Process for purifying a hydroalcoholic feed comprising ethanol, acetaldehyde

Abstract

A process for purifying a hydroalcoholic load comprising ethanol and acetaldehyde.The present invention relates to a process for purifying a hydroalcoholic feedstock, comprising: a) a countercurrent liquid-liquid extraction step, comprising an extraction section fed at the top by said hydroalcoholic feedstock and at least a fraction of an intermediate raffinate from step b) and at the bottom by an extraction solvent, and producing at the top an extraction stream and at the bottom a raffinate, said extraction section being operated at an average temperature in the extractor between 10 and 40°C; b) a countercurrent liquid-liquid counterextraction step comprising a counterextraction section fed at the top by an acidic aqueous solution having a pH between 0.5 and 5.0, and at the bottom by the extraction stream from step a), and producing at the top an extract and at the bottom said intermediate raffinate, said counterextraction section being operated at an average temperature between 40 and 80°C.

Description

1 / 27 Descriptive Report of the Invention Patent for a PROCESS FOR PURIFYING A HYDROALCOHOLIC FILL COMPRISING ETHANOL AND ACETALDEHYDE. TECHNICAL FIELD

[0001] The present invention relates to a process for treating a feedstock comprising at least water, ethanol, and acetaldehyde by liquid-liquid extraction and counter-extraction, allowing for the maximization of the elimination of impurities, particularly slightly or non-polar ones, optimizing the recovery of ethanol and acetaldehyde.

[0002] The process according to the present invention can be advantageously integrated into a more comprehensive process for converting ethanol to butadiene, also called the Lebedev process. It allows for the purification of the liquid effluent from the conversion reactors, improving the recovery of ethanol and acetaldehyde not converted to butadiene. BACKGROUND OF THE TECHNIQUE

[0003] The process of producing butadiene from ethanol was developed, in particular, by American teams during the Second World War, based on the work of Ostromilenski.

[0004] In this process, the conversion per pass is less than 50%, which implies significant recycling of ethanol and acetaldehyde. Furthermore, a wide variety of impurities of different natures are produced (saturated, unsaturated, aromatic hydrocarbons, oxygenated products such as alcohols, ketones, aldehydes, phenols, acids, esters, ethers) and having very different molar masses (between 50 and 10,000 g / mol).

[0005] Therefore, it is necessary to carry out a chain of unit operations in order to eliminate as many impurities as possible, losing as little ethanol and acetaldehyde as possible. From an economic point of view, it is essential to reduce the production cost of butadiene. Petition 870240048686, dated 10 / 06 / 2024, page 14 / 50 2 / 27 no, which requires: Losing as little ethanol and acetaldehyde as possible; Not recycling impurities in the reactors would induce a drop in selectivity for butadiene or would accumulate unacceptable levels, requiring a purge and therefore losses of ethanol and acetaldehyde.

[0006] At the outlet of the catalytic reactors, the effluent produced, comprising butadiene, ethanol, water, acetaldehyde and impurities, undergoes several unit operations in order to separate the unwanted gaseous and liquid byproducts of the butadiene formed and the compounds ethanol, water, acetaldehyde, called noble compounds, liquid and gaseous being understood at ambient temperature and pressure.

[0007] Among the gaseous byproducts at ambient temperature and pressure, hydrogen, carbon monoxide, carbon dioxide, alkanes, and C1-C4 olefins can be mentioned. It is essential to eliminate these byproducts from the butadiene-rich effluent in order to obtain a butadiene product that meets the required specifications. Among the liquid byproducts at ambient temperature and pressure, acetone, diethyl ether, butanal, butanol, butanone, ethyl acetate, crotonaldehyde, and acetic acid can be mentioned. Other byproducts may be generated in smaller quantities in the reaction zone. In the remainder of this document, the term impurities will refer to this set of thousands of hydrocarbon or oxygenated compounds.

[0008] In the early process schemes of the American teams, ethanol, acetaldehyde, water, and liquid byproducts are separated by a chain of three distillation columns (US patent 2,403,742). The effluent rich in ethanol, acetaldehyde, water, and liquid byproducts feeds a first distillation column, in which an effluent rich in acetaldehyde is separated from the rest of the effluent. A second distillation column allows the separation of the liquid byproducts. Petition 870240048686, dated 10 / 06 / 2024, page 15 / 50 3 / 27 of an effluent rich in ethanol and water. The last distillation column allows the ethanol to be separated from the water. Most of the process patents filed between 1940 and 1960 by the companies Carbide & Carbon or Koppers (US 2,043,743; US 2,393,381; US ​​2,395,057 and US 2,439,587) aim to improve this part of the scheme.

[0009] One of the problems in the process, observed in the years Since 1945, it has been important to form diethylacetal and / or hemyethylacetal, notably resulting from the reaction of ethanol with acetaldehyde, which entails a non-negligible loss of reagents (ethanol, acetaldehyde) and, therefore, a decrease in butadiene yield. Toussaint et al., Industrial and Engineering Chemistry; 1947; Vol. 39, No. 2, pp. 120-125, indicate, in particular, that 200 kg of diethylacetal are produced by a tower of butadiene formed.

[0010] In patents FR 3,026,100 and RF 3,026,101, the elimination of liquid impurities is done, at least in part, by liquid-liquid extraction. The liquid effluent at the reactor outlet, comprising ethanol, acetaldehyde, water, and impurities, feeds a liquid-liquid extraction column. This column is fed, at the base, by a washing solvent intended to wash the feed in countercurrent. At the end of this washing section, the extract is composed mainly of the washing solvent and the extracted byproducts (such as diethyl ether) and includes small amounts of ethanol and acetaldehyde. This extract is then washed with water to re-extract the ethanol and acetaldehyde and thus minimize losses of ethanol and acetaldehyde. The washing solvent used for this unit operation consists of a mixture of hydrocarbons, having between 6 and 40 carbon atoms.

[0011] In this configuration, a large proportion of the diethylacetal and hemyethylacetal, formed upstream of the liquid-liquid extraction step, notably by reaction of ethanol and acetaldehyde, are not contained. Petition 870240048686, dated 10 / 06 / 2024, page 16 / 50 4 / 27 of the liquid effluent present at the reactor outlet is extracted by the washing solvent. This results in a significant loss of ethanol and acetaldehyde equivalent, and therefore increases the production cost of butadiene.

