Modeling of molecular weights in industrial autoclave reactors for high pressure polymerization of ethylene and ethylene‐vinyl acetate

Abstract

We have incorporated mass balances of monomer, radical and polymer species to a previously developed mixing model for high pressure autoclave polymerization reactors. The customary quasi steady state approximation is not used, and the method of moments is used to simplify the mass balance calculations. The resulting moment model is able to calculate conversions, average molecular weights, long chain branching and melt flow indexes at any point in the reactor. It may also calculate concentration and temperature profiles along the reactor. Results for two base cases are presented in detail. Model predictions were compared with experimental data obtained at the industrial reactor; excellent agreement was obtained. The moment balance equations are presented in a modular way so that they may be easily adapted to be used with any other mixing model for this type of reactor. A m F e m h d e z fflddle L wall cells shaft cells Moment ModelFWk-l J.FZk

Controlled rheology of polypropylene: Modeling of molecular weight distributions

“…When each of these probabilities is used, the resulting pgf is the transform of the number, weight, and chromatographic distribution. A detailed explanation is found elsewhere 17–19. Through appropriate numerical inversion of these transforms, the corresponding entire MWDs can be obtained.…”

“…A detailed explanation is found elsewhere. [17][18][19] Through appropriate numerical inversion of these transforms, the corresponding entire MWDs can be obtained. pgf's are defined for both polymer and radical distributions, for which we use the symbols a (z) and a (z), respectively.…”

“…The chosen transform is the probability generating function (pgf), which we described extensively elsewhere 17. It has already been used for the prediction of the MWD of polyethylene both in polymerization processes and postreactor modification 18, 19. The pgf transforms are defined for discrete distributions, as the MWD is, so it is not necessary to assume the chain length to be a continuous variable.…”

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

“…In fact, the setback of obtaining only limited low conversion of ethylene in high‐pressure polymerization reactors has motivated numerous researchers to perform investigations for data collection and kinetics modeling . For instance, Sarmoria et al proposed a kinetics model to describe the progress of ethylene and vinyl acetate copolymerization in an autoclave reactor. A maximum conversion of 16% was reported.…”

Modeling and simulation of high-pressure industrial autoclave polyethylene reactor

“…This work has developed a mathematical model based on the mixing model for the production of low density polyethylene in an industrial high-pressure autoclave vessel reactor and has compared the results with industrial data. Several modeling techniques have been used to model this type of reactor [1][2][3][4][5][6] and some authors have shown that the mixing model is best fitted to this process. Although the mixing model is already known, few studies [1,[7][8][9][10] have reported and compared the results obtained from the mixing model with actual industrial data.…”