کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
6455554 1419756 2017 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Alkylation of titanium tetrachloride on magnesium dichloride in the presence of Lewis bases
ترجمه فارسی عنوان
آلکیلینگ تترا کلرید تیتانیوم در دی کلرید منیزیم در حضور پایگاه های لوئیس
موضوعات مرتبط
مهندسی و علوم پایه مهندسی شیمی کاتالیزور
چکیده انگلیسی


- All relevant catalyst components are included in the periodic calculations.
- TiCl4 prefers octahedral coordination on both (1 0 4) and (1 1 0) catalytical surfaces.
- Coadsorption of TiCl4 and internal donor stabilizes the (1 0 4) over the (1 1 0) surface.
- Combined effect of internal and external donors is to stabilize the both surfaces.
- Both (1 1 0) and (1 0 4) surfaces are relevant in catalysis.

We report the first quantum chemical description of the initial steps of Ziegler-Natta olefin polymerization catalysis involving all the relevant catalyst components. TiCl4 binds on the (1 0 4) surface of MgCl2 as a binuclear Ti2Cl8 and on the (1 1 0) surface as a mononuclear TiCl4, both binding modes being stabilized by octahedral six-coordination of Ti and Mg. Aluminum alkyl (triethylaluminum) coordinates to the MgCl2 surface via an unsaturated Cl to initiate catalyst alkylation reactions, thermodynamically driven by dimerization of the chlorinated aluminum alkyl. Addition of an internal donor (dimethyl phthalate) greatly stabilizes the (1 0 4) and (1 1 0) surfaces, ending up directing the alkylation reactions to the binuclear (1 0 4) site. External donor (dimethoxydimethylsilane) further assists the process, stabilizing similarly both catalytic surfaces. The spatial requirements of the donors are shown to be greater on the (1 1 0) surface than on the (1 0 4) surface, rationalizing the role of Lewis bases in the stereocontrol of polyolefins.

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ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Catalysis - Volume 353, September 2017, Pages 89-98
نویسندگان
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