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03280 Preparation of thin carbon fibers from phenolformaldehyde polymer micro-beads dispersed in polyethylene matrix
04
titrations). Palladium was deposited from anionic (Hz PdQ), neutral (Pd(OAc)z, in acetone), and cationic ([Pd(NH?),](NO?)x) complexes. Temperature-programmed reduction, CO chemisorption, and testing in olefin hydrogenation were used to study the possible effects of preparation variables. The origin of the carbon support and the temperature of the catalyst reduction with hydrogen proved to have a profound influence on the properties of the catalysts. In contrast, no unambiguous correlation has been found between catalyst properties and the pre-treatments of the carbons. It is concluded that the effect of the support comes mainly from the differences in the porous structure of the carbons, and occurrence of steric hindrance for organic substrates in contacting the metal particles on the microporous supports is suggested. 00103277 Petroleum pitch pyrolysis Davini, P. Proc. World Per. Congr., 1998. 2, X06-807. It is possible to obtain useful compounds from petroleum pitches (byproducts of oil refining) such as cokes and hydrocarbons. Cokes can be used as starting materials of active carbons, while hydrocarbons have a utilization closely related to their molecular weight and structure. In the present investigation the process of pyrolysis of certain pitches is studied (in different thermal conditions, gaseous atmospheres and catalysts) in order to obtain good quality cokes. The study was carried out by a thermogravimetric apparatus having high sensibility and very fast response time (in order to obtain information in the first instants of the pyrolysis reaction) as well. Gaseous atmospheres, where the pitch samples were heated, were carbon dioxide, nitrogen and argon (pure or containing small and controlled amounts of oxygen) or hydrogen (pure or mixed with nitrogen). The obtained cokes were accurately classified (by determining their elementary composition) and submitted to surface characterization (by determining BET surface area, meso and macropore distribution, surface oxygenated functional groups, etc.). Surface characteristics are related to the type of thermal treatment. Cokes were washed with HCI and HF boiling aqueous solution in order to minimize their content of metal derivatives (ashes). They were then submitted to certain selective oxidation processes with boiling nitric acid solutions, air (at 350°C) and Nz containing small amounts of Oz (at 800°C) with the aim to obtain surface oxygenated groups with selective chemical structures. The cokes, thus treated were accurately characterized and submitted to adsorptionidesorption processes of several chemical compounds (testing their general sorption capacities and the degradation, in time, of their starting properties). The results were correlated to the type of parent pitch, the thermal treatment used (temperature, heating rate and conditions, etc.) and to the composition of gaseous atmosphere of pyrolysis. Interesting results were obtained by comparing the behaviours of the pitch cokes with the similar ones obtained from ordinary active carbons. 00/03278 Pilot-scale investigation of coal ash transformations under staged combustion Slater, P. N. Diss. Ahsrr. Inr., B. 1999, 59, (I I), 5965. The transformations of coal ash under staged combustion were investigated. The results of the investigation are presented. 00103279 Polynuclear aromatic hydrocarbons in fly ash from pressurized fluidired bed gasification of fuel blends. A discussion of the contribution of textile to PAHs Padban, N. and Odenbrand, 1. Energy RX/~, 1999, 13. (5). 1067-1073. The identification and quantification of 20 different polynuclear aromatic hydrocarbons (PAHs) in the fly ash from a pressurized fluidized bed (PFB) air gasification system based on hot gas filtering were detected by CC-MS analysis. The results obtained from two different sets of experiments with varying gasifier feedstock were compared and contrasted. In the first set, four experiments were performed and the gasifier fuel was wood biomass. In the second set a mixture of biomass and 10 wt% textile waste was utilized. The conclusions drawn from the comparison indicate that the distribution of the PAHs in the fly ash was strongly dependent on the gasifier feedstock but that the operational parameters, such as pressure and air/fuel ratio, showed minor effects. For the pure biomass experiments the relative content of the heavier compounds was larger, while the lighter compounds became predominant in the case of the mixtures. The study demonstrated