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'''Petroleum naphtha''' is an intermediate hydrocarbon liquid stream derived from the [[Petroleum refining processes|refining]] of [[crude oil]]. It is most usually [[Hydrodesulfurization|desulfurized]] and then [[Catalytic reforming|catalytically reformed]], which re-arranges or re-structures the [[hydrocarbon]] [[molecule]]s in the naphtha as well as breaking some of the molecules into smaller molecules to produce a high-[[octane]] component of [[gasoline]] (or [[petrol]]). | '''Petroleum naphtha''' is an intermediate hydrocarbon liquid stream derived from the [[Petroleum refining processes|refining]] of [[crude oil]].<ref name=Handwerk>{{cite book|author=Gary, J.H. and Handwerk, G.E.|title=Petroleum Refining Technology and Economics|edition=2nd Edition|publisher=Marcel Dekker, Inc|year=1984|id=ISBN 0-8247-7150-8}}</ref><ref name=Leffler>{{cite book|author=Leffler, W.L. |title=Petroleum refining for the nontechnical person|edition=2nd Edition|publisher=PennWell Books|year=1985|id=ISBN 0-87814-280-0}}</ref><ref>{{cite book|author=James G, Speight|title=The Chemistry and Technology of Petroleum|edition=Fourth Edition|publisher=CRC Press|year=2006|id=0-8493-9067-2}}</ref> It is most usually [[Hydrodesulfurization|desulfurized]] and then [[Catalytic reforming|catalytically reformed]], which re-arranges or re-structures the [[hydrocarbon]] [[molecule]]s in the naphtha as well as breaking some of the molecules into smaller molecules to produce a high-[[octane]] component of [[gasoline]] (or [[petrol]]). | ||
There are quite literally hundreds of different petroleum crude oil sources worldwide and each crude oil has its own unique composition or [[assay]]. There are also hundreds of petroleum refineries worldwide and each of them is designed to process either a specific crude oil or specific types of crude oils. That means that it is virtually impossible to provide a definitive, single definition of the word naphtha since each refinery produces its own naphthas with their own unique initial and final boiling points and other physical and compositional characteristics. In other words, naphtha is a ''generic term'' rather than a ''specific term''. | There are quite literally hundreds of different petroleum crude oil sources worldwide and each crude oil has its own unique composition or [[assay]]. There are also hundreds of petroleum refineries worldwide and each of them is designed to process either a specific crude oil or specific types of crude oils. That means that it is virtually impossible to provide a definitive, single definition of the word naphtha since each refinery produces its own naphthas with their own unique initial and final boiling points and other physical and compositional characteristics. In other words, naphtha is a ''generic term'' rather than a ''specific term''. | ||
In addition, naphthas may also be produced from [[coal tar]], [[shale]] deposits, [[tar sands]] such as in [[Canada]], the[[destructive distillation]] of wood and [[coal gasification]] or [[biomass gasification]] to produce a [[syngas]] followed by the [[Fischer-Tropsch]] process to convert the syngas into liquid hydrocarbon products. For that reason, this article is entitled'''Petroleum naphtha''' and deals only with naphthas produced by the processing of crude oil in petroleum refineries. | In addition, naphthas may also be produced from [[coal tar]], [[shale]] deposits, [[tar sands]] such as in [[Canada]], the [[destructive distillation]] of wood and [[coal gasification]] or [[biomass gasification]] to produce a [[syngas]]<ref>[http://sasol.investoreports.com/sasol_ar_2006/review/downloads/segmented/sasol_ar_2006_business_model.pdf Exploiting the Benefits of Fischer-Tropsch Technology] (Sasol’s integrated business model)</ref><ref>Beychok, M.R., ''Process and environmental technology for producing SNG and liquid fuels'', [[U.S. EPA]] report EPA-660/2-75-011, May 1975</ref> followed by the [[Fischer-Tropsch]] process to convert the syngas into liquid hydrocarbon products. For that reason, this article is entitled '''Petroleum naphtha''' and deals only with naphthas produced by the processing of crude oil in petroleum refineries. | ||
