Carbon Coke Research Articles

Steam treatment on Ni/γ-Al2O3 for enhanced carbon resistance in combined steam and carbon dioxide reforming of methane

Coke deposition on reforming reaction catalysts, typically Ni particles deposited on alumina supports, has been a major obstacle barring their practical industrial application. In this work, a Ni/γ-Al2O3 catalyst was stabilized by a pretreatment with steam at high temperature of 850°C. The steam-treated Ni/γ-Al2O3 catalyst showed thermodynamically possible highest conversion (98.3% for methane and 82.4% for carbon dioxide) and H2/CO ratio of 2.01 for combined steam and carbon dioxide reforming of methane, and operated stably for 200h. The amount of deposited carbon coke was 3.6% for steam-treated catalysts whereas conventional catalysts had 15.4% of coke after 200h of the reaction. The steam pretreatment removed unstable aluminum that can otherwise leach out, which causes severe carbon deposition at the early stage of the reaction. This novel steam pretreatment enhanced the carbon resistance of the catalysts significantly, resulting in improved activity and long-term stability.

Combustion of carbon in the firing of ceramic heat insulation based on fuel-shale wastes

The firing of ceramic heat insulation based on fuel-shale wastes without traditional materials is investigated. On heating insulation in the range 400–600°C, most of the volatiles are removed. Above 800°C, pyrolytic forms of carbon (coke and semicoke) are produced. In the range 1050–1100°C, the reduction of iron is markedly accelerated. At 1100°C, there are practically no organic compounds in the fired ceramic.

Modeling of solid oxide electrolysis cell for syngas generation with detailed surface chemistry

A solid oxide electrolysis cell model for syngas generation is developed using a button cell test system as a physical base. The model coherently bridges the multi transport processes of charge, mass, momentum, and energy with detailed surface chemistry. The model is validated using experimental polarization curves. Upon the validation, extensive simulations are performed to elucidate surface electrolysis processes. Results indicate that the electrolysis processes of CO2 and H2O are pretty much independent with each other in the H2 electrode (electrolysis cathode). The carbon coking effect is mainly determined by the content of CO2 in the H2 electrode. Increasing the applied cell voltage may improve syngas production, it also causes the enhancement of the surface coverage of C(s) and the deposition of carbon on the surface of Ni catalyst. High operating temperature may effectively improve adsorption/desorption rate and enhance surface electrolysis process as well as potentially mitigate carbon deposition on Ni surface.

Testing Amorphous, Multi-component, Organic Dielectrics According to Their Electronic Spectrums and Color Charcteristics

The original methods of determining physicochemical properties (e.g. relative density, fixed carbon coking ability, viscous flow activation energy, number-average molecular weight, initial material destruction temperature) and characteristics of electronic structure (ionization potentials and electron affinity) of hydrocarbon systems were generalized. In the considered methods for testing dielectrics based on these systems named characteristics are estimated according to radiation absorption coefficients, color characteristics of substance solutions and integral oscillator strength in visible and UV spectrum region. The proved regularities are confirmed with statistical processing of data.

Phase Behaviors of Talc Minerals in Carbothermal Reduction Process

In this paper, we focus on the phase behaviors of talc minerals by carbothermal reduction (CR) method. The effects of temperature and carbon addition are both discussed in our work. In the experiment, acid-leaching talc was employed as raw material, carbon coke powders were adopted as reducing agent. The XRD results show that: When acid-leaching talc was used as raw material, quartz and few enstatite can be obtained at 1300 °C, with the temperature increasing, the diffraction intensities of enstatite increased. At 1550 °C, enstatite transformed to magnesium silicate and obvious β-SiC can be detected. At 1600 °C, the main phases in the final product are magnesium silicate and β-SiC. The SEM results reveal that the preferred, as-fabricated silicon carbide has morphology of irregular shape. Relatively pure β-SiC can be obtained by using acid-leaching talc mixed together with excess 50% of theoretical quantity of carbon powder sintered at 1550 °C for 4 h.

