Dibenzothiophene
From Wikipedia, the free encyclopedia
Jump to: navigation, search
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
2008年5月16日 星期五
離子液體
離子液體當作溶劑的應用
近年來，離子液體在化學上的應用非常廣泛。由於離子液體具有極低蒸氣壓、低熔點、高極性、不可燃性、耐強酸、高熱穩定性、高導電度、電化學性佳及較廣的液體溫度範圍( -96 ~ 400 ℃)等特殊性質，可替代一般所用之揮發性有機溶劑(volatile organic compounds VOCs)，應用在化學合成，而且離子液體可在常壓下操作，不但可降低操作成本，且可消除VOCs對環境的污染，並可避免操作人員暴露於VOCs的風險，可再回收使用，所以離子液體有時被認為是一種新的綠色溶劑“green solvent”[1]。
離子液體是由陰離子及陽離子所組成的有機熔鹽，依不同組合方式，可超過一兆種。鹽類的熔點可高達 801 ℃或低到–96 ℃，所以為方便與高溫熔鹽做區分，通常把熔點低於 100 ℃的熔鹽稱為室溫離子液體(room temperature ion liquids-RTILs)，簡稱為離子液體(IL)，目前所發現的離子液體已超過 200 多種，常用的離子液體結構如圖一[2]。離子液體的陽離子包含有1-alkyl-3-methylimidazolium ([CnMIM]+, n為線性烷基碳的數目)、N-alkylpyridinium([CnPY]+)、tetraalkylammonium及tetraalkylphosphonium等陽離子，這些陽離子可結合不同的有機或無機的陰離子形成數目龐大的離子液體[3]，常見的陰離子有hexafluorophosphate(PF6-)、tetrafluoroborate(BF4-)、trifluoromethylsulfonate(CF3SO3-)、bis[(trifloromethyl)sulfonyl]amide [(CF3SO2)2N]-、trifluoroethanoate(CF3CO2-)、ethanoate(CH3CO2-)及halide(Br-,Cl-,I-)。
雖然早在 1914 年Walden即首先報導低溫的離子液體ethylammonium nitrate[4]，接下來於 1951 年Hurley首先合成室溫離子液體N-ethylpyridinium bromide- aluminium chloride[5]，但一直到 1970 年代，Osteryong和Willkers成功製備出chloroaluminate melts[6]，從此離子液體被大量應用於電化學、反應介質及催化劑。 1992 年，Wilkes等人發展出一係列咪唑(imidazolium)陽離子及BF4-、PF6-等陰離子組成的離子液體[7]，此類離子液體在空氣及水中相當穩定，使得這些類離子液體的應用引起廣大重視[8]，之後離子液體的發展大多以咪唑鹽類為主，進而發展出含DNA離子液體[9]、適合電化學的兩性離子液體[10]、磁性離子液體[11]及以胺基酸作為陰離子的離子液體等特殊功能的離子液體[12]，近年來離子液體的研究趨勢往功能性上發展。
離子液體的物理性質:
親水性：離子液體的親水性主要是取決於陰離子的結構，對水溶解度趨勢如圖一[3]，另外陽離子碳鏈愈長親水性愈差。
酸鹼性：一般離子液體可由陰離子部分判斷其酸鹼性，如表一[13]，因此可藉由陰離子的部分來調控溶劑的酸鹼度，而不必再加入額外的酸或鹼。
熔點：陽離子的對稱性愈低，會影響晶體的堆疊性，使熔點降低，而分子間的氫鍵會使熔點提高，常用雙烷基咪唑鹽類(dialkylimidazolium)的離子液體熔點，如表二。[14]
黏度：由於正負離子的作用力，使得離子液體黏度通常比水的黏度大很多，離子液體黏度的大小受分子間的氫鍵及凡得瓦作用力影響，陽離子碳鏈愈長，凡得瓦力愈強則黏度愈高。對於相同種類的陽離子，不同陰離子所形成的離子液體其黏度高低順序為Cl->PF6->BF4->NO3->(CF3SO3)2N-，如表二。
密度：大部分的離子液體是密度在 1 到 1.6 g/cm3之間，隨著溫度增加密度會降低。
離子液體在化學領域上有許多其特殊的物理性質，例如可溶解許多的無機和有機物質，但與部分的有機溶劑不互溶，可形成兩相反應系統，其優點是反應與分離可同時進行。不具揮發性，在高度真空下操作不易流失。不可燃性及有高的熱穩定性，加上其液體範圍廣，使其可應用的反應溫度範圍廣。另外，還可改變陰離子及陽離子的組成以調控其特性，所以離子液體亦被認為是“designer solvent”。離子液體的這些特殊物理性質，離子液體做為溶劑除了在電化學當作“nonaqueous elelctrolyte”外，其做為溶劑已被廣泛應用，其應用簡述如下：
a.有機合成的應用: 由於離子液體可溶解有機或無機物質，可當有機反應之溶劑取代傳統有機溶劑，不祇可減少傳統揮發性溶劑的危害，有時還可提高反應之選擇性和產率[16]，Jaeger等人首先以離子液體[EtNH3][NO3]進行Diels-Alder反應[17]，與有機溶劑甲苯及四氫夫喃比較[18]，可提高產率及Endo/Exo選擇性。Wasserscheid[19]等人及Ishida[20]等人合成不同對掌性陽離子型式的離子液體，此種對掌性離子液體於不對稱合成時可增加產物的立體選擇性，亦可作為對掌性分離中所填充靜相異構物。使用離子液體於合成時溶劑的應用，在過去十年呈現快速的發展。
b.催化反應的應用：離子液體可與催化劑形成共催化劑，增加催化劑的活性、選擇性及穩定性。例如Friedel–Crafts reaction在傳統條件下須加入固體的AlCl3作為催化劑，而[emim][AlCl3]可以代替催化劑及溶劑增加反應速率及選擇性[21]。離子液體在催化反應上的應用，包含hydrogenation [22]、hydroformylation[23]、olefin dimerisation[22]、Heck reaction[24]、alkoxycarbonylation[25]、catalytic oxidation[26]等反應；在酵素催化方面，離子液體可提高酵素功能[27]，以親水性的離子液體[C4MIM][BF4]不但可溶解有機反應物與生成物，而且可溶解酵素，且酵素的觸媒在其溶液仍具有活性且相當穩定，與在傳統的有機溶劑中酵素容易失去活性兩相比較，具有相當的優勢。
