Benzene alkylation, with ethylene

ZSM-5 Benzene alkylation with ethylene Higher ethylbenzene yield [41]... 

Mordenite Benzene alkylation with ethylene Increased lifetime Higher activity and ethylbenzene selectivity [45]... 

Acid sites were shown to be located in the three-pore system of protonated samples (HMWW), and methods were recently proposed for determining the distribution of these sites as well as their respective role in o-, m-, and p-xylene transformations. While xylene transformation was shown to occur in the three locations, benzene alkylation with ethylene was catalyzed by the acidic sites of the external hemicups only. Indeed, the activity for this reaction is completely suppressed by adding a base molecule (collidine) to the feed that is too bulky to enter the inner micropores. Moreover, adsorption experiments show that collidine does not influence the rate of ethylbenzene adsorption, so that the suppression of alkylation activity was not caused by pore mouth blocking. ... 

General characteristics of benzene alkylation with ethylene... 

The phenomenological Horiuti Boreskov Onsager equations allow in some cases a first approximation to be made for the kinetic description of catalytic transformations in systems that involve numerous parallel trans formation channels. Consider how these equations can be applied with the process of benzene alkylation with ethylene as an example. 

Benzene is alkylated with ethylene to produce ethylbenzene, which is then dehydrogenated to styrene, the most important chemical iatermediate derived from benzene. Styrene is a raw material for the production of polystyrene and styrene copolymers such as ABS and SAN. Ethylbenzene accounted for nearly 52% of benzene consumption ia 1988. 

Ethylbenzene can also be produced by catalytic alkylation of benzene with ethylene. Benzene is alkylated with ethylene in a fixed bed alkylator. An excess of benzene is used to suppress the formation of di- and triethyl- benzenes. The excess benzene is removed from the alkylate by fractionation and recycled to the alkylator. The ethylbenzene is separated from the polyalkylated benzenes which are in turn fed to a separate reactor. Here benzene is added to convert the polyalkylated benzenes to monoethylbenzene by transalkylation. 

Styrene, one of the world s major organic chemicals, is derived from ethylene via ethylbenzene. Several recent developments have occurred with respect to this use for ethylene. One is the production of styrene as a co-product of the propylene oxide process developed by Halcon International (12). In this process, benzene is alkylated with ethylene to ethylbenzene, and the latter is oxidized to ethylbenzene hydroperoxide. This hydroperoxide, in the presence of suitable catalysts, can convert a broad range of olefins to their corresponding oxirane compounds, of which propylene oxide presently has the greatest industrial importance. The ethylbenzene hydroperoxide is converted simultaneously to methylphenyl-carbinol which, upon dehydration, yields styrene. Commercial application of this new development in the use of ethylene will be demonstrated in a plant in Spain in the near future. 

ReCl5 has been found to act as a Friedel-Crafts catalyst for the alkylation of benzene with ethylene. Ethylbenzene, x-butylbenzene and hexaethylbenzene were formed.612 When propylene was used in place of ethylene, cumene and di-, tri- and tetra-isopropylbenzenes were obtained.613 Ethylbenzene and anisole were also alkylated with ethylene. A carbonium ion mechanism was proposed, in some cases with dimerization of ethylene preceding alkylation. 

Catalytic activity measurements and correlations with surface acidity have been obtained by numerous investigators. The reactions studied most frequently are cracking of cumene or normal paraffins and isomerization reactions both types of reactions proceed by carbonium ion mechanisms. Venuto et al. (219) investigated alkylation reactions over rare earth ion-exchanged X zeolite catalysts (REX). On the basis of product distributions, patterns of substrate reactivity, and deuterium tracer experiments, they concluded that zeolite-catalyzed alkylation proceeded via carbonium ion mechanisms. The reactions that occurred over REX catalysts such as alkylation of benzene/phenol with ethylene, isomerization of o-xylene, and isomerization of paraffins, resulted in product distribu-... 

BTX Chemistry (Benzene, Toluene, Xylene). Styrene, discussed under C-2 chemistry, is one of the main industrial chemicals made from benzene. Most benzene is alkylated with ethylene to form ethylbenzene, which is dehydrogenated to styrene (see Equation 10). 

The target process of benzene (B) alkylation with ethylene (E) to yield ethylbenzene (EB)... 

Figure 4.10 Typical results of the calculations of expected variations in the stationary concentrations of components at the benzene (B) alkylation with ethylene (E) along a plug-flow reactor of length L at 210 C x is the distance from the inlet of the reactor. The calculations were performed in terms of the Horiuti-Boreskov-Onsager reciprocity relations to optimize the composition of the initial reaction mixture so the outlet and inlet diethylbenzene (DBE) concentrations would be identical, which means 100% selectivity of the process in respect to the target product ethylbenzene (EB).

