Computational investigation on adsorption characteristics of aromatic amine for SiHCl₃-BCl₃ system

Recently, after initial rectification, adsorption has become a viable method for further purification of SiHCl3, but much work remains to be done to find a suitable adsorbent. Quantum chemical calculations offers a feasible way to study the mechanism of adsorption, which help develop appropriate adsorbents. Aromatic amines are widely used as adsorbents for BCl3 in SiHCl3, but the adsorption mechanism remains unclear, which impedes the development of efficient adsorbents. In this work, density functional theory is used to investigate the adsorption configuration, adsorption energy and electronic properties of BCl3-SiHCl3 on aromatic amines and the mechanism of interaction between BCl3/SiHCl3 and aromatic amines is analyzed and discussed. The results show that BCl3/SiHCl3 could achieve the separation criteria after two-stage adsorption using aromatic amines (except diphenylamine and triphenylamine) as adsorbent. The adsorption performance decreases as the hydrogen on the nitrogen is gradually replaced by the aromatic ring. When the hydrogen on the benzene ring is substituted with methyl, the adsorption performance of adsorbents changes, which is also position specific. The adsorption energy (-30.63kJ/mol) of p-methylaniline for BCl3 is the highest at 298 K and 1atm. Besides, the desorption behavior of aromatic amines on BCl3 is investigated by increasing the temperature and lowering the pressure by evacuation, and it is found that varying pressure is less energy intensive than increasing the temperature. A combination of adsorption capacity and desorption degree considerations suggest that aromatic amines can be used as adsorbent materials.