[0012] Patent FR 3,057,467 proposes a process for purifying liquid effluent comprising ethanol, water, and acetaldehyde, from the Lebedev process described notably in patent FR 3,026,100 or FR 3,026,101, by liquid-liquid extraction and counter-extraction with decomposition of diethylacetal catalyzed by the presence of an acid in the aqueous counter-extraction solvent in the step. However, such a process with the creation of an acid dissolved in the aqueous phase entails a consumption and, therefore, a more or less significant loss of acidic molecules introduced into the counter-extraction solvent.

[0013] The process, according to the present invention, aims to eliminate this acid consumption problem. More generally, the present invention aims at publishing a hydroalcoholic feedstock comprising ethanol and acetaldehyde, maximizing the elimination of impurities, particularly slightly polar or non-polar ones, contained in this aqueous feedstock and limiting losses in ethanol and acetaldehyde. When the present invention is advantageously integrated into a Lebedev-type process, such as that described in patent FR 3,026,100 or patent FR 3,026,101, it aims to purify the liquid effluent from the butadiene separation step at the reactor outlet, and more particularly from the ethanol / acetaldehyde / water effluent from D1) of patent FR 3,026,100 or from the ethanol / acetaldehyde / water effluent from step B) of patent FR 3,026.101, maximizing the elimination of impurities, particularly slightly polar or non-polar ones (such as diethyl ether) contained in said liquid effluent, optimizing the amounts of ethanol and acetaldehyde not converted and recycled to the reactors, and minimizing acid consumption. Petition 870240048686, dated 10 / 06 / 2024, page 17 / 50 5 / 27 The present invention thus allows for an improvement in the overall yield of the Lebedev process for converting ethanol to butadiene, with reduced additive consumption. SUMMARY OF THE INVENTION

[0014] The present invention relates to a process for purifying a hydroalcoholic feedstock 1 comprising at least water, ethanol, acetaldehyde and impurities, said process comprising:

[0015] a countercurrent liquid-liquid extraction step, comprising an extraction section comprising an extractor 2 fed, at the top, by said hydroalcoholic feedstock 1 and at least a fraction of an intermediate raffinate from the counter-extraction step b) and, at the bottom, by an extraction solvent 3, and producing, at the top, an extraction stream 5 and, at the bottom, a raffinate 4 comprising water, ethanol and acetaldehyde, said extraction section being operated at an average temperature in the extractor between 10 and 40°C;

[0016] a countercurrent liquid-liquid counter-extraction stage comprising a counter-extraction section comprising a counter-extractor 6 distinct from the extractor of stage a) and fed, at the top, by an acidic aqueous solution 7 originating from stage a), and producing, at the top, an extract 8 and, at the bottom, said intermediate raffinate, said counter-extraction section being operated at an average temperature in the counter-extractor distinct from the average temperature in the extractor of stage a) and comprised between 40 and 80°C.

[0017] The present invention relates to a chain of unit operations for the extraction of impurities and the decomposition of diethylacetal and / or hemyethylacetal contained in a feedstock composed of water, ethanol, acetaldehyde and impurities, in particular a Lebedev type feedstock.

[0018] Surprisingly, the inventors found that, Petition 870240048686, dated 10 / 06 / 2024, page 18 / 50 6 / 27 By imposing a particular liquid-liquid extraction / counter-extraction system in two separate columns and controlling a number of operational parameters such as extraction and counter-extraction temperatures, as well as the pH of the aqueous solution used to perform the re-extraction step, the extraction of impurities, particularly slightly or non-polar ones from the hydroalcoholic feedstock, is maximized, the re-extraction of diethylacetal and hemyethylacetal is optimized and, therefore, the losses in ethanol and acetaldehyde are limited, with reduced consumption of acid used to acidify the aqueous counter-extraction solvent.

[0019] Advantageously, the process according to the present invention is integrated into a Lebedev (or Lebedev-type) process, that is, a process for converting ethanol into butadiene, notably into 1,3-butadiene. When advantageously integrated into a Lebedev-type process, such as that described in patent FR 3,026,100 or FR 3,026,101, the process according to the present invention thus allows for the effective purification, by a relatively simple liquid-liquid extraction / counter-extraction method, of the hydroalcoholic effluent obtained after separating the butadiene from the effluent directly from the conversion reactors, reducing losses in unconverted reagents and therefore improving the performance of the butadiene production process from ethanol, decreasing operating costs. DESCRIPTION OF THE MODALITIES

[0020] According to the present invention, the compound 1,1-diethoxyethane, also called diethylacetal, ethylidene diethyl ether or acetaldehyde diethylacetal, is referred to in the present description as diethylacetal or DEA. It can be defined, according to the present invention, as a condensed form of ethanol with acetaldehyde. The corresponding hemiacetal is 1-ethyloxyethane-1-ol or acetaldehyde hemiacetal and is referred to in the present description as hemiacetal or Petition 870240048686, dated 10 / 06 / 2024, p. 19 / 50 7 / 27 HEA.

[0021] According to the present invention, the average temperature in the extraction section or counter-extraction section is a temperature calculated according to the arithmetic mean of at least two temperature values ​​given by thermal pairs distributed in a regular manner along the extractor (or counter-extractor), or the temperature determined with the aid of a thermal pair located in the center of the extractor (or counter-extractor). For example, in the case where there are two thermocouples to determine the average temperature in the extraction column, one thermocouple is placed in the upper half of the column, the second in the lower half, and preferably so that the thermocouple in the upper part of the column is at a distance from the top of the extraction column equal to that between the thermocouple in the lower part and the base of the extraction column.The greater the number of thermocouples arranged regularly along the extractor (or counter-extractor), the more accurate the average temperature in the extractor (or counter-extractor) will be.

[0022] According to the present invention, the expression between... and... means that the limit values ​​of the interval are included in the range of values ​​described. If this is not the case and the limit values ​​are not included in the range described, such precision will be provided by the present invention.

