Oligomérisation sélective de l'éthylène avec des complexes de chrome : étude théorique et expérimentale combinée - et extensions à d'autres métaux

The selective catalytic oligomerization of ethylene to alpha-olefins constitutes a process of significant scientific as well as economic interest both in industry and academics. The present thesis gives both experimental and theoretical contributions to the catalyzed selective tri- and tetramerization with chromium coordination complexes. Important aspects of the mechanism of this reaction are adressed, including the oxidation state of the active species, the origin of cyclic secondary products, as well as the influence of the ligand steric bulk, are comprehensively adressed. A number of alternative bidentate ligands have been evaluated in the oligomerization reaction. Another part of this thesis concerns the selective ethylene dimerization with nickel(II) complexes bearing mixed heteroatomic iminophosphorane (N,O), (N,S), and (N,P) ligands. The synthesis of these new ligands, their coordination to Ni(II), as well as the catalytic evaluation of the obtained complexes are reported. The last part of this work concerns the preparation of two new phosphatitanocenes and catalytic evaluation in the ethylene oligomerization/polymerization reaction

Oligomérisation sélective de l éthylène avec des complexes de chrome (étude théorique et expérimentale combinée et extensions à d autres métaux)

PALAISEAU-Polytechnique (914772301) / SudocSudocFranceF

The Selective Chromium-Catalyzed Oligomerization of Ethylene

communication par afficheCatalytic ethylene oligomerization processes are of paramount interest to the chemical industry due to the importance of the formed linear α-olefins (LAOs) as feedstock in copolymerization processes; the fabrication of lubricants, detergents, and others. Recently, chromium-based catalytic systems comprising chelating bisphosphine ligands have received increased attention both in academic and industrial research due to their extraordinary efficiency in the selective tri- and tetramerization reaction of ethylene. Basicity, steric bulk and the coordination mode of the bisphosphine ligand to the chromium metal have been found to influence the selectivity towards a particular oligomer. This is demonstrated using a particular P^N^P ligand in the chromium-catalyzed oligomerization reaction. The metalacyclic mechanistic pathway and the factors determining the observed selectivity with this ligand are rationalized by DFT calculations. It can be shown that the selectivity towards the trimerization product in the case of the P^N^P ligand is essentially a result of the steric bulk of the ligand prohibiting metalacyclic ring growth beyond a seven-membered ring

Chromium catalyzed ethylene oligomerization – new ligands and mechanistic insights (affiche)

communication par afficheCatalyzed selective ethylene oligomerization for the production of short-chain linear α-olefins (LAOs) is a subject of paramount interest both from a industrial and academic viewpoint due to the importance of LAOs as feedstock in a great variety of processes ranging from copolymerization to the fabrication of detergents and plasticizer alcohols, only to name a few. Catalyst precursors comprising a chromium metal center and chelating bisphosphine ligands figure amongst the most efficient systems for the selective tri- and tetramerization of ethylene. P^N^P type ligands were synthesized in a Mannich-type reaction, and coordinated to chromium (III), affording novel octahedral complexes, which proved to be active in the oligomerization of ethylene upon activation with methylaluminoxane. It is demonstrated, that the coordination mode to the metal center, the basicity and the steric bulk of the ligand determine the selectivity of the catalyst towards the formation of a particular oligomer chain length. The experimental findings are rationalized by DFT calculations on the metalacyclic mechanism of the oligomerization reaction. It will be shown that in the case of the P^N^P ligand, growth of the metalacycle beyond a seven-membered ring is hindered depending on the steric bulk of the ligand and thus responsible for the selectivity towards 1-hexene, or inversely, the formation of 1-octene becomes possible

New Iminophosphorane Ligands – Synthesis and Applications in Catalysis (affiche)

communication par afficheOrganometallic complexes comprising iminophosphorane ligands have recently found an increasing application in both coordination chemistry and catalysis. The integration of supplemental donor sites D into the iminophosphorane structure yields polydentate mixed ligands of type A or B. Ligands of this type are of particular interest due to the analogy of the iminophosphorane unit with imines, ubiquitous in coordination chemistry. New ligands of type A and B with either anionic or neutral oxygen or sulfur donor atoms have been synthesized via two different pathways, both straightforward and easy to scale up. The coordination of these ligands to NiIIBr2(DME) (DME = dimethoxyethane) has been evaluated and preliminary results in the catalyzed oligomerization reaction of ethylene employing these complexes are reported

