KR102520479B1 - Method of Melt Crystallization of Anhydrosugar Alcohols - Google Patents

Abstract

The present invention comprises the steps of recovering anhydrosugar alcohol having a purity of 59% or more by subjecting the crude anhydrous sugar alcohol melt to FF crystallization in a falling film crystallizer; And it relates to a melt crystallization method of anhydrous sugar alcohol comprising the step of recovering anhydrosugar alcohol having a purity of 59% or more by introducing the FF crystallization residue into a static crystallizer for SC crystallization.

Description

Method of Melt Crystallization of Anhydrosugar Alcohols {Method of Melt Crystallization of Anhydrosugar Alcohols}

The present invention relates to a method for melt crystallization of anhydrous sugar alcohol, and more particularly, to a combination of falling film melt crystallization and static crystallization of crude anhydrous sugar alcohol obtained by direct distillation. It relates to a melt crystallization method of anhydrous sugar alcohol, characterized in that it undergoes a crystallization process.

Due to the depletion of traditional energy sources along with the increase in global energy demand, the development of alternative energy is currently being accelerated. Among these, biomass is a renewable and quantitative biological resource that is receiving great attention.

Among biomass-based industrial raw materials, isosorbide (C ₆ H ₁₀ O ₄ ), which is produced by dehydrating sorbitol (C ₆ H ₁₄ O ₆ ), replaces Bisphenol A (BPA). It is in the limelight as an eco-friendly material such as polycarbonate (PC), monomer for epoxy or raw material for eco-friendly plasticizer. In other words, isocarbide is a material that can be obtained through a simple dehydration process of sorbitol, and is attracting attention as a monomer necessary for the synthesis of next-generation high-performance, eco-friendly materials that can replace previously used polymer products. A lot of research is going on.

In general, when using eco-friendly raw materials, while physical properties are poorer than those of petrochemical-based raw materials, isosorbide has the advantage of being environmentally friendly and exhibiting superior characteristics than existing petrochemical-based raw materials. In addition, ISO carbide can be used as an additive that can make plastics stronger and tougher, and ISO carbide combined with nitrate is also used as a treatment for heart disease.

Sorbitol is produced when D-glucose, which has undergone a pretreatment process in biomass, is hydrogenated under a catalyst. This sorbitol is double dehydrated to produce isosorbide. This cyclization reaction is affected by various reaction conditions such as temperature, pressure, solvent, and catalyst.

In the conventional method for producing anhydrous sugar alcohol containing isosorbide, a process of reacting under reduced pressure using sulfuric acid as a catalyst is widely used (Republic of Korea Patent Registration 10-1079518). However, when a strong acid such as sulfuric acid is used as a catalyst, the reactor is easily corroded, so an expensive reactor must be used to prevent corrosion, and a large amount of energy is consumed because the reduced pressure condition must be continuously achieved, resulting in an overall increase in production cost. . In addition, it is not easy to manufacture a highly reliable continuous vacuum reactor, so most processes use batch or semi-batch reactors.

On the other hand, since anhydrosugar alcohol has a high boiling point and is easily decomposed by high-temperature heat, when using general atmospheric distillation, it is difficult to separate, so a vacuum distillation process is often used (US 6,639,067). However, it is necessary to maintain reduced pressure conditions not only in the reaction process but also in the separation process, and since the yield rate of anhydrous sugar alcohol is lowered each time a multi-step process is performed, the manufacturing cost rapidly increases.

Therefore, in order to solve the above problems, the present inventors prepared anhydrous sugar alcohol by heating a reactor while supplying a mixture of a catalyst and sugar alcohol, and at the same time, after distilling and separating anhydrous sugar alcohol, the melt was subjected to falling film type melt crystallization ( It was confirmed that the yield of the crystallization process and the purity of anhydrous sugar alcohol could be improved when performing a process in which falling film crystallization and static melt crystallization were combined, and the present invention was completed.

An object of the present invention is to provide a method for melt crystallization of anhydrous sugar alcohol that can improve the yield and purity of anhydrous sugar alcohol in the reaction of preparing and refining sugar alcohol into anhydrous sugar alcohol.

In order to achieve the above object, the present invention comprises the steps of recovering anhydrous sugar alcohol by falling film crystallization of crude (crude) anhydrous sugar alcohol; And it provides a method for melt crystallization of anhydrous sugar alcohol comprising the step of further recovering anhydrous sugar alcohol by static crystallization of the residue of the subfractional crystallization.

According to the present invention, crude anhydrous sugar alcohol obtained by distilling and cooling a reactant obtained by the reaction of sugar alcohol is sequentially subjected to falling film crystallization and static melt crystallization. Thus, there is an effect of improving the yield and purity of the melt crystallization process.

