Functional or telechelic polyolefin, derivatives thereof, and process for preparing same

US Patent App. 15/534,668International audienc

Traitement chimique des surfaces des alumines silicées (application à l'hydrocraquage)

L objectif de notre travail était de rechercher de nouveaux catalyseurs d hydrocraquage permettant de transformer de façon sélective les distillats sous vide en gazole. Les catalyseurs d hydrocraquage sont bifonctionnels, associant une fonction métallique (hydro-déshydrogénante) et une fonction acide (isomérisante). Les distillats sous vide contenant des composés azotés et soufrés, la fonction hydro-déshydrogénante sera assurée par des sulfures de métaux. D autre part, si on désire orienter l hydrocraquage vers la production de gazole, la fonction acide devra être modérément forte. Les catalyseurs les plus utilisés actuellement sont du type sulfures de Ni et W déposés sur silice-alumine. Nous avons choisi dans ce travail d utiliser un type de support un peu différent : les alumines silicées, et d étudier l effet de traitements thermiques de ce support, calcination ou steaming, sur l activité et la sélectivité en hydrocraquage des catalyseurs sulfures de NiW / alumine silicée correspondants. La calcination ou le steaming de l alumine silicée provoquent des modifications importantes de la surface et du volume poreux, mais ne modifient pas les caractéristiques du solide. D autre part, ces traitements, et en particulier le steaming, font apparaître à la surface de nouveaux sites acides de Brönsted. L activité isomérisante de ces catalyseurs est alors plus forte, et par voie de conséquence leur activité en hydrocraquage est elle aussi plus forte. Nous avons en effet observé que sur ces catalyseurs, l étape cinétiquement limitante de la réaction était l étape acide. A la différence de ce qui est généralement observé, cette augmentation d'activité ne s'accompagne d'aucune perte de sélectivité. Les catalyseurs sulfures de NiW / alumine silicée pourraient donc être d excellents catalyseurs industriels d hydrocraquage. Nous avons également montré qu il était possible de protéger les sites acides de l alumine silicée pendant l imprégnation par le nickel et le tungstène, en bloquant ces sites par adsorption de pyridine. Malheureusement, la présence de pyridine nuit considérablement à la formation de la phase sulfures, et les catalyseurs obtenus ne sont pas très performants en hydrocraquage.The aim of our work was to find new hydrocracking catalysts allowing a selective transformation of vacuum distillates into gas oil. Hydrocracking catalysts are bifunctional, associating a metallic function (hydro-dehydrogenating) and an acidic function (isomerizing). The vacuum distillates containing nitrogen and sulphur compounds, the hydro-dehydrogenating function will be provided by metal sulphides. On the other hand, if gas oil is the desired product, the acid function must be fairly strong. The most currently used catalysts are sulphides of Ni and W deposited on silica-alumina. We chose in this work to use a little different support : silicated aluminas, and to study the effect of heat treatments of this support, calcination or steaming, on the activity and the selectivity for hydrocracking of the sulphided catalysts. Calcination or steaming of silicated alumina brings important modifications of surface and pore volume, but do not modify the characteristics of the solid. In addition, these treatments, and in particular the steaming, create new Brönsted acid sites on the surface. The isomerizing activity of the corresponding catalysts is higher, and consequently their activity in hydrocracking is also higher. Indeed we observed that on these catalysts, the rate limiting step of hydrocracking was the acidic step. At the difference of what is generally observed, this increase in activity is not accompanied by a decrease in selectivity. Thus, the sulphided NiW/silicated alumina catalysts could be excellent industrial catalysts for hydrocracking. We also showed that it was possible to protect the acid sites of silicated alumina during the impregnation by nickel and tungsten, by blocking these sites by adsorption of pyridine. Unfortunately, the presence of pyridine considerably harms the formation of the sulphided phase, which makes the catalysts not very efficient in hydrocracking.POITIERS-BU Sciences (861942102) / SudocSudocFranceF

Monofunctional and Telechelic Polyethylenes Carrying Phosphonic Acid End Groups

International audienc

Activity Enhancement of MgCl2-supported Ziegler-Natta Catalysts by Lewis-acid Pre-treatment for Ethylene Polymerization

International audienc

Telechelic Polyethylene from Catalyzed Chain-Growth Polymerization

International audienc

Synthesis of block copolymers based on polyethylene by thermally induced controlled radical polymerization using Mn2 (CO) 10

International audienc

Amino End-Functionalized Polyethylenes and Corresponding Telechelics by Coordinative Chain Transfer Polymerization

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Investigation of the kinetics of ethylene polymerization for the bi-component catalyst Cp* 2NdCl2Li (OEt2) 2/MgR2

International audienc

Organocatalytic synthesis of vinylene carbonates

The organocatalytic synthesis of vinylene carbonates from benzoins and acyloins was studied using diphenyl carbonate as a carbonyl source. A range of N-Heterocyclic Carbene (NHC) precursors were screened and it was found that imidazolium salts were the most active for this transformation. The reaction occurs at 90°C under solvent-free conditions. A wide range of vinylene carbonates (symmetrical and unsymmetrical, aromatic or aliphatic), including some derived from natural products, were prepared with 20-99% isolated yields (24 examples). The reaction was also developed using thermomorphic polyethylene-supported organocatalysts as recoverable and recyclable species. The use of such species facilitates the workup and allows the synthesis of vinylene carbonates on the preparative scale (> 30 g after 5 runs)

Bifunctional Catalysts Based on Tungsten Hydrides Supported on Silicated Alumina for the Direct Production of 2,3-Dimethylbutenes and Neohexene from Isobutene

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