Mol CH4 Research Articles

Utilization of Dual-PSA Technology for Natural Gas Upgrading and Integrated CO2 Capture

In this study, we have considered Pressure Swing Adsorption (PSA) technology natural gas purification and integrated CO2 capture. We present the utilization of Dual-PSA technology for obtaining pipeline-quality methane and integrated CO2 capture. In the initial simulation example, a binary stream of 10% CO2 – 90% CH4 could be separated into two streams where the CH4-rich stream has a purity of 98% and the CO2-rich stream has a purity of 91%. The overall recovery of methane is higher than 99% and unit productivity of the Dual-PSA is 3.3mol CH4/(kgads.h).

Quantifying in-situ gas hydrates at active seep sites in the eastern Black Sea using pressure coring technique

Abstract. In the eastern Black Sea, we determined methane (CH4) concentrations, gas hydrate volumes, and their vertical distribution from combined gas and chloride (Cl−) measurements within pressurized sediment cores. The total gas volume collected from the cores corresponded to concentrations of 1.2–1.4 mol CH4 kg−1 porewater at in-situ pressure, which is equivalent to a gas hydrate saturation of 15–18% of pore volume and amongst the highest values detected in shallow seep sediments. At the central seep site, a high-resolution Cl− profile resolved the upper boundary of gas hydrate occurrence and a continuous layer of hydrates in a sediment column of 120 cm thickness. Including this information, a more precise gas hydrate saturation of 22–24% pore volume could be calculated. This volume was higher in comparison to a saturation calculated from the Cl− profile alone, resulting in only 14.4%. The likely explanation is an active gas hydrate formation from CH4 gas ebullition. The hydrocarbons at Batumi Seep are of shallow biogenic origin (CH4 > 99.6%), at Pechori Mound they originate from deeper thermocatalytic processes as indicated by the lower ratios of C1 to C2–C3 and the presence of C5.

Dissolved methane distribution in the South Pacific and the Southern Ocean in austral summer

Oceanic methane (CH4) was examined in the South Pacific and the Southern Ocean from December 2001 to February 2002. From the oligotrophic South Pacific (10°S) to the Subtropical Front (STF), we observed the maximum concentrations of CH4 in the subsurface layer which ranged from 2.7 to 3.9 nmol kg−1. South of the STF, higher levels of CH4 were often detected in both the surface and the subsurface layers. Elevated surface CH4 concentrations (3.4–6.1 nmol kg−1) south of the STF tended to be higher than those north of the STF. Higher CH4 were often concomitant with an increase in chlorophyll a levels in the Seasonal Ice Zone (SIZ). Considering that phytoplankton does not generate methane directly, the high CH4 production probably resulted from the grazing processes of Antarctic krill and/or zooplankton fed on phytoplankton and the subsequent microbial methanogenesis in addition to the aerobic CH4 production in the water column. Present results showed a good relation between surface CH4 data (<50 m) and σθ between 10°S and the Polar Front (PF), which allow us to provide interpolation/extrapolation schemes for CH4 concentration and sea‐air CH4 flux in the wide area ([CH4] = 0.15 σθ − 0.98 (RMS = 0.21 nmol kg−1, r = 0.68, n = 49, p < 0.001). The sea‐air fluxes estimated during our survey were from 2.4 to 4.9 mol CH4 km−2 d−1 between 10°S and the PF (54°S), and from 0.8 to 2.3 mol CH4 km−2 d−1 south of the PF, where the sea‐air CH4 flux was largely affected by the wind speed.

Methane emissions from sheep pasture, measured with an open‐path eddy covariance system

