JP2010150249A - Method for producing high-purity bisphenol a by using direct crystallization method of bisphenol a (bpa) - Google Patents

Abstract

A method for producing high purity bisphenol A is provided.
Manipulating the phase equilibrium behavior of a ternary system consisting of phenol, bisphenol A and a solvent (which is a mixture of 95% by weight acetone and 5% by weight water) in a specific process stream to produce crystals from solution. Analysis produces directly a substantially pure bisphenol A and produces a method for producing bisphenol A that further increases the crystal purity of bisphenol A by washing and recrystallization, and a product solution containing bisphenol A and phenol. A production system having a reaction unit, a mixing / separation unit, a crystallization stage, an impurity removal unit, and a recrystallization stage.
[Selection] Figure 1

Description

  The present invention provides a process for producing bisphenol A (BPA). More particularly, the present invention manipulates the phase equilibrium behavior of a particular process stream, recovers substantially pure bisphenol A directly by crystallization from solution, and crystal purity of bisphenol A by washing and recrystallization. A process for producing bisphenol A is provided which further improves

  Since bisphenol A is used as a raw material or intermediate for the production of various polymers (eg, epoxy resins and polycarbonate resins), 2,2-bis (4-hydroxyphenyl) propane, (bisphenol A, hereinafter “4, Bisphenol production methods such as “4-BPA” or simply “BPA”) are important processes. In one application, bisphenol A is reacted with phosgene to create a commercial polycarbonate resin. High quality polycarbonates (eg, they are used as optical media in the electronics and disk drive industries) require very pure bisphenol A as a raw material. Therefore, great efforts have been directed toward developing a method for producing high purity bisphenol A.

  In general, bisphenol A is produced by a known liquid phase condensation reaction between acetone and phenol using an acid catalyst such as hydrochloric acid or more generally an acidic ion exchange resin as a catalyst. The reaction product generally contains the desired bisphenol A, unreacted reactants, water, the most notable by-product, and various impurities including bisphenol A isomers, analogs and congeners. These are 2- (2-hydroxyphenyl) -2- (4-hydroxyphenyl) propane (hereinafter also referred to as “o, p-bisphenol isomer” or “2,4-BPA”), dianine compounds, and chromans. , Trisphenols, polyphenols, and undesirable colored substances. Various methods are used to purify and recover bisphenol A crystals from the reaction product. The purification and recovery of bisphenol A generally requires an investment of half or more of the entire system, and the known techniques are often very expensive and use a great deal of energy.

  After the condensation reaction, the resulting mixture is usually concentrated by distillation to remove unreacted acetone, reaction product water, and some phenol before recovering the bisphenol A product by crystallization. US Pat. No. 5,783,733 describes the prior art of a process for producing bisphenol A by reacting phenol and ketone in the presence of an ion exchange resin catalyst to produce a reaction product stream containing bisphenol A. Prior to crystallization, excess phenol, water and acetone are removed from the product stream. Crystallization is melt crystallization in this case, but is used to purify crude bisphenol A. In particular, multistage split melt crystallization is used, with continuous crystallization steps of partial melting (sweat) and complete melting. This type of phenol removal and melt crystallization technology is very expensive with respect to major equipment and energy consumption.

  In another known technique, first, an adduct crystal of bisphenol A and phenol (hereinafter, sometimes referred to as “adduct crystal”) is obtained by crystallization, and the adduct crystal is known. To produce high purity bisphenol A by extraction, distillation, dephenol, steam stripping or prilling.

  In this prior art, for example, in the US Legal Invention Registration US H1943, a reaction solution is directly supplied to a crystallizer to form a slurry comprising a liquid phase and a solid crystal phase of equimolar adduct crystals of bisphenol A and phenol. To do. The adduct crystals are separated from the liquid (referred to as “mother liquor”) and the phenol is removed from the adduct crystals in a series of phenol removal or dephenol steps. Finally, the product bisphenol A is produced after performing multistage split melt crystallization.

  The step of removing phenol from the adduct crystals is very expensive to construct and complicates the system. Often, this type of step exposes bisphenol A and phenol adduct crystals to high temperatures up to about 250 ° C., where decomposition or undesirable reactions may occur.

  In US Pat. No. 4,294,994, adduct crystals are exposed to a temperature range of about 50 ° C. to about 150 ° C., and typically in the temperature range of about 150 ° C. to about 250 ° C., the boiling point of phenol. A method is described for removing phenol from bisphenol A and phenol adduct crystals by supplying a small amount of liquid component having a lower boiling point under spray drying conditions and recovering bisphenol A from the removed phenol. ing. The purity of the bisphenol A obtained is up to about 99% by weight, however, this process has the serious disadvantage that the adduct crystals of bisphenol A and the phenol typically experience high temperatures at which thermal decomposition occurs. I have it.

  Another technique for removing phenol from adduct crystals is distillation, as described in the examples of US Pat. No. 4,798,654. Specifically, the patent discloses bisphenol A and adduct crystals of phenol distilled in a dephenol tower at a temperature range of about 160 ° C. to about 200 ° C., recovering phenol from the top of the distillation tower and recovering bisphenol A from the bottom of the distillation tower In addition, a method for producing bisphenol A is described which comprises recycling a part of the column bottom liquid to the feed liquid of the dephenol tower. It is said that consolidation of the distillation column is prevented and continuous operation for a long period such as one year is possible. However, the phenol content of the bisphenol A product obtained from the bottom of the dephenol tower is still up to about 2%.

  Various studies have been made in the production of bisphenol A, but further improvements are needed. The prior art described above includes an intermediate step of separation of adduct crystals of bisphenol A and phenol, an expensive step to completely remove phenol from the adduct crystals, and further to obtain bisphenol A in a pure solid state. Requires expensive steps. Furthermore, as the crystal purity requirements for bisphenol A become more stringent, the complexity and cost of the bisphenol A manufacturing process increases. Accordingly, it is desirable to provide an improved process for producing high purity bisphenol A.

  Accordingly, the present invention provides an improved process for producing bisphenol A. As described, the process of the present invention selectively controls the phase equilibrium behavior of the system consisting of phenol, bisphenol A, impurities and solvent so that bisphenol A is crystallized directly from the product solution. Among various advantages, the method of the present invention is a direct crystallization method of substantially pure bisphenol A following the reaction without requiring an intermediate step to recover the adduct crystals of phenol and bisphenol A. I will provide a. This leads to a significant reduction in production steps, thereby reducing construction and energy costs and providing a much simpler process for the production of bisphenol A.

