Method and apparatus for the production of alcohol

Abstract

A method for the production of at least one alcohol is provided. The method comprises providing a crude aldehyde stream comprising at least one aldehyde to at least one liquid-phase hydrogenation reactor, hydrogenating 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 at least one alcohol to 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 carrying out distillation on the crude alcohol stream to obtain a purified alcohol stream comprising at least one alcohol and a heavy stream comprising 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% hydrogen to separate the heavy stream into a recycle stream comprising at least one alcohol and a waste stream, and returning at least a portion of the recycle stream to at least one liquid-phase hydrogenation reactor.

Description

Technical Field

[0001] The present invention relates to methods and apparatuses for the production of alcohols. Specifically, the methods and apparatuses according to the present invention provide an improved yield of synthetic alcohol.

Background Art

[0002] Alcohols, especially C 1 ~C 10 Alcohols are used in a wide variety of applications in the chemical industry, including as solvents, fuels, and chemical intermediates in the synthesis of organic compounds. Worldwide, a wide variety of alcohols are produced annually. For certain alcohols (e.g., ethanol), biosynthetic methods such as fermentation may be suitable for the production of alcohols. However, for longer-chain and branched-chain alcohols, synthetic production may be required.

[0003] Existing methods for the synthetic production of alcohols involve the hydroformylation of olefins (also referred to as the "oxo" process) in the presence of a catalyst, followed by a hydrogenation reaction step. The advantage of such methods is the use of inexpensive small-molecule organic starting materials.

[0004] Hydroformylation introduces a formyl group into an unsaturated olefin to provide an aldehyde. Hydroformylation can be induced by contacting the olefin with synthesis gas (a mixture of carbon monoxide and hydrogen). Once the aldehyde is produced, it is reduced by hydrogenation to give the corresponding alcohol. When longer-chain alcohols are required, this process includes an aldolization step to condense two aldehydes, thus providing a longer-chain unsaturated aldehyde. The longer-chain unsaturated aldehyde is then subsequently reduced by hydrogenation to provide the corresponding saturated alcohol.

[0005] Following hydrogenation, the reaction effluent contains the alcohol product in the crude mixture, i.e., the crude alcohol mixture. The crude alcohol mixture is subjected to a distillation process to isolate 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 cut point (i.e., a narrow boiling range). As a result, a significant amount of alcohol can be disposed of as waste. Specifically, a significant amount of alcohol may remain in the higher-boiling fraction, which is referred to in the art as the "heavy stream," and this is typically disposed of as a waste stream. When distillation is carried out to recover all of the alcohol as a product (i.e., the purified alcohol fraction has a wider boiling range), contaminants (e.g., heavy-chain hydrocarbons) are present in the purified alcohol. Contaminants can include by-products of the hydroformylation and hydrogenation reactions (e.g., undesirable oxidation and condensation products such as esters, ketones, and other oxygenates). To reduce contamination of the purified alcohol product, distillation is carried out such that some alcohol remains in the heavy stream. Also, carrying out distillation such that some alcohol remains in the heavy stream can be beneficial to prevent excessive temperatures at the bottom of the distillation column. Such excessive temperatures can lead to the decomposition of heavy components into lighter components that can reverse through the distillation column and contaminate the product.

[0006] Due to the significant amount of alcohol product being disposed of, existing methods for alcohol production are inefficient.

[0007] Prior art methods may dispose of the heavy stream or, alternatively, subject the heavy stream to further processing or purification steps.

[0008] U.S. Patent No. 5,004,845 describes a heavy stream containing butanol, which is mixed with hydrogen, preheated, and vaporized in a vaporizer. The resulting vapor gas mixture is then sent to a vapor phase hydrogenation (VPH) reactor. As the entire heavy stream is vaporized, contaminants that can adversely affect the performance of the hydroformylation and hydrogenation catalysts, as well as the quality and purity of the alcohol product, can accumulate in the process. Chinese Patent No. 10,703,2953 also describes a vapor phase hydrogenation (VPH) reaction scheme. Hydrogenation can be used to thermally decompose heavier chain hydrocarbon contaminants. For example, butyl butyrate (BuBu) is a common by-product of butanal hydrogenation, and this can be hydrogenated to provide butanol.

[0009] Other methods operate under reduced pressure and treat the heavy stream in a column that maintains a low temperature to enable the removal of lighter components without decomposing the heavier components. Alternatively, the column may be operated at a higher temperature or an additive (e.g., hydroxide) may be provided to facilitate the decomposition of heavier contaminant compounds into lighter compounds such as alcohols and aldehydes. German Patent No. 2,713,434 describes separating higher boiling fractions in a column.

[0010] Another method treats the heavy stream in a steam stripper, using steam to separate lighter compounds from the heavy compounds. The product stream may contain the desired alcohol or may contain aldehydes or other components. Water is removed from the product stream, and the resulting light stream is sent to a hydrogenation reactor or a light product column for further separation. U.S. Patent No. 2,614,128 describes recovering alcohol from a heavy stream in a steam stripper and recycling the alcohol for use in the hydrogenation stage of the oxo reaction.

[0011] Recovering alcohol from the heavy stream using any of the foregoing methods requires additional equipment and an increase in energy costs, and may cause accumulation of contaminants during the process.

[0012] Some prior art vapor-phase hydrogenation systems strip alcohol from an alcohol-containing heavy stream using a hydrogen gas stream as a stripping gas before passing the resulting alcohol-containing hydrogen gas stream through the vapor-phase hydrogenation. However, there is already a vaporizer for vaporizing the aldehyde feed to the vapor-phase hydrogenation reaction, and the heavy stream can be passed through this to vaporize the alcohol from the heavy stream. Thus, adding another stripper may increase the number of equipment without any overall benefit, and such a system can be cost-inefficient.

[0013] An object of the present invention is to prevent or reduce one or more of the foregoing problems.

