Ethane ethylene hydrogenation

Reactive characterization involves the use of simple test reactions to determine the patterns of activity of catalysts. For this study ethylene hydrogenation, ethane hydrogenolysis, and methanation have been chosen. Each of these model reactions tests a certain reactive functionality (simple olefin hydrogenation, C-C bond cleavage, and CO reduction, respectively), is simple to run, and primarily yields a single product. Also, there is substantial data in the literature for the activity of conventional catalysts. 

Carbon dioxide Carbon monoxide Chlorine Ethane Ethylene Hydrogen ... 

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... 

Diol Components. Ethylene glycol (ethane 1,2-diol) is made from ethylene by direct air oxidation to ethylene oxide and ring opening with water to give 1,2-diol (40) (see Glycols). Butane-1,4-diol is stiU made by the Reppe process acetylene reacts with formaldehyde in the presence of catalyst to give 2-butyne-l,4-diol which is hydrogenated to butanediol (see Acetylene-DERIVED chemicals). The ethynylation step depends on a special cuprous... 

Oxychlorination reactor feed purity can also contribute to by-product formation, although the problem usually is only with low levels of acetylene which are normally present in HCl from the EDC cracking process. Since any acetylene fed to the oxychlorination reactor will be converted to highly chlorinated C2 by-products, selective hydrogenation of this acetylene to ethylene and ethane is widely used as a preventive measure (78,98—102). 

A selective poison is one that binds to the catalyst surface in such a way that it blocks the catalytic sites for one kind of reaction but not those for another. Selective poisons are used to control the selectivity of a catalyst. For example, nickel catalysts supported on alumina are used for selective removal of acetjiene impurities in olefin streams (58). The catalyst is treated with a continuous feed stream containing sulfur to poison it to an exacdy controlled degree that does not affect the activity for conversion of acetylene to ethylene but does poison the activity for ethylene hydrogenation to ethane. Thus the acetylene is removed and the valuable olefin is not converted. 

Since both complete hydrogenation of acetylene or any hydrogenation of the ethylene results in the production of a less valuable product such as ethane, conditions must be chosen carefiiUy and a catalyst must be used that is both sufficiently active for acetylene hydrogenation and extremely selective to avoid ethylene hydrogenation. Since hydrogenation of acetylenic bonds proceeds stepwise and since acetylene is more strongly adsorbed on the catalytic... 

The increasing ranges of pressure and temperature of interest to technology for an ever-increasing number of substances would necessitate additional tables in this subsection as well as in the subsec tion Thermodynamic Properties. Space restrictions preclude this. Hence, in the present revision, an attempt was made to update the fluid-compressibihty tables for selected fluids and to omit tables for other fluids. The reader is thus referred to the fourth edition for tables on miscellaneous gases at 0°C, acetylene, ammonia, ethane, ethylene, hydrogen-nitrogen mixtures, and methyl chloride. The reader is also... 

The depropanizer overhead, Cj and lighter feed is compressed to about 300 psi and then passed over a fixed bed of acetylene removal catalyst, generally palladium on alumina. Because of the very large amount of hydrogen contained in this stream, the operating conditions are critical to selectively hydrogenate the acetylene without degrading the valuable ethylene to ethane. 

The simplest paraffin (alkane) and the most widely used feedstock for producing ethylene is ethane. As mentioned earlier, ethane is obtained from natural gas liquids. Cracking ethane can be visualized as a free radical dehydrogenation reaction, where hydrogen is a coproduct ... 

A typical ethane cracker has several identical pyrolysis furnaces in which fresh ethane feed and recycled ethane are cracked with steam as a diluent. Figure 3-12 is a block diagram for ethylene from ethane. The outlet temperature is usually in the 800°C range. The furnace effluent is quenched in a heat exchanger and further cooled by direct contact in a water quench tower where steam is condensed and recycled to the pyrolysis furnace. After the cracked gas is treated to remove acid gases, hydrogen and methane are separated from the pyrolysis products in the demethanizer. The effluent is then treated to remove acetylene, and ethylene is separated from ethane and heavier in the ethylene fractionator. The bottom fraction is separated in the deethanizer into ethane and fraction. Ethane is then recycled to the pyrolysis furnace. 

