The atomic defects on the (104) and (110) surfaces of the MgCl2-supported Ziegler–Natta catalyst: a periodic DFT study

Abstract

The MgCl₂ support is widely used in the Ziegler–Natta system catalyzed olefin polymerization. In this work, three types of atomic defects on the ideal MgCl₂(110) and (104) surfaces were designed, including (i) the mono-Cl vacancy, (ii) the di-Cl vacancy, and (iii) the mono-MgCl₂ vacancy. The adsorption of TiCl₄, ethyl benzoate (EB), and 2,2-methyl-1,3-dimethoxypropane (DMDOMe) on the ideal and atom defective MgCl₂(110) and (104) surfaces was systematically investigated by using periodic DFT calculations. The adsorption of EB and DMDOMe is much stronger than that of TiCl₄ on the ideal (110) and (104) surfaces. Interestingly, the atom defective surfaces, such as mono-Cl and di-Cl atom defective (110) and (104) surfaces, lead to sites for strong TiCl₄ adsorption. Accordingly, a possible pathway for the formation of the Ti-alkyl active site starting from the adsorbed TiCl₄ on the mono-Cl atom defective (110) surface was proposed. In addition, the adsorption behaviors of TiCl₄ on the ideal and concave surfaces indicate that the monomeric TiCl₄ tends to adsorb on the concave (104) surface compared to the ideal (110) surface.