that the decisive parameter influencing the formation was the structure of each PAH as opposed to its molecular weight. Thermal decomposition of the added textile resulted in the formation of phenylic radicals. The excessive occurrence of such intermediates/compounds favoured the formation of the simple structured PAHs with relatively low molecular weights. The largest contribution of the textile was to PAHs consisting of two benzene rings with at least one C-C bond between, such as dibenzofurane, fluorene, and biphenyl. Formation of the PAHs consisting of two joined benzene rings, such as naphthalene and 1 and 2methylnaphthalene, was also strongly affected by the textile addition. The smallest effect of the mixing was observed in the contents of the heavier compounds consisting of more than three benzene rings. Different in the relative reactivities can be used to explain the differences concentrations of compounds such as triphenylene and phenanthrene. 00103280 Preparation of thin carbon fibers from phenolformaldehyde polymer micro-beads dispersed in polyethylene matrix Oya, A. and Kasahara, N. Corhon 2000. 38. (8). I 141~1144
By-products relatedto fuels
Phenol-formaldehyde polymer (PF) micro-beads ImaIler than a few micrometers were blended into a polyethylene (PE) matrix with the ratio of 3:7 for PF:PE by weight. PF and PE showed around 50 and 0 wt% carbon yields after heating to 600°C in a nitrogen atmosphere. respectively. The PF-PE blend was melt-spun continuously, stabilized in an acid solution, neutralized with aqueous ammonia, washed with deiomzed water, dried and finally carbonized at 600°C for 10 min under a nitrogen atmosphere. The stabilized fibres were several tens of micrometers in diameter. After carbonization of the fibre, a bundle of PF-derived thin carbon fibres smaller than several hundred nanometers in diameter was left after removal of the PE matrix. The bundle was easily separated into thin fibres. A thinner fibre showed a more irregular surface, this could possibly have been caused from a larger contraction of the PF fibre than 01 the PE matrix during the stabilization process. The present method can he used for a mass production of long and thin carbon fibres. 00103281 Puffing behavior during the graphitization of coal-tarbased needle coke impregnated with iron sulfate and boric acid Kawano, Y. cr al. Carhon, 2000, 38, (5), 7599/65. The puffing inhibiting ability of iron sulfate impregnated into coal-tarbased needle coke was examined in comparison with that of boric acid. Both inhibitors exhibited similar ability to suppress the puffing of coal-tar-based needle coke by impregnating from their aqueous solutions, drying and heattreating at 1223 K before kneading with the binder pitch. Addition of iron(II1) oxide at the kneading stage to the needle coke impregnated with iron(I1) sulfate was very effective in suppressing the puffing regardless of repeated impregnation of pitch and baking. The bulk density of the graphitized rod was found also to be increased by hoth inhibitors. Rapid heating at graphitization enhanced puffing of the rod in any case, however this inhibitor always suppressed the puffing. In contrast to the iron(II1) oxide, addition of boric acid together with iron(I1) sulfate was not effective in providing additional inhibition, suggesting their similar roles in the puffing inhibition. Iron(l1) sulfate impregnated into the pore of needle coke is converted into iron(Il1) oxide during the heat-treatment which plugs the pore preventing it from being fully filled with the binder and impregnated pitches during repeated impregnation and baking. lton(lI1) oxide was reduced to iron at an early stage of graphitization, which melts, migrates within the carbon and reacts with carbon to form FeaC, and decompose to Fe and graphite, finally vapourizing out of the coke grain. Such conversions of iron sulfate open .and induce the porosity for puffing causing sulfur- and nitrogen-containing gases to be liberated without provoking the puffing. No remaining iron in the graphitized rod may support the role of the present puffing inhibitor. Addition of iron(lI1) oxide at the kneading stage may decrease the puffing due to the coke derived from impregnation pitch, suppressing the puffing at repeated impregnation together with iron sulfate in the pores of needle coke. An additional advantage of increased bulk density of the graphitized rod was emphasized by both inhibitors, catalytic carbonization and graphitization performed by the inhibitors contributing such advantages. 00/03282 Reaction of NO with carbonaceous materials. 