The oldest method of alkylation with ethylene is the liquid phase reaction using anhydrous aluminum chloride as the catalyst. This reaction is a form of the classic Friedel-Crafts reaction and was discovered in 1879 by Balsohn. Most Lewis and Bronsted acids are known to be active for olefin alkylations. Alkylation by H2SO1, and H3PO1, was first shown by Ipatieff, et al, in 1936 who extended the reaction to isoparaffins. For the liquid phase alkylation of benzene with ethylene, however, aluminum chloride is preferred over the other acids, although a co-catalyst or promoter is usually needed to obtain efficient alkylation. AICI3 when dissolved in benzene containing some HCl forms a complex which can be simply described as ... 

The manufacture of vlnyltoluene is analogous to that of styrene where toluene is substituted for benzene (Equations 1 and 2) in a conventional acid catalyzed alkylation with ethylene. The process gives rise to three Isomers during alkylation (Equation 1). The close boiling points (Table 2) of the meta and para isomers make it impractical to accomplish a separation by distillation (10). The ortho Isomer, however, is removed and recycled by a careful and costly distillation. This step is necessary because some of the ortho isomer undergoes cycllzatlon (Equation 3) during the dehydrogenation step to produce indan and Indene (11). 

Dry benzene was alkylated with ethylene in either the liquid or gas phases using acidic catalysts ... 

The EB present in recovered mixed xylenes is largely converted to xylenes or benzene. The EB used to make styrene is predominately manufactured by the alkylation of benzene with ethylene. 

Friedel-Crafts alkylation using alkenes has important industrial appHcations. The ethylation of benzene with ethylene to ethylbenzene used in the manufacture of styrene, is one of the largest scale industrial processes. The reaction is done under the catalysis of AlCl in the presence of a proton source, ie, H2O, HCl, etc, although other catalysts have also gained significance. 

For example, ia the iadustriaHy important alkylation of benzene with ethylene to ethylbenzene, polyethylbenzenes are also produced. The overall formation of polysubstituted products is minimized by recycling the higher ethylation products for the ethylation of fresh benzene (14). By adding the calculated equiUbrium amount of polyethylbenzene to the benzene feed, a high conversion of ethylene to monoethylbenzene can be achieved (15) (see also... 

Ethjlben ne Synthesis. The synthesis of ethylbenzene for styrene production is another process in which ZSM-5 catalysts are employed. Although some ethylbenzene is obtained direcdy from petroleum, about 90% is synthetic. In earlier processes, benzene was alkylated with high purity ethylene in liquid-phase slurry reactors with promoted AlCl catalysts or the vapor-phase reaction of benzene with a dilute ethylene-containing feedstock with a BF catalyst supported on alumina. Both of these catalysts are corrosive and their handling presents problems. 

Most of the industrially important alkyl aromatics used for petrochemical intermediates are produced by alkylating benzene [71-43-2] with monoolefins. The most important monoolefins for the production of ethylbenzene, cumene, and detergent alkylate are ethylene, propylene, and olefins with 10—18 carbons, respectively. This section focuses primarily on these alkylation technologies. 

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. 

Styrene. Commercial manufacture of this commodity monomer depends on ethylbenzene, which is converted by several means to a low purity styrene, subsequendy distilled to the pure form. A small percentage of styrene is made from the oxidative process, whereby ethylbenzene is oxidized to a hydroperoxide or alcohol and then dehydrated to styrene. A popular commercial route has been the alkylation of benzene to ethylbenzene, with ethylene, after which the cmde ethylbenzene is distilled to give high purity ethylbenzene. The ethylbenzene is direcdy dehydrogenated to styrene monomer in the vapor phase with steam and appropriate catalysts. Most styrene is manufactured by variations of this process. A variety of catalyst systems are used, based on ferric oxide with other components, including potassium salts, which improve the catalytic activity (10). 

All lation. Friedel-Crafts alkylation (qv) of benzene with ethylene or propjiene to produce ethylbenzene [100-41 -4] CgH Q, or isopropylbenzene [98-82-8] (cumene) is readily accompHshed ia the Hquid or vapor phase with various catalysts such as BF (22), aluminum chloride,... 

All lation. An exceUent example of alkylation is the Mobil-Badger process, which uses ZSM-5-type zeoHte to produce ethylbenzene by alkylation of benzene with ethylene (12,40) ... 

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