Process for dehydrogenating an alkanol to produce acetic acid

Abstract

A process for dehydrogenating an alkanol to form acetic acid includes contacting a feed comprising ethanol and water with a catalyst in a reactor, contacting the feed in a vapor phase with the catalyst, and forming acetic acid and hydrogen in response to the contacting. The feed comprises a mole ratio of ethanol to water between about 5:1 to about 0.1:1.

Description

PROCESS FOR DEHYDROGENATING AN ALKANOL TO PRODUCE ACETICACIDCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of and priority to U.S. Provisional Patent Application No. 63 / 582,429 filed on September 13, 2023 and entitled ‘‘Process for Dehydrogenating an Alkanol,’' the entire disclosure of which is incorporated herein by reference.BACKGROUND

[0002] The following discussion is provided solely to assist the understanding of the reader, and does not constitute an admission that any of the information discussed or references cited constitute prior art to the present invention.

[0003] Ethanol can be dehydrogenated to produce a variety of products. One particular problem in the dehydrogenation of ethanol is that the reaction product mixture tends to be a complex mixture including esters, alcohols, aldehydes and ketones, and the conversion of the ethanol can vary widely. The reaction mixture can be even more complex when the ethanol feed contains impunties. The reaction product mixtures contain components with close boiling points, including components which can form azeotropes with other components of the mixture. Another problem is that w ater present in the feed ethanol or produced as a by-product during dehydrogenation has an inhibiting effect on dehydrogenation catalysts based on the concentration of the water so that any recycle to the dehydrogenation reactor of unconverted ethanol should desirably contain only a low level, if any, of water.SUMMARY

[0004] The present disclosure relates generally to processes for dehydrogenating an alkanol to form acetic acid, and / or for separating acetic acid from ethanol and other components such as ethyl acetate and / or acetaldehyde. More particularly, the present disclosure relates to contacting a feed including ethanol and water with a catalyst, which can comprise copper, zinc, chromium, manganese, aluminum, nickel, zirconium, each optionally in tire form of at least one oxide, a salt, or as elemental metal, or a combination thereof, in a dehydrogenation zone, including a dehydrogenation section of a reactor, to obtain a conversion product comprising acetic acid, and optionally introducing a feed from the dehydrogenation section comprising acetic acid, ethyl acetate, and ethanol to a separation system comprising a distillation column.

[0005] In some embodiments, a process for dehydrogenating an alkanol comprises contacting a feed comprising ethanol with a catalyst in a dehydrogenation section of a reactor to obtain a conversion product comprising acetic acid, wherein the dehydrogenation section comprises a vapor phase. In some embodiments, water is not introduced separately from the feed to the dehydrogenation section, and dehydrogenation can be undertaken under any suitable conditions, such as a pressure in the dehydrogenation section up to about 5 bar, the temperature in the dehydrogenation section from about 200 °C to about 400 °C, and a liquid hourly space velocity in the dehydrogenation section from about 1 hr1to about 10 hr1. The mole ratio of alkanol, such as ethanol, to water can range from about 5 : 1 to about 0.1 : 1.

[0006] In some embodiments, the catalyst can include at least one metal, salt, and / or at oxide of copper, chromium, manganese, aluminum, zinc, nickel, or a combination thereof. In some embodiments, the catalyst can include a copper oxide and zinc or a zinc oxide, and further comprises chromium, manganese, aluminum, zinc, nickel, zirconium, or a combination thereof. In some embodiments, the catalyst may include a copper oxide and zinc or a zinc oxide. In some embodiments, the catalyst may further include a support, such as an alumina or zirconia. The catalyst may consist of a copper oxide, a zinc oxide, and a support, such as an alumina or zirconia. Moreover, the catalyst may include about 30 weight percent (wt. %) to about 70 wt. % copper based on the total weight of the catalyst. In some embodiments, the catalyst can be copper and a zinc oxide, or the catalyst can be copper, chromium, and a zinc oxide.

[0007] In some embodiments, a process for separating acetic acid from ethyl acetate and ethanol, can include: introducing a feed including acetic acid, ethyl acetate, and ethanol to a distillation column; separating an overhead stream including ethyl acetate and ethanol; refluxing at least a portion of the overhead stream to the distillation column and recovering a distillate; and separating a bottoms stream comprising acetic acid.

[0008] In some embodiments, a process for dehy drogenating an alkanol, the process can include contacting a feed including ethanol and water with a catalyst comprising copper, chromium, manganese, aluminum, zinc, nickel, each optionally in the form of at least one oxide, a salt, or an elemental metal, or a combination thereof in a dehydrogenation section of a reactor to obtain a conversion product including acetic acid. The dehydrogenation section can perform the contacting in the vapor phase. The process can further include introducing a dehydrogenation section effluent comprising acetic acid, ethyl acetate, and ethanol to a distillation column, separating an overhead stream comprising acetaldehyde, water, and ethanol, refluxing at least a portion of the overhead stream to the distillation column andrecovering a distillate, and separating a bottoms stream including acetic acid, ethyl acetate, and ethanol.

[0009] These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] For a more complete understanding of the present disclosure and the advantages thereof, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description.

[0011] FIG. 1 shows a simplified schematic of a dehydrogenation process of a chemical manufacturing facility according to some embodiments.

[0012] FIG. 2A shows a simplified schematic of a reaction section according to some embodiments.

[0013] FIG. 2B shows another simplified schematic of another reaction section according to some embodiments.

