Understanding the Role of Sulfonyl Amine Donors in Propylene Polymerization Using MgCl2-Supported Ziegler–Natta Catalyst

Ziegler–Natta catalysts are one of the mainly used industrial catalysts for the large-scale production of polyolefins. As one of the important components in a Ziegler–Natta catalyst, the internal donor and external donor pair is responsible for increasing the stereoregularity of polypropylene. In this work, a series of sulfonyl amine internal donors were systematically investigated by density functional theory (DFT) calculations. The adsorption behavior of the sulfonyl aromatic amine BTFMSPA-m-Cl indicates that the O atom exhibited an excellent coordinating affinity to the 4-coordinated Mg atoms on the MgCl2(110) surface among the three functional atoms (F, Cl, O). In addition, the substituents have a great influence on the adsorption behavior of the sulfonyl amines. The functional atom of the substituent (Cl or OMe) in the phenyl ring and the oxygen of the sulfonyl group tend to form a more stable bridge-coordination (Cl-Mg1,Mg2-O3, or O-Mg1,Mg2-O3) than the chelate-coordination (O1-Mg2-O2). In all considered internal donors, the stereoselectivity of the Ti active site can be greatly enhanced in the presence of BTFMSPA-m-Cl, which presumably results from the steric hindrance around the Ti active site caused by the bridge-coadsorbed BTFMSPA-m-Cl.