Effect Of Chlorobenzene And Nitrobenzene To Coal Tar Pitch On The Structure Of Needle Coke

Needle coke, as a main material, is widely used in electrode area for steel and aluminum production, and it can be prepared with coal tar pitch. It is believed to be significant for reducing the dependence on foreign products, if a large amount of coal tar pitch was used fully to prepare the high-quality needle coke in our country. In the paper, based on studies on coal asphalt at home and abroad, we have analyzed its comprehensive properties and the effect on the needle coke quality systematically. To solve the problems in needle coke preparation, nitrobenzene and chlorobenzenes were introduced to modify coal tar pitch, with hopes to improve the carbon yield and coking value, increase the anisotropic mesophase content and further enhance the polymerization reaction and order of the microstructure; which would provide experimental support for ordered needle coke preparation. The results concluded are as follows:(1) Compared with the unmodified coal tar pitch, for which modified with 10% of 3-chloro-nitrobenzene, the β-resin content and CV value increase by 36.67% and 20.32% respectively, and SP value increases about 36 ℃. At temperature in the range of 0-200 ℃, the viscosity increases greatly; while, no obvious change was observed with the increasing warming.TG analysis shows the carbon yield increases 21.41% 1HNMR analysis shows, compared with the original coal tar pitch, the content of aliphatic hydrogen decreases, in contrast, aromatic increases about 2.37 times. The XRD and polarizing microscope results conclude the needle coke presents a long fibrous tissue structure, and after calcination it tends to graphite structure with a larger nucleation stack height, showing a good performance.(2) Still compared with the unmodified coal tar pitch, the β-resin and CV increase 11.02% and 21.32% respectively, and SP increases about 21℃, by using 10% of 1,2,3-trichlorobenzene as modifier. The change of viscosity versus temperature is the same with that in result (1). By TG analysis the carbon yield increases by 22.06%. By 1HNMR analysis, the content of aliphatic hydrogen decreases, while, aromatic improves about 2.1 times than that in original coal tar pitch. XRD and polarizing microscope analysis also conclude a positive result as have described for 3-chloro-nitrobenzene, showing another preferable modifier.(3) Studies on the semi-coke structure under various electric field strength and heating rates show that the field intensity and heating rate with value of 25～37.5 kv/m and 3℃/min respectively are relatively better for the intermediate phase structure, but not significant. While the diffraction peak of XRD has increased obviously, indicating a higher crystallization degree has been formed.