Carbon-containing Gases Research Articles

Heterogeneous iron-containing carbon gels as catalysts for oxygen electroreduction: Multifunctional role of sulfur in the formation of efficient systems

(Co)polycondensation of resorcinol and heterocyclic aldehydes yields heteroaromatic porous polymers. Carbonization of such polymers results in N-doped, S-doped, N/S-co-doped or undoped carbon gels depending on the starting composition of reactants. If the (co)polycondensation is initiated with FeCl3, Fe-containing carbon gels are obtained. Depending on the nature of the heteroatom doping (solely N or S, both N and S or no heteroatom) the Fe-containing carbon gels exhibit distinct structural properties. While the presence of sulfur hinders Fe-driven graphitization, yielding carbons with high specific surface area (SSA), N-doping exhibits the contrary effect, resulting in highly graphitic structures with low SSAs. More importantly, increasing the Fe content in the N/S-co-doped carbons results in remarkable increases in microporosity, yielding materials with SSA of up to 1240 m2g-1. The Fe-containing carbon gels are considered non-precious metal catalysts for the oxygen reduction reaction. It is demonstrated that in the case of Fe/N/C/S type catalysts, the interaction between S, C and Fe (at the pyrolysis stage) results in the enhancement of microporosity, where S acts as a soft oxidant toward carbon, while Fe recaptures the sulfur- and carbon-containing pyrolytic gases. The incidental deposition of pyrolytic gases contributes significantly to the final structure of the catalysts.

In-Situ Investigation on the Crystal and Microstructure Change of Nickel Interacted with Methane at High Temperatures

The solid oxide fuel cell (SOFC) is a novel electricity generation technology which converts the chemical energy of fuels into electrical power, with high efficiency and low pollution. One of the superiors of SOFCs over other kinds of fuel cell is that carbon-containing fuels can be directly used, leading to much lower operation cost. Nickel cermet is the most commonly used anode material for SOFCs. However, nickel promotes carbon deposition reaction, which results in significant performance degradation, when carbon-containing fuels are used. While there have been quite a few studies on replacing nickel with other materials in the anode of SOFCs operated with carbon-containing fuels, none of the alternatives can surpass nickel for practical application. Meanwhile, there are some evidences showing that carbon can be used as a fuel for SOFCs (the so-called direct carbon solid oxide fuel cells, DC-SOFCs), suggesting that carbon itself is not the cause of deactivation of Ni-based anode exposed to carbon-containing fuels in SOFCs. It is the interaction between nickel and carbon-containing gas that destroys the structure of nickel bulk, resulting in pulverization of the anode. Some previous researches have shown that carbon fiber may grow when transition metals, including nickel, are exposed to carbon-containing gases. The crystal lattice and microstructure changes were assumed but rarely verified by direct experimental evidences. In this report, we present our recent work of in situ investigation on the crystal lattice and microstructure changes of nickel-based bulk interacted with methane at high temperatures. In situ thermal expansion measurements are carried out, using a thermal dilatometer, on Ni-YSZ bulk samples exposed to methane at temperatures of 650 and 800°C, respectively. The samples for the thermal dilatation measurements are of cylindrical shape with relatively thin wall. In situ XRD characterizations are carried out on Ni-YSZ powder, which also exposed to methane at 650 and 800°C, respectively. The thermal dilatation measurement results show that the Ni-YSZ bulk expands when it is exposed to methane at both 650 and 800°C. The expansion leads to the bulk broken or destroyed. At 800°C, the time it takes, from the moment of nickel exposed to methane to that when it is destroyed, is 14 minutes, which is 4 times shorter than that it takes at 650°C, 70 minutes. Room temperature TEM measurements show that carbon deposits on nickel interacted with methane at 800°C is in the form of encapsulation while that of 650°C is carbon fiber. The in situ XRD characterizations show that when nickel is exposed to methane, its crystal lattice parameter increases, both in the situations of 650 and 800°C. At the beginning of nickel exposed to methane (i.e., 10 minutes) at 650°C, its crystal lattice parameter increases. However, the increased parameter reduces almost back to the initial value after a while (i.e., 20 minutes). In the situation of nickel exposed to methane at 800°C, its lattice parameter increases to maximum in 10 minutes and the value is stable in the following time. The above experimental results are analyzed and discussed in detail in the report.