c.雷射脫附基質的應用：由於離子液體的不揮發性及可溶解生物樣品寡醣、蛋白質和高分子，可作為較軟性(soft)的離子源，將其吸收雷射之能量轉移至分析物中，除了可提升基質輔助雷射脫附的離子化效果[28,29]，亦可解決MALDI再現性的問題。
d.氣相層析管柱固定相的應用：在 1986 年Poole等人曾經使用alkylammonium和tetraalkylammonium鹽類作為氣相層析(GC)管柱的固定相[30,31]，但由於這種鹽類操作溫度的限制，降低其實用性。而Armstrong等人使用1-benzyl-3-methylimidazolium trifluoromethanesulfonate及1-(4-methoxyphenyl)-3-methylimidazolium Trifluoromethanesulfonate的離子液體的作為GC液相固定相(GLC)，分析揮發性或半揮發性有機物，分離效果相當好[32]，並利用[C4MIM][Cl]溶解25%(w/w) 的β-Cyclodextrins (β-CDs)[33]及合成具對掌性的離子液體[34]作為GC的對掌性固定相，分離對掌性化合物；由於這類的離子液體可耐高溫的特性，大大提高其商業化的潛力。
e.萃取的應用：疏水性的離子液體可被利用疏水性來萃取水中金屬離子[35,36]與染料萃取[37]，也利用其在柴油中氧化/萃取達成脫硫的目的[38]，Stepnowski使用固相萃取及Liu等人使用液相微萃取來濃縮水中的有機物[39,40]，Andre等人使用頂空式(head space)方法萃取分析物後再以GC分析[41]，離子液體具有特殊溶解性可萃取水溶液中球狀及棒狀金奈米[42]。
f.電化學的應用: 由於離子液體具導電性，可取代傳統的電解液，且有電化學視窗較廣的優點，可改善電化學過程中使用溶劑的偵測限制。使用離子液體在電化學的研究，開啟了離子液體在綠色化學領域之重視，另外也推展其在鋰離子電池[43]、燃料電池[44]、太陽能電池[45]、電容[46]及可偵測O2、CO2、SO2氣體的薄膜電極[47-51]等方面應用。
g.其它功能上的應用：離子液體可溶解纖維素[52]、作為溶膠-凝膠(Sol-Gel)的溶劑[53]及潤滑劑[54]等應用，所以離子液體的應用隨著新的離子液體發現而陸續增加，加上離子液體已突破實驗室的限制，已初步應用於商業發展上[55]，另外，離子液體可結合超臨界CO2於反應、萃取及分離相關應用[56]。
基本上，隨著離子液體的研究發展，其應用將更深入、更廣泛，使其在綠色化學的重要性相對增加，但其邁向廣泛工業上應用仍有許多問題需要克服[57-58]，此有待進一步研究來達成。
http://gc.chem.sinica.edu.tw/new-no-ionic.html
近年來，離子液體在化學上的應用非常廣泛。由於離子液體具有極低蒸氣壓、低熔點、高極性、不可燃性、耐強酸、高熱穩定性、高導電度、電化學性佳及較廣的液體溫度範圍( -96 ~ 400 ℃)等特殊性質，可替代一般所用之揮發性有機溶劑(volatile organic compounds VOCs)，應用在化學合成，而且離子液體可在常壓下操作，不但可降低操作成本，且可消除VOCs對環境的污染，並可避免操作人員暴露於VOCs的風險，可再回收使用，所以離子液體有時被認為是一種新的綠色溶劑“green solvent”[1]。
離子液體是由陰離子及陽離子所組成的有機熔鹽，依不同組合方式，可超過一兆種。鹽類的熔點可高達 801 ℃或低到–96 ℃，所以為方便與高溫熔鹽做區分，通常把熔點低於 100 ℃的熔鹽稱為室溫離子液體(room temperature ion liquids-RTILs)，簡稱為離子液體(IL)，目前所發現的離子液體已超過 200 多種，常用的離子液體結構如圖一[2]。離子液體的陽離子包含有1-alkyl-3-methylimidazolium ([CnMIM]+, n為線性烷基碳的數目)、N-alkylpyridinium([CnPY]+)、tetraalkylammonium及tetraalkylphosphonium等陽離子，這些陽離子可結合不同的有機或無機的陰離子形成數目龐大的離子液體[3]，常見的陰離子有hexafluorophosphate(PF6-)、tetrafluoroborate(BF4-)、trifluoromethylsulfonate(CF3SO3-)、bis[(trifloromethyl)sulfonyl]amide [(CF3SO2)2N]-、trifluoroethanoate(CF3CO2-)、ethanoate(CH3CO2-)及halide(Br-,Cl-,I-)。
雖然早在 1914 年Walden即首先報導低溫的離子液體ethylammonium nitrate[4]，接下來於 1951 年Hurley首先合成室溫離子液體N-ethylpyridinium bromide- aluminium chloride[5]，但一直到 1970 年代，Osteryong和Willkers成功製備出chloroaluminate melts[6]，從此離子液體被大量應用於電化學、反應介質及催化劑。 1992 年，Wilkes等人發展出一係列咪唑(imidazolium)陽離子及BF4-、PF6-等陰離子組成的離子液體[7]，此類離子液體在空氣及水中相當穩定，使得這些類離子液體的應用引起廣大重視[8]，之後離子液體的發展大多以咪唑鹽類為主，進而發展出含DNA離子液體[9]、適合電化學的兩性離子液體[10]、磁性離子液體[11]及以胺基酸作為陰離子的離子液體等特殊功能的離子液體[12]，近年來離子液體的研究趨勢往功能性上發展。
離子液體的物理性質:
親水性：離子液體的親水性主要是取決於陰離子的結構，對水溶解度趨勢如圖一[3]，另外陽離子碳鏈愈長親水性愈差。
酸鹼性：一般離子液體可由陰離子部分判斷其酸鹼性，如表一[13]，因此可藉由陰離子的部分來調控溶劑的酸鹼度，而不必再加入額外的酸或鹼。
熔點：陽離子的對稱性愈低，會影響晶體的堆疊性，使熔點降低，而分子間的氫鍵會使熔點提高，常用雙烷基咪唑鹽類(dialkylimidazolium)的離子液體熔點，如表二。[14]