Summary of the Invention

[0014] The present invention relates to improving the overall yield and purity of alcohol obtained from a process for the production of alcohol. Specifically, the present invention recovers an increased amount of alcohol from the effluent of a hydroformylation and hydrogenation process. The present invention advantageously uses a stripping gas containing hydrogen to recover alcohol from a heavy stream, which is obtained from the distillation of alcohol from a crude alcohol stream. The resulting recycle stream contains both the 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 apparatuses disclosed herein advantageously (i) increase the alcohol yield by recovering alcohol from the heavy stream and returning the alcohol to the process, and (ii) provide a recycle stream that can be used directly in a liquid-phase hydrogenation reaction.

[0015] According to a first aspect of the present invention, a method for the production of at least one alcohol, comprising: (i) providing a crude aldehyde stream comprising at least one aldehyde to at least one liquid-phase hydrogenation reactor and hydrogenating 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 at least one alcohol, preferably through a recycle cooler in which heat in the liquid recycle stream is recovered by raising steam, to at least one liquid hydrogenation reactor; (iii) providing the crude alcohol stream to a distillation column and performing distillation on the crude alcohol stream to provide a purified alcohol stream comprising at least one alcohol and a heavy stream comprising 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 at least one alcohol and a waste stream; and (v) returning at least a portion of the recycle stream to at least one liquid-phase hydrogenation reactor in step (i).

[0016] In embodiments, the at least one alcohol is at least one C 3 ~C 20 alcohol, optionally at least one C 3 ~C 10 alcohol, and further optionally at least one C 4 ~C 10 alcohol. In embodiments, the at least one alcohol is selected from butanol, 2-ethylhexanol, 2-propylheptanol, and isononyl alcohol.

[0017] In embodiments, the reactor output 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 an embodiment, the crude alcohol stream comprises at least 50 wt% of at least one alcohol, optionally at least 60 wt% of at least one alcohol, and further optionally at least 70 wt% of at least one alcohol.

[0019] In an embodiment, the purified alcohol stream comprises at least one alcohol in excess of 95 wt%, optionally at least one alcohol in excess of 97 wt%, and further optionally at least one alcohol in excess of 99 wt% based on the total weight of the purified alcohol stream.

[0020] In an embodiment, the heavy stream comprises less than 80 wt% of at least one alcohol, optionally less than 70 wt% of at least one alcohol, and optionally less than 60 wt% of at least one alcohol. Preferably, the heavy stream comprises at least 40 wt%, preferably at least 50 wt% of at least one alcohol. An advantage of the present invention is that since the alcohol in the heavy stream is recovered, a high alcohol ratio in the heavy stream can be tolerated. A high alcohol ratio in the heavy stream, for example, due to the resulting lower temperature, reduces the thermal decomposition of the heavy components at the bottom of the distillation column, enabling a more efficient operation of the distillation while maintaining the quality of the alcohol product.

[0021] Another advantage of the present invention in the liquid-phase hydrogenation reaction is that the alcohol recovered from the heavy stream is condensed in at least one liquid-phase hydrogenation reactor, and thus energy is introduced into at least one liquid-phase hydrogenation reactor. This energy is then recovered, for example, in the form of excess vapor that has risen in the recycle cooler. Thus, in the liquid-phase hydrogenation reaction, by combining a hydrogen stripper for recovering alcohol from the heavy stream through vaporization and the recycle of the liquid recycle stream through a recycle cooler where heat is recovered, a particularly energy-efficient operation is achieved. The prior art gas-phase hydrogenation reactor systems do not benefit from this advantage. The recycle cooler can recover heat by raising the vapor. It will be understood that the recovered heat can be used elsewhere in the plant or process.

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

[0023] In embodiments, the stripping gas stream comprises at least 70 mol% hydrogen, optionally at least 90 mol% hydrogen, and further optionally at least 98 mol% hydrogen. In embodiments, the recycle stream comprises at least 60 wt% hydrogen, optionally at least 70 wt% hydrogen, and further optionally at least 80 wt% hydrogen. In embodiments, the recycle stream comprises at least 2 wt% alcohol, optionally at least 5 wt% alcohol, and further 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 column are selected to strip at least one alcohol from the heavy stream, such that heavier compounds remain in the heavy stream. In an embodiment, the temperature and pressure in the stripping column 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 column is 15 - 45 bara, optionally 20 - 35 bara. The temperature and pressure in the stripping column can be controlled to keep the temperature of the liquid output above a minimum value. The liquid output may be cooled by the vaporization of alcohol into the stripping gas, and thus the liquid output may represent the lowest temperature in the stripping column. In an embodiment, the temperature of the liquid output from the stripping column is 40 °C or higher, and preferably 50 °C or higher. Low temperatures can result in an output with too high a viscosity or poor recovery of alcohol.

[0025] In an embodiment, (i) the stripping gas stream is provided at the lower part of the stripping column, optionally at the bottom of the stripping column, and (ii) the heavy stream is provided at the upper part of the stripping column, optionally at the top of the stripping column. In an embodiment, the recycle stream is obtained from the upper part of the stripping column, optionally from the top of the stripping column. The heavy stream descends through the stripping column under the influence of gravity, and the stripping stream ascends through the stripping column, which is of lower density than 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 thus are "stripped" from the heavy stream.

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

[0027] In an embodiment, the stripping gas stream may contain at least 50 wt%, optionally at least 70 wt%, and further optionally at least 90 wt% of the hydrogen supplied 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 for the hydrogenation of aldehydes in the liquid-phase hydrogenation reactor is provided in the stripping gas stream and not in a separate hydrogen feed stream to the liquid-phase hydrogenation reactor. By using hydrogen in a larger flow rate of the stripping gas, advantageously, a lower temperature can be brought about in the stripping column, and thus it may be beneficial to include all 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 includes providing an olefin stream to at least one hydroformylation reactor and contacting the olefin stream with a hydroformylation gas stream containing hydrogen and carbon monoxide to induce a hydroformylation reaction to provide a crude aldehyde stream.

[0029] In an embodiment, the crude aldehyde stream contains at least one C 3 ~C 20 aldehyde, optionally at least one C 3 ~C 10 aldehyde, and further optionally at least one C 4 ~C 10 aldehyde. In an embodiment, at least one aldehyde is selected from butanal, 2-ethylhexenal, 2-propylheptenal, and isononanal. In an embodiment, the crude aldehyde stream contains at least 40 wt% aldehyde, optionally at least 50 wt% aldehyde, and further optionally at least 60 wt% aldehyde.