Global climatology based on the ACE-FTS version 3.5 dataset: Addition of mesospheric levels and carbon-containing species in the UTLS

In this paper, we present a new climatology based on the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) version 3.5 data set from February 2004 to February 2013. This extends the ACE-FTS climatology to include profile information in the mesosphere and carbon-containing species in the upper troposphere and lower stratosphere. Climatologies of 21 species, based on nine years of observations, are calculated, providing the most comprehensive and self-consistent climatology available from limb-viewing satellite measurements. Pressure levels from the upper troposphere to the mesosphere and lower thermosphere are included with ~3 to 4km vertical resolution up to 10−4hPa (~105km). Volume mixing ratio values are filtered prior to the climatology estimation using the ACE-FTS data quality recommendations. The multi-year mean climatology contains zonal mean profiles for monthly and three-monthly (DJF, MAM, JJA, and SON) periods. These are provided with 5-degree spacing in either latitude or equivalent latitude. Also, the local daytime and nighttime distributions are provided separately for nitrogen-containing species, enabling diurnal differences to be investigated. Based on this climatology, examples of typical spatiotemporal patterns for trace gases in the mesosphere and for carbon-containing gases in the upper troposphere and lower stratosphere are discussed.

Comparative study of degradation of trans-1,3,3,3-trifluoropropene, 2,3,3,3-tetrafluoropropene, perfluoro-3-methylbutanone-2, and sulfur hexafluoride in dielectric-barrier discharge

Degradation of gaseous dielectrics after aging in barrier discharge has been experimentally studied and comparative analysis of their properties has been performed. The gases used as gaseous dielectrics have been trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)), 2,3,3,3-tetrafluoropropene (HFO-1234yf), perfluoro-3-methylbutanone-2 CF3C(O)CF(CF3)2, and sulfur hexafluoride SF6. The product composition of gas degradation before and after 5-h aging in the barrier discharge has been determined by gas chromatography–mass spectrometry and gas chromatography. According to the measurement data, 2,3,3,3-tetrafluoropropene is less prone to degradation and has the highest dielectric strength among the test carbon-containing gases.

Life Cycle Assessments of Ethanol Production via Gas Fermentation: Anticipated Greenhouse Gas Emissions for Cellulosic and Waste Gas Feedstocks

LanzaTech has developed novel microbial bioreactor systems capable of direct gas fermentation to produce ethanol from carbon-containing gases. In this study, a life-cycle assessment method is used to quantify the global warming potential of several scenarios for producing renewable ethanol with the LanzaTech process. Scenarios considering ethanol produced from steel mill waste gases or biomass (corn stover, forest residue, or switchgrass, via gasification) have been considered, using input data from peer-reviewed literature, government reports, life cycle inventory databases, and LanzaTech process engineering estimates. Using standardized life-cycle assessment methods, ethanol produced via LanzaTech fermentation appears to result in greenhouse gas emissions that are at least 60% lower than that of conventional fossil gasoline, with biomass-based ethanol achieving close to 90% emission reductions. Results indicate that the LanzaTech gas fermentation technology can be a viable alternative for producing next...

Synthesis and electronic structure of graphene on a nickel film adsorbed on graphite

The formation of graphene on the surface of a nickel thin film on a highly oriented pyrolytic graphite substrate has been investigated using the photoelectron spectroscopy methods. It has been shown that the formation of graphene occurs through the phase of surface nickel carbide with the Ni2C stoichiometry, which is formed already at a temperature of 180°C. During the subsequent heating, the nickel carbide phase transforms into a graphene monolayer strongly bound to the surface. All the phase transitions have been thoroughly analyzed in terms of the fine structure of the photoelectron lines. The surface morphology has been examined using atomic force microscopy, and the obtained data have been presented. It has been especially emphasized that the advantage of the studied method of a “solid-state” source of carbon is the possibility of the formation of graphene at lower temperatures (at least no higher than 280°C) as compared to the cracking of carbon-containing gases, which requires the temperature ranging from 400 to 500°C.