1 is a flowchart schematically illustrating a method for producing and purifying anhydrous sugar alcohol according to an embodiment of the present invention.
2 is a diagram schematically illustrating an apparatus for falling film melt crystallization according to an embodiment of the present invention.
3 is a view sequentially showing the reaction steps of falling film melt crystallization according to an embodiment of the present invention.
4 is a diagram schematically illustrating an apparatus for static melt crystallization according to an embodiment of the present invention.
5 is a view sequentially showing reaction steps of static melt crystallization according to an embodiment of the present invention.
6 is a flowchart schematically showing a method for producing and purifying anhydrous sugar alcohol to which an adsorption process is added according to an embodiment of the present invention.
Figure 7 is a flow chart in which a recycling process is added in the method for producing and purifying anhydrous sugar alcohol according to an embodiment of the present invention.
Figure 8 is a flow chart in which a recycling process using a filter is added in the method for producing and purifying anhydrous sugar alcohol according to an embodiment of the present invention.
9 is a view showing the inside of a direct distiller of anhydrous sugar alcohol according to an embodiment of the present invention.
Figure 10 is a graph measuring the YI (Yellowness Index) of crude isosorbide feed according to an embodiment of the present invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclature used herein is one well known and commonly used in the art.

In general, there are two types of melt crystallization methods: falling film melt crystallization (hereinafter referred to as 'FF crystallization') and static melt crystallization (hereinafter referred to as 'SC crystallization').

Falling film melt crystallization (FF crystallization)

It is a method of forming an isosorbide crystal on the surface of the layer by flowing crude isocarbide on a tubular layer maintained at a low temperature. It has the advantage of being simple, easy to scale-up and easy to operate.

2 schematically shows an apparatus for FF crystallization according to the present invention. The falling film crystallization may include forming crystals by flowing the crude anhydrous sugar alcohol on a surface maintained at a temperature lower than the freezing point of pure anhydrous sugar alcohol, and the temperature of the surface on which the crystal is formed is pure It may further include the step of raising the temperature to a value between the freezing point of anhydrous sugar alcohol and the temperature at which crystals of the crude anhydrous sugar alcohol are formed.

As shown in FIG. 3, FF crystallization goes through three stages in which crystallization is formed through temperature control: crystallization -> partial melting (sweating) -> melting.

Step 1: Crystallization

Since the melting point of isosorbide is ~ 63 ° C, crystallization is possible at a temperature of 63 ° C or less. Cooling below -40°C lowers the cooling efficiency, resulting in high operating costs. So, the temperature at which the isosorbide crystal is formed may be -40 to 63 ° C, preferably 30 to 60 ° C, and more preferably 40 to 60 ° C.

Step 2: Partial melting

Impurities may be intercalated between the crystals when the isosorbide crystals are formed. Therefore, when the temperature of the layer is slightly higher than the temperature at which crystals are formed (40 to 60 ° C), impurities have fluidity. Impurities having fluidity are pushed out of the crystal surface and removed, and there is an effect of increasing the purity of ISO carbide.

Step 3: Melting

The temperature of the layer is raised to more than the melting point of isocarbide (60 ° C.) to melt and recover the isosorbide crystal.

static Static melt crystallization (SC crystallization)

SC crystallization is a method of making an isocarbide crystal by putting crude isosorbide in a container and contacting a plate through which a heat transfer medium (HTM) is circulated with the crude isosorbide.

The principle by which the isosorbide crystal is formed is the same as that of FF crystallization. However, it has the advantage that it can be used even if the purity of the crude isocarbide melt is slightly low, and the device configuration is very simple. An apparatus for SC crystallization according to the present invention is schematically shown in FIG. 4 . Inside the vessel in which the remnants of subfilm crystallization are stored, an object whose surface temperature is maintained at a temperature lower than the freezing point of pure anhydrous sugar alcohol is brought into contact with the remnants of subfilm subtype crystallization to form crystals on the surface of the object. It may include the step of forming, and may further include the step of raising the temperature of the surface on which the crystals are formed to a value between the freezing point of pure anhydrous sugar alcohol and the temperature at which the crystals of the remnant of the subfilm crystallization are formed.

As shown in FIG. 5, SC crystallization goes through the steps of crystallization, draining, partial melting (sweating) and melting.

Since FF crystallization has an advantage of excellent crystallization efficiency even when the concentration of impurities is high, the yield and purity of the crystallization process can be improved by treating the crystallization residue of FF crystallization with SC crystallization.

In the present invention, when crude anhydrous sugar alcohol obtained by distilling and cooling a reactant obtained by the reaction of sugar alcohol is sequentially subjected to falling film crystallization and static melt crystallization , it was confirmed that the yield and purity of the melt crystallization process were improved.

Therefore, the present invention, in one aspect, the step of recovering the anhydrous sugar alcohol by falling film crystallization (falling film crystallization) the crude (crude) anhydrous sugar alcohol; And it relates to a melt crystallization method of anhydrous sugar alcohol comprising the step of further recovering anhydrous sugar alcohol by static crystallization of the residue of the subfractional crystallization.

