Toluene petroleum refining

Because phenols are weak acids, they can be freed from neutral impurities by dissolution in aqueous N sodium hydroxide and extraction with a solvent such as diethyl ether, or by steam distillation to remove the non-acidic material. The phenol is recovered by acidification of the aqueous phase with 2N sulfuric acid, and either extracted with ether or steam distilled. In the second case the phenol is extracted from the steam distillate after saturating it with sodium chloride (salting out). A solvent is necessary when large quantities of liquid phenols are purified. The phenol is fractionated by distillation under reduced pressure, preferably in an atmosphere of nitrogen to minimise oxidation. Solid phenols can be crystallised from toluene, petroleum ether or a mixture of these solvents, and can be sublimed under vacuum. Purification can also be effected by fractional crystallisation or zone refining. For further purification of phenols via their acetyl or benzoyl derivatives (vide supra). 

A minor route, which now accounts for 2% of phenol, takes advantage of the usual surplus of toluene from petroleum refining. Oxidation with a number of reagents gives benzoic acid. Further oxidation to p-hydroxybenzoic acid and decarboxylation yields phenol. Here phenol competes with benzene manufacture, also made from toluene when the surplus is large. The last 2% of phenol comes from distillation of petroleum and coal gasification. 

ZSM-5 is a Mobil-proprietary, shape-selective zeolite which is used commercially in synthetic fuels (methanol-to-gasoline), petrochemicals (xylene isomerization, toluene disproportionation, benzene alkylation) and in petroleum refining (lube and... 

As examples of vapors may be cited those of petroleum hydrocarbons in petroleum refining plants, vapors of solvents (such as alcohol, ether, acetone, carbon tetrachloride, carbon disulfide, etc used in plants manufg expls and propints) vapors of liquid expls (such as DNB, DNT, NG, NGc, DEGDN, etc), and vapors of liquids (such as benzene, toluene or xylene) used as primary materials in the manuf of expls such as TNB, TNT or TNX. Some solid expls such as TNT evolve, when in molten condition, explosive vapors... 

Xylenes are produced from the reformulation of naphthas during petroleum refining in a process that also produces benzene, toluene, and ethylbenzene. Collectively, these are... 

T he petroleum industry entered the field of aromatics production largely because the unprecedented demand for toluene for the manufacture of TNT at the outbreak of World War II in 1939 could not be met by other sources. As a result of its efforts, the industry supplied 75 to 85% of all the toluene which was nitrated for TNT production during the latter years of World War II. Since that time the petroleum refiners have remained in the field and at present they are major suppliers of toluene and xylenes. In Table I it is shown that in 1949 about 59% of the toluene and 84% of the xylenes produced in the United States were derived from petroleum sources. The petroleum industry has diversified its operations in the field of aromatics production until at present a variety of materials is offered. Table II presents a partial list of the commercially available aromatics, together with some of their uses. A number of other aromatics, such as methylethyl-benzene and trimethylbenzene, have been separated in small scale lots both as mixtures and as pure compounds. 

Following the cessation of hostilities of World War II, there was a short period of abundant supply of aromatics, particularly toluene, caused by the sudden decline in consumption of aromatics for nitration and for use in aviation gasoline. Soon, however, the peacetime uses for aromatics created a demand which could be satisfied only by the combined production of aromatics from petroleum and coal-tar sources. Consequently, many of the toluene plants were purchased from the Government by the petroleum refiners and utilized for manufacture of the many aromatic products available on the market today. 

