Polymerize olefins

Ziegler catalysts Complex catalysts prepared by interaction between an organometallic derivative and a transition metal derivative. A typical catalyst is the product of the interaction of TiCU and AIBU3. These catalysts polymerize olefins, particularly ethylene, to polyolefins, the polymerization generally being in a siereoregular manner. 

In 1929, polymerized olefins were the first synthetic oils to be produced commercially in an effort to improve on the properties of petroleum oils. Interest in esters as lubricants appears to date back to 1937 in Germany, and their production and use expanded rapidly during and following World War II to meet the needs of the military and the newly developed jet engines (2). 

Titanium bromide [7789-68-6] TiBr, is claimed as a catalyst for olefin polymerizations (18). Chromous bromide [10049-25-9] CrBr2, is used in chromizing. Chromic bromide [10031-25-1], CrBr, and tungsten bromide [13701 -86-5], are catalysts for polymerizing olefins (19). Manganese... 

Heterogeneous Ziegler-Natta catalysts used to polymerize olefins exhibit phenomena characteristic of active site heterogeneity (1- 5). Complex kinetic models which account for this likelihood have been developed and used only in simulation studies (6-7). 

Besides the mirror and addition reactions already discussed, gas phase radicals dimerize, disproportionate, transfer hydrogen, and polymerize olefins. Similar reactions in the liquid phase are an indication (but not proof) of free radical intermediates. 

Generally speaking, a monomer with electron-releasing groups will be more rapidly polymerized by cationic initiators. Anionic initiators polymerize olefins with electron-withdrawing groups more rapidly. A more sensitive test of the nature of the reaction is the behavior of a mixture of two such monomers in copolymerization in which they compete for the intermediate. This will be discussed in more detail in Chapter XII on polar versus radical mechanisms. 

EP2 A process for polymerizing olefins in the slurry phase. Developed by Borealis. 

Insite Not a process, but a range of constrained-geometry metallocene catalysts for polymerizing olefins. Developed by Dow Chemical. 

A major part of the work described in this section has been carried out with the aim of applying these silsesquioxane complexes of Ti, Zr and Hf in catalytic processes such as ethylene polymerization, olefin epoxidation and Oppenauer oxidation. These catalytic aspects have been highlighted in several recent review articles. 

Since Zr-H is able both to (i) activate the C-H bonds of alkanes (via cr-bond metathesis) [15, 48] and to carry out their hydrogenolysis (transfer of a least two carbons via a P-alkyl transfer) and (ii) polymerize olefins (via insertion), the ability of such supported Zr-H was tested in the homologation of propane. 

In the early 1950s Karl Ziegler in Germany and Giulio Natta in Italy found catalysts that polymerized olefins and dienes with stereoregularity and with mild polymerization conditions. For this revolutionary discovery they both won the Nobel Prize. Let us take the example of propylene, which we... 

Base fluids (BFs) represent the major ingredient of nonaqueous drilling mud systems. They act as the continuous phase in OBMs and SBMs. Oil-based fluids (OBFs) such as diesel and mineral oils have been replaced with synthetic-based fluids (SBFs) because of the deleterious environmental hazards of OBMs. The SBFs contain fatty adds which are usually derived from vegetable oil (e.g., palm oil) or fish oil. SBFs usually constitute about 50-90% by volume of the fluid portion of the SBM [27] and about 20-40 % of the mass of the mud [35]. Ethers, esters, acetals, polymerized olefins (poly-a-olefins, linear a-oleftns, and internal olefins), enhanced mineral oils, and paraffins are used most frequently as SBFs (Table 11.2) in mud formulations [8, 36, 37]. 

Polymerized olefins include poly-a-olefins (PAOs), linear a-olefins (LAOs), and internal olefins (IOs) [24]. Hydrocarbon chain length and branching are selected to optimize the drilling properties and minimize the environmental toxicity [20]. 

The addition of carbon-centered radicals to C-C double bonds (for a review see Giese 1983) is the key reaction in the free-radical-induced polymerization. In general, the rate constants of these reactions are only moderately high, but this process becomes fast and efficient, because in technical applications the polymerizing olefin is usually present at high concentrations. In aqueous solutions, the rate constant of the addition of the hydroxyethyl radical to ethene [reaction (29)], a non-activated C-C double bond, has been determined at 3 x 104 dm3 mol1 s1 (Soylemez and von Sonntag 1980). 

The purpose of hydrofining reactions may vary with the feedstock. Gasolines or coke-oven light oil are treated to remove gum formers, that is, readily polymerizing olefins and sulfur compounds, while hydrogenation of aromatics must be avoided. Hydrogenation of kerosenes and Diesel... 

The intensive search for the active cocatalyst responsible for this activation led in 1977 to the isolation of MAO, a component in which aluminum and oxygen atoms are positioned alternately and free valences are saturated by methyl groups (65, 66). When metallocenes, especially zirconocenes, are combined with MAO, the resulting catalyst can polymerize olefins 10-100 times faster than those used in the most active Ziegler-Natta systems (67). 

Titanium—Vanadium Mixed Metal Alkoxides. Titanium—vanadium mixed metal alkoxides, VO(OTi(OR)3)2, are prepared by reaction of titanates, eg, TYZOR TBT, with vanadium acetate in a high boiling hydrocarbon solvent. The by-product butyl acetate is distilled off to yield a product useful as a catalyst for polymerizing olefins, dienes, styrenics, vinyl chloride, acrylate esters, and epoxides (159,160). 

Group 4 elements (e.g., Ti, Zr) are used as typical catalyst precursors for olefin polymerization and serve as potent cationic components for polymer chain growth with the aid of aluminum (e.g., MAO) or boron co-catalysts. It would be more efficient and convenient if organoaluminum cations were used to polymerize olefins. From this viewpoint, following an earlier precedent with two-coordinate cations (Equation (98)),319,320 some three-coordinate organoaluminum cations hold promise, and their ability to promote polymerization of ethylene or terminal olefins is now... 

Insite Not a process, but a range of constrained-geometry metallocene catalysts for polymerizing olefins. Olefin block copolymers made using these catalysts have the trade name Infuse. Developed by J.C. Stevens at the Dow Chemical Company, for which he received several medals. 

---