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175. Structural change during desulphurization of petroleum coke
236
ABSTRACTS
of sintered and graphitized carbon was obtained by discharge for a duration time from 60 set to 300 set under a pressure of 175-350 kg/ems. The degree of sintering and graphitization of the compact specimen was examined by microscope and X-ray analysis. The more compactly sintered carbon for petroleum coke and thermal black was obtained by using a longer discharging time. Some of the sintered thermal black specimens were gradually decomposed to fine powders within a month or so. 174. Graphitisation of organic compounds-I. benzyne precoursers.
Graphitization enhancement by copyrolysis with
L. G. Isaacs (S’eer Carbon Company, Research Laboratory, Niagara Falls, New York). Mixtures of phthalic anhydride, and similar aromatic anhydrides or imides, and organic compounds which normally yield nongraphitizing carbons have been copyrolyzed. The graphites prepared from these mixtures have smaller interlayer spacings and larger crystallite sizes than those prepared from either compounds of the mixture. Fluorene and carbazole, when carbonized and the carbons heated to 28OO”C, yield materials with interlayer spacings of 3.43 A or larger. Phthalic anhydride, pyromellitic dianhydride, and phthalimide similarly give non-graphitizing carbons with even greater interlayer spacings. However, carbons prepared from mixtures of these two sets of compounds had much lower interlayer spacings and larger crystallite sizes. Over the range 35-65 per cent fluorene with phthalic anhydride, this graphitization enhancement was not affected by concentration. Pyromellitic dianhydride was slightly more effective than the mono-anhydride or the imide. It has been shown that pyrolysis of phthalic anhydride yields benzyne as a reactive intermediate. Reaction of benzyne with the nongraphitizing organic compounds may be responsible for the improved graphitization qualities of the copyrolyzates. Evidence for such reactions and the effect of other benzyne-type precoursers on the graphitization of a variety of organic compounds will be discussed. 175. Structural change during desulphurization of petroleum coke. J. Gillot and B. Lux (Imtitut Battelle, Geneva, Switzerland) and P. Cornault and F. DuChaffaut (So&f Peching, Paris, France). A petroleum coke with a sulphur content of 1.27 per cent was treated for desulphurization in a hydrogen atmosphere at 13OO”C,and under vacuum at 13OO”C, 14OO”C, 1500°C. During these treatments four phenomena occur simultaneously: (1) The slow departure of part of the sulphur; (2) a weight loss of the coke; (3) the transformation of a small fraction of the coke into well crystallized graphite
;=
3*36A,L,~500A
which is indicated by the appearance of a second peak in the (002) 1ine; (4) the formation of small cracks or granulations in the coke. 176. A mass spectrometric study of the species involved in carbon depositlon from RF discharges in carbon containing gases. H. E. Evans and P. P. Jennings (Berkeley Nuclear Laboratories, Berkeley, England). A mass spectrometric study of species present in radio frequency discharges in binary mixtures of carbon dioxide, carbon monoxide, methane, oxygen and helium has been made. The results have been correlated with visual observations of deposit formation. Rates of formation and rates of oxidation of deposits have been measured gravimetrically in situ. Deposits were formed from all carbon monoxide/methane mixtures and from a number of the other mixtures. In the absence of methane the ions C+, C,O+, C801+ and possibly C&f or their neutral precursors were thought to be involved in deposition. In methane-containing mixtures the ion distribution was complex. The distribution has been interpreted in terms of ion-molecule reactions of CH,+ and reactions of atomic oxygen with methane. The results are interpreted as showing that deposition and corrosion reactions occur simultaneously. Deposition occurs when the rate of the deposition reaction exceeds that of the corrosion reaction. 177. Characterization of carbons and graphites by X-ray examination. E. Fitzer, W. Fritz, N. Christu and D. Overhoff (Tech&he Hochxhule, Karlsruhe, Germany). In this paper the influence of the preparation of specimens and of different standards on the results of the Warren-Averbach analysis are studied. The graphite types used are based on cokes from acenaphthylene and decacyclene, on petrol cokes as well as pyrolytic graphites. It is shown that the mean square fractional displacements, in most cases, give an additional characterization of the crystalline order. Above all, spirally grown pyrolytic graphites
ABSTRACTS
of sintered and graphitized carbon was obtained by discharge for a duration time from 60 set to 300 set under a pressure of 175-350 kg/ems. The degree of sintering and graphitization of the compact specimen was examined by microscope and X-ray analysis. The more compactly sintered carbon for petroleum coke and thermal black was obtained by using a longer discharging time. Some of the sintered thermal black specimens were gradually decomposed to fine powders within a month or so. 174. Graphitisation of organic compounds-I. benzyne precoursers.