Hydrogen production by supercritical water gasification of glucose with Ni/CeO2/Al2O3: Effect of Ce loading

Ni-based SCWG catalysts attract more attention for its high activity and relatively low cost. However, carbon deposition, which is one of the serious problems, reduces the activity of Ni-based catalysts. Ni/CeO2/Al2O3 catalysts with different Ce loading were prepared by a wet impregnation method. The performance of catalyst in supercritical water was tested in an autoclave reactor at 673K, 24.5MPa. The catalysts before and after reaction were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), BET specific surface area measurements and thermo-gravimetric analyses (TGA). The effects of Ce loading in catalysts on glucose gasification were studied. The results showed that hydrogen yield and hydrogen selectivity increased sharply with addition of Ni/CeO2/Al2O3 catalysts. When the Ce loading content was 8.46wt.%, the maximum H2 yield and H2 selectivity were obtained. The carbon deposition and coking will lead to the deactivation of the catalysts. Based on the thermo-gravimetric analyses, the oxidant kinetic data of carbon deposited on the used catalysts with air was obtained. CeO2 in the Ni/CeO2/Al2O3 catalyst plays an important role in inhibiting carbon deposition by increasing the Ni dispersion and reacting with deposited carbon.

Application of Carbonaceous Materials to Phenol Removal from Aqueous Solution by Adsorption

Low cost carbonaceous materials were evaluated for their ability to remove phenol from wastewater. The effects of adsorbents dosage, contact time and maximum adsorption capacity were investigated for granular activated carbon, powdered activated carbon, petroleum coke and multi-walled carbon nanotube (MWNT). Equilibrium studies were conducted in 50mg/L initial phenol concentration, solution pH of 5 and at temperature of 23°C. The results showed the adsorption process was fast and it reached equilibrium in 3 h. Petroleum coke and MWNT had poor adsorption which could reach the removal efficiency of phenol with 43.18% and 36.64% respectively. The granular activated carbon possessed good adsorption ability to phenol with 96.40% at the optimum dosage 5g and optimum time 90min.The powdered activated carbon was an effective adsorbent with a maximum adsorption capacity of 42.32 mg/g.

Thermodynamic analysis of hydrogen production for fuel cells from oxidative steam reforming of methanol

A thermodynamic analysis of hydrogen production from oxidative steam reforming (OSR) of methanol has been carried out by a Gibbs free energy minimization method. The equilibrium yields of hydrogen, carbon monoxide, methane and coke as a function of H2O/MeOH ratio (0.0–10.0), O2/MeOH ratio (0.0–1.0), and temperature (200°C, 400°C, 600°C, 800°C) at 0.1MPa are investigated. Methanol can be fully converted at any H2O/MeOH and O2/MeOH ratio in the condition range evaluated. Methane is the main product at low temperatures (200°C, 400°C), while hydrogen and carbon monoxide become dominant products with the increase of the temperature. 600°C is favorable for hydrogen production at which the highest hydrogen yield appears. Carbon monoxide yield increases monotonically with the increase of the temperature and shows its maximum at 800°C. An increase of the H2O/MeOH ratio leads to a preference for hydrogen production as well as an inhibition of the formation of carbon monoxide, methane and coke. The major contribution of adding oxygen is lowering the energy supply and suppressing the potential of coke formation at low H2O/MeOH ratio. However, the total oxidation of methanol tends to dominant in this case. For the purpose of producing hydrogen-rich gas, no oxygen addition is preferred. The favorable operation window is obtained as 600°C, H2O/MeOH ratio=6.0–8.0 and O2/MeOH ratio=0. Under this optimal condition, 2.77–2.84mol/mol methanol hydrogen yield and 0.13–0.17mol/mol methanol carbon monoxide yield with trace amount methane (0.0070–0.017mol/mol methanol) can be achieved without the risk of carbon deposition.

