Thermal behavior of Al-, AlFe- and AlCu-pillared interlayered clays

The purified bentonite parent clay, fraction ≤; 2 mm of montmorillonite type, has been pillared by various polyhydroxy cations, Al, AlFe and AlCu, using conventional pillaring methods. The thermal behavior of PILCs was investigated by combination of X-ray diffraction (XRD), thermal analysis (DTA, TG) and low temperature N2 adsorption/desorption (LTNA). Thermal stability of Al-, AlFe- and AlCu-PILC samples was estimated after isothermal pretreatment in static air on the temperatures 300, 500, 600 and 900°C. Crucial structural changes were not registered up to 600°C, but the fine changes in interlayer surrounding and porous/microporous structure being obvious at lower temperatures, depending on the nature of the second pillaring ion. AlFe-PILC showed higher thermal stability of the texture, the AlCu-PILC having lower values and lower thermal stability concerning both overall texture and micropore surface and volume. Poorer thermal stability of AlCu-PILC sample at higher temperatures was confirmed, the presence of Cu in the system contributing to complete destruction of aluminum silicate structure, by 'extracting' aluminum in stabile spinel form. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.     

Emanation Thermal Analysis of Intercalated Montmorillonitic clay

Emanation Thermal Analysis (ETA), based on the measurement of the release of radon from previously labelled samples, has been used for 'in-situ’ characterisation of the morphology changes of intercalated montmorillonitic clay. The thermal behaviour of hydroxyaluminium intercalated montmorillonite was monitored in course of the preparation of alumina pillared montmorillonite, making possible to determine optimal temperature for the isothermal treatment of the intermediate product. Moreover, the thermal stability of alumina pillared montmorillonite porous structure was determined from the ETA data. A good agreement of ETA data and surface area, XRD patterns. DTA, and TG resulted was found. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.     

Synthesis and Characterization of New Material——La/Zr/MMT Employed in Acetone Oxidation

A new material of zirconium pillared montmorillonite added with lanthanum （denoted as La/Zr/MMT） was prepared for acetone oxidation. Surface properties of the catalysts were investigated by means of XRD, TEM, TG-DTA and BET methods. The XRD result indicated that the interlayer space of the montmorillonite was enlarged from 1.57 to 4.85 um after the treatment with zirconium pillaring and the addition of lanthanum. N2 adsorption-desorption result showed that by the process of zirconium pillaring, the specific surface area of the sample was increased to 128.0 m^2/g, which was two times almost as large as pure montmorillonite. Simultaneously, the thermal stability was also enhanced. The activity of the new material on the total oxidation of acetone was investigated, and the results indicated that the catalytic activity of the montmorillonite was greatly improved. Over the sample of La/Zr/MMT, the T98 of acetone was obtained at 350 ℃, while it needs 400 ℃ over the pure montmorillonite. After 0.1% Pd was supported on the sample of La/Zr/MMT, the T98 decreased from 350 to 280 ℃, indicating the montmorillonite is a promising material for the control of some types of the volatile organic compounds such as acetone.     

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。     

Thermal degradation of poly(lactic acid) measured by thermogravimetry coupled to Fourier transform infrared spectroscopy

Thermogravimetric (TG), differential thermal analysis (DTA) and thermal degradation kinetics, FTIR and X-ray diffraction (XRD) analysis of synthesized glycine–montmorillonite (Gly–MMT) and montmorillonite bound dipeptide (Gly–Gly–MMT) along with pure Na–MMT samples have been performed. TG analysis at the temperature range 25–250 °C showed a mass loss for pure Na–MMT, Gly–MMT and Gly–Gly–MMT of about 8.0%, 4.0% and 2.0%, respectively. DTA curves show the endothermic reaction at 136, 211 and 678 °C in pure Na–MMT whereas Gly–MMT shows the exothermic reaction at 322 and 404 °C and that of Gly–Gly–MMT at 371 °C. The activation energies of the first order thermal degradation reaction were found to be 1.64 and 9.78 kJ mol⁻¹ for Gly–MMT and Gly–Gly–MMT, respectively. FTIR analyses indicate that the intercalated compounds decomposed at the temperature more than 250 °C in Gly–MMT and at 250 °C in Gly–Gly–MMT.     