[0023] The present invention relates to a process for purifying a hydroalcoholic feedstock, comprising at least water, ethanol, acetaldehyde and impurities, said process preferably comprising the following steps:

[0024] a countercurrent liquid-liquid extraction step, comprising an extraction section comprising an extractor 2 fed at the top by said hydroalcoholic feedstock 1 and at least a fraction of an intermediate raffinate from step b) of con Petition 870240048686, dated 10 / 06 / 2024, page 20 / 50 8 / 27 extraction and, at the base, by an extraction solvent 3, and producing, at the top, an extraction stream 5 and, at the base, a raffinate 4 comprising water, ethanol and acetaldehyde, said extraction section being operated at an average temperature in the extractor between 10 and 40°C;

[0025] a countercurrent liquid-liquid counter-extraction step, comprising a counter-extraction section comprising a counter-extractor 6 distinct from the extractor of step a) and fed, at the top, by an acidic aqueous solution 7, having a pH between 0.5 and 5.0 and, at the bottom, by an extraction stream 5 from step a), and producing, at the top, an extract 8 and, at the bottom, said intermediate raffinate, said counter-extraction section being operated at an average temperature in the counter-extractor distinct from the average temperature in the extractor of step a) and between 40 and 80°C. Hydroalcoholic load

[0026] The process according to the present invention allows the extraction of ethanol and acetaldehyde from a hydroalcoholic feedstock comprising water, ethanol, and acetaldehyde. Said hydroalcoholic feedstock also comprises impurities, notably organic ones, which can be of very varied natures, for example, saturated, unsaturated, aromatic hydrocarbons, oxygenated products, among which alcohols, ketones, aldehydes, phenolic compounds, acids, esters, and ethers can be mentioned, the molar mass of the different impurities being from 50 to 10,000 g / mol. Typically, the impurities can be acetone, diethyl ether, butanal, butanols, butanones, ethyl acetate, crotonaldehyde, pentenes, pentadienes, hexenes, and hexadienes.

[0027] The hydroalcoholic feedstock in the process according to the invention may also comprise at least one acetal and / or hemiacetal. In particular, the hydroalcoholic feedstock to be treated may comprise diethylacetal and / or hemiacetal. Diethylacetal and Petition 870240048686, dated 10 / 06 / 2024, p. 21 / 50 9 / 27 Hemyethylacetals are known to be products of the reaction of ethanol with acetaldehyde.

[0028] According to the invention, the term impurities thus designates any compound, notably organic, other than water, ethanol and acetaldehyde and other than acetals and hemiacetals, in particular other than diethylacetal and hemyethylacetal. Impurities may be, for example, saturated, unsaturated, aromatic hydrocarbons such as pentenes, pentadienes, hexenes and hexadienes, or demanded products such as acetone, diethyl ether, butanal, butanols, butanones, ethyl acetate, crotonaldehyde.

[0029] In particular, some of the impurities may be considered as slightly or non-polar when they have a partition coefficient, in particular a mass coefficient, between the organic extraction phase and the aqueous extraction phase, preferably greater than or equal to 1, preferably greater than or equal to 2.

[0030] The purification process according to the present invention is thus advantageously fed by a hydroalcoholic feedstock comprising at least water, ethanol, acetaldehyde, impurities and possibly acetals and / or hemiacetals, in particular diethylacetal and / or hemyethylacetal.

[0031] Preferably, the hydroalcoholic load comprises between 30% to 70% by weight of ethanol, preferably between 40% and 60% by weight of ethanol, relative to the total weight of the hydroalcoholic charge; between 1% and 30% by weight of acetaldehyde, preferably between 5% and 10% by weight of acetaldehyde, relative to the total weight of the hydroalcoholic charge; and between 0.5% and 20% by weight of impurities, notably between 1% and 20% by weight of impurities, relative to the total weight of the hydroalcoholic charge. When the charge also includes at least one acetal and / or hemiacetal, such as diethylacetal and / or hemyethylacetal, the weight content of acetals and hemiacetals in said hydroalcoholic charge is comprised of... Petition 870240048686, dated 10 / 06 / 2024, page 22 / 50 10 / 27 preferably between 1 and 20% by weight, and preferably between 1 and 15% by weight.

[0032] Advantageously, said hydroalcoholic feedstock is derived from the conversion of ethanol into butadiene, in particular into 1,3-butadiene, after separation of the noncondensables and butadiene. Said hydroalcoholic feedstock is preferably a hydroalcoholic effluent from a butadiene separation step at the outlet of conversion reactors in a Lebedev process, for example, an effluent similar to the ethanol / acetaldehyde / water effluent from D1) of patent FR 3,026,100 or the ethanol / acetaldehyde / water effluent from step B) of patent FR 3,026,101. Step a) Extraction of impurities:

[0033] According to the present invention, the purification process according to the invention comprises a countercurrent liquid-liquid extraction step comprising an extraction section comprising an extractor 2 fed at the top by said hydroalcoholic feedstock 1 and at least a fraction of the intermediate raffinate from the counterextraction step b) and at the bottom by an extraction solvent 3, and producing at the top an extraction stream 5, also called intermediate extract and at the bottom a raffinate 4 comprising water, ethanol and acetaldehyde, also called hydroalcoholic raffinate.

[0034] According to the present invention, said extraction section is operated at an average temperature in the extractor between 10 and 40°C, preferably between 15 and 30°C. If the average temperature in the extractor is below 10°C or above 40°C, the extraction of impurities, particularly slightly non-polar or non-polar ones, will be less effective.

[0035] The extraction solvent and the hydroalcoholic feedstock feeding said extraction section of step a) are, advantageously, each independently at an inlet temperature of Petition 870240048686, dated 10 / 06 / 2024, page 23 / 50 11 / 27 between 10 and 40°C.

[0036] Advantageously, the pressure of said extraction section of step a) is adjusted so that the different flows passing through said section are in liquid form. Preferably, said extraction section of step a) is operated at a pressure between 0.1 and 0.5 MPa, preferably between 0.2 and 0.4 MPa.

[0037] The residence time in the extraction section of said stage a) is advantageously adjusted in order to obtain the desired performance in terms of recovery rate, as known to a person skilled in the art. In particular, the residence time in the extraction section of said stage a) is between 0.5 and 10.00 h, preferably between 0.5 and 8.0 h, and most preferably between 1.0 and 6.0 h. The residence time in the extraction section is defined as the residence time of the aqueous phase and corresponds to the ratio between the total volume occupied by the considered aqueous phase in the extraction section and the volume flow rate of this aqueous phase at the outlet of the extraction section.