黏度：由於正負離子的作用力，使得離子液體黏度通常比水的黏度大很多，離子液體黏度的大小受分子間的氫鍵及凡得瓦作用力影響，陽離子碳鏈愈長，凡得瓦力愈強則黏度愈高。對於相同種類的陽離子，不同陰離子所形成的離子液體其黏度高低順序為Cl->PF6->BF4->NO3->(CF3SO3)2N-，如表二。
密度：大部分的離子液體是密度在 1 到 1.6 g/cm3之間，隨著溫度增加密度會降低。
離子液體在化學領域上有許多其特殊的物理性質，例如可溶解許多的無機和有機物質，但與部分的有機溶劑不互溶，可形成兩相反應系統，其優點是反應與分離可同時進行。不具揮發性，在高度真空下操作不易流失。不可燃性及有高的熱穩定性，加上其液體範圍廣，使其可應用的反應溫度範圍廣。另外，還可改變陰離子及陽離子的組成以調控其特性，所以離子液體亦被認為是“designer solvent”。離子液體的這些特殊物理性質，離子液體做為溶劑除了在電化學當作“nonaqueous elelctrolyte”外，其做為溶劑已被廣泛應用，其應用簡述如下：
a.有機合成的應用: 由於離子液體可溶解有機或無機物質，可當有機反應之溶劑取代傳統有機溶劑，不祇可減少傳統揮發性溶劑的危害，有時還可提高反應之選擇性和產率[16]，Jaeger等人首先以離子液體[EtNH3][NO3]進行Diels-Alder反應[17]，與有機溶劑甲苯及四氫夫喃比較[18]，可提高產率及Endo/Exo選擇性。Wasserscheid[19]等人及Ishida[20]等人合成不同對掌性陽離子型式的離子液體，此種對掌性離子液體於不對稱合成時可增加產物的立體選擇性，亦可作為對掌性分離中所填充靜相異構物。使用離子液體於合成時溶劑的應用，在過去十年呈現快速的發展。
b.催化反應的應用：離子液體可與催化劑形成共催化劑，增加催化劑的活性、選擇性及穩定性。例如Friedel–Crafts reaction在傳統條件下須加入固體的AlCl3作為催化劑，而[emim][AlCl3]可以代替催化劑及溶劑增加反應速率及選擇性[21]。離子液體在催化反應上的應用，包含hydrogenation [22]、hydroformylation[23]、olefin dimerisation[22]、Heck reaction[24]、alkoxycarbonylation[25]、catalytic oxidation[26]等反應；在酵素催化方面，離子液體可提高酵素功能[27]，以親水性的離子液體[C4MIM][BF4]不但可溶解有機反應物與生成物，而且可溶解酵素，且酵素的觸媒在其溶液仍具有活性且相當穩定，與在傳統的有機溶劑中酵素容易失去活性兩相比較，具有相當的優勢。
c.雷射脫附基質的應用：由於離子液體的不揮發性及可溶解生物樣品寡醣、蛋白質和高分子，可作為較軟性(soft)的離子源，將其吸收雷射之能量轉移至分析物中，除了可提升基質輔助雷射脫附的離子化效果[28,29]，亦可解決MALDI再現性的問題。
d.氣相層析管柱固定相的應用：在 1986 年Poole等人曾經使用alkylammonium和tetraalkylammonium鹽類作為氣相層析(GC)管柱的固定相[30,31]，但由於這種鹽類操作溫度的限制，降低其實用性。而Armstrong等人使用1-benzyl-3-methylimidazolium trifluoromethanesulfonate及1-(4-methoxyphenyl)-3-methylimidazolium Trifluoromethanesulfonate的離子液體的作為GC液相固定相(GLC)，分析揮發性或半揮發性有機物，分離效果相當好[32]，並利用[C4MIM][Cl]溶解25%(w/w) 的β-Cyclodextrins (β-CDs)[33]及合成具對掌性的離子液體[34]作為GC的對掌性固定相，分離對掌性化合物；由於這類的離子液體可耐高溫的特性，大大提高其商業化的潛力。
e.萃取的應用：疏水性的離子液體可被利用疏水性來萃取水中金屬離子[35,36]與染料萃取[37]，也利用其在柴油中氧化/萃取達成脫硫的目的[38]，Stepnowski使用固相萃取及Liu等人使用液相微萃取來濃縮水中的有機物[39,40]，Andre等人使用頂空式(head space)方法萃取分析物後再以GC分析[41]，離子液體具有特殊溶解性可萃取水溶液中球狀及棒狀金奈米[42]。
f.電化學的應用: 由於離子液體具導電性，可取代傳統的電解液，且有電化學視窗較廣的優點，可改善電化學過程中使用溶劑的偵測限制。使用離子液體在電化學的研究，開啟了離子液體在綠色化學領域之重視，另外也推展其在鋰離子電池[43]、燃料電池[44]、太陽能電池[45]、電容[46]及可偵測O2、CO2、SO2氣體的薄膜電極[47-51]等方面應用。
g.其它功能上的應用：離子液體可溶解纖維素[52]、作為溶膠-凝膠(Sol-Gel)的溶劑[53]及潤滑劑[54]等應用，所以離子液體的應用隨著新的離子液體發現而陸續增加，加上離子液體已突破實驗室的限制，已初步應用於商業發展上[55]，另外，離子液體可結合超臨界CO2於反應、萃取及分離相關應用[56]。
基本上，隨著離子液體的研究發展，其應用將更深入、更廣泛，使其在綠色化學的重要性相對增加，但其邁向廣泛工業上應用仍有許多問題需要克服[57-58]，此有待進一步研究來達成。
http://gc.chem.sinica.edu.tw/new-no-ionic.html
綠色化學的 12 基本法則
1. 預防廢棄物的產生。
2. 充分利用反應物的所有原子。
3. 設計合成方法時，儘量考慮反應物與生成物的毒性。
4. 設計低毒性的化學品。
5. 少用或使用安全的溶劑與輔助物。
6. 為節省能源、降低環境衝擊，反應條件以常溫常壓狀態為主。
7. 使用永續資源為原料。
8. 簡化反應步驟，減少非必要性衍生物的產生。
9. 盡可能使用高選擇性的催化劑。
10. 設計可分解的化學品。
11. 污染物的及時偵測。
12. 慎選製程中的化學物質，以減少意外災害的發生。
http://www.nsc.gov.tw/_newfiles/popular_science.asp?add_year=2005&popsc_aid=140
2. 充分利用反應物的所有原子。
3. 設計合成方法時，儘量考慮反應物與生成物的毒性。
4. 設計低毒性的化學品。
5. 少用或使用安全的溶劑與輔助物。
6. 為節省能源、降低環境衝擊，反應條件以常溫常壓狀態為主。
7. 使用永續資源為原料。
