Carbon Coke Research Articles

Improved catalytic activity under internal reforming solid oxide fuel cell over new rhodium-doped perovskite catalyst

The catalytic partial oxidation of methane is evaluated over a Rh (2–15 mol%)-doped Sr0.92Y0.08TiO3-δ (SYT) perovskite-based catalyst prepared by the Pechini method for fuel-cell applications. The Rh dopant replaces titanium in the SYT catalyst, resulting in a catalyst with excellent and stable catalytic performance during thermal cycling in the temperature range 600–900 °C and in long-term stability tests at 750 °C for 130 h, without deactivation due to carbon coking or sintering. A systematic round-robin characterization is carried out by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and CO chemisorption to establish the chemical and physical properties of the catalyst. Adding Rh as a dopant in the catalyst significantly promotes the catalytic activity due to the presence of exsoluted rhodium particles on the catalyst surface. Small particles (2–5 nm) of Rh on the SYT surface are observed to be evenly dispersed, without agglomeration, and the turnover frequency (TOF) of the POM reaction increased. In the long-term stability tests, catalysts are tested in direct internal reforming at an SOFC anode, achieving high methane conversion (∼99%) in both dry and wet conditions.

Development of Technology for Recycling Copper Smelting Production Waste

Extensive research is conducted and a production scheme is proposed, including recovery of copper-containing slag with coke carbon and neutralization of waste copper electrolyte with the product obtained.

Emission inventory of carbonyl sulfide (COS) from primary anthropogenic sources in China

An emission inventory of carbonyl sulfide (COS) from primary anthropogenic sources in China was compiled from 2010 to 2015. The national total emission was estimated at 174 Gg S yr−1 in 2015, with an annually average sustainable growth rate of 7.2% from 2010 to 2015. Industrial sources, biomass burning, coal combustion, agricultural sources and vehicle exhaust contributed 68.2%, 22.0%, 6.1%, 2.2%, and 1.5%, respectively, of total COS emissions in 2015. Aluminum production, carbon black production, titania production, coke production, pulp and paper industry, were the main industrial sources of COS, with the emission about 118 Gg S yr−1 COS in 2015, accounting for 98.5% of total direct emissions from the Chinese industry. The distribution of COS emissions in China showed significant differences at the provincial level. In Shandong and Xinjiang province, they were much bigger than other provinces, with total emissions of 31 and 15 Gg S yr−1, respectively. Uncertainty analysis of COS emission inventories showed that the emission range was 70–267 Gg S yr−1 at a 95% confidence interval. In this study, COS emissions in China were much higher than prior underestimated estimations, even for Asian and global emissions, which could be resolved part of missing sources in the global COS budget.

High performance, coking-resistant and sulfur-tolerant anode for solid oxide fuel cell

Solid oxide fuel cell can efficiently generate electricity using methane fuel; however, methane cracking at high temperature often results in carbon deposition that leads to degradation of power output. Here, metal-oxide interface is in stiu constructed in LSCM anode to enhance methane oxidation. The anchored interface demonstrated exceptionally high resistance to carbon coking and sulfur poisoning. The peak power density with Cu0.5Fe0.5 -LSCM anode is as high as 0.64 W cm−2 using methane fuel at 850 °C. Electrochemical measurement shows a stable power output under current density of 0.4 A cm−2 using methane fuel even after 10 redox cycles at 850 °C.

Effects of nascent char on ex-situ catalytic fast pyrolysis of wheat straw

This study aims to investigate the effects of nascent char in pyrolysis process on the product distribution from ex-situ catalytic fast pyrolysis (CFP) of biomass. Fast pyrolysis of wheat straw without HZSM-5 as well as with insufficient/sufficient HZSM-5 were performed with controlled extents of volatile-char interaction in a two-stage fluidized-bed/fixed-bed combination reactor. The results show that nascent char has the catalytic ability to promote the secondary cracking of pyrolysis vapors and the secondary formation of solid organics. The carbon yield of olefins + aromatics increased from 12.33% to 14.70% and then decreased to 12.68% with intensified volatile-char interaction when HZSM-5 was insufficient. The initial increase can be explained by the higher conversion efficiency of residual light compounds for HZSM-5 catalysis after volatile-char interaction. Nascent char was observed to have negative effects on the production of aromatics and olefins when HZSM-5 was sufficient. However, with a slight decrease (by 2.04%) in the carbon yield of olefins + aromatics at the beginning of char accumulation, coke carbon yield significantly decreased by 15.88%. CFP of raw and acid-washed wheat straw over insufficient HZSM-5 with controlled extents of volatile-char interaction were further compared. It is demonstrated that the inorganic minerals in raw biomass play as the active components of nascent char in volatile-char interaction.

