Dibenzothiophene
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Dibenzothiophene
IUPAC name Dibenzothiophene
Other names Diphenylene sulfide
Identifiers
CAS number 132-65-0
RTECS number HQ3490550
Properties
Molecular formula C12H8S
Molar mass 184.26 g/mol
Appearance Colourless crystals
Density ? g/cm3
Melting point 97-100 °C(lit.)
Boiling point 332-333 °C
Solubility in water insol.
Solubility in other solvents benzene and related
Hazards
Main hazards flammable
R-phrases 22
S-phrases 36
Related compounds
Related compounds Thiopheneanthracenebenzothiophene
Except where noted otherwise, data are given formaterials in their standard state(at 25 °C, 100 kPa)Infobox references
Dibenzothiophene is the organic compound consisting of two benzene rings fused to a central thiophene ring. This tricyclic heterocycle, and especially its alkyl substituted derivatives occur widely in heavier fractions of petroleum.
Dibenzothiophene is prepared by the reaction of biphenyl with sulfur dichloride in the presence of aluminium trichloride.
http://en.wikipedia.org/wiki/Dibenzothiophene
2009年2月24日 星期二
2009年2月19日 星期四
Hydrodesulfurization
From Wikipedia, the free encyclopedia
Jump to: navigation, search
Hydrodesulfurization (HDS) is a catalytic chemical process widely used to remove sulfur (S) from natural gas and from refined petroleum products such as gasoline or petrol, jet fuel, kerosene, diesel fuel, and fuel oils.[1][2] The purpose of removing the sulfur is to reduce the sulfur dioxide (SO2) emissions that result from using those fuels in automotive vehicles, aircraft, railroad locomotives, ships, gas or oil burning power plants, residential and industrial furnaces, and other forms of fuel combustion.
Another important reason for removing sulfur from the naphtha streams within a petroleum refinery is that sulfur, even in extremely low concentrations, poisons the noble metal catalysts (platinum and rhenium) in the catalytic reforming units that are subsequently used to upgrade the octane rating of the naphtha streams.
The industrial hydrodesulfurization processes include facilities for the capture and removal of the resulting hydrogen sulfide (H2S) gas. In petroleum refineries, the hydrogen sulfide gas is then 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 refineries and other hydrocarbon processing plants.[3][4]
An HDS unit in the petroleum refining industry is also often also referred to as a Hydrotreater.
History
Although reactions involving catalytic hydrogenation of organic substances were known prior to 1897, the property of finely divided nickel to catalyze the fixation of hydrogen on hydrocarbon (ethylene, benzene) double bonds was discovered by the French chemist, Paul Sabatier.[5][6] Thus, he found that unsaturated hydrocarbons in the vapor phase could be converted into saturated hydrocarbons by using hydrogen and a catalytic metal. His work was the foundation of the modern catalytic hydrogenation process.
Soon after Sabatier's work, a German chemist, Wilhelm Normann, found that catalytic hydrogenation could be used to convert unsaturated fatty acids or glycerides in the liquid phase into saturated ones. He was awarded a patent in Germany in 1902[7] and in Britain in 1903,[8] which was the beginning of what is now a worldwide industry.
In the mid-1950's, the first noble metal catalytic reforming process (the Platformer process) was commercialized. At the same time, the catalytic hydrodesulfurization of the naphtha feed to such reformers was also commercialized. In the decades that followed, various proprietary catalytic hydrodesulfurization processes such as the one depicted in the flow diagram below have been commercialized. Currently, virtually all of the petroleum refineries world-wide have one or more HDS units.
By 2006 miniature microfluidic HDS units had been implemented for treating JP-8 jet fuel to produce clean feed stock for a fuel cell hydrogen reformer.[9] By 2007 this had been integrated into an operating 5kW fuel cell generation system.[10]
The process chemistry
Hydrogenation is a class of chemical reactions in which the net result is the addition of hydrogen (H). Hydrogenolysis is a type of hydrogenation and results in the cleavage of the C-X chemical bond, where C is a carbon atom and X is a sulfur, nitrogen (N) or oxygen (O) atom. The net result of a hydrogenolysis reaction is the formation of C-H and H-X chemical bonds. Thus, hydrodesulfurization is a hydrogenolysis reaction. Using ethanethiol (C2H5SH), a sulfur compound present in some petroleum products, as an example, the hydrodesulfurization reaction can be simply expressed as
Ethanethiol + Hydrogen → Ethane + Hydrogen sulfide
C2H5SH + H2 → C2H6 + H2S
For the mechanistic aspects of, and the catalysts used in this reaction see the section catalysts and mechanisms
Process description
In an industrial hydrodesulfurization unit, such as in a refinery, the hydrodesulfurization reaction takes place in a fixed-bed reactor at elevated temperatures ranging from 300 to 400 °C and elevated pressures ranging from 30 to 130 atmospheres of absolute pressure, typically in the presence of a catalyst consisting of an alumina base impregnated with cobalt and molybdenum.
The image below is a schematic depiction of the equipment and the process flow streams in a typical refinery HDS unit.
Schematic diagram of a typical Hydrodesulfurization (HDS) unit in a petroleum refinery
The liquid feed (at the bottom left in the diagram) is pumped up to the required elevated pressure and is joined by a stream of hydrogen-rich recycle gas. The resulting liquid-gas mixture is preheated by flowing through a heat exchanger. The preheated feed then flows through a fired heater where the feed mixture is totally vaporized and heated to the required elevated temperature before entering the reactor and flowing through a fixed-bed of catalyst where the hydrodesulfurization reaction takes place.
