Preparation of mesophase pitch from aromatic hydrocarbons by the aid of HF BF₃

Two procedures to prepare mesophase pitch from naphthalene using HF BF₃, are described. The first procedure heats naphthalene at 80°C with HF BF₃ 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 BF₃, 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 BF₃ could be removed from the pitch.