Benzene ethylene alkylation

TIME ON STREAM, MINUTES Fio. 24. Rapid aging in benzene-ethylene alkylations over REX catalyst (43). 

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. 

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. 

Fig. 6. Key intermediates derived from benzene. The alkylation reaction shown employs ethylene oxide. Hydrazine condenses with acetoacetic acid to form...

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. 

Replacement of an aromatic hydrogen by an aliphatic group is called alkylation and the attached group is called an alkyl group. Industrially, benzene is alkylated by reaction with an olehnic hydrocarbon such as ethylene to make ethylbenzene, or with propylene to produce isopropylbenzene. The replaced benzene hydrogen becomes part of the attached group. 

Benzene and para-xylene are the most sought after components from reformate and pygas, followed by ortho-xylene and meta-xylene. While there is petrochemical demand for toluene and ethylbenzene, the consumption of these carmot be discussed in the same way as the other four. Toluene is used in such a large quantity in gasoline blending that its demand as a petrochemical pales in comparison. Fthylbenzene from reformate and pygas is typically dealkylated to make benzene or isomerized to make xylenes. On-purpose production of petrochemical ethylbenzene (via ethylene alkylation of benzene) is primarily for use as an intermediate in the production of another petrochemical, styrene monomer. Ethylbenzene plants are typically built close coupled with styrene plants. 

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. 

Alkylation of benzene with ethylene gives ethylbenzene,283,284,308,309 which is the major source of styrene produced by catalytic dehydrogenation. High benzene ethylene ratios are applied in all industrial processes to minimize polyethylation. Polyethylbenzenes formed are recycled and transalkylated with benzene. Yields better than 98% are usually attained. Reactants free of sulfur impurities and water must be used. 

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. 

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). 

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... 

With the experimental data1 1, the reacting temperature and pressure of the SCFP alkylation is above its critical point when the Benzene/Ethylene molar ratio is 4.5. 

Description Benzene is alkylated to EB over a zeolite catalyst in a fixed-bed, liquid-phase reactor. Fresh benzene is combined with recycled benzene and fed to the alkylation reactor (1). The benzene feed flows in series through the beds, while fresh ethylene feed is distributed equally between the beds. The reaction is highly exothermic, and heat is removed between reaction stages by generating steam. 

CDTECH Ethylbenzene Benzene, ethylene Patented fix-bed, catalytic distillation technology uses zeolite catalyst to alkylate benzene with ethylene NA NA... 

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).

Since only a small amount of aluminum chloride is used in this homogeneous alkylation process, more care has to be taken to control the method and rate of addition of ethylene to the benzene. The alkylation reaction vessel is designed to accommodate simultaneously both the very rapid ethylene-benzene reaction and the relatively slow polyethylbenzene transalkylation reactions. By careful design of the reactor and control of operating conditions, the formation of higher polyethylbenzenes can be minimized. 

Monsanto s reactor layout, in simplified form, is shown in Figure 2. Dry benzene, ethylene, catalyst, and promoter are fed continuously to the reactor. The alkylator effluent is mixed with polyethylbenzenes, mainly diethyl benzene recycled from the subsequent recovery system. The transalkylator allows enough residence time for the product to approach equilibrium. The aluminum... 

Derivation Benzene is alkylated with dodecene, to which it attaches itself in any secondary position the resulting dodecylbenzene is sulfonated with sulfuric acid and neutralized with caustic soda. For ABS (branched-chain alkyl) the dodecene is usually a propylene tetramer, made by catalytic polymerization of propylene. For LAS (straight-chain alkyl), the dodecene may be removed from kerosene or crudes by molecular sieve, may be formed by Ziegler polymerization of ethylene, or by cracking wax paraffins to a-olefins. 

Alkylation Benzene, ethylene, isopentane, isobutene CO2 or SC reactant Zeolite... 

An analysis of the aging process in the alkylation of benzene with ethylene over a rare earth-exchanged X zeolite (REX) (43) provides insight into the physicochemical phenomena operative. In this reaction, a catalyst lifetime of over 792 hours was observed at 204°, benzene ethylene molar ratio of 5, and pressure of 500 psig. Under similar conditions, but at atmospheric pressure, a drastic increase in the rate of catalyst aging was observed, with catalytic activity lasting only 2 to 3 hours. Subsequent mechanistic studies showed that most of the catalyst aging in this reaction could be attributed to complex, temperature-dependent side reactions of ethylene (44,44a). 

Benzene alkylation (Union Carbide/ Badger) Ethylbenzene 2-4 125-140 AICI3 Benzene/ ethylene Liquid-phase reaction corrosive medium... 

Benzene alkylation (Mobil/Badger) Ethylbenzene 20 420-430 Zeolite Benzene/ ethylene Gas-phase reaction low corrosion... 

One of the more common ways to manufacture ethylbenzene (Figure 11-3) is to use a fixed-bed reactor filled with a special catalyst, a series of distillation columns, and a special process for alkylation of benzene/ethylene. 

Liquid phase ethylene alkylation of benzene in the presence of AICI3 in a dispersed phase (Lewis acids). 

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

Ethyl /m s -2-butenyl sulfone (86) together with some ethyl vinyl sulfone are obtained by the reaction of ethylene and. SO2 in wet benzene using PdCl2. SO2 behaves mechanistically similarly to CO in this reaction[66]. Hydrosulfination of alkenes with SO2 and H2 is catalyzed by the Pd(dppp) complex. The sulfinic acid 87 is a primary product, which reacts further to give the. S-alkyl alkanethiosulfonates 88 as the major product, and 89 and the sulfonic acid 90 as minor products[67]. 

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. 

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