That is, the present invention is characterized in that FF crystallization and SC crystallization are performed in combination to improve the yield and purity of the melt crystallization process. Figure 6 schematically shows the steps of the combined form of FF crystallization and SC crystallization. Since the crystallization residue has a higher concentration of impurities than the feed, crystallization must be performed at a lower temperature than the feed in order to further separate the isocarbide from the crystallization residue. That is, when the FF crystallization → SC crystallization process is combined, the crystallization temperature (-40 to 20 ° C) of SC crystallization is lower than the FF crystallization temperature (0 to 60 ° C).

In the present invention, in order to produce anhydrous sugar alcohol, when sugar alcohol is reacted in the presence of an acid catalyst and subjected to distillation, a crude (crude) anhydrous sugar alcohol melt mixed with impurities, particularly a crude isosorbide melt, followed by 'crude' (Crude) Isosorbide') A mixture of steam and water vapor is obtained from the overhead of the reactor. Crude isocarbide is introduced into a melt crystallization process and purified to a purity of 59% or more, particularly 99.8% or more.

On the other hand, the SC crystallization process directly produces high-purity Isocarbide of 1) 99% or more (99.8% or more), or 2) converts the FF crystallization residue to a purity level (90 ~99%), which can be recycled to FF crystallization. The impurity concentration of the SC crystallization residue is as high as 40~90% or more. The method of 1) recycling the residue of SC crystallization by supplying it to the reaction/distillation unit 2) recycling it inside the SC crystallization method and 3) discarding high-concentration impurities can be recycled in any way. In addition, although the efficiency of the crystallization process is low when the impurity concentration is very high, the yield of the separation process can be maximized by recycling the SC crystallization residue by supplying it to the reaction/distillation unit.

Hereinafter, the overall process of the production and purification method of anhydrous sugar alcohol according to the present invention is described below.

In the present invention, as shown in Figure 1, crude (crude) anhydrous sugar alcohol is reacted with sugar alcohol in the presence of an acid catalyst in a reactor and at the same time evaporating the reaction product; and cooling the evaporated product to obtain crude anhydrous sugar alcohol.

The present invention is characterized by preparing and purifying high-purity isocarbide through melt crystallization (melt crystallization) combining FF crystallization and SC crystallization after direct distillation.

Direct Distillation

Direct distillation is a process in which the reaction of converting sorbitol into isocarbide and the process of separating the produced isocarbide by distillation are performed simultaneously inside one reactor.

The catalyst according to the present invention satisfies the following conditions.

(a) boiling point

In order to maintain catalytic activity without evaporation of the catalyst during the reaction and to easily separate the catalyst and ISO carbide in a purification process such as vacuum distillation, a catalyst with a higher boiling point than ISO carbide (160 ° C. at 10 mmHg) is selected. That is, the boiling point at 10 mmHg is 160° C. or higher.

(b) Acidity (pK _a )

A catalyst having an appropriate acidity to reduce the formation of side reactants such as polymer or coke under high temperature reaction conditions is used. The pKa range for yield increase is -3.0 <pK _a < 3.0, preferably the range is -2.0 <pK _a < 2.5, and more preferably the range may be -1.0 <pK _a < 1.9.

(c) homogeneous phase

A catalyst that increases the contact efficiency between the catalyst and the feed and reacts in a homogeneous phase under reaction conditions is used. To this end, the melting point may be 180°C or less, preferably 160°C or less, more preferably 140°C or less, and particularly preferably 120°C or less.

As the catalyst, naphthalenesulfonic acid may be used. Specific compounds of naphthalene sulfonic acid include 2-naphthalene sulfonic acid and 1-naphthalene sulfonic acid, and these compounds are isomers formed when naphthalene is sulfonated. 2-naphthalene sulfonic acid has pK _a =0.27, mp=91 °C, bp=391.6 °C (boiling point greater than 160 °C at 10 mmHg), and 1-naphthalene sulfonic acid has pK _a =0.17, mp=90 °C, bp = It is 392°C.

The temperature of the reactor may be 150 to 220 °C, preferably 170 to 190 °C. If the reaction temperature is less than 150 ° C, the reaction time or residence time becomes very long, and if it exceeds 220 ° C, side reactions may be promoted and the yield may decrease. In addition, the pressure of the reactor may be 1 to 50 torr, preferably 1 to 20 torr. When the reaction pressure is less than 1 torr, there is a problem in that the process operation cost greatly increases due to high vacuum, and when the reaction pressure exceeds 50 torr, the reaction rate decreases. There is a problem that it is slow and the yield is low.

