Ethylbenzene, styrene from

Alkenyl halides such as vinyl chloride (H2C=CHC1) do not form carbocations on treatment with aluminum chloride and so cannot be used m Friedel-Crafts reactions Thus the industrial preparation of styrene from benzene and ethylene does not involve vinyl chloride but proceeds by way of ethylbenzene... 

Dehydrogenation (Section 5 1) Elimination in which H2 is lost from adjacent atoms The term is most commonly en countered in the mdustnal preparation of ethylene from ethane propene from propane 1 3 butadiene from butane and styrene from ethylbenzene... 

Styrene is manufactured from ethylbenzene. Ethylbenzene [100-41-4] is produced by alkylation of benzene with ethylene, except for a very small fraction that is recovered from mixed Cg aromatics by superfractionation. Ethylbenzene and styrene units are almost always installed together with matching capacities because nearly all of the ethylbenzene produced commercially is converted to styrene. Alkylation is exothermic and dehydrogenation is endothermic. In a typical ethylbenzene—styrene complex, energy economy is realized by advantageously integrating the energy flows of the two units. A plant intended to produce ethylbenzene exclusively or mostly for the merchant market is also not considered viable because the merchant market is small and sporadic. 

The ethylene feedstock used in most plants is of high purity and contains 200—2000 ppm of ethane as the only significant impurity. Ethane is inert in the reactor and is rejected from the plant in the vent gas for use as fuel. Dilute gas streams, such as treated fluid-catalytic cracking (FCC) off-gas from refineries with ethylene concentrations as low as 10%, have also been used as the ethylene feedstock. The refinery FCC off-gas, which is otherwise used as fuel, can be an attractive source of ethylene even with the added costs of the treatments needed to remove undesirable impurities such as acetylene and higher olefins. Its use for ethylbenzene production, however, is limited by the quantity available. Only large refineries are capable of deUvering sufficient FCC off-gas to support an ethylbenzene—styrene plant of an economical scale. 

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. 

Commercial polystyrenes are normally rather pure polymers. The amount of styrene, ethylbenzene, styrene dimers and trimers, and other hydrocarbons is minimized by effective devolatilization or by the use of chemical initiators (33). Polystyrenes with low overall volatiles content have relatively high heat-deformation temperatures. The very low content of monomer and other solvents, eg, ethylbenzene, in PS is desirable in the packaging of food. The negligible level of extraction of organic materials from PS is of cmcial importance in this appHcation. 

There are notable cases where plate columns have been converted to packed columns to gain advantage of the low pressure drop exacted from the vapor stream. More recently the packings have been largely of the stmctured type. Illustrative of this is the trend toward the use of stmctured packing in ethylbenzene—styrene fractionators, some of which have diameters of 10 m or higher. 

Example 4 Styrene from Ethylbenzene The principal reaction in the dehydrogenation of ethylbenzene is to styrene and hydrogen. 

The generation of caibocations from these sources is well documented (see Section 5.4). The reaction of aromatics with alkenes in the presence of Lewis acid catalysts is the basis for the industrial production of many alkylated aromatic compounds. Styrene, for example, is prepared by dehydrogenation of ethylbenzene made from benzene and ethylene. 

Data from an existing collection system were analyzed for failure modes and distribution. The results of Pareto analyses indicate the principal causes of failure. A few values of mean times to maintenance action (MTBM) are given for ethylene plant pumps (85 electric driven centrifugal pumps over a 19-month period), and ethylbenzene-styrene monomer plant equipment from 10 months data 4 gas compressors, 3 screw conveyors, 121 pumps, and 235 other items... 

Problem 16.21 Styrene, the simplest alkenylbenzene, is prepared commercially for use in plastics manufacture by catalytic dehydrogenation of ethylbenzene. How might you prepare styrene from benzene using reactions you ve studied ... 