  More particularly, in one embodiment, the present invention relates to a process for producing bisphenol A from a product solution comprising primarily bisphenol A and phenol, i.e., if necessary, removing a portion of the phenol from the product solution. Remove and supply a selected amount of solvent to obtain a product solution having the desired phase equilibrium behavior, and supply a product solution having the selected composition to the crystallization stage operated at the selected temperature Thus, there is provided a method of recovering substantially pure bisphenol A in the form of crystals and washing the crystals of bisphenol A to remove residual liquid adhering to the crystals. If necessary, higher purity bisphenol A crystals can be obtained through recrystallization of solid bisphenol A. In this case, the method of the present invention also includes one or more recrystallization stages, and each step is selected to be a next step, i.e., removing a portion of the phenol from the product solution as needed. Supplying a quantity of solvent to obtain a product solution having a desired phase equilibrium behavior, supplying a product solution having a selected composition to a crystallization stage operating at a selected temperature and in the form of crystals Recovering substantially pure bisphenol A, washing the crystals of bisphenol A to remove residual liquid adhering to the crystals.

In one embodiment, the method of the present invention provides crystals of bisphenol A containing reduced impurities. The method of the present invention includes the following steps:
Phenol and acetone are reacted in the presence of a catalyst to produce a product solution containing at least bisphenol A and phenol, wherein bisphenol A, phenol and solvent exhibit a phase equilibrium relationship between the components of the product solution, which is bisphenol A And the steps shown in the plots represented by the projection diagram of the multi-thermal ternary phase equilibria capable of crystallizing the bisphenol A / phenol adduct, respectively;
In the crystallization stage, the bisphenol A crystal is first crystallized so that the bisphenol A crystal is directly generated without crystallization of the adduct with the selective composition of the supply liquid to the crystallization stage. Step;
Reducing the impurities of the bisphenol A crystals so that the total amount of impurities of the bisphenol A crystals excluding the solvent does not exceed 1.0 wt%;
Recrystallizing the bisphenol A crystal in the recrystallization stage, which crystallizes directly to produce substantially pure bisphenol A crystal without crystallization of the adduct.

In another aspect, the present invention provides a system for producing crystals of bisphenol A with reduced impurities. The system includes:
A reaction unit that produces a product solution comprising at least bisphenol A and phenol; to receive the product solution from the reactor unit and selectively adjust the composition of the product solution by mixing with one or more recycle streams; Configured, mixing / separation unit;
A crystallization stage that receives the prepared product solution from the mixing / separation unit and selectively produces adduct crystals and bisphenol A crystals by crystallization;
The adduct crystal and the bisphenol A crystal are received from the crystallization stage, and the total amount of impurities of the bisphenol A crystal excluding the solvent does not exceed 1.0 wt%. , Impurity removal unit;
A recrystallization stage that receives adduct crystals and bisphenol A crystals from the impurity removal unit and crystallizes to produce substantially pure bisphenol A crystals directly without crystallization of the adducts.

  The system and method of the present invention provides a direct crystallization method of bisphenol A from the product solution after reaction without requiring an intermediate step of recovering the adduct crystals of phenol and bisphenol A. This is an important advantage of the present invention and is also contrary to the teachings of the prior art.

  Since the intermediate adduct crystallization stage is omitted, the present invention does not require the complete removal of phenol from the adduct crystals, for example, usually in expensive steps as in a dephenolizer. Is a further advantage. The process of the present invention requires only partial removal of phenol from the product solution after the reaction. Thus, the energy cost for phenol evaporation is greatly reduced. Furthermore, this partial phenol removal is performed at a very high concentration of phenol and is therefore much more cost effective than conventional processes.

Furthermore, the present invention provides a process for recovering high quality bisphenol A in crystalline form directly from solution. And it does not require expensive solidification equipment such as a prill tower.
Further details regarding various aspects of the invention are provided in the following disclosure.
Other objects and advantages of the present invention will become apparent from the following detailed description and the following drawings.

FIG. 1 is a projection of a multi-thermal phase diagram for a ternary system of bisphenol A, phenol, and solvent, and supplies for placement at a desired location on the ternary diagram according to the method of the present invention. The composition adjustment is shown. FIG. 2 shows a schematic diagram of the process blocks of a system for producing bisphenol A, according to one embodiment of the method of the present invention.

Certain terms are used throughout this specification, including the background and summary section of the invention. For these terms, reference is made to the following.
The term “stage” (eg, “crystallization stage”) refers herein to a portion of a process that is repeated several times until the required result is achieved, and is one step for all iterations. .
The term “step” indicates a basic element of the process that accomplishes a particular task (eg, reaction step, crystallization step, dephenolization step) or indicates part of the overall process.
The term “unit” (eg, equipment unit) is used to refer to equipment such as, for example, a crystallizer, a reactor, and the like.

  The inventors have selectively controlled the phase equilibrium behavior of the product solution (sometimes referred to as the feed solution to the crystallization stage) fed to the crystallization stage for process operation. We have found a process for producing substantially pure bisphenol A that yields selected results. The present invention provides for the manipulation and selective control of the phase equilibrium of bisphenol A, phenol and solvent. It should be well understood by those skilled in the art that the system may contain other components or solutes (eg, impurities, unreacted reactants, isomers, etc.). However, to achieve the objectives of the present invention, we consider only the major components of the solution (phenol, bisphenol A and solvent). Here, the solvent is a pseudo component and represents a pure solvent component or a mixture of two or more solvent components. Thus, the system is characterized as a three component phase equilibrium system.

  In embodiments of the invention, the phase equilibrium behavior of the ternary system is manipulated by adding a selected amount of a suitable solvent. Suitable solvents include, but are not limited to: water, ketones (eg, acetone, methyl ethyl ketone and methyl isobutyl ketone), alcohols (eg, methanol, ethanol, isopropanol, 2-butanol, t-butanol and 1,2-ethylene glycol), amines (eg, dimethylamine, N-methyl-2-pyrrolidone), hydrocarbons (eg, aromatic hydrocarbons), and other solvents (eg, dimethylformamide and dimethylsulfoxide). Since acetone is a reactant and is present in the system, it is useful when employed as a solvent. Also, since water is a reaction byproduct, it is a natural choice as a solvent. In a preferred embodiment of the present invention, the solvent comprises a mixture of acetone and water.