The hot reaction products are partially cooled by flowing through the heat exchanger where the reactor feed was preheated and then flows through a water-cooled heat exchanger before it flows through the pressure controller (PC) and undergoes a pressure reduction down to about 3 to 5 atmospheres. The resulting mixture of liquid and gas enters the gas separator vessel at about 35 °C and 3 to 5 atmospheres of absolute pressure.
Most of the hydrogen-rich gas from the gas separator vessel is recycle gas which is routed through an amine contactor for removal of the reaction product H2S that it contains. The H2S-free hydrogen-rich gas is then recycled back for reuse in the reactor section. Any excess gas from the gas separator vessel joins the sour gas from the stripping of the reaction product liquid.
The liquid from the gas separator vessel is routed through a reboiled stripper distillation tower. The bottoms product from the stripper is the final desulfurized liquid product from hydrodesulfurization unit.
The overhead sour gas from the stripper contains hydrogen, methane, ethane, hydrogen sulfide, propane and perhaps some butane and heavier components. That sour gas is sent to the refinery's central gas processing plant for removal of the hydrogen sulfide in the refinery's main amine gas treating unit and through a series of distillation towers for recovery of propane, butane and pentane or heavier components. The residual hydrogen, methane, ethane and some propane is used as refinery fuel gas. The hydrogen sulfide removed and recovered by the amine gas treating unit is subsequently converted to elemental sulfur in a Claus process unit.
Note that the above description assumes that the HDS unit feed contains no olefins. If the feed does contain olefins (for example, the feed is a naphtha derived from a refinery fluid catalytic cracker (FCC) unit), then the overhead gas from the HDS stripper may also contain some ethene, propene, butenes and pentenes or heavier components.
It should also be noted that the amine solution to and from the recycle gas contactor comes from and is returned to the refinery's main amine gas treating unit.
Sulfur compounds in refinery HDS feedstocks
The refinery HDS feedstocks (naphtha, kerosene, diesel oil and heavier oils) contain a wide range of organic sulfur compounds, including thiols, thiophenes, organic sulfides and disulfides, and many others. These organic sulfur compounds are products of the degradation of sulfur containing biological components, present during the natural formation of the fossil fuel, petroleum crude oil.
When the HDS process is used to desulfurize a refinery naphtha, it is necessary to remove the total sulfur down to the parts per million range or lower in order to prevent poisoning the noble metal catalysts in the subsequent catalytic reforming of the naphthas.
When the process is used for desulfurizing diesel oils, the latest environmental regulations in the United States and Europe, requiring what is referred to as ultra-low sulfur diesel (ULSD), in turn requires that very deep hydrodesulfurization is needed. In the very early 2000's, the governmental regulatory limits for highway vehicle diesel was within the range of 300 to 500 ppm by weight of total sulfur. As of 2006, the total sulfur limit for highway diesel is in the range of 15 to 30 ppm by weight.[11]
Thiophenes
A family of substrates that are particularly common in petroleum are the aromatic sulfur-containing heterocycles called thiophenes. Many kinds of thiophenes occur in petroleum ranging from thiophene itself to more condensed derivatives called benzothiophenes and dibenzothiophenes. Thiophene itself and its alkyl derivatives are easier to hydrogenolyse, whereas dibenzothiophene, especially its 4,6-disubstituted derivatives, are considered the most challenging substrates. Benzothiophenes are midway between the simple thiophenes and dibenzothiophenes in their susceptibility to HDS.
Catalysts and mechanisms
The main HDS catalysts are based on MoS2 together with smaller amounts of other metals.[12] The nature of the sites of catalytic activity remains an active area of investigation, but it is generally assumed basal planes of the MoS2 structure are not relevant to catalysis, rather the edges or rims of these sheet.[13] At the edges of the MoS2 crystallites, the molybdenum centre can stabilize a coordinatively unsaturated site (CUS), also known as an anion vacancy. Substrates, such as thiophene, bind to this site and undergo a series a reactions that result in both C-S scission and C=C hydrogenation. Thus, the hydrogen serves multiple roles - generation of anion vacancy by removal of sulfide, hydrogenation, and hydrogenolysis. A simplified diagram for the cycle is shown:
Simplified diagram of a HDS cycle for thiophene
Catalysts
Most metals catalyse HDS, but it is those at the middle of the transition metal series that are most active. Ruthenium disulfide appears to be the single most active catalyst, but binary combinations of cobalt and molybdenum are also highly active.[14] Aside from the basic cobalt-modified MoS2 catalyst, nickel and tungsten are also used, depending on the nature of the feed. For example, Ni-W catalysts are more effective for hydrodenitrification (HDN).
Supports
Metal sulfides are "supported" on materials with high surface areas. A typical support for HDS catalyst is γ-alumina. The support allows the more expensive catalyst to be more widely distributed, giving rise to a larger fraction of the MoS2 that is catalytically active. The interaction between the support and the catalyst is an area of intense interest, since the support is often not fully inert but participates in the catalysis.
Other uses
The basic hydrogenolysis reaction has a number of uses other than hydrodesulfurization.
Hydrodenitrogenation
The hydrogenolysis reaction is also used to reduce the nitrogen content of a petroleum stream and, in that case, is referred to Hydrodenitrogenation (HDN). The process flow scheme is the same as for an HDS unit.
