Three dimensional microstructures of carbon deposition on Ni-YSZ anodes under polarization

In the present study,two Ni/YSZ anodes with different volume ratios of Ni and YSZ,30:70 and 45:55 vol%,are operated in dry methane under open circuit and polarized conditions.Three-dimensional(3D)Ni/YSZ microstructures after carbon deposition are reconstructed by the focused ion beam-scanning electron microscopy(FIB-SEM)with the help of machine learning segmentation.From the reconstructed mircostructures,volume fraction,connectivity,three phase boundary(TPB)density,and tortuosity are quantified.In addition,local carbon microstructures are quantitatively reconstructed,and the effect of polarization on carbon morphology is investigated.It is demonstrated that Ni surface in the vicinity of active TPB near the electrolyte is free from carbon formation,while remaining Ni surface at some distances from TPB exhibits severe carbon deposition.In average,total amount of carbon deposition is larger near the electrolyte.These observations imply complex interplay between the electrochemical steam generation and methane cracking on Ni surface which take place very locally near the active TPB.

Effects of Syngas Particulate Fly Ash Deposition on the Mechanical Properties of Thermal Barrier Coatings on Simulated Film-Cooled Turbine Vane Components

Research is being conducted to study the effects of particulate deposition from contaminants in coal synthesis gas (syngas) on the mechanical properties of thermal barrier coatings (TBC) employed on integrated gasification combined cycle (IGCC) turbine hot section airfoils. West Virginia University (WVU) had been working with US Department of Energy, National Energy Technology Laboratory (NETL) to simulate deposition on the pressure side of an IGCC turbine first stage vane. To model the deposition, coal fly ash was injected into the flow of a combustor facility and deposited onto TBC coated, angled film-cooled test articles in a high pressure (approximately 4 atm) and a high temperature (1560 K) environment. To investigate the interaction between the deposition and the TBC, a load-based multiple-partial unloading micro-indentation technique was used to quantitatively evaluate the mechanical properties of materials. The indentation results showed the Young’s Modulus of the ceramic top coat was higher in areas with deposition formation due to the penetration of the fly ash. This corresponds with the reduction of strain tolerance of the 7% yttria-stabilized zirconia (7YSZ) coatings.

Syngas Production by Methane Reforming with Carbon Dioxide on Noble Metal Catalysts

在稳定氧化铝的氧化镁(尖晶石) 上支持的一系列贵金属催化剂(Ru，坚牢酸性蓝 RH，红外，磅，和 Pd ) 被用来由甲烷与二氧化碳改过生产 syngas。综合催化剂用赌注， TPR， TPO， TPH，和 H2S 化学吸着技术被描绘。活动结果为 Ru 干旱坚牢酸性蓝 RH 催化剂显示出高活动和稳定性。TPO 和 TPH 分析显示为 Pd 催化剂的更低的活动和稳定性的主要原因是不太反应的扔的碳的形成和催化剂的 sintering。给词调音：贵金属；syngas；干燥改过；二氧化碳；

Carbon Dioxide Reforming of Methane to Syngas by Thermal Plasma

Experiments were conducted on syngas preparation from dry reforming of methane by carbon dioxide with a DC arc plasma at atmospheric pressure.In all experiments,nitrogen gas was used as the working gas for thermal plasma to generate a high-temperature jet into a horizontal tube reactor.A mixture of methane and carbon dioxide was fed vertically into the jet.In order to obtain a higher conversion rate of methane and carbon dioxide,chemical energy efficiency and fuel production efficiency,parametric screening studies were conducted,in which the volume ratio of carbon dioxide to methane in fed gases and the total flux of fed gases were taken into account.Results showed that carbon dioxide reforming of methane to syngas by thermal plasma exhibited a larger processing capacity,higher conversion of methane and carbon dioxide and higher chemical energy efficiency and fuel production efficiency.In addition,thermodynamic simulation for the reforming process was conducted.Experimental data agreed well with the thermodynamic results,indicating that high thermal efficiency can be achieved with the thermal plasma reforming process.

Characterization of Carbon Deposits Formed During Plasma Pyrolysis of Xinjiang Candle Coal

Carbon deposits were formed on the reactor wall during plasma pyrolysis of theXinjiang candle coal in our V-style plasma pyrolysis pilot-plant. The carbon deposits were studiedusing a scanning electronic microscope (SEM) and the X-ray diffraction (XRD) method. It wasfound that carbon deposits located at different parts in the reactor exhibited different microscopicpatterns. The formation mechanism of the carbon deposits was deduced. The downward increasein the graphitization degree of the carbon deposits was found and interpreted.

