A method for refining crude bpa

Abstract

The present application relates to a refining method of crude BPA, comprising the following steps: 1) crude BPA from upstream waste PC recycling device enters a dissolving tank, and is dissolved by a solvent to obtain a crude BPA solution; 2) the crude BPA solution after step 1) treatment enters a resin treatment bed, and sodium ions are adsorbed and removed to obtain a low-salt BPA solution; 3) the low-salt BPA solution obtained in step 2) enters a water washing tower, and sodium ions are further removed to obtain a refined BPA solution; 4) the refined BPA solution after step 3) treatment is mixed with phenol and then enters a rectifying tower, and the solvent is removed and recovered to obtain a phenol / BPA solution; 5) the phenol / BPA solution obtained in step 4) enters a crystallization unit of a BPA device for further crystallization and purification, and phenol is removed to obtain a BPA product, wherein the dry basis purity of the BPA is above 99.96%, the PTBP content is below 20 ppm, the phenol content is below 15 ppm, the sodium ion content is below 1 ppm, the alcohol content is below 0.1 ppm, the carbonate content is 0.1 ppm, and the melt color number is below 20.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of BPA preparation and relates to a refining method of crude BPA. BACKGROUND

[0002] Bisphenol A (abbreviation: BPA) is an important chemical raw material, which is mainly used for manufacturing polycarbonate and epoxy resin. Polycarbonate has high requirements for raw materials, and needs a purity of more than 99.85% and a melting color number of less than 5. BPA is synthesized by using phenol and acetone as raw materials for alkylation reaction, and high-purity products are obtained by using a crystallization process for purification to meet the demand of polycarbonate for raw materials.

[0003] Polycarbonate (abbreviation: PC) is an important engineering plastic, and the annual consumption is increasing year by year. It is predicted that the annual consumption will reach 3.5 million tons in 2025.

[0004] CN 116368179A discloses a polycarbonate regeneration and refining route, in which alcoholysis BPA is respectively washed by dichloromethane to remove the residue of diethyl carbonate, dissolved in ethanol, adsorbed by activated carbon, recrystallized by adding water, and dried to obtain BPA products. The purity of the BPA products obtained by the process route is only 99.4%, which cannot be directly used for polycarbonate production, and it is difficult to realize the closed-loop cycle of polycarbonate.

[0005] CN 116368098A discloses a polycarbonate regeneration and refining route, in which alcoholysis BPA is respectively dissolved in toluene, washed by desalted water for 5 times, precipitated by cooling, filtered and dried to obtain BPA products. The purity of the BPA obtained by the process is only 99.8%, and the melting color number is 165, which cannot be directly used for polycarbonate production.

[0006] Therefore, it is necessary to develop a refining route for the crude BPA obtained by degradation of PC products. SUMMARY

[0007] In the research on the crude BPA produced by degradation of polycarbonate, the inventors found that the crude BPA mainly contains phenol, PTBP, methanol, DMC and BPA sodium, in which the phenol, PTBP, methanol and DMC will cause abnormal molecular weight and affect the product quality in the polycarbonate production process; the BPA sodium will produce high color number substances in the storage and transportation process, which will also affect the product quality. Therefore, how to completely remove the phenol, PTBP, methanol, DMC and BPA sodium in the crude BPA is the key to realize the direct application of the regenerated BPA in the polycarbonate production cycle. On the basis of the research, the application is completed.

[0008] The application aims at the problem that the crude BPA obtained by alcoholysis of waste polycarbonate cannot meet the national standard due to low purity and high impurity content, and provides a method for pretreatment and product recycling of crude BPA, which can realize chemical recycling of PC products.

[0009] To achieve the above application purposes, the application adopts the following technical solutions:

[0010] A refining method of crude BPA comprises the following steps:

[0011] 1) The crude BPA from the upstream waste PC recycling device enters a dissolving tank, and is dissolved by a solvent to obtain a crude BPA solution;

[0012] 2) The crude BPA solution after step 1) treatment enters a resin treatment bed to adsorb and remove sodium ions, and obtain a low-salt BPA solution;

[0013] 3) The low-salt BPA solution obtained in step 2) enters a water washing tower to further remove sodium ions, and obtain a refined BPA solution;

[0014] 4) The refined BPA solution after step 3) treatment is mixed with phenol and then enters a rectifying tower to remove and recycle the solvent, and obtain a phenol / BPA solution;

[0015] 5) The phenol / BPA solution obtained in step 4) enters a crystallization unit of a BPA device for further crystallization and purification, removes phenol, and obtains a BPA product.

