Patent application title: PROCESS TO PRODUCE CLEAN GASOLINE/BIO-ETHERS USING ETHANOL
Yi-Gang Xiong (Pasadena, TX, US)
Kerry L. Rock (Pasadena, TX, US)
Arvids Judzis (Pasadena, TX, US)
Mitchell E. Loescher (Pasadena, TX, US)
CATALYTIC DISTILLATION TECHNOLOGIES
IPC8 Class: AC10L1185FI
Class name: Ether dialkyl ether tertiary carbon bonded directly to the ether oxygen
Publication date: 2009-08-06
Patent application number: 20090193710
A fuel or fuel blendstock comprising ethanol, ethyl ethers, olefins, and
alkanes. In some embodiments, the fuel or fuel blendstock of claim 1,
wherein the fuel or fuel blendstock may have an octane number greater
than 92 (RON+MON)/2). In other embodiments, the fuel or fuel blendstock
may have a Reid vapor pressure less than 7.2 psi. Also disclosed is a
process for the production of a fuel, the process including: contacting
ethanol and at least one gasoline fraction including alkanes and olefins
in the presence of a catalyst to form a fuel mixture including ethyl
ethers, alkanes, unreacted olefins, and unreacted ethanol; and recovering
the fuel mixture for use as a gasoline or gasoline blendstock without
separation of the ethanol from the fuel mixture.
1. A fuel or fuel blendstock comprising ethanol, ethyl ethers, olefins,
2. The fuel or fuel blendstock of claim 1, wherein the fuel or fuel blendstock has an octane number greater than 92 (RON+MON)/2).
3. The fuel or fuel blendstock of claim 1, wherein the fuel or fuel blendstock has a Reid vapor pressure less than 7.2 psi.
4. The fuel or fuel blendstock of claim 1, wherein the fuel or fuel blendstock has an oxygen content of at least 3.5 weight percent.
5. A process for the production of a fuel, the process comprising:contacting ethanol and at least one gasoline fraction comprising alkanes and olefins in the presence of a catalyst to form a fuel mixture comprising ethyl ethers, alkanes, unreacted olefins, and unreacted ethanol;recovering the fuel mixture for use as a gasoline or gasoline blendstock without separation of the ethanol from the fuel mixture.
6. The process of claim 5, wherein the contacting comprises:feeding ethanol and a gasoline fraction comprising isoolefins to a distillation column reactor system containing at least one etherification reaction zone; andwithdrawing the fuel mixture from the distillation column reactor system as a bottoms fraction.
7. The process of claim 5, wherein the contacting comprises:feeding ethanol and a gasoline fraction comprising isoolefins to a fixed-bed reactor system containing at least one etherification reaction zone.
8. The process of claim 5, further comprising blending at least one of ethanol and a second gasoline fraction with the fuel mixture.
9. The process of claim 5, further comprising transporting at least one of the ethanol and the gasoline fraction to a site for performing the contacting and recovering.
10. The process of claim 5, wherein the transporting comprises using of at least one of a pipeline, barge, tanker truck, and rail car.
11. The process of claim 5, wherein the gasoline fraction comprises C4 to C9 alkanes.
12. The process of claim 5, wherein the gasoline fraction comprises C4 to C7 olefins.
13. The process of claim 5, wherein the ethyl ethers comprise at least one of ethyl tertiary butyl ether, tertiary amyl ethyl ether, tertiary hexyl ethyl ethers, and tertiary heptyl ethyl ethers.
14. The process of claim 5, wherein the gasoline fraction comprises at least one of a C4 cut, a C5 cut, a C6 cut, and a light naphtha fraction.
15. The process of claim 5, wherein the fuel mixture comprises a Reid Vapor Pressure less than 7.2 psi.
16. The process of claim 5, wherein an oxygen content of the fuel mixture is at least 3.5 weight percent.
BACKGROUND OF DISCLOSURE
1. Field of the Disclosure
Embodiments disclosed herein relate generally to processes for using renewable resources, such as ethanol, as a fuel component. In another aspect, embodiments disclosed herein relate to a fuel composition comprising alkanes, olefins, ethanol and ethyl ethers. More specifically, embodiments disclosed herein relate to various processes for chemical and splash blending of ethanol with a gasoline fraction.
