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Hydration Reaction (hydration + reaction)
Selected AbstractsInnentitelbild: Graphene Oxide: A Convenient Carbocatalyst for Facilitating Oxidation and Hydration Reactions (Angew. Chem.ANGEWANDTE CHEMIE, Issue 38 201038/2010) Kohlenstoffkatalyse , die Schnittmenge aus Kohlenstoffmaterialien und Katalyse , ist der Einsatz von großflächigem metallfreiem Kohlenstoff, um chemische Reaktionen zu erleichtern. In der Zuschrift auf S.,6965,ff. schildern C.,Bielawski et,al. die Verwendung von graphenbasierten Materialien als Kohlenstoffkatalysatoren in einer Vielzahl nützlicher Umsetzungen, darunter die Oxidation von Alkoholen und Alkenen zu Aldehyden und Ketonen sowie die Hydrierung von Alkinen. [source] Graphene Oxide: A Convenient Carbocatalyst for Facilitating Oxidation and Hydration Reactions,ANGEWANDTE CHEMIE, Issue 38 2010Daniel Nützlicher Kohlenstoff: Graphenoxid katalysiert in guten bis ausgezeichneten Ausbeuten die Oxidation von vielen Alkoholen und Alkenen sowie die Hydrierung von Alkinen zu den entsprechenden Aldehyden und Ketonen. Es genügen relativ milde Reaktionsbedingungen, und einfaches Filtrieren erwies sich als bequeme und effektive Methode, um den Katalysator zurückzugewinnen. [source] Progress of actinolite-forming reactions in mafic schists during retrograde metamorphism: an example from the Sanbagawa metamorphic belt in central Shikoku, JapanJOURNAL OF METAMORPHIC GEOLOGY, Issue 5 2005A. OKAMOTO Abstract Hydration reactions are direct evidence of fluid,rock interaction during regional metamorphism. In this study, hydration reactions to produce retrograde actinolite in mafic schists are investigated to evaluate the controlling factors on the reaction progress. Mafic schists in the Sanbagawa belt contain amphibole coexisting with epidote, chlorite, plagioclase and quartz. Amphibole typically shows two types of compositional zoning from core to rim: barroisite , hornblende , actinolite in the high-grade zone, and winchite , actinolite in the low-grade zone. Both types indicate that amphibole grew during the exhumation stage of the metamorphic belt. Microstructures of amphibole zoning and mass-balance relations suggest that: (1) the actinolite-forming reactions proceeded at the expense of the preexisting amphibole; and (2) the breakdown reaction of hornblende consumed more H2O fluid than that of winchite, when one mole of preexisting amphibole was reacted. Reaction progress is indicated by the volume fraction of actinolite to total amphibole, Yact, with the following details: (1) reaction proceeded homogeneously in each mafic layer; (2) the extent of the hornblende breakdown reaction is commonly low (Yact < 0.5), but it increases drastically in the high-grade part of the garnet zone (Yact,>,0.7); and (3) the extent of the winchite breakdown reaction is commonly high (Yact,>,0.7). Many microcracks are observed within hornblende, and the extent of hornblende breakdown reaction is correlated with the size reduction of the hornblende core. Brittle fracturing of hornblende may have enhanced retrograde reaction progress by increasing of influx of H2O and the surface area of hornblende. In contrast to high-grade rocks, the winchite breakdown reaction is well advanced in the low-grade rocks, where reaction progress is not associated with brittle fracturing of winchite. The high extent of the reaction in the low-grade rocks may be due to small size of winchite before the reaction. [source] Dating metamorphic reactions and fluid flow: application to exhumation of high- P granulites in a crustal-scale shear zone, western Canadian ShieldJOURNAL OF METAMORPHIC GEOLOGY, Issue 3 2006K. H. MAHAN Abstract The Legs Lake shear zone is a crustal-scale thrust fault system in the western Canadian Shield that juxtaposes high-pressure (1.0+ GPa) granulite facies rocks against shallow crustal (< 0.5 GPa) amphibolite facies rocks. Hangingwall decompression is characterized by breakdown of the peak assemblage Grt + Sil + Kfs + Pl + Qtz into the assemblage Grt + Crd + Bt ± Sil + Pl + Qtz. Similar felsic granulite occurs throughout the region, but retrograde cordierite is restricted to the immediate hangingwall of the shear zone. Textural observations, petrological analysis using P,T/P,MH2O phase diagram sections, and in situ electron microprobe monazite geochronology suggest that decompression from peak conditions of 1.1 GPa, c. 800 °C involved several distinct stages under first dry and then hydrated conditions. Retrograde re-equilibration occurred at 0.5,0.4 GPa, 550,650 °C. Morphology, X-ray