[0016] The crude BPA in step 1) contains phenol 0.001%-0.05%, BPA 90%-96%, PTBP 0.4%-2.5%, methanol 0.005%-3%, DMC 0.005%-3%, and BPA sodium salt 0.1%-2% in the composition by total mass.

[0017] The solvent in step 1) is at least one of methanol, ethanol, butanol, phenol, acetone, MTBE, and isopropyl ether, and is preferably isopropyl ether.

[0018] Preferably, the mass concentration of BPA in the prepared crude BPA solution is 10%-30%, and preferably 20%-25%.

[0019] The resin in step 2) is a macroporous cation resin, and is preferably one or more of Seplite LX-160, AMBERLITE IR120Na, and D001 resin.

[0020] The feeding speed of the resin treatment bed in step 2) is 0.5-5 BV / h, and preferably 1-2 BV / h.

[0021] The water washing column in step 3) is one or a combination of a plate column, a packed column, preferably a plate column.

[0022] The water / oil ratio of the water washing column in step 3) is 0.1-2, preferably 0.2-0.5, and the oil is one or more of isopropyl ether, methanol, ethanol, butanol, phenol, acetone, MTBE, preferably isopropyl ether.

[0023] The rectification column in step 4) is selected from any one of a plate column, a structured packed column, a random packed column, preferably a plate column.

[0024] The mass fraction of BPA in the phenol / BPA mixed solution is 20%-40%, preferably 28-35%.

[0025] The rectification column has a theoretical plate number of 20-35, preferably 28-32, a reflux ratio of 0.2-2, preferably 1-1.5, a column pressure of 10-30 kPa, preferably 18-22 kPa, and a column temperature of 190-210℃, preferably 196-205℃.

[0026] In the crystallization step in step 5), the phenol / BPA solution enters a primary crystallizer, and after BPA is partially crystallized, the crystallization liquid enters a secondary crystallizer for further crystallization. The slurry of crystals and crystallization liquid in the secondary crystallizer is sent to a centrifuge to separate a primary mother liquor and a primary crystal. The primary crystal is washed with a secondary crystallization mother liquor to obtain a washed primary crystal, and the primary mother liquor is sent to a resin reactor.

[0027] The washed primary crystal is melted by heating and then enters a primary flash evaporator and a secondary flash evaporator. The low-phenol BPA solution after flash evaporation enters a stripping column to obtain a BPA product.

[0028] The melting temperature by heating is 90℃-150℃, preferably 120℃-140℃.

[0029] The temperature of the primary crystallization in step 1) is 60-72℃, preferably 64-70℃, the pressure is 65-80 kPa, preferably 72-78 kPa, and the residence time is 2-4 h, preferably 2.5-3 h.

[0030] The temperature of the secondary crystallization in step 1) is 50-55℃, preferably 53-54℃, the pressure is 22-32 kPa, preferably 27-30 kPa, and the residence time is 2-4 h, preferably 2.5-3 h.

[0031] The pressure of the primary centrifugation is 30-50 kPa, preferably 40-45 kPa, and the ratio of the secondary crystallization mother liquor to the primary crystal is 0.5-1.1, preferably 0.6-0.7.

[0032] The first-stage flash pressure is 10-25 kPa, preferably 15-20 kPa, and the temperature is 155-180 DEG C, preferably 160-170 DEG C.

[0033] The second-stage flash pressure is 1-3 kPa, preferably 2-2.5 kPa, and the temperature is 158-170 DEG C, preferably 160-165 DEG C.

[0034] The stripping column is selected from any one of a plate column, a structured packing column and a random packing column, and is preferably a plate column. The theoretical plate number is 15-25, preferably 18-20.

[0035] The stripping column pressure is 8-15 kPa, preferably 10-12 kPa; the stripping temperature is 165-175 DEG C, preferably 168-170 DEG C; and the steam to stripping feed ratio is 0.08-0.12, preferably 0.1-0.11.

[0036] The BPA dry basis purity is above 99.96%, the PTBP content is below 50 ppm, the phenol content is below 15 ppm, the sodium ion content is below 1 ppm, the alcohol content is below 0.1 ppm, and the melt color number is below 20.

[0037] Compared with the prior art, the present application has the following beneficial effects:

[0038] The crude BPA obtained by degrading waste polycarbonate in the prior art cannot be directly applied to the high-end polycarbonate industry, resulting in resource waste and product quality degradation. The method of the present application can convert by-product BPA into products, with a dry basis purity of above 99.96%, thereby achieving great economic benefits and resource utilization rate. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 The figure is a flowchart of the preparation method of the present application.