Desorption of stearic acid upon surfactant adsorbed montmorillonite

Thermal analysis and differential thermal analysis offers a novel means of studying the desorption of acids such as stearic acid from clay surfaces. Both adsorption and chemisorption can be distinguished through the differences in the temperature of mass losses. Increased adsorption is achievable by adsorbing onto a surfactant adsorbed montmorillonite. Stearic acid sublimes at 179 °C but when adsorbed upon montmorillonite sublimes at 207 and 248 °C. These mass loss steps are ascribed to the desorption of the stearic acid on the external surfaces of the organoclays and from the de-chemisorption from the surfactant held in the interlayer of the montmorillonite.     

高比表面积多孔Si层柱蒙脱土材料的合成和表征

汽车排放是大气的重要污染源之一。柴油中的含硫分子燃烧后产生的硫氧化物直接导致酸雨,也是城市氮氧化物和颗粒物排放的主要来源。为减少柴油中硫对环境的危害,世界各国相继颁布了严格的柴油含硫标准,加之市场对超低硫柴油的需求,使得各种柴油脱硫技术的开发成为一大热点。而开发高活性的加氢脱硫催化剂则是既经济又简单的方法。     

The Characterization of Organic Modified Montmorillonite and Its Filled PMMA Nanocomposite

Thermogravimetric analysis (TG) and Fourier transform infrared (FTIR)results of commercial montmorillonite were compared to that exchanged with trimethyloctadecyl quaternary ammonium chloride (SCPX2048), both were treated up to500°C. The time-of-flight mass spectrometer (TOF/MS) results of SCPX2048 trapped under300 and 500°C were compared with that of N,N,Ntrimethyl-1-dodecanammonium chloride(A 18-50) trapped under 200 and 300°C. The degradation mechanism of organic modified montmorillonite was proposed. PMMA-clay nanocomposite was synthesized through intercalation method and its properties were examined by both TG and DSC techniques. The thermal stability and glass transition temperature of montmorillonite filled PMMA increase comparing with that of the pure PMMA. This revised version was published online in July 2006 with corrections to the Cover Date.     

Comparative Studies of the Micropore Size Distributions of an Alumina Pillared Montmorillonite and a Molecular Sieve Carbon

The aim of this work is to applicate and to compare various analysis methods for the characterization of the microporous structure from nitrogen adsorption at 77 K of an alumina pillared montmorillonite and a molecular sieve carbon. The adsorption potential distribution (X(A)), the Horvath-Kawazoe (HK) method, the Jaroniec-Gadkare-Choma (JGC) one and a numerical algorithm for the reconstruction of the micropore size distribution (MPSD) from the adsorption equilibrium isotherm have been applied. Comparison of all distributions revealed that the molecular sieve carbon shows smaller micropores and smaller structural hetereogeneity than the alumina pillared montmorillonite.     

Non-isothermal crystallization kinetics of some aventurine decorative glaze

Thermal and structural properties of three clays (sepiolite and two kaolinites) from Turkey were studied by thermal analysis (TG–DTA), X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared (FT-IR), and surface area measurement techniques The adsorption of sulfur dioxide (SO₂) gas by these clays was also investigated. SO₂ adsorption values of K1, K2, and S clay samples were measured at 20 °C and pressures up to 106 kPa. Sepiolite sample (S) primarily consists of pure sepiolite, only dolomite present as accompanying mineral. Both kaolinite samples, K1 and K2, mainly contain kaolinite as the major clay mineral and quartz as impurity. In K2 sample, muscovite phase is also present. Simultaneous TG–DTA curves of all clay samples were obtained at three different heating rates 10, 15, and 20 °C min⁻¹ over the temperature range 30–1200 °C. It was found that the retention value of SO₂ by S clay (2.744 mmol/g) was higher than those of K1 (0.144 mmol/g) and K2 (0.164 mmol/g) samples.     

