Ethylene catalysts

Derived from an aldehyde or ketone and an alcohol using an acid catalyst. Ethylene glycol or 1,3-dihydroxypropane are frequently used to give 5-or 6-member cyclic products. 

Ethylene. Under the influence of pressure and a catalyst, ethylene yields a white, tough but flexible waxy sohd, known as Polythene. Polyethylene possesses excellent electric insulation properties and high water resistance it has a low specific gravity and a low softening point (about 110°). The chemical inertness oi Polythene has found application in the manufacture of many items of apparatus for the laboratory. It is a useful lubricant for ground glass connexions, particularly at relatively high temperatures. 

Promoters. Many industrial catalysts contain promoters, commonly chemical promoters. A chemical promoter is used in a small amount and influences the surface chemistry. Alkali metals are often used as chemical promoters, for example, in ammonia synthesis catalysts, ethylene oxide catalysts, and Fischer-Tropsch catalysts (55). They may be used in as Httie as parts per million quantities. The mechanisms of their action are usually not well understood. In contrast, seldom-used textural promoters, also called stmctural promoters, are used in massive amounts and affect the physical properties of the catalyst. These are used in ammonia synthesis catalysts. 

The exothermic reaction occurs at approximately 4 atmospheres and 40-50°C in the presence of EeCls, CuCl2 or SbCls catalysts. Ethylene bromide may also be used as a catalyst. 

The simplest synthetic polymers are those that result when an alkene is treated with a small amount of a radical as catalyst. Ethylene, for example, yields polyethylene, an enormous alkane that may have up to 200,000 monomer units incorporated into a gigantic hydrocarbon chain. Approximately 14 million tons per year of polyethylene is manufactured in the United States alone. 

The catalytic route, however, is simple and clean, although it does produce a small amount of CO2. Using silver, promoted by small amounts of chlorine, as the catalyst, ethylene oxide is formed directly from C2H4 and O2 at a selectivity of around 90%, with about 10% of the ethylene ending up as CO2. Nowadays all production facilities for ethylene oxide use catalysts. 

The kinetics of ethylene hydrogenation on small Pt crystallites has been studied by a number of researchers. The reaction rate is invariant with the size of the metal nanoparticle, and a structure-sensitive reaction according to the classification proposed by Boudart [39]. Hydrogenation of ethylene is directly proportional to the exposed surface area and is utilized as an additional characterization of Cl and NE catalysts. Ethylene hydrogenation reaction rates and kinetic parameters for the Cl catalyst series are summarized in Table 3. The turnover rate is 0.7 s for all particle sizes these rates are lower in some cases than those measured on other types of supported Pt catalysts [40]. The lower activity per surface... 

Using the above preformed catalysts, ethylene can be hydroaminated by primary and secondary amines under much lower pressures (3-55 atm) than those required for the reactions catalyzed by alkali metals (800-1200 atm). The example of N-ethyl-ation of piperidine has been described in full details in Organic Syntheses (Eq. 4.14) [120]. 

The anion vacancy sites have acid properties. As stated above, the catalytic activity and the hydrogenolytic behavior correlated with the acid properties of the catalyst, as well as the extent of reduction. Therefore, the adsorption of an aryl group will occur on the coordinatively unsaturated molybdenum sites generated during reduction. According to the reaction scheme for the hydrogenation of ethylene over a reduced MoOj-AljOj catalyst, ethylene becomes it-bonded at a second vacant ligand position of a coordinatively unsaturated Mo species and inserts to form the [Pg.267]

As a polar solvent for the catalyst ethylene carbonate (EC), propylene carbonate (PC) and acetonitrile were used. Tricyclohexylphosphine, triphenyl-phosphine and the monosulfonated triphenylphosphine (TPPMS) were investigated as ligands with Pd(acac)2 as the precursor. Cyclohexane, dodecane, p-xylene and alcohols (1-octanol, 2-octanol and 1-dodecanol) were tested as non-polar solvents for the product. To determine the distribution of the product and of the catalyst, the palladium precursor and the hgand were dissolved in the polar solvent and twice as much of the non-polar solvent was added. After the addition of 5-lactone, the amounts of the product in both phases was determined by gas chromatography. The product is not soluble in cyclohexane and dodecane, more than 99% of it can be found in the polar catalyst phase. With the alcohols 1-octanol, 2-octanol and dodecanol about 50 to 60% of the 5-lactone are located in the non-polar phase. With p-xylene biphasic systems can only be achieved when EC is used as the polar solvent and even in this solvent system one homogeneous phase is formed at a temperature higher than 70 °C. In a 1 1 mixture of EC and p-xylene about 50 to 60% of the product is contained in the polar phase. 

