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01953 Microstructure of an industrial char by diffraction techniques and Reverse Monte Carlo modelling
01 Sofid fuels (derived solid fuels) pure iron crystal/carbon composite was successfully produced above 760~'C. As an option, Fe203 or Fe304/carbon composite was also successfully produced by the oxidation or gasification of it at low temperature. The irons in these composites were reduced by carbon with evolving CO and CO2 at high temperature. Thus, it is clarified that the proposed method is attractive for producing a recycle material for the iron melting furnace prior to revolving furnaces from waste iron using low rank coal.
05/01948
U.S. coal operators hope to sustain the 2004 rally
Fiscor, S. Coal Age, 2005, 110, (1), 24 27. This forecast survey article takes an optimistic view of the future of the US coal industry. Building on its record-making safety and production results during 2004, the industry looks set to continue to thrive.
Derived solid fuels 05/01949 Catalytic activity of carbon nanotubes in the oxidative dehydrogenation of ethylbenzene Pereira, M. F. R. et al. Carhon, 2004, 42, (14), 2807 2813. Multi-walled carbon nanotubes (MWNT), before and after different oxidative treatments and hence possessing different oxygen surface groups, were used as catalysts for the oxidative dehydrogenation of ethylbenzene (ODE), and their performances compared to those of activated carbon and graphite samples. MWNT are active catalysts for ODE and show the highest specific activity per initial surface area amongst all the materials tested in this study. Moreover, the main advantage of using MWNT over activated carbons is their higher stability under oxidative conditions. It was shown that pre-oxidized MWNT are more active for ODE during the initial stages of the reaction, highlighting the importance of oxygenated surface groups.
05/01950 Coal-derived carbon nanotubes by thermal plasma jet Tian, Y. et al. Carhon, 2004, 42, (12 13), 2597 2601. A coal/arc-jet technique by directly and successively injecting coal fine particles into the arc plasma jet instead of arcing graphite or coal-based electrodes for producing carbon nanotubes (CNTs) from coal was developed. The derived carbon products by this technique were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), high-resolution TEM (HRTEM), X-ray energy dispersive spectrum (EDS), X-ray diffraction (XRD) and Raman spectrum. The experimental results clearly indicated that the certain metal catalyst favoured the growth of CNTs in the process, and the relevant growth mechanism was discussed in terms of the characterizations.
05•01951 Dielectric relaxation due to interfacial polarization for heat-treated wood Sugimoto, H. and Norimoto, M. Carhon, 2004, 42, (1), 211 218. The dielectric properties of totally dried sugi (Cryptomeria japonica) wood block and powder specimens treated at various temperatures up to 800c'C were measured in the range from 20 Hz to 1 MHz and from 150 to 20~'C. Relaxation ascribed to the motion of methylol groups was detected in specimens treated at temperatures below 300~'C and its magnitude decreased with increasing temperature. The electric conductivity decreased with increasing temperature up to 400~'C. Another form of relaxation was recognized for block specimens treated at temperatures between 500 and 600~'C. Cole Cole's circular arc law was applied to the experimental results. The relaxation magnitude was 60 75 and 24 28 in the longitudinal and radial directions of the block specimens, respectively. Identical relaxation was also observed in the powder specimen. The electric conductivity began to increase remarkably from 500c'C. These results suggested that a small volume fraction of particles with large conductivity is formed at microscopic levels in the cell walls. It is considered that this relaxation is due to interfacial polarization.