  Since pressure has little effect on the phase equilibrium between a solid and a liquid, as taught by the present invention, the phase equilibrium behavior of a ternary system is a temperature-concentration line at isobaric pressure representing an image in three-dimensional space. It can be represented in the figure. Composition coordinates can be plotted in weight fraction on a triangular grid in the XY plane. The temperature can then be plotted on the added vertical axis (Z-axis). This leads to a three-dimensional triangular prism-shaped multithermal phase diagram. However, it is inconvenient for studies using multidimensional phase diagrams. Fortunately, because of this ternary system, much of the important information about crystallization design can be represented in a two-dimensional projection onto a triangle reference. This is obtained by projecting a phase diagram along the temperature axis (Z axis) onto the prism bottom surface (XY plane), and is referred to as a multi-thermal projection diagram of a phase equilibrium diagram. Further details regarding the phase equilibrium diagram can be found in US Pat. No. 6,960,697, all of which is expressly incorporated herein by reference.

  The multi-thermal projection of the phase equilibrium diagram features multiple phase regions, but in accordance with the teachings of the present invention (ie, the bisphenol A compartment), the key regions or compartments of the diagram for the production of bisphenol A are There is only one. When considering the process design, on the two-point phase diagram of the composition, ie the feed liquid to the crystallization stage and the outlet liquid composition of the crystallization stage (the outlet liquid from the crystallization stage is commonly referred to as “mother liquor”) It is important to control the position. In order to crystallize substantially pure bisphenol A crystals by various means such as cooling the mixture to the appropriate temperature, or by evaporating the solvent, both of the two points are in the phase diagram of bisphenol A. Must be located in a parcel. These two points are on the same line as the position of the third point which is the composition of the crystallized solid. In order to maximize the recovery rate of the desired solid product from the crystallization stage as much as possible, the two points representing the supply liquid to the crystallization stage and the outlet liquid (mother liquid) of the crystallization stage are the distances. The interval should be increased. Thus, to produce the substantially pure bisphenol A described in the present system, the crystallization stage feed and crystallization stage outlet liquid compositions are within the bisphenol A compartment, while the two Must be controlled to have a maximum distance between. The multi-thermal projection phase diagram can be used to clearly delineate the region in the composition zone where the feed to the crystallization stage can produce bisphenol A crystals.

  In particular, referring to FIG. 1, a projection of a ternary multi-thermal phase diagram consisting of phenol, bisphenol A and a solvent, in this case a mixture of 95% by weight acetone and 5% by weight water, is shown. ing. In this specification, it should be noted that the ternary phase equilibrium diagram is represented as a right triangle for the sake of clarity relative to the substitute equilateral triangle diagram. According to the present invention, the position of the boundary of the bisphenol A compartment and thus the size of the compartment is selectively controlled or manipulated by adjusting the concentration ratio of the two solvent components, in this case acetone and water. Is done. In the present invention, the composition of the feed liquid to the crystallization stage and hence the position of the feed point on the phase diagram is adjusted so that the feed liquid composition is in the bisphenol A region. Preferably, the composition of the feed liquid to the crystallization stage is in the shaded area shown in FIG. In this example, the solvent concentration in the feed liquid of the crystallization stage is about 0-40% by weight, and the concentration of bisphenol A in the feed liquid is in the range of about 55-100% by weight. More preferably, the solvent concentration in the feed solution is in the range of about 0-15% by weight and the concentration of bisphenol A in the feed solution is in the range of about 55-100% by weight.

  As explained in the teachings of the present invention, the feed solution composition to the crystallization stage partially removes phenol from the reaction unit outlet liquid in order to create a feed solution to the crystallization stage in the composition within the compartment of bisphenol A. And controlled by adding a selected amount of solvent. Such removal is done, for example, by subjecting the reaction unit outlet liquid to one or more distillation columns, in which some phenol in the reaction unit outlet liquid evaporates.

  As noted above, the composition of the crystallization stage outlet liquid (also known as the mother liquor) must also be in the bisphenol A compartment in the ternary phase diagram. The position of this point depends on the amount of bisphenol A recovered in the crystallization stage, which in turn depends on the crystallization operating conditions in the crystallization stage, for example the operating temperature for the cooled crystallizer. As contemplated by the present invention, in order to form substantially pure bisphenol A crystals, the crystallizer in the bisphenol A crystallization stage is preferably in the temperature range between about 0-160 ° C. In the range of 50-125 ° C and most preferably in the range of 70-100 ° C.

  As is well known by those skilled in the art, the purity of the solid product obtained from the crystallization stage is determined not only by phase equilibrium behavior, but also by kinetic and mass transfer problems. Impurities present in the supply liquid to the crystallization stage may be taken into the crystal by various mechanisms. One of the most important is the inclusion of impurities into the crystal by the incorporation of a mother liquor in which the impurities being crystallized are dissolved. The amount of this type of impurity (referred to as an inclusion impurity) depends on several factors.

  Of these factors, the most important is supersaturation. In practice, the crystallizer in the crystallization stage is not exactly operated in solid-liquid equilibrium or saturation, and the actual crystallizer temperature is different from the saturation temperature at which the mother liquor composition is in equilibrium with the solid. . In this way, a driving force for crystallization (generally called “supersaturation”) is generated. In order to minimize the inclusion impurities in the crystals of bisphenol A, the supersaturation is in the range of about 0.1 to 15 ° C, preferably in the range of 0.5 to 10 ° C, and most preferably 1 Must be in the range of ~ 5 ° C. The degree of supersaturation may be controlled by any conceivable means, for example, by adjusting the slurry recirculation rate through a heat exchanger that cools the crystallizer.

  Impurities can also be incorporated into the product crystals by incomplete removal of the mother liquor from the crystals. After most of the mother liquor is separated in a solid-liquid separation unit such as a filter or centrifuge, a solid cake is formed. Some mother liquor remains in the voids of the solid cake. This liquid is called residual liquid, but it contains dissolved impurities and is brought to the next processing step. If the crystals are later dried, only the solvent component of the residual liquid will evaporate, but relatively non-volatile impurities will precipitate on the crystals, reducing the purity of the final solid product. These impurities are referred to as surface layer impurities.

In order to minimize the amount of surface layer impurities, the crystals obtained from the solid-liquid separator are washed and drained, but they may be implemented in different apparatuses or in the same solid-liquid separator. In the washing operation, a liquid containing a considerably lower concentration of impurities compared to the mother liquor is referred to as a washing liquid, which is brought into the solid cake obtained in the solid-liquid separation unit. The mass flow rate ratio of the cleaning liquid to the remaining liquid is known as the cleaning ratio. The cleaning liquid mixes with the residual liquid to some extent, but also replaces some of the residual liquid, and replaces the initial residual liquid with a large amount of impurities with a liquid with a small amount of impurities to give the overall efficiency. Reduce. The surplus liquid is separated from the solid cake and is referred to as washing drain. In addition to mixing and substitution with the residual liquid, partial dissolution of the crystals can also occur. Thereby, a part of the inclusion impurities in the crystal outer layer part is taken out.
The characteristic capability of the cleaning stage is defined as a function of the cleaning ratio as follows, and can also be expressed in terms of the dimensionless impurity concentration of the cleaning effluent.

