Kinetics study of slurry‐phase propylene polymerization with highly active Mg(OEt)₂/benzoyl chloride/TiCl₄ catalyst

Abstract

SYNOPSISPropylene was polymerized in a slurry phase over superactive and stereospecific catalyst prepared by the reaction of Mg( OEt)* with benzoyl chloride and TiC14 in the presence of A1Et3 with or without an external donor. A kinetic analysis of propylene polymerization was carried out. The polymerization rate was first order with respect to monomer concentration and the dependence of overall polymerization rate on the concentration of A1Et3 can be explained by the Langmuir adsorption mechanism. Maximum activity was observed around an Al/Ti mole ratio of 20. The average rate over 90 min of polymerization as a function of temperature showed a maximum around 42°C and the overall activation energy was 8.5 kcal/mol at T < 42°C and -4.0 kcal/mol at T > 42°C. The analysis of the phenomenon of a n optimum temperature gave 2.2 kcal/mol for the activation energy of the rate-determining step, and 6.3 kcal/mol, for the adsorption energy of A1Et3. The addition of small amount of p-ethoxyethyl benzoate (PEEB) as an external donor increased the percentage of isotactic polymer to 98% and slightly increased activity in spite of the decrease in the concentration of active centers due to the stabilizing effect of the active centers by the external donor. The temperature showing maximum yield was shifted to the higher temperature when A1Et3 and PEEB ( [A1Et3]/[PEEB] = 5 ) was used as a cocatalyst.

Effect of polymerization time on the molecular weight and molecular weight distribution of polypropylene

“…The effect of various parameters such as polymerization temperature, monomer pressure, polymerization time and the amount of triethyl aluminum (TEA), hydrogen (as a chain transfer agent), internal and external donors on the catalyst activity, and stereoselectivity was reported in the literature. [5][6][7][8][9][10][11] Polymer residence time in the polymerization reactors is one of the most important parameters that should be exactly calculated and also controlled in the industrial plants, because it has a noticeable effect on the catalyst activity (it decreases with increase in the polymerization time). [7][8][9][10] Since the molecular weight of polypropylene and its distribution have strong effects on the processability and end-use properties of the propylene polymers, in this article, we present the effects of the polymerization time on the numberaverage molecular weight (M n ), weight-average molecular weight (M w ), molecular weight distribution (MWD), and relative MWD (the ratio of two MWDs in the two consecutive period of the polymerization time) in propylene polymerization by using a Mg(OEt) 2 /DIBP/TiCl 4 /PTES/AlEt 3 catalyst system.…”

“…[1][2][3][4][5][6][7] Propylene polymerization was investigated with the catalytic system Mg(OEt) 2 /DIBP/TiCl 4 /PTES/ AlEt 3 . [5][6][7][8][9] These kinds of catalyst systems are used in some industrial process and give high activity and selectivity. The effect of various parameters such as polymerization temperature, monomer pressure, polymerization time and the amount of triethyl aluminum (TEA), hydrogen (as a chain transfer agent), internal and external donors on the catalyst activity, and stereoselectivity was reported in the literature.…”

Highly active Ziegler–Natta catalyst for propylene polymerization

“…The solid product was treated with 50 mL TiCl 4 for 2 h. Finally, it was allowed to settle and the liquid was siphoned off while hot; the residual solid was washed 10 times with 100 mL hot n-hexane until no traces of titanium were detected in the washing liquid. [3][4][5][6][7][8][9]15 Polymerization Polymerization was carried out in a 1.6-L steel-jacket Buchi autoclave reactor (Reactor Vessels Ltd., Kent, UK), equipped with a mechanical seal stirrer in the slurry phase.…”

“…There are many ways to prepare MgCl 2 having high surface area, such as ball-milling, precipitation of soluble MgCl 2 complex, reaction of magnesium alkoxides and aryls with TiCl 4 , and the other titanium compounds as the catalysts and diisobutyl phthalate (DIBP) as the internal donor (ID). These catalysts are cocatalyzed by triethyl aluminum (TEA) plus an external donor (ED), which is usually an organic monoester such as ethyl benzoate, p-toluate, or silanes such as cyclohexylmethyl dimethoxysilane (cHMDMS), phenyl triethoxysilane (PTES), and so on.…”

“…These catalysts are cocatalyzed by triethyl aluminum (TEA) plus an external donor (ED), which is usually an organic monoester such as ethyl benzoate, p-toluate, or silanes such as cyclohexylmethyl dimethoxysilane (cHMDMS), phenyl triethoxysilane (PTES), and so on. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] These catalyst systems, the most commonly used in current industrial processes, promote high activity and stereoselectivity. In addition to activity and stereoselectivity of the catalysts, the control of size and shape of catalysts is a very important factor because it has a determinative role in the control of morphology of the resulting polymer particles; on the other hand, the spherical and globular shapes of catalysts and polymers are the best.…”