Recovery of monoethylene glycol

Abstract

A process for recovering monoethylene glycol from a mixture feed comprising a bio-derived diol is disclosed.SOLUTION: The mixture feed comprises monoethylene glycol in an amount of at least 80 wt% of the total weight of the mixture feed. The method comprises providing a mixture feed into a distillation column in which a distillation process is carried out, wherein the distillation column comprises at least 80 theoretical stages, wherein the mixture feed is fed into the distillation column at a point which is at a height of 5 to 20% of the total height of the distillation column calculated from the top of the distillation column, wherein the total height of the distillation column is determined based on the number of theoretical stages, and wherein the distillation process is carried out at a reflux ratio of 20 to 200, and recovering monoethylene glycol. A distillation apparatus is further disclosed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] Technical Field The present disclosure relates to a method for recovering monoethylene glycol from a mixture feed containing a bio-based diol. The present disclosure further relates to a distillation apparatus for recovering monoethylene glycol from a mixture feed containing a bio-based diol. [Background technology]

[0002] background Monoethylene glycol, also known as ethylene glycol or ethane-1,2-diol, is an organic compound with the formula (CHOH)-. Monoethylene glycol can be used, for example, as a raw material in the production of polyester fibers and for antifreeze formulations. Monoethylene glycol is an odorless, colorless, sweet-tasting, viscous liquid.

[0003] Monoethylene glycol can be produced from sugars along with other diols, such as monopropylene glycol. However, when monoethylene glycol and polyols, such as monopropylene glycol, and other diols are also produced from sugars, alcohols and other substances are formed as by-products. Purification of biomass-based monoethylene glycol can face the challenge that during the production process, other diols besides monoethylene glycol are also produced due to different reactions, which have boiling points close to those of monoethylene glycol. One example of such a substance is 1,2-butanediol, which has approximately the same boiling point as monoethylene glycol. Therefore, the present inventors have recognized the need to provide a method for recovering purified monoethylene glycol. Summary of the Invention [Means for solving the problem]

[0004] overview A method for recovering monoethylene glycol from a mixture feed containing a bio-derived diol is disclosed. The mixture feed contains monoethylene glycol in an amount of at least 80 wt% of the total weight of the mixture feed. The method includes: providing the mixture feed into a distillation column in which a distillation process is carried out, the distillation column including at least 80 theoretical plates, the mixture feed being fed into the distillation column at a height that is 5 to 20% of the total height of the distillation column calculated from the top of the distillation column, the total height of the distillation column being determined based on the number of theoretical plates, and the distillation process being carried out at a reflux ratio of 20 to 200; and recovering monoethylene glycol.

[0005] Also disclosed is a distillation apparatus for recovering monoethylene glycol from a mixture feed containing a bio-derived diol, the mixture feed comprising monoethylene glycol in an amount of at least 80 wt.% of the total weight of the mixture feed. The distillation apparatus comprises: a distillation column comprising at least 80 theoretical plates and configured to operate at a reflux ratio of 20 to 200; - an inlet for providing a mixture feed into a distillation column in which a distillation process is carried out, the inlet being located at a height of 5 to 20% of the total height of the distillation column calculated from the top of the distillation column, the total height of the distillation column being determined based on the number of theoretical plates; - outlet for recovering monoethylene glycol; Includes.

[0006] BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the embodiments and constitute a part of this specification, illustrate embodiments. [Brief explanation of the drawings]

[0007] [Figure 1] One embodiment of the distillation apparatus disclosed herein is disclosed. DETAILED DESCRIPTION OF THE INVENTION

[0008] Detailed Description A method for recovering monoethylene glycol from a mixture feed containing a bio-derived diol is disclosed. The mixture feed contains monoethylene glycol in an amount of at least 80 wt% of the total weight of the mixture feed. The method includes: providing the mixture feed into a distillation column in which a distillation process is carried out, the distillation column including at least 80 theoretical plates, the mixture feed being fed into the distillation column at a height that is 5 to 20% of the total height of the distillation column calculated from the top of the distillation column, the total height of the distillation column being determined based on the number of theoretical plates, and the distillation process being carried out at a reflux ratio of 20 to 200; and recovering monoethylene glycol.

[0009] Also disclosed is a distillation apparatus for recovering monoethylene glycol from a mixture feed containing a bio-derived diol, the mixture feed comprising monoethylene glycol in an amount of at least 80 wt.% of the total weight of the mixture feed. The distillation apparatus comprises: a distillation column comprising at least 80 theoretical plates and configured to operate at a reflux ratio of 20 to 200; - an inlet for providing a mixture feed into a distillation column in which a distillation process is carried out, the inlet being located at a height of 5 to 20% of the total height of the distillation column calculated from the top of the distillation column, the total height of the distillation column being determined based on the number of theoretical plates; - outlet for recovering monoethylene glycol; Includes.

