1-Butyne, hydrogenation over

This review covers the personal view of the authors deduced from the literature starting in the middle of the Nineties with special emphasis on the very last years former examples of structure-sensitive reactions up to this date comprise, for example, the Pd-catalyzed hydrogenation of butyne, butadiene, isoprene [11], aromatic nitro compounds [12], and of acetylene to ethylene [13], In contrast, benzene hydrogenation over Pt catalysts is considered to be structure insensitive [14] the same holds true for acetonitrile hydrogenation over Fe/MgO [15], CO hydrogenation over Pd [16], and benzene hydrogenation over Ni [17]. For earlier reviews on this field we refer to Coq [18], Che and Bennett [9], Bond [7], as well as Ponec and Bond [20]. 

Over zinc oxide it is clear that only a limited number of sites are capable of type I hydrogen adsorption. This adsorption on a Zn—O pair site is rapid with a half-time of less than 1 min hence, it is fast enough so that H2-D2 equilibration (half-time 8 min) can readily occur via type I adsorption. If the active sites were clustered, one might expect the reaction of ethylene with H2-D2 mixtures to yield results similar to those obtained for the corresponding reaction with butyne-2 over palladium That is, despite the clean dideutero addition of deuterium to ethylene, the eth-... 

For 1,3-butadiene hydrogenation, the toxicity of sulfur is 3 (Fig. 13). which is lower than the toxicity for olefin hydrogenation. The hydrogenation of 1-butyne has also been studied for various ratios of sulfur over palladium. As was already published (86), the 1-butyne hydrogenation rate increases with time. The same effect has been observed on sulfided palladium. The turnover number is consequently presented for 1-butyne hydrogenation versus the sulfur content for various 1-butyne conversions (see Fig. 14). During the first minutes of reaction (0-25% conversion), the toxicity of sulfur appears close to 1 the rates are proportional to the free surface. However, at higher conversion, the rate becomes independent from the sulfur ratio. The toxicity is zero. 

The Reppe process is used to make 1,4-1 butanediol from acetylene. In this process, acetylene and formaldehyde are reacted in the presence of a copper-bismuth catalyst. The resulting intermediate, 2-butyne-l,4-diol is hydrogenated over a Raney nickel catalyst ... 

Acetylenes are hydrogenated over many metals, but the most frequently used is Pd, usually on carriers, and then Ni. Other metal catalysts include Pt, Ru, Rh, Ir, Fe, Co, and Os-on-alumina for the vapor phase hydrogenation of 2-butyne to cw-2-butene at 80-150°C . Selectivity of unsupported metals for the conversion of methylacetylene to propene decreases Pd (98%) > Pt (92%) > Rh (87%) > Ni (76%) > R (44%) > Ir (29%), whereas their stereoselectivity to cis-olefins lies between 91-98%. The efficiency of the metal is also dependent on the support charcoal, alumina, BaS04 and, more widely, CaC03 are used. 

Isaeva V, Tkachenko O, Afonina E, Kozlova LM, Gruenert W, Solov eva SE, et al. 2-butyne-l, 4-diol hydrogenation over palladium supported on Ztf+-based — MOE and host—guest MOE/caUx[4]arene materials. Micropor Mesopor Mater 2013 166 167-75. 

A unique mechanism was suggested to interpret the difference observed in the isomerization and hydrogenation of 1-butene and ds-2-butene over a stepped Pt(775) surface.360 It was observed that the hydrogenation rates were insensitive to surface structure for both 1-butene and ds-2-butene. The isomerization rates of cis-2-butene to give only trans-2-butene on the stepped Pt(775) surface, however, was double that of 1-butene to yield both cis- and trans-2-butenes. The Horiuti-Polanyi associative mechanism, that is, the involvement of the 2-butyl intermediate (see Section 4.3.2), cannot explain this difference. However, a facile dehydrogenation of ds-2-butene to 2-butyne followed by a rehydrogenation is consistent with the experimental observations ... 