1. Reaction and adsorption of NO on ashless carbon black Yang, J. er al. Carbon, 2000, 38, (5), 715-727 The mechanism of the reaction of NO with ashless carbon black was studied in detail. The differences between the amounts of oxygen and nitrogen measured and the calculated concentrations of oxygen and nitrogen suggest the formation of surface carbon-oxygen complexes C(0) and carbonnitrogen complexes C(N). The dependence of the specific rate of reaction at its initial stage on temperature is different from that at steady state, pointing to different rate-determining steps for the two reaction regimes. The decomposition of surface complexes 1s suggested to be the ratedetermining step for the reaction under steady-state conditions. This explains very well the measured zero, reaction order with respect to NO. NO is proposed to adsorb parallel to the carbon black surface. The dissociation of the N-O bond leads to the formation of C(0) and C(N) complexes which are heterogeneous in structure. The adsorbed NO molecules are not stable on the carbon black surface at temperatures above 300°C. The reaction of NO with carbon at higher temperatures results in the formation of more surface complexes with higher thermal stability. The surface C(0) complexes involved in the CO formation differ in structure from those involved in the CO: formation. The mechanism of the NO-carbon reaction at low temperature:< appears to he different from that at high temperatures (>75o”C). 00/03283 Reaction of NO with carbonaceous materials. 2. Effect of oxygen on the reaction of NO with ashless carbon black Yang, J. er al. Carbon, 2000, 38, (5), 7299740. The reaction rate in the reaction of NO with an ashless carbon black was considerably enhanced in the presence of oxygen. A similar effect has also been observed in the reaction of NO with the oxidized carbon black. The creation of more active sites on the carbon surface in the reaction with oxygen and NOz (produced by the reaction of NO with O?) is proposed to be responsible for this enhancement. A lower apparent activation energy was observed in the reaction of NO with the oxidized carbon black than with the unmodified carbon black. It was found that the adsorption of NO is restrained to some extent on the carbon black surface mostly covered by complexes of carbon and oxygen. However, the adsorption of NO and the formation of products at about 4WC were enhanced only when carbon-
Fuel and Energy Abstracts
November 2000
369
titrations). Palladium was deposited from anionic (Hz PdQ), neutral (Pd(OAc)z, in acetone), and cationic ([Pd(NH?),](NO?)x) complexes. Temperature-programmed reduction, CO chemisorption, and testing in olefin hydrogenation were used to study the possible effects of preparation variables. The origin of the carbon support and the temperature of the catalyst reduction with hydrogen proved to have a profound influence on the properties of the catalysts. In contrast, no unambiguous correlation has been found between catalyst properties and the pre-treatments of the carbons. It is concluded that the effect of the support comes mainly from the differences in the porous structure of the carbons, and occurrence of steric hindrance for organic substrates in contacting the metal particles on the microporous supports is suggested. 00103277 Petroleum pitch pyrolysis Davini, P. Proc. World Per. Congr., 1998. 2, X06-807. It is possible to obtain useful compounds from petroleum pitches (byproducts of oil refining) such as cokes and hydrocarbons. Cokes can be used as starting materials of active carbons, while hydrocarbons have a utilization closely related to their molecular weight and structure. In the present investigation the process of pyrolysis of certain pitches is studied (in different thermal conditions, gaseous atmospheres and catalysts) in order to obtain good quality cokes. The study was carried out by a thermogravimetric apparatus having high sensibility and very fast response time (in order to obtain information in the first instants of the pyrolysis reaction) as well. Gaseous atmospheres, where the pitch samples were heated, were carbon dioxide, nitrogen and argon (pure or containing small and controlled amounts of oxygen) or hydrogen (pure or mixed with nitrogen). The obtained cokes were accurately classified (by determining their elementary composition) and submitted to surface characterization (by determining BET surface area, meso and macropore distribution, surface oxygenated functional groups, etc.). Surface characteristics are related to the type of thermal treatment. Cokes were washed with HCI and HF boiling aqueous solution in order to minimize their content of metal derivatives (ashes). They were then submitted