Influence of Supports on Catalytic Performance and Carbon Deposition of Palladium Catalyst for Methane Partial Oxidation

The catalytic performance of methane partial oxidation was investigated on Pd/CeO2-ZrO2 and Pd/α-Al2O3 catalysts.The catalysts were characterized by XRD,Raman spectra,and TG-DTA techniques.The results show that CeO2-ZrO2 support is more advantageous for the catalytic activity and stability of catalysts compared to α-Al2O3.TG-DTA and Raman spectra results indicated that carbon deposited on the catalysts was in the form of graphite,which is the main reason for the deactivation of catalysts after a 24-hour reaction.Moreover,CeO2-ZrO2 had positive effect on inhibiting carbon deposition.

Topography,structure,and formation kinetic mechanism of carbon deposited onto nickel in the temperature range from 400 to 850°C

The carbon deposition behavior on nickel particles was observed within the temperature range from 400 to 800°C in a pure methane atmosphere.The topography,properties,and molecular structure of the deposited carbon were investigated using field-emission scanning electron microscopy(FESEM),temperature-programmed oxidation(TPO) technology,X-ray diffraction(XRD),and Raman spectroscopy.The deposited carbon is present in the form of a film at 400–450°C,as fibers at 500–600°C,and as particles at 650–800°C.In addition,the structure of the deposited carbon becomes more ordered at higher temperatures because both the TPO peak temperature of deposited carbon and the Raman shift of the G band increase with the increase in experimental temperature,whereas the intensity ratio between the D bands and the G band decreases.An interesting observation is that the carbon deposition rate is suppressed in the medium-temperature range(M-T range) and the corresponding kinetic mechanism changes.Correspondingly,the FWHM of the G and D1 bands in the Raman spectrum reaches a maximum and the intensities of the D2,D3,and D4 bands decrease to low limits in the M-T range.These results indicate that carbon structure parameters exhibit two different tendencies with respect to varying temperature.Both of the two group parameters change dramatically as a peak function with increasing reaction temperature within the M-T range.

Minimizing carbon deposition in plasma-induced methane coupling with structured hydrogenation catalysts

The effect of temperature and hydrogen addition on undesired carbonaceous deposit formation during methane coupling was studied in DBD-plasma catalytic-wall reactors with Pd/Al2 O3, using electrical power to drive the reaction.Experiments with thin catalyst layers allowed comparison of the performance of empty reactors and catalytic wall reactors without significantly influencing the plasma properties.The product distribution varies strongly in the temperature window between 25 and 200℃Minimal formation of deposits is found at an optimal temperature around 75℃ in the catalytic-wall reactors.The selectivity to deposits was c.a.10% with only 9 mg of catalyst loading instead of 45% in the blank reactor,while decreasing methane conversion only mildly.Co-feeding H2 to an empty reactor causes a similar decrease in selectivity to deposits,but in this case methane conversion also decreased significantly.Suppression of deposits formation in the catalytic-wall reactor at 75℃ is due to catalytic hydrogenation of mainly acetylene to ethylene.In the empty reactor,H2 co-feed decreases conversion but does not change the product distribution.The catalytic-wall reactors can be regenerated with H2-plasma at room temperature,which produces more added-value hydrocarbons.

Kinetics of Carbon Deposition on Hexaaluminate LaNiAl_(11)O_(19) Catalyst During CO_2 Reforming of Methane

In this paper, the properties of carbon deposited on hexaaluminate LaNiAl11O19 catalyst were characterized by X-ray photoelectron spectroscopy (XPS), and in the meantime, the amount of carbon deposited on the catalyst, after both CH4 decomposition and CO2 reforming of CH4, was determined by means of thermogravimetric analysis (TGA), respectively. The rates of carbon deposited on the catalyst were also investigated and the apparent kinetic equation of CO2 reforming of CH4:carbon and the pressure ratio of CH4 and CO2.

