TW201307268A - Process for purifying a crude ethanol product - Google Patents

Abstract

In one embodiment, the invention is to a process for purifying a crude ethanol product. The process comprises the step of hydrogenating acetic acid in a first reaction zone in the presence of a first catalyst to form the crude ethanol product comprising ethanol, acetaldehyde, acetic acid, water, and acetal. The process further comprises the step of separating at least a portion of the crude ethanol product into a refined ethanol stream and a by-product stream. The refined ethanol stream comprises ethanol and acetaldehyde; and the by-product stream comprises acetic acid and a substantial portion of the water from the crude ethanol product. The process further comprises the step of hydrolyzing in a second reaction zone at least a portion of the acetal.

Description

Process for purifying crude ethanol product

The present invention generally relates to a process for producing ethanol, particularly a process for reducing energy consumption to recover ethanol.

The traditional production of ethanol used in industry is derived from petrochemical feedstocks, such as from petroleum, natural gas and coal, or from feed intermediates such as syngas, or from starchy feedstocks or cellulosic feedstocks such as corn. Or sugar cane. Conventional methods for producing ethanol from petrochemical feedstocks and cellulosic feedstocks include ethylene acid catalyzed hydration, methanol homologation, direct alcohol synthesis, and "Fischer-Tropsch synthesis". The price of unstable petrochemical feedstocks can cause fluctuations in the cost of ethanol produced in the traditional way. When the price of raw materials rises, the demand for alternative sources to produce ethanol will increase. The starch raw material and the cellulose raw material can be fermentatively converted into ethanol. However, fermentation methods are commonly used for consumer ethanol production, and the ethanol produced therefrom can also be used for fuel or human consumption. In addition, the fermentation of starch or cellulosic feedstock will compete with the source of food, thus limiting the amount of ethanol that can be used in industrial production.

The production of ethanol by reduction of alkanoic acids and/or other carbonyl compounds has been extensively studied, and combinations and operating conditions of various catalysts and supports have been mentioned in the literature. When alkanoic acid (e.g., acetic acid) is reduced, other compounds are formed together with ethanol or by side reactions. As an example, esters and/or acetals, such as diethyl acetal, can be formed by these side reactions. These impurities (1), restrict ethanol production; (2) hinder the purification of ethanol in the crude reaction product. In general, the separation of esters and acetals from ethanol has proven to require excessive resource requirements, such as the need for high energy and/or a large number of trays.

In view of these shortcomings, there is still a need to improve the separation process to provide more efficient separation of impurities from ethanol.

In one embodiment, the invention provides a process for purifying a crude ethanol product comprising ethanol, acetaldehyde, acetic acid, water, and an acetal such as diethyl acetal. The process includes the step of hydrogenating acetic acid in the presence of a first catalyst in the first reaction zone to form a crude ethanol product. The process also includes the step of separating at least a portion of the crude ethanol product into a refined ethanol stream and a by-product stream. The refined ethanol stream comprises ethanol and acetaldehyde, while the by-product stream comprises acetic acid and most of the water from the crude ethanol product. The process also includes the step of hydrolyzing at least a portion of the acetals. Preferably, this step is carried out in the second reaction zone, and the second reaction zone may comprise a second catalyst.

In another embodiment, the separating step is carried out in a first distillation column. The first distillation column produces a first distillate comprising ethanol and acetaldehyde, and a first residue comprising acetic acid. In a preferred embodiment, the first distillate is separated in a second distillation column to produce a second distillate comprising acetaldehyde, and a second residue comprising ethanol. In some embodiments, the second distillation column comprises a second reaction zone. In another embodiment, the separating step is performed by a membrane separation device.

In particular, the invention relates to a process for recovering ethanol obtained by hydrogenation of acetic acid, particularly a process for removing acetals from crude ethanol products. The hydrogenation reaction can be carried out in the presence of the first catalyst in the first reaction zone. This reaction produces a crude ethanol product comprising ethanol, acetaldehyde, water, unreacted acetic acid, ethyl acetate, and other impurities such as acetals, for example, diethyl acetal, ethyl propyl acetal, Ethyl butyl acetal and its hemiacetals. Generally, it is preferred to remove such impurities from the crude ethanol product. In some embodiments, the amount of acetal in the crude ethanol product is greater than 0.0005 wt%, for example, greater than 0.01 wt%, or greater than 0.1 wt%, based on the total weight of the feed stream. In terms of ranges, the content of the acetal in the crude ethanol product may be from 0.0005 wt% to 1 wt%, for example, from 0.001 wt% to 1 wt%, or from 0.01 wt% to 1%, which is a crude ethanol In terms of the total weight of the product. In terms of the upper limit, the crude ethanol product contains less than 1% acetals, such as less than 0.1% by weight of acetals or less than 0.05% by weight of acetals.

Surprisingly and unexpectedly, it has been found that at least a portion of the acetals in the crude ethanol product are hydrolyzable, preferably to produce additional ethanol or acetaldehyde. Hydrolysis of acetals helps to increase operational efficiency. In addition to the hydrolysis step, the process of the present invention further comprises the steps of separating the crude ethanol product into a refined ethanol stream comprising ethanol and acetaldehyde, and a by-product stream comprising water and unreacted acetic acid; wherein the majority of the water in the crude ethanol product The by-product stream is separated. Advantageously, the present invention combines step (1), increases overall ethanol production, and step (2), reducing energy requirements to achieve recovery of ethanol from the crude ethanol product.

To separate the crude ethanol product, the process of the present invention can employ a separation zone that includes one or more separation devices. Any suitable separation device can be employed, and the suitable separation device is not limited to those mentioned herein. The first separation unit produces a refined ethanol stream and a by-product stream. In a preferred embodiment, the first separation unit is a first distillation column, such as a reactive distillation column, and the resulting refined ethanol stream comprises a first distillate and a by-product stream comprising the first residue . In this case, the first residue contains most of the water initially in the crude ethanol product. In one embodiment, the first separation device operating conditions are adjusted such that a small amount, if any, of acetic acid is carried to the refined ethanol stream, and a small amount, if any, of the ethanol is leaked into the by-product stream.

The present invention advantageously removes most of the water from the crude ethanol product by a by-product stream (e.g., the first residue), which substantially reduces the energy requirements of the separation process relative to the refined ethanol stream (for example, the first distillate). The amount of water removed from the crude ethanol product and present in the by-product stream may vary, depending on the composition of the crude ethanol product, which is affected by the acetic acid conversion and the selectivity to ethanol. In one embodiment, from 30% to 90% of the water in the crude ethanol product, for example, 40% to 88% water, or 50 to 84% water is removed from the residue. By removing less water from the residue, the amount of acetic acid carried in the distillate can be increased. In addition, leaving too much water in the residue may also result in an increase in ethanol leaking into the residue. In addition, depending on the conversion rate, if too much water remains in the distillate, the energy demand may also increase. Preferably, most of the water in the crude ethanol product fed to the first separation unit, for example, can remove up to about 90% of the water from the crude ethanol product, such as up to about 75% water in the by-product stream. in. In some embodiments, at lower acetic acid conversions and/or selectivity, most of the water pumped to the by-product stream may be from 30% to 80%, for example, from 40% to 75%.

As described above, according to the present invention, the acetal in the crude ethanol product is hydrolyzed. Preferably, the hydrolysis is carried out in the second reaction zone. In one embodiment, the second reaction zone different from the first reaction zone is used to carry out the hydrogenation reaction of acetic acid. The acetals are hydrolyzed to form the respective alcohols and/or aldehydes. As an example, diethyl acetal is hydrolyzed to form additional ethanol and/or acetaldehyde. In this case, "extra" ethanol and/or acetaldehyde is ethanol and/or acetaldehyde formed after the hydrolysis reaction and the hydrogenation reaction. The acetal in the crude ethanol product is preferably hydrolyzed such that any stream exiting the separation zone comprises any stream that can be recycled back to the first reaction zone from the separation zone, in terms of weight, contained The acetal will be less than the acetal in the crude ethanol product. As an example, the weight ratio of the acetal in the crude ethanol product to the acetal discharged from the separation zone is preferably from 100:1 to 2:1, for example from 50:1 to 5:1 or from 25 1 Until 8:1. Both the overall ethanol yield and the separation efficiency are improved in accordance with the hydrolysis and separation steps of the present invention.

In some embodiments, the hydrolysis can be carried out by a catalyst, such as a second catalyst, which is separate from the first catalyst. For example, the second reaction zone can include a second catalyst. The hydrolysis reaction is preferably carried out using an acidic catalyst. If not bound by theory, it is generally believed that the residual acid in the crude ethanol product acts as a catalyst for the hydrolysis reaction. However, other suitable catalysts may also be employed. The ion exchange resin reaction bed may comprise a strongly acidic heterogeneous or homogenous catalyst such as, for example, Lewis acid, a strongly acidic ion exchange resin catalyst, a mineral acid, and methanesulfonic acid. A typical catalyst comprises ^{Amberlyst TM 15, Amberlyst70 TM (Rohm} & Haas Company, Philadelphia), DOWEX-M-31 (Dow Chemical Company), DOWEX Monosphere M-31 ( Dow Chemical Company), Purolite CT-type catalyst (Purolite International SRL). However, the catalyst is not required to carry out the hydrolysis step. In one embodiment, the resonance time is sufficient to hydrolyze the acetal. In another embodiment, the hydrolysis reaction can continue if sufficient acetic acid is present. The hydrolysis can be carried out in any phase, but is preferably carried out in the liquid phase.

In some embodiments, the second reaction zone is placed in one or more separation devices, for example, in one or more distillation columns. For example, hydrolysis can be carried out in a reactive distillation column, The separation step and the hydrolysis step are simultaneously performed in the middle. In this case, the distillation column includes a second reaction zone, for example, the second reaction zone is in a distillation column. In these cases, the acetal content of the two streams exiting the distillation column is lower than the feed to the separation zone, i.e., the acetal content of the crude ethanol product, which is by weight. The acetal content in the crude ethanol product is preferably from 100:1 to 2:1, for example, from 50:1 to 5:1 or from 25, in terms of the weight of the acetal content of the distillate and the residue in the distillation column. : 1 to 8:1. In one embodiment, the overhead of the first distillation column may comprise less than 5% by weight, such as less than 2% by weight, or less than 1% by weight of acetal, the percentage being the total weight of the distillate In terms of. The residue of the first distillation column may contain less than 0.5% by weight, for example, less than 0.001% by weight, or less than 0.0001% by weight of acetal, based on the total weight of the residue. Preferably, the residue in the first distillation column has substantially no detectable amount of acetal. The total acetal weight of the distillate of the first distillation column and the residue of the first distillation column is preferably lower than the amount of acetal introduced into the first distillation column feed. The acetal content in the feed is less than the amount of acetal in the distillate and can be reduced by at least 50%, for example, at least 75%, or at least 90%. The acetal content at the feed amount is less than the sum of the distillate and the residue, and can be reduced by at least 50%, for example, at least 75%, or at least 90%. Although hydrolysis is discussed by the first distillation column, the same discussion applies to other separation units and/or distillation columns that may be present in the separation zone. For example, in one embodiment, a separation zone comprises a first distillation column and a second distillation column, and a second reaction zone is placed in the second distillation column.

