Role Of H2O Research Articles

Direct synthesis of N-acylpyrrolidines from tetrahydrofuran and nitriles of aliphatic and aromatic acids on zeolite catalysts under supercritical conditions

The tetrahydrofuran-nitrile (CH3CN, n-C4H9CN, C6H5CN)-zeolite (faujasites, mordenite, beta, pentasils) system and its transformations under supercritical conditions were studied. The feasibility of direct synthesis of the corresponding N-acylpyrrolidines from THF and nitriles of aliphatic and aromatic acids was shown for the first time. The dependence of the THF reaction with nitriles on the temperature, the reaction time, the nature of the exchanged cations in zeolite, the type of zeolite, and the catalyst pretreatment conditions was revealed. Acid zeolites were shown to exhibit a high catalytic activity. The yield of N-acylpyrrolidines at 350°C in the presence of the most active catalysts (HNaY and HCaLnY) was 10–40% at a selectivity of up to 80%. The key role of H2O was found, and a two-step scheme of the process, including the hydrolysis of nitrile to amide and the reaction of the latter with tetrahydrofuran resulting in the formation of N-acylpyrrolidine, was proposed.

Crystallization of primitive basaltic magmas at crustal pressures and genesis of the calc-alkaline igneous suite: experimental evidence from St Vincent, Lesser Antilles arc

Near-liquidus crystallization experiments have been carried out on two basalts (12.5 and 7.8 wt% MgO) from Soufriere, St Vincent (Lesser Antilles arc) to document the early stages of differentiation in calc-alkaline magmas. The water-undersaturated experiments were performed mostly at 4 kbar, with 1.6 to 7.7 wt% H2O in the melt, and under oxidizing conditions (ΔNNO = −0.8 to +2.4). A few 10 kbar experiments were also performed. Early differentiation of primitive, hydrous, high-magnesia basalts (HMB) is controlled by ol + cpx + sp fractionation. Residual melts of typical high-alumina basalt (HAB) composition are obtained after 30–40% crystallization. The role of H2O in depressing plagioclase crystallization leads to a direct relation between the Al2O3 content of the residual melt and its H2O concentration, calibrated as a geohygrometer. The most primitive phenocryst assemblage in the Soufriere suite (Fo89.6 olivine, Mg-, Al- and Ti-rich clinopyroxene, Cr–Al spinel) crystallized from near-primary (Mg# = 73.5), hydrous (∼5 wt% H2O) and very oxidized (ΔNNO = +1.5–2.0) HMB liquids at middle crustal pressures and temperatures from ∼1,160 to ∼1,060°C. Hornblende played no role in the early petrogenetic evolution. Derivative HAB melts may contain up to 7–8 wt% dissolved H2O. Primitive basaltic liquids at Soufriere, St Vincent, have a wide range of H2O concentrations (2–5 wt%).

The Role of H2O in Nitric Oxide Removal by Wet-Type Corona Discharge Plasma Reactor

We have applied the dc corona discharge process to the removal of NO from a simulated flue gas. The effect of H2O on the oxidation of NO to NO2 was investigated. The experimental results show the removal rate of NO is improved in wet-type reactor than that of dry-type reactor. NO is mostly oxidized into NO2 by the reaction with O and O3 and NO2 is changed into HNO3 by the reaction with OH, which is generated from H2O.

Role of H2O in subduction-zone magmatism: New insights from melt inclusions in high-Mg basalts from central Mexico

