Dehydrogenation of ethyl benzene

The procedure described is essentially that of Ballard and Dehn.1 Stilbene has also been prepared by reduction of desoxy-benzoin,20 benzaldehyde,23 and benzil 2o-2c by dehydrogenation of ethyl benzene,30 toluene,30- 33- 3, and bibenzyl 33-3alkaline reduction of phenylnitromethane,40 phenylnitroacetonitrile,40 and desoxybenzoin 43 by distillation of benzyl sulfone,50 benzyl sulfide,60-63 calcium cinnamate,5 cinnamic acid,5d phenyl cinna-mate,6e-6/ and diphenyl fumarate ie by dehydrohalogenation of a,a -dichlorobibenzyl60 and benzyl chloride 63 by dehalogenation of a,a,c/,a -tetrachlorobibenzyl70 and benzal chloride 73 by the coupling of cinnamic acid and phenyldiazonium chloride 8 by de-... 

Catalytic dehydrogenation of ethyl benzene to styrene is accompanied by the formation of benzene and some toluene, but the latter will be neglected in this problem (Wenner Dybdal, Chem Eng Progress 44 275, 1948). The reactions and their rate equations are... 

Styrene was obtained by catalytic dehydrogenation of ethyl benzene. Styrene gets readily polymerised... 

The separation of benzene from a mixture with toluene, for example, requires only a simple single unit as shown in Figure 11.1, and virtually pure products may be obtained. A more complex arrangement is shown in Figure 11.2 where the columns for the purification of crude styrene formed by the dehydrogenation of ethyl benzene are shown. It may be seen that, in this case, several columns are required and that it is necessary to recycle some of the streams to the reactor. 

Monomeric styrene (95% purity) 17 500 tons Catalytic dehydrogenation of ethyl benzene. 

The Langmuir-Hinshelwood kinetic model describes a reaction in which the rate-limiting step is reaction between two adsorbed species such as chemisorbed CO and 0 reacting to form C02 over a Pt catalyst. The Mars-van Krevelen model describes a mechanism in which the catalytic metal oxide is reduced by one of the reactants and rapidly reoxidizd by another reactant. The dehydrogenation of ethyl benzene to styrene over Fe203 is another example of this model. Ethyl benzene reduces the Fe+3 to Fe+2 whereas the steam present reoxidizes it, completing the oxidation-reduction (redox) cycle. This mechanism is prevalent for many reducible base metal oxide catalysts. There are also mechanisms where the chemisorbed species reacts... 

The same catalysts could also be used in the dehydrogenation of ethyl benzene to form styrene ... 

Example 13-1 Wenner and DybdaE studied the catalytic dehydrogenation of ethyl benzene and found that with a certain catalyst the rate could be represented by the reaction... 

Design a reactor system to produce styrene by the vapor-phase catalytic dehydrogenation of ethyl benzene. The reaction is endothermic, so that elevated temperatures are necessary to obtain reasonable conversions. The plant capacity is to be 20 tons of crude styrene (styrene, benzene, and toluene) per day. Determine the bulk volume of catalyst and number of tubes in the reactor by the one-dimensional method. Assume that two reactors will be needed for continuous production of 20 tons/day, with one reactor in operation while the catalyst is being regenerated in the other. Also determine the composition of the crude styrene product. 

Fig. 28. Permselective membrane reactor concept for dehydrogenation of ethyl benzene to produce styrene.

Styrene is produced by the catalytic dehydrogenation of ethyl benzene (EB) in a two-stage fixed-bed adiabatic reactor. Equilibrium and heat capacity data are as given shortly. 

The dehydrogenation of ethyl benzene (EB) to styrene (S) is carried out in 3-inch tubes packed with -inch catalyst pellets. The feed contains 15 moles H20/mole EB and enters the reactor at 1.3 atm and 600°C. The particle Reynolds number is 800 and Pr = 1.0. The heat of reaction is 33 kcal/mol, and E = 2 kcal/mol. 

However when "basic" X type zeolites are used the ring alkylation is depressed and the side chain alkylation occured to yield a mixture of ethylbenzene and styrene (70). Styrene was found to be a secondary reaction product formed via the dehydrogenation of ethyl benzene (71). 

Styrene is obtained almost exclusively by dehydrogenation of ethyl benzene, and in small quantities by the dehydration of a-methyl benzyl alcohol, the by-product of the propylene oxide synthesis from propylene and a-methyl benzyl hydroperoxide. Styrene can be polymerized free radically, cationically, anionically, and with Ziegler-Natta catalysts. Only the free radical polymerizations have commercial significance. 

The dehydrogenation of ethyl benzene and diethyl benzene to styrene and divinyl benzene. 

Styrene is obtained almost exclusively from the catalytic dehydrogenation of ethyl benzene (600°C, metal oxide). Ethyl benzene is obtained by a Friedel-Crafts reaction of benzene with ethylene. The separation of the styrene from the tetrafunctional, and therefore cross-linkable, divinyl benzene is important. In order to prevent premature polymerization, sulfur or dinitrophenols are added before distillation and t-butyl catechol is added before storing. 

Herman, C., Quicker, P., Dittmeyer, D. (1997). Mathematical simulation of catalytic dehydrogenation of ethyl benzene styrene in a composite palladium membrane reactor. Journal of Membrane Science, 136, 161—172. 

EA Technology carried out a feasibihty study of induction heating of reactor walls (Gardner, 1991). The reaction was the electrically-driven dehydrogenation of ethyl benzene to styrene. The walls of a channel packed with catalyst were inductively heated at low frequency. This reduced the temperature gradient across the wall for cases where external heating is required. The power supply for induction heating... 

Addition of Inert Feed Material to Control Equilibrium Reactions. Sometimes it is necessary to add an inert material to shift the equilibrium of the desired reaction. Consider the production of styrene via the catalytic dehydrogenation of ethyl benzene ... 

Corrosion prevention by chemicals is not ordinarily practical in refinery work for acids that are either concentrated or strong. However, dilute acid streams often may be rendered non-corrosive by use of inexpensive neutralizers and/or filming inhibitors. Examples include the mixed condensate composed of water and hydrocarbon liquids from dehydrogenation of ethyl benzene to styrene in the presence of steam, various acidic wash streams, etc. 

Problem 1-11 (Level 2) Styrene, the monomeric building block for the polymer polystyrene, is made by the catalytic dehydrogenation of ethyl benzene. Ethyl benzene, in turn, is made by the alkylation of benzene with ethylene, as shown by Reaction (A) below. A common side reaction is that addition of another alkyl group to ethyl benzene to form diethyl benzene. This reaction is shown as Reaction (B). The second alkyl group may be in the ortho, meta, or para position. 

The dehydrogenation of ethyl benzene is endothermic so that heat must be sup-pUed during operation. The two commercial styrene processes either incorporate several adiabatic beds with interbed heat exchange/steam addition or isothermal tubular reactors with a siritable heating mediirm in order to maintain operating... 

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