University of South Alabama (Mobile, AL) Professor of Chemistry James H. Davis, Jr details a series of boronium-ion-based ionic liquids which he invented and their wide range of applications in U.S. Patent 7,709,635.
Because of their unique properties and the ability to fine tune a ionic liquid (IL) to a particular need, ionic liquids have a wide array of applications. An incomplete list of beneficial properties of ionic liquids includes: no vapor pressure, reasonable thermal stability, good solubility for organic and organometallic compounds, gas solubility (CO, O2, H2, and the like) is good, can be immiscible with alkanes, tunable solvent properties (solubility, polarity, etc.), non-coordinating solvent, electrically conducting, low viscosity, low toxicity, good electrochemical stability, and, in the case of lipophilic room temperature ionic liquids, they can be used with aqueous biphasic systems.
Ionic liquids have been used in a number of broad and varied areas including the following non-limiting examples: 1) energy, which encompasses batteries, fuel cells, photovoltaic cells, heat storage (based on the large evolution of heat upon crystallization), and supercaps; 2) coatings, which encompasses metal depositions, analytic, lubricants, and surfactants; 3) chemical, which encompasses organic synthesis, chiral synthesis, polymerization, and catalysis; 4) biotechnology, which encompasses enzyme reactions and purification of proteins; 5) chemical engineering, which encompasses extractions, separations, membranes, and extractive distillations; and 6) other, which encompasses light emitting electrochemical cells (LECs), liquid crystals, nano particles, artificial muscles, oils/advanced fluids, and electrosynthesis of conducting polymers.
Ionic liquids that preferentially dissolve certain gaseous species can be used in conventional gas absorption applications. The non-volatile nature of ionic liquids plays two important roles. First, there will be no cross-contamination of the gas stream by the solvent during operation. This means no solvent loss and no air pollution. Second, regeneration of the solvent is easy; a simple flash or mild distillation step is all that is required to remove the gas from the solvent, again with no cross-contamination.
In addition to their use as conventional absorbents, ionic liquids may be immobilized on a support and used in a supported liquid membrane (SLM). The membrane will work if a gas preferentially dissolves in the liquid. SLMs may be used in a continuous separation process without a regeneration step. Conventional SLM technology is undermined by the fact that the liquid in which the gas dissolves eventually evaporates, thus rendering the membrane useless. Since ionic liquids are completely non-volatile, this problem is eliminated.
Ionic liquids also find use in the conversion of brown coal and oil shale into value-added products, such as alternative synthetic fuels and/or high-quality chemical feedstocks. For example, 1-butyl-3-methyl imidazolium, has been used to extract organic compounds from Estonian oil shale kerogen at various temperatures. Results at 175.degree. C. yielded soluble products with an increase of ten times over that obtained using conventional organic solvents.
Bronsted-acidic ILs also act as proton shuttles, functionally carrying protons from acidic resin surfaces (e.g., Nafion) to the surrounding medium, where they are more free to react than if the proton is held at the polymer surface. Moreover, the Bronsted-acidic ILs have absolutely no vapor pressure when dissolved in water. For example, a relatively concentrated solution of HCl gives off HCl gas; in contrast, a Bronsted-acidic IL gives off no gaseous acid--pH paper suspended above the surface does not change colors.
Many product streams, particularly in the field of petroleum chemistry, include olefins and non-olefins. For example, ethane crackers tend to produce a mixture of ethane and ethylene. The ethylene is typically separated from the ethane via distillation. Because the boiling points of ethylene and ethane are relatively close to one another, the distillation is typically done at very low temperatures and/or high pressures; the separation is relatively expensive. The same problems are observed when separating propane from propylene in dehydrogenation facilities. Ionic liquids are useful is separating such mixtures. For example, an ionic liquid with a pendant functional group that coordinates the pi-bond of an olefin may be used to dissolve selectively the olefinic components of such a mixture. Likewise, an ionic liquid with a pendant functional group that coordinates a transition metal capable of coordinating the pi-bond of an olefin may be used to dissolve selectively the olefinic components of such a mixture. In either case, the dissolved olefins subsequently can be isolated by desorption.