Research Article| March 01, 2003 Role of H2O in subduction-zone magmatism: New insights from melt inclusions in high-Mg basalts from central Mexico Pablo Cervantes; Pablo Cervantes 1Department of Geology and Geophysics, Texas A&M University, College Station, Texas 77845, USA Search for other works by this author on: GSW Google Scholar Paul J. Wallace Paul J. Wallace 2Ocean Drilling Program, Texas A&M University, College Station, Texas 77845, USA Search for other works by this author on: GSW Google Scholar Geology (2003) 31 (3): 235–238. https://doi.org/10.1130/0091-7613(2003)031<0235:ROHOIS>2.0.CO;2 Article history received: 17 Jun 2002 rev-recd: 08 Nov 2002 accepted: 14 Nov 2002 first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Pablo Cervantes, Paul J. Wallace; Role of H2O in subduction-zone magmatism: New insights from melt inclusions in high-Mg basalts from central Mexico. Geology 2003;; 31 (3): 235–238. doi: https://doi.org/10.1130/0091-7613(2003)031<0235:ROHOIS>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Although there is a growing body of data on H2O in arc magmas, there is still considerable uncertainty about the relationship between H2O and various incompatible elements during enrichment of the mantle wedge by subduction processes. We report data for H2O, other volatiles (CO2, S, Cl), and trace elements in olivine-hosted melt inclusions from high-Mg basalts in central Mexico that exhibit varying degrees of subduction-related enrichment. Most melt inclusions were trapped at low pressure, but rare inclusions (Mg# 65–78, olivine hosts Fo85–90) trapped at upper to middle crustal pressures (1–6 kbar) contain high CO2 (250–2120 ppm). The high-pressure inclusions indicate magmatic H2O contents from 1.3 to 5.2 wt%. Enrichment of H2O relative to Nb correlates positively with K/Nb, Ba/Nb, and La/Nb, indicating a clear link between H2O and trace element enrichment of the mantle wedge. Our results show that fluxing of the wedge with an H2O-rich component from the subducted slab is important in formation of magmas that are enriched in large ion lithophile (LILE) and light rare earth (LREE) elements relative to high field strength elements (HFSE). In contrast, magmas with low LILEs and LREEs relative to HFSEs have relatively low H2O, and must have formed largely by decompression melting of unmodified mantle. Our data for volcanoes <50 km apart show evidence of significant variability in the composition of H2O-rich subduction components that are added to the mantle wedge beneath central Mexico. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Structure of Glasses in the Na2SO4–P2O5–H2O System

The structure of sulfate–phosphate glasses is investigated by high-resolution 31P solid-state nuclear magnetic resonance with magic-angle sample spinning (31P MAS NMR spectroscopy). The structure parameters that account for the number of different types of phosphorus–oxygen structural units involved in the glass network are determined, and the main structural units of the glasses under investigation are revealed. The role of H2O and Na2SO4 as modifiers of the structural network of sulfate–phosphate glasses is clarified.

1B0915 チトクロムc酸化酵素による酸素還元反応の初期段階における水分子の役割に関する理論的研究(6.電子状態,一般演題,日本生物物理学会第40回年会)

1B0915 チトクロムc酸化酵素による酸素還元反応の初期段階における水分子の役割に関する理論的研究(6.電子状態,一般演題,日本生物物理学会第40回年会)

The role of H2O during crystallization of primitive arc magmas under uppermost mantle conditions and genesis of igneous pyroxenites: an experimental study

Exposed, subduction-related magmatic arcs commonly include sections of ultramafic plutonic rocks that are composed of dunite, wehrlite, and pyroxenite. In this experimental study we examined the effects of variable H2O concentration on the phase proportions and compositions of igneous pyroxenites and related ultramafic plutonic rocks. Igneous crystallization experiments simulated natural, arc magma compositions at 1.2 GPa, corresponding to conditions of the arc lower crust. Increasing H2O concentration in the liquid changes the crystallization sequence. Low H2O concentration in the liquid stabilizes plagioclase earlier than garnet and amphibole while derivative liquids remain quartz normative. Higher H2O contents (>3%) suppress plagioclase and lead to crystallization of amphibole and garnet thereby producing derivative corundum normative andesite liquids. The experiments show that alumina in the liquid correlates positively with Al in pyroxene, as long as no major aluminous phase crystallizes. Extrapolation of this correlation to natural pyroxenites in the Talkeetna and Kohistan arc sections indicates that clinopyroxenes with low Ca-Tschermaks component represent near-liquidus phases of primitive, Si-rich hydrous magmas. Density calculations on the residual solid assemblages indicate that ultramafic plutonic rocks are always denser than upper mantle rocks in the order of 0.05 to 0.20 g/cm3. The combination of high pressure and high H2O concentration in the liquid suppresses plagioclase crystallization, so that ultramafic plutonic rocks form over a significant proportion of the crystallization interval (up to 50% crystallization of ultramafic rocks from initial, mantle-derived liquids). This suggests that in subduction-related magmatic arcs the seismic Moho might be shallower than the petrologic crust/mantle transition. It is therefore possible that calculations based on seismic data have overestimated the normative plagioclase content (e.g., SiO2, Al2O3) of igneous crust in arcs.