Using pyridine (C5H5N), a nitrogen compound present in some petroleum fractionation products, as an example, the hydrodenitrogenation reaction has been postulated as occurring in three steps:[15][16]
Pyridine + Hydrogen → Piperdine + Hydrogen → Amylamine + Hydrogen → Pentane + Ammonia
C5H5N + 5H2 → C5H11N + 2H2 → C5H11NH2 + H2 → C5H12 + NH3
and the overall reaction may be simply expressed as:
Pyridine + Hydrogen → Pentane + Ammonia
C5H5N + 5H2 → C5H12 + NH3
Many HDS units for desulfurizing naphthas within petroleum refineries are actually simultaneously denitrogenating to some extent as well.
Saturation of olefins
The hydrogenolysis reaction may also be used to saturate or convert olefins (alkenes) into paraffins (alkanes). The process used is the same as for an HDS unit.
As an example, the saturation of the olefin, pentene, can be simply expressed as:
Pentene + Hydrogen → Pentane
C5H10 + H2 → C5H12
Some hydrogenolysis units within a petroleum refinery or a petrochemical plant may be used solely for the saturation of olefins or they may be used for simultaneously desulfurizing as well as denitrogenating and saturating olefins to some extent.
Hydrogenation in the food industry
Further information: Hydrogenation, Wilhelm Normann, and Trans fat
The food industry uses hydrogenation to completely or partially saturate the unsaturated fatty acids in liquid vegetable fats and oils to convert them into solid or semi-solid fats, such as those in margarine and shortening.
Desulfurization technology research
Hundreds of research publications appear annually on HDS technologies. Illustrative of the range of ideas being discussed are reports on ultrasonically assisted desulfurization.[17]
See also
Timeline of hydrogen technologies
References
^ Gary, J.H. and Handwerk, G.E. (1984). Petroleum Refining Technology and Economics (2nd Edition ed.). Marcel Dekker, Inc. ISBN 0-8247-7150-8.
^ Hydrodesulfurization Technologies and Costs Nancy Yamaguchi, Trans Energy Associates, William and Flora Hewlett Foundation Sulfur Workshop, Mexico City, May 29-30, 2003
^ Sulfur production report by the United States Geological Survey
^ Discussion of recovered byproduct sulfur
^ C.R.Acad.Sci. 1897, 132, 210
^ C.R.Acad.Sci. 1901, 132, 210
^ DE Patent DE141029 (Espacenet, record not available)
^ UK Patent GB190301515 GB190301515 (Espacenet)
^ Microchannel HDS (March 2006)
^ Fuel cells help make noisy, hot generators a thing of the past (December 2007) Pacific Northwest National Laboratory
^ Diesel Sulfur published online by the National Petrochemical & Refiners Association (NPRA)
^ Topsøe, H.; Clausen, B. S.; Massoth, F. E., Hydrotreating Catalysis, Science and Technology, Springer-Verlag: Berlin, 1996.
^ Daage, M.; Chianelli, R. R., "Structure-Function Relations in Molybdenum Sulfide Catalysts - the Rim-Edge Model", J. of Catalysis, 1994, 149, 414-427.
^ Chianelli, R. R.; Berhault, G.; Raybaud, P.; Kasztelan, S.; Hafner, J. and Toulhoat, H., "Periodic trends in hydrodesulfurization: in support of the Sabatier principle", Applied Catalysis, A, 2002, volume 227, pages 83-96
^ Kinetics and Interactions of the Simultaneous Catalytic Hydrodenitrogenation of Pyridine andHydrodesulfurization of Thiophene(John Wilkins, PhD Thesis, MIT, 1977)
^ Simultaneous Catalytic Hydrodenitrogenation of Pyridine and Hydrodesulfurization ofThiophene(Satterfield,C.N., Modell, M. and Wilkens, J.A., Ind. Eng. Chem. Process Des. Dev., 1980 Vol. 19, pages 154-160)
^ Deshpande, A., Bassi, A., Prakash, A. (2004) "Ultrasound-Assisted, Base-Catalyzed Oxidation of 4,6-Dimethyldibenzothiophene in a Biphasic Diesel-Acetonitrile System" Energy Fuels, 19 (1), 28 -34, 2005.
External links
Albemarle Catalyst Company (Petrochemical catalysts supplier)
UOP Company (Engineering design and construction of large-scale, industrial HDS plants)
Mustang Engineering Company (Description and flow diagram of an HDS unit, from an article published in the Oil & Gas Journal)
Hydrogenation for Low Trans and High Conjugated Fatty Acids by E.S. Jang, M.Y. Jung, D.B. Min, Comprehensive Reviews in Food Science and Food Safety, Vol.1, 2005
Oxo Alcohols (Engineered and constructed by Aker Kvaerner)
Catalysts and technology for Oxo-Alcohols
http://en.wikipedia.org/wiki/Hydrodesulfurization
Jump to: navigation, search
Hydrodesulfurization (HDS) is a catalytic chemical process widely used to remove sulfur (S) from natural gas and from refined petroleum products such as gasoline or petrol, jet fuel, kerosene, diesel fuel, and fuel oils.[1][2] The purpose of removing the sulfur is to reduce the sulfur dioxide (SO2) emissions that result from using those fuels in automotive vehicles, aircraft, railroad locomotives, ships, gas or oil burning power plants, residential and industrial furnaces, and other forms of fuel combustion.
Another important reason for removing sulfur from the naphtha streams within a petroleum refinery is that sulfur, even in extremely low concentrations, poisons the noble metal catalysts (platinum and rhenium) in the catalytic reforming units that are subsequently used to upgrade the octane rating of the naphtha streams.
The industrial hydrodesulfurization processes include facilities for the capture and removal of the resulting hydrogen sulfide (H2S) gas. In petroleum refineries, the hydrogen sulfide gas is then 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 refineries and other hydrocarbon processing plants.[3][4]
An HDS unit in the petroleum refining industry is also often also referred to as a Hydrotreater.