AbstractMethane (CH4) is an important greenhouse gas, contributing 0.4–0.5 W m−2 to global warming. Methane emissions originate from several sources, including wetlands, rice paddies, termites and ruminating animals. Previous measurements of methane flux from farm animals have been carried out on animals in unnatural conditions, in laboratory chambers or fitted with cumbersome masks. This study introduces eddy covariance measurements of CH4, using the newly developed LI‐COR LI‐7700 open‐path methane analyser, to measure field‐scale fluxes from sheep grazing freely on pasture. Under summer conditions, fluxes of methane in the morning averaged 30 nmol m−2 s−1, whereas those in the afternoon were above 100 nmol m−2 s−1, and were roughly two orders of magnitude larger than the small methane emissions from the soil. Methane emissions showed no clear relationship with air temperature or photosynthetically active radiation, but some diurnal pattern was apparent, probably linked to sheep grazing behaviour and metabolism. Over the measurement period (days 60–277, year 2010), cumulative methane fluxes were 0.34 mol CH4 m−2, equating to 134.3 g CO2 equivalents m−2. By comparison, a carbon dioxide (CO2) sink of 819 g CO2 equivalents m−2 was measured over the same period, but it is likely that much of this would be released back to the atmosphere during the winter or as off‐site losses (through microbial and animal respiration). By dividing methane fluxes by the number of sheep in the field each day, we calculated CH4 emissions per head of livestock as 7.4 kg CH4 sheep−1 yr−1, close to the published IPCC emission factor of 8 kg CH4 sheep−1 yr−1.

Natural flux of greenhouse methane from the Timor Sea to the atmosphere

[1] Methane gas bubbles from the Cornea Seep were sampled at the sea surface in the Timor Sea continental shelf area in June 2005. Total bubble gas flux was 0.076 to 0.76 L m−2 h−1 during the 6 h d−1 periods of low neap tides in June 2005. This bubble gas contained an average of 26 mmol CH4 L−1 and about 0.16 and 0.006 mmol L−1 of ethane and propane. We estimate the daily flux from the sea surface to the atmosphere to be 0.012 to 0.12 mol CH4 m−2 d−1 or 0.13 to 1.3 t CH4 d−1 from an area of about 0.7 km2. This methane flux came from a 500 × 1400 m carbonate pavement dome on the seafloor at 84 m water depth. The seep hard ground was swath mapped, and 3.5 kHz subbottom profile data indicate that the seep dome was strongly reflective with poor penetration into the subsurface, consistent with the presence of a carbonate hard ground. Carbon and deuterium isotope ratios (δ13C = −41 to −42‰, δD = −157 to −158‰) of the seep bubble gas indicate that this methane had a thermogenic origin and was in the same isotopic range as gas within the Late Cretaceous Cornea oil and gas field. We could not detect inputs of fluids containing nutrients or short-lived radium isotopes at this site, commonly associated with other cold seeps. Tens to a hundred of kilometers seaward from the Cornea seep site, water column dissolved methane concentrations in this sector of the Timor Sea shelf and slope were 100–500 times supersaturated with respect to the atmosphere, and thus the water column is expected to be degassing additional methane to the atmosphere. Perhaps there are thousands of other methane seeps (of similar magnitude to the Cornea Seep) on this shelf and slope to account for all the excess dissolved methane (∼86,000 t) measured in the water column. These measured and calculated fluxes provide evidence for the hypothesis that shallow sea seeps may be a significant source of atmospheric methane, in contrast to deep sea vents, where most of the methane is dissolved and oxidized in seawater and does not reach the atmosphere.

Quantification of seep-related methane gas emissions at Tommeliten, North Sea

Tommeliten is a prominent methane seep area in the Central North Sea. Previous surveys revealed shallow gas-bearing sediments and methane gas ebullition into the water column. In this study, the in situ methane flux at Tommeliten is re-assessed and the potential methane transport to the atmosphere is discussed, with regards to the hydrographic setting and gas bubble modeling. We have compiled previous data, acquired new video and acoustic evidence of gas bubble release, and have measured the methane concentration, and its C-isotopic composition in the water column. Parametric subbottom sonar data reveal the three-dimensional extent of shallow gas and morphologic features relevant for gas migration. Five methane ebullition areas are identified and the main seepage area appears to be 21 times larger than previously estimated. Our video, hydroacoustic, subbottom, and chemical data suggest that ∼1.5×10 6 mol CH 4/yr (∼26 tons CH 4/yr) of methane gas is being released from the seepage area of Tommeliten. Methane concentration profiles in the vicinity of the gas seeps show values of up to 268 nM (∼100 times background) close to the seafloor. A decrease in δ 13C-CH 4 values at 40 m water depth indicates an unknown additional biogenic methane source within the well oxygenated thermocline between 30 and 40 m water depth. Numerical modeling of the methane bubbles due to their migration and dissolution was performed to estimate the bubble-derived vertical methane transport, the fate of this methane in the water column, and finally the flux to the atmosphere. Modeling indicates that less than ∼4% of the gas initially released at the seafloor is transported via bubbles into the mixed layer and, ultimately, to the atmosphere. However, because of the strong seasonality of mixing in the North Sea, this flux is expected to increase as mixing increases, and almost all of the methane released at the seafloor could be transferred into the atmosphere in the stormy fall and winter time.