[0040] Wherein, 1 is crude BPA, 2 is a dissolving tank, 3 is BPA solution, 4 is a resin treatment bed, 5 is low-salt BPA solution, 6 is a water washing column, 7 is phenol, 8 is BPA / phenol solution, 9 is recycled isopropyl ether, and 10 is a rectifying column.

[0041] Figure 2 The figure is a flowchart of BPA production.

[0042] Wherein, 11 is phenol, 12 is acetone, 13 is a reactor, 14 is BPA reaction liquid, 15 is a first-stage primary crystallizer, 16 is a first-stage secondary crystallizer, 17 is first-stage primary crystallization liquid, 18 is first-stage secondary crystallization liquid, 19 is a first-stage centrifuge, 20 is first-stage crystal, 21 is flushing phenol, 22 is first-stage flash, 23 is second-stage flash, 24 is recovered phenol, 25 is tail gas, 26 is steam, 27 is BPA product, and 28 is a stripping column. Detailed Implementation

[0043] To better understand the technical solution of the present invention, the following embodiments will further illustrate the method provided by the present invention. However, the present invention is not limited to the listed embodiments, but should also include any other known modifications within the scope of the claims of the present invention.

[0044] The present invention will be further described below with reference to specific embodiments, but this does not constitute any limitation on the present invention.

[0045] Crude BPA is obtained by degrading PC products in the presence of alkaline solution and methanol. The reaction solution is filtered to remove insoluble impurities from the pigments, and then dried to remove methanol and DMC solvent. Analysis shows that, by mass, it contains 0.001%-0.05% phenol, 90%-96% BPA, 0.4%-2.5% PTBP, 0.005%-3% methanol, 0.005%-3% DMC, and 0.1%-2% BPA salt.

[0046] The resin was Seplite LX-160 macroporous cationic resin purchased externally.

[0047] Isopropyl ether was purchased from Kailin Chemical, with a purity of over 99.0%.

[0048] BPA testing method:

[0049] Test for phenol / BPA / PTBP content in BPA: Weigh 1g of solid, accurately measure the mass, dilute 100 times with acetonitrile, and analyze the impurity content using liquid chromatography.

[0050] BPA melt color test: Weigh 30g of solid and place it in a colorimetric tube, heat it to 170℃ to melt it, store it stably for 1 hour, and then put it into a colorimeter to read the color number.

[0051] Test for sodium BPA in BPA: Weigh 1g of solid, accurately record the mass, add it to a nickel dry pot, add 10g of aqua regia and digest at 250℃ for 30 minutes. Then dilute with pure water to 100ml. Measure using ICP.

[0052] Test for methanol / DMC in BPA: Weigh 10g of solid and place it in a headspace vial. Heat the solid in the headspace vial to 110℃ and analyze the methanol and DMC content by gas phase analysis.

[0053] Example 1

[0054] The crude BPA from the previous step, containing 0.001% phenol, 96% BPA, 2.5% PTBP, 0.005% methanol, 0.005% DMC, 1.489% BPA sodium salt, was fed into the dissolving tank at a feed rate of 5 kg / h, and 20 kg / h of isopropyl ether was added to form a 20% BPA solution.

[0055] The BPA solution was fed into the Seplite LX-160 macroporous resin bed at a rate of 1 BV / h in a down-up mode, and the treated low-salt BPA solution was fed into the plate-type water washing tower, which had 2 stages and a water / oil ratio of 0.2, to obtain a refined BPA solution.

[0056] The refined BPA solution was fed into the rectification tower, and 15 kg / h of phenol was introduced into the tower. The rectification tower had 20 theoretical plates, a reflux ratio of 0.2, a tower bottom pressure of 10 kPa, and a tower bottom temperature of 190°C. Isopropyl ether was recovered from the top of the tower, and a BPA / phenol solution was obtained from the bottom of the tower.

[0057] The BPA / phenol solution was fed into the first-stage primary crystallizer, which was controlled at a pressure of 65 kPaG and a temperature of 60°C, and the residence time was 2.5 h. After the BPA partially crystallized, the crystallized solution was fed into the first-stage secondary crystallizer, which was controlled at a pressure of 50 kPaG and a temperature of 22°C, and the residence time was 2.5 h. The slurry of crystals and crystallized solution in the first-stage secondary crystallizer was fed into the first-stage centrifuge, and the first-stage mother liquor and the first-stage crystals were separated. The first-stage crystals were washed with phenol, and the mass ratio of the washing solution to the crystals was 0.5. The centrifugal pressure was controlled at 30 kPaG. The first-stage mother liquor was fed into the resin reactor, which was controlled at a reaction temperature of 80°C and a reaction rate of 1 BV / h. The service life of the resin was 30 months.

