2 Introduction 3 Results and Discussion 17 A Chromium Diphosphine System for Selective and Catalytic Ethylene Oligomerization 17 Synthesis of PNP Ligands with Ether Groups Tethered to Nitrogen 17 Preparation and Characterization of PNP Chromium Complexes 18 Catalytic Runs at 1 atm of Ethylene Using Precatalysts 21-24 24 Catalytic Runs at Higher Pressures of Ethylene 28 Role of the Ether Tether ...

The metal-catalyzed polymerization of simple olefins, such as ethylene and propylene, has been one of the transformational discoveries in chemistry of the 20th century. It is difficult to imagine today’s civilization without ubiquitous plastics, such as polyethylene and related polymers. Although often attributed to Karl Ziegler and Giulio Natta, the winners of the 1963 Nobel Prize in Chemistry...

BACKGROUND 2,6-dimethylphenol (2,6-DMP) is a product of phenol methylation, especially important for the plastics industry. The process of phenol methylation in the gas phase is strongly exothermic. In order to ensure good temperature equalization in the catalyst bed, the process was carried out using a catalyst in the form of a fluidized bed - in particular, the commercial iron-chromium cataly...

chromium(III) up to 100 ng mL−1, and for chromium(VI) up to 200 ng mL−1) were obtained, using the “fixed time” method with detection limits of 4.9 ng mL−1 and 3.8 ng mL−1, respectively. The results suggest that at the reaction conditions chromium(VI) is reduced and chromium(III) is oxidized to an intermediate oxidation state and the catalytic action of chromium is due to the formation of an act...

Magnetically separable photocatalyst beads containing nano-sized iron oxide in alginate polymer were prepared. This magnetic photocatalyst beads are used in slurry-type reactors. The magnetism of the catalyst arises from the nanostructured particles gamma-Fe(2)O(3), by which the catalyst can be easily recovered by the application of an external magnetic field. These synthesized beads are sunlig...

We report the growth of high density silicon Oxide (SiOx) nanowires at an elevated temperature. The nanowires density is enhanced by inserting a thin layer of chromium metal in gold/Si catalyst system. The SiOx nanowires were grown with gold/chromium catalysts stack layer on the Si substrate at different temperatures ranging from 1050oC to 1150oC. Under the catalysis reaction of the gold/chromi...

This work aims at the reutilization of a Cr-loaded NaY zeolite obtained by biorecovery of chromium from water as catalyst in the oxidation of volatile organic compounds (VOC). Cr-NaY catalysts were obtained after biosorption of Cr(VI) using a bacterium, Arthrobacter viscosus, supported on the zeolite. The biosorption experiments were conducted at different pH values in the range 1-4. The cataly...

ethylene polymerization was carried out using phillips chromium catalyst based on silica supports such as silicaaerogel, sio2 (grace 643), and titanium modified sio2 (g 643), and the results were compared with othercatalysts based on sio2 (aldrich), sba-15(hex), sba-15(sp) and mcm-41. a combination of tga, dsc, xrd,nitrogen adsorption, sem, icp, ftir and other analyses were used to characterize...

A series of bis(diphenylphosphino)amine ligands with a donor group attached to the nitrogen linker have been prepared. Metalation of these ligands with chromium trichloride provides precursors to highly active, relatively stable, and selective catalysts for trimerization and tetramerization of ethylene. It has been demonstrated in oligomerization reactions performed at 1 and 4 atm of ethylene t...

Chromium-based catalyst systems with polar-substituted diphosphinoamine ligands are selective for either trimerisation or tetramerisation of ethylene, depending on the position of the polar groups on the aryl rings.