Styrene from toluene

Serra, J.M., Corma, A., Farrusseng, D. et al. (2003) Styrene from toluene by combinatorial catalysis. Catal. Today, 81, 425. 

There is increasing interest in studying the alkylation of methylbenzenes in the side chain with methyl alcohol over zeolite catalysts.270 These reactions may lead to new nontraditional technologies in the synthesis of styrene from toluene and that of p-methy I styrene from p-xylene. A one-step route from toluene or p-xylene to the corresponding styrenes would be of great practical importance compared with the presently practiced two-step syntheses (alkylation followed by dehydrogenation). 

Serra et al. [122] used an evolutionary strategy for the design of catalyst libraries to evaluate a synthesis route for styrene from toluene. 

Serra, JM Corma. A Famisseng. D Baumes, L Mirodatos, C Flego, C Perego, C. Styrene from toluene by combinatorial catalysis. Catafysis To[Pg.123]

The synthesis (13.175) of styrene from toluene and ethylene seems to be a promising process. 

ExSyM [Exelus Styrene Monomer] A one-step process for making styrene from toluene and methanol. A special zeolite catalyst is used at 400°C-425°C, under atmospheric pressure. Developed by Exelus, NJ, and piloted from 2008 to 2012. 

Figure 5 illustrates a typical distillation train in a styrene plant. Benzene and toluene by-products are recovered in the overhead of the benzene—toluene column. The bottoms from the benzene—toluene column are distilled in the ethylbenzene recycle column, where the separation of ethylbenzene and styrene is effected. The ethylbenzene, containing up to 3% styrene, is taken overhead and recycled to the dehydrogenation section. The bottoms, which contain styrene, by-products heavier than styrene, polymers, inhibitor, and up to 1000 ppm ethylbenzene, are pumped to the styrene finishing column. The overhead product from this column is purified styrene. The bottoms are further processed in a residue-finishing system to recover additional styrene from the residue, which consists of heavy by-products, polymers, and inhibitor. The residue is used as fuel. The residue-finishing system can be a flash evaporator or a small distillation column. This distillation sequence is used in the Fina-Badger process and the Dow process. 

Because much toluene is demethylated for use as benzene, considerable effort has been expended on developing processes in which toluene can be used in place of benzene to make directiy from toluene the same products that are derived from benzene. Such processes both save the cost of demethylation and utilize the methyl group already on toluene. Most of this effort has been directed toward manufacture of styrene. An alternative approach is the manufacture of i ra-methylstyrene by selective ethylation of toluene, followed by dehydrogenation. Resins from this monomer are expected to displace... 

The performance of many metal-ion catalysts can be enhanced by doping with cesium compounds. This is a result both of the low ionization potential of cesium and its abiUty to stabilize high oxidation states of transition-metal oxo anions (50). Catalyst doping is one of the principal commercial uses of cesium. Cesium is a more powerflil oxidant than potassium, which it can replace. The amount of replacement is often a matter of economic benefit. Cesium-doped catalysts are used for the production of styrene monomer from ethyl benzene at metal oxide contacts or from toluene and methanol as Cs-exchanged zeofltes ethylene oxide ammonoxidation, acrolein (methacrolein) acryflc acid (methacrylic acid) methyl methacrylate monomer methanol phthahc anhydride anthraquinone various olefins chlorinations in low pressure ammonia synthesis and in the conversion of SO2 to SO in sulfuric acid production. 

Table 3. Pseudo-first order rate constant kapp of propagation of lithium o-methoxy styrene in toluene at 20 °C. The values collected in the first two columns are taken from Table 2 of Ref. 69)...

The use of lightly crosslinked polymers did result in hydrophilic surfaces (contact angle 50°, c-PI, 0.2 M PhTD). However, the surfaces displayed severe cracking after 5 days. Although qualitatively they appeared to remain hydrophilic, reliable contact angle measurements on these surfaces were impossible. Also, the use of a styrene-butadiene-styrene triblock copolymer thermoplastic elastomer did not show improved permanence of the hydrophilicity over other polydienes treated with PhTD. The block copolymer film was cast from toluene, and transmission electron microscopy showed that the continuous phase was the polybutadiene portion of the copolymer. Both polystyrene and polybutadiene domains are present at the surface. This would probably limit the maximum hydrophilicity obtainable since the RTD reagents are not expected to modify the polystyrene domains. 

