CH4 Atmosphere Research Articles

Cu promoted Ni-Ca dual functional materials for integrated CO2 capture and utilization in O2-containing flue gas: Eliminating the delay in the utilization stage

Integrating CO2 capture and utilization by dry reforming methane (ICCU-DRM) technology is promising in concentrating and utilizing diluted CO2 from flue gas, which depends on developing Dual Functional Materials (DFMs) with adsorption and catalytic sites. Ni-Ca materials are widely applied in ICCU-DRM due to their excellent catalytic and CO2 adsorption properties. Nevertheless, the challenge remains that oxygen in the actual flue gas would oxidize the active Ni, leading to a delay in the DRM stage. In this work, Cu-promoted, ZrO2-stabilized Ni-Ca based DFMs were developed, which suppressed the delay and enhanced the performance of the DRM reaction. Attribute to the excellent reducing properties, Cu could be rapidly reduced in the CH4 atmosphere and further promote the reduction of NiO to the catalytically active Ni monomers by activating methane to generate reactive hydrogen (H*). What’s more, attributed to the disappearance of delay times, it is accompanied by a satisfying yield distribution with a 0.11 decrease in H2/CO ratio and an improvement in conversion, especially CH4 conversion with an increase of more than 10%. In addition, the bifunctional material also exhibits favorable cycling stability due to the stabilizers.

Direct reduction of calcium carbonate by coupling with methane dry reforming using NiO/S-1 as catalyst

Thermal decomposition of carbonate is an important process in the production of cement, refractory materials, and steel. Nevertheless, this process requires high temperature and is always accompanied with large amounts of CO2 emission. To reduce the decomposition temperature and simultaneously mitigate CO2 emissions, direct reduction of carbonate under a reducing atmosphere has been proposed as a novel strategy. This work mainly investigated the feasibility of direct reduction of CaCO3 by CH4 in the presence of a highly dispersed NiO/S-1 catalyst. It was found that the introduction of a CH4 atmosphere without a catalyst had little promotion effect on CaCO3 decomposition (as compared to air atmosphere), and no notable conversion of CO2 was observed. However, the presence of a highly dispersed NiO/S-1 catalyst significantly decreased the decomposition temperature of CaCO3 in a CH4 atmosphere, and most of the carbon species in CaCO3 can be converted to CO. To gain a comprehensive understanding of CaCO3 reduction in CH4, the effects of reaction temperature, CH4 concentration, and NiO loading in the NiO/S-1 catalyst were systematically explored. With the best-performing catalyst, i.e., 7NiO/S-1, complete CaCO3 decomposition and approximate 90 % CH4/CO2 conversion can be achieved under the condition of 750 °C and 25 vol% CH4. Characterization results indicated that the CaO particles obtained in the CH4 reducing atmosphere exhibited a more porous structure compared to that attained in air, due to the more intensive CaCO3 decomposition in CH4. Further data analysis revealed that reverse water-gas shift reaction also contributed to CO2 conversion during the reduction of CaCO3 in CH4. The findings obtained in this research can provide new perspectives for CO2 emission control and energy saving in traditional heavy-emission and high energy consumption industries.

Ethylene electrosynthesis from low-concentrated acetylene via concave-surface enriched reactant and improved mass transfer

Electrocatalytic semihydrogenation of acetylene (C2H2) provides a facile and petroleum-independent strategy for ethylene (C2H4) production. However, the reliance on the preseparation and concentration of raw coal-derived C2H2 hinders its economic potential. Here, a concave surface is predicted to be beneficial for enriching C2H2 and optimizing its mass transfer kinetics, thus leading to a high partial pressure of C2H2 around active sites for the direct conversion of raw coal-derived C2H2. Then, a porous concave carbon-supported Cu nanoparticle (Cu-PCC) electrode is designed to enrich the C2H2 gas around the Cu sites. As a result, the as-prepared electrode enables a 91.7% C2H4 Faradaic efficiency and a 56.31% C2H2 single-pass conversion under a simulated raw coal-derived C2H2 atmosphere (~15%) at a partial current density of 0.42 A cm−2, greatly outperforming its counterpart without concave surface supports. The strengthened intermolecular π conjugation caused by the increased C2H2 coverage is revealed to result in the delocalization of π electrons in C2H2, consequently promoting C2H2 activation, suppressing hydrogen evolution competition and enhancing C2H4 selectivity.