Influence of Coke Quenching Method on its Reactivity

The results of investigation for the influence of the coke quenching method on the coke reactivity were shown. Using thermogravimetry and scanning electron microscopy significant differences of the porous structure and peculiarities of the structure of coke carbon, which forms the pores walls in both wet and dry quenching coke, were discovered. It was established that higher reactivity of wet quenching coke is due to its higher porosity (60 % higher than that of dry quenching coke).

Coke Formation and Carbon Atom Economy of Methanol‐to‐Olefins Reaction

The methanol-to-olefins (MTO) process is becoming the most important non-petrochemical route for the production of light olefins from coal or natural gas. Maximizing the generation of the target products, ethene and propene, and minimizing the production of byproducts and coke, are major considerations in the efficient utilization of the carbon resource of methanol. In the present work, the heterogeneous catalytic conversion of methanol was evaluated by performing simultaneous measurements of the volatile products generated in the gas phase and the confined coke deposition in the catalyst phase. Real-time and complete reaction profiles were plotted to allow the comparison of carbon atom economy of methanol conversion over the catalyst SAPO-34 at varied reaction temperatures. The difference in carbon atom economy was closely related with the coke formation in the SAPO-34 catalyst. The confined coke compounds were determined. A new type of confined organics was found, and these accounted for the quick deactivation and low carbon atom economy under low-reaction-temperature conditions. Based on the carbon atom economy evaluation and coke species determination, optimized operating conditions for the MTO process are suggested; these conditions guarantee high conversion efficiency of methanol.

Effect of Sm0.2Ce0.8O1.9 on the carbon coking in Ni-based anodes for solid oxide fuel cells running on methane fuel

To directly use hydrocarbon fuel without a reforming process, a new microstructure for Ni/Sm0.2Ce0.8O2−δ (Ni/SDC) anodes, in which the Ni surface of the anode is covered with a porous Sm0.2Ce0.8O2−δ thin film, was investigated as an alternative to conventional Ni/YSZ anodes. The porous SDC thin layer was coated on the pores of the anode using the sol–gel coating method. The cell performance was improved by 20%–25% with the Ni/SDC anode relative to the cell performance with the Ni/YSZ anode due to the high ionic conductivity of the Ni/SDC anode and the increase of electrochemical reaction sites. For the SDC-coated Ni/SDC anode operating with methane fuel, no significant degradation of the cell performance was observed after 180 h due to the surface modification with the SDC film on the Ni surface, which opposes the severe degradation of the cell performance that was observed for the Ni/YSZ anode, which results from carbon deposition by methane cracking. Carbon was hardly detected in the SDC-coated Ni/SDC anode due to the catalytic oxidation of the deposited carbon on the SDC film as well as the electrochemical oxidation of methane in the triple-phase-boundary.

Enhanced sulfur and carbon coking tolerance of novel co-doped ceria based anode for solid oxide fuel cells

Doubly doped CeO 2 based anode with Y and Yb is first reported for direct methane solid oxide fuel cells. The power output of the cell with Ni–Ce 0.8Y 0.1Yb 0.1O 1.9 anode and stability at various temperatures are investigated when air is used as oxidant and pure H 2, 5 ppm H 2S containing H 2 and dry CH 4 as fuel, respectively. At 750 °C, the cell displays stable power output for 120 h at 200 mA cm −2 when fueled with dry CH 4, suggesting the carbon deposit is largely absent on the anode, which is confirmed by the SEM observation and EDS results. The results also prove that the rare earth elements Y and Yb affect the sulfur tolerance performance of the anode in a cooperative fashion leading to good anode stability in the contaminated fuel. The SEM and EDS results provide evidence that the cell with Ni–Ce 0.8Y 0.1Yb 0.1O 1.9 anode is tolerant toward the H 2S contamination. The remarkable performances suggest that co-doped CeO 2 anode is an attractive electrode component for direct hydrocarbon solid oxide fuel cells and might also be used as a catalyst for reforming of hydrocarbon fuels and for removal of fuel gas contaminations such as sulfur.