maps, and microprobe dates indicate several distinct monazite generations. Populations 1 and 2 are relatively high yttrium (Y) monazite that grew at 2.55,2.50 Ga and correspond to an early granulite facies event. Population 3 represents episodic growth of low Y monazite between 2.50 and 2.15 Ga whose general significance is still unclear. Population 4 reflects low Y monazite growth at 1.9 Ga, which corresponds to the youngest period of high-pressure metamorphism. Finally, population 5 is restricted to the hydrous retrograded granulite and represents high Y monazite growth at 1.85 Ga that is linked directly to the synkinematic garnet-consuming hydration reaction (KFMASH): Grt + Kfs + H2O = Bt + Sil + Qtz. Two samples yield weighted mean microprobe dates for this population of 1853 ± 15 and 1851 ± 9 Ma, respectively. Subsequent xenotime growth correlates with the reaction: Grt + Sil + Qtz + H2O = Crd. We suggest that the shear zone acted as a channel for fluid produced by dehydration of metasediments in the underthrust domain. [source] Metamorphic evolution of kyanite,staurolite-bearing epidote,amphibolite from the Early Palaeozoic Oeyama belt, SW JapanJOURNAL OF METAMORPHIC GEOLOGY, Issue 4 2004T. Tsujimori Abstract Early Palaeozoic kyanite,staurolite-bearing epidote,amphibolites including foliated epidote,amphibolite (FEA), and nonfoliated leucocratic or melanocratic metagabbros (LMG, MMG), occur in the Fuko Pass metacumulate unit (FPM) of the Oeyama belt, SW Japan. Microtextural relationships and mineral chemistry define three metamorphic stages: relict granulite facies metamorphism (M1), high- P (HP) epidote,amphibolite facies metamorphism (M2), and retrogression (M3). M1 is preserved as relict Al-rich diopside (up to 8.5 wt.% Al2O3) and pseudomorphs after spinel and plagioclase in the MMG, suggesting a medium- P granulite facies condition (0.8,1.3 GPa at >,850 °C). An unusually low-variance M2 assemblage, Hbl + Czo + Ky ± St + Pg + Rt ± Ab ± Crn, occurs in the matrix of all rock types. The presence of relict plagioclase inclusions in M2 kyanite associated with clinozoisite indicates a hydration reaction to form the kyanite-bearing M2 assemblage during cooling. The corundum-bearing phase equilibria constrain a qualitative metamorphic P,T condition of 1.1,1.9 GPa at 550,800 °C for M2. The M2 minerals were locally replaced by M3 margarite, paragonite, plagioclase and/or chlorite. The breakdown of M2 kyanite to produce the M3 assemblage at <,0.5 GPa and 450,500 °C suggests a greenschist facies overprint during decompression. The P,T evolution of the FPM may represent subduction of an oceanic plateau with a granulite facies lower crust and subsequent exhumation in a Pacific-type orogen. [source] Growth of Cement Hydration Products on Single-Walled Carbon NanotubesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2009Jonathan M. Makar Single-walled carbon nanotubes (SWCNT) were distributed on the surface of ordinary Portland cement (OPC) grains. The OPC/SWCNT composite was then hydrated at a 0.5 w/c ratio. The effects of the SWCNT on the early hydration process were studied using isothermal conduction calorimetry, high-resolution scanning electron microscopy and thermogravimetric analysis. The observed behavior of the composite samples was compared with both OPC sonicated without SWCNT and previously published data on as-delivered OPC. The SWCNT were found to accelerate the hydration reaction of the C3S in the OPC. The morphology of both the initial C3A and the C3S hydration products were found to be affected by the presence of the SWCNT. In particular, the nanotubes appeared to act as nucleating sites for the C3S hydration products, with the nanotubes becoming rapidly coated with C,S,H. The resulting structures remained on the surface of the cement grains while those in the sonicated and as-delivered OPC samples grew out from the grain surfaces to form typical C,S,H clusters. Classical evidence of reinforcing behavior, in the form of fiber pullout of the SWCNT bundles, was observed by 24 h of hydration. [source] Gold Activation of Nitriles: Catalytic Hydration to AmidesCHEMISTRY - A EUROPEAN JOURNAL, Issue 35 2009Rubén Innocence lost: The unprecedented gold-mediated activation of nitriles is reported. A [(NHC)AuI]-based catalytic system was found to be efficient for the nitrile hydration reaction of a broad spectrum of substrates that includes aromatic, heteroaromatic, and aliphatic examples. [source] Infiltration of basinal fluids into high-grade basement, South Norway: sources and behaviour of waters and brinesGEOFLUIDS (ELECTRONIC), Issue 1 2003S. A. Gleeson Abstract Quartz veins hosted by the high-grade crystalline rocks of the Modum complex, Southern Norway, formed when basinal fluids from an overlying Palaeozoic foreland basin infiltrated the basement at temperatures of c. 220°C (higher in the southernmost part of the area). This infiltration resulted in the formation of veins containing both two-phase and halite-bearing aqueous fluid inclusions, sometimes with bitumen and hydrocarbon inclusions. Microthermometric results demonstrate a very wide range of salinities of aqueous fluids preserved in these veins, ranging from c. 0 to 40 wt% NaCl equivalent. The range in homogenization temperatures is also very large (99,322°C for the entire dataset) and shows little or no correlation with salinity. A combination of aqueous fluid microthermometry, halogen geochemistry and oxygen isotope studies suggest that fluids from a range of separate aquifers were responsible for the quartz growth, but all have chemistries comparable to sedimentary formation waters. The bulk of the quartz grew from relatively low ,18O fluids derived directly from the basin or equilibrated in the upper part of the basement (T < 200°C). Nevertheless, some fluids acquired higher salinities due to deep wall-rock hydration reactions leading to salt saturation at high temperatures (>300°C). The range in fluid inclusion homogenization temperatures and densities, combined with estimates of the ambient temperature of the basement rocks suggests that at different times veins acted as conduits for influx of both hotter and colder fluids, as well as experiencing fluctuations in fluid pressure. This is interpreted to reflect episodic flow linked to seismicity, with hotter dry basement rocks acting as a sink for cooler fluids from the overlying basin, while detailed flow paths reflected local effects of opening and closing of individual fractures as well as reaction with wall rocks. Thermal considerations suggest that the duration of some flow events was very short, possibly in the order of days. As a result of the complex pattern of fracturing and flow in the Modum basement, it was possible for shallow fluids to penetrate basement rocks at significantly higher temperatures, and this demonstrates the potential for hydrolytic weakening of continental crust by sedimentary fluids. [source] Progress of actinolite-forming reactions in mafic schists during retrograde metamorphism: an example from the Sanbagawa metamorphic belt in central Shikoku, JapanJOURNAL OF METAMORPHIC GEOLOGY, Issue 5 2005A. OKAMOTO Abstract Hydration reactions are direct evidence of fluid,rock interaction during regional metamorphism. In this study, hydration reactions to produce retrograde actinolite in mafic schists are investigated to evaluate the controlling factors on the reaction progress. Mafic schists in the Sanbagawa belt contain amphibole coexisting with epidote, chlorite, plagioclase and quartz. Amphibole typically shows two types of compositional zoning from core to rim: barroisite , hornblende , actinolite in the high-grade zone, and winchite , actinolite in the low-grade zone. Both types indicate that amphibole grew during the exhumation stage of the metamorphic belt. Microstructures of amphibole zoning and mass-balance relations suggest that: (1) the actinolite-forming reactions proceeded at the expense of the preexisting amphibole; and (2) the breakdown reaction of hornblende consumed more H2O fluid than that of winchite, when one mole of preexisting amphibole was reacted. Reaction progress is indicated by the volume fraction of actinolite to total amphibole, Yact, with the following details: (1) reaction proceeded homogeneously in each mafic layer; (2) the extent of the hornblende breakdown reaction is commonly low (Yact < 0.5), but it increases drastically in the high-grade part of the garnet zone (Yact,>,0.7); and (3) the extent of the winchite breakdown reaction is commonly high (Yact,>,0.7). Many microcracks are observed within hornblende, and the extent of hornblende breakdown reaction is correlated with the size reduction of the hornblende core. Brittle fracturing of hornblende may have enhanced retrograde reaction progress by increasing of influx of H2O and the surface area of hornblende. In contrast to high-grade rocks, the winchite breakdown reaction is well advanced in the low-grade rocks, where reaction progress is not associated with brittle fracturing of winchite. The high extent of the reaction in the low-grade rocks may be due to small size of winchite before the reaction. [source] | |||||||||||||