Evaluation procedures for the traffic and linking qualities of main roads

Hauptverkehrsstraßen sind in der Regel Bestandteil überörtlicher Straßennetze, bilden aber gleichzeitig auch wichtige städtebauliche und stadtverkehrliche Achsen, und befinden sich somit in einem Spannungsfeld zwischen den Funktionen aus dem Verbindungsbedarf von Orten und Ortsteilen und der Erschließungsfunktion aus dem städtebaulichen Zusammenhang mit angrenzenden baulichen und sonstigen Umfeldnutzungen. Für die Netzkapazität sind in erster Linie die Knotenpunkte gleichrangiger Hauptverkehrsstraßen maßgebend, da hier Straßen mit gleicher Verbindungsbedeutung und entsprechend hohen Verkehrsstärken zusammentreffen. Die Qualität des Verkehrsablaufs auf den Streckenabschnitten zwischen diesen Knotenpunkten ist dagegen in starkem Maße durch die im Straßenraum jeweils festzustellenden Nutzungsbilder geprägt. Die Verkehrs und Verbindungsqualität in städtischen Hauptverkehrsstraßenzügen und damit auch netzen sind somit nicht nur von den Knotenpunkten, deren Abständen sowie dem Ausbau und der lichtsignaltechnischen Steuerung (besonders bedeutsam ist in diesem Zusammenhang deren Koordinierungsqualität), sondern auch von den dazwischen liegenden Streckenabschnitten und deren Erschließungsfunktion abhängig. Zielsetzungen dieses Forschungsvorhabens sind - zum einen die Erarbeitung differenzierter Qualitätsstufenkonzepte für den Kraftfahrzeug und den Stadt /Straßenbahnverkehr zur Bewertung des Verkehrsablaufs auf Hauptverkehrsstraßen mit straßenbündigen Bahnkörpern (Teil 1) und - zum anderen die Ermittlung von Verfahren zur Bestimmung der Verkehrs und Verbindungsqualitäten in städtischen Hauptverkehrsstraßenzügen unter Berücksichtigung des Verkehrsablaufs auf/an den Einzelanlagen und eventueller Netzeffekte (Teil 2). Die im hier vorliegenden Teil 2 entwickelten Verfahren zur übergreifenden Bewertung der Verkehrs und Verbindungsqualitäten von Straßenzügen gelten für alle Hauptverkehrsstraßen der Kategorie C III der RAS N(1988) beziehungsweise der Kategorie HS III der RIN (2008). Des Weiteren wurden angepasste Stufen der verbindungsbezogenen Angebotsqualität abgeleitet, die eine praxisgerechte Beurteilung der Erreichbarkeitsqualität in innerörtlichen Straßennetzen ermöglichen. Die Ergebnisse dienen als Grundlage zur Fortschreibung des HBS, die für das Jahr 2009 vorgesehen ist. Darüber hinaus sollen sie dazu dienen, Diskussionen zur Netzgestaltung zu objektivieren.As a rule, main roads are a component of supralocal road networks but at the same time also represent important urban planning and urban traffic axes and are therefore situated in a conflicted area between the connectivity requirements of municipalities and urban districts and the service function of the urban infrastructural context with allied architectural and other peripheral utilities. First of all, the hubs of equivalent main roads are critical to network capacity because here roads with the same connection importance and correspondingly high traffic volumes coincide. The quality of traffic flow on the road sections between these hubs is on the other hand affected to a high degree by the respective utilization profiles of the road area that can be determined. The quality of traffic and connectivity in stretches urban main road and consequently also in main road networks are consequently not only dependent on the hubs, whose separations and the structure of the traffic signal control (their coordination quality is particularly important in this context) but also on the segments situated between them and their service function. Two objectives were monitored in this research project: - on the one hand, the definition of differentiated concepts of quality levels for motor vehicle and commuter rail/streetcar traffic for the evaluation of traffic flow on main roads with track centers flush with the street (Part 1) and - on the other hand, definition of methods for determination of traffic and connectivity qualities in stretches of urban main roads while taking into account traffic flow on/at the individual systems and any network effects (Part 2). The methods developed in this Part 2 for overall assessment of the traffic and connectivity qualities of stretches of road apply to all RAS N (1988) Category C III or RIN Category HS III (2008) main roads. In addition adapted levels of connectivity related service quality were deduced that enable practical evaluation of the accessibility quality in intraregional road networks. The results are used as the basis for the updated HBS that is planned for 2009. Furthermore, they should also be used to objectify discussions on network design