In one embodiment, the second reaction zone comprises a reactor such as a reaction bed. Preferably, the second reaction zone comprises an ion exchange resin reaction bed which hydrolyzes the acetal present in the crude ethanol product or hydrolyzes the acetal present in the middle distillate stream of any subsequent crude ethanol product. . The ion exchange resin bed as discussed above may comprise a catalyst. Preferably, the ion exchange resin catalyst employed in the reaction bed comprises a solid acid catalyst or an acidic ion exchange catalyst. In another embodiment, the ion exchange resin can be disposed in one or more distillation columns, for example, in a first distillation column and/or in a second distillation column. In one embodiment, a refined ethanol stream, such as an overhead stream of a first distillation column, is introduced to an ion exchange resin reaction bed to hydrolyze the acetal present. The ethanol, acetaldehyde and/or acetic acid obtained by the hydrolysis reaction can be returned to the first reaction zone or further processed in one or more distillation columns.

In other embodiments, the ion exchange resin reaction bed can be located outside of any distillation column or inside the distillation column.

In a typical embodiment, the energy requirements of the first separation unit, for example, the first distillation column, may be less than 5.5 million British thermal units (MMBtu) per ton of refined ethanol, such as less than 4.5, in accordance with the process of the present invention. Millions of British thermal units per ton of refined ethanol, or less than 3.5 million British thermal units per ton of refined ethanol. In some embodiments, if compared to the residue, for example, greater than 65% of the water is compared to the crude ethanol product, the total energy requirement is lower than the energy required to remove most of the water from the crude ethanol product of the distillate, This process can operate at higher energy requirements. If more water is removed from the distillate and/or residue of the first distillation column, additional energy is required to operate. If the water concentration in the distillate is close to the azeotropic amount, for example, from about 4% by weight to about 7% by weight, the energy of the first distillation column needs to increase rapidly. In order to achieve these low water concentrations, it is necessary to increase the reflux ratio, which results in an increase in the energy requirements of the distillation column. To remove more water, for example more than 90% of the water is removed from the residue, a greater reflux ratio is required - above 5:1, above 10:1 or above 30:1. As a result, this will require additional energy for the distillation column.

The by-product stream may comprise at least 85% acetic acid in the crude ethanol product, for example, at least 90%, more preferably at least about 100% acetic acid. In terms of ranges, the by-product stream preferably comprises from 85% to 100% unreacted acetic acid in the crude ethanol product, and more preferably from 90% to 100% unreacted acetic acid. In one embodiment, substantially all of the unreacted acetic acid is recovered in the by-product stream. By removing most of the unreacted acetic acid from the crude ethanol product, in some aspects, the process does not require further separation of the acetic acid from the crude ethanol product. In this regard, the ethanol product may comprise some acetic acid, for example, very small or trace amounts of acetic acid.

As discussed below, depending on the acetic acid conversion, the composition of the by-product stream may vary and depends on the composition of the crude ethanol product and the separation conditions of the separation unit. Depending on the composition, the by-product stream can be: (i) recycled to the hydrogenation reactor in whole or in part, (ii) separated into acid and aqueous streams, and (iii) treated as a solvent in a weak acid recovery process, ( Iv) react with the alcohol to consume unreacted acetic acid, or (v) be discharged to the wastewater treatment facility.

Hydrogenation of acetic acid

The process of the invention can be used in any hydrogenation process for the production of ethanol. Materials, catalysts, reaction conditions, and separation processes that can be used in the acetic acid hydrogenation process are further illustrated below.

The feedstocks used in the process of the present invention - acetic acid, and hydrogen, may be derived from any suitable source, including natural gas, petroleum, coal, biomass, and the like. For example, acetic acid can be produced by methanol carbonylation, acetaldehyde oxidation, ethylene oxidation, oxidative fermentation, anaerobic fermentation, and the like. Methanol carbonylation processes suitable for the production of acetic acid are disclosed in U.S. Patent Nos. 7,208,624, 7,115, 772, 7,005, 541, 6, 657, 078, 6, 627, 770, 6, 143, 930, 5, 599, 976, 5, 144, 068, 5, 026, 908, 5, 001, 259, and 4, 994, 608, the entire disclosures of which are incorporated herein by reference. Alternatively, ethanol production can be integrated with these methanol carbonylation processes, as appropriate.

As a result of fluctuations in oil and natural gas prices, the use of alternative carbon sources to produce acetic acid, as well as processes such as intermediates of methanol and carbon monoxide, has generated increasing interest. In particular, when petroleum prices are higher than natural gas, it may be advantageous to produce acetic acid from a "syn gas" derived from other readily available carbon sources. For example, U.S. Patent No. 6,232,352 discloses a method of modifying a methanol plant to produce acetic acid, which is incorporated herein by reference. By modifying the methanol plant, significant capital costs, as well as the carbon monoxide that is associated with it, can be significantly reduced or largely removed. Derived from a methanol synthesis loop produces all or part of the synthesis gas, which is supplied to a separation unit to recover carbon monoxide, which is then used to produce acetic acid. In a similar manner, the hydrogen used in the hydrogenation step can also be provided by syngas.

In some embodiments, some or all of the feedstock in the acetic acid hydrogenation process described above may be derived in part or in whole from the syngas. For example, acetic acid can be formed from methanol and carbon monoxide, all of which can be derived from syngas. The synthesis gas can be formed by partial oxidation reforming or steam reforming, and carbon monoxide can be separated from the synthesis gas. Similarly, hydrogen used to hydrogenate acetic acid to form a crude ethanol product can be separated from the synthesis gas. Syngas can in turn be derived from different carbon sources. The carbon source, for example, may be selected from the group consisting of natural gas, crude oil, petroleum, coal, biomass, and combinations thereof. Group of. Syngas or hydrogen can also be obtained from biologically derived methane gas, such as methane gas derived from biological sources produced by landfills or agricultural waste.

In another embodiment, the acetic acid used in the hydrogenation step can be formed from fermentation of the biomass. Preferably, the fermentation process uses an acetogenic process or by homoacetogenic microorganisms to ferment the sugar to produce acetic acid, and if present, there are few as by-products. carbon dioxide. The carbon efficiency of the fermentation process is preferably greater than 70%, greater than 80% or greater than 90%, whereas conventional yeast processes typically have a carbon efficiency of about 67%. Optionally, the microorganism used in the fermentation process is a genus selected from the group consisting of Clostridium, Lactobacillus, Clostridium Morrow, Thermophilic anaerobic bacteria, Propionic acid bacteria, Propionate prop. a group consisting of Bacillus, Gram-negative anaerobic bacteria and Mycobacterium, and especially the species selected from Clostridium malic acid, Clostridium butyricum, Thermosilophila, and A group consisting of a thermophilic anaerobic bacterium, a De Brucella lactic acid bacterium, a propionic acid bacterium, a propionic acid Helicobacter, a Susinick anaerobic bacterium, a lactic acid bacterium, and an endoglucanase. Optionally, in this process, all or part of the unfermented residue from the biomass, such as lignans, can be vaporized to form hydrogen, which can be used in the hydrogenation step of the present invention. Typical fermentation processes for the formation of acetic acid are disclosed in U.S. Patent Nos. 6,509,180, 6,927,048, 7,074, 603, 7,507, 562, 7, 351, 559, 7, 601, 865, 7, 682, 812, and 7, 888, 082, incorporated herein by reference. See also U.S. Patent Application Publication Nos. 2008/0193989 and 2009/0281354, the entire contents of each of which are incorporated herein by reference.

For example, biological materials may include, but are not limited to, agricultural waste, forest products, grass and other cellulosic materials, wood harvest residues, cork sheets, hardwood chips, branches, stumps, leaves, bark, sawdust, unqualified pulp, Corn, corn stover, wheat straw, straw, sugarcane residues, switchgrass, miscanthus, animal manure, municipal waste, municipal sewage, commercial waste, grape residue, almond shell, walnut shell, coconut shell, coffee residue, grass granule , grass balls, wood balls, cardboard, paper, plastic and cloth. See, for example, U.S. Patent No. 7,884,253, the disclosure of which is incorporated herein by reference. Another source of biological material is black liquor, a thick, dark liquid that transforms wood into pulp. A by-product of the Kraft process (which is then dried to make paper). Black liquor is an aqueous solution of lignin residues, hemicellulose, and inorganic chemicals.

U.S. Reissue Patent No. RE35,377, incorporated herein by reference, which is incorporated herein by reference in its entirety in its entirety in the the the the the the the the the the This process involves hydrogasification of solid and/or liquid carbon materials to obtain a process gas that is steam pyrolyzed by additional natural gas to form a syngas. The synthesis gas is converted to methanol, which is then carbonylated to give acetic acid. The process also produces hydrogen gas as such, which can be used in the present invention as described above. U.S. Patent No. 5,821,111, the disclosure of which is incorporated herein by reference in its entirety, the disclosure of the disclosure of the disclosure of the disclosure of the entire disclosure of the disclosure of the disclosure of the disclosure of the disclosure of the disclosure of the disclosure of the disclosure of the disclosure of the disclosure of the disclosure of the disclosure of Inclusion in the reference.

The acetic acid fed to the hydrogenation reaction may also contain other carboxylic acids and their anhydrides, as well as acetaldehyde and acetone. Preferably, a suitable acetic acid feed stream comprises one or more compounds selected from the group consisting of acetic acid, acetic anhydride, acetaldehyde, ethyl acetate, and mixtures thereof. These other compounds can also be hydrogenated in the process of the invention. In some embodiments, the presence of a carboxylic acid, such as propionic acid or its anhydride, can be beneficial for the production of propanol. Water can also be present in the acetic acid feed.

