A systematic study of propylene polymerization using a 4th generation Ziegler-Natta catalyst is presented in this thesis. The apparent kinetic rate constants for propylene polymerization were estimated in the presence and absence of hydrogen and/or donor. The estimated activation energies for activation, propagation, and deactivation were found to be close to values previously reported in the literature for similar catalysts. The polypropylene samples were characterized using high-temperature gel permeation chromatography (GPC), carbon-13 nuclear magnetic resonance (13C NMR), and crystallization elution fractionation (CEF). The effect of hydrogen and external electron donor on polypropylene microstructure was investigated at two polymerization temperatures. In addition to the expected electron donor positive effect on tacticity, hydrogen was also found to increase polypropylene tacticity. The effect of changing these polymerization conditions on molecular weight and polydispersity was also investigated. Finally, CEF profiles show how the distribution of polypropylene crystallizability changes by adding hydrogen and electron donor to the reactor. The concentrations of hydrogen and external donor were also varied to study their effect of polymerization kinetics and polymer microstructure. The estimated activation energies were close to those found in the first part of this investigation in the presence and/or absence of donor and hydrogen. A polypropylene microstructural study showed a positive effect of hydrogen concentration on mmmm pentad at low donor concentration, likely due to an increase in stereoselectivity of the aspecific sites by hydrogen. However, increasing donor concentration over a given threshold seems to transform the aspecific sitess into stereospecific sites that are no longer significantly affected by hydrogen. These experimental results were compared to a previously developed Monte Carlo model and found to agree with the trends predicted by simulation. Finally, the effect of diisopropyldimethoxysilane (P), n-propyltrimethoxysilane (N), paraethoxyethylbenzoate (PEEB), and dicyclopentyldimethoxysilane (D) external donors on catalyst activity and stereoselectivity was investigated. P and D donors were more stereoselective than N and PEEB donors; however, D donor had the best activity among all donors investigated. Therefore, D donor was mixed with PEEB to combine its high activity with the self-extinguishing properties of PEEB. The D/PEEB 90/10 (mol/mol) mixture generated a catalyst with good stereoselectivity but poor activity. When the ratio was increased to 95/5 and 98/2, the resulting catalyst had high activity and good stereoselectivity. Interestingly, the D/PEEB combination with just a small fraction of PEEB has a positive effect on the catalysts activation term which may decrease polymerization costs with this system.

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This thesis is focused on the determination of the propene polymerization kinetics on phthalate and nonphthalate diester Ziegler-Natta MgCl2-supported catalysts under the industrial conditions. The kinetic profiles were determined by various laboratory techniques for propene polymerization. For assessing the profiles were utilized batch gas and liquid polymerization modes in 2-litre and 4-litre reactors. Finally, the results were complemented with the runs performed in a unique Stopped-Flow apparatus, which allows polymerization of liquid propene at very short polymerization times. The kinetics profiles of both catalysts were determined and compared by combination of experimental data of these techniques. The basic properties of the synthesized polymeric powders were measured, such as the melt flow index, bulk density and amount of polypropene fraction soluble in cold xylene.

Thesis is focused on structural study of ethylene-propylene copolymers (E/P copolymers) produced by gas phase polymerization. Goal of work was to determine the effect of used catalysts on the distribution of ethylene units in the resulting material. Three E/P copolymers were prepared on commercial Ziegler Natta catalysts with diether or phthalate based internal donors. The copolymers were fractionated according crystallization ability and molar mass. Next, the mass content and the distribution of the ethylene units in the copolymer were determined in each fraction by nuclear magnetic resonance (NMR). Together with other structural analytical methods, phthalate internal donor has been found to produce ethylene blocks under certain conditions, while the diether ID lacks this ability.

The aim of the study will be the determination of the kinetic profiles of the polymerization of propene, ethene and their mixtures with commercial Ziegler-Natta catalyst by application of two different experimental procedures. The prepared polymer material will be utilized for the SEC analysis and subsequent evaluation of the concentration of active sites. The determined molecular mass distribution curves will be further investigated by the application of the procedure, which deconvolute the overall profile on the basic Flory's distribution functions. Then the comprehensive study about character and behavior of various types of active centers in dependence on time and type of monomer will result from this investigation.

A fourth generation multiple site Ziegler-Natta catalyst was used to synthesize ethylene and propylene homo-and copolymers in the presence of hydrogen. This type of catalysts produce polymers with broader molecular weight distribution (MWD), chemical composition distribution (CCD) and stereoregularity than other coordination polymerization catalysts since it has more than one active site. The ratio of propylene/ethylene was varied to study its effect on polymer microstructure. In addition, by having two different electron donors, namely diisopropyldimethoxysilane (P) and dicyclopentyldimethoxysilane (D), the molecular weight distribution (MWD) and stereospecificity of the synthesized polymers were examined. The polymer samples were characterized using 13C-NMR and high-temperature gel permeation chromatography (GPC). Using the 13C-NMR data, the triad distribution for the copolymers and also the isotactic triad distribution for homo-polymers were calculated. The effects of electron donors on different feed ratios of ethylene and propylene in the synthesis were investigated. Co-polymer produced with D-donors showed higher isospecificity and also higher content of ethylene in the final polymer. In contrast, polymers produced using with P-donor showed lower polydispersity indices (PDI), and had higher contents of propylene in final polymer. In addition, the “Deconvolution method” was applied to GPC data in order to determine the number of sites on the Ziegler-Natta catalyst; which showed that 4 active site types were adequate to explain the molecular weight distributions.

