Naphtha is a liquid petroleum product that boils from about 30°C (86°F) to approximately 200°C (392°F), although there are different grades of naphtha within this extensive boiling range that have different boiling ranges .
The term petroleum solvent is often used synonymously with naphtha. On a chemical basis, naphtha is difficult to define precisely because it can contain varying amounts of its constituents (paraffins, naphthenes, aromatics,
and olefins) in different proportions, in addition to the potential isomers of the paraffins that exist in the naphtha boiling range. Naphtha is also represented as having a boiling range and carbon number similar to those of gasoline a precursor to gasoline.
The so-called petroleum ether solvents are specific-boiling-range naphtha as is ligroin. Thus the term petroleum solvent describes special liquid hydrocarbon fractions obtained from naphtha and used in industrial processes and formulations.These fractions are also referred to as industrial naphtha. Other solvents include white spirit,
which is subdivided into industrial spirit [distilling between 30°C and 200°C (86°F–392°F)] and white spirit [light oil with a distillation range of 135°C– 200°C (275°F–392°F)]. The special value of naphtha as a solvent lies in its
stability and purity.
Naphtha Production and Properties:
Naphtha is produced by any one of several methods, which include (1) fractionation of straight-run, cracked, and reforming distillates or even fractionation of crude petroleum; (2) solvent extraction; (3) hydrogenation of cracked distillates; (4) polymerization of unsaturated compounds (olefins); and (5) alkylation processes. In fact, naphtha may be a combination of product streams from more than one of these processes.
The more common method of naphtha preparation is distillation. Depending on the design of the distillation unit, either one or two naphtha steams may be produced: (1) a single naphtha with an end point of about 205∞C (400∞F) and similar to straight-run gasoline or (2) this same fraction divided into a light naphtha and a heavy naphtha.The end point of the light naphtha is varied to suit the subsequent subdivision of the naphtha into narrower boiling fractions and may be of the order of 120∞C (250∞F).
Sulfur compounds are most commonly removed or converted to a harmless form by chemical treatment with lye, Doctor solution, copper chloride or similar treating agents Hydrorefining processes (Speight, 1999) are also often used in place of chemical treatment.When used as a solvent, naphtha is selected for low sulfur content, and the usual treatment processes remove only sulfur compounds. Naphtha with a small aromatic content has a slight odor, but the aromatics increase the solvent power of the naphtha and there is no need to remove aromatics unless odor-free
naphtha is specified.
The variety of applications emphasizes the versatility of naphtha. For example, naphtha is used by paint, printing ink and polish manufacturers and in the rubber and adhesive industries as well as in the preparation of edible oils, perfumes, glues, and fats. Further uses are found in the drycleaning, leather, and fur industries and also in the pesticide field. The characteristics that determine the suitability of naphtha for a particular use are volatility, solvent properties (dissolving power), purity, and odor (generally, the lack thereof).
To meet the demands of a variety of uses, certain basic naphtha grades are produced that are identified by boiling range.The complete range of naphtha solvents may be divided, for convenience, into four general categories:
1. Special boiling point spirits having overall distillation range within the limits of 30–165°C (86–329°F);
2. Pure aromatic compounds such as benzene, toluene, xylenes, or mixtures (BTX) thereof;
3. White spirit, also known as mineral spirit and naphtha, usually boiling within 150–210°C (302–410°F);
4. High-boiling petroleum fractions boiling within the limits of 160– 325°C (320–617°F).
Because the end use dictates the required composition of naphtha, most grades are available in both high- and low-solvency categories and the various text methods can have major significance in some applications and lesser significance in others. Hence the application and significance of tests must be considered in the light of the proposed end use.
Odor is particularly important because, unlike most other petroleum liquids, many of the manufactured products containing naphtha are used in confined spaces, in factory workshops, and in the home.
