Kiyoyuki Shimizu

Preparation of mesophase pitch from aromatic hydrocarbons by the aid of HFBF3

Abstract Two procedures to prepare mesophase pitch from naphthalene using HF BF 3 , are described. The first procedure heats naphthalene at 80°C with HF BF 3 to give a naphthene rich pitch followed by either (a) heat treatment at 400–480°C under vacuum (0.1 kPa) or (b) Heat treatment at 2.1 MPa followed by vacuum treatment at 0.1 kPa. Approach (a) gives a spinnable mesophase pitch of S.P. 228°C of 98% anisotropy, 23 wt% yield, and approach (b) of 40–60 wt% yield. Stabilization in air was very slow especially with the pitch made by approach (b), taking 90–120 min or longer at 300°C. Programmed heating was effective to reduce the stabilization time. The second procedure heated naphthalene with HF BF 3 , under pressure at 260–300°C. The resultant pitches had 100% anisotropy and S.P. of 215–285°C with BS amounts of 52-12 wt% in yields of up to 60 wt%. Smoothly spun fibers were stabilized, 15–30 min at 270°C. Noncatalytic preparation produced mesophase pitch of high aromaticity: catalytic preparations maintained naphthenic hydrogen, the cause of stabilization reactivity. HF BF 3 could be removed from the pitch.

Structure and carbonization properties of pitches produced catalytically from aromatic hydrocarbons with HF/BF3

Carbonization properties of pitches synthesized from some aromatic hydrocarbons by the aid of HFBF3 were studied under atmospheric 1.1 and 3.1 MPa pressures. The highest coke yields obtained under atmospheric pressure and 3.1 MPa were 64% and 85%, respectively, both of which were observed with anthracene pitch. Pyrene pitch exhibited a low coke yield of 37% under atmospheric pressure, but as high as 85% under 3.1 MPa. The pitches were revealed with 1H-NMR and FD-MS to consist essentially of oligomers of starting aromatic rings such as dimers, trimers, and tetramers. The oligomers carried significant amounts of naphthenic hydrogens, which provide their low softening point and enable the development of an anisotropic flow texture when the pitch was carbonized. The carbonization scheme is discussed in relation to the coke yield.

Mesophase pitch catalytically prepared from anthracene with HF/BF3

Abstract Structure and properties of mesophase pitches prepared catalytically from anthracene by the aid of HF/BF 3 were studied to reveal the influences of starting aromatic hydrocarbons. In comparison to naphthalene mesophase pitch, the anthracene pitch exhibited higher yield and slightly higher softening point under milder conditions of preparation. More naphthenic and aryl-aryl bonds with fewer methyl groups were characteristic of the anthracene pitch. Such characterizations are ascribed to the high reactivity of 9,10 positions in the anthracene ring. Although difficulty of spinning reduced the tensile strength of its resultant carbon fiber, its larger molecular units provided higher young modulus, especially at lower graphitization temperature. Lower spinning viscosity was found to give higher modulus of the carbon fiber from the same mesophase pitch at the same graphitization temperature. Molecular alignment at the spinning is briefly discussed.