BTX fraction

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. 

Both DMSO and sulfolane are extensively used in the chemical, pharmaceutical, polymer, and electronics industries as polar aprotic solvents, with unique properties such as a high dielectric constant, high polarity, and high miscibility with organic and aqueous materials. For example, sulfolane finds use in the refining industry for the separation of benzene, toluene, and xylene (BTX) fractions from paraffins. 

Pyrotol Houdry Process and Chemical Co. Pyrolysis gasoline impure BTx fractions High-purity benzene... 

Pl(NH3)4Cl2. However, the aromatics distribution in the BTX fraction was shilled towards benzene (48.8 %) and toluene (35.7 %) as compared with Ga/H7.SM-5. 

It is worth to remark that benzene is the major product in the BTX fraction, even if no GajOj is used on the ZSM-5, while during cracking of n-alkanes (Cg-Cg) and gasoil little benzene is observed in the BTX fraction. Moreover, the reaction of different C5-C7 hydrocarbons (1-hexene, 1-heptene, methylcyclohexene) on GajOj produces isomerization or aroma-tization but not cyclization (5). From these results it has been concluded that oligomerization and cyclization are produced on the acid sites of zeolite. 

The BTX fraction shows a similar variability arising from pyrolysis severity and feedstock (Table III). In general, the aromatic content ranges upwards of 50% and may reach nearly 100% in high severity operation. BTX ratios vary widely, depending on feedstock. LPG-type feeds yield benzene predominantly among the aromatics, while the heavier feeds show increased yields of toluene and C8 aromatics. In all cases benzene appears to be synthesized predominantly from paraffin or naphthene chain fragments by condensation reactions. Toluene and the C8 aromatics appear to derive principally from aromatics in the feed with some pyrolytic side-chain dealkylation. In all cases styrene predominates in the C8 fraction (7). 

The third and final hydrocarbon family to be discussed is known as the aromatic hydrocarbons, sometimes referred to as the BTX fraction (benzene, toluene, xylene). One additional aromatic beyond the BTX fraction is called styrene and will be covered as the fourth aromatic compound. Aromatics as a group are toxic and flammable. They have moderate boiling and flash points, narrow flammable ranges, high ignition temperatures, and are nonpolar. 

However, the meta-xylene and para-xylene isomers typically reqnire a crystallization or adsorption on molecular sieves (UOP Parex process) [8], Because of the complexity of the BTX separation plant, we do not include BTX fractionation in this work. However, future work will address the special requirements and workflow for simulating a BTX separation plant... 

Properly speaking, steam cracking is not a refining process. A key petrochemical process, it has the purpose of producing ethylene, propylene, butadiene, butenes and aromatics (BTX) mainly from light fractions of crude oil (LPG, naphthas), but also from heavy fractions hydrotreated or not (paraffinic vacuum distillates, residue from hydrocracking HOC). 

Proof of the existence of benzene in the light oil derived from coal tar (8) first estabHshed coal tar and coal as chemical raw materials (see Eeedstocks, COAL chemicals). Soon thereafter the separation of coal-tar light oil into substantially pure fractions produced a number of the aromatic components now known to be present in significant quantities in petroleum-derived Hquid fuels. Indeed, these separation procedures were for the recovery of benzene—toluene—xylene (BTX) and related substances, ie, benzol or motor benzol, from coke-oven operations (8) (see BTX processing). 

In general, when the product is a fraction from cmde oil that includes a large number of individual hydrocarbons, the fraction is classified as a refined product. Examples of refined products are gasoline, diesel fuel, heating oils, lubricants, waxes, asphalt, and coke. In contrast, when the product is limited to, perhaps, one or two specific hydrocarbons of high purity, the fraction is classified as a petrochemical product. Examples of petrochemicals are ethylene (qv), propylene (qv), benzene (qv), toluene, and xylene (see Btx processing). 

The mixed monocyclic aromatics are called BTX as an abbreviation for ben2ene, toluene, and xylene (see Btxprocessing). The benzene and toluene are isolated by distillation, and the isomers of the xylene are separated by superfractionation, fractional crystallisation, or adsorption (see Xylenes and ethylbenzene). Bensene is the starting material for styrene (qv), phenol (qv), and a number of fibers and plastics. Toluene (qv) is used to make a number of... 

