Size exclusion chromatography in the analysis of pitch

04 By-products from pyromellitic dianhydride (PMDA) and 4,4’-oxydianiline (ODA). Upon thermal treatment of the poly(urethane-imide) films at 300 to 400°C. the thermally less stable urethane domains decomposed, leaving porous polyimide films. The porous polyimide films were further pyrolysed at 900°C for 1 h to give porous carbon films. The formation of macropores was confirmed from scanning electron microscopy (SEM) of the surface and the cross-section of the films. The size distribution of the macropore was relatively narrow. With the increase of urethane content, the size of the macropore increased. The average pore size was found to be controlled between 0.6 pm and 10 pm by changing the ratio of the imide and the urethane components. It was also revealed from nitrogen adsorption isotherms that macroporous carbon films also contain micropores that were formed during the pyrolysis of the polyimide films. The progress of the micropore formation was studied by measuring nitrogen adsorption isotherms of the carbonized films treated at various temperatures. 02lOO910 Production of activated carbon from acorns and olive seeds Lafi, W.K. Biomass creel Biom~rgy. 2001, 20, (l), 57-62. This study has been designed to produce activated carbon from acorns and olive seeds. The starting materials are low in cost and they are the cause of solid waste pollution problems in Jordan. A chemical procedure is used to produce the required activated carbon. The results indicate that activated carbon produced from acorns compares favourably with that from olive seeds which rank second, along side commercial type activated carbon which comes last with respect to adsorption capacity. However, the optimum activation temperature is 800°C and the optimum regeneration temperature is also 800°C. 02lOO911 Redox characterization of furnace carbon black surfaces Goeringer, S. et crl. Carbon, 2001. 39, (4), 515-522. The redox properties of furnace-type carbon blacks were studied by UV-visible spectrophotometry and potentiometry. The carbon black surface was exposed to redox reagents such as Cr(VI), Nn(VII), Fe(III), and sulfite. The ability of the carbon black surface to undergo redox reactions with these reagents was correlated with the morphological attributes of the black such as crystallite size and surface area. The effect of high temperature treatment was also explored. These data show that the ability of carbon black to accept or donate electrons is a sensitive function of the defect site density of the carbon black surface. Thus an initially inert graphitic surface could be rendered redox active by mechanically damaging it. Conversely, high temperature treatment ‘graphitized’ the carbon black and weakened its redox activity. The ‘structure’ of carbon black (as probed by dibutylphthalate absorption) did not appear to influence its redox activity. Laser Raman spectroscopy and cyclic voltammetry provided further insights into the redox activity of the furnace carbon black surface. 02lOO912 Reference data for the adsorption of dichloromethane on carbon materials Carrott, P.J.M. emcrl. Carbon, 2001, 39, (3), 465-472. The adsorption of dichloromethane at 298K on non-porous carbon blacks and microporous activated carbons, including Takeda molecular sieves and Maxsorb superactivated carbons, has been studied. The results suggest that the exact shape of the isotherm on non-porous carbons is sensitive to the degree of uniformity of the surface and that it is therefore not possible to define a universal standard dichloromethane isotherm. On the other hand, it is possible to define reference data which can be used to analyse adsorption isotherms of dichloromethane determined on non-porous and microporous carbon materials by means of the ok, method. An indication of the range of applicability and the likely precision obtained when using the data is given. 02/00913 Size exclusion chromatography in the analysis of pitch Hansen, B.E. e, trl. Ligllr Me!. I Wrrrrent/cr/e, PA. C'.S.).2001, 559-564. Size exclusion chromatography (SEC) has been investigated as a tool to analyse pitch. SEC is a high pressure liquid chromatography (HPLC) method where the components are separated by hydrodynamic volume. The method is well known from polymer science where it is used to obtain molecular weight distributions. Several mobile phases were investigated. It was found that when the column was used at elevated temperature and N-methyl-2-pyrollidinone (NMP) was used as the mobile phase, the chromatography system could be operated without interference from effects not related to molecular size. The chromatography system also allowed analysis of the entire quinoline solute fraction. The method was applied to pitch that, as part of the preparation procedure had received mild thermal treatment of the feedstock tar. The study followed the formation of large molecular species by analysing the toluene insoluble fraction of pitch dissolved in NMP. Chromatography fractions were collected for further analysis by fluorescence spectroscopy.

