Showing papers on "Methane published in 2002"
TL;DR: A review of the existing gas separation applications and the expected growth of these and potential new applications of gas separation membranes over the next 20 years are described in this paper, and improvements in gas separation technology needed to produce these changes in the membrane industry are also discussed.
Abstract: During the past 20 years, sales of membrane gas separation equipment have grown to become a $150 million/year business. More than 90% of this business involves the separation of noncondensable gases: nitrogen from air; carbon dioxide from methane; and hydrogen from nitrogen, argon, or methane. However, a much larger potential market for membrane gas separation lies in separating mixtures containing condensable gases such as the C3+ hydrocarbons from methane or hydrogen, propylene from propane, and n-butane from isobutane. These applications require the development of new membranes and processes. In this review, the existing gas separation applications are surveyed, and the expected growth of these and potential new applications of gas separation membranes over the next 20 years are described. The improvements in gas separation technology needed to produce these changes in the membrane industry are also discussed.
1,764 citations
TL;DR: In this article, a review examines recent developments in the complete oxidation of methane at low temperature over noble metal based catalysts in patents and open literature, focusing on low-temperature reaction conditions.
Abstract: This review examines recent developments in the complete oxidation of methane at low temperature over noble metal based catalysts in patents and open literature. The abatement of natural gas vehicle (NGV) methane emissions is taken as one example among possible applications. The review develops current ideas about the properties of palladium and platinum catalysts supported on silica and alumina supports in the complete oxidation of methane under oxidising conditions, focusing on low-temperature reaction conditions. The influence of residual chloride ions on the catalytic activity, the kinetic aspects of the oxidation of methane over these catalysts, the nature of the active sites, the influence of metal particle size and reaction products on the activity, the observed changes in catalytic activity with reaction time and the effect of sulphur containing compounds are examined. The latest studies concerned with improved palladium and platinum supported catalysts which would exhibit enhanced and stable catalytic activity at low temperature in the presence of water and sulphur containing compounds are reported. Possible routes for preparing catalysts able to meet future regulations concerning methane emissions from lean-burn NGV vehicles are discussed.
998 citations
TL;DR: In this paper, the solubility of nine different gases in 1-n-butyl-3-methylimidazolium hexafluorophosphate was investigated.
Abstract: This work presents the solubility of nine different gases in 1-n-butyl-3-methylimidazolium hexafluorophosphate. The gases considered include carbon dioxide, ethylene, ethane, methane, argon, oxygen, carbon monoxide, hydrogen, and nitrogen. We also report the associated Henry's constants and enthalpies and entropies of absorption. We found carbon dioxide to have the highest solubility and strongest interactions with the ionic liquid, followed by ethylene and ethane. Argon and oxygen had very low solubilities and immeasurably weak interactions. Carbon monoxide, hydrogen, and nitrogen all had solubilities below the detection limit of our apparatus. Our results suggest that the mass transfer of gases into ionic liquids likely will be an important issue for reactions involving these gases. We also determined that ionic liquids show good potential for use as a gas-separation medium.
896 citations
TL;DR: In this article, the authors examined past trends in the concentration of methane in the atmosphere, the sources and sinks that determine its growth rate, and the factors that will affect its growth rates in the future.
763 citations
TL;DR: Obviously, anaerobic microbial consortia can generate both carbonate precipitation and substantial biomass accumulation, which has implications for the understanding of carbon cycling during earlier periods of Earth's history.
Abstract: Massive microbial mats covering up to 4-meter-high carbonate buildups prosper at methane seeps in anoxic waters of the northwestern Black Sea shelf. Strong 13C depletions indicate an incorporation of methane carbon into carbonates, bulk biomass, and specific lipids. The mats mainly consist of densely aggregated archaea (phylogenetic ANME-1 cluster) and sulfate-reducing bacteria (Desulfosarcina/Desulfococcus group). If incubated in vitro, these mats perform anaerobic oxidation of methane coupled to sulfate reduction. Obviously, anaerobic microbial consortia can generate both carbonate precipitation and substantial biomass accumulation, which has implications for our understanding of carbon cycling during earlier periods of Earth's history.
