Methane Oxidation to Synthesis Gas Using Lattice Oxygen of La_(1-x)Sr_xMO_(3-λ)(M =Fe,Mn) Perovskite Oxides Instead of Molecular Oxygen

In this paper, the partial oxidation of methane to synthesis gas using lattice oxygen of La1- SrxMO3-λ (M=Fe, x Mn) perovskite oxides instead of molecular oxygen was investigated. The redox circulation between 11% O2/Ar flow and 11% CH4/He flow at 900℃ shows that methane can be oxidized to CO and H2 with a selectivity of over 90.7% using the lattice oxygen of La1- SrxFeO3-λ (x≤0.2) perovskite oxides in an appropriate reaction condition, while the lost lattice x oxygen can be supplemented by air re-oxidation. It is viable for the lattice oxygen of La1- SrxFeO3-λ (x≤0.2) perovskite x oxides instead of molecular oxygen to react with methane to synthesis gas in the redox mode.

Effect of MgO promoter on Ni-based SBA-15 catalysts for combined steam and carbon dioxide reforming of methane

A series of Ni/SBA-15 catalysts with Ni contents ranging from 5 wt% to 15 wt%, as well as another series of 10%Ni/MgO/SBA-15 catalysts, in which the range of the MgO content was from 1 wt% to 7 wt%, were prepared, and their catalytic performances for the reaction of combined steam and carbon dioxide reforming of methane were investigated in a continuous flow microreactor. The structures of the catalysts were characterized using the XRD, H2-TPR and CO2-TPD techniques. The results indicated that the CO selectivity for this reaction was very close to 100%, and the H2/CO ratio of the product gas could be controlled by changing the H2O/CO2 molar ratio of the feed gas. The simultaneous and plentiful existing of steam and CO2 had a significant influence on the catalytic performance of the 10%Ni/SBA-15 catalyst without modification. After reacting at 850 °C for 120 h over this catalyst, the CH4 conversion dropped from 98% to 85%, and the CO2 conversion decreased from 86% to 53%. However, the 10%Ni/3%MgO/SBA-15 catalyst exhibited a much better catalytic performance, and after reacting for 620 h, the CO2 conversion over this catalyst dropped from 92% to around 77%, while the CH4 conversion was not decreased. Oxidation of the Ni0 species as well as carbon deposition during the reaction were the main reasons for the deactivation of the catalyst without modification. On the other hand, modification by the MgO promoter improved the dispersion of the Ni0 species, and enhanced the CO2 adsorption affinity which in turn depressed the occurring of carbon deposition, and thus retarded the deactivation process.

Comparison of LaFeO_3,La_(0.8)Sr_(0.2)FeO_3,and La_(0.8)Sr_(0.2)Fe_(0.9)CO_(0.1)O_3 perovskite oxides as oxygen carrier for partial oxidation of methane

Comparison of LaFeO3, La0.8Sr0.2FeO3, and La0.8Sr0.2Fe0.9CO0.1O3 perovskite oxides as oxygen carrier for partial oxidation of methane in the absence of gaseous oxygen was investigated by continuous flow reaction and sequential redox reaction, Methane was oxidized to syngas with high selectivity by oxygen species of perovskite oxides in the absence of gaseous oxygen. The sequential redox reaction revealed that the structural stability and continuous oxygen supply in redox reaction decreased over La0.8Sr0.2Fe0.9Co0. 1O3 oxide, while LaFeO3 and La0.8Sr0.2FeO3 exhibited excellent structural stability and continuous oxygen supply.

Meta-analysis of calorimeter data to establish relationships between methane and carbon dioxide emissions or oxygen consumption for dairy cattle

Recent developments suggest the use of other gases such as carbon dioxide(CO_2) to estimate methane(CH_4)emissions from livestock,yet little information is available on the relationship between these two gases for a wide range of animals.A large respiration calorimeter dataset with dairy cattle(n=987 from 30 experiments)was used to investigate relationships between CH_4 and CO_2 production and oxygen(O_2)consumption and to assess whether the predictive power of these relationships could be improved by taking into account some dietary variables,including forage proportion,fibre and metabolisable energy concentrations.The animals were of various physiological states(young n=60,dry cows n=116 and lactating cows n=811)and breeds(Holstein-Friesian cows n=876,Jersey×Holstein-Friesian n=47,Norwegian n=50 and Norwegian×Holstein-Friesian n=14).The animals were offered forage as a sole diet or a mixture of forage and concentrate(forage proportion ranging from 10 to 100%,dry matter basis).Data were analysed using a series of mixed models.There was a strong positive linear relationship between CH_4and CO_2,and observations within an experiment were very predictable(adjusted R^2=0.93).There was no effect of breed on the relationship between CH_4 and CO_2.Using O_2 instead of CO_2 to predict CH_4 production also provided a very good fit to the observed empirical data,but the relationship was weaker(adjusted R^2=0.86).The inclusion of dietary variables to the observed CO_2 emissions,in particular forage proportion and fibre concentration,provided a marginal improvement to the prediction of CH_4.The observed variability in the CH_4:CO_2 ratio could only marginally be explained by animal physiological state(lactating vs.dry cows and young cattle)and dietary variables,and thus most likely reflected individual animal differences.The CH_4:CO_2 ratio can therefore be particularly useful to identify low CH_4 producing cows.These findings indicate that CO_2 production data can be used to accurately predict CH_4 emissions to generate large scale data for management and genetic evaluations for the dairy industry.