The chemical field has made good use of ionic liquids where the potential for even greater use is constantly being explored. Known chemical reactions carried out in ionic liquids include butene oligomerization, hydrodimerization of dienes, alkylation of olefins, hydrogenation (e.g. of cyclohexene), hydroformylation, oxidation (e.g. epoxidation of 2,2-dimethyl chromene), alkoxycarbonylation (of styrene), and hydrodimerizations/telomerizations (e.g. of 1,3-butadiene). An advantage to using ionic liquids as the medium for chemical reactions is that the rates and selectivities can be modified by modifying the ionic liquid. Reaction mechanisms are similar to those in organic solvents.
In particular, research published since the early 1990's points to significant opportunities to replace solution polymerizations using VOCs with ionic liquids. Polymerizations that have been carried out in ionic liquid mediums include homopolymerizations with faster rates and higher MW; living radical homopolymerization where the catalyst has been retained in the ionic liquid phase; statistical copolymerization which may create copolymers having monomer sequences not readily achievable using conventional solvents; and block copolymerization where ionic liquid routes may simplify, reduce cost of producing block copolymers with defined structures. In another related area, polymer-ionic liquid composites as new possible materials have been explored.
Separations are another area in particular that is making use of ionic liquids. Highlights in this area include liquid extractions of organics and metals from aqueous solutions; sulfur removal and selective separations by solubility, extractive distillation, etc. in hydrocarbon processing; gas separations where task-specific ionic liquids have been developed based on solubilities; solvent regeneration as applied to, for example, supercritical fluids, pervaporation, and distillations; supported liquid membranes; electrorefining; and analytical separations.
Significant academic and industrial interest has also been directed towards using ionic liquids in fuel technology with the potential for high-volume, energy saving applications. Highlights in this area include liquefaction, gasifaction, and chemical modification of solid fuels (e.g., coal, oil shale, kerogen, and the like); sweetening of sour gas; optimization for high-octane fuel additives; environmental removal of contaminants from waste streams; desulfurization of fossil fuels; and safer and more efficient nuclear fuel cycles.
Another particularly important aspect of boronium-ion-based ionic liquids is the possibility for these ionic liquids to dissolve other salts, in particular metallic salts, such as lithium salts, to give highly conductive solutions. In a similar manner, the ionic liquids, or their mixtures with other metallic salts, are excellent solvents or plasticizers for a great number of polymers, in particular those bearing polar or ionic functions. Liquid compounds as well as polymers plasticized by ionic mixtures behaving like solid electrolytes are applicable in electrochemistry to generators of the primary or secondary type, supercapacitors, electrochromic systems, antistatic coatings, batteries or electroluminescent diodes.
Ionic liquids have been used in a number of broad and varied areas including the following non-limiting examples: 1) energy, which encompasses batteries, fuel cells, photovoltaic cells, heat storage (based on the large evolution of heat upon crystallization), and supercaps; 2) coatings, which encompasses metal depositions, analytic, lubricants, and surfactants; 3) chemical, which encompasses organic synthesis, chiral synthesis, polymerization, and catalysis; 4) biotechnology, which encompasses enzyme reactions and purification of proteins; 5) chemical engineering, which encompasses extractions, separations, membranes, and extractive distillations; and 6) other, which encompasses light emitting electrochemical cells (LECs), liquid crystals, nano particles, artificial muscles, oils/advanced fluids, and electrosynthesis of conducting polymers.
Ionic liquids that preferentially dissolve certain gaseous species can be used in conventional gas absorption applications. The non-volatile nature of ionic liquids plays two important roles. First, there will be no cross-contamination of the gas stream by the solvent during operation. This means no solvent loss and no air pollution. Second, regeneration of the solvent is easy; a simple flash or mild distillation step is all that is required to remove the gas from the solvent, again with no cross-contamination.
In addition to their use as conventional absorbents, ionic liquids may be immobilized on a support and used in a supported liquid membrane (SLM). The membrane will work if a gas preferentially dissolves in the liquid. SLMs may be used in a continuous separation process without a regeneration step. Conventional SLM technology is undermined by the fact that the liquid in which the gas dissolves eventually evaporates, thus rendering the membrane useless. Since ionic liquids are completely non-volatile, this problem is eliminated.