In terms of process efficiency, the smaller the amount of catalyst added, the higher the economic efficiency. The amount of catalyst used in the present invention may be 0.01 to 10 parts by weight based on 100 parts by weight of sugar alcohol, preferably 0.1 to 5 parts by weight. part, more preferably 0.2 to 3 parts by weight. When the added amount of the catalyst is less than 0.01 parts by weight, there is a problem in that the dehydration reaction time takes too long, and when the amount exceeds 10 parts by weight, the production of saccharide polymers, which are by-products, increases and the economic feasibility decreases due to the increase in the amount of catalyst used.

In the present invention, the sugar alcohol may be hexitol, and may be at least one selected from the group consisting of sorbitol, mannitol, and iditol, preferably sorbitol, and the anhydrous sugar alcohol is isocarbide, isoman It may be nide or isoidide, etc., preferably isocarbide.

The method for producing anhydrous sugar alcohol according to the present invention may be carried out batchwise or continuously. It may be performed in a Continuous Stirred Tank Reactor (CSTR), a Plug Flow Reactor (PFR) or a Batch Reactor (BR).

In addition, the reactor is a preferred embodiment, as shown in Figure 9, (a) there is a distributor 140 is installed on the top, the reactor 100 in which the raw material flows down and reacts along the inner wall surface; (b) a raw material supply unit 110 installed on one side of the upper part of the reactor; (c) an unreacted raw material and by-product separation/recovery means (300) installed inside the reactor at a certain distance from the lower end of the reactor; (d) a condenser 200 located in the center of the reactor and installed through the separation/recovery means; (e) a means (500) located on one side of the reactor and lowering the pressure inside the reactor; and (f) a product discharge port 130 located at the center of the lower end of the reactor and discharging the product flowing down from the condenser 200.

Unreacted materials (unreacted sugar alcohol) and intermediates (when sugar alcohol is sorbitol, 1,4-sorbitan, etc.) removed from the bottom of the direct distillation unit can be recycled back to the direct distillation process. At this time, unreacted materials and intermediates discharged from the bottom of the reactor may be recycled after passing through an impurity removal means, and high-temperature/high-pressure steam may be mixed with the recycled feed to promote further conversion of unreacted materials under hydrothermal conditions. can In addition, the added steam may serve as a stripping agent that helps the isocarbide evaporate during the direct distillation process.

Cooling of evaporated products

As in the above, when direct distillation is performed, a mixture of crude anhydrous sugar alcohol vapor and water vapor mixed with impurities is obtained from the overhead of the reactor. The reactant obtained by cooling the mixture of water vapor is referred to as 'crude anhydrous sugar alcohol melt', and in particular, when the anhydrous sugar alcohol is isosorbide, it is referred to as crude isosorbide. Crude isocarbide is introduced into a melt crystallization process and purified to a purity of 59% or more, particularly 99.8% or more. When a mixture of crude isosorbide vapor and water vapor is cooled to 60-100° C., the water is removed and only a crude isosorbide melt is obtained. The purity of the crude isocarbide melt is 90-99% (about 97%). The temperature of the receiver is 60 to 100°C, and it is in the same reduced pressure state as the reactor.

Most of the water can be removed from the receiver, and the moisture content can be controlled by adjusting the temperature of the receiver. When the adsorption process is performed before the melt crystallization process, there is an advantage in that no additional adsorption solvent needs to be added if the melt contains moisture.

In the present invention, crude (crude) anhydrous sugar alcohol is reacted with sugar alcohol in the presence of an acid catalyst in a reactor and at the same time evaporating the reaction product; cooling the evaporated product to obtain crude anhydrous sugar alcohol; And it can be obtained through the step of adsorbing the crude (crude) anhydrous sugar alcohol.

That is, the purity can be further increased by performing the adsorption process using water contained in the melt as a solvent without separately adding a solvent between direct distillation and melt crystallization (FIG. 6). The adsorption process may be performed at room temperature to 60° C. and normal pressure. By controlling the temperature of the overhead receiver (room temperature ~ 60 ℃), it is possible to recover in the state of a mixed solution of isosorbide and water having a water content of 1 to 30% by weight without completely removing the water, The water acts as a solvent or diluent in the adsorption process, so there is no need to separately add water for crystallization. Because ISOcarbide becomes a liquid above 63 °C and has a high viscosity, previous techniques required additional mixing of the solvent before adsorption was performed. However, in the present invention, an isocarbide solution containing water can be prepared only by controlling the temperature of the direct distillation receiver. Therefore, the process is simple and the operating cost and equipment cost can be reduced. The adsorption process proceeds by passing a mixed solution of isosorbide and water through an adsorbent such as activated carbon, ion exchange resin, or a combination thereof to remove color bodies and impurities. The type of adsorbent is not limited, but it is preferable to use activated carbon, and it is possible to use ion exchange resins or all of them. Activated carbon may be performed after performing the ion exchange resin, and vice versa. An evaporation process such as a flash evaporation process may optionally be additionally performed to remove water contained in the adsorption product.