Optimization of a chemical-looping auto-thermal reforming system working with a Ni-based oxygen-carrier

Abstract In chemical-looping auto-thermal reforming (CLRa), hydrogen is produced without the need of an exterior heat supply. Thus, an important aspect to be considered in the design of a CLRa system is the heat balance. In this work, mass and heat balances have been done to determine the auto-thermal operating conditions that maximize H 2 production in a CLRa system working with a Ni-based oxygen carrier with a 20 wt % of active metal oxide (NiO). It was found that the oxygen-to-methane molar ratio should be higher than 1.25 to reach auto-thermal conditions, which means that the H 2 yield is 2.7 mol H 2 /mol CH 4 . The control of the oxygen-to-methane ratio by the air flow to the air-reactor was preferred against controlling the oxygen transferred by the solids circulation rate because a lower excess of air was needed in the first case to reach auto-thermal conditions.

New cycle configuration to enhance performance of kinetic PSA processes

This work shows a new column arrangement to improve the utilization of the adsorbent in multi-column Pressure Swing Adsorption (PSA) processes. This cycle was specifically designed to increase the unit productivity for gas separations using adsorbents with slow diffusion kinetics where mass transfer zone (MTZ) inside the column is important. In this column arrangement, when the heavy (most adsorbed) gas breaks through one column, the exit of this column is connected to a second column (trim bed) where more heavy gas can be adsorbed. In this way, also more heavy gas will be adsorbed in the first (lead) column. The increase of process performance is directly related to the length of the MTZ: the larger the MTZ, the better will perform using the lead-trim beds concept. The cycle performance was tested for biogas upgrading to obtain high purity bio-methane (purity >98%) that can be used as renewable fuel. Two different adsorbents were employed in the process simulations: zeolites 13X (fast diffusion) and carbon molecular sieve (slow diffusion). Furthermore, the possibility of using less power in the purge step was considered. Using this process, it was possible to obtain unit productivity of 5.5 mol CH 4 per hour per kilogram of adsorbent.

Oxygen-carrier selection and thermal analysis of the chemical-looping process for hydrogen production

The three-reactor chemical-looping process (TRCL) for the production of hydrogen from natural gas is quite attractive for both CO 2 capture and hydrogen production. The TRCL process consists of a fuel reactor, a steam reactor and an air reactor. In the fuel reactor, natural gas is oxidized to CO 2 and H 2O by the lattice oxygen of the oxygen carrier. In the steam reactor, the steam is reduced to hydrogen through oxidation of the reduced oxygen carrier. In the air reactor, the oxygen carrier is fully oxidized by air. In this process, the oxygen carrier is recirculated among the three reactors, which avoids direct contact between fuel, steam and air. In this study, various candidate materials were proposed for the oxygen carrier and support, and a thermal analysis of the process was performed. The oxygen carrier for the process must have the ability to split water into hydrogen in its reduced state, which is a different chemical property from that of the chemical-looping combustion medium. The selection of the oxygen carrier and support require careful consideration of their physical and chemical properties. Fe 2O 3, WO 3 and CeO 2 were selected as oxygen carriers. Thermal analysis indicated an expected hydrogen production of 2.64 mol H 2 per mol CH 4 under thermoneutral process conditions. The results indicated that hydrogen production was affected mainly by the steam-conversion rate. The solid-circulation rate and temperature drop in the fuel reactor were calculated for the selected oxygen carriers with different metal oxide contents and solid-conversion rates.