To the question of improving steel processing technology by converter vanadium slag

The results of thermodynamic modeling and laboratory study of the process of steel microalloying by vanadium from converter vanadium slag using coke carbon and silicon ferrosilicon are presented. These experimental studies on a laboratory arc furnace confirmed the results of thermodynamic modeling.

Ethanol Decomposition on Pd–Au Alloy Catalysts

The mechanisms of ethanol (EtOH) decomposition via C–C or C–O bond cleavage on alloy surfaces are currently not well understood. In this study, we model EtOH decomposition on close-packed Pd–Au catalytic surfaces using density functional theory (DFT) calculations and derived Bronsted–Evans–Polanyi (BEP) relationships. Three characteristic Pd–Au surfaces are considered, Pd1Au2(111), Pd2Au1(111), and a Pd monolayer (ML), PdML(111), on a Au substrate. We show that, on close-packed Pd–Au surfaces, the C–C bond is easier to cleave than C–O, indicating that the formation of CH4 and CO is favored as the products of EtOH decomposition. Interestingly, we find that, though the C–C and C–O activation barriers on PdML(111) are generally lower than those on the other two surfaces, it is less active for EtOH decomposition due to a slow release of H2 and possible carbon coking. Pd2Au1(111), on the other hand, has a higher theoretical reaction rate due to facile H2 evolution from the surface and less carbon coking. A com...

Structure and Evolution of Confined Carbon Species during Methane Dehydroaromatization over Mo/ZSM-5

Surface carbon (coke, carbonaceous deposits) is an integral aspect of methane dehydroaromatization catalyzed by Mo/zeolites. We investigated the evolution of surface carbon species from the beginning of the induction period until the complete catalyst deactivation by the pulse reaction technique, TGA, 13C NMR, TEM, and XPS. Isotope labeling was performed to confirm the catalytic role of confined carbon species during MDA. It was found that “hard” and “soft” coke distinction is mainly related to the location of coke species inside the pores and on the external surface, respectively. In addition, MoO3 species act as an active oxidation catalyst, reducing the combustion temperature of a certain fraction of coke. Furthermore, after dissolving the zeolite framework by HF, we found that coke formed during the MDA reaction inside the zeolite pores is essentially a zeolite-templated carbon material. The possibility of preparing zeolite-templated carbons from the most available hydrocarbon feedstock is important for the development of these interesting materials.

Element Distribution in the Silicomanganese Production Process

A pilot scale, silicomanganese alloy production campaign was performed in a 440 kVA, single phase electric furnace in order to establish an overview of the minor- and trace element contents in process input raw materials and their distribution in the resulting primary and secondary products. Samples of the in-going raw materials (manganese ore, coke, quartzite, and high carbon ferromanganese slag) and the out-going products (silicomanganese alloy, silicomanganese slag, and dust) were analyzed by inductively coupled plasma mass spectrometry. The distribution of 51 elements between the product phases was discussed in terms of their boiling temperatures, Gibbs energies of oxidation and activity coefficients of elements in the metal. A thermochemical simulation using the thermochemical software FactSage 7.1 was also carried out in order to model element phase distribution between the alloy, slag, and dust/gas. The correlation between the model and experimental element concentrations in the silicomanganese slag and dust is fair for most elements. However, in the metal phase, fewer elements show good correlation between modeled results and measured experimental concentrations. The discrepancy could be explained by a lack of accurate thermodynamic descriptions for several minor species in the database.

Palladium Nanoparticles on Nickel for Direct Methanol Solid Oxide Fuel Cell Catalyst

Direct Methanol Solid Oxide Fuel Cell (DMSOFCs) has been drawn comparable attentions in fuel cell society for its fuel flexibility and high energy density of methanol compared to that of hydrogen. However, carbon coking and carbon monoxide poisoning occur due to usage of methanol as fuel, which hinder electrode kinetics and eventually cause performance degradation. Therefore, demand of high performance catalyst with excellent stability has been risen for the widespread usage of DMSOFC. To these days, bimetallic Pt-Ru is known as the best DMSOFC catalyst for its superior methanol oxidation capability. However, high scarcity of Pt and Ru hinders the widespread commercialization of DMSOFC for its expensive price. Recently, Ni has been considered as promising alternative for Pt-Ru. Price of Ni is far lower than that of Pt or Ru, and Ni has respectable methanol oxidation ability. During electrochemical oxidation of methanol, however, carbon tends to deposited on the surface of Ni, which leads performance and stability degradation of Ni catalyst. In this study, we deposited the palladium nanoparticles on the surface of Ni in order to obtain bimetallic Pd/Ni catalyst for DMSOFC application. Pd nanoparticles were deposited by DC magnetron sputtering and atomic layer deposition. DMSOFC with Pd/Ni catalyst were analyzed by current-voltage measurement and electrochemical impedance spectroscopy at the temperature range of 300 - 450 ºC. Pd/Ni catalyst showed enhanced performance and stability compared to bare Ni catalyst. Detailed analysis of experiment will be discussed in the presentation.

