Reactions of propene and butene

There is no evidence that these reactions may play a rate-controlling part in high-temperature combustion or ignition processes. Since the available data are scarce (see Tables 27 and 31 and Figs. 88 to 90) and may be complicated by unresolved pressure dependences, more knowledge about the rate coefficients and products is desirable. Propene and butenes are important intermediates in the decomposition of propyl and butyl radicals, respectively, and must be consumed somehow in the reaction zones of flames of C3- and higher hydrocarbons. 

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Reactions of propene and butene, which are formed by alkyl radical thermal decomposition. 

The process involves reacting butenes and mixtures of propenes and butenes with either a phosphoric acid type catalyst (UOP Process) or a nickel complex-alkyl aluminum type catalyst (IFP Dimersol Process) to produce primarily hexene, heptene, and octene olefins. The reaction first proceeds through the formation of a carbocation which then combines with an olefin to form a new carbocation species. The acid proton donated to the olefin initially is then released and the new olefin forms. Hydrotreatment of the newly formed olefin species results in stable, high-octane blending components. 

The validity of this new method was assured in the hydrogenation reaction of 1,3-butadiene on the two different types of catalysts, MoS2 and ZnO, so that it was extended to the hydrogenation of a-olefins, propene and 1-butene, on MoS2 and MoOx/TiOz catalysts. The ratios of alkane-2- to alkane-l-d, obtained in the reaction of propene and 1-butene with HD molecule on MoS2 catalyst at room temperature, and the isotope effect in the reaction with H2 and D2 are plotted in Fig. 26. In these experiments, the analysis of propane-1-d, and propane-2-dj was carried out by microwave spectroscopy... 

However, despite the cited advantages in the hydroformylation of propene and butene, it has to be admitted that the biphasic system nears its limits when olefins with increasing chain lengths are considered. Due to the decreasing solubility of the olefins in the aqueous catalyst phase, the reaction rate slows down (cf. Section 6.1.3.2). 

In the case of hydroformylation, there is great interest in the use of alkenes higher than hexene. The previous technology is restricted to the use of propene and butenes (cf. Section 6.1). A reason which has been postulated for this (and other conversions) is the decreasing solubility in water with increasing number of carbon atoms in the starting alkenes and the products (Figure 2) and the associated mass-transfer problems in the two-phase reaction. 

As our first illustration we consider the co-dimerization of propene and butene to produce heptenes (Reaction 1). This reaction is accompanied by two competing, undesirable, reactions dimerization of propene to hexene (Reaction 2), and dimerization of butene to octene (Reaction 3). The second reaction proceeds extremely rapidly and in order to suppress the formation of hexenes we should have progressive injection of propene into the reactor with all the butenes at the beginning of the operation, as is shown in Fig. 22 (Trambouze et al., 1988). 

Figure 6.3. The degree to which organic solvents inhibit enzymes is dependent on their log P value. P is the partition coefficient of the solvent measured between octanol and water (i.e. P = solubility in octanol/solubility in water). Each point on the graph represents the activity of the enzyme in an reaction mixture containing water saturated with a solvent having the log P value shown. The reaction in this example is the microbial epoxidation of propene and butene. (From Laane et al., 1987, p. 73 reproduced by kind permission of Elsevier Science Publishers BV.)...

This reaction proceeds through a borohydride intermediate, which arises from dehydroboration. As in thermal isomerization, a mixture of boron heterocyclics is obtained. Tripropyl and tributylborane are particularly suitable for displacement reactions because propene and butene are easily removed from the reaction mixture. Ethylene is not evolved under similar conditions, and triethylborane does not appear to undergo this type of reaction (33, 57). 

Small olefins, notably ethylene (ethene), propene, and butene, form the building blocks of the petrochemical industry. These molecules originate among others from the FCC process, but they are also manufactured by the steam cracking of naphtha. A wealth of reactions is based on olefins. As examples, we discuss here the epoxida-tion of ethylene and the partial oxidation of propylene, as well as the polymerization of ethylene and propylene. 

Fig. 10.1. Minimum-energy transition structures for ene reactions (a) propene and ethene (b) propene and formaldehyde (c) butene and methyl glyoxylate-SnCl4 (d) butene and methyl glyoxylate-AlCl3. Reproduced from Helv. Chim. Acta, 85, 4264 (2002), by permission of Wiley-VCH.