Fuel producers are experiencing increasing pressure to use renewable resources as blendstocks. Ethanol is often cited as the prime example of such a material. Of all of the readily-producible renewable compounds, ethanol is the most suitable for use in gasoline. Indeed, engines can be designed to run on pure ethanol with modifications in the fuel system.
For an entire economy, the use of ethanol may increase energy independence. This is due to that fact that the source, agricultural carbohydrates, can be produced almost anywhere food can be grown. In addition, this production system will have the added social benefit of transferring some of the transportation-related economic surplus to rural areas.
The most straightforward way to incorporate ethanol into gasoline is by mixing, or "splash blending." Such a process is disclosed in, for example, U.S. Pat. No. 6,258,987 ('987). Various subgrades of gasoline, including catalytically cracked naphtha, reformate, virgin naphtha, isomerate, alkylate, and others are mixed with a desired amount of alcohol at a mixing site. The blending site is preferably (1) geographically proximate to the area from which the gasoline is to be distributed, and (2) geographically distant from the place where the subgrade is prepared. The resulting blend is passed to a suitable storage facility such as a holding tank, or to an element of a distribution system, such as a pipeline, rail car, tanker truck, or barge.
A different method of incorporating ethanol is through "chemical blending." In this case, ethanol is supplied to the refinery itself and covalently bonded to the base gasoline. For example, U.S. Pat. No. 5,633,416 and others describe a process in which a C1 to C4 alcohol is reacted with etherifiable olefins in a gasoline subgrade. For example, ethanol may be reacted with isobutylene to form ethyl tertiary butyl ether (ETBE).
A major benefit to the use of either chemical or splash blending is the boost in octane quality. Adding to the need for more unleaded octane quality is the growing demand for premium fuel. The blending values for various oxygenates in typical unleaded gasoline are given in Table 1. As can be seen, the octane value ((Research Octane Number (RON)+Motor Octane Number (MON))/2) for ethanol and ETBE are in the range from 109-113.
TABLE-US-00001 TABLE 1 Oxygenate Octane Reid Vapor Pressure (psi) Methanol 116 61 Ethanol 113 21.5 MTBE 106-110 8-9.3 ETBE 109-113 4-6
Although use of ethanol has many benefits as a splash blending feedstock, incorporation of ethanol into gasoline has not been readily accepted in the motor fuel industry, including the petroleum refining industry, common carrier pipelines, and automobile manufacturers. The fundamental issues detrimental to the acceptance of ethanol at the refinery operating and marketing levels include that ethanol is a blending agent not commonly manufactured at the refinery site; as described in the '987 patent, blending sites are typically remote from the refinery (i.e., the ethanol produced in the Midwest, close to the corn supply, must be combined with the gasoline produced on the Gulf Coast).
Additionally, ethanol-hydrocarbon blending requires the elimination of water from the refinery or blending site tank farm and product delivery system as ethanol is completely miscible in water. Also, marketing of ethanol blends are typically restricted as they are not accepted by all oil companies. Even further, pipelines may not accept ethanol blends due to the potential for water and the associated corrosion. Environmentally, ethanol may increase volatile organic chemical (VOC) emissions and does not reduce toxics and NOx emissions as effectively as ethers such as ETBE.
Another serious problem associated with splash ethanol blending involves gasoline volatility. As an example, refiners must decrease the Reid vapor pressure (RVP) of their summer grade of gasoline in the South about 0.8 psi to 7.2 psi. As noted in Table 1, ethanol has a much higher Reid vapor pressure than ETBE. Thus, where ethanol is to be blended, a special gasoline subgrade or blendstock must be produced, suitable for ethanol splash blending at the terminal. This is a special low-RVP material, such that after splash blending with ethanol to reach 10 volume percent, the resulting ethanol blend fuel will have the specified RVP. The resulting RVP-adjusted ethanol blend typically has a lower octane value, due to the removal of C4 and C5 compounds such that the blend meets RVP specifications, partially offset by the higher octane value of ethanol. The D86 T5 and T10 values for the RVP-adjusted blend are also much higher due to the removal of the C4 and C5 compounds. The removal of C4 and C5 compounds may also result in a decrease in available gasoline volume.