Study of methane and carbon dioxide adsorption-desorption hysteresis in coals from Sydney Basin:A theoretical and experimental approach OA

Methane(CH_(4))and carbon dioxide(CO_(2))are primary components of coal seam gas(CSG).Understanding their adsorption-desorption hysteresis characteristics,along with the fundamental mechanism,is crucial for CSG exploitation and related hazards mitigation.This research focused on the representative Bulli coal seam in the Sydney Basin,Australia.Through the purpose-built indirect gravimetric high-pressure isothermal adsorption-desorption hysteresis experiment,a novel Langmuir-based desorption model,incorporating hysteresis effect and residual gas,was proposed.Quantitative characterization of the adsorption-desorption hysteresis degrees of CO_(2)and CH_(4)i n coal particles of various sizes and inΦ50mm 100 mm intact coal samples were achieved using the improved hysteresis index(IHI).The experimental findings validated that the proposed desorption model accurately describes the desorption behavior of CO_(2)and CH_(4)in coal(R2>0.99).Based on the adsorption-desorption properties of inkbottle-shaped micropores and pore deformation caused by gas adsorption-induced coal expansion,the occurrence mechanism of adsorption–desorption hysteresis and the fundamental reasons for the presence of residual gas were elucidated.Furthermore,the study explored the impact of CO_(2)and CH_(4)adsorption-desorption hysteresis effects on coal and gas outbursts,suggesting that coal seams rich in CO_(2)do not have a higher propensity for outbursts than those rich in CH_(4).

Carbon dioxide reforming of methane over mesoporous nickel aluminate/γ-alumina composites

A series of xNiAl2O4/γ-Al2O3composites with various Ni contents have been prepared via one-step partial hydrolysis of metal nitrate salts in the absence of surfactants and used for carbon dioxide reforming of methane. The characterization results demonstrated that the NiAl2O4/γ-Al2O3materials possessed mesoporous structures of uniform pore sizes; and the Ni2+ions were completely reacted with alumina to NiAl2O4spinel in the matrices using N2sorption, XRD, TEM, and XPS. The NiAl2O4/γ-Al2O3materials exhibited excellent catalytic properties and superior long-term stability for carbon dioxide reforming of methane. The effects of Ni content on the intrinsic activities and the amounts of coke disposition of the xNiAl2O4/γ-Al2O3catalysts were discussed in detail for the carbon dioxide reforming of methane. The results revealed that the Ni particle sizes did not affect the intrinsic activity of metallic Ni, but smaller Ni particles could reduce the rate of coke deposition. © 2016 Science Press

Photocatalytic Synthesis of Oxygenates from Gaseous CO_2 and CH_4 over Semiconductor

Photoinduced synthesis of CO2 and CH4 was investigated using a batch reaction system on several photoactive materials supported on silicon dioxide. Single semiconductor showed higher selectivity to C1 compounds. The production of C2-C3 oxygenates took place preferentially on composite semiconductor photocatalysts. In particular, it was found that acetone was the primary product over Cu / CdS –TiO2 / SiO2.

Selective Oxidation of Light Hydrocarbons Using Lattice Oxygen Instead of Molecular Oxygen

In this paper, selective oxidation of n-butane to maleic anhydride (MA) and partial oxidation of methane to synthesis gas with lattice oxygen instead of molecular oxygen are investigated. For the oxidation of butane to MA in the absence of molecular oxygen, the Ce-Fe promoted VPO catalyst has more available lattice oxygen and provides higher conversion and selectivity than that of the unpromoted one. It is supposed that the introduction of Ce-Fe complex oxides improves redox performance of VPO catalyst and increases the activity of lattice oxygen. For partial oxidation of methane to synthesis gas over LaFeO3 and La0.8Sr0.2FeO3 oxides, the reaction with flow switched between 11% O2-Ar and 11% CH4-He at 900℃ was carried out. The results show that methane can be oxidized to CO and H2 with selectivity over 93% by the lattice oxygen of the catalyst in an appropriate reaction condition, while the lost lattice oxygen can be supplemented by air re-oxidation. It is viable for the lattice oxygen of the LaFeO3 and La0.8Sr0.2FeO3 catalyst instead of molecular oxygen to react with methane to synthesis gas in the redox mode.