In addition, acetic acid in the form of a vapor from a flash tank of a methanol carbonylation unit introduced as described in U.S. Patent No. 6,657,078, which is incorporated herein by reference in its entirety, is incorporated herein by reference. For example, the crude steam product can be fed directly into the ethanol synthesis reaction zone of the present invention without the need to condense acetic acid and light ends, or remove water, thereby saving overall processing costs.

The acetic acid can be evaporated at the reaction temperature, and the evaporated acetic acid can be fed to the reactor together with hydrogen in an undiluted state or hydrogen diluted with a relatively inert carrier gas such as nitrogen, argon, helium or carbon dioxide. In order for the reaction to operate in the gas phase, the temperature in the system should be controlled so that the temperature is not below the dew point of acetic acid. In one embodiment, acetic acid can evaporate at the boiling point of acetic acid at a particular pressure, and then the evaporated acetic acid can be further heated to the reactor inlet temperature. In another embodiment, the acetic acid is mixed with other gases prior to evaporation and then the mixed vapor is heated to the reactor inlet temperature. Preferably, the temperature is equal to or lower than At 125 ° C, hydrogen and/or recovered gas is passed through the acetic acid to transfer the acetic acid to a vapor state, which is then heated to the reactor inlet temperature.

A number of configurations can be used in some embodiments of the hydrogenation of acetic acid to form an ethanol process, including fixed bed reactors or fluidized bed reactors. In many embodiments of the invention, an "adiabatic" reactor can be used; that is, in such embodiments, there is little or no need to pass an internal conduit into the reaction zone for heat addition or removal. In other embodiments, a radial flow reactor or a reactor set can be used, or a series of reactors can be used, with or without heat exchange, quenching, or introducing more feed. In addition, a shell-and-tube reactor having a heat transfer medium can be used. In many cases, the reaction zone can be disposed within a vessel or a series of vessels (sets) in which the heat exchanger is interposed.

In a preferred embodiment, the catalyst is used in a fixed bed reactor, such as in the form of a pipe or tube, wherein the reactants are typically delivered in the form of steam or through a catalyst. Other reactors may be employed, such as fluidized or bunk bed reactors. In some cases, the hydrogenation catalyst can be combined with an inert material to adjust the pressure drop of the reactant stream through the catalyst bed and the contact time of the reactants with the catalyst particles.

The hydrogenation reaction can be carried out in the liquid phase or in the gas phase. Preferably, the reaction is carried out in the gas phase under the following conditions. The reaction temperature may range from 125 ° C to 350 ° C, for example, from 200 ° C to 325 ° C, from 225 ° C to 300 ° C, or from 250 ° C to 300 ° C. The pressure ranges from 10 kilopascals (kPa) to 3,000 kilopascals, for example, from 50 kilopascals to 2,300 kilopascals, or from 100 kilopascals to 1,500 kilopascals. The "vapor hourly space velocity" (GHSV) of the reactant feed to the reactor can be above at least 500/hour, for example: above at least 1,000/hour, above at least 2,500/hour, and even above at least 5,000/hour. In terms of ranges, GHSV can range from 50/hour to 50,000/hour, for example: from 500/hour to 30.000/hour, from 1.000/hour to 10.000/hour, or from 1,000/hour to 6,500/hour.

The hydrogenation can optionally be carried out at a selected vapor hourly space velocity (GHSV) sufficient to overcome the pressure of the catalytic bed pressure drop, although there is no limit to the use of higher pressures, but it should be understood at high space velocity (GHSV), for example, A 5000/hour or 6,500/hour pass through the reactor bed would result in considerable pressure drop.

Although the reaction consumes two moles of hydrogen per mole of acetic acid to produce one mole of ethanol, the molar ratio of hydrogen to acetic acid in the actual feed stream may vary from 100:1 to 1:100. , for example, from 50:1 to 1:50, from 20:1 to 1:2, or from 12:1 to 1:1. Preferably, the molar ratio of hydrogen to acetic acid is above 2:1, such as above 4:1 or above 8:1.

Contact or residence times are also very different depending on the amount of acetic acid, catalyst, reactor, temperature and pressure. Typical contact times range from less than 1 second to more than a few hours. If a catalyst system other than a fixed bed is used, the preferred contact time for the gas phase reaction is from 0.1 second to 100 seconds, for example from 0.3 to 80 seconds, or 0.4 seconds to 30 seconds.

Hydrogenation of acetic acid to form ethanol is preferably carried out in the presence of a hydrogenation catalyst. Suitable hydrogenation catalysts comprise a metal catalyst comprising a first metal and any one or more second metals, a third metal or any of several other metals, optionally supported on a catalyst support. The first metal and the optional second metal and third metal are selected from the group consisting of transition metals of Groups IB, IIB, IIIB, IVB, VB, VIB, VIIB, Group VIII, lanthanide metals, lanthanide metals or selected Any metal from the group of Groups IIIA, IVA, VA or VIA of the Periodic Table of the Elements. Preferred metal combinations in some typical catalyst compositions include platinum/tin, platinum/ruthenium, platinum/ruthenium, palladium/iridium, palladium/ruthenium, cobalt/palladium, cobalt/platinum, cobalt/chromium, cobalt/ruthenium , cobalt/tin, silver/palladium, copper/palladium, copper/zinc, nickel/palladium, gold/palladium, rhodium/ruthenium and iridium/iron. Typical catalysts are further described in U.S. Patent Nos. 7,608,744 and 7, 863, 489, the disclosure of each of which is incorporated herein by reference. In another embodiment, the catalyst comprises a cobalt/molybdenum/sulfur type of catalyst as described in U.S. Patent Application Publication No. 2009/0069609, the entire disclosure of which is incorporated herein by reference.

In one embodiment, the catalyst comprises a first metal selected from the group consisting of copper, iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, titanium, zinc, chromium, lanthanum, molybdenum, and tungsten. group. Preferably, the first metal is selected from the group consisting of platinum, palladium, cobalt, nickel and ruthenium. More preferably, the first metal is selected from the group consisting of platinum and palladium. In one embodiment of the invention, when the first metal-based platinum, preferably the catalyst, has a platinum content of no more than 5% by weight, such as less than 3% by weight or less than 1% by weight, due to the high commercial demand for platinum. And caused by expensive prices.

As noted above, in some embodiments, the catalyst can optionally also comprise a second metal that will generally act as a promoter. If present, the second metal is preferably selected from the group consisting of copper, molybdenum, tin, chromium, iron, cobalt, vanadium, tungsten, palladium, platinum, rhodium, ruthenium, manganese, osmium, iridium, gold, and nickel. group. More preferably, the second metal is selected from the group consisting of copper, tin, cobalt, ruthenium and nickel. More preferably, the second metal is selected from the group consisting of tin and antimony.

If the catalyst comprises two or more metals, such as a first metal and a second metal, the first metal may be used in an amount of from 0.1 to 10% by weight, such as from 0.1 to 5% by weight, or from 0.1 to 3% by weight. . The second metal is preferably used in an amount of from 0.1 to 20% by weight, for example from 0.1 to 10% by weight, or from 0.1 to 5% by weight. For a catalyst containing two or more metals, the two or more metals may be metal compounds or mixtures which may be alloys with each other or may comprise non-alloys.

The preferred metal ratios may vary slightly depending on the type of metal used in the catalyst. In some embodiments, the first metal to the second metal molar ratio is preferably from 10:1 to 1:10, for example: 4:1 to 1:4, 2:1 to 1:2, 1.5:1 to 1 : 1.5, or 1.1:1 to 1:1.1.

The catalyst may also comprise a third metal, which may be selected from any of the first or second metals listed above, as long as the third metal is different from the first metal and the second metal. In a preferred aspect, the third metal is selected from the group consisting of cobalt, palladium, rhodium, copper, zinc, platinum, tin, and antimony. More preferably, the third metal is selected from the group consisting of cobalt, palladium and rhodium. If present, the total weight of the third metal is from 0.05 to 4% by weight, for example from 0.1 to 3% by weight, or from 0.1 to 2% by weight.

In addition to one or more metals, in some embodiments of the invention the catalyst further comprises a support or a modified support. The term "modified support" as used herein means that the support comprises a support material and a support modifier that modulates the acidity of the support material.

The total weight of the support or modified support is preferably from 75% to 99.9% by weight of the total weight of the catalyst, for example from 78% to 97% by weight, or from 80% to 95% by weight. In a preferred embodiment of the preferred embodiment using the modified support, the support modifier content is from 0.1% by weight to 50% by weight based on the total weight of the catalyst, For example: from 0.2% by weight to 25% by weight, from 0.5% by weight to 15% by weight, or from 1% by weight to 8% by weight. The metal of the catalyst may be dispersed throughout the support, coated over the entire support, overlaid on the outer layer of the support (like an eggshell shell) or coated on the surface of the support.

Those skilled in the art will recognize that the support material is selected such that the contact medium has suitable activity, selectivity and stability robustness under the process conditions for forming ethanol.

Suitable support materials may include, for example, a stable metal oxide based support or a ceramic support. Preferred supports comprise a ruthenium-containing support such as ruthenium dioxide, ruthenium oxide/alumina, Group IIA ruthenate such as calcium metasilicate, pyrogenic ruthenium dioxide, high purity ruthenium dioxide and mixtures thereof. Other supports include, but are not limited to, iron oxide, aluminum oxide, titanium dioxide, zirconium oxide, magnesium oxide, carbon, graphite, high surface area graphitized carbon, activated carbon, and mixtures thereof.

As stated, the catalyst support may be modified by the support modifier. In some embodiments, the support modifier may be an acidic modifier that increases the acidity of the catalyst. Suitable for acidic support modifiers may be selected from the group consisting of Group IVB metal oxides, Group VB metal oxides, Group VIB metal oxides, Group VIIB metal oxides, Group VIIIB metal oxides, aluminum oxides, and mixtures thereof. group. The acidic support modifiers include those selected from the group consisting of titanium dioxide, zirconium oxide, cerium oxide, cerium oxide, aluminum oxide, boron oxide, phosphorus oxide, and antimony trioxide. The acidic support modifiers include those selected from the group consisting of titanium dioxide (TiO ₂ ), zirconium oxide (TiO ₂ ), niobium oxide (Nb ₂ O ₅ ), tantalum oxide (Ta ₂ O ₅ ), aluminum oxide (Al ₂ O ₃ ), A group consisting of boron oxide (B ₂ O ₃ ), phosphorus pentoxide (P ₂ O ₅ ), and antimony trioxide (Sb ₂ O ₃ ). Preferred acidic support modifiers include those selected from the group consisting of titanium dioxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), niobium oxide (Nb ₂ O ₅ ), tantalum oxide (Ta ₂ O ₅ ), and aluminum oxide (Al _{2 ).} O ₃ ) The group consisting of. The acid modifier may also include tungsten oxide (WO ₃ ), molybdenum oxide (MoO ₃ ), ferric oxide (Fe ₂ O ₃ ), chromium oxide (Cr ₂ O ₃ ), vanadium oxide (V ₂ O _{5 ).} ), manganese dioxide (MnO ₂ ), copper oxide (CuO), cobalt oxide (Co ₂ O ₃ ) or bismuth oxide (Bi ₂ O ₃ ).

