2- Butenes pyrolysis products

Earlier workers have identified some of the products of 1-butene pyrolysis (3,4). In this work, several previously unreported products were found along with many of those previously noted. Acetylene was observed among the products from 1-butene as well as 2-butene in yields that paralleled the formation of ethylene. Yields varied from a trace at low temperatures to between 5%-10% of the total C2 product at the highest temperatures. Methylacetylene + propadiene (MAP) yield varied in a similar manner for 1-butene pyrolysis ranging between 2% and 20% of the C3 product. In 2-butene pyrolysis, the MAP yield comprised approximately 10% of the C3 product in all of the runs. 

Tabulations of yields of all identified products from runs in the 80-wt % conversion range are given in Tables III and IV for 1-butene and mixed 2-butene pyrolysis, respectively. These product distributions are typical of those observed in all of the high conversion runs. 

Figure 3 shows the selectivity diagram for the major products from 1-butene pyrolysis. This shows that molecular hydrogen is not an initial product of decomposition. Initial products appear to be (in mol/100 mol) butadiene, 25 methane, 30 ethylene, 15 propylene, 40 C5 products, 10 and isomerization products as cis- and trans-2-butene, 25. 

The lead-oxygen chain is embedded into a glove of cluster units exposing only carbonyl groups to the exterior. It is worth mentioning that one of the pyrolysis products of this material has catalytic activity in the hydrogenation of 2-butenal. 

The rate of decomposition of 1-butene was found to be much faster than that of cis-2-butene. Pyrolysis of 1-butene was studied in the temperature range of 530 to 605 C, whereas the temperatures used for the pyrolysis of cis-2-butene were 575 to 620 C. As can be seen in Figure 1 and Tables I and II, the product distribution for these two pyrolyses were very different. Cracking is the main course of the reaction for 1-butene, but isomerization is the main result of cis-2-butene pyrolysis. 

The mechanism of butene pyrolysis is obviously more complex than the mechanism operative in butane pyrolysis. The complexity of butene pyrolysis is emphasized by the larger number of products and the larger nuinber of possible free radicals. 

An Important feature of butene pyrolysis Is the existence of free radicals with resonant stabilization energy. The allyl and the 2-butenyl (methylallyl) radicals are stabilized by the fact that they have delocalized electrons. Added stability of these free radicals Is about 10 to 13 kcal/mole (16), which significantly increases the rate of their production and decreases the rate of their consumption. 

The thermal decomposition of propylene involves a series of primary and secondary reactions leading to a complex mixture of products. Studies showed that the distribution of pyrolysis products varies considerably with the pyrolysis conditions and the type of reactor used. There is agreement among the studies on propylene pyrolysis that the three major products of pyrolysis are methane, ethylene, and hydrogen. However, there is disagreement on the types and amounts of minor or secondary product species. Ethane, butenes, acetylene, methylacetylene, allene, and heavier aromatic components are reported in different studies, Laidler and Wojciechowski (1960), Kallend, et al. (1967), Amano and Uchiyama (1963), Sakakibara (1964), Sims, et al. (1971), Kunugi, et al. (1970), Mellouttee, et al. (1969), conducted at different conversion and temperature levels. Carbon was also reported as a product in the early work of Hurd and Eilers (1943) and in the more recent work of Sims, et al. (1971). 

Pyrolysis stndies XPS has been applied to the stndy of pyrolysis products of poly(l,4-diphenyl-l-buten-3-yne) [266] and poly(phenyl silsesqnioxane) [267, 268]. 

Two other butene isomers are formed besides PFIB, namely perfluoro-1-butene and perfluoro-2-butene. However, as with PFIB, a mechanism of formation from TFE or other pyrolysis products is lacking. 

Table 10. Pyrolysis of Zinc di (2-butyl) diathiophosphate butene-2 product distribution...

Krishen [42] obtained the products listed in Table 4.10 by pyrolysis of ethylene-butadiene rubber and ethylene-propylene-diene terpolymer. He showed that the 2-methyl-2-butene peak was linear with the natural rubber content of the sample. Styrene-butadiene rubber was determined from the peak area of the 1,3-butadiene peak. The ethylene-propylene-terpolymer content was deducted from the 1-pentane peak area of the pyrolysis products. 

The pattern of commercial production of 1,3-butadiene parallels the overall development of the petrochemical industry. Since its discovery via pyrolysis of various organic materials, butadiene has been manufactured from acetylene as weU as ethanol, both via butanediols (1,3- and 1,4-) as intermediates (see Acetylene-DERIVED chemicals). On a global basis, the importance of these processes has decreased substantially because of the increasing production of butadiene from petroleum sources. China and India stiU convert ethanol to butadiene using the two-step process while Poland and the former USSR use a one-step process (229,230). In the past butadiene also was produced by the dehydrogenation of / -butane and oxydehydrogenation of / -butenes. However, butadiene is now primarily produced as a by-product in the steam cracking of hydrocarbon streams to produce ethylene. Except under market dislocation situations, butadiene is almost exclusively manufactured by this process in the United States, Western Europe, and Japan. 