[0010] Distillation can generally be considered a process that separates components or substances from a mixture using selective boiling and condensation. Distillation can result in essentially complete separation into nearly pure components or partial separation that increases the concentration of selected components in the mixture. The distillation process takes advantage of differences in the relative volatility of different components in the mixture.

[0011] "Theoretical plates," or "theoretical plates," or "distillation plates," as they may be referred to in many separation processes, can be viewed as hypothetical regions or stages where two phases, such as the liquid and vapor phases of a substance, establish equilibrium with one another. Such equilibrium stages may also be called equilibrium stages, ideal stages, or theoretical trays. The performance of many separation processes depends on having consecutive equilibrium stages and can be enhanced by providing more such stages. In other words, increasing the number of theoretical plates increases the efficiency of the separation process, whether it be distillation, absorption, chromatography, adsorption, or a similar process.

[0012] When designing a distillation of a particular medium, the number of theoretical plates is usually first designed or considered, and then the physical height of the distillation column is determined. The theoretical or distillation plates in a distillation column can be formed by trays or packing, also called a packed bed. The packed bed can be a structured or random packed bed.

[0013] The inventors have surprisingly discovered that a combination of a specified number of theoretical plates and a specified reflux ratio allows for the efficient separation of monoethylene glycol at high purity or yield from a mixture feed containing a bio-derived diol. The combination of a specified number of theoretical plates and a specified reflux ratio has the additional utility of allowing the mixture feed to be fed to a distillation column that beneficially assists in the recovery of monoethylene glycol at high purity.

[0014] A mixture feedstock containing bio-derived diols may include, for example, monoethylene glycol (MEG, also known as ethylene glycol or 1,2-ethanediol), monopropylene glycol (MPG, also known as 1,2-propanediol), and butylene glycol (BDO, also known as butanediol). Such a mixture feedstock of bio-derived diols may be derived, for example, from a glycol production process, such as a process for producing monoethylene glycol. In one embodiment, the mixture feedstock containing bio-derived diols includes monoethylene glycol, monopropylene glycol, and butylene glycol. Butylene glycol may occur in different structures depending on the position of the OH unit. Examples of such structures include 1,2-butanediol, 2,3-butanediol, and 1,4-butanediol. These have different boiling points. 2,3-butanediol has a lower boiling point than monoethylene glycol, 1,2-butanediol has about the same boiling point as monoethylene glycol, and 1,4-butanediol has a boiling point higher than that of monoethylene glycol.

[0015] The blend feed may comprise monoethylene glycol in an amount of at least 85% by weight or at least 87% by weight of the total weight of the blend feed. The blend feed may comprise monoethylene glycol, monopropylene glycol, and butylene glycol in an amount of at least 90% by weight, or at least 95% by weight, or at least 97% by weight, or at least 99% by weight of the total weight of the blend feed.

[0016] The mixture feed containing the bio-derived diol may further contain water. In one embodiment, the mixture feed contains water in an amount of 0 to 2 wt % or 0.5 to 1.5 wt %, based on the total weight of the mixture feed. In one embodiment, the mixture feed is essentially free of water.

[0017] The mixture feed may be fed into the distillation column in liquid form or as a steam or vapor.

[0018] Monoethylene glycol and monopropylene glycol can be produced, for example, from a process for preparing a liquid glycol composition containing monoethylene glycol. Such a liquid glycol composition can be prepared from a plant-based raw material. The plant-based raw material can be a wood-based raw material derived from hardwood or softwood, for example. The wood-based raw material can be derived from, for example, pine, poplar, beech, cottonwood, spruce, eucalyptus, ash, oak, maple, chestnut, willow, or birch. The wood-based raw material can be any combination or mixture thereof.

[0019] Such a method for producing a liquid composition of glycols comprises: - providing a wood-based feedstock derived from a wood-based raw material and comprising wood chips, and subjecting the wood-based feedstock to at least one pretreatment, wherein a liquid fraction and a fraction comprising solid cellulose particles are formed; - subjecting the fraction comprising the solid cellulose particles to enzymatic hydrolysis, whereby a lignin fraction and a carbohydrate fraction are formed; - subjecting the carbohydrate fraction to catalytic conversion to form a liquid composition of glycols; may include:

[0020] Providing the wood-based feedstock may include subjecting the wood-based feedstock to a mechanical treatment selected from debarking, chipping, splitting, cutting, beating, crushing, crushing, splitting, screening, and / or washing the wood-based feedstock to form the wood-based feedstock. Providing the wood-based feedstock may include purchasing the wood-based feedstock.