Chemical looping conversion of methane via Fe_(2)O_(3)-LaFeO_(3)calcined from LaFe-MOF precursor

The effective utilization of natural gas resources is a promising option for the implementation of the"dual carbon"strategy.However,the capture of carbon dioxide with relatively lower concentration after the combustion of natural gas is the crucial step.Fortunately,the lattice oxygen is used for chemical cycle conversion of methane to overcome the shortcomings mentioned above.A method was proposed to synthesize perovskite for methane cycle conversion using metal organic framework as a precursor.Morphology and pore structure of Fe_(2)O_(3)-LaFeO_(3)composite oxides were regulated by precursor synthesis conditions and calcination process.Moreover,the chemical looping conversion performance of methane was evaluated.The results showed that the pure phase precursor of La[Fe(CN)_(6)]·5H_(2)O was synthesized with the specific surface area of 23.91 m^(2)·g^(-1)under the crystallization of 10 h and the pH value of10.5.Fe_(2)O_(3)-LaFeO_(3)was obtained by controlled calcination of La[Fe(CN)_(6)]·5H_(2)O and Fe_(2)O_(3)with variable mass ratio.The selectivity of CO_(2)can reach more than 99%under the optimal parameters of methane chemical looping conversion:m(Fe_(2)O_(3)):m(LaFeO_(3))=2:1,the reaction temperature is 900℃,the lattice oxygen conversion is less than 40%.Fe_(2)O_(3)-LaFeO_(3)still has good phase and structure stability after five redox reaction and regeneration cycles.

Numerical study on soot removal in partial oxidation of methane to syngas reactors

The serious carbon deposition existing in catalytic partial oxidation of methane(CPOM) to syngas process is one of the key problems that impede its industrialization. In this study, 3-dimensional unsteady numerical simulations of the soot formation and oxidation in oxidation section in a heat coupling reactor were carried out by computational fluid dynamics(CFD) approach incorporating the Moss-Brookes model for soot formation. The model has been validated and proven to be in good agreement with experiment results. Effects of nozzle type,nozzle convergence angle, channel spacing, number of channels, radius/height ratio, oxygen/carbon ratio, preheat temperature and additional introduction of steam on the soot formation were simulated. Results show that the soot formation in oxidation section of the heat coupling reactor depends on both nozzle structures and operation conditions, and the soot concentration can be greatly reduced by optimization with the maximum mass fraction of soot inside the oxidation reactor from 2.28% to 0.0501%, and so that the soot mass fraction at the exit reduces from0.74% to 0.03%.

A microporous aluminum-based metal-organic framework for high methane,hydrogen,and carbon dioxide storage

We report a microporous aluminum-based metal-organic framework(MOF),BUT-22 for high methane(CH_(4)),hydrogen(H_(2)),and carbon dioxide(CO2)storage.At 296 K and 80 bar,BUT-22 exhibits a high gravimetric CH4 storage capacity of 530 cm^(3)(STP)/g(0.379 g/g).BUT-22 also has a high gravimetric H_(2)storage capacity of 12 wt.%at 100 bar and 77 K.In addition,the CO_(2)adsorption studies revealed that BUT-22 exhibits a high absolute gravimetric CO2 uptake of 1.7 g/g at 296 K and 40 bar.

Industrial Feasiblity of Direct Methane Conversion to Hydrocarbons over Fe-Based Fischer Tropsch Catalyst

Recently, as a direct consequence of the dwindling world oil reserves and the growing awareness of the environmental problems associated with the use of coal as energy source, there is growing interest in cheaper, abundant and cleaner burning methane. The Gas-to-Liquid technology offers perhaps the most attractive routes for the exploitation of the world huge and growing natural gas resources. Using this process the erstwhile stranded gas is converted to premium grade liquid fuels and chemicals that are easily transported. However, a widespread application of the GTL process is being hampered by economical and technical challenges. The high cost of synthesis gas, for instance, weighs heavily on the economics and competitiveness of the process limiting its wider application. This work presented a modified Gas-to-Liquid process that eliminates the costly synthesis gas production step. The proposed process utilized an alternative pathway for methane activation via the production of chloromethane derivatives which are then converted to hydrocarbons. It established that hydrocarbons mainly olefins can be economically produced from di- and tri-chloro- methanes over a typical iron-based Fischer Tropsch catalysts in a moving bed reactor at industrially relevant conditions. Some of the attractions of the proposed process include a) the elimination of the costly air separation plant requirement b) high process selectivity and c) significant reduction of carbon dioxide emissions thereby saving on feedstock loss and the costly CO2 removal and isolation processes.

