Ethylbenzene pyrolysis

Significant amounts of CH4 and C2H2 are also formed but will be ignored for the purposes of this example. The ethane is diluted with steam and passed through a tubular furnace. Steam is used for reasons very similar to those in the case of ethylbenzene pyrolysis (Section 1.3.2., Example 1.1) in particular it reduces the amounts of undesired byproducts. The economic optimum proportion of steam is, however, rather less than in the case of ethylbenzene. We will suppose that the reaction is to be carried out in an isothermal tubular reactor which will be maintained at 900°C. Ethane will be supplied to the reactor at a rate of 20 tonne/h it will be diluted with steam in the ratio 0.3 mole steam 1 mole ethane. The required fractional conversion of ethane is 0.6 (the conversion per pass is relatively low to reduce byproduct formation unconverted ethane is separated and recycled). The operating pressure is 1.4 bar total, and will be assumed constant, i.e. the pressure drop through the reactor will be neglected. 

The results for other conditions for polystyrene pyrolysis were reported. For example, pyrolysis on different catalysts was shown to lead to modifications of the yield of specific components in the pyrolysate. During the pyrolysis of PS on solid acid catalysts, the increase of contact time and surface acidity enhanced the production of ethylbenzene. Pyrolysis in the presence of water increases the yield of volatile products and that of monomer [30]. Studies on the generation of polycyclic aromatic hydrocarbons (PAHs) in polystyrene pyrolysates also were reported [36]. It was demonstrated that the content in PAHs in polystyrene pyrolysates increases as the pyrolysis temperature increases. The analysis of the end groups in polystyrenes with polymerizable end groups (macromonomers) was reported using stepwise pyrolysis and on-line methylation [46]. 

A comparison between a conventional and a TS-PFR study of methanol reforming is contained in the paper by Asprey et al. (1999) and the associated paper by Peppley (1999). Other workers have used gas phase TS-PFRs in a number of studies carried out in industry. An example of industrial work is given in Investigation of the Kinetics of Ethylbenzene Pyrolysis Using a Temperature Scanning Reactor , Domke et al. (2001). Below we present some of the results and observations from selected studies and relate them to the issues raised above. 

Domke, S.B., R.F. Pogue, F.J.R. Van Neer, C.M. Smith and B.W. Wojciechowski, 2001, Investigation of Ethylbenzene Pyrolysis Using a Temperature-Scanning Reactor, Ind. Eng. Chem. (Kinetics, Catalysis, and Reaction Engineering), 40, pp. 5878-5884. 

Sources of Raw Materials. Coal tar results from the pyrolysis of coal (qv) and is obtained chiefly as a by-product in the manufacture of coke for the steel industry (see Coal, carbonization). Products recovered from the fractional distillation of coal tar have been the traditional organic raw material for the dye industry. Among the most important are ben2ene (qv), toluene (qv), xylene naphthalene (qv), anthracene, acenaphthene, pyrene, pyridine (qv), carba2ole, phenol (qv), and cresol (see also Alkylphenols Anthraquinone Xylenes and ethylbenzenes). 

In 1869 Berthelot- reported the production of styrene by dehydrogenation of ethylbenzene. This method is the basis of present day commercial methods. Over the year many other methods were developed, such as the decarboxylation of acids, dehydration of alcohols, pyrolysis of acetylene, pyrolysis of hydrocarbons and the chlorination and dehydrogenation of ethylbenzene." ... 

Figure 3.24 shows the process flowsheet for an ethylene/ethylbenzene plant, Gas oil is cracked with steam in a pyrolysis furnace to form ethylene, low BTU gases, hexane, heptane, and heavier hydrocarbons. The ethylene is then reacted with benzene to form ethylbenzene (Stanley and El-Halwagi, 1995). Two wastewater streams are formed R ... 

Ethylbenzene (C6H5CH2CH3) is one of the Cg aromatic constituents in reformates and pyrolysis gasolines. It can be obtained by intensive fractionation of the aromatic extract, but only a small quantity of the demanded ethylbenzene is produced by this route. Most ethylbenzene is obtained by the alkylation of benzene with ethylene. Chapter 10 discusses conditions for producing ethylbenzene with benzene chemicals. The U.S. production of ethylbenzene was approximately 12.7 billion pounds in 1997. Essentially, all of it was directed for the production of styrene. 