[0058] The first-stage washed crystals were melted at a temperature of 140°C, and then fed into the primary flash evaporator, which was controlled at a pressure of 10 kPa and a temperature of 155°C. The melted crystals were then fed into the secondary flash evaporator, which was controlled at a pressure of 1 kPa and a temperature of 158°C. The low-phenol BPA solution obtained after flash evaporation was fed into the stripping tower, which was controlled at 15 theoretical plates, a pressure of 12 kPa, a temperature of 165°C, and a stripping steam ratio of 0.1, to obtain the BPA product.

[0059] The BPA product had a purity of 99.96% on a dry basis, a PTBP content of 1 ppm, a phenol content of less than 5 ppm, a sodium ion content of 1 ppm, a methanol content of 0.1 ppm, a DMC content of 0.1 ppm, and a melt color number of less than 10.

[0060] Example 2

[0061] The crude BPA from the previous step, containing 0.05% phenol, 90% BPA, 2.5% PTBP, 3% methanol, 3% DMC, 1.45% BPA sodium salt, was fed into the dissolving tank at a feed rate of 5 kg / h, and 45 kg / h of isopropyl ether was added to form a 10% BPA solution.

[0062] The BPA solution was fed into the Seplite LX-160 macroporous resin bed at a rate of 2 BV / h in a bottom-to-top manner, and the treated low-salt BPA solution was fed into the plate-type water washing tower, which had 3 stages and a water / oil ratio of 0.3, to obtain a refined BPA solution.

[0063] The refined BPA solution was fed into the rectifying tower, and 15 kg / h of phenol was introduced into the tower. The rectifying tower had 35 theoretical plates, a reflux ratio of 1, a tower bottom pressure of 15 kPa, and a tower bottom temperature of 200°C. Isopropyl ether was recovered from the top of the tower, and a BPA / phenol solution was obtained from the bottom of the tower.

[0064] The BPA / phenol solution was fed into the first-stage primary crystallizer, which was controlled at a pressure of 72 kPaG and a temperature of 64°C, and the residence time was 2 h. After the BPA partially crystallized, the crystallized solution was fed into the first-stage secondary crystallizer, which was controlled at a pressure of 27 kPaG and a temperature of 53°C, and the residence time was 2 h. The slurry of crystals and crystallized solution in the first-stage secondary crystallizer was fed into the first-stage centrifuge, which separated the first-stage mother liquor and the first-stage crystals. The first-stage crystals were washed with phenol at a mass ratio of 0.6, and the centrifugal pressure was controlled at 50 kPaG. The first-stage mother liquor was fed into the resin reactor, which was controlled at a reaction temperature of 80°C and a reaction rate of 1 BV / h, and the service life of the resin was 30 months.

[0065] The first-stage washed crystals were melted at a temperature of 140°C, and then fed into the primary flash evaporator, which was controlled at a pressure of 20 kPa and a temperature of 160°C, and then fed into the secondary flash evaporator, which was controlled at a pressure of 2 kPa and a temperature of 160°C. The low-phenol BPA solution after flash evaporation was fed into the stripping tower, which had 18 theoretical plates, a pressure of 10 kPa, a temperature of 170°C, and a stripping steam ratio of 0.08, to obtain the BPA product.

[0066] The BPA product had a purity of 99.96% on a dry basis, a PTBP content of 3 ppm, a phenol content of less than 10 ppm, a sodium ion content of 0.5 ppm, a methanol content of 0.05 ppm, a DMC content of 0.05 ppm, and a melt color number of 12.

[0067] Example 3

[0068] The crude BPA from the previous step, containing 0.02% phenol, 92.58% BPA, 0.4% PTBP, 2.5% methanol, 2.5% DMC, 2% BPA sodium salt, was fed into the dissolving tank at a feed rate of 5 kg / h, and 15 kg / h of isopropyl ether was added to form a 25% BPA solution.

[0069] The BPA solution was fed into the Seplite LX-160 macroporous resin bed at a rate of 1.5 BV / h in a down-up mode, and the treated low-salt BPA solution was fed into the plate-type water washing tower, with 2 stages of water washing and a water / oil ratio of 0.4, to obtain a refined BPA solution.