[0014] FIG. 3 shows a simplified schematic of a downstream separation section for the chemical manufacturing facility according to some embodiments.

[0015] FIG. 4 illustrates the conversion of ethanol to acetic acid as described in Example 5.

[0016] FIG. 5 illustrates the selectivity to acetic acid as described in Example 5.DETAILED DESCRIPTION

[0017] As used herein, the term “zone” or “section” can refer to an area including one or more equipment items and / or one or more sub-zones. Equipment items can include one or more reactors or reactor vessels, heaters, exchangers, pipes, pumps, compressors, and controllers. Additionally, an equipment item, such as a reactor, dryer, or vessel, can further include one or more zones or sub-zones.

[0018] Acetic acid can be produced from ethanol. One particular problem in production of acetic acid by dehydrogenation of ethanol is that the reaction product mixture tends to be a complex mixture. The reaction product mixtures contain other byproducts in addition to acetic acid (such as water, ethanol, acetaldehyde, ethyl acetate, n-butanol. carbon dioxide, and hydrogen), and / or other components of the mixture.

[0019] As disclosed herein, an acetic acid reaction process can include contacting a stream comprising ethanol and water with a catalyst in a vapor phase to produce acetic acid. Other reaction products can also be formed in the reaction, and a separation system can be used to produce a purified acetic acid product stream. The separation system can comprise at least one distillation column that can produce an overhead stream comprising gaseous components such as carbon dioxide and hydrogen along with more volatile components such as acetaldehyde, ethanol and water. A bottoms stream from the distillation column can comprise some amount of ethanol, acetic acid, and ethyl acetate. A secondary column can be used to separate acetic acid as a bottoms product and ethanol and acetic acid as an overhead stream. The ethyl acetate stream can be further separated from the ethanol to produce ethyl acetate as a secondary product while allowing the ethanol to be recycled to the inlet of the reactor.

[0020] In some aspects, a reaction system can include any suitable number of reaction and separation sections to undertake processes, e.g., to convert a feed into a product comprising acetic acid, and subsequently separate the product for other components. The reaction of ethanol with water to produce acetic acid can comprise a dehydrogenation reaction that may occur in an endothermic reaction within one or more reactors. Any suitable reactor(s) may be utilized, such as a fixed bed reactor, although other types of reactors could be utilized such as a batch or a fluidized bed reactor. Often, the reactor can contain a heterogenous catalyst with the reactants in the vapor phase.

[0021] In some embodiments, the catalyst useful in the acetic acid production reactor can comprise copper, chromium (e g., chromite, barium chromate, etc.), manganese (e.g., trimanganese tetroxide, etc.), aluminum, zinc, nickel, zirconium, each in the form of an oxide, salt, or elemental metal, or a combination thereof. In some embodiments, the catalyst can include at least one metal and / or at least one oxide of copper, chromium, manganese, aluminum, zinc, nickel, zirconium, or a combination thereof. In some embodiments, the catalyst can comprise a copper oxide and zinc, or a zinc oxide, and further comprises chromium, manganese, aluminum, zinc, nickel, zirconium, or a combination thereof. In some embodiments, the catalyst may include a copper oxide and zinc, or a zinc oxide absent other catalytically effective amounts of metal. In some embodiments, the catalyst can comprise copper oxide, barium chromate, trimanganese tetraoxide, and chromium trioxide. In some embodiments, the catalyst may further include a support, such as an alumina and / or zirconia. The catalyst may comprise a copper oxide, a zinc oxide, and a support, such as an alumina and / or zirconia. Moreover, the catalyst may include about 30% to about 70%, by weight, copper based on the total weight of the catalyst. In some embodiments, the catalyst can be copper and a zinc oxide, or the catalyst can be copper, chromium,and a zinc oxide. Generally, such a catalyst can have an average bulk density of no more than about 0.8 gram per milliliter (g / ml), or greater than 0.00001 (g / ml) and no more than about 0.8 g / ml, a side crush strength of at least about 90 newtons (N), or at least about 90 N to about 100,000 N, and a surface area of at least about 50 meter-squared per gram (m2 / g), or at least about 50 m2 / g to about 100,00 m2 / g.

[0022] Any of the materials useful as a dehydrogenation catalyst may be synthesized using a variety of methods. In some embodiments, the dehydrogenation catalyst may be prepared via wet impregnation of a catalyst support. Using a wet-impregnation technique, a metal nitrate dissolved in a suitable solvent may be used to prepare the catalyst, however any soluble compound would be suitable. A sufficient amount of solvent can be used to fully dissolve the metal nitrate and appropriately wet the support. In some embodiments, copper nitrate and ethanol and / or water may be mixed in an amount sufficient such that the copper nitrate dissolves. Additional metal nitrates may also be added to provide a catalyst with additional components. The solute may then be combined with a suitable support material of appropriate particle size. The mixture may then be refluxed at a temperature of approximately 100 degrees Celsius (°C) for several hours (e.g., about three to about five hours) and then allowed to dry at a temperature of about 110 °C. The dried material may then be heated to about 200 °C to remove the nitrous oxide (NOx) component, and then the materials may be calcined at about 450 °C to about 550 °C at a heating rate of about one to ten °C per minute (°C / min). The amount of metal nitrate used in the wet-impregnation technique can be adjusted to achieve a desired final metal weight loading of the catalyst support.

