Ethylene polymerizations were performed in toluene using the neodymocene complex (C5Me5)2NdCl2Li­(OEt2)2 or {(Me2Si­(C13H8)2)­Nd­(μ-BH4)­[(μ-BH4)­Li­(THF)]}2 in combination with n-butyl-n-octylmagnesium used as both alkylating and chain transfer agent. The kinetics were followed for various [Mg]/[Nd] ratios, at different polymerization temperatures, with or without ether as a cosolvent. These systems allowed us to (i) efficiently obtain narrowly distributed and targeted molar masses, (ii) characterize three phases during the course of polymerization, (iii) estimate the propagation activation energy (17 kcal mol–1), (iv) identify the parameters that control chain transfer, and (v) demonstrate enhanced polymerization rates and molar mass distribution control in the presence of ether as cosolvent. This experimental set of data is supported by a computational investigation at the DFT level that rationalizes the chain transfer mechanism and the specific microsolvation effects in the presence of cosolvents at the molecular scale. This joint experimental/computational investigation offers the basis for further catalyst developments in the field of coordinative chain transfer polymerization (CCTP).

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The design of countercurrent packed columns operating under high-pressure conditions requires knowledge of their hydrodynamic and mass transfer behavior. A laboratory-scale continuous supercritical fluid extraction apparatus was developed with the purpose of obtaining data needed for such designs. The current work is part of a study to assess the feasibility of supercritical carbon dioxide in fractionating a mixture of squalene and methyl oleate. This mixture partly emulates the residues obtained from the olive oil refining process. Phase equilibrium data were previously measured to evaluate the best operating conditions. Here, we examine the continuous fractionation of two different feeds, with 40 and 70 wt % of squalene, under various extraction conditions. An extraction yield as high as 90 wt % of squalene in the raffinate phase was achieved.The selectivity and extraction efficiency were determined as functions of the oil-to-carbon dioxide flow ratio as well as the reflux ratio. In a subsequent paper (Part II), the measured hold-up and mass transfer coefficients will be compared with mass transfer correlations from the literature, and a model will be developed.