[0021] Pre-treatment of the wood-based feedstock may include at least one of press-steaming the wood-based feedstock, subjecting the wood-based feedstock to an impregnation treatment, and subjecting the wood-based feedstock to steam explosion.

[0022] Pretreatment may include subjecting the wood-based feedstock to steam press. Pretreatment may include impregnation and / or steam explosion, and may include subjecting the wood-based feedstock to steam press before subjecting the wood-based feedstock to impregnation and / or steam explosion. Steam press of the wood-based feedstock may be performed with steam at a temperature of 100-130°C at atmospheric pressure. During steam press, the wood-based feedstock is treated with low-pressure steam. Steam press may also be performed with steam having a temperature below 100°C, below 98°C, or below 95°C.

[0023] Furthermore, the pretreatment may include subjecting the wood-based feedstock to at least one impregnation treatment with an impregnation liquid. The impregnation treatment may be performed on wood-based feedstock received from mechanical treatment and / or press steam. The pretreatment may include subjecting the wood-based feedstock to at least one impregnation treatment with an impregnation liquid selected from water, at least one acid, at least one alkali, at least one alcohol, or any combination or mixture thereof, prior to steam explosion. The impregnation liquid may include water, at least one acid, at least one alkali, at least one alcohol, or any combination or mixture thereof.

[0024] Pretreatment may include subjecting the wood-based feedstock to steam explosion. Wood-based feedstock from mechanical treatment, press steaming and / or impregnation treatment may be subjected to steam explosion.

[0025] The pretreatment may include at least one of mechanically treating the wood-based material, steaming the wood-based feedstock, impregnating the wood-based feedstock, and steam exploding the wood-based feedstock to form the wood-based feedstock. The pretreatment may include mechanically treating the wood-based material, steaming the wood-based feedstock, impregnating the steamed wood-based feedstock, and steam exploding the impregnated wood-based feedstock to form the wood-based feedstock. The pretreatment may include steaming the wood-based feedstock, impregnating the steamed wood-based feedstock, and steam exploding the impregnated wood-based feedstock. The pretreatment may include impregnating the wood-based feedstock and steam exploding the impregnated wood-based feedstock. That is, the wood-based feedstock that has been subjected to the impregnation treatment may then be subjected to steam explosion. The wood-based feedstock that has been subjected to the steaming treatment may then also be subjected to the impregnation treatment, and the wood-based feedstock that has been subjected to the impregnation treatment may then be subjected to steam explosion.

[0026] As used herein, the term "steam explosion" refers to a semi-hydrolysis process in which a wood-based feedstock is treated in a reactor with steam at a temperature of 130-240°C under a pressure of 0.17-3.25 MPaG, followed by a sudden explosive decompression of the steam-treated wood-based feedstock, resulting in rupture of the fibrous structure. The output from the steam explosion can be mixed with a suitable liquid, such as water, to form a slurry containing solid cellulose particles. The fraction containing the solid cellulose particles can be separated from the liquid fraction by a suitable separation method, such as solid-liquid separation.

[0027] Enzymatic hydrolysis of the fraction containing solid cellulose particles can be carried out at temperatures of 30-70°C, 35-65°C, 40-60°C, 45-55°C, or 48-53°C while maintaining the pH of the fraction containing solid cellulose particles at 3.5-6.5, 4.0-6.0, or 4.5-5.5. The enzymatic hydrolysis can be continued for 20-120 hours, 30-90 hours, or 40-80 hours. As a result of the enzymatic hydrolysis, a lignin fraction and a carbohydrate fraction can be formed. The enzyme serves as a catalyst for the enzymatic hydrolysis. The enzymatic reaction lowers the pH and can also reduce the viscosity by shortening the length of the cellulose fibers. As a result of subjecting the fraction containing solid cellulose particles to enzymatic hydrolysis, the enzyme can convert cellulose to glucose monomers. The lignin present in the fraction containing solid cellulose particles can remain essentially in a solid state.

[0028] At least one enzyme may be used to perform the enzymatic hydrolysis. The at least one enzyme may be selected from the group consisting of cellulases, hemicellulases, laccases, and lignin peroxidases. Cellulases are multiprotein complexes consisting of synergistic enzymes with different specific activities, which can be divided into exo- and endo-cellulases (glucanases) and β-glucosidases (cellobioses). The enzymes may be commercially available cellulase mixtures or may be produced in-situ.