== The major source of petroleum naphtha in a petroleum refinery == | == The major source of petroleum naphtha in a petroleum refinery == | ||
The first unit process in a petroleum refinery is the [[Petroleum refining processes#The crude oil distillation unit|crude oil distillation unit]]. The overhead liquid distillate from that unit is called ''virgin'' or ''straight-run'' naphtha and that distillate is the largest source of naphtha in most petroleum refineries. The naphtha is a mixture of very many different hydrocarbon compounds. It has an initial [[boiling point]] (IFP) of about 35 °C and a final boiling point (FBP) of about 200 °C, and it contains [[paraffin]], [[naphthene]] (cyclic [[paraffins]]) and [[aromatic]] hydrocarbons ranging from those containing 4[[carbon]] [[atom]]s to those containing about 10 or 11 carbon atoms. | The first unit process in a petroleum refinery is the [[Petroleum refining processes#The crude oil distillation unit|crude oil distillation unit]]. The overhead liquid distillate from that unit is called ''virgin'' or ''straight-run'' naphtha and that distillate is the largest source of naphtha in most petroleum refineries. The naphtha is a mixture of very many different hydrocarbon compounds. It has an initial [[boiling point]] (IFP) of about 35 °C and a final boiling point (FBP) of about 200 °C, and it contains [[paraffin]], [[naphthene]] (cyclic [[paraffins]]) and [[aromatic]] hydrocarbons ranging from those containing 4 [[carbon]] [[atom]]s to those containing about 10 or 11 carbon atoms. | ||
The virgin naphtha is often further [[Continuous distillation|distilled]] into two streams: | The virgin naphtha is often further [[Continuous distillation|distilled]] into two streams:<ref>[http://www.faqs.org/faqs/sci/chem-faq/part6/section-1.html Fuel Chemistry] (scroll down to "What is naphtha")</ref> | ||
* a virgin ''light'' naphtha with an IFP of about 30 °C and a FBP of about 145 °C containing most (but not all) of the hydrocarbons with 6 or less [[carbon]] [[atoms]] | * a virgin ''light'' naphtha with an IFP of about 30 °C and a FBP of about 145 °C containing most (but not all) of the hydrocarbons with 6 or less [[carbon]] [[atoms]] | ||
* a virgin ''heavy'' naphtha containing most (but not all) of the hydrocarbons with more than 6 carbon atoms. The heavy naphtha has an IFP of about 140 °C and a FBP of about 205 °C. | * a virgin ''heavy'' naphtha containing most (but not all) of the hydrocarbons with more than 6 carbon atoms. The heavy naphtha has an IFP of about 140 °C and a FBP of about 205 °C. | ||
It is the virgin heavy naphtha that is usually processed in a catalytic reformer because the light naphtha has molecules with 6 or less carbon atoms which, when reformed, tend to crack into butane and lower molecular weight hydrocarbons which are not useful as high-octane gasoline blending components. Also, the molecules with 6 carbon atoms tend to form aromatics which is undesirable because governmental environmental regulations in a number of countries limit the amount of aromatics (most particularly[[benzene]]) that gasoline may contain. | It is the virgin heavy naphtha that is usually processed in a catalytic reformer because the light naphtha has molecules with 6 or less carbon atoms which, when reformed, tend to crack into butane and lower molecular weight hydrocarbons which are not useful as high-octane gasoline blending components. Also, the molecules with 6 carbon atoms tend to form aromatics which is undesirable because governmental environmental regulations in a number of countries limit the amount of aromatics (most particularly [[benzene]]) that gasoline may contain.<ref>[http://www.ec.gc.ca/CEPARegistry/regulations/detailReg.cfm?intReg=1 Canadian regulations on benzene in gasoline]</ref><ref>[http://www.ukpia.com/Portals/0/Repository/documents/Benzene%20in%20petrol.pdf Briefing on Benzene in Petrol] From website of [[United Kingdom Petroleum Industry Association]] (UKPIA)</ref><ref>[http://www.washingtonpost.com/wp-dyn/content/article/2006/03/01/AR2006030102113.html USA regulations on benzene in gasoline]</ref> | ||
== Types of virgin naphthas == | == Types of virgin naphthas == | ||
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|- | |- | ||
