Ethylbenzene, synthesis

In shape-selective catalysis, the pore size of the zeoHte is important. For example, the ZSM-5 framework contains 10-membered rings with 0.6-nm pore size. This material is used in xylene isomerization, ethylbenzene synthesis, dewaxing of lubricatius oils and light fuel oil, ie, diesel and jet fuel, and the conversion of methanol to Hquid hydrocarbon fuels (21). 

Zeolite-Based All lation. Zeohtes have the obvious advantages of being noncorrosive and environmentally benign. They have been extensively researched as catalysts for ethylbenzene synthesis. Eadier efforts were unsuccessful because the catalysts did not have sufficient selectivity and activity and were susceptible to rapid coke formation and deactivation. 

Currently, benzene alkylation to produce ethylbenzene and cumene is routinely carried out using zeohtes. We performed a study comparing a zeohte Y embedded in TUD-1 to a commercial zeolite Y for ethylbenzene synthesis. Two different particle diameters (0.3 and 1.3 mm) were used for each catalyst. In Figure 41.7, the first-order rate constants were plotted versus particle diameter, which is analogous to a linear plot of effectiveness factor versus Thiele modulus. In this way, the rate constants were fitted for both catalysts. 

More recently, using the same methodology as described above, a commercially available alumina-bound zeolite Beta (80 wt %) was tested for ethylbenzene synthesis (28). A first-order rate constant of 0.29 cm /g-sec was obtained. A 16% zeolite Beta in TUD-1 catalyst also had a rate constant of 0.30 cm ... 

Ethylbenzene plants, 23 330-331 Ethylbenzene-styrene complex, 23 328 Ethylbenzene synthesis molecular sieves in, 16 845 zeolite-based alkylation in, 23 331-333 Ethyl benzoate, 3 635 Ethyl P-D-glucopyranoside, 4 701 7-Ethylbicyclooxazolidine, antimicrobial used in cosmetics, 7 831t Ethyl bromide, physical properties of, 4 351t... 

The titanium-silicalite composihon, TS-1, has achieved commercializahon in selective oxidation processes and iron-siUcalite in ethylbenzene synthesis. 

Another opportunity for advancement in ethylbenzene synthesis is in the development of liquid phase processes that can handle low cost feedstocks, including dilute ethylene such as ethane/ethylene mixtures. The use of dilute ethylene has become increasingly attractive since it has the potential to debottleneck ethylene crackers. Currently higher temperature, vapor phase technologies can tolerate contaminants that enter with the dilute ethylene feed from FCC units. However, these same contaminants can accelerate catalyst aging in lower temperature, liquid phase operations because they are more strongly adsorbed at the lower temperatures. Acid catalysts that tolerate elevated levels of contaminants would facilitate the development of dilute ethylene-based processes. These same catalysts could be useful in applications where lower cost or lower quality benzene feeds are all that are available. 

Distillate dewaxing Lube dewaxing Gas to aromatics Gas to Aromatics Light olefins to gasoline and distillate Methanol to gasoline Methanol to light olefins Xylene isomerization Toluene disproportionation Ethylbenzene synthesis 58-59) p-Xylene synthesis p-ethyltoluene synthesis... 

The unknown Q was made into a Grignard reagent. It deprotonates water to form ethylbenzene. Since Grignard reagent formation and protonation do not change the skeletal structure of a compound, unknown Q must be an aryl halide. The possible structures of unknown Q are shown below as reactants in the process of ethylbenzene synthesis. 

The deactivation problem was overcome by using ZSM-5 as catalyst through the Mobil-Badger ethylbenzene synthesis. At present, more than ten plants are using this process, which works at 370 C, 14-27 bars. Diethylbenzene is the main subproduct, and its production is strongly decreased by adjusting the benzene ethylene ratio (208,209). 

Zeolite MCM-22 in its Br0nsted-acid form has been described in the hterature as a useful catalyst for a variety of acid-catalyzed reactions, such as iso-alkane/olefin alkylation [e.g.40,41],skeletal and double-bond isomerization of olefins [42] and ethylbenzene synthesis via alkylation of benzene with ethylene [43], to name merely a few. Moreover, due to its very large intracrystalline cavities, zeolite MCM-22 has also been demonstrated to be a suitable host material for a variety of catalytically active guests, e.g. transition metal complexes which are useful in selective oxidation [44] or hydrogenation [45] reactions. Due to these interesting properties it seems worthwhile to focus on the synthesis features of MCM-22 (see below). 

Another method to remove benzene is to react it with propylene or ethylene (benzene alkylation) to produce propylbenzene (cumene) or ethylbenzene. Commercial benzene alkylation processes in the chemical industry have been known for many years. Typically these processes require fairly pure benzene and ethylene feed. The shape selective ZMS-5 catalyst is used as a basis for ethylbenzene synthesis in the Mobil-Badger process (Chen et. al, 1989). ZSM-5 is very selective in this process as a result this process is currently used in the chemical industry to produce about 25% of world s ethylbenzene. Currently there are 12 operating Mobil-Badger EB units including a recent Shell Chemical unit which uses FCC off-gas as the ethylene feedstock source. 

The aromatics alkylation with olefins is a well-known technology, especially in the case of ethylbenzene (a Mobil-Badger process [109]) and cumene production [110], Ethylbenzene synthesis can be catalyzed by diverse modified HZSM-5, BEA, rare-earth Y, and MCM-22 zeohtes. In most cases, the selectivity is pretty high (99%), but the process must be carried out at a large excess of benzene and the conversion of the latter typically does not exceed 20-25% at 400°C and WHSV= 3 h . For cumene production, a few commercial processes have been developed by CD-Tech (Y zeolite), Lummus-Unocal (Y zeolite), Enichem (H-BEA), Mobil-Raytheon (MCM-22), Dow Chemical (dealuminated mordenite (MOR)), and UOP (a Q-Max process with MgSAPO-31). 