A major drawback of alkene metathesis is lack of control over the stereochemistry of the newly formed double bond. For unstrained systems, E/Z ratios are virtually unpredictable. Alkyne metathesis, on the other hand, can always be combined with subsequent Lindlar hydrogenation, thereby giving access to stereochemically pure 2-olefins. In 1998, Ftirstner and Seidel were the first to report a ring-closing alkyne metathesis [7]. Under high-dilution conditions (0.02 m) and reduced pressure (20 mbar, removal of 2-butyne, solvent 1,2,4-trichlorobenzene (b.p. 214 °C)) the Schrock catalyst was applied to assemble macrocydic... 

The hydrogenation of 2-butyne has been studied over the other metals of Group VIII and over copper (84, 95) using a static system and alumina-supported catalysts in the temperature range 100 to 200°. Under these conditions more complex distributions of products have been observed than was the case for palladium at room temperature. 

Initial Butene Distributions and Selectivities Obtained in the Hydrogenation of 2-Butyne over Some Alumina-Supported... 

The selective catalytic hydrogenation of 2-butyne-l,4-diol to ciJ-2-butene-l,4-diol over palladiiun represents a common situation involving a multifimctional conpound. Fortunately, the reduction of triple bonds is very selective over palladium [1,2]. Butenediol is an important chemical intermediate due to its use in the production of several insecticides and pharmaceuticals (i.e. endosulfan and vitamin B6). The use of supported palladium [3-8], Raney nickel [9] or nickel [10] catalyst has been reported for this reaction under relatively mild operating conditions. However, due to the possibility of several side reactions [3-4], the problem of selectivity towards c/r-butenediol becomes important. Over Pd/C, it was reported... 

L. Kiwi-Minsker, E. Joannet, A. Renken, Solvent-free selective hydrogenation of 2-butyne-l,4-diol over structured Pd-catalyst, Ind. Eng. Chem. Res. 44 (2005) 6148. 

M. Crespo-Quesada, M. Grasemann, N. Semagina, A. Renken, L. Kiwi-Minsker, Kinetics of the solvent-free hydrogenation of 2-methyl-3-butyn-2-ol over a structured Pd-based catalyst, Catal. Today 147 (2009) 247. 

The catalyst particles were 0.3 x 0.3-cm cylinders, 10% Ni on alumina. Surface area was 30m /g, and the diffusivity of hydrogen within the catalyst at 25 °C was 0.07cm /s. Is there evidence that diffusion was important Assume Knudsen diffusion in the catalyst pore structure. The rate of addition of deuterium to 2-butyne at 25 °C over a 0.03% Pd/ AI2O3 catalyst was reported to be 0.11 gmol/h-cm3 (catalyst). Experimental conditions were feed, D2 saturated with 2-butyne nt 25 °C catalyst dimension, 40 mesh D ff 0.15 of the bulk diffusivity of 2-butyne in hydrogen at 25 °C. Was intraparticle diffusion important in this experiment Note Persevere in obtaining all the exact numbers you need to do this calculation. They come from various sources, and it takes some time. After all, this is real life). 

TABLE 9.8. Product Distributions from the Hydrogenation of 2-Butyne over Alumina-Supported Metals, and Certain Activation Energies... 

As an illustration, when a gaseous mixture of 2-butyne and deuterium is passed over a palladium catalyst at 14 C, the composition of the hydrocarbon fraction in the product is as shown in Table 5.2.1. In this example, Ai is2-butyne, A2 is j-2-butene-2,3-d2 and Aj is butane. The selectivity to butene is 99.9%. The stereoselectivity to cw-2-butene is 99%. The quantitative yield of butene is due to the occupancy of the surface by butyne. As long as there remains in the system enough unconverted butyne, butene has no access to the surface for its further hydrogenation to butane. Yet, all the butene will be hydrogenated readily to butane in the absence of butyne. 

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