An outlet must also be found for the removed C4 and C5 compounds, which may result in additional capital equipment at the refineries or increased recycle and reprocessing of these compounds. The economic incentive to absorb a gallon of butane in gasoline typically ranges from 10 to 20 cents, depending on geography and season. The octane value of butane is equally attractive (92) and, as a gasoline component, butane is several blend numbers above regular unleaded gasoline (typically 87-89). The incentive with respect to C5 compounds is similar. Chemical blending provides a means to recapture some of the value in the C4 compounds, such as butanes or isobutylene.
Accordingly, there exists a need for processes that use renewable resources, such as ethanol. The processes should also provide for gasoline blends having improved octane quality, where the processes may provide an outlet for the C4 and C5 compounds that are typically removed to create RVP "room" for the ethanol.
SUMMARY OF THE DISCLOSURE
In one aspect, embodiments disclosed herein relate to a fuel or fuel blendstock comprising ethanol, ethyl ethers, olefins, and alkanes. In some embodiments, the fuel or fuel blendstock of claim 1, wherein the fuel or fuel blendstock may have an octane number greater than 92 (RON+MON)/2). In other embodiments, the fuel or fuel blendstock may have a Reid vapor pressure less than 7.2 psi.
In another aspect, embodiments disclosed herein relate to a process for the production of a fuel, the process including: contacting ethanol and at least one gasoline fraction including alkanes and olefins in the presence of a catalyst to form a fuel mixture including ethyl ethers, alkanes, unreacted olefins, and unreacted ethanol; and recovering the fuel mixture for use as a gasoline or gasoline blendstock without separation of the ethanol from the fuel mixture.
Other aspects and advantages will be apparent from the following description and the appended claims.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a simplified process flow diagram for producing a fuel or fuel component containing chemically blended and splash blended ethanol, according to an embodiment disclosed herein.
FIG. 2 is a simplified process flow diagram for producing a fuel containing chemically blended and splash blended ethanol, according to an embodiment disclosed herein.
FIG. 3 is a simplified process flow diagram for producing a fuel containing chemically blended and splash blended ethanol, according to another embodiment disclosed herein.
In one aspect, embodiments disclosed herein relate to processes for using renewable resources, such as ethanol, as a fuel component. In another aspect, embodiments disclosed herein relate to a fuel composition comprising alkanes, olefins, ethanol and ethyl ethers. More specifically, embodiments disclosed herein relate to various processes for chemical and splash blending of ethanol with a gasoline fraction.
In some embodiments, ethanol and a gasoline fraction, comprising olefins, are contacted in the presence of an etherification catalyst to form a fuel mixture comprising ethyl ethers, alkanes, unreacted olefins, and unreacted ethanol. The fuel mixture may then be recovered for use as a gasoline or gasoline blendstock without separation of the ethanol from the fuel mixture. The contacting with the etherification catalyst may occur in at least one of a catalytic distillation column and a fixed-bed etherification reactor.
As used herein, a gasoline fraction includes (1) individual refinery streams suitable for use as a blend stock for gasoline, and/or (2) a blended gasoline stream formed by blending two or more streams, each of which are suitable for use as a gasoline blend stock. A suitable gasoline blend stock, when blended with other refinery streams, produces a combined stream which meets the requirements for gasoline, which are well documented in Federal and State regulations.
The feeds to the processes disclosed herein may include one or more petroleum fractions which boil in the gasoline boiling range, including FCC gasoline, coker pentane/hexane, coker naphtha, FCC naphtha, straight run gasoline, and mixtures containing two or more of these streams. Such gasoline blending streams typically have a normal boiling point within the range of 0° C. and 260° C., as determined by an ASTM D86 distillation. Feeds of this type include light naphthas typically having a boiling range of about C6 to 165° C. (330° F.); full range naphthas, typically having a boiling range of about C5 to 215° C. (420° F.), heavier naphtha fractions boiling in the range of about 125° C. to 210° C. (260° F. to 412° F.), or heavy gasoline fractions boiling at, or at least within, the range of about 165° C. to 260° C. (330° F. to 500° F.), preferably about 165° C. to 210° C. In general, a gasoline fuel will distill over the range of from about room temperature to 260° C. (500° F.). In some embodiments, these streams may be treated to remove sulfur, nitrogen, and other undesired components.
