A Comparison of Ethylene-Tar-Derived Isotropic Pitches Prepared by Air Blowing and Nitrogen Distillation Methods and Their Carbon Fibers

Abstract

Two isotropic pitches were prepared by air blowing and nitrogen distillation methods using ethylene tar (ET) as a raw material. The corresponding carbon fibers were obtained through conventional melt spinning, stabilization, and carbonization. The structures and properties of the resultant pitches and fibers were characterized, and their differences were examined. The results showed that the introduction of oxygen by the air blowing method could quickly increase the yield and the softening point of the pitch. Moreover, the air-blown pitch (ABP) was composed of aromatic molecules with linear methylene chains, while the nitrogen-distilled pitch (NDP) mainly contained polycondensed aromatic rings. This is because the oxygen-containing functional groups in the ABP could impede ordered stack of pitch molecules and led to a methylene bridge structure instead of an aromatic condensed structure as in the NDP. Meanwhile, the spinnability of the ABP did not decrease even though it contained 2.31 wt % oxygen. In contrast, the ABP had narrower molecular weight distribution, which contributed to better stabilization properties and higher tensile strength of the carbon fiber. The tensile strength of carbon fibers from the ABP reached 860 MPa with fiber diameter of about 10 μm, which was higher than the tensile strength of 640 MPa for the NDP-derived carbon fibers.

A Superior Potassium-Ion Anode Material from Pitch-based Activated Carbon Fibers with Hierarchical Pore Structure Prepared by Metal Catalytic Activation

“…23,24 As one of the most important carbonaceous precursors, ethylene bottom oil has advantages of high carbon−hydrogen ratio, compact molecular structure, low ash content, and low heavy metal content, which is generally used to prepare the pitch precursors for the production of carbon fiber (CF) as a raw material. 25 Meanwhile, the pitch-based CF is also used to produce activated carbon fiber (ACF) due to the pitches having higharomatic and low-aliphatic carbon contents and giving high yields on carbonization. 26,27 More importantly, pitch-based ACF from ethylene bottom oil has the advantages of high specific surface area, large adsorption capacity, fast absorption, and desorption rate and low cost 28,29 which show potential to solve the negative problems of low storage capacity and slow dynamics caused by excessive potassium-ion radius.…”

“…Among them, various strategies have been proposed to solve the problems caused by excessive potassium-ion radius about PIBs: (1) increase the graphite layer spacing to improve the potassium-ion transport dynamics, reducing the volume change of the anode; (2) prepare the anode material with a mesoporous structure, improving potassium-ion storage capacity; and (3) metal sulfide doping provides abundant active sites and increases the storage capacity of potassium-ion. − Thus, to construct high-performance PIBs, the design and synthesis of carbon-based anodes with controllable pore structures are highly demanded . At the same time, low-cost raw materials and simple preparation technology are also the key factor to the large-scale application of the PIB’s anode. , As one of the most important carbonaceous precursors, ethylene bottom oil has advantages of high carbon–hydrogen ratio, compact molecular structure, low ash content, and low heavy metal content, which is generally used to prepare the pitch precursors for the production of carbon fiber (CF) as a raw material . Meanwhile, the pitch-based CF is also used to produce activated carbon fiber (ACF) due to the pitches having high-aromatic and low-aliphatic carbon contents and giving high yields on carbonization. , More importantly, pitch-based ACF from ethylene bottom oil has the advantages of high specific surface area, large adsorption capacity, fast absorption, and desorption rate and low cost , which show potential to solve the negative problems of low storage capacity and slow dynamics caused by excessive potassium-ion radius.…”