Upon examining the data for the reactions of all four butene isomers (Fig. 37), the most striking observation is that the data for all four isomers are quite similar, except that there is no YH2 formed from isobutene. In addition, the branching ratios for each isomer are similar, except that 4>ych2 OyCiHe, is approximately a factor of two greater for isobutene than for the other isomers, and for propene, YCH2 is a much more important channel than is YH2 (Fig. 40), a situation that is exactly the opposite to that for the butene reactions (Fig. 37). 

Dinitrogen tetraoxide reacts explosively between —32° and — 90°C with propene, 1-butene, isobutene, 1,3-butadiene, cyclopentadiene and 1-hexene, but 6 other unsaturates failed to react [1]. Reaction of propene with the oxide at 2 bar/30°C to give lactic acid nitrate was proceeding in a pump-fed tubular reactor pilot plant. A violent explosion after several horns of steady operation was later ascribed to an overheated pump gland which recently had been tightened. A similar pump with a tight gland created a hot-spot at 200°C [2],... 

Many other compounds have been shown to act as co-catalysts in various systems, and their activity is interpreted by analogous reactions [30-33]. However, the confidence with which one previously generalised this simple picture has been shaken by some extremely important papers from Eastham s group [34], These authors have studied the isomerization of cis- and Zraws-but-2-ene and of but-l-ene and the polymerization of propene and of the butenes by boron fluoride with either methanol or acetic acid as cocatalyst. Their complicated kinetic results indicate that more than one complex may be involved in the reaction mechanism, and the authors have discussed the implications of their findings in some detail. 

Chloroalkyl-2-naphthyltellurium dichloride (general procedure). 2-Naphthyltellurium trichloride (2.98 g, 0.83 mmol) is heated under reflux with the olefin (1.2 mmol) in dry, ethanol-free CHCI3 (15 mL) until the trichloride has dissolved (0.5-1 h). Filtration from a small amount of elemental Te and evaporation gives an oil or a semi-solid that is recrystallized from a large amount of petroleum ether at 40-60°C. The reactions with propene and 2-butenes are performed in a sealed tube at 80°C. The yields are in the range 70-95%. 

As is outlined above (Equation 1-3), with ethene in hand the way to propene and butene/butadiene is paved. Finally, two other base chemicals which can be obtained from methanol are isoprene and toluene - the first by the reaction of methanol with 1-butene and the second by alkylation of benzene with methanol. 

Ni-catalyzed dimerization of propene and/or butenes, which was intensively studied in the 1960 s [96] and later commercialized as the Dimersol process by the Institut Franjais du Petrole (IFF). The active catalytic species is formed in situ through the reaction between a Ni(ll) source and an alkylaluminium co-catalyst. 

Somewhat analogous reactions would be expected for the reaction of ethylene with 02 ions but the observed reaction rate is lower than for propene, suggesting that the reaction pathway may be controlled by the C—H bond energies. For reactions of propane and 1-butene with 02, oxygenated compounds of the same carbon number as the reactants were produced. The initial step is thought to involve a hydrogen atom abstraction from a secondary carbon atom. 

The reactions of the n -butenes with deuterium have been studied over alumina-supported platinum and iridium [103] and palladium [124]. In general, the results obtained are similar to those discussed above for ethylene—deuterium and propene—deuterium reactions. A comparison of the deuteroalkane distributions over platinum is shown in Fig. 17. 

Remarkably, however, the logarithm of the rate constant varies linearly with the dissociation energy of the allylic C—H bond, which indicates that the rupture of the C—H bond is included in the rate-determining reaction step. Mixed olefin feeds (propene and butene) were also used. It appears that co-dimerization can occur yielding C2 -dimers. 

Two recent papers report the main features of the heterogeneously catalysed addition of alcohols to alkenes [364,365]. The reaction proceeds both in the liquid and gas phase [364], and the temperature must be kept well under 150°C with respect to the position of the equilibrium [364], The reactivity of isobutene and 2-methyl-l-butene is much higher than that of propene, 2-butene and 3-methyl-l-butene [364,365]. 2-Methyl-l-butene reacts faster than 2-methyl-2-butene [365]. The reactivity of alcohols with isobutene decreases in the order methanol > ethanol > 1-propanol > 1-butanol [365]. 

One of the most curious catalytic reactions of alkenes ever discovered is alkene metathesis or alkene dismutation, in which two alkenes exchange alkyli-dene groups, usually over a tungsten catalyst. The essence of the reaction is illustrated by a commercial process for converting excess propene to a mixture of ethene and butenes ... 

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