[0030] In an embodiment, providing the crude aldehyde stream may further comprise subjecting the reaction effluent of the hydroformylation reaction to an aldol reaction between at least two aldehydes contained in the reaction effluent by contacting the reaction effluent with at least one base or at least one acid, for example, to provide the crude aldehyde stream. In such an embodiment, the crude aldehyde stream comprises at least one aldol condensation product. In such an embodiment, the crude aldehyde stream may comprise at least 20 wt% aldol condensation product, optionally at least 30 wt% aldol condensation product, and further optionally at least 40 wt% aldol condensation product. In a preferred embodiment, the crude aldehyde stream comprises at least one unsaturated aldehyde, for example, 2-ethylhexenal or 2-propylheptenal. 2-Ethylhexenal is an aldol condensation product of butanal. 2-Propylheptenal is an aldol condensation product of pentanal. In an embodiment, butanal and pentanal can be obtained from the hydroformylation of olefins propene and butene, respectively.

[0031] In an embodiment, prior to step (v), the recycle stream is sent to a secondary hydrogenation reactor configured to hydrogenate the ester to at least one alcohol, and the recycle stream contacts hydrogen to induce 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 may be stripped from the heavy stream with the alcohol by a stripping gas. Stripping these esters from the heavy stream according to the present invention and hydrogenating them to the corresponding alcohols can advantageously increase the overall alcohol yield of the liquid-phase hydrogenation and thus improve the efficiency of the feedstock for the entire process.

[0032] According to a second aspect of the present invention, there is provided an apparatus for the production of alcohol, comprising at least one liquid-phase hydrogenation reactor 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; a distillation column in fluid communication with the at least one liquid-phase hydrogenation reactor, the distillation column being configured to perform distillation on the crude alcohol stream to provide a purified alcohol stream containing at least one alcohol and a heavy stream containing at least one alcohol; and 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 containing at least 20 mol% hydrogen to separate the heavy stream into a recirculation stream containing at least one alcohol and a waste stream. The stripping column is in fluid communication with the at least one liquid-phase hydrogenation reactor to provide the recirculation stream to the at least one liquid-phase hydrogenation reactor.

[0033] In an embodiment, the stripping column is a hydrogen stripping column, that is to say, hydrogen is used as the stripping gas.

[0034] In an embodiment, the apparatus further comprises a hydroformylation reactor configured to contact an olefin stream containing at least one olefin with hydrogen and carbon monoxide to induce a hydroformylation reaction on the at least one olefin, and optionally an aldolization unit configured to induce an aldol condensation reaction to convert the aldehyde produced in the hydroformylation reaction into a longer-chain unsaturated aldehyde to provide a crude aldehyde stream.

[0035] In an embodiment, at least one olefin contained in the olefin stream is propene, at least one aldehyde contained in the crude aldehyde stream is butanal and / or 2-ethylhexenal, and at least one alcohol contained in the crude alcohol stream is butanol and / or 2-ethylhexanol.

[0036] In an embodiment, at least one olefin contained in the olefin stream is butylene, at least one aldehyde contained in the crude aldehyde stream is pentanal and / or 2-propylheptenal, and at least one alcohol contained in the crude alcohol stream is pentanol and / or 2-propylheptanol.

Brief Description of the Drawings

[0037]

Figure 1A

Figure 1B

Figure 2A

Figure 2B

Figure 3A

Figure 3B

Figure 4

Modes for Carrying Out the Invention

[0038] Here, the present invention is described by way of examples only with reference to the accompanying drawings and examples. The scope of protection is defined in the appended claims.

[0039] As used herein, "alcohol" refers to straight-chain or branched-chain C 3 ~C 20 alcohol. The alcohol produced according to the present invention can be a mono-alcohol (i.e., containing one hydroxyl group) or a polyol (i.e., containing a plurality of hydroxyl groups). The polyol contains 2 to 8 hydroxyl groups and preferably may contain 2 hydroxyl groups. In an embodiment, the produced alcohol is a monohydroxylated straight-chain or branched-chain C 3 ~C 20 alcohol. In an embodiment, the produced alcohol is selected from propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, and their isomers. In an embodiment, the produced alcohol is selected from butanol, 2-ethylhexanol, and 2-propylheptanol. 2-Ethylhexanol is widely used to produce plasticizer alcohols such as bis-2-ethylhexyl-phthalate.

[0040] As used herein, the term "crude" means that the "crude" stream has not been purified and contains a mixture of compounds. Thus, the "crude" stream requires further processing and / or purification to provide the final product (i.e., alcohol). Thus, the "crude" stream described herein can be an effluent from a reaction process (e.g., an effluent from a hydrogenation reaction and / or an effluent from a hydroformylation reaction). As such, the crude stream can contain several contaminant compounds that are not the alcohol to be produced. Thus, the crude aldehyde stream contains at least one aldehyde and contaminant compounds. Thus, the crude alcohol stream contains at least one alcohol and contaminant compounds.

[0041] As used herein, the term "contaminant" refers to an undesirable non-alcoholic compound. Contaminants can include the products of reactions resulting from the hydroformylation reaction and / or the hydrogenation reaction. For example, contaminant by-products formed from the hydroformylation reaction can include the products of aldehyde condensation reactions (aldol reactions), esters, ketones, heterocycles, cycloalkanes, cycloalkenes, olefins, etc. Contaminants that are particularly encountered include aldol condensation products and esters. Contaminant by-products formed from the hydrogenation reaction can include catalyst residues, heterocycles, cycloalkanes, cycloalkenes, olefins, etc. It is desirable to remove these contaminants from the product purified alcohol stream.

[0042] As used herein, the term "heavy stream" refers to a fraction of organic compounds having a boiling point above 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 100-130 °C, the minimum boiling point of the heavy stream is above 130 °C. One of ordinary skill in the art will understand that the lower limit of the boiling point range (the lower limit of the cut point) depends on the upper limit of the boiling point range of at least one alcohol to be purified in the purified alcohol stream.

[0043] As used herein, the term "unsaturated" means a compound having a carbon-carbon double bond. A "saturated" compound does not contain a carbon-carbon double bond.

