Abstract  The multi-ether compounds with different numbers of methoxy groups containing 1,3-dimethoxy-2,2-bis(methoxymethyl) propane and 1-methoxy-2,2-bis(methoxymethyl) butane were synthesized using the Williamson reaction from pentaerythritol and 1,1,1-tris(hydroxymethyl) propane, respectively, in the presence of sodium hydride and methyl iodide in tetrahydrofuran and they were characterized by H-1 NMR, C-13 NMR, and FTIR spectroscopy. These compounds were employed as external donors in the polymerization of propylene using the industrial Ziegler-Natta catalyst. A commercial spherical MgCl2-supported Ziegler-Natta catalyst containing diisobutyl phthalate as the internal donor was used for the polymerization of propylene. The role of ether compounds and industrial alkoxysilanes on the properties of polypropylene were studied using the xylene solubility method, melt flow index, gel permeation chromatography, scanning electron microscopy, and differential scanning calorimetry. The addition of the electron donors has led to improvements in the activity and selectivity of the Ziegler-Natta catalyst system.

Abstract  Four new diester compounds were prepared and used as internal donors (ID) to prepare MgCl2 supported titanium catalysts. Different diesters had notable influences on the porosity and the specific surface areas of the catalysts. The propylene polymerizations results showed that isopropyl groups(ID-2), cyclopentyl(ID-4) were more suitable substituents for diester compounds to replace phenyl(DIBP). The effects of different external donor (ED), Si/Ti ratio and hydrogen response on new ID precatalysts were evaluated by propylene polymerization.

Abstract  Roles of a novel dibenzoyl sulfide donor in Ziegler–Natta (ZN) catalyzed propylene polymerization were examined using DFT calculations. The adsorption mode for dibenzoyl sulfide and diisobutyl phthalate electron donors on the MgCl2(110) surface is the chelate coordination mode, similar to malonate electron donors. The dibenzoyl sulfide/diisobutyl phthalate donor provides regio- and stereo-selectivity to the ZN catalyst. Factors that control the isotacticity and activity of the ZN catalyst are steric repulsion and π-complex stabilization by electron donors. The steric repulsion signifies intrinsic activation energy and π-complex formation energy for π-complex stabilization. The two factors are combined in the apparent activation energy and dibenzoyl sulfide gives the lowest apparent activation energy. Therefore, dibenzoyl sulfide shows the best catalytic enhancement as compared to diisobutyl phthalate and di-n-butyl-2-cyclopentyl malonate, which is in good agreement with the results obtained from the experiments.