Styrene process

However, the ethylben2ene or styrene process based on side-chain alkylation has not been developed for commercial appHcations. 

Fig. 5. Purification of styrene in the dehydrogenation reactor effluent in the FinaBadger styrene process A, ben2ene—toluene column B, ethylbenzene recycle column C, styrene finishing column and D, residue finishing. Courtesy of The Badger Company, Inc.

In most existing styrene processes, the catalyst is loaded into large, radial flow reactors, which are operated adiabaticaHy at low pressure and temperatures near 600°C. Heat is suppHed by superheated steam. During start-up, dehydrogenation begins slowly and accelerates as the Fe (HI) is reduced to Fe (II,III). The catalyst, which was red in color when fresh, turns to the characteristic black color of Fe O. ... 

The feedstocks to the styrene process are ethylbenzene and superheated steam, and a typical unit produces hydrogen, small amounts of light hydrocarbons and carbon dioxide as gaseous products, and a Hquid product stream containing 95% + styrene and minor amounts of toluene, benzene, and other aromatics. In an integrated plant, the benzene can be recycled to the ethylbenzene unit, while the other by-products usually are consumed as fuel for the highly endothermic process. 

Filtration rate, 77 330-332 Filtration time, optimizing, 77 346 Fina-Badger s PAR technology, 23 335 Fina-Badger styrene process, 23 339, 340... 

The PO/styrene process is one of those coproduct operations where the economics get muddled easily. When styrene is in short supply and high-priced, PO from these plants look good. When PO is in long supply and low-priced, styrene from these plants looks anemic. The product managers of both products are rarely in the same mood. 

Acetone could be considered as by- or coproduct of cumene manufacture. Propylene oxide is a by- or coproduct in one of the styrene processes. 

The so-called toluene-to-styrene process [Eq. (12.33)], first reported in a patent by Monsanto,148 applies bismuth or lead oxides in dehydrodimerization of toluene to stilbene, which, in turn, is cleaved with ethylene to styrene 149... 

The Cu+/zeolite-catalyzed cyclodimerization of 1,3-butadiene at 100°C and 7 atm was found to give 4-vinylcyclohexene [Eq. (13.12)] with high (>99%) selectivity. Subsequent oxidative dehydrogenation over an oxide catalyst in the presence of steam gives styrene. The overall process developed by Dow Chemical113 offers an alternative to usual styrene processes based on ethylation of benzene (see Section 5.5.2). 

Thus, in those cases in which reversibility of the reaction imposes a serious limitation, the equilibrium conversion must be calculated in order that the most advantageous conditions to be employed in the reactors may be chosen this may be seen in detail in the following example of the styrene process. A study of the design of this process is also very instructive in showing how the basic features of the reaction, namely equilibrium, kinetics, and suppression of byproducts, have all been satisfied in quite a clever way by using steam as a diluent. 

Final choice of reaction conditions in the styrene process ... 

The use of steam has a number of other advantages in the styrene process. The most important of these is that it acts as a source of internal heat supply so that the reactor can be operated adiabatic-ally. The dehydrogenation reaction is strongly endothermic, the heat of reaction at 560°C being (- AH) - 125,000 kJ/kmoL It is instructive to look closely at the conditions which were originally worked out for this process (Fig. 1.7). Most of the.steam, 90 per cent of the total used, is heated separately from the ethylbenzene stream, and to a higher temperature (7I0SC) than is required at the inlet to the... 

The use of steam in the styrene process above is an example of how an engineer can exercise a degree of ingenuity in reactor design. The advantages conferred by... 

As the styrene process shows, it is not generally feasible to operate a reactor with a conversion per pass equal to the equilibrium conversion. The rate of a chemical reaction decreases as equilibrium is approached, so that the equilibrium conversion can only be attained if either the reactor is very large or the reaction unusually fast. The size of reactor required to give any particular conversion, which of course cannot exceed the maximum conversion predicted from the equilibrium constant, is calculated from the kinetics of the reaction. For this purpose we need quantitative data on the rate of reaction, and the rate equations which describe the kinetics are considered in the following section. 

It was not only gasoline production that was fundamental in the late 30s synthetic rubber was just as important. In 1934 BASF and Bayer had developed Buna-S rubber, which was a copolymer containing styrene. Processes were also developed in the U.S. to produce styrene. 

Example 2 Synthesis of a styrene process. Styrene, the monomer of polystyrene, has enjoyed strong market growth over the past two decades. It is prepared starting with benzene and ethylene which react to form ethylbenzene the ethylbenzene is dehydrogenated to yield styrene. Further information about styrene manufacture, properties, and uses is available. 3 In this example, the steps involved in synthesizing a process to produce styrene from ethylbenzene will be illustrated. The procedure followed is analogous to that followed by the PIP program. 

Figure 4.5 shows the styrene process that has been devised as a result of this analysis. 

Example 3 Degrees of freedom for styrene process. Determine the degrees of freedom for the styrene process using the process flow diagram, Fig. 4-5. 

Chemical processes more often than not contain recycle, a feature that complicates their analysis. Recycle often occurs, as in the styrene process where unreacted ethylbenzene is recovered and recycled back to the reactor as a physical mass flow. Recycle also occurs in the form of heat exchange (again in the styrene process) and sometimes as information, e.g., a specification that two variable temperatures must equal each other. The sequential-modular solution strategy is based upon knowing all inputs to a module and using these to calculate all outputs. When an input stream to a module is the output of a downstream module (i.e., there is recycle), calculations cannot be performed for the upstream module because one of its inputs is not yet known. This is illustrated in Fig. 4.7 unit 1 cannot be calculated because input stream 4 is the output of unit 2 nor can unit 2 be calculated because input stream 2 is an output of unit 1. This same problem of circular reasoning was encountered in Example 1. This dilemma in the sequential modular solution scheme can be... 

Example 4 Computational order for styrene process. A styrene process flow diagram is shown in Fig. 4-5. From this flow sheet it is apparent that there are two recycle streams in this simple process the unreacted ethylberizene is recycled and mixed with the fresh feed and the reactor effluent is recycled back to the heat exchanger. 

Application To produce polymer-grade styrene monomer (SM) by dehydrogenating ethylbenzene (EB) to form styrene using the Lummus/UOP "Classic" styrene process for new plants and the Lummus/UOP SMART process for revamps involving plant capacity expansion. 

Application To directly recover styrene from raw pyrolysis gasoline derived from steam cracking of naphtha, gas oils and NGLs using the GT-Styrene process. 

Innes, R. A Swift, H. E, Toluene to styrene. A difficult goal CHEMTECH, 244-248 (April 198U Wett, Tn Monsanto/Lummus styrene process is efficient 00 and Gas J., 79 (29) 76-80 (IMl). 

However, the probability for the reaction progression greatly depends on the monomer conversion. Because the viscosity of the dispersed phase, in the first stage, is fairly low and the quantity of styrene is sufficiently high, the decomposition process (Figure 9.4) occurs only up to the benzoyloxy radical, which can directly start the kinetic chain. The purely thermal start of chains with reactive dimers of styrene, as a result of Diels-Alder reaction, can be ignored at fairly low temperatures of suspension polymerization, in contrast to the conditions for the bulk styrene process [4-7]. 

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