Surface geochemical measurements applied to monitoring, verification, and accounting of leakage from sequestration projects

A detailed study of [Formula: see text] and [Formula: see text] surface fluxes, shallow soil gas composition, 10-m hole soil gas composition was made at Rangely, Colorado, Teapot Dome, Wyoming, USA, and the results of geochemical verification measurements at Weyburn, Saskatchewan, Canada. Summer and winter soil gas and gas flux measurements were made at Rangely, and winter only at Teapot Dome. The objectives were to determine if leakage of [Formula: see text] and/or [Formula: see text] could be detected in the overpressured Rangely and the underpressured Teapot Dome systems. At Weyburn, the objective was the determination of the presence or absence of an alleged leak. Seasonal surface [Formula: see text] fluxes at Rangely were similar at on-field locations and an off-field control area. Methane fluxes were much higher at on-field locations than in the control area, suggesting a reservoir source. Seasonal differences in [Formula: see text] fluxes suggested methanotrophic oxidation was occurring in the soils. Shallow soil gas concentration measurements of [Formula: see text] were similar at a 100-cm depth, on-field and in the control area. Methane soil gas concentrations were higher on-field than in the control area; summer and winter. These data were used to select locations with and without evidence for seepage allowing nested sampling up to a 10-m depth. More complex chemical and isotopic measurements were made in 10-m holes at Rangely and Teapot Dome. Methanotrophy was operational at the active Rangely and the passive Teapot Dome systems. A small methane leakage rate of 400–700 tonnes [Formula: see text] and [Formula: see text] of [Formula: see text] tonnes [Formula: see text] were determined at Rangely, and rates near zero at Teapot Dome. Inert gases, carbon-containing gases, as well as isotopic ratios supported the presence of pathways at geochemically anomalous locations at Teapot Dome. Measurements of soil gas and inert gas isotopes in shallow groundwater by other authors at Weyburn, Saskatchewan, found no evidence of leakage.

Kinetic study of steam gasification of two mineralogically different lignite chars: An active site/intermediate model

A new active site/intermediate model (ASIM) is formulated in terms of a simplified calcium-catalyzed mechanism of char gasification to characterize a conversion-dependent maximum in reaction rate. In a limited case, the model is retrogressed to a common volumetric model (VM). Two sets of kinetic data were experimentally gathered by steam gasification of two lignite chars in a fixed bed reactor with negligible mass diffusion limitation. The gasification behaviors of two chars were, respectively, representative of catalyzed and uncatalyzed gasification as a result of the influences of different mineral components in them. It was found that ASIM intimately fit the kinetic profiles over the entire range of conversion for both catalyzed and uncatalyzed char gasification, demonstrating the good adaptability to varying chars. The model could determine the activation energies for the formation of the total carbon-containing gases and of two individual gases (CO and CO2) from the oxygenated intermediate. Moreover, for the case of catalyzed gasification, ASIM reasonably predicted the formation, growth and decline of the intermediate with carbon conversion as well as the change in the intermediate concentration with gasification temperature. For the case of uncatalyzed gasification, the model portrayed essentially a linear decline in the intermediate concentration with increasing carbon conversion, similar to VM.

Deactivation of nickel-based anode in solid oxide fuel cells operated on carbon-containing fuels

Deactivation of Ni–YSZ (yttrium stabilized zirconia) anode of SOFCs operated on CH4 and CO, respectively, is investigated systematically. Experiments show that the rate of carbon deposition on Ni–YSZ substrate from CH4 increases with temperature in the whole testing temperature range (550–800 °C), while the rate from CO increases with temperature at lower temperatures but decreases at higher temperatures. Larger amount of carbon deposit results in more significant substrate deformation and destruction, which can be explained by the mechanism of carbon fiber growth on Ni exposed to carbon-containing gases. Carbon deposition can be avoided by oxygen ion flux through the electrolyte of SOFCs operated on either CH4 or CO.