However, it was found that the effect on the equilibrium formation of aromatics is not substantial due to thermodynamic considerations. A more favorable effect was found for the reaction between ethylene (formed via cracking during aromatization of propane) and hydrogen. The reverse shift reaction consumes hydrogen and decreases the chances for the reduction of ethylene to ethane byproduct. 

Fig. 2. Pressure fall —AP (Torr) against time t (arbitrary units) in hydrogenation of acetylene on Pt/AhOa catalyst at 110°C and Pst/Pctnt 2. In the initial slow period of the reaction the main product is ethylene, and after the acceleration, further hydrogenation of ethylene to ethane predominates. From G. C. Bond and P. B. Wells, J. CaM. 4, 211 (1965).

The above described experiments over atomically clean single crystal catalysts have been extended to studies of the kinetics of various catalytic reactions over chemically modified catalysts. Examples are recent studies Into the nature of poisoning by sulfur of the catalytic activity of nickel, ruthenium, and rhodium toward methana-tlon of CO (11,12) and CO2 (15). ethane (12) and cyclopropane (20) hydrogenolysls, and ethylene hydrogenation (21). 

We could account for our result by the same mechanism, if the Cp2NbH3-derived system also contains (or generates) a species capable of catalyzing the hydrogenation of ethylene to ethane. 

In the case of ethylene hydrogenation, the mechanism proposed by Parshall [61] involves the coordination of an alkene molecule through a five-coordinate intermediate (Eq. (13)) the subsequent alkene insertion into the Pt-H bond (Eq. (14)) and intervention of a second molecule of H2 (Eq. (15)) leads to the elimination of ethane and restoration of the catalytic active species [PtH(SnCl3)]2. However, in 1976 Yasumori and coworkers reported a kinetic analysis conducted on the hydrogenation of ethylene catalyzed by the Pt-Sn complex [(Me)4N]3[Pt(SnCl3)5] [70], under much milder conditions than those... 

More recently the flash photolysis of diethyl mercury has been re-investigated by Fischer and Mains92. At 1.54 torr and 24 °C the major products are butane (36 %), ethylene (32 %), ethane (22 %), propane (6 %) and hydrogen (4 %). Only traces of methane were detected. The addition of perfluorodimethylcyclo-butane vapour did not alter the extent of photolysis, but the butane yield increased approximately 25 % while the yield of ethylene, ethane, hydrogen and propane all decreased. The change in product distribution occurred as the inert gas pres-... 

Platinum metal is used as a heterogeneous catalyst for the hydrogenation of gaseous ethylene to ethane. 

Hydrogenation of Ethylene to Ethane Porous AI2O3 membranes... 

Downstream of the compressor is a series of fractionators (generally the tallest towers in an ethylene plant) which separate the methane and hydrogen, the ethylene, the ethane, and the propane and heavier. All are heavy metallurgy to handle the pressures and insulated to maintain the low temperatures. There s also an acetylene hydrogenator or converter in there. Trace (very small) amounts of acetylene in ethylene can really clobber some of the ethylene derivative processes, particularly polyethylene manufacture. So the stream is treated with hydrogen over a catalyst to convert the little acetylene present into ethylene. 

Titanium dioxide suspended in an aqueous solution and irradiated with UV light X = 365 nm) converted benzene to carbon dioxide at a significant rate (Matthews, 1986). Irradiation of benzene in an aqueous solution yields mucondialdehyde. Photolysis of benzene vapor at 1849-2000 A yields ethylene, hydrogen, methane, ethane, toluene, and a polymer resembling cuprene. Other photolysis products reported under different conditions include fulvene, acetylene, substituted trienes (Howard, 1990), phenol, 2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol, 2,6-dinitro-phenol, nitrobenzene, formic acid, and peroxyacetyl nitrate (Calvert and Pitts, 1966). Under atmospheric conditions, the gas-phase reaction with OH radicals and nitrogen oxides resulted in the formation of phenol and nitrobenzene (Atkinson, 1990). Schwarz and Wasik (1976) reported a fluorescence quantum yield of 5.3 x 10" for benzene in water. 

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