Ethylene reduction

Arnold WA, Roberts AL. Development of a quantitative model for chlorinated ethylene reduction by zero-valent metals. 213th National Meeting, San Francisco, CA, American Chemical Society 1997 37(l) 76-77. 

Fig. 4. Potential-current density curves for some electrogenerative and fuel cell reactions (O) benzene reduction on Pt (4S) (A) vinyl chloride reduction on Pt (31) (A) ethylene reduction on Pt (25) ( ) ethylene reduction on Pd (48a) (O) oxygen reduction on Pt (49). (Reprinted by permission of the publisher, The Electrochemical Society, Inc.)...

Similarly, the difficulty for electrocatalytic, electrogenerative hydrogenation of alkenes on platinum parallels the strength of gas phase adsorption of the substrate (55) acetylene > ethylene > propylene > cyclopropane. Palladium is a more active electrocatalyst for ethylene reduction than platinum (55), in agreement with adsorption strength on each metal. Selectivity and reduction rate of substituted alkenes also depends on adsorption... 

Campbell TJ, Burris DR, Roberts AL, Wells JR. (1997). Trichloroethylene and tetrachloro-ethylene reduction in a metallic iron-water-vapor batch system. Environmental Toxicology and Chemistry 16(4) 625-630. 

Lt-Dpm)2Rh2(CO)2 is a catalyst for the reduction of acetylene to ethane by dihydrogen. The rate of acetylene reduction exceeds that of ethylene reduction and no cyclotrimerization of acetylene is observed. Treatment of (/x-dpm)2Rh2(CO)2 with carbon monoxide and NaBH(OMe)3... 

Motoo and Furuya[139, 140] demonstrated an enhancement of the ethylene reduction on Pt by Cu and Ag and inhibition by Se and Tl adlayers. Cu and Ag adatoms, which block one Pt site, desorb the ethylene molecule that blocks 2.5 Pt sites, thus leaving 1.5 sites available for H adsorption. Hydrogen adatoms at these sites facilitate a higher rate of ethylene reduction. Tl and Se adatoms cause inhibition since they block 2.5 sites as ethylene does. 

Scheme 12 Two different possible routes for ethylene reduction/activation of silica-supported chromates (le, 2e) embedded in six-membered chromasiloxane rings (Wue). In the absence of coordinated siloxane ligands, the bis(ethylene) complex 7e is transformed readily to the polymerization-inactive chromacyclopentane 8e [120], while a non-displaceable siloxane ligand in the monofethylene) complex 9e prevents metallacycle formation and therefore opens an alternate, as-yet unknown, path to a monoalkylchromivim(III) site capable of polymerizing ethylene. Additional siloxane, ethylene monomer and subsequent formed txmds are shown in red...

Pol5miers containing a R2Si-CH2CH2 repeat unit can be prepared by the hydrosilylation reaction of the difimctional monomer [CH=CH2SiH2Cl]. This leads to the formation of poly [(dichlorosilylene)ethylene]. Reduction of this polymer with lithiumaluminumhydride affords poly(silyleneethylene),[H2SiCH2CH2]n (Fig. 7.33) [104]. 

In this sequence, ethylene reduction of RhCls gives the initial rhodium(I) complex. The addition step may involve transient formation of an Rh—H bond By protonation of the rhodium or can occur by direct protonation of a coordinated ethylene. The solvent-promoted insertion resembles the base-assisted carbonyl insertion in CH3Mn(CO)5 (Section Elimination... 

One of the main advantages of the stochastic dynamics methods is that dramatic tirn savings can he achieved, which enables much longer stimulations to he performed. Fc example, Widmalm and Pastor performed 1 ns molecular dynamics and stochastic dynamic simulations of an ethylene glycol molecule in aqueous solution of the solute and 259 vvatc jnolecules [Widmalm and Pastor 1992]. The molecular dynamics simulation require 300 hours whereas the stochastic dynamics simulation of the solute alone required ju 24 minutes. The dramatic reduction in time for the stochastic dynamics calculation is du not only to the very much smaller number of molecules present hut also to the fact the longer time steps can often he used in stochastic dynamics simulations. 

Reduction of the ethylenic compound gives a ketone, propiophenone (III), with one more methylene group than the ketone used in the original preparation ... 

Thus ethylene is oxidized continuously through a series of oxidation—reduction reactions (87,88). The overall reaction is... 

