Aromatics from pyrolysis

Application Recovery via extraction of high purity C6-C9 aromatics from pyrolysis gasoline, reformate, coke oven light oil and kerosene fractions. 

Polyalkylated benzenes - production and uses Table 8.1 Composition of C9-aromatics from pyrolysis gasoline and catalytic reforming (in percentage) ... 

C9-aromatics from pyrolysis benzene from catalytic reformer... 

Aromatic Hydrocarbons. These are the most toxic of the hydrocarbons and inhalation of the vapor can cause acute intoxication. Benzene is particularly toxic and long-term exposure can cause anemia and leukopenia, even with concentrations too low for detection by odor or simple instmments. The currendy acceptable average vapor concentration for benzene is no more than 1 ppm. PolycycHc aromatics are not sufftcientiy volatile to present a threat by inhalation (except from pyrolysis of tobacco), but it is known that certain industrial products, such as coal tar, are rich in polycycHc aromatics and continued exposure of human skin to these products results in cancer. 

The primary sources of toluene and xylenes are reformates from catalytic reforming units, gasoline from catcracking, and pyrolysis gasoline from steam reforming of naphtha and gas oils. As mentioned earlier, solvent extraction is used to separate these aromatics from the reformate mixture. 

DISTAPEX A process for removing aromatic hydrocarbons from pyrolysis gasoline or coke-oven benzole by extractive distillation with added N-methyl pyrrolidone. The operating temperature is at least 170°C. Developed by Lurgi. First announced in 1961 by 1993, 22 plants had been built. 

E. 1. Shin, M. Nimlos, and R. 1. Evans, The formation of aromatics from the gas-phase pyrolysis of stigmasterol Kinetics, Fuel 80(12 Special Edition SI), 1681-1688 (2001). 

Value of aromatics-rich pyrolysis naphtha determined by value of its components as finished chemicals, and the costs incurred in treating and separation required to produce them from pyrolysis naphtha. Breakdown of pyrolysis naphtha is as follows ... 

The principal source of toluene is catalytic reforming of refinery streams. This source accounts for ca 79% of the total toluene produced. An additional 16% is separated from pyrolysis gasoline produced in steam crackers during the manufacture of ethylene and propylene. The reactions taking place in catalytic reforming to yield aromatics are dehydrogenation or aromatization of cyclohexanes, dehydroisomerization of substituted cyclopentanes, and the cyclodehydrogenation of paraffins. The formation of toluene by these reactions is shown. 

Originally, extractive distillation was limited to two-component problems. However, recent developments in solvent technology enabled applications of this hybrid separation in multicomponent systems as well. An example of such application is the BTX process of the GTC Technology Corp., shown in Figure 6, in which extractive distillation replaced the conventional liquid-liquid extraction to separate aromatics from catalytic reformate or pyrolysis gasoline. This led to a ca. 25% lower capital cost and a ca. 15% decrease in energy consumption (170). Some other examples of existing and potential applications of the extractive distillations are listed in Table 6. 

Ethane occurs in natural gas, from which it is isolated. Ethane is among the chemically less reactive organic substances. However, ethane reacts with chlorine and bromine to form substitution compounds. Ethyl iodide, bromide, or chlorides are preferably made by reaction with ethyl alcohol and the appropriate phosphorus halide. Important ethane derivatives, by successive oxidation, are ethyl alcohol, acetaldehyde, and acetic acid. Ethane can also be used for the production of aromatics by pyrolysis (Fig. 1). 

Later the estrone produced for commercial purposes was obtained from diosgenin. Diosgenin was first oxidized to its l,4,6-triene-3-one derivative, which was aromatized by pyrolysis at 500-600°C,50 subjected to the Marker degradation and the 17-acetyl group removed by Beckmann rearrangement of the 20-oxime. The overall Syntex process51 for the manufacture of Norethindrone from diosgenin (XVIII) is outlined in Scheme 5. 

A clear long-term development will be the production of aromatics from biomass. As the direct extraction of aromatics from lignin still needs a breakthrough in research, the detour via pyrolysis or gasification of lignin is the current alternative for the production of aromatics. 

Application The Sulfolane process recovers high-purity C6-C9 aromatics from hydrocarbon mixtures, such as reformed petroleum naphtha (reformate), pyrolysis gasoline (pygas), or coke oven light oil (COLO), by extractive distillation with or without liquid-liquid extraction. 

Application Recovery of high-purity aromatics from reformate, pyrolysis gasoline or coke-oven light oil using extractive distillation. 

The cracked gases are cooled and fractionated to remove fuel oil and water (2-5) then compressed (6), processed for acid-gas removal (8) and dried (9). The C3 and lighter material is separated as an overhead product in the depropanizer (10) and acetylene is hydrogenated in the acetylene converter (11). The acetylene converter effluent is processed in the demethanizer system (12-14) to separate the fuel gas and hydrogen products. The demethanizer bottoms is sent to the deethanizer (15) from which the overhead flows to the C2-splitter (16), which produces the polymer-grade ethylene product and the ethane stream, which is recycled to the furnaces as a feedstock. The deethanizer bottoms flows to the C3-splitter (18) where the polymer-grade propylene is recovered as the overhead product. The C3-splitter bottoms product, propane, is typically recycled to the furnaces as a feedstock. The depropanizer bottoms product, C4S and heavier, flow to the debutanizer (19) for recovery of the mixed-C4 product and aromatic-rich pyrolysis gasoline. 

Krupp Uhde Aromatics Pyrolysis gasoline, reformate or light oils Extractive distillation process uses selective solvents to separate aromatics from feed streams 30 NA... 

To obtain low amonnts of gas and aromatics, the pyrolysis temperature was mild and varied from 450 to 530°C. Only 1-8 wt% of gas is produced. With a heat of combustion of some 47 MJ/kg, it can be used for the indirect heating of the fluidized bed. The waxes... 

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