Catalytic dehydrogenation, ethylbenzene

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 ... 

Problem 16.21 Styrene, the simplest alkenylbenzene, is prepared commercially for use in plastics manufacture by catalytic dehydrogenation of ethylbenzene. How might you prepare styrene from benzene using reactions you ve studied ... 

Example 3.3 Fixed-bed reactors are used for the catalytic dehydrogenation of ethylbenzene to form styrene ... 

Styrene is to be produced by the catalytic dehydrogenation of ethylbenzene according to the reaction ... 

A fluidized bed reactor is used to accomplish the catalytic dehydrogenation of ethylbenzene in the presence of steam which serves as an inert diluent. The reaction is... 

Another route to ethylbenzene is available for those remote places where olefin plants or refinery crackers are not nearby but a supply of ethane is— catalytic dehydrogenation of ethane to ethylene followed by its reaction with benzene to produce EB. The first of two steps in Figure 8-4 use a gallium zinc zeolyte catalyst that promotes ethane dehydrogenation to ethylerie at 86% selectivity and up to 50% conversion per pass. 

Styrene. All commercial processes use the catalytic dehydrogenation of ethylbenzene for the manufacture of styrene.189 A mixture of steam and ethylbenzene is reacted on a catalyst at about 600°C and usually below atmospheric pressure. These operating conditions are chosen to prevent cracking processes. Side reactions are further suppressed by running the reaction at relatively low conversion levels (50-70%) to obtain styrene yields about 90%. The preferred catalyst is iron oxide and chromia promoted with KzO, the so-called Shell 015 catalyst.190... 

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. 

As is obvious, hydrogen sulfide active under current conditions is one of the reaction products. Its aggressiveness, the ability to interact with S02 even under natural conditions, promotes sulfur accumulation in the system, affects synthesis of condensation products and can alter their catalytic activity. Therefore, despite high effectiveness, oxidative catalytic dehydrogenation of ethylbenzene by sulfur dioxide may be found unacceptable for production management in relation to ecology and protection of the environment. 

Hydrogen and water desorption measurements indicated that only the a-Fe203 (0001) face can dissociate hydrogen, which then reacts with lattice oxygen to form water, thereby reducing the oxide film. This result highlights the role of water in the catalytic dehydrogenation of ethylbenzene. Water not... 

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... 

Stamicarbon bv Ethylbenzene Butadiene Butadiene is converted to EB using liquid-phase catalytic dimerization and vapor-phase catalytic dehydrogenation NA NA... 

Central to Germany s development of polystyrene technology was Herman F. Mark (Figure 1.4). Mark worked at I. G. Farben Industrie for 6 years from 1927 to 1932, first as a research chemist (1927-28), then as Group Leader (1928-30) and finally as Assistant Research Director (1930-32). Because of the changing political climate, Mark moved to the University of Vienna, where he became Professor of Chemistry and Director of the First Chemical Institute (1932-38). While at I. G. Farben Industrie, Mark played a major role in the development of styrene monomer and PS. Mark patented a process in 1929 for the production of styrene from ethylbenzene via catalytic dehydrogenation [8]. 

A fixed-bed reactor often suffers from a substantially small effectiveness factor (e.g., 10 to 10 for a fixed-bed steam reformer according to Soliman et al. [1988]) due to severe diffusional limitations unless very small particles are used. The associated high pressure drop with the use of small particles can be prohibitive. A feasible alternative is to employ a fluidized bed of catalyst powders. The effectiveness factor in the fluidized bed configuration approaches unity. The fluidization system also provides a thermally stable operation without localized hot spots. The large solid (catalyst) surface area for gas contact promotes effective catalytic reactions. For certain reactions such as ethylbenzene dehydrogenation, however, a fluidized bed operation may not be superior to a fixed bed operation. To further improve the efficiency and compactness of a fluidized-bed reactor, a permselective membrane has been introduced by Adris et al. [1991] for steam reforming of methane and Abdalla and Elnashaie [1995] for catalytic dehydrogenation of ethylbenzene to styrene. 

Abdalla B.K. and Elnashaie S.S.E.H., Catalytic dehydrogenation of ethylbenzene to styrene in membrane reactors, AlChE J, 40 2055 (1994). 

Derivation From ethylene and benzene in the presence of aluminum chloride to yield ethylbenzene, which is catalytically dehydrogenated at 630C to form styrene. 

The demand for styrene, however, outstrips the supply available from its coproduction with propylene oxide so the other major process for the production of styrene is the catalytic dehydrogenation of ethylbenzene ... 

Although the previous discussion had centered on the catalytic dehydrogenation of paraffins, a study on the subject would not be complete without analysis of the dehydrogenation of ethylbenzene to styrene. 

Catalytic dehydrogenation of paraffins and of ethylbenzene is a commercial reality in numerous applications, from the production of light olefins, heavy olefins, to that of alkenylaromatics. Oxydehydrogenation, on the other hand, is still in the developmental stage, but, if successful, holds great promise on account of its potential energy savings. 

Ethylbenzene is catalytically dehydrogenated in the presence of steam according to the equation ... 

The benzoic acid might also be made by the Diels-Alder reaction of 1,3-butadiene with acrylic acid followed by catalytic dehydrogenation. Treatment of phenol with ammonia at high temperatures produces aniline, as mentioned in Chap. 2. Ethylbenzene can be rearranged to xylenes with zeolite catalysts. Thus, it could serve as a source of ph-thalic, isophthalic, and terephthalic acids by the oxidation of o, m, and p-xylenes. (The xylenes and other aromatic hydrocarbons can also be made by the dehydrocyclization of ethylene, propylene, and butenes, or their corresponding alkanes.44 Benzene can also be made from methane.195)... 

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