Styrene ethylbenzene production

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). 

The ethylene feedstock used in most plants is of high purity and contains 200—2000 ppm of ethane as the only significant impurity. Ethane is inert in the reactor and is rejected from the plant in the vent gas for use as fuel. Dilute gas streams, such as treated fluid-catalytic cracking (FCC) off-gas from refineries with ethylene concentrations as low as 10%, have also been used as the ethylene feedstock. The refinery FCC off-gas, which is otherwise used as fuel, can be an attractive source of ethylene even with the added costs of the treatments needed to remove undesirable impurities such as acetylene and higher olefins. Its use for ethylbenzene production, however, is limited by the quantity available. Only large refineries are capable of deUvering sufficient FCC off-gas to support an ethylbenzene—styrene plant of an economical scale. 

Figure 5 illustrates a typical distillation train in a styrene plant. Benzene and toluene by-products are recovered in the overhead of the benzene—toluene column. The bottoms from the benzene—toluene column are distilled in the ethylbenzene recycle column, where the separation of ethylbenzene and styrene is effected. The ethylbenzene, containing up to 3% styrene, is taken overhead and recycled to the dehydrogenation section. The bottoms, which contain styrene, by-products heavier than styrene, polymers, inhibitor, and up to 1000 ppm ethylbenzene, are pumped to the styrene finishing column. The overhead product from this column is purified styrene. The bottoms are further processed in a residue-finishing system to recover additional styrene from the residue, which consists of heavy by-products, polymers, and inhibitor. The residue is used as fuel. The residue-finishing system can be a flash evaporator or a small distillation column. This distillation sequence is used in the Fina-Badger process and the Dow process. 

The selectivity is 100% in this simple example, but do not believe it. Many things happen at 625°C, and the actual effluent contains substantial amounts of carbon dioxide, benzene, toluene, methane, and ethylene in addition to styrene, ethylbenzene, and hydrogen. It contains small but troublesome amounts of diethyl benzene, divinyl benzene, and phenyl acetylene. The actual selectivity is about 90%. A good kinetic model would account for aU the important by-products and would even reflect the age of the catalyst. A good reactor model would, at a minimum, include the temperature change due to reaction. 

No commercial process is offered at this time for side chain alkylation of toluene with methanol for styrene and ethylbenzene production. In the literature the reaction is typically carried out at toluene to methanol molar ratios from 1.0 7.5 to 5 1 from 350 to 450 °C at atmospheric pressures. In some cases inert gas is introduced to assist vaporizing the liquid feed. In other cases H2 is co-fed to improve activity, selectivity and stability. Exelus recently claimed 80% yields in their ExSyM process at full methanol conversion using a 9 4 toluene methanol feed ratio at 400-425 °C and latm (101 kPa) in a bench-scale operation. This performance appears to be... 

The catalyst consists of basic and acid sites in a microporous structure provided by zeolite and microporous materials [58-62]. Basic sites are provided by framework oxygen and/or occluded CsO. Acid sites are provided by the Cs cation and, possibly, additives such as boric and phosphoric acids. The addition of Cu and Ag increased the activity [63, 64]. Incorporation of li, Ce, Cr and Ag also has been shown to increase the styrene to ethylbenzene product ratio [65]. The reactivity of catalysts is sensitive to the presence of occluded CsO, which is in turn influenced by the preparative technique as shown by Lacroix and co-authors [64] and pointed out by Lercher [61]. 

Because ethylbenzene is used almost exclusively to produce styrene, the product specification on ethylbenzene is set to provide a satisfactory feedstock for styrene production. Levels of cumene, -propylbenzene, ethyltoluenes and xylenes in ethylbenzene are controlled to meet the required styrene purity specification. A typical sales specification is as follows purity, 99.5 wt% min. benzene, 0.1-0.3 wt% toluene, 0.1-0.3wt% ort/io-xylene + cumene, 0.02 wt% max. meto-xylene + para-xylene, 0.2 wt% max. allylbenzene + a-propylbenzene + ethyltoluene, 0.2 wt% max. diethylbenzene, 20 mg/kg max. total chlorides (as chlorine), 1-3 mg/kg max. and total organic sulfur, 4 mg/kg max. (Coty et al., 1987). 