[0044] As used herein, the term "stripping gas" refers to a gas mixture capable of stripping light compounds such as alcohol and esters from a heavy stream containing a mixture of organic compounds. The term "light matter" in this context means a compound contained in the heavy stream having a lower boiling point compared to the remaining compounds contained in the heavy stream, and a compound that is easily stripped / vaporized 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.

[0045] As used herein, the term "stripping column" refers to a column configured to contact a stripping gas with a heavy stream to remove alcohol from the heavy stream and provide a recycle stream containing the stripping gas and the recovered alcohol. One skilled in the art would be familiar with stripping columns. In an embodiment, the stripping column is a hydrogen stripping column. In an embodiment, the stripping column includes a zone for providing stages inside the column. The internal structure can be of any shape or form that enables gas-liquid contact and provides the number of stages necessary to strip lighter compounds from the heavy stream. The stripping column can be provided with an "internal structure" disposed inside the column to provide the stages. In an embodiment, the stripping column includes from 1 to 20 stages, optionally from 1 to 8 stages. The internal structure can be selected, for example, from sieve trays, valve trays, bubble cap trays, random packings, or structured packings.

[0046] As used herein, the "corresponding" alcohol to an aldehyde is the reduced alcohol form of that aldehyde. Conversely, the "corresponding" aldehyde to an alcohol is the oxidized aldehyde form of that alcohol. For example, one skilled in the art would understand that the "corresponding alcohol" to butanal is butanol. In the context of the present invention, the corresponding alcohol of an unsaturated aldehyde is typically the corresponding saturated alcohol.

[0047] One skilled in the art would understand that the desired aldehyde to provide the desired alcohol product can be obtained from the hydroformylation of an olefin, and that the olefin typically has one fewer carbon atom than the desired aldehyde corresponding thereto. For example, one skilled in the art would understand that butanal can be obtained from the hydroformylation of propene. Similarly, pentanal can be obtained from the hydroformylation of butylene.

[0048] The methods described herein relate to the production of alcohols. In embodiments, at least one alcohol is produced, and optionally, at least two alcohols are produced. In typical embodiments, a specific alcohol, also referred to herein as the "desired" alcohol, is produced. In embodiments, the method according to the invention is for the production of butanol. In other embodiments, the method according to the invention is for the production of 2-ethylhexanol. In other embodiments, the method according to the invention is for the production of 2-propylheptanol.

[0049] The crude alcohol stream according to the invention contains at least one alcohol and may contain a mixture of alcohols. One skilled in the art will understand that fractional distillation can be used to isolate different alcohols based on their respective boiling points.

[0050] The crude alcohol stream may contain a major alcohol, also referred to as the "desired" alcohol. The crude alcohol stream may contain more than 50% by weight of the desired alcohol, based on the total weight of the crude alcohol stream. In embodiments, the crude alcohol stream contains more than 60% by weight of the desired alcohol, optionally more than 70% by weight of the desired alcohol. In embodiments, the desired alcohol is selected from butanol, 2-ethylhexanol, 2-propylheptanol, and isononyl alcohol.

[0051] The crude alcohol stream is distilled to provide a purified alcohol stream.

[0052] The purified alcohol stream may contain more than 95% by weight of alcohol, optionally more than 97% by weight of alcohol, and further optionally more than 99% by weight of alcohol, based on the total weight of the purified alcohol stream.

[0053] The purified alcohol fraction may contain a mixture of alcohols, but preferably contains more than 50 wt% of the desired alcohol. In a preferred embodiment, the purified alcohol fraction contains more than 80 wt% of the desired alcohol, optionally more than 95 wt% of the desired alcohol, optionally more than 97 wt% of the desired alcohol, and further optionally more than 99 wt% of the desired alcohol, based on the total weight of the purified alcohol fraction. In some embodiments, for example, when the desired alcohol is 2-propylheptanol, the desired alcohol may exist as two or more isomers. In such embodiments, the purified alcohol fraction preferably contains more than 95 wt% of the desired alcohol and its isomers, optionally more than 97 wt% of the desired alcohol and its isomers, and further optionally more than 99 wt% of the desired alcohol and its isomers. In embodiments, the desired alcohol is selected from butanol, 2-ethylhexanol, and 2-propylheptanol.

[0054] Distillation of the crude alcohol stream further provides a heavy stream. In embodiments, the heavy stream contains less than 80 wt% alcohol, optionally less than 70 wt% alcohol, optionally less than 60 wt% alcohol. Preferably, the heavy stream contains at least 40 wt%, more preferably at least 50 wt% alcohol. One of ordinary skill in the art will understand that the term "heavies" as used herein refers to the fraction having the higher boiling purified alcohol stream. The heavy stream contains contaminants. As already mentioned above, it is desirable to avoid the presence of contaminants in the purified alcohol stream. For this reason, the boiling point cut point range used to isolate the purified alcohol stream is narrow. This effect is that a significant amount of alcohol can remain in the heavy stream. Also, having a high alcohol content in the heavy stream advantageously suppresses the boiling temperature of the heavy stream, and thus reduces the bottom temperature of the distillation column from which the heavy stream is withdrawn. A high bottom temperature can lead to decomposition of heavy compounds in the distillation column, forming light decomposition products, which may contaminate the alcohol product stream with the light decomposition products.

[0055] It has been found that the alcohol present in the heavy stream can be recovered from the heavy stream and reintroduced into the alcohol production process. Specifically, the inventors have found that by contacting the heavy stream with a stripping gas, the alcohol can be stripped from the heavy stream into a recycle stream, and this recycle stream can be directly provided to the liquid-phase hydrogenation reaction. In this way, the inventors have surprisingly found that 50-90% of the alcohol in the heavy stream can be recovered, typically 60-80% of the alcohol in the heavy stream can be recovered. This represents a significant improvement in the overall yield of the recovered alcohol compared to prior art methods where the alcohol in the heavy stream is not recovered. Unlike gas-phase hydrogenation where the aldehyde feed has to be vaporized, liquid-phase hydrogenation does not have a feed vaporizer where the heavy stream can be provided for alcohol recovery. Therefore, the addition of a stripping column to the liquid hydrogenation system represents a valuable addition to the process. Furthermore, the alcohol vaporized in the strip gas can either recondense in the liquid-phase hydrogenation reactor or prevent the vaporization of other alcohols in the liquid-phase hydrogenation reactor by changing the vapor-liquid equilibrium in the liquid-phase hydrogenation reactor, so that more heat can be extracted through the recycle cooler. In a gas-phase hydrogenation system, the temperature is typically such that any heat has to be transferred to the cooling water. However, in a liquid-phase hydrogenation system as in the present invention, the recycle cooler can operate at a temperature where the vapor rises, and thus the extra heat provided by the alcohol vaporized in the strip gas can be recovered as useful vapor, resulting in an overall increase in energy efficiency compared to the prior art gas-phase hydrogenation process.