Thermodynamic evaluation of hydrazine assisted glycerol reforming for syngas production and coke inhibition

Thermodynamic investigation of glycerol reforming has been performed to study hydrogen production, carbon dioxide evolution and coke formation. Gibb's free energy direct minimization procedure was used to calculate the concentration of different components at equilibrium. The analysis was performed at temperatures from 300K to 1000K under unit atmospheric pressure. A comparative study on steam reforming of glycerol (SRG) and glycerol reforming reaction with hydrazine has been conducted in the presence of hydrazine that act as a suitable reducing agent. Incorporation of hydrazine into glycerol reforming system helped in minimizing coke formation, maximizing hydrogen and syn-gas production. A complete conversion of glycerol with coke free products, along with reduced level of carbon dioxide and maximum hydrogen generation was obtained when glycerol steam reforming process (S/G = 1) was combined with higher moles of hydrazine. Reformation at higher temperatures could enhance the hydrogen production and decrease carbon generation due to methanation reaction and hence optimum results were accomplished at 1000K and atmospheric pressure.

Transformation of Coke Carbon Textures and Minerals during Gasification Investigated by SEM/EDS

The carbon textures, minerals, and their interactions of a metallurgical coke during gasification reaction were investigated using scanning electron microscopy/energy dispersive spectroscopy by analyzing exactly the same sites of coke surfaces before and after reaction. The results indicate that most inert maceral-derived component (IMDC) had a greater propensity to react with CO2 than the reactive maceral-derived component (RMDC). A portion of the carbon in mineral-carrying IMDC was removed as a result of the reaction with CO2, leaving minerals, primarily alumino-silicates, more pronounced. However, the reactivity of IMDC was found to be similar to that of RMDC in some cases. The physical features of the alumino-silicates in the coke were barely altered but bound with alkalis during the reaction. The Fe-containing phases were highly active and had strong interactions with the carbon matrix. Voids were formed in the carbon matrix associated with the Fe-containing phases as a result of the catalytic carbon...

Ignition of Particles of Wet Woody Biomass under Convective Diffusion of Water Vapor in the Near-Wall Region

This paper presents the results of an experimental and theoretical study of heat and mass transfer during ignition of wet wood particles in a high-temperature gas medium. Experiments were carried out in a setup which provides conditions similar to the combustion spaces of boiler units. The main heat transfer parameters (ambient temperature) and integrated ignition characteristics (ignition delay) were measured. The measurement error of these parameters did not exceed 18%. The convective transfer of water vapor formed during evaporation of pore moisture and pyrolysis products were found to have an insignificant effect on the ignition characteristics and conditions. From the results of the experiments, a mathematical model of the ignition process was developed which describes the simultaneous occurrence of the main processes of thermal preparation under conditions of intense phase (evaporation of water) and thermochemical transformations (thermal decomposition of the organic part of the fuel, thermochemical interaction between water vapor and carbon coke, ignition of volatiles) taking into account the convective diffusion of water vapor and pyrolysis products in the near-wall gas area during the induction period. The theoretical ignition delay is in satisfactory (within the confidence interval) agreement with the experimental value. The numerical model of the diffusion flame adequately (good agreement between experimental and theoretical ignition delays) describes the ignition of a wet wood particle.