Μελετήθηκαν με μία σειρά από επιφανειακά ευαίσθητες τεχνικές δύο πρότυπα συστήματα με ενδιαφέρον για την ετερογενή κατάλυση. (Α) Στο διμεταλλικό σύστημα Sn/Ni διερευνήθηκαν οι συνθήκες και ο μηχανισμός κραματοποίησης του Sn στην επιφάνεια Ni(111). Το πλήρες επιφανειακό κράμα με δομή (√3×√3)R30°(από περίθλαση ηλεκτρονίων) σχηματίζεται θερμαίνοντας στους 7000C πάνω από 1,2 μονοστρώματα Sn. Οι διατεταγμένες δομές c(4x2) και c(2x2) αποτελούν ένα ενδιάμεσο στάδιο της κραματοποίησης σε χαμηλότερες θερμοκρασίες. Με θερμοπρογραμματισμένη εκρόφηση CO διαπιστώθηκε η βαθμιαία παρεμπόδιση της ρόφησης κατά το σχηματισμό του κράματος. Η διεπιφανειακή αλληλεπίδραση Sn/Ni(111) διερευνήθηκε τόσο με φασματοσκοπίες φωτοηλεκτρονίων, όσο και με θεωρητικούς υπολογισμούς από πρώτες αρχές. (Β) Μελετήθηκαν με φασματοσκοπίες ηλεκτρονίων και σκέδαση ιόντων He ρεαλιστικά πρόδρομα καταλυτικά συστήματα Ziegler – Natta (ZN), παρασκευάζοντας διάφορες σχετικές διεπιφάνειες με εξάχνωση MgCl2 σε υποστρώματα Si(111)7×7, Ti(0001) και SiO2. Η ασθενής αλληλεπίδραση μεταξύ MgCl2 και Si(111)7×7 γίνεται κυρίως μέσω των ατόμων Mg, τα οποία σε χαμηλές καλύψεις συμμετέχουν στη δημιουργία της υπερδομής (√3×√3)R30°. Η αλληλεπίδραση ενισχύεται μετά από θέρμανση, οπότε παραμένει στην επιφάνεια υπομονοστρωματική ποσότητα Mg. Από την άλλη πλευρά, το MgCl2, ακόμα και σε θερμοκρασία δωματίου αλληλεπιδρά ισχυρά με το Ti(0001), κυρίως μέσω των ατόμων Cl. Μετά από θέρμανση, ποσότητα Cl παραμένει συνδεδεμένη με το Ti ενώ απομακρύνεται από την επιφάνεια το Mg. Ασθενής αλληλεπίδραση παρατηρήθηκε μεταξύ MgCl2 και SiO2, ενώ η θέρμανση άφησε στην επιφάνεια υπομονοστρωματική ποσότητα οξειδωμένου Mg. Τέλος, μεταλλικό Ti που αποτέθηκε σε μικτό υπόστρωμα MgCl2 /SiO2 παρουσιάζει οξειδωτικές καταστάσεις οφειλόμενες στην ύπαρξη ατόμων Cl και O στην επιφάνεια, ενώ η θέρμανση οδηγεί στη δημιουργία επιφανειακών συμπλόκων, τα οποία είναι πιθανόν να προσομοιάζουν αντίστοιχα είδη στους πρακτικούς καταλύτες. / Two model systems, important in heterogeneous catalysis, where investigated using surface sensitive spectroscopies. (A) In the bi-metallic system Sn/Ni, the formation conditions and the mechanism of Sn surface alloying on Ni(111) were initially studied. The epitaxial surface alloy formation with LEED structure(√3×√3)R30°, requires annealing at 7000C of more than 1.2 monolayers Sn. The c(4x2) and c(2x2) structures were found to be an intermediate step of surface alloying. Temperature-programmed desorption showed a gradual blocking of CO adsorption with progressing alloying. The interfacial interactions in Sn /Ni(111) were demonstrated both by electron spectrosopies and via first principle calculations. (B) Surface science compatible model catalysts of the Ziegler-Natta (ZN) system were investigated by electron spectroscopies and He ion scattering on relevant interfaces formed via evaporation of MgCl2 on Si(111)7×7, Ti(0001) and SiO2 and upon evaporation of Ti on a MgCl2 /SiO2 mixed substrate.. The weak interaction between MgCl2 and Si(111)7×7 takes place through the Mg atoms, which at low coverage form a new surface structure, namely (√3×√3)R30°. The interaction was stronger after annealing, whereby a submonolayer coverage of Mg atoms remain on the surface. On the other hand, MgCl2 interacts strongly with the Ti substrate even at room temperature via the Cl atoms. Annealing causes the desorption of MgCl2 followed by decomposition, that leaves on the surface only Cl atoms attached to Ti, while no Mg atoms remain on the surface. Only a weak interaction was observed between MgCl2 and SiO2, while annealing resulted in the desorption and decomposition of MgCl2 leaving on the surface a sub-monolayer coverage of oxidized Mg. Upon Ti metal evaporation on the mixed MgCl2 / SiO2 support at room temperature, Ti appears at higher oxidation states, due to reaction with Cl and O atoms at the surface. Annealing causes the formation of surface complexes, which are very likely similar to species formed on practical ZN catalysts.