[0029] The catalytic conversion of the carbohydrate fraction may include subjecting the carbohydrate fraction to catalytic hydrogenolysis. That is, the carbohydrate fraction may be subjected to a catalyst in the presence of hydrogen. The catalytic conversion may be carried out in the presence of water. In one embodiment, the catalytic conversion of the carbohydrate fraction may include subjecting the carbohydrate fraction to catalytic hydrogenation in the presence of a solvent, preferably water, and a catalyst system. The catalytic conversion may be carried out in the presence of a catalyst system comprising one or more catalysts. Alternatively, the catalytic conversion may be carried out on a carbohydrate feedstock derived from sugarcane, sugarbeet, corn, and / or wheat.

[0030] A liquid glycol composition can be produced by subjecting the carbohydrate fraction to catalytic conversion. The catalytic conversion achieves at least hydrogenation and hydrocracking reactions, resulting in the hydrogenation and hydrocracking of the carbohydrate fraction, resulting in the formation of a liquid glycol composition. The liquid glycol composition can comprise or consist of monoethylene glycol, monopropylene glycol, and butylene glycol. These glycols can be present in a concentration of 0.1 to 40 wt. % based on the total weight of the liquid glycol composition. The liquid glycol composition can also include other by-products. The liquid composition can also include water.

[0031] For example, monoethylene glycol may be recovered from the liquid composition of glycols by a separation technique selected from, for example, adsorption, evaporation, distillation, extractive distillation, azeotropic distillation, vacuum distillation, atmospheric distillation, membrane separation, filtration, reactive purification, or a combination thereof.

[0032] However, the bio-based diol-containing mixture feedstocks applied herein may also be provided by other processes that produce glycols, and the methods described herein should not be construed as being limited to the above-described processes that produce liquid compositions of glycols.

[0033] One or more separation or purification steps may precede the distillation process described herein. For example, water, alcohols such as methanol and ethanol, organic acids, sugar alcohols such as glycerol, catalysts, and residual sugars may be removed in separate steps in any desired order. Generally, water and alcohols with the lowest boiling points may be removed first, followed by components with boiling points higher than monoethylene glycol. The remaining components may primarily comprise diols with boiling points close to that of monoethylene glycol, which may then be separated in further purification steps.

[0034] The expression "mixture feedstock containing bio-derived diol" should be understood as a mixture feedstock of one or more diols derived from bio-based sources or raw materials, unless otherwise specified herein. In one embodiment, the bio-derived diol is a plant-derived diol, such as a wood-derived diol. Thus, the diol can be derived, for example, from hardwood, softwood, or a combination thereof. The diol can also be derived from broadleaf trees. The diol can be derived from pine, poplar, beech, cottonwood, spruce, eucalyptus, ash, or birch, or any combination or mixture thereof. The diol can further be derived from sugarcane, sugarbeet, corn, wheat, or any combination or mixture thereof.

[0035] The method described herein has the additional benefit of enabling the separation of monoethylene glycol at high purity from a mixture feed that also contains other diols with boiling points close to that of monoethylene glycol. One example of such a material is 1,2-butanediol, which has approximately the same boiling point as monoethylene glycol. Monoethylene glycol and 1,2-butanediol also form an azeotrope with a lower boiling point than monoethylene glycol, which can then be separated from monoethylene glycol. Thus, some loss of monoethylene glycol in the azeotrope may occur during the distillation process. However, the molar ratio of monoethylene glycol to 1,2-butanediol in the azeotrope is about 50:50, e.g., 45:55. Thus, even if some monoethylene glycol is lost with the azeotrope, the amount of monoethylene glycol lost is rather small as a result of the favorable molar ratio.

[0036] An azeotrope can be considered a mixture that exhibits the same concentration in the vapor and liquid phases. This is an ideal solution, as opposed to one component, which is generally more volatile than the other. When a mixture forms an azeotrope, the vapor and liquid concentrations are the same, and this approach can prevent separation.

[0037] The distillation process described herein is carried out in a distillation column. In one embodiment, the distillation column may contain at least 85, or at least 90, or at least 100, or at least 105, or at least 110, or at least 120, or at least 120, or at least 150, or at least 200 theoretical plates. The distillation column may contain up to 1000, or up to 800, or up to 600, or up to 400 theoretical plates. A number of theoretical plates of at least 80 has the additional benefit of allowing separation to occur at a rather high efficiency.