History
Although reactions involving catalytic hydrogenation of organic substances were known prior to 1897, the property of finely divided nickel to catalyze the fixation of hydrogen on hydrocarbon (ethylene, benzene) double bonds was discovered by the French chemist, Paul Sabatier.[5][6] Thus, he found that unsaturated hydrocarbons in the vapor phase could be converted into saturated hydrocarbons by using hydrogen and a catalytic metal. His work was the foundation of the modern catalytic hydrogenation process.
Soon after Sabatier's work, a German chemist, Wilhelm Normann, found that catalytic hydrogenation could be used to convert unsaturated fatty acids or glycerides in the liquid phase into saturated ones. He was awarded a patent in Germany in 1902[7] and in Britain in 1903,[8] which was the beginning of what is now a worldwide industry.
In the mid-1950's, the first noble metal catalytic reforming process (the Platformer process) was commercialized. At the same time, the catalytic hydrodesulfurization of the naphtha feed to such reformers was also commercialized. In the decades that followed, various proprietary catalytic hydrodesulfurization processes such as the one depicted in the flow diagram below have been commercialized. Currently, virtually all of the petroleum refineries world-wide have one or more HDS units.
By 2006 miniature microfluidic HDS units had been implemented for treating JP-8 jet fuel to produce clean feed stock for a fuel cell hydrogen reformer.[9] By 2007 this had been integrated into an operating 5kW fuel cell generation system.[10]
The process chemistry
Hydrogenation is a class of chemical reactions in which the net result is the addition of hydrogen (H). Hydrogenolysis is a type of hydrogenation and results in the cleavage of the C-X chemical bond, where C is a carbon atom and X is a sulfur, nitrogen (N) or oxygen (O) atom. The net result of a hydrogenolysis reaction is the formation of C-H and H-X chemical bonds. Thus, hydrodesulfurization is a hydrogenolysis reaction. Using ethanethiol (C2H5SH), a sulfur compound present in some petroleum products, as an example, the hydrodesulfurization reaction can be simply expressed as
Ethanethiol + Hydrogen → Ethane + Hydrogen sulfide
C2H5SH + H2 → C2H6 + H2S
For the mechanistic aspects of, and the catalysts used in this reaction see the section catalysts and mechanisms
Process description
In an industrial hydrodesulfurization unit, such as in a refinery, the hydrodesulfurization reaction takes place in a fixed-bed reactor at elevated temperatures ranging from 300 to 400 °C and elevated pressures ranging from 30 to 130 atmospheres of absolute pressure, typically in the presence of a catalyst consisting of an alumina base impregnated with cobalt and molybdenum.
The image below is a schematic depiction of the equipment and the process flow streams in a typical refinery HDS unit.
Schematic diagram of a typical Hydrodesulfurization (HDS) unit in a petroleum refinery
The liquid feed (at the bottom left in the diagram) is pumped up to the required elevated pressure and is joined by a stream of hydrogen-rich recycle gas. The resulting liquid-gas mixture is preheated by flowing through a heat exchanger. The preheated feed then flows through a fired heater where the feed mixture is totally vaporized and heated to the required elevated temperature before entering the reactor and flowing through a fixed-bed of catalyst where the hydrodesulfurization reaction takes place.
The hot reaction products are partially cooled by flowing through the heat exchanger where the reactor feed was preheated and then flows through a water-cooled heat exchanger before it flows through the pressure controller (PC) and undergoes a pressure reduction down to about 3 to 5 atmospheres. The resulting mixture of liquid and gas enters the gas separator vessel at about 35 °C and 3 to 5 atmospheres of absolute pressure.
Most of the hydrogen-rich gas from the gas separator vessel is recycle gas which is routed through an amine contactor for removal of the reaction product H2S that it contains. The H2S-free hydrogen-rich gas is then recycled back for reuse in the reactor section. Any excess gas from the gas separator vessel joins the sour gas from the stripping of the reaction product liquid.
The liquid from the gas separator vessel is routed through a reboiled stripper distillation tower. The bottoms product from the stripper is the final desulfurized liquid product from hydrodesulfurization unit.
The overhead sour gas from the stripper contains hydrogen, methane, ethane, hydrogen sulfide, propane and perhaps some butane and heavier components. That sour gas is sent to the refinery's central gas processing plant for removal of the hydrogen sulfide in the refinery's main amine gas treating unit and through a series of distillation towers for recovery of propane, butane and pentane or heavier components. The residual hydrogen, methane, ethane and some propane is used as refinery fuel gas. The hydrogen sulfide removed and recovered by the amine gas treating unit is subsequently converted to elemental sulfur in a Claus process unit.
Note that the above description assumes that the HDS unit feed contains no olefins. If the feed does contain olefins (for example, the feed is a naphtha derived from a refinery fluid catalytic cracker (FCC) unit), then the overhead gas from the HDS stripper may also contain some ethene, propene, butenes and pentenes or heavier components.
It should also be noted that the amine solution to and from the recycle gas contactor comes from and is returned to the refinery's main amine gas treating unit.
Sulfur compounds in refinery HDS feedstocks
The refinery HDS feedstocks (naphtha, kerosene, diesel oil and heavier oils) contain a wide range of organic sulfur compounds, including thiols, thiophenes, organic sulfides and disulfides, and many others. These organic sulfur compounds are products of the degradation of sulfur containing biological components, present during the natural formation of the fossil fuel, petroleum crude oil.
