Aromatics from Petroleum

In 1978, world production of petroleum amounted to 3056 million t [4]. Crude oil contains between 16.5% (South Louisiana) and 21.9% (Kuwait) aromatics benzene and its homologues account for 3.9%-4.8%, and naphthalene and its homologues for 0.7%-1.3% [5]. In the order of magnitude the annually extracted petroleum before refining contains about 5 million t benzene, about 12 million t toluene, about 22 million t xylenes and about 30 million t naphthalenes. 

It is estimated that annually some 6 million t crude oil and refinery products are introduced into the sea [6]. Of this amount, probably about 40% is crude oil (natural influences, in-shore production, tanker accidents and transportation by tanker) and about 60% are further processed petroleum fractions (refineries, rivers, town sewage, transportation means, precipitation from the atmosphere) [6]. This annual emission into the seas can, in addition to other fractions, correspond to about 75,000 t benzene, 480,000 t toluene, 560,0001 xylenes, and at least 40,0001 naphthalenes. 

Every year, about 50 million t hydrocarbons are discharged into the atmosphere from refineries and automobile exhausts, about 20 million t from incineration plants, and about 20 million t from other man-made sources [10, 11], of which only part is aromatic. These emissions could contain some 10-20 million t volatile aromatics [12]. Another estimate is based on world emissions of hydrocarbons from stationary plants of 54 million t (USA 7-18 million t) and from mobile sources (transportation means) of 34 million t (USA 12-20 million t) [13]. It has also been calculated that world evaporation losses of hydrocarbons from the production and processing of petroleum amount to 44.7-68 million t (approx, one-quarter of this in refineries), and emissions from the combustion of by-products in the oil processing industry to 28 million t [5]. In these figures, too, the volatile aromatics naturally account for only a portion, perhaps one-fifth. 

Attempts have been made to estimate the quantities of motor fuel that evaporate into the atmosphere during storage, transloading and transportation. A total emission factor of 0.44% (averaged over the whole year) has been calculated for 

An additional load on the environment is imposed by the unburnt portion in automobile exhaust gases. In 1969, US motor vehicles emitted 16.9 million t hydrocarbons [13], which contained about 2.4% benzene (about 400,000 t), about 3.1%-7.9% toluene (about 800,000 t), and about 1.9% m- and p-xylene (about 

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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. 

Shenderovich, F. S., Aromatics from Petroleum. Trans, of TsIATIM 4, 151-9, Moscow-Leningrad, 1947. 

Detol Houndry Process and Chemical Co. Toluene /xylenes, heavy catalytic cycle oil, aromatics from petroleum coking, steam cracking A process for production of benzene and naphthalene... 

At the same time as the lower paraffins were being pressed into service, the second world war led to the manufacture of aromatics from petroleum. New methods of isolating, isomerizing, and dehydrogenating petroleum naphthenes were devised on the basis of petroleum techniques. During the war, manufacture of toluene and xylene was established since then, benzene has been added, because the growing demands of the chemical industry could not be met from the conventional source, coke-oven tar. 

Dimethylformamide (DMF) has been known since 1893, but since the 1950s, it has evolved as an important solvent. Its main uses are as a solvent for spinning acrylic fibers, polyurethane and polyamide coatings and films, PVC, polyacrylonitrile, extraction of aromatics from petroleum, selective solvent for removal of acid gases from natural gas, solvent for dyes, electrolyses in galvanization processes, and paint remover and cleaner [16]. By 1980, the worldwide production of DMF had grown equal to the production of formic acid at 220,000 metric tons per year [18]. By 1993 the U.S. production of formic acid was 30 to 35 mm pounds and DMF production had grown to 60 to 65 mm pounds. 

Experiments have been carried out on the partitioning of aromatics between gasoline and diesel and superheated water [84]. The increase in the partition coefficient between ambient and 200°C was —10 for benzene, toluene, ethyl benzene and xylenes and -60 for naphthalene, for example. This behavior could be the basis of a process for the removal of benzene from gasoline in particular, and for the removal of aromatics from petroleum products in general. 

A major factor in the rapid commercial utilization of catalytic reforming processing for upgrading low octane naphthas, and the production of aromatics from petroleum sources, has been the development of more active and selective dual-functional catalysts. These catalysts contain a very active hydrogenation-dehydrogenation agent such as platinum, in combination with an acidic oxide support such as alumina or silica-alumina. 

