Petroleum fractions catalytic cracking, discussion

Toluene. The sources of toluene lie primarily in the catalytic reforming of selected petroleum fractions rich in naphthenes or in the recovery of toluene contained in aromatic concentrate (pyrolysis gasoline) produced as a byproduct of ethylene manufacture—mostly from naphtha/gas oil cracking. U.S. production and pricing for benzene and the aromatics discussed in Sections... 

The major part of these catalytic processes is carried out in fixed bed reactors. Some of the main fixed bed catalytic processes are listed in Table 11.1-1. Except for the catalytic cracking of gas oil, which is carried out in a fluidized bed to enable the continuous regeneration of the catalyst, the main solid catalyzed processes of today s chemical and petroleum refining industry appear in Table 11.1-1. However, there are also fluidized bed alternatives for phthalic anhydride— and ethylene dichloride synthesis. Furthermore, Table 11.1-1 is limited to fixed bed processes with only one fluid phase trickle bed process (e.g., encountered in the hydrodesulfurization of heavier petroleum fractions) are not included in the present discussion. Finally, important processes like ammonia oxidation for nitric acid production or hydrogen cyanide synthesis, in which the catalyst is used in the form of a few layers of gauze are also omitted from Table 11.1-1. 

Butadiene, the simplest of the conjugated dienes, is produced commercially by thermal cracking of petroleum fractions and catalytic dehydrogenation of butane and butene. Polymerization of butadiene can potentially lead to three poly(l,2-butadiene)s, atactic, isotactic, and syndiotactic, and two cis and irons forms of poly(l,4-butadiene). This is discussed in Chapters 2 and 3. 

Another analytical challenge presented to the researcher involved with thermal stability and catalytic reactivity of hydrocarbons relates to cracking of heavy fractions of petroleum. Thermal analysis is not discussed in this chapter. However, one should be aware that, although paraffins are considered to be chemically inactive, the application of certain analytical techniques may cause cracking, rearrangement and isomerization. 

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