Process and apparatus for producing alcohol

Abstract

A process for producing at least one alcohol is provided. The process comprises providing a crude aldehyde stream comprising at least one aldehyde to at least one liquid phase hydrogenation reactor, and hydrogenating the at least one aldehyde in a liquid phase hydrogenation reaction to provide a crude alcohol stream comprising at least one alcohol; recycling a liquid recycle stream comprising the at least one alcohol to the at least one liquid hydrogenation reactor via a recycle cooler in which heat in the liquid recycle stream is recovered; providing the crude alcohol stream to a distillation column and distilling the crude alcohol stream to obtain a purified alcohol stream comprising the at least one alcohol and a heavy stream comprising the at least one alcohol; providing the heavy stream to a stripping column and contacting the heavy stream with a stripping gas comprising at least 20 mol% of hydrogen to separate the heavy stream into a recycle stream comprising the at least one alcohol and a waste stream; and returning at least a portion of the recycle stream to the at least one liquid phase hydrogenation reactor.

Description

[0001] The present invention relates to a method and an apparatus for producing alcohols. In particular, the method and the apparatus according to the present invention provide an increased yield of synthetic alcohols. Background Art

[0002] Alcohols, especially C1-C 10 Alcohols are widely used in the chemical industry for a variety of applications, including as solvents, fuels, chemical intermediates in the synthesis of organic compounds, etc. A variety of alcohols are produced each year worldwide. For some alcohols (e.g., ethanol), biosynthetic methods such as fermentation can be used to produce the alcohol. However, for longer chain alcohols and branched chain alcohols, synthetic production may be required.

[0003] Existing processes for the synthetic production of alcohols include the hydroformylation of olefins in the presence of a catalyst (also known as the "oxo process"), followed by a hydrogenation step. Such processes have the advantage of inexpensive small-molecule organic starting materials.

[0004] Hydroformylation introduces formyl groups into unsaturated olefins to provide aldehydes. Hydroformylation can be carried out by contacting olefins with synthesis gas (a mixture of carbon monoxide and hydrogen). Once aldehydes have been produced, hydrogenation reduces the aldehydes to provide corresponding alcohols. When longer chain alcohols are needed, the method can include an aldol condensation step that condenses two aldehydes, thereby providing longer chain unsaturated aldehydes. Subsequently, the longer chain unsaturated aldehydes are reduced by hydrogenation to provide corresponding saturated alcohols.

[0005] After hydrogenation, the reaction effluent comprises the alcohol product in the crude mixture, i.e., the crude alcohol mixture. The crude alcohol mixture is subjected to a distillation step to separate and purify the alcohol. However, the requirement for high product purity (i.e., high purity alcohol) means that the purified alcohol fraction has a narrow fractionation point (i.e., a narrow boiling point range). Therefore, a large amount of alcohol can be disposed of as waste. Specifically, a large amount of alcohol can be retained in a higher boiling point fraction, which is referred to as a "heavy stream" in the art, and it is usually disposed of as a waste stream. If distillation is performed to recover all alcohol as a product (i.e., the purified alcohol fraction has a wider boiling point range), pollutants (e.g., heavy chain hydrocarbons) will be present in the purified alcohol. Pollutants may include by-products (e.g., undesirable oxidation and condensation products, such as esters, ketones, and other oxygenates) of hydroformylation and hydrogenation reactions. In order to mitigate the pollution of the purified alcohol product, distillation is performed so that some alcohols are retained in the heavy stream. In order to prevent the temperature at the bottom of the distillation tower from being too high, distillation is performed so that some alcohols are retained in the heavy stream, which can also be beneficial. Such excessively high temperatures can cause the heavy components to decompose into lighter components which can travel back along the distillation column and contaminate the product.

[0006] Current processes for producing alcohols are inefficient because large amounts of the alcohol product are disposed of.

[0007] Prior art processes may treat the heavy stream or subject the heavy stream to further processing or refining steps.

[0008] US5004845 describes a heavy stream comprising butanols, which is mixed with hydrogen, preheated and evaporated in an evaporator. The resulting vapor mixture is then directed to a vapor phase hydrogenation (VPH) reactor. When the entire heavy stream evaporates, pollutants can accumulate in the method, which can adversely affect the performance of hydroformylation and hydrogenation catalysts and the quality and purity of alcohol products. CN107032953 also describes a vapor phase hydrogenation (VPH) reaction scheme. Hydrogenation can be used for cracking heavier hydrocarbon pollutants. For example, butyl butyrate (BuBu) is a common byproduct of butyraldehyde hydrogenation, which can be hydrogenated to provide butanols.

[0009] Other methods process heavy streams in towers operated under reduced pressure and maintained at low temperatures to allow removal of lighter components without causing decomposition of heavier components. Alternatively, the tower can be operated at higher temperatures, or additives (e.g., hydroxides) are provided to promote the decomposition of heavier pollutant compounds into lighter compounds, such as alcohols and aldehydes. DE2713434 describes separating higher boiling fractions in a tower.

[0010] Other methods process heavy streams in steam strippers, wherein steam is used to separate lighter compounds from heavy compounds. The product stream may contain the desired alcohol, and may also contain aldehydes or other components. Water is removed from the product stream, and the resulting light stream is directed to a hydrogenation reactor or a light component tower for further separation. US2614128 describes recovering alcohol from a heavy stream in a steam stripper and recovering the alcohol for recycling to the hydrogenation stage of the oxo reaction.

[0011] Recovery of alcohol from heavies streams using any of the above methods requires additional equipment, increased energy costs, and may result in the build-up of contaminants in the process.

[0012] Some prior art gas phase hydrogenation systems have used a hydrogen stream as a stripping gas to strip alcohol from an alcohol-containing heavy stream before passing the resulting alcohol-containing hydrogen stream into the gas phase hydrogenation. However, such systems may not be cost effective because there is already an evaporator to evaporate the aldehyde feed to the gas phase hydrogenation reaction, and the heavy stream can be sent to the evaporator to evaporate alcohol from the heavy stream, and adding another stripper may therefore increase the equipment count without overall benefit.

[0013] It is an object of the present invention to obviate or mitigate one or more of the aforementioned problems. Summary of the invention

[0014] The present invention relates to improvements in the overall yield and purity of alcohols obtained from a process for producing alcohols. In particular, the present invention recovers increased amounts of alcohol from the effluents of hydroformylation and hydrogenation processes. The present invention advantageously uses a stripping gas comprising hydrogen to recover alcohol from a heavy stream, wherein the heavy stream is obtained by distilling alcohol from a crude alcohol stream. The resulting recycle stream comprises alcohol recovered from the heavy stream and the stripping gas, and can be used directly in a liquid phase hydrogenation reaction. Thus, the methods and apparatus disclosed herein advantageously provide (i) an increased alcohol yield by recovering alcohol from the heavy stream and returning the alcohol to the process; and (ii) a recycle stream that can be used directly in a liquid phase hydrogenation reaction.