Several processes based on air or oxygen have been developed.890-895 Oxidation with air (260-280°C) or oxygen (230°C) is carried out at about 15-25 atm at a limited conversion (about 10-15%) to achieve the highest selectivity.896-898 High-purity, sulfur-free ethylene is required to avoid poisoning of the catalyst. Ethylene concentration is about 20-30 vol% or 5 vol% when oxygen or air, respectively, is used as oxidants. The main byproducts are C02 and H20, and a very small amount of acetaldehyde is formed via isomerization of ethylene oxide. Selectivity to ethylene oxide is 65-75% (air process) or 70-80% (02 process).867... 

Direct hydration of ethylene is by far the major route to synthetic ethanol. It is accomplished under pressure at 250-300°C over an acidic catalyst. Ethylene and high temperature steam are mixed and passed over an acidic catalyst, usually phosphoric acid on a support. A modest conversion is achieved even with the severe conditions. Cooling of the exit stream and passage through a separations system give ethylene and water for recycle. Ethanol is made either as a 95 percent azeotrope with water or as an anhydrous material from a drying system. 

The metallocene pre-catalyst, ethylene-bis2-(4-butenyldiisopropylsiloxy)-1 -indenyl) zirconium dichloride, has been prepared. When blended with co-catalyst methyla-lumoxane forming an aluminum/zirconium ratio of 300 1, respectively, the catalytic mixture had very high ethylene polymerization activity. 

Successful examples of selective oxidation catalysis in industry include the conversions of ethylene to ethylene oxide and of methanol to formaldehyde, both on silver catalysts. Ethylene oxide, with an annual worldwide production capacity over 11 million tons, is an important intermediate for the production of glycols (antifreeze agents), ethoxylates (additives in washing powder), cosmetics, polyester fibers, and pharmaceuticals. The partial oxidation of ethylene to ethylene oxide is carried out on silver metal particles supported on o -Al203 or SiC and promoted by alkaline earth or alkali metals. Trace amounts of ethylene dichloride are also fed continuously into the reactor to suppress deep oxidation. Selectivities of about 75-85% are typical nowadays for this process. Formaldehyde, with a production capacity of... 

Explodes on contact with bromine trifluoride chlorine trifluoride fluorine hydrogen peroxide + catalysts acetylene + ethylene. Explodes when heated with calcium carbonate + magnesium 3,4-dichloronitrobenzene + catalysts vegetable oils + catalysts ethylene + nickel catalysts difluorodiazene (above 90°C) 2-nitroanisole (above 250°C/34 bar + 12% catalyst) copper(II) oxide nitryl fluoride (above 200°C) polycarbon mono fluoride (above 500°C). 

Keywords hydrosilylation, catalysts, ethylene, cyclohexene, allyl chloride... 

In the presence of CS the reaction did not begin at 25,40, 50, 60, or 70 °C. At 80 - 85 °C instant catalyst conversion from yellow insoluble salt to brown solution, evidently of a Pt(0) complex, takes place. On this catalyst, ethylene was adsorbed to frill tiiethoxysilane conversion. The catalyst proved to be stable in the presence of ethylene, thus testifying to the combined character of the compound. The next day, when a new portion of triethoxysilane was added to the previous synthesis, the reaction proceeded quantitatively, but a little more slowly (lower platinum concentration). In the absence of ethylene on the next day a black residue of platinum metal precipitated where synthesis did not proceed. 

This reaction is conducted either at 195°C under pressure or at lower temperatures (50-70°C) with sulfuric acid as a catalyst. Ethylene glycol is a dialcohol, or diol, in which two —OH groups are attached to adjacent carbon atoms. Its primary use is as antifreeze to decrease the freezing point of water in automobile radiators. 

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