The primary products obtained from 2-butanol are of mechanistic. significance and may be compared with other eliminations in the sec-butyl system 87). The direction of elimination does not follow the Hofmann rule 88) nor is it governed by statistical factors. The latter would predict 60% 1-butene and 40% 2-butene. The greater amount of 2-alkene and especially the unusual predominance of the cis-olefin over the trans isomer rules out a concerted cis elimination, in which steric factors invariably hinder the formation of cis-olefin. For example, the following ratios oicisjtrans 2-butene are obtained on pyrolysis of 2-butyl compounds acetate, 0.53 89, 90) xanthate, 0.45 (S7) and amine oxide, 0.57 86) whereas dehydration of 2-butanol over the alkali-free alumina (P) gave a cisjtrans ratio of 4.3 (Fig. 3). 

Neither the thermal nor the cobalt-catalyzed decomposition of 3-butene-2-hydroperoxide in benzene at 100 °C. produced any acetaldehyde or propionaldehyde. In the presence of a trace of sulfuric acid, a small amount of acetaldehyde along with a large number of other products were produced on mixing. Furthermore, on heating at 100°C., polymerization is apparently the major reaction no volatile products were detected, and only a slight increase in acetaldehyde was observed. Pyrolysis of a benzene or carbon tetrachloride solution at 200°C. in the injection block of the gas chromatograph gave no acetaldehyde or propionaldehyde, and none was detected in any experiments conducted in methanol. 

N 13 59% oxygen-rich monomer no props are reported except 1R spectrum was prepd by reaction of ethyl methyl ketone with formaldehyde, hydrogenation of the product with Gi chromite catalyst, acetylation to the triacetate, pyrolysis, deacerylation, and nitration of 3,3"bis(hydroxymethyl) -butene-1. The subject compd was synthesized as a binder constituent, which might be polymer-... 

Decreased deactivation efficiency may also account for changing product ratios, such as increased formation of 3-methylbutene-l. Although Frey found no 3-methylbutene-l in photolysis experiments without added argon, this product was reported by Setser and Rabinovitch in pyrolysis of CH2N2-butene-2 mixtures and is also found to some extent in the thermal decomposition of 1,2-dimethylcyclopropane. It appears, therefore, that the formation of 3-methylbutene-l depends more on reaction conditions than on the electronic state of CH2. 

All this was later put on a sound basis as a result of more precise measurements of rate constants and of activation energies. However, it did not require precise measurements to predict which chlorinated hydrocarbons would decompose by a radical chain mechanism and which by the unimolecular mechanism. Clearly, if the chlorinated hydrocarbon, or the product from the pyrolysis of the chlorinated hydrocarbon reacted with chlorine atoms to break the chain then the chain mechanism would not exist. Such chlorinated hydrocarbons would decompose by the unimolecular mechanism. Mono-chlorinated derivatives of propane, butane, cyclohexane, etc. would afford propylene, butenes, cyclohexene, etc. All these olefins are inhibitors of chlorine radical chain reactions because of the attack of chlorine atoms at their allylic positions to give the corresponding stabilized allylic radicals which do not carry the chain. 

In connection with the methoxy participation, the gas-phase pyrolytic elimination of 4-chloro-1 -butanol was investigated177. The products are tetrahydrofuran, propene, formaldehyde and HCl. It is implied that the OH group provides anchimeric assistance from the fact that, besides formation of the normal unstable dehydrochlorinated intermediate 3-buten-l-ol, a ring-closed product, tetrahydrofuran, was also obtained. The higher rate of chlorobutanol pyrolysis with respect to chlorethanol and ethyl chloride (Table 27) confirmed the participation of the OH group through a five-membered ring in the transition state. 

The procedure described is essentially the same as that of Buck-ley and Scaife.3 The yield has been increased from 55.5% up to 72% by using 1.3 mol eq of phthalic anhydride and by carefully controlling the pressure and cooling the receiving flask. Although 2-nitropropene has previously been prepared by pyrolysis of 2-nitro-1-propyl benzoate in 72% overall yield from 2-nitro-l-propanol,4 the present method is preferred for its preparation since the procedure is much simpler and the product is directly obtainable from 2-nitro-l-propanol without first preparing its ester. It is also applicable to the preparation of 1-nitro-l-propene (58%),5-6 2-nitro-1 -butene (82%),7 and 2-nitro-2-butene (60%).6,7 In general, aliphatic nitroolefins have the tendency to polymerize readily with alkali. 

Cyclobutene has been reported to undergo 1,3 cycloaddition to benzene under photolysis conditions.355 Although the endo stereochemistry of the cyclobutane ring in this adduct is assumed (see 371), pyrolysis of the hydrocarbon at ca 250 °C gave dihydrotriquinacene 372 as the major product. Using cis-3,4-dimethylcyclo-butene, 373 was obtained and similarly transformed to 374 without loss of stereochemistry by thermolysis.376 ... 

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