[0023] When multiple components are used to provide a catalyst disposed on a support, each component can be added via a wet-impregnation technique. The appropriate salts can be dissolved and impregnated on a support in a co-impregnation process or a sequential process. In a co-impregnation process, a measured amount of the appropriate plurality of metal salts may be dissolved in a suitable solvent and used to wet a desired catalyst support. The impregnated support can then be dried and calcined to provide a final catalyst with a desired weight loading. In the sequential impregnation process, one or more measured amounts of salts may be dissolved in a suitable solvent and used to wet the desired catalyst support. The impregnated support can then be dried and calcined. The resulting material can then be wetted with one or more additional salts that are dissolved in a suitable solvent. The resulting material can then be dried and calcined again. This process may be repeated to provide a final catalyst material with a desired loading of each component. In some embodiments, a single metal may be added with each cycle. The order in which the metals are added in the sequential processcan be varied. Various metal weight loadings may be achieved through the wet-impregnation technique. In some embodiments, the wet-impregnation technique may be used to provide a catalyst having a copper weight loading ranging from about 20 wt. % to about 90 wt. %, or between about 30 wt. % to about 70 wt. % with one or more additional components having a weight loading between about 40 wt. % to about 60 wt. % based on the total weight of the catalyst.

[0024] The dehydrogenation catalyst may also be prepared via a co-precipitation technique. In this technique, a measured amount of one or more appropriate metal nitrates (or other appropriate metal salts) are dissolved in de-ionized water. The total metal concentration can vary and may generally be between about 1 molar (M) and about 3M. The metal-nitrate solution may then be precipitated through a drop- ise addition of the solution to a stirred, equal volume of a sodium hydroxide solution at room temperature (about 20 °C). The sodium hydroxide solution may generally have a concentration of about 4M, though other concentrations may also be used. After addition of the metal nitrate solution, the resulting suspension can be filtered and washed with de-ionized water. The filtered solids can be dried overnight, for example, at a temperature of about 110 °C. The resulting mixed metal oxide can then be processed to a desired particle size. For example, the resulting mixed metal oxide can be pressed to a desired form, ground, and then sieved to recover a catalyst material with a particle size in a desired range. Catalysts prepared using the co-precipitation technique may have higher metal loadings than the catalysts prepared using the wet-impregnation technique.

[0025] The catalyst prepared via the co-precipitation technique may be used in the prepared form and / or a catalyst binder can be added to impart additional mechanical strength. In some embodiments, the prepared catalyst may be ground to a fine powder and then stirred into a colloidal suspension (e.g., a colloidal suspension of silica and / or alumina) in an aqueous solution. The resulting suspension may be stirred while being heated and allowed to evaporate to dryness. The heating may take place at about 80 °C to about 130 °C. The resulting solid can then be processed to a desired particle size. For example, the resulting solid can be pressed to a desired form, ground, and then sieved to recover a catalyst material with a particle size in a desired range. Alternatively, the colloidal suspension may be added to the 4M sodium hydroxide precipitation solution prior to addition of the metal nitrate solution in the co- precipitation technique. Various metal weight loadings may be achieved through the co- precipitation technique. In some embodiments, the co-precipitation technique may be used to provide a catalyst having a copper weight loading ranges as described herein along with the weight loading of the other components.

[0026] The resulting catalyst from either the wet-impregnation technique and / or the coprecipitation technique may be further treated prior to use in the dehydrogenation section disclosed herein. In some embodiments, the catalyst may be treated with hydrogen to reduce the active components and / or a sodium carbonate solution for a period of time to improve the selectivity7of the catalyst. In this process, the catalyst may be soaked in an aqueous solution of sodium carbonate. In some embodiments, the sodium carbonate solution may have a concentration of about 1 molar (M) to about 10 M. preferably about 4 M. The catalyst may then be filtered and allowed to dry' at about room temperature.

[0027] In another treatment process, the catalyst may be reduced with hydrogen prior to use. In this embodiment, the catalyst may be heated and contacted with hydrogen, which may be flowing over the catalyst, for a period of time sufficient to reduce the catalyst to a desired degree. In some embodiments, the catalyst may be contacted with hydrogen at a temperature of about 160 °C to about 230 °C. The hydrogen treatment may be conducted in combination with the sodium carbonate treatment, and may be performed prior to and / or after the sodium carbonate treatment.

[0028] An embodiment of a chemical manufacturing facility 10 is depicted in FIGS. 1-3. Referring to FIGS. 1-3, the chemical manufacturing facility 10 can include a pre-processing section 100, a reaction section 200, and a downstream separation section 300.

[0029] The pre-processing section 100 can include suitable facilities for receiving feedstocks, such as any suitable alkanol, such as ethanol, and processing the feedstocks for reaction in the reaction section 200. The raw material may' comprise only ethanol and water. In addition, bio-derived ethanol may be used to allow the process to be operated from renewable ethanol sources. Prior to entering the reaction section 200, the feed stream comprising ethanol can be combined with a stream comprising water to form a combined feed fed into the reaction section 200. The ethanol may comprise some amount of water initially, and the amount of water combined with the ethanol can be controlled to provide a final mixture of ethanol and water having an ethanol to water molar ratio between about 5: 1 to about 1 :1.