Role of H2O in Oxidative Regeneration of ZnS Formed from High-Temperature Desulfurization ZnO Sorbent

To develop an easily regenerable zinc oxide high-temperature desulfurization sorbent, the role of H2O in the course of oxidative regeneration of zinc sulfide in the presence of O2 were studied using ZnO without support material as a sorbent. Oxidative regeneration of ZnS in the presence of water vapor was examined using TPR technique and H218O. From this study, the following results were obtained: ZnS was converted to SO2 and H2 by H2O in the absence of O2 at high temperature (> ca. 600 °C); in the first step in the oxidative regeneration, ZnS predominantly reacted with H2O more than O2; the SO2 formed from ZnS contained oxygen from H2O. From the experimental results, it was found that the oxidative regeneration of ZnS in the presence of H2O and O2 can be expressed by the following two equations: ZnS + 3H2O ⇔ ZnO + SO2 + 3H2; 3H2 + 3/2O2 ⇒ 3H2O. In the absence of H2O or in the case of very low value of H2O/O2 concentration ratio, the following reaction also occurred: ZnS + 3/2O2 ⇒ ZnO + SO2

Melting of Biotite + Plagioclase + Quartz Gneisses: the Role of H2O in the Stability of Amphibole

Melting of Biotite + Plagioclase + Quartz Gneisses: the Role of H2O in the Stability of Amphibole

First Results from the Submillimeter Wave Astronomy Satellite – H2O and O2 Discoveries

The Submillimeter Wave Astronomy Satellite (SWAS) was successfully launched on 5 December 1998 with the goals of studying: (1) the distribution of oxygen in the interstellar medium; (2) the role of H2O and O2 as gas coolants; and (3) the UV-illuminated surfaces of molecular clouds. To achieve these goals, SWAS is conducting pointed observations of dense (n(H2) &gt; 103 cm–3) molecular clouds throughout our Galaxy in either the ground-state or a low-lying transition of five astrophysically important species: H2O, H218O, O2, CI, and 13CO. SWAS has made great strides in each of these areas of investigation. This paper will summarize our H2O and O2 findings one year into the mission.

Effect of Sample Matrix Dehydration During Supercritical Fluid Extraction on the Recoveries of Drug Residues from Fortified Chicken Liver

The role of H2O in the supercritical fluid extraction (SFE) of zoalene (3,5-dinitro-o-toluamide) and its metabolites from fortified chicken livers is reported. Dehydration of the sample matrix during SFE results in adsorption of the analytes, limiting their extraction. Adding 0.5 mL of additional water to the sample matrix prior to SFE prolongs the effective extraction period, thereby increasing the recoveries of the metabolites 12–20%. The following recoveries are found for zoalene, 3-amino-5-nitro-o-toluamide, 5-amino-3-nitro-o-toluamide, and N5-acetyl-3-nitro-o-toluamide extracted from a liver-Na2SO4 mixture with added H2O at 60°C and 1034 bar (density, 1.069) using 3 L CO2/min (expanded gas) for 30 min: 87, 92, 77, and 66%, respectively.