In Situ Exsolved Core-Shell Nanoparticles on Perovskite Parent: A Novel High-Performance Anode for Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) with a high energy conversion efficiency and low emissions are considered as promising substitutes for traditional thermal power devices[ 1 ,2]. However, the conventional Ni based anode suffers from agglomeration, sulfur poisoning and carbon coking with hydrocarbon fuels, which limit its application[3]. Various alternative materials have been studied as promising SOFC anodes. Meanwhile, in situ exsolution has been developed as a fabrication strategy to prepare perovskite oxides with uniformly dispersed nanometallic particles[4]. Recently, A-site ordered PrBaMn2O5+d has been reported as a promising anode with high electrical conductivity and good catalytic activity for the electrochemical oxidation of both hydrogen and hydrocarbons[5]. In this work, La0.5Ba0.5Mn1-2xCoxFexO3-δ (x=0, 0.05, 0.1) has been synthesized with the Pechini method and investigated as an anode material of SOFCs with H2 and methane as fuels. The structure of the anode converts from a mixture of cubic and hexagonal phases to a perovskite structure with core-shell nanoparticles on the surface after reduction. The in situ exsolution process of the metals on the B sites is studied with an X-ray photoelectron spectrometer, a thermogravimetric analyzer and a transmission electron microscope. The results of the electrochemical tests demonstrate that the doping of Co and Fe into B sites effectively improve the performance of the single cell with H2 as the fuel. A single cell with a 2CF-LBM anode layer and a 300-μm La0.8Sr0.2Ga0.8Mg0.2O3-δ electrolyte layer exhibits a maximum power density (P max) of 98, 210, 383, 653 and 1479 mW cm-2 with wet H2 as the fuel at 650, 700, 750, 800 and 850 oC, respectively, and achieves a peak power density of 503 mW cm-2 at 850 oC when fueled with wet CH4. Moreover, the 2CF-LBM anode exhibits a high coking resistance, and no remarkable degradation of the performance is observed when the cell is operated with methane as the fuel for more than 200 hours. Keywords: Solid oxide fuel cell; Perovskite; Anode; In situ exsolution Table 1. Abbreviations of various anode materials and the maximum output power densities of the cells fed with H2 and CH4 at 850 oC Anode composition Abbreviation P max,H2 (mW cm-2) P max,CH4 (mW cm-2) La0.5Ba0.5MnO3-δ LBM 962 336 La0.5Ba0.5Mn0.9Co0.05Fe0.05O3-δ 1CF-LBM 1241 389 La0.5Ba0.5Mn0.8Co0.1Fe0.1O3-δ 2CF-LBM 1479 503 Figure 1. (a) Bright-field TEM image, (b) HAADF imagine with the EDS linear scanning and (c) EDS elemental map of the reduced 2CF-LBM; (d) I-V and I-P curves of the single cell in 650-850 oC with H2 as fuel. References S. Tao, J.T. Irvine, Nature materials 2003, 2, 320-323.Z. Shao, S.M. Haile, Nature 2004, 431, 170-173.X.M. Ge, S.H. Chan, Q.L Liu, et al., Advanced energy materials 2012, 2, 1156-1181.D. Neagu, G. Tsekouras, D. N. Miller, et al., Nature Chemistry 2013, 5, 916-923.S. Sengodan, S. Choi, A. Jun, et al., Nature materials 2015, 14, 205-209. Figure 1

Carbon Dioxide Capture Using Amine Functionalized Hydrothermal Carbons from Technical Lignin

Amine scrubbing is the most optimized and widely researched post combustion carbon dioxide capture technology till date. However, amine scrubbing remains costly because of high energy inputs during the regeneration stage. Although less researched, “solid sorbents” such as zeolite, active carbon, carbon coke, metal–organic frameworks and mesoporous silica are currently under development for CO2 capture as potential alternatives to amine scrubbers. In this study, sorbents were synthesized from carbonaceous materials (CMs) obtained from hydrothermally treated (350 °C) lignin, a waste material from forest biorefineries. CMs were activated with potassium hydroxide (KOH) at 800 °C to improve their textural properties and finally functionalized with polyethyleneimine (PEI) to also improve its CO2 capture properties. This study evaluated synergistic effect of these two treatments on adsorption capacity of CO2. Activation increased surface area of CMs from 2.8 to 1341 m2 g−1. CO2 capacities of 2 mmol g−1 (L350 PEI 5%) and 1.53 mmol g−1 (L350) could be reached at 30 °C, due to improved textural and chemical properties of the samples. Optimal PEI loading was determined to be 5%, after which CO2 sorption decreased with further additions of PEI. This was ascribed to blockage of the micro-pores in the activated samples at high PEI impregnation. Also, activated samples showed faster adsorption kinetics compared to PEI functionalized activated samples. The feasibility of using waste lignin with improved surface area and surface functionalities as alternative materials for CO2 adsorption was demonstrated.