[0070] The refined BPA solution was fed into the rectifying tower, and 15 kg / h of phenol was introduced, with a theoretical plate number of 25, a reflux ratio of 1.5, a tower bottom pressure of 20 kPa, and a tower bottom temperature of 205°C. Isopropyl ether was recovered at the top of the tower, and a BPA / phenol solution was obtained at the bottom of the tower.

[0071] The BPA / phenol solution was fed into the first-stage primary crystallizer, with a pressure control of 80 kPaG and a temperature control of 72°C, and a residence time of 3 h. After the BPA partially crystallized, the crystallized solution was fed into the first-stage secondary crystallizer for further crystallization, with a pressure control of 30 kPaG and a temperature control of 54°C, and a residence time of 3 h. The slurry of crystals and crystallized solution in the first-stage secondary crystallizer was fed into the first-stage centrifuge to separate the first-stage mother liquor and the first-stage crystals. The first-stage crystals were washed with phenol, with a mass ratio of wash liquid to crystals of 0.7, and the centrifugal pressure was controlled at 40 kPaG. The first-stage mother liquor was fed into the resin reactor, with a reaction temperature of 80°C and a reaction rate of 1 BV / h, and the service life of the resin was 30 months.

[0072] The first-stage washed crystals were melted at 140°C, fed into the primary flash evaporator at a pressure of 22 kPa and a temperature of 175°C, and then fed into the secondary flash evaporator at a pressure of 2.5 kPa and a temperature of 165°C. The low-phenol BPA solution after flash evaporation was fed into the stripping tower, with a theoretical plate number of 25, a pressure of 8 kPa, a temperature of 175°C, and a stripping steam ratio of 0.11, to obtain the BPA product.

[0073] The BPA product had a purity of 99.97% on a dry basis, a PTBP content of 1 ppm, a phenol content of less than 3 ppm, a sodium ion content of 0.1 ppm, a methanol content of 0.01 ppm, a DMC content of 0.01 ppm, and a melt color number of 8.

[0074] Example 4

[0075] The crude BPA from the previous step, containing 0.03% phenol, 95% BPA, 0.5% PTBP, 2.4% methanol, 1.97% DMC, 0.1% BPA sodium salt, was fed into the dissolving tank at a feed rate of 5 kg / h, and 11.7 kg / h of isopropyl ether was added to form a 30% BPA solution.

[0076] The BPA solution was fed into the Seplite LX-160 macroporous resin bed at a rate of 1 BV / h in a down-up mode, and the treated low-salt BPA solution was fed into the plate-type water washing tower, which had 3 stages and a water / oil ratio of 0.5, to obtain a refined BPA solution.

[0077] The refined BPA solution was fed into the rectifying tower, and 15 kg / h of phenol was introduced into the tower. The rectifying tower had 30 theoretical plates, a reflux ratio of 2, a tower bottom pressure of 30 kPa, and a tower bottom temperature of 210°C. Isopropyl ether was recovered from the top of the tower, and a BPA / phenol solution was obtained from the bottom of the tower.

[0078] The BPA / phenol solution was fed into the first-stage primary crystallizer, which was controlled at a pressure of 78 kPaG and a temperature of 70°C, and the residence time was 4 h. After the BPA partially crystallized, the crystallized solution was fed into the first-stage secondary crystallizer, which was controlled at a pressure of 32 kPaG and a temperature of 55°C, and the residence time was 4 h. The slurry of crystals and crystallized solution in the first-stage secondary crystallizer was fed into the first-stage centrifuge, and the first-stage mother liquor and the first-stage crystals were separated. The first-stage crystals were washed with phenol at a mass ratio of 1.1, and the centrifugal pressure was controlled at 45 kPaG. The first-stage mother liquor was fed into the resin reactor, which was controlled at a reaction temperature of 80°C and a reaction rate of 1 BV / h, and the service life of the resin was 30 months.

[0079] The first-stage washed crystals were melted at a temperature of 140°C, and then fed into the primary flash evaporator, which was controlled at a pressure of 25 kPa and a temperature of 180°C, and then fed into the secondary flash evaporator, which was controlled at a pressure of 3 kPa and a temperature of 170°C. The low-phenol BPA solution after flash evaporation was fed into the stripping tower, which was controlled at 20 theoretical plates, a pressure of 15 kPa, a temperature of 168°C, and a stripping steam ratio of 0.12, to obtain the BPA product.

