scholarly journals Formation of Hydrocarbons in the Presence of Native Iron under Upper Mantle Conditions: Experimental Constraints

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 88
Author(s):  
Sokol ◽  
Tomilenko ◽  
Sokol ◽  
Zaikin ◽  
Bul’bak
Keyword(s):  
Upper Mantle ◽  
Hydrogen Permeability ◽  
Experimental Conditions ◽  
Light Alkanes ◽  
Fully Depleted ◽  
Native Iron ◽  
Consumption Rates ◽  
Higher Temperature ◽  
Direct Hydrogenation ◽  
Metal Phases

The formation of hydrocarbons (HCs) upon interaction of metal and metal–carbon phases (solid Fe, Fe3C, Fe7C3, Ni, and liquid Fe–Ni alloys) with or without additional sources of carbon (graphite, diamond, carbonate, and H2O–CO2 fluids) was investigated in quenching experiments at 6.3 GPa and 1000–1400 °C, wherein hydrogen fugacity (fH2) was controlled by the Fe–FeO + H2O or Mo–MoO2 + H2O equilibria. The aim of the study was to investigate abiotic generation of hydrocarbons and to characterize the diversity of HC species that form in the presence of Fe/Ni metal phases at P–T–fH2 conditions typical of the upper mantle. The carbon donors were not fully depleted at experimental conditions. The ratio of H2 ingress and consumption rates depended on hydrogen permeability of the capsule material: runs with low-permeable Au capsules and/or high hydrogenation rates (H2O–CO2 fluid) yielded fluids equilibrated with the final assemblage of solid phases at fH2sample ≤ fH2buffer. The synthesized quenched fluids contained diverse HC species, predominantly light alkanes. The relative percentages of light alkane species were greater in higher temperature runs. At 1200 °C, light alkanes (C1 ≈ C2 > C3 > C4) formed either by direct hydrogenation of Fe3C or Fe7C3, or by hydrogenation of graphite/diamond in the presence of Fe3C, Fe7C3, and a liquid Fe–Ni alloy. The CH4/C2H6 ratio in the fluids decreased from 5 to 0.5 with decreasing iron activity and the C fraction increased in the series: Fe–Fe3C → Fe3C–Fe7C3 → Fe7C3–graphite → graphite. Fe3C–magnesite and Fe3C–H2O–CO2 systems at 1200 °C yielded magnesiowüstite and wüstite, respectively, and both produced C-enriched carbide Fe7C3 and mainly light alkanes (C1 ≈ C2 > C3 > C4). Thus, reactions of metal phases that simulate the composition of native iron with various carbon donors (graphite, diamond, carbonate, or H2O–CO2 fluid) at the upper mantle P–T conditions and enhanced fH2 can provide abiotic generation of complex hydrocarbon systems that predominantly contain light alkanes. The conditions favorable for HC formation exist in mantle zones, where slab-derived H2O-, CO2- and carbonate-bearing fluids interact with metal-saturated mantle.

scholarly journals The influence of pressure on the spontaneous ignition of inflammable gas-air mixtures - IV—methane-, ethane-, and propane-air mixtures

1936 ◽  
Vol 154 (881) ◽  
pp. 95-112 ◽  
Keyword(s):  
Critical Pressure ◽  
Spontaneous Ignition ◽  
Lower Range ◽  
Experimental Conditions ◽  
Temperature Range ◽  
Limited Temperature ◽  
Tentative Hypothesis ◽  
Temperature Ranges ◽  
Higher Temperature ◽  
Temperature And Pressure

In previous papers the results of investigations into the influence of varying initial pressures up to 15-20 atmospheres on the spontaneous ignition of mixtures with air of butane, iso -butane, pentane, and hexane were described. On the attainment of a critical pressure, which varied both with the hydrocarbon concerned and the composition of its mixture with air, the ignition points were always found to fall sharply from a higher temperature range above 500°C to a lower range at about 300°C. At pressures just exceeding the critical transition pressures ignition occurred at first only within limited temperature ranges which widened and ultimately merged with increasing pressure. The striking relationship between the behaviours of the hydrocarbons referred to under the experimental conditions and their “knocking” propensities in an engine was also indicated. While the data available were inadequate for drawing any final con­clusion as to the character of the phenomena referred to, a tentative hypothesis was advanced that while ignition in the higher temperature range pertains mainly to the thermal decomponents of intermedially formed compounds, ignition in the lower system occurs when temperature and pressure conditions favour the survival and further oxidation of such bodies, particularly aldehydes.