[0030] Within the reaction section 200, at least a portion of the ethanol and water in the feed can be converted, although not wanting to be bound by theory7, to acetic acid and hydrogen according to the reaction:EiOH H2O - HO Ac + 2 HThe reactions can occur in the vapor phase in the presence of a catalyst to produce a reaction mixture. Any suitable reactor configurations can be used such as one or more reactors arrangedin series and / or parallel. The reactors can comprise fixed bed reactors, reactive distillation units, fluidized bed reactors, or any other reactors configured to contact the ethanol with the catalyst under conditions suitable for carrying the formation of acetic acid. The reaction section 200 can comprise one or more heater or vaporizers to heat the reaction mixture to a temperature between about 250 °C to about 370 °C, or between about 260 °C to about 315 °C at a pressure between about 0 bar to about 5 bar, about 0.001 to about 5 bar, about 0 to 3 bar. or about 0.001 bar to about 3 bar. At the reaction temperature and pressure, the reactant can be in the vapor phase upon contact with the catalyst.

[0031] A resulting product stream can pass to the separation section 300. The product stream can comprise unreacted ethanol and water along with the acetic acid and hydrogen products. Various byproducts such as ethyl acetate, acetaldehyde, and carbon dioxide can also be present in the product stream. The separation section 300 can be used to separate a purified acetic acid stream, and optionally purified ethyl acetate, purified acetaldehyde, and hydrogen streams. The separated water and ethanol from the separation section 300 can be recycled to upstream of the reaction section 200 for further reaction over the catalyst.

[0032] The reaction of water and ethanol to produce acetic acid can be endothermic. As a result, one or more reactors can be used in series with corresponding upstream heaters used to heat the reaction mixture to a desired temperature prior to the reactant passing into the reactors. This can be represented as a series of heater exchangers each followed by a reactor containing a catalyst. An exemplary reaction system 200 is shown in FIGS. 2A and 2B. As shown, the reaction section 200 can comprise at least one heater 84 and at least one reactor 1 12. The at least one heater can include a first heater 84 and a second heater 96. The reactors can be configured to receive the heated feed in the feed stream 88. In some aspects, a first reactor 112 can be in fluid communication downstream of the first heater 84, and can be configured to react the ethanol and water to form acetic acid. The reactor effluent stream 114 from the first reactor 112 can pass to the second heater 96, and the heated product stream can then pass to a second reactor 116 once reheated to further react the ethanol and water to form acetic acid. The resulting product stream 118 from the reaction section can then pass to the separation section 300.

[0033] While only two heater-reactor pairs are shown in FIG. 2A, any suitable number of heater-reactor pairs can be used in series. In some aspects, only one heater-reactor pair may be used, or alternatively between about 2-6 reactor pairs may be used. Typically, the heaters can be fired with natural gas or other suitable fuel, or may utilize pressurized steam. The first reactor 112 and the second reactor 116 may be, independently, a fixed bed reactor or other typeof reactor. As such, a first reactor effluent 114 can be from the first reactor 112 provided to the second reactor 116. and a second reactor effluent 118 can be passed from the second reactor 116 that includes a conversion product or a dehydrogenation section effluent including acetic acid and hydrogen along with unreacted ethanol and water. Other compounds such as n- butanol, acetaldehyde, ethyl acetate, and carbon dioxide can also be present as byproducts.

[0034] Although not wanting to be bound by theory’, the reaction typically removes hydrogen from ethanol to convert at least a portion of the feed to acetic acid using the oxygen in a water molecule. The reaction can be undertaken under any suitable conditions, such as the pressure in the one or more reactor(s) 112, 116 between about 0 to about 5 bar, about 0.001 bar to about 5 bar, about 0 to about 3 bar. or about 0.001 bar to about 3 bar. The temperature in the one or more reactor(s) 112, 116 can be between about 250 °C to about 370 °C, or between about 260 °C to about 315 °C. The first reactor effluent 114 from the first reactor 112 can leave the first reactor 112 at a lower temperature such as between about 10 °C to about 30 °C lower than the inlet temperature of the first reactor 112, and at a slight pressure drop. The second heater 96 can then serve to reheat the first reactor effluent 114 from the first reactor 112 to the reaction temperature of between about 250 °C to about 370 °C. or between about 260 °C to about 315 °C.

[0035] In some aspects, other heater reactor pair configurations are possible including parallel configurations. Another exemplary reaction system 200 is shown in FIG. 2B. In this configuration, the heater-reactor pairs are arranged in parallel. As shown, the reaction section 200 can comprise at least one heater 84 in series with at least one reactor 1 12 to form a heaterreactor pair, which can be arranged in parallel with at least one additional heater 96 arranged in series with at least one reactor 116 to form a second heater-reactor pair. The reactors can be configured to each receive a portion of the heated feed in the feed stream 88. The product stream 154 from the first reactor 112 can be combined with the product stream from the second reactor 116 to form a reactor effluent 118 that can pass to the separation section 300.

[0036] While only two heater-reactor pairs are shown in FIG. 2B, any suitable number of heater-reactor pairs can be used in parallel. For example, between about 2-6 heater-reactor pairs may be arranged in parallel with a common feed header supplying the feed stream 88 and one or more effluent headers to pass one or more effluent streams from the heater reactor pairs to the separation section 300. The heaters and reactors can comprise any of those described with respect to FIG. 2A, where each individual heater and reactor can be the same or different, which can allow for different reaction conditions and product selections. In some aspects, the catalyst within each reactor can be the same or different, including any of those describedherein, to produce a desired product mixture. In some aspects, only a portion of the plurality of heater-reactor pairs may be operated at a given time when the heater-reactor pairs are arranged in parallel. The reaction conditions within each reactor can also be the same or different. The ability to control the flowrate and conditions within the separate reactors can allow for different residence times, space velocities, conditions, and catalysts or catalyst blends to be used within each reactor such that different product compositions can be achieved.