720 citations
TL;DR: An improved synthesis process was developed for large-scale production of a highly porous material, [Cu 3 (BTC) 2 (H 2 O) x ] n, i.e., polymeric copper(II) benzene-1,3,5-tricarboxylate with molecular-sieve character, denoted as Cu-BTC as mentioned in this paper.
705 citations
TL;DR: In this paper, a review of the use of catalysts for methane combustion in high temperature natural gas-turbines can be found, where a large amount of work has been undertaken to develop catalysts both for controlling methane emission as well as for generating power.
Abstract: The important greenhouse effect of methane (more than an order of magnitude greater than CO2) makes it essential to eliminate/control the methane emission from natural gas engines/power plants and petroleum industries. Catalytic combustion of methane is favored over homogeneous combustion, because the former greatly facilitates the oxidative destruction of methane. Moreover, use of catalysts for methane combustion in gas-turbines affords lower working temperatures (as compared to gas-fired turbines) and thermodynamically limits NOx (which is an extremely harmful environmental pollutant) emission. A large amount of work has been undertaken to develop catalysts both for controlling methane emission as well as for generating power in high temperature natural gas-turbines. This review will address the different issues related to the variety of catalysts which have been employed for methane/lower alkane combustion. Although all the related important aspects of the combustion catalysts will be addressed, greater emphasis will be placed on recent work in this field.
599 citations
TL;DR: In this paper, the combined information from Arctic gas hydrate studies shows that, in permafrost regions, gas hydrates may exist at subsurface depths ranging from about 130 to 2000 m.
Abstract: The discovery of large gas hydrate accumulations in terrestrial per mafrost regions of the Arctic and beneath the sea along the outer continental margins of the world's oceans has heightened interest in gas hydrates as a possible energy resource. However, significant to potentially insurmountable technical issues must be resolved be fore gas hydrates can be considered a viable option for affordable supplies of natural gas. The combined information from Arctic gas hydrate studies shows that, in permafrost regions, gas hydrates may exist at subsurface depths ranging from about 130 to 2000 m. The presence of gas hydrates in offshore continental margins has been inferred mainly from anomalous seismic reflectors, known as bottom-simulating reflectors, that have been mapped at depths below the sea floor ranging from about 100 to 1100 m. Current estimates of the amount of gas in the world's marine and permafrost gas hydrate accumulations are in rough accord at about 20,000 trillion m3. Disagreements over fundamental issues such as the volume of gas stored within delineated gas hydrate accumulations and the concentration of gas hydrates within hydrate-bearing strata have demonstrated that we know little about gas hydrates. Recently, however, several countries, including Japan, India, and the United States, have launched ambitious national projects to further examine the resource potential of gas hydrates. These projects may help answer key questions dealing with the properties of gas hydrate reservoirs, the design of production systems, and, most important, the costs and economics of gas hydrate production.
543 citations
TL;DR: In this paper, a review of the literature on supported Pd catalysts for combustion of methane is presented, taking into consideration the oxidation/reduction mechanisms for supported palladium, poisoning, restructuring, the form of oxygen on the surface, methane activation over Pd and PdO phases, and transient behavior.
Abstract: Palladium-based catalysts are widely applied in exhaust catalytic converter and catalytic combustion systems. The mechanism for methane oxidation on a Pd-based catalyst is complex. Catalyst activity is influenced by variations in the process pressure and temperature, by the gas mixture composition, by the type of support and various additives, and by pretreatment under reducing or oxidizing atmospheres. In this paper, we review the literature on supported Pd catalysts for combustion of methane. The mechanisms involved are discussed taking into consideration the oxidation/reduction mechanisms for supported palladium, poisoning, restructuring, the form of oxygen on the surface, methane activation over Pd and PdO phases, and transient behavior. Our review helps explain the array of experimental results reported in the literature.
529 citations
TL;DR: The progressive isotopic trends for the series of C1–C4 alkanes indicate that hydrocarbon formation occurs by way of polymerization of methane precursors, and it can now be rule out the presence of a globally significant abiogenic source of hydrocarbons.
