In order to use the petroleum pitch for binder pitch of carbon material, the pitch material was prepared from petroleum vacuum residue by heat-treatment at 400-450°C. Vacuum residues as starting materials which were obtained from a mixture of various crude oils (I) and from Khafji crude oil (K) were selected. The obtained pitches were investigated for the relations between their properties and heat-treatment conditions. The obtained results were as follows;
1) The changes of properties of the pitch obtained from I were remarkable than those of properties of the pitch from K under the same heat-treatment conditions in spite of the similarity of their properties.
2) The properties of the pitches obtained were similar to those of coal-tar pitches. It is suggested, therefore, that the pitches obtained can be used for binder of carbon materials.
3) The oils obtained from vacuum residues under the heat-treatment consisted of mainly n-paraffinic hydrocarbons having wide range boiling points.

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Properties of pitch material prepared from nine kinds of petroleum residues were investigated, and the pitches were examined for capability of the binder pitch for carbon material by the compressive strength of the carbon block. Pitches which had the benzene-insoluble, quinoline-insoluble and fixed-carbon content similar to that of coal-tar binder pitch were prepared from eight kinds of residues by the selection of heat-treatment conditions, which varied depending on the kind of residue. The compressive strength of carbon blocks varied depending on properties of pitches. The pitch showing the maximum compressive strength of carbon block had the benzene-insoluble and fixed-carbon content similar to that of the coal-tar binder pitch. In the case of benzene-insoluble and fixed-carbon content in the pitch is the same as that of the coaltar pitch, the specific gravity and the C/H atomic ratio of the pitch were lower than those of the coal-tar pitch. The characteristics of the pitch can be determined by the amount of benzene-insoluble and fixed-carbon content in the pitch, even if the chemical composition of the petroleum pitch is different from that of coal-tar pitch.

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In order to investigate an influence of the amount of components separated with fractionation of the pitch on the compressive strength of carbon block made by using the pitches as a binder, the pitch produced from various petroleum residues was fractionated into seven fractions by the solvent extraction and the liquid chromatography. The solvent extraction was carried out by use of quinoline, benzene, carbon tetrachloride and n-heptane as solvents. Carbon block was prepared by baking at 1, 000°C after molding a mixture of 35wt% of the pitch and 65wt% of the petroleum coke powder.
The following results were obtained:
1) There was casual relation between the amount of three fractions, C₁+C₂, C₃+C₄ and d-component in a whole pitch, and the compressive strength of carbon block. This relation was expressed by the following formulae;
σ=5.86D₁²-372D₁-6020 (φ<70)
σ=900e-(D₂-36.3/4)²+770e-|D₂-47.3/4| (φ_??_70)
where σ is the compressive strength of carbon block, φ=1.26(C₁+C₂)+(C₃+C₄), D₁=0.656(C₁+C₂)+0.753(C₃+C₄), D₂=0.993(C₁+C₂)+0.119(C₃+C₄).
2) The compressive strength of carbon block showed a maximum value when the pitch had a composition within the range of 20-35% C₁+C₂, 30-45% C₃+C₄ and 25-40% d-component respectively.
3) The pitch which had the mixed rate of three fractions mentioned above was prepared from residues of thermal cracked oil by the selection of heat-treatment condition, but could not be prepared from vacuum residues of crude oil under these experimental conditions.

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It was attempted to remove and recover metals contained in petroleum residues. Petroleum residues from Gachsaran and Khafji crude oils were heat-treated at 420-430°C, and mesophase formed in the heat-treated residues was separated with quinoline. The separated mesophase was called meso-carbon microbeads. Behaviors of metals (Fe, Cu, V and Ni) in the residues were investigated from the relation between yields of the meso-carbon microbeads and concentration of the metals in the microbeads. Additionally, the microbeads were treated with HCl, HNO₃ and organic solvents for recovery of the metals. The following results were obtained.
1. All kinds of the metals contained in residues were concentrated in mesophase, but the rate of concentration depended on the kind of metal.
2. Most of Fe and Cu in the residues were concentrated in the microbeads. V and Ni in the residues, on the other hand, were concentrated in the microbeads with an increase of the yield of the microbeads.
3. The metals in the microbeads could be recovered by treatment with HCl and HNO₃, but could not by organic solvent. The recovery of Fe and Cu was about 75% by HCl and HNO₃, and that of V and Ni was little by HCl, but about 50% by HNO₃.
4. From the changes of metal content in the microbeads obtained by heat-treatment of the residues and of amount of metals recovered from the microbeads by treatment with HCl and HNO₃, it is considered that Fe and Cu exist on the surface of the microbeads, and V and Ni distributed widely in the microbeads.

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In order to study the conversion of aromatics and resins to asphaltenes by heating in the air, a structural investigation was made of asphaltenes obtained from oxidized aromatics or resins and constituents fractionated from asphalts by means of high resolution nuclear magnetic resonance. The following results were obtained. The aromatic content was found to exist as condensed structures of 4 rings in aromatics and 5 to 6 rings in resins. The molecular weight, the condensation degree of aromatic rings, and the aromaticity of aromatics or resins increased by heating and both constituents were converted structurally to asphaltenes. The fundamental structure of asphaltenes is of a stratified nature, consisting of condensed aromatic ring sheets. Numbers of sheet unit of a molecule, which were approximately 1.5 to 2, did not change largely among asphaltenes fractionated from asphalts or oxidized aromatics and resins. But numbers of average condensed aromatic rings per sheet unit for asphaltenes varied from 6 to 16 with the starting materials or conditions for oxidation. Aromatic rings of a single sheet increased with the increasing molecular weight by heating under severer conditions. Especially, asphaltenes having polycondensed nuclear ring sheets were produced from aromatics, but in case of resins aromatic rings of a single sheet did not increase excessively. The condensation of aromatic rings by heating appeared to be of peri-type at a very low condensation degree but to be principally of cata-type at a higher extent of condensation.

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