Residues obtained from the bottom of the direct distillation process include 1) unreacted sorbitol, 2) intermediates such as 1,4-sorbitan, 3) polymers/oligomers, and 4) carbides.

If the reaction temperature is increased and the time is increased, the amounts of unreacted materials and intermediates decrease, but the amounts of polymers/oligomers and carbides increase. When the polymer / oligomer and carbide increase, the yield of isocarbide is lowered, and the viscosity of the residue increases, making continuous operation difficult. In severe cases, all of the polymers/oligomers are carbonized, sticking to the reactor walls and outlets, and may cause a shutdown situation. Therefore, it is necessary to suppress the formation of polymers / oligomers and carbides by shortening the residence time (reaction time) inside the direct distillation reactor, and it is necessary to further convert unreacted materials and intermediates through recycling to increase the yield of isocarbide. It is important. In direct distillation, it is not easy to control the reaction temperature because distillation of isocarbide is difficult when the reaction temperature is lowered. In the present invention, unreacted materials and intermediates discharged from the bottom of the reactor can be recycled to the reactor, and as shown in FIG. 7, when recycling the bottom residue of the direct distillation process to the reactor, in the recycle flow Further conversion of unreacted materials and intermediates can be induced by mixing high-temperature/high-pressure steam or hot water. Since direct distillation is a reduced pressure process, in order to mix high temperature/high pressure steam or hot water, back pressure regulators (BPRs) are installed before and after the recycle flow to maintain the reduced pressure condition inside the direct distillation. The residue is mixed with steam or hot water at high temperature/pressure.

The temperature of the recycle flow is 150 to 300 ° C, preferably 170 to 250 ° C, more preferably maintained at a higher temperature than the inside of the distillation. The pressure is maintained above the saturated water vapor pressure at the temperature. For example, it is maintained at 4.76 bar or more at 150 ° C and 85.81 bar or more at 300 ° C.

In the present invention, high-temperature and high-pressure steam or hot water can perform three roles.

First, since the internal pressure of the recycle flow is maintained above the saturated water vapor pressure, high-temperature liquid water exists. High-temperature liquid water can act as an acid catalyst through self-ionization, and unreacted materials and 1,4-sorbitan intermediates along with a naphthalenesulfonic acid catalyst It promotes the reaction that converts to isocarbide.

That is, in the direct distillation apparatus, isosorbide is formed through a reduced pressure reaction of the naphthalene sulfonic acid catalyst, and in the recycle flow, the high temperature / high pressure hot water and the naphthalene sulfonic acid catalyst act together to further form isocarbide. In the recycle flow, even if the temperature is maintained at a higher temperature than the inside of the direct distillation, there is an advantage that steam or hot water dilutes the residue and suppresses the carbonization phenomenon.

The reason for applying a reduced pressure reaction in the conventional reaction of dehydrating sorbitol to isosorbide is to continuously remove water from the reactants because the dehydrated water molecules dilute the concentration of the catalyst and hinder the reaction. Therefore, when reacting using sulfuric acid under a reduced pressure condition of about 10 mmHg, the reaction can be reacted even at a low temperature of about 120 to 140 ° C. because there are few factors inhibiting the reaction. On the other hand, since the high-pressure reaction without removing water contains more water, which is a reaction inhibitor, than the reduced-pressure reaction, a high reaction temperature is required even if the same catalyst is used. However, when the reaction temperature is increased, more side reactions such as decomposition, polymerization, and char may proceed. In particular, when a strong acid catalyst such as sulfuric acid is used, a large amount of side reactions may proceed at high temperatures. Therefore, it is important to select an effective catalyst that has weaker acid properties than sulfuric acid and can suppress side reactions at high temperatures. So, in the present invention, in the dehydration reaction at a temperature of 160 ~ 260 ℃ and high temperature and high pressure of 10 ~ 50 bar to convert sorbitol to isocarbide, it has a higher boiling point than isocarbide, thereby catalytic activity without evaporation of the catalyst during the reaction It can be maintained, it can easily separate isosorbide and catalyst in a purification process such as vacuum distillation, reacts in a homogeneous phase under reaction conditions to increase the contact efficiency between catalyst and feed, and polymer under high temperature reaction conditions Alternatively, the yield of isocarbide could be increased by using a catalyst having an acidity suitable for reducing the production of side reactants such as coke.

Second, the steam and hot water mixed in the recycle flow can directly maintain the internal temperature of the distillation and additionally supply energy required for the dehydration reaction. The dehydration reaction to convert sorbitol to isocarbide is a weakly endothermic reaction. Inside the direct distillation maintained under reduced pressure, since the water produced by the reaction and the isocarbide are continuously distilled, in addition to the reaction heat, the phase change energy used for distillation is continuously consumed. In the case of a commercial process, it is difficult to supply energy to the inside through the outer wall of the reactor and maintain a constant internal temperature.