[0038] According to the present invention, the extraction solvent feeding step a) is advantageously an organic solvent, preferably non-polar. Preferably, the extraction solvent feeding step a) is a mixture of hydrocarbons having between 6 and 40 carbon atoms, preferably between 10 and 20 carbon atoms, or any other solvent that allows demixing with the hydroalcoholic phase. Not being limited to, said hydrocarbon mixture may be a desulfurized gas oil or kerosene cut, or even a hydrocarbon cut produced by a Fischer-Tropsch type unit. Preferably, the extraction solvent feeding step a) is hexadecane.

[0039] It is well known to a person skilled in the art that a liquid-liquid extraction, particularly in countercurrent, works with du Petition 870240048686, dated 10 / 06 / 2024, page 24 / 50 12 / 27 The liquid phases, one of which constitutes the continuous phase and the other the dispersed phase, present in the form of distinct droplets. The continuous or dispersed nature depends on the relative flow rate of one phase in relation to the other. According to the known phenomenon, the nature of the dispersed phase and the continuous phase depends on the relative flow rates of these phases. Thus, if the flow rate of the continuous phase is reduced while increasing the flow rate of the dispersed phase, the dispersed phase will become continuous, and vice versa. Advantageously, the extraction section is operated with a mass flow rate ratio of the continuous phase to the mass flow rate of the dispersed phase of less than 70, preferably less than 35, preferably less than 10, and preferably less than 3, preferably less than 1.5. Beyond 70, the hydrodynamic operation of the extraction section is compromised.It matters little whether the extraction solvent (organic phase) forms the continuous or dispersed phase, this criterion being a hydrodynamic criterion. Preferably, in extraction step a), the continuous phase is the organic phase and the dispersed phase is the aqueous phase.

[0040] The higher the mass flow rate of extraction solvent (i.e., the mass flow rate of extraction solvent entering the extraction section) relative to the feed flow rate of said extraction section of said stage a), composed of the hydroalcoholic feed and at least a fraction of the intermediate raffinate from the counter-extraction stage b), the more effective the extraction of impurities will be. However, the high flow rate ratio leads to the extraction of a significant fraction of ethanol and acetaldehyde in the extraction stream produced at the top of the extraction section of stage a) and, consequently, to an increase in the flow rate of aqueous solution required in stage b) to limit losses in ethanol and acetaldehyde. The value of the ratio of extraction solvent mass flow rate to aqueous feed mass flow rate must therefore be adjusted in order to extract the maximum amount of Petition 870240048686, dated 10 / 06 / 2024, page 25 / 50 13 / 27 impurities, notably non-polar or slightly polar, limiting losses in ethanol and acetaldehyde. The ratio of the extraction solvent mass flow rate to the feed mass flow rate of step a), composed of the hydroalcoholic feed and at least a fraction of the intermediate raffinate from step b), is preferably between 0.1 and 5.0, preferably between 0.2 and 2.0, and most preferably between 0.3 and 1.0.

[0041] The mass flow rate of extraction solvent, as well as the mass flow rate of acidic aqueous solution (i.e., the mass flow rate of counter-extraction solvent) feeding step b), are advantageously adjusted so that the extract produced in step b) comprises at least 50% by weight, preferably at least 60% by weight, preferably at least 70% by weight, most preferably at least 80% by weight, or even at least 90% by weight, of the slightly or non-polar impurities contained in the hydroalcoholic feedstock feeding said step a) of the process according to the present invention, and at most 5% by weight, preferably at most 2% by weight, preferably at most 1% by weight of the total weight amount of ethanol and acetaldehyde (in free and / or condensed form, for example, in the form of diethylacetal and / or hemyethylacetal) contained in said hydroalcoholic feedstock feeding the said stage a).Preferably, the ratio of the mass flow rate of the aqueous acidic solution (i.e., the mass flow rate of extraction solvent) feeding step b) to the mass flow rate of extraction solvent feeding step a) is between 0.1 and 5.0, preferably between 0.2 and 2.0, preferably between 0.3 and 1.0, and most preferably between 0.4 and 0.5.

[0042] The contact between the two liquid phases in the said extraction section of step a) is advantageously carried out within an extractor. Different extractor technologies can be considered: the extractor Petition 870240048686, dated 10 / 06 / 2024, page 26 / 50 14 / 27 can be, for example, a full column, a pulsed column, a compartmentalized agitated column, compartmentalized with the aid of perforated plates, discs or crowns, or even a battery of mixer-settlers or mixer-centrifuges. Preferably, the extractor is a blown column, a compartmentalized agitated column. Advantageously, the extractor, used in extraction step a), comprises between 1 and 20, preferably between 2 and 8 theoretical extraction stages.

[0043] The intermediate extract (or extraction stream) 5, which is produced at the top of said extraction section of step a) of the process according to the present invention, advantageously comprises at least 50% by weight, preferably at least 60% by weight, preferably at least 70% by weight and most preferably at least 80% by weight of the slightly or non-polar impurities of the hydroalcoholic feedstock. Said intermediate extract 5 comprises ethanol and acetaldehyde present in the hydroalcoholic feedstock that feeds the process according to the present invention, in their free and / or condensed forms.Thus, the intermediate extract 5 produced at the top of the extraction section in step a) most likely comprises diethylacetal and / or hemyethylacetal, possibly included in the hydroalcoholic feedstock that feeds the process according to the present invention, and / or formed by reaction of ethanol with acetaldehyde during the process according to the present invention, in particular in said extraction section in step a).

[0044] The refined hydroalcoholic beverage produced at the base of the extraction section of said section a) comprises water and between 80 and 100% by weight of the total amount of ethanol and acetaldehyde contained in said hydroalcoholic feedstock that feeds the process according to the present invention. In other words, between 80 and 100% by weight of the total amount of ethanol and acetaldehyde of the hydroalcoholic feedstock that feeds the process Petition 870240048686, dated 10 / 06 / 2024, page 27 / 50 15 / 27 so according to the present invention are recovered in the refined hydroalcoholic solution produced at the base of the extraction section of step a) of the process according to the present invention.

