Susumu Fujiyama

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 pitches prepared from methylnaphthalene by the aid of HFBF3

Abstract Mesophase pitches were prepared from methylnaphthalenes using HF BF 3 as a catalyst to improve their spinning and stabilization properties in comparison with those from naphthalene. Methylnaphthalene-derived mesophase pitch carried a number of methyl groups in addition to naphthenic groups which were introduced by nondehydrogenative polymerization reaction of naphthalene rings. Many methyl groups in methylnaphthalene were left in the mesophase pitch to be very effective for lowering the softening point and improving the spinnability and stabilization reactivity, stabilization being achieved within 10 minutes at 270°C. It was found that the methyl group migrated between 1-and 2-positions on the naphthalene ring in the presence of super strong acid of HF BF 3 , giving the same structure and properties of mesophase pitches regardless of its positions in the starting materials. Effects of the methyl group on the reactivity and structural changes of the stabilization were discussed based on the infrared (IR) spectra.