Modification of isotropic coal-tar pitch by acid treatments for carbon fiber melt-spinning

Abstract

In this work, thermal treatment accompanied with different acid treatments was applied to a commercial coal tar pitch (CTP) to obtain a spinnable precursor pitch for carbon fiber. In the case of thermal treatment only, a relatively high reaction temperature of between 380°C and 400°C was required to obtain a softening point (SP) range of 220°C-260°C and many meso-phase particles were created during the application of high reaction temperature. When nitric acid or sulfuric acid treatment was conducted before the thermal treatment, the precursor pitch with a proper SP range could be obtained at reaction temperatures of 280°C-300°C, which were about 100°C lower than those for the case of thermal treatment only. With the acid treatments, the yield and SP of the precursor pitch increased dramatically and the formation of meso-phase was suppressed due to the lower reaction temperatures. Since the precursor pitches with acid and thermal treatment were not spinnable due to the inhomogeneity of properties such as molecular weight distribution and viscosity, the CTP was mixed with ethanol before the consecutive nitric acid and thermal treatments. The precursor pitches with ethanol, nitric acid, and thermal treatments were easily spinnable, and their spinning and carbon fiber properties were compared to those of air blowing and thermal treated CTP.

Fabrication and Characterization of Activated Carbon Fibers from Oil Palm Trunk

“…These may be attributed to the partial cleavage of PEG moiety from primary fibers after incubation with diluted acid, which can be confirmed by decreasing in the intensity of C-H stretching vibration of methylene groups at 2930 cm −1 as showed in Figure 2A. Besides, the above result might be also caused by the diluted sulfuric acid solution failing to act as a catalyst for poly-condensation and cross-linking with the structure of the ligno-humin based primary fibers at low temperatures, resulting in the reformation of furanics in humin into phenolics and benzofurans [29][30][31]. For the thermal degradation characterization, the obtained incubated fiber showed more stable than primary fiber ( Figure 2B), indicating that the chemical treatment with a dilute sulfuric acid solution at room temperature was helpful to improve the thermal stability of the primary fiber.…”

Activated carbons prepared from mixtures of coal tar pitch and petroleum pitch and their electrochemical performance as electrode materials for electric double-layer capacitor

“…The CTP, having a softening point of 292°C, was stabilized at 300°C for 2 h under air in a tube ) and aliphatic (2955, 2920, 2855, and 1450 cm -1 ) groups. Specifically, we can see the existence of aromatic C-H stretch at 3050 cm -1 and the stretching of aromatic C=C at 1611-1470 cm -1 [25][26][27][28]. Compared to the PP, the CTP and stabilized CTPS had noticeable increases of absorption at 3050 cm -1 and decreases of absorption at 2920 cm -1 but there were no significant differences between CTP and CTPS.…”

Preparation and evaluation of isotropic and mesophase pitch-based carbon fibers using the pelletizing and continuous spinning process

“…The pitches are derived from coal tar or petroleum through thermal treatment and are classified as isotropic pitch (IP) or mesophase pitch (MP) based on their crystal structure. Anisotropic MP-based carbon fibers are used in higher value-added industries such as aerospace and expensive sporting goods [7–10] due to their higher tensile strength and electrical properties, whereas IP-based carbon fibers are used in other industries. The most popular method to prepare pitch-based carbon fibers is to spin the pitch fibers using a batch extruder composed of a cylindrical apparatus.…”