In another embodiment, the support modifier may be an alkaline modifier with low or no volatility. Such a basic modifier, for example, may be selected from the group consisting of (i) an alkaline earth metal oxide, (ii) an alkali metal oxide, (iii) an alkaline earth metal metasilicate, (iv) an alkali metal metasilicate, (v) Group IIB metal oxides, (vi) Group IIB metal metasilicates, (vii) Group IIIB metal oxides, (viii) Group IIIB metal metasilicates, and mixtures thereof. In addition to oxides and metasilicates, other types of modifiers including nitrates, nitrites, acetates and lactates can also be used. The alkaline support modifier is selected from the group consisting of oxides of sodium, potassium, magnesium, calcium, strontium, barium, and zinc and bismuth citrate, and mixtures of any of the foregoing. A preferred support modifier is calcium citrate, and more preferably calcium metasilicate (CaSiO ₃ ). If the support modifier comprises calcium metasilicate, it is preferred that at least a portion of the calcium metasilicate is in crystalline form.

A preferred ceria support material is SS61138 high surface (HSA) ceria catalyst carrier (Saint-Gobain NorPro). The SS61138 cerium oxide comprises about 95% by weight of high surface area cerium oxide; the surface area is about 250 square meters per gram; the median pore diameter is about 12 nm measured by a mercury extrusion type pore analyzer, and the average pore volume is about 1.0 cubic centimeter. / gram; and the reactor reactor density of about 0.352 grams / cubic centimeter (22 pounds / cubic foot).

A preferred cerium oxide/alumina support material is KA-160 cerium oxide (Süd Chemie) having a nominal diameter of about 5 mm, a density of about 0.562 g/cc, and an absorbance of about 0.583 gram water/gram of support. The surface area is about 160 to 175 square meters per gram, and the pore volume is about 0.68 milliliters per gram.

The catalyst suitable for use in the present invention is preferably obtained by impregnating a metal with a modified support, but other processes such as chemical vapor deposition may also be used. This impregnation technique is described in U.S. Patent Nos. 7,608,744 and 7, 863, 489, the disclosure of which is incorporated herein by reference.

In particular, hydrogenation of acetic acid achieves good acetic acid conversion and good selectivity to ethanol and yield. For the purposes of the present invention, "conversion" means the amount of a compound other than acetic acid converted to acetic acid in the feed. The conversion is expressed as the molar ratio of acetic acid in the feed. Conversion rate can be at least 10%, for example, at least 20%, at least 40%, at least 50 %, at least 60%, at least 70%, or at least 80%. While it is desirable for the catalyst to have a higher conversion, such as a conversion of at least 80% or at least 90%, in some embodiments, a lower conversion is acceptable if there is a high selectivity to ethanol. This is of course well understood. In many cases, the conversion rate can be compensated by a suitable recycle stream or by using a larger reactor, but the difference in selectivity is difficult to compensate.

"Selection rate" is expressed as the percentage of moles of acetic acid converted. It should be recognized that each compound converted from acetic acid has an independent selectivity, and the selectivity is also independent of the conversion. For example, if 60 mole % of acetic acid is converted to ethanol, we mean that the selectivity for ethanol is 60%. Preferably, the catalyst has a selectivity to ethoxylate of at least 60%, for example at least 70%, or at least 80%. The term "ethoxylated compound" as used herein specifically refers to ethanol, acetaldehyde and ethyl acetate. Preferably, the selectivity for ethanol is above 80%, for example: at least 85% or at least 88%. It is also preferred in embodiments of the invention to have lower selectivity for undesirable products such as methane, ethane and carbon dioxide. The selectivity of these unanticipated products is less than 4%, such as less than 2% or less than 1%. Preferably, these undesired products are not detected during the hydrogenation process. In some embodiments of the invention, the formation rate of alkanes is low, typically less than 2%, often less than 1%, and in many cases less than 0.5% of the acetic acid is converted to alkanes by a catalyst, and the alkanes are used as fuel. It doesn't have much value.

"Yield" refers to the number of grams of a particular product, such as ethanol, formed per gram of catalyst per hour in the hydrogenation process. The yield is at least 100 grams of ethanol per gram of catalyst per hour, for example: at least 400 grams of ethanol per gram of catalyst per hour or preferably at least 600 grams of ethanol. In terms of range, the yield is preferably from 100 to 3,000 grams of ethanol per gram of catalyst per hour, for example: 400 to 2,500 grams or 600 to 2,000 grams of ethanol.

Operating under the conditions of the present invention, the level of ethanol production can be at least 0.1 tons of ethanol per hour, for example, at least 1 ton of ethanol per hour, at least 5 tons of ethanol per hour, or at least 10 tons of ethanol per hour. Larger scale industrial production of ethanol, depending on size, should generally have at least 1 ton of ethanol per hour, for example: at least 15 tons of ethanol per hour or at least 30 tons of ethanol per hour. In terms of scope, for large-scale industrial production of ethanol, the process of the invention can produce from 0.1 to 160 tons of ethanol per hour, for example: hourly From 15 to 160 tons of ethanol or from 30 to 80 tons of ethanol per hour. If ethanol is produced by fermentation, it is generally not suitable to implement an embodiment in which ethanol is produced in a single facility in the embodiment of the present invention due to economic scale considerations.

In various embodiments of the invention, the crude ethanol product produced by the hydrogenation process typically comprises unreacted acetic acid, ethanol and water prior to any subsequent processing, such as purification and separation. The term "ethanol crude product" as used herein refers to any composition comprising from 5 to 70% by weight of ethanol and from 5 to 40% by weight of water. A typical composition range of the crude ethanol product is provided in Table 1. "Others" as defined in Table 1 may include, for example, esters, ethers, aldehydes, ketones, alkanes, and carbon dioxide.

In one embodiment, the crude ethanol product comprises acetic acid in an amount less than 20% by weight, such as less than 15% by weight, less than 10% by weight or less than 5% by weight. In embodiments having a lower amount of acetic acid, the conversion of acetic acid is preferably greater than 75%, such as greater than 85%, or greater than 90%. In addition, the selectivity of ethanol may also be preferably higher, preferably greater than 75%, such as greater than 85% or greater than 90%.

Ethanol recovery

A typical ethanol recovery system in accordance with an embodiment of the present invention is shown in Figures 1, 2 and 3. According to one embodiment of the invention, each hydrogenation/purification system 100 provides a suitable hydrogenation reactor and a separation system that separates the ethanol from the crude reaction mixture. System 100 includes a first reaction zone 101 and a separation zone 102. The first reaction zone 101 includes a reactor 103, a hydrogen feed line 104, and an acetic acid feed line 105. The separation zone 102 includes a flash column 106 and a separation device, such as a first distillation column 107.

Hydrogen and acetic acid are fed to evaporator 108 via line 104 and line 105, respectively, and a vapor feed stream is established in line 109 and directed to first reactor 103. In one embodiment, the line 104 and the line 105 can be combined and fed to the evaporator 108. Preferably, the temperature of the steam inflow in line 109 is from 100 ° C to 350 ° C, such as from 120 ° C to 310 ° C, or from 150 ° C to 300 ° C. Any unvaporized feed is removed from evaporator 108 and can be recycled or discarded. Further, although the line 109 is shown as being introduced into the top of the reactor 103 as shown, it may be introduced into the side, upper or bottom of the reactor 103. Further modifications and other component components of reaction zone 101 and separation zone 102 are described below.

The first reactor 103 comprises a catalyst for the hydrogenation of a carboxylic acid, preferably acetic acid. In one embodiment, one or more guard beds (not shown) may be used upstream of the reactor to prevent the catalyst from contacting poisons or undesirable impurities contained in the feed or return/circulation streams. Such a guard bed can be used for a steam stream or a liquid stream. Suitable guard bed materials may include, for example, carbon, cerium oxide, aluminum oxide, ceramics or resins. In one aspect, the guard bed media is functionalized to capture a particular species, such as sulfur or a halogen. In the hydrogenation process, it is preferred to continuously withdraw the crude ethanol product from reactor 103 through line 110.

The crude ethanol product stream in line 110 can be condensed and passed to separator 106, which in turn provides steam stream 111 and liquid stream 112. Of course, flash column 106 can be replaced with other suitable separators. As an example, a knock-out pot can be employed. Flash column 106 can be operated at a temperature of from 20 ° C to 250 ° C, for example, from 30 ° C to 225 ° C or from 60 ° C to 200 ° C. The pressure of the flash column 106 can range from 50 kPa to 2,000 kPa, for example, from 75 kPa to 1,500 kPa or 100 to 1,000 kPa. Or, in line 110 The crude ethanol product can be separated from hydrogen and/or other non-condensable gases by one or more separation membranes (not shown in Figure 1).

The vapor stream 111 exiting the flash column 106 can comprise hydrogen and hydrocarbons that can be purged off and/or returned to the first reaction zone 101. As indicated above, the vapor stream 111 is combined with the hydrogen feed 104 and fed into the evaporator 108 in common. In some embodiments, the returned steam stream 111 can be compressed prior to combining the hydrogen feed 104.

The liquid stream 112 from the flash column 106 is pumped and pumped to the separation unit 107. Although Figure 1 shows a distillation column, the separation unit can be any suitable separation device, such as a membrane separation device. In the case of using a distillation column, such a distillation column may be referred to as an "acid separation distillation column". In one embodiment, the composition of liquid stream 112 is substantially the same as the crude ethanol product obtained from the reactor, except that there is substantially no hydrogen, carbon dioxide, methane or ethane in the composition because it has been Remove. Thus, liquid stream 112 can also be referred to as a crude ethanol product. A typical composition of liquid stream 112 is provided in Table 2. It should be understood that the liquid stream 112 may contain other components not listed, such as components from the feed.

The amount shown below (<) in the entire application form is preferably absent, if present, only trace amounts may be present, or greater than 0.0001% by weight.

