scholarly journals Kinetic and Thermal Study of Ethylene and Propylene Homo Polymerization Catalyzed by ansa-Zirconocene Activated with Alkylaluminum/Borate: Effects of Alkylaluminum on Polymerization Kinetics and Polymer Structure

Polymers ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 268
Author(s):  
Amjad Ali ◽  
Nadeem Muhammad ◽  
Shahid Hussain ◽  
Muhammad Imran Jamil ◽  
Azim Uddin ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Propagation Rate ◽  
Propylene Polymerization ◽  
Chain Growth ◽  
Molar Ratios ◽  
Propagation Rate Constant ◽  
Olefin Polymerizations ◽  
Kinetics Of ◽  
Polymer Chain Growth ◽  
Chain Propagation Rate

The kinetics of ethylene and propylene polymerization catalyzed by homogeneous metallocene were investigated using 2-thiophenecarbonyl chloride followed by quenched-flow methods. The studied metallocene catalysts are: rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2 (Mt-I), rac-Et(Ind)2ZrCl2 (Mt-II) activated with ([Me2NPh][B(C6F5)4] (Borate-I), [Ph3C][B(C6F5)4] (Borate-II), and were co-catalyzed with different molar ratios of alkylaluminum such as triethylaluminium (TEA) and triisobutylaluminium (TIBA). The change in molecular weight, molecular weight distribution, microstructure and thermal properties of the synthesized polymer are discussed in detail. Interestingly, both Mt-I and Mt-II showed high activity in polyethylene with productivities between 3.17 × 106 g/molMt·h to 5.06 × 106 g/molMt·h, activities were very close to each other with 100% TIBA, but Mt-II/borate-II became more active when TEA was more than 50% in cocatalyst. Similarly, Polypropylene showed the highest activity of 11.07 106 g /molMt·h with Mt-I/Borate-I/TIBA. The effects of alkylaluminum on PE molecular weight were much more complicated; MWD curve changed from mono-modal in Mt-I/borate-I/TIBA to bimodal type when TIBA was replaced by different amounts of TEA. In PE, the active center fractions [C*]/[Zr] of Mt-I/borate were higher than that of Mt-II/borate and average chain propagation rate constant (kp) value slightly decreased with the increase of TEA/TIBA ratio, but the Mt-II/borate systems showed higher kp 1007 kp (L/mol·s). In PP, the Mt-I/borate presented much higher [C*]/[Zr] and kp value than the Mt-II. This work also extend to investigate the mechanistic features of zirconocenes catalyzed olefin polymerizations that addressed the largely unknown issues in zirconocenes in the distribution of the catalyst, between species involved in polymer chain growth and dormant state. In both metallocene systems, chain transfer with alkylaluminum is the dominant way of chain termination. To understand the mechanism of cocatalyst effects on PE Mw and (MWD), the unsaturated chain ends formed via β-H transfer have been investigated by 1H NMR analysis.

Synthesis and Polymerization Kinetics of PMMA in Imidazolium Ionic Liquids

2013 ◽  
Vol 423-426 ◽  
pp. 528-531
Author(s):  
Pei Wang ◽  
Yuan Liu ◽  
Wen Su ◽  
Lian Liu
Keyword(s):  
Molecular Weight ◽  
Rate Constant ◽  
Average Molecular Weight ◽  
Propagation Rate ◽  
Polymerization Kinetics ◽  
Growth Rate Constant ◽  
Weight Average Molecular Weight ◽  
Propagation Rate Constant ◽  
Kinetics Of ◽  
Chain Propagation Rate

Polymerization of high molecular weight PMMA was achieved in [BMIM]PF4at reaction temperature 60oC, 65°C and 70 °C, reaction time 60min. The data including the yield, molecular weight and molecular weight distribution of PMMA were analysized. The results showed that the weight average molecular weight of PMMA in [BMIM]PF4is up to 275867, respectively 4 and 7 times of molecular weight in cyclohexane and toluene. Secondly, the polymerization kinetics of PMMA in [BMIM]PF4were tested, the apparent chain propagation rate constant of PMMA are 0.93×104,1.11 ×104and 14.1×104in 60 °C, 65°C and 70 °C. Compared with the growth rate constant in toluene, the polymerization rate constant PMMA in the ionic liquid increased by 4~7 times.