Oxidation of methane and ethylene in water at ambient conditions

Available spectroscopic, labelling and reactivity data show that stable μ-nitrido diiron phthalocyanine activates H 2O 2 to form a high-valent diiron oxo species. This species is a very powerful oxidant which oxidizes methane in pure water at 25–60 °C to methanol, formaldehyde and formic acid. The catalytic activity can significantly be increased in the presence of a diluted acid solution. Thus, a high turnover number of 209 was attained in 0.075 M H 2SO 4. Oxidation of ethylene resulted in the formation of formic acid as a major product and formaldehyde with high turnover numbers. Under optimal conditions, 426 mol HCOOH and 37 mol CH 2O per mole of catalyst were obtained in pure water. The practical and green features of this novel approach (H 2O 2 as the clean oxidant, water as the clean reaction medium, easily accessible solid catalyst) as well as the relevance to biological oxidation (binuclear structure of bio-inspired complex) are of great importance both from practical and fundamental points of view.

Estimation of microbial methane generation and oxidation rates in the municipal solid waste landfill of Kaluga city, Russia

Using a theoretical model and mass isotopic balance, biogas (methane and CO2) released from buried products at their microbial degradation was analysed in the landfill of municipal and non-toxic industrial solid organic waste near Kaluga city, Russia. The landfill contains about 1.34×106 tons of waste buried using a ‘sandwich technique’ (successive application of sand–clay and waste layers). The δ13C values of biogenic methane with respect to CO2 were−56.8 (±2.5) ‰, whereas the δ13C of CO2 peaked at+9.12‰ (+1.4±2.3‰ on average), reflecting a virtual fractionation of carbon isotopes in the course of bacterial CO2 reduction at the landfill body. After passing through the aerated soil layers, methane was partially oxidised and characterised by δ13C in the range of−50.6 to−38.2‰, evidencing enrichment in 13C, while the released carbon dioxide had δ13C of−23.3 to−4.04‰, respectively. On the mass isotopic balance for the δ13C values, the methane production in the landfill anaerobic zone and the methane emitted through the aerated landfill surface to the atmosphere, the portion of methane oxidised by methanotrophic bacteria was calculated to be from 10 to 40% (averaged about 25%). According to the theoretical estimation and field measurements, the annual rate of methane production in the landfill reached about 2.9(±1.4)×109 g C CH4 yr−1 or 5.3(±2.6)×106 m3 CH4 yr−1. The average rates of methane production in the landfill and methane emission from landfill to the atmosphere are estimated as about 53 (±26) g C CH4 m−2 d−1 (or 4 (±2) mol CH4 m−2 d−1) and 33 (±12) g C CH4 m−2 d−1 (or 2.7 (±1) mol CH4 m−2 d−1), respectively. The calculated part of methane consumed by methanotrophic bacteria in the aerated part of the landfill was 13(±7) g C CH4 m−2 d−1 (or 1.1(±0.6) mol CH4 m−2 d−1) on average.

Hydrogeochemical modelling of CO2 equilibria and mass transfer induced by organic–inorganic interactions in siliciclastic petroleum reservoirs

AbstractDifferent feldspar types control complex hydrogeochemical processes in hydrocarbon‐bearing siliciclastic reservoirs, which have undergone different degrees of degradation. To test such processes generically, carbon dioxide equilibria and mass transfers induced by organic–inorganic interactions have been modelled for different hydrogeochemical scenarios. The approach is based on and compared with data from the Norwegian continental shelf (Smith & Ehrenberg 1989) and assumes local thermodynamic equilibrium among solids and fluids. Equilibrating mineral assemblages (different feldspar types, quartz, kaolinite, calcite) are based on the primary reservoir composition. Equilibration and coupled mass transfer were triggered by the addition and reaction of different amounts of CO2, CH4 and H2 (plus acetic acid) at temperatures between 50 and 95°C (323 and 368 K). These components occur in oil fields as products of anaerobic bacterial degradation, hydrolytic disproportionation of hydrocarbons and/or thermal maturation of kerogen. We apply two different computer codes and two different thermodynamic data bases to calculate the results. Reaction of 0.32–0.6 mol CO2, 0.16–0.3 mol CH4 and 0.8–1.5 mol H2 with K‐feldspar, quartz, kaolinite and calcite in 1 l of pore water results in modelled values of 0.3–2.3 mol% CO2 in a multicomponent gas phase that resembles measured data (0.2–1.5 mol%). Similar CO2 contents result from acetic acid addition (CO2, CH4, H2 + 0.016 mol CH3COOH). Equilibration with albite or anorthite reduces the release of CO2 into the multicomponent gas phase dramatically, by 1 or 4 orders of magnitude compared with the equilibration with K‐feldspar. Minor differences in the modelled CO2 content (0.1–0.2 mol%) result from calculations with different computer codes if the same thermodynamic data base is applied. Relevant differences (up to 1.9 mol% CO2) result from calculations using different thermodynamic data bases.