However, in the present invention, the high-temperature steam or hot water mixed with the recycle flow is directly introduced into the distillation to supply the energy necessary for the reaction and phase change, so that the temperature inside the direct distillation reactor can be maintained constant.

Third, steam or hot water serves as a stripping agent that helps the produced isocarbide to be distilled inside the distillation directly. Since isocarbide has a high boiling point, high vacuum conditions are required to distill it, and special distillation equipment such as a thin film evaporator is generally used. The present invention is characterized in that the reaction and distillation are simultaneously performed inside one reaction device (direct still) without using a thin film still.

Steam or hot water can form an azeotrope with isosorbide to promote the distillation of isosorbide. In addition, when steam or hot water under high pressure in the recycle flow is introduced into the distillation chamber under reduced pressure, rapid boiling occurs. made, it is possible to further promote the distillation of isocarbide.

Meanwhile, as shown in FIG. 8, a filter may be installed between the direct distillation outlet and the recycle flow to remove polymers/oligomers and carbides contained in the direct distillation residue, and then only unreacted materials and intermediates may be recycled. there is. The type of filter is not particularly limited.

Hereinafter, the present invention will be described in more detail through examples. These examples are only for exemplifying the present invention, and it will be apparent to those skilled in the art that the scope of the present invention is not limited by these examples.

[Example]

Example One

Add 500 to 1000 g of sorbitol (D-sorbitol, Aldrich Co.) to a 1,000 mL reactor, melt the sorbitol at a reaction temperature of 110 to 200 ° C, then add 3.0 wt% of naphthalenesulfonic acid hydrate (Aldrich Co.) and stir and the reaction pressure was reduced to 5 to 10 mmHg. The material evaporated and discharged from the top of the reactor for 2 to 5 hours is defined as crude isosorbide, and the crude isosorbide tested under various conditions is collected and used in a rotary evaporator at 90 ° C. and 30 mbar The moisture was evaporated for 1 hour or more under the condition. Distilled water was injected into the crude isocarbide from which the moisture was evaporated so that the moisture content was 2%.

When the solution prepared as described above is put into a 1.5L stirring tank and a small amount of isocarbide powder is added and stirred, an isocarbide crystal is produced. After the crystals were formed, if there was no internal change, the remaining liquid other than the crystals was poured out, and the internal temperature of the stirring tank was raised to 47 ° C. to dissolve some of the impurities trapped in the crystals or attached to the outside of the crystals.

The above-obtained isocarbide crystals and the solution before the crystallization step were diluted 25-fold with water and analyzed by high-performance liquid chromatography (HPLC, manufactured by Agilent, using a REZEX Monosaccharide column). At this time, the isocarbide purity of the solution before crystallization was 95.1wt%, and the isocarbide purity after crystallization was 96.4wt%.

Example 2

In Example 1, crystallization was performed in the same manner as in Example 1 with respect to the remaining liquid extracted after the crystal production of ISO carbide. After crystal formation, the remaining liquid was poured out, and the internal temperature of the stirring bath was raised to 37° C. to further dissolve impurities.

The purity of the isocarbide crystals obtained above and the composition of the solution used as the feed were analyzed in the same manner as in Example 1. The isocarbide purity of the solution before crystallization was 91.5wt%, and the isocarbide purity after crystallization was 94.2wt%.

Example 3

After preparing crude isocarbide in the same manner as in Example 1 and evaporating moisture, distilled water was injected into the evaporated crude isocarbide so that the moisture content was 6%.

The solution prepared as described above was crystallized in the same manner as in Example 1 to obtain crystals. However, in order to remove additional impurities, the stirring bath was raised to about 30°C.

The purity of the isocarbide crystals obtained above was analyzed in the same manner as in Example 1. At this time, the isocarbide purity of the solution before crystallization was 96.1wt%, and the isocarbide purity after crystallization was 98.7wt%.

Example 4

Crude isocarbide was prepared in the same manner as in Example 1, and a color-developing material was adsorbed onto activated carbon. Activated carbon was prepared by NORIT's Granule type product (GAC 1240) and dried in an oven at 150 ° C for 8 hours or more. After densely packing 130 g of activated carbon in an STS tube having a diameter of 50 mm and a length of 150 mm, crude isosorbide was flowed in an upward flow. The flow rate was set to 1 mL/min, and the flow was maintained for 10 days or more. The color of the crude isosorbide passing through the adsorption tower was measured through Yellowness Index (YI).

As shown in FIG. 10, the YI of crude isocarbide used as a feed was 21.7, and the YI of the flow passing through the adsorption tower showed a value of 1 or less until about 100 hours, and then increased to a value of about 3 to 5 after 150 hours. seemed YI at the rear end of the adsorption tower maintained this level until 12 days (= 288 hours).

