U-methylstyrene

Alkene Aromatic Hydrc enation Investigated in Micro Reactors Cas/liquid reaction 17 [CL 17] Catalytic hydrc enation of u-methylstyrene... 

CH4, CO. CO , propene. dimethyl ketene, toluene, styrene 4-phenylbutene. 4-phenyl-2-methylbutene. phenyl methacrylate, u-methylstyrene, short chain fragments... 

Production of a-methylstyrene (AMS) from cumene by dehydrogenation was practiced commercially by Dow until 1977. It is now produced as a by-product in the production of phenol and acetone from cumene. Cumene is manufactured by alkylation of benzene with propylene. In the phenol—acetone process, cumene is oxidized in the Hquid phase thermally to cumene hydroperoxide. The hydroperoxide is spHt into phenol and acetone by a cleavage reaction catalyzed by sulfur dioxide. Up to 2% of the cumene is converted to a-methylstyrene. Phenol and acetone are large-volume chemicals and the supply of the by-product a-methylstyrene is weU in excess of its demand. Producers are forced to hydrogenate it back to cumene for recycle to the phenol—acetone plant. Estimated plant capacities of the U.S. producers of a-methylstyrene are Hsted in Table 13 (80). 

The 1998 U.S. cumene production was approximately 6.7 hillion pounds and was mainly used to produce phenol and acetone. A small amount of cumene is used to make a-methylstyrene hy dehydrogenation. 

The results of external quenching studies using fra/u-jS-methylstyrene as a quencher are shown in Figures 6.15 and 6.16. 

Gaur, U. and Wunderlich, B. Study of microphase separation in block copolymers of styrene and alpha-methylstyrene in the glass transition region using quantitative thermal analysis. Macromolecules 13, 1618 (1980)... 

Reaction Order. Rate Constants and Activation Energy (Slurry-Reactor). Hydrogentation of a-methylstyrene was selected for a test reaction. This reaction has been studied extensively by a number of investigators (6, 11. 14, 15, 17). Previous studies used Pd/A 203 or Pd-black catalysts in a-methylstyrene-cumene mixtures. We wanted to verify the kinetics of this reaction in various solvents of different physical properties (cyclohexane, hexane (u.v.), hexane (A.C.S), toluene, 2-propanol) and examine the effect of Pd concentration on the rate. The above solvents were to be utilized in trickle-bed reaction studies also to provide a range of liquid physical properties. 

The reaction is found to be zeroth order with respect to a-methylstyrene and approximately first order with respect to hydrogen in all solvents as shown in Table I. Reaction dependence on hydrogen in cyclohexane solvent is shown in Figure 2 and a typical Arrhenius plot is presented in Figure 3. Reaction rate is independent of Pd concentration (structure insensitive) in pure nonpolar solvents (cyclohexane, hexane (U.V.)) but becomes structure sensitive (i.e. dependent on Pd concentration) in solvents with impurities or which are more polar. The activation energy of 10.2 kcal/mol found in cyclohexane agreed well with the one determined by Germain et al. (6). 

The styrene copolymers were prepared by bulk polymerization at 100°, using benzoyl peroxide as initiator. Methyl methacrylate styrene mole ratios in the feed were 10 90, 25 75, 50 50, 75 25, and 90 10. Conversions varied from 4.5 to 8.1%. Methyl methacrylate a-methyl-styrene copolymers were prepared using benzoyl peroxide at lower a-methylstyrene ratios and U.V. or Co60 gamma radiation to initiate copolymerization at the highest a-methylstyrene ratios, in which reaction is very slow. The mole ratios in the monomer feed were 12 88, 28 72, 54 46, 78 22, and 91.5 8.5. 

Alkylation of toluene with ethene u g shape selective catalysts can yield p-ethyholuene which upon dehydrogenation yields p-methylstyrene [51], Using a modified ZSM-5 catalyst p-ethyhohiene can be produced very selectively (97 %) at high toluene conversion [46], The polymer from this starting material may possess more interesting properties th polystyrene. 