Thermal decomposition of magnesium carbonate in methane atmosphere for the synthesis of syngas: The effect of O2

Excess CO2 emissions from the conventional decomposition of carbonate process industry, have a lasting and detrimental effect on the global climate. It is a significant task to figure out how to minimize these processes' CO2 emissions from sustainable development of society. In this work, the thermal decomposition of MgCO3 in CH4 reduction environment for the formation of syngas was investigated in great depth. The addition of O2 to the thermal decomposition of MgCO3 in CH4 atmosphere reaction system reduced the reaction temperature by 300 °C and prevented the coke formation on the metal oxide (near zero carbon high quality MgO), as demonstrated by both theoretical calculations and experiments. And the formation of valuable syngas byproducts (CO/H2 =1:3) and the noteworthy reduction of CO2 emissions (with a suppressed selectivity of 15%) can be obtained through this process. This research gives a helpful and long-term strategy for cutting down on CO2 emissions in the conventional process industries (ie. carbonate decomposition) and provides a new view for valuable product (ie. syngas) synthesis.

Performance optimization of metal-supported solid oxide fuel cells using cathode and full cell impregnation with La0.4Sr0.6Co0.2Fe0.7Nb0.1O3-δ electrode.

In this study, precursor solutions of La0.4Sr0.6Co0.2Fe0.7Nb0.1O3-δ (LSCFN) symmetric electrode were prepared, and the applications of cathode impregnation and full cell impregnation in the preparation and performance optimization of four-layer metal-supported solid oxide fuel cells (MSCs) were thoroughly investigated. Test results indicate that the polarization impedance of cathode impregnated MSCs under H2 and CH4 atmospheres at 750 °C is approximately 0.1 Ω cm2 and 0.41 Ω cm2, respectively, with power densities of 1115 mW cm-2 and 700 mW cm-2, respectively. Meanwhile, the polarization impedance of full cell impregnated MSCs under the same conditions is 0.12 Ω cm2 and 0.40 Ω cm2, with power densities of 945 mW cm-2 and 840 mW cm-2, respectively. Remarkably, MSCs full cell impregnated LSCFN exhibit outstanding stability performance under CH4 atmosphere in a 100 h stability test. Research on the application of impregnation method for performance optimization of metal-supported cells is relatively scarce. The results reveal the feasibility of simplifying MSCs preparation steps using full cell impregnation method, further promoting the widespread application of metal-supported overall cells.

Experimental erosion of microbial diversity decreases soil CH4 consumption rates.

Biodiversity-ecosystem functioning (BEF) experiments have predominantly focused on communities of higher organisms, in particular plants, with comparably little known to date about the relevance of biodiversity for microbially driven biogeochemical processes. Methanotrophic bacteria play a key role in Earth's methane (CH4 ) cycle by removing atmospheric CH4 and reducing emissions from methanogenesis in wetlands and landfills. Here, we used a dilution-to-extinction approach to simulate diversity loss in a methanotrophic landfill cover soil community. Replicate samples were diluted 101 -107 -fold, preincubated under a high CH4 atmosphere for microbial communities to recover to comparable size, and then incubated for 86 days at constant or diurnally cycling temperature. We hypothesize that (1) CH4 consumption decreases as methanotrophic diversity is lost, and (2) this effect is more pronounced under variable temperatures. Net CH4 consumption was determined by gas chromatography. Microbial community composition was determined by DNA extraction and sequencing of amplicons specific to methanotrophs and bacteria (pmoA and 16S gene fragments). The richness of operational taxonomic units (OTU) of methanotrophic and nonmethanotrophic bacteria decreased approximately linearly with log-dilution. CH4 consumption decreased with the number of OTUs lost, independent of community size. These effects were independent of temperature cycling. The diversity effects we found occured in relatively diverse communities, challenging the notion of high functional redundancy mediating high resistance to diversity erosion in natural microbial systems. The effects also resemble the ones for higher organisms, suggesting that BEF relationships are universal across taxa and spatial scales.