Methane Generation and Capture of U.S.Landfills

Analysis of the U.S.EPA(Environmental Protection Agency)database of 2,549 MSW(Municipal Solid Waste)landfills showed that there were 1,164 operating landfills in which 348 million short tons(316 million metric tons)of waste were landfilled in 2017.In total,these landfills occupy about 370 million square meters of land so it is not possible to monitor the generation of LFG(Landfill Gas)generation accurately,or collect most of the LFG generated.This study was based on the hypothesis that,on the average,methane generation is proportional to the tonnage of wastes landfilled annually.The Landfill Methane Outreach Program of the EPA(EPA-LMOP)compiles annual operating data of all methane-capturing landfills.Our analysis of the 2018 data for 396 LMOP operating landfills showed that 210 million short tons of wastes were deposited and 5.06 million short tons of methane were captured,i.e.,an average capture of 0.024-ton CH4/ton waste.On the basis of the anaerobic reaction of the DOC(Degradable Organic Carbon)in landfilled wastes,the average rate of methane generation from all operating U.S.landfills was estimated to be 0.05 ton of CH4 per ton of annual capacity;this number corresponds to bioreaction of about one half of the total organic carbon in MSW.On this basis,the average rate of CH4 emission from the 396 LMOP landfills was estimated to be 0.026-ton CH4 per annual ton of deposition and the average efficiency of LFG capture,48%.Adding up all 1,164 operating landfills,their total emission of methane was estimated at 11.9 million metric tons of CH4.At CH4/CO2 equivalence of 25,this number corresponds to CO2-eq emissions of 270 million metric tons,i.e.,5.1%of the U.S.energy related carbon dioxide emissions.

Low-temperature utilization of CO_2 and CH_4 by combining partial oxidation with reforming of methane over Ru-based catalysts

Combination of partial oxidation of methane （POM） with carbon dioxide reforming of methane （CRM） has been studied over Ru-based catalysts at 550℃.POM,CRM and combined reaction were performed over 8wt%Ru/γ-Al2O 3 and the results show that both POM and CRM contribute to the combined reaction,between which POM plays a more important role.Moreover,the addition of Ce to Ru-based catalyst results in an improvement in the activity and CO selectivity under the adopted reaction conditions.The Ce-doped catalyst was characterized by N2 adsorption-desorption,SEM,XRD,TPR,XPS and in situ DRIFTS.The mechanism has been studied by in situ DRIFTS together with the temperature distribution of catalyst bed.The mechanism of the combined reaction is more complicated and it is the combination of POM and CRM mechanisms in nature.The present paper provides a new catalytic system to activate CH4 and CO2 at a rather low temperature.

Improvement of catalytic stability for CO_2 reforming of methane by copper promoted Ni-based catalyst derived from layered-double hydroxides

Copper-promoted nickel-based metal nanoparticles (NPs) with high dispersion and good thermal stability were derived from layered-double hydroxides (LDHs) precursors that were facilely developed by a co-precipitation strategy. The copper-promoted Ni-based metal NPs catalysts were investigated for methane reforming with carbon dioxide to hydrogen and syngas. A series of characterization techniques including XRD, N2adsorption and desorption, H2-TPR, XPS, CO2-TPD, TEM, TGA and in situ CH4-TPSR were utilized to determine the structure-function relationship for the obtained catalysts. The copper addition accelerated the catalyst reducibility as well as the methane activation, and made the Ni species form smaller NPs during both preparation and reaction by restricting the aggregation. However, with higher copper loading, the derived catalysts were less active during methane reforming with CO2to syngas. It was confirmed that the catalyst with 1 wt% Cu additive gave the higher catalytic activity and remained stable during long time reaction with excellent resistance to coking and to sintering. Furthermore, the mean size of metal NPs changed minimally from 6.6 to 7.9 nm even after 80 h of time on stream at temperature as high as 700 °C for this optimized catalyst. Therefore, this high dispersed anti-coking copper-promoted nickel catalyst derived from LDHs precursor could be prospective catalyst candidate for the efficient heterogeneous catalysis of sustainable CO2conversion. © 2016 Science Press

Ni-Al mixed metal oxide with rich oxygen vacancies: CO methanation performance and density functional theory study

