Olefins selective

Carboxylation/Oxidation of Straight-Chain 1-Olefins. Selective carboxylation of a-olefins to predominately straight-chain aldehydes is realized through specific catalyst systems and by careful control of reaction conditions. The aldehyde produced is then air-oxidized to the acid using a Mn catalyst. Heptanoic acid [111-14-8] and pelargonic acid [112-05-0] are produced commercially in this manner. 

While the dehydrohalogenation of 3-halo-5a-steroids gives the A -olefin selectively, it has been shown that in the 5j5-series dehydrochlorination of 3j5-chloro compounds with quinoline gives a mixture of A - and A -olefins in a 45 55 ratio. 

The complex Ni[(S2C2(CF3)2)]2 (392) is able to bind light olefins selectively and reversibly.1081 According to Scheme 4, the reaction of olefins with (392) can be controlled electrochemically, where the oxidation state-dependent binding and release of olefins is fast on the electrochemical timescale. Olefin binding is supposed to occur via the ligand S-donors. 

It is found that addition of Cu in high K content iron catalyst (100Fe/4.6Si/5.0K/2.0Cu) results in an increase in C02 selectivity compared to catalysts without Cu (100Fe/5.1Si/5.0K) at a similar CO conversion level. Promotion by Cu in high K content catalysts also enhances the olefin selectivity (higher olefin ratio of 100Fe/4.6Si/5.0K/2.0Cu in comparison with 100Fe/5.1Si/5.0K ... 

FIGURE 9.16 Olefin contents in carbon number fractions primary and secondary olefin selectivity. 

Traditionally, iron-based catalysts have been used for FT synthesis when the syngas is coal derived, because of their activity in both FTS and WGS reactions. Complex mixtures of straight-chain paraffins, olefins, and oxygenate (in substantial proportions) compounds are known to be formed during iron-based FTS. Olefin selectivity of iron catalysts is typically greater than 50% of the hydrocarbon products at low carbon numbers, and more than 60% of the produced olefins are a-olefins.13 For iron-based catalysts, the olefin selectivity decreases asymptotically with increasing carbon number. 

The developed model allows the simultaneous prediction of both the reactants conversion and n-paraffins and a-olefins selectivity from C, to C49 as a function of process conditions. 

C35H72, C45H92, C5+, and olefins selectivity. Extradiagonal terms in the correlation matrix were lower than 0.9 in over 80% of the cases. 

Iodolactonization of anti,syn-1 could result in four iodolactones, two resulting from face selectivity, and two resulting from diastereotopic olefin selectivity. In practice only three lactones are formed in a 142 4.7 1 ratio, with 4 being essentially the only product. In fact this kinetic iodolactonization proceeds with 147 1 olefin selectivity and 30 1 face selectivity, considerably higher than the selectivity observed in previous iodolactonization of 3-methyl-4-pentenoic acid (8, 257). Lac-tonization of 1 also shows cis-C4,C5 selectivity. 

The effect of the Si/Al ratio of H-ZSM5 zeolite-based catalysts on surface acidity and on selectivity in the transformation of methanol into hydrocarbons has been studied using adsorption microcalorimetry of ammonia and tert-butylamine. The observed increase in light olefins selectivity and decrease in methanol conversion with increasing Si/Al ratio was explained by a decrease in total acidity [237]. 

It is necessary, however, to maximize the intermediate olefin product at the expense of the aromatic/paraffin product which makes up the gasoline ( ). The olefin yield increases with increasing temperature and decreasing pressure and contact time. Judicious selection of process conditions result in high olefin selectivity and complete methanol conversion. The detailed effect of temperature, pressure, space velocity and catalyst silica/alumina ratio on conversion and selectivity has been reported earlier ( ). The distribution of products from a typical MTO experiment is compared to MTG in Figure 4. Propylene is the most abundant species produced at MTO conditions and greatly exceeds its equilibrium value as seen in the table below for 482 C. It is apparently the product of autocatalytic reaction (7) between ethylene and methanol (8). 

Hembre et al disclosed a process for which one olefin selected from certain ot,p-dihydroxyalkenes and 4-(alkenyl)ethylenecarbonates was reacted with a second olefin to produce a metathesis product. When the first olefin reactant... 

Initially Mn was discovered to lower the methane selectivity and increase the olefin selectivity. More specifically, it was reported by Kolbel and Tillmetz that more than 50% Mn the remainder being Fe or by Bussemeir et about equal parts of Fe and Mn led to these beneficial F-T effects. In contrast to these results, van Dijk et did not find any changes in the product formation when adding manganese oxide to an Fe F-T catalyst, although this work had been performed at atmospheric pressures, whereas the work of Kolbel and Tillmetz and Bussemeier was done at conditions close to industrial ones. 

One important application of selective hydrogenation of alkynes is their removal from the industrial steam cracker products. These can contain several percents of alkynes as byproducts. They are particularly unwelcome in that they poison the catalysts used for the downstream polymerization of the olefins. Selective hydrogenation of these steam cracker cuts has two advantages. It removes acetylenes and converts them to desired alkenes, thereby increasing the overall yields (see Section 11.6.1). 

Because the unsaturated nitrile does not react with osmium tetroxide as rapidly as a simple A17(20)-olefin, selectivity between other unsaturated centers is difficult to achieve. 

Table VI shows that regardless of the starting isomeric olefin, selectivity is lower with Co2(CO)8 than with rhodium this is especially true when the starting isomer is conjugated. Moreover, when hydroformylation is done with Co2(CO)8, two aromatic ring effects are observed ...

BROWN, HERBET C. (1912-). An English-born chemist who was the recipient of the Nobel prize for chemistry with Wuug. Georg in 1979. Via his work in organic synthesis, he discovered new routes to arid substituents to olefins selectively. His early education was irregular and disjointed as a result of family circumstances and the economic depression of the 1930s. He eventually received his Ph.D. from the University of Chicago. The reduction of carbonyl compounds with diborane was the topic of... 

E)-olefin selectivity under kinetic control, J. Org. Chem. 52 (1987) 4637-4639. 

Hydrocarbon production and selectivities at comparable CO conversion are given in Table 19.2. The ultrafine iron oxide catalyst had a very poor C2-C4 olefin selectivity while the olefin selectivity of the precipitated catalyst was slightly higher than the iron carbide catalyst. This is surprising because Rice et al. report higher olefin selectivity for a similar iron carbide catalyst than a conventional Fe/Co catalyst.6 Soled et al. have subsequently reported that the conventional catalyst contains acidic sites which... 

The chiral Mo-alkylidene complex derived from AROM of a cyclic olefin may also participate in an intermolecular cross metathesis reaction. As depicted in Scheme 16, treatment of meso-72a with a solution of 5 mol % 4a and 2 equivalents of styrene leads to the formation of optically pure 73 in 57% isolated yield and >98% trans olefin selectivity [26]. The Mo-catalyzed AROM/CM reaction can be carried out in the presence of vinylsilanes the derived optically pure 74 (Scheme 16) may subsequently be subjected to Pd-catalyzed cross-coupling reactions, allowing access to a wider range of optically pure cyclopentanes. 

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