Trace gas and particle emissions from open burning of three cereal crop residues: Increase in residue moistness enhances emissions of carbon monoxide, methane, and particulate organic carbon

We determined emission factors for open burning of straw of rice, wheat, and barley, as well as rice husks, and we incorporated the effects of moisture content on the emission factors for the straw. A closed system that simulated on-site backfiring of residues on the soil surface under moderate wind conditions was used to measure the gas and particle emissions from open burning of the residues on an upland field. Two moisture content conditions were evaluated: a dry condition (air-dried residues, 11–13% by weight) and a moist condition (20%). When a linear regression model with the initial moisture content of the residue as the explanatory variable showed good correlation between the primary emission data of a substance and the moisture content, the regression model was adopted as a function to give the emission factors. Otherwise, the unmodified primary data were used as the emission factors. The magnitudes of the gas and particle emissions differed among the residue types. For example, carbon monoxide (CO) emissions from straw of rice, wheat, and barley and rice husks burned under the dry condition were 27.2 ± 1.7, 41.8 ± 24.2, 46.9 ± 2.1, and 66.1 g kg−1 dry matter, and emissions of methane (CH4) were 0.75 ± 0.01, 2.01 ± 0.93, 1.47 ± 0.06, and 5.81 g kg−1 dry matter, respectively (n = 2 for straw with the standard deviation; n = 1 for husks). Emissions of carbon-containing gases and particles (e.g., CO, CH4, and particulate organic carbon) were higher under the moist condition than under the dry condition, which suggests that emission factors for open burning should incorporate the effects of moisture content except open burning performed in the dry season or arid zones.

Functions of amorphous carbon in catalyst fabrication for carbon nanofiber growth in the poly(ethylene glycol) thermal decomposition method

To investigate the growth mechanism of carbon nanofibers (CNF) through a process using the thermal decomposition of poly(ethylene glycol) (PEG), we researched the phenomena that occurred from PEG decomposition to CNF growth during a temperature elevation process of CNF synthesis. In the PEG thermal decomposition method, the selective synthesis of platelet CNF (PCNF) and cup-stacked CNF was accomplished by changing only the ramp rate (without any other difference in experimental conditions). As a result, it was confirmed that carbon-containing gases generated by PEG thermal decomposition were converted to amorphous carbon and deposited on the substrate. There was a clear correlation between the amount of deposited amorphous carbon and the size of the nickel catalyst particle for CNF growth. Therefore, in the PEG thermal decomposition method, amorphous carbon deposition was found to be important to control the dispersity and morphology of the catalyst particle, and it was probably crucial to the determination of the type of CNF. In addition, the PCNF prepared in this study showed multidirectional growth from polyhedral catalyst particles, and this could be why the PEG thermal decomposition was able to create PCNF with small diameters compared to PCNF synthesized by conventional methods.

Problems of climate as a problem of optics

This paper discusses the causes of present-day climate changes, obtained at S. I. Vavilov State Optical Institute in recent years. The main conclusions relate to the relationship of the contribution of natural sources (solar-geomagnetic activity) and anthropogenic sources of action on the weather and climate. It is shown that the determining mechanisms for controlling the weather-climatic characteristics are the processes of aerospace physical optics. The main source of the global warming observed in recent decades is an increase in solar activity on a secular scale, the chief channel of action of solar-geomagnetic activity is the control of the condensation-cluster mechanism of cloud nucleation, and the strongest energy effect is the regulation of the thermal radiation fluxes of the underlying surface by optically thin clouds. The greenhouse effect based on carbon-containing gases makes an insignificant contribution to global warming.

A model for remote estimation of ultraviolet absorption by chromophoric dissolved organic matter based on the global distribution of spectral slope