[0015] According to a first aspect of the present invention, there is provided a process for producing at least one alcohol, the process comprising the steps of: (i) providing a crude aldehyde stream comprising at least one aldehyde to at least one liquid phase hydrogenation reactor, and hydrogenating the at least one aldehyde in a liquid phase hydrogenation reaction to provide a crude alcohol stream comprising at least one alcohol; (ii) recycling a liquid recycle stream comprising the at least one alcohol to the at least one liquid hydrogenation reactor via a recycle cooler, recovering heat in the liquid recycle stream in the recycle cooler, preferably by generating steam, (iii) providing the crude alcohol stream to a distillation column and distilling the crude alcohol stream to provide a purified alcohol stream comprising the at least one alcohol and a heavy stream comprising the at least one alcohol; (iv) providing the heavy stream to a stripping column and contacting the heavy stream with a stripping gas comprising at least 20 mol % hydrogen to separate the heavy stream into a recycle stream comprising the at least one alcohol and a waste stream; and (v) returning at least a portion of the recycle stream to the at least one liquid phase hydrogenation reactor in step (i).

[0016] In an embodiment, the at least one alcohol is selected from at least one C3-C 20 alcohol, optionally at least one C3-C 10 alcohol, and optionally at least one C4-C 10 Alcohol. In an embodiment, the at least one alcohol is selected from butanol, 2-ethylhexanol, 2-propylheptanol, and isononanol.

[0017] In embodiments, the reactor outlet stream is split to provide a crude alcohol stream and a liquid recycle stream. In alternative embodiments, the liquid recycle stream and the crude alcohol stream are separately recovered from at least one liquid phase hydrogenation reactor.

[0018] In embodiments, the crude alcohol stream comprises at least 50 wt% of the at least one alcohol, optionally at least 60 wt% of the at least one alcohol, and further optionally at least 70 wt% of the at least one alcohol.

[0019] In embodiments, the purified alcohol stream comprises greater than 95 wt % of the at least one alcohol, optionally greater than 97 wt % of the at least one alcohol, and further optionally greater than 99 wt % of the at least one alcohol, relative to the total weight of the purified alcohol stream.

[0020] In embodiments, the heavies stream comprises less than 80 wt % of at least one alcohol, optionally less than 70 wt % of at least one alcohol, optionally less than 60 wt % of at least one alcohol. Preferably, the heavies stream comprises at least 40 wt %, preferably at least 50 wt % of at least one alcohol. An advantage of the present invention is that high alcohol percentages in the heavies stream can be tolerated because the alcohol is recovered. A higher alcohol percentage in the heavies stream can allow for more efficient distillation operations while maintaining alcohol product quality, for example because of reduced cracking of the heavies at the bottom of the distillation column due to subsequent lower temperatures.

[0021] Another advantage of the present invention in liquid phase hydrogenation reaction is that the alcohol recovered from the heavy stream is condensed in at least one liquid phase hydrogenation reactor and energy is therefore introduced into at least one liquid phase hydrogenation reactor. This energy is then recovered in a recycle cooler, for example in the form of additional steam produced in the recycle cooler. In the liquid phase hydrogenation reaction, the combination of a hydrogen stripper that recovers alcohol from the heavy stream by evaporation and a liquid recycle stream that is recirculated via a recycle cooler in which heat is recovered therefore results in particularly energy-efficient operation. The gas phase hydrogenation reactor systems of the prior art do not benefit from this advantage. The recycle cooler can recover heat by generating steam. It should be understood that the recovered heat can be used elsewhere in a plant or process.

[0022] In embodiments, the recycle stream comprises from 1 wt% to 25 wt% of the at least one alcohol, optionally from 5 wt% to 20 wt% of the at least one alcohol, optionally from 10 wt% to 15 wt% of the at least one alcohol.

[0023] In embodiments, the stripping gas stream comprises at least 70 mol% hydrogen, optionally at least 90 mol% hydrogen, and optionally at least 98 mol% hydrogen. In embodiments, the recycle stream comprises at least 60 wt% hydrogen, optionally at least 70 wt% hydrogen, and optionally at least 80 wt% hydrogen. In embodiments, the recycle stream comprises at least 2 wt% alcohol, optionally at least 5 wt% alcohol, and optionally at least 7 wt% alcohol. In embodiments, the recycle stream comprises at least 70 wt% hydrogen and at least 5 wt% alcohol.

[0024] In an embodiment, the pressure and temperature in the stripping tower are selected to strip at least one alcohol from the heavy stream, while the heavier compounds remain in the heavy stream. In an embodiment, the temperature and pressure inside the stripping tower are such that the heavy stream remains in the liquid phase and the stripping gas remains in the gas phase. In an embodiment, the pressure in the stripping tower is 15 bar to 45 bar, optionally 20 bar to 35 bar. The temperature and pressure in the stripping tower can be controlled to keep the temperature in the liquid outlet above a minimum value. The liquid outlet can be cooled by evaporating the alcohol into the stripping gas, so the liquid outlet can represent the lowest temperature in the stripping tower. In an embodiment, the temperature of the liquid outlet of the stripping tower is not less than 40°C and preferably not less than 50°C. Lower temperatures may cause the outlet to be too viscous or the recovery rate of the alcohol to be poor.

[0025] In an embodiment, (i) a stripping gas stream is provided to a lower portion of a stripping column, optionally to the bottom of the stripping column; and (ii) a heavy stream is provided to an upper portion of a stripping column, optionally to the top of the stripping column. In an embodiment, a recycle stream is obtained from an upper portion of a stripping column, optionally from the top of a stripping column. The heavy stream descends along the stripping column under the action of gravity, and the stripping stream rises along the stripping column, having a density less than that of the heavy stream. When the heavy stream and the stripping gas contact each other, volatile molecules such as at least one alcohol move from the liquid phase (heavy stream) to the gas phase (stripping gas) and are thus "stripped" from the heavy stream.

[0026] In an embodiment, the temperature of the stripping gas stream entering the stripper is from 50° C. to 250° C., optionally from 60° C. to 200° C. In an embodiment, the temperature of the heavy stream entering the stripper is from 50° C. to 300° C., optionally from 100° C. to 200° C., and optionally from 125° C. to 175° C. (e.g., about 130° C. to 160° C.).

[0027] In embodiments, the stripping gas stream may comprise at least 50 wt%, optionally at least 70 wt%, and also optionally at least 90 wt% of the hydrogen fed to the liquid phase hydrogenation reactor. Preferably, the stripping gas stream is the sole source of hydrogen feed to the liquid phase hydrogenation reactor. In other words, the hydrogen required to hydrogenate the aldehydes in the liquid phase hydrogenation reactor is provided in the stripping gas stream rather than in a separate hydrogen feed stream entering the liquid phase hydrogenation reactor. Using a larger hydrogen flow rate in the stripping gas can advantageously result in a lower temperature in the stripping column, and thus can advantageously include all of the hydrogen required for the liquid phase hydrogenation reaction in the stripping gas stream.