Organic carbon deposition flux on the North Chukchi Sea shelf based on ^(210)Pb radioactivity dating

Deposition of organic carbon forms the final net effect of the ocean carbon sink at a certain time scale. Organic carbon deposition on the Arctic shelves plays a particularly important role in the global carbon cycle because of the broad shelf area and rich nutrient concen tration. To determine the organic carbon deposition flux at the northern margin of the Chukchi Sea shelf, the 210Pb dating method was used to analyze the age and deposition rate of sediment samples from station R17 of the third Chinese National Arctic Research Expedition. The results showed that the deposition rate was 0.6 mm·a-1, the apparent deposition mass flux was 0.72 kg·m-2·a-1, and the organic carbon deposition flux was 517 mmol C·m-2·a-1,.It was estimated that at least 16% of the export organic carbon flux out of the euphotic zone was transferred and chronically buried into the sediment, a value which was much higher than the average ratio (-10%) for lowto mid-latitude regions, indicating a highly effective carbon sink at the northern margin of the Chukchi Sea shelf. With the decrease of sea ice coverage caused by wanning in the Arctic Ocean, it could be inferred that the Arctic shelves will play an increasingly important role in the global carbon cycle.

Effects of specific surface area of metallic nickel particles on carbon deposition kinetics

Carbon deposition on nickel powders in methane involves three stages in different reaction temperature ranges. Temperature programing oxidation test and Raman spectrum results indicated the formation of complex and ordered carbon structures at high deposition temperatures. The values of I(D)/I(G) of the deposited carbon reached 1.86, 1.30, and 1.22 in the first, second, and third stages, respectively. The structure of carbon in the second stage was similar to that in the third stage. Carbon deposited in the first stage rarely contained homogeneous pyrolytic deposit layers. A kinetic model was developed to analyze the carbon deposition behavior in the first stage. The rate-determining step of the first stage is supposed to be interfacial reaction. Based on the investigation of carbon deposition kinetics on nickel powders from different resources, carbon deposition rate is suggested to have a linear relation with the square of specific surface area of nickel particles.

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%.

Study on Highly Active Catalysts and a Once-Through Process for Methanol Synthesis from Syngas

Highly active CNT-promoted co-precipitated Cu-ZnO-Al2O3 catalysts, symbolized asCuiZnjAlk-x%CNTs, were prepared, and their catalytic activity for once-through methanol synthesis fromsyngas was investigated. The results illustrated that, under the reaction conditions (at 493 K, 5.0 MPa, thevolume ratio of H2/CO/CO2/N2＝ 62/30/5/3, GHSV＝ 4000 h-1), the observed single-pass CO-conversionand methanol-STY over a Cu6Zn3Al1-12.5%CNTs catalyst reached 64% and 1210 mg/(h@g), which wasabout 68% and 66% higher than those (38% and 730 mg/(h@g)) over the corresponding CNT-free catalyst,Cu6Zn3Al1, respectively. The characteristic studies of the catalysts revealed that appropriate incorporationof a minor amount of the CNTs into the CuiZnjAlk brought about little change in the apparent activationenergy of the methanol synthesis reaction, however, led to a considerable increase in the catalyst's active Cusurface area and pronouncedly enhanced the stationary-state concentration of active hydrogen-adspecieson the surface of the functioning catalyst, which would be favorable to increasing the rate of the CO hydro-genation reactions. Moreover, the operation temperature for methanol synthesis over the CNT-promotedcatalysts can be 10-20 degrees lower than that over the corresponding CNT-free contrast system, whichwould contribute considerably to an increase in equilibrium CO-conversion and CH3OH-yield.

Simultaneous syngas production with different H_2/CO ratio in a multi-tubular methane steam and dry reformer by utilizing of CLC

For syngas production, the combustion of fossil fuels produces large amounts of CO2 as a greenhouse gas annually which intensifies global warming. In this study, chemical looping combustion(CLC) has been utilized for the elimination of CO2 emission to atmosphere during simultaneous syngas production with different H2/CO ratio in steam reforming of methane(SR) and dry reforming of methane(DR) in a CLC-SR-DR configuration. In CLC-SR-DR with 184 reformer tubes(similar to an industrial scale steam reformer in Zagros Petrochemical Company, Assaluyeh, Iran), DR reaction occurs over Rh-based catalysts in 31 tubes. Also, SR reaction is happened over Ni-based catalysts in 153 tubes. CLC via employment of Mn-based oxygen carriers supplies heat for DR and SR reactions and produces CO2 and H2O as raw materials simultaneously. A steady state heterogeneous catalytic reaction model is applied to analyze the performance and applicability of the proposed CLC-SR-DR configuration. Simulation results show that combustion efficiency reached 1 at the outlet of fuel reactor(FR). Therefore,pure CO2 and H2O can be recycled to DR and SR sides, respectively. Also, CH4 conversion reached 0.2803 and 0.7275 at the outlet of SR and DR sides, respectively. Simulation results indicate that, 3223 kmol h-1syngas with a H2/CO ratio equal to 9.826 was produced in SR side of CLC-SR-DR. After that, 1844 kmol h-1syngas with a H2/CO ratio equal to 0.986 was achieved in DR side of CLC-SR-DR. Results illustrate that by increasing the number of DR tubes to 50 tubes and considering 184 fixed total tubes in CLC-SR-DR, CH4 conversions in SR and DR sides decreased 2.69% and 3.31%, respectively. However, this subject caused total syngas production in SR and DR sides(in all of 184 tubes)enhance to 5427 kmol h-1. Finally, thermal and molar behaviors of the proposed configuration demonstrate that CLC-SR-DR is applicable for simultaneous syngas production with high and low H2/CO ratios in an environmental friendly process.