Used in extraction of aromatics from petroleum and in resin manuf. Solv. for nitrocellulose. Plasticiser. Hygroscopic liq. Misc. H2O, MeOH insol. C H, ... 

Edeleanu process An extraction process utilizing liquid sulphur dioxide for the removal of aromatic hydrocarbons and polar molecules from petroleum fractions. 

Petroleum ether fractions free from aromatic hydrocarbons are marketed, as are also n-hexane and n-heptane from petroleum. 

Petroleum and Petrochemical Processes. The first large-scale appHcation of extraction was the removal of aromatics from kerosene [8008-20-6J to improve its burning properties. Jet fuel kerosene and lubricating oil, which requite alow aromatics content (see Aviation and OTHER gas... 

TURBINE fuels), are both in demand. Solvent extraction is also extensively used to meet the growing demand for the high purity aromatics such as ben2ene, toluene, and xylene (BTX) as feedstocks for the petrochemical industry (see BTX PROCESSING FEEDSTOCKS,PETROCHEMICALS). Additionally, the separation of aromatics from aUphatics is one of the largest appHcations of solvent extraction (see Petroleum, refinery processes survey). 

Many valuable chemicals can be recovered from the volatile fractions produced in coke ovens. Eor many years coal tar was the primary source for chemicals such as naphthalene [91-20-3] anthracene [120-12-7] and other aromatic and heterocycHc hydrocarbons. The routes to production of important coal-tar derivatives are shown in Eigure 1. Much of the production of these chemicals, especially tar bases such as the pyridines and picolines, is based on synthesis from petroleum feedstocks. Nevertheless, a number of important materials continue to be derived from coal tar. 

The principal secondary variable that influences yields of gaseous products from petroleum feedstocks of various types is the aromatic content of the feedstock. For example, a feedstock of a given H/C (C/H) ratio that contains a large proportion of aromatic species is more likely to produce a larger proportion of Hquid products and elemental carbon than a feedstock that is predominantly paraffinic (5). 

Cyclic Hydrocarbons. The cyclic hydrocarbon intermediates are derived principally from petroleum and natural gas, though small amounts are derived from coal. Most cycHc intermediates are used in the manufacture of more advanced synthetic organic chemicals and finished products such as dyes, medicinal chemicals, elastomers, pesticides, and plastics and resins. Table 6 details the production and sales of cycHc intermediates in 1991. Benzene (qv) is the largest volume aromatic compound used in the chemical industry. It is extracted from catalytic reformates in refineries, and is produced by the dealkylation of toluene (qv) (see also BTX Processing). 

Petrochemicals are those chemicals produced from petroleum or natural gas and can be generally divided into three groups (/) aliphatics, such as butane and butene (2) cycloaliphatics, such as cyclohexane, cyclohexane derivatives, and aromatics (eg, ben2ene, toluene, xylene, and naphthalene) and (J) inorganics, such as sulfur, ammonia, ammonium sulfate, ammonium nitrate, and nitric acid. 

M-iscellaneousFxtractions. Additional extractive separations using sulfolane involve (/) mercaptans and sulfides from sour petroleum (45) (2) /-butylstyrene from /-butylethjlbenzene (46) (J) mixtures of close boiling chlorosHanes (47) and (4) aromatics from kerosene (48—50), naphtha (49,51—53), and aviation turbine fuel (54). 

Until the end of World War II, coal tar was the main source of these aromatic chemicals. However, the enormously increased demands by the rapidly expanding plastics and synthetic-fiber industries have greatly outstripped the potential supply from coal carbonization. This situation was exacerbated by the cessation of the manufacture in Europe of town gas from coal in the eady 1970s, a process carried out preponderantly in the continuous vertical retorts (CVRs), which has led to production from petroleum. Over 90% of the world production of aromatic chemicals in the 1990s is derived from the petrochemical industry, whereas coal tar is chiefly a source of anticorrosion coatings, wood preservatives, feedstocks for carbon-black manufacture, and binders for road surfacings and electrodes. 

With each succeeding year in the 1950s and 1960s there was a swing away from coal and vegetable sources of raw materials towards petroleum. Today such products as terephthalic acid, styrene, benzene, formaldehyde, vinyl acetate and acrylonitrile are produced from petroleum sources. Large industrial concerns that had been built on acetylene chemistry became based on petrochemicals whilst coal tar is no longer an indispensable source of aromatics. 

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