[0028] In an embodiment, the step of providing a crude aldehyde stream comprises the steps of providing an olefin stream to at least one hydroformylation reactor and contacting the olefin stream with a hydroformylation gas stream comprising hydrogen and carbon monoxide to conduct a hydroformylation reaction to provide a crude aldehyde stream.

[0029] In embodiments, the crude aldehyde stream comprises at least one C3-C 20 aldehyde, optionally at least one C3-C 10 aldehyde, and optionally at least one C4-C 10 Aldehydes. In embodiments, the at least one aldehyde is selected from butyraldehyde, 2-ethylhexenal, 2-propylheptenal, and isononanal. In embodiments, the crude aldehyde stream comprises at least 40 wt% aldehydes, optionally at least 50 wt% aldehydes, and optionally at least 60 wt% aldehydes.

[0030] In embodiments, providing a crude aldehyde stream also includes, for example, by contacting the reaction effluent with at least one base or at least one acid, subjecting the reaction effluent of the hydroformylation reaction to an aldol reaction between at least two aldehydes contained in the reaction effluent to provide a crude aldehyde stream. In such embodiments, the crude aldehyde stream comprises at least one aldol condensation product. In such embodiments, the crude aldehyde stream may comprise at least 20% by weight of aldol condensation products, optionally at least 30% by weight of aldol condensation products, and optionally at least 40% by weight of aldol condensation products. In preferred embodiments, the crude aldehyde stream comprises at least one unsaturated aldehyde, such as 2-ethylhexenal or 2-propylhexenal. 2-ethylhexenal is the aldol condensation product of butyraldehyde. 2-propylhexenal is the aldol condensation product of valeraldehyde. In embodiments, butyraldehyde and valeraldehyde can be obtained from the hydroformylation of olefins propylene and butene, respectively.

[0031] In an embodiment, prior to step (v), the recycle stream is directed to a secondary hydrogenation reactor configured to hydrogenate the esters to at least one alcohol, wherein the recycle stream is contacted with hydrogen to carry out a hydrogenation reaction. In an embodiment, the hydrogenation reaction in the secondary hydrogenation reactor is a gas phase hydrogenation reaction. In an embodiment, the hydrogenation reaction in the secondary hydrogenation reactor is a liquid phase hydrogenation reaction. The ester may be contained in the heavy stream and stripped from the heavy stream together with the alcohol by the stripping gas. Stripping those esters from the heavy stream and hydrogenating them to the corresponding alcohol according to the present invention can advantageously increase the total alcohol yield of the liquid phase hydrogenation and thus improve the feedstock efficiency of the entire method.

[0032] According to a second aspect of the present invention, there is provided an apparatus for producing alcohols, the apparatus comprising at least one liquid phase hydrogenation reactor, the at least one liquid phase hydrogenation reactor being configured to hydrogenate at least one aldehyde contained in a crude aldehyde stream in a liquid phase hydrogenation reaction to provide a crude alcohol stream containing at least one alcohol; a recirculation loop in fluid communication with the at least one liquid phase hydrogenation reactor and a recirculation cooler, the recirculation loop being configured to recirculate a liquid recirculation stream from the at least one liquid phase hydrogenation reactor to the at least one liquid phase hydrogenation reactor via the recirculation cooler; and a recirculation loop in fluid communication with the at least one liquid phase hydrogenation reactor and a recirculation cooler. a distillation column fluidly connected to the liquid-phase hydrogenation reactor, the distillation column being configured to distill the crude alcohol stream to provide a purified alcohol stream comprising the at least one alcohol and a heavy stream comprising the at least one alcohol; a stripping column fluidly connected to the distillation column, the stripping column being configured to contact the heavy stream with a stripping gas stream comprising at least 20 mol% hydrogen to separate the heavy stream into a recycle stream comprising the at least one alcohol and a waste stream; wherein the stripping column is fluidly connected to the at least one liquid-phase hydrogenation reactor to provide the recycle stream to the at least one liquid-phase hydrogenation reactor.

[0033] In an embodiment, the stripper is a hydrogen stripper, ie hydrogen is used as stripping gas.

[0034] In an embodiment, the apparatus further comprises a hydroformylation reactor configured to contact an olefin stream comprising at least one olefin with hydrogen and carbon monoxide to perform a hydroformylation reaction on the at least one olefin, and an optional aldol condensation unit that performs an aldol condensation reaction to convert aldehydes produced in the hydroformylation reaction into long-chain unsaturated aldehydes, thereby providing a crude aldehyde stream.

[0035] In embodiments, the at least one olefin contained in the olefin stream is propylene, the at least one aldehyde contained in the crude aldehyde stream is butyraldehyde and / or 2-ethylhexenal, and the at least one alcohol contained in the crude alcohol stream is butanol and / or 2-ethylhexanol.

[0036] In embodiments, the at least one olefin contained in the olefin stream is butene, the at least one aldehyde contained in the crude aldehyde stream is valeraldehyde and / or 2-propylheptenal, and the at least one alcohol contained in the crude alcohol stream is pentanol and / or 2-propylheptenol. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1A A schematic diagram of a prior art process for producing alcohols is shown.

[0038] Figure 1B shows that it is suitable for implementing Figure 1A Schematic diagram of the apparatus of the method.

[0039] Figure 2AA schematic diagram of a method for producing alcohol according to the present invention is shown.

[0040] Figure 2B shows that it is suitable for implementing Figure 2A Schematic diagram of the apparatus of the method.

[0041] Figure 3A A schematic diagram of a method for producing alcohol according to the present invention is shown.

[0042] Figure 3B shows that it is suitable for implementing Figure 3A Schematic diagram of the apparatus of the method.

[0043] Figure 4 A schematic diagram of an apparatus suitable for carrying out the process for producing alcohol according to the present invention is shown. DETAILED DESCRIPTION

[0044] The invention will now be described by way of example only with reference to the accompanying drawings and examples: the scope of protection is defined in the appended claims.

[0045] As used herein, "alcohol" refers to a straight or branched C3-C 20 Alcohols. The alcohols produced according to the present invention may be monohydric alcohols (i.e., containing one hydroxyl group) or polyhydric alcohols (i.e., containing multiple hydroxyl groups). The polyhydric alcohol may contain 2 to 8 hydroxyl groups, and preferably contains 2 hydroxyl groups. In an embodiment, the alcohol produced is a monohydroxylated straight or branched C3-C 20 Alcohol. In an embodiment, the alcohol produced is selected from propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol and isomers thereof. In an embodiment, the alcohol produced is selected from butanol, 2-ethylhexanol and 2-propylheptanol. 2-ethylhexanol is widely used in the preparation of plasticizer alcohols, such as bis-2-ethylhexyl phthalate.

