Vapor-phase dehydrocyclidimerization of isobutene aromatic hydrocarbons over reduced V₂O₅-MgO catalyst in the presence and the absence of gaseous oxygen has been investigated with reference to the nature of active site and the effect of introduction of gaseous oxygen on the distribution of aromatic hydrocarbons formed. In the absence of gaseous oxygen, the formation of p-xylene with 40% selectivity was observed, whereas in the presence of gaseous oxygen, toluene and benzene were formed with 40% selectivity and without any formation of p-xylene. Vanadium ions existing on the surface on which isobutene is adsorbed were found to be V³⁺, independent of the presence and the absence of gaseous oxygen. Thus, a change in the formation of aromatic hydrocarbons by the introduction of gaseous oxygen was attributed to a role played by oxygen rather than the difference in the nature of hydrocarbon species adsorbed on the vanadium ions.
The reaction of 2, 5-dimethyl-1, 5-hexadiene formed by coupling of π-allyls from isobutene with unreduced V₂O₅-MgO showed a preferential formation of toluene and benzene at the initial stage of the reaction followed by increase in the yield of p-xylene with an elapse of reaction time. A role of oxygen was further studied, and the formation of toluene and benzene via 2-methyl-1, 3, 5-hexatriene and 1, 3, 5-hexatriene not via p-xylene was proposed.

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Cocarbonization properties of modified ethylene tar pitches (MET) with the BI-QS of SRC pitches were investigated in order to solve the relationship between their chemical structure and compatibility in the carbonization. MET-II-BS and MET-III-BS which were obtained by the catalytic modification with ferric chloride and via the thermal treatment, respectively, still had a poor compatibility to give a fine mosaic coke as the original ET did, whereas MET-I-BS which was obtained with aluminum chloride showed an excellent compatibility to give a needle coke.
The structural differences among these MET-BS were examined by means of UV, IR and NMR spectroscopy. The significant structural characteristic of MET-I-BS was the naphthenic ring structure adjacent to the aromatic ring system which was revealed by IR and NMR.
The preferable influence of the naphthenic ring structure for the excellent compatibility may be explained in terms of the lowered melting points and suitable reactivity which may keep the carbonizing substances including BI-QS fusible during the important stage of carbonization. Such an explanation was supported by the improved compatibility of MET-II-BS brought about by the partial hydrogenation.
The mechanism of the modification reaction of pitch materials was discussed in relation to that of the catalytic carbonization.

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The purpose of this experimental program was: (a) to determine the relationship between the fixed carbon (FC) content of a pitch with the FC of its component, and (b) to determine the relationship between the softening point (SP) of a pitch and the SP of its component.
The pithes were prepared by heat treatment of petroleum residue at 420-440°C, and were solvent fractionated into three components; benzene insolubles (C₁+C₂ fraction), benzene solubles but n-heptane insolubles (C₃+C₄ fraction) and n-heptane solubles (d fraction).
Values of FC and SP of the pitch and its components were measured.
Values of FC and SP of the pitch could be expressed by the following formula:
FC_pitch=(FC)_C1+C2×(C₁+C₂)+(FC)_C3+C4×(C₃+C₄)+(FC)_d×(d)+α……(1)
SP_pitch=a(C₁+C₂)+(SP)_C3+C4×(C₃+C₄)+(SP)_d×(d)+β……(2)
where (FC)_C1+C2, (FC)_C3+C4, (FC)_d, (SP)_C3+C4, (SP)_d are the values of FC and SP of each component, (C₁+C₂), (C₃+C₄) and (d) are the amount of each component, α and β are the correction values, respectively. The correction value α was approximately 7.2. The correction value α is believed necessary probably due to an effect of mutual interaction between each component during carbonization of pitches. The regression method based on the above formula (2) resulted in "α" to be 413 and β to be -96, with a good correlation. As in the care with α in the FC relationship, the correction factor β is considered necessary due to an effect of chemical and/or physical interction between each component. From the above the degree of mutual interaction and the contribution of each componet to FC and SP of the pitch were made known. Also, it seemed probablle that characteristics of the binder pitch can be clarified in detail by such an analytical method as outlined above, because the structural pattern of FC and SP of each component varies depending upon the feedstock used, even when the values of the whole pitch appear the same.

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