[0037] Referring to FIG. 3, the separation section 300 can be used to separate the acetic acid to produce a purified acetic acid stream. The separation section can be configured to receive the reaction section effluent 118 and pass the reaction section effluent 118 to a distillation column 301. In some embodiments, the effluent stream 118 can comprise between about 15 wt. % and about 30 wt. % acetic acid, between about 5 wt. % and about 20 wt. % acetaldehyde between about 30 wt. % and about 50 wt. % ethanol, between about 1 wt. % and about 10 wt. % of hydrogen, carbon dioxide, ethyl acetate, water, or a combination thereof based on the total weight of the effluent stream 118. In some aspects, the distillation column can operate from vacuum to about 2 bar, about 0.001 bar to about 2 bar, or at or below atmospheric pressure. The distillation column can produce an overhead stream that can pass to a condenser 302 before passing to a separator 304. The overheat stream can comprise a majority of carbon dioxide, hydrogen, water, ethanol, and any acetaldehyde. The distillation column can produce a bottoms stream 316 that can comprise a majority of the acetic acid and ethyl acetate, with some minor amount of ethanol.

[0038] The overhead stream from the distillation column 301 can pass through the condenser 302 using a cooling fluid such as cooling water or a refrigerant to form a condenser effluent 303 at a temperature between about 5 °C to about 15 °C that can be sent to a separator 304 such as a knock out drum or a distillation column. An overhead stream 306 from separator 304 can comprise primarily the gaseous components such as the carbon dioxide and hydrogen produced in the reaction. A bottoms stream can pass to a pump to increase the pressure of the bottoms stream from the separator 304. A first portion 305 of the bottoms stream can pass back to the distillation column 301 as reflux. A second portion can pass to a heat exchanger 308 before passing to a third separator 312. The third separator 312 can comprise a knock-out drum or a distillation column. Within the third separator 312, the stream can be separated into an overhead stream 310 comprising carbon dioxide and hydrogen, and a bottoms stream 314 comprising ethanol, water, and acetaldehyde. In some aspects, at least a portion of the bottoms stream 314 can be recycled back to the inlet of the reaction section 200 for further reaction. The bottoms stream 314 can optionally be further processed to separate the acetaldehyde fromthe water and ethanol prior to recycling the water and ethanol to an inlet of the reaction section 200.

[0039] Turning to the bottoms stream 316, the bottoms stream 316 can be sent to a heavies distillation column 318. In some embodiments, the bottoms stream 316 can have at least about 10 wt. %, at least about 20 wt. %, or at least about 40 wt. %, or about 10 wt. % to about 95 wt. % acetic acid, based on the total weight of the bottoms stream. The bottoms stream 316 can be at a temperature of between about 70 °C and about 105 °C and at a pressure between about 2 pounds per square inch gauge (psig) and about 7 psig.

[0040] Within the heavies distillation column 318, an overhead stream can be produced that can comprise the majority of the ethanol and ethyl acetate in the bottoms stream 316. The overhead stream 320 can pass to an ethyl acetate column 324 that can separate the overhead stream 320 into an overhead stream 326 comprising primarily ethanol and a bottoms stream 328 comprising primarily ethyl acetate. In some embodiments, the bottoms stream 328 can have at least about 10 wt. %, at least about 15 wt. %, or at least about 25 wt. % ethyl acetate, or about 10 wt. % to about 95 wt. %, based on the total weight of the bottoms stream 328.

[0041] Turning back to the heavies distillation column 318 can produce a bottoms stream comprising the majority of the acetic acid. In some embodiments, the bottoms stream 322 can have at least about 80 wt. %, at least about 98 wt. %, or at least about 99.9 wt. % acetic acid, or about 80 wt. % to about 99.9 wt. % acetic acid, based on the total weight of the bottoms stream 322.

[0042] As disclosed herein, a system and process for producing acetic acid from ethanol and water is disclosed. The reaction system can comprise one or more reactors. A separation system can then be used to separate the reaction product mixture, which in some aspects can comprise a complex mixture of components comprising other valuable by-products such as ethyl acetate and acetaldehyde.EXAMPLES

[0043] The embodiments having been generally described, the following examples are given as particular embodiments of the disclosure and to demonstrate the practice and advantages thereof. It is understood that the examples are given by way of illustration and are not intended to limit the specification or the claims in any manner.EXAMPLE 1

[0044] In this example, small scale reactions were run to verify the production of acetic acid. A reactor received a feed of water and ethanol in a weight ratio of 1 : 1.25. The reactor feed was not supplemented with hydrogen. The reactor was at a temperature of 260 °C and a pressure of 0.4 bar gauge (barg). The conversion is 29.3 wt.%. The normal average selectivity', based on weight, in percent for the reactor products was:TABLE 1The mass flow rate at the reactor outlet and composition percent (%) based on weight outside the reactor were:TABLE 2Thus, the reaction product included at least 1%, by weight, acetic acid or almost 1.94%, by weight, acetic acid.EXAMPLE 2

[0045] Example 2 was performed under the same conditions as Example 1, except the weight ratio of water to ethanol was 1: 1, and 10%, by weight, hydrogen external addition based on the weight of the total feed. The conversion based on weight was 33.5%. The normal average selectivity, based on weight, in percent for the reactor products was:TABLE 3

[0046] The mass flow rate at the reactor outlet and composition percent (%) based on weight outside the reactor were:TABLE 4Thus, the reaction product included at least 2%, by weight, acetic acid.EXAMPLE 3