Example 5

In an autoclave reactor, 90 g (sorbitol = 63 g) of 70 wt % sorbitol (D-sorbitol, Aldrich) aqueous solution and 1.5 g of a naphthalenesulfonic acid catalyst were added, followed by stirring at 220° C. for 1 hour. Since autogeneous pressure was used for the reaction pressure, the reaction pressure showed a slight difference between the initial reaction and the end of the reaction depending on the progress of the reaction.

After the reaction was completed, the reaction product was diluted 20-fold with water and analyzed by high-performance liquid chromatography (HPLC, manufactured by Agilent, using a Carbohydrate column). At this time, the yield of isocarbide was 47.1wt%.

Example 6

The process when the dehydration reaction of sorbitol was performed by the direct distillation method was simulated using ASPEN. The feed containing 1 wt% of water after the drying process of the sorbitol aqueous solution was introduced into the first reactor at 110° C. and 8 torr, and reacted for 90 minutes. This reactant was added to the second reactor under conditions of 180° C. and 8 torr and reacted for 30 minutes. In the first and second reactors, water and ISOcarbide are distilled upwards to obtain products.

The bottom stream of the second reactor was recycled back to the reactor, conditioned to have about 10% of ISOcarbide to maintain fluidity. 10wt% was discarded to prevent accumulation of oligomers and polymers in the bottom flow.

Example 7

The sorbitol dehydration reaction process was simulated in the same manner as in Example 6. However, the residual liquid generated after crystallization was performed in the same manner as in Example 1 was recycled to the second reactor.

Example 8

The sorbitol dehydration reaction process was simulated in the same manner as in Example 6. However, the residual liquid generated after crystallization was performed in the same manner as in Example 3 was recycled to the second reactor.

Example 9

The sorbitol dehydration reaction process was simulated in the same manner as in Example 6. However, the residual liquid generated after crystallization was performed in the same manner as in Example 1 was recycled to the second reactor after the hydrothermal reaction in Example 6.

Example 10

The sorbitol dehydration reaction process was simulated in the same manner as in Example 6. However, the residual liquid generated after crystallization was performed in the same manner as in Example 3 was recycled to the second reactor after the hydrothermal reaction in Example 5.

comparative example One

The sorbitol dehydration reaction process was simulated in the same manner as in Example 6. However, the flow at the bottom of the reactor was not recycled, and the remaining ISO carbide in the bottom flow was distilled through evaporation conditions of 180 ° C. and 1 torr to combine with the product at the top.

The yields of the products according to Examples 6 to 10 and Comparative Example 1 were calculated according to the following equation and are shown in Table 1.

wt% yield = weight of produced material / weight of sorbitol added X 100

In all cases, other products other than isocarbide were not mentioned separately as they appeared to be less than 0.1 wt%.

recycle flow Hydrothermal reaction Isocarbide yield (wt%) Example 6 Reactor Bottom doesn't exist 61.5 Example 7 Moisture 2wt% crystallization mother liquor doesn't exist 65.9 Example 8 Moisture 2wt% crystallization mother liquor has exist 69.0 Example 9 Moisture 6wt% crystallization mother liquor doesn't exist 65.5 Example 10 Moisture 6wt% crystallization mother liquor has exist 68.7 Comparative Example 1 doesn't exist doesn't exist 60.1

As shown in Table 1, anhydrous sugar alcohol was recovered by falling film crystallization of crude anhydrous sugar alcohol according to Examples 6 to 10, and anhydrosugar alcohol was added by static crystallization of the residue of fall film crystallization. It was confirmed that the yield of the separation process of anhydrous sugar alcohol was improved when the SC crystallization residue was supplied to the reaction/distillation apparatus and recycled, and the feed with improved anhydrosugar alcohol content was subjected to the crystallization process under the same conditions. Since it is obvious that the purity is improved under the condition, it can be seen that the purity is also improved through such process improvement.

Having described specific parts of the present invention in detail above, it will be clear to those skilled in the art that these specific descriptions are only preferred embodiments, and the scope of the present invention is not limited thereby. will be. Accordingly, the substantial scope of the present invention will be defined by the claims and their equivalents.

100: reactor
110: raw material supply unit
120: unreacted raw materials and by-product outlet
130: product outlet
140: divider
200: condenser
300: separation/recovery means
400: heating means
410: Heating Media inlet
420: fruit outlet
500 means for lowering the pressure

Claims (20)