[0046] As used herein, the term "rough" means that the "rough" stream has not been purified and contains a mixture of compounds. Therefore, the "rough" stream needs further processing and / or purification to provide a final product (i.e., alcohol). Therefore, the "rough" stream described herein can be the effluent from the reaction process (e.g., the effluent from the hydrogenation reaction and / or the effluent from the hydroformylation reaction). Therefore, the rough stream can include several pollutant compounds that are not alcohols to be produced. The rough aldehyde stream therefore includes at least one aldehyde and pollutant compounds. The rough alcohol stream therefore includes at least one alcohol and pollutant compounds.

[0047] As used herein, the term "pollutant" refers to undesirable non-alcohol compounds. Pollutant can include the side reaction products produced by hydroformylation and / or hydrogenation. For example, the pollutant by-product formed by hydroformylation can include the product, ester, ketone, heterocycle, cycloalkane, cycloolefin, alkene etc. of aldehyde condensation reaction (aldol reaction). The pollutant encountered especially includes aldol condensation product and ester. The pollutant by-product formed by hydrogenation can include catalyst residue, heterocycle, cycloalkane, cycloolefin, alkene etc. It is desirable to remove these pollutants from the alcohol feed stream as the purification of product.

[0048] As used herein, the term "heavy stream" refers to a fraction of organic compounds having a boiling point greater than the cut point (i.e., boiling point range) of the alcohol to be purified. For example, if the cut point of the alcohol to be purified is 100° C. to 130° C., the lowest boiling point of the heavy stream will be greater than 130° C. Those skilled in the art will understand that the lower limit of the boiling point range (lower limit of the cut point) will depend on the upper limit of the boiling point range of the at least one alcohol to be purified in the purified alcohol stream.

[0049] As used herein, the term "unsaturated" refers to compounds having carbon-carbon double bonds. "Saturated" compounds do not contain carbon-carbon double bonds.

[0050] As used herein, the term "stripping gas" refers to a gaseous mixture capable of stripping light compounds such as alcohols and esters from a heavy stream comprising a mixture of organic compounds. In this article, the term "light" refers to compounds contained in the heavy stream that have a lower boiling point relative to the remaining compounds contained in the heavy stream and are easily stripped / evaporated from the heavy stream when contacted with the stripping gas. Under the conditions in the stripping column, the stripping gas remains in the gas phase. The stripping gas is typically hydrogen.

[0051] As used herein, the term "stripping tower" refers to a tower configured to contact a stripping gas with a heavy stream to remove alcohol therefrom and to provide a recycle stream comprising the stripping gas and the recovered alcohol. Those skilled in the art are familiar with stripping towers. In an embodiment, the stripping tower is a hydrogen stripping tower. In an embodiment, the stripping tower includes a section providing a stage in the tower. The internals can be any shape or form capable of achieving vapor-liquid contact and providing the number of stages required for stripping lighter compounds from the heavy stream. The stripping tower can be equipped with "internals" arranged inside the tower to provide the stage. In an embodiment, the stripping tower includes 1 to 20 stages, optionally 1 to 8 stages. The internals can be selected from, for example, sieve plates, valve plates, bubble cap plates, random packings or structured packings.

[0052] As used herein, the "corresponding" alcohol of an aldehyde is the reduced alcohol form of the aldehyde. Conversely, the "corresponding" aldehyde of an alcohol is the oxidized aldehyde form of the alcohol. For example, one skilled in the art will appreciate that the "corresponding alcohol" of butyraldehyde is butanol. In the context of the present invention, the corresponding alcohol of an unsaturated aldehyde is typically the corresponding saturated alcohol.

[0053] Those skilled in the art will appreciate that the desired aldehydes that provide the desired alcohol product can be obtained by hydroformylation of olefins, wherein the olefins typically have one less carbon atom than the corresponding desired aldehyde. For example, those skilled in the art will appreciate that butyraldehyde can be obtained by hydroformylation of propylene. Similarly, valeraldehyde can be obtained by hydroformylation of butenes.

[0054] The methods described herein relate to the production of alcohols. In embodiments, at least one alcohol is produced, optionally at least two alcohols are produced. In typical embodiments, a specific alcohol is produced, also referred to herein as a "desired" alcohol. In embodiments, the methods according to the present invention are used to produce butanol. In other embodiments, the methods according to the present invention are used to produce 2-ethylhexanol. In other embodiments, the methods according to the present invention are used to produce 2-propylheptanol.

[0055] The crude alcohol stream according to the present invention comprises at least one alcohol, and may comprise a mixture of alcohols.One skilled in the art will appreciate that fractional distillation can be used to separate different alcohols based on their respective boiling points.

[0056] The crude alcohol stream may comprise a predominant alcohol, also referred to as a "desired" alcohol. The crude alcohol stream may comprise greater than 50 wt % of the desired alcohol relative to the total weight of the crude alcohol stream. In embodiments, the crude alcohol stream comprises greater than 60 wt % of the desired alcohol, and optionally greater than 70 wt % of the desired alcohol. In embodiments, the desired alcohol is selected from butanol, 2-ethylhexanol, 2-propylheptanol, and isononanol.

[0057] The crude alcohol stream is distilled to provide a purified alcohol stream.

[0058] The purified alcohol stream may comprise greater than 95 wt% alcohol, optionally greater than 97 wt% alcohol, and further optionally greater than 99 wt% alcohol, relative to the total weight of the purified alcohol stream.

[0059] The alcohol fraction of purification can contain alcohol mixture, but preferably comprises the desired alcohol greater than 50 wt %.In a preferred embodiment, relative to the gross weight of the alcohol fraction of purification, the alcohol fraction of purification comprises the desired alcohol greater than 80 wt %, optionally greater than 95 wt %, optionally greater than 97 wt % and also optionally greater than 99 wt % of the desired alcohol.In some embodiments, for example, when the desired alcohol is 2-propyl heptanol, the desired alcohol can exist as two or more isomers.In such embodiments, the alcohol fraction of purification preferably comprises the desired alcohol greater than 95 wt % and its isomer, optionally greater than 97 wt % and also optionally greater than 99 wt % of the desired alcohol and its isomer.In embodiments, the desired alcohol is selected from butanol, 2-ethylhexanol and 2-propyl heptanol.