上記の等式で、φ^’は洗浄排液中の不純物濃度であり、φ₀は洗浄前の残液中の不純物濃度であり、φ_ｆは洗浄液中の不純物濃度である。洗浄能力は、例えば粘性および拡散係数のような液物性だけではなく、粒径分布および空隙率のような固体ケーキ物性にも依存し、そして、それは次に洗浄溶媒の選択にも影響する。洗浄能力を知っていることはプロセス設計に非常に役立つ。それは表層不純物の量を望ましい範囲に下げるために必要な洗浄液量を決定するからである。洗浄能力は最もよく実験的に決定される。

In the above equation, φ ^′ is the impurity concentration in the cleaning waste liquid, φ ₀ is the impurity concentration in the remaining liquid before cleaning, and φ _f is the impurity concentration in the cleaning liquid. Detergency depends not only on liquid properties such as viscosity and diffusion coefficient, but also on solid cake properties such as particle size distribution and porosity, which in turn affects the choice of washing solvent. Knowing the cleaning ability is very useful for process design. This is because the amount of cleaning liquid necessary to reduce the amount of surface layer impurities to the desired range is determined. The cleaning ability is best determined experimentally.

  The choice of washing solvent depends on several factors such as solubility, miscibility with the crystallization solvent, viscosity, ease of recovery, and availability from other parts of the process. For the bisphenol A production system of the present invention, suitable choices include pure water, n-heptane, and acetone saturated with bisphenol A containing lower concentrations of impurities compared to the mother liquor from the crystallization stage, and Although it is a liquid mixture of water, it is not limited to these. Suitable washing ratios are between 0-20, more preferably between 0-10 and most preferably between 0.5-4. The washing ratio is such that the impurity concentration of the solid cake after washing is considerably reduced, ie the phenol content does not exceed 2.0% by weight and the 2,4-BPA content does not exceed 1.0% by weight. And all impurities except acetone and water are chosen not to exceed 3.0% by weight. More preferably, the phenol content does not exceed 1.0% by weight, the 2,4-BPA content does not exceed 0.5% by weight, and the total impurity content excluding acetone and water is 2.0% by weight. % Is not exceeded. Most preferably, the phenol content does not exceed 0.5% by weight, the 2,4-BPA content does not exceed 0.3% by weight, and the total impurity content excluding acetone and water is 1.0% by weight. Not exceed.

  The liquid removal operation can be performed before or after washing, or both before and after washing, and the purpose is to reduce the amount of residual liquid in the solid cake. Thus, the amount of surface layer impurities is minimized. Since the final purity of the bisphenol A product is highly influenced by the amount of surface impurities, it is important that an appropriate solid-liquid separation unit is selected to provide sufficient drainage. Suitable choices include, but are not limited to, vacuum filters, pressure filters, centrifugal filters and belt filters. The residual liquid content of the solid cake after devolatilization should be less than 30 wt%, preferably less than 20 wt%, and most preferably less than 10 wt%.

  In another embodiment of the process, bisphenol A is recrystallized from bisphenol A and a mixture comprising impurities, ie, phenol, 2,4-BPA, dian compounds, chromans, trisphenols, polyphenols and undesirable colored substances. Is recrystallized. The purity of the bisphenol A crystals present in this feed mixture is quite high, typically greater than 98.0 wt%, preferably greater than 99.0 wt%, and most preferably greater than 99.5 wt%. There must be. In particular, the phenol content should not exceed 0.1% by weight, the 2,4-BPA content must not exceed 0.3% by weight, and the total impurity content excluding acetone and water is , 1.0% by weight should not be exceeded. However, recrystallization further reduces the impurity concentration to the desired level, ie, less than 20 parts per million (20 ppm) phenol, less than 200 ppm 2,4-BPA and less than 1000 ppm acetone and water impurities. is necessary.

  As with the feed solution for the previous crystallization stage, to achieve the objectives of the present invention, we consider only the main components of phenol, bisphenol A and solvent, so the feed mixture to the recrystallization stage is It can be described as a ternary phase equilibrium system. Here, a solvent is a pseudo-component that represents a pure solvent component or a mixture of two or more solvent components. In order to achieve crystallization of high purity bisphenol A, the ternary phase equilibrium behavior is manipulated by adding a selected amount of a suitable solvent. Any solvent that can be used in the crystallization stage is suitable for the recrystallization stage as well. In a preferred embodiment of the present invention, the solvent comprises a mixture of acetone and water.

  Since the supply liquid to the restage is almost pure bisphenol A, the position of the supply liquid composition to the recrystallization apparatus in the recrystallization stage after the addition of the solvent is in the bisphenol A section. The composition and amount of solvent added to the feed mixture can be adjusted according to the desired recovery of the crystallizer bisphenol A at the desired operating conditions of the crystallizer, such as the operating temperature for the cooled crystallizer. . The recovery of bisphenol A crystals is usually chosen so that the solids content of the slurry in the crystallizer is between 25 and 35% by weight to ensure sufficient uniform mixing within the crystallizer. It is. In order to avoid the need for costly refrigeration, the crystallizer in the recrystallization stage is preferably in the temperature range between about 25-80 ° C, more preferably in the range of 35-60 ° C, Most preferably, it must be operated in the range of 40-50 ° C. Based on these constraints, the solvent content of the feed to the recrystallization stage is preferably between about 10-50 wt%, more preferably between 15-40 wt%, and most preferably 20 Must be between ˜30% by weight.

  In order to reduce the inclusion impurities of the bisphenol A crystal as much as possible, the supersaturation degree of the recrystallization apparatus in the recrystallization stage is in the range of approximately 0.1 to 15 ° C, more preferably 0.5 to 10 ° C. And most preferably must be controlled to be in the range of 1-5 ° C. In order to minimize surface layer impurities, the bisphenol A crystals from the recrystallization stage are washed and drained (may be implemented in different equipment or in the same equipment such as a solid-liquid separator). . The selection of the washing solvent also depends on such things as solubility, miscibility with the recrystallization solvent, viscosity, ease of recovery, and availability from other parts of the process. Suitable choices for the bisphenol A system of the present invention include, but are not limited to, pure water and n-heptane. Suitable washing ratios are between 0-20, more preferably between 0-10 and most preferably between 0.5-4. To ensure that the target impurity concentration of the final bisphenol A product can be met, the cleaning ratio is selected based on the cleaning capability (which can be determined experimentally). Appropriate solid-liquid separators are then selected to provide sufficient drainage. The amount of residual liquid in the solid cake after devolatilization should be less than 30 wt%, more preferably less than 20 wt% and most preferably less than 10 wt%.

