In Situ ATR-FTIR Studies on MgCl₂-Diisobutyl Phthalate Interactions in Thin Film Ziegler–Natta Catalysts

Abstract

To study the surface structure of MgCl(2) support and its interaction with other active components in Ziegler-Natta catalyst, such as electron donors, we prepared a thin film analogue for Ziegler-Natta ethylene polymerization catalyst support by spin-coating a solution of MgCl(2) in ethanol, optionally containing a diester internal donor (diisobutyl-ortho-phthalate, DIBP) on a flat Si crystal surface. The donor content of these films was quantified by applying attenuated total internal reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Changes in the interaction of DIBP with MgCl(2) at various temperatures were monitored by in situ ATR-FTIR. Upon increasing the temperature, a shift in the (C═O) band toward lower wavenumbers was observed together with the depletion of (O-H) stretching band due to the desorption of residual ethanol. We assign this shift to gradual redistribution of adsorbed DIBP from adsorption sites on the MgCl(2) (104) surface toward the more acidic MgCl(2) (110) surface. The morphologies of MgCl(2) and MgCl(2)/DIBP films were studied by transmission electron microscopy (TEM) revealing a preferential orientation of ClMgCl layers (001) parallel to the lateral film dimensions. This orientation becomes more pronounced upon annealing. In the absence of donor, the MgCl(2) grow in to large crystals aligned in large domains upon annealing. Both crystal growth and alignment is impeded by the presence of donor.

Vanadium Modification Effects on the (SiO2/MgO/MgCl2)•TiClxZiegler-Natta Polyethylene Catalyst

“…The function of the cocatalyst is well known to act as activator to reduce and alkylate the transition metal generating a Ti-C bond, which is responsible for the generation of active sites and essential for monomer insertion. [30][31][32] Alkyl aluminum can also scavenge impurities in the polymerization system. But too large amount of cocatalyst may lead to deactivation of the active sites through over-reduction of the active transition metal and also enhanced the chain transfer reaction to cocatalyst, which was not benefi cial for increasing the catalyst activity.…”

Discovering Hidden Material Properties of MgCl2 at Atomic Resolution with Structured Temporal Electron Illumination of Picosecond Time Resolution

“…Of note, Ziegler–Natta catalysts, which are composed of titanium active sites supported on magnesium chloride, produce a significant fraction of the world's polyethylene . Due to the acute sensitivity of the MgCl 2 to both ambient conditions and electron irradiation, electron microscopy has not fully characterized the pristine atomic and defect structure of Ziegler–Natta catalyst supports . Moreover, previous works have paid little respect to the impact of electron dose on the observed atomic structure of MgCl 2 , despite the fact that the beam‐sensitivity of MgCl 2 has been known.…”

Investigating Alkoxysilane Coverage and Dynamics on the (104) and (110) Surfaces of MgCl2-Supported Ziegler–Natta Catalysts

“…They demonstrated that in the absence of donors the sintering of MgCl 2 leads to very large MgCl 2 platelets that offer only a very small number of coordination sites whereas in the presence of donors the MgCl 2 crystallites remain much smaller because of the stabilization of the surface sites by donor adsorption. 36 However, all of these studies offered a static picture of the most likely situation with and without donors, but it did not give insight into the dynamics of these processes. In other words, they provided no clue as to the dynamics of MgCl 2 reconstruction or the capability of the donors to move on the MgCl 2 surfaces and to induce MgCl 2 reconstruction or the capability of the donors to move on the MgCl 2 surfaces even during polymerization.…”