Industrial Aromatic Chemistry

Frontmatter

1. History

Abstract

Aromatic compounds are currently defined as cyclic hydrocarbons in which the carbon skeleton is linked by a specified number of conjugated π-bonds in addition to σ-bonds (Hückel’s rule). During the early days of industrial aromatic chemistry in the mid-19th century, the structure of aromatic compounds had not yet been elucidated. The name of this class of compounds is historically-based since the first members were obtained from aromatic, i. e. pleasant-smelling resins, balsams and oils; examples of this are benzoic acid, which was obtained from gum benzoin, toluene from tolu balsam and benzaldehyde from oil of bitter almonds.

Heinz-Gerhard Franck, Jürgen Walter Stadelhofer

2. The nature of the aromatic character

Abstract

Since the middle of the last century, chemists have devoted considerable effort trying to explain the chemical bond. The knowledge hitherto accumulated has also been enormously beneficial in expanding the understanding of the nature of aromatic compounds.

Heinz-Gerhard Franck, Jürgen Walter Stadelhofer

3. Base materials for aromatic chemicals

Abstract

The chemical industry meets its demand for carbon-containing feedstocks for the production of organic compounds from fossil raw materials — coal, oil and natural gas — as well as from renewable raw materials.

Heinz-Gerhard Franck, Jürgen Walter Stadelhofer

4. Production of benzene, toluene and xylenes

Abstract

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.

Heinz-Gerhard Franck, Jürgen Walter Stadelhofer

5. Production and uses of benzene derivatives

Abstract

Benzene is not only the most important aromatic raw material in terms of quantity, but it is also the most versatile from the viewpoint of its uses.

The major industrial products from benzene are alkylated derivatives such as ethylbenzene and cumene, which are used as basic materials for the production of styrene and phenol, and long-chain alkylbenzenes, which are used as feedstocks in the manufacture of surfactants.

Heinz-Gerhard Franck, Jürgen Walter Stadelhofer

6. Production and uses of toluene derivatives

Abstract

Basically there are three classes of reactions of toluene, namely electrophilic substitution, side-chain reactions and cleavage of the methyl-phenyl bond. From an industrial point of view the most important electrophilic substitutions are nitration and chlorination; among the side-chain reactions oxidation and chlorination are of large industrial significance. Cleavage of the bond between the methyl group and the aromatic ring of toluene occurs during dealkylation to produce benzene, with biphenyl as a by-product (see Chapters 4.4.1 and 10.1).

Heinz-Gerhard Franck, Jürgen Walter Stadelhofer

7. Production and uses of xylene derivatives

Abstract

Whereas benzene and toluene serve as the raw materials for a wide range of products, applications for the three xylene isomers, o-, m- and p-xylene, are basically limited to chemicals arising through oxidation, i.e. phthalic anhydride (PA) from o-xylene, isophthalic acid from m-xylene and terephthalic acid from p-xylene.

Heinz-Gerhard Franck, Jürgen Walter Stadelhofer

8. Polyalkylated benzenes — production and uses

Abstract

Petroleum- and coal-derived heavy gasoline fractions with a boiling range of around 160 to 220 °C contain polymethylated benzenes, such as trimethylbenzenes (pseudocumene, mesitylene and hemimellitene), together with the tetramethylated benzenes durene, isodurene and prehnitene. Indane and indene compounds, penta- and hexamethylbenzene and cumene, are also present in these heavy gasoline fraction. (Cumene is predominantly converted to phenol as described in Chapter 5.2).

Heinz-Gerhard Franck, Jürgen Walter Stadelhofer

9. Naphthalene — production and uses

Abstract

Naphthalene was first isolated from coal tar in 1819 by Alexander Garden; it represents about 10% of this complex mixture of aromatics. The industrial importance of naphthalene dates from the latter half of the last century, owing mainly to the ease with which it can be converted into sulfonic acids and thence also to the naphthols, for use as dyestuffs intermediates. However, the first synthetic naphthalene-based dye was a nitro-derivative, Martius Yellow (Acid Yellow 24), which was patented in 1864 by Carl Alexander Martius.

Heinz-Gerhard Franck, Jürgen Walter Stadelhofer

10. Alkylnaphthalenes and other bicyclic aromatics — production and uses

Abstract

Apart from naphthalene, other commercially important bicyclic aromatics are especially biphenyl (also referred to as diphenyl), acenaphthene and acenaphthylene. Like the methylnaphthalenes, they are present in varying concentrations in coal tar. Where the concentration is sufficiently high, as is the case for methylnaphthalenes and acenaphthene (or acenaphthylene), then they are recovered from coal tar; for compounds present in low concentrations, on the other hand, such as biphenyl, production is normally via a synthetic route.

Heinz-Gerhard Franck, Jürgen Walter Stadelhofer

11. Anthracene — production and uses

Abstract

Anthracene was first discovered in coal tar by Jean B.A. Dumas and Auguste Laurent in 1832. The importance of anthracene for industrial aromatic chemistry began with the synthesis of the dyestuff alizarin by Carl Graebe and Carl Th. Liebermann, as well as by William H.Perkin in 1868, replacing the natural dye produced from madder. Anthraquinone dyestuffs have remained the most important class of dyes, alongside azo-dyes, since the beginning of the chemistry of synthetic dyestuffs.

Heinz-Gerhard Franck, Jürgen Walter Stadelhofer

12. Additional polynuclear aromatics — production and uses

Abstract

Next to anthracene, the higher condensed aromatics which are of commercial importance are phenanthrene, fluorene, fluoranthene and pyrene. Worldwide production of these polynuclear aromatics is around 2,000 tpa.

Heinz-Gerhard Franck, Jürgen Walter Stadelhofer

13. Production and uses of carbon products from mixtures of condensed aromatics

Abstract

Aromatic residue fractions produced in coal tar refining, naphtha pyrolysis and thermal as well as catalytic cracking (see Chapter 3) are suitable feedstocks for the manufacture of carbon products, especially because of their high C/H ratio. Graphitic carbon products include synthetic graphite and graphitic carbon fibers which are distinguished by both the anisotropy in the structure of the carbon lattice, and a lattice plane distance which is very close to the theoretical value for graphite. In addition, carbon products with a high proportion of isotropic regions are used on a large scale, especially for the manufacture of anodes for the aluminum industry.

Heinz-Gerhard Franck, Jürgen Walter Stadelhofer

14. Aromatic heterocyclics — production and uses

Abstract

The industrial chemistry of the heterocyclic aromatics is extraordinarily diverse. A large number of mono- and polynuclear heterocyclics (vide infra) is present in coal tar and can be recovered from this source. Synthetic means of production, principally from petroleum-derived feedstocks have been added to the coal-derived raw materials since the fifties.

Heinz-Gerhard Franck, Jürgen Walter Stadelhofer

15. Toxicology/Environmental aspects

Abstract

Toxicology, the science concerning the studies of harmful effects of chemicals of both natural and industrial origin on living organisms, has the prime objective of investigating the possible risk to all forms of life from chemical substances.

Heinz-Gerhard Franck, Jürgen Walter Stadelhofer

16. The future of aromatic chemistry

Abstract

The rise of industrial organic chemistry in the mid-19th century was initiated by pioneering innovations in the field of aromatic chemistry. It has since undergone continuous further development. Plastics and pesticides followed dyes and pharmaceuticals as the main areas of innovation.

Heinz-Gerhard Franck, Jürgen Walter Stadelhofer

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