The supramolecular architecture of the polyhydroxyalkanoate inclusions inPseudomonas oleovorans

A study has been initiated to further clarify the role of H2O and protein in maintaining a functional amorphous state of poly-β-hydroxyalkanoates (PHAs) in the living cell. It has been clearly demonstrated that the ordered hydrophobic hydrocarbon chains of these materials crystallize at varying rates, depending on repeating unit heterogeneity, subsequent to the removal of the polymer granule from the cell and after solvent extraction. Both isolation and extraction procedures remove water and some protein from the polymer granule, and the polymer crystallizes. We have developed a procedure for the isolation of poly-β-hydroxyoctanoate (PHO) containing granules that maintain their “in vivo” fluid, amorphous and functional state with water and proteins intact. These purified granules have been observed and their purity determined by ‘in vivo’ Nomarski computer-enhanced imaging light microscopy. Both this technique and low temperature rapid freeze-fracture electron microscopy have demonstrated an organized para-crystalline network of proteins on the surface of the granule. The structural role of these proteins in maintaining granule integrity and function both in the cell and after granule isolation is discussed. It is suggested that these procedures may permit in vitro studies of the mechanisms of synthesis and degradation of PHAs in a variety of polyester producing microbial systems.

An experimental study of glaucophanic amphiboles in the system Na2O-MgO-Al2O3-SiO2-SiF4 (NMASF): some implications for glaucophane stability in natural and synthetic systems at high temperatures and pressures

The phase relations of glaucophanic amphiboles have been studied at 18–31 kbar/680–950°C in the synthetic system Na2O−MgO−Al2O3−SiO2−SiF4 (NMASF) using the bulk composition of fluor-glaucophane, Na2Mg3Al2Si8O22F2. Previous experimental studies of glaucophane in the water-bearing system (NMASH) have been hampered by problems of fine grain size (electron microprobe analyses with low oxide totals and contamination by other phases), and consequently good compositional data are lacking. Fluor-amphiboles, on the other hand, generally have much higher thermal stabilities than their hydrous counterparts. By using the fluorine-analogue system NMASF, amphibole crystals sufficiently coarse for electron microprobe analysis have been obtained. Furthermore, NMASH amphibole phase relations are directly analogous to those of the NMASF system because SiF4 fills the role of H2O as the fluid species. High-pressure NMASF amphibole parageneses are comparable to those obtained for NMASH amphiboles under similar pressure-temperature conditions, except that the NMASF solidus was not encountered. In the pressure-temperature range of the NMASF experiments, fluor-glaucophane is unstable relative to glaucophanenyboite-Mg-magnesio-katophorite amphiboles. Variations in synthetic fluor-amphibole composition with P and T are discussed in terms of changes in the thermodynamic activities of the principal amphibole end-members, such as glaucophane (aGp) and nyboite (aNy) using an ideal-mixing-on-sites model. The most glaucophanic amphiboles analysed have aGp=0.50–0.60 and coexist with jadeite and coesite at 30 kbar/800°C. Amphiboles become increasingly nyboitic with decreasing pressure through the NaAlSi-1 exchange, which is the principal variation observed. The most nyboitic amphiboles have aNy =0.65–0.70 and coexist with fluor-sodium-phlogopite and quartz at 21–24 kbar/800–850°C. At 800°C amphiboles are essentially glaucophane-nyboite solid solutions. At 850°C there is some minor displacement along MgMgSi-1, but Mg-magnesio-katophorite activities are very low (<0.06). Activities of the eight other NMASF amphibole end-members are <0.001, except for eckermannite activity which varies from 0.01–0.11. Our results indicate that: (a) synthetic amphiboles mimic the essential stoichiometries observed in blueschist amphiboles; (b) synthetic studies should be relevant to petrologically important high-pressure parageneses and reactions involving glaucophanicamphiboles, sodic pyroxenes, albite and talc; (c) the high-pressure stability limit of fluorglaucophane lies at pressures higher than those reached in this study (31 kbar); (d) in natural systems an approach to glaucophane stoichiometry should be favoured by high water activities as well as high pressures.