8. 簡化反應步驟，減少非必要性衍生物的產生。
9. 盡可能使用高選擇性的催化劑。
10. 設計可分解的化學品。
11. 污染物的及時偵測。
12. 慎選製程中的化學物質，以減少意外災害的發生。
http://www.nsc.gov.tw/_newfiles/popular_science.asp?add_year=2005&popsc_aid=140
Ionic liquid(From Wikipedia)
An ionic liquid is a liquid that contains essentially only ions. Some ionic liquids, such as ethylammonium nitrate are in a dynamic equilibrium where at any time more than 99.99% of the liquid is made up of ionic rather than molecular species. In the broad sense, the term includes all molten salts, for instance, sodium chloride at temperatures higher than 800 °C. Today, however, the term "ionic liquid" is commonly used for salts whose melting point is relatively low (below 100 °C). In particular, the salts that are liquid at room temperature are called room-temperature ionic liquids, or RTILs. There also exist mixtures of substances which have low melting points, called Deep eutectic solvent, or DES, that have many similarities with ionic liquids.
History
The date of discovery, as well as discoverer, of the "first" ionic liquid is disputed. Ethanolammonium nitrate (m.p. 52-55 °C) was reported in 1888 by Gabriel.[1] However, one of the earlier known truly room temperature ionic liquids was [EtNH3]+ [NO3]- (m.p. 12 °C), the synthesis of which was published in 1914.[2] Much later, series of ionic liquids based on mixtures of 1,3-dialkylimidazolium or 1-alkylpyridinium halides and trihalogenoaluminates, initially developed for use as electrolytes, were to follow.[3][4] An important property of the imidazolium halogenoaluminate salts was that they were tuneable – viscosity, melting point and the acidity of the melt could be adjusted by changing the alkyl substituents and the ratio of imidazolium or pyridinium halide to halogenoaluminate.[5]
A major drawback was their moisture sensitivity and, though to a somewhat lesser extent, their acidity/basicity, the latter which can sometimes be used to an advantage. In 1992, Wilkes and Zawarotko reported the preparation of ionic liquids with alternative, 'neutral', weakly coordinating anions such as hexafluorophosphate ([PF6]-) and tetrafluoroborate ([BF4])-, allowing a much wider range of applications for ionic liquids.[6] It was not until recently that a class of new, air- and moisture stable, neutral ionic liquids, was available that the field attracted significant interest from the wider scientific community.
More recently, people have been moving away from [PF6]- and [BF4]- since they are highly toxic, and towards new anions such as bistriflimide [(CF3SO2)2N]- or even away from halogenated compounds completely. Moves towards less toxic cations have also been growing, with compounds like ammonium salts (such as choline) being just as flexible a scaffold as imidazole.