[0038] The mixture feed may be fed into the distillation column at a point located between two theoretical plates. However, the distillation column may include packing or packed beds, where one packed bed includes two or more theoretical plates. In such a situation, the mixture feed may be fed to the distillation column at a point between two such packed beds. In one embodiment, the mixture feed may be fed to the distillation column at a point located at least one theoretical plate below.

[0039] In one embodiment, the mixture feed is fed to the distillation column at a height of 7-18%, or 9-17%, or 12-16%, or 13-15%, or 14-16% of the total height of the distillation column calculated from the top of the distillation column. In one embodiment, the inlet is located at a height of 7-18%, or 9-17%, or 12-16%, or 13-15%, or 14-16% of the total height of the distillation column calculated from the top of the distillation column.

[0040] In one embodiment, the distillation process is carried out using a reflux ratio of 25 to 150, or 30 to 100, or 35 to 80, or 40 to 50, or 35 to 45. In one embodiment, the distillation column is configured to operate at a reflux ratio of 25 to 150, or 30 to 100, or 35 to 80, or 40 to 50, or 35 to 45. The reflux ratio is generally defined as the ratio of the overhead liquid returned to the distillation column divided by the liquid removed or recovered from the distillation column as product.

[0041] The inventors have surprisingly discovered that the combination of points at which the mixed feed is fed to the distillation column, particularly at the reflux ratio employed, has the additional benefit of enabling the recovery of monoethylene glycol with high purity and yield. In one embodiment, the process includes recovering monoethylene glycol at a concentration of 96-99 wt%, or 97-98 wt%, or 96-97 wt%. The yield is calculated as the percentage of the amount of monoethylene glycol recovered compared to the monoethylene glycol in the mixed feed. In one embodiment, monoethylene glycol is recovered at a purity of 99.3-99.99 wt%, or 99.5-99.9 wt%, or 99.6-99.8 wt%. The purity is calculated as the percentage of the amount of monoethylene glycol in the recovered product compared to the total amount of recovered product stream.

[0042] In one embodiment, the distillation process is carried out at an overhead temperature of up to 160°C and an overhead pressure of up to 0.4 bar. In one embodiment, the distillation process is carried out at an overhead temperature of up to 159°C, or up to 157°C, or up to 155°C, or up to 155°C, or up to 150°C, or up to 145°C. In one embodiment, the distillation process is carried out at an overhead pressure of up to 0.35 bar, or up to 0.3 bar. In one embodiment, the distillation process is carried out at an overhead temperature of 50-160°C, or 65-155°C, or 75-150°C, or 100-145°C. In one embodiment, the distillation process is carried out at an overhead pressure of 0.1-0.4 bar, or 0.2-0.35 bar, or 0.25-0.3 bar.

[0043] In one embodiment, the distillation column is configured to operate at an overhead temperature of up to 160°C and an overhead pressure of up to 0.4 bar. In one embodiment, the distillation column is configured to operate at an overhead temperature of up to 159°C, or up to 157°C, or up to 155°C, or up to 155°C, or up to 150°C, or up to 145°C. In one embodiment, the distillation column is configured to operate at an overhead pressure of up to 0.35 bar, or up to 0.3 bar. In one embodiment, the distillation column is configured to operate at an overhead temperature of 50-160°C, or 65-155°C, or 75-150°C, or 100-145°C. In one embodiment, the distillation column is configured to operate at an overhead pressure of 0.1-0.4 bar, or 0.2-0.35 bar, or 0.25-0.3 bar.

[0044] In one embodiment, the pressure drop across the distillation column is from 0.02 to 0.2 bar, or from 0.05 to 0.12 bar.

[0045] The bottom temperature of the distillation column may be maintained at a temperature of up to 170° C. Maintaining the bottom temperature of the distillation column at a temperature of up to 170° C. has the additional benefit of preventing or reducing decomposition of compounds from occurring.

[0046] The term "overhead temperature" is used herein to mean the temperature of the vapor space in a distillation column above the top packing layer or tray and below the vapor pipe of the distillation column. It will be apparent to those skilled in the art that the temperature of the distillation column itself may be different from the temperature in, for example, a condenser or reboiler that may be operatively connected to the distillation column.

[0047] As used herein, the term "overhead pressure" refers to the pressure in the vapor space in a distillation column above the top packing layer or tray and below the vapor pipe of the column.

[0048] In one embodiment, at least one condenser is used in the distillation process. In one embodiment, the distillation apparatus includes at least one cooler. That is, one condenser or a series of at least two condensers can be used in the distillation process. For example, if a series of at least two condensers is used, the vapor fraction after the first condenser can be 5-20%, for example, about 15%, and the vapor fraction after the second condenser can be less than 1%. The condensers used can be (a) partial condensers, (a) total condensers, or a combination thereof. The condensers can be of the heat exchange type, or can use a cooling medium such as cooling water, or can function with air cooling.