[0045] Step a) of the process according to the present invention is configured in such a way as to extract the maximum amount of impurities, in particular slightly or non-polar ones (such as diethyl ether), and the minimum amount of ethanol and acetaldehyde (in free and / or condensed form).

[0046] In such a configuration, the acetals and / or hemiacetals, in particular diethylacetal and / or hemyethylacetal, possibly present in the hydroalcoholic feedstock and / or formed during the process according to the present invention, notably in extraction step a), are extracted significantly by the extraction solvent in the extraction stream, with the particularly non-polar or slightly polar impurities during extraction step a), insofar as said acetals and / or hemiacetals are much less polar than free ethanol and acetaldehyde. The extraction stream 5 extracted at the top of the extraction section of said step a) feeds the counter-extraction step b). Step b) of counter-extraction:

[0047] According to the present invention, the purification process comprises a step b) of countercurrent liquid-liquid counterextraction, the objective of which is to counterextract the noble compounds, i.e., ethanol and acetaldehyde, in free form and / or condensed in hemi- or di-ethylacetal, in an effective manner.

[0048] According to the present invention, the countercurrent liquid-liquid counter-extraction step b) comprises a counter-extraction section comprising a counter-extractor 6 distinct from the extractor 2 of step a), fed at the top by an acidic aqueous solution 7 having a pH between 0.5 and 5.0, and at the bottom by an extraction stream 5 from step a), and producing, at the top, an extract 8 and, at the bottom, an intermediate raffinate. Petition 870240048686, dated 10 / 06 / 2024, page 28 / 50 16 / 27

[0049] The counter-extraction section is operated, according to the present invention, at an average temperature in the counter-extractor distinct from the average temperature in the extractor of step a) and between 40 and 80°C, preferably between 45 and 70°C, and more preferably between 45°C and 60°C. Most preferably, the extraction section in step a) is operated at an average temperature in the extractor between 15 and 30°C and the counter-extraction section in step b) is operated at an average temperature in the counter-extractor between 45 and 70°C, in particular between 45 and 60°C. For average temperature values ​​in the counter-extraction section above 80°C, there is, in addition to an increase in production costs generated by an increase in energy consumption required for heating, a risk of bubble formation in the aqueous and organic phases, resulting in a loss of counter-extraction effectiveness. When the average temperature in the countercurrent section is below 40°C, the counter-extraction effectiveness appears not to be optimal.

[0050] The said acidic aqueous solution and the extraction stream from step a) advantageously feed the said counter-extraction section of step b), each independently, at an inlet temperature between 10 and 90°C, preferably between 40°C and 90°C.

[0051] According to a particular embodiment of the present invention, the counter-extraction section comprises an adiabatic column (called insulated), as a counter-extractor, fed at the top by the aqueous acidic solution at an inlet temperature of said aqueous acidic solution into said adiabatic column between 50 and 90°C, preferably between 60 and 85°C, and at the bottom by the extraction flow from step a). The inlet temperature of said adiabatic column of the extraction flow from step a) is fixed by the temperature at which extraction step a) is operated, i.e., on average between 10°C and 40°C. In this particular embodiment of the present invention Petition 870240048686, dated 10 / 06 / 2024, page 29 / 50 17 / 27 invention, a general temperature gradient between the top of the column and the base allows obtaining an average temperature in the adiabatic counter-extraction section distinct from the average temperature in the extraction section of step a), sufficiently high, advantageously between 40 and 80°C, to obtain the desired effects, i.e., an optimized re-extraction of ethanol and acetaldehyde and / or diacetals and hemiacetals contained in the extraction stream from step a).

[0052] Advantageously, the pressure of said backdraft section is adjusted so that the different flows passing through said section are in liquid form. Preferably, the backdraft section of step b) is operated at a pressure between 0.1 and 0.5 MPa, preferably between 0.2 and 0.4 MPa.

[0053] Advantageously, the counter-extraction section of step b) is operated with a residence time, more precisely a residence time in the aqueous phase, in the counter-extraction section, between 0.5 and 10.0 h, preferably between 1 and 6.0 h. Said residence time in the counter-extraction section is defined as the average time required for a water molecule injected with the acidic aqueous solution feeding said counter-extraction section of said step b) to be extracted in the intermediate raffinate from said counter-extraction section of said step b). This residence time is classically determined by measuring DTS, or Residence Time Distribution, in which a marker (dye or other) is injected pointwise at the inlet, the marker concentration being observed at the outlet.

[0054] According to the present invention, the counter-extraction solvent used in step b) is an acidic aqueous solution having a pH between 0.5 and 5.0, preferably between 2 and 4.0, and most preferably between 2.5 and 3.5. Said acidic aqueous solution feeding step b) is advantageously water acidified by the addition of an acidic compound. Petition 870240048686, dated 10 / 06 / 2024, p. 30 / 50 18 / 27 so that the pH of the aqueous solution is between 0.5 and 5.0, preferably between 2 and 4.0, and preferably between 2.5 and 3.5. The acidic aqueous solution may thus contain, but is not limited to, strong acids and / or weak acids. But is not limited to, the water is acidified with a weak acid such as acetic acid, or a strong acid such as sulfuric acid or nitric acid, preferably with acetic acid. Preferably, the acidic aqueous solution is water acidified with acetic acid, such that said acidic aqueous solution comprises an acetic acid content of less than 3% by weight of acetic acid, preferably less than or equal to 3.0% by weight, preferably less than or equal to 1.5% by weight relative to the total weight of said acidic aqueous solution.Furthermore, the said acidic aqueous solution that feeds step b) preferably contains less than 2% by weight, preferably less than 1% by weight, of the total amount (ethanol + acetaldehyde) relative to the total weight of the said acidic aqueous solution, that is, the sum of the mass contents of ethanol and acetaldehyde in the said acidic aqueous solution is less than 2% by weight, preferably less than 1% by weight, relative to the total weight of the said acidic aqueous solution. Most preferably, the said acidic aqueous solution contains neither ethanol nor acetaldehyde.