Gasoline fractions for use in embodiments of the etherification process described herein may include C3 to C9 and higher hydrocarbons. For example, refinery streams are usually separated by fractional distillation. A light naphtha cut is one such refinery stream, and because such a cut often contains compounds that are very close in boiling points, the separations are not precise. The light naphtha refinery cut is valuable as a source of isoolefins (iC5= and iC6=compounds, for example) for forming an ether by reaction with ethanol. Thus, a C5 stream, for instance, may include C4s and up to C8s and higher. These components may be saturated (alkanes), unsaturated (mono-olefins, including isoolefins), and poly-unsaturated (diolefins, for example). Additionally, the components may be any or all of the various isomers of the individual compounds. Such a mixture may easily contain 150 to 200 components. Other hydrocarbon streams of C4 to C9 carbon atoms may be used in embodiments disclosed herein.
In some embodiments, gasoline fractions may include a C4 cut, which may include C3 to C5 or higher hydrocarbons (i.e., C6+). In other embodiments, gasoline fractions may include a C5 cut, which may include C4 to C8 or higher hydrocarbons, including olefins. In other embodiments, gasoline fractions may include a C6 cut, which may include C4 to C9 or higher hydrocarbons, including olefins. In other various embodiments, gasoline fractions may include mixtures of one or more of C4, C5, C6, and C7+ hydrocarbons, where the mixture includes olefinic compounds. The above described streams may include C4 to C7 streams, gasoline fractions, FCC gasoline, coker gasoline, and other refinery streams having similar properties.
Saturated compounds included in the above described gasoline fractions may include various isomers of butane, various isomers of pentane, and various isomers of hexane, among others, for example. Olefinic compounds included in the above described gasoline fractions may include isobutylene and other butene isomers, various isomers of pentene, various isomers of hexene, and various isomers of heptene, among others, for example. In some embodiments, the gasoline fractions may be derived from any source, and may include a concentration of 1 to 45 weight percent etherifiable isoolefins; a concentration of 10 to 30 weight percent isoolefins in other embodiments; and a concentration of 15 to 25 weight percent isoolefins in yet other embodiments.
Other embodiments disclosed herein are broadly applicable to the production of a wide variety of ethers from a number of different gasoline fractions. The primary ethers resulting in processes disclosed herein may include tertiary-amyl, tertiary-butyl, tertiary-hexyl ethers, and tertiary-heptyl ethers. Where the etherification process is one for the production of butyl ethers, the typical feed stream will consist of a mixture of C4 isomers comprising isobutane, isobutylene, normal butane, 1-butene and 2-butene. Where the process is one for the production of amyl ethers, the feed stream components will include 3-methyl-1-butene, isopentane, 1-pentene, 2-methyl-1-butene, normal pentane, trans-2-pentene, cis-2-pentene, neopentane, and 2-methyl-2-butene in a typical distribution of isomers. Although a variety of sources are available to provide such gasoline fractions, the most common sources for the feed streams for these processes are light cracked hydrocarbon streams from an FCC unit or a C4 stream from a steam cracker after butadiene extraction. In one embodiment, the gasoline fraction fed to the etherification reactor may include isoamylene, which may include both the reactive isomers (2-methyl-1-butene and 2-methyl-2-butene) and unreactive isomer (3-methyl-1-butene ).
A gasoline fraction containing isoolefins may be mixed with ethanol, which may be from a biological or petrochemical origin. Preferably, the ethanol is from a biological origin, such as ethanol produced from corn or other agricultural products. In other embodiments, an diluent containing ethyl ethers may also be mixed with the gasoline fraction and the ethanol, such as a recycle stream containing a portion of the product from the etherification reactor.
The isoolefins and ethanol in the resulting mixture may be reacted over a suitable etherification catalyst to form ethyl ethers. For example, the mixture may be contacted with a sulfuric acid macroporous ion exchange resin acid-form in a suitable reactor to react ethanol and isobutylene to form ethyl ethers with high selectivity to ethers and low yield to isoolefin dimers. Etherification catalysts are described in more detail below.