[0049] In one embodiment, a reboiler is used in the distillation process. In one embodiment, the distillation apparatus includes a reboiler. The reboiler can be operated at a steam pressure of 0.1 to 0.5 bar or 0.3 to 0.5 bar. In one embodiment, the distillation apparatus includes a reboiler, and the reboiler is configured to operate at a pressure of 0.1 to 0.5 bar or 0.3 to 0.5 bar.

[0050] The distillation process or distillation column, respectively, may include a heat exchanger, in which heat recovered from at least one condenser is directed or transferred to a reboiler, i.e., heat recovered from at least one condenser may be recycled in the reboiler.

[0051] In one embodiment, recovering monoethylene glycol comprises removing monoethylene glycol from the distillation column at a point below the point at which the mixed feed is fed to the distillation column. In one embodiment, the outlet for recovering monoethylene glycol is located at a point below the point at which the inlet for feeding the mixed feed to the distillation column is located.

[0052] Monoethylene glycol may be removed from the distillation column or the side of the distillation column as a so-called side draw. Monoethylene glycol may be removed from the distillation column as a side draw below the lowest packing layer but above the bottom of the distillation column. Monoethylene glycol may be removed from the distillation column as a side draw below the point where the inlet for supplying the mixed feed to the distillation column is located but above the lowest packing layer. Alternatively or additionally, monoethylene glycol may be removed from the distillation column in a bottoms stream taken from the bottom of the distillation column.

[0053] In one embodiment, the point at which monoethylene glycol is removed from the distillation column is located below the lowest theoretical plate of the distillation column.

[0054] In one embodiment, the method includes removing an overhead stream from the distillation column, the overhead stream comprising monopropylene glycol and an azeotropic mixture of monoethylene glycol and 1,2-butylene glycol.

[0055] The process described herein has the additional utility of allowing for the separation of monoethylene glycol in high purity and yield from a mixed feed that also contains other diols with boiling points close to that of monoethylene glycol.

[0056] The method described herein has the additional utility of being an economical process for recovering monoethylene glycol from a mixed feedstock. [Example]

[0057] Example Reference will now be made in detail to various embodiments.

[0058] The following description discloses some embodiments in detail so that those skilled in the art can utilize the embodiments based on the present disclosure. Not all steps or features of the embodiments are described in detail because many of the steps or features will be apparent to those skilled in the art based on this specification.

[0059] For the sake of brevity, when elements are repeated, item numbers are maintained in the following exemplary embodiments.

[0060] The accompanying Figure 1 discloses an exemplary embodiment of a distillation apparatus 9 for recovering monoethylene glycol from a mixture feed containing a bio-derived diol. The mixture feed 2 contains monoethylene glycol in an amount of at least 80 wt% of the total weight of the mixture feed. The mixture feed is first fed to a distillation column 1, where a distillation process takes place. The distillation column includes an inlet 2 for feeding the mixture feed to the distillation column. The distillation column 1 includes a packed bed including at least 80 theoretical plates 5a, 5b, ... 5n. The mixture feed 2 is fed to the distillation column 1 at a point 6 that is 5 to 20% of the total height of the distillation column 1, calculated from the top of the distillation column. The total height of the distillation column is determined based on the number of theoretical plates 5a, 5b, ... 5n. The distillation column is configured to operate at a reflux ratio of 20 to 200. Monoethylene glycol is recovered from the distillation column at points (outlets) 3a1, 3a2, and 3b, which are located below point 6 where the mixture feed is fed into the distillation column. 1 discloses the possibility of removing monoethylene glycol through an outlet as side draw 3a1 and / or side draw 3a2. In such a case, for example, heavy compound impurities may be removed from the bottom of the distillation column. Alternatively, monoethylene glycol may be removed from the bottom of the distillation column through an outlet as bottoms stream 3b.

[0061] Example 1 - Distillation of a mixture containing bio-based diols In this example, a mixed feed containing bio-based diols was subjected to a distillation process.

[0062] The mixture feed comprises:

[0063] [Table 1]

[0064] The separated products recovered or removed from the distillation column had the following compositions and proportions:

[0065] [Table 2]

[0066] The distillation column was operated at an overhead temperature of 159° C. and an overhead pressure of 0.35 bar. Monoethylene glycol was removed as a side draw below the lowest theoretical plate (3 a1 in FIG. 1).