Effect of CeO_(2) on carbon deposition resistance of Ni/CeO_(2) catalyst supported on SiC porous ceramic for ethanol steam reforming

Ni/CeO_(2) catalysts(nCeO_(2):n_(Ni)=0,1,4,7,10)supported on SiC porous ce ramics for ethanol steam reforming(ESR)were investigated with respect to hydrogen production performance and growth of carbon deposition.The oxygen released from CeO_(2) enables the oxidation of CH_(x) species to serve as carbon precursors,thus providing Ni/CeO_(2) catalysts with stronger resistance to carbon deposition compared with Ni catalysts.The Ni/CeO_(2) catalysts prepared by inverse microemulsion and impregnation methods exhibit regular semicircular spherical shape on SiC porous ceramics.Under 500℃for 25 h of ESR reaction,the ethanol conversion rate over Ni/CeO_(2) catalysts(n_(CeO_(2)):n_(Ni)=7)is sustained up to 100%and H_(2) selectivity is essentially kept at 74%.The by-product selectivity declines stepwise with increasing content of CeO_(2),which is attributed to the adsorption and oxidation of CO and of CH_(x) species as CH_4 precursor from CeO_(2).The scanning electron microscopy(SEM)and transform electron microscopy(TEM)results reveal that further loading of CeO_(2) on the surface of Ni catalysts can alleviate both migration and sintering of Ni particles.Furthermore,carbon deposition on Ni/CeO_(2) catalysts preferentially outgrow filamentous rather than amorphous carbon,with a tendency for the latter to be more deactivated.

Modeling of Crack Development Associated with Proppant Hydraulic Fracturing in a Clay-Carbonate Oil Deposit

Survey and novel research data are used in the present study to classify/identify the lithological type of Verey age reservoirs’rocks.It is shown how the use of X-ray tomography can clarify the degree of heterogeneity,porosity and permeability of these rocks.These data are then used to elaborate a model of hydraulic fracturing.The resulting software can take into account the properties of proppant and breakdown fluid,thermal reservoir conditions,oil properties,well design data and even the filtration and elastic-mechanical properties of the rocks.Calculations of hydraulic fracturing crack formation are carried out and the results are compared with the data on hydraulic fracturing crack at standard conditions.Significant differences in crack formation in standard and lithotype models are determined.It is shown that the average width of the crack development for the lithotype model is 2.3 times higher than that for the standard model.Moreover,the coverage of crack development in height for the lithotype model is almost 2 times less than that for the standard model.The estimated fracture half-length for the lithotype model is 13.3%less than that of for the standard model.A higher dimensionless fracture conductivity is also obtained for the lithotype model.It is concluded that the proposed approach can increase the reliability of hydraulic fracturing crack models.

Dissolved organic carbon fractionation in wet deposition and its potential impact on radiative forcing in the central Tibetan Plateau

