Ethylbenzene aluminum chloride catalyst process

In this appHcation, ZSM-5 acts as a strong, soHd acid, and may be viewed as supported on the surfaces of the crystalline zeoHte stmcture. The older, Friedel-Crafts aluminum chloride catalyzed process for ethylbenzene produces considerably more by-products and suffers from the corrosivity of the catalyst system. Because of the intermediate pore size of ZSM-5, those reactions that produce coke from larger molecules that cannot enter the ZSM-5 pore stmcture are significantly reduced, which greatly extends catalyst lifetime. 

Alkylation. Ethylbenzene [100-41 -4] the precursor of styrene, is produced from benzene and ethylene. The ethylation of benzene is conducted either ia the Hquid phase ia the preseace of a Eriedel-Crafts catalyst (AlCl, BE, EeCl ) or ia the vapor phase with a suitable catalyst. The Moasanto/Lummus process uses an aluminum chloride catalyst that yields more than 99% ethylbenzene (13). More recently, Lummus and Union Oil commercialized a zeoHte catalyst process for Hquid-phase alkylation (14). Badger and Mobil also have a vapor-phase alkylation process usiag zeoHte catalysts (15). Almost all ethylbenzene produced is used for the manufacture of styrene [100-42-5] which is obtained by dehydrogenation ia the preseace of a suitable catalyst at 550—640°C and relatively low pressure, <0.1 MPa (<1 atm). 

Styrene. Styrene is the largest benzene derivative with annual consumption about 11.5 billion lb in the United States. It is produced mainly by catalytic dehydrogenation of high-purity ethylbenzene (EB) in the vapor phase. The manufacture process for EB is based on ethylene alkylation with excess benzene. This can be done in a homogeneous system with aluminum chloride catalyst or a heterogeneous solid acid catalyst in either gas or liquid-phase reaction. In the past decade, the liquid-phase alkylation with zeolite catalyst has won acceptance. Those processes have advantages of easier product separation, reducing waste stream, and less corrosion. In addition, it produces less xylene due to lower... 

Ethylbenzene is commercially produced almost entirely as an intermediate for the manufacture of styrene. Since only a limited amount can be made by the superfractionation of Ce petroleum aromatics, most ethylbenzene is produced by the alkylation of benzene with ethylene. The alkylation reaction can occur eUher in the vapor phase or the liquid phase. A number of proven processes exist. The liquid phase processes using aluminum chloride catalysts are currently the most widely used. The purpose of this paper is to describe a new and improved version of this latter process which has been commercialized. 

Most of the ethylbenzene used in the manufacture of styrene is produced by the classical Friedel-Crafts alkylation. The process involves the reaction of benzene and ethylene in the presence of an anhydrous aluminum chloride catalyst promoted by hydrochloric acid. An alkylation mixture containing mono-, di-, tri-, and higher ethylbenzenes together with unreacted benzene is formed in this reaction which is separated by conventional distillation. 

Styrene is produced mainly by catalytic dehydrogenation of high-purity ethylbenzene in the vapor phase. A typical integrated process scheme for the manufacture of styrene and ethylbenzene is shown in Fig. 22.17, in the earlier section on ethylbenzene. The alkylation reaction, with excess benzene, takes place in a homogeneous system with an aluminum chloride catalyst. The ethylbenzene dehydrogenation also is catalytic, using a commercially available catalyst. The fractionation train separates high-purity styrene, unconverted ethylbenzene, and minor reaction by-products such as toluene. 

Alkylation of benzene for the production of ethylbenzene, the raw material for making styrene and subsequently synthetic rubber, was also greatly expanded during the war because of the shortage of natural rubber. The catalyst in most of the original ethylbenzene units was aluminum chloride, but other catalysts are now preferred by many refiners. Alkylation for the production of ethylbenzene was the first large-scale alkylation process used for the production of petrochemicals. Since that time, others, such as cumene, dodecylbenzene, alkylated phenols, diisopropylbenzene, and secondary butylbenzene, have been added to the list, and others have been developed and should soon be in commercial production. 

Ethylbenzene is manufactured by the alkylation process from ethylene and benzene feeds. The catalyst employed has mostly been aluminum chloride with a small addition of ethyl chloride promoter. Normally, aluminum chloride is somewhat corrosive and causes relatively high maintenance on the equipment. 

Over 90 percent of all ethylbenzene is produced by alkylation of benzene with ethylene in the presence of an acidic catalyst such as aluminum chloride or an acidic zeolite. Figure 10.13 shows a liquid phase alkylation process with zeolite catalyst. 

Friedel-Crafts alkylation of benzene was first commercialized for ethylbenzene and cumene in the 1940s. Aluminum chloride is the Friedel-Crafts catalyst, and the process is operated in the liquid phase. Several alternatives to aluminum chloride technology were developed later, but zeolitic catalysts are a rather recent introduction. UOP began using zeolitic catalysts in the 1990s. 

It is concluded that elimination of the separate catalyst complex phase in the AICI3 alkylation process adds significantly to its attractiveness. In addition to the ease with which a liquid phase catalyst can overcome any poisoning and get back on stream, the new homogeneous process can operate at higher temperatures and recover the heat of reaction to generate steam. It can also operate in a less corrosive environment while producing an ethylbenzene product of exceptional purity and can reduce the amount of aluminum chloride required several fold. 

Ethylbenzene production has a smaller demand for the ethylene stream than the products already described and currently stands 19th in volume of production. It is made by both liquid phase processes under moderate conditions employing aluminum chloride catalysis and by vapor phase processes at 150-250°C and 30-50 atm in the presence of a supported boron trifluoride catalyst (Eq. 19.26). 

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