Sometimes the orientation of two substituents m an aromatic compound precludes Its straightforward synthesis m Chloroethylbenzene for example has two ortho para directing groups m a meta relationship and so can t be prepared either from chloroben zene or ethylbenzene In cases such as this we couple electrophilic aromatic substitution with functional group manipulation to produce the desired compound... 

Sales demand for acetophenone is largely satisfied through distikative by-product recovery from residues produced in the Hock process for phenol (qv) manufacture. Acetophenone is produced in the Hock process by decomposition of cumene hydroperoxide. A more selective synthesis of acetophenone, by cleavage of cumene hydroperoxide over a cupric catalyst, has been patented (341). Acetophenone can also be produced by oxidizing the methylphenylcarbinol intermediate which is formed in styrene (qv) production processes using ethylbenzene oxidation, such as the ARCO and Halcon process and older technologies (342,343). 

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. 

Among the wide variety of organic reactions in which zeolites have been employed as catalysts, may be emphasized the transformations of aromatic hydrocarbons of importance in petrochemistry, and in the synthesis of intermediates for pharmaceutical or fragrance products.5 In particular, Friede 1-Crafts acylation and alkylation over zeolites have been widely used for the synthesis of fine chemicals.6 Insights into the mechanism of aromatic acylation over zeolites have been disclosed.7 The production of ethylbenzene from benzene and ethylene, catalyzed by HZSM-5 zeolite and developed by the Mobil-Badger Company, was the first commercialized industrial process for aromatic alkylation over zeolites.8 Other typical examples of zeolite-mediated Friedel-Crafts reactions are the regioselective formation of p-xylene by alkylation of toluene with methanol over HZSM-5,9 or the regioselective p-acylation of toluene with acetic anhydride over HBEA zeolites.10 In both transformations, the p-isomers are obtained in nearly quantitative yield. 

The ODH of ethylbenzene to styrene is a highly promising alternative to the industrial process of non-oxidative dehydrogenation (DH). The main advantages are lower reaction temperatures of only 300 500 °C and the absence of a thermodynamic equilibrium. Coke formation is effectively reduced by working in an oxidative atmosphere, thus the presence of excess steam, which is the most expensive factor in industrial styrene synthesis, can be avoided. However, this process is still not commercialized so far due to insufficient styrene yields on the cost of unwanted hydrocarbon combustion to CO and C02, as well as the formation of styrene oxide, which is difficult to remove from the raw product. 

Since zeolite catalysts are successfully introduced in the refining and petrochemical industries, it is not surprising that most of the recent advances concern incremental improvements of existing processes with the development of new generations of catalysts (e.g., dewaxing, ethylbenzene and cumene synthesis). The number of newer applications is much more limited, for example, direct synthesis of phenol from benzene and aromatization of short-chain alkanes, etc. However, both the improvement and development of processes contribute significantly to environmental advances. 

The synthetic importance of non-nucleophilic strong bases such as lithium diisopro-pylamide (LDA) is well known but its synthesis involves the use of a transient butyl lithium species. In order to shorten the preparation and make it economically valuable for larger scale experiments an alternate method of synthesis has been developed which also involves a reaction cascade (Scheme 3.14) [92]. The direct reaction of lithium with diisopropylamine does not occur, even with sonication. An electron transfer agent is necessary, and one of the best in this case is isoprene. Styrene is used in the commercial preparation of LDA, but it is inconvenient in that it is transformed to ethylbenzene which is not easily removed. It can also lead to undesired reactions in the presence of some substrates. The advantages of isoprene are essentially that it is a lighter compound (R.M.M. = 68 instead of 104 for styrene) and it is transformed to the less reactive 2-methylbutene, an easily eliminated volatile compound. In the absence of ultrasound, attempts to use this electron carrier proved to be unsatisfactory. In this preparation lithium containing 2 % sodium is necessary, as pure lithium reacts much more slowly. 

There are nine chemicals in the top 50 that are manufactured from benzene. These are listed in Table 11.1. Two of these, ethylbenzene and styrene, have already been discussed in Chapter 9, Sections 5 and 6, since they are also derivatives of ethylene. Three others—cumene, acetone, and bisphenol A— were covered in Chapter 10, Sections 3-5, when propylene derivatives were studied. Although the three carbons of acetone do not formally come from benzene, its primary manufacturing method is from cumene, which is made by reaction of benzene and propylene. These compounds need not be discussed further at this point. That leaves phenol, cyclohexane, adipic acid, and nitrobenzene. Figure 11.1 summarizes the synthesis of important chemicals made from benzene. Caprolactam is the monomer for nylon 6 and is included because of it importance. 

There is some increase in selectivity with functionally substituted carbenes, but the selectivity is still not high enough to prevent formation of mixtures. Phenylchlorocarbene gives a relative reactivity ratio of 2.1 1 0.09 in insertion reactions with isopropylbenzene, ethylbenzene, and toluene.132 For cycloalkanes, tertiary positions are about 15 times more reactive than secondary positions toward phenylchlorocarbene.133 Carbethoxycarbene inserts at tertiary C—H bonds about three times as fast as at primary C—H bonds in simple alkanes.134 Because of low selectivity, intermolecular insertion reactions are seldom useful in synthesis. Intramolecular insertion reaction are of considerably more use. Intramolecular insertion reactions usually occur at the C—H bond that is closest to the carbene, and good yields can frequently be obtained. Intramolecular insertion reactions can provide routes to highly strained structures that would be difficult to obtain in other ways. 

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