to certain selective oxidation processes with boiling nitric acid solutions, air (at 350°C) and Nz containing small amounts of Oz (at 800°C) with the aim to obtain surface oxygenated groups with selective chemical structures. The cokes, thus treated were accurately characterized and submitted to adsorptionidesorption processes of several chemical compounds (testing their general sorption capacities and the degradation, in time, of their starting properties). The results were correlated to the type of parent pitch, the thermal treatment used (temperature, heating rate and conditions, etc.) and to the composition of gaseous atmosphere of pyrolysis. Interesting results were obtained by comparing the behaviours of the pitch cokes with the similar ones obtained from ordinary active carbons. 00/03278 Pilot-scale investigation of coal ash transformations under staged combustion Slater, P. N. Diss. Ahsrr. Inr., B. 1999, 59, (I I), 5965. The transformations of coal ash under staged combustion were investigated. The results of the investigation are presented. 00103279 Polynuclear aromatic hydrocarbons in fly ash from pressurized fluidired bed gasification of fuel blends. A discussion of the contribution of textile to PAHs Padban, N. and Odenbrand, 1. Energy RX/~, 1999, 13. (5). 1067-1073. The identification and quantification of 20 different polynuclear aromatic hydrocarbons (PAHs) in the fly ash from a pressurized fluidized bed (PFB) air gasification system based on hot gas filtering were detected by CC-MS analysis. The results obtained from two different sets of experiments with varying gasifier feedstock were compared and contrasted. In the first set, four experiments were performed and the gasifier fuel was wood biomass. In the second set a mixture of biomass and 10 wt% textile waste was utilized. The conclusions drawn from the comparison indicate that the distribution of the PAHs in the fly ash was strongly dependent on the gasifier feedstock but that the operational parameters, such as pressure and air/fuel ratio, showed minor effects. For the pure biomass experiments the relative content of the heavier compounds was larger, while the lighter compounds became predominant in the case of the mixtures. The study demonstrated that the decisive parameter influencing the formation was the structure of each PAH as opposed to its molecular weight. Thermal decomposition of the added textile resulted in the formation of phenylic radicals. The excessive occurrence of such intermediates/compounds favoured the formation of the simple structured PAHs with relatively low molecular weights. The largest contribution of the textile was to PAHs consisting of two benzene rings with at least one C-C bond between, such as dibenzofurane, fluorene, and biphenyl. Formation of the PAHs consisting of two joined benzene rings, such as naphthalene and 1 and 2methylnaphthalene, was also strongly affected by the textile addition. The smallest effect of the mixing was observed in the contents of the heavier compounds consisting of more than three benzene rings. Different in the relative reactivities can be used to explain the differences concentrations of compounds such as triphenylene and phenanthrene. 00103280 Preparation of thin carbon fibers from phenolformaldehyde polymer micro-beads dispersed in polyethylene matrix Oya, A. and Kasahara, N. Corhon 2000. 38. (8). I 141~1144
By-products relatedto fuels
Phenol-formaldehyde polymer (PF) micro-beads ImaIler than a few micrometers were blended into a polyethylene (PE) matrix with the ratio of 3:7 for PF:PE by weight. PF and PE showed around 50 and 0 wt% carbon yields after heating to 600°C in a nitrogen atmosphere. respectively. The PF-PE blend was melt-spun continuously, stabilized in an acid solution, neutralized with aqueous ammonia, washed with deiomzed water, dried and finally carbonized at 600°C for 10 min under a nitrogen atmosphere. The stabilized fibres were several tens of micrometers in diameter. After carbonization of the fibre, a bundle of PF-derived thin carbon fibres smaller than several hundred nanometers in diameter was left after removal of the PE matrix. The bundle was easily separated into thin fibres. A thinner fibre showed a more irregular surface, this could possibly have been caused from a larger contraction of the PF fibre than 01 the PE matrix during the stabilization process. The present method can he used for a mass production of long and thin carbon fibres. 