Absorption of ultraviolet radiation (UV, 280–400nm) by chromophoric dissolved organic matter (CDOM) precedes a host of light-sensitized surface ocean processes relevant to global climate. These include photo- and biogeochemical cycling of organic material, release of sulfur and carbon-containing gases to the atmosphere, and the photoprotection of marine microorganisms. Synoptic CDOM absorption data in the UV is highly desired yet difficult to estimate by satellite methods as the atmosphere interferes with direct detection of water-leaving UV radiance. The absorption spectrum of CDOM is typically modeled as an exponential function in which a spectral slope parameter, S, describes the rate of decrease in absorption with increase in wavelength. Significant functional relationships are observed in aquatic environments between S and the CDOM absorption coefficient at 443nm, aCDOM(443). In this paper, we use a large, systematic dataset of spectroscopic CDOM measurements from the U.S. CO2/CLIVAR Repeat Hydrography Survey to examine the relationship between S and aCDOM(443) as a means to model aCDOM(λ) in the UV from ocean color. Our resultant model predicts aCDOM(λ) at wavelengths from 325 to 412nm from the absorption coefficient of colored dissolved and detrital materials (CDM) at 443nm, aCDM(443), retrieved by an existing semi-analytical ocean color algorithm. Expected agreement (near 1:1) with the training dataset was achieved (r2=0.71–0.85, p=0, n=127). Considering inherent satellite data uncertainties as well as the model's limitations in regions with potential terrestrial influence, good correspondence between modeled and in situ values was observed during independent validation with open ocean CDOM data, such as from BIOSOPE (r2=0.77–0.85, p<0.05, n=29). The model has immediate application in global scale assessments of photochemical rate processes and CDOM cycling in the open ocean due to its simplicity and optimization using a large base of field data (>7500 samples) from diverse Case I waters.

The role of solar activity in global warming

The author associates the recently observed climate warming and carbon dioxide concentration growth in the lower atmospheric layers with variations of solar-geomagnetic activity in global cloud formation and the significant decrease in the role of forests in carbon dioxide accumulation in the process of photosynthesis. The contribution of the greenhouse effect of carbon-containing gases to global warming turns out to be insignificant.

In Situ Production of Ni Catalysts at the Tips of Carbon Nanofibers and Application in Catalytic Ammonia Decomposition

Ni-carbon nanofibers (Ni-CNFs) catalysts were synthesized in situ by the decomposition of carbon-containing gases (i.e., CH4, CO, and C2H4) over Ni/Al2O3 catalyst and directly used to catalyze ammonia decomposition. The results showed that Ni nanoparticles were found to locate at the tips of CNFs when using CH4 and CO as carbon sources, while they located at the roots of CNFs when using C2H4 as a carbon source. For ammonia decomposition, Ni catalysts at the tips of CNFs showed higher activity, which could be due to the more accessible surfaces to the reactants. Interestingly, the Ni catalyst at the tips of CNFs with CH4 as a carbon source exhibited higher activity than that with CO as a carbon source, even though the former catalyst had a larger average particle size. The possible mechanism was given by combining characterization results with our previous simulation results. Finally, when using CH4 as a carbon source, the effect of the Ni-CNFs catalysts with different growth times on the activity was further studied.

Effect of active gas mixtures on the efficiency of plasma surface hardening

Investigations were carried out into the possibilities of obtaining special properties of the surface of a metal by a moving nitrogen-containing direct action plasma arc. Analysis of the calculated and experimental data indicates the effect of ‘freezing’ of nitrogen after implantation in the surface layer (up to 100 μm thick) as a result of a reduction of the rate of desorption from the surface and diffusion into the metal. At the same time, nitrogen dissolves to the concentration required for the formation of iron nitrides of different phase composition, and the metal with higher wear resistance of the surface layer can be produced. When carbon-containing gases are added to the mixture, the hardness and endurance limit of the surface of the metal increase.

Characteristics of Carbon-containing Gases Release During Combustion of Main Arbor in Heilongjiang Province of China

Abstract Based on the study on spatiotemporal pattern of fires in forestry areas in Heilongjiang Province of China, outside field investigation is combined with indoor experiment to calculate the emission amount of carbon-containing gases and emission factors when combustible material coming from fourteen main arbor trees combust via emission factor method in forestry areas in Heilongjiang Province. The results showed that CO2 is the main components generated by combustible material of trees when they burn. The emission amount of carbon-containing gases remain diverse when different tree species combust but to varying degrees. The average value is 54531.82 14612.08 1269.27 respectively. The CO2 emission factors of each tree species are significantly higher than other gases. The average value of CO2 CO CxHy factors are 2.6827 g·kg-1 0.5800 g·kg-1 0.0264 g·kg-1 respectively. The average value of emission amount given off by five kilogram test sample is 5802.54mg 1398.18mg 82.06mg. The average total emission amount of carbon-containing gases is 7282.78mg.