Role of H2O on the degradation process of Y-TZP

Role of H2O on the degradation process of Y-TZP

Measurement of the absolute third-order rate constant for the reaction between Cs + OH + He determined by time-resolved molecular resonance-fluorescence spectroscopy, OH(A2Σ+–X2Π), coupled with steady atomic resonance fluorescence, Cs(72PJ–62S1/2)

We present the first direct measurement of the absolute third-order rate constant (k1) for the reaction Cs + OH + He → CsOH + He (T= 481 K) completing the series of analogous studies with the present experimental system we have also described for Na, K and Rb. OH(X2Π), generated by the pulsed irradiation of H2O vapour through CaF2 optics in a slow-flow system, kinetically equivalent to a static system, was monitored by time-resolved resonance fluorescence at λ= 307 nm [OH(A2Σ+–X2Π), (0, 0)] in the presence of an excess of atomic caesium derived from a heat-pipe oven and helium buffer gas. The atomic caesium was monitored in the steady mode using atomic resonance fluorescence of the unresolved Rydberg doublet at λ= 457 nm [Cs(72PJ– 62S1/2)] coupled with phase-sensitive detection. The following value of k1 was obtained: k1(481 K)=(10.0 ± 1.5)× 10–31 cm6 molecule–2 s–1. This result was extrapolated to 2000 K using the unimolecular reaction rate theory by Troe, including the quantitative effects of hindered rotation on the low-frequency bending modes of CsOH. We have employed the same formalism to calculate the rate constant for the reaction between Li + OH + He at 500 and 2000 K. The resulting calculated temperature dependences of the third-order rate constants (kR) for the reaction X + OH + He → XOH + He are thus compared: [graphic omitted]. Extrapolation of the rate data to flame conditions is considered with particular emphasis on the role of H2O as a third body in recombination reactions of this type. It is concluded that a reassessment of the standard collisional deactivation efficiency, βc, for H2O at elevated temperatures can be used to reconcile former differences between recombination rate data extrapolated from measurements of the present type with those derived from modelling on flames.

Radiative Heating Due to Increased CO2: The Role of H2O Continuum Absorption in the 12–18 μm Region

Abstract In the 12–18 μm spectral region, the CO2 bands are overlapped by the H2O pure rotational band and the H2O continuum band. The 12–18 μm H2O continuum absorption is neglected in most studies concerned with the climatic effects of increased CO2. In this study, we examine the role of H2O–CO2 overlap in detail. Specifically, the effect of the water vapor continuum in the 12–18 μm region on the radiative heating due to increased CO2 is investigated. It is found that although the longwave surface radiative heating due to increased CO2 is considerably reduced at low latitudes by H2O continuum absorption, where water vapor partial pressures are high, the radiative heating of the surface/troposphere system as a whole is minimally altered.

Charnockite geobarometers based on coexisting garnet—pyroxene—plagioclase—quartz

Numerous geothermometers based on compositions of coexisting minerals have been calibrated experimentally or theoretically during the past 10 yr. In contrast, few continuous-reaction geobarometers exist which have had wide application. One, based on the reaction of cordierite to garnet, sillimanite and quartz, is limited by a relatively narrow pressure range of application and also by conflicting calibrations1,2 because the mixing relations of Mg and Fe and the role of H2O in cordierite3 are not understood. Another successful barometer uses the assemblage garnet, plagioclase, Al2SiO5 and quartz4,5. Continuous geobarometers based on the reaction of orthofer-rosilite to fayalite plus quartz6 and on the aluminium content of enstatite in equilibrium with garnet7 have been used to a lesser extent. The former barometer is limited by rarity of the requisite assemblage, and the latter by uncertain experimental calibration for crustal rocks. We calibrate here two mineralogical geobarometers from measured thermodynamic data. The participating minerals, pyroxenes, garnet, plagioclase and quartz, are frequently associated in high-grade metamorphic rocks. Calculation of pressures for several terrains show that the geobarometers yield reasonable and consistent results for the entire range of crustal pressures.