[0056] Figure 1A is a schematic diagram of a prior art method for the production of alcohol. A crude aldehyde stream containing at least one aldehyde 2 is provided to a hydrogenation reactor 6 together with a hydrogen stream 4. The hydrogenation reactor is at a temperature and pressure suitable for inducing the hydrogenation of at least one aldehyde to provide the corresponding alcohol in a crude alcohol stream 8. The crude alcohol stream 8 is provided to a distillation column 10, and the crude alcohol stream 8 is separated into a light stream 12, a purified alcohol stream 14, and a heavy stream 16. In the prior art method depicted, the heavy stream 16 is disposed of.

[0057] Figure 1B is a schematic diagram of a prior art apparatus for implementing the method for the production of alcohol illustrated in Figure 1. In Figure 1B, the hydrogenation reactor 6 is a liquid-phase hydrogenation reactor. The hydrogenation reactor is provided with an outlet 28 for adjusting the pressure within the reactor 6. Additionally, the hydrogen reactor is provided with a gas recycle compressor loop that can be used instead of or in addition to the outlet 28. The gas recycle compressor loop includes an input stream 30 in fluid communication with a compressor 32 and an output stream 34 downstream of the compressor 32. The output stream 34 is in fluid communication with the hydrogen stream 4 supplied to the hydrogenation reactor 6. Additionally, a liquid recycle loop is provided that includes a liquid recycle stream 18 downstream of the reactor 6 and in fluid communication with a pump 20 for providing a pumped liquid recycle stream 22. The liquid recycle stream 18 branches from the crude alcohol stream 8 but can alternatively be withdrawn directly from the hydrogenation reactor 6. The pumped liquid recycle stream 22 is cooled in a recycle cooler 24 before rejoining the crude aldehyde stream 2 to provide a cooled and pumped liquid recycle stream 26.

[0058] As described below, the methods and apparatuses according to the present invention and as described herein have some features in common with the prior art methods and apparatuses described above. Thus, those skilled in the art will understand that the aspects of Figures 1A and 1B described above may be common to the methods and apparatuses according to the present invention, and thus, the descriptions of Figures 1A and 1B apply to the present invention as long as there are common features.

[0059] Figure 2A is a schematic diagram of a method for producing alcohol according to the present invention. Figure 2A is identical to Figure 1A except that further processing is performed on the heavy stream 16 and the hydrogen stream 4 is not directly provided to the hydrogenation reactor 6.

[0060] The crude aldehyde stream 2 can be provided as the effluent of a hydroformylation reaction (not illustrated). By hydroformylation, aldehydes are provided from olefins. Hydroformylation requires contacting an olefin with carbon monoxide and hydrogen over a catalyst (e.g., a cobalt or rhodium-based catalyst) to produce an aldehyde containing one more carbon than the original olefin. Thus, the starting olefin material can determine which alcohol is produced in the reaction process. For example, hydroformylation of propylene provides a mixture of n-butyraldehyde and iso-butyraldehyde. Hydrogenation of n-butyraldehyde and iso-butyraldehyde provides 1-butanol and iso-butanol, respectively. In addition, aldol condensation products of n-butyraldehyde such as 2-ethylhexenal can also be provided, which provides 2-ethylhexanol when hydrogenated. As another example, hydroformylation of propylene and butylene provides butyraldehyde and pentanal, which can be converted to 2-propylhexenal by aldol condensation and hydrogenated to 2-propylhexanol.

[0061] Olefins suitable for use in accordance with the present invention include propylene, butylene, pentene, hexene, heptene, octene, and isomers thereof. Particularly preferred olefins are selected from propylene and butylene. In an embodiment, the crude aldehyde stream further comprises at least one aldol and / or at least one acrolein as a condensation product of at least two aldehydes. For example, the aldol condensation of butanal (also referred to as butyl aldehyde) with itself results in 2-ethyl-hexenal (also referred to as ethyl-propyl-acrolein). In an embodiment, conditions suitable for the hydroformylation reaction are used to promote the aldol reaction between at least two aldehydes. However, during the hydroformylation synthesis, some undesirable contaminants are generated and present in the crude aldehyde stream.

[0062] Hydrogenation requires contacting at least one aldehyde with hydrogen on a catalyst. Hydrogenation reduces the carbon-oxygen double bond to provide the corresponding carbon-oxygen single bond and thus an alcohol. Hydrogenation can also reduce a carbon-carbon double bond, for example, when at least one aldehyde in the crude aldehyde stream is unsaturated (e.g., an aldol condensation product). Hydrogenation can also cleave the carbon-oxygen single bond in an ester to provide the corresponding alcohol. Thus, at least one aldehyde contained in the crude aldehyde stream 2 may be saturated (i.e., does not contain a carbon-carbon double bond) or unsaturated (i.e., contains a carbon-carbon double bond).

[0063] The catalyst used for use in the hydrogenation reactor is a liquid-phase hydrogenation reaction catalyst. The catalyst can typically be selected from copper-based, copper / zinc-based, copper / chromium-based, and nickel-based catalysts.

[0064] During the hydroformylation and hydrogenation reactions, some undesirable contaminants are generated in the crude alcohol stream. Examples of contaminants may include esters. A specific contaminant ester formed in the production of butanol is, for example, butyl butyrate.