The initial oxidation behavior of a UCxN1-x layer prepared by the pulsed laser ablation in the 1:1 N2+CH4 atmosphere

The uranium surface is CN-co-doped by the pulsed laser ablation technique in the 1:1 mixed atmosphere of CH4 and N2. The results of X-ray diffraction, Auger electron spectroscopy and X-ray photoelectron spectroscopy show that the modified layer prepared is a UCxN1-x solid solution with trace metallic U. When contacted with O2, the NaCl-like structure of the outmost surface layer is soon transferred to a UO2-x-like structured UO2-x(C/N)y (y < x), which can be subsequently oxidized to a CaF2-like structured UO2-x(C/N)y (y ≈ x), in which the C, N and O atoms share the tetrahedral interstitials of the U lattice. After the formation of the CaF2-like structure, the surface C and N atoms are gradually replaced by O atoms during the following oxidation process. During the oxidation of the outmost surface layer, C is more preferentially oxidized than N to produce a product of UO2-x(C/N)y, in which the ratio of C/N is lower than that in the as-prepared layer. Besides, C is easily oxidized to CO and adsorbed on the layer surface while there is no obvious evidence for the escape and adsorption of N2 or NO, implying that the migration of N may be different from that of C during the oxidation of the UCxN1-x solid solution. After oxidation, a tri-layered structure, composing of UO2 located on the outmost surface, UO2-x(C/N)y and UCxN1-x distributed in the superficial layer, and a UCxN1-x solid solution with trace metal U in the inner layer, is formed. This structure of layer can effectively prevent the further migration of O atoms into the layer from the surface and maintain the existence of C and N in the inner layer, and thus provide an excellent passivation layer for U metal against O2.

Reductive calcination of calcium carbonate in hydrogen and methane: A thermodynamic analysis on different reaction routes and evaluation of carbon dioxide mitigation potential

Calcium carbonate (CaCO3) minerals represent a valuable resource, but its exploitation is based on the decarboxylation reaction at high temperatures, which inevitably release carbon dioxide (CO2) into the atmosphere. Here, a reductive calcination of CaCO3 in the hydrogen (H2) and methane (CH4) atmospheres was proposed, thermodynamic analysis and process simulation were carried out. In CH4 atmosphere, lower CaCO3 decomposition temperature and higher CO2 conversion can be achieved, while undesirable solid carbon deposition was produced as well. Optimized H2:CH4 ratio in feeding can effectively avoid carbon deposition and achieve the complete decomposition of CaCO3 at 738 °C which reaching CO2 conversion of 69.69 %. In addition, this work established the traditional route as a reference process to compare the energy efficiency and carbon footprint of the different CaCO3 calcination processes. CaCO3 calcination in H2:CH4 atmosphere with 1:1 ratio achieved an energy efficiency of 67.01 % and a GWP value of 0.954 kgCO2/kgCaCO3. With sustainable energy (bio-power, bio-H2, and bio-CH4) substitution, even lower GWP value of −0.640 kgCO2/kgCaCO3 can be achieved. This work performed that direct reduction of CaCO3 to syngas and CaO under H2 or CH4 atmosphere, which not only reduces the reaction temperature but also alleviates the CO2 emission, which offers a promising option for carbon emission reduction in the carbonate industry.