The etherification reactor effluent includes the ethyl ethers, unreacted isoolefins, and unreacted ethanol, among other components. The effluent may then be recovered for use as a fuel or a fuel blending stock, without the need to separate the ethanol from the fuel mixture. When a downflow boiling point reactor is used, for example, at least a portion of the reactor effluent may be recycled to provide the ether-containing diluent and reactor temperature control.
The etherification reactor effluent may then be recovered for use as a fuel or a fuel blendstock. For example, the etherification reactor effluent may be recovered, stored if necessary, and transported for use as a fuel. In other embodiments, the etherification reactor effluent may be splash blended with ethanol or other gasoline fractions, where the resulting splash blend may be stored and transported for use as a fuel.
In some embodiments, the gasoline fraction is transported to a blending site which is: geographically proximate to the area in which the finished alcohol-containing gasoline is to be distributed for use as a fuel and geographically distant from the place where the gasoline fraction is prepared. The etherification of a portion of the olefins may then occur at the blending site. The reactor effluent, containing ethanol and ethyl ethers, may then be used as a fuel or a fuel blendstock. For example, the fuel containing ethanol and ethyl ethers may then be prepared by admixture with a desired amount of alcohol or other gasoline fractions at said blending site.
As described above, isoolefins and alcohols may be reacted to form ethers. Examples of ethers formed in embodiments disclosed herein may include: ethyl tertiary butyl alcohol (ETBE), the reaction product of isobutylene and ethanol; tertiary amyl ethyl ether (TAEE), the reaction product of isoamylenes and ethanol; and tertiary hexyl ethyl ether (THEE), the reaction product of various C6 isoolefins with ethanol; among others.
Referring initially to FIG. 1, a distillation column reactor system 5 according to some embodiments disclosed herein is illustrated. Gasoline fraction 10 containing isoolefins may be fed to a distillation column reactor 12. The feed location of gasoline fraction 10 may be above, below, or intermediate to a catalyst containing region 14. Isoolefins contained in hydrocarbon stream 10 may react with ethanol, fed via stream 15, in catalyst containing region 14 to produce ethers. Distillation column reactor 12 may include a reboiler 16 and an overhead system 17, each providing for control of the liquid and vapor traffic in distillation column reactor 12.
Distillation column reactor system 5 may be operated in a manner such that at least a portion of the unreacted ethanol exits distillation column reactor 12, along with heavier hydrocarbons contained in hydrocarbon stream 10 and the ethers formed due to reaction of the olefins and the alcohols, in bottoms stream 18. Light hydrocarbons, including alkanes and some unreacted olefins may be condensed in the overhead system 17 and recovered in overheads stream 20 or recycled as reflux to the top of distillation column reactor 12 via line 21.
Ethanol may be fed to distillation column reactor 12 along with hydrocarbon stream 10, as illustrated, or may be fed to a different location on distillation column reactor 12, including stages above or below the feed point of hydrocarbon feed stream 10. Due to azeotropes that may form between ethanol and the various hydrocarbons, as well as the selected operating conditions, ethanol may be present in both bottoms stream 18 and overheads stream 20. Stream 18, containing chemically blended and splash blended ethanol, may then be used as a fuel or fuel blendstock, typically without separating the ethanol.
In other embodiments, additional ethanol may be added to the distillation column reactor system at a location above that of the gasoline fraction feed. For example, ethanol may be added to one or more of the top of the column, above the etherification catalyst zone, within the etherification catalyst zone, or to a tray below the etherification catalyst zone. In this manner, the concentration of ethanol within various portions of the column may be increased or controlled to a desired level.
In some embodiments, the hydrocarbon and alcohol feeds may be passed through a fixed-bed etherification reactor, converting at least a portion of the feed to ethers. U.S. Pat. Nos. 5,003,124 and 4,950,803 disclose a liquid phase process for the etherification and oligomerization of C4 or C5 isoolefins with alcohols in a boiling point fixed bed reactor that is controlled at a pressure to maintain the reaction mixture at its boiling point and which may be directly attached to a catalytic distillation reactor. The fixed-bed reactor may be a single-phase reactor, such as a liquid or vapor phase reactor, a fixed-bed boiling point reactor, or a combination thereof In some embodiments, the fixed-bed boiling point reactor may be operated in the pulse flow regime.