[0060] The distillation of the crude alcohol stream further provides a heavy stream. In embodiments, the heavy stream comprises less than 80% by weight of alcohol, optionally less than 70% by weight of alcohol, optionally less than 60% by weight of alcohol. Preferably, the heavy stream comprises at least 40% by weight, preferably at least 50% by weight of alcohol. It will be appreciated by those skilled in the art that, as used herein, the term "heavy" refers to a fraction having a boiling point higher than that of the purified alcohol stream. The heavy stream comprises pollutants. As described above, it is desirable to avoid pollutants being present in the purified alcohol stream. Therefore, the fractionation point range for the boiling point temperature of the purified alcohol stream is narrow. The effect of this situation is that a large amount of alcohol can be retained in the heavy stream. Having a high alcohol content in the heavy stream also advantageously suppresses the boiling point temperature of the heavy stream, thereby reducing the bottom temperature of the distillation tower from which the heavy stream is taken out. High bottom temperature can cause heavy compounds to decompose in the distillation tower to form light decomposition products, and cause the alcohol product stream to be contaminated by the light decomposition products.

[0061] It has been found that alcohol present in the heavy stream can be recovered from the heavy stream and reintroduced into the alcohol production process. In particular, the inventors have found that by contacting the heavy stream with a stripping gas, alcohol can be stripped from the heavy stream to a recycle stream that can be directly provided to a liquid phase hydrogenation reaction. In this way, the inventors have surprisingly found that 50% to 90% of the alcohol in the heavy stream can be recovered, and typically 60% to 80% of the alcohol in the heavy stream can be recovered. This represents a significant improvement in the total yield of the recovered alcohol relative to the prior art methods in which the alcohol in the heavy stream is not recovered. Unlike gas phase hydrogenation in which the aldehyde feed must be evaporated, liquid phase hydrogenation does not have a feed evaporator to which the heavy stream can be provided to recover the alcohol. Therefore, adding a stripper to the liquid hydrogenation system represents a valuable addition to the method. In addition, because the alcohol evaporated into the stripping gas can be recondensed in the liquid phase hydrogenation reactor or prevent other alcohols from evaporating in the liquid phase hydrogenation reactor by changing the gas-liquid equilibrium in the liquid phase hydrogenation reactor, more heat is made available for extraction via the recirculation cooler. In gas phase hydrogenation systems, the temperature is usually such that any heat must be transferred to cooling water. However, in a liquid phase hydrogenation system such as in the present invention, the recirculation cooler can be operated at a temperature at which the steam is elevated, and the additional heat generated by the evaporated alcohol in the stripping gas can therefore be recovered as useful steam, resulting in an overall increase in energy efficiency compared to prior art gas phase hydrogenation processes.

[0062] Figure 1Ais a schematic diagram of a prior art process for producing alcohols. A crude aldehyde stream comprising at least one aldehyde 2 is provided to a hydrogenation reactor 6 together with a hydrogen stream 4. The hydrogenation reactor performs hydrogenation of the at least one aldehyde at a suitable temperature and pressure to provide the corresponding alcohol in a crude alcohol stream 8. The crude alcohol stream 8 is provided to a distillation column 10, wherein the crude alcohol stream 8 is separated into a light stream 12, a purified alcohol stream 14, and a heavy stream 16. In the depicted prior art process, the heavy stream 16 is processed.

[0063] Figure 1B FIG. 1 is a schematic diagram of a prior art apparatus for implementing the process for producing alcohols shown in FIG. Figure 1B In the embodiment of the present invention, the hydrogenation reactor 6 is a liquid phase hydrogenation reactor. The hydrogenation reactor is provided with an exhaust port 28 to regulate the pressure in the reactor 6. In addition, the hydrogenation reactor is provided with a gas recycle compressor loop, which can be used instead of the exhaust port 28 or in addition to the exhaust port 28. The gas recycle compressor loop includes an input stream 30 in fluid communication with a compressor 32 and an outlet stream 34 downstream of the compressor 32. The outlet stream 34 is in fluid communication with the hydrogen stream 4 fed into the hydrogenation reactor 6. In addition, a liquid phase recycle loop is provided, which includes a liquid recycle stream 18 in fluid communication with a pump 20 downstream of the reactor 6 to provide a pumped liquid recycle stream 22. The liquid recycle stream 18 is branched from the crude alcohol stream 8, although it can also be discharged directly from the hydrogenation reactor 6 instead. The pumped liquid recycle stream 22 is cooled in the recycle cooler 24 to provide a cooled pumped liquid recycle stream 26 before being added to the crude aldehyde stream 2.

[0064] As described below, the methods and apparatus according to the present invention and as described herein have several features in common with the methods and apparatus of the prior art described above. Figure 1A and Figure 1B The aspects may be the same as the method and apparatus according to the present invention, and thus Figure 1A and Figure 1B The description of also applies to the present invention, as long as common features exist.

[0065] Figure 2A is a schematic diagram of a method for producing alcohol according to the present invention. Figure 2A and Figure 1A The same except that the heavy stream 16 undergoes further processing and the hydrogen stream 4 is not provided directly to the hydrogenation reactor 6.

[0066] Crude aldehyde stream 2 can be provided as the effluent of hydroformylation reaction (not shown).Hydroformylation provides aldehyde from olefin.Hydroformylation needs to make olefin contact with carbon monoxide and hydrogen on catalyst (for example, catalyst based on cobalt or rhodium) to produce aldehyde containing 1 carbon more than original olefin.The starting olefin material can therefore determine which alcohol is produced in the reaction process.For example, the hydroformylation of propylene obtains a mixture of n-butyraldehyde and isobutyraldehyde.The hydrogenation of n-butyraldehyde and isobutyraldehyde provides 1-butanol and isobutanol respectively.In addition, the aldol condensation product of n-butyraldehyde can also be provided, such as 2-ethyl hexenaldehyde, which provides 2-ethyl hexanol when hydrogenated.As another example, the hydroformylation of propylene and butene provides butyraldehyde and valeraldehyde, which can be converted into 2-propyl hexenaldehyde and hydrogenated into 2-propyl hexanol by aldol condensation.

[0067] Olefins suitable for use in the present invention include propylene, butenes, pentenes, hexenes, heptenes, octenes and their isomers. Particularly preferred olefins are selected from propylene and butenes. In embodiments, the crude aldehyde stream also comprises at least one hydroxyaldehyde and / or at least one acrolein as the condensation product of at least two aldehydes. For example, the aldol condensation of butanal (also referred to as butyraldehyde) and itself produces 2-ethyl-hexenal (also referred to as ethyl-propyl-acrolein). In embodiments, suitable conditions are used in the hydroformylation reaction to promote the aldol reaction between at least two aldehydes. However, during the hydroformylation synthesis, several undesirable pollutants are produced and present in the crude aldehyde stream.

