A kinetic model for olefin polymerization in high-pressure tubular reactors: a review and update

Free-radical copolymerization in high-pressure tubular reactors is considered. Kinetic mechanisms to describe the polymerization rate and polymer properties, including copolymer composition, molecular weight, branching frequencies, melt flow index and polymer density, have been proposed. Based upon this kinetic scheme, a mathematical model has been derived and implemented as a computer program to simulate commercial tubular reactors. For calculation of molecular-weight averages, the method of moments is used in conjunction with pseudo kinetic rate constants to allow for copolymerization. The model parameters were fitted to industrial data to give useful steady-state simulation software, allowing for multiple feed points, multiple initiators (including oxygen) and non-isothermal polymerization. The effects of the pulse valve and the product cooler are incorporated. Comparisons are made between the model predictions and industrial data. A new approach and considerations for solving the moment closure problem are presented.