[0065] The crude alcohol stream 8 is provided as the effluent of the hydrogenation reaction. The distillation of the crude alcohol stream 8 is carried out in a distillation column 10 at a temperature and pressure effective to obtain a desired purified alcohol product stream 14 of the desired purity, which will be readily apparent to those skilled in the art.

[0066] In Figure 2A, the heavy stream 16 is sent to a stripping column 36, which is preferably a hydrogen stripping column. In contrast to Figures 1A and 1B, the hydrogen stream 4 is provided directly to the stripping column instead of being provided directly to the hydrogenation reactor 6. The hydrogen stream 4 strips light components from the heavy stream 16, which contains alcohols not collected in the purified alcohol stream 14. When the hydrogen stream 4 strips lighter molecules (e.g., at least one alcohol to be recovered) from the heavy stream (i.e., the transfer of lighter molecules from the liquid phase in the heavy stream to the gas phase in the stripping gas), a recycle stream 40 containing hydrogen and the desired alcohol product is provided, which is returned to the hydrogenation reactor 6. The recycle stream 40 may contain lighter molecules other than at least one alcohol that was also stripped from the heavy stream. These other lighter molecules include esters and aldehydes that were not successfully reduced in the hydrogenation reactor 6, and condensation products of aldehydes that were not successfully reduced in the hydrogenation reactor 6.

[0067] The waste stream 38 containing the remaining heavy fraction compounds is sent for further treatment (not illustrated), such as pyrolysis, to obtain further usable aldehyde or alcohol molecules, or can be used as fuel.

[0068] Within the hydrogenation reactor 6, a recycle stream 40 containing hydrogen and the desired alcohol contacts a fresh crude aldehyde stream 2 which may contain at least one aldehyde. As already described above, the liquid-phase hydrogenation is carried out using a solid catalyst in order to hydrogenate the aldehyde to the corresponding alkanol (saturated alcohol). Thus, the recycle stream 40 returns to the process at the point of the hydrogenation reactor 6 the alcohol which would otherwise be discarded, together with alcohol precursor molecules such as aldehydes and esters.

[0069] The stripping column 36 is described herein mainly with respect to stripping alcohol from the heavy stream 16, but those skilled in the art will understand that, as described above, other lighter molecular compounds such as aldehydes and esters are also stripped and can thus be present in the recycle stream 40. This is especially the case when the stripping column 36 is designed and operates to strip a higher proportion of alcohol from the heavy stream 16. For example, in a process for the production of butanol, the hydrogen stripper can be designed and operated to recover most of the alcohol in the heavy stream 16 and can thus also strip the butyl butyrate (BuBu) ester formed as a by-product in the production process. Then, since the recycle stream 40 contains BuBu, the process illustrated in Figure 2A and the apparatus illustrated in Figure 2B are likely to produce an accumulation of BuBu. BuBu can be hydrogenated to butanol within the hydrogenation reactor 6, but the conversion may be insufficient. For this reason, it may be desirable to subject the recycle stream 40 to further treatment to remove contaminants such as BuBu before the recycle stream 40 enters the hydrogenation reactor 6 (see Figures 3A, 3B, and 4). This can increase the alcohol yield by both converting at least some of the contaminants to further alcohol products and facilitating the design and operation of the stripping column 16 to maximize the recovery of alcohol from the heavy stream 16.

[0070] Figure 2B is a schematic diagram of an apparatus suitable for implementing the method depicted in Figure 2A. Figure 2B is identical to Figure 1B except that the heavy stream 16 is subjected to further processing as described below, the hydrogen stream 4 is not directly provided to the hydrogenation reactor 6, and there is no (optional) gas recycle compressor loop.

[0071] As shown in Figure 2B, the heavy stream 16 is sent to the top of the stripper column 36. The heavy stream 16 can be pumped to the stripper column 36 by a pump 42. The hydrogen stream 4 is sent to the bottom of the stripper column 36 and is optionally heated using a heater 44. The heated hydrogen stream 4 rises within the stripper column 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 product) in the heavy stream to transfer from the liquid phase in the heavy stream to the gas phase in the hydrogen stream. Ideally, only the lighter components (e.g., alcohol product) are vaporized and the heavier components remain in the liquid phase. Advantageously, the degree of vaporization of the lighter components (e.g., alcohol) from the heavy stream can be controlled by adjusting the temperature of the hydrogen stream 4 supplied to the hydrogen stripper column 36, adjusting the temperature of the heavy stream 16, and / or bypassing a portion of the hydrogen stream 4 around the stripping column 36. For example, when the temperature of the hydrogen stream 4 increases, a greater fraction of the heavy vapor evaporates. The recycle stream 40, which contains hydrogen and the recovered alcohol, is extracted from the top of the stripper column and sent to the hydrogenation reactor 6 as described above.

[0072] The waste stream 38 is extracted from the bottom of the stripper column. The waste stream 38 can be further distilled or subjected to a pyrolysis process to obtain useful smaller carbon molecules such as saturated and unsaturated aldehydes, enols, acetals, etc. These products may be used to produce valuable secondary products or may be reintroduced into the process to contribute to the yield of the alcohol product.

[0073] In the embodiment, the operating pressure inside the distillation column 10 is lower than the operating pressure inside the hydrogenation reactor 6, and the operating pressure inside the stripper column 36 is higher than that of the hydrogenation reactor 6. The fact that the operating pressure of the stripper column 36 is high means that the flow of the recycle stream 40 is provided to the hydrogenation reactor 6 without the need for a compressor. Alternatively, a compressor may be provided in the flow path of the recycle stream 40.

[0074] The inclusion of gas make-up to the hydrogen stripper can assist the stripper or reduce the temperature in the preheater.

[0075] The provision of the outlet 28 and the gas recycle compressor loop (30, 32, 34) as described above in connection with FIG. 1B are each optional features of the present invention. The outlet 28 operates to discharge the inerts from the liquid-phase hydrogenation reactor 6 and prevent their deposition. The outlet also contains some hydrogen. The hydrogen 4 entering the reactor is readily consumed within the hydrogenation reactor and can be adsorbed in the liquid phase therein. If the hydrogen consumption is reduced and hydrogen remains in the gas phase within the reactor, it can be discharged via the outlet 28 or compressed via the gas recycle compressor loop for reuse. This can be particularly beneficial when a secondary gas-phase hydrogenation reactor (such as described in connection with FIG. 3B below) is used. Those skilled in the art will understand that since the crude aldehyde stream and the crude alcohol stream remain in the liquid phase and thus the reaction within the liquid-phase hydrogenation reactor 6 is a liquid-phase hydrogenation reaction, the gas recycle compressor loop does not provide the hydrogen to induce a gas-phase hydrogenation reaction to the liquid-phase hydrogenation reactor 6.

