Propylene reactions

On the other hand, if the non-classical ion is a stable intermediate, the transition state for the 3,2 hydride shift requires a subst mtial reorganization, including the cleavage of the cyclopropyl ring, and, by analogy with unimolecular gas phase processes, a much higher pre-exponential factor might be expected. [In the cyclopropane-propylene reaction log A is 1ST 7 (Chambers and Kistiakowsky, 1954).] Contrary to expectation, the observed pre-exponential for the 3,2-shift is actually a little lower than for the 1,2,6-equilibration process. 

Thus, the Milas reagents may be considered to be the progenitors of the metal catalyst/alkyl hydroperoxide reagents5 5 that were later developed cy, inter alia, Halcon, Arco and Shell workers and culminated in the realization of commercial processes for the epoxidation of propylene (reaction II). These reagents involve the very same metal catalysts, e.g. MoVI, WVI, vv and TiIV, as the Milas reagents and they are mechanistically closely related. 

In order to differentiate between the two formaldehyde forming reactions in the case of propylene, reaction (6), attack on CH3 group, and (8), attack on CH2 group of the double bond, Avramenko and Kolesnikova carried out experiments with 1,3-butadiene, which leaves only the latter alternative. Quantitative analyses were carried out only for the carbonyl compounds and the acids. Carbonyl compounds consisted of acrolein, formaldehyde, and higher aldehydes. Acrolein appeared to be a primary product, and formaldehyde and acid secondary ( quadratic ) products. The postulated primary reaction was... 

The early value of the relative rate of propylene reactions obtained by the molybdenum trioxide technique (column A) is very much out of line, and so is its subsequent confirmation (column B). This discrepancy was realized at the time and the value was obtained again by Bradley et al. (15) using a direct competitive technique. A much larger relative rate of about 1.6 was obtained (column C, Table VII), in reasonable agreement with the values found by the other techniques. 

In the propylene reaction with a 02-H2 mixture, the contact structure of Au NPs and the selection of support metal oxides are critical for producing propylene oxide (PO). 

Mechanism 3 has, as a first step, reactions between surface radicals on the coke and the acetylene, butadiene, and gaseous free radicals reactions probably also occur with ethylene and propylene. Reactions with gaseous free radicals were discussed earlier as a termination step in the gas-phase reactions. When acetylene reacts with the surface radicals, aromatic structures are formed on the surface. When the C—H bonds on the surface later break, graphitic coke is formed. The cokes produced by both Mechanisms 1 and 3 tends to be highly graphitic. Microscopic photographs have shown that Mechanism 3 thickens filamentous coke and causes spherical coke particles formed by Mechanism 2 to grow in diameter. 

The pyrolysis of substituted cyclopropane leads to three types of unimolecular isomerizations (see Fig. 3). The first kinetic study of the conversion of cyclopropane into propylene (reaction a) was undertaken by Trautz and Winkler in 1922 ... 

Propylene Reactions. The following reaction mechanisms are generally 7ecognTzeTM tlTeprinci pa I ones occurring in propylene-isobutane alkylation with hydrofluoric acid catalyst (Ciapetta, 1945). In pnirenthe-ses are shown amounts of oroducts from each mechanism these are from Table VII for propylene ... 

Fig. 9. Experimental (a and b) and simulated (c and d) partial pressure oscillations for the CO/02/propylene reaction (a and c), and the CO/O2/1-butene reaction (b and d), both over Pt. The simulated curves are obtained by an elementary-step model. (From Ref. 207.)...

From the propylene reaction three principal sulfur-containing products have been found propylene episulfide, methyl vinyl mercaptan (probably propene-l-thiol), and allyl mercaptan. Rates of product formation as a function of propylene pressure are given in Table VIII. It can be seen that the two types of mercaptans are formed in nearly equal yields, while the ratio fimer pten/Repi umde again increases with pressure, but the limiting yield is only half of that obtained for ethylene. 

The allyl mercaptan formed in the propylene reaction most likely results from the paraffinic C—H insertion of S( D) atoms (28e). 

Olefins. A problem that has fascinated polymer chemists has been obtaining polyethylene by polymerizing propylene (Reaction 22). 

The mixture C02 C3H6 = 4 1 with small concentration of propane impurity (<1,5%) was used. The space velocity of reagents was 150-200h. To elucidate the mechanism of CO2 + propylene reaction the physicochemical and quantum methods have been used. IR-spectra of CO2 were registered by UR-75-Spectrometer at room temperature in the 1200 - 3500 cm range. 

Complex composition of reaction products shows that interaction of C02-t-propylene is not selective process and occurs in several directions simultaneously. The IR-spectroscopy study of CO2 chemisorption was carried out to determine the mechanism of CO2 -i-propylene reaction. 

The state of the art in partial oxidation of propane to propylene is assessed below. Unlike the preceding sections which dealt with commercially practical processes this section will concern itself with evaluating the promise of the partial oxidants—oxygen, halogens, and sulfur— that have been proposed for effecting the propane to propylene reaction. 

It is also clear that accumulated chemical evidence on warmed products may in some instances permit reasonable, although not optimum, deductions about low-temperature reactions. For example, it seems clear from experiments with deuterium that addition of hydrogen atoms to some olefins followed by abstraction does occur at 77°K, while with some other olefins this abstraction is not apparent [ ]. From the propylene reaction with D rather than with H atoms, it was established that virtually all of the propane was formed by... 

Acrolein, CH2 = CH —CHO, is obtained by the oxidation of propylene, reaction of formaldehyde with acetaldehyde, or by the (outdated) method of dehydrating glycerine. Free radical polymerization produces copolymers with different kinds of repeating units ... 

When the reactors were then cooled to 475 to 525 c, significant propylene reactions were still noted. Clearly the reac-... 

Figure 29 The influence of average residence time of catalyst in reactor on the selectivity of ethylene and propylene. Reaction conditions 7=500 °C catalyst inventory=1 kg, WHSV=2 h water MeOH = 20 80, and gas-solid contact time =1.3 s.

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