Effects of solid acidity of clay minerals on the thermal decomposition of 12-aminolauric acid

In this study, the effects of four types of clay minerals on the thermal decomposition of 12-aminolauric acid (ALA) were investigated. The decomposition temperature of ALA in ALA–clay complexes was in the range of 200–500 °C. The derivative thermogravimetry results indicated that all clay minerals exhibited catalytic activity on the decomposition of ALA. Pure ALA decomposed at approximately 464 °C, a temperature higher than the decomposition temperature of ALA in the presence of clay minerals. The decomposition temperature of ALA in different ALA–clay complexes follows the order illite (452 °C) > kaolinite (419 °C) > rectorite (417 °C) > montmorillonite (400 °C). This order is negatively correlated with the amounts of solid acid sites in the clay minerals, indicating that ALA is catalyzed by the solid acid sites in these minerals.     

Phase composition and texture of Sr(La)Mn hexaaluminates

Hexaaluminates synthesized by precipitation and calcined at 700–1400°C have been characterized by atomic absorption spectroscopy, thermal analysis, X-ray powder diffraction, and adsorption methods. The heat treatment of the Mn-substituted and unsubstituted materials at 1100 and 1200°C yields a hexaaluminate phase. The specific surface area of the samples calcined at 1100°C is 20–49 m²/g. The texture of the samples calcined at 1000°C is characterized by a unimodal mesoporous pore size distribution with a mean pore diameter of 290 Å.     

Influence of different templates on the morphology of mesoporous aluminas

Mesoporous alumina has many environmental applications as catalysts support and adsorption or separation material. We studied the synthesis conditions for the mesoporous alumina formation from aluminum isopropoxide in the presence of anionic (lauric and stearic acid), cationic (cetyltrimethylammonium bromide, CTAB) and non-ionic (triblock poly(ethylene oxide)-poly(propylene oxide)-polyethyleneoxide, P123) templates. The X-ray diffraction data show that the alumina mesophases obtained at 550°C in the presence of fatty acids or P123 have amorphous walls, whereas the samples prepared at 500°C by using CTAB, in alkaline medium are crystalline with a γ-alumina structure. The solvothermal treatment caused the alumina mesophase with crystalline walls to be obtained at 550°C. The samples were investigated by nitrogen adsorption-desorption isotherms and scanning electron microscopy. The obtained alumina mesophases have specific surface areas in the range of 300–450 m² g⁻¹, narrow pore size distribution, and different morphology depending on the template used in the synthesis.      

Environmentally benign sol–gel derived nanocrystalline rod shaped calcium doped cerium phosphate yellow-green pigment

Nanocrystalline rod shaped calcium doped cerium phosphate yellow-green pigment particles having an average length of ~100 nm and aspect ratio 10 even after calcination at 600 °C have been realized through an aqueous sol–gel process. The morphology, particle size and identification of the phase are determined by using different analytical tools such as transmission electron microscopy (TEM), photon correlation spectroscopy (PCS), Fourier-transform IR (FTIR) and X-ray diffraction (XRD). Brunauer–Emmett–Teller (BET) nitrogen adsorption analysis showed the pigment particles are mesoporous texture having specific surface area 42 m² g^?1 and average pore size 153 Å. Thermogravimetric (TG) analysis is used to explain the thermal phase stability of the pigment. UV–Visible spectroscopy and colorimetric analysis are also done. The typical yellow-green color has been obtained even after heating to as low as 600 °C, which is 300 °C lesser than reported. Systematic study on synthesis and effect of temperature on color are presented.     