The reaction of olefin epoxidation by peracids was discovered by Prilezhaev [235]. The first observation concerning catalytic olefin epoxidation was made in 1950 by Hawkins [236]. He discovered oxide formation from cyclohexene and 1-octane during the decomposition of cumyl hydroperoxide in the medium of these hydrocarbons in the presence of vanadium pentaoxide. From 1963 to 1965, the Halcon Co. developed and patented the process of preparation of propylene oxide and styrene from propylene and ethylbenzene in which the key stage is the catalytic epoxidation of propylene by ethylbenzene hydroperoxide [237,238]. In 1965, Indictor and Brill [239] published studies on the epoxidation of several olefins by 1,1-dimethylethyl hydroperoxide catalyzed by acetylacetonates of several metals. They observed the high yield of oxide (close to 100% with respect to hydroperoxide) for catalysis by molybdenum, vanadium, and chromium acetylacetonates. The low yield of oxide (15-28%) was observed in the case of catalysis by manganese, cobalt, iron, and copper acetylacetonates. The further studies showed that molybdenum, vanadium, and... 

Ethylbenzene is a high volume petrochemical used as the feed stock for the production of styrene via dehydrogenation. Ethylbenzene is currently made by ethylene alkylation of benzene and can be purified to 99.9%. Ethylbenzene and styrene plants are usually built in a single location. There is very little merchant sale of ethylbenzene, and styrene production is about 30x10 t/year. For selective adsorption to be economically competitive on this scale, streams with sufficiently high concentration and volume of ethylbenzene would be required. Hence, although technology has been available for ethylbenzene extraction from mixed xylenes, potential commercial opportunities are limited to niche applications. 

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. 

Fig. 1.7. A process for styrene from ethylbenzene using IS moles steam 1 mole ethylbenzene. Operating pressure 1 bar. Conversion per pass 0.40. Overall relative yield 0.90...

Y. C. Yen, Styrene from Ethylbenzene using membrane reactors in PEP... 

Industrial interest in this reaction was stimulated by the discovery that it constitutes a commercially attractive route to propylene oxide 426a,b Thus, the metal-catalyzed epoxidation of propylene with ethylbenzene hydroperoxide forms the basis of the Halcon process426a,b 427 for the coproduction of propylene oxide and styrene from propylene, ethylbenzene, and oxygen via the following sequence ... 

Gramshaw, J.W., and Vandenburg, H.J., 1995. Compositional analysis of thermoset polyester and migration of ethylbenzene and styrene from thermosct polyester into pork during cooking. Food Add. and Contam. 12, 2, 223-234. 

Example 2 Synthesis of a styrene process. Styrene, the monomer of polystyrene, has enjoyed strong market growth over the past two decades. It is prepared starting with benzene and ethylene which react to form ethylbenzene the ethylbenzene is dehydrogenated to yield styrene. Further information about styrene manufacture, properties, and uses is available. 3 In this example, the steps involved in synthesizing a process to produce styrene from ethylbenzene will be illustrated. The procedure followed is analogous to that followed by the PIP program. 

A total fractional extent-of-reaction less than 1.0 (0.5 in this example) means that not all of the reactant in the feed reacts, so unreacted reactant is present in the reactor-product stream. The latter stream contains ethylbenzene, all the reaction products, by-products, and steam. It is essential to separate the main product, styrene, from the rest of this mixture. Economically it is desirable and generally it is necessary to recover unreacted reactants and recycle them to the reactor. By-products must be separated and, if possible, effectively utilized. The condensed steam must be separated from the product stream and removed. 

EPA 1989d. National Emission Standards for Hazardous Air Pollutants Benzene Emissions from Maleic Anhydride Plants, Ethylbenzene/Styrene Plants, Benzene Storage Vessels, Benzene Equipment Leaks, and Coke By-Products Recovery Plants. U.S. Environmental Protection Agency. 54 FR 38044. 

The thermal reactions of dihydrobenzo[c]furan 258 were studied behind reflected shock waves in a single pulse shock tube over the temperature range 1050-1300 K to lead to products from a unimolecular cleavage of 258 <2001PCA3148>. Intriguingly, carbon monoxide and toluene were among the products of the highest concentration, while benzo[f]furan, benzene, ethylbenzene, styrene, ethylene, methane, and acetylene were the other products. Trace amounts of allene and propyne were also detected. 

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