Papers by Keyword: Carbon Deposition

Abstract: Recent developments in nanochemistry offer precise morphology control of nanomaterials, which has significant impacts in the field of heterogeneous catalysis. Rational design of bifunctional catalysts can influence various aspects of catalytic properties. In the present work, a new type of Ni-M(Co, Zr, Ce)@SiO₂ yolk-shell nanoreactor framework comprising Ni-M cores inside hollow silica shells has been prepared through direct silica coating. The Ni-M@SiO₂ nanoreactor structure is employed as a model catalyst for the partial oxidation of methane reaction. The Ni/ZrO₂@SiO₂ catalyst proved to be more active and possessed less carbon deposition reduced effectively by movable lattice oxygen. This nanoreactor framework is remarkably stable at high temperatures up to 750 °C, because the silica hollow shells around the cores essentially block particle sintering. The catalyst exhibited a continuous conversion rate of methane and significantly enhanced stability at high temperatures.

Abstract: Carbon was successfully deposited on AISI 304 stainless steel rod cathode through electrolysis process in three molten salt mixtures, namely K₂CO₃-Li₂CO₃ (mole ratio: 1:1), CaCO_3-Li₂CO₃-LiCl (mole ratio 0.09:0.28:0.63) and CaCO₃-CaCl₂-KCl-LiCl (mole ratio: 0.13:0.31:0.10:0.45), under CO₂ atmospheres as continuous source of carbon. The process were carried out for 1 hour at temperature range 545–585°C and electrolysis voltage of 4.0V to drive the deposition of carbon through electrochemical conversion. EDX analysis on deposited products shown carbon as dominant element (89-98%). SEM revealed carbon with Flakes and grapes aggregation shapes for different salt mixtures. The achieved current efficiency of 83.8%, 80.46% and 92.41% were found in the respective salt mixtures, and energy consumption promotes several ways for efficiency improvement on the electrochemical conversion of CO₂.

Abstract: Carbon deposit is pollutant with complicated composition and a large number of particles, it is very difficult to remove in the process of remanufacture cleaning. In this paper , carbon deposition were analyzed from the aspects of microscopic appearance, and it explains the reasons for the formation of carbon deposition.

Abstract: Dry reforming reaction of CH₄ by CO₂ was carried out over alumina-supported Ni catalysts. Main products were H₂ and CO with small amount of H₂O by-production because of reverse water gas shift reaction. The activity was gradually decreased with time on stream by carbon deposition. The addition of Ce component was investigated to improve the catalyst stability. The Ce addition brought decrease of carbon deposition during the reaction. The role of Ce has been considered that an inactive coke formation is significantly suppressed.

Abstract: This paper pertains to the reduction process of local low grade iron ore using palm kernel shell (PKS). It is well known that low grade iron ores contain high amount of gangue minerals and combined water. Biomass waste (aka agro-residues) from the palm oil industry is an attractive alternative fuel to replace coal as the source of energy in mineral processing, including for the treatment and processing of low grade iron ores. Both iron ore and PKS were mixed with minute addition of distilled water and then fabricated with average spherical diameter of 10-12mm. The green composite pellets were subjected to reduction test using an electric tube furnace. The rate of reduction increased as temperature increases up to 900 °C. The Fe content in the original ore increased almost 12% when 40 mass% of PKS was used. The reduction of 60:40 mass ratios of iron ore to PKS composite pellet produced almost 11.97 mass% of solid carbon which was dispersed uniformly on the surface of iron oxide. The aim of this work is to study carbon deposition of PKS in iron ore through reduction process. Utilization of carbon deposited in low grade iron ore is an interesting method for iron making process as this solid carbon can act as energy source in the reduction process.

Abstract: Iron ore reduction and carbon deposition in pure CO was investigated by using thermogravimetric (TG) method over the temperature range of 0-1200°C. The results of the work may be summarized as follows: in CO stream, carbon deposition occurred below 900°C, no carbon deposition was found above 1000°C. X-Ray analysis of the reacted sample indicated that the carbon deposition occurred with the iron was reduced. The iron reduction process and carbon deposition occurred simultaneously. The rate of carbon deposition changed with the transformation of iron oxides. The specific surface area and pore structure of reduced samples were analyzed. The specific surface area changed with the amount of carbon deposition.

Abstract: The activities of cermet catalysts composed of Ni/CeO₂-ZnO anode for steam reforming of methanol were investigated for internal reforming of solid oxide fuel cell. Ni/CeO₂-ZnO anodes with specific percentage of ceria versus zinc were fabricated by wet impregnation method. The catalysts were characterized by X-ray diffraction, Scanning electron microscope (SEM) and temperature-programmed reduction. Area specific resistance (ASR) of these anodes was also examined to prove the thermal stability of them, and possible reasons for degradation were analyzed. Furthermore, The promoting effect of zinc metals included a decrease in the reduction temperature of NiO species interacting with the support, due to the hydrogen spillover effect. It was seen that the addition of zinc metal stabilized the Ni sites in the reduced state along the reforming reaction, increasing the methanol conversions and decreasing the coke formation. The maximum power density of the single cell reached 560mW cm^-2 and 380mW cm^-2 at 750°C in hydrogen and methanol steam respectively, and the cell obtained stable output in methanol steam over an operation period of 30 h.

Abstract: In the preparation of hydrogen, the bio-oil from pyrolysis of biomass must be further upgraded (catalytic steam reforming)SO as to improve its quality．However the catalyst used in the steam reforming reaction is easy to lose its activity due to being coked' SO that it is important to study the coke formation and its efects on the catalyst activity in the steam reforming process．Fourier Transform Infrared Spectroscopy were used to analyze the precursor of coke on the catalyst Ni/MgO-La₂O₃-Al₂O₃ used in steam reforming reaction and the mechanism of coking Was also discussed based on it．The results indicate that precursors of coke deposited inside the pore of the molecular sieve are mainly paraffin, alcohols, aldehydes and ketones, and aromatic compounds.

Abstract: Iron ore reduction and carbon deposition under H₂-CO mixtures were investigated by using the non-isothermal method. Iron ore in three different configurations were used in this work: pellet, coarse granularity particles and fine granularity particles. The reduced samples were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and accelerated surface area and porosimetry System(ASAP 2020M+C). In pure CO, the carbon deposition increases with decreasing of the sample size. In H₂-CO mixtures, the rate of carbon deposition is accelerated dramatically. Morphologies of samples treated in different reducing ambinent were investigated. Specific surface area of the treated sample increases with higher level of carbon deposition.

Abstract: Carbon deposition on Ni/YSZ cermets and the role of Zr-doped ceria catalysts on carbon deposition have been investigated in the present study. Upon exposure to methane, large amounts of filamentous carbon formed on the surface of the cermets. In addition, carbon dissolved into the Ni particles, significantly expanding the dimensions of the entire pellet. The addition of Zr-doped ceria catalyst pellets on each side of the Ni/YSZ cermet significantly reduced the amount of deposited carbon and affected the structure of the deposits. In particular, the carbon was more weakly bound to the surface and appeared only to be deposited on the Ni/YSZ surface and not dissolved into the structure.