The pore structure of pitch-based activated carbon prepared by physical activation was improved by nitric acid treatment of pitch. The nitric acid treatment introduced oxygen and nitrogen functional groups on pitch, and increased pitch molecular weight by cross-linking. The introduced oxygen and nitrogen functional groups on pitch were removed during the carbonization process, so they did not directly affect the physical activation process. The increased pitch molecular weight induced an increase of the pitch softening point. The increased softening point prevented rearrangement between the pitch molecules during the carbonization process, thereby inhibiting the orientation improvement of pitch molecules. The crystal degree of the carbonized pitch was reduced due to the inhibition of the orientation improvement. The reduced crystal degree increased reactivity between carbonized pitch and activation agent (CO₂) and formed micropores, so that activated carbon with a high specific surface area could be prepared.

通过物理活化制备的沥青基活性炭的孔结构通过硝酸对沥青的处理得以改善。硝酸处理在沥青上引入了氧和氮官能团，并通过交联增加了沥青分子量。在碳化过程中除去了沥青上引入的氧和氮官能团，因此它们不会直接影响物理活化过程。沥青分子量的增加引起沥青软化点的增加。增加的软化点防止了碳化过程中沥青分子之间的重排，从而抑制了沥青分子的取向改善。碳化沥青的结晶度由于抑制取向改善而降低。₂）并形成微孔，从而可以制备具有高比表面积的活性炭。