Ethylbenzene dehydrogenation to styrene

Consider, for instance, ethylbenzene dehydrogenation to styrene. The traditional plant used in the process industry [32] is based on an fixed-bed catalytic reactor to which a preheated mixture of ethylbenzene and steam, which prevents coke formation, is fed. The reaction products then normally undergo a rather complex separation scheme, mostly based on distillation columns, aimed at recovering styrene (the desired product), benzene, toluene and H2 (by products), and a certain amount of unconverted ethylbenzene, which has to be recycled. The overall conversion per pass is typically around 60%, whereas selectivity is close to 90%. 

Caija, G., Nakamura, R.. Aida. T. and Niiyama, H. (2003). Mg-V-AI mixed oxides with mesoporous properties using layered double hydroxides as precursors catalytic behavior for the process of ethylbenzene dehydrogenation to styrene under a carbon dioxide flow. 7. Coto/., 218, 104-110. 

Hossain, M. M., Atanda, L., Al-Yassir, N., Al-Khattaf, S. (2012). Kinetics modeling of ethylbenzene dehydrogenation to styrene over a mesoporous alumina supported iron catalyst. Chemical Engineering Journal, 207—208, 308—321. 

Vanadium-based catalysts have been widely explored. For example, Sakurai et al. [120] observed high EB conversirai (67.1 %) and selectivity to styrene (80 %) for vanadium supported oti activated carbon in the presence of CO2 at 823 K (EB conversion was 14 % higher than in the presence of argon). Vanadium-substitution in Mg-Al hydrotalcite-Uke catalysts resulted in Mg-V-Al mixed oxides with high surface area and mesoporous characteristics, which are favourable for ethylbenzene dehydrogenation to styrene under CO2 flow [121]. In addition, V was identified as the active site for the dehydrogenation process [121]. The key properties of this catalyst, besides its mesoporous characteristics, are the weak Lewis acid sites cmitributed by aluminum, which reduce the catalyst deactivation. 

It has been stated in this work that the kind and contamination degree of the initial iron compound used for the Fe-K/Ca-Cr catalyst preparation, which can be used in ethylbenzene dehydrogenation to styrene, exerted rather substantial influence on the catalyst activity and selectivity in the mentioned reaction. Hence, a proper selection of the kind of initial iron compound, as well as the selection of appropriate conditions for these compounds preparation can substantially help us to enhance the catalyst activity and selectivity. 

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). 

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. 

Example 4 Styrene from Ethylbenzene The principal reaction in the dehydrogenation of ethylbenzene is to styrene and hydrogen. 

The bulk of commercial styrene is prepared by the Dow process or some similar system. The method involves the reaction of benzene and ethylene to ethylbenzene, its dehydrogenation to styrene and a final finishing stage. It is therefore useful to consider this process in each of the three stages. 

Ethylbenzene is dehydrogenated to styrene over a fixed bed of catalyst and in the presence of a large excess of steam at 1150-1200°F and 1 atmosphere. 

Ethylbenzene is mainly used to produce styrene. Over 90% of the 12.7 billion pounds of EB produced in the U.S. during 1998 was dehydrogenated to styrene. 

In the Monsanto/Lummus Crest process (Figure 10-3), fresh ethylbenzene with recycled unconverted ethylbenzene are mixed with superheated steam. The steam acts as a heating medium and as a diluent. The endothermic reaction is carried out in multiple radial bed reactors filled with proprietary catalysts. Radial beds minimize pressure drops across the reactor. A simulation and optimization of styrene plant based on the Lummus Monsanto process has been done by Sundaram et al. Yields could be predicted, and with the help of an optimizer, the best operating conditions can be found. Figure 10-4 shows the effect of steam-to-EB ratio, temperature, and pressure on the equilibrium conversion of ethylbenzene. Alternative routes for producing styrene have been sought. One approach is to dimerize butadiene to 4-vinyl-1-cyclohexene, followed by catalytic dehydrogenation to styrene ... 

Consider a fixed-bed catalytic reactor (FBCR), with axial flow, for the dehydrogenation of ethylbenzene (A) to styrene (S) (monomer). From the information given below, calculate the temperature (TIK) in the first-stage bed of the reactor,... 

The important derivatives of benzene are shown in Table 8.8. Ethylbenzene is made from ethylene and benzene and then dehydrogenated to styrene, which is polymerized for various plastics applications. Cumene is manufactured from propylene and benzene and then made into phenol and acetone. Cyclohexane, a starting material for some nylon, is made by hydrogenation of benzene. Nitration of benzene followed by reduction gives... 

Styrene. Still another process in which petroleum-derived ethylene serves as a raw material in the production of synthetic polymers is the reaction of ethylene with benzene to produce ethylbenzene, followed by dehydrogenation to styrene. 

In the process, ethylbenzene is dehydrogenated to styrene in a fixed-bed catalytic reactor. The feed stream is preheated and mixed with superheated steam before being injected into the reactor at a temperature above 490°C. The steam serves as a dilutant and decokes the catalyst, thereby extending its life. The steam also supplies the necessary heat for the endothermic dehydrogenation reaction. For our model we have chosen six reactions to represent the plant data. 

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 benzene-derived petrochemicals in Figure 4.15 are intermediate feedstocks for styrenic and phenolic plastics. In the styrenics chain, ethylbenzene is dehydrogenated to styrene, to be used as polystyrene monomer or as a copolymer with acrylonitrile and butadiene. In the phenolics chain, cumene is an intermediate for making phenol. Bisphenol A is the condensation product of two moles of phenol and acetone. Phenol and Bisphenol A are used to manufacture resins and polycarbonates. Phenol and cyclohexane are the starting materials for the manufacture of nylon 6. 

Application Process to manufacture styrene monomer (SM) by dehydrogenating ethylbenzene (EB) to styrene. Feedstock EB is produced by alkylating benzene with ethylene using the Mobil/Badger EBMax process. 

Figure 1 A Model of the surface crystallography of iron oxide (Fe20s) as determined from LEED analysis of a thin fdm grown at Imbar oxygen pressure. The numbers indicate the positional changes of the atomic layers in percent with respect to the position in the bulk structure. B LEED image of a film before and after use as catalyst of dehydrogenation of ethylbenzene (EB) to styrene reaction temperature 873 K, reactant pressure Ibar, composition steam to EB 10 1, LHSV 0.5 h. The unit cell reflections for (001) Fe20s are indicated by circles. C Evolution of the conversion to styrene as function of time on stream under the conditions given in (B)...

The first and most elementary type of reactor to be considered is the adiabatic. In this case, the reactor is simply a vessel of relatively large diameter. Such a simple solution is not always applicable, however. Indeed, if the reaction is very endothermic, the temperature drop may be such as to extinguish the reaction before the desired conversion is attained—this would be the case with catalytic reforming of naphtha or with ethylbenzene dehydrogenation into styrene. Strongly exothermic reactions lead to a temperature rise that may be prohibitive for several reasons for its unfavorable influence on the equilibrium conversion, as in ammonia, methanol, and SO3 synthesis, or on the selectivity, as in maleic anhydride or... 

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