Polystyrene was prepared by the anionic polymerisation of styrene in toluene plus THF mixtures (4 1 volume ratio) using n-butyl lithium as initiator. After removing a sample for analysis at this stage, the remainder of the living polystyrene was reacted with a five molar excess of trichloromethylsilane for 15 min and then excess methanol introduced. The methoxy-terminated polystyrene was freeze-dried from dioxan. The method described here essentially follows the route proposed by Laible and Hamann (6). 

Reaction with solvent - The solvent influences the course of cationic reactions not only through its dielectric constant, but also because many substances used as solvents are far from inert in these reactions [22, 23]. Although much more experimental material is required before a full treatment of the subject becomes possible, at least one example, the cationic polymerisation of styrene in toluene, is amenable to quantitative discussion. Experiment shows that polymerisation is rapid and complete, the molecular weight is low and the polymer contains para-substituted rings which are almost certainly tolyl endgroups [22]. Theoretically, a polystyryl carbonium ion can react with toluene in six different ways, only two of which (a.l and b. 1 below) can lead to tolyl endgroups in the first case the tolyl group is at the end of the terminated chain, in the second it is the start of a new chain. The alternative reactions can be represented as follows... 

For EVE and 4-methoxystyrene in CH2C12 the addition of the solvent produces a dramatic fall in rate. This is explained by a change from unimolecular to bimolecular propagation at high m, near mB. The rate of polymerization of styrene in toluene and in CH2C12 from... 

Benzene and toluene by-products are recovered in the overhead of the benzene-toluene distillation column. The bottoms from the benzene-toluene column are distilled in the ethylbenzene recycle column, where the separation of ethylbenzene and styrene is effected. The bottoms, are pumped to file styrene finishing column. The overhead product from this column is purified styrene. The bottoms are further processed in a residue-finishing system to recover additional styrene from the residue. 

Cohen et al. (1990) studied a poly(styrene)-poly(ethylene) (PS-PE) diblock that was solvent cast from toluene. Crystallization within microphase-separated PE spheres occurred when solvent-casting was done above the PE block melting temperature, Tm (see Fig. 5.2). When solvent was removed below Tm crystallization did not occur within spherical microdomains, instead TEM and SANS experiments suggested an irregular structure. Nojima et al. (1994) suggest that crystallization from the melt in this sample occurred within the microphase-separated block in the former case due to the high molecular weight of the... 

There are yet more similarities between protein and dairy products. For example, highly processed protein products (e.g., ground, mixed and canned) also contain disinfection byproducts. Thus, hot dogs, ground beef, bologna, salami, and canned tuna are contaminated with chloroform and sometimes with bromodichloromethane. Benzene, toluene, ethyl benzene, and xylenes, as well as the other detected chlorinated petroleum solvents (e.g., PCE, TCA, and TCE), also occur in protein products because these chemicals were in products used to lubricate or clean machinery that contacted the dairy products, or because these chemicals were in the ambient air of the meatpacking plant. Protein products also contain styrene from contact with plastics. Finally. PCB (a banned industrial chemical) was found to occur in every Market Basket sample of salmon. 

For components resulting from a single reaction, such as styrene, benzene, toluene, and carbon dioxide, the molar flow rates from the industrial reactor are divided by the corresponding rates obtained from the heterogeneous model and multiplying factors are established for the respective four reactions. 

The effectiveness factors for the reactions and the components are changing along the length of the reactor. The data above shows the effectiveness factors and rates at the exit. Here the effectiveness factor of a component is computed from the rate of its consumption at the exit. For components which are formed in a single reaction and are not involved in any other reactions, such as styrene, benzene, toluene and carbon dioxide, the effectiveness factor is determined by the effectiveness factor of their reaction, i.e., by the reactions (1) to (3) and (6). Note that for most of the reactions (except for reactions (5)... 

Fig. 1.8 Concentration dependence of coil radius for PS in d-toluene. Line, least-squares fit to the sample pairs for x = 0.50 and 0.0. Here, n is the mole fraction of styrene residues, and x the mole fraction of d-styrene in a mixture of h- and d- styrenes. (From ref. [45])...

Fig. 5 Influence of incubation time on average SWV peak current ratios for (PDDA/ds-DNA)2 films in 20 pM Co(bpy)3 + at pH 5.5 after incubations with styrene oxide, toluene, or pure buffer. /p,final corresponds to the peak current after each incubation /p.initial corresponds to peak current before incubation. (From Ref. [46] with permission. Copyright 2002 Wiley-VCH.) (View this art in color at www.dekker.com.)...

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