Palladium catalysts ethylene hydrogenation

Until 1958 no ethylene plant had used a tail-end palladium catalyst to hydrogenate all of the acetylene formed in the steam cracker. This was an attractive possibility, however, and many of the large new US plants built in the 1960s were designed in this way. The less efficient front-end nickel and iron catalysts were soon obsolete. Several significant changes followed the use of tail-end catalysts ... 

A similar reaction was studied by Kowaka Jfi) who investigated the catalytic activity of palladium and its alloys with silver in the hydrogenation of ethylene. The author alluded to the poisoning effect of hydrogen pretreatment of the palladium catalyst. 

Quite recently Yasumori el al. (43) have reported the results of their studies on the effect that adsorbed acetylene had on the reaction of ethylene hydrogenation on a palladium catalyst. The catalyst was in the form of foil, and the reaction was carried out at 0°C with a hydrogen pressure of 10 mm Hg. The velocity of the reaction studied was high and no poisoning effect was observed, though under the conditions of the experiment the hydride formation could not be excluded. The obstacles for this reaction to proceed could be particularly great, especially where the catalyst is a metal present in a massive form (as foil, wire etc.). The internal strains... 

The demethanizer, deethanizer, and debutanizer are fractionating columns that separate the lighter and heavier compounds from each other. Traces of triple bonds are removed by catalytic hydrogenation with a palladium catalyst in both the C2 and C3 stream. Cumulated double bonds are also hydrogenated in the C3 fraction. These are more reactive in hydrogenation than ethylene or propylene. The C2 and C3 splitters (Fig. 8.4) are distillation columns that can be as high as 200 ft. The mechanism of cracking was previously discussed in Chapter 7, Section 6. 

A stereospecific synthesis for cw-3-hexen-l-ol starts with the ethylation of sodium acetylide to 1 -butyne, which is reacted with ethylene oxide to give 3-hexyn-l-ol. Selective hydrogenation of the triple bond in the presence of palladium catalysts yields cw-3-hexen-l-ol. Biotechnological processes have been developed for its synthesis as a natural flavor compound, e.g., [12]. 

The co-existence of at least two modes of ethylene adsorption has been clearly demonstrated in studies of 14C-ethylene adsorption on nickel films [62] and various alumina- and silica-supported metals [53,63—65] at ambient temperature and above. When 14C-ethylene is adsorbed on to alumina-supported palladium, platinum, ruthenium, rhodium, nickel and iridium catalysts [63], it is observed that only a fraction of the initially adsorbed ethylene can be removed by molecular exchange with non-radioactive ethylene, by evacuation or during the subsequent hydrogenation of ethylene—hydrogen mixtures (Fig. 6). While the adsorptive capacity of the catalysts decreases in the order Ni > Rh > Ru > Ir > Pt > Pd, the percentage of the initially adsorbed ethylene retained by the surface which was the same for each of the processes, decreased in the order... 

There have been used essentially only three catalysts foi the hydrogenation of ethylene oxides nickel, palladium on charcoal, and platinum black. Solvent normally employed include ethanol wait nickel, and ethanol, ethyl acetate, or acetic acid with the other. Reduction over platinum or palladium catalysts is usually conducted at room temperature and low pressure, whereas nickel catalysth Imvi-been employed in autoclaves at temperatures ranging from 3fT to nearly 200° and high pressures. For excellent general discussions ol catalytic redaction any of several outstanding sources14" 11-ltni m.i> be consulted. 

A.F.Y. Al-Shammary, I T. Caga, J.M. Winterbottom, A.Y. Tate and I.R. Harris, Palladium-Based Diffusion Membranes as Catalysts in Ethylene Hydrogenation , J. Chem. Tech. Biotech., 52 571-85 (1991). 

The product of interest is ethylene and this is contaminated with ethane and acetylene. The most common practice is for acetylene to be selectively hydrogenated to ethylene using supported palladium catalysts ... 

Fully saturated SBC polymers have also been investigated. Vinylcyclohex-ane-ethylene/propylene-vinylcyclohexane triblock copolymers have been prepared by complete hydrogenation of SIS polymers using a supported palladium catalyst [53]. Under the appropriate conditions, hydrogenation of the styrene blocks can also be accomplished using Ziegler-type catalysts [54]. 

McGowan WT, KembaU C, Whan DA, ScurreU MS (1977) Hydrogenation of acetylene in excess ethylene on an alumina supported palladium catalyst in static system. J Chem Soc Faraday Trans 73 632... 

Menshikov WA, Falkovitsch JG, Aerov ME (1975) Hydrogenation kinetics of acetylene on a palladium catalyst in the presence of ethylene. Kinet Catal 16 1538... 

Borodzinski A (1997) A, Golebiowski, Surface heterogeneity of supported palladium catalyst for the hydrogenation of acetylene-ethylene mixtures. Langmuir 13 883... 

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