! Crude oil name <math>\Rightarrow</math><br>Location <math>\Rightarrow</math> | ! Crude oil name <math>\Rightarrow</math><br>Location <math>\Rightarrow</math> | ||
! Barrow Island<br>Australia | ! Barrow Island<br>Australia<ref>[http://www.santos.com/library/barrow_crude.pdf Barrow Island crude oil assay]</ref> | ||
! Mutineer-Exeter<br>Australia | ! Mutineer-Exeter<br>Australia<ref>[http://www.santos.com/library/refining_characteristics.pdf Mutineer-Exeter crude oil assay]</ref> | ||
! CPC Blend<br>Kazakhstan | ! CPC Blend<br>Kazakhstan<ref>[http://crudemarketing.chevron.com/overview.asp?cpc CPC Blend crude oil assay]</ref> | ||
! Draugen<br>North Sea | ! Draugen<br>North Sea<ref>[http://www.statoil.com/en/OurOperations/TradingProducts/CrudeOil/Crudeoilassays/Downloads/Draugen%202002%2011.pdf Draugen crude oil assay]</ref> | ||
|- | |- | ||
| Initial boiling point, °C ||align=center|149||align=center|140||align=center|149||align=center|150 | | Initial boiling point, °C ||align=center|149||align=center|140||align=center|149||align=center|150 | ||
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Most uses of petroleum refinery naphtha require the removal of [[sulfur]] compounds down to very low levels (a few [[parts per million]] or less). That is usually accomplished in a [[catalytic]] chemical process called ''hydrodesulfurization'' which converts the sulfur compounds into [[hydrogen sulfide]] [[gas]] that is removed from the naphtha by [[Continuous distillation|distillation]]. | Most uses of petroleum refinery naphtha require the removal of [[sulfur]] compounds down to very low levels (a few [[parts per million]] or less). That is usually accomplished in a [[catalytic]] chemical process called ''hydrodesulfurization'' which converts the sulfur compounds into [[hydrogen sulfide]] [[gas]] that is removed from the naphtha by [[Continuous distillation|distillation]]. | ||
The hydrogen sulfide gas is then captured in ''amine gas treating'' units and subsequently converted into byproduct elemental sulfur. In fact, the vast majority of the 64,000,000 metric tons of sulfur produced worldwide in 2005 was byproduct sulfur from petroleum refining and [[natural gas processing]] plants (which also use amine gas treating units to remove hydrogen sulfide from the raw [[natural gas]]). | The hydrogen sulfide gas is then captured in ''amine gas treating'' units and subsequently converted into byproduct elemental sulfur. In fact, the vast majority of the 64,000,000 metric tons of sulfur produced worldwide in 2005 was byproduct sulfur from petroleum refining and [[natural gas processing]] plants (which also use amine gas treating units to remove hydrogen sulfide from the raw [[natural gas]]).<ref>[http://minerals.usgs.gov/minerals/pubs/commodity/sulfur/sulfumcs06.pdf Sulfur production report] by the [[United States Geological Survey]]</ref><ref>[http://www.agiweb.org/geotimes/july03/resources.html Discussion of recovered byproduct sulfur]</ref> | ||
In lieu of hydrodesulfurization, light naphthas may be treated in a [[Merox]] unit to remove any hydrogen sulfide and, more particularly, to remove [[mercaptan]]s. | In lieu of hydrodesulfurization, light naphthas may be treated in a [[Merox]] unit to remove any hydrogen sulfide and, more particularly, to remove [[mercaptan]]s. | ||
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Some petroleum refineries also produce small amounts of specialty naphthas for use as solvents, cleaning fluids, paint and varnish diluents, [[Asphalt (petroleum)|asphalt]] diluents, rubber industry solvents, dry-cleaning, cigarette lighters, and portable camping stove and lantern fuels. Those specialty naphthas are subjected to various purification processes. | Some petroleum refineries also produce small amounts of specialty naphthas for use as solvents, cleaning fluids, paint and varnish diluents, [[Asphalt (petroleum)|asphalt]] diluents, rubber industry solvents, dry-cleaning, cigarette lighters, and portable camping stove and lantern fuels. Those specialty naphthas are subjected to various purification processes. | ||