[0067] The reflux ratio and number of theoretical stages were varied, and the height at which the mixed feed was fed into the distillation column was determined. Based on the tests performed, it was noted that monoethylene glycol could be recovered in high yield and purity if the vapor parameters were maintained within the claimed ranges.

[0068] The yield of monoethylene glycol in this example was 96 wt%. The target purity was set at 99.8 wt%, which is in the range of polymer-grade ethylene glycol. This is close to the theoretical maximum for the applied feedstock. The theoretical maximum purity is 99.83 wt%.

[0069] The results are shown in the table below.

[0070] [Table 3]

[0071] Additionally, the effect of reflux ratio and number of theoretical plates on the purity of the recovered monoethylene glycol was tested and determined, the results of which are shown in the table below.

[0072] [Table 4]

[0073] As can be seen from the table above, the purity of the recovered monoethylene glycol increases when 80 or more theoretical plates are used. Table 2 shows that the highest purity was achieved for various combinations of theoretical plates and reflux ratios. Table 2 shows that the majority of the theoretical plate and reflux ratio combinations achieved a target purity of 99.8 wt.%, and even a maximum purity of 99.83 wt.%.

[0074] From Table 1 it can be seen that the more theoretical plates used and the higher the reflux ratio, the higher the point in the distillation column at which the mixed feed can be fed into the distillation column.

[0075] Example 2 - Distillation of a mixture containing bio-based diol and water In this example, the same mixture feed as in Example 1 was applied, except that the mixture feed contained an additional amount of water.

[0076] The mixture feed included:

[0077] [Table 5]

[0078] The separated products recovered or removed from the distillation column had the following compositions and proportions:

[0079] [Table 6]

[0080] The distillation column was operated at an overhead temperature of 151-152°C and an overhead pressure of 0.35 bar. As a result of the presence of water, the temperature was lower at the same pressure compared to that in Example 1. Monoethylene glycol was removed as a side draw below the lowest theoretical plate (3 a1 in Figure 1).

[0081] The reflux ratio and the number of theoretical plates were varied, and the height at which the mixed feed material was fed into the distillation column was determined. Based on the tests conducted, it was noted that when the above parameters were maintained within the ranges set forth in the claims, monoethylene glycol could be recovered in high yield and purity. Compared to Example 1, a higher ethylene glycol flow was used, and therefore the ethylene glycol yield was a higher 97 wt%. The results are shown in the table below.

[0082] [Table 7]

[0083] Again, the target purity was achieved when the mixed feed was fed into the distillation column at a height of 5-20% of the total height of the distillation column calculated from the top of the column. Compared to Example 1, these points were slightly lower in the distillation column.

[0084] The main effect of the presence of water in the mixed feed is a lower overhead temperature and a lower reflux ratio. Since the reflux ratio is the reflux flow returned to the column divided by the distillate flow, the amount of water increases the reflux flow, thus decreasing the reflux ratio.

[0085] [Table 8]

[0086] Table 4 shows that the target purity was reached for most of the theoretical stage and reflux ratio combinations.

[0087] It is obvious to a person skilled in the art that with the advancement of technology the basic idea can be realized in various ways, therefore the embodiments are not limited to the examples described above but can instead vary within the scope of the claims.

[0088] The embodiments described herein above may be used in any combination with each other. Several of the embodiments may be combined together to form further embodiments. The methods and distillation apparatuses disclosed herein may include at least one of the above-described embodiments. It will be understood that the benefits and advantages described above may relate to one embodiment or to several embodiments. The embodiments are not limited to embodiments that solve any or all of the specified problems or have any or all of the specified benefits and advantages. Reference to "an" or "an" item is further understood to mean one or more of those items. The term "comprising" is used herein to mean the inclusion of subsequent features or acts without excluding the presence of one or more additional features or acts.

Claims

1. 1. A method for recovering monoethylene glycol from a mixture feed containing a bio-derived diol, the mixture feed comprising monoethylene glycol in an amount of at least 80 wt.% of the total weight of the mixture feed, the method comprising: providing the mixture feed into a distillation column in which a distillation process is carried out, the distillation column comprising at least 80 theoretical plates, the mixture feed being fed into the distillation column at a height that is 5 to 20% of the total height of the distillation column calculated from the top of the distillation column, the total height of the distillation column being determined based on the number of theoretical plates, and the distillation process being carried out at a reflux ratio of 20 to 200; - recovering monoethylene glycol; A method comprising:

2. 10. The method of claim 1, wherein the mixture feed comprises monoethylene glycol in an amount of at least 85% by weight or at least 87% by weight of the total weight of the mixture feed.

