| 학회 | 한국고분자학회 |
| 학술대회 | 2005년 가을 (10/13 ~ 10/14, 제주 ICC) |
| 권호 | 30권 2호 |
| 발표분야 | 고분자 합성 |
| 제목 | A Theoretical Study on the Stereoselectivity and the Kinetics of Propylene Insertion in MgCl2-supported Heterogeneous Ziegler-Natta Catalytic System: A Non-local Density Functional Theory |
| 초록 | In this study, the stereoselctivity of propylene insertion is investigated in MgCl2-supported heterogeneous Zigler-Natta catalyst including the effect of internal donors by means of Density Functional Theory (DFT). In order to describe (110) and (100) surfaces of MgCl2 where TiClx (x=4 or 3) and Ti2Cl7 adsorb, model clusters with relaxed geometry are used. To inspect the stereoselectivity, structures and energetics of reactants, π-complexes, transition states and products during propylene insertion are calculated at possible active sites formed by both mononuclear and dinuclear Ti adsorption. From the results, it is found that active sites formed by TiCl3 adsorption on MgCl2 are more stable than that formed by unreduced TiCl4 adsorption. As for stereoselectivity, however, only the active sites formed by TiCl4 and Ti2Cl7 adsorption on (100) surface of MgCl2 have chiral structures and therefore can discriminate the enantioface of propylene and other active sites do not show stereoselectivity. We also examine the role of internal donors by calculations of the binding energies of three different 1,3-diethers on the (110) and (100) surfaces of MgCl2. The DFT calculation reveals that the internal donors bind on (110) surface roughly 10 kcal/mol more strongly than on the (100) surface. Furthermore, the internal donors with bulkier substituents in C2 position are bound on (110) surface more selectively. As a result, the role of the internal donors is the prevention of the formation of non-stereospecific active site on (110) surface. Fig. 1. The structure of MgCl2 (a) and its lateral surfaces cleaved from the bulk: (110) surface (b) and (100) surface (c). The surfaces where TiCl4 adsorbs are represented by gray plane. Mg atoms are represented by the gray balls while the black balls refer to the Cl atoms. |
| 저자 | 이진우, 양성훈, 허준, 조원호 |
| 소속 | 서울대 |
| 키워드 | ziegler-natta catalyst; Density Functional; Stereoselectivity; olefin polymerization |
