibrational spectroscopy. Investigation of Fourier-transform infrared and Fourier-transform Raman spectra of adsorbed 4,4-bipyridyl indicate the presence of chemisorbed species. However, any evidence for the generation of anionic species on the surface of the phyllosilicates has not been detected. It is proposed that the adsorbed bipyridyl molecules on sepiolite are centrosymmetric and H-bonded to the surface hydroxyls through both the nitrogen lone pairs as bidentate ligands. The adsorbed bipyridyl molecules on the smectite group clays are coordinated to exchangeable cations both directly and also indirectly through water as monodentate ligands. XRD patterns of the clays studied are also recorded.     

Structural and Catalytic Activity of V2O5-Supported on AlPO4 Catalysts

Summary. A series of AlPO₄-V₂O₅ (APV) systems with various vanadia amounts 1–30mol% were prepared by the impregnation method and calcinated at 400 and 600°C for 4h. The catalysts were characterized by TG/DTG, DSC, IR spectroscopy, XRD, N₂ adsorption, and electrical conductivity measurements. The surface acidity and basicity of the catalysts were studied by the dehydration-dehydrogenation of isopropyl alcohol and the adsorption of pyridine. The catalytic gas phase esterification of acetic acid with ethyl alcohol was carried out at 210°C in a flow system at 1atm using air as a carrier gas. The results showed that the catalysts calcinated at 400°C were active and selective towards the formation of ethyl acetate whereas the calcination of samples at 600°C led to a drastic reduction in both activity and selectivity. Good correlations were obtained between catalytic activities towards ester formation and acidity of the prepared catalysts.     

QSAR and conformational analysis of the antiinflammatory agent amfenac and analogues

Summary The new nonsteroidal antiinflammatory drug (NSAID) arylacetic amfenac (2-amino-3-benzoylphenylacetic acid) and 19 substituted derivatives were studied in order to correlate the biological activities with the structure-related parameters.The geometry of amfenac in neutral and anionic form was totally optimized, starting from standard geometries and crystallographic data, using semiempirical AM1 and MNDO quantum-mechanical methods. Conformational analysis shows the existence of a rigid structure for rotations of the acetic acid chain (°) and the central carbonyl group (°) around the bonds with the phenylamine ring, whereas the carboxyl group (°) and the phenyl ring of the benzoyl group (°) can rotate almost freely.Electrostatic potential maps were analyzed and showed that the electrostatic orientation effect seems to make an important contribution to the binding of the active compounds to prostaglandin synthase. An electrostatic orientation model of the binding site is proposed. The frontier orbital charge distribution was also described for each compound. On the other hand, steric, electronic and hydrophobic (log P) parameters were calculated and QSAR analysis showed that the most significant parameter for the antiinflammatory activity was the -electron density of the HOMO orbital in the second aromatic ring. These results suggest a possible electronic charge transfer between the aromatic fragments and the receptor.