Measurement of the amount and isotopic composition of the CO2 released from the cyanobacterium Synechococcus UTEX 625 after rapid quenching of the active CO2 transport system

1997 ◽  
Vol 75 (6) ◽  
pp. 981-997 ◽  
Author(s):  
Anthony G. Miller ◽  
Christophe Salon ◽  
David T. Canvin ◽  
George S. Espie
Keyword(s):  
Isotopic Composition ◽  
Cell Volume ◽  
Mass Spectrometer ◽  
Transport System ◽  
Time Course ◽  
Rapid Quenching ◽  
Experimental Conditions ◽  
Extracellular Medium ◽  
Fully Depleted ◽  
Entire Cell

Air-grown cells of the cyanobacterium Synechococcus UTEX 625 were suspended in a cuvette connected to a mass spectrometer and supplied with H13C18O3− to investigate the intracellular interconversion between CO2 and HCO3− as determined from the isotopic composition of CO2 appearing in the extracellular medium under a wide variety of experimental conditions. Upon injection of H13C18O3− to the cell suspension in the light, the extracellular [13C16O2] increased. As the CO2 species were 13C labelled, this demonstrated that the 18O-depleted CO2 was originating from the added H13C18O3−. A comparison of the rates of 13C16O16O appearance in the medium with the formation of 13C16O16O from spontaneous dehydration–hydration in the extracellular medium in the presence of cells demonstrated that most of it had to originate from a series of intracellular dehydration–hydration cycles of H13C18O3− that had been recently transported into the cells. During the time course of the experiments both the m/z (mass to charge) = 49 (i.e., 13C18O18O) and 47 (i.e., 13C18O16O) signals decreased constantly, whereas the m/z = 45 signal (i.e.,13C16O2) always increased. Inhibiting CO2 fixation enhanced the amount of CO2 arising in the medium but did not change its isotopic composition, and the CO2 was always fully depleted of 18O. When the CO2 transport system was inhibited by darkening the cells, adding inhibitors such as Na2S or COS, or quenching the uptake of inorganic 13C with an excess of inorganic 12C, the magnitude of the extracellular [13C16O2] was increased but the CO2 species were still always depleted of 18O. Various incubation times of the illuminated cells in the presence of H13C18O3− were used to obtain a variety of internal Ci pool sizes. When the inhibitor (COS) was added, the amount of 13C16O2 arising during the response time of the mass spectrometer was equivalent to the amount of CO2 that would have been present in the whole cell if CO2 and HCO3− were in equilibrium throughout the entire cell volume, but it was at least 40 times higher than the amount of CO2 that would have been present in the cell if the CO2 was confined to the carboxysomes. Experiments were also conducted at pH 9.0 where the spontaneous rate of 13C16O2 production from H13C1803− dehydration–hydration would be negligible, and again the same features were observed. Results show that intracellular HCO3− and CO2 are in rapid equilibrium throughout the entire cell volume. Key words: Synechococcus UTEX 625, cyanobacteria, CO2 leakage, 18O exchange, active CO2 transport, carboxysomes, inorganic C concentrating mechanism.

Temperature distributions at the Paleozoic and Precambrian surfaces and their implications for geothermal energy recovery in Alberta

1985 ◽  
Vol 22 (12) ◽  
pp. 1774-1780 ◽  
Author(s):  
F. W. Jones ◽  
H.-L. Lam ◽  
J. A. Majorowicz
Keyword(s):  
Upper Mantle ◽  
Geothermal Energy ◽  
Energy Recovery ◽  
Energy Potential ◽  
The North ◽  
Bottom Hole ◽  
Crystalline Crust ◽  
Higher Temperature ◽  
Temperature Maps ◽  
Western Half