[0068] Hydrogenation needs to contact at least one aldehyde with hydrogen on a catalyst. Hydrogenation reduces carbon-oxygen double bonds to provide corresponding carbon-oxygen single bonds, and therefore provides alcohol. Hydrogenation can also reduce carbon-carbon double bonds, such as wherein at least one aldehyde in the crude aldehyde stream is unsaturated (such as aldol condensation product). Hydrogenation can also crack the carbon-oxygen single bond in the ester to provide corresponding alcohol. Therefore, at least one aldehyde included in the crude aldehyde stream 2 can be saturated (i.e., not including carbon-carbon double bonds) or can be unsaturated (i.e., including carbon-carbon double bonds).

[0069] The catalyst used in the hydrogenation reactor is a liquid phase hydrogenation reaction catalyst. The catalyst can generally be selected from catalysts based on copper, copper / zinc, copper / chromium and nickel.

[0070] During the hydroformylation and hydrogenation reactions, several undesirable contaminants are generated that are contained in the crude alcohol stream. The contaminants may include, for example, esters. A specific contaminating ester formed in butanol production is, for example, butyl butyrate.

[0071] Crude alcohol stream 8 is provided as the effluent of the hydrogenation reaction. Distillation of crude alcohol stream 8 is conducted in distillation column 10 at a temperature and pressure effective to obtain the desired purified alcohol product stream 14 of the desired purity and as will be apparent to one skilled in the art.

[0072] exist Figure 2A In the embodiment of the present invention, the heavy stream 16 is directed to a stripping column 36, which is preferably a hydrogen stripping column. Figure 1A and Figure 1B In contrast, the hydrogen stream 4 is provided directly to the stripper, rather than directly to the hydrogenation reactor 6. The hydrogen stream 4 strips light components from the heavy stream 16, including alcohols that are not collected in the purified alcohol stream 14. As the hydrogen stream 4 strips lighter molecules (e.g., at least one alcohol to be recovered) from the heavy stream (i.e., the lighter molecules are converted from the liquid phase in the heavy stream to the gas phase in the stripping gas), a recycle stream 40 comprising hydrogen and the desired alcohol product is provided, which is fed back to the hydrogenation reactor 6. The recycle stream 40 may contain lighter molecules other than the at least one alcohol that are also stripped from the heavy stream. These other lighter molecules include esters and aldehydes that were not successfully reduced in the hydrogenation reactor 6, as well as condensation products of aldehydes that were not successfully reduced in the hydrogenation reactor 6.

[0073] The waste stream 38 comprising the remaining heavy end compounds may be sent for further processing (not shown), such as cracking, to obtain further usable aldehyde or alcohol molecules, or for use as a fuel.

[0074] In the hydrogenation reactor 6, a recycle stream 40 comprising hydrogen and the desired alcohol is contacted with a fresh crude aldehyde stream 2 which may comprise at least one aldehyde. As already described above, liquid phase hydrogenation is carried out using a solid catalyst to hydrogenate the aldehydes to the corresponding alkanols (saturated alcohols). Thus, the recycle stream 40 returns the otherwise waste alcohols together with the alcohol precursor molecules such as aldehydes and esters to the process at the site of the hydrogenation reactor 6.

[0075] Although the stripper 36 is described herein primarily with reference to stripping alcohol from the heavy stream 16, those skilled in the art will appreciate that other lighter molecular compounds may also be stripped and thus present in the recycle stream 40, such as aldehydes, esters, etc., as described above. This is particularly true when the stripper 36 is designed and operated so as to strip a higher proportion of alcohol from the heavy stream 16. For example, in a process for producing butanol, the hydrogen stripper may be designed and operated to recover a majority of the alcohol in the heavy stream 16 and thus may also strip the ester butyl butyrate (BuBu) formed as a by-product in the production process. Since the recycle stream 40 then contains BuBu, Figure 2A The method shown in Figure 2BThe apparatus shown in FIG. 4 may result in accumulation of BuBu. Although BuBu may be hydrogenated to butanol in hydrogenation reactor 6, insufficient conversion may occur therein. For this reason, it may be desirable to subject recycle stream 40 to further treatment to remove contaminants such as BuBu (see FIG. 4 ) before recycle stream 40 enters hydrogenation reactor 6. Figure 3A , Figure 3B and Figure 4 This can increase alcohol yield by converting at least some of the contaminants into additional alcohol product and by facilitating the design and operation of stripper 16 so as to maximize recovery of alcohol from heavy stream 16.

[0076] Figure 2B is suitable for implementation Figure 2A Schematic diagram of the apparatus of the method depicted. Figure 2B and Figure 1B Same, except that heavy stream 16 is subjected to further processing as described below, hydrogen stream 4 is not provided directly to hydrogenation reactor 6, and there is no (optional) gas recycle compressor loop.

[0077] like Figure 2B As shown, the heavy stream 16 is directed to the top of the stripping tower 36. The heavy stream 16 can be pumped into the stripping tower 36 by a pump 42. The hydrogen stream 4 is directed to the bottom of the stripping tower 36 and optionally heated using a heater 44. The heated hydrogen stream 4 rises in the stripping tower 36 and contacts the descending heavy stream 16 to strip alcohol from the heavy stream. This enables at least a portion of the lighter components (e.g., alcohol products) in the heavy stream to migrate from the liquid phase in the heavy stream to the gas phase in the hydrogen stream. Ideally, only the lighter components (e.g., alcohol products) are evaporated, while the heavier components remain in the liquid phase. Advantageously, the evaporation degree of the lighter components (e.g., alcohols) in the heavy stream can be controlled by adjusting the temperature of the hydrogen stream 4 fed into the hydrogen stripping tower 36, adjusting the temperature of the heavy stream 16, and / or bypassing the stripping tower 36. For example, if the temperature of the hydrogen stream 4 increases, a larger portion of the heavy steam will be evaporated. A recycle stream 40 comprising hydrogen and recovered alcohol is withdrawn from the top of the stripper and directed to the hydrogenation reactor 6 as previously described.

[0078] From the bottom of the stripper a waste stream 38 is extracted. The waste stream 38 may be further distilled, or subjected to a cracking process to obtain useful smaller carbon molecules, such as saturated and unsaturated aldehydes, enols, acetals, etc. These products may be used to generate valuable secondary products or may be reinserted in the process to contribute to the yield of the alcohol product.

[0079] In an embodiment, the operating pressure within the distillation column 10 is less than the operating pressure within the hydrogenation reactor 6, and the operating pressure within the stripping column 36 is higher than the hydrogenation reactor 6. The greater operating pressure of the stripping column 36 means that a compressor is not required to provide the flow of the recycle stream 40 to the hydrogenation reactor 6. Alternatively, a compressor may be provided in the flow path of the recycle stream 40.

[0080] Including make-up gas to the hydrogen stripper can assist the stripper or reduce the temperature in the preheater.

