Naphtha is a group of various volatile flammable liquid hydrocarbon mixtures used primarily as feedstocks in refineries for the reforming process and in the petrochemical industry for the production of olefins in steam crackers. It is also used in solvent applications.
Production of naphtha in refineries and uses
Naphtha is obtained from petroleum refineries as a portion of the distillation (also referred to as a cut). It is an intermediate between the lighter gasoline and the heavier benzine. Naphtha has a specific gravity of about 0.7. The generic name naphtha describes a range of different refinery cuts used in the different applications. To further complicate the matter similar naphtha types are often referred to by different names
The different naphthas are distinguished by:
- density (kg/m3 or specific gravity
- PONA or PIONA (usually in volume percent but can also be in weight percent)
- paraffin content (volume percent)
- in case of a PIONA measurement the iso-paraffins are measured
- naphthenes content (volume percent)
- aromatics content (volume percent)
- olefins content (volume percent)
Paraffinic naphthas
Generally speaking "lighter" or rather less dense naphthas will have a higher paraffin content, these are therefore also referred to as paraffinic naphtha. The main application these naphthas are used for are as a feedstock in the petrochemical production of olefins. This is also the reason they are sometimes referred to as "light distillate feedstock" or LDF (as described above a variety of names exist and these types can also be called "straight run gasoline"/SRG or "light virgin naphtha"/LVN).
When used as feedstock in petrochemical steam crackers, the naphtha is heated in the presence of water vapour and the absence of oxygen or air until the hydrocarbon molecules fall apart. The primary products of the cracking process are olefins (ethylene / ethene, propylene / propene and butadiene) and aromatics (benzene and toluene). These are used as feedstocks for derivative units that produce plastics (polyethylene and polypropylene for example), fibre precursors (acrylonitrile), industrial chemicals (glycols for instance).
Heavy naphthas
The "heavier" or rather denser types are usually richer in naphthenes and aromatics and therefore also referred to as N&A's. These can also be used in the petrochemical industry but more often are used as a feedstock for refinery catalytic reformers where they convert the lower octane naphtha to a higher octane product - reformate. Alternative names for these types are straight run benzene/SRB or heavy virgin naphtha/HVN.
Other applications / descriptions
Napthas are also used in other applications such as
- (as an unprocessed component - in contrast to reforming above) in the production of petrol/motor gasoline .
- as industrial solvents and cleaning fluids
- as an ingredient in some lighter fluids for wick type lighters like Zippo lighters.
Etymology
There is a theory that the word naphtha came (via Greek, where it meant any sort of petroleum) from the name of the Vedic Hindu and Avestic god Apam Napat, who was a form of Agni and his name is Sanskrit and Avestic for "son of waters", referring to flames from natural gas or oil seepages surfacing through water. See this link about a fire temple at Baku in Azerbaijan.
See also: naphthalene olefin reforming refinery.