05/01952 Initial coke deposition on hydrotreating catalysts, Part II, Structure elucidation of initial coke on hydrodematallation catalysts Hauser, A. et al. Fuel, 2005, 84, (2 3), 259 269. Kuwait atmospheric residue (KAR) was hydrodemetallized (HDM) over a commercial Mo/A1203 catalyst using a fixed-bed reactor unit. Initial coke deposition on the catalyst vs. time-on-stream (TOS) was studied by solid-state 13C NMR to derive structural information on the initial coke deposited in the first 240 h of TOS. 13C NMR spectral editing (cross-polarization technique in combination with the polarization inversion pulse sequence) was applied to distinguish on the one hand between quaternary and tertiary aromatic carbon and on the other hand between secondary and primary aliphatic carbon. Structural
parameters, derived from those NMR measurements in combination with the aromaticity from single pulse excitation 13C NMR and the H/C ratio from elemental analysis, have been used to assemble the hypothetical structure of initial coke. The 1 h coke has nearly the same H/C ratio as the KAR and represents an intermediate between heavy coke generating molecules from KAR and real coke. In the following 12 h, aromatic carbon is accumulated and aromatic rings are dealkylated but the coke is still rich in hydrogen. As the carbon deposition slows down (after 50 h) further aromatic carbon is built-up and aliphatic carbon decreases. After 120 h the hydrogenation activity of the HDM catalyst is still high and prevents the coke from getting hydrogen depleted, merely the degree of alkyl-substitution has dropped compared with the start of run. With further increase of run time, carbon deposition reaches a steady state (240 h). As the analysis of a spent HDM catalyst (6500 h) from an industrial ARDS unit shows, throughout the following months of operation the porous hydrogen rich coke is increasingly converted into highly condensed polynuclear aromatic coke. THF-extraction of the used catalysts (TOS; 1, 12, 120, and 6500 h) has mainly removed small aromatic compounds with a high degree of alkyl-substitution.
05/01953 Microstructure of an industrial char by diffraction techniques and Reverse Monte Carlo modelling Petersen, T. et al. Carhon, 2004, 42, (12 13), 2457 2469. The disordered microstructure of an industrial carbonaceous char has been characterized using X-ray, neutron and electron diffraction techniques to obtain pair correlation functions. Whilst consistency has been observed between all three techniques, electron diffraction has been found to have advantages by allowing data to be collected over a large range of scattering angles as well as without interference from crystalline regions within the char. Based on the experimentally obtained pair correlation functions, Hybrid Reverse Monte Carlo (HRMC) simulations have also been performed to generate experimentally consistent nanoscale models of the disordered carbonaceous char. The model char structures comprise disordered and buckled graphitic sheets containing a small percentage of interstitial diamondlike atoms between the sheets.
05/01954 Spectrophotometric study of molecular complex formation of asphaltene with two isomeric chloranils Ghosh, A. K. Fuel, 2005, 84, (2 3), 153 157. Coal-derived asphaltene has been observed spectrophotometrically to form molecular complexes of charge transfer type with o- and pchloranils. The CT absorption peaks have been detected by difference spectral method and the wavelengths of the CT peaks are in the expected order of electron affinities of the chloranils. The formation constants (K) have been determined using the Benesi Hildebrand equation. The magnitudes of K are large compared to those of weak charge transfer complexes (for which K~10 1 103 dm 3 mol 1 ) but are comparable to those of some recently reported supramolecular or inclusion complexes. The study reveals the presence of re-donor (i.e. aromatic) type of compounds in asphaltene molecule. It also supports the view that asphaltene molecules exist in solution forming micellar aggregate, in the cavities of which the chloranil molecules are included.
05/01955 Synthesis of zeolite from coal fly ashes with different silica-alumina composition Inada, M. et al. Fuel, 2005, 84, (2 3), 299 304. Coal fly ashes can be converted into zeolites by hydrothermal alkaline treatment. This study focuses on the effect of Si/A1 molar ratio of the fly ash source on the type of formed zeolite, which also is affected by the alkaline condition. The fly ashes were mixed with an aqueous NaOH solution and hydrothermally treated at about 100c'C. Zeolite Na P1 and/or hydroxy-sodalite appeared after the treatment. Zeolite Na P1 predominantly formed from silica-rich fly ash at a low-NaOH concentration. The cation exchange capacity of the product with a large content of zeolite Na P1 reached a value of 300 meq/100 g. The type of the product was controlled by addition of aerosil silica or alumina. It was found that silica addition effectively enhances the formation of zeolite Na P1, even at a high-NaOH concentration. These results were discussed on the basis of a formation mechanism of zeolite from coal fly ash through dissolution precipitation process.