[0081] As mentioned above about Figure 1B The provision of the exhaust port 28 and the gas recycle compressor loop (30, 32, 34) are each optional features of the present invention. The exhaust port 28 is used to discharge inert materials from the liquid phase hydrogenation reactor 6 and prevent their accumulation. The exhaust port will also contain some hydrogen. The hydrogen 4 entering the reactor is easily consumed in the hydrogenation reactor and can be adsorbed into the liquid phase therein. If the hydrogen consumption is reduced and the hydrogen remains in the gas phase in the reactor, it can be discharged via the exhaust port 28 or compressed via the gas recycle compressor loop for reuse. When using a secondary gas phase hydrogenation reactor (such as, for example, below with respect to Figure 3B Those skilled in the art will appreciate that the gas recycle compressor loop does not provide hydrogen to the liquid phase hydrogenation reactor 6 for vapor phase hydrogenation reactions therein because the crude aldehyde and crude alcohol streams remain in the liquid phase and thus the reaction in the liquid phase hydrogenation reactor 6 is a liquid phase hydrogenation reaction.

[0082] As mentioned above about Figure 1B As described, liquid phase recirculation loop (18,20,22,24,26), and particularly recirculation cooler 24, can be combined with other features of the present invention to produce energy efficiency favorable compared with prior art gas phase method.Hydrogenation reactor 6 as liquid phase hydrogenation reactor includes solid catalyst, and the temperature and pressure therein make the crude aldehyde stream and crude alcohol stream produced remain in liquid form.Operate liquid phase circulation loop to cool crude aldehyde stream.Because the alcohol in recirculation stream 40 is in gas phase, it will condense in liquid phase hydrogenation reactor 6 or affect gas-liquid equilibrium, so that other alcohols do not evaporate.Therefore, at least some of the energy for evaporating alcohol in stripper 36 is effectively transferred to the liquid phase in liquid phase hydrogenation reactor 6 and can be recovered again in recirculation cooler 24.Because recirculation cooler 24 recovers available heat, for example, by operating at a temperature suitable for generating steam, the energy is recovered in available form, rather than only lost to cooling water as in the prior art gas phase process. The additional energy costs of the stripping column 26 are therefore reduced by its combined use with the liquid phase recirculation loop and in particular the recirculation cooler 24 .

[0083] Figure 3A is a schematic diagram of a method for producing alcohol according to the present invention. Figure 3A As mentioned above Figure 2A The same except that recycle stream 40 undergoes further processing as described below.

[0084] Figure 3B is suitable for implementation Figure 3A Schematic diagram of the apparatus of the method depicted. Figure 3B and Figure 2B The same except that the recycle stream 40 undergoes further processing as described below.

[0085] The recycle stream 40 is directed to a heater 50 and then to a gas phase hydrogenation reactor 46 to provide a treated stream 48. The purpose of the gas phase hydrogenation reactor 46 is to crack the esters present in the recycle stream 40. For example, the gas phase hydrogenation reactor can crack the ester butyl butyrate to provide butanol, thereby increasing the yield of the alcohol product in the treated stream 48 returned to the reaction process. Advantageously, treating the recycle stream 40 in this manner can prevent the accumulation of heavy contaminant esters such as butyl butyrate in the main hydrogenation reactor 6, which in the liquid phase can hinder the effective hydrogenation of the crude aldehyde feedstock. It can also advantageously allow the stripper 36 to be operated to maximize the alcohol recovery from the heavy stream 16 without causing the accumulation of contaminants such as those esters.

[0086] Figure 4 is a schematic diagram of an apparatus suitable for carrying out the method of the present invention. Figure 4 and Figure 2B The same except that the heavy stream 16 undergoes further processing as described below.

[0087] Downstream of pump 42, heavy stream 16 is directed to heater 52 to provide heated heavy stream 54, which is then directed to liquid phase hydrogenation reactor 58. Liquid phase hydrogenation reactor 58 provides treated stream 60, which is then heated to 100°C. Figure 2B Compared to the untreated heavy stream 16, it advantageously contains fewer contaminants such as esters (e.g., butyl butyrate), etc. The treated stream 60 is then directed to the stripping column 36, as described above with respect to Figure 2B The liquid phase hydrogenation reactor 58 advantageously hydrogenates contaminants such as esters into useful products such as desired alcohols, thereby improving and increasing the overall yield of the products obtained.

[0088] Example

[0089] Example 1

[0090] High-pressure hydrogen stripper in the liquid phase hydrogenation (LPH) loop for butanol

[0091] A heavy stream (flow rate 530 kg / h) from butanol distillation containing about 41 wt.-% butanol, 44 wt.-% C8 oxygenates and 15 wt.-% C12 oxygenates is supplied to a hydrogen stripper at 137° C. The pressure in the hydrogen stripper is 32 bar at the top. A stripping gas (hydrogen) stream (flow rate 1294 kg / h) containing about 99 mol.-% hydrogen and 1 mol.-% methane is heated to 75° C. and supplied to the bottom of the hydrogen stripper. The hydrogen stripper comprises internals to provide 6 theoretical plates.

[0092] From the bottom of the hydrogen stripper a liquid waste stream (flow rate 350 kg / h) comprising about 22 wt.-% butanol, 56 wt.-% C8 oxygenates and 22 wt.-% C12 oxygenates at 71°C was obtained.

[0093] A recycle (hydrogen-rich vapor) stream (flow rate 1476 kg / h) containing about 81 wt% hydrogen, 6.5 wt% methane, 9.5 wt% butanol and 2.7 wt% C8 oxygenates (and trace amounts of C12 oxygenates) at 75°C was obtained from the top of the hydrogen stripper.

[0094] A recycle stream comprising butanol is fed to a liquid phase hydrogenation reactor upstream of a distillation column for providing a heavies stream.

[0095] In this example, 64.5% of the butanol was recovered from the heavies stream and returned to the process.

[0096] Example 2

[0097] High-pressure hydrogen stripper in the liquid phase hydrogenation (LPH) loop for 2-ethylhexanol

[0098] A heavy stream (flow rate 644 kg / h) from the distillation of 2-ethylhexanol (2EH) containing about 15.5 wt% of 2EH, 75 wt% of C12 oxygenates and 9 wt% of C16 oxygenates is supplied to a hydrogen stripper at 152°C. The pressure of the hydrogen stripper is 32 bar at the top. A stripping gas (hydrogen) stream (flow rate 467 kg / h) containing about 98 mol% of hydrogen and 2 mol% of methane is heated to 160°C and supplied to the bottom of the hydrogen stripper. The hydrogen stripper includes internals to provide 6 theoretical plates.

[0099] A liquid waste stream (flow rate 550 kg / h) containing about 5 wt% 2EH, 85 wt% C12 oxygenates and 10 wt% C16 oxygenates at 156°C was obtained from the bottom of the hydrogen stripper.