Geological, hydrodynamic and biogeochemical variability of a New Zealand deep-water methane cold seep during an integrated three-year time-series study

Cold seeps are widely distributed on active and passive margins and display considerable temporal variability in terms of gas and fluid expulsion rates and volume, over scales of hours to days. To constrain this variability, two cold seeps, the North and South Tower, located at the Wairarapa Seep site on Opouawe Bank, Cook Strait, New Zealand, were monitored in an integrated geological and biogeochemical study during eight surveys between 2005 and 2008. To ensure sampling of the water column within the flare overlying the seeps the vessel was manoeuvred in response to the backscatter data from a hull-mounted 38 kHz single-beam echo-sounder. High methane concentrations (> 100 nmol l − 1 ) were found within 400–450 m-high flares at both sites, and within an 825 m-high flare at a newly identified seep, southeast of Pahaua Bank. Elevated bottom water methane was also found over newly identified mud volcanoes on the Campbell Bank, Cook Strait. The locations of the seeps appear to be structurally controlled with active methane vents occurring on anticlinal ridges and associated with a 30 m-high normal fault scarp on Opouawe Bank. Fluid flow is facilitated by sedimentary layer permeability properties, structural focusing and dilational fracturing on the crest of a large anticlinal ridge, cored by a seaward-verging reverse fault. The South Tower cold seep did not significantly influence bulk sediment and water column particulates and nutrients, although high bacterial biomass, productivity and methane oxidation rates were associated with elevated methane in the flare. The seep flares exhibited depleted δ 13C–CH 4 values (− 63 to − 70‰), characteristic of shallow biogenic gas sources. Incorporation of the δ 13C–CH 4 and CH 4 concentration data in a mixing model, and comparison of the water residence time with methane oxidation rates, indicated that the primary fate of methane in the flare was dilution. The dissolved methane originating from the seeps was retained in the water column at depths > 700 m, with minimal contribution to atmospheric emissions, as confirmed by surface methane mapping. Nevertheless, the South Tower seep was a significant source of methane with a column-integrated burden below 700 m of 5.6 mmol m − 2 , and an estimated annual emission of 0.5–1 × 10 6 mol CH 4. The structural and tectonic setting of the Wairarapa Seep provides a useful analogue model for other convergent margin cold seeps on the Hikurangi Margin and elsewhere. This unique, three-year integrated study provided valuable insights into the linkage between geological structure and overlying water column biogeochemistry, and confirmed the value of this cold seep site for long-term monitoring.

A thermodynamic analysis of the anaerobic oxidation of methane in marine sediments

Anaerobic oxidation of methane (AOM) in anoxic marine sediments is a significant process in the global methane cycle, yet little is known about the role of bulk composition, temperature and pressure on the overall energetics of this process. To better understand the biogeochemistry of AOM, we have calculated and compared the energetics of a number of candidate reactions that microorganisms catalyse during the anaerobic oxidation of methane in (i) a coastal lagoon (Cape Lookout Bight, USA), (ii) the deep Black Sea, and (iii) a deep-sea hydrothermal system (Guaymas basin, Gulf of California). Depending on the metabolic pathway and the environment considered, the amount of energy available to the microorganisms varies from 0 to 184 kJ mol(-1). At each site, the reactions in which methane is either oxidized to HCO3(-), acetate or formate are generally only favoured under a narrow range of pressure, temperature and solution composition--particularly under low (10(-10 )m) hydrogen concentrations. In contrast, the reactions involving sulfate reduction with H2, formate and acetate as electron donors are nearly always thermodynamically favoured. Furthermore, the energetics of ATP synthesis was quantified per mole of methane oxidized. Depending on depth, between 0.4 and 0.6 mol of ATP (mol CH4(-1) was produced in the Black Sea sediments. The largest potential productivity of 0.7 mol of ATP (mol CH4(-1) was calculated for Guaymas Basin, while the lowest values were predicted at Cape Lookout Bight. The approach used in this study leads to a better understanding of the environmental controls on the energetics of AOM.

