Klaus Hauschild

13C NMR studies of ethene-norbornene copolymers : assignment of sequence distributions using 13C-enriched monomers and determination of the copolymerization parameters

Ethene and norbornene were copolymerized using metallocene catalysts that produce copolymers having isolated norbornene units or microblocks with a maximum of two norbornene units. The resonances of the norbornene C 5/6 and the ethene carbon atoms, which overlap extensively in the 13 C NMR spectrum, were differentiated and assigned by comparing the 13 C NMR spectra of the copolymers obtained from monomers having 13 C at natural abundance with those prepared from feedstocks containing 13 C 1 -enriched ethene or 13 C 5/6 -enriched norbornene. The NMR analysis revealed that the chemical shifts of the norbornene C 5/6 carbon atoms are triad sensitive and those of the ethene carbon atoms are pentad sensitive. 13 C NMR analysis of copolymers containing isolated norbornene units in various proportions allowed the resonances of the norbornene C 5/6 and the ethene carbon atoms to be assigned to the respective triads and pentads. The complete triad distributions of these copolymers determined in this way were used to calculate the copolymerization parameters for a representative metallocene catalyst.

Silica supported metallocene/MAO‐systems: comparison of the polypropylene growth during bulk phase polymerization with slurry phase experiments

A kinetic investigation of the bulk phase propylene polymerization with a silica supported metallocene/MAO system has been carried out. in spite of the high monomer concentration and the resulting high activity it was possible todistinguish between different polymerization phases producing polymers with differing properties. Similar to prior experiments in slurry phase we noticed an induction period at lower reaction temperatures. Even at the drastic conditions of polymerizing in the liquid monomer we were able to prove strong initial diffusion limitation toward the monomer resulting from a polymer layer formed during the first minutes. The use of an 1-octene prepolymerized catalyst system leads to a markedly improved activity. This arises from a better monomer diffusion through the more amorphous poly(1-octene) layer compared to a highly isotactic polypropylene layer.

Reaction Calorimetric Investigation of the Propylene Slurry Phase Polymerization with a Silica‐Supported Metallocene/MAO Catalyst

The slurry phase polymerization of propylene with a silica-supported metallocene/MAO catalyst was kinetically investigated by two different methods at several polymerization conditions. Heat flow calorimetry on the one hand as an innovative method and flowmeter-technique on the other hand as a well established classical method led to consistent kinetic profiles. Thus, the principle applicability of the heat flow calorimetry for the kinetic investigation of the described polymerization process was demonstrated, contrary to some expectations in literature. Furthermore, the sensitivity of the calorimetric method is shown and polymerization heats for the slurry process have been determined.

An in situ powder diffraction cell for high-pressure hydrogenation experiments using laboratory X-ray diffractometers

An in situ diffraction cell is presented which has been designed and constructed for in-house powder diffraction experiments under high gas pressures up to 30 MPa. For a proof of principle, the in situ cell has been tested for several hydrogenation experiments under elevated pressures and temperatures. LaNi5 was chosen as an example for hydrogenation, applying simultaneously 5.5 MPa H2 pressure at a temperature of 423 K. For testing the high-pressure–temperature suitability of the in situ cell, pressure–temperature experiments up to 14 MPa at 373 K were performed, studying the rehydrogenation of NaH and Al to NaAlH4. The experimental setup enables recording of in situ X-ray diffraction data on laboratory instruments with short data acquisition times at elevated hydrogen pressures and temperatures.