The "other esters" in Table 2 may include, but are not limited to, ethyl propionate, methyl acetate, isopropyl acetate, n-propyl acetate, butyl acetate or a mixture thereof. The "other ethers" in Table 2 may include, but are not limited to, diethyl ether, methyl ethyl ether, isobutyl ethyl ether or a mixture thereof. The "other alcohols" in Table 2 may include, but are not limited to, methanol, isopropanol, n-propanol, n-butanol or a mixture thereof. In one embodiment, liquid stream 112 may comprise propanol, such as isopropanol and/or n-propanol, in an amount from 0.001 to 0.1% by weight, from 0.001 to 0.05% by weight or from 0.001 to 0.03% by weight. It should be understood that these other ingredients may be carried by any of the distillates or residue streams described herein and will not be further described herein unless otherwise noted.

Optionally, the ethanol crude product or liquid stream 112 in line 110 can be further fed to an esterification reactor, a hydrogenolysis reactor (discussed below), or a combination of both. The esterification reactor can be used to consume acetic acid present in the crude ethanol product, further reducing the amount of acetic acid to be removed.

In the embodiment illustrated in Figure 1, liquid stream 112 is introduced below first distillation column 107, for example, the lower third or lower third of the lower portion. In one embodiment, no entrainer is added to the first distillation column 107. In the first distillation column 107, a major amount of ethanol, water, acetic acid, and other heavy fractions, if any, are preferably continuously withdrawn from the liquid stream 112 as a residue in the line 114. . The first distillation column 107 also forms an overhead which is pumped by line 115 and which can be condensed and refluxed, for example, at a reflux ratio of from 10:1 to 1:10, for example, from 3:1 to 1 :3, or reflow from 1:2 to 2:1. In one embodiment, it is preferred to operate at a reflux ratio of less than 5:1.

According to the invention, the hydrolysis reaction can be used to convert acetals in the crude ethanol product. In some embodiments, the hydrolysis reaction is carried out in conjunction with the separation of the first separation unit 107. Preferably, the diethyl acetal is converted to ethanol and/or acetaldehyde. Figure 1 shows a second reaction zone 113 for the hydrolysis of at least a portion of the acetals in the crude ethanol product. In Fig. 1, the second reaction zone 113 is shown as a reaction bed, such as an ion exchange resin reaction bed. Preferably, the ion exchange resin reaction bed 113 is a gel or a large mesh bed. As shown in FIG. 1, in one embodiment, the second reaction zone 113 is within the separation device 107, and the contents of the liquid stream 112 can pass through the separation device 107 and be directed to the second reaction zone 113. In some embodiments, the ion exchange resin reaction bed 113 is placed above the point at which the liquid stream 112 is introduced into the separation device 107. In other embodiments, the ion exchange resin reaction bed 113 is placed below the point at which the liquid stream 112 is introduced into the separation unit 107. A similar internal ion exchange resin reaction bed can also be used in one or more other distillation columns if there are other distillation columns in the separation zone. Although FIG. 1 shows the second reaction zone 113 as a reaction bed, the second reaction zone 113 may be any reaction zone suitable for carrying out a hydrolysis reaction.

In the case where the separation unit 107 is a distillation column, the distillation column 107 can be operated at a pressure of about 170 kPa, and the temperature at the residue of the line 114, such as the by-product stream 114, is preferably from 90 ° C to 130 °. For example, from 95 ° C to 120 ° C, or from 100 ° C to 115 ° C. The bottom of the distillation column 107 can be maintained at a relatively low temperature to pump a residual stream comprising water and acetic acid, thereby providing an energy efficiency advantage, accompanied by a conversion advantage obtained by the hydrolysis reaction. The temperature of the distillate of the discharge line 115 is preferably from 60 ° C to 90 ° C, for example, from 65 ° C to 85 ° C, or from 70 ° C to 80 ° C. In some embodiments, the first distillation column 107 can have a pressure ranging from 0.1 kPa to 510 kPa, for example, from 1 kPa to 475 kPa, or from 1 kPa to 375 kPa. A typical composition of the distillate and residue of the first distillation column 107 is provided in Table 3 below. It should also be understood that the distillate and residue may also contain other ingredients not listed, such as ingredients from the feed. For convenience, the distillate and residue of the first distillation column may also be referred to as "first distillate" or "first residue." Distillates or residues of other distillation columns may also have similar numerical modifiers (second, third, etc.) to distinguish one another, but such modifications are not to be construed as requiring any particular order of separation.

In one embodiment, the acetic acid concentration in the residue may be less than 3% by weight at high conversions above 90%, for example from 0.5 to 3 weights from 1% or 2.9% by weight. Furthermore, at low acetic acid conversions, for example below 50%, the water concentration in the residue may be less than 30% by weight or less than 20% by weight, while the acetic acid concentration in the residue may be higher than 40% by weight, for example high It is 60% by weight or higher than 80% by weight.

In another embodiment, the reaction bed does not require a hydrolysis reaction. In some cases, the acetal in the distillation column 107 can be decomposed, for example, hydrolyzed, so that the content of the acetal remaining in the distillate or residue is very low, or even undetectable. In these cases, distillation column 107 will include a second reaction zone 113.

Further, an equilibrium reaction between acetic acid and ethanol or ethyl acetate and water may occur in the crude ethanol product after exiting the reactor 103. This equilibrium may tend to form ethyl acetate depending on the concentration of acetic acid in the crude ethanol product. This reaction can be adjusted by the residence time and/or temperature of the crude ethanol product.

Depending on the amount of water and acetic acid contained in the by-product stream, for example, the residue exiting the first separation unit can be treated by a suitable separation process, some of which are discussed herein. child. It should be understood that any of the following methods can be employed regardless of the concentration of acetic acid. If a by-product stream, such as a residue of a first distillation column, contains a major amount (mostly) of acetic acid, for example more than 70% by weight of acetic acid, the residue can be recycled back to the reactor without having to do any Water separation. In one embodiment, if the by-product stream contains a major portion (eg, greater than 50% by weight) of acetic acid, the by-product stream can be separated into an acetic acid stream and an aqueous stream. In some embodiments, acetic acid can also be recovered from a by-product stream having a lower acetic acid concentration. The by-product stream can be separated into acetic acid and aqueous streams by distillation columns or one or more separation membranes or by pressure swing adsorption. In one embodiment, at least a portion of the water in the byproduct stream 114 is recovered. Then, preferably, at least a portion of this recovered water can be delivered to the second reaction zone. In one embodiment, the water in the by-product stream is recovered by passing the by-product stream through a pressure swing adsorption unit. In another embodiment, the water in the by-product stream is recovered by passing the by-product stream through a membrane separation unit. In both cases, a dry by-product stream and an aqueous stream are produced. If the separation membrane or separation membrane array is used to separate acetic acid from water, the separation membrane or separation membrane array can be selected from any suitable acid resistant membrane capable of removing the permeate water stream. The acetic acid stream obtained can optionally be returned to the first reactor. As indicated above, the aqueous stream obtained can be introduced into the second reaction zone to hydrolyze the acetals. In another embodiment, water can be used as an extractant for other separation devices.

In other embodiments, such as where the by-product stream comprises less than 50% by weight acetic acid, possible measures include one or more of the following options: (i) returning a portion of the residue to reactor 103, (ii) neutralizing Acetic acid, (iii) reacting acetic acid with an alcohol, or (iv) treating the residue at a wastewater treatment facility. It is also possible to separate a by-product stream comprising 50% by weight of acetic acid by means of a weak acid recovery distillation column, to which a solvent (optionally as an entraining agent) can be added. Typical solvents suitable for this purpose may include ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, vinyl acetate, diisopropyl ether, carbon disulfide, tetrahydrofuran, isopropanol, ethanol, and C ₃ -C ₁₂ alkane. When the acetic acid is neutralized, it is preferred that the residue contains less than 10% by weight of acetic acid. The acetic acid can be neutralized with any suitable alkali or alkaline earth metal base such as sodium hydroxide or potassium hydroxide. When acetic acid is reacted with ethanol, it is preferred that the residue comprises less than 50% by weight of acetic acid. The alcohol can be any suitable alcohol such as methanol, ethanol, propanol, butanol or mixtures thereof. The ester forming reaction can be combined with other systems, such as carbonylation production or ester production processes. Preferably, the alcohol comprises ethanol and the ester obtained comprises ethyl acetate. Optionally, the obtained ester can be fed to a hydrogenation reactor.

In some embodiments, if the second residue comprises a very small amount of acetic acid, such as less than 5% by weight acetic acid, the second residue can be directly discharged to the wastewater treatment facility without further processing. The organic matter in the residue, such as acetic acid, can be advantageously adapted to feed the microorganisms used in the wastewater treatment plant.

The refined ethanol stream in line 115 is preferably ethyl acetate, acetaldehyde, and water comprising ethanol and optionally selectivity. The final ethanol product can be derived from the refined ethanol stream of line 115. In one embodiment, if a distillation column is employed as the first separation unit, the weight ratio of water in the distillate to water in the residue is above 1:1, such as above 2:1, or above 4: 1. Furthermore, the weight ratio of acetic acid in the residue to acetic acid in the distillate may optionally be higher than 10:1, for example, above 15:1, or above 20:1. Preferably, the distillate in line 114 is substantially free of acetic acid and, if any, contains only traces of acetic acid.

Where the first separation unit produces a refined ethanol stream 115 wherein the hydrolysis step has removed at least a portion of the acetals, one or more additional distillation columns or separation units can be used to recover the resulting final ethanol product.

For example, Figure 2 shows a separation flow diagram using a multiple distillation column. Preferably, the distillate in line 115 contains ethanol, ethyl acetate, water, and other impurities, but this may be difficult to separate due to the formation of a binary azeotrope and a ternary azeotrope. To further separate the distillate, line 115 is directed to a second distillation column 123, also referred to as a "light fraction distillation column", preferably to the middle portion of distillation column 123, for example, a half portion in the middle or One third of the middle. Preferably, the second distillation column 123 is an extractive distillation column and an extractant is added via line 124 and/or line 125. The extractive rectification is a method of distilling a feed in the presence of an extractant to separate a component having a boiling point close to, for example, an azeotrope. Preferably, the boiling point of the extractant is higher than the compound to be separated in the feed. In a preferred embodiment, the extractant consists essentially of water. As described above, the first distillate fed to the line 115 of the second distillation column 123 contains ethyl acetate, ethanol, and water. These compounds often form a binary Azeotrope and ternary azeotrope reduce separation efficiency. As shown, in one embodiment the extractant comprises a third residue from line 124. Preferably, the third residue recirculated in line 124 is fed to the second distillation column 123 at a point above the feed point of the first distillate of line 115. In one embodiment, the third residue recycled in line 124 is fed near the top of second distillation column 123, or fed, for example, above the feed of line 115, and below the overhead from the condensing column. The return line of the product. In the tray distillation column, the third residue in the line 124 is continuously added to the vicinity of the top of the second distillation column 123, so that a considerable amount of the third residue exists in the liquid phase in all of the lower trays. In another embodiment, the extractant is fed from the external source of process 100 through line 125 to second distillation column 123. Preferably, the extractant comprises water.