In some embodiments, the effluent from the fixed bed reactor may be used directly as a fuel or fuel blendstock. In other embodiments, the effluent from the reactor may then be forwarded to a catalytic distillation reactor system for further processing, where the catalytic distillation reactor system is operated as described above.
In other embodiments, the gasoline fraction fed to the etherification reactor may undergo processing steps prior to entry into the catalytic distillation reactor system. For example, various gasoline fractions may undergo hydrotreating, selective hydrogenation of dienes and/or acetylenes, hydrodesulfurization, hydrodenitrogenation, and other processes known to those skilled in the art.
Referring now to FIG. 2, a simplified flow diagram for a process for producing ethanol-containing fuel, according to embodiments disclosed herein, is illustrated. A separate gasoline fraction or blendstock is passed through each of input lines 41, 42, 43, 44, 45, and 46. Although six input lines are shown in FIG. 2, it will be appreciated that a larger or smaller number of input lines may be used. Each of input lines 41-46 discharges into blending chamber 47, in which the blendstocks are mixed to form a subgrade blend. The subgrade blend may then be converted to an ethyl ether and ethanol-containing fuel or fuel blendstock of desired specifications by reacting and/or mixing with a desired amount of ethanol, fed via line 37, in reactor 35. Recycle, if necessary, may be returned to the reactor inlet via flow line 38.
The resulting fuel or fuel blendstock is recovered from reactor 35 via output line 48, and is passed to a suitable storage facility such as a holding tank or to an element of a distribution system (not shown), such as a pipeline, rail car, tanker truck or barge. If desired, additional splash blended ethanolor other gasoline blendstocks may be added via line 39. Each of the input lines 37, 39, 41-46 may be provided with an associated metering device to control the final composition of the fuel to within the desired specifications, such as ethanol concentration, oxygen content, Reid vapor pressure, octane number, and other appropriate properties.
Although illustrated in FIG. 2 as feeding a mixture of various gasoline blendstocks to the etherification reactor, the etherification reactor may be used to etherify a specific fraction. The remaining fractions may then be blended with the etherified gasoline blendstock to the desired fuel specifications, as illustrated in FIG. 3, where like numerals represent like parts.
The octane number (motor octane, or (RON+MON)/2) value of the fuels or fuel blendstocks resulting from the above described chemical and splash blending, according to embodiments disclosed herein, may be greater than 90. In other embodiments, the octane number may be greater than 91; greater than 92 in other embodiments; greater than 93 in other embodiments; greater than 95 in other embodiments; greater than 98 in other embodiments; and greater than 100 in yet other embodiments.
The Reid Vapor Pressure of the fuels or fuel blendstocks resulting from the above described chemical and splash blending, according to embodiments disclosed herein may be less than 7.5 psi. In other embodiments, the Reid vapor pressure may be less than 7.2 psi; less than 7 psi in other embodiments; less than 6.9 psi in other embodiments; less than 6.8 psi in other embodiments; less than 6.7 psi in other embodiments; less than 6.6 psi in other embodiments; and less than 6.5 psi in yet other embodiments.
The oxygen content of the fuels or fuel blendstocks disclosed herein, including chemical and splash blended ethanol, may be similar to splash blended ethanol fuels. In some embodiments, the fuels and fuel blendstocks disclosed herein may have an oxygen content of at least 2 weight percent; at least 2.25 weight percent in other embodiments; at least 2.5 weight percent in other embodiments; at least 2.75 weight percent in other embodiments; at least 3.0 weight percent in other embodiments; at lest 3.25 weight percent in other embodiments; and at least 3.5 weight percent in yet other embodiments.
As described above, fuels and fuel blendstocks disclosed herein include both splash blended and chemically blended ethanol, where the chemically blended ethanol is in the form of ethers. A total ethanol content in the fuel or fuel blendstock, inclusive of chemically blended ethanol in the fuel mixture, is at least 8 volume percent, at least 9 volume percent in other embodiments; at least 10 volume percent in other embodiments; at least 11 volume percent in other embodiments; at least 12 volume percent in other embodiments; and at least 15 volume percent in yet other embodiments.