A large number of bottom-hole temperature (BHT) data from Alberta (55 246 BHT from 28 260 wells) have been used to construct Paleozoic and Precambrian surface-temperature maps. A northward increase of average heat flow in Alberta results in higher subsurface temperatures at the Precambrian basement and at the top of the Paleozoic toward the north and northeast than at the same depths in the south and southeast. However, the temperature distribution at these surfaces is more depth dependent than gradient dependent, and so higher temperature values occur in the western part of the basin. As a result, good geothermal energy potential exists throughout the western half of the province, especially for regions west of the Calgary – Swan Hills – Grande Prairie – Rainbow Lake line. Through the central part of the basin, zones occur where the isotherms and the isopach lines of the Phanerozoic are parallel. These zones probably represent regions where little disturbance to heat transport by vertical water motion occurs. It is suggested that zones in the central part of the basin where such parallelism does not occur may represent areas where conductive transport of heat is perturbed by local, nonlateral fluid flow or zones with nonuniform heat contribution from the crystalline crust or upper mantle. The effect of hydrodynamics in the deeper sediments of the Paleozoic that lie below the BHT observations may also contribute to such zones.

Selective Phenol Hydrogenation to Cyclohexanone Over a Dual Supported Pd–Lewis Acid Catalyst

Science ◽  
2009 ◽  
Vol 326 (5957) ◽  
pp. 1250-1252 ◽  
Author(s):  
Huizhen Liu ◽  
Tao Jiang ◽  
Buxing Han ◽  
Shuguang Liang ◽  
Yinxi Zhou
Keyword(s):  
Lewis Acid ◽  
Acid Catalyst ◽  
Spectroscopic Studies ◽  
Phenol Hydrogenation ◽  
Reaction Conversion ◽  
Lewis Acid Catalyst ◽  
Important Intermediate ◽  
Higher Temperature ◽  
Direct Hydrogenation ◽  
Supported Pd

Cyclohexanone is an industrially important intermediate in the synthesis of materials such as nylon, but preparing it efficiently through direct hydrogenation of phenol is hindered by over-reduction to cyclohexanol. Here we report that a previously unappreciated combination of two common commercial catalysts―nanoparticulate palladium (supported on carbon, alumina, or NaY zeolite) and a Lewis acid such as AlCl3―synergistically promotes this reaction. Conversion exceeding 99.9% was achieved with >99.9% selectivity within 7 hours at 1.0-megapascal hydrogen pressure and 50°C. The reaction was accelerated at higher temperature or in a compressed CO2 solvent medium. Preliminary kinetic and spectroscopic studies suggest that the Lewis acid sequentially enhances the hydrogenation of phenol to cyclohexanone and then inhibits further hydrogenation of the ketone.

THE 5β-METABOLITES OF TESTOSTERONE: MODE AND SEX-SPECIFICITY OF THEIR FORMATION IN THE RAT LIVER

1973 ◽  
Vol 73 (3) ◽  
pp. 577-584 ◽  
Author(s):  
Rüdiger Ghraf ◽  
Hanns-Georg Hoff ◽  
Edmund Rodney Lax ◽  
Herbert Schriefers
Keyword(s):  
Rat Liver ◽  
Formation Rate ◽  
Hepatic Metabolism ◽  
Male Rats ◽  
Test Model ◽  
Experimental Conditions ◽  
Liver Slices ◽  
Male Animal ◽  
Sex Specificity ◽  
Direct Hydrogenation

ABSTRACT Rat liver slices provide a suitable test model which, with simple and variable experimental conditions, contributes direct evidence for the formation of the 5β-metabolites, 17β-hydroxy-5β-androstan-3-one, 5β-androstane-3α,17β-diol and 3α-hydroxy-5β-androstan-17-one, from a direct hydrogenation of testosterone glucuronide. When liver slices are incubated with testosterone in a KHR-phosphate medium no glucuronidation occurs and no 5β-metabolites are formed. They are produced, however, in a KHR-hydrogencarbonate medium, in which the slices are able to form glucuronides. Moreover, the production rate of 5β-hydrogenated products like that of testosterone glucuronide formation is sex-specific. The male animal metabolizes less testosterone by oxidoreductive pathways than the female and thus exhibits the higher testosterone glucuronide formation. This higher glucuronide formation rate is closely associated with the appearance of 5β-metabolites in the aglucone fraction. Apparently, the testosterone glucuronide formation rate of the female animal is not sufficiently high to allow the production of 5β-configurated C19O2-aglucones in measurable quantities. An experimentally induced feminization of the hepatic metabolism of genetically male rats by a single injection of 300 μg oestradiol benzoate on day 2 of life reduces the testosterone glucuronide formation rate to the female level and causes the 5β-metabolites to disappear. Thus, it is evident that at least those 5β-metabolites mentioned above are products of a direct hydrogenation of testosterone glucuronide.