Hydrogen production by chemical-looping reforming in a circulating fluidized bed reactor using Ni-based oxygen carriers

This work presents the experimental results obtained during auto-thermal chemical-looping reforming (CLR) in a 900 W th circulating fluidized bed reactor under continuous operation using methane as fuel. Two oxygen carriers based on NiO and supported on γ-Al 2O 3 and α-Al 2O 3 were used during more than 50 h of operation with each oxygen carrier. During operation the effect of different operating variables, like fuel reactor temperature, H 2O/CH 4 molar ratio and solid circulation rate, on CH 4 conversion and gas product distribution was analyzed. It was found that in all operating conditions CH 4 conversion was very high (>98%) and the most important variable affecting to the gas product distribution was the solid circulation rate, that is, NiO/CH 4 molar ratio. Similar gas product distribution was obtained working with both oxygen carriers although at different NiO/CH 4 molar ratios. The oxygen carrier of NiO on α-Al 2O 3 needed lower NiO/CH 4 molar ratio to reach the same gas product composition than the oxygen carrier of NiO on γ-Al 2O 3. Working at optimal operating conditions, 2.5 moles of H 2 per mol of CH 4 could be obtained in this process. During operation the oxygen carrier particles maintained their physical and chemical properties. These results suggest that these oxygen carriers could have a high durability, being suitable oxygen carriers for a CLR system.

Cogeneration of hydrogen and methane from glucose to improve energy conversion efficiency

In order to reutilize the residual solutions derived from hydrogen production and increase the energy conversion efficiency, a novel process of cogenerating hydrogen and methane from glucose using a two-phase anaerobic fermentation process was proposed and investigated. The effects of substrate concentration, weight ratio of inoculation to substrate, pH value and nutrient medium on hydrogen production were studied. The maximum specific hydrogen yield is 2.75 mol H 2/mol glucose when the initial glucose concentration is 1%, the weight ratio of inoculation to substrate is 2:1 and the pH value is 6. The residual solutions derived from hydrogen production were reused to produce methane by methanogen in another reactor. The maximum specific methane yield is 2.13 mol CH 4/mol glucose when the reutilization rates of ethanol, acetic acid, butyric acid, valeric acid, and caproic acid are all above 90%. The cogeneration process can dramatically increase the energy conversion efficiency from 23% (hydrogen only production) to 82%.

Sulphur poisoning of transition metal oxides used as catalysts for methane combustion

Abstract Different bulk metal oxides (NiO, CuO, Mn 2 O 3 , Cr 2 O 3 and Co 3 O 4 ) were prepared and tested for the combustion of methane–air lean mixtures (5000 ppmV of CH 4 ) in presence of SO 2 (40 ppmV). Methane combustion experiments were carried out at ambient pressure, 425 and 625 °C and a space time of 93.3 g h mol CH4 −1 . Catalysts aged (60 h on stream) both in absence and in presence of SO 2 , were characterised by nitrogen physisorption (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature-programmed desorption (TPD-MS) and infrared spectroscopy (DRIFTS). It was observed that Cr 2 O 3 is not deactivated at the studied conditions, whereas all the other materials present fast deactivation in presence of SO 2 . Aged catalysts characterisation reveals that the outstanding behaviour of the Cr 2 O 3 catalyst is caused by the absence of formation of surface sulphates. By contrast, Mn 2 O 3 and Co 3 O 4 are more active than Cr 2 O 3 for methane oxidation in absence of sulphur species, but they are strongly deactivated in presence of SO 2 . Finally, the performance of the Cr 2 O 3 catalysts was compared to the corresponding to Pd/Al 2 O 3 catalyst and to a highly sulphur-tolerant perovskite (La 0.9 Ce 0.1 CoO 3 ) for the oxidation of methane in a real industrial emission from a coke oven, containing different inorganic gases (NH 3 , N 2 , H 2 , H 2 O, CO, CO 2 , SO 2 and H 2 S). Cr 2 O 3 catalyst shows to be also the most stable catalyst for the treatment of these emissions.