One-pot synthesis of nylon 6–clay hybrid

Nylon 6–clay hybrid is a molecular composite of nylon 6 and uniformly dispersed silicate layers of montmorillonite. One-pot synthesis of the hybrid was carried out by the following procedures. Montmorillonite was dispersed in water, and then ε-caprolactam, acid (phosphoric acid, hydrochloric acid, benzenesulfonic acid, isophthalic acid, trichloroacetic acid, or acetic acid), and 6-aminocaproic acid were added to the dispersion. The mixtures were reacted at 260°C for 6 h, yielding the nylon 6–clay hybrids (1potNCHs). X-ray diffraction revealed that the silicate layers of 1potNCH by phosphoric acid were uniformly dispersed in the nylon 6 matrix. The 1potNCH had excellent mechanical properties. The strength and the modulus of the hybrid increased compared with previously reported nylon 6–clay hybrid (NCH) synthesized by montmorillonite intercalated with 12-aminolauric acid. The heat distortion temperature (HDT) of the 1potNCH was 160°C, which was 8°C higher than that of NCH. In other 1potNCHs, montmorillonite had a smaller effect on the increase of those properties, and interlayer spacing of montmorillonite was observed at ca. 20 Å. © 1993 John Wiley & Sons, Inc.     

Synthesis of new NiO-SiO<Subscript>2</Subscript>-sol pillared montmorillonite and its catalytic activity in the hydrogenation of benzene

NiO-SiO₂-sol pillared montmorillonite was synthesized using a novel method. Tetraethyl orthosilicate (TEOS) and hexahydrate nickel nitrate (Ni(NO₃)₂ · 6H₂O) were intercalated into the interlayers of H-montmorillonite simultaneously with the intercalation of octylamine. Interlamellar hydrolysis of TEOS catalyzed by octylamine resulted in the siloxane-pillared montmorillonite. A new NiO-SiO₂-sol pillared montmorillonite was obtained after removing the organic compounds at 550°C. The nitrogen adsorption-desorption isotherm for the pillared sample revealed that a large number of micro- and mesopores were created between the silicate layers, giving rise to a large surface of 554 m²/g and total porosity of 0.626 ml/g. The catalytic activity of the NiO-SiO₂-sol pillared montmorillonite was evaluated in hydrogenation of benzene.     

Physico-chemical study of selected surfactant-clay mineral systems

A physicochemical study of the systems formed by the clay minerals, montmorillonite and kaolinite (layered) and sepiolite (non-layered) and the surfactants Triton X-100 (TX100, non-ionic), dodecyl sodium sulfate (SDS, anionic) and trimethyloctadecyl-ammonium bromide (ODTMA, cationic), with different chemical structure, was carried out by X-ray diffraction (XRD), infrared spectroscopy (FTIR) and thermogravimetric and differential thermal analysis (TG/DTA). TG/DTA results indicated an increase in the thermal stabilization of non-ionic (TX100) and cationic (ODTMA) surfactants adsorbed by all clay minerals in relation to pure compounds. This effect was greater in montmorillonite and sepiolite than in kaolinite owing to these minerals must allow the establishment of a stronger bond with the surfactants as indicated by XRD and FTIR results. Differences in decomposition of anionic surfactant SDS are not emphasized due to the low adsorbed amount of this surfactant by all systems. The results obtained indicate the interest of taking into account the structure of surfactant and the clay mineral type when preparing customized surfactant-clay mineral systems which contribute to establish more efficient soil and water remediation strategies based in the use of these systems.     

Na-montmorillonite clay as thermal energy storage material

Sodium montmorillonite (Na-M) was investigated as an energy storage material. The study was conducted through the adsorption isotherms, infrared (IR) spectroscopic and differential thermal analysis (DTA). The clay systems were subjected to different preheating temperature, 125, 160, and 200°C, before subjecting the clay to the adsorption process carried out. The adsorptive capacities of Na-M ranged between 0.12 and 0.48 g H₂O/g of dry clay, depending on the preheating conditions of the clay. The stored energy of Na-M 781 cal/g when the clay preheated to 200°C, at which the clay has lost all the water molecules that could be evaporated, and become, therefore, able to adsorb the maximum amount of water vapor allowed. Na-M, when appropriately set, could be considered as an energy storage material.