Influce Mechanism on Compressive Strength of Coke in Blast Furnace

Coke is the unique role of supporting material column in blast furnace high temperature region. Therefore the most important property is the high temperature compressive strength after reaction. This paper used decarburization electric furnace, electric mirrors, adjustable atmosphere high temperature compression testing machine and other equipments, study on the relationships between coke carbon loss rate and reactivity and size, the distribution rule between high temperature compressive strength and coke carbon loss rate. The study found that the carbon loss rate was affected by reactivity and size, in the same piece of coke, external rate of carbon loss higher than the internal loss, the surface carbon losses affect on coke strength is less, it make coke size decrease; carbon losses occur inside will not affect the size of coke, but it may affect the coke compressive strength seriously. The compressive strength can be divided into two parts: a constant and an amount proportional to carbon loss rate.

Effect of Temperature on the Phase Behaviors of Zircon by Carbothermal Reduction-Nitridation

Phase behaviors of zircon at different temperatures via carbothermal reduction-nitridation were investigated in this study. By using zircon as raw material, with carbon coke as reducing agent, the influence of reaction temperatures (1450, 1500, 1550 and 1600 °C, respectively) on phase behaviors and microstructure of the products was characterized by X-ray diffraction analysis (XRD), scanning electronic microscopy (SEM) and energy dispersive spectroscopy (EDS). The results shows that by carbothermal reduction-nitridation, the main phases in the final products of zircon are m-ZrO2, c-ZrO2, β-SiC, ZrN and β-Si3N4at different temperatures for 4 hours.

Phase Behavior of Silica Brick Used in Carbothermal Reduction

In this study we observed the phase behavior of silica brick used in the process of carbothermal reduction. At 1550°C, there are liner β-SiC in clumps huddled together; At 1550°C, short line clumps changed into filamentous, mixed together. There are many particles and some β-SiC lines and few filamentous β-SiC at 1600°C . Different ratio of carbon coke also effect the phase behavior. From the results we obtained SiC powders. SiC refractory powders were prepared via carbothermal reduction method using used silica bricks as raw materials. The effects of carbon content, temperature and holding time on the phase composition and microstructure were analyzed. XRD and SEM analyses show that: β-SiC refractory powders were synthesized at 1600°C for 6 h with100 wt% excessive of carbon content. With the increase of carbon content, the reaction temperature and holding time, content of β-SiC gradually increased while that of cristobalite decreased.

Gel-hydrothermal synthesis of carbon and boron co-doped TiO 2 and evaluating its photocatalytic activity

Carbon and boron co-doped TiO 2 photocatalysts were prepared firstly by the gel-hydrothermal method, that is, synthesized through sol–gel process followed by hydrothermal in the glucose solution. The prepared photocatalysts were characterized by XRD, Raman spectra, TEM, N 2 physical adsorption, XPS, and UV–vis absorption spectra. It was found that the co-doped TiO 2 has a larger BET surface areas and a narrower band gap than undoped TiO 2. The experimental results show that the coke carbon generated on the carbon doped TiO 2 surface act as a photosensitizer and has the photosensitization effect under the visible light. Except for carbon sensitization effect, the boron and carbon co-doped TiO 2 has synergistic effect which is responsible for effective photo-degradation of 2,4-dichlorophenol in the visible light irradiation.

The Influence on the Properties of Microporous Mullite of Adding Different Burning-Out Materials

Mullite has low thermal conductivity, advanced volume stability at high temperature, and is suit to prepare lightweight refractories. The micropored mullite aggregates has been produced by using industrial alumina and natural silica as starting materials, adding some burning-out materials, then fired at 1350°C for 6h. The influences on the bulk density, pore size distribution and microstructure of microporous mullite of adding these burning-out materials, such as carbon black, coke, and anthracite have been investigated. The conclusions are that the influences on the bulk density and microstructure of micropored mullite aggregates are significant. These three burning-out materials have a similar effect for the pore size distribution. The microporous mullite aggregates has the smallest bulk density and more uniform microstructure by using anthracite as the burning-out material.