The water of the extractant is preferably at least 0.5:1, for example at least 1:1, or at least 3:1, for the molar amount of ethanol fed to the second distillation column feed. In terms of range, the preferred molar ratio is from 0.5:1 to 8:1, for example, from 1:1 to 7:1, or from 2:1 to 6.5:1. A higher molar ratio can be used, but in the case of additional ethyl acetate in the second distillate of the second distillation column and a decrease in the ethanol concentration in the second distillate, the return is reduced.

In one embodiment, additional extractant, such as water from an external source, dimethyl hydrazine, glycerin, diethylene glycol, 1-naphthol, hydroquinone, N, N'-dimethylformamide , 1,4-butanediol, glycol-1,5-pentanediol, propylene glycol-tetraethylene glycol-polyethylene glycol, glycerol-propylene glycol-tetraethylene glycol-1,4-butanediol, diethyl ether, formic acid Methyl ester, cyclohexane, N,N'-dimethyl-1,3-propanediamine, N,N'-dimethyl-ethylenediamine, diethyltriamine, hexamethylenediamine, 1,3 - Diamine pentane, alkylated thiophene, dodecane, tridecane, tetradecane, chlorinated paraffin or a combination thereof may be added to the second distillation column 123. Some suitable extractants include those described in U.S. Patent Nos. 4,379,028, 4,569,726, 5,993, 610, and 6, 375, 807, the entire disclosures of The additional extractant can be combined with the third residue recycled in line 124 and fed together into second distillation column 123. Additional extractants may also be added to the second distillation column 123, respectively. In one aspect, the extractant comprises an extractant, for example, water derived from line 125, but no extractant is derived from the third residue.

The second distillation column 123 may be a tray distillation column or a packed distillation column. In one embodiment, the second distillation column 123 is a tray distillation column having 5 to 70 trays, such as From 15 to 50 trays, or from 20 to 45 trays. Although the temperature and pressure of the second distillation column 123 may vary, at atmospheric pressure, the temperature of the second residue discharged in the line 126 is preferably from 60 ° C to 90 ° C, for example, from 70 ° C to 90 ° °C, or 80 ° C to 90 ° C. The temperature of the second distillate discharged from the second distillation column 123 via the line 127 is preferably from 50 ° C to 90 ° C, for example, from 60 ° C to 80 ° C, or from 60 ° C to 70 ° C. Distillation column 123 can be operated at atmospheric pressure. In other embodiments, the second distillation column 123 may have a pressure ranging from 0.1 kPa to 510 kPa, for example, from 1 kPa to 475 kPa, or from 1 kPa to 375 kPa. Typical compositions of the distillate and residue of the second distillation column 123 are provided in Table 4 below. It should be understood that the distillate and residue may also contain other ingredients not listed, such as ingredients in the feed.

In a preferred embodiment, the recycle of the third residue promotes the separation of ethyl acetate from the residue of the second distillation column 123. For example, the ethyl acetate of the second residue is preferably less than 0.4:1, such as less than 0.2:1, or less than 0.1:1, based on the weight of the ethyl acetate in the second distillate. Using the second distillation column 123 as an extract with water as an extractant In an embodiment of the distillation column, the weight ratio of ethyl acetate to the ethyl acetate in the second distillate of the second residue approaches zero.

Preferably, the weight ratio of ethanol to second ethanol in the second distillate is at least 3:1, for example, at least 6:1, at least 8:1, at least 10:1, or at least 15:1. . All or part of the third residue is recycled back to the second distillation column. In one embodiment, all of the third residue can be recycled until process 100 reaches a steady state, then a portion of the third residue is recycled and the remainder is purged from system 100. The composition of the second residue will tend to have a lower ethanol content than when the third residue is not recycled. Due to the third residue recycle, the composition of the second residue, as shown in Table 4, comprises less than 30% by weight of ethanol, such as less than 20% by weight or less than 15% by weight of ethanol. Preferably, the second residue comprises primarily water. Despite this effect, the extractive distillation step advantageously reduces the amount of ethyl acetate sent to the third distillation column, which is very beneficial for the eventual formation of a high purity ethanol product.

As shown, the residue from the second distillation column 123, which contains ethanol and water, is passed via line 126 to a third distillation column 128, also referred to as a "product distillation column." More preferably, the second residue in line 126 is introduced below the third distillation column 128, for example, in the lower third or lower third. The ethanol recovered by the third distillation column 128 is preferably pure and substantially free of organic impurities and other azeotropic moisture, as in the distillate in line 129. The distillate of the third distillation column 128 is preferably refluxed, as shown in Fig. 2, for example, at a reflux ratio of from 1:10 to 10:1, such as from 1:3 to 3:1, or From 1:2 to 2:1. The third residue in line 124, which primarily contains water, is preferably returned to second distillation column 123 as an extractant as described above. In one embodiment, the first portion of the third residue in line 124 is recycled back to the second distillation column, while the second portion is purged and removed from the system via line 130. In one embodiment, once the process reaches a steady state, the second portion of water to be purged is substantially the same as the amount of water formed by hydrogenation of acetic acid. In one embodiment, a portion of the third residue can be used to hydrolyze any other stream, such as one or more streams comprising ethyl acetate.

Although Figure 2 shows that the third residue is recycled directly back to the second distillation column 123, the third residue may also be returned indirectly, for example, storing some or all of the third residue in a storage tank (not shown) or processing. A third residue to further separate any minor components, such as aldehydes, higher molecular weight alcohols, or esters in one or more other distillation columns (not shown).

The third distillation column 128 is preferably a tray distillation column as described above which is operated at atmospheric pressure or may be operated at a pressure above or below atmospheric pressure. The temperature of the third distillate discharged via line 129 is preferably from 60 ° C to 110 ° C, for example, from 70 ° C to 100 ° C, or from 75 ° C to 95 ° C. The temperature of the third residue in line 124 is preferably from 70 ° C to 115 ° C, for example, from 80 ° C to 110 ° C, or from 85 ° C to 105 ° C. The typical composition of the distillate and residue of the third distillation column 128 is provided in Table 5 below. It should be understood that the distillate and residue may also contain other ingredients not listed, such as ingredients in the feed.

In one embodiment, the third residue is withdrawn from the third distillation column 128 by line 124 at a temperature above the operating temperature of the second distillation column 123. Preferably, prior to returning to the second distillation column 123, the third residue of line 124 is integrated to heat one or more other streams or to be boiled again.

Any compound which is passed from the feed or crude reaction product through the distillation process is generally maintained in the third distillate in an amount of less than 0.1% by weight, for example, less than 0.05% by weight or less than 0.02% by weight, the percentage being In terms of the total weight of the three distillate compositions. In one embodiment, one or more of the side streamable systems 100 remove impurities from any of the distillation columns. Preferably, at least one side stream is used to remove impurities from the third distillation column 128. These impurities can be purged and/or retained within system 100.

The third distillate of line 129 can be further purified by using one or more additional separation systems, such as distillation columns, adsorption units, separation membranes or molecular sieves, to form an anhydrous ethanol product stream, ie, "completed anhydrous Ethanol." Suitable adsorption units include pressure swing adsorption units and thermal swing adsorption units.

For the purposes of the present invention, the third distillate in line 129 of Figure 2 is an intermediate stream comprising one or more impurities selected from the group consisting of ethyl acetate, acetic acid, acetaldehyde, and optionally a small amount of acetal. The group formed. In terms of ranges, the total concentration of impurities may range from 0.01% to 12% by weight, for example, from 0.05% to 8% by weight, or from 0.05 to 5% by weight. The process of Figure 2 employs a post-hydrogenation reactor 140. The third distillate in line 129 is condensed and fed to reactor 140 in the liquid phase. If necessary, hydrogen may be supplied to the reactor 140 from the line 113 to react with impurities in the intermediate stream. In addition, hydrogen can be supplied from other sources, such as syngas produced from many carbonaceous feedstocks or purified syngas. Reactor 140 comprises a catalyst as described above which hydrogenates at least 25%, for example at least 50%, or at least 75% of impurities. Preferably, the hydrogenation of the impurities produces an alcohol, and more preferably ethanol. The mixture discharged from the reactor 140 serves as a purified ethanol product 141. The purified ethanol product 141 preferably does not require further liquid-liquid separation to remove impurities and thus does not have to be returned to the separation zone 102. The concentration of one or more impurities in the purified ethanol product 141 is lower than the concentration of one or more impurities in the third distillate (i.e., intermediate stream) of line 129.

The second distillate which is returned to the second distillation column 123 is preferably refluxed as shown in Fig. 2, and optionally has a reflux ratio of 1:10 to 10:1, for example, 1:5 to 5:1. , or 1:3 to 3:1. The second distillate in line 127 can be purged or recycled back to the reaction zone. In one embodiment, the second distillate in line 127 is further processed in a fourth distillation column 131 (also referred to as an "acetaldehyde removal distillation column"). In the fourth distillation column 131, the second distillate is separated into a fourth distillate containing acetaldehyde in the line 132, and a fourth residue containing ethyl acetate in the line 133. The fourth distillate is preferably refluxed at a reflux ratio of from 1:20 to 20:1, for example, from 1:15 to 1:15, or from 10:1 to 10:1, and a portion of the fourth fraction The product is returned to the reaction zone 101. For example, the fourth distillate can be combined with the acetic acid feed and added to the evaporator 108 or added directly to the reactor 103. The fourth distillate is preferably fed to the evaporator 108 along with the acetic acid in the feed line 105. Without being bound by theory, since acetaldehyde can be hydrogenated to form ethanol, a stream comprising acetaldehyde is recycled back to the reaction zone, which can increase ethanol production and reduce by-product and waste generation. In another embodiment, acetaldehyde can be collected and utilized with or without further purification to produce useful products including, but not limited to, n-butanol, 1,3-butanediol, and/or crotonaldehyde and derivatives thereof. .

The fourth residue of the fourth distillation column 131 can be purged by blowing through the line 133. The fourth residue mainly comprises ethyl acetate and ethanol, which are suitable as solvent mixtures or for ester production. In a preferred embodiment, acetaldehyde is removed from the second distillate of fourth distillation column 131 such that the residue of distillation column 131 has no detectable amount of acetaldehyde.