[0076] The liquid phase recirculation loop (18, 20, 22, 24, 26), and in particular the recirculation cooler 24, described above in connection with FIG. 1B, in combination with other features of the present invention, can produce advantageous energy efficiency compared to prior art gas phase processes. The hydrogenation reactor 6, which is a liquid phase hydrogenation reactor, contains a solid catalyst, and the temperature and pressure therein are such that the resulting crude aldehyde stream and crude alcohol stream remain in liquid form. The liquid phase recirculation loop operates to cool the crude aldehyde stream. Since the alcohol in the recirculation stream 40 is in the gas phase, the alcohol is either condensed within the liquid phase hydrogenation reactor 6 or affects the vapor-liquid equilibrium so that other alcohols do not vaporize. As a result, at least some of the energy used to vaporize the alcohol in the stripping column 36 is effectively transferred to the liquid phase within the liquid phase hydrogenation reactor 6 and can be recovered within the recirculation cooler 24. The recirculation cooler 24, for example, by operating at a temperature suitable for raising steam, recovers the heat that can be used, so that the energy is recovered in a usable form and is not just lost to cooling water as in the case of prior art gas phase processes. Thus, the additional energy cost of the stripping column 26 is reduced by the liquid phase recirculation loop, and in particular its use in combination with the recirculation cooler 24.

[0077] Figure 3A is a schematic diagram of a method for producing alcohol according to the present invention. Figure 3A is identical to Figure 2A described above, except that the recirculation stream 40 is subjected to further processing as described below.

[0078] Figure 3B is a schematic diagram of an apparatus suitable for implementing the method depicted in Figure 3A. Figure 3B is identical to Figure 2B, except that the recirculation stream 40 is subjected to further processing as described below.

[0079] The recycle stream 40 is sent to a heater 50 and then to a vapor-phase hydrogenation reactor 46 to provide a process stream 48. The purpose of the vapor-phase hydrogenation reactor 46 is to cleave the esters present in the recycle stream 40. For example, the vapor-phase hydrogenation reactor can cleave butyl butyrate ester to provide butanol, thus increasing the yield of alcohol products in the process stream 48 that is returned to the reaction process. Advantageously, by treating the recycle stream 40 in this way, the accumulation of heavy contaminant esters such as butyl butyrate in the main hydrogenation reactor 6 that can interfere with the efficient hydrogenation of the crude aldehyde feedstock in the liquid phase can be prevented. It also advantageously enables the stripping column 36 to operate to maximize the alcohol recovery from the heavy stream 16 without causing the accumulation of contaminants such as those esters.

[0080] Figure 4 is a schematic diagram of an apparatus suitable for implementing the method of the present invention. Figure 4 is identical to Figure 2B except that the heavy stream 16 is subjected to further processing as described below.

[0081] Downstream of the pump 42, the heavy stream 16 is sent to a heater 52 to provide a heated heavy stream 54, which is then sent to a liquid-phase hydrogenation reactor 58. The liquid-phase hydrogenation reactor 58 advantageously provides a process stream 60 with fewer contaminants such as esters (e.g., butyl butyrate) compared to the untreated heavy stream 16 of Figure 2B. The process stream 60 is then sent to the stripper column 36 as described above in connection with Figure 2B. The liquid-phase hydrogenation reactor 58 advantageously hydrogenates contaminants such as esters to useful products such as the desired alcohol, thus improving and increasing the overall yield of the resulting products.

Examples

[0082] Example 1 High-Pressure Hydrogen Stripper in a Liquid Phase Hydrogenation (LPH) Loop for Butanol A heavy stream (flow rate 530 kg / h) from the distillation of butanol containing about 41 wt% butanol, 44 wt% C8 oxygenates, and 15 wt% C12 oxygenates was fed to a hydrogen stripper column at 137 °C. The pressure in the hydrogen stripper column was 32 bara at the top. A stripping gas (hydrogen) stream (flow rate 1294 kg / h) containing about 99 mol% hydrogen and 1 mol% methane was heated to 75 °C and fed to the bottom of the hydrogen stripper column. The hydrogen stripper column was equipped with internal structures to provide six theoretical trays.

[0083] A liquid waste stream (flow rate 350 kg / h) at 71 °C containing about 22 wt% butanol, 56 wt% C8 oxygenates, and 22 wt% C12 oxygenates was obtained from the bottom of the hydrogen stripper.

[0084] A recycle (hydrogen-rich vaporized gas) stream (flow rate 1476 kg / h) at 75 °C 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) was obtained from the top of the hydrogen stripper.

[0085] The recycle stream containing butanol was fed to a liquid-phase hydrogenation reactor upstream of the distillation column used to provide the heavy stream.

[0086] In this example, 64.5% of the butanol was recovered from the heavy stream and returned to the process.

[0087] Example 2 High-Pressure Hydrogen Stripper in the Liquid-Phase Hydrogenation (LPH) Loop for 2-Ethylhexanol A heavy stream (flow rate 644 kg / h) from the distillation of 2-ethylhexanol (2-EH) containing about 15.5 wt% 2-ethylhexanol (2-Ethylhexanol, 2EH), 75 wt% C12 oxygenates, and 9 wt% C16 oxygenates was fed to a hydrogen stripper column at 152 °C. The pressure of the hydrogen stripper column was 32 bara at the top. A stripping gas (hydrogen) stream (flow rate 467 kg / h) containing about 98 mol% hydrogen and 2 mol% methane was heated to 160 °C and fed to the bottom of the hydrogen stripper column. The hydrogen stripper column was equipped with internal structures to provide six theoretical trays.