Characteristics
Ionic liquids are electrically conductive and have extremely low vapor pressure. (Their noticeable odours are likely due to impurities.) Their other properties are diverse. Many have low combustibility, excellent thermal stability, a wide liquid range, and favorable solvating properties for diverse compounds. Many classes of chemical reactions, such as Diels-Alder reactions and Friedel-Crafts reactions, can be performed using ionic liquids as solvents. Recent work has shown that ionic liquids can serve as solvents for biocatalysis [7]. The miscibility of ionic liquids with water or organic solvents varies with sidechain lengths on the cation and with choice of anion. They can be functionalized to act as acids, bases or ligands, and have been used as precursor salts in the preparation of stable carbenes. Because of their distinctive properties, ionic liquids are attracting increasing attention in many fields, including organic chemistry, electrochemistry, catalysis, physical chemistry, and engineering; see for instance magnetic ionic liquid.
Despite their extremely low vapor pressures, some ionic liquids can be distilled under vacuum conditions at temperatures near 300 °C.[8] Some ionic liquids (such as 1-butyl-3-methylimidazolium nitrate) generate flammable gases on thermal decomposition. Thermal stability and melting point depend on the components of the liquid. Thermal stability of various RTILs are available. The thermal stability of a task-specific ionic liquid, protonated betaine bis(trifluoromethanesulfonyl)imide is of about 534 K and N-Butyl-N-Methyl pyrrolidinium bis(trifluoromethanesulfonyl)imide was thermally stable up to 640 K [9]
The solubility of different species in imidazolium ionic liquids depends mainly on polarity and hydrogen bonding ability. Simple aliphatic compounds are generally only sparingly soluble in ionic liquids, whereas olefins show somewhat greater solubility, and aldehydes can be completely miscible. This can be exploited in biphasic catalysis, such as hydrogenation and hydrocarbonylation processes, allowing for relatively easy separation of products and/or unreacted substrate(s). Gas solubility follows the same trend, with carbon dioxide gas showing exceptional solubility in many ionic liquids, carbon monoxide being less soluble in ionic liquids than in many popular organic solvents, and hydrogen being only slightly soluble (similar to the solubility in water) and probably varying relatively little between the more popular ionic liquids. (Different analytical techniques have yielded somewhat different absolute solubility values.)
Room temperature ionic liquids
Room temperature ionic liquids consist of bulky and asymmetric organic cations such as 1-alkyl-3-methylimidazolium, 1-alkylpyridinium, N-methyl-N-alkylpyrrolidinium and ammonium ions. A wide range of anions is employed, from simple halides, which generally inflect high melting points, to inorganic anions such as tetrafluoroborate and hexafluorophosphate and to large organic anions like bistriflimide, triflate or tosylate. There are also many interesting examples of uses of ionic liquids with simple non-halogenated organic anions such as formate, alkylsulfate, alkylphosphate or glycolate. As an example, the melting point of 1-butyl-3-methylimidazolium tetrafluoroborate or [bmim][BF4] with an imidazole skeleton is about -80 °C, and it is a colorless liquid with high viscosity at room temperature.
It has been pointed out that in many synthetic processes using transition metal catalyst, metal nanoparticles play an important role as the actual catalyst or as a catalyst reservoir. It also been shown that ionic liquids (ILs) are an appealing medium for the formation and stabilization of catalytically active transition metal nanoparticles. More importantly, ILs can be made that incorporate co-ordinating groups,[10], for example, with nitrile groups on either the cation or anion (CN-IL). In various C-C coupling reactions catalyzed by palladium catalyst, it has been found the palladium nanoparticles are better stabilized in CN-IL compared to non-functionalized ionic liquids; thus enhanced catalytic activity and recyclability are realized.
Low temperature ionic liquids
Low temperature ionic liquids (below 130 kelvins) have been proposed as the fluid base for an extremely large diameter spinning liquid mirror telescope to be based on the earth's moon.[12] Low temperature is advantageous in imaging long wave infrared light which is the form of light (extremely red-shifted) that arrives from the most distant parts of the visible universe. Such a liquid base would be covered by a thin metallic film that forms the reflective surface. A low volatility is important for use in the vacuum conditions present on the moon.
Food science
Ionic liquids have been used in food science. [bmim]Cl for instance is able to completely dissolve freeze dried banana pulp and the solution with an additional 15% DMSO lends itself to Carbon-13 NMR analysis. In this way the entire banana compositional makeup of starch, sucrose, glucose, and fructose can be monitored as a function of banana ripening.
Applications
Nowadays ionic liquids find a number of industrial applications which vary greatly in character. A few of their industrial applications are briefly described below; more detailed information can be found in a recent review article.
BASIL
The first major industrial application of ILs was the BASIL (Biphasic Acid Scavenging utilizing Ionic Liquids) process by BASF, in which a 1-alkylimidazole was used to scavenge the acid from an existing process. This then results in the formation of an IL which can easily be removed from the reaction mixture.[15] But the easier removal of an unwanted side-product (as an IL rather than as a solid salt) is not the only advantage of the IL based process. By using an IL it was possible to increase the space/time yield of the reaction by a factor of 80,000. It should, however, be kept in mind that improvements of such scale are rare.
Cellulose Processing
Occurring at a volume of some 700 billion tons, cellulose is the earth’s most widespread natural organic chemical and, thus, highly important as a bio-renewable resource. But even out of the 40 billion tons nature renews every year, only approx. 0.2 billion tons are used as feedstock for further processing. A more intensive exploitation of cellulose as a biorenewable feedstock has to date been prevented by the lack of a suitable solvent that can be used in chemical processes. Robin Rogers and co-workers at the University of Alabama have found that by means of ionic liquids, however, real solutions of cellulose can now be produced for the first time at technically useful concentrations [16]. This new technology therefore opens up great potential for cellulose processing.