EBMax is a liquid phase ethylbenzene process that uses Mobil s proprietary MCM-22 zeolite as the catalyst. This process was first commercialized at the Chiba Styrene Monomer Co. in Chiba, Japan in 1995 (16-18). The MCM-22-based catalyst is very stable. Cycle lengths in excess of three years have been achieved commercially. The MCM-22 zeolite catalyst is more monoalkylate selective than large pore zeolites including zeolites beta and Y. This allows the process to use low feed ratios of benzene to ethylene. Typical benzene to ethylene ratios are in the range of 3 to 5. The lower benzene to ethylene ratios reduce the benzene circulation rate which, in turn, improves the efficiency and reduces the throughput of the benzene recovery column. Because the process operates with a reduced benzene circulation rate, plant capacity can be improved without adding distillation capacity. This is an important consideration, since distillation column capacity is a bottleneck in most ethylbenzene process units. The EBMax process operates at low temperatures, and therefore the level of xylenes in the ethylbenzene product is very low, typically less than 10 ppm. 

Fina/Badger Styrene Ethylbenzene Two-stage adiabatic dehydrogenation yields high-purity product 50 2000... 

For the production of styrene/ethylbenzene, cumene/phenol, and cyclohexane as a solvent as an additive in petrol to increase the octane number 3511,3521,353, 354,... 

Identifying of individual compounds in liquid products, especially branched molecules from polypropylene, is rather difficult, because of the cracking of polypropylene yields a great number of isomer compounds. The liquid product obtained by cracking of polyethylene consisted mostly of n-alkenes and n-aUcanes, which were evenly distributed by carbon number, whereas the cracking of polystyrene yielded blends of aromatic compounds, styrene, ethylbenzene, benzene, toluene [45, 54],... 

Woodle, G.B. Zarchy, A.S. Morita, M. Shinohara, K. Leading-edge ethylbenzene production, Lummus/ UOP liquid phase EB process. 1998 International Styrene Symposium Sappora, Japan, Jun 14-18,1998. 

Oxygen is not justified for the oxidation of ethylbenzene for propylene oxide and styrene by-product. The difference is that the unreacted ethylbenzene feedstock in the liquid phase at the reactor outlet conditions is easily separated from the oxidation reactor effluent. Therefore, the presence of nitrogen in the reactor effluent is of little consequence. It is easy to separate the unreacted ethylbenzene from nitrogen and pump it back to the reactor. 

Further studies by Bargon and co-workers used PHIP to obtain evidence for coordination of styrene hydrogenation products to rhodium through the arene group." Upon reaction of styrene and p-Wz with [Rh(cod)(dppbu)]BF4 as catalyst (dppbu= l,4- A(diphenylphosphino)butane), polarized resonances for the ethyl resonances of the ethylbenzene product appeared in the NMR spectrum in addition to resonances further upfield with the same coupling constants. The fact that the former resonances were downfield relative to those of free ethylbenzene led to the suggestion that the ethylbenzene product remained bound to the Rh center immediately after it was produced (Scheme 9). (The iridium analogs of these complexes are thermodynamically stable and had been isolated and... 

Synthesis of alkylaromatics. Alkylaromatics are widely used for production of styrene (ethylbenzene), phenol (isopropylbenzene), and long chain alkylated benzene for detergent intermediates. 

Side Chain Aikyiation ofAikyiaromatiCS. Alkylation of alkylbenzenes with alkenes or alcohols over base catalysts yield the products alkylated at the side chain, while ring-alkylation proceeds over acidic catalysts. To abstract a proton from the alkyl groups, strongly basic catalysts are required. The pKa values of toluene and cumene are 35 and 37, respectively. In the vapor-phase reaction of toluene with methanol, alkali ion-exchanged zeolites, especially, RbX and CsX give ethylbenzene and styrene as products, while acidic zeollites afford xylenes (52). 

Although Ag- -Nafion membranes were unable to separate alkylarene isomers, the difference between ethyl and vinyl substituents on arenes does result in significant separation factors, e.g. the styrene/ethylbenzene separation. An even more subtle separation of this type is the separation of 3- and 4-divinylbenzene isomers (DVB) from 3- and 4-ethylvinylbenzene isomers (EVB). Commercially available DVB, which is important in pol5mier production, can contain over 40% EVB because these two substances are extremely difficult to separate by distillation. Perstraction of such a 58%/42% DVB/EVB mixture through a 25 pm Ag- --Nation membrane into isooctane produces a mixture containing less than 15% EVB. Better selectivity is obtained if the feed mixture is diluted into isooctane. 

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