Synthesis and Polymerization Kinetics of PMMA in [BMIM]BF6 Imidazolium Ionic Liquids

2013 ◽  
Vol 395-396 ◽  
pp. 411-414 ◽  
Author(s):  
Pei Wang ◽  
Yuan Liu ◽  
Wen Su ◽  
Lian Liu
Keyword(s):  
Molecular Weight ◽  
Rate Constant ◽  
Average Molecular Weight ◽  
Propagation Rate ◽  
Polymerization Kinetics ◽  
Growth Rate Constant ◽  
Weight Average Molecular Weight ◽  
Propagation Rate Constant ◽  
Kinetics Of ◽  
Chain Propagation Rate

Polymerization of high molecular weight PMMA was achieved in [BMIPF6by contrasted in cyclohexane, toluene solvent at reaction temperature 60 C, 65C and 70 C, reaction time 60min. The data including the yield, molecular weight and molecular weight distribution of PMMA were analysized in 3 kind of solvent. The results showed that the weight average molecular weight of PMMA in [BMIPF6is up to 730000, respectively 7 and 10 times of molecular weight in cyclohexane and toluene. Secondly, the polymerization kinetics of PMMA in [BMIPF6were tested, the apparent chain propagation rate constant of PMMA are 10.7×10412.9 ×104and 19.9×104in 60 C, 65C and 70 C. Compared with the growth rate constant in toluene, the polymerization rate constant PMMA in the ionic liquid increased by 5~10 times.

The Mechanism Which Restricts Chain Growth in Polymerization with Alkylaluminum-Titanium Tetrachloride Complex Catalysts

1961 ◽  
Vol 34 (3) ◽  
pp. 986-990
Author(s):  
S. E. Bresler ◽  
M. I. Mosevitskiĭ ◽  
I. Ya Poddubnyĭ ◽  
Shi Guan-I
Keyword(s):  
Molecular Weight ◽  
Regular Structure ◽  
Chain Growth ◽  
Time Interval ◽  
Stationary Condition ◽  
Kinetics Of Polymerization ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Kinetics Of ◽  
Isoprene Polymerization

Abstract In the production of polymers having a highly regular structure of the molecular chains, catalyst complexes of the Ziegler type are currently in wide use. The development of mechanisms for the separate steps in the catalytic process is of primary significance. This report outlines some results on a study of the mechanisms involved in isoprene polymerization with complexes formed through the interaction of Al (iso-C4H9)3 and TiCl4; the data were obtained from the sedimentation of the polymers in the ultracentrifuge, in combination with data on the kinetics of polymerization. We have indicated previously1 that in isoprene polymerization using the specified catalysts, the growth of the macromolecules proceeds quite rapidly, the time interval between the first appearance of active chains and the termination of reaction being only a few minutes; subsequently there follows an immediate stationary condition. However, with use of the ultracentrifuge we have obtained molecular weight distributions of polymers which are substantially different from the equilibrium distribution expected from present-day kinetic theories of polymerization. They were characterized by relatively low dispersion and, in the main, strongly distorted by high-molecular bands; in most cases, there was practically a complete absence of molecules with a molecular weight less than 200–300 thousand.

Halogenation with N-haloamines in strong acids. II. Kinetics and rate constants

1970 ◽  
Vol 48 (4) ◽  
pp. 554-560 ◽  
Author(s):  
J. Spanswick ◽  
K. U. Ingold
Keyword(s):  
Rate Constant ◽  
Decanoic Acid ◽  
Propagation Rate ◽  
The Self ◽  
Radical Chain ◽  
Rate Of Reaction ◽  
Propagation Rate Constant ◽  
Strong Acids ◽  
Kinetics Of ◽  
Rate Controlling Step

The kinetics of the radical chain chlorination of decanoic acid by N-chlorodimethylamine and N-chloropiperidine in 2 and 4 M H2SO4 in acetic acid have been examined at 30°. The rate of reaction is proportional to the decanoic acid concentration and to the square root of the rate of chain initiation. The rate controlling step for propagation involves the attack of an aminium radical on decanoic acid, and termination involves the self-reaction of two aminium radicals. The latter reaction may involve the prior, rapid deprotonation of one or both radicals. The propagation rate constant has been estimated to be in the range 7 × 102 to 1 × 104 M−1 s−1 and the termination rate constant to be in the range 6 × 106 to 5 × 107 M−1 s−1.