When the HDS process is used to desulfurize a refinery naphtha, it is necessary to remove the total sulfur down to the parts per million range or lower in order to prevent poisoning the noble metal catalysts in the subsequent catalytic reforming of the naphthas.
When the process is used for desulfurizing diesel oils, the latest environmental regulations in the United States and Europe, requiring what is referred to as ultra-low sulfur diesel (ULSD), in turn requires that very deep hydrodesulfurization is needed. In the very early 2000's, the governmental regulatory limits for highway vehicle diesel was within the range of 300 to 500 ppm by weight of total sulfur. As of 2006, the total sulfur limit for highway diesel is in the range of 15 to 30 ppm by weight.[11]
Thiophenes
A family of substrates that are particularly common in petroleum are the aromatic sulfur-containing heterocycles called thiophenes. Many kinds of thiophenes occur in petroleum ranging from thiophene itself to more condensed derivatives called benzothiophenes and dibenzothiophenes. Thiophene itself and its alkyl derivatives are easier to hydrogenolyse, whereas dibenzothiophene, especially its 4,6-disubstituted derivatives, are considered the most challenging substrates. Benzothiophenes are midway between the simple thiophenes and dibenzothiophenes in their susceptibility to HDS.
Catalysts and mechanisms
The main HDS catalysts are based on MoS2 together with smaller amounts of other metals.[12] The nature of the sites of catalytic activity remains an active area of investigation, but it is generally assumed basal planes of the MoS2 structure are not relevant to catalysis, rather the edges or rims of these sheet.[13] At the edges of the MoS2 crystallites, the molybdenum centre can stabilize a coordinatively unsaturated site (CUS), also known as an anion vacancy. Substrates, such as thiophene, bind to this site and undergo a series a reactions that result in both C-S scission and C=C hydrogenation. Thus, the hydrogen serves multiple roles - generation of anion vacancy by removal of sulfide, hydrogenation, and hydrogenolysis. A simplified diagram for the cycle is shown:
Simplified diagram of a HDS cycle for thiophene
Catalysts
Most metals catalyse HDS, but it is those at the middle of the transition metal series that are most active. Ruthenium disulfide appears to be the single most active catalyst, but binary combinations of cobalt and molybdenum are also highly active.[14] Aside from the basic cobalt-modified MoS2 catalyst, nickel and tungsten are also used, depending on the nature of the feed. For example, Ni-W catalysts are more effective for hydrodenitrification (HDN).
Supports
Metal sulfides are "supported" on materials with high surface areas. A typical support for HDS catalyst is γ-alumina. The support allows the more expensive catalyst to be more widely distributed, giving rise to a larger fraction of the MoS2 that is catalytically active. The interaction between the support and the catalyst is an area of intense interest, since the support is often not fully inert but participates in the catalysis.
Other uses
The basic hydrogenolysis reaction has a number of uses other than hydrodesulfurization.
Hydrodenitrogenation
The hydrogenolysis reaction is also used to reduce the nitrogen content of a petroleum stream and, in that case, is referred to Hydrodenitrogenation (HDN). The process flow scheme is the same as for an HDS unit.
Using pyridine (C5H5N), a nitrogen compound present in some petroleum fractionation products, as an example, the hydrodenitrogenation reaction has been postulated as occurring in three steps:[15][16]
Pyridine + Hydrogen → Piperdine + Hydrogen → Amylamine + Hydrogen → Pentane + Ammonia
C5H5N + 5H2 → C5H11N + 2H2 → C5H11NH2 + H2 → C5H12 + NH3
and the overall reaction may be simply expressed as:
Pyridine + Hydrogen → Pentane + Ammonia
C5H5N + 5H2 → C5H12 + NH3
Many HDS units for desulfurizing naphthas within petroleum refineries are actually simultaneously denitrogenating to some extent as well.
Saturation of olefins
The hydrogenolysis reaction may also be used to saturate or convert olefins (alkenes) into paraffins (alkanes). The process used is the same as for an HDS unit.
As an example, the saturation of the olefin, pentene, can be simply expressed as:
Pentene + Hydrogen → Pentane
C5H10 + H2 → C5H12
Some hydrogenolysis units within a petroleum refinery or a petrochemical plant may be used solely for the saturation of olefins or they may be used for simultaneously desulfurizing as well as denitrogenating and saturating olefins to some extent.
Hydrogenation in the food industry
Further information: Hydrogenation, Wilhelm Normann, and Trans fat
The food industry uses hydrogenation to completely or partially saturate the unsaturated fatty acids in liquid vegetable fats and oils to convert them into solid or semi-solid fats, such as those in margarine and shortening.
Desulfurization technology research
Hundreds of research publications appear annually on HDS technologies. Illustrative of the range of ideas being discussed are reports on ultrasonically assisted desulfurization.[17]
See also
Timeline of hydrogen technologies
References
^ Gary, J.H. and Handwerk, G.E. (1984). Petroleum Refining Technology and Economics (2nd Edition ed.). Marcel Dekker, Inc. ISBN 0-8247-7150-8.
^ Hydrodesulfurization Technologies and Costs Nancy Yamaguchi, Trans Energy Associates, William and Flora Hewlett Foundation Sulfur Workshop, Mexico City, May 29-30, 2003
^ Sulfur production report by the United States Geological Survey
^ Discussion of recovered byproduct sulfur
^ C.R.Acad.Sci. 1897, 132, 210
^ C.R.Acad.Sci. 1901, 132, 210
^ DE Patent DE141029 (Espacenet, record not available)
^ UK Patent GB190301515 GB190301515 (Espacenet)
^ Microchannel HDS (March 2006)
^ Fuel cells help make noisy, hot generators a thing of the past (December 2007) Pacific Northwest National Laboratory
^ Diesel Sulfur published online by the National Petrochemical & Refiners Association (NPRA)
^ Topsøe, H.; Clausen, B. S.; Massoth, F. E., Hydrotreating Catalysis, Science and Technology, Springer-Verlag: Berlin, 1996.