Graphitization enhancement by copyrolysis with
L. G. Isaacs (S’eer Carbon Company, Research Laboratory, Niagara Falls, New York). Mixtures of phthalic anhydride, and similar aromatic anhydrides or imides, and organic compounds which normally yield nongraphitizing carbons have been copyrolyzed. The graphites prepared from these mixtures have smaller interlayer spacings and larger crystallite sizes than those prepared from either compounds of the mixture. Fluorene and carbazole, when carbonized and the carbons heated to 28OO”C, yield materials with interlayer spacings of 3.43 A or larger. Phthalic anhydride, pyromellitic dianhydride, and phthalimide similarly give non-graphitizing carbons with even greater interlayer spacings. However, carbons prepared from mixtures of these two sets of compounds had much lower interlayer spacings and larger crystallite sizes. Over the range 35-65 per cent fluorene with phthalic anhydride, this graphitization enhancement was not affected by concentration. Pyromellitic dianhydride was slightly more effective than the mono-anhydride or the imide. It has been shown that pyrolysis of phthalic anhydride yields benzyne as a reactive intermediate. Reaction of benzyne with the nongraphitizing organic compounds may be responsible for the improved graphitization qualities of the copyrolyzates. Evidence for such reactions and the effect of other benzyne-type precoursers on the graphitization of a variety of organic compounds will be discussed. 175. Structural change during desulphurization of petroleum coke. J. Gillot and B. Lux (Imtitut Battelle, Geneva, Switzerland) and P. Cornault and F. DuChaffaut (So&f Peching, Paris, France). A petroleum coke with a sulphur content of 1.27 per cent was treated for desulphurization in a hydrogen atmosphere at 13OO”C,and under vacuum at 13OO”C, 14OO”C, 1500°C. During these treatments four phenomena occur simultaneously: (1) The slow departure of part of the sulphur; (2) a weight loss of the coke; (3) the transformation of a small fraction of the coke into well crystallized graphite
;=
3*36A,L,~500A
which is indicated by the appearance of a second peak in the (002) 1ine; (4) the formation of small cracks or granulations in the coke. 176. A mass spectrometric study of the species involved in carbon depositlon from RF discharges in carbon containing gases. H. E. Evans and P. P. Jennings (Berkeley Nuclear Laboratories, Berkeley, England). A mass spectrometric study of species present in radio frequency discharges in binary mixtures of carbon dioxide, carbon monoxide, methane, oxygen and helium has been made. The results have been correlated with visual observations of deposit formation. Rates of formation and rates of oxidation of deposits have been measured gravimetrically in situ. Deposits were formed from all carbon monoxide/methane mixtures and from a number of the other mixtures. In the absence of methane the ions C+, C,O+, C801+ and possibly C&f or their neutral precursors were thought to be involved in deposition. In methane-containing mixtures the ion distribution was complex. The distribution has been interpreted in terms of ion-molecule reactions of CH,+ and reactions of atomic oxygen with methane. The results are interpreted as showing that deposition and corrosion reactions occur simultaneously. Deposition occurs when the rate of the deposition reaction exceeds that of the corrosion reaction. 177. Characterization of carbons and graphites by X-ray examination. E. Fitzer, W. Fritz, N. Christu and D. Overhoff (Tech&he Hochxhule, Karlsruhe, Germany). In this paper the influence of the preparation of specimens and of different standards on the results of the Warren-Averbach analysis are studied. The graphite types used are based on cokes from acenaphthylene and decacyclene, on petrol cokes as well as pyrolytic graphites. It is shown that the mean square fractional displacements, in most cases, give an additional characterization of the crystalline order. Above all, spirally grown pyrolytic graphites