Any catalyst typically used in etherification processes may be used in embodiments disclosed herein. Conventional cation exchange resins and/or zeolites may be used in various embodiments. Thus, the resin may contain sulfonic acid groups and may be obtained by polymerization or copolymerization of aromatic vinyl compounds followed by sulfonation. Examples of aromatic vinyl compounds suitable for preparing polymers of copolymers include: styrene, vinyl toluene, vinyl naphthalene, vinyl ethyl-benzene, methyl styrene, vinyl chlorobenzene and vinyl xylene. The acid cation exchange resin may contain some 1.3 to 1.9 sulfonic acid groups per aromatic nucleus. In some embodiments, resins may be based on copolymers of aromatic monovinyl compounds with aromatic polyvinyl compounds in which the polyvinyl benzene content is from about 1 to 20 weight percent of the copolymer. The ion exchange resin may have a granular size of about 0.15 to 1 mm in some embodiments. In addition to the above resins, perfluorosulfonic acid resins, which are copolymers of sulfonyl fluorovinyl ethyl and fluorocarbon, may be used.
The catalysts useful in the etherification processes disclosed herein may contain a zeolite sometimes referred to as medium pore or ZSM-5 type. In other embodiments, the zeolite may be a medium pore shape selective acidic metallosilicate zeolite selected from the group consisting of ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35, ZSM-50, MCM-22, as well as larger pore zeolite Y and zeolite Beta. The original cations associated with zeolites utilized herein may be replaced by a wide variety of other cations according to techniques well known in the art, e.g., by ion exchange. Typical replacing cations include hydrogen, ammonium, alkyl ammonium, and metal cations, and their mixtures. In the case of metal cations, metals of Groups IB to VIIIA of the Periodic Table, including, by way of example, iron, nickel, cobalt, copper, zinc, palladium, calcium, chromium, tungsten, molybdenum, rare earth metals, etc. may be used. These metals may also be present in the form of their oxides.
In other embodiments, etherification catalysts for the isoalkene reactants include mineral acids such as sulfuric acid, boron trifluoride, phosphoric acid on kieselguhr, phosphorous-modified zeolites, heteropoly acids, and various sulfonated resins. These resin type catalysts may include the reaction products of phenolformaldehyde resins and sulfuric acid and sulfonated polystyrene resins including those crosslinked with divinylbenzene. A particular etherification catalyst is a macroporous acid-form of a sulfonic ion exchange resin such as a sulfonated styrene-divinylbenzene resin, as described in U.S. Pat. No. 2,922,822, having a degree of crosslinking of about 5 to 60%. Specialized resins have been described in the art and include copolymers of sulfonyl fluorovinyl ether and fluorocarbons, as described in U.S. Pat. No. 3,489,243. Another specially prepared resin consists of SiO2-modified cation exchangers described in U.S. Pat. No. 4,751,343. The macroporous structure of a suitable resin is described in detail in U.S. Pat. No. 5,012,031 as having a surface area of at least about 400 m2/g, a pore volume of about 0.6 to 2.5 ml/g, and a mean pore diameter of 40 to 1000 Angstroms. It is contemplated that the subject process could be performed using a metal-containing resin which contains one or more metals from sub-groups VI, VII or VIII of the Periodic Table such as chromium, tungsten, palladium, nickel, chromium, platinum, or iron as described in U.S. Pat. No. 4,330,679. Further information on suitable etherification catalysts may be obtained by reference to U.S. Pat. Nos. 2,480,940, 2,922,822, and 4,270,929.
In some embodiments, a catalytic distillation structure for use herein includes placing the cation exchange resin particles into a plurality of pockets in a cloth belt, which is supported in the distillation column reactor by open mesh knitted stainless steel wire by twisting the two together in a helical form. This allows the requisite flows and prevents loss of catalyst. The cloth may be any material which is inert in the reaction, such as cotton, linen, fiber glass cloth, or TEFLON. U.S. Pat. Nos. 4,302,356, 4,443,559, and 5,730,843 disclose catalyst structures which are useful as distillation structures, and are incorporated herein by reference. Other suitable etherification catalysts are described in, for example, U.S. Pat. Nos. 5,190,730, 5,231,234, 5,248,836, 5,292,964, 5,637,777, and 6,107,526, among others.