^ Daage, M.; Chianelli, R. R., "Structure-Function Relations in Molybdenum Sulfide Catalysts - the Rim-Edge Model", J. of Catalysis, 1994, 149, 414-427.
^ Chianelli, R. R.; Berhault, G.; Raybaud, P.; Kasztelan, S.; Hafner, J. and Toulhoat, H., "Periodic trends in hydrodesulfurization: in support of the Sabatier principle", Applied Catalysis, A, 2002, volume 227, pages 83-96
^ Kinetics and Interactions of the Simultaneous Catalytic Hydrodenitrogenation of Pyridine andHydrodesulfurization of Thiophene(John Wilkins, PhD Thesis, MIT, 1977)
^ Simultaneous Catalytic Hydrodenitrogenation of Pyridine and Hydrodesulfurization ofThiophene(Satterfield,C.N., Modell, M. and Wilkens, J.A., Ind. Eng. Chem. Process Des. Dev., 1980 Vol. 19, pages 154-160)
^ Deshpande, A., Bassi, A., Prakash, A. (2004) "Ultrasound-Assisted, Base-Catalyzed Oxidation of 4,6-Dimethyldibenzothiophene in a Biphasic Diesel-Acetonitrile System" Energy Fuels, 19 (1), 28 -34, 2005.
External links
Albemarle Catalyst Company (Petrochemical catalysts supplier)
UOP Company (Engineering design and construction of large-scale, industrial HDS plants)
Mustang Engineering Company (Description and flow diagram of an HDS unit, from an article published in the Oil & Gas Journal)
Hydrogenation for Low Trans and High Conjugated Fatty Acids by E.S. Jang, M.Y. Jung, D.B. Min, Comprehensive Reviews in Food Science and Food Safety, Vol.1, 2005
Oxo Alcohols (Engineered and constructed by Aker Kvaerner)
Catalysts and technology for Oxo-Alcohols
http://en.wikipedia.org/wiki/Hydrodesulfurization
2009年2月17日 星期二
Pervaporation
Pervaporation is a method for the separation of mixtures of liquids by partial vaporization through a non-porous or porous membrane.
Contents
1 Theory
2 Applications
3 External links
4 References
Theory
The name of this membrane-based process is derived from the two basic steps of the process, firstly the permeation through the membrane by the permeate, then its evaporation into the vapor phase. This process is used by a number of industries for several different processes, including purification and analysis, due to its simplicity and in-line nature.
The membrane acts as a selective barrier between the two phases, the liquid phase feed and the vapor phase permeate. It allows the desired component(s) of the liquid feed to transfer through it by vaporization. Separation of components is based on a difference in transport rate of individual components through the membrane.
Typically, the upstream side of the membrane is at ambient pressure and the downstream side is under vacuum to allow the evaporation of the selective component after permeation through the membrane. Driving force for the separation is the difference in the partial pressures of the components on the two sides and not the volatility difference of the components in the feed.
The driving force for transport of different components is provided by a chemical potential difference between the liquid feed/retentate and vapor permeate at each side of the membrane. The retentate is the remainder of the feed leaving the membrane feed chamber, which is not permeated through the membrane. The chemical potential can be expressed in terms of fugacity, given by Raoult's law for a liquid and by Dalton's law for (an ideal) gas. It should be noted that during operation, due to removal of the vapor-phase permeate, the actual fugacity of the vapor is lower than anticipated on basis of the collected (condensed) permeate.
Separation of components (e.g. water and ethanol) is based on a difference in transport rate of individual components through the membrane. This transport mechanism can be described using the solution-diffusion model, based on the rate/ degree of dissolution of a component into the membrane and its velocity of transport (expressed in terms of diffusivity) through the membrane, which will be different for each component and membrane type leading to separation.
Applications
Pervaporation is effective for diluting solutions containing trace or minor amounts of the component to be removed. Based on this, hydrophilic membranes are used for dehydration of alcohols containing small amounts of water and hydrophobic membranes are used for removal/recovery of trace amounts of organics from aqueous solutions. Hydrophobic membranes are often PDMS based where the actual separation mechanism is based on the solution-diffusion model described above.
A relatively new membrane in the field of hydrophilic membranes is the ceramic membrane with the actual separation layer being made of amorphous silica. This is in fact a membrane which is porous, with pores ranging around 4 Å, large enough to let water molecules pass through and retain any other solvents that have a larger molecular size such as ethanol. Recent novell hydrophilic ceramic membranes can also be based on titania or zirconia.
Pervaporation is a very mild process and hence very effective for separation of those mixtures which can not survive the harsh conditions of distillation.
Solvent Dehydration: dehydrating the ethanol/water and isopropanol/water azeotropes
Continuous water removal from condensation reactions such as esterifications to enhance conversion and rate of the reaction.
Membrane introduction mass spectrometry
Removing organic solvents from industrial waste waters.
Combination of distillation and pervaporation/vapour permeation
Recently, a number of organophilic Pervaporation membranes have been introduced to the market. Organophilic Pervaporation membranes can be used for the separation of organic-organic mixtures, e.g.:
Reduction of the aromatics content in refinery streams
Breaking of azeotropes
Purification of extraction media
Purification of product stream after extraction
Purification of organic solvents
External links
http://www.membrane-guide.com/membrane_separation/pervaporation/pervaporation_europe.htm suppliers, products, news and facts for engineers involved in the design or the operation of pervaporation systems.