Ethylbenzene or Phenylethane, C2H.5.C H5 mw 106.16 colorless liq, resembling methyl-benzene (toluene), sp gr 0.867 at 20/4°, nD 1.4959 at 20°, fr p -95-0°, bp 136.2°, fl p 85°F (29-5°C) sp heat 0.41cal/g, viscosity 0.64 centipoise at 25° heat of combstn at Cy 108.9kcal/fnole, heat of vaporization 81.1cal at bp very si sol in w (0.01% at 15°) v sol in ale, eth, benz chlf insol in Amm hydroxide. It can be prepd by heating benzene and ethylene in presence of A1 chloride with subsequent distillation, or by fractionation directly from the mixed xylene stream in petroleum refining. Purification is by rectification. It is used in org synthesis, as solvent diluent and for prepn of explosive azidonitro-, dinitro-, trinitro- higher nitrated derivatives... 

Use and exposure Toluene is a clear, colorless liquid with an aromatic odor. It is a natural constituent of crude oil and is produced from petroleum refining and coke-oven operations. It is used in household aerosols, nail polish, paints and paint thinners, lacquers, rust inhibitors, adhesives, and solvent-based cleaning agents. Toluene is also used in printing operations, leather tanning, and chemical processes. Benzene and other PAHs are common... 

Escherichia coli (see Draths and Frost, 1994). Hydroquinone is a very practical intermediate in the manufacture of polymeric materials—almost 2 billion kg of adipic acid are produced from it and used annually in the manufacture of nylon 66. Most commercial syntheses of adipic acid utilize benzene as the starting material, derived from the benzene/toluene/xylene (BTX) fraction of petroleum refining. Benzene is hydrogenated over a metal catalyst to form cyclohexane, which is then oxidized over another catalyst that produces both cyclohexanone and cyclohexanol. See Figure 12.6. These molecules are catalytically oxidized in the presence of nitric acid to form adipic acid. 

Benzene and toluene, the simplest aromatic hydrocarbons obtained from petroleum refining, are useful starting materials for synthetic polymers. They are two components of the BTX mixture added to gasoline to boost octane ratings. 

Petroleum, unlike coal, contains few aromatic compounds and consists largely of alkanes (See Gasoline from Petroleum at the end of Chapter 3). During petroleum refining, however, aromatic molecules are formed when alkanes are passed over a catalyst at about 500°C under high pressure. Heptane (C Hk ), for example, is converted into toluene (CyHs) by dehydrogenation and cyclization. 

Toluene is a clear, flammable liquid with a sweet odor that is widely used in both the chemical and the pharmaceutical industries. In terms of production, it is the 24th highest volume chemical in the United States. It is derived mainly from petroleum refining and only a small percentage of that produced is used directly. 

Cobalt compounds are useful chemical catalysts for the synthesis of fuels (Fi-scher-Tropsch process), the synthesis of alcohols and aldehydes from olefins, hydrogen and carbon monoxide at elevated temperatures and pressures ( oxo process , hydroformylation ). They are also used in petroleum refining and the oxidation of organic compounds. In the oxo process, cobalt carbonyl, Co2(CO)g, is employed or generated in situ. For the selective production of n-butanol from propylene, hydrogen and CO, an organophosphine-modified cobalt carbonyl complex is used as the catalyst. Cobalt salts are proven oxidation catalysts examples include the production of terephthalic acid by the oxidation of p-xylene, and the manufacture of phenol by the oxidation of toluene. 

Since the BTX-aromatics benzene, toluene and xylene are co-generated, alongside other aromatics and non-aromatics during coal conversion and petroleum refining, their concurrent recovery is described jointly in this chapter. 

BTX is a mixture of benzene, toluene, and xylene. It comes from petroleum refining. Depending on the source, the composition will vary. For example, BTX from die cracking of naphtha is typically richer in benzene than BTX from a gasoline reforming process. The boiling points are sufficiently different that they can be separated. In approximate order of importance, benzene is used to make ethyl benzene, cumene, cyclohexane, and nitrobenzene as well as many other chemicals. Toluene is used as a solvent and to make toluene diisocyanate, a monomer used to make polyurethane. Toluene can also be disproportionated to xylene and benzene. 

On the other hand, benzene is derived from toluene, directly from petroleum refining or coal as shown in Figure 3.8. 

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