Abstract: Natural hydrocarbons are largely formed by the thermal decomposition of organic matter (thermogenesis) or by microbial processes (bacteriogenesis). But the discovery of methane at an East Pacific Rise hydrothermal vent and in other crustal fluids supports the occurrence of an abiogenic source of hydrocarbons. These abiogenic hydrocarbons are generally formed by the reduction of carbon dioxide, a process which is thought to occur during magma cooling and-more commonly-in hydrothermal systems during water-rock interactions, for example involving Fischer-Tropsch reactions and the serpentinization of ultramafic rocks. Suggestions that abiogenic hydrocarbons make a significant contribution to economic hydrocarbon reservoirs have been difficult to resolve, in part owing to uncertainty in the carbon isotopic signatures for abiogenic versus thermogenic hydrocarbons. Here, using carbon and hydrogen isotope analyses of abiogenic methane and higher hydrocarbons in crystalline rocks of the Canadian shield, we show a clear distinction between abiogenic and thermogenic hydrocarbons. The progressive isotopic trends for the series of C1-C4 alkanes indicate that hydrocarbon formation occurs by way of polymerization of methane precursors. Given that these trends are not observed in the isotopic signatures of economic gas reservoirs, we can now rule out the presence of a globally significant abiogenic source of hydrocarbons.
446 citations
TL;DR: Anaerobic oxidation of methane (AOM) and sulphate reduction were examined in sediment samples from a marine gas hydrate area (Hydrate Ridge, NE Pacific) and did not provide evidence for one of these compounds acting as a free extracellular intermediate (intercellular shuttle) during AOM by the presently investigated consortia.
Abstract: Anaerobic oxidation of methane (AOM) and sulphate reduction were examined in sediment samples from a marine gas hydrate area (Hydrate Ridge, NE Pacific). The sediment contained high numbers of microbial consortia consisting of organisms that affiliate with methanogenic archaea and with sulphate-reducing bacteria. Sediment samples incubated under strictly anoxic conditions in defined mineral medium (salinity as in seawater) produced sulphide from sulphate if methane was added as the sole organic substrate. No sulphide production occurred in control experiments without methane. Methane-dependent sulphide production was fastest between 4 degree C and 16 degree C, the average rate with 0.1 MPa (approximately 1 atm) methane being 2.5 micro mol sulphide day(-1) and (g dry mass sediment)(-1). An increase of the methane pressure to 1.1 MPa (approximately 11 atm) resulted in a four to fivefold increase of the sulphide production rate. Quantitative measurements using a special anoxic incubation device without gas phase revealed continuous consumption of dissolved methane (from initially 3.2 to 0.7 mM) with simultaneous production of sulphide at a molar ratio of nearly 1:1. To test the response of the indigenous community to possible intermediates of AOM, molecular hydrogen, formate, acetate or methanol were added in the absence of methane; however, sulphide production from sulphate with any of these compounds was much slower than with methane. In the presence of methane, such additions neither stimulated nor inhibited sulphate reduction. Hence, the experiments did not provide evidence for one of these compounds acting as a free extracellular intermediate (intercellular shuttle) during AOM by the presently investigated consortia.
TL;DR: In this paper, the authors identify three distinct active fluid regimes at Hydrate Ridge, where the bulk of the flow occurs through channels in which gas velocities reach 1 m s−1.
TL;DR: In this paper, the performance of different carbon materials in methane storage has been studied, including physically activated carbon fibres (ACFs), chemically activated carbons (ACs), activated carbon monoliths (ACMs), and activated carbon cloths and felts.
TL;DR: This review will consider the microbial ecology and biogeochemistry of anaerobic methane oxidation with a special emphasis on the interactions between the responsible organisms and their environment.