Technology of pervaporation Pervaporation with ceramic membranes
[1] Environmental Importance & as a Green Chemistry solution.
This chemistry article is a stub. You can help Wikipedia by expanding it.
References
Fontalvo Alzate, Javier (2006). Design and performance of two-phase flow pervaporation and hybrid distillation process.. Technische Universiteit Eindhoven, The Netherlands: JWL boekproducties. ISBN 978-90-386-3007-6.
Matuschewski, Heike (2008). MSE — modified membranes in organophilic pervaporation for aromatics/aliphatics separation.. www.desline.com: Desalination.
Retrieved from "http://en.wikipedia.org/wiki/Pervaporation"
http://en.wikipedia.org/wiki/Pervaporation
Contents
1 Theory
2 Applications
3 External links
4 References
Theory
The name of this membrane-based process is derived from the two basic steps of the process, firstly the permeation through the membrane by the permeate, then its evaporation into the vapor phase. This process is used by a number of industries for several different processes, including purification and analysis, due to its simplicity and in-line nature.
The membrane acts as a selective barrier between the two phases, the liquid phase feed and the vapor phase permeate. It allows the desired component(s) of the liquid feed to transfer through it by vaporization. Separation of components is based on a difference in transport rate of individual components through the membrane.
Typically, the upstream side of the membrane is at ambient pressure and the downstream side is under vacuum to allow the evaporation of the selective component after permeation through the membrane. Driving force for the separation is the difference in the partial pressures of the components on the two sides and not the volatility difference of the components in the feed.
The driving force for transport of different components is provided by a chemical potential difference between the liquid feed/retentate and vapor permeate at each side of the membrane. The retentate is the remainder of the feed leaving the membrane feed chamber, which is not permeated through the membrane. The chemical potential can be expressed in terms of fugacity, given by Raoult's law for a liquid and by Dalton's law for (an ideal) gas. It should be noted that during operation, due to removal of the vapor-phase permeate, the actual fugacity of the vapor is lower than anticipated on basis of the collected (condensed) permeate.
Separation of components (e.g. water and ethanol) is based on a difference in transport rate of individual components through the membrane. This transport mechanism can be described using the solution-diffusion model, based on the rate/ degree of dissolution of a component into the membrane and its velocity of transport (expressed in terms of diffusivity) through the membrane, which will be different for each component and membrane type leading to separation.
Applications
Pervaporation is effective for diluting solutions containing trace or minor amounts of the component to be removed. Based on this, hydrophilic membranes are used for dehydration of alcohols containing small amounts of water and hydrophobic membranes are used for removal/recovery of trace amounts of organics from aqueous solutions. Hydrophobic membranes are often PDMS based where the actual separation mechanism is based on the solution-diffusion model described above.
A relatively new membrane in the field of hydrophilic membranes is the ceramic membrane with the actual separation layer being made of amorphous silica. This is in fact a membrane which is porous, with pores ranging around 4 Å, large enough to let water molecules pass through and retain any other solvents that have a larger molecular size such as ethanol. Recent novell hydrophilic ceramic membranes can also be based on titania or zirconia.
Pervaporation is a very mild process and hence very effective for separation of those mixtures which can not survive the harsh conditions of distillation.
Solvent Dehydration: dehydrating the ethanol/water and isopropanol/water azeotropes
Continuous water removal from condensation reactions such as esterifications to enhance conversion and rate of the reaction.
Membrane introduction mass spectrometry
Removing organic solvents from industrial waste waters.
Combination of distillation and pervaporation/vapour permeation
Recently, a number of organophilic Pervaporation membranes have been introduced to the market. Organophilic Pervaporation membranes can be used for the separation of organic-organic mixtures, e.g.:
Reduction of the aromatics content in refinery streams
Breaking of azeotropes
Purification of extraction media
Purification of product stream after extraction
Purification of organic solvents
External links
http://www.membrane-guide.com/membrane_separation/pervaporation/pervaporation_europe.htm suppliers, products, news and facts for engineers involved in the design or the operation of pervaporation systems.
Technology of pervaporation Pervaporation with ceramic membranes
[1] Environmental Importance & as a Green Chemistry solution.
This chemistry article is a stub. You can help Wikipedia by expanding it.
References
Fontalvo Alzate, Javier (2006). Design and performance of two-phase flow pervaporation and hybrid distillation process.. Technische Universiteit Eindhoven, The Netherlands: JWL boekproducties. ISBN 978-90-386-3007-6.
Matuschewski, Heike (2008). MSE — modified membranes in organophilic pervaporation for aromatics/aliphatics separation.. www.desline.com: Desalination.
Retrieved from "http://en.wikipedia.org/wiki/Pervaporation"
http://en.wikipedia.org/wiki/Pervaporation
2009年2月12日 星期四
BASF to present BASIL™ ionic liquid process at technology transfer forum
BASF to present BASIL™ ionic liquid process at technology transfer forum'Smart' process improves yields, economics of chemical operations
MOUNT OLIVE, N.J., May 10, 2004 -- Dr. Uwe Vagt, New Business Development, for BASF's Intermediates Division in Ludwigshafen, Germany, will present BASF's proprietary BASIL technology that utilizes ionic liquids to improve chemical operations on a commercial scale. The presentation will be at 9:30 a.m., on Monday, May 10, 2004, at the 21st Annual International Technology Transfer Forum, hosted by Technology Catalysts, at the Hyatt Regency Reston Town Center in Reston, Va.