  The ability of the recrystallization stage to produce bisphenol A crystals of the desired purity depends on the impurity content of the feed solution. If the bisphenol A crystals from the previous crystallization stage do not meet the purity requirements of the recrystallization stage feed, an intermediate step is required to provide additional impurity removal. This intermediate step may be another recrystallization stage, or if only phenol removal is required, the vapor is passed through a dissolved feed to evaporate and remove most of the phenol in the feed. It may be a stripping process. The mass ratio of steam to feed of such a stripping process is generally between 0.01 and 0.2, preferably between 0.02 and 0.1, and most preferably 0.1. It is between 03 and 0.05. It should be understood that other relatively less volatile impurities such as 2,4-BPA and trisphenol cannot be removed using the stripping process described above. If the content of these relatively low volatile impurities is higher than the feed requirements for the recrystallization stage, an additional recrystallization device must be provided as an impurity removal unit. Each recrystallizer includes a crystallizer feed mixture solvent, bisphenol A crystallisation, solid-liquid separation, washing, and devolatilization, as described in one embodiment of the present invention. If desired, multiple recrystallization devices can be used to achieve the desired level of impurities.

  The present invention provides a particularly advantageous process by direct crystallization to produce high purity bisphenol A products that are suitable as raw materials for polycarbonate production. One embodiment of the present invention is illustrated in FIG. In general, the system consists of a reaction unit 25, a partial phenol removal unit 30 for partial removal of phenol, a bisphenol A crystallization stage 35, an optional impurity removal unit 40 for impurity removal, a bisphenol A recrystallization. It comprises an analysis stage 45 and a solvent recovery unit 50. Upstream of the bisphenol A crystallization stage 35, the mixing / separation unit 33 is used to adjust the solvent composition of the product solution before the crystallization stage. Downstream of the crystallization stage 35, a solid-liquid (S / L) separator 37 is used to separate the bisphenol A crystals from the remaining solution. Upstream of the bisphenol A recrystallization stage 45, the recycle stream mixing unit 43 is used to adjust the solvent composition of the feed solution before the recrystallization stage. Downstream of the recrystallization stage 45, a solid-liquid (S / L) separator 47 is used to separate the bisphenol A crystals from the remaining solution. Although not shown, the crystals of bisphenol A produced from the crystallization stage 35 and the recrystallization stage 45 can be further processed by washing and devolatilization. The bisphenol A crystals from the recrystallization stage 45 can then be dried or sent to a further washing step to produce the final product.

  To produce bisphenol A, phenol (preferably purified and preferably in stoichiometric excess) and acetone are sent to reaction unit 25 where the condensation reaction is carried out. The product solution contains bisphenol A, unreacted reactants (eg excess phenol and / or acetone), reaction byproducts (eg water) and impurities (eg isomers, analogues and homologs). The condensation reaction can be carried out at a temperature in the range of about 45-120 ° C, and preferably at a temperature in the range of about 50-100 ° C, most preferably at a temperature of about 75 ° C. The reaction pressure is in the range of 1-8 bar, more preferably 1-6 bar, most preferably about 4.4 bar.

  The product solution after the reaction is stream number 3 in FIG. 2 (the stream is represented in a box). In this embodiment, stream 3 is first mixed with recycle stream 9 from solvent recovery unit 50. The solvent recovery unit can use a separation method such as distillation to recover part or all of the solvent components from the product solution. The resulting product mixture (Stream 9) is richer in bisphenol A and has fewer solvent components than before. The composition of the mixed and adjusted product solution is then adjusted to be placed in the bisphenol A crystallization zone. As a result, sufficiently pure bisphenol A can be recovered by crystallization.

  The composition of the product solution can be adjusted in several ways. Most commonly, removal of a portion of the phenol and / or solvent from the product solution to increase the concentration of bisphenol A in the product solution. If the composition of the reaction unit outlet liquid is already in the bisphenol A crystallization zone, such a step to reduce the phenol concentration of the product solution is not necessary. Phenol removal can be accomplished by distillation, typically at a temperature of about 120 ° C. to 140 ° C. at the bottom of the column.

  According to one embodiment of the system of the present invention shown in FIG. 2, the feed liquid to the bisphenol A crystallization stage 35 is indicated by stream 4. Solvent streams recovered from the solvent recovery unit can each be added to the recycle stream mixing unit 33 to adjust the composition of the mixture prior to the bisphenol A crystallization stage. The solvent component may also be used to wash the crystals of bisphenol A in a washing step (not shown) downstream of the crystallization stage.

  After achieving the desired composition in the bisphenol A compartment, the solution is fed to the bisphenol A crystallization stage 35, where substantially pure bisphenol A is recovered in crystalline form. The bisphenol A crystallization stage 35 may comprise one or more crystallizers. The crystallizers are known in the prior art and generally form crystals indirectly indirectly by external cooling, such as heat exchange or circulating refrigerant. Crystallization may also be performed by reduced pressure or by a combination of external heating and reduced pressure. In one embodiment, the solution is preferably cooled in the bisphenol A crystallization stage 35 at a temperature in the range of about 0 ° C. to 160 ° C., preferably at a temperature in the range of 50 ° C. to 125 ° C. Most preferably, the solution is cooled to a temperature in the range of 70 ° C to 100 ° C. The operating pressure range depends on the type of solvent used and the temperature of the crystallizer included in the crystallization stage. And the pressure must be chosen so that the vapor fraction of the crystallization is low or minimized. The crystallization of bisphenol A is typically pressure operated in the range of about 0.1 to 6 bar. In one embodiment, when a mixture of acetone and water is used as the solvent, the pressure of the crystallizer included in the bisphenol A crystallization stage 35 is in the range of about 0.5-5 bar, most preferably crystallization. About 3 bar to maximize the liquid fraction of the device.

  As crystallization proceeds, solid bisphenol A is produced. The residence time of the bisphenol A crystallization stage 35 is ideally in the range of about 0.5-5 hours, preferably in the range of about 1-3 hours. The optimum residence time must be understood to be a function of the crystal growth rate in a given solvent, and thus the optimum residence time varies depending on the type of solvent used. In order to minimize the inclusion impurities, the supersaturation should be in the range of approximately 0.1-15 ° C, more preferably in the range of 0.5-10 ° C, and most preferably in the range of 1-5 ° C. . The degree of supersaturation can be controlled by any possible means, for example by adjusting the amount of slurry circulating to the heat exchanger that provides cooling to the crystallizer included in the crystallization stage.