05/01956 The effect of the activating agent and temperature on the porosity development of physically activated coal chars Arenas, E. and Chejne, F. Carhon, 2004, 42, (12 13), 2451 2455. An experimental work on the influence of temperature and the activating agent on the development of surface area and porosity for activated carbons was carried out. Three coals from different regions of Colombia were activated with CO2, steam and a CO2 steam mixture. Coal from the Antioquia Region (La Capotera) was activated with a CO2 steam mixture at 1073, 1123 and 1173 K and with CO2 and steam at 1073 K. Other two coals from Antioquia and Cesar regions (La Grande and Borrego) regions were activated with a CO2 steam mixture
Fuel and Energy Abstracts
September 2005
291
05/01948
U.S. coal operators hope to sustain the 2004 rally
Fiscor, S. Coal Age, 2005, 110, (1), 24 27. This forecast survey article takes an optimistic view of the future of the US coal industry. Building on its record-making safety and production results during 2004, the industry looks set to continue to thrive.
Derived solid fuels 05/01949 Catalytic activity of carbon nanotubes in the oxidative dehydrogenation of ethylbenzene Pereira, M. F. R. et al. Carhon, 2004, 42, (14), 2807 2813. Multi-walled carbon nanotubes (MWNT), before and after different oxidative treatments and hence possessing different oxygen surface groups, were used as catalysts for the oxidative dehydrogenation of ethylbenzene (ODE), and their performances compared to those of activated carbon and graphite samples. MWNT are active catalysts for ODE and show the highest specific activity per initial surface area amongst all the materials tested in this study. Moreover, the main advantage of using MWNT over activated carbons is their higher stability under oxidative conditions. It was shown that pre-oxidized MWNT are more active for ODE during the initial stages of the reaction, highlighting the importance of oxygenated surface groups.
05/01950 Coal-derived carbon nanotubes by thermal plasma jet Tian, Y. et al. Carhon, 2004, 42, (12 13), 2597 2601. A coal/arc-jet technique by directly and successively injecting coal fine particles into the arc plasma jet instead of arcing graphite or coal-based electrodes for producing carbon nanotubes (CNTs) from coal was developed. The derived carbon products by this technique were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), high-resolution TEM (HRTEM), X-ray energy dispersive spectrum (EDS), X-ray diffraction (XRD) and Raman spectrum. The experimental results clearly indicated that the certain metal catalyst favoured the growth of CNTs in the process, and the relevant growth mechanism was discussed in terms of the characterizations.
05•01951 Dielectric relaxation due to interfacial polarization for heat-treated wood Sugimoto, H. and Norimoto, M. Carhon, 2004, 42, (1), 211 218. The dielectric properties of totally dried sugi (Cryptomeria japonica) wood block and powder specimens treated at various temperatures up to 800c'C were measured in the range from 20 Hz to 1 MHz and from 150 to 20~'C. Relaxation ascribed to the motion of methylol groups was detected in specimens treated at temperatures below 300~'C and its magnitude decreased with increasing temperature. The electric conductivity decreased with increasing temperature up to 400~'C. Another form of relaxation was recognized for block specimens treated at temperatures between 500 and 600~'C. Cole Cole's circular arc law was applied to the experimental results. The relaxation magnitude was 60 75 and 24 28 in the longitudinal and radial directions of the block specimens, respectively. Identical relaxation was also observed in the powder specimen. The electric conductivity began to increase remarkably from 500c'C. These results suggested that a small volume fraction of particles with large conductivity is formed at microscopic levels in the cell walls. It is considered that this relaxation is due to interfacial polarization.
05/01952 Initial coke deposition on hydrotreating catalysts, Part II, Structure elucidation of initial coke on hydrodematallation catalysts Hauser, A. et al. Fuel, 2005, 84, (2 3), 259 269. Kuwait atmospheric residue (KAR) was hydrodemetallized (HDM) over a commercial Mo/A1203 catalyst using a fixed-bed reactor unit. Initial coke deposition on the catalyst vs. time-on-stream (TOS) was studied by solid-state 13C NMR to derive structural information on the initial coke deposited in the first 240 h of TOS. 13C NMR spectral editing (cross-polarization technique in combination with the polarization inversion pulse sequence) was applied to distinguish on the one hand between quaternary and tertiary aromatic carbon and on the other hand between secondary and primary aliphatic carbon. Structural
parameters, derived from those NMR measurements in combination with the aromaticity from single pulse excitation 13C NMR and the H/C ratio from elemental analysis, have been used to assemble the hypothetical structure of initial coke. The 1 h coke has nearly the same H/C ratio as the KAR and represents an intermediate between heavy coke generating molecules from KAR and real coke. In the following 12 h, aromatic carbon is accumulated and aromatic rings are dealkylated but the coke is still rich in hydrogen. As the carbon deposition slows down (after 50 h) further aromatic carbon is built-up and aliphatic carbon decreases. After 120 h the hydrogenation activity of the HDM catalyst is still high and prevents the coke from getting hydrogen depleted, merely the degree of alkyl-substitution has dropped compared with the start of run. With further increase of run time, carbon deposition reaches a steady state (240 h). As the analysis of a spent HDM catalyst (6500 h) from an industrial ARDS unit shows, throughout the following months of operation the porous hydrogen rich coke is increasingly converted into highly condensed polynuclear aromatic coke. THF-extraction of the used catalysts (TOS; 1, 12, 120, and 6500 h) has mainly removed small aromatic compounds with a high degree of alkyl-substitution.
