Kinetic modeling of copolymerization of ethylene with carbon monoxide using Pd complex catalyst

Abstract

The kinetics of the copolymerization of ethylene with carbon monoxide has been studied in a batch slurry reactor using the homogeneous Pd complex [(dppp)Pd(H₂O)(TsO)](TsO) as the catalyst precursor in methanol. The effects of the catalyst loading and the partial pressures of CO and ethylene on the rate of copolymerization have been studied over a temperature range of 353-373 K. The rate of copolymerization was found to increase with increasing catalyst loading and partial pressures of CO and ethylene. The approximate orders of reaction were found to be 0.63 and 0.72 with respect to dissolved CO and ethylene, respectively. Different rate equations based on probable reaction mechanisms were evaluated for fitting the rate data. The rate data were interpreted in terms of the activities of the monomers in solution instead of their concentrations. This is particularly important because the copolymerization involves the reaction of two gaseous monomers with significant differences in their solubilities and ideal behavior. The rate models were discriminated using statistical as well as thermodynamic criteria. A model derived by assuming the insertion of ethylene into the tetracoordinated Pd-acyl species as the rate-determining step has been found to represent the kinetics in good agreement with experimental results. The apparent energy of activation for copolymerization was found to be 49 kJ/mol.