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2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a highly toxic environmental contaminant found in soils and sediments. Because of its exceptionally low water solubility, this compound exists predominantly in the sorbed state in natural environments. Clay minerals, especially expandable smectite clays, are one of the major component geosorbents in soils and sediments that can function as an effective adsorbent for environmental dioxins, including TCDD. In this study, TCDD was intercalated in the smectite clay saponite by an incipient wetness method. The primary goal of this study was to intercalate TCDD in natural K-saponite clay and evaluate its immunotoxic effects in vivo. The relative bioavailability of TCDD was evaluated by comparing the metabolic activity of TCDD administered in the adsorbed state as an intercalate in saponite and freely dissolved in corn oil. This comparison revealed nearly identical TCDD-induced suppression of humoral immunity, a well-established and sensitive sequela, in a mammalian (mouse) model. This result suggests that TCDD adsorbed by clays is likely to be available for biouptake and biodistribution in mammals, consistent with previous observations of TCDD in livestock exposed to dioxin-contaminated ball clays that were used as feed additives. Adsorption of TCDD by clay minerals does not appear to mitigate risk associated with TCDD exposure substantially., (Copyright © 2011 SETAC.)

The proton transfer process mediated by water molecules adsorbed in an aluminosilicate framework has been studied using ab initio molecular dynamics simulations. This investigation has been carried out using a quasi-one-dimensional model simulating the mesoporous aluminosilicate channel structures. The effects of both the water loading and temperature of the system have been considered. At low coverage (one water molecule per acid site), the hydroxonium ion (H(3)O)(+) is found to be a transition state, in agreement with earlier studies on zeolites. At a higher water coverage (two water molecules per acid site), the (H(5)O(2))(+) species and the hydrogen bonded "neutral complex" structure are both found to be stable complexes at finite temperatures. The vibrational frequency spectrum is simulated by performing a Fourier transform of the velocity autocorrelation function (VAF), and the peak positions in the VAF are compared with IR measurements and zero-temperature calculations.

Reports on an example of nanosized mesoporous aluminosilicate with the hydrothermal stability and acidity needed for the cracking of high molecular weight hydrocarbons. Use of protozeolitic aluminosilicate nanoclusters in the construction of acidic pore walls and starch as a porogen.

The conversion of diphenylamine (DPA) and α-methylstyrene (AMS) to the antioxidants mono- and dicumenyldiphenylamine was carried out over mesostructured aluminosilicate catalysts with hexagonal (2% Al-MCM-41), wormhole (2% Al-HMS), and lamellar/vesicular (2% Al-MSU-G) framework structures. A commercial acid-treated clay catalyst, Engelhard F-20, was included for comparison perposes. The yields of the desired antioxidant, namely dicumenyldiphenylamine (DCDPA), increased in the order F-20 (∼57%)<2% Al-MCM-41 (∼85%)<2% Al-HMS, 2% Al-MSU-G (∼90%) when the reaction was carried out under stoichiometric reaction conditions at 90 °C. The DCDPA yields obtained with the mesostructured catalysts are the highest reported to date for this technologically important antioxidant. A heteropolyacid catalyst, H3PW12O40·xH2O (PW12) supported on mesostructured wormhole HMS and lamellar/vesicular MSU-G silica, also was examined as a catalyst for DCDPA production. The supported catalyst systems, however, afforded lower maximum yields of DCDPA (∼73–80%) in comparison to the mesostructured aluminosilicate catalysts. The exceptionally high yields of alkylated products obtained with the mesoporous aluminosilicate catalysts in comparison to the F-20 clay and the supported PW12 catalysts are attributable in part to intermediate acid strengths that minimize completing dimerization reactions of the AMS alkylating agent. Also, the pore structures of the mesostructured catalysts facilitate access to active sites on the framework walls and provide more efficient transport of reagents to framework reaction centers. Also, the regular mesoporosity of the aluminosilicate catalysts makes these structures less prone to pore plugging and to the masking of acidity through the adsorption of the high molecular weight reaction products. [Copyright &y& Elsevier]

A comparative evaluation of ten catalysts for biomass pyrolysis was performed using poplar (DN-34) as the feedstock. Five of the catalysts consisted of HZSM-5 with different silica:alumina ratios (SAR, 23, 30, 55, 80 and 280). The other five catalysts were sulfated zirconia (SO4 2− ZrO 2 ), 20% SO4 2− ZrO 2 dispersed on a mesoporous MCM-41 silica support, Al–MSU–S alumnosilicate exhibiting a foam-like mesopore structure, Al–MSU–S aluminosilicate exhibiting wormhole mesopores, and a bauxite waste product known as red mud. Analytical pyrolysis in tandem with GC/MS showed that all of the catalysts except for HZSM-5 resulted in low aromatic chemical production. Highly acidic sulfated zirconia catalysts were not selective to aromatics and produced significant coke and non-condensable gases. Mesoporous MSU–S catalysts exhibiting high pore volume and acidity also gave high gas and coke yields. Among the HZSM-5 catalysts evaluated, those with the lowest SAR provided the highest yields of total aromatics and the lowest levels of undesired coke. [ABSTRACT FROM AUTHOR]

Abstract: The in situ upgrading of biomass pyrolysis vapors with two mesoporous aluminosilicate materials (MSU-SBEA) assembled from zeolite Beta (BEA) seeds was tested in the present study, in comparison to conventional Al-MCM-41 and to non-catalytic biomass pyrolysis. The first sample (MSU-S/HBEA) exhibited an hexagonal mesopore structure while the second one (MSU-S/WBEA) possessed a wormhole-like mesopore structure with high textural porosity. The catalytic tests were performed on a fixed-bed reactor, the reaction temperature was 500°C and the feed was a lignocellulosic biomass based on beech wood. The use of the MSU-S catalytic materials led to significantly lower organic phase in the produced bio-oil and also to higher coke and char yields, compared to non-catalytic pyrolysis and to the use of Al-MCM-41 which induced a small increase in the yields of liquid oil and coke. Pyrolysis gases were also affected by all mesoporous catalysts. The MSU-S catalytic materials were very selective towards polycyclic aromatic hydrocarbons (PAHs) and heavy fractions, while they produced negligible amounts of acids, alcohols and carbonyls, and very few phenols. The MSU-S materials appeared to possess stronger acid sites than Al-MCM-41, resulting in enhanced yields of aromatics, PAHs and coke, as well as propylene in the pyrolysis gases. [Copyright &y& Elsevier]