Naphthalene pitch is a kind of asphalt obtained from pure naphthalene or naphthalene homologue through self reaction. Naphthalene pitch has the characteristics of less heteroatom and concentrated molecular weight, which is commonly used to prepare binder asphalt and mesophase pitch with excellent performance.
① Molecular structure of naphthalene and its copolymer
Molecular structure of naphthalene
According to the valence bond structure model of naphthalene, the structure of naphthalene is a highly uniform and symmetrical six membered ring molecule with high stability and does not decompose below 570 ℃. When the temperature is above 500 ℃, the main component of naphthalene is naphthalene, and the main component is naphthalene
Because of the harsh self polymerization reaction conditions, the preparation method of naphthalene pitch mainly relies on cationic catalytic polymerization to make naphthalene pitch synthesized at lower temperature, mainly including AlCl3 catalyst and HF / BF3 catalyst.
① AlCl3 catalytic method
Under the catalysis of AlCl 3, the condensation reaction and intramolecular and intermolecular transformations of naphthalene can begin at about 100 ℃. AlCl3 catalyst is mainly cationic polymerization, which can produce intermediates containing naphthenic structure, which is easy to form streamline mesophase structure. Therefore, naphthalene based mesophase pitch can be prepared by AlCl3 catalytic polymerization.
In addition, the product can be polymerized in the form of CL3 in the presence of the catalyst at a certain degree of temperature due to the high solubility of the product. The residual AlCl3 makes the ash content of asphalt higher, so it affects the performance of carbon products. At present, Jining carbon uses this method to prepare mesophase pitch, and the ash content is about 400 ppm.
② HF / BF3 catalytic method
HF is a kind of protonic acid, its anion acid radical f-nucleophilic is very strong, and the diameter of f-is very small, which makes f-tightly adhere to H +, on the one hand, it weakens the affinity of H + to C = C double bond, on the other hand, it prevents other groups from contacting with H +, which is relatively difficult to carry out the reaction; that is, cationic polymerization can also easily terminate the reaction. HF / BF3 system is an ideal catalyst for the preparation of naphthalene pitch because of its strong acidity, weak nucleophilicity and large volume.
After controlling the synthesis conditions, the softening point of the synthesized naphthalene pitch is not more than 90 ℃, and the benzene insoluble substance can be 0. This kind of pitch is the precursor of preparing excellent carbon materials, which can be directly used as binder. After treatment, mesophase pitch with good fluidity can be prepared.
The above is the introduction of naphthalene asphalt preparation method, hope to help you, if you want to know more about the content, please click the website: refined naphthalene http://www.jnjdbc.cn 。