The System CaO-Al2O3-SiO2-H2O at High Pressures and Temperatures

Subsolidus and liquidus relationships in the system CaO-Al2O3-SiO2-H2O have been experimentally investigated over the temperature interval 580 to 1150 °C, to a pressure of 35 kb. Phases encountered include anorthite, clinozoisite, coesite, corundum, gehlenite, grossularite, kyanite, liquid, quartz, sillimanite, vapor, wollastonite, and zoisite. Phase relationships are developed in a manner useful to students of phase equilibria. Experimental results are first presented in terms of simple compositions joins, including CaAl2Si2O8-H2O and CaAl2Si2O8-SiO2-H2O, and in terms of the key minerals zoisite and grossularite. Clinozoisite was synthesized only when using scolecite as a reactant. These results, together with previous data, are compiled in a P-T projection, which illustrates that all of the vapor-saturated melting curves change from negative to positive dP/dT slopes in the interval 5–15 kb, where they intersect subsolidus phase transformations. The beginning of incongruent melting of anorthite-vapor below 10 kb causes the solidus for these compositions to drop from 1122 °C at 10 kb to 755 °C at 12.5 kb, the latter being the lowest melting temperature in the system. Using available evidence coupled with the methods of Schreinemakers, a schematic P-T projection for 50 univariant reactions in this system is developed. Divariant equilibria are portrayed in isobaric-polythermal and isothermal-polybaric diagrams, using compositions of liquids estimated from phase relationships. The stability of plagioclase of intermediate composition is considered, and it is concluded that plagioclase is stable to higher pressures than either albite or anorthite. These experiments also provide a model for melting and the role of H2O in the earth's mantle, and they indicate that the maximum high-temperature stability of hydrous phases at very high pressures occurs for values of fH2O less than when an aqueous vapor is present. Many of the reactions in this system provide clues to the temperature-pressure conditions during regional and contact metamorphism, and the addition of Na2O to this system may provide a basis for classification of such rocks.

Isograds and the Role of H2O in Metamorphic Facies of Orthogneisses of the Northwest Adirondack Area, New York

Four isograds are shown on a geologic map of the northwest Adirondack area based on the first development of: (1) regional metamorphic garnet in biotite-quartz-oligoclase paragneiss; (2) orthopyroxene as a major member of the mafic assemblage in amphibolitic gneiss, and the disappearance of sphene in hornblende quartz syenite and old granite orthogneisses; (3) garnet in amphibolitic orthogneiss and metagabbro; and (4) garnet in pyroxene quartz syenitic and hornblende quartz syenitic orthogneisses. The successive new mineral assemblages are inferred to represent development under conditions of increasing temperatures and load pressures. An attempt is made to correlate them with the metamorphic facies of progressive metamorphism. The orthogneisses between any two isograds show a variety of mineral assemblages which are best interpreted in terms of development under a wide range of P H 2 O . The hypothesis of partial pressure of H 2 O about equivalent to load presure for the origin of the Adirondack orthogneisse gives results inconsistent with the data. In each of the metamorphic zones from that of almandine amphibolite facies to that of the pyroxene granulite subfacies, igneous rocks that were pyroxene syenite or quartz syenite have been metamorphosed to equivalent pyroxenic gneisses, and hornblende quartz syenite or hornblende granite to equivalent hornblende gneisses. The rocks have, in general, been impermeable either to access or to loss of H 2 O during plastic flow and any subsequent recrystallization. Evidence is presented that most of the hornblende-hypersthene amphibolites, with or without garnet, associated with rocks of the pyroxene granulite subfacies were formed at the same T and Pi as this facies, but at relatively high P H 2 O . The late-stage development of a network of rescrystallized garnetiferous shear zones in otherwise nongarnetiferous host rock is discussed.