Pyrolysis of ethylbenzene was carried out at 950 F in a flow reactor (Rase Kirk, Chem Eng Prog 30 35, 1954) with the tabulated data of fractional conversion at two pressures against W/F g catalyst/(gmol feed/hr). Find the fractional conversion at P = 1.5 and W/F = 25. 

The pyrolysis of 4-ethylphenylthallium(III) difluoride, for example, gives ethylbenzene (41 %) as the only identifiable product.10 Conversion to the aryl fluorides can be performed by using boron trifluoride. 

The pyrolysis gas chromatogram of ABS at 550°C changes considerably when the pyrolysis products are passed over zeolite catalysts. The specific activity towards certain reactions, e.g., cycliza-tion, aromatization, or chain cleavage is somewhat dependent on the nature of the individual zeolite. In general, enhanced benzene, toluene, ethylbenzene at the cost of dimer, trimer formation is observed. Nitrogen containing compounds do not appear in the pyrolysis oil after catalytic conversion. However, the product gas is rich in nitriles (132). 

The term mixed xylenes describes a mixture containing the three xylene isomers and usually EB. Commercial sources of mixed xylenes include catalytic refonuate. pyrolysis gasoline, toluene disproportionation product, and coke-oven light oil. Ethylbenzene is present in all of these sources except toluene disproportionation product. Catalytic reformate is the product obtained from catalytic reforming processes. 

Pyrolysis gasoline is a by-product of the steam cracking of hydrocarbon feeds in ethylene crackers. Pyrolysis gasoline typically contains about 50 to 70% by weight of aromatics, of which roughly 50% is benzene, 30% is toluene, and 20% is mixed xylenes (which includes ethylbenzene). 

The feedstock consists of a mixture of C8 aromatics typically derived from catalytically reformed naphtha, hydrotreated pyrolysis gasoline oran LPG aromatization unit. The feed may contain up to 40% ethylbenzene, which is converted either to xylenes or benzene by the Isomar reactor at a high-conversion rate per pass. Feedstocks may be pure solvent extracts or fractional heartcuts containing up to 25% nonaromatics. Hydrogen may be supplied from a catalytic reforming unit or any suitable source. Chemical hydrogen consumption is minimal. 

Krupp Uhde Styrene Pyrolysis gasoline MORPHYLANE process uses extractive distillation to separate styrene form xylenes and ethylbenzene NA NA... 

Example 7.2. Pyrolysis of n-pentadecylbenzene [5]. Upon pyrolysis, n-pentadecyl-benzene decomposes to about sixty different products. The major ones are toluene, styrene, n-tridecane, 1-n-tetradecene, and ethylbenzene. First-rank Delplots of experimental results are shown in Figure 7.2. 

Decomposition according to both previous schemes combined (PS, PIB). In a polystyrene production plant, PS could conveniently be converted into monomer, since facilities for separating the various pyrolysis products (styrene and its oligomers, ethylbenzene, toluene, benzene, etc.) are available already on site. However, huge PS production plants generally generate insufficient off-spec, scrap to feed a pyrolysis unit of even a small industrial size ... 

Polystyrene (PS). The thermal degradation proceeds again by C-C scission, which is then followed by a complex radical chain reaction. In the early stages of reaction and at low temperatures (290°C), the primary products are styrene, diphenylbutene, and triphenyUiexene. At higher temperature or longer residence times, the final stable products are toluene, ethylbenzene, cumene, and triphenylbenzene [47]. Fluidized-bed pyrolysis was applied successfully to pure PS more than 60% of monomer and 25% of other aromatics were obtained at a pyrolysis temperatnre of 515°C [25, 26]. 

In terms of the individual compounds found in the condensable products, as with conventional pyrolysis, a-alkenes alkanes and dialkenes were the most abundant compounds. A large number of other aliphatic and aromatic compounds ranging from C3 to approximately 55 were also found, including methylcyclopentene, benzene, cyclohexene, toluene, ethylbenzene, xylene, propylbenzene and methyl-ethylbenzene. The analysis also showed that the condensables obtained at 500 and 700°C, although possessing similar levels of cleavage, showed important differences in the individual compounds present [85],... 

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