Boron Removal from Water Using Takovite: Adsorption vs. Anion Exchange

2013 ◽  
Vol 781-784 ◽  
pp. 2150-2156 ◽  
Author(s):  
Yao Wu Cao ◽  
Qing Hai Guo
Keyword(s):  
Anion Exchange ◽  
Boron Concentration ◽  
Boron Removal ◽  
Boron Uptake ◽  
X Ray Diffraction ◽  
Structural Restoration ◽  
Experimental Conditions ◽  
Sorption Data ◽  
Freundlich Model ◽  
Higher Temperature

Takovite, a kind of hydrotalcite-like compounds (HTlcs), was used for boron removal from water. It was prepared by coprecipitation method and characterized by X-ray diffraction technique (XRD). The equilibrium time of boron sorption by takovite as well as its boron uptake capacities was determined by the reaction kinetic experiments and isotherm sorption experiments. The effects of experimental conditions on boron removal efficiency were also evaluated. Generally, the boron uptake by takovites increases with increasing initial boron concentration in solution. The isotherm sorption data match well with the Freundlich model, indicating that the anion exchange contributes a lot to solution deboronation. Moreover, at higher temperature, greater boron removal by takovite was observed. As compared to calcined takovite, uncalcined takovite has better performance in terms of boron uptake, since the structural restoration of calcined takovite didnt happen during its contact with boron-containing solution, which is quite different from the behavior of other HTlcs as reported.

NITROGEN ISOTOPE FRACTIONATION ASSOCIATED WITH THE NO2− → N2O STEP OF DENITRIFICATION IN SOILS

1982 ◽  
Vol 62 (2) ◽  
pp. 227-241 ◽  
Author(s):  
A. MARIOTTI ◽  
A. LECLERC ◽  
J. C. GERMON
Keyword(s):  
Reaction Rate ◽  
Nitrogen Isotopes ◽  
Reduction Rate ◽  
Isotopic Fractionation ◽  
Nitrogen Isotope ◽  
Isotopic Enrichment ◽  
Experimental Conditions ◽  
Helium Atmosphere ◽  
Higher Temperature ◽  
Incubation Temperatures

The fractionation of the nitrogen isotopes 14N and 15N in the denitrification process has been studied in laboratory experiments for the step NO2− → N2O. This study has been carried out on natural soils under anaerobic conditions (helium atmosphere). Reduction of N2O is blocked by introduction of a small amount of acetylene in the incubator atmosphere. Variation of experimental conditions of incubation (temperatures, direct or after air-drying incubation of the soil, addition of glucose), greatly modify the reaction rate. 15N is enriched in the substrate during denitrification. The isotopic enrichment factor changes with experimental conditions from about −33 to −11‰. Greatest enrichment is obtained for the lowest reduction rate (low temperature, undried soil). For high rates of denitrification (higher temperature, addition of glucose), the isotopic fractionation decreases. An exponential relation is found between isotopic enrichment, εp/s, and the reaction rate.

f-Element Influence on the Size of Nanophase Phosphate Inclusions in Silica

2003 ◽  
Vol 802 ◽  
Author(s):  
James V. Beitz ◽  
S. Skanthakumar ◽  
S. Seifert ◽  
P. Thiyagarajan
Keyword(s):  
Porous Silica ◽  
Vitreous Silica ◽  
Metal Phosphate ◽  
Uranyl Ions ◽  
Pore Collapse ◽  
X Ray Diffraction ◽  
Experimental Conditions ◽  
X Ray ◽  
X Ray Scattering ◽  
Higher Temperature

ABSTRACTInsight into the factors that control the formation and size of heavy metal phosphate nanophases in vitreous silica has been gained by combining conventional and anomalous small angle x-ray scattering studies with powder x-ray diffraction and laser-induced fluorescence investigations. Europium, thorium, and uranyl ions were sorbed from aqueous solutions into a chemically functionalized porous silica (termed Diphosil). Aliquots of those samples were heated to a series of temperatures that spanned the pore collapse point. Loading with trivalent europium ions resulted in production of nanophases whose size corresponded to the average number of metal ions per pore. Thorium or uranyl ions resulted in retention of porosity to higher temperature with eventual pore collapse that evidently resulted in formation of nanophases whose size exceeded that determinable under the experimental conditions.