[0055] The contact between the two liquid phases, the organic phase and the aqueous phase, in said counter-extraction section of step b) is advantageously carried out within a counter-extractor. Different technologies for said counter-extractor can be considered: full column, pulsed column, agitated compartmentalized column, compartmentalized with the aid of perforated trays, discs or crowns, or even a battery of mixer-decanters or mixer-centrifuges. Preferably, the counter-extractor is a pulsed column, an agitated compartmentalized column. Advantageously, the counter-extractor used in step b) of counter-extraction comprises between 1 and 20, preferably Petition 870240048686, dated 10 / 06 / 2024, page 31 / 50 19 / 27 mind between 1 and 5 theoretical stages.

[0056] Advantageously, the mass flow rates of the aqueous phase and the organic phase in the counter-extraction section are adjusted so that the ratio (Qaq. inlet / Qorga. outlet) of the mass flow rate of the aqueous phase entering the counter-extraction section (Qaq. inlet) to the flow rate of the organic phase leaving the counter-extraction section (Qorga. outlet) is preferably between 0.1 and 5.0, preferably between 0.2 and 2.0, and most preferably between 0.3 and 1.0.

[0057] Preferably, step b) is operated in such a way that the aqueous phase constitutes the continuous phase in the counter-extraction section and the organic phase the dispersed phase in said counter-extraction section of said step b).

[0058] In a very advantageous way, the aqueous phase constitutes the dispersed phase in the extraction section of step a) and the continuous phase in the counter-extraction section of step b).

[0059] Under such operating conditions, the acetals and / or hemiacetals, in particular diethylacetal and / or hemyethylacetal, possibly present in said hydroalcoholic feedstock and / or formed during the process according to the present invention, notably by reaction between ethanol and acetaldehyde, decompose particularly into ethanol and acetaldehyde, which can be re-extracted in the aqueous phase of the counter-extraction section, preferably the continuous phase of the counter-extraction section, thus allowing improved recovery of ethanol and acetaldehyde losses. This decomposition thus allows, when the purification process according to the present invention is integrated into a Lebedev process, limiting reagent losses and consequently improving the butadiene yield of the overall Lebedev process.

[0060] Step b) of the counter-extraction of the process according to the invention produces, at the top of the counter-extraction section, an extract 8 Petition 870240048686, dated 10 / 06 / 2024, page 32 / 50 20 / 27 advantageously comprising at least 50% by weight, preferably at least 60% by weight, preferably at least 70% by weight, most preferably at least 80% by weight, or even 90% by weight, of impurities, in particular slightly or non-polar impurities, from the hydroalcoholic feedstock feeding step a) of the process according to the invention. The extract 8 produced at the top of the counter-extraction section of step b) advantageously comprises less than 1.0% by weight, preferably less than 0.1% by weight, preferably less than 0.001% by weight of acetals and / or hemiacetals, in particular diethylacetal and / or hemyethylacetal. Most preferably, the extract produced at the top of the counter-extraction section of step b) is free of acetals and / or hemiacetals, in particular free of diethylacetal and / or hemyethylacetal.

[0061] The extract from step b) can then be treated, for example, in a purification / separation step in order to recover the extraction solvent so that it can be recycled to extraction step a).

[0062] The counter-extraction section of step b) produces, at the base, an intermediate raffinate advantageously comprising water, ethanol and acetaldehyde. At least a fraction of said intermediate raffinate, advantageously the entirety of said intermediate raffinate, is introduced at the top of the extraction section of step a). Even when the entirety of the intermediate raffinate is introduced into the extraction section, a withdrawal can advantageously be carried out, continuously or discontinuously, in said intermediate raffinate, the withdrawal being called purging, in order to limit the accumulation of impurities in said intermediate raffinate.

[0063] Surprisingly, the inventors found that, by performing extraction (or washing) and counter-extraction (or counterwashing) in two separate extractors, using an aqueous acidic solution Petition 870240048686, dated 10 / 06 / 2024, p. 33 / 50 21 / 27 of the counter-extraction solvent and imposing two distinct temperatures in the two columns, the elimination of particularly slightly or non-polar impurities from the hydroalcoholic feed to be treated, for example, the liquid effluent from the ethanol-to-butadiene conversion reactors, as in a Lebedev process, was very effective, while losses in ethanol and acetaldehyde were surprisingly limited and the consumption of acid, necessary to acidify the counter-extraction water, was substantially reduced.

[0064] Advantageously, the process according to the present invention allows achieving an extraction efficiency of slightly or non-polar impurities, in particular an extraction efficiency of diethyl ether, greater than or equal to 75% by weight, preferably greater than or equal to 80% by weight, and a counter-extraction efficiency, particularly of diethylacetal, a condensed form of ethanol and acetaldehyde, greater than or equal to 90% by weight, preferably greater than or equal to 95% by weight, and preferably greater than or equal to 97% by weight.

[0065] Extraction efficiency, according to the present invention, means the extraction efficiency of diethyl ether, defined by the ratio a (qDEE extracted / Qdee entering) between the mass flow rate of diethyl ether (DEE) leaving the process, i.e., present in the extract obtained at the top of the counter-extraction section (qdee extracted), over the mass flow rate of diethyl ether (DEE) entering the extraction section, i.e., present in the hydroalcoholic feed that feeds the extraction section (qDEE entering). More specifically, the extraction efficiency of diethyl ether (DEE) is calculated as follows: DEE extraction efficiency = ((mass content of DEE in the extract exiting at the top of the counter-extraction section) x (mass flow rate of the extract exiting at the top of the counter-extraction section) / (mass content of DEE in the hydroalcoholic feedstock) x (mass flow rate of the hydroalcoholic feedstock)).

[0066] Counter-extraction effectiveness means the effectiveness of Petition 870240048686, dated 10 / 06 / 2024, page 34 / 50 22 / 27 Diethylacetal extraction, defined by the ratio between the mass amount of diethylacetal counter-extracted from the intermediate extract and the mass amount of diethylacetal present in the intermediate extract entering the counter-extraction section. More specifically, the diethylacetal counter-extraction efficiency (DEA) is calculated as follows: DEA counter-extraction efficiency = 1 - ((mass content of DEA of the extract exiting at the top of the counter-extraction section) x (mass rate of the extract exiting at the top of the counter-extraction section) / (mass content of DEA of the intermediate extract entering the counter-extraction section) x (mass rate of the intermediate extract entering the counter-extraction section)).

