A critical examination of polyethylene molecular weight distribution control through the combination of soluble metallocene/methylalumoxane catalysts

Control of molecular weight distribution of polyethylene in gas-phase fluidized bed reactors

“…The results are shown in Figs. [10][11]. To further investigate the influence of model uncertainty on the control performance, additional +15% error on the bed mass, B w is injected into the model.…”

“…There is therefore a strong incentive to develop control strategies that can handle the complete distribution, and not only pre-specified parameters. The second observation that could be made from Table 1 is that most of the work that was carried out in controlling the entire MWD of the produced polyolefins used a mixture of different metallocenes [6][7][8][9][10][11][12][13] or a hybrid catalyst of Ziegler-Natta and metallocene catalysts in a one stage process [14][15][16]. The use of a single reactor to produce the desired polymer is a cost-efficient alternative.…”

“…However, for each polymer grade a sophisticated catalyst has to be developed in order to adjust the amount, the molecular weight distribution, the comonomer incorporation, and the comonomer distribution of both fractions formed in the polymerization reaction. Moreover, the mixture of different catalysts may lead to complex undesirable catalyst interactions and non-reproducible catalyst behavior due to the high variability of the polymerization rate of each catalyst [11,17]. For these reasons, this method is still in the research stage and it may take some time before it can be implemented in industry.…”

Broadening the polyethylene molecular weight distribution by controlling the hydrogen concentration and catalyst feed rates

“…Using a mixture of different metallocenes [15][16][17][18][19][20] θ Coefficient of the disturbance prediction model concentration). This technology is already commonly used with Ziegler-Natta catalysts.…”

Control of Polymer Quality in Gas Phase Polyethylene Reactors Using Feed Flow Rates

“…Different methods were examined for this purpose. For example, a mixture of different metallocenes is used [6][7][8][9][10][11] or a hybrid catalyst of Al-haj Ali M., and Ali Emad + Chemical Engineering Department, King Saud University P.O.Box: 800, 11421 Riyadh, Saudi Arabia + corresponding author, email: amkamal@ksu.edu.sa…”