Toluene, Benzene, and BTX Reeoveiy. The composition of aromatics centers on the C - and Cg-fraction, depending somewhat on the boihng range of the feedstock used. Most catalytic reformate is used directiy in gasoline. That part which is converted to benzene, toluene, and xylenes for commercial sale is separated from the unreacted paraffins and cycloparaffins or naphthenes by hquid—hquid extraction or by extractive distillation. It is impossible to separate commercial purity aromatic products from reformates by distillation only because of the presence of azeotropes, although comphcated further by the closeness in boihng points of the aromatics, t/o-paraffin, and unreacted C -, C -, and Cg-paraffins. 

Deep C t lytic Crocking. This process is a variation of fluid catalytic cracking. It uses heavy petroleum fractions, such as heavy vacuum gas oil, to produce propylene- and butylene-rich gaseous products and an aromatic-rich Hquid product. The Hquid product contains predorninantiy ben2ene, toluene, and xylene (see BTX processing). This process is being developed by SINOPEC in China (42,73). SINOPEC is currentiy converting one of its fluid catalytic units into a demonstration unit with a capacity of 60,000 t/yr of vacuum gas oil feedstock. 

The extract, which is composed of BTX and ethylhenzene, is then fractionated. Benzene and toluene are recovered separately, and ethylhenzene and xylenes are obtained as a mixture (Cg aromatics). 

Increasing the octane number of a low-octane naphtha fraction is achieved by changing the molecular structure of the low octane number components. Many reactions are responsible for this change, such as the dehydrogenation of naphthenes and the dehydrocyclization of paraffins to aromatics. Catalytic reforming is considered the key process for obtaining benzene, toluene, and xylenes (BTX). These aromatics are important intermediates for the production of many chemicals. 

Products from catalytic reformers (the reformate) is a mixture of aromatics, paraffins and cycloparaffins ranging from Ce-Cg. The mixture has a high octane rating due to presence of a high percentage of aromatics and branched paraffins. Extraction of the mixture with a suitable solvent produces an aromatic-rich extract, which is further fractionated to separate the BTX components. Extraction and extractive distillation of reformate have been reviewed by Gentray and Kumar. 

As feedstocks progress from ethane to heavier fractions with lower H/C ratios, the yield of ethylene decreases, and the feed per pound ethylene product ratio increases markedly. Table 3-15 shows yields from steam cracking of different feedstocks, and how the liquid by-products and BTX aromatics increase dramatically with heavier feeds. 

The process consists of a reactor section, continuous catalyst regeneration unit (CCR), and product recovery section. Stacked radial-flow reactors are used to minimize pressure drop and to facilitate catalyst recirculation to and from the CCR. The reactor feed consists solely of LPG plus the recycle of unconverted feed components no hydrogen is recycled. The liquid product contains about 92 wt% benzene, toluene, and xylenes (BTX) (Figure 6-7), with a balance of Cg aromatics and a low nonaromatic content. Therefore, the product could be used directly for the recovery of benzene by fractional distillation (without the extraction step needed in catalytic reforming). 

Benzene oxychlorination process, of phenol manufacture, 18 751 Benzeneperoxyseleninic acid, 13 466 Benzene rings, in liquid crystalline materials, 15 103-104 Benzene sulfonation process, of phenol manufacture, 18 751 Benzenesulfonic acid, 3 602 Benzene-toluene fraction, in styrene manufacture, 23 341-342 Benzene-toluene-xylene (BTX), 10 782 ... 

Aromatic extraction removes benzene, toluene, and xylene (BTX) that are formed as byproducts in the reforming process. The reformed products are fractionated to give a BTX concentrate cut, which, in turn, is extracted from the napthalene and the paraffinics with a glycol base solvent. 

Several potent fractions isolated from laboratory cultures of brevis have been prepared by a number of research groups, but due to a lack of standardized nomenclature, the number of toxins produced by the organism is uncertain. The structures for three "brevetoxins" have now been reported(15-17). BTX-B, the major toxin reported by Lin al.(15)(Figure 2a), is thought to be identical to GB-2 isolated earlier by Shimizu(16). Likewise, T34 isolated from our laboratory cultures of the organism( ), is also thought to be identical to GB-2. GB-3, isolated by Chou and Shimizu(17), was identified as Fig-... 

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