  The solid bisphenol A is separated from the mother liquor in a solid-liquid separation device 37 used downstream of the bisphenol A crystallization stage. Any suitable type of solid-liquid separation device known may be used, such as a centrifuge or a filtration device. The mother liquor corresponding to the stream 6 in FIG. 2 is sent to the solvent recovery unit 50, where the solvent is recovered and reused. The crystals of bisphenol A are preferably washed with a solvent in the solid-liquid separator 37 in order to remove any residual mother liquor.

  The solid bisphenol A from the solid-liquid separator 37 is referred to as a crude bisphenol A crystal and is sent to an arbitrary impurity removal unit 40. The aim is to reduce the impurity content, in which the phenol content of the outlet liquid of the unit should not exceed 0.1% by weight, the 2,4-BPA content should be 0.3% by weight. Do not exceed, and the total impurity content, excluding acetone and water, must not exceed 1.0% by weight. The impurity removal unit 40 may consist of a steam stripping unit and / or an additional recrystallization stage.

  In order to produce a feed to the bisphenol A recrystallization stage 45, identified as stream 7 in FIG. 2, the solvent stream recovered from the solvent recovery unit 50 is prior to the bisphenol A recrystallization stage. Each may be added to the recycle stream mixing unit 43 to adjust the composition of the mixture. The solvent component may also be used to wash bisphenol A crystals in a washing stage (not shown) downstream of the recrystallization stage.

  Via one or more crystallization units, the solution adjusted to the desired composition is fed to the bisphenol A recrystallization stage 45, where substantially pure bisphenol A is recovered in crystalline form. Again, the crystals can be formed by, for example, heat exchange or indirect or external cooling with a circulating cooling medium, pressure reduction, or a combination of external heating and pressure reduction. As an example, the solution is cooled in the bisphenol A recrystallization stage 45 to a temperature in the range of 25-80 ° C, preferably in the range of 35-60 ° C, and most preferably in the range of 40-50 ° C. Crystallizers during the recrystallization stage of bisphenol A are typically operated at pressures in the range of about 0.1 to 6 bar. In one embodiment, when a mixture of acetone and water is used as the solvent, the crystallizer pressure in the recrystallization stage 45 of bisphenol A is in the range of about 0.5-5 bar, most preferably about 2 bar. The residence time of the crystallizer in the bisphenol A recrystallization stage 45 is ideally in the range of about 0.5-5 hours, more preferably in the range of about 1-3 hours. In order to minimize inclusion impurities, the supersaturation should be in the range between approximately 0.1 and 15 ° C, more preferably in the range of 0.5-10 ° C, most preferably in the range of 1-5 ° C. .

Solid bisphenol A is separated from the mother liquor in a solid-liquid separator 47 used downstream of the bisphenol A recrystallization stage. Any suitable type of known solid-liquid separation device can be used. The mother liquor corresponding to stream 8 in FIG. 2 is sent to the solvent recovery unit 50 for recovery and reuse of the solvent. Preferably, the bisphenol A crystals are washed with a solvent in a solid-liquid separator 47 to remove any residual mother liquor.
It is noted that it is advantageous to combine the solvent recovery unit 50 with the phenol purification unit 20 in practice that they have the same separation function, ie the ability to produce substantially pure acetone and water in separate streams. There is a need.

  To further illustrate the method of the present invention, experimental results are provided below. These experiments are provided for illustrative purposes only and are not intended to limit the scope of the invention in any way.

Batch crystallization of crude bisphenol A crystals 2.75 g multi-component solid (16.52 wt% phenol, 38.93 wt% 4,4′-BPA, 16.05 wt% 2,4-BPA and 28 1.5% other impurities) in a 125 ml glass flask, 61.77 g pure 4,4′-BPA, 17.24 g pure phenol, 1.05 g pure 2,4- Mixed with BPA, 9.1 g acetone and 0.49 g water. The mixture is heated to about 110 ° C. to completely dissolve all solids and then cooled to about 88 ° C. where crystals precipitate. Heating is repeated twice until all solids are melted. The dissolution temperature is recorded as 108 ° C. The mixture is then finally cooled to 88.1 ° C. at a cooling rate of 0.4 ° C./min, where a slurry is formed. The mixture is continuously stirred at 1250 rpm during all operations. After reaching the final temperature, the mixture is left to stand overnight before separating the crystals from the liquid (mother liquor). The crystals are collected on filter paper and then dried and then washed using 750 mL of n-heptane at room temperature. The weight of crystals obtained from this experiment is 27.79 g. Thus, the recovery of bisphenol A in this experiment is calculated to be 44.2% based on the total amount of bisphenol A in the feed (62.48 g).
The composition of the resulting crude bisphenol A crystals is determined using high performance liquid chromatography (HPLC). The analysis results are summarized below with the initial feed composition.

  Washing with n-heptane aims to remove surface layer impurities from the crystals. As a result, the above analysis results reflect the composition of the crystal center including inclusion impurities but not surface layer impurities.

The continuous crystallization experiment of crude bisphenol A crystals is carried out using a continuous crystallizer consisting of a 1.5 liter glass-lined stainless steel crystallizer equipped with a motor stirrer, jacket and condenser. The crystallizer is fed from a 20 liter stainless steel tank equipped with a stirrer and a heating coil. A 20 liter stainless steel receiver tank is also installed to receive the overflow liquid from the crystallizer. After steady state is achieved, the slurry from the crystallizer is drained onto a stainless steel pressure filter to separate the crystals from the mother liquor. A feed flow rate of 1.5-3 liters / hour and a residence time of 1-2 hours are achieved in the crystallizer.

  A feed tank in which a feed consisting of 2606.2 g phenol, 6683.3 g 4,4′-BPA, 2410.5 g multi-component solid, 1235 g acetone, and 65.0 g water was heated to 120 ° C. It is prepared with. This feed mixture is transferred to the crystallizer (which is first heated to 95 ° C.) with a circulation rate of 27.6 ml / min. Under this condition, the residence time of the crystallizer is approximately 1 hour. Samples are taken from the supply line to the crystallizer to determine the actual feed composition. The crystallizer is then cooled to 70 ° C. and kept at this temperature for 3 hours. The slurry is then transferred to a filter vessel and a pressure of approximately 0.2 MPa (gauge) is applied. Crystals are removed at 55 ° C. The amount of crystals obtained is 592.7 g and the amount of mother liquor collected is 980.0 g. No scaling is observed in the crystallizer.

