Synthesis of ethylbenzene

The synthesis of ethylbenzene from benzene and ethylene was discovered in 1879 by M.Balsohn, who introduced ethylene gas into a mixture of benzene and aluminum chloride, and with heating to 70 to 80 °C obtained ethylbenzene and higher alkylated benzenes. In 1891, ethylbenzene was found in the xylene fraction of coal tar. 

Ethylbenzene is produced either by the alkylation of benzene with a C2 component, or by isolation from aromatic fractions derived from coal or petroleum refining. 

The synthesis of ethylbenzene is carried out by Friedel-Crafts alkylation of benzene with ethylene. 

A fundamental problem in the alkylation of aromatics is the likelihood of polyalkylation of the initially produced reactive alkyl aromatics. Therefore, to obtain high yields, alkylation is operated with low primary conversion and recycle of polyalkylated aromatics. In the ethylation of benzene, the primary conversion rate is kept to around 40%, and a total yield of 98 mol% of ethylbenzene is achieved after transalkylation. 

The optimum molar ratio of ethylene to benzene is around 0.9 as ethylene concentration increases, so the level of polyalkylated benzene derivatives rises. In order to assure high selectivity with satisfactory conversion rates, the synthesis of ethylbenzene is carried out industrially with molar ratios of ethylene to benzene of only 0.35 to 0.55. 

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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. 

Figure 2 Suggested Scheme for the Ir-catalyzed synthesis of ethylbenzene.

The synthesis of ethylbenzene involves the following exothermic reaction CfiHs-CjHs = - U4 kJ/mol... 

Outline all steps in the synthesis of ethylbenzene from each of the following compounds, using any needed aliphatic or inorganic reagents. 

Reaction Mechanisms Sections 4.5C, 5.1 B, and 6.4B.2 The mechanism of electrophilic substitution for the synthesis of ethylbenzene is one of two-step substitution the electrophile bonds and forms a carbocation which is neutralized upon elimination of hydrogen ion. 

This type of process does not provide for a separate reactor for the transalkylation of the polyalkylbenzenes formed, as in the case of the synthesis of ethylbenzene. So far, their formation has been limited preferably by using a large excess of benzene. 

The two most important applications in this field are the synthesis of ethylbenzene and cumene, in which zeolites replaced the former liquid HF and AICI3 catalysts. 

Fan MH, Jiang PW, Bi PY, Deng SM, Yan LF, Zhai Q, Wang TJ, Li QX (2013) Directional synthesis of ethylbenzene through catalytic transformation of lignin. Bioresour Technol 143 59... 

In the same year Eliel ( 2) reported the synthesis of ethylbenzene with one deuterium in the a TOsition. The optical activity of this compound ([o] = -0.30°) clearly derives from... 

Alkylation of aromatic compounds (eqs. 4.10 and 4.11) is referred to as the Friedel-Crafts reaction, after Charles Friedel (French) and James Mason Crafts (American), who first discovered the reaction in 1877. The electrophile is a carbocation, which can be formed either by removing a halide ion from an alkyl halide with a Lewis acid catalyst (for example, AICI3) or by adding a proton to an alkene. For example, the synthesis of ethylbenzene can be carried out as follows ... 

Improvements in chemical processes are very often based on the discovery or development of new catalysts or adsorbents. One particularly exciting example in the field of zeolite catalysis is the replacement of the formerly used amorphous silica-aliunina catalysts in fluid catalytic cracking (FCC) of vacuiun gas oil by rare earth exchanged X-type zeoUtes [1]. This resulted in considerably improved yields of the desired gasoUne and, hence, a much more efficient utilization of the crude oil. Fiuther examples are the introduction of zeolite HZSM-5 as catalyst in the synthesis of ethylbenzene from benzene and ethylene [2], for xylene isomerization [3] and for the conversion of methanol to high-... 

The Friedel-Crafts process is frequently the most useful method for the introduction of an alkyl group. The reaction is capable of many practical applications, and a large number of patents have appeared on the preparation of alkyl derivatives of various aromatic compounds such as xylene, naphthalene, and phenols. Patents have covered the utilization of such alkylating agents as the olefins derived from cracking, the mixtures prepared by chlorination of petroleum fractions, and various naturally occurring waxy esters. The most important application is the synthesis of ethylbenzene from ethylene and benzene. 

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