Creep life assessment of an overheated 9Cr-1Mo steel tube

Crude oil heater 9Cr–1Mo steel tubes from a refinery plant were studied, after 24 years of service at nominally 650 °C and 27 MPa, to predict their remanent lives. The investigation included dimensional, hardness and tensile measurements in addition to accelerated stress rupture tests between 650 °C and 700 °C and microstructural examination. Tube specimens were taken from two sections, the overheated side and the side which only saw the nominal operating temperature. The method employed involved the prediction of the increase in temperature with increasing sediment deposition during the operating life times using an FEM model. In addition the predicted temperatures are used to derive appropriate creep properties at relevant temperatures in a 3D pipe FEM creep analysis to predict the pipe deformation rate. All compare well with the actual service exposed pipe measurements and layer deposition. The overheated side revealed a small loss of creep strength in a stress rupture test. A layer of sediment (appr. 10 mm thickness) consisting basically of sintered carbon (coke) spread over the inside of the tube was acting as a thermal barrier causing the temperature to rise above 650 °C. Analysis for the overheated side predicted an upper bound temperature of ≈800 °C and a life of about 50 h suggesting that failure by creep rupture could occur rapidly in the sediment region.

Thermal Emission Effect of Electronic Parts Using Carbon Materials

Recent high efficiency electronic devices have been found to have heat emission problems. As for LEDs, an excessive increase in the device temperature causes a drop of the luminous efficiency and circuit lifetime. Therefore, heat release in the limited space of such electronic parts is very important. This is a study of the possibility of using a coating of carbon materials as a solution for the thermal emission problem of electronic devices. Powdered carbon materials, cokes, carbon blacks, amorphous graphite, and natural flakes were coated with an organic binder on an aluminum sheet and the subsequent thermal emissivity was measured with an FT-IR spectrometer and was found to be in the range of <TEX>$5{\sim}20\;{\mu}m$</TEX> at <TEX>$50^{\circ}C$</TEX>. The emissivity of the carbon materials coated on the aluminum sheet was shown to be over 0.8 and varied according to carbon type. The maximum thermal emissivity on the carbon black coated-aluminum surface was shown to be 0.877. The emissivity of the anodized aluminum sheets that were used as heat releasing materials of the electronic parts was reported to be in the range of 0.7~0.8. Therefore, the use of a coating of carbon material can be a potential solution that facillitates heat dissipation for electronic parts.

Hydrogen production for PEM fuel cell by gas phase reforming of glycerol as byproduct of bio-diesel. The use of a Pd–Ag membrane reactor at middle reaction temperature

Glycerol as a byproduct of biodiesel production represents a renewable energy source. In particular, glycerol can be used in the field of hydrogen production via gas phase reforming for proton exchange membrane fuel cell (PEMFC) applications. In this work, glycerol steam reforming (GSR) reaction was investigated using a dense palladium–silver membrane reactor (MR) in order to produce pure (or at least CO-free) hydrogen, using 0.5wt% Ru/Al2O3 as reforming catalyst. The experiments are performed at 400°C, water to glycerol molar feed ratio 6:1, reaction pressure ranging from 1 to 5bar and weight hourly space velocity (WHSV) from 0.1 to 1.0h−1. Moreover, a comparative study is given between the Pd–Ag MR and a traditional reactor (TR) working at the same MR operating conditions. The effect of the WHSV and reaction pressure on the performances of both the reactors in terms of glycerol conversion and hydrogen yield is also analyzed. The MR exhibits higher conversion than the TR (∼60% as best value for the MR against ∼40% for the TR, at WHSV=0.1h−1 and 5bar), and high CO-free hydrogen recovery (around 60% at WHSV=0.1h−1 and 5bar). During reaction, carbon coke is formed limiting the performances of the reactors and inhibiting, in particular, the hydrogen permeation through the membrane with a consequent reduction of hydrogen recovery in the permeate side.