Ni-Al mixed metal oxides have been successfully prepared by high shear mixer(HSM)and coprecipitation(CP)methods for low temperature CO methanation.In this work,Ni-Al(HSM-CP)catalyst presented small Ni crystallite size and high surface area,which all contribute to the methanation reaction at low temperature conditions.The obtained Ni-Al(HSM-CP)sample exhibited a mass of defective oxygen,thereby accelerating the dissociation of CO and ultimately increasing the activity of the catalyst.Ni-Al(HSM-CP)catalyst offered the best activity with CO conversion=100%and CH_(4) selectivity=93%at 300℃,and the CH_(4) selectivity can reach 81.8%at 200℃.In situ Fourier transform infrared spectroscopy and density functional theory show that CHO and COH intermediates with lower activation energy barriers are produced during the reaction,and hydrogen-assisted carbon–oxygen bond scission is more favorable.

Tracing the Methane Events by Stable Carbon Isotopes of Benthic Foraminifera at Glacial Periods in the Andaman Sea

Stable isotopes of carbon and oxygen variations in foraminiferal shells have been widely used in paleo-environment studies.However,studies about the shells of benthic foraminifera in methanehydrate-bearing sediments as reliable geochemical proxies to reconstruct the potential methane release events in the geologic past are rare.In this study,we present the stable carbon and oxygen isotopes of fossil benthic foraminifera including one epifaunal species(Cibicidoides wuellerstorfi)and two infaunal species(Bulimina mexicana and Uvigerina peregrina)from the Site U1447 of IODP 353 Expedition to trace methane events in the Andaman Sea,where one of the thickest and deepest gas hydrate stability zones was discovered.Theδ^(13)C values of benthic foraminifera show that there are eight distinct intervals with negative values in the last~10 Myr,interpreted as a record of long-term fluctuations in methane emission.Six of these methane events occurred during the glacial sea-level lowstands in the last~1.1 Myr.We,therefore,infer that the trigger mechanism for these events might be the hydrate destabilization caused by sea level fall.The methane events that occurred at~2.11 and~5.93 Ma are more likely related to the sudden changes in sedimentation,either slide events or marked variations in sedimentation rate.

A review on transport of coal seam gas and its impact on coalbed methane recovery

This paper presents a summary review on mass transport of coal seam gas(CSG)in coal associated with the coalbed methane(CBM)and CO_(2) geo-sequestration enhanced CBM(CO_(2)-ECBM)recovery and current research advances in order to provide general knowledge and fundamental understanding of the CBM/ECBM processes for improved CBM recovery.It will discuss the major aspects of theory and technology for evaluation and development of CBM resources,including the gas storage andflow mechanism in CBM reservoirs in terms of their differences with conventional natural gas reservoirs,and their impact on CBM production behavior.The paper summarizes the evaluation procedure and methodologies used for CBM exploration and exploitation with some recommendations.

Effect of CeO_2 Promoter on the Performance of Catalyst for CH_4, CO_2with O_2 to Synthesis Gas

In the reaction of mathane, carbon dioxide with oxygen to synthesis gas, conversion ofCH4 was increased, but CO selectivity was reduced when CeO2 was added to Ni/CaO-Al2O3catalyst The characterization of TPR, XPS. XRD and H2-TPD exhibited that, on one hand, theCeO2 promoter decreased the reduction temperature of catalyst. On the other hand, addition ofCeO2 resulted in an increase in the electron density of active component Ni, and as a result,reduced the ability of CH4 deep cracking and enhanced the resistance to carbon-deposition ofcatalyst. In addition, the existence of CeO2 was beneficial to decrease the Ni crystal particle size.

Anaerobic digestion of cyanobacteria and chlorella to produce methane for biofuel

The methane potentials of cyanobacteria and chlorella have been investigated in eight different lab scale reactors at 25℃for three-day Hydraulic Retention Time(HRT).Autoclavation pre-treatment was applied to the cyanobacteria to aid digestion,while the Chlorella was obtained and digested in powdery form.The organic loading rates were 1g VS,2 g VS,3 g VS,4 g VS,5 g VS,6 g VS,7 g VS,8 g VS and 9 g VS.Methane production rates increased with increasing loading rates and started declining at loading rate higher than 7 g VS,while the HRT was kept constant.The highest methane production rates for cyanobacteria and chlorella were(78±25)mL/(L·d)and(100±25)mL/(L·d),respectively,at loading rate of 7 g VS.Digester instability occurred at loading rates of 8 g VS and 9 g VS with higher accumulation of methane concentrations.Lipid compositions of both feeds were close and the methane production potentials of both biomasses were also close and followed the same trend.