For example, making cellulosic fibers from so-called dissolving pulp currently involves the use, and subsequent disposal, of great volumes of various chemical auxiliaries, esp. carbon disulfide (CS2). Major volumes of waste water are also produced for process reasons and need to be disposed of. These processes can be greatly simplified by the use of ionic liquids, which serve as solvents and are nearly entirely recycled. The “Institut für Textilchemie und Chemiefasern” (ITCF) in Denkendorf and BASF are jointly investigating the properties of fibers spun from an ionic liquid solution of cellulose in a pilot plant setup.
Eastman chemical’s DHF plant
Eastman operated an ionic liquid-based plant for the synthesis of 2,5-dihydrofuran from 1996 to 2004. However, the plant is now defunct because demand for the product has ceased.
Dimersol - Difasol
The dimersol process is a traditional way to dimerise short chain alkenes into branched alkenes of higher molecular weight. Nobel laureate Yves Chauvin and Hélène Olivier-Bourbigou at IFP (France) have developed an ionic liquid-based add-on to this process called the Difasol process. However, while may be licensed it has as yet not been put into commercial practice.
Petrochina
Petrochina have announced the implementation of an ionic liquid-based process called Ionikylation. This process, the alkylation of C4 olefins with iso-butane, is retrofitted into a 65,000 tonne per year alkylation plant, making it the biggest industrial application of ILs to date.
Degussa paint additives
Ionic liquids can enhance the finish, appearance and drying properties of paints. Degussa are marketing such ILs under the name of TEGO Dispers. These products are also added to the Pliolite paint range.
Air products - ILs as a transport medium for reactive gases
Air products make use of ILs as a medium to transport reactive gases in. Reactive gases such as trifluoroborane, phosphine or arsine, BF3, PH3 or AsH3, respectively, are stored in suitable ILs at sub-ambient pressure. This is a significant improvement over pressurised cylinders. The gases are easily withdrawn from the containers by applying a vacuum.
Linde's IL 'piston'
Whereas Air Product’s Gasguard system relies on the solubility of some gases in ILs, Linde are exploiting other gases’ insolubility in ILs. As mentioned above, the solubility of Hydrogen in ILs is very low. Linde now make use of this insolubility by using a body of ionic liquid to compress Hydrogen in filling stations; and in so doing they reduced the number of moving parts from about 500 in a conventional piston pump engine down to 8.
Nuclear industry
RTILs are extensively explored for various innovative applications in nuclear industry. It includes application of ionic liquid as extractant/diluent in solvent extraction systems, as alternate electrolyte media for the high temperature pyrochemical processing, etc. Fundamental studies on the extraction cum electrodeposition of fission products like uranium, palladium etc., from spent nuclear fuel using RTILs as extractants are reported. Reports on employing using Ionic liquids as non-aquoues electrolyte media for the recovery of uranium [18]and useful fission products like palladium [19] and rhodium [20] from spent nuclear fuel are also available.Studies on the electrochemical behavior of uranium(VI) in ionic liquid, 1-butyl-3-methylimidazolium chloride and also the recovery of valuable fission products from tissue paper waste was studied in room temperature ionic liquids.
Safety
Due to their non-volatility, effectively eliminating a major pathway for environmental release and contamination, ionic liquids have been considered as having a low impact on the environment and human health, and thus recognized as solvents for green chemistry. However, this is distinct from toxicity, and it remains to be seen how 'environmentally-friendly' ILs will be regarded once widely used by industry. Research into IL aquatic toxicity has shown them to be as toxic or more so than many current solvents already in use [22]. A review paper on this aspect has been published in 2007.[23] Available research also shows that mortality isn't necessarily the most important metric for measuring their impacts in aquatic environments, as sub-lethal concentrations have been shown to change organisms' life histories in meaningful ways. According to these researchers balancing between zero VOC emissions, and avoiding spills into waterways (via waste ponds/streams, etc.) should become a top priority. However, with the enormous diversity of substituents available to make useful ILs, it should be possible to design them with useful physical properties and less toxic chemical properties.
With regard to the safe disposal of ionic liquids, a 2007 paper has reported the use of ultrasound to degrade solutions of imidazolium-based ionic liquids with hydrogen peroxide and acetic acid to relatively innocuous compounds.[24]
Despite their low vapor pressure many ionic liquids have also found to be combustible and therefore require careful handling [25]. Brief exposure (5 to 7 seconds) to a flame torch will ignite these IL's and some of them are even completely consumed by combustion.
http://en.wikipedia.org/wiki/Ionic_liquid
History
The date of discovery, as well as discoverer, of the "first" ionic liquid is disputed. Ethanolammonium nitrate (m.p. 52-55 °C) was reported in 1888 by Gabriel.[1] However, one of the earlier known truly room temperature ionic liquids was [EtNH3]+ [NO3]- (m.p. 12 °C), the synthesis of which was published in 1914.[2] Much later, series of ionic liquids based on mixtures of 1,3-dialkylimidazolium or 1-alkylpyridinium halides and trihalogenoaluminates, initially developed for use as electrolytes, were to follow.[3][4] An important property of the imidazolium halogenoaluminate salts was that they were tuneable – viscosity, melting point and the acidity of the melt could be adjusted by changing the alkyl substituents and the ratio of imidazolium or pyridinium halide to halogenoaluminate.[5]
A major drawback was their moisture sensitivity and, though to a somewhat lesser extent, their acidity/basicity, the latter which can sometimes be used to an advantage. In 1992, Wilkes and Zawarotko reported the preparation of ionic liquids with alternative, 'neutral', weakly coordinating anions such as hexafluorophosphate ([PF6]-) and tetrafluoroborate ([BF4])-, allowing a much wider range of applications for ionic liquids.[6] It was not until recently that a class of new, air- and moisture stable, neutral ionic liquids, was available that the field attracted significant interest from the wider scientific community.