Rocking chair-like movement of ex-solved nanoparticles on the Ni-Co doped La0.6Ca0.4FeO3-δ oxygen carrier during chemical looping reforming coupled with CO2 splitting

Chemical looping reforming coupled with CO2 splitting is a promising CO2 utilization method that produces a valuable fuel. Here, we present a novel perovskite oxide with the composition of La0.6Ca0.4Fe0.95M0.05O3-δ (M = Ni, Co, Ni-Co) that functions both as an oxygen carrier and as a redox catalyst. Using a multi technique approach with HR-TEM, XRD, XAS, and Mössbauer spectroscopy, we find that alloy nanoparticles spontaneously form on the surface of Ni-Co doped carriers in a CH4 atmosphere, and as they are repeatedly exposed to CO2 and CH4 during the chemical loop, Fe atoms move back and forth between the inside (as Fe cations in the lattice) and the outside (as a part of metallic alloy) of the host scaffold. Eventually, the co-doped samples become highly reactive towards both gases and have excellent coking and redox stability, demonstrating record-level syngas yield (total ∼10 mmol/g) at 850 °C, over 50 redox cycles.

Investigation of Microstructure and Magnetic Properties of CH4 Heat Treated Sr-Hexaferrite Powders during Re-Calcination Process

The microstructure and magnetic properties of methane (CH4) heat-treated Sr-hexaferrite powders during the re-calcination process were investigated and compared with the magnetic properties of conventionally synthesized Sr-hexaferrite powder. Gradual changes in the magnetic behavior of the produced powder in each re-calcination stage were investigated using magnetization curves obtained from the vibration sample magnetometry (VSM) technique. First, the initial Sr-hexaferrite powder was prepared by the conventional route. Then the powder was heat treated in a dynamic CH4 atmosphere in previously optimized conditions (temperature: 950 °C, gas flow rate:15 cc min−1 and time: 30 min), and finally, re-calcined in various temperatures from 200 to 1200 °C. By investigating the hysteresis loops, we found the transition temperature of soft to hard magnetic behavior to be 700 °C. The maximum ratio Mr/Ms was obtained at temperatures of 800–1100 °C. At 1100 °C, and despite the Sr-hexaferrite single phase, the magnetic behavior showed a multiphase behavior that was demonstrated by a kink in the hysteresis loop. Uniform magnetic behavior was observed only at 900 °C and 1000 °C. Although the ratio Mr/Ms was almost the same at these temperatures, the values of Mr and Ms at 1000 °C were almost double of 900 °C. At 1000 °C, the second quadrant of hysteresis curve had the maximum area. Therefore, 1000 °C was the optimum temperature for re-calcination after CH4 gas heat treatment in the optimized conditions. Due to the presence of a small amount of hematite soft phase at 1000 °C, the most probable reason for the exclusive properties of the optimized product may be the exchange coupling phenomenon between the hard Sr-hexaferrite phase and the impurity of the soft hematite phase.

Thermal Behavior and Kinetics of Shenmu Coal Pyrolyzed under Hydrogen-Rich or Methane-Gas-Rich Atmosphere

The pyrolysis characteristics of Shenmu coal under an atmosphere containing H2 (40%) and another containing CH4 (40%) were studied via a thermogravimetric analysis, and the kinetic parameters of pyrolysis were calculated by using a distributed activation energy model (DAEM). The results showed that H2 promoted the cleavage of CH-like functional groups by providing reactive hydrogen groups to combine with CH groups and –OH groups in the coal. However, the H2 and CH4 atmosphere inhibits the cleavage of oxygen-containing functional groups such as carbonyl groups and C–O groups, and this is unfavorable to the production of CO2 and CO. The pyrolysis weight-loss rate of raw coal decreases with the increase of the heating rate, and the weight-loss curve shifts to the high-temperature region. At the same conversion rate and pyrolysis temperature, the activation energy of pyrolysis under the H2 and CH4 atmospheres is lower than that under the N2 atmosphere, and the activation energy does not conform to the Gaussian distribution. The activation energy of pyrolysis was distributed in a narrow range, in which the activation energy of the H2 and CH4 atmospheres was concentrated in the range of 175–215 kJ/mol and 225–230 kJ/mol, respectively, and the activation energy of the H2 atmosphere was lower than that of the CH4 atmosphere under the same conversion rate.