Progress in Ni-based anode materials for direct hydrocarbon solid oxide fuel cells

Ni-based anode materials of solid oxide fuel cells (SOFCs) are susceptible to carbon deposition and deactivation in direct hydrocarbon fuels, greatly limiting the commercialization. Extensive studies on finding new alternative anode materials have been developed; however, new problems such as low electrochemical performance and complex cell preparation process destroyed the further research passion of Ni-free anode materials. Considering the superior catalytic activity and mature technology of Ni-based anode materials, a large number of recent research results proved that it is still important and promising to solve the carbon coking of Ni-based anode materials. In this review, progress in four typically promising Ni-based anode materials free from carbon coking has been summarized, including the noble metals, ceria, Ba-containing oxides and titanium oxide. Correspondingly, the mechanisms that improve the carbon tolerance of Ni-based modified SOFCs anodes are clearly concluded, providing the materials and theoretical basis for the use of direct hydrocarbon SOFCs as early as possible.

Carbothermal Reduction of Quartz and Carbon Pellets at Elevated Temperatures

In this study, the carbothermal reduction of pellets composed of quartz and carbon at temperatures between 1898 K and 1948 K (1625 °C and 1675 °C) are investigated. The main product from this reaction is silicon carbide (SiC). The reduction of quartz with carbon black, charcoal, coke, coal, and pre-heated coal in the pellet were compared to investigate the different carbon resources used in silicon production. Charcoal and coke have high SiO reactivity, while carbon black and coal (pre-heated coal) have low SiO reactivity. Charcoal and carbon black show better matching between quartz/carbon reactivity and SiO reactivity, and will lose less SiO gas than coke and pre-heated coal. Coal has a high volatile content and is thus not recommended as a raw material for the pellets.

Activating C–H bonds with isolated atoms

Sprinkling individual platinum atoms across a copper surface yields an energy-efficient and durable bimetallic catalyst that effectively mediates reactions involving C–H bond activation, according to a study (Nat. Chem. 2018, DOI: 10.1038/nchem.2915). Breaking C–H bonds is the first step in converting relatively inert compounds such as methane and other alkanes to more valuable fuels and chemicals. Industrial processes for carrying out this type of chemistry are well developed. Many manufacturers rely on steam cracking, for example, to convert ethane to ethylene. But that process is energy intensive. Catalysts can mediate C–H-activation chemistry and reduce the required energy input, but they have shortcomings. Platinum, for example, can dramatically reduce the temperature for C–H activation, but it is expensive. Nickel, which is relatively inexpensive, also works as a C–H activation catalyst, but both it and platinum are prone to coking, a process that generates a film of carbon (coke) that gunks up

The Conditions and Characteristics of Wood Particles Ignition in the Stream of the High Temperature Gases

ABSTRACTThe results of the experimental and theoretical studies of the ignition processes of the single woody biomass particles have been given. The experiments have been carried out on the setup, providing the closest conditions to the combustion space of the boiler units. The main parameters of heat transfer (the ambient temperature Tg) and the main characteristic of the process—the ignition delay time (tign) have been registered. The equipment has been used in the experiments providing with high precision the determination of the main conditions and characteristics of ignition. According to the results of the experiments, the mathematical model has been formulated describing the heating and thermal decomposition of the wood taking into account the formation of the gaseous and solid products. The model also describes the moisture evaporation, the thermochemical interaction of water vapor and carbon coke, and oxidation of the pyrolysis products with oxygen in the gas area. The nature of the relations of the heat exchange conditions, the temperature field of the particle, and ignition dynamics has been determined. It has been shown that the determining factor is not only the content of the volatiles and moisture of wood, but also the distribution of moisture in the particle. The record of the distribution of moisture content across the thickness of the layer results in the change of moisture from 0% to 60% to increase the time delay of the ignition 2–3 times. The relation has been determined between the particle size, the moisture content, and the ignition delay time.

Combustion control system for coke ovens embedded with auto positioning systems

ABSTRACTA good grade coke produces highest thermal energy and it is highly efficient in hot metal reduction. In order to concentrate the carbon in coke, the coke making process involves carbonisation of coal to high temperature (1100°C) in an oxygen-free atmosphere. There is always a need to efficiently automate the coke oven operations as much as possible. In order to improve the level of control and management of coke oven, the research on intelligent control system is carried out. In modern advanced control system of coke oven, the control scheme of combination of feedback and feed-forward merged with management is widely utilised. The integrated management and control system of coke oven is introduced systematically, including the production plan and scheduling management (dynamic scheduling) and heating control system (mathematical modelling) i.e. evaluating battery temperature, intelligent combustion control system and the pressure control of gas collector of coke oven battery.