More recently, people have been moving away from [PF6]- and [BF4]- since they are highly toxic, and towards new anions such as bistriflimide [(CF3SO2)2N]- or even away from halogenated compounds completely. Moves towards less toxic cations have also been growing, with compounds like ammonium salts (such as choline) being just as flexible a scaffold as imidazole.
Characteristics
Ionic liquids are electrically conductive and have extremely low vapor pressure. (Their noticeable odours are likely due to impurities.) Their other properties are diverse. Many have low combustibility, excellent thermal stability, a wide liquid range, and favorable solvating properties for diverse compounds. Many classes of chemical reactions, such as Diels-Alder reactions and Friedel-Crafts reactions, can be performed using ionic liquids as solvents. Recent work has shown that ionic liquids can serve as solvents for biocatalysis [7]. The miscibility of ionic liquids with water or organic solvents varies with sidechain lengths on the cation and with choice of anion. They can be functionalized to act as acids, bases or ligands, and have been used as precursor salts in the preparation of stable carbenes. Because of their distinctive properties, ionic liquids are attracting increasing attention in many fields, including organic chemistry, electrochemistry, catalysis, physical chemistry, and engineering; see for instance magnetic ionic liquid.
Despite their extremely low vapor pressures, some ionic liquids can be distilled under vacuum conditions at temperatures near 300 °C.[8] Some ionic liquids (such as 1-butyl-3-methylimidazolium nitrate) generate flammable gases on thermal decomposition. Thermal stability and melting point depend on the components of the liquid. Thermal stability of various RTILs are available. The thermal stability of a task-specific ionic liquid, protonated betaine bis(trifluoromethanesulfonyl)imide is of about 534 K and N-Butyl-N-Methyl pyrrolidinium bis(trifluoromethanesulfonyl)imide was thermally stable up to 640 K [9]
The solubility of different species in imidazolium ionic liquids depends mainly on polarity and hydrogen bonding ability. Simple aliphatic compounds are generally only sparingly soluble in ionic liquids, whereas olefins show somewhat greater solubility, and aldehydes can be completely miscible. This can be exploited in biphasic catalysis, such as hydrogenation and hydrocarbonylation processes, allowing for relatively easy separation of products and/or unreacted substrate(s). Gas solubility follows the same trend, with carbon dioxide gas showing exceptional solubility in many ionic liquids, carbon monoxide being less soluble in ionic liquids than in many popular organic solvents, and hydrogen being only slightly soluble (similar to the solubility in water) and probably varying relatively little between the more popular ionic liquids. (Different analytical techniques have yielded somewhat different absolute solubility values.)
Room temperature ionic liquids
Room temperature ionic liquids consist of bulky and asymmetric organic cations such as 1-alkyl-3-methylimidazolium, 1-alkylpyridinium, N-methyl-N-alkylpyrrolidinium and ammonium ions. A wide range of anions is employed, from simple halides, which generally inflect high melting points, to inorganic anions such as tetrafluoroborate and hexafluorophosphate and to large organic anions like bistriflimide, triflate or tosylate. There are also many interesting examples of uses of ionic liquids with simple non-halogenated organic anions such as formate, alkylsulfate, alkylphosphate or glycolate. As an example, the melting point of 1-butyl-3-methylimidazolium tetrafluoroborate or [bmim][BF4] with an imidazole skeleton is about -80 °C, and it is a colorless liquid with high viscosity at room temperature.
It has been pointed out that in many synthetic processes using transition metal catalyst, metal nanoparticles play an important role as the actual catalyst or as a catalyst reservoir. It also been shown that ionic liquids (ILs) are an appealing medium for the formation and stabilization of catalytically active transition metal nanoparticles. More importantly, ILs can be made that incorporate co-ordinating groups,[10], for example, with nitrile groups on either the cation or anion (CN-IL). In various C-C coupling reactions catalyzed by palladium catalyst, it has been found the palladium nanoparticles are better stabilized in CN-IL compared to non-functionalized ionic liquids; thus enhanced catalytic activity and recyclability are realized.
Low temperature ionic liquids
Low temperature ionic liquids (below 130 kelvins) have been proposed as the fluid base for an extremely large diameter spinning liquid mirror telescope to be based on the earth's moon.[12] Low temperature is advantageous in imaging long wave infrared light which is the form of light (extremely red-shifted) that arrives from the most distant parts of the visible universe. Such a liquid base would be covered by a thin metallic film that forms the reflective surface. A low volatility is important for use in the vacuum conditions present on the moon.
Food science
Ionic liquids have been used in food science. [bmim]Cl for instance is able to completely dissolve freeze dried banana pulp and the solution with an additional 15% DMSO lends itself to Carbon-13 NMR analysis. In this way the entire banana compositional makeup of starch, sucrose, glucose, and fructose can be monitored as a function of banana ripening.
Applications
Nowadays ionic liquids find a number of industrial applications which vary greatly in character. A few of their industrial applications are briefly described below; more detailed information can be found in a recent review article.
