Buta-1:2-diene, hydrogenation

Fig. 34. Mechanisms for buta-1 2-diene hydrogenation operative over Types A and B nickel catalysts [207]. (Numbers refer to species in Fig. 33.)...

Copper-nickel alloy films similarly deposited at high substrate temperatures and annealed in either hydrogen or deuterium were used to study the hydrogenation of buta-1,3-diene (119) and the exchange of cyclopentane with deuterium (120). Rates of buta-1,3-diene hydrogenation as a function of alloy composition resemble the pattern for butene-1 hy-... 

TABLE 3. Product distribution in hydrogen chloride addition to halogeno-substituted 1,3-buta-dienes, R1CH=CR2-CR3=CH2... 

Bond Thompson mechanistic proposal, 46 bridges, 6 bromide, 185 brookite, 56, 68 Bmst method, 93 Bronsted acidic site, 77 Brpnsted acid sites, 144 buta-1,3-diene hydrogenation, 283... 

Perbenzoic acid fcrf-butjl ester (51) is the source — under copper I) bromide catalysis —of a benzoate anion (52) and radical 53. Radical 53 subsequently abstracts a hydrogen atom selective ) from the 11 -position of 55 in a homolytic bond cleavage to give a buta diene system with opening of the cyclopropane ring.Jn... 

Application To produce polymer-grade ethylene and propylene, a buta-diene-rlch cut, an aromatic C -Cg rich-raw pyrolysis gasoline and high-purity hydrogen by using the T-PAR process for gas separation and product purification from raw cracked gas. 

Tables I, II, and III show the effect of the neutral surfactant Brij 35 (Ci2H25(OCH2CH2)230H, Concentration = 5.0 X 10 M) on the hydrogenation of three dienes at various CN Co ratios (11). Rate accelerations measured by hydrogen uptake were moderate, less than twofold. For isoprene (Table I), the micelles favor the production of 2-methyl-2-butene, making the reaction virtually regiospecific. For 2,3-dimethyl-l,3-buta-diene (Table II), the micelles favor production of 2,3-dimethyl-1-butene.

Elastomeric styrene containing compounds, such as styrene-buta-diene-styrene block copol mriers, or styrene-isoprene-styrene block copolymers, including its hydrogenated homologues, all of them containing vegetal or even mineral oils in their formulations, can be made biodegradable (13). This is achieved by the admixture of brewer s yeast or yeast mother in amounts of 1-4%. 

Styrene-hydrogenated butadiene-styrene styrene-ethylene-buta-diene-styrene) terpolymers offer a further level of sophistication in terms of bulk compounds added to engineering plastics. Commercially available functionalized versions of these can be used either pure or in combination with their precursors for effective toughening of several engineering resins. 

The latter is reacted with hydrogen chloride to give 4-chloro-l, 2-butadiene which rearranges in the presence of Cu2Cl2-containing catalyst to give the 2-chloro-l,3-buta-diene. 

Fig. 3.24 Catalytic activities of ZrOj pretreated at different temperatures. O. hydrogenation of 1,3-butadiene with Hjl %, Hj—Dj exchange A, hydrogenation of 1,3-buta-diene with cyclohexadiene.

Scheme 11.4 Products of HBr addition to buta-1,2-diene (lb) in the gas phase (top), preferred site of hydrogen atom trapping of 2-bromobutenyl radical 7b (center) and isomerization of methylallyl radical (Z)-8 (bottom) [13, 37, 38].

Buta-1,3-diene (BD) hydrogenation is a widely used model reaction to investigate surface modification by promoters or alloy formation.The reaction is usually described as a consecutive mechanism " without direct hydrogenation of buta-1, 3-diene to butane (BA). ... 

S. Verdier, B. Didillon, S. Morin, and D. Uzio, PdSn/Al203 catalysts from colloidal oxide synthesis II. Surface characterization and catalytic properties for buta-1,3-diene selective hydrogenation, J. Catal. 218, 288-295 (2003). 

Aluminum amalgam in wet tetrahydrofuran reduced cumulene 1,1,4,4-tetraphenylbutatriene to 1,1,4,4-buta-1,2-diene, which on hydrogenation over Raney nickel was converted to 1,1,4,4-tetraphenylbutane [14S]. 

Buta-1 3-diene h2 n-Butenes n-Butane Selective hydrogenation... 

The second approach is that developed to interpret the products of the reactions of octalins with deuterium [144] and is equally applicable to the reactions of mono- or di-unsaturated hydrocarbons with deuterium. Smith and Burwell [144] pointed out that, whereas the experimental deuterohydrocarbon distributions are obtained in terms of the number of deuterium atoms in the product hydrocarbon, the quantities of fundamental importance to the discussion of the mechanisms of catalytic reactions are the fractions of the hydrocarbon sample which have equilibrated with the surface deuterium—hydrogen pool. Thus, for example, in the reaction of buta-1 3-diene with deuterium, the product butenes consist of a series of species, butene-(/i, d)2, -(h, d)3,..., -(h, d)n in which 2,3. .., n positions... 

Nn, and to the ratio a/b such that the calculated deuterium distribution, derived from the IV-profile, is in good agreement with the experimentally observed distribution. This method has been used by Wells and co-workers [166,167] to interpret the deuterobutene distributions observed in the catalysed hydrogenation of buta-1 3-diene (see Sect. 4.9). 

With palladium—alumina, the products of the reaction of but-l-yne with deuterium [189] were but-l-ene, 99.1% frans-but-2-ene, 0.2% cis-but-2-ene, 0.2% n-butane, 0.5%, until at least 75% of the but-l-yne had reacted. But-l-ene hydrogenation and hydroisomerisation were observed to occur when all the but-l-yne had reacted. The formation of but-2-ene as an initial product was postulated as being the result of a slow isomerisation of but-l-yne to absorbed buta-1 2-diene... 

Over all the metals studied, except cobalt, nickel and copper, the selectivity and stereoselectivity decreased slightly as the reaction proceeded. In addition to the products shown in Table 20, in the rhodium- and iridium-catalysed reactions small yields (2—3%) of buta-1 2-diene were also observed. For all the catalysts, except rhodium, iridium and platinum, which were not investigated, the initial rate kinetic orders were unity in hydrogen and zero or slightly negative (Ni) in but-2-yne. 

The formation of but-2-ene and the more highly deuterated cis- and frans-but-2-enes (-d3 and above) were considered to arise from the hydrogenation of adsorbed buta-1 2-diene formed by isomerisation of but-... 

The hydrogenation of buta-1 2-diene appears to have received relatively little attention. Over palladium—alumina at room temperature, the products of the gas phase hydrogenation were c/s-but-2-ene, 52% but-l-ene, 40% frans-but-2-ene, 7% and n-butane, 1% [189]. Some isomerisation of the buta-1 2-diene to but-2-yne (10%) together with traces of but-l-yne and buta-1 3-diene was also observed. A similar butene distribution (namely, cis-but-2-ene 52%, but-l-ene 45% and frans-but-2-ene 3%) was observed in the liquid phase hydrogenation over palladium [186]. 

---