3. 3. The method of claim 1 or 2, wherein the mixture feed comprises monoethylene glycol, monopropylene glycol, and butylene glycol in an amount of at least 90 wt%, or at least 95 wt%, or at least 97 wt%, or at least 99 wt% of the total weight of the mixture feed.

4. 4. The process of any one of claims 1 to 3, wherein the distillation column comprises at least 85, or at least 90, or at least 100, or at least 105, or at least 110, or at least 120, or at least 150, or at least 200 theoretical plates.

5. 5. The method of claim 1, wherein the mixture feed is fed into the distillation column at a point that is at a height of from 7 to 18%, or from 9 to 17%, or from 12 to 16%, or from 13 to 15%, or from 14 to 16% of the total height of the distillation column calculated from the top of the distillation column.

6. 6. The process of any one of claims 1 to 5, wherein the distillation process is carried out at a reflux ratio of from 25 to 150, or from 30 to 100, or from 35 to 80, or from 40 to 50, or from 35 to 45.

7. 7. The method according to any one of claims 1 to 6, wherein the distillation process is carried out at an overhead temperature of up to 160°C and an overhead pressure of up to 0.4 bar.

8. 8. The method of claim 7, wherein the distillation process is carried out at an overhead temperature of at most 159°C, or at most 157°C, or at most 155°C, or at most 150°C.

9. 8. The method of claim 7, wherein the distillation process is carried out at an overhead pressure of from 0.1 to 0.4 bar, or from 0.2 to 0.35 bar, or from 0.25 to 0.3 bar.

10. 10. The process of any one of claims 1 to 9, wherein the pressure drop across the distillation column is from 0.02 to 0.2 bar or from 0.05 to 0.12 bar.

11. The method according to any one of claims 1 to 10, wherein at least one condenser is used in the distillation process.

12. 12. The method of any one of claims 1 to 11, wherein a reboiler is used in the distillation process, the reboiler being operated at a pressure of 0.1 to 0.5 bar or 0.3 to 0.5 bar.

13. 13. The method of any one of claims 1 to 12, wherein recovering monoethylene glycol comprises removing monoethylene glycol from the distillation column at a point located below the point at which the mixed feed is fed into the distillation column.

14. 14. The method of claim 13, wherein the point at which monoethylene glycol is removed from the distillation column is located below the lowest theoretical plate of the distillation column.

15. 15. The process of any one of claims 1 to 14, comprising removing an overhead stream from the distillation column, the overhead stream comprising monopropylene glycol and an azeotropic mixture of monoethylene glycol and 1,2-butylene glycol.

16. 16. The process of any one of claims 1 to 15, comprising recovering monoethylene glycol at a concentration of at least 99.5 wt%, or at least 99.7 wt%, or at least 99.8 wt%, or at least 99.9 wt%.

17. A distillation apparatus (9) for recovering monoethylene glycol from a mixture feed containing a bio-derived diol, the mixture feed (2) comprising monoethylene glycol in an amount of at least 80 wt. % of the total weight of the mixture feed, the distillation apparatus comprising: a distillation column (1) comprising at least 80 theoretical plates (5a, 5b, . . . 5n) and adapted to operate at a reflux ratio of between 20 and 200; an inlet (2) for providing the mixture feed into the distillation column (1) where the distillation process takes place, the inlet (2) being located at a height of 5 to 20% of the total height of the distillation column calculated from the top (1a) of the distillation column, the total height of the distillation column being determined based on the number of theoretical plates; - outlet for recovering monoethylene glycol (3a １ , 3a ２ , 3b) and A distillation apparatus comprising:

18. 18. Distillation apparatus according to claim 17, wherein the distillation column (1) comprises at least 85, or at least 90, or at least 100, or at least 105, or at least 110, or at least 120, or at least 150, or at least 200 theoretical plates (5a, 5b, ... 5n).

19. The distillation apparatus according to claim 17 or 18, wherein the inlet (2) is located at a point (6) that is at a height of 7 to 18%, or 9 to 17%, or 12 to 16%, or 13 to 15%, or 14 to 16% of the total height of the distillation column calculated from the top of the distillation column.

20. 20. The distillation apparatus according to any one of claims 17 to 19, wherein the distillation column (1) is configured to operate at a reflux ratio of from 25 to 150, or from 30 to 100, or from 35 to 80, or from 40 to 50, or from 35 to 45.

21. Distillation apparatus according to any one of claims 17 to 21, comprising at least one condenser (7).

22. 23. Distillation apparatus according to any one of claims 17 to 22, comprising a reboiler (8), said reboiler configured to operate at a pressure of 0.1 to 0.5 bar or 0.3 to 0.5 bar.

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