The effect of the amido substituent on polymer molecular weight in propene homopolymerisation by titanium cyclopentadienyl-amide catalysts

In the homopolymerisation of propene by the cyclopentadienyl-amide titanium catalyst systems [η5,η1-C5H4(CH2)2NR]TiCl2/MAO and [η5,η1-C5H4(CH2)2NR]Ti(CH2Ph)2/B(C6F5)3 (R = tBu, iPr, Me), the catalyst with the smallest substituent (Me) on the amido moiety consistently gives the highest polymer molecular weight. This differs from the trend usually observed in related catalysts with tetramethylcyclopentadienyl-amide ancillary ligands, where larger amide substituents result in higher molecular weights. Based on the present information a hypothesis is formulated in which an increased cation-anion interaction for the less sterically hindered catalyst is responsible for disfavouring chain transfer relative to chain growth.

Optimise initial spare parts inventories: an analysis and improvement of an electronic decision tool.

Control of spare parts is very difficult as demands can be very low (once in a few years is no exception), while the consequences of a stockout can be severe. While in the past many companies choose to have very large spares inventories, one now observe trends in areas with good transportation connections to keep spare parts at the suppliers. Hence it is very important to make a good selection of which spare parts to stock at the start-up of new plants. To this end Shell Global Solutions has developed an electronic decision tool, called E-SPIR. In this report we analyse the decision rules used in it. We consider stockout penalties and advise to use criticality classifications instead. Furthermore, we investigate minimum stock levels, demand distributions and order quantities.

Carbon-bridged cyclopentadienyl amido group 4 metal complexes : ligand tuning and olefin polymerization

De organometaalchemie en vooral die van overgangsmetalen en lanthaniden heeft zich in 40-50 jaar buitengewoon sterk ontwikkeld. Niet alleen werd een breed gebied van synthese en karakterisatie van nieuwe verbindingen en uitgebreid reactiviteitsonderzoek ontsloten maar ook werd de ontwikkeling van nieuwe methoden en inzichten in meer toepassingsgerichte gebieden zoals de organische synthese maar vooral de (homogene en heterogene) katalyse door de organometaalchemie sterk gestimuleerd. ... Zie: Samenvatting