In helium quantitative yield of HCI. remainder residue and hydrocarbons, benzene is major volatile hydrocarbons product aliphatic hydrocarbons, benzene (major product), toluene, ethylbenzene, o-xyiene, monochlorobenzene styrene, vinyl tcriuerre. p-dichlorobenzene, o-dichlorobenzene, indene, 1,3.5-trichlorobenzene 1.2.4. richlorobenzene. naphthalene, u-methylnaphthalene. p-methylnaphthatene effect of ZnO. SnOj, and Ab03 on the yields of products Is also recorded HCI. CO2. ethene. ethane, propane, 1-butene. 2-butene. 1-pentene. cydopentene, n-pentane, 2-methylbulane, 1,3-pentadiene. 2-methyl-1,3-pentadiene, complex series (60 Identlfled) of aromatic and polyaromatic species including benzene, styrene, methylstyrenes, toluene, o-xytene, m-xylene, p-xylene, biphenyl, naphthalene, anthracene, phenanthrene. pyrene, etc. 

Styrene and a-Methylstyrene in Organic Solvents. Pulse radiolysis studies have been made on styrene and a-methylstyrene dissolved in methanol, benzene, carbon tetrachloride, dioxane, tetrahydrofuran, hexane, and cyclohexane (9, 24, 29, 30, 31). The results are easiest to understand for the aliphatic hydrocarbons and especially for the styrene in cyclohexane, which has been studied the most (31). For such solutions, two absorption bands were seen after the pulse by Keene, Land, and Swallow (24) and Schneider and Swallow (30) with peaks at 320 and 390 m/. The absorption at 320 m/u disappeared slowly by complex kinetics, and the 390-m/x absorption was very short lived, decaying by second-order kinetics with k/c = 4-7 X 10 cm. sec.-1. The relative intensities of the two peaks were quite variable. Chambers et al. saw the long lived absorption at 320 m/, but did not see a separate peak at 390 m/a, although it was observed that the absorption at 375 mfi decayed rapidly with k/e = 2.6 X 106 cm. sec.-1. 

One of the chlorine atoms in phosphorus pentachloride appears to hold a unique position in that the products of the reaction mth indene, styrene, a-methylstyrene and 5 u.-diphenylethylene m cold benzene solution, suffer hydrolysis accompanied by intramolecular separation of the fifth chlorine atom as hydrogen chloride when treated with water. At much higher temperatures certain indones add on two chlorine atoms when treated with phosphorus pentachloride, this decisively indicating the fission PCI5 PClg + Clg. 

GL2 Glbckner, G., Francuskiewicz, F., and Reichardt, H.-U., On the behaviour of styrene-acrylonitrile copolymers in solution V. Light scattering investigation of a-methylstyrene copolymers with about 46 mol% acrylonitrile in tetrahydrofuran as a sohrsiA, Acta Polym., 30, 628, 1979. 

Gaur U, Wunderlich B (1980) Study of Microphase Separation in Block Copolymers of Styrene and a-Methylstyrene in the Glass Transition Region using Quantitative Thermal Analysis. Macromolecules 13 1618-1625. 

On the addition of anionic initiator, such as n-BuLi, K-naphtha1ene, Na-naphthalene, and disodium c(-methylstyrene tetramer dianion U-MeSt " 2Na ), to the THF solution of p-trimethylsilylStyrene, color of the mixture changed to characteristic dark red and the quantitative polymerization was completed within a few minutes. After the reaction was over, the red color persisted even at 30 C, suggesting that the propagating end was stable and still remained in the solution. 

Both systems yielded polymers with molecular weights of about 35000g/mol, with the initiated polymerization being three to four times faster than the thermal one. Olaj [286] reports on the kinetics of thermally and AIBN-started radical polymerization of u-ClSt in bulk at 30 °C. He found the rate of polymerization to be about 15 times higher than that of styrene. Propagation kinetics of para substituted styrenes have been investigated by Coote and Davis [246] (see also Section II.C on ur-methylstyrenes). 

Rubber grade 1,3-butadiene was purchased from the Phillips Petroleum Company. Two columns, one packed with the potassium form of a sulfonic acid ion exchange resin (Dowex MSC-l-K) and the other packed with an activated alumina, were used to purify the butadiene. Isoprene was purchased from Aldrich Chemical Company. Stabilizer-free styrene monomer was obtained directly from the Dow styrene monomer plant. Alpha-methylstyrene (AMS) was purchased from U.S. Steel Corporation. The last three monomers were all purified by passing through a column packed with activated alumina and then vacuum distilled over calcium hydride. 

Tarallo, O., Esposito, G., Passarelli, U., Petraccone, V. A clathrate form of syndiotactic poly (p-methylstyrene) containing two different types of cavities. 

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