related to fuels

02/00914 Small-angle X-ray scattering study of the pore structure of carbon fibers prepared from a polymer blend of phenolic resin and polystyrene Fukuyama, K. CI rrl. Carbon, 2001, 39, (2), 287-324. A novel technique to make porous carbon fibres without activation was developed, where the fibres are prepared from the polymer blend of carbon precursor resin that is forming carbon matrix by heat treatment and pore forming resin that disappears by pyrolysis. 02/00915 Temperature programmed desorption study on the mechanism of SO* oxidation by activated carbon and activated carbon fibres Raymundo-Phiero, E. e/ crl. Curbon, 2001, 39, (2), 231-242. The mechanism of SO1 oxidation by 02 on ACs and ACFs has been studied over a wide variety of samples with different porosity and surface oxygen content. Temperature programmed desorption experiments after SOZ adsorption at room temperature and using gas mixtures with different compositions and in-situ FTIR experiments during the adsorption and the subsequent desorption, show that SO1 oxidation is inhibited by the oxygen complexes existing on the carbon surface. The experiments also suggest that the SO1 oxidation occurs through the interaction of adsorbed SO2 with 02 in the gas phase by a mechanism that follows an Eley-Rideal kinetic model. Desorption of SO, produces carbon gasification and generates selectively CO-type oxygen complexes at the surface; CO: gas is only formed through secondary reactions between SO? and CO. 02/00916 The effect of certain metallic derivatives on the adsorption of sulphur dioxide on active carbon Davini, P. C&on, 2001, 39, (3). 419-424. The SO* adsorption characteristics of low ash active carbons are strongly influenced by the presence of certain transition metal derivatives and by the composition of the gaseous sorption mixture; in particular, the effect of oxygen and water vapour is very important. In the SOZ sorption-desorption cycles on these supported carbons (simulating their application in a real desulphurization process) the decrease of sorption activity of the carbon matrix appears to be strongly reduced in the presence of Sol. especially when HZ0 is also present. Moreover, the presence of vanadium and iron particularly enhances this effect. This is probably related to the catalytic activity of these elements in the SO2 oxidation process. 02100917 The effects of different activated carbon supports and support modification on the properties of PffAC catalysts Erhan Aksoyly, A. PI crl. Curhon, 2001, 39, (2), 175-185. Two commercial activated carbons were used as catalyst supports in Pt/ AC catalysts. Activated carbons were used in their unoxidized form or after either liquid phase oxidation with HNOl or gas phase oxidation with 5% OZ. All six activated carbons were characterized by nitrogen adsorption, TPD, and SEM. Selected samples were tested by XPS. The types and abundance of the oxygen bearing surface groups on each of the activated carbon supports were determined from the deconvolution of the TPD profiles of the activated carbons. An evaluation of the results obtained from TPD and XPS together indicates that both oxidation treatments led to a nearly homogeneous increase of oxygen bearing groups on the outer surface as well as interior surfaces. XPS analysis revealed that the HNOx oxidized samples have the highest concentration of oxygen bearing groups on the outermost surface. Pt/ AC catalysts (1 wt.%) were prepared on these supports. The catalysts were characterized by TPR, HZ adsorption, SEM-EDS and tested in structure insensitive benzene hydrogenation as well. The results obtained indicate that the oxidation treatments affect drastically the properties of the activated carbons as well as the catalysts prepared on them. A comparison between benzene hydrogenation activities validates the dispersion values obtained from Hz adsorption at room temperature. 02/00916 The influence of rimary QI on the oxidation behaviour of pitch-based CPC composites Granda, M. e! crl. Carbon, 2001, 39, (4). 483-492. Three unidirectional C/C composites were prepared from PAN-based carbon fibres and three coal-tar pitches obtained from the same parent coal-tar pitch hut differing in their primary QI content. The effect of the amount of primary QI present in pitches on the air reactivity of pitch-cokes and C/C composites was studied by thermogravimetric analysis. The oxidation of pitch-cokes was performed at 10°C min ’ up to 1000°C. The air reactivity of C/C composites was assessed from the weight loss curves obtained under isothermal conditions in the temperature range of 500 to 575°C for 4 h. The topography of the oxidized composites. was examined by scanning electron microscopy. The results showed that pitch-cokes were more reactive than carbon fibres because the presence of QI particles increased their reactivity. With the increase of primary QI content in the pitches, C/C composites showed a higher percentage of ‘carbon matrix, with the finer optical Fuel and Energy

Abstracfs

March 2002

111