As an important component of carbonaceous matters,dissolved organic carbon(DOC)can absorb and scatter the solar radiation at ultraviolet and blue wavelengths.The wet deposition process has great impact on the con-centration and light absorption ability of precipitation DOC,affecting the climatic effect caused by DOC in the atmosphere.In this study,light absorption and fluorescence characteristics of precipitation DOC was investigated in the central Tibetan Plateau(TP).The results showed that the mean DOC concentration and mass absorption cross-section measured at 365 nm(MAC_(365)) in Tanggula(TGL)station were 0.59±0.42 mg/L and 0.37±0.19 m^(2)/g,respectively,while both values showed much higher volatilities than those of aerosols.DOC concentrations had significant negative correlation with the precipitation amount,while MAC_(365) values increase with the precipitation amount in TGL station.Therefore,DOC with high light-absorbing ability was preferred to be retained in the atmosphere during wet deposition.In this study,precipitation DOC contained three fluorescent components(one humic-like component and two tyrosine-like components)mainly from local biomass burning sources.DOC concentration showed a negative relationship with MAC_(365) value in TGL station.The wet deposition of DOC with low light-absorbing ability can reduce the strong negative radiative forcing caused by secondary organic aerosol due to high proportion of DOC in secondary organic carbon.Similar phenomenon was also found in Nam Co,Lulang and Everest stations of previous study,which may have a potential impact on radiative forcing in the atmosphere of TP.

Origin of the Dashuigou independent tellurium deposit at Qinghai–Xizang Plateau: constraints from the light stable isotopes C, O, and H

By studying the light isotopic compositions of carbon,oxygen,and hydrogen,combined with previous research results on the ore-forming source of the deposit,the authors try to uncover its metallogenic origin.The δ^(18)O and δ^(13)C isotope signatures of dolomite samples vary between 10.2 and 13.0‰,and between−7.2 and−5.2‰,respectively,implying that the carbon derives from the upper mantle.δD and δ^(18) O of quartz,biotite,and muscovite from diff erent ore veins of the deposit vary between−82 and−59‰,and between 11.6 and 12.4‰,respectively,implying that the metallogenic solutions are mainly magmatic.According to the relevant research results of many isotope geologists,the fractionation degree of hydrogen isotopes increases as the depth to the Earth’s core increases,and the more diff erentiated the hydrogen isotopes are,the lower their values will be.In other words,mantle-derived solutions can have extremely low hydrogen isotope values.This means that the δD‰ value−134 of the pyrrhotite sample numbered SD-34 in this article may indicate mantle-derived oreforming fl uid of the deposit.The formation of the Dashuigou tellurium deposit occurred between 91.71 and 80.19 Ma.

Bamboo-like N-doped carbon nanotubes encapsulating M(Co,Fe)-Ni alloy for electrochemical production of syngas with potential-independent CO/H_(2) ratios

The electrochemical conversion of CO_(2)-H_(2)O into CO-H_(2) using renewable energy is a promising technique for clean syngas production.Low-cost electrocatalysts to produce tunable syngas with a potential-independent CO/H_(2) ratio are highly desired.Herein,a series of N-doped carbon nanotubes encapsulating binary alloy nanoparticles(MxNi-NCNT,M=Fe,Co)were successfully fabricated through the co-pyrolysis of melamine and metal precursors.The MxNi-NCNT samples exhibited bamboo-like nanotubular structures with a large specific surface area and high degree of graphitization.Their electrocatalytic performance for syngas production can be tuned by changing the alloy compositions and modifying the electronic structure of the carbon nanotube through the encapsulated metal nanoparticles.Consequently,syngas with a wide range of CO/H_(2) ratios,from 0.5:1 to 3.4:1,can be produced on MxNi-NCNT.More importantly,stable CO/H_(2) ratios of 2:1 and 1.5:1,corresponding to the ratio to produce biofuels by syngas fermentation,could be realized on Co1Ni-NCNT and Co2Ni-NCNT,respectively,over a potential window of-0.8 to-1.2 V versus the reversible hydrogen electrode.Our work provides an approach to develop low-cost and potential-independent electrocatalysts to effectively produce syngas with an adjustable CO/H_(2) ratio from electrochemical CO_(2) reduction.

Carbon deposition and catalytic deactivation during CO_2 reforming of CH_4 over Co/MgO catalyst

The deactivation mechanism of Co/MgO catalyst for the reforming of methane with carbon dioxide was investigated. The conversion of CH4 displayed a significant decrease in the initial stage caused by carbon deposition.There were two types of cokes, carbon nanotubes(CNTs) and carbon nano-onions(CNOs). The number of the CNO layers that coated on the surface of Co nanoparticles(NPs) increased rapidly in the initial reforming time,which was responsible for the deactivation of the Co/MgO catalyst. The deposition of CNOs was attributed to the oxidation of Co NPs. Therefore, the deactivation of the Co/MgO catalyst was originated from the first oxidization of the Co NPs into Co3 O4 by O species(OH intermediate, CO_2, H2 O) during the reforming reaction,which accelerates the formation of coke that blocked the active metal, thus led to catalyst deactivation.