05/01953 Microstructure of an industrial char by diffraction techniques and Reverse Monte Carlo modelling Petersen, T. et al. Carhon, 2004, 42, (12 13), 2457 2469. The disordered microstructure of an industrial carbonaceous char has been characterized using X-ray, neutron and electron diffraction techniques to obtain pair correlation functions. Whilst consistency has been observed between all three techniques, electron diffraction has been found to have advantages by allowing data to be collected over a large range of scattering angles as well as without interference from crystalline regions within the char. Based on the experimentally obtained pair correlation functions, Hybrid Reverse Monte Carlo (HRMC) simulations have also been performed to generate experimentally consistent nanoscale models of the disordered carbonaceous char. The model char structures comprise disordered and buckled graphitic sheets containing a small percentage of interstitial diamondlike atoms between the sheets.
05/01954 Spectrophotometric study of molecular complex formation of asphaltene with two isomeric chloranils Ghosh, A. K. Fuel, 2005, 84, (2 3), 153 157. Coal-derived asphaltene has been observed spectrophotometrically to form molecular complexes of charge transfer type with o- and pchloranils. The CT absorption peaks have been detected by difference spectral method and the wavelengths of the CT peaks are in the expected order of electron affinities of the chloranils. The formation constants (K) have been determined using the Benesi Hildebrand equation. The magnitudes of K are large compared to those of weak charge transfer complexes (for which K~10 1 103 dm 3 mol 1 ) but are comparable to those of some recently reported supramolecular or inclusion complexes. The study reveals the presence of re-donor (i.e. aromatic) type of compounds in asphaltene molecule. It also supports the view that asphaltene molecules exist in solution forming micellar aggregate, in the cavities of which the chloranil molecules are included.
05/01955 Synthesis of zeolite from coal fly ashes with different silica-alumina composition Inada, M. et al. Fuel, 2005, 84, (2 3), 299 304. Coal fly ashes can be converted into zeolites by hydrothermal alkaline treatment. This study focuses on the effect of Si/A1 molar ratio of the fly ash source on the type of formed zeolite, which also is affected by the alkaline condition. The fly ashes were mixed with an aqueous NaOH solution and hydrothermally treated at about 100c'C. Zeolite Na P1 and/or hydroxy-sodalite appeared after the treatment. Zeolite Na P1 predominantly formed from silica-rich fly ash at a low-NaOH concentration. The cation exchange capacity of the product with a large content of zeolite Na P1 reached a value of 300 meq/100 g. The type of the product was controlled by addition of aerosil silica or alumina. It was found that silica addition effectively enhances the formation of zeolite Na P1, even at a high-NaOH concentration. These results were discussed on the basis of a formation mechanism of zeolite from coal fly ash through dissolution precipitation process.
05/01956 The effect of the activating agent and temperature on the porosity development of physically activated coal chars Arenas, E. and Chejne, F. Carhon, 2004, 42, (12 13), 2451 2455. An experimental work on the influence of temperature and the activating agent on the development of surface area and porosity for activated carbons was carried out. Three coals from different regions of Colombia were activated with CO2, steam and a CO2 steam mixture. Coal from the Antioquia Region (La Capotera) was activated with a CO2 steam mixture at 1073, 1123 and 1173 K and with CO2 and steam at 1073 K. Other two coals from Antioquia and Cesar regions (La Grande and Borrego) regions were activated with a CO2 steam mixture
Fuel and Energy Abstracts
September 2005
291