Kinetics of the Formation of Poly(Methyldecylsiloxane) by Hydrosilylation of Poly(Methylhydrosiloxane) and 1-Decene

Poly(methylhydrosiloxane) [PMHS], prepared by siloxane equilibration reaction, was used for the hydrosilylation with 1-decene to obtain poly(methyldecylsiloxane) [PMDS]. Pt(0)-1,3- divinyltetramethyldisiloxane complex was used as a catalyst for hydrosilylation reaction. In order to investigate the kinetics of the formation of PMDS, a series of experiments was performed at different reaction temperatures (from 48 to 64 °C) with catalyst concentrations of 7.0 · 10-7 mol of Pt per mol of CH=CH2. All reactions were carried out in bulk, with equimolar amounts of the reacting Si-H and CH=CH2 groups. The course of the reactions was monitored by following the disappearance of the Si-H bands by quantitative infrared spectroscopy. The obtained results show that an induction period occurs at lower reaction temperatures and that the rate of Si-H conversion follows the first-order kinetics.

In Situ Fourier Transform Infrared (FTIR) Study of Nonthermal-Plasma-Assisted Methane Oxidative Conversion

Nonthermal plasma-assisted methane conversion has been widely investigated as a potential low-temperature process. The desired end objective is synthesis gas production, one-step production of liquid oxygenates, or coupling products. Either oxygen or steam or both is used as a second reactant or reactants, to provide additional O atoms and initiate plasma-assisted radical processing. The present paper intends to investigate the various possible products/reactive species that are formed during plasma processing. In situ Fourier transform infrared (FTIR) absorption spectrometry is used to monitor the products/reactive groups. Experiments are performed at room temperature and at low energy inputs (50 kJ/(mol CH4)) in a gas mixture of CH4/O2/N2/H2O (atmospheric humidity). In the absence of oxygen, alkane, alkene, and alkyne groups are formed as the products, which indicates termination reactions. With increasing oxygen concentration (11, 15, and 33%) a gradual shift from alkane to a −CHO group is observed. In...

In vitro cell growth of marine archaeal‐bacterial consortia during anaerobic oxidation of methane with sulfate

Anoxic sediment from a methane hydrate area (Hydrate Ridge, north-east Pacific; water depth 780 m) was incubated in a long-term laboratory experiment with semi-continuous supply of pressurized [1.4 MPa (14 atm)] methane and sulfate to attempt in vitro propagation of the indigenous consortia of archaea (ANME-2) and bacteria (DSS, Desulfosarcina/Desulfococcus cluster) to which anaerobic oxidation of methane (AOM) with sulfate has been attributed. During 24 months of incubation, the rate of AOM (measured as methane-dependent sulfide formation) increased from 20 to 230 micromol day(-1) (g sediment dry weight)(-1) and the number of aggregates (determined by microscopic counts) from 0.5 x 10(8) to 5.7 x 10(8) (g sediment dry weight)(-1). Fluorescence in situ hybridization targeting 16S rRNA of both partners showed that the newly grown consortia contained central archaeal clusters and peripheral bacterial layers, both with the same morphology and phylogenetic affiliation as in the original sediment. The development of the AOM rate and the total consortia biovolume over time indicated that the consortia grew with a doubling time of approximately 7 months (growth rate 0.003 day(-1)) under the given conditions. The molar growth yield of AOM was approximately 0.6 g cell dry weight (mol CH(4) oxidized)(-1); according to this, only 1% of the consumed methane is channelled into synthesis of consortia biomass. Concentrations of biomarker lipids previously attributed to ANME-2 archaea (e.g. sn-2-hydroxyarchaeol, archaeol, crocetane, pentamethylicosatriene) and Desulfosarcina-like bacteria [e.g. hexadecenoic-11 acid (16:1omega5c), 11,12-methylene-hexadecanoic acid (cy17:0omega5,6)] strongly increased over time (some of them over-proportionally to consortia biovolume), suggesting that they are useful biomarkers to detect active anaerobic methanotrophic consortia in sediments.