  100.7 g of crystals from the filter are washed 3 times at 90 ° C., initially with 500 ml of n-heptane, and the second and third time with 400 ml of n-heptane, respectively. The outer layer containing surface impurities is removed by this treatment. And after washing, 88.8 g of crystals are left. The composition of this product analyzed by HPLC is given below along with the measured feed composition.

  From the above results it is calculated that the actual amount of solid product (expressed by the proportion of crystal mass remaining after washing with n-heptane) is 447 g. And it is consistent with the 45% recovery of 4,4'-BPA. The supersaturation level inside the crystallizer is estimated to be approximately 9 ° C.

Washing crude bisphenol A crystals with saturated bisphenol A solution To examine the performance of the washing process after the crystallization step, the wet cake has a composition that matches the crude bisphenol A crystals and the mother liquor from the crystallization stage. And is prepared by mixing the saturated mother liquor. Approximately 5.4 g of crude bisphenol A crystals (from the continuous crystallization experiment described in Example 2) are placed in a jacketed filter funnel and maintained at a constant temperature of approximately 79 ° C. The saturated mother liquor is prepared by mixing pure 4,4′-BPA, pure phenol, solid mixture, acetone, and water so that the following final composition is obtained: 29.3 Wt% phenol, 49.8 wt% 4,4'-BPA, 5.66 wt% 2,4'-BPA, 2.73 wt% other impurities, 11.92 wt% acetone, and 0.63% by weight of water. The mother liquor is transferred to the filter funnel so that it contacts the crude bisphenol A crystals, and suction (degree of vacuum: 0.11 bar) is applied to achieve filtration. Suction is stopped after approximately 20 seconds and the amount of filtrate collected is measured. Due to the mass balance, the resulting wet cake drainage rate (ratio of liquid to solid mass) is calculated to be 0.527. The wash liquor is also prepared by mixing in a ratio of 2.72 g of pure 4,4′-BPA to 1 g of a solvent mixture (95 wt% acetone and 5 wt% water).

  This washing solution is kept at 79 ° C., where it is saturated with 4,4′-BPA. At the same time, filtration is carried out at a vacuum of 0.11 bar, and the washing liquid is then transferred to the filter funnel at a flow rate of 0.280 ml / sec. Displacement washing occurs and the amount and concentration of filtrate collected is approximately measured every 10 seconds. From this data, the relationship between the cleaning ratio and the dimensionless concentration (F) of each impurity is obtained. Furthermore, the amount of each impurity remaining in the washed crystals (as a percentage of the initial amount prior to washing) is also calculated. The results are summarized below.

  These results show that approximately 60% of surface impurities present in the crude bisphenol A crystals immediately after the crystallization stage are removed at a wash ratio of about 2, which is a common value in typical solid-liquid separation units. Indicates.

Recrystallization to produce high purity bisphenol A crystals The test production is carried out in a 600 liter crystallizer equipped with a baffle and a flat anchor impeller and operated in batch mode. As feedstock, 450.8 kg of pure 4,4′-BPA, 14.86 kg of concentrated impurities (various proportions of phenol, 4,4′-BPA, 2,4-BPA, and other impurities Mixture) 137.32 kg of acetone and 7.6 kg of water are added to the crystallizer. The mixture is then heated at about 100 ° C. until completely dissolved and stirred. Samples are taken to determine the actual composition of this feed mixture. After holding for 30 minutes, the solution is cooled at a rate of 0.3 ° C./min. When the temperature reaches approximately 80 ° C., 1.7 kg of pure 4,4′-BPA seed crystals are charged and cooling is continued until the temperature of the mixture reaches 50 ° C. After standing overnight, the crystals are separated using a centrifuge.
These crystals were washed with n-heptane and then vacuum dried to recover 93.7 kg of cake.
The crystal composition of the product determined by HPLC is summarized below with the feed composition.

Washing the recrystallized bisphenol A crystals with water In order to investigate the performance of the washing process after the recrystallization step, the wet cake is composed of pure 4,4′-BPA crystals with the same composition as the mother liquor from the recrystallization step. Prepared by mixing saturated mother liquor. A mixture containing 27.52 g pure 4,4′-BPA, 0.20 g solid mixture, 11.39 g acetone, and 0.620 g water was prepared, and the mother liquor from the recrystallization step had a composition Heat to approximately 51 ° C. to produce a similar saturated mother liquor. This mother liquor is mixed with 9.89 g of pure 4,4′-BPA crystals to produce a slurry. It is then stirred for approximately 1 hour. The crystals are then separated from the mother liquor by filtration and washed in approximately 60 g of water heated to about 51 ° C. After washing, the crystals are filtered and dried. The mother liquor from the previous filtration is then recharged to form a slurry, which is transferred to the filter funnel. Aspiration was performed under reduced pressure of 0.11 bar and filtration was performed. Suction stops after approximately 20 seconds. The amount of filtrate collected is then measured. Due to the mass balance, the resulting wet cake drainage (ratio of liquid to solid mass) is calculated to be 0.8.

  The washing liquid (purified water heated to 51 ° C.) is then transferred to the filter funnel at a flow rate of 0.420 ml / sec while simultaneously reducing the pressure to 0.11 bar for effective filtration. With displacement wash, the amount and concentration of filtrate collected is measured about every 10-20 seconds. From this data, the relationship between the cleaning ratio and the dimensionless concentration (F) of each impurity is obtained. Furthermore, the amount of each impurity remaining in the washed crystals (as a percentage of the initial amount prior to washing) is also calculated. The results are summarized below.

The results show that washing with a ratio of approximately 2 led to the removal of approximately 90% of the surface layer impurities present in the bisphenol A crystals obtained in the recrystallization step. Increasing the cleaning rate does not lead to further removal of surface impurities.
In summary, using the method of the present invention, high purity bisphenol A crystals can be obtained by crystallization directly from the product solution after the reaction without the need for an intermediate step to recover the phenol and bisphenol A adduct. It has been shown to be obtained.
The foregoing descriptions of specific embodiments and examples of the present invention have been presented for purposes of illustration and description, and the present invention is illustrated by, but not limited to, the specific embodiments described above. It is not interpreted. These examples are not exhaustive and are not intended to limit the invention to the precise forms disclosed, and, obviously, many modifications, implementations in light of the above teachings of the invention. Examples and variations are possible. The scope of the present invention is disclosed herein and includes the generic region such as the appended claims and their equivalents.