[0067] The mass contents of DEE and DEA of the different streams considered to calculate the extraction and counter-extraction efficiencies are determined by any method known to a person skilled in the art, for example, by gas chromatography.

[0068] The purification process according to the present invention can be advantageously integrated into an overall Lebedev-type process, that is, an overall process for converting ethanol to butadiene, as a purification step for the hydroalcoholic liquid effluent from a butadiene separation step at the outlet of the ethanol-to-butadiene conversion reactors. In a Lebedev-type process, the hydroalcoholic liquid effluent from the separation step at the outlet of the ethanol-to-butadiene conversion reactors comprises, in fact, water, notably from the conversion of ethanol to butadiene, and reagents, ethanol and acetaldehyde, unconverted or only partially converted. Said hydroalcoholic liquid effluent also comprises impurities consisting of organic molecules, such as acetone, diethyl ether, butanal, pentadienes, hexenes or hexadienes, and possibly acetals and / or hemiacetals, notably diethylacetal and / or hemyethylacetal.When the treatment process according to the present invention is integrated into a... Petition 870240048686, dated 10 / 06 / 2024, page 35 / 50 23 / 27 In the Lebedev-type process, the recycling rate of the reactant compounds, i.e., ethanol and acetaldehyde, is improved, thus allowing an optimization of the overall butadiene yield of the Lebedev process, and this without causing additional costs that may be due to consumption of acidic compounds or post-treatment of the aqueous phase.

[0069] The figures incorporated into the present description and the examples that follow are presented by way of illustration and not limitation of the purification process according to the present invention. List of figures

[0070] Figure 1 schematically and non-limitingly represents an arrangement of the process according to the present invention. The hydroalcoholic feedstock comprising water, ethanol, acetaldehyde and impurities 1 feeds, at the top, a liquid-liquid extraction section 2, in which step a) is carried out. The liquid-liquid extraction section 2 is also fed at the top by an intermediate raffinate from the counter-extraction section 6 of step b), and at the bottom by an extraction solvent 3. An extraction stream 5, also called the intermediate extract, is produced at the top of the extraction section 2, while a raffinate 4 is withdrawn at the bottom of the extraction section 2. The extraction stream 5 feeds, at the bottom, the counter-extraction section 6 of step b). The counter-extraction section 6 is fed, at the top, by an acidic aqueous solution 7. An extract 8 is withdrawn at the top of the counter-extraction section 6, while, at the bottom, an intermediate raffinate is produced.The aforementioned refined intermediate feeds into the liquid-liquid extraction section 2. Examples

[0071] In the following examples, a hydroalcoholic feedstock comprising ethanol, acetaldehyde, water and particularly slightly or non-polar impurities, such as diethyl ether (considered as an impurity), of composition given in Table 1 and a flow rate of 3.65 kg / hour Petition 870240048686, dated 10 / 06 / 2024, page 36 / 50 24 / 27 mass, is treated. Compounds Weight percentage (% by weight relative to the total weight of the load) Acetaldehyde 3.91% Ethanol 62.95% Acetone 0.07% Ethyl vinyl ether 0.04% Diethyl ether 1.00% Butanal 0.03% Butanone 0.01% Ethyl acetate 1.37% Acetic acid 0.63% Butanol 0.41% Diethylacetal 4.46% Styrene 0.10% Water 25.01%

[0072] In the following examples, the extraction and counter-extraction sections are operated under the same conditions as below, differing only in the average temperatures of the extraction and counter-extraction sections and the mass content of acetic acid in the aqueous acidic solution used as a counter-extraction solvent.

[0073] The countercurrent extraction columns are distinct columns, both of the Sulzer ECR type with interiors having 40% plate openings, 32mm internal diameter and a useful height of 1.8m.

[0074] The extraction column is fed, at the bottom, with hexadecane at a rate of 1.28 kg / hour. The counter-extraction column is fed, at the top, with water acidified with acetic acid, the rate of this counter-extraction solvent being 0.56 kg / hour.

[0075] The extraction column is operated with a dispersed aqueous phase. Petition 870240048686, dated 10 / 06 / 2024, p. 37 / 50 25 / 27 The counter-extraction column is operated with a continuous aqueous phase.

[0076] The agitation speed is adjusted in the two columns so that the volume fraction of the dispersed phase is about 15% by volume in the extraction column and 3% by volume in the counter-extraction column.

[0077] The extraction column produces, at the top, an extraction stream that is injected into the base of the counter-extraction column. The extraction column produces, at the base, a raffinate comprising ethanol and acetaldehyde. The counter-extraction column produces, at the top of the column, an extract and, at the base, an intermediate raffinate, the latter being injected into the top of the extraction column.

[0078] In different examples, the acetic acid concentration of the aqueous acidic solution (counter-extraction solvent), therefore the pH of this aqueous acidic column, as well as the average temperatures of the extraction and counter-extraction sections, vary. Table 2 below summarizes the variable operating conditions and the results obtained in terms of diethyl ether impurity extraction efficiency and diethylacetal counter-extraction efficiency.

[0079] The extraction efficacy of diethyl ether (DEE) and the counter-extraction efficacy of diethyl acetal (DEA) are calculated, for each example, as presented below in the description, that is, as follows:

[0080] DEE extraction efficiency = ((mass content of DEE in the extract) x (mass flow rate of the extract) / (mass content of DEE in the hydroalcoholic load) x (mass flow rate of the hydroalcoholic load))

[0081] Counterextraction efficacy DEA = 1 - ((mass content of DEA of the extract) x (mass debit of the extract) / (mass content of DEA of the intermediate extract) x (mass debit of the intermediate extract)).

[0082] The mass contents of DEE of the extract and the hydroalcoholic load and the mass contents of DEA of the extract and the intermediate extract Petition 870240048686, dated 10 / 06 / 2024, page 38 / 50 Daily values ​​26 / 27 were determined by gas chromatography. Examples Acetic acid content (% by weight) pH of the aqueous acidic solution Extraction temperature (°C) 1 3% 2.5 20 2 1% 2.8 20 3 1% 2.8 40 4 1% 2.8 50 5 1% 2.8 20 -continuation- Examples Counter-extraction temperature (°C) DEE extraction efficacy (% by weight) DEA counter-extraction efficacy (% by weight) 1 20 81% 93% 2 20 81% 74% 3 40 72% 92% 4 50 43% 98% 5 50 81% 98%

[0083] Example 1 illustrates the reference case according to the state of the art. With an acetic acid content of the counter-extraction solvent of 3% by weight and an operating temperature of 20°C for both columns, the extraction efficiency of diethyl ether (DEE) and the counter-extraction efficiency of diethylacetal (DEA) are satisfactory, as they are greater than 80% by weight (81% DEE extraction efficiency) and greater than 90% by weight (93% DEA counter-extraction efficiency), respectively.