Kinetics of Alkyllithium Initiated Polymerizations

1970 ◽  
Vol 43 (1) ◽  
pp. 22-73 ◽  
Author(s):  
H. L. Hsieh ◽  
W. H. Glaze
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Propagation Rate ◽  
Polymerization Rate ◽  
Vinyl Monomers ◽  
Polar Solvents ◽  
Organolithium Compounds ◽  
Rate Of Polymerization ◽  
Kinetics Of

Abstract The kinetics of alkyllithium initiated polymerizations is reviewed for publication in Rubber Reviews for 1970. It contains nine sections: introduction, the structure of organolithium compounds, rate of polymerization, rate of propagation, rate of initiation, molecular weight and molecular weight distribution, polymerization of diene and vinyl monomers in polar solvents, copolymerizations, and polymerizations of polar monomers. A total of 205 references are cited.

Kinetics of hydrolysis of peroxodisulphate ions in acidic medium to peroxomonosulphuric acid

1981 ◽  
Vol 46 (5) ◽  
pp. 1229-1236 ◽  
Author(s):  
Jan Balej ◽  
Milada Thumová
Keyword(s):  
Ionic Strength ◽  
Rate Constants ◽  
Acidic Medium ◽  
Measured Data ◽  
Molar Ratios ◽  
Starting Solution ◽  
Kinetics Of Hydrolysis ◽  
Rate Of Hydrolysis ◽  
Kinetics Of ◽  
Hydrolysis Of

The rate of hydrolysis of S2O82- ions in acidic medium to peroxomonosulphuric acid was measured at 20 and 30 °C. The composition of the starting solution corresponded to the anolyte flowing out from an electrolyser for production of this acid or its ammonium salt at various degrees of conversion and starting molar ratios of sulphuric acid to ammonium sulphate. The measured data served to calculate the rate constants at both temperatures on the basis of the earlier proposed mechanism of the hydrolysis, and their dependence on the ionic strength was studied.

The effect of electrondonors on the polymerization kinetics of isoprene

1980 ◽  
Vol 45 (12) ◽  
pp. 3338-3346
Author(s):  
Miroslav Kašpar ◽  
Jiří Trekoval
Keyword(s):  
Induction Period ◽  
Ethyl Ether ◽  
Reaction Order ◽  
Propagation Rate ◽  
Reaction Scheme ◽  
Polymerization Kinetics ◽  
Polymerization Rate ◽  
Constant Concentration ◽  
Initial Concentration ◽  
Kinetics Of

The effect of small additions of 1-octene, butyl ethyl ether and triethylamine on the polymerization kinetics of isoprene (2-methyl-1,3-butadiene) in benzene initiated with butyllithium was investigated by employing the GLC analysis. The addition of 1-octane was reflected only in a shorter induction period of the reaction; the effect on the propagation rate was insignificant. With the increasing amount of butyl ethyl ether, the polymerization rate increases linearly, while the reaction order with respect to the concentration of triethylamine is variable and increases from 0.33 to 0.66 with the increasing concentration of the initiator. For a constant concentration of triethylamine, the reaction order with respect to the initial concentration of the initiator was found to vary considerably, reaching even negative values. A reaction scheme was suggested, taking into account the competition between two different solvates of alkyllithium.

Kinetics of carbon monoxide methanation on a Ni/SiO2 catalyst

1990 ◽  
Vol 55 (7) ◽  
pp. 1678-1685
Author(s):  
Vladimír Stuchlý ◽  
Karel Klusáček
Keyword(s):  
Carbon Monoxide ◽  
Reaction Rate ◽  
Catalyst Activity ◽  
Adsorbed Hydrogen ◽  
Reaction Products ◽  
Co Methanation ◽  
Molar Ratios ◽  
Rate Determining Step ◽  
Higher Temperature ◽  
Kinetics Of

Kinetics of CO methanation on a commercial Ni/SiO2 catalyst was evaluated at atmospheric pressure, between 528 and 550 K and for hydrogen to carbon monoxide molar ratios ranging from 3 : 1 to 200 : 1. The effect of reaction products on the reaction rate was also examined. Below 550 K, only methane was selectively formed. Above this temperature, the formation of carbon dioxide was also observed. The experimental data could be described by two modified Langmuir-Hinshelwood kinetic models, based on hydrogenation of surface CO by molecularly or by dissociatively adsorbed hydrogen in the rate-determining step. Water reversibly lowered catalyst activity and its effect was more pronounced at higher temperature.

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