The fourth distillation column 131 is preferably a tray type distillation column as described above, and particularly preferably operated at a pressure of more than atmospheric pressure. In one embodiment, the pressure is from 120 kPa to 5,000 kPa, for example, from 200 kPa to 4,500 kPa, or from 400 KPa to 3,000 kPa. In a preferred embodiment, the fourth distillation column 131 to the operating pressure is higher than the pressure of the other distillation columns.

The temperature of the fourth distillate discharged from line 132 is preferably from 60 ° C to 110 ° C, for example, from 70 ° C to 100 ° C, or from 75 ° C to 95 ° C. The temperature of the residue of the line 133 is preferably from 70 ° C to 115 ° C, for example, from 80 ° C to 110 ° C or from 85 ° C to 110 ° C. The distillate and residue of the fourth distillation column 131 are provided in the following table. 6. It should be understood that the distillate and residue may also contain other ingredients not listed, such as ingredients in the feed.

In one embodiment, a portion of the third residue in line 124 is recycled back to second distillation column 123. In one embodiment, recovering the third residue further reduces the aldehyde component in the second residue, and concentrating the aldehyde component in the second distillate of line 127 to be sent to the fourth distillation column 131, wherein It is easy to separate aldehydes. Due to the recycle of the third residue in line 124, a third distillate in line 129, such as an intermediate stream, may have lower concentrations of aldehydes and esters.

Figure 3 illustrates another typical separation system. The primary reaction zone 101 of Figure 3 is similar to Figures 1 and 2, which produces a liquid stream 112, such as a crude ethanol product, for further separation. In a preferred embodiment, the primary reaction zone 101 of Figure 3 operates at a acetic acid conversion of greater than 80%, such as greater than 90%, or greater than 99%. Thus, the concentration of acetic acid in liquid stream 112 can be lower.

The liquid stream 112 is introduced into the middle or lower portion of the first distillation column 107. In these embodiments, the first distillation column may be referred to as an acid-water distillation column. In an embodiment, no added The entrainer is applied to the first distillation column 107. In FIG. 3, the first distillation column 107 is removed from the liquid stream 112 if water and unreacted acetic acid are present along with any other components, preferably continuously pumping as the first residue in line 114. A product, such as by-product stream 114. Preferably, most of the water in the crude ethanol product fed to the first distillation column 107 can be removed from the first residue, for example, about 75% or about 90% of the water is removed from the crude ethanol product. The first distillation column 107 also forms a first distillate which is pumped in line 115, for example, into a refined ethanol stream 115.

If the distillation column 107 is operated at a pressure of about 170 kPa, the temperature at which the residue is discharged in the line 114 is preferably from 90 ° C to 130 ° C, for example, from 95 ° C to 120 ° C or from 100 ° C to 115 ° C. The temperature of the distillate discharged in line 115 is preferably from 60 ° C to 90 ° C, for example, from 65 ° C to 85 ° C, or from 70 ° C to 80 ° C. In some embodiments, the first distillation column 107 can have a pressure ranging from 0.1 kPa to 510 kPa, for example, from 1 kPa to 475 kPa, or from 1 kPa to 375 kPa.

In addition to ethanol and other organics in the first distillate of line 115, water is also included. In terms of range, the concentration of the first distillate of water in the line 115 is preferably from 4% by weight to 38% by weight, for example, from 7% by weight to 32% by weight, or from 7% by weight to 25% by weight. A portion of the first distillate in line 115 can be condensed and refluxed, for example, from 10:1 to 1:10, for example, from 3:1 to 1:3 or 1:2 to 2:1. Returning. It is understood that the reflux ratio will vary with the number of stages, the location of the feed, the efficiency of the distillation column, and/or the coarseness of the feed. Operation with a reflux ratio above 3:1 may be poor because more energy may be required to operate the first distillation column 107. The condensed portion of the first distillate may also be fed to the second distillation column 154.

The remainder of the first distillate in line 115 is fed to water separator 156. The water separator 156 can be a pressure swing adsorption (PSA) unit, a separation membrane, a molecular sieve, an extractive distillation unit, or a combination thereof. The separation membrane or separation membrane array can also be used to separate water from the distillate. The separation membrane or separation membrane array can be selected from any suitable separation membrane capable of removing the permeate aqueous stream from a stream that also contains ethanol and ethyl acetate.

In a preferred embodiment, water separator 156 is a pressure swing adsorption (PSA) device. The PSA device can optionally operate at temperatures ranging from 30 ° C to 160 ° C, for example, from 80 ° C to 140 ° C, and pressure from 0.01 kPa to 550 kPa, for example, from 1 kPa to 150 kPa. The PSA unit can contain two to five adsorbent beds. The water separator 156 can remove at least 95% of the water from a portion of the first distillate in line 155, preferably from 99% to 99.99% of the water removed from the first distillate in the aqueous stream 157. All or a portion of the aqueous stream 157 can be returned via line 158 to distillation column 107 and/or second reaction zone 113 where the water is preferably ultimately recovered from distillation column 107 in the first residue of line 114. Additionally, alternatively, all or a portion of the aqueous stream 157 can be purged by blowing through line 159. The remainder of the first distillate is passed out of water separator 156 as an ethanol mixture stream 160. The ethanol mixture stream 160 can have a low concentration of water of less than 10% by weight, such as less than 6% by weight or less than 2% by weight. Typical compositions of the first residue of the ethanol mixture stream 160 and line 115 are provided in Table 7 below. It should also be understood that these streams may also contain other ingredients not listed, such as ingredients from the feed.

Preferably, the ethanol mixture stream 160 is not returned or is refluxed to the first distillation column 107. An ethanol mixture stream 160 may be combined in the first distillate condensing portion of line 153 to control the concentration of water fed to second distillation column 154. For example, in some embodiments, the first distillate can be divided into aliquots, while in other embodiments, all of the first distillate can be condensed or all of the first distillate can be processed in a water separator. In Fig. 3, the condensed portion of line 153 and the ethanol mixture stream 160 are fed together to second distillation column 154. In other embodiments, the condensed portion of line 153 and the ethanol mixture stream 160 can be fed to second distillation column 154, respectively. The combined distillate and ethanol mixture has a total water concentration of greater than 0.5% by weight, for example, greater than 2% by weight or greater than 5% by weight. In terms of ranges, the total water concentration of the combined distillate and ethanol mixture can range from 0.5 to 15% by weight, for example from 2 to 12% by weight, or from 5 to 10% by weight.

In the third diagram, the second distillation column 154 is also referred to as a "light fraction distillation column" which removes ethyl acetate and acetaldehyde from the first distillate and/or ethanol mixture stream 160 in line 153. Ethyl acetate and acetaldehyde were removed as the second distillate of line 161 and ethanol was removed as the second residue of line 162. The second distillation column 154 may be a tray distillation column or a packed distillation column. In one embodiment, the second distillation column 154 is a tray distillation column having from 5 to 70 trays, for example from 15 to 50 trays or from 20 to 45 trays.

The pressure operation of the second distillation column 154 ranges from 0.1 kPa to 510 kPa, for example, from 10 kPa to 450 kPa, or from 50 kPa to 350 kPa. Although the temperature of the second distillation column 154 may vary, at a pressure of about 20 kPa to 70 kPa, the second residue temperature of the discharge line 162 is preferably from 30 ° C to 75 ° C, for example From 35 ° C to 70 ° C, or from 40 ° C to 65 ° C. The temperature of the second distillate discharged via line 161 is preferably from 20 ° C to 55 ° C, for example, from 25 ° C to 50 ° C, or from 29 ° C to 45 ° C.

The total water concentration delivered to the second distillation column 154 is preferably less than 10% by weight, as described above. If the first distillate and/or ethanol mixture stream in line 153 contains a small amount of water, for example less than 1% by weight or less than 0.5% by weight, additional water may be fed to the upper portion of second distillation column 154. As an extractant. Preferably, a sufficient amount of water is added through the extractant so that the total concentration of water fed to the second distillation column 154 is from 1 to 10% by weight. For example, from 2 to 6% by weight, the percentage is based on the total weight of all components fed to the second distillation column 154. If the extractant comprises water, the water can be obtained from an external source or recovered/recycled from the interior of one or more other distillation columns or water separators.

Suitable extractants may also include, for example, dimethyl hydrazine, glycerol, diethylene glycol, 1-naphthol, hydroquinone, N,N'-dimethylformamide, 1,4-two Alcohol, ethylene glycol, 1,5-pentanediol; propylene glycol-tetraethylene glycol-polyethylene glycol, glycerol-propylene glycol, tetraethylene glycol-1,4-butanediol, diethyl ether, methyl formate, cyclohexane , N,N'-dimethyl-1,3-propanediamine, N,N'-dimethylethylenediamine, diethylenetriamine, hexamethylenediamine and 1,3-diaminepentane, alkyl Thiophene, dodecane, tridecane, tetradecane, chlorinated paraffin, or a combination thereof. If an extractant is used, the extractant can be recovered using a suitable recovery system, such as another distillation column.

Typical compositions of the second distillate and the second residue of the second distillation column 154 are provided in Table 8 below. It should be understood that the distillate and residue may also contain other ingredients listed in Table 9.

The second residue in Figure 3 is an intermediate stream comprising one or more impurities selected from the group consisting of ethyl acetate, acetic acid, acetaldehyde, and diethyl acetal. The second residue of line 162 may comprise at least 100 ppm by weight, such as at least 250 ppm by weight or at least 500 ppm by weight of these impurities. In some embodiments, the second residue can be substantially free of ethyl acetate or acetaldehyde.

In one embodiment, the second residue of line 162 can be further processed, for example, fed with hydrogen from the main reaction zone into a hydrogenation reactor for processing. Preferably, the second residue is fed in the liquid phase. The post-hydrogenation reactor produces a purified ethanol product having a lower impurity concentration than the second residue. Preferably, the purified ethanol product does not require further liquid-liquid separation to remove impurities and thus does not have to be returned to the separation zone.

Ethanol composition

A typical range of ingredients for the finished ethanol product is provided in Table 9 below.