[0084] Example 2 shows that, at the same previous operating temperature (20°C in both columns), when the acetic acid content in the aqueous acidic solution used as a counter-extraction solvent decreases (1% by weight instead of 3% by weight), the counter-extraction effectiveness of DEA decreases significantly and falls below 75% by weight.

[0085] According to examples 3 and 4, the combined rise of the tem Petition 870240048686, dated 10 / 06 / 2024, pp. 39 / 50 27 / 27 temperature in both columns (extraction and counter-extraction), at 40°C for example 3 and 50°C for example 4, allows for a satisfactory counter-extraction efficiency (respectively 92% and 98%) for low acetic acid contents in the aqueous counter-extraction solvent (1%). However, the effect on DEE extraction is detrimental, as the DEE extraction efficiency falls below 75%: more precisely, the DEE extraction efficiency is 72% by weight in example 3 and 43% by weight in example 4.

[0086] Example 5, according to the present invention, clearly demonstrates that, even for a low acetic acid content in the aqueous acidic solution used as a counter-extraction solvent, imposing two distinct temperatures between extraction and counter-extraction, and in particular a temperature of 20°C in the extraction column and an average temperature of 50°C in the counter-extraction column, allows obtaining an optimized DEE extraction, with a DEE extraction efficiency equal to 81% by weight, and a high DEA ​​counter-extraction, with a DEA counter-extraction efficiency equal to 98% by weight, a counter-extraction efficiency that is superior to that obtained in Example 1 according to the prior art.

[0087] Thus, it appears clearly that the process according to the present invention, for purifying a hydroalcoholic feedstock comprising water, ethanol, acetaldehyde and impurities, allows for the optimal extraction of slightly or non-polar impurities, and improves the counter-extraction of the condensed form of ethanol and acetaldehyde, with a substantially reduced consumption of acetic acid. Petition 870240048686, dated 10 / 06 / 2024, pp. 40 / 50

Claims

1 / 3 CLAIMS 1. A process for purifying a hydroalcoholic feedstock (1) comprising at least water, ethanol, acetaldehyde and impurities, characterized in that it comprises: a) a countercurrent liquid-liquid extraction step, comprising an extraction section comprising an extractor (2) fed at the top by said hydroalcoholic feedstock (1) and at least a fraction of an intermediate raffinate from the counter-extraction step b) and at the bottom by an extraction solvent (3), and producing at the top an extraction stream (5) and at the bottom a raffinate (4) comprising water, ethanol and acetaldehyde, said extraction section being operated at an average temperature in the extractor between 15 and 30 °C;b) a countercurrent liquid-liquid counter-extraction stage comprising a counter-extraction section comprising a counter-extractor (6) distinct from the extractor of stage a) and fed, at the top, by an acidic aqueous solution (7), having a pH between 0.5 and 5.0, and at the bottom by the extraction stream (5) from stage a), and producing, at the top, an extract (8) and, at the bottom, said intermediate raffinate, said counter-extraction section being operated at an average temperature in the counter-extractor distinct from the average temperature in the extractor of stage a) and between 40 and 80 °C.; 2. Process according to claim 1, characterized in that the average temperature in the counter-extraction column (6) of step b) is between 45 and 60 °C.

3. Process according to claim 1 or 2, characterized in that the counter-extractor of step b) is an adiabatic column fed, at the top, by said aqueous acidic solution (7), at an inlet temperature of said aqueous acidic solution in said adiabatic column between 50 and 90°C, preferably between 60 and 85°C.

4. Process according to any of the preceding claims, characterized in that said aqueous acidic solution (7) feeding the counter-extraction column (6) of step b) has a pH between 2 and 4, preferably between 2.5 and 3.

5.

5. Process, according to one of the preceding claims, characterized in that said aqueous acidic solution (7) is acidified in water with acetic acid, such that said aqueous acidic solution comprises an acetic acid content of less than 3% by weight of acetic acid, preferably less than or equal to 1.5% by weight, relative to the total weight of said aqueous acidic solution.

6. Process according to any of the preceding claims, characterized in that the hydroalcoholic charge (1) comprises between 30% and 70% by weight of ethanol, preferably between 40% and 60% by weight of ethanol, relative to the total weight of the hydroalcoholic charge, between 1% and 30% by weight of acetaldehyde, preferably between 5% and 10% by weight of acetaldehyde, relative to the total weight of the hydroalcoholic charge, and between 0.5% and 20% by weight of impurities, notably between 1% and 20% by weight of impurities relative to the total weight of the hydroalcoholic charge.

7. Process according to any of the preceding claims, characterized in that the hydroalcoholic charge (1) further comprises at least one acetal and / or hemiacetal, in particular diethylacetal and / or hemyethylacetal.

8. Process according to any of the preceding claims, characterized in that the hydroalcoholic feedstock (1) is a hydroalcoholic effluent from a butadiene separation step at the outlet of conversion reactors in a Lebedev process. Petition 870240048686, dated 10 / 06 / 2024, p. 42 / 50 3 / 3 9. Process according to any of the preceding claims, characterized in that the extraction solvent (3) is an organic solvent, preferably nonpolar, preferably a mixture of hydrocarbons having between 6 and 40 carbon atoms, preferably between 10 and 20 carbon atoms.

10. Process according to claim 9, characterized in that the extraction solvent (4) is hexadecane.

11. Process according to any of the preceding claims, characterized in that said aqueous acidic solution (7) feeding the counter-extraction column (6) of step b) comprises less than 2% by weight, preferably less than 1% by weight, of the ethanol and acetaldehyde combination, preferably is free of ethanol and acetaldehyde. Petition 870240048686, dated 10 / 06 / 2024, pp. 43 / 50

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