Sorption–Dilatometric Properties of Coal from a High-Methane Mine in a CO2 and CH4 Atmosphere

Although highly developed countries are trying to diversify away from coal-based energy, many economies rely on this resource. Its consumption results in the production of carbon dioxide, which promotes global warming, necessitating its sequestration. This paper presents the sorption–dilatometric relationships of hard coal samples differing in vitrinite and inertinite content. The studies were carried out under isothermal conditions (298 K) at a free pressure drop complemented by measurements under non-isothermal conditions (298 K to 323 K). The tests were performed on an original apparatus, based on the operation of an Arduino microcontroller. For the natural porosity to be preserved and for a better representation of the behaviour of the coal–gas system, samples in the form of cuboidal blocks were used, making this apparatus unique worldwide. Based on the study, it appears that the difference in petrographic composition affects the behaviour of the coal structure, influencing differences in the sorption–dilatometric properties. In the case of the sample with higher vitrinite content, the amount of adsorbed gases is higher.

The effect of VOx species polymerization degree and coordination environments of V-KIT-6 catalysts on the performance for the selective oxidation of methane

V-incorporated mesoporous KIT-6 silica materials with different V content (xV-KIT-6) were used for partial oxidation of methane (POM) with dioxygen under atmospheric pressure. Turnover frequency of CH4 (TOFCH4) is basically indistinguishable for highly dispersed VOx species under (sub-)monolayer coverage on SiO2. However, the polymerization degree of VOx species significant affect HCHO selectivity. At 625 °C, 3V-KIT-6 catalyst exhibited best catalytic performance of POM: methane conversion was 8.1%, formaldehyde selectivity was 26.1% and selectivity of the incomplete oxidation products was 90.5%. Compared with 3V-KIT-6 catalyst, the supported 1.1V/KIT-6 catalyst with same vanadium content and dispersity exhibit poor high-temperature TOFHCHO and low-temperature HCHO selectivity, suggesting that the supported and incorporated VOx species possess different coordination environments, such as VO and VOSi bond length and bond angle. To further investigate their microstructure effect on catalytic performance, in situ and operando UV Raman spectroscopy was used to investigate their different redox properties of VOx species. Under the pure CH4 atmosphere, their VOV or VOSi lattice oxygen are more reducible than VO lattice oxygen, suggesting the former are active sites. Supported VOx species are more easily reduced by CH4 than the incorporated ones, the VO lattice oxygen of 3V-KIT-6 catalyst cannot be completely consumed by CH4 after 1h, at least 30% VO bonds maintained. When 5% O2 was cofed, the VO bonds on 3V-KIT-6 and 1.1V/KIT-6 recovered quickly, indicating that the partially reduced VOx species are oxidized by O2 faster than their reduction by CH4. Thus, the activation of CH4 on VOx species should be the rate-determining step. Some unsaturated VOx species are present on 1.1V/KIT-6 easily, those may generate unselective electrophilic oxygen species for overoxidation.

Gas-liquid competitive adsorption characteristics and coal wetting mechanism under different pre-adsorbed gas conditions

Coal seam water injection was widely used to prevent mine gas and dust disasters. It is undeniable that the gas adsorbed on coal surface can influence the coal-water wettability. In order to investigate how the gas environment affects the coal-water contact characteristics, the coal-water contact angle was tested under different gas environments, including CH4, N2 and He. Then the microscopic wetting mechanism were revealed by combing with the molecular dynamic simulation. Results showed that, the coal-water contact angle gradually increases in the range of 0 ∼ 2 MPa. The contact angle shows the most significant growth trend in CH4 environment, increasing from 72.11° to 106.9°, and the wettability transits from hydrophilic wetting (<90°) to neutral wetting (=90°), eventually it becomes hydrophobic wetting (>90°). At the same gas pressure, the coal-water contact angle in the CH4 atmosphere is the largest, followed by N2 atmosphere and He atmosphere. Molecular dynamics simulation results showed that the adsorption capacity of water molecules decreases as the pre-adsorption gas pressure grows. The adsorption capacity of water molecules decreased from 1.84 mmol/g, 2.04 mmol/g and 2.23 mmol/g to 1.46 mmol/g, 1.51 mmol/g and 1.69 mmol/g under CH4, N2 and He atmosphere, respectively. Furthermore, the surface free energy and adsorption energy of water and gas were analyzed, finding that the surface free energy drops down with the rising pressure and the gas adsorption capacity, leading to the poor wettability. The adsorptive gas shows a more remarkable effect in weakening coal-water wettability due to the gas adsorption layer and gas–water competitive adsorption.