[0080] The BPA product had a purity of 99.96% on a dry basis, a PTBP content of 1 ppm, a phenol content of less than 10 ppm, a sodium ion content of 0.1 ppm, a methanol content of 0.05 ppm, a DMC content of 0.05 ppm, and a melt color number of 12.

[0081] Comparative Example 1

[0082] The crude BPA from the previous step, containing 0.01% phenol, 91.91% BPA, 2.5% PTBP, 3% methanol, 1% DMC, and 1.5% BPA sodium salt, was fed into a dissolving tank at a feed rate of 5 kg / h, and 20 kg / h of isopropyl ether was added to prepare a 20% BPA solution.

[0083] The BPA solution was fed into a plate-type water washing tower, with 1 stage of water washing and a water / oil ratio of 0.1, to obtain a refined BPA solution.

[0084] The refined BPA solution was fed into a rectification tower, with 15 kg / h of phenol being introduced, a theoretical plate number of 20, a reflux ratio of 0.2, a tower bottom pressure of 10 kPa, and a tower bottom temperature of 190°C. Isopropyl ether was recovered at the top of the tower, and a BPA / phenol solution was obtained at the bottom of the tower.

[0085] The BPA / phenol solution was fed into a first-stage one-level crystallizer, with a pressure of 65 kPaG and a temperature of 60°C, and a residence time of 3.5 h. After the BPA partially crystallized, the crystallized liquid was fed into a first-stage two-level crystallizer for further crystallization, with a pressure of 24 kPaG and a temperature of 51°C, and a residence time of 3.5 h. The slurry of crystals and crystallized liquid in the first-stage two-level crystallizer was fed into a first-stage centrifuge to separate a first-stage mother liquor and a first-stage crystal. The first-stage crystal was washed with a flushing phenol, with a mass ratio of washing liquid to crystal of 0.8, and a centrifugal pressure of 35 kPaG. The first-stage mother liquor was fed into a resin reactor, with a reaction temperature of 80°C and a reaction rate of 1 BV / h, and the service life of the resin was 8 months.

[0086] The first-stage washed crystal was melted at a temperature of 140°C, fed into a first-stage flash evaporator at a pressure of 10 kPa and a temperature of 165°C, and then fed into a second-stage flash evaporator at a pressure of 1 kPa and a temperature of 160°C. The low-phenol BPA solution after flash evaporation was fed into a stripping tower, with a theoretical plate number of 20, a pressure of 10 kPa, a temperature of 165°C, and a stripping steam ratio of 0.08, to obtain a BPA product.

[0087] The BPA product had a purity of 99.90% on a dry basis, a PTBP content of 34 ppm, a phenol content of less than 15 ppm, a sodium ion content of 30 ppm, a methanol content of 1 ppm, a DMC content of 1 ppm, and a melt color number of 130.

[0088] It is known in the technical field that, in the absence of resin adsorption, metal ions entering the crystallization process can cause BPA degradation, and the sodium ion content and melt color number of the refined BPA product are significantly worse.

[0089] Comparative Example 2

[0090] The crude BPA from the previous step, containing 0.05% phenol, 94% BPA, 1.5% PTBP, 1.5% methanol, 2% DMC, 0.95% BPA sodium salt, was fed into the dissolving tank at a feed rate of 5 kg / h, and 15 kg / h of isopropyl ether was added to prepare a 25% BPA solution.

[0091] The BPA solution was fed into the Seplite LX-160 macroporous resin bed at a rate of 5 BV / h in a bottom-to-top manner.

[0092] The low-salt BPA solution was fed into the rectification tower, and 15 kg / h of phenol was introduced. The rectification tower had a theoretical plate number of 30, a reflux ratio of 1, a column pressure of 15 kPa, and a column temperature of 200°C. Isopropyl ether was recovered at the top of the tower, and a BPA / phenol solution was obtained at the bottom of the tower.

[0093] The BPA / phenol solution was fed into the first-stage primary crystallizer, which was controlled at a pressure of 74 kPaG and a temperature of 65°C, with a residence time of 3 h. After the BPA partially crystallized, the crystallization liquid was fed into the first-stage secondary crystallizer for further crystallization, which was controlled at a pressure of 29 kPaG and a temperature of 54°C, with a residence time of 3 h. The slurry of crystals and crystallization liquid in the first-stage secondary crystallizer was sent to the first-stage centrifuge, which separated the first-stage mother liquor and the first-stage crystals. The first-stage crystals were washed with phenol, with a mass ratio of wash liquid to crystals of 0.9, and the centrifugal pressure was controlled at 45 kPaG. The first-stage mother liquor was sent to the resin reactor, which was operated at a reaction temperature of 80°C and a reaction rate of 1 BV / h, with a resin service life of 7 months.