[0100] A recycle (hydrogen-rich vapor) stream (flow rate 560 kg / h) comprising about 71.7 wt.-% hydrogen, 11.6 wt.-% methane, 12.8 wt.-% 2EH, 3.3 wt.-% C12 oxygenates and 0.4 wt.-% C16 oxygenates at 154° C. is obtained at the top of the hydrogen stripper.

[0101] The recycle stream comprising 2EH is fed to the liquid phase hydrogenation reactor, upstream of the distillation column used to provide the heavies stream.

[0102] In this example, 72% of the 2EH is recovered from the heavy fraction and returned to the process.

Claims

1. A method for producing at least one alcohol, the method comprising: (i) providing a crude aldehyde stream comprising at least one aldehyde to at least one liquid phase hydrogenation reactor and hydrogenating the at least one aldehyde in a liquid phase hydrogenation reaction to provide a crude alcohol stream comprising at least one alcohol; (ii) recycling a liquid recycle stream comprising the at least one alcohol to the at least one liquid hydrogenation reactor via a recycle cooler in which heat in the liquid recycle stream is recovered; (iii) providing the crude alcohol stream to a distillation column and distilling the crude alcohol stream to obtain a purified alcohol stream comprising the at least one alcohol and a heavy stream comprising the at least one alcohol; (iv) providing the heavy stream to a stripping column and contacting the heavy stream with a stripping gas comprising at least 20 mol% hydrogen to separate the heavy stream into a recycle stream comprising the at least one alcohol and a waste stream; (v) returning at least a portion of the recycle stream to the at least one liquid phase hydrogenation reactor in step (i).

2. The method of claim 1, wherein the at least one alcohol is at least one C3-C 20 alcohol, optionally at least one C3-C 10 alcohol.

3. The method according to claim 2, wherein the at least one alcohol is selected from butanol, 2-ethylhexanol, 2-propylheptanol and isononanol.

4. The process according to any one of claims 1 to 3, wherein the crude alcohol stream comprises at least 50 wt% of the at least one alcohol, optionally at least 60 wt% of the at least one alcohol, and optionally at least 70 wt% of the at least one alcohol.

5. The process according to any one of claims 1 to 4, wherein the purified alcohol stream comprises greater than 95 wt. % of the at least one alcohol, optionally greater than 97 wt. % of the at least one alcohol, and optionally greater than 99 wt. % of the at least one alcohol, relative to the total weight of the purified alcohol stream.

6. The process according to any one of claims 1 to 5, wherein the heavy stream comprises less than 80 wt% of the at least one alcohol, optionally less than 70 wt% of the at least one alcohol, optionally less than 60 wt% of the at least one alcohol.

7. The process according to any one of claims 1 to 6, wherein the stripping gas stream comprises at least 70 mol% hydrogen, optionally at least 90 mol% hydrogen, further optionally at least 98 mol% hydrogen.

8. The process of claim 7, wherein the recycle stream comprises at least 60 wt% hydrogen, optionally at least 70 wt% hydrogen, and optionally at least 80 wt% hydrogen.

9. A process according to claim 7 or claim 8, wherein the recycle stream comprises at least 70 wt% hydrogen and at least 5 wt% alcohol.

10. The process according to any one of claims 1 to 9, wherein the pressure in the stripping column is from 15 to 45 bar, optionally from 20 to 35 bar.

11. The method according to any one of claims 1 to 10: (i) wherein the stripping gas stream is provided to a lower portion of the stripping column, optionally to the bottom of the stripping column; and (ii) wherein the heavy stream is provided to the upper part of the stripping column, optionally to the top of the stripping column.

12. The process according to claim 11, wherein the recycle stream is obtained from the upper part of the stripping column, optionally from the top of the stripping column.

13. The process according to any one of claims 1 to 12, wherein the temperature of the stripping gas stream entering the stripping column is from 50°C to 250°C, optionally from 60°C to 200°C.

14. The process according to any one of claims 1 to 13, wherein the temperature of the heavy stream entering the stripping column is from 50°C to 300°C, optionally from 100°C to 200°C, optionally from 125°C to 175°C.

15. The process according to any one of claims 1 to 14, wherein the step of providing a crude aldehyde stream comprises the steps of: The olefin stream is provided to a hydroformylation reactor, and the olefin stream is contacted with a hydroformylation gas stream comprising hydrogen and carbon monoxide to perform a hydroformylation reaction, thereby providing the crude aldehyde stream.

16. The process according to any one of claims 1 to 15, wherein the crude aldehyde stream comprises at least one C3-C 20 aldehyde, optionally at least one C3-C 10 Aldehyde, optionally at least one C3-C8 aldehyde.

17. The method of claim 16, wherein the at least one aldehyde is selected from butyraldehyde, 2-ethylhexenal, 2-propylheptenal, and isononanal.

18. The process of any one of claims 15 to 17, wherein providing the crude aldehyde stream further comprises subjecting the reaction effluent of the hydroformylation reaction to an aldol reaction between at least two aldehydes contained in the reaction effluent to provide the crude aldehyde stream.

19. The process of any one of claims 1 to 18, wherein prior to step (v), the recycle stream is directed to a secondary hydrogenation reactor configured to hydrogenate the esters to at least one alcohol.

20. The method according to claim 19, wherein the hydrogenation reaction in the secondary hydrogenation reactor is a gas phase hydrogenation reaction or a liquid phase hydrogenation reaction.

21. A device for producing alcohol, the device comprising: at least one liquid phase hydrogenation reactor configured to hydrogenate at least one aldehyde contained in the crude aldehyde stream in a liquid phase hydrogenation reaction to provide a crude alcohol stream comprising at least one alcohol; a recirculation loop in fluid communication with the at least one liquid phase hydrogenation reactor and a recirculation cooler, the recirculation loop being configured to recirculate a liquid recycle stream from the at least one liquid phase hydrogenation reactor to the at least one liquid phase hydrogenation reactor via the recirculation cooler; a distillation column in fluid communication with the at least one liquid-phase hydrogenation reactor, the distillation column configured to distill the crude alcohol stream to provide a purified alcohol stream comprising the at least one alcohol and a heavy stream comprising the at least one alcohol; a stripping column in fluid communication with the distillation column, the stripping column being configured to contact the heavy stream with a stripping gas stream comprising at least 20 mol% hydrogen to separate the heavy stream into a recycle stream comprising the at least one alcohol and a waste stream; Wherein in step (i), the stripping tower is fluidly connected to the at least one liquid phase hydrogenation reactor to provide at least a portion of the recycle stream to the at least one liquid phase hydrogenation reactor.

22. The apparatus according to claim 21, further comprising: a hydroformylation reactor configured to contact an olefin stream comprising at least one olefin with hydrogen and carbon monoxide to hydroformylate the at least one olefin to provide the crude aldehyde stream; Wherein the at least one liquid phase hydrogenation reactor is in fluid communication with the hydroformylation reactor.

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