Laser fabrication of Pt anchored Mo2C micropillars as integrated gas diffusion and catalytic electrode for proton exchange membrane water electrolyzer

The efficient electrocatalysts for hydrogen evolution reaction (HER) are indispensable. Herein, Mo2C micropillars decorated with Pt nanoparticles (<4 nm) on Mo foil (Pt/Mo2C-L/Mo) are synthesized by laser ablation in a focused mode in CH4 atmosphere and laser-induced reduction in an under-focused mode in Ar/H2 atmosphere. The Pt/Mo2C-L/Mo possesses excellent HER performance (21 mV at 10 mA cm−2) and stability (1317 mA cm−2 for 100 h) in acid media. Integrated gas diffusion and catalytic electrodes of Pt/Mo2C-L/Mo are constructed by laser in a mixed model and used in proton exchange membrane water electrolyzer (PEMWE). The voltage of the constructed PEMWE of (−) Pt/Mo2C-L/Mo || IrO2/Ti (+) (1.55 V at 10 mA cm−2) is lower than that of (−) 20 wt.% Pt/C || IrO2 (+) (1.69 V at 10 mA cm−2) for overall water splitting. This work provides a universal laser synthetic strategy of integrated electrodes with promising application in the field of hydrogen energy.

Technical benefits of using methane as a pyrolysis medium for catalytic pyrolysis of Kraft lignin

Catalytic fast pyrolysis of low sulfonated Kraft lignin was performed under different atmospheric environments such as N2, CH4, and the gas derived from CH4 decomposition (CH4-D). The use of Zn- or Mo-loaded HZSM-5 as catalyst led to a higher pyrolytic oil yield compared to parent HZSM-5 in CH4 and CH4-D atmospheres. The yields of benzene, toluene, and xylenes were increased by the synergistic effects from metal loading, higher H/Ceff ratio, higher acidity, and CH4 activation. The enhanced CH4 activation via metal loading resulted in higher methylation of alkyl moieties and 33% increase in the total yield of benzene, toluene, and xylenes in comparison to parent HZSM-5. A higher H/Ceff ratio of 6 via CH4 decomposition led to the formation of a hydro-pyrolysis environment. Moreover, the CH4-D environment showed H2/CH4 ratio of 0.36 in the product gas which warranted the presence of more H2 under the CH4-D pyrolysis environment.

Nickel Hydroxide Nanosheets Prepared by a Direct Manual Grinding Strategy for High-Efficiency Catalytic Combustion of Methane.

Nickel hydroxide nanosheets were prepared by a very simple direct manual grinding strategy and then calcined at 200, 300, 400, and 500°. The synthesized samples were tested in lean methane (1.0% CH4, air balanced) catalytic combustion and subjected to a series of physical and chemical characterizations. The sample calcined at 200 °C (Ni(OH)2-200) presented a typical nanosheet structure and the best methane catalytic activity in all the samples, which can completely catalyze methane at 400 °C. The crystal structure changed from β-Ni(OH)2 to NiO at a calcination temperature of 300 °C. The β-Ni(OH)2 nanosheets began to partially agglomerate into nanoparticles at 400 °C and almost transformed into nanoparticles at 500 °C. Interestingly, the original nanosheet samples Ni(OH)2-200 and NiO-300 still maintained their morphology and structure although they all went through an activity test at 500 °C in a 1.0% CH4 atmosphere, which proves that the calcination of nanosheets in a CH4 atmosphere tended to maintain their nanosheet morphology compared with calcination in the air. Furthermore, through the activity test, X-ray photoelectron spectroscopy results, TPx, and in situ DRIFTS characterization, it was proved that the hydroxyl groups on the Ni(OH)2-200 and NiO nanosheets were beneficial to the dissociation of methane on the catalyst surface, and the nanosheet structure was also prone to generating more active adsorbed oxygen, so the activation energy of methane was lowered. A methane catalytic mechanism on the Ni(OH)2 nanosheets and NiO nanoparticles was proposed, which further proved the key role of hydroxyl groups in methane combustion.