[0047] A simulation is conducted of two distillation towers in series with the bottoms product of the first tower being the feed to the second tower. The first tower has a mass reflux ratio of 9.9, and a total liquid entering stage 5 of 150 pound per hour (Ib / hr) at 82.8 degrees Celcius (°C). The second tower has a mass reflux ratio of 1.4, and a total liquid entering stage 5 of 166 Ib / hr at 90.6 °C. Each tower has ten stages of a structured column design system with the following property profiles:TABLE 5FIRST TOWERTABLE 6SECOND TOWER

[0048] The simulation uses a feed of the following mass fraction composition and overall properties for the first distillation tower:TABLE 7FEED to FIRST TOWERTABLE 8PROPERTIES OF OVERALL FEED COMPOSITION

[0049] The simulated overhead of the first distillation tower has the following mass fraction composition and overall properties for the first distillation tower:TABLE 9FIRST TOWER OVERHEADTABLE 10PROPERTIES OF FIRST TOWER OVERHEAD

[0050] The simulated bottoms of the first distillation tower (feed to the second distillation tower) has the following mass fraction composition and overall properties for the first distillation tower:TABLE 11FIRST TOWER BOTTOMS / SECOND TOWER FEEDTABLE 12PROPERTIES OF FIRST TOWER BOTTOMS / SECOND TOWER FEED

[0051] The simulated overhead of the first distillation tower has the following mass fraction composition and overall properties for the first distillation tower:TABLE 13SECOND TOWER OVERHEADTABLE 14PROPERTIES OF SECOND TOWER OVERHEAD

[0052] The simulated bottoms of the first distillation tower (feed to the second distillation tower) has the following mass fraction composition and overall properties for the first distillation tower:TABLE 15SECOND TOWER BOTTOMSTABLE 16PROPERTIES OF SECOND TOWER BOTTOMSThe mass fraction of acetic acid can exceed 0.98.EXAMPLE 4

[0053] A simulation is conducted of two distillation towers in series with the bottoms product of the first tower being the feed to the second tower. The first tower has a mass reflux ratio of 9.9, and a total liquid entering stage 5 of 150 pound per hour (Ib / hr) at 82.8 °C. The second tower has a mass reflux ratio of 1.6, and a total liquid entering stage 10 of 251 Ib / hr at 98.9 °C. The first tower has ten stages and the second tower has twenty stages of a structured column design system with the following property profiles:TABLE 17FIRST TOWERTABLE 18SECOND TOWER

[0054] The simulation uses a feed of the following mass fraction composition and overall properties for the first distillation tower:TABLE 19FEED to FIRST TOWERTABLE 20PROPERTIES OF OVERALL FEED COMPOSITION

[0055] The simulated overhead of the first distillation tower has the following mass fraction composition and overall properties for the first distillation tower:TABLE 21FIRST TOWER OVERHEADTABLE 22PROPERTIES OF FIRST TOWER OVERHEAD

[0056] The simulated botoms of the first distillation tower (feed to the second distillation tower) has the following mass fraction composition and overall properties for the first distillation tower:TABLE 23FIRST TOWER BOTTOMS / SECOND TOWER FEEDTABLE 24PROPERTIES OF FIRST TOWER BOTTOMS / SECOND TOWER FEED

[0057] The simulated overhead of the first distillation tower has the following mass fraction composition and overall properties for the first distillation tower:TABLE 25SECOND TOWER OVERHEADTABLE 26PROPERTIES OF SECOND TOWER OVERHEAD

[0058] The simulated bottoms of the first distillation tower (feed to the second distillation tower) has the following mass fraction composition and overall properties for the first distillation tower:TABLE 27SECOND TOWER BOTTOMSTABLE 28PROPERTIES OF SECOND TOWER BOTTOMSThe mass fraction of acetic acid can exceed 0.99 with a second distillation tower having twenty stages.EXAMPLE 5

[0059] In this example, an eight channel reactor was used that allowed each channel to have a different catalyst. Each channel has an internal diameter of 6 mm and was filled with a height of approximately 260 mm of catalyst to determine the performance and output. The gasphase operation proceeded with evaporation of the liquid feed stock. The feed stock used mostly pure ethanol or ethanol and water mixtures. The temperature ranged from 250 °C to 350 °C. The pressure ranged from 0.5 to 5 bar gauge in the various tests. Multiple sets or runs were conducted at varying conditions. The data for the runs is listed in Table 1 below:TABLE 29

[0060] The catalyst used are indicated as catalyst 1, catalyst 2. etc. and are characterized by composition and amount used in Table 2 below.TABLE 30

[0061] The results are shown in FIG. 4 and FIG. 5. As shown in FIG. 4, the ethanol conversions are as high as 97-98%, and as shown in FIG. 5, the selectivities to acetic acid are as high as 50% to approximately 58% for catalysts 1 and 3. As used herein, the conversion and selectivity are defined by:* Conversion* SelectivityWhere X; = conversion of the ithcomponent, Si = selectivity of the ithcomponent, n = weight concentration of the ithcomponent, and i denotes the specific component. The values provided in this example are normalized values.

[0062] Thus, the use of various catalysts including those with copper (e.g., copper oxide, elemental copper, etc.), chromia, alumina, and / or zinc (e.g., zinc oxide, elemental zinc) can effectively produce acetic acid from ethanol at the conditions disclosed herein.