Abstract: Evidence supporting a key role for anaerobic methane oxidation in the global methane cycle is reviewed Emphasis is on recent microbiological advances The driving force for research on this process continues to be the fact that microbial communities intercept and consume methane from anoxic environments, methane that would otherwise enter the atmosphere Anaerobic methane oxidation is biogeochemically important because methane is a potent greenhouse gas in the atmosphere and is abundant in anoxic environments Geochemical evidence for this process has been observed in numerous marine sediments along the continental margins, in methane seeps and vents, around methane hydrate deposits, and in anoxic waters The anaerobic oxidation of methane is performed by at least two phylogenetically distinct groups of archaea, the ANME-1 and ANME-2 These archaea are frequently observed as consortia with sulfate-reducing bacteria, and the metabolism of these consortia presumably involves a syntrophic association based on interspecies electron transfer The archaeal member of a consortium apparently oxidizes methane and shuttles reduced compounds to the sulfate-reducing bacteria Despite recent advances in understanding anaerobic methane oxidation, uncertainties still remain regarding the nature and necessity of the syntrophic association, the biochemical pathway of methane oxidation, and the interaction of the process with the local chemical and physical environment This review will consider the microbial ecology and biogeochemistry of anaerobic methane oxidation with a special emphasis on the interactions between the responsible organisms and their environment
TL;DR: In this paper, the classical hybrid combustion theory is generalized to solid fuels that form a liquid layer on their burning surface, leading to substantial droplet entrainment into the gas stream.
Abstract: In this paper classical hybrid combustion theory is generalized to solid fuels that form a liquid layer on their burning surface. For several classes of liquefying fuels, the layer is hydrodynamically unstable in a gas e ow environment leading to substantial droplet entrainment into the gas stream. The susceptibility of a given fuel to this shear driven instability increases with decreasing viscosity and surface tension of the melt layer. The entrainment mass transfer, which acts in addition to the conventional gasie cation mechanism, is not affected by the blocking phenomenon induced by blowing from the surface. For practical oxidizer e ux levels encountered in hybrid rocket applications, droplet entrainment can dominate direct gasie cation. Such liquefying fuels can exhibit greatly increased surface regression rates compared to classical materials such as Hydroxyl Terminated Polybutadiene. One application of the theory is to solid cryogenic hybrids, which utilize frozen materials for the solid propellant. The theory successfully predicts why high regression rates are observed in tests of cryogenic solid pentane, solid methane, and solid oxygen. In addition, the theory explains the dependence of the burning rates of other tested cryogenic materials on the physical properties of the liquid layer. The theory also leads to the conclusion that certain noncryogenic materials such as parafe n and Polyethylene waxes will also exhibit high regression rates. This important result is cone rmed by lab scale tests performed at Stanford University on a high melting point parafe n wax.
TL;DR: In this paper, the authors present new high-resolution stable isotope records based on analyses of single planktonic and benthic foraminiferal shells from Ocean Drilling Program Site 690.
Abstract: Dramatic warming and upheaval of the carbon system at the end of the Paleocene Epoch have been linked to massive dissociation of sedimentary methane hydrate. However, testing the Paleocene-Eocene thermal maximum hydrate dissociation hypothesis has been hindered by the inability of available proxy records to resolve the initial sequence of events. The cause of the Paleocene-Eocene thermal maximum carbon isotope excursion remains speculative, primarily due to uncertainties in the timing and duration of the Paleocene-Eocene thermal maximum. We present new high-resolution stable isotope records based on analyses of single planktonic and benthic foraminiferal shells from Ocean Drilling Program Site 690 (Weddell Sea, Southern Ocean), demonstrating that the initial carbon isotope excursion was geologically instantaneous and was preceded by a brief period of gradual surface-water warming. Both of these findings support the thermal dissociation of methane hydrate as the cause of the Paleocene-Eocene thermal maximum carbon isotope excursion. Furthermore, the data reveal that the methane-derived carbon was mixed from the surface ocean downward, suggesting that a significant fraction of the initial dissociated hydrate methane reached the atmosphere prior to oxidation.
01 Jan 2002
TL;DR: In this paper, the propagation and morphology of spark-ignited expanding spherical methane flames were imaged using schlieren cinematography and a high-speed digital camera, and stretch-free laminar burning velocities were subsequently determined for methane/air flames up to 20 atm and methane/oxygen/helium flame up to 60 atm.
Abstract: Using a specially designed high- and constant-pressure combustion chamber, the propagation and morphology of spark-ignited expanding spherical methane flames were imaged using schlieren cinematography and a high-speed digital camera. Stretch-free laminar burning velocities were subsequently determined for methane/air flames up to 20 atm and methane/oxygen/helium flames up to 60 atm. Computational simulation using GRI-MECH 3.0 showed satisfactory agreement with the experimental data up to 20 atm, and moderate deviation for pressures above 40 atm. Markstein lengths, global activation energies, and overall reaction orders were also determined as functions of pressure, with the latter two parameters exhibiting non-monotonic behavior caused by the changeover from H-O2 to HO2 chemistry similar to that of the explosion limits of homogeneous hydrogen/oxygen mixtures.