As shown in Table 9, the ethanol composition completed by the present invention contains no or very few acetals and/or acetates due to the hydrolysis step. Furthermore, the finished ethanol composition of the present invention preferably comprises other alcohols such as methanol, n-butanol, isobutanol, isoamyl alcohol and other C _{4 which} contain very low amounts, for example less than 0.5% by weight. -C ₂₀ alcohols. In one embodiment, the amount of isopropanol in the finished ethanol composition is from 80 to 1,000 ppm by weight, for example, from 95 to 1,000 ppm by weight, from 100 to 700 ppm by weight, or from 150 to 500 ppm by weight. In one embodiment, the finished ethanol composition is substantially free of acetaldehyde, optionally containing less than 8 ppm by weight, such as less than 5 ppm by weight or less than 1 ppm by weight of acetaldehyde.

In some embodiments, if another water separation is performed, the ethanol product can be pumped as the stream from the water separator discussed above. In such embodiments, the ethanol product may have an ethanol concentration greater than that shown in Table 9, and preferably has greater than 97% by weight, such as greater than 98% by weight or greater than 99.5% by weight ethanol. Preferred in this regard is that the ethanol product comprises less than 3% by weight, such as less than 2% by weight or less than 0.5% by weight of water.

The ethanol composition completed in accordance with embodiments of the present invention is suitable for use in a variety of applications, including fuels, solvents, chemical materials, pharmaceuticals, detergents, disinfectants, hydrogen storage or hydrogen consumption. In fuel applications, the finished ethanol composition can be blended with gasoline for use in motor vehicles such as automobiles, boats and small piston engine aircraft. In non-fuel applications, the finished ethanol composition can be used as a solvent, detergent, disinfectant, coating, ink, and pharmaceutical for cosmetic and cosmetic preparations. The finished ethanol composition can also be used as a process solvent for pharmaceutical products, food preparations, dyes, photochemicals, and latex processing.

The completed ethanol composition can also be used as a chemical raw material to manufacture other chemical materials such as vinegar, ethyl acrylate, ethyl acetate, ethylene, glycol ethers, ethylamines, aldehydes, higher alcohols, especially alcohol. In the production of ethyl acetate, the finished ethanol composition can be esterified by acetic acid. In another application, the finished ethanol composition can be dehydrated to produce ethylene. Any of the known dehydration catalysts can be used to dehydrate the ethanol, as described in U.S. Patent Application Publication Nos. 2010/0030002 and 2010/0030001, the entire contents of which are incorporated herein by reference. The zeolite catalyst, for example, can be used as a dehydration catalyst. Preferably, the zeolite has a pore diameter of at least 0.6 nm. Preferably, the zeolite comprises a dehydration catalyst selected from the group consisting of mordenite, ZSM-5, zeolite X and zeolite Y. X-type zeolites are described, for example, in U.S. Patent No. 2,882,244, and Y-type zeolites are described in U.S. Patent No. 3,130,007, the entire disclosure of which is incorporated herein by reference.

It is to be understood that the examples are for illustrative purposes only and are not to be construed as limiting the invention in any way.

While the invention has been described in detail, the various modifications and Relevant knowledge and techniques discussed above The background and detailed description of the literature, the disclosure of which is incorporated herein by reference. In addition, it should be understood that the aspects of the present invention and the various embodiments and the various features and/or the scope of the appended claims may be combined or interchanged in whole or in part. In the description of the various embodiments, the other embodiments mentioned above may be combined with other embodiments as will be understood by those skilled in the art. Furthermore, those skilled in the art will understand that the foregoing description is only illustrative and not intended to limit the scope of the invention.

100‧‧‧Hydrogenation/purification system/process/system

101‧‧‧First reaction zone

102‧‧‧Separation zone

103‧‧‧Reactor

104‧‧‧Hydrogen feed line/hydrogen feed/pipe

105‧‧‧Acetic acid feed line/pipe

106‧‧‧Flash Tower

107‧‧‧First Distillation Tower/Separation Unit/Acid-Water Distillation Tower

108‧‧‧Evaporator

109‧‧‧pipe

110‧‧‧pipe

111‧‧‧Steam flow

112‧‧‧Liquid flow

113‧‧‧Second reaction zone/reaction bed

114‧‧‧Line/by-product stream

115‧‧‧Pipe/refined ethanol flow

123‧‧‧Second Distillation Tower/Light Distillation Distillation Tower

124‧‧‧ pipeline

125‧‧‧pipe

126‧‧‧pipe

127‧‧‧ pipeline

128‧‧‧ Third Distillation Tower/Product Distillation Tower

129‧‧‧pipe

130‧‧‧pipe

131‧‧‧The fourth distillation column / acetaldehyde removal distillation tower

132‧‧‧ pipeline

133‧‧‧pipe

140‧‧‧Reprocessing reactor/reactor

141‧‧‧ Purified ethanol product

153‧‧‧pipe

154‧‧‧Second Distillation Tower/Light Distillation Distillation Tower

155‧‧‧pipe

156‧‧‧Water separator

157‧‧‧Waterborne Logistics

158‧‧‧pipe

159‧‧‧pipe

160‧‧‧Ethanol mixture flow

161‧‧‧pipe

162‧‧‧pipe

The invention is explained in detail below with reference to the various drawings, wherein like numerals refer to the same elements.

Figure 1 shows a flow diagram of a hydrogenation/purification system in accordance with an embodiment of the present invention.

Figure 2 is a flow chart showing a hydrogenation/purification system having a plurality of distillation columns in accordance with one embodiment of the present invention.

Figure 3 is a flow chart showing a hydrogenation/purification system having two distillation columns in accordance with one embodiment of the present invention.

100‧‧‧Hydrogenation/purification system/process/system

101‧‧‧First reaction zone

102‧‧‧Separation zone

103‧‧‧Reactor

104‧‧‧Hydrogen feed line/hydrogen feed/pipe

105‧‧‧Acetic acid feed line/pipe

106‧‧‧Flash Tower

107‧‧‧First Distillation Tower/Separation Unit/Acid-Water Distillation Tower

108‧‧‧Evaporator

109‧‧‧pipe

110‧‧‧pipe

111‧‧‧Steam flow

112‧‧‧Liquid flow

113‧‧‧Second reaction zone/reaction bed

114‧‧‧Line/by-product stream

115‧‧‧Pipe/refined ethanol flow

153‧‧‧pipe

Claims (32)

A process for purifying a crude ethanol product, comprising the steps of: (a) hydrogenating acetic acid in the presence of a first catalyst in a first reaction zone to form a crude ethanol product comprising ethanol, acetaldehyde, acetic acid, water, and acetal (b) separating at least a portion of the crude ethanol product into a refined ethanol stream comprising ethanol and acetaldehyde; and a by-product stream comprising acetic acid and water from a majority of the crude ethanol product; and (c) hydrolyzing at least in the second reaction zone Part of the acetal. The process of claim 1, further comprising the step of feeding at least a portion of the by-product stream back to the second reaction zone. The process of claim 1, further comprising the steps of: recovering at least a portion of the water from the by-product stream; and feeding the recovered water back to the second reaction zone. The process of claim 3, wherein the recovering comprises passing the by-product stream through a pressure swing adsorption system to produce a dry by-product stream and an aqueous stream. The process of claim 3, wherein the recovering comprises passing a by-product stream through the separation membrane to produce a dried by-product stream and an aqueous stream. The process of claim 1, wherein the refined ethanol stream further comprises water, and further comprising the steps of: recovering at least a portion of the water from the refined ethanol stream; feeding the recovered water back to the second reaction zone. The process of claim 1, wherein the acetal comprises diethyl acetal. The process of claim 1, wherein at least a portion of the acetal is hydrolyzed to form additional ethanol. The process of claim 1, wherein at least a portion of the acetal is hydrolyzed to form acetaldehyde and additional ethanol. The process of claim 1, wherein at least one of the crude ethanol product, the refined ethanol product, and the by-product stream further comprises ethyl acetate, and wherein the ethyl acetate is hydrolyzed to form ethanol and acetic acid. The process of claim 1, wherein the step (c) is carried out in the liquid phase. The process of claim 1, wherein the first catalyst is selected from the group consisting of platinum/tin, platinum/ruthenium, platinum/ruthenium, palladium/ruthenium, palladium/ruthenium, cobalt/palladium, cobalt/platinum, cobalt/ A group consisting of chromium, cobalt/ruthenium, silver/palladium, copper/palladium, nickel/palladium, gold/palladium, rhodium/iridium, and rhodium/iron. The process of claim 1, wherein the second reaction zone comprises a second catalyst. For example, the process described in claim 13 wherein the second catalyst is an acidic catalyst. The process of claim 1, wherein the step (b) is carried out in the first distillation column. The process of claim 15 wherein the refined ethanol stream comprises a first distillate and the by-product stream comprises a first residue. The process of claim 15, wherein the first distillation column comprises a second reaction zone. The process of claim 15, wherein the first distillation column is a reactive distillation column. The process of claim 15, further comprising the step of separating at least a portion of the refined ethanol stream in the second distillation column into a second distillate comprising acetaldehyde and a second residue comprising ethanol. The process of claim 19, wherein the second distillation column comprises a second reaction zone. The process of claim 19, wherein the second distillation column has a pressure operating range of from 0.1 kPa to 510 kPa. The process of claim 15, wherein the second reaction zone is disposed outside the first distillation column. The process of claim 1, wherein the step (c) is carried out on a catalyst bed. The process of claim 1, wherein the step (b) is carried out in a membrane separation apparatus. The process of claim 1, wherein the crude ethanol product comprises less than 10% ethyl acetate. The process of claim 1, wherein the crude ethanol product comprises less than 1% by weight of acetal. The process of claim 1, wherein the crude ethanol product comprises from 1% to 30% by weight of water. The process of claim 1, wherein the by-product stream comprises more than 30% by weight water. The process of claim 1, wherein the acetic acid is formed from methanol and carbon monoxide, and each of the methanol, carbon monoxide and hydrogen used in the hydrogenation step are each derived from a synthesis gas, wherein the synthesis gas is derived from a carbon source, A group of free natural gas, crude oil, petroleum, coal, biomass, and combinations thereof. A process for purifying a crude ethanol product, comprising the steps of: (a) hydrogenating acetic acid in the presence of a first catalyst in a first reaction zone to form a crude ethanol product, wherein the crude ethanol product comprises ethanol, acetaldehyde, acetic acid And acetal and ethyl acetate; (b) hydrolyzing the acetal and ethyl acetate from the crude ethanol product in the second reaction zone; and (c) separating at least a portion of the crude ethanol product in the first distillation column to become A first distillate comprising ethanol and acetaldehyde, and a first residue comprising water. The process of claim 30, wherein the first residue further comprises water from the crude ethanol product. The process of claim 31, further comprising the steps of: recovering water from the first residue; and feeding the recovered water back to the first distillation column.