[0088] A liquid waste stream (flow rate 550 kg / h) at 156 °C containing about 5 wt% 2-EH, 85 wt% C12 oxygenates, and 10 wt% C16 oxygenates was obtained from the bottom of the hydrogen stripper.

[0089] A recycle (hydrogen-rich vaporized gas) stream (flow rate 560 kg / h) at 154 °C containing about 71.7 wt% hydrogen, 11.6 wt% methane, 12.8 wt% 2-EH, 3.3 wt% C12 oxygenates, and 0.4 wt% C16 oxygenates was obtained at the top of the hydrogen stripper.

[0090] The recycle stream containing 2-EH was fed to a liquid-phase hydrogenation reactor upstream of the distillation column used to provide the heavy stream.

[0091] In this example, 72% of the 2-EH was recovered from the heavy draw and returned to the process.

Claims

1. A method for producing at least one alcohol, (i) to provide a crude aldehyde stream containing at least one aldehyde to at least one liquid-phase hydrogenation reactor, and to hydrogenate the at least one aldehyde in the liquid-phase hydrogenation reaction to provide a crude alcohol stream containing at least one alcohol, (ii) Recirculating the liquid recirculation flow containing the at least one alcohol to at least one liquid hydrogenation reactor via a recirculation cooler from which heat in the liquid recirculation flow is recovered, (iii) The crude alcohol stream is supplied to a distillation column, and distillation is performed on the crude alcohol stream to obtain a purified alcohol stream containing the at least one alcohol and a heavy alcohol stream containing the at least one alcohol. (iv) The heavy flow is supplied to a stripping tower, and the heavy flow is brought into contact with a stripping gas containing at least 20 mol% hydrogen to separate the heavy flow into a recirculation flow containing at least one alcohol and a waste flow. (v) A method for producing at least one alcohol, comprising returning at least a portion of the recirculated flow to the at least one liquid-phase hydrogenation reactor in step (i).

2. The aforementioned at least one alcohol is at least one C ３ ~C ２０ Alcohol, optionally, at least one C ３ ~C １０ The method according to claim 1, wherein the alcohol is used.

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

4. The method according to claim 1, wherein the crude alcohol stream comprises at least 50% by weight of the at least one alcohol, optionally at least 60% by weight of the at least one alcohol, and optionally at least 70% by weight of the at least one alcohol.

5. The method according to claim 1, wherein the purified alcohol stream comprises, in proportion to the total weight of the purified alcohol stream, at least one alcohol in an amount exceeding 95% by weight, optionally at least one alcohol in an amount exceeding 97% by weight, and optionally at least one alcohol in an amount exceeding 99% by weight.

6. The method according to claim 1, wherein the heavy flow comprises less than 80% by weight of the at least one alcohol, optionally less than 70% by weight of the at least one alcohol, and optionally less than 60% by weight of the at least one alcohol.

7. The method according to claim 1, wherein the stripping gas stream comprises at least 70 mol% hydrogen, optionally at least 90 mol% hydrogen, and further optionally at least 98 mol% hydrogen.

8. The method according to claim 7, wherein the recirculating flow comprises at least 60% by weight of hydrogen, optionally at least 70% by weight of hydrogen, and further optionally at least 80% by weight of hydrogen.

9. The method according to claim 7 or 8, wherein the recirculating flow comprises at least 70% by weight of hydrogen and at least 5% by weight of alcohol.

10. The method according to claim 1, wherein the pressure inside the stripping tower is 15 to 45 bara, optionally 20 to 35 bara.

11. (i) The stripping gas flow is optionally supplied to the lower portion of the stripping tower, to the bottom of the stripping tower, (ii) The method according to claim 1, wherein the heavy flow is optionally supplied to the upper part of the stripping tower and to the top of the stripping tower.

12. The method according to claim 11, wherein the recirculating flow is optionally obtained from the top of the stripping tower, rather than from the upper part of the stripping tower.

13. The method according to claim 1, wherein the temperature of the stripping gas flow entering the stripping tower is 50 to 250°C, and optionally 60 to 200°C.

14. The method according to claim 1, wherein the temperature of the heavy flow entering the stripping tower is 50 to 300°C, optionally 100 to 200°C, optionally 125 to 175°C.

15. The process of providing a crude aldehyde flow is The method according to claim 1, comprising the steps of supplying an olefin stream to a hydroformylation reactor, contacting the olefin stream with a hydroformylation gas stream containing hydrogen and carbon monoxide to induce a hydroformylation reaction and provide the crude aldehyde stream.

16. The crude aldehyde stream contains at least one C ３ -C ２０ aldehyde, optionally at least one C ３ -C １０ aldehyde, optionally at least one C ３ -C ８ aldehyde, The method according to claim 1.

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

18. The method according to claim 15, further comprising providing the crude aldehyde stream by subjecting the reaction effluent of the hydroformylation reaction to an aldol reaction between at least two aldehydes contained in the reaction effluent.

19. The method according to claim 1, wherein, prior to step (v), the recirculating flow is sent to a secondary hydrogenation reactor configured to hydrogenate the ester 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, A liquid-phase hydrogenation reactor is 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 having fluid communication with the at least one liquid-phase hydrogenation reactor and a recirculation cooler, configured to recirculate the liquid recirculation flow 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 having fluid communication with the at least one liquid-phase hydrogenation reactor, configured to perform distillation on the crude alcohol stream to provide a purified alcohol stream containing the at least one alcohol and a heavy alcohol stream containing the at least one alcohol, A stripping column, which is in fluid communication with the distillation column, is configured to separate the heavy mass flow into a recirculation flow containing at least one alcohol and a waste flow by bringing the heavy mass flow into contact with a stripping gas flow containing at least 20 mol% hydrogen. An apparatus wherein the stripping tower is in fluid communication with the at least one liquid-phase hydrogenation reactor in step (i) to supply at least a portion of the recirculated flow to the at least one liquid-phase hydrogenation reactor.

22. The hydroformylation reactor is further configured to provide the crude aldehyde stream by contacting an olefin stream containing at least one olefin with hydrogen and carbon monoxide to induce a hydroformylation reaction in the at least one olefin, The apparatus according to claim 21, wherein the at least one liquid-phase hydrogenation reactor is in fluid communication with the hydroformylation reactor.

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