TL;DR: In this article, the use of metal alloys as anodes for the direct oxidation of methane in solid-oxide fuel cells (SOFC) at 1073 K was examined and shown that carbon formation is greatly suppressed on the Cu-Ni alloys compared to that of pure Ni.
Abstract: We have examined the use of Cu-Ni alloys as anodes for the direct oxidation of methane in solid-oxide fuel cells (SOFC) at 1073 K. Ceramic-metal (cermet) composites having alloy compositions of 0, 10, 20, 50 and 100% Ni were exposed to dry methane at 1073 K for 1.5 h to demonstrate that carbon formation is greatly suppressed on the Cu-Ni alloys compared to that of pure Ni. Increased reduction temperatures also reduced the carbon formation on the alloys. The performance of a fuel cell made with a Cu(80%)-Ni(20%) cermet was tested in dry methane for 500 h and showed a significant increase in power density with time. Impedance spectra of similar fuel cells suggest that small carbon deposits are formed with time and that the increase in performance is due to enhanced electronic conductivity in the anode. Finally, the implications of the use of metal alloys for SOFC applications are discussed.
01 Jan 2002
TL;DR: In this paper, a premixed, swirl-stabilized flame was studied to determine the effects of enriching methane with hydrogen under fuel-lean conditions, and the results showed that the addition of a moderate amount of hydrogen to the methane/air mixture increased the peak OH concentration.
Abstract: The combustion characteristics of a premixed, swirl-stabilized flame were studied to determine the effects of enriching methane with hydrogen under fuel-lean conditions. The burner consisted of a center-body with an annular, premixed fuel-air jet. Swirl was introduced to the flow using 45-degree swirl vanes. The combustion occurred within an air-cooled quartz chamber at atmospheric pressure. Flame stability and blowout maps were obtained for different amount of hydrogen addition at several fuel-air flow rates. Gas probe measurements were obtained to demonstrate reductions in CO concentration with hydrogen addition, without adversely affecting the NO x emissions. The flame structure near the lean stability limit was described by direct luminous photographs and planar laser-induced fluorescence measurements of the OH radical. Results show that the addition of a moderate amount of hydrogen to the methane/air mixture increased the peak OH concentration. Hydrogen addition resulted in a significant change in the flame structure, indicated by a shorter and more robust appearing flame. The observed trends concur with the strained opposed premixed flame analysis using RUN-1DL. The computations revealed that enriching the methane with hydrogen increased the strain resistance of the flame as well as the OH levels in the flame.
TL;DR: In this article, the relationship between the catalytic performance of the binary MgO-based solid solution and its properties in the CO2 reforming, the partial oxidation and the steam reforming of methane is discussed.
Abstract: The excellent catalytic performance and high stability of MgO–NiO solid solution catalysts in CH4 conversion to syngas generated the recent outburst of interest for the binary MgO-based solid solutions. This review will focus on the relationship between the catalytic performance of the binary MgO-based solid solution and its properties in the CO2 reforming, the partial oxidation and the steam reforming of methane. First, the development of methane conversion to syngas will be summarized. Second, the role of the basicity and of the solid solution in the design of a catalyst that can inhibit carbon deposition and active metal sintering will be examined. Third, the main results regarding the catalytic performance of the MgO-based solid solutions will be presented. Fourth, detailed information regarding the effects of the NiO/MgO composition, surface area, pore distribution, crystal lattice parameter, precursors, and preparation condition on its catalytic behavior will be provided.
TL;DR: A preliminary global estimate indicates that there are likely more than enough sources to provide the amount of methane required to account for the suspected missing source of fossil CH4.
TL;DR: In this paper, the authors suggested that these geological sources and reservoirs influence the direction and speed of global climate change, and constrain the extremes of climate, and suggested that, together, they can be used as positive and negative feedback to global warming and global cooling.
