Ethylene site density calculations

Ethylene oxide polymerizes over metal oxides, hydroxides, and carbonates. In 1964 Krylov and coworkers ( ) reported weighing the amount of adsorbed polymer since they knew its average molecular weight, they could calculate the number of reactant molecules adsorbed on active sites, thus providing the site density. 

Li,Na,K,Mg,Ca) faujasites, examining the dipole moment of the interacting molecule and the charge density within the cluster. Sauer et al. have performed ab initio cluster calculations for simple models of interaction sites for water, methane, ethylene and the ammonium ion, obtaining interaction energies which appear to be... 

Copolymerization with a-olefins over a Phillips catalyst is a key method for controlling the density and microstmctures of the polyethylene products in industrial processes. Table 5 also listed the energy barriers for the primary 1,2-insertion of 1-butene and 1-hexene, and the subsequent chain transfer by p-H elimination for all the three kinds of Ti-modified models. The calculated energy barriers showed that Ti-modification could also promote the activity for ethylene copolymerization with a-olefins. The energy differences between comonomer insertion and chain transfer can lead to a conclusion on the effect of Ti-modification on the distribution of the inserted comonomers in polyethylene chains. As listed in Table 5, the difference between energy barriers for chain propagation and for chain transfer decreased for model sites 4g, 12g, and 15g. Therefore, it was reasonable to conclude that Ti-modified catalyst was likely to make low MW polyethylene with much less comonomer insertion because the inserted comonomer mainly led to a chain transfer reaction and left the inserted comonomer at the chain end. As a result, the increased chain termination by comonomer resulted in less SCBs in the low MW fraction and higher density of the polyethylene product for the Ti-modified Phillips catalyst. 

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