RocketPropella.nts, Liquid propellants have long been used to obtain maximum controUabiUty of rocket performance and, where required, maximum impulse. Three classes of rocket monopropellants exist that differ ia the chemical reactions that release energy (/) those consisting of, eg, hydrogen peroxide, ethylene oxide, C2H4O and nitroethane, CH2CH2NO2 that can undergo internal oxidation—reduction reactions (2) those... 

Manufacture. The manufacture of 1,4-cyclohexanedimethanol can be accompHshed by the catalytic reduction under pressure of dimethyl terephthalate ia a methanol solution (47,65). This glycol also may be prepared by the depolymerization and catalytic reduction of linear polyesters that have alkylene terephthalates as primary constituents. Poly(ethylene terephthalate) may be hydrogenated ia the presence of methanol under pressure and heat to give good yields of the glycol (see Polyesters) (66,67). 

The metals are impregnated together or separately from soluble species, eg, Na2PdCl4 and HAuCl or acetates (159), and are fixed by drying or precipitation prior to reduction. In some instances sodium or potassium acetate is added as a promoter (160). The reaction of acetic acid, ethylene, and oxygen over these catalysts at ca 180°C and 618—791 kPa (75—100 psig) results in the formation of vinyl acetate with 92—94% selectivity the only other... 

Hydrogenation. Acetylene can be hydrogenated to ethylene and ethane. The reduction of acetylene occurs in an ammoniacal solution of chromous chloride (20) or in a solution of chromous salts in H2SO4 (20). The selective catalytic hydrogenation of acetylene to ethylene, which proceeds... 

The economics of the arc-coal process is sensitive to the electric power consumed to produce a kilogram of acetylene. Early plant economic assessments indicated that the arc power consumption (SER = kwh/kgC2H2) must be below 13.2. The coal feedcoal quench experiments yielded a 9.0 SER with data that indicated a further reduction to below 6.0 with certain process improvements. In the propane quench experiment, ethylene as well as acetylene is produced. The combined process SER was 6.2 with a C2H2/C2H4 production ratio of 3 to 2. Economic analysis was completed uti1i2ing the achieved acetylene yields, and an acetylene price approximately 35% lower than the price of ethylene was projected. 

Content of Ot-Olefin. An increase in the a-olefin content of a copolymer results in a decrease of both crystallinity and density, accompanied by a significant reduction of the polymer mechanical modulus (stiffness). Eor example, the modulus values of ethylene—1-butene copolymers with a nonuniform compositional distribution decrease as shown in Table 2 (6). A similar dependence exists for ethylene—1-octene copolymers with uniform branching distribution (7), even though all such materials are, in general, much more elastic (see Table 2). An increase in the a-olefin content in the copolymers also results in a decrease of their tensile strength but a small increase in the elongation at break (8). These two dependencies, however, are not as pronounced as that for the resin modulus. 

The presence of inorganic salts in solutions of poly(ethylene oxide) also can reduce the hydrodynamic volume of the polymer, with attendant reduction in intrinsic viscosity this effect is shown in Figure 7. 

Hydroxypyrroles. Pyrroles with nitrogen-substituted side chains containing hydroxyl groups are best prepared by the Paal-Knorr cyclization. Pyrroles with hydroxyl groups on carbon side chains can be made by reduction of the appropriate carbonyl compound with hydrides, by Grignard synthesis, or by iasertion of ethylene oxide or formaldehyde. For example, pyrrole plus formaldehyde gives 2-hydroxymethylpyrrole [27472-36-2] (24). The hydroxymethylpyrroles do not act as normal primary alcohols because of resonance stabilization of carbonium ions formed by loss of water. 

Catalysts. Silver and silver compounds are widely used in research and industry as catalysts for oxidation, reduction, and polymerization reactions. Silver nitrate has been reported as a catalyst for the preparation of propylene oxide (qv) from propylene (qv) (58), and silver acetate has been reported as being a suitable catalyst for the production of ethylene oxide (qv) from ethylene (qv) (59). The solubiUty of silver perchlorate in organic solvents makes it a possible catalyst for polymerization reactions, such as the production of butyl acrylate polymers in dimethylformamide (60) or the polymerization of methacrylamide (61). Similarly, the solubiUty of silver tetrafiuoroborate in organic solvents has enhanced its use in the synthesis of 3-pyrrolines by the cyclization of aHenic amines (62). 

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