BASF's BASIL (Biphasic Acid Scavenging utilizing Ionic Liquids) "smart" process technology economically solves several chemical processing problems associated with acid production during some chemical reactions.
Many organic chemical processes, such as esterifications, produce byproduct acids that must be scavenged in order to prevent decomposition of the primary reaction product, or to prevent unwanted side-reactions. To address this problem, tertiary amines, such as triethylamine, are typically added to the reaction mixture, resulting in the production of a solid ammonium salt. This solid presents a host of problems, including reduction of heat transfer and reaction rates, reduction of yields, and solids separation.
The BASIL process economically avoids the problems resulting from solids generation by making use of ionic liquids to scavenge acids. Instead of using a tertiary amine, a 1-alkylimidazole is used to scavenge acids produced. As the imidazole reacts with the acid, an alkylimidazolium salt is formed which is an ionic liquid at the reaction temperature. As a liquid, the alkylimidazolium salt can be easily removed by a liquid-liquid phase separation. In addition, economic reclamation of the 1-alkylimidazole through deprotonation is possible.
Ionic liquid technology provides the added advantage of having the alkylimidazole act as a nucleophilic catalyst, thereby improving reaction rates, and increasing yields and selectivities.
BASF representatives will be available throughout the technology transfer forum to answer questions and discuss potential licenses for this innovative technology.
Details about the Technology Catalysts 21st Annual International Technology Transfer Forum can be found at http://www.technology-catalysts.com//.
BASF - The Chemical Company. We don't make a lot of the products you buy. We make a lot of the products you buy better.®BASF Corporation, headquartered in New Jersey, is the North American affiliate of BASF AG, Ludwigshafen, Germany. We employ about 11,000 people in North America and had sales of approximately $9 billion in 2003. For more information about BASF's North American operations, or to sign up to receive news releases by e-mail, visit www.basf.com/usa.
BASF is the world's leading chemical company. Our goal is to grow profitably and further increase the value of our company. We help our customers to be more successful through intelligent system solutions and high-quality products. BASF's portfolio ranges from chemicals, plastics, performance products, agricultural products and fine chemicals to crude oil and natural gas. Through new technologies we can tap into additional market opportunities. We conduct our business in accordance with the principles of sustainable development. In 2003, BASF had sales of approximately $42 billion and over 87,000 employees worldwide. Further information on BASF is available on the Internet at http://www.basf.com/.
For more information, contact:Bill PaganoBASFTel: (973)426-2139E-mail: paganow@basf.com
MOUNT OLIVE, N.J., May 10, 2004 -- Dr. Uwe Vagt, New Business Development, for BASF's Intermediates Division in Ludwigshafen, Germany, will present BASF's proprietary BASIL technology that utilizes ionic liquids to improve chemical operations on a commercial scale. The presentation will be at 9:30 a.m., on Monday, May 10, 2004, at the 21st Annual International Technology Transfer Forum, hosted by Technology Catalysts, at the Hyatt Regency Reston Town Center in Reston, Va.
BASF's BASIL (Biphasic Acid Scavenging utilizing Ionic Liquids) "smart" process technology economically solves several chemical processing problems associated with acid production during some chemical reactions.
Many organic chemical processes, such as esterifications, produce byproduct acids that must be scavenged in order to prevent decomposition of the primary reaction product, or to prevent unwanted side-reactions. To address this problem, tertiary amines, such as triethylamine, are typically added to the reaction mixture, resulting in the production of a solid ammonium salt. This solid presents a host of problems, including reduction of heat transfer and reaction rates, reduction of yields, and solids separation.
The BASIL process economically avoids the problems resulting from solids generation by making use of ionic liquids to scavenge acids. Instead of using a tertiary amine, a 1-alkylimidazole is used to scavenge acids produced. As the imidazole reacts with the acid, an alkylimidazolium salt is formed which is an ionic liquid at the reaction temperature. As a liquid, the alkylimidazolium salt can be easily removed by a liquid-liquid phase separation. In addition, economic reclamation of the 1-alkylimidazole through deprotonation is possible.
Ionic liquid technology provides the added advantage of having the alkylimidazole act as a nucleophilic catalyst, thereby improving reaction rates, and increasing yields and selectivities.
BASF representatives will be available throughout the technology transfer forum to answer questions and discuss potential licenses for this innovative technology.
Details about the Technology Catalysts 21st Annual International Technology Transfer Forum can be found at http://www.technology-catalysts.com//.
BASF - The Chemical Company. We don't make a lot of the products you buy. We make a lot of the products you buy better.®BASF Corporation, headquartered in New Jersey, is the North American affiliate of BASF AG, Ludwigshafen, Germany. We employ about 11,000 people in North America and had sales of approximately $9 billion in 2003. For more information about BASF's North American operations, or to sign up to receive news releases by e-mail, visit www.basf.com/usa.
BASF is the world's leading chemical company. Our goal is to grow profitably and further increase the value of our company. We help our customers to be more successful through intelligent system solutions and high-quality products. BASF's portfolio ranges from chemicals, plastics, performance products, agricultural products and fine chemicals to crude oil and natural gas. Through new technologies we can tap into additional market opportunities. We conduct our business in accordance with the principles of sustainable development. In 2003, BASF had sales of approximately $42 billion and over 87,000 employees worldwide. Further information on BASF is available on the Internet at http://www.basf.com/.
For more information, contact:Bill PaganoBASFTel: (973)426-2139E-mail: paganow@basf.com
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