00103281 Puffing behavior during the graphitization of coal-tarbased needle coke impregnated with iron sulfate and boric acid Kawano, Y. cr al. Carhon, 2000, 38, (5), 7599/65. The puffing inhibiting ability of iron sulfate impregnated into coal-tarbased needle coke was examined in comparison with that of boric acid. Both inhibitors exhibited similar ability to suppress the puffing of coal-tar-based needle coke by impregnating from their aqueous solutions, drying and heattreating at 1223 K before kneading with the binder pitch. Addition of iron(II1) oxide at the kneading stage to the needle coke impregnated with iron(I1) sulfate was very effective in suppressing the puffing regardless of repeated impregnation of pitch and baking. The bulk density of the graphitized rod was found also to be increased by hoth inhibitors. Rapid heating at graphitization enhanced puffing of the rod in any case, however this inhibitor always suppressed the puffing. In contrast to the iron(II1) oxide, addition of boric acid together with iron(I1) sulfate was not effective in providing additional inhibition, suggesting their similar roles in the puffing inhibition. Iron(l1) sulfate impregnated into the pore of needle coke is converted into iron(Il1) oxide during the heat-treatment which plugs the pore preventing it from being fully filled with the binder and impregnated pitches during repeated impregnation and baking. lton(lI1) oxide was reduced to iron at an early stage of graphitization, which melts, migrates within the carbon and reacts with carbon to form FeaC, and decompose to Fe and graphite, finally vapourizing out of the coke grain. Such conversions of iron sulfate open .and induce the porosity for puffing causing sulfur- and nitrogen-containing gases to be liberated without provoking the puffing. No remaining iron in the graphitized rod may support the role of the present puffing inhibitor. Addition of iron(lI1) oxide at the kneading stage may decrease the puffing due to the coke derived from impregnation pitch, suppressing the puffing at repeated impregnation together with iron sulfate in the pores of needle coke. An additional advantage of increased bulk density of the graphitized rod was emphasized by both inhibitors, catalytic carbonization and graphitization performed by the inhibitors contributing such advantages. 00/03282 Reaction of NO with carbonaceous materials. 1. Reaction and adsorption of NO on ashless carbon black Yang, J. er al. Carbon, 2000, 38, (5), 715-727 The mechanism of the reaction of NO with ashless carbon black was studied in detail. The differences between the amounts of oxygen and nitrogen measured and the calculated concentrations of oxygen and nitrogen suggest the formation of surface carbon-oxygen complexes C(0) and carbonnitrogen complexes C(N). The dependence of the specific rate of reaction at its initial stage on temperature is different from that at steady state, pointing to different rate-determining steps for the two reaction regimes. The decomposition of surface complexes 1s suggested to be the ratedetermining step for the reaction under steady-state conditions. This explains very well the measured zero, reaction order with respect to NO. NO is proposed to adsorb parallel to the carbon black surface. The dissociation of the N-O bond leads to the formation of C(0) and C(N) complexes which are heterogeneous in structure. The adsorbed NO molecules are not stable on the carbon black surface at temperatures above 300°C. The reaction of NO with carbon at higher temperatures results in the formation of more surface complexes with higher thermal stability. The surface C(0) complexes involved in the CO formation differ in structure from those involved in the CO: formation. The mechanism of the NO-carbon reaction at low temperature:< appears to he different from that at high temperatures (>75o”C). 00/03283 Reaction of NO with carbonaceous materials. 2. Effect of oxygen on the reaction of NO with ashless carbon black Yang, J. er al. Carbon, 2000, 38, (5), 7299740. The reaction rate in the reaction of NO with an ashless carbon black was considerably enhanced in the presence of oxygen. A similar effect has also been observed in the reaction of NO with the oxidized carbon black. The creation of more active sites on the carbon surface in the reaction with oxygen and NOz (produced by the reaction of NO with O?) is proposed to be responsible for this enhancement. A lower apparent activation energy was observed in the reaction of NO with the oxidized carbon black than with the unmodified carbon black. It was found that the adsorption of NO is restrained to some extent on the carbon black surface mostly covered by complexes of carbon and oxygen. However, the adsorption of NO and the formation of products at about 4WC were enhanced only when carbon-
Fuel and Energy Abstracts
November 2000
369