Abstract: Geological methane, generated by microbial decay and the thermogenic breakdown of organic matter, migrates towards the surface (seabed) to be trapped in reservoirs, sequestered by gas hydrates or escape through natural gas seeps or mud volcanoes (via ebullition). The total annual geological contribution to the atmosphere is estimated as 16–40 Terragrammes (Tg) methane; much of this natural flux is ‘fossil’ in origin. Emissions are affected by surface conditions (particularly the extent of ice sheets and permafrost), eustatic sea-level and ocean bottom-water temperatures. However, the different reservoirs and pathways are affected in different ways. Consequently, geological sources provide both positive and negative feedback to global warming and global cooling. Gas hydrates are not the only geological contributors to feedback. It is suggested that, together, these geological sources and reservoirs influence the direction and speed of global climate change, and constrain the extremes of climate.
TL;DR: In this paper, the effect of Ni content on the Ni/Ce-ZrO2 catalyst has been investigated in the methane conversion reactions to syngas, such as oxy-reforming, steam reforming and oxy-steam reforming.
Abstract: The effect of Ni content on the Ni/Ce-ZrO2 catalyst has been investigated in the methane conversion reactions to syngas, such as oxy-reforming, steam reforming and oxy-steam reforming. Among the catalysts examined, Ni/Ce-ZrO2 catalyst with 15% Ni loading exhibits not only the highest catalytic activity and selectivity but also remarkable stability. The TPR results reveal that strong interaction between support and metal exists and that some part of NiO incorporates into the surface of the Ce-ZrO2 support. Combined with H2 chemisorption results, one may deduce that Ni surface area and the chemical environment of nickel, as well as the properties of the Ce-ZrO2 support, play very important roles in the catalytic activity and stability of Ni/Ce-ZrO2 catalysts. It seems that two kinds of active sites, i.e. one for methane and the other for steam or oxygen, are well-balanced on 15% Ni/Ce-ZrO2 catalyst.
TL;DR: Effect of dyes and salts present in textile wastewater on methanogenesis was evaluated based on maximum methane production and methanogenic activity and it was observed that the black dye concentration of 400 mg/l seemed to cause inhibition of meethanogenesis.
TL;DR: In this article, the authors investigated the effect of MgO, CaO, SrO and CeO2 addition to Ni-Y2O3-stabilized zirconia (Ni-YSZ) cermets anodes on their catalytic activity and carbon deposition.
TL;DR: In this paper, an anode support planar SOFC with a 4×4-cm2 active area was fabricated with LSM (La 0.78Sr0.22MnxO3), 8YSZ and Ni/YSZ.
TL;DR: In this article, the structural transformations of water around methane during methane hydrate formation have been studied using neutron diffraction with isotope substitution over the temperature range 4-18°C and at pressures of 3.4-14.5
TL;DR: It is suggested that gas-rich vertical intrusions into the hydrate stability zone are associated with upward flow of warmer fluids, which implies that significantly more methane hydrate lies close to being unstable and hence closer to dissociation in the event of a lowering of pressure due to sea-level fall.
Abstract: Below water depths of about 300 metres, pressure and temperature conditions cause methane to form ice-like crystals of methane hydrate. Marine deposits of methane hydrate are estimated to be large, amassing about 10,000 gigatonnes of carbon, and are thought to be important to global change and seafloor stability, as well as representing a potentially exploitable energy resource. The extent of these deposits can usually be inferred from seismic imaging, in which the base of the methane hydrate stability zone is frequently identifiable as a smooth reflector that runs parallel to the sea floor. Here, using high-resolution seismic sections of seafloor sediments in the Cascadia margin off the coast of Vancouver Island, Canada, we observe lateral variations in the base of the hydrate stability zone, including gas-rich vertical intrusions into the hydrate stability zone. We suggest that these vertical intrusions are associated with upward flow of warmer fluids. Therefore, where seafloor fluid expulsion and methane hydrate deposits coincide, the base of the hydrate stability zone might exhibit significant roughness and increased surface area. Increased area implies that significantly more methane hydrate lies close to being unstable and hence closer to dissociation in the event of a lowering of pressure due to sea-level fall.
TL;DR: In this article, the potential for high gas content is controlled directly by the amount of thermogenic and secondary biogenic gases generated from the coal which in turn are controlled by burial history, maceral composition, and basin hydrodynamics.