[0063] Having described various catalysts, processes, and systems, certain aspects can include, but are not limited to:

[0064] In a first aspect, a process for dehydrogenating an alkanol comprises contacting a feed comprising ethanol and water with a catalyst in a reactor, wherein the feed comprises a mole ratio of ethanol to water between about 5: 1 to about 0.1: 1, and contacting the feed with the catalyst comprises contacting the feed in a vapor phase with the catalyst; and forming acetic acid and hydrogen in response to tire contacting.

[0065] A second aspect can include the process of the first aspect, wherein the catalyst comprises copper, chromium, manganese, aluminum, zinc, nickel, zirconium, or any combination thereof.

[0066] A third aspect can include the process of the second aspect, wherein the catalyst is in the form of an oxide, a salt, or a metal.

[0067] A fourth aspect can include the process of any one of the first to third aspects, wherein tire pressure in the reactor is between about 0 and about 5 bar.

[0068] A fifth aspect can include the process of any one of the first to fourth aspects, wherein the temperature in tire reactor is between about 250 °C to about 370 °C.

[0069] A sixth aspect can include the process of any one of the first to fifth aspects, wherein the catalyst comprises a copper oxide and zinc or a zinc oxide.

[0070] A seventh aspect can include tire process of any one of the first to sixth aspects, wherein tire catalyst further comprises a support comprising alumina or zirconia.

[0071] An eighth aspect can include tire process of any one of the first to seventh aspects, wherein tire catalyst comprises a copper oxide and zinc or a zinc oxide.

[0072] A ninth aspect can include the process of any one of the first to seventh aspects, wherein the catalyst consists of a copper oxide, a zinc oxide, and a support.

[0073] In a tenth aspect, a process for separating acetic acid from ethyl acetate and ethanol comprises: introducing a feed comprising acetic acid, ethyl acetate, ethanol, acetaldehyde, and water to a distillation column; separating an overhead stream comprising a majority of tire acetaldehyde, water, and ethanol; refluxing at least a portion of the overhead stream to the distillation column and recovering a distillate; and separating a bottoms stream comprising ethanol, acetic acid, and ethyl acetate for fonning a purified acetic acid stream.

[0074] An eleventh aspect can include the process of the eleventh aspect, wherein the feed comprises about 15% to about 30%, by weight, acetic acid, about 5% to about 20%. by weight, acetaldehyde, and about 30 wt. % and about 50 wt. % %, by weight, ethanol, based on the total weight of the feed.

[0075] A twelfth aspect can include the process of the eleventh or twelfth aspect, wherein the bottoms stream comprises at least about 10%, by weight, acetic acid, based on the total weight of tire bottoms stream.

[0076] A thirteenth aspect can include the process of any one of the eleventh to fourteenth aspects, further comprising introducing at least a portion of the overhead stream to a separator to recover a liquid; and recycling the liquid to the feed.

[0077] A fourteenth aspect can include the process of any one of the eleventh to fifteenth aspects, further comprising introducing tire bottoms stream to an ethanol recovery column; separating an ethanol recovery overhead stream comprising ethanol and ethyl acetate; and separating an acetic acid recovery bottoms stream comprising acetic acid.

[0078] In a fifteenth aspect, a process for dehydrogenating an alkanol comprises contacting a feed comprising ethanol and water with a catalyst in one or more reactors, wherein the catalyst comprises copper, chromium, manganese, aluminum, zinc, nickel, zirconium, or any combination thereof; forming a conversion product comprising acetic acid, hydrogen, ethanol, water, and acetaldehyde, wherein feed is in a vapor phase during the contacting; passing tire conversion product to a distillation column; separating an overhead stream comprising acetaldehyde, water, and ethanol with the distillation column; refluxing at least a portion of the overhead stream to the distillation column and recovering a distillate; and separating a bottoms stream comprising acetic acid, ethyl acetate, and ethanol from tire distillation column.

[0079] A sixteenth aspect can include the process of the fifteenth aspect, wherein a pressure in the one or more reactors is up to about 5 bar.

[0080] A seventeenth aspect can include the process of the fifteenth or sixteenth aspect, wherein a temperature in the one or more reactors is between about 250 °F to about 370 °C.

[0081] An eighteenth aspect can include the process of any one of the fifteenth to seventeenth aspects, wherein the catalyst comprises a copper oxide and zinc or a zinc oxide and further comprises chromium, manganese, aluminum, zinc, nickel, zirconium, or a combination thereof.

[0082] A nineteenth aspect can include the process of any one of the fifteenth to eighteenth aspects, wherein the catalyst comprises a copper oxide, a zinc oxide, and a support.

[0083] A twentieth aspect can include the process of any one of the fifteenth to nineteenth aspects, wherein the catalyst further comprises a support comprising alumina or zirconia.

[0084] A twenty first aspect can include tire process of any one of tire fifteenth to twentieth aspects, further comprising: introducing the bottoms stream to an acetic acid recover}’ column; separating an ethanol recovery overhead stream comprising ethyl acetate and ethanol; and separating an acetic acid recovery bottoms stream comprising acetic acid.

[0085] A twenty second aspect can include the process of the twenty first aspect, wherein the acetic acid recovery’ bottoms stream comprises at least about 80 wt. % acetic acid.