BASIL
The first major industrial application of ILs was the BASIL (Biphasic Acid Scavenging utilizing Ionic Liquids) process by BASF, in which a 1-alkylimidazole was used to scavenge the acid from an existing process. This then results in the formation of an IL which can easily be removed from the reaction mixture.[15] But the easier removal of an unwanted side-product (as an IL rather than as a solid salt) is not the only advantage of the IL based process. By using an IL it was possible to increase the space/time yield of the reaction by a factor of 80,000. It should, however, be kept in mind that improvements of such scale are rare.
Cellulose Processing
Occurring at a volume of some 700 billion tons, cellulose is the earth’s most widespread natural organic chemical and, thus, highly important as a bio-renewable resource. But even out of the 40 billion tons nature renews every year, only approx. 0.2 billion tons are used as feedstock for further processing. A more intensive exploitation of cellulose as a biorenewable feedstock has to date been prevented by the lack of a suitable solvent that can be used in chemical processes. Robin Rogers and co-workers at the University of Alabama have found that by means of ionic liquids, however, real solutions of cellulose can now be produced for the first time at technically useful concentrations [16]. This new technology therefore opens up great potential for cellulose processing.
For example, making cellulosic fibers from so-called dissolving pulp currently involves the use, and subsequent disposal, of great volumes of various chemical auxiliaries, esp. carbon disulfide (CS2). Major volumes of waste water are also produced for process reasons and need to be disposed of. These processes can be greatly simplified by the use of ionic liquids, which serve as solvents and are nearly entirely recycled. The “Institut für Textilchemie und Chemiefasern” (ITCF) in Denkendorf and BASF are jointly investigating the properties of fibers spun from an ionic liquid solution of cellulose in a pilot plant setup.
Eastman chemical’s DHF plant
Eastman operated an ionic liquid-based plant for the synthesis of 2,5-dihydrofuran from 1996 to 2004. However, the plant is now defunct because demand for the product has ceased.
Dimersol - Difasol
The dimersol process is a traditional way to dimerise short chain alkenes into branched alkenes of higher molecular weight. Nobel laureate Yves Chauvin and Hélène Olivier-Bourbigou at IFP (France) have developed an ionic liquid-based add-on to this process called the Difasol process. However, while may be licensed it has as yet not been put into commercial practice.
Petrochina
Petrochina have announced the implementation of an ionic liquid-based process called Ionikylation. This process, the alkylation of C4 olefins with iso-butane, is retrofitted into a 65,000 tonne per year alkylation plant, making it the biggest industrial application of ILs to date.
Degussa paint additives
Ionic liquids can enhance the finish, appearance and drying properties of paints. Degussa are marketing such ILs under the name of TEGO Dispers. These products are also added to the Pliolite paint range.
Air products - ILs as a transport medium for reactive gases
Air products make use of ILs as a medium to transport reactive gases in. Reactive gases such as trifluoroborane, phosphine or arsine, BF3, PH3 or AsH3, respectively, are stored in suitable ILs at sub-ambient pressure. This is a significant improvement over pressurised cylinders. The gases are easily withdrawn from the containers by applying a vacuum.
Linde's IL 'piston'
Whereas Air Product’s Gasguard system relies on the solubility of some gases in ILs, Linde are exploiting other gases’ insolubility in ILs. As mentioned above, the solubility of Hydrogen in ILs is very low. Linde now make use of this insolubility by using a body of ionic liquid to compress Hydrogen in filling stations; and in so doing they reduced the number of moving parts from about 500 in a conventional piston pump engine down to 8.
Nuclear industry
RTILs are extensively explored for various innovative applications in nuclear industry. It includes application of ionic liquid as extractant/diluent in solvent extraction systems, as alternate electrolyte media for the high temperature pyrochemical processing, etc. Fundamental studies on the extraction cum electrodeposition of fission products like uranium, palladium etc., from spent nuclear fuel using RTILs as extractants are reported. Reports on employing using Ionic liquids as non-aquoues electrolyte media for the recovery of uranium [18]and useful fission products like palladium [19] and rhodium [20] from spent nuclear fuel are also available.Studies on the electrochemical behavior of uranium(VI) in ionic liquid, 1-butyl-3-methylimidazolium chloride and also the recovery of valuable fission products from tissue paper waste was studied in room temperature ionic liquids.
Safety
Due to their non-volatility, effectively eliminating a major pathway for environmental release and contamination, ionic liquids have been considered as having a low impact on the environment and human health, and thus recognized as solvents for green chemistry. However, this is distinct from toxicity, and it remains to be seen how 'environmentally-friendly' ILs will be regarded once widely used by industry. Research into IL aquatic toxicity has shown them to be as toxic or more so than many current solvents already in use [22]. A review paper on this aspect has been published in 2007.[23] Available research also shows that mortality isn't necessarily the most important metric for measuring their impacts in aquatic environments, as sub-lethal concentrations have been shown to change organisms' life histories in meaningful ways. According to these researchers balancing between zero VOC emissions, and avoiding spills into waterways (via waste ponds/streams, etc.) should become a top priority. However, with the enormous diversity of substituents available to make useful ILs, it should be possible to design them with useful physical properties and less toxic chemical properties.
With regard to the safe disposal of ionic liquids, a 2007 paper has reported the use of ultrasound to degrade solutions of imidazolium-based ionic liquids with hydrogen peroxide and acetic acid to relatively innocuous compounds.[24]
Despite their low vapor pressure many ionic liquids have also found to be combustible and therefore require careful handling [25]. Brief exposure (5 to 7 seconds) to a flame torch will ignite these IL's and some of them are even completely consumed by combustion.
http://en.wikipedia.org/wiki/Ionic_liquid
訂閱：
文章 (Atom)