Sometimes the specialty naphthas are called ''petroleum ether'', ''petroleum spirits'', ''mineral spirits'', ''paraffin'',''benzine'', ''hexanes'', ''ligroin'', ''white oil'' or ''white gas'', ''painters naphtha'', ''refined solvent naphtha'' and''Varnish makers' & painters' naphtha (VM&P)'' . The best way to determine the boiling range and other compositional characteristics of any of the specialty naphthas is to read the [[Material Safety Data Sheet]] (MSDS) for the specific naphtha of interest. | Sometimes the specialty naphthas are called ''petroleum ether'', ''petroleum spirits'', ''mineral spirits'', ''paraffin'', ''benzine'', ''hexanes'', ''ligroin'', ''white oil'' or ''white gas'', ''painters naphtha'', ''refined solvent naphtha'' and ''Varnish makers' & painters' naphtha (VM&P)'' . The best way to determine the boiling range and other compositional characteristics of any of the specialty naphthas is to read the [[Material Safety Data Sheet]] (MSDS) for the specific naphtha of interest. | ||
On a much larger scale, petroleum naphtha is also used in the [[petrochemicals]] industry as feedstock to [[steam reformer]]s and[[steam crackers]] for the production of [[hydrogen]] (which may be and is converted into [[ammonia]] for fertilizers), [[ethylene]]and other olefins. Natural gas is also used as feedstock to steam reformers and steam crackers. | On a much larger scale, petroleum naphtha is also used in the [[petrochemicals]] industry as feedstock to [[steam reformer]]s and [[steam crackers]] for the production of [[hydrogen]] (which may be and is converted into [[ammonia]] for fertilizers), [[ethylene]] and other olefins. Natural gas is also used as feedstock to steam reformers and steam crackers. | ||
==References== | == References == | ||
{{reflist}} |
Revision as of 15:19, 7 August 2010
Petroleum naphtha is an intermediate hydrocarbon liquid stream derived from the refining of crude oil.[1][2][3] It is most usually desulfurized and then catalytically reformed, which re-arranges or re-structures the hydrocarbon molecules in the naphtha as well as breaking some of the molecules into smaller molecules to produce a high-octane component of gasoline (or petrol).
There are quite literally hundreds of different petroleum crude oil sources worldwide and each crude oil has its own unique composition or assay. There are also hundreds of petroleum refineries worldwide and each of them is designed to process either a specific crude oil or specific types of crude oils. That means that it is virtually impossible to provide a definitive, single definition of the word naphtha since each refinery produces its own naphthas with their own unique initial and final boiling points and other physical and compositional characteristics. In other words, naphtha is a generic term rather than a specific term.
In addition, naphthas may also be produced from coal tar, shale deposits, tar sands such as in Canada, the destructive distillation of wood and coal gasification or biomass gasification to produce a syngas[4][5] followed by the Fischer-Tropsch process to convert the syngas into liquid hydrocarbon products. For that reason, this article is entitled Petroleum naphtha and deals only with naphthas produced by the processing of crude oil in petroleum refineries.
The major source of petroleum naphtha in a petroleum refinery
The first unit process in a petroleum refinery is the crude oil distillation unit. The overhead liquid distillate from that unit is called virgin or straight-run naphtha and that distillate is the largest source of naphtha in most petroleum refineries. The naphtha is a mixture of very many different hydrocarbon compounds. It has an initial boiling point (IFP) of about 35 °C and a final boiling point (FBP) of about 200 °C, and it contains paraffin, naphthene (cyclic paraffins) and aromatic hydrocarbons ranging from those containing 4 carbon atoms to those containing about 10 or 11 carbon atoms.
The virgin naphtha is often further distilled into two streams:[6]
- a virgin light naphtha with an IFP of about 30 °C and a FBP of about 145 °C containing most (but not all) of the hydrocarbons with 6 or less carbon atoms
- a virgin heavy naphtha containing most (but not all) of the hydrocarbons with more than 6 carbon atoms. The heavy naphtha has an IFP of about 140 °C and a FBP of about 205 °C.