Toward CH4dissociation and C diffusion during Ni/Fe-catalyzed carbon nanofiber growth: A density functional theory study

First-principles calculations have been performed to investigate CH(4) dissociation and C diffusion during the Ni∕Fe-catalyzed growth of carbon nanofibers (CNFs). Two bulk models with different Ni to Fe molar ratios (1:1 and 2:1) are constructed, and x-ray diffraction (XRD) simulations are conducted to evaluate their reliability. With the comparison between the calculated and experimental XRD patterns, these models are found to be well suited to reproduce the crystalline structures of Ni∕Fe bulk alloys. The calculations indicate the binding of the C(1) derivatives to the Ni∕Fe closest-packed surfaces is strengthened compared to that on Ni(111), arising from the upshift of the weighted d-band centers of catalyst surfaces. Then, the transition states for the four successive dehydrogenation steps in CH(4) dissociation are located using the dimer method. It is found that the energy barriers for the first three steps are rather close on the alloyed Ni∕Fe and Ni surfaces, while the activation energy for CH dissociation is substantially lowered with the introduction of Fe. The dissolution of the generated C from the surface into the bulk of the Ni∕Fe alloys is thermodynamically favorable, and the diffusion of C through catalyst particles is hindered by the Fe component. With the combination of density functional theory calculations and kinetic analysis, the C concentration in catalyst particles is predicted to increase with the Fe content. Meanwhile, other experimental conditions, such as the composition of carbon-containing gases, feedstock partial pressure, and reaction temperature, are also found to play a key role in determining the C concentration in bulk metal, and hence the microstructures of generated CNFs.

Catalytic decomposition of hydrous hydrazine to hydrogen over oxide catalysts at ambient conditions for PEMFCs

Hydrous hydrazine is a hydrogen carrier in liquid state at room temperature, having high hydrogen content, and free of CO and other carbon-containing gases. In this study, the effects of oxides properties on the initial catalytic activity towards hydrous hydrazine decomposition as hydrogen source for proton exchange membrane fuel cells (PEMFCs) were systematically investigated. The results showed that the perovskite structure, cobalt ion and oxygen nonstoichiometry of oxides have important influence on the catalytic decomposition of hydrous hydrazine. The hydrogen selectivity of Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3−δ (BSCF), SrCoO 3−δ (SC) and La 0.2Sr 0.8CoO 3−δ (LSC2) catalysts with KOH promoter for hydrous hydrazine decomposition was compared at 55 °C, which indicated that hydrogen selectivity of BSCF and LSC2 could reach 100%. The performance of a PEMFC operating on the decomposition products from hydrous hydrazine was also studied and compared with that operating on pure hydrogen. The cell delivered a peak power density of 510 mW cm −2 at 50 °C by operating on the gaseous decomposition products of hydrous hydrazine, which was only slightly lower than that of a similar cell with pure hydrogen as fuel, due to the diluting effect of nitrogen. It highly promises hydrous hydrazine as a indirect fuel of PEMFCs for portable application.

A Novel Technology for Green(er) Manufacturing of CNTs via Recycling of Waste Plastics

ABSTRACTCostly and often highly-flammable chemicals, such as hydrogen and carbon-containing gases, are largely used for carbon supply in current carbon nanotube (CNT) synthesis technologies. To mitigate related economic and safety concerns, we have developed a versatile CNT synthesis sequence, where low-cost and safe-to-handle-and-store waste solid polymers (plastics) are used for in situ generation of hydrogen and carbon-containing gases. Introduction of different waste plastics, such as polyethylene, polypropylene and polystyrene, into a multi-stage pyrolysis/ combustion/synthesis reactor allows for efficient CNT formation. This process is largely exothermic and scalable. It uses low-cost stainless steel screens to serve both as substrates as well as catalysts for CNT synthesis. This technique enables a solution for both waste plastic utilization and sustainable CNT production.