Claims (20)

A method for producing bisphenol A crystals with reduced impurities, comprising the following steps:
In the step of reacting phenol and acetone in the presence of a catalyst to produce a product solution containing at least bisphenol A and phenol, bisphenol A, phenol and solvent exhibit a phase equilibrium relationship between the components of the product solution, A step represented by a compartment represented by a projection diagram of a multi-thermal ternary phase equilibrium capable of crystallizing bisphenol A and bisphenol A / phenol adduct, respectively;
In the crystallization stage, the bisphenol A crystal is first formed so that the bisphenol A crystal is directly generated without crystallization of the bisphenol A / phenol adduct with the selective composition of the supply liquid to the crystallization stage. Crystallizing into
Reducing the impurities of the bisphenol A crystal so that the total amount of impurities in the bisphenol A crystal excluding the solvent does not exceed 1.0 wt%;
Recrystallizing the bisphenol A crystal in the recrystallization stage for crystallization directly producing substantially pure bisphenol A crystal without crystallization of the bisphenol A / phenol adduct.   The method according to claim 1, wherein the recrystallization step is performed at a supersaturation in the range of 0.1 to 15 ° C.   The method according to claim 1, wherein the recrystallization step is performed at a supersaturation in the range of 0.5 to 10 ° C.   The method according to claim 1, wherein the recrystallization step is performed at a supersaturation in the range of 1 to 5 ° C.   The method according to claim 1, wherein the recrystallization step is performed in a temperature range of 30 to 60 ° C. with a solvent content of 15 to 40 wt%.   The process according to claim 1, wherein the recrystallization step is carried out at a temperature range of 40-50 ° C and a solvent content of 20-30 wt%.   The method of claim 1, further comprising the step of washing substantially pure bisphenol A crystals to reduce surface impurities of the bisphenol A crystals. A process for producing bisphenol A crystals with reduced impurities from a product solution characterized by:
The product solution contains components shown in a phase equilibrium relationship that defines the phase compartment represented by the projection diagram of the multi-thermal ternary phase equilibrium, and the solid bisphenol A and bisphenol A / phenol adducts crystallize respectively. Can be
The product solution is first treated to produce crude bisphenol A crystals such that the total impurity concentration excluding solvent does not exceed 1.0 wt%;
The crude bisphenol A crystal is then recrystallized to select the composition of the product solution fed to the recrystallization stage and to be a substantially pure solid such that the total impurity concentration does not exceed 0.1 wt% Bisphenol A is produced by crystallization. The system which manufactures the bisphenol A crystal | crystallization which reduced the impurity characterized by having the following unit or stage.
A reaction unit that produces a product solution comprising at least bisphenol A and phenol; receiving the product solution from the reaction unit and selectively adjusting the composition of the product solution by mixing it with one or more recycle streams A mixing / separation unit configured as follows;
A crystallization stage that receives the conditioned product solution from the mixing / separation unit and selectively produces bisphenol A / phenol adduct crystals and bisphenol A crystals by crystallization;
The bisphenol A / phenol adduct crystal and the bisphenol A crystal are received from the crystallization stage, and the total impurity amount of the bisphenol A crystal excluding the solvent does not exceed 1.0 wt%. An impurity removal unit configured to reduce the amount of impurities in the substrate;
Recrystallization receiving bisphenol A / phenol adduct crystals and bisphenol A crystals from the impurity removal unit and crystallizing to produce substantially pure bisphenol A crystals directly without crystallization of bisphenol A / phenol adducts Analysis stage.   From selectively adjusting the composition of bisphenol A / phenol adduct crystals, bisphenol A crystals and solvent by mixing one or more recycle streams between the impurity removal unit and the recrystallization stage. The system of claim 9 further comprising a recycle stream mixing unit.   A solvent recovery unit connected to at least one mixer / separator for recovering the solvent used in the system and selectively adjusting the composition of the feed to each unit and / or stage; The system of claim 10 further comprising:   The system of claim 11, comprising the recrystallization stage being adjusted such that the degree of supersaturation during recrystallization is in the range of 0.1-15 ° C.   The system of claim 9, comprising the recrystallization stage being adjusted so that the degree of supersaturation during recrystallization is in the range of 0.5 to 10 ° C.   The system of claim 9, comprising the recrystallization stage being adjusted so that the degree of supersaturation during recrystallization is in the range of 1 to 5 ° C.   The system of claim 9, comprising the recrystallization stage tuned to operate at a temperature range of 30-60 ° C. and a solvent composition of 15-40 wt%.   The system of claim 9, comprising the recrystallization stage being tuned to operate at a temperature range of 30-60 ° C. and a solvent composition of 20-30 wt%.   The system of claim 9 further comprising a cleaning stage in which substantially pure bisphenol A crystals are cleaned and / or lysed to reduce surface impurities of the bisphenol A crystals. A process for producing bisphenol A crystals with reduced impurities, characterized by having the following units or stages.
A reaction unit that produces a product solution comprising at least bisphenol A and phenol; a partial phenol removal unit that receives the product solution from the reaction unit and selectively adjusts the phenol composition of the product solution to partially remove phenol ;
Receiving the partially phenol-depleted product solution from the partially phenol-removing unit and mixing it with one or more circulating streams to selectively adjust the composition of the partially phenol-depleted product solution. Configured, mixing / separation unit;
A bisphenol A crystallization stage configured to receive the conditioned product solution from the mixing / separation unit and directly produce bisphenol A crystals without crystallization of the bisphenol A / phenol adduct;
The bisphenol A crystal is received from the bisphenol A crystallization stage, and the amount of impurities in the bisphenol A crystal is reduced so that the total impurity amount of the bisphenol A crystal excluding the solvent does not exceed 1.0 wt%. Bisphenol A impurity removal unit;
Receiving bisphenol A crystals from the bisphenol A impurity removal unit and mixing this with one or more recycle streams to selectively adjust the composition of the bisphenol A crystals and the solvent and recycling Flow mixing unit;
A bisphenol A recrystallization stage configured to receive conditioned bisphenol A crystals from the mixing unit and directly produce substantially pure bisphenol A crystals without crystallization of the bisphenol A / phenol adduct.   The mixing / separation unit is configured to adjust the partially phenol-depleted product solution so that the concentration of the solvent in the feed to the bisphenol A crystallization stage is in the range of 0-15 wt%. The process of claim 18.   19. The process of claim 18, comprising a recrystallization stage of the bisphenol A that is adjusted so that the degree of supersaturation during recrystallization is in the range of 0.1 to 15 [deg.] C.

Images