The promotion effect of pyrolysis conditions on alkali metal pretreatment during pyrolysis of sub-bituminous Zhundong coal: Carbon engulfment control and subsequent sodium transformation

Alkali metal pretreatment in pyrolysis is proposed to address alkali-induced issues in high-alkali coal utilization, on the basis of staged fuel combustion. However, the newfound carbon engulfment remains an intractable problem. This work investigated the effect of pyrolysis conditions on enhancing alkali metal pretreatment during Zhundong coal pyrolysis over 500–1000 °C in a laboratory fixed-bed apparatus, which focused on heating rate, volatile-char interaction, and CH4 atmosphere. Multiple analytical methods were integrated to relate the facilitation effect of pyrolysis conditions on sodium pretreatment with the suppression of carbon engulfment. The results indicated carbon engulfment primarily blocked mesopores with a size <5 nm to retain large quantities of water-soluble sodium species. It resulted from coal swelling induced by the fusibility of semi-fusinites. Fortunately, volatile-char interaction and CH4 atmosphere eliminated carbon engulfment through the intra-particle reaction between gasification agents/active radicals and char matrix. They fully eliminated carbon engulfment at 800 °C, which mainly reopened mesopores with a diameter of 4–5 nm. They also promoted the formation of sodium silicates/aluminosilicates. A slow heating rate weakened carbon engulfment by limiting the fusibility of semi-fusinites, but to a lower extent. Volatile-char interaction and CH4 atmosphere were proposed as universal enhancements for alkali metal pretreatment.

The role of borosilicate glass in Miller\u2013Urey experiment

We have designed a set of experiments to test the role of borosilicate reactor on the yielding of the Miller–Urey type of experiment. Two experiments were performed in borosilicate flasks, two in a Teflon flask and the third couple in a Teflon flask with pieces of borosilicate submerged in the water. The experiments were performed in CH4, N2, and NH3 atmosphere either buffered at pH 8.7 with NH4Cl or unbuffered solutions at pH ca. 11, at room temperature. The Gas Chromatography-Mass Spectroscopy results show important differences in the yields, the number of products, and molecular weight. In particular, a dipeptide, multi-carbon dicarboxylic acids, PAHs, and a complete panel of biological nucleobases form more efficiently or exclusively in the borosilicate vessel. Our results offer a better explanation of the famous Miller's experiment showing the efficiency of borosilicate in a triphasic system including water and the reduced Miller–Urey atmosphere.

Studies of electric and spectral characteristics of surface spark discharge in atmosphere of carbon dioxide. Conversion of CO2 and CO2:H2 to CO

The results are presented from studies of the high-voltage pulse-periodic surface spark discharge propagating along the water-gas interface. In the case of CO2 or CO2:H2 mixture used as gaseous medium, the plasma-chemical conversion of CO2 to carbon monoxide CO was also studied. In the experiments, we used the generator with reservoir capacitor energy of 1.6 J, a voltage of 20 kV, and pulse duration of 2–3 μs. The average velocity was determined of the discharge propagation along the water surface in the CO2, CH4 and Ar atmospheres. It was shown that the leader velocities in the CO2 and CH4 atmospheres coincide, and they turned out to be 3–4 times lower than that in the Ar atmosphere. The integrated emission spectra are presented of the discharge in the CO2 atmosphere, in which the lines corresponding to CO2, CO, Hα, Hβ, and OI are distinguished. The electron concentration in the discharge channel was Ne = 1017 cm-1. The dynamics of conversion of CO2 to CO was traced at different energies inputted into the discharge. For the discharges in the atmospheres of CO2 and CO2:3H2 mixture, the degrees of conversion were 24 and 61%, respectively. And in the quasi-linear stage, the energy efficiencies of conversion were ∽13 and ∽6 eV per molecule for the CO2 and CO2:3H2 atmospheres, respectively.