[0086] In the preceding discussion and in the claims, the terms “including’' and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to ... ” At least one embodiment is disclosed and variations, combinations, and / or modifications of the embodiment(s) and / or features of the embodiment(s) made by a person having ordinary’ skill in the art are within the scope of the disclosure. Alternative embodiments that result from combining, integrating, and / or omitting features of the embodiment(s) are also within the scope of the disclosure. Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from about 1 to about 10 includes, 2. 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example, whenever a numerical range with a lower limit, Ri, and an upper limit, Ru, is disclosed, any number falling within the range is specifically disclosed. In particular, the following numbers within the range are specifically disclosed: R=Ri+k*(Ru-Ri), wherein k is a variable ranging from 1 percent to 100 percent with a 1 percent increment, i.e.. k is 1 percent. 2 percent, 3 percent, 4 percent. 5 percent, ... , 50 percent. 51 percent, 52 percent, .... 95 percent, 96 percent, 97 percent. 98 percent, 99 percent, or 100 percent. Moreover, any numerical range defined by two R numbers as defined in the above is also specifically disclosed. As used herein, the term “and / or” can mean one, some, or all elements depicted in a list. As an example, “A and / or B” can mean A, B, or a combination of A and B. Use of the term "optionally" with respect to any element of a claim means that the element is required, or alternatively, the element is not required, both alternatives being within the scope of the claim. Use of broader terms such as comprises, includes, and having should be understood to provide support for narrower terms such as consisting of, consisting essentially of, and comprised substantially of. Accordingly, the scope of protection is not limited by the description set out above but is defined by the claims that follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated as further disclosure into the specification and the claims are embodiment(s) of the present invention.

Claims

CLAIMSWhat is claimed is:

1. A process for dehydrogenating an alkanol, the process comprising: contacting a feed comprising ethanol and water with a catalyst in a reactor, wherein the feed comprises a mole ratio of ethanol to water between about 5: 1 to about0.1: 1, and contacting the feed with the catalyst comprises contacting the feed in a vapor phase with the catalyst; and forming acetic acid and hydrogen in response to the contacting.

2. The process of claim 1, wherein the catalyst comprises copper, chromium, manganese, aluminum, zinc, nickel, zirconium, or any combination thereof.

3. The process of claim 2, wherein the catalyst is in the form of an oxide, a salt, or a metal.

4. The process of claim 1 , wherein the pressure in the reactor is between about 0 and about 5 bar.

5. The process of claim 1, wherein the temperature in the reactor is between about 250 °C to about 370 °C.

6. The process of claim 1 , wherein the catalyst comprises a copper oxide and zinc or a zinc oxide.

7. The process of claim 1, wherein the catalyst further comprises a support comprising alumina or zirconia.

8. The process of claim 1, wherein the catalyst comprises a copper oxide and zinc or a zinc oxide.

9. The process of claim 1, wherein the catalyst consists of a copper oxide, a zinc oxide, and a support.

10. A process for separating acetic acid from ethyl acetate and ethanol, comprising:introducing a feed comprising acetic acid, ethyl acetate, ethanol, acetaldehyde, and water to a distillation column; separating an overhead stream comprising a majority of the acetaldehyde, water, and ethanol; refluxing at least a portion of the overhead stream to the distillation column and recovering a distillate; and separating a bottoms stream comprising ethanol, acetic acid, and ethyl acetate for forming a purified acetic acid stream.

11. The process of claim 10, wherein the feed comprises about 15% to about 30%, by weight, acetic acid, about 5% to about 20%. by weight, acetaldehyde, and about 30 wt. % and about 50 wt. % %, by weight, ethanol, based on the total weight of the feed.

12. The process of claim 11, wherein the bottoms stream comprises at least about 10%, byweight. acetic acid, based on the total weight of the bottoms stream.

13. The process of claim 1 1, further comprising introducing at least a portion of the overhead stream to a separator to recover a liquid; and recycling the liquid to the feed.

14. The process of claim 1 1 , further comprising introducing the bottoms stream to an ethanol recovery column; separating an ethanol recovery overhead stream comprising ethanol and ethyl acetate; and separating an acetic acid recovery bottoms stream comprising acetic acid.

15. A process for dehydrogenating an alkanol, the process comprising: contacting a feed comprising ethanol and water with a catalyst in one or more reactors, wherein the catalyst comprises copper, chromium, manganese, aluminum, zinc, nickel, zirconium, or any combination thereof; forming a conversion product comprising acetic acid, hydrogen, ethanol, water, and acetaldehyde, wherein feed is in a vapor phase during the contacting; passing the conversion product to a distillation column;separating an overhead stream comprising acetaldehyde, water, and ethanol with the distillation column; refluxing at least a portion of the overhead stream to the distillation column and recovering a distillate; and separating a bottoms stream comprising acetic acid, ethyl acetate, and ethanol from the distillation column.

16. The process of claim 15, wherein a pressure in the one or more reactors is up to about 5 bar.

17. The process of claim 15, wherein a temperature in the one or more reactors is between about 250 °F to about 370 °C.

18. The process of claim 15, wherein the catalyst comprises a copper oxide and zinc or a zinc oxide and further comprises chromium, manganese, aluminum, zinc, nickel, zirconium, or a combination thereof.

19. The process of claim 15, wherein the catalyst comprises a copper oxide, a zinc oxide, and a support.

20. The process of claim 15, wherein the catalyst further comprises a support comprising alumina or zirconia.

21. The process of claim 15, further comprising: introducing the bottoms stream to an acetic acid recovery column; separating an ethanol recovery overhead stream comprising ethyl acetate and ethanol; and separating an acetic acid recovery bottoms stream comprising acetic acid.

22. The process of claim 21, wherein the acetic acid recovery bottoms stream comprises at least about 80 wt. % acetic acid.

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