Melt crystallization method of anhydrous sugar alcohol comprising the following steps:
Recovering anhydrous sugar alcohol by falling film crystallization of crude anhydrous sugar alcohol; and
Further recovering anhydrous sugar alcohol by static crystallization of the residue of the falling film crystallization;
Here, the falling film crystallization includes forming crystals by flowing the crude anhydrous sugar alcohol onto a surface maintained at a temperature lower than the freezing point of pure anhydrous sugar alcohol,
The static crystallization is carried out by contacting an object whose surface temperature is maintained at a temperature lower than the freezing point of pure anhydrous sugar alcohol with the remnant of the falling film crystallization in a container in which the remnant of the falling film crystallization is stored, on the surface of the object. Including forming crystals.
delete According to claim 1,
The falling film crystallization further comprises raising the temperature of the surface where the crystals are formed to a value between the freezing point of the pure anhydrous sugar alcohol and the temperature at which the crystals of the crude anhydrous sugar alcohol are formed,
The static crystallization further comprises the step of raising the temperature of the surface on which the crystals are formed to a value between the freezing point of the pure anhydrous sugar alcohol and the temperature at which the crystals of the residue of the falling film crystallization are formed. crystallization method.
According to claim 1 or 3,
Melt crystallization method of anhydrous sugar alcohol, characterized in that the temperature at which crystals are formed in the static crystallization is lower than the temperature at which crystals are formed in the falling film crystallization.
According to claim 1 or 3,
The temperature at which crystals are formed in the static crystallization is -40 to 20 ° C, and the temperature at which crystals are formed in the falling film crystallization is 0 to 60 ° C. Melt crystallization method of anhydrous sugar alcohol.
According to claim 1 or 3,
Melt crystallization method of anhydrous sugar alcohol, characterized in that for recycling a part of the static crystallization product as a raw material for the falling film crystallization.
According to claim 1 or 3,
Melt crystallization method of anhydrous sugar alcohol, characterized in that for recycling the residue of the static crystallization as a raw material for static crystallization.
According to claim 1 or 3,
Melt crystallization method of anhydrous sugar alcohol, characterized in that the purity of the anhydrous sugar alcohol recovered from the falling film crystallization and static crystallizer is 99% or more.
According to claim 1,
Melt crystallization method of anhydrous sugar alcohol, characterized in that the crude (crude) anhydrous sugar alcohol is obtained through the following steps:
Reacting the sugar alcohol in the presence of an acid catalyst in a reactor and simultaneously evaporating the reaction product; and
Cooling the evaporated product to obtain crude anhydrous sugar alcohol.
According to claim 1,
Melt crystallization method of anhydrous sugar alcohol, characterized in that the crude (crude) anhydrous sugar alcohol is obtained through the following steps:
Reacting the sugar alcohol in the presence of an acid catalyst in a reactor and simultaneously evaporating the reaction product;
cooling the evaporated product to obtain crude anhydrous sugar alcohol; and
Adsorbing the crude anhydrous sugar alcohol.
The method of claim 9 or 10,
Melt crystallization method of anhydrous sugar alcohol, characterized in that the residue of the static crystallization is recycled to the reactor.
The method of claim 9 or 10,
The acid catalyst has a boiling point of 160 ° C. or more at 10 mmHg, a pKa of -3.0 to 3.0, and a melt crystallization method of anhydrous sugar alcohol, characterized in that it reacts homogeneously with sugar alcohol.
According to claim 12,
The acid catalyst is a melt crystallization method of anhydrous sugar alcohol, characterized in that naphthalene sulfonic acid.
The method of claim 9 or 10,
Melt crystallization method of anhydrous sugar alcohol, characterized in that the temperature of the reactor is 150 ~ 220 ℃, the pressure is 1 ~ 50torr.
The method of claim 9 or 10,
The anhydrous sugar alcohol is isocarbide, and the sugar alcohol is a melt crystallization method of anhydrous sugar alcohol, characterized in that sorbitol.
The method of claim 9 or 10,
The reactor melt crystallization method of anhydrous sugar alcohol comprising the following configuration:
(a) a reactor in which a distributor is installed at the top so that the raw material flows down and reacts along the inner wall;
(b) a raw material supply unit installed on one side of the upper part of the reactor;
(c) means for separating/recovering unreacted raw materials and by-products installed inside the reactor at a certain distance from the lower end of the reactor;
(d) a condenser located in the center of the reactor and installed through the separation/recovery means;
(e) means located on one side of the reactor and lowering the pressure inside the reactor; and
(f) A product outlet located at the center of the lower part of the reactor and discharging the product flowing down from the condenser.
According to claim 9,
Melt crystallization method of anhydrous sugar alcohol, characterized in that for cooling the evaporated product to 60 ~ 100 ℃.
According to claim 10,
Melt crystallization method of anhydrous sugar alcohol, characterized in that by cooling the evaporated product to room temperature ~ 60 ℃, to obtain a crude (crude) anhydrous sugar alcohol containing 1 to 30% by weight of water.
According to claim 10,
The adsorption process is a melt crystallization method of anhydrous sugar alcohol, characterized in that carried out by activated carbon, ion exchange resin or a combination thereof.
According to claim 10,
Melt crystallization method of anhydrous sugar alcohol, characterized in that by further performing a flash evaporation process after the adsorption process to remove water.

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