Gas‐phase polymerization of ethylene using MgCl₂/ethyl benzoate/TiCl₄ + triethylaluminum catalyst: Effects of triethylaluminum and temperature

Abstract

A gas-phase reactor system was developed to polymerize ethylene using the MgC12/ethyl benzoate (EB)/TiC1, + triethylaluminum (TEA) catalyst. The reproducibility of the reactor was tested and found to be adequate for kinetic study. The effects of TEA and temperature were studied with the multisite model that assumes a multiplicity of active sites. It was found that the productivity increased with Al/Ti molar ratio while initial activity leveled off. The deactivation rate, after an initial increase, decreased with Al/Ti. This corresponded with a transition in deactivation order: below Al/Ti = 70, first-order deactivation was predominant; above A1 /Ti = 70, second-order deactivation was predominant. The secondorder deactivation reactions were made less disperse at higher Al/Ti. Molecular weight of the polyethylene was very high (> 1,000,000) indicating negligible transfer reactions. For Al/Ti > 130 a monomer sorption limitation for polymerization was found. The effect of temperature was also studied with a maximum in productivity at 55OC for Al/Ti = 98.0 and no maximum when Al/Ti = 53.0. Apparent activation energies (E,) for activity were found to be 19.5 f 3.3 kJ/mol at Al/Ti = 98.0 and 9.3 f 1.1 kJ/mol at Al/Ti = 53.0. For deactivation E, was found to be 36.6 f 5.0 kJ/mol at Al/Ti = 98.0 and -15.5 f 4.4 kJ/ mol at Al/Ti = 53.0. Temperature increased the dispersity of second-order deactivation reactions.

Method for quantitative evaluation of kinetic constants in olefin polymerizations. I. Kinetic study of a conventional Ziegler–Natta catalyst used for propylene polymerizations

“…It is intriguing to observe that remaining catalyst variables do not seem to exert any influence upon the final quality of the polymer resin and catalyst productivity. Polymer yield is assumed to be of first order in respect to catalyst concentration and solubles and XO are assumed to be functions of the A/T ratio used during both the catalyst preparation and the polymerization reaction 21–23. These effects may be due do the large influence of temperature upon the polymerization results and due to the narrow ranges of variation of the catalyst variables, as imposed by plant operation constraints.…”

“…The sixth variable is the batch time (1 < t < 3 h), included in the experimental design to allow the evaluation of the well‐known catalyst decay 11. The seventh variable is the amount of alkyl‐aluminum added to the reaction environment during polymerization, evaluated as the Al/Ti ratio (1.4 < A/T 2 < 2), expected to influence both catalyst activity and the average molecular weight of the final polymer resin 23. The experimental ranges selected in all cases are in accordance with actual industrial operation conditions.…”

Kinetic study of gas phase olefin polymerization with a TiCl4/MgCl2 catalyst I. Effect of polymerization conditions

“…Using the yield data, maximum activity is much higher (ú90). 31 If the r c has been estimated to be around 0.02-0.04 mm.…”

Polymerization of olefins through heterogeneous catalysis. XVII. Experimental study and model interpretation of some aspects of olefin polymerization over a TiCl4/MgCl2 catalyst

“…Its role in the transition metal oxiSince the discovery of high-activity-supported titanium catalysts, intensive research efforts have been dation state reduction has been widely demonstrated through both physical analysis and chemdirected toward a comprehensive understanding of their structure and kinetic behavior. [1][2][3] In spite of ical measurements. Using techniques such as electron spin resonance spectrometry (ESR), 4 their successful applications in industrial practice, a complete knowledge of these catalyst systems is photometry, 5 chemical ionization-mass spectrometry (CI-MS), 6 X-ray absorption spectrosstill lacking.…”