Changes in grain-size and sedimentation rate of the Neogene Red Clay deposits along the Chinese Loess Plateau and implications for the palaeowind system

IEECAS SKLLQG

Kinetics of acetic acid esterification with 2-ethoxyethanol over an Al-pillared clay catalyst

The Al-pillared clay catalyst obtained by exposing activated clay powder to sulfuric acid and aluminium salts and calcining in air at 373-673 K, was found to be highly active for the title reaction. The results indicated that pillared layer clay of the mixed oxide has been employed as parent catalysts for their definite structure and special properties which can be modified by the substitution of L and B acid sites cations. Solid acid catalyst of Supported aluminium was found to be highly active and selective at the 373-473 K temperature range for heterogeneous esterification. The activity is mainly attributed to the Lewis (and a considerably small number of Bronsted) acid sites whose number and strength increased due to pillaring. The water produced in the esterification can be induced by Al3+, which makes the catalyst surface to form strong B acid. Their acidities are obtained by pH measurement. If only B acid sites are > 70%, and pH < 1 in the 2-ethoxyethanol, there exists an activity of esterification. The used catalyst gave identical results with that of the fresh one. X-ray diffraction spectra show that the composition and active phase of the used catalysts are the same as the fresh ones. The kinetic study of the reaction was carried out by an integral method of analysis. The kinetic equation of surface esterification is y = 2.36x - 0.98.

The Effect of MMT/Modified MMT on the Structure and Performance of the Superabsorbent Composite

A series of superabsorbent composites containing Montmorillonite (MMT), modified- Montmorillonite (OMMT) and sodium acrylate were synthesized by free-radical polymerization in aqueous solution. The structure of composites was characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and X-ray diffraction (XRD), and the results showed that the polymer chains were grafted onto the edge and the surface of MMT or OMMT. At the same time, the equilibrium swelling ratio of the composites was investigated as a function of the clay content and the results showed that the equilibrium swelling ratio of composites was improved by the introduction of clay.

Mechanism on flame retardancy of polystyrene/clay composites-The effect of surfactants and aggregate state of organoclay

Effects of organically modified montmorillonites (OMMTs) with different type and amount of modifiers on flame retardancy of polystyrene (PS) have been studied. The results from morphology analysis, gas chromatography-mass spectrometry and cone calorimeter have showed different mechanisms for the flame retardancy of PS/OMMTs composites, depending on surface property of OMNTrs. One is the catalysis of acid sites formed on the surface of octadecylammonium modified MMT (c-MMT) via Hoffman decomposition on the carbonization of degradation products, which promotes the formation of clay-enriched char barrier.

Influence of montmorillonite on syndiotactic polymerization behavior of styrene

The influence of montmorillonite (MMT) on the syndiotactic polymerization behavior of styrene was studied. To avoid the hydrophilic surface of the MMT coming into contact with the catalyst, which could poison it, SAN was introduced between the MMT and Cp*Ti (OCH3)(3). MMT was introduced into the catalytic system as a supporter for the Ti catalyst (supported catalytic system) or just dispersed in the polymerization solvent directly (in situ polymerization system). The polymerization results showed that surface modification of MMT dramatically affected the catalytic activity as well as the syndiotacticity of the polymers. This is mainly explained by the insulator SAN preventing the formation of the inactive/little active species Si-O-Ti and other atactic active species resulting from the reaction of the -OH on the MMT layer surface with Cp*Ti(OCH3)(3).

Polyampholytes superabsorbent nanocomposites with excellent gel strength

A series of novel polyampholyte superabsorbent nanocomposites with excellent gel strength were synthesized by in situ solution polymerization in aqueous solution. Acrylic acid and acryloyloxyethyl trimethyl ammonium chloride (DAC) were employed as ionic monomers and montmorillonite (MMT) was used as inorganic component. The addition of cationic component could supply the positive charge in the network of nanocomposite and promote the formation of nanostructure of composites due to the interaction between DAC and clay platelets. The performance of polyampholyte nanocomposites were investigated and the result showed that the gel strength of nanocomposite hydrogel in distilled water and 0.9 wt% NaCl solution could reach 198.85 and 204.23 mJ/g, respectively, which were 13 times of the gel strength of matrix. The investigation of swelling behaviors showed that the nanocomposites had particular swelling behaviors of polyampholytes hydrogel in solution with different pH values and concentration of NaCl.

Enhanced electrochemical properties of nanocomposite polymer electrolyte based on copolymer with exfoliated clays

In this present work, a polymer electrolyte based on polymer/clay nanocomposite has been developed. Montmorillonite (MMT) clay was used as the filler. due to its special size in length and thickness, and its sandwich type structure. The obtained gel polymer electrolytes have high ionic conductivity up to 2.5 mS cm(-1) with high cationic transference number (about 0.64) at room temperature. The influences of the filler on the membrane morphology. the solvent uptake, the ionic conductivity, and the cation transport number were investigated, and thus the significant contribution from the exfoliated organophilic MMT was identified.