Properties of three fuels, a typical base gasoline, an RVP-adjusted ethanol splash blended gasoline, and a fuel formed using processes disclosed herein having chemical and splash blended ethanol, are compared in Table 2. For the comparison, the RVP was held constant for all three fuels so as to determine the effect on octane (RON), and the volume that may be produced in a typical process per day. Additionally, for the fuels containing ethanol, the mixtures were further constrained by having equivalent oxygen contents.
TABLE-US-00002 TABLE 2 RVP adjusted Chemical + Base ETOH blend (splash Splash Property Gasoline blended ETOH) Blended ETOH RVP (psi) 6.45 6.45 6.45 RON 93.0 90.8 90.6 Specific 0.7438 0.7618 0.7600 Gravity Oxygen (wt. %) 0.0 3.7 3.7 Olefins (wt. %) 38.9 31.8 30.0 D86 Distillation T5 (° F.) 120 140 126 T10 (° F.) 128 161 155 T50 (° F.) 213 216 216 T90 (° F.) 326 327 325 Volume (bbl/ 100,000 94,960 104,300 day) (normalized)
For the RVP-adjusted ethanol blend, the gasoline blendstock was adjusted to make the blendstock suitable for ethanol splash blending by removal of lighter fuel components such that the final fuel will meet the RVP specifications. The RON of the splash blended ethanol is lower than the base gasoline due to the removal of C4 and C5 compounds to meet the RVP specifications, which are high octane value components. This reduction is partially offset by the high octane value of ethanol. The volume of available splash blended gasoline is also lower than the conventional gasoline because of the removal of the light fraction.
The chemical and splash blended ethanol fuel was prepared by reacting most (˜95%) of the indigenous isobutene and reactive isoamylenes with ethanol to form ETBE and TAEE. Additionally, a fraction of the C6 isoolefins are also converted to C6 ethyl ethers. Additional ethanol was then splash blended to bring the basis oxygen content up to 3.7 weight percent. While the RON decreases slightly as compared to the RVP-adjusted ethanol splash blend, the available gasoline volume is higher. In addition, the chemical blending to produce ethers favorably reduces the olefin content of the finished fuel. If a refiner is hydrotreating a base conventional gasoline to reduce the olefin content, the chemical blending process may reduce the required hydrotreating. Thus, the chemical blending step in conjunction with further splash blending of ethanol may result in the gain of significant gasoline volume and octane-point-barrels compared to splash blending only.
As described above, embodiments of the processes disclosed herein may provide for fuels and fuel blendstocks including both chemical and splash blended ethanol. Processes disclosed herein may provide for a simplified etherification process, where the ethanol recovery section may be completely eliminated saving both capital and operating costs.
Advantageously, embodiments disclosed herein may provide for at least one of: an outlet for C4 olefins; additional C4 and C5 hydrocarbons to be included in fuel compositions, effective use of ethanol in clean fuels while reducing automotive emissions; effectively reducing olefins in the gasoline at a profit. Additionally, processes disclosed herein may provide an alternative to ethanol splash blending.
By a synergistic combination of chemically blending and splash blending ethanol into a clean gasoline (to similar oxygen concentrations), not only are the economic, social, and environmental benefits of ethanol use retained, they are actually increased. By use of processes disclosed herein, more gasoline volume may be made available, and with it, more ethanol exploited. The quality of the fuels may be improved, and the amount of C4 and C5 materials that have to be re-run in the refinery may be reduced.
While octane value of the fuel is preserved, olefins can be significantly reduced without hydrotreating, and therefore hydrogen consumption is zero for the olefin-constrained refiner. Consequently, less overall CO2 may be produced in meeting hydrogen supply requirements at refineries.
While the disclosure includes a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments may be devised which do not depart from the scope of the present disclosure. Accordingly, the scope should be limited only by the attached claims.
Patent applications by Arvids Judzis, Pasadena, TX US
Patent applications by CATALYTIC DISTILLATION TECHNOLOGIES