Cat carotid body oxygen metabolism and chemoreception described by a two-cytochrome model

1986 ◽  
Vol 250 (2) ◽  
pp. H202-H207 ◽  
Author(s):  
P. K. Nair ◽  
D. G. Buerk ◽  
W. J. Whalen
Keyword(s):  
Oxygen Metabolism ◽  
Disappearance Rate ◽  
Nerve Activity ◽  
Experimental Conditions ◽  
Carotid Bodies ◽  
Tissue Po2 ◽  
O2 Concentration ◽  
Consumption Rates ◽  
The Mean ◽  
Increased Activity

We have analyzed O2 disappearance curves (DCs) in cat carotid bodies (CBs) measured with our O2 microelectrode, after stopping flow of either blood (108 DCs in 12 cats) or a hemoglobin-free (Locke) perfusion solution (35 DCs in 6 cats). Prior to occlusion, the mean tissue PO2 levels were 74.5 +/- 2.8 (SE) Torr in blood-perfused CBs and 103.4 +/- 2.6 in Locke-perfused CBs. The O2 consumption rates (VO2) determined from the initial 3 s of the DCs were 1.46 +/- 0.08 and 1.50 +/- 0.10 (SE) ml O2 . 100 g-1 . min-1, respectively, for the blood-perfused and Locke-perfused CBs. The change in total sinus nerve activity from the CB was also measured following stopped flow. The nerve activity began to increase immediately, providing further evidence that classic hypoxia is not the mechanism of chemoreceptor discharge. However, about two-thirds of the increased activity in blood-perfused CBs occurred after tissue PO2 levels fell below 20 Torr. As the CB tissue PO2 decreased, the O2 disappearance rate (-dPO2/dt) also decreased for both experimental conditions, indicating that the CB VO2 varies with O2 concentration. The increase in nerve discharge and O2 disappearance rate can be interpreted by a two-cytochrome model for O2 metabolism, with both high and low affinities.

scholarly journals Tolerance Differences and Interspecific Competition in three Members of the Amphipod Genus Gammarus

1974 ◽  
Vol 44 (1) ◽  
pp. 83-99 ◽  
Author(s):  
Henk G. Dennert
Keyword(s):  
Survival Rate ◽  
Interspecific Competition ◽  
Competitive Exclusion ◽  
Salinity Range ◽  
Temperature Dependent ◽  
Experimental Conditions ◽  
Lower Survival Rate ◽  
Lower Survival ◽  
Higher Temperature ◽  
Series Of Experiments

In a series of experiments with G. pulex, G, duebeni celticus and G. duebeni duebeni populations, pure or mixed, their tolerances for several temperature/salinity conditions have been determined. Tested were 100%, 10%, 1% and 0.1% seawater in combination with temperatures of 5°, 10° or 15°C. In general all species preferred the 5°C conditions above those with a higher temperature, and the middle salinity range (1% for G. pulex, 1% and 10% for G. d. celticus and G. d. duebeni) above the lower or higher salinities. In nearly all situations tested G. pulex had a lower survival rate than G. d. celticus and G. d. duebeni. Notwithstanding the sometimes unfavourable conditions for G. pulex, this species can compete successfully with G. d. celticus under most of the experimental conditions, but the interspecific relations between G. pulex and G. d. duebeni end in the competitive exclusion of the first species. These results support two theories: (1) G. pulex is able to compete successfully with G. d. celticus and to expel the latter from its niche, and (2) G. d. duebeni is able to invade freshwater and to establish inland populations. The differences demonstrated between G. d. celticus and G. d. duebeni are an argument for a different development and different capabilities of both subspecies. Sterile interspecific matings between G. pulex and both subspecies of G. duebeni are temperature dependent and do not play a major role in the interspecific relations connected with competition.

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