It is the virgin heavy naphtha that is usually processed in a catalytic reformer because the light naphtha has molecules with 6 or less carbon atoms which, when reformed, tend to crack into butane and lower molecular weight hydrocarbons which are not useful as high-octane gasoline blending components. Also, the molecules with 6 carbon atoms tend to form aromatics which is undesirable because governmental environmental regulations in a number of countries limit the amount of aromatics (most particularly benzene) that gasoline may contain.[7][8][9]
Types of virgin naphthas
The table just below lists some fairly typical virgin heavy naphthas, available for catalytic reforming, derived from various crude oils. It can be seen that they differ significantly in their content of paraffins, naphthenes and aromatics:
Crude oil name Location |
Barrow Island Australia[10] |
Mutineer-Exeter Australia[11] |
CPC Blend Kazakhstan[12] |
Draugen North Sea[13] |
---|---|---|---|---|
Initial boiling point, °C | 149 | 140 | 149 | 150 |
Final boiling point, °C | 204 | 190 | 204 | 180 |
Paraffins, liquid volume % | 46 | 62 | 57 | 38 |
Naphthenes, liquid volume % | 42 | 32 | 27 | 45 |
Aromatics, liquid volume % | 12 | 6 | 16 | 17 |
Cracked naphthas
Some refinery naphthas also contain some olefinic hydrocarbons, such as naphthas derived from the fluid catalytic cracking, visbreakers and coking processes used in many refineries. Those olefin-containing naphthas are often referred to as cracked naphthas.
In some (but not all) petroleum refineries, the cracked naphthas are desulfurized and catalytically reformed (as are the virgin naphthas) to produce additional high-octane gasoline components.
Removal of sulfur compounds from naphthas
- For more information, see: Hydrodesulfurization, Amine gas treating, and Merox
Most uses of petroleum refinery naphtha require the removal of sulfur compounds down to very low levels (a few parts per million or less). That is usually accomplished in a catalytic chemical process called hydrodesulfurization which converts the sulfur compounds into hydrogen sulfide gas that is removed from the naphtha by distillation.
The hydrogen sulfide gas is then captured in amine gas treating units and subsequently converted into byproduct elemental sulfur. In fact, the vast majority of the 64,000,000 metric tons of sulfur produced worldwide in 2005 was byproduct sulfur from petroleum refining and natural gas processing plants (which also use amine gas treating units to remove hydrogen sulfide from the raw natural gas).[14][15]
In lieu of hydrodesulfurization, light naphthas may be treated in a Merox unit to remove any hydrogen sulfide and, more particularly, to remove mercaptans.
Other uses
Some petroleum refineries also produce small amounts of specialty naphthas for use as solvents, cleaning fluids, paint and varnish diluents, asphalt diluents, rubber industry solvents, dry-cleaning, cigarette lighters, and portable camping stove and lantern fuels. Those specialty naphthas are subjected to various purification processes.
Sometimes the specialty naphthas are called petroleum ether, petroleum spirits, mineral spirits, paraffin, benzine, hexanes, ligroin, white oil or white gas, painters naphtha, refined solvent naphtha and Varnish makers' & painters' naphtha (VM&P) . The best way to determine the boiling range and other compositional characteristics of any of the specialty naphthas is to read the Material Safety Data Sheet (MSDS) for the specific naphtha of interest.
On a much larger scale, petroleum naphtha is also used in the petrochemicals industry as feedstock to steam reformers and steam crackers for the production of hydrogen (which may be and is converted into ammonia for fertilizers), ethylene and other olefins. Natural gas is also used as feedstock to steam reformers and steam crackers.
References
- ↑ Gary, J.H. and Handwerk, G.E. (1984). Petroleum Refining Technology and Economics, 2nd Edition. Marcel Dekker, Inc. ISBN 0-8247-7150-8.
- ↑ Leffler, W.L. (1985). Petroleum refining for the nontechnical person, 2nd Edition. PennWell Books. ISBN 0-87814-280-0.
- ↑ James G, Speight (2006). The Chemistry and Technology of Petroleum, Fourth Edition. CRC Press. 0-8493-9067-2.
- ↑ Exploiting the Benefits of Fischer-Tropsch Technology (Sasol’s integrated business model)
- ↑ Beychok, M.R., Process and environmental technology for producing SNG and liquid fuels, U.S. EPA report EPA-660/2-75-011, May 1975
- ↑ Fuel Chemistry (scroll down to "What is naphtha")
- ↑ Canadian regulations on benzene in gasoline
- ↑ Briefing on Benzene in Petrol From website of United Kingdom Petroleum Industry Association (UKPIA)
- ↑ USA regulations on benzene in gasoline
- ↑ Barrow Island crude oil assay
- ↑ Mutineer-Exeter crude oil assay
- ↑ CPC Blend crude oil assay
- ↑ Draugen crude oil assay
- ↑ Sulfur production report by the United States Geological Survey
- ↑ Discussion of recovered byproduct sulfur
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