Pyrolysis of ethylbenzene

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. 

Bl3d h and Hoffman noted the high refractive power of the "metastyrol" and suggested its use for optical purposes. In 1866, Erlenmeyer showed that styrene was actually vinylbenzene and in 1869 Berthelot produced this monomer by the pyrolysis of ethylbenzene which he obtained by the condensation of ethylene and benzene. 

In the present paper we have tried to describe our development of a reaction scheme for the pyrolysis of ethylbenzene. It seemed to us that this reaction was complicated enough to get sufficient details and some of them with more general significance. On the other hand, we hoped that, due to a single initiation reaction within a fairly wide temperature range, the reaction would be relatively easily covered by the methods applied. 

Normal Pressure Apparatus (NPA). To verify our calculations based on the reaction scheme from the LPA experiments we set up a reactor which allowed us to carry out accurate quantitative measurements on the pyrolysis of ethylbenzene. This apparatus was made of quartz and is depicted in detail in Figure 2. The reaction in this flow reactor starts in the mixing chamber in which overheated argon joins the ethylbenzene flow. The temperature of the argon flow was kept at a specific value in order that the reaction temperature was obtained simply by the mixing of the two streams. The reaction zone of 10cm length was kept at a constant temperature by independent control of several coils. 

Experimental results on the pyrolysis of ethylbenzene obtained in the low pressure apparatus (LPA) are shown in Figure 3, in which the distribution of the various species is shown in dependence on the reaction temperatures as an analog plotting. 72 different species were detected. Those with an abundance smaller than 2% are suppressed in Figure 3. 

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." ... 

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. 

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. 

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. 

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. 

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]. 

Figure 6.- Total Ion Chromatogram of the thermal degradative products obtained after pyrolysis of the HA isolated from the Konin (Poland) brown coal in the presence ot TMAH. Key labels for aromatic compunds are (9) 4-memoxybenzenecarboxylic acid methyl ester, (14) benzenedicarboxylic acid dimethyl ester, (16) 3,4-dimelhoxybenzenecarboxylic acid methyl ester, (17) 3,4-dimethoxybenzeneacetic acid methyl ester, (18) 4-medioxycinnamic acid methyl ester, (19) 3,4,5-trimethoxy-l-ethylbenzene. Key labels for aliphatic compounds are (Cn) monocarboxylic acid methyl esters, (Cn l) unsaturated monocarboxylic acid methyl esters, (Cn) dicarboxylic acid dimethyl esters.

Thermal cracking of ethane, propane, butane, naphthas, gas oils, and/or vacuum gas oils is the main process employed for the production of ethylene and propylene butadiene and benzene, toluene, and xylenes (BTX) are also produced. Thermal cracking of these hydrocarbons is also called pyrolysis of hydrocarbons. Ethylene is the organic chemical produced worldwide in the largest amoimts and has been called keystone to the petrochemical industry. This technology is well documented in the literature. Somewhat similar thermal cracking processes are used to produce vinyl chloride monomer (VCM) from ethylene dichloride (EDQ, styrene from ethylbenzene, and allyl chloride from propylene dichloride (PDC). Production of charcoal and coke from wood and coal is actually a pyrolysis process, but it is not discussed here. 

In the present study, silicon and transition metal substituted aluminophosphate molecular sieves have also been evaluated for activity and selectivity for para-xylene production via Cg aromatic isomerization. In commercial practice, Cg aromatic cuts are obtained from reformate gasoline and from pyrolysis naphtha streams. Both feeds contain a significant fraction of ethylbenzene which is difficult to separate from xylenes by physical techniques,... 

Feedstocks processed commercially include C8 aromatic extracts from catalytic reformates and pyrolysis liquids resulting from ethylene cracking plants. Composition of these stocks vary widely, the major differences being their ethylbenzene content. Fresh feeds from which ethylbenzenes have been removed typically contain 2-4 wt % ethylbenzene. Inclusion of C8 aromatic extracts from pyrolysis liquids can increase ethylbenzene content to 30 wt % or higher. Fresh feeds with this range of ethylbenzene contents have been processed successfully over octafining catalyst. 

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. 

Badger, G.M. and J. Novotny The formation of aromatic hydrocarbons at high temperatures. XVlll. The pyrolysis of -decane Australian J. Chem. 16 (1963) 613-622. Badger, G.M. and T.M. Spotswood The formation of aromatic hydrocarbons at high temperatures. Part IX. The pyrolysis of toluene, ethylbenzene, propylbenzene, and butylbenzene J. Chem. Soc. (1960) 4420-4427. 

The commercial production of styrene nowadays is carried out almost exclusively by catalytic dehydrogenation of ethylbenzene. Toray has developed a process for recovery from pyrolysis gasoline, which contains 3 to 5% styrene. The method involves hydrogenation of the aliphatic diene components of a close-cut pyrolysis gasoline (130 to 140 °C) followed by extractive distillation with dimethyl-acetamide. 

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