Wioletta Ochędzan-Siodłak

Effect of immobilization of titanocene catalyst in aralkyl imidazolium chloroaluminate media on performance of biphasic ethylene polymerization and polyethylene properties

Abstract1-(2-Phenylethyl)-3-methylimidazolium and 1-benzyl-3-methylimidazolium chloroaluminates, [Ph-C2mim][AlCl4] and [Bzlmim][AlCl4], were applied as media of the Cp2TiCl2 catalyst for biphasic ethylene polymerization. The studied aralkyl ionic liquids ensure greater stability of the catalyst at higher temperatures and more regular morphology of the produced polyethylene than analogous 1-n-alkyl-3-methylimidazolium chloroaluminates. The alkylaluminium compound participates in the termination reaction of the polymer chain. The catalyst is stable and enables recycling of the ionic liquid phase in the consecutive polymerization reactions. The [Ph-C2mim][AlCl4] ionic liquid and AlEt2Cl alkylaluminium compound turned out to be the most suitable for the biphasic process. The influence of the kind of ionic liquid, alkylaluminium compound (AlEt2Cl and AlEtCl2), activator/catalyst molar ratio, reaction temperature, reaction time and catalyst recycling on the polymerization performance as well as polyethylene properties such as molecular weight (Mw), polydispersity, melting temperature, crystallinity degree, bulk density and particle size is presented.

High crystallinity polyethylene obtained in biphasic polymerization using pyridinium chloroaluminate ionic liquid

A series of N-n-alkylpyridinium chloroaluminate ionic liquids [Cn-py][AlCl4] (where n-alkyl = n-butyl, n-hexyl, and n-octyl) was applied as a medium of the Cp2TiCl2 catalyst, activated by AlEtCl2 or AlEt2Cl, to evaluate the influence of the studied ionic liquids on the performance of the biphasic ionic liquid/hexane ethylene polymerization and the properties of the produced polyethylene (PE). The best results were obtained using N-n-butylpyridinium chloroaluminate. The polyethylene obtained in the biphasic polymerization have the high crystallinity, which was confirmed by DSC, WAXS and PALS methods, as well as the bulk density comparable to commercial HDPE. These unique properties results from the biphasic mode of the ethylene polymerization where the ionic liquid is used to immobilize the catalyst, and polyethylene is produced in the ionic liquids phase.

A NEW SUPPORTED ZIRCONOCENE CATALYST FOR ETHYLENE POLYMERIZATION

Metallocene catalysts enable the structure of polymers to be tailored in a way which has not been reached before. However, they are more active than the conventional Ziegler — Natta catalysts only as homogeneous metalocene systems, a fact that has essentially restricted their use to industrial processes producing polymers in solution. Modern polymerization processes are solvent free slurry (with liquid monomer) or gas phase processes. To use metallocene catalysts in these modern processes, it is necessary to convert them to heterogeneous catalysts [1, 2]. However, problems have appeared chiefly concerning the activity of the supported catalysts, because heterogeneous metallocene catalysts are much less active than supported Ziegler—Natta catalysts [3,4]. Most solid systems that have been reported cause a dramatic decrease in the activity when compared with the corresponding metallocenes in the solution. Generally, developing of heterogeneous catalyst, with the metallocene as active component supported on the surface of a solid carrier, is the point of extreme interest of resent years.

2-(1,3-Oxazolin-2-yl)pyridine and 2,6-bis(1,3-oxazolin-2-yl) pyridine

The data presented in this article are related to research articles “Titanium and vanadium catalysts with oxazoline ligands for ethylene-norbornene (co)polymerization (Ochędzan-Siodłak et al., 2018). For the title compounds, 2-(1,3-oxazolin-2-yl)pyridine (Py-ox) and 2,6-bis(1,3-oxazolin-2-yl)pyridine (Py-box), the single-crystal X-ray diffraction measurement together with NMR, GC, MS, DSC analysis, like also the method of crystallization are presented.

Pyrazole amino acids: hydrogen bonding directed conformations of 3-amino-1H-pyrazole-5-carboxylic acid residue

A series of model compounds containing 3‐amino‐1H‐pyrazole‐5‐carboxylic acid residue with N‐terminal amide/urethane and C‐terminal amide/hydrazide/ester groups were investigated by using NMR, Fourier transform infrared, and single‐crystal X‐ray diffraction methods, additionally supported by theoretical calculations. The studies demonstrate that the most preferred is the extended conformation with torsion angles ϕ and ψ close to ±180°. The studied 1H‐pyrazole with N‐terminal amide/urethane and C‐terminal amide/hydrazide groups solely adopts this energetically favored conformation confirming rigidity of that structural motif. However, when the C‐terminal ester group is present, the second conformation with torsion angles ϕ and ψ close to ±180° and 0°, respectively, is accessible. The conformational equilibrium is observed in NMR and Fourier transform infrared studies in solution in polar environment as well as in the crystal structures of other related compounds. The observed conformational preferences are clearly related to the presence of intramolecular interactions formed within the studied residue. Copyright