Ethylene ethylbenzene from

If the byproduct reaction is reversible and inerts are present, then changing the concentration of inerts if there is a change in the number of moles should be considered, as discussed above. Whether or not there is a change in the number of moles, recycling byproducts can suppress their formation if the bj iroduct-forming reaction is reversible. An example is in the production of ethylbenzene from benzene and ethylene ... 

Among the wide variety of organic reactions in which zeolites have been employed as catalysts, may be emphasized the transformations of aromatic hydrocarbons of importance in petrochemistry, and in the synthesis of intermediates for pharmaceutical or fragrance products.5 In particular, Friede 1-Crafts acylation and alkylation over zeolites have been widely used for the synthesis of fine chemicals.6 Insights into the mechanism of aromatic acylation over zeolites have been disclosed.7 The production of ethylbenzene from benzene and ethylene, catalyzed by HZSM-5 zeolite and developed by the Mobil-Badger Company, was the first commercialized industrial process for aromatic alkylation over zeolites.8 Other typical examples of zeolite-mediated Friedel-Crafts reactions are the regioselective formation of p-xylene by alkylation of toluene with methanol over HZSM-5,9 or the regioselective p-acylation of toluene with acetic anhydride over HBEA zeolites.10 In both transformations, the p-isomers are obtained in nearly quantitative yield. 

EBMax A continuous, liquid-phase process for making ethylbenzene from ethylene and benzene, using a zeolite catalyst. Developed by Raytheon Engineers and Constructors and Mobil Oil Corporation and first installed at Chiba Styrene Monomer in Japan in 1995. Generally similar to the Mobil/Badger process, but the improved catalyst permits the reactor size to be reduced by two thirds. 

Since approximately 2.2 lb of /-butyl alcohol would be produced per 1 lb of propylene oxide, an alternative reactant in this method is ethylbenzene hydroperoxide. This eventually forms phenylmethylcarbinol along with the propylene oxide. The alcohol is dehydrated to styrene. This chemistry was covered in Chapter 9, Section 6 as one of the syntheses of styrene. Thus the side product can be varied depending on the demand for substances such as /-butyl alcohol or styrene. Research is being done on a direct oxidation of propylene with oxygen, analogous to that used in the manufacture of ethylene oxide from ethylene and oxygen (Chapter 9, Section 7). But the proper catalyst and conditions have not yet been found. The methyl group is very sensitive to oxidation conditions. 

Ethylbenzene has not been separated commercially from Cg aromatics because it cannot be obtained therefrom in high purity as readily as it can be synthesized from benzene and ethylene by alkylation to provide the necessary stock for styrene manufacture. The current shortage of benzene, however, re-establishes interest in separating ethylbenzene from hydroformed stocks. 

We have seen previously shape-selective catalysis by ZSM-5 in the conversion of methanol to gasoline (Chapter 15).-7 Other commercial processes include the formation of ethylbenzene from benzene and ethylene and the synthesis of p-xylene. The efficient performance of ZSM-5 catalyst has been attributed to its high acidity and to the peculiar shape, arrangement, and dimensions of the channels. Most of the active sites are within the channel so a branched chain molecule may not be able to diffuse in, and therefore does not react, while a linear one may do so. Of course, once a reactant is in the channel a cavity large enough to house the activated complex must exist or product cannot form. Finally, the product must be able to diffuse out. and in some instances product size and shape exclude this possibility. For example, in the methylu-uon of toluene to form xylene ... 

In the case where there are two reactants, one of which is involved in an undesirable series reaction (A + B — C and C + B —> D), the concentration of B in the reactor can be kept small to improve selectivity. An important industrial example of this type of series reactions is in the production of ethylbenzene. The desired reaction is the formation of ethylbenzene from ethylene and benzene. The undesirable reaction is the formation of diethylbenzene from ethylene and ethylbenzene. To suppress this second series reaction, the concentration of ethylene is kept low and an excess of benzene is employed, which must be recovered and recycled. 

Another opportunity for advancement in ethylbenzene synthesis is in the development of liquid phase processes that can handle low cost feedstocks, including dilute ethylene such as ethane/ethylene mixtures. The use of dilute ethylene has become increasingly attractive since it has the potential to debottleneck ethylene crackers. Currently higher temperature, vapor phase technologies can tolerate contaminants that enter with the dilute ethylene feed from FCC units. However, these same contaminants can accelerate catalyst aging in lower temperature, liquid phase operations because they are more strongly adsorbed at the lower temperatures. Acid catalysts that tolerate elevated levels of contaminants would facilitate the development of dilute ethylene-based processes. These same catalysts could be useful in applications where lower cost or lower quality benzene feeds are all that are available. 

TYPICAL OPERATING DATA ETHYLBENZENE FROM BENZENE AND ETHYLENE... 

Alkylation of aromatics and aliphatics, e.g., ethylbenzene from ethylene and benzene, cumene from propylene and benzene, alkylation of isobutane with normal butenes... 

In a substitution, a molecular fragment of a reactant is replaced by a fragment of another reactant. A prominent example is the alkylation where an alkyl group is transferred from one molecule to another. E.g., the production of Ethylbenzene from Benzene and Ethylene by the so-called Priedel-Crafts alkylation is a standard process in chemical industry. " ... 

Since it is basically more economical to synthesize ethylbenzene from benzene and ethylene (see Chapter 5.1.2), distillation is used only in isolated cases, particularly in the USA (Cosden),... 

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. 

The following alkylated benzenes are of major industrial importance ethylbenzene produced from benzene and ethylene cumene from benzene and propylene and dodecylbenzenes from benzene and linear C12 olefins. Both liquid catalysts and more recently solid catalysts are employed commercially. 

The use of a solid catalyst for alkylating benzene with ethylene was investigated at least 50 years ago. The Alkar process (43) of UOP employed a fixed bed of 3/-AI2O3 on which BF3 had been adsorbed. The temperatures of the bed increased from about 150 to 175°C as the conversion of the ethylene increased from 0% to essentially 100%. A transalkylation reactor was used to convert the overalkylated benzene to ethylbenzene. The costs to remove sulfur compounds, CO, and water from the feedstreams were high. 

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. 

Figure 3.6 Production of ethylbenzene from benzene and ethylene...

Styrene is an important monomer of the plastics industry, generally produced from benzene (a known carcinogen) and ethylene (produced from thermal cracking of hydrocarbons). A more desirable process would be to convert toluene to ethylbenzene through a reaction with methane, the primary component of natural gas. In a 2009 BASF patent, they report a new catalyst that allows such a process to occur. Our goal is to identify the temperature at which the unreacted toluene can be recovered as a liquid when the system is operating at 100 psia. The composition of the vapor product contains 80% ethylbenzene and the remainder toluene. What is the liquid composition at the dew point ... 

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... 

It is convenient to divide the petrochemical industry into two general sectors (/) olefins and (2) aromatics and their respective derivatives. Olefins ate straight- or branched-chain unsaturated hydrocarbons, the most important being ethylene (qv), [74-85-1] propjiene (qv) [115-07-17, and butadiene (qv) [106-99-0J. Aromatics are cycHc unsaturated hydrocarbons, the most important being benzene (qv) [71-43-2] toluene (qv) [108-88-3] p- s.y en.e [106-42-3] and (9-xylene [95-47-5] (see Xylenes and ethylbenzene) There are two other large-volume petrochemicals that do not fall easily into either of these two categories ammonia (qv) [7664-41-7] and methanol (qv) [67-56-1]. These two products ate derived primarily from methane [74-82-8] (natural gas) (see Hydrocarbons, c -c ). 

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. 

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. 

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