[0094] The first-stage washed crystals were melted at a temperature of 140°C, fed into the primary flash evaporator at a pressure of 20 kPa and a temperature of 170°C, and then fed into the secondary flash evaporator at a pressure of 2 kPa and a temperature of 165°C. The low-phenol BPA solution after flash evaporation was fed into the stripping tower, which had a theoretical plate number of 15, a pressure of 15 kPa, a temperature of 168°C, and a stripping steam ratio of 0.1, to obtain the BPA product.

[0095] The BPA product had a dry basis purity of 99.90%, a PTBP content of 40 ppm, a phenol content of less than 18 ppm, a sodium ion content of 32 ppm, a methanol content of 1 ppm, a DMC content of 1 ppm, and a melt color number of 134.

[0096] In the absence of water washing, metal ions entering the crystallization process can cause BPA degradation, and the sodium ion content and melt color number of the refined BPA product are significantly worse.

[0097] Comparative Example 3

[0098] The crude BPA from the previous step, containing 0.02% phenol, 96% BPA, 2% PTBP, 0.6% methanol, 0.6% DMC, and 0.78% BPA sodium salt, was fed into the dissolving tank at a feed rate of 5 kg / h, and 17 kg / h of isopropyl ether was added to form a 22.7% BPA solution.

[0099] The BPA solution was fed into the Seplite LX-160 macroporous resin bed at a rate of 1 BV / h in a bottom-to-top manner, and the low-salt BPA solution after treatment was fed into the plate-type water washing tower, with a water / oil ratio of 0.5 and 3 stages of water washing to obtain a refined BPA solution.

[0100] The BPA solution was fed into the rectifying column, and 15 kg / h of phenol was introduced into the column. The rectifying column had a theoretical plate number of 5, a reflux ratio of 1.5, a column bottom pressure of 20 kPa, and a column bottom temperature of 205°C. Isopropyl ether was recovered at the top of the column, and a BPA / phenol solution was obtained at the bottom of the column.

[0101] The BPA / phenol solution was fed into the first-stage primary crystallizer, with a pressure control of 78 kPaG and a temperature control of 70°C, and a residence time of 2 h. After the BPA partially crystallized, the crystallized solution was fed into the first-stage secondary crystallizer for further crystallization, with a pressure control of 31 kPaG and a temperature control of 55°C, and a residence time of 2 h. The slurry of crystals and crystallized solution in the first-stage secondary crystallizer was fed into the first-stage centrifuge to separate the first-stage mother liquor and the first-stage crystals. The first-stage crystals were washed with flushing phenol, with a mass ratio of washing liquid to crystals of 1, and the centrifugal pressure was controlled at 30 kPaG. The first-stage mother liquor was fed into the resin reactor, with a reaction temperature of 80°C and a reaction rate of 1 BV / h. The service life of the resin was 3 months.

[0102] The first-stage washed crystals were melted by heating to 140°C, and then fed into the primary flash evaporator, with a pressure of 15 kPa and a temperature of 175°C, and then fed into the secondary flash evaporator, with a pressure of 3 kPa and a temperature of 170°C. The low-phenol BPA solution after flash evaporation was fed into the stripping tower, with a theoretical plate number of 25, a pressure of 8 kPa, a temperature of 170°C, and a stripping steam ratio of 0.11, to obtain the BPA product.

[0103] The BPA product had a dry basis purity of 99.91%, a PTBP content of 45 ppm, a phenol content of less than 130 ppm, a sodium ion content of 0.1 ppm, a methanol content of 4 ppm, a DMC content of 4 ppm, and a melt color number of 90.

[0104] As known in the art, when the distillation is not complete during the refining process of BPA after PC degradation, the organic solvent enters the crystallization process, and the product has significantly worse indicators such as organic impurities and melt color number.

[0105] Comparative Example 4

[0106] The crude BPA from the previous step, containing 0.03% phenol, 95% BPA, 0.5% PTBP, 2.4% methanol, 1.97% DMC, and 0.1% BPA sodium salt, was fed into a dissolving tank at a feed rate of 5 kg / h, and 5 kg / h of isopropyl ether was added to form a 30% BPA solution.

