Direct observation of MgCl2-supported Ziegler catalysts by high resolution transmission electron microscopy

Abstract

SUMMARY: The surface atomic structure of MgCl 2 crystalline particles and MgCl 2 -supported Ziegler catalysts was observed by means of high resolution transmission electron microscopy.Step-terrace surface structures, characteristic of the structure of the MgCl 2 crystal, are found in the observed images of MgCl 2 particles. The observation of the structure of MgCl 2 -supported Ziegler catalysts shows that the MgCl 2 crystals are severely deformed by the processes of catalyst preparation. Due to the preparation procedure used the structure of the catalyst changes from crystalline to amorphous.

MgCl2‐supported Ziegler‐Natta catalysts: A DFT‐D ‘flexible‐cluster’ approach. TiCl4 and probe donor adducts

“…CLU‐27‐110, in turn, has undergone relaxation not only at lateral terminations, but also in the interior; this resulted into a slight wave‐like deformation of the whole cluster (see arrows in Figure ‐bottom/right, and SI). Similar effects have been reported before in computational as well as experimental studies of ‘activated’ MgCl 2 . For this cluster too, terminal Mg‐Cl bonds at corners are quite short ( r 3 = 2.2 Å in Figure ‐top/right).…”

The role of two different internal donors (phthalate and 1,3‐diether) on the formation of surface structure in MgCl2‐supported Ziegler–Natta catalysts and their catalytic performance of propylene polymerization

“…A study using density functional theory (DFT) calculations showed that MgCl 2 had the (001) and (104) planes at crystallographic equilibrium, but activated MgCl 2 could also have the (110) plane if internal donors or TiCl 4 were present . Mori et al observed with high‐resolution transmission electron microscopy, that lateral planes of mechanically activated MgCl 2 were predominantly composed of the (110) and (104) planes. Andoni et al reported preferential growth of MgCl 2 crystal along the (110) direction in the presence of 1,3‐diethers, while the growth occurred along both the (110) and (104) directions in the presence of phthalates.…”

Bridging the Gap between Industrial and Well‐Defined Supported Catalysts

“…[339,340] The( 110) surface contains four-coordinate Lewis acidic Mg sites,a nd the (104) surface contains fivecoordinate Mg sites (Figure 3). [339,340] The( 110) surface contains four-coordinate Lewis acidic Mg sites,a nd the (104) surface contains fivecoordinate Mg sites (Figure 3).…”