Ionic liquids also find use in the conversion of brown coal and oil shale into value-added products, such as alternative synthetic fuels and/or high-quality chemical feedstocks. For example, 1-butyl-3-methyl imidazolium, has been used to extract organic compounds from Estonian oil shale kerogen at various temperatures. Results at 175.degree. C. yielded soluble products with an increase of ten times over that obtained using conventional organic solvents.
Bronsted-acidic ILs also act as proton shuttles, functionally carrying protons from acidic resin surfaces (e.g., Nafion) to the surrounding medium, where they are more free to react than if the proton is held at the polymer surface. Moreover, the Bronsted-acidic ILs have absolutely no vapor pressure when dissolved in water. For example, a relatively concentrated solution of HCl gives off HCl gas; in contrast, a Bronsted-acidic IL gives off no gaseous acid--pH paper suspended above the surface does not change colors.
Many product streams, particularly in the field of petroleum chemistry, include olefins and non-olefins. For example, ethane crackers tend to produce a mixture of ethane and ethylene. The ethylene is typically separated from the ethane via distillation. Because the boiling points of ethylene and ethane are relatively close to one another, the distillation is typically done at very low temperatures and/or high pressures; the separation is relatively expensive. The same problems are observed when separating propane from propylene in dehydrogenation facilities. Ionic liquids are useful is separating such mixtures. For example, an ionic liquid with a pendant functional group that coordinates the pi-bond of an olefin may be used to dissolve selectively the olefinic components of such a mixture. Likewise, an ionic liquid with a pendant functional group that coordinates a transition metal capable of coordinating the pi-bond of an olefin may be used to dissolve selectively the olefinic components of such a mixture. In either case, the dissolved olefins subsequently can be isolated by desorption.
The chemical field has made good use of ionic liquids where the potential for even greater use is constantly being explored. Known chemical reactions carried out in ionic liquids include butene oligomerization, hydrodimerization of dienes, alkylation of olefins, hydrogenation (e.g. of cyclohexene), hydroformylation, oxidation (e.g. epoxidation of 2,2-dimethyl chromene), alkoxycarbonylation (of styrene), and hydrodimerizations/telomerizations (e.g. of 1,3-butadiene). An advantage to using ionic liquids as the medium for chemical reactions is that the rates and selectivities can be modified by modifying the ionic liquid. Reaction mechanisms are similar to those in organic solvents.
In particular, research published since the early 1990's points to significant opportunities to replace solution polymerizations using VOCs with ionic liquids. Polymerizations that have been carried out in ionic liquid mediums include homopolymerizations with faster rates and higher MW; living radical homopolymerization where the catalyst has been retained in the ionic liquid phase; statistical copolymerization which may create copolymers having monomer sequences not readily achievable using conventional solvents; and block copolymerization where ionic liquid routes may simplify, reduce cost of producing block copolymers with defined structures. In another related area, polymer-ionic liquid composites as new possible materials have been explored.
Separations are another area in particular that is making use of ionic liquids. Highlights in this area include liquid extractions of organics and metals from aqueous solutions; sulfur removal and selective separations by solubility, extractive distillation, etc. in hydrocarbon processing; gas separations where task-specific ionic liquids have been developed based on solubilities; solvent regeneration as applied to, for example, supercritical fluids, pervaporation, and distillations; supported liquid membranes; electrorefining; and analytical separations.
Significant academic and industrial interest has also been directed towards using ionic liquids in fuel technology with the potential for high-volume, energy saving applications. Highlights in this area include liquefaction, gasifaction, and chemical modification of solid fuels (e.g., coal, oil shale, kerogen, and the like); sweetening of sour gas; optimization for high-octane fuel additives; environmental removal of contaminants from waste streams; desulfurization of fossil fuels; and safer and more efficient nuclear fuel cycles.
Another particularly important aspect of boronium-ion-based ionic liquids is the possibility for these ionic liquids to dissolve other salts, in particular metallic salts, such as lithium salts, to give highly conductive solutions. In a similar manner, the ionic liquids, or their mixtures with other metallic salts, are excellent solvents or plasticizers for a great number of polymers, in particular those bearing polar or ionic functions. Liquid compounds as well as polymers plasticized by ionic mixtures behaving like solid electrolytes are applicable in electrochemistry to generators of the primary or secondary type, supercapacitors, electrochromic systems, antistatic coatings, batteries or electroluminescent diodes.
0 comments:
Post a Comment