Modeling of ethylene copolymerization in nonisothermal high-pressure reactors using bifunctional initiators

Enhancing the performance of high-pressure LDPE process is valuable for polymer industry. However, the severe thermodynamics requirement of high pressure and temperature hinders the reaction process from getting simultaneously high monomer conversion and polymer molecular weights. Bifunctional peroxides used as initiators can boost the polymerization rate and alter rheological polymer properties. This article proposes a new kinetics model of ethylene/butyl acrylate copolymerization with bifunctional initiators in a high-pressure nonisothermal tubular reactor. Model predictions are compared with available data. A SQP optimization scheme is employed to determine a suitable wall temperature for each zone along the nonisothermal tubular reactor. In comparison with the monofunctional TBPPI peroxide, a lower amount of the bifunctional DHBPPI peroxide is needed to get a higher conversion in shorter residence time, but at the expense of higher thermal energy. The results also showed that polymers produced with bifunctional peroxides are significantly more branched.