[0107] The BPA solution was fed into a Seplite LX-160 macroporous resin bed at a rate of 1 BV / h in a bottom-to-top manner, and the treated low-salt BPA solution was fed into a plate-type water washing tower, which had 3 stages and a water / oil ratio of 0.5, to obtain a refined BPA solution.

[0108] The refined BPA solution was fed into a rectifying tower, and 15 kg / h of phenol was introduced into the tower. The rectifying tower had 30 theoretical plates, a reflux ratio of 2, a tower bottom pressure of 30 kPa, and a tower bottom temperature of 210°C. Isopropyl ether was recovered from the top of the tower, and a BPA / phenol solution was obtained from the bottom of the tower.

[0109] The BPA / phenol solution was fed into a first-stage primary crystallizer, which was controlled at a pressure of 78 kPaG and a temperature of 70°C, and the residence time was 4 h. After the BPA partially crystallized, the crystallized solution was fed into a first-stage secondary crystallizer, which was controlled at a pressure of 32 kPaG and a temperature of 55°C, and the residence time was 4 h. The slurry of crystals and crystallized solution in the first-stage secondary crystallizer was fed into a first-stage centrifuge to separate a first-stage mother liquor and a first-stage crystal. The first-stage crystal was washed with phenol at a mass ratio of 1.1, and the centrifugal pressure was controlled at 45 kPaG. The first-stage mother liquor was fed into a resin reactor, which was controlled at a reaction temperature of 80°C and a reaction rate of 1 BV / h, and the service life of the resin was 30 months.

[0110] The first-stage washed crystal was melted at a temperature of 140°C, and then was fed into a primary flash evaporator, which was controlled at a pressure of 25 kPa and a temperature of 180°C, and then was fed into a secondary flash evaporator, which was controlled at a pressure of 3 kPa and a temperature of 170°C. The low-phenol BPA solution after flash evaporation was fed into a stripping tower, which was controlled at 20 theoretical plates, a pressure of 15 kPa, a temperature of 168°C, and a stripping steam ratio of 0.12, to obtain a BPA product.

[0111] The BPA product had a purity of 99.93% on a dry basis, a PTBP content of 20 ppm, a phenol content of less than 40 ppm, a sodium ion content of 6 ppm, a methanol content of 0.05 ppm, a DMC content of 0.05 ppm, and a melt color number of 120.

[0112] As known by those skilled in the art, when the solubility of the crude BPA in isopropyl ether is high, the water washing for desalination is not complete, and the product has significantly poorer indicators such as organic impurities and melt color number.

[0113] Although the present application has been described in detail through the preferred embodiments, it should be appreciated that the above description is not to be construed as limiting the present application. Those skilled in the art can understand that some modifications or adjustments can be made to the present application under the teaching of the present specification. These modifications or adjustments should also be within the scope defined by the claims of the present application.

Claims

1. A refining method of crude BPA, comprising the following steps: 1) crude BPA from an upstream waste PC recycling device enters a dissolving tank, and is dissolved by a solvent to obtain a crude BPA solution; 2) the crude BPA solution after step 1) treatment enters a resin treatment bed to adsorb and remove sodium ions, to obtain a low-salt BPA solution; 3) the low-salt BPA solution obtained in step 2) enters a water washing tower to further remove sodium ions, to obtain a refined BPA solution; 4) the refined BPA solution after step 3) treatment is mixed with phenol and then enters a rectifying tower to remove and recover the solvent, to obtain a phenol / BPA solution; 5) the phenol / BPA solution obtained in step 4) enters a crystallization unit of a BPA device for further crystallization and purification, to remove phenol, to obtain a BPA product.

2. The refining method according to claim 1, characterized by, In step 1), the crude BPA contains, in terms of total mass, 0.001%-0.05% phenol, 90%-96% BPA, 0.4%-2.5% PTBP, 0.005%-3% methanol, 0.005%-3% DMC, and 0.1%-2% BPA sodium salt.

3. The refining method according to claim 1, characterized by, The solvent in step 1) is at least one of methanol, ethanol, butanol, phenol, acetone, MTBE, and isopropyl ether; and / or, the mass concentration of BPA in the crude BPA solution is 10%-30%.

4. The refining method according to claim 1, characterized by, The mass concentration of BPA in the crude BPA solution in step 1) is 20%-25%.

5. The purification method according to any one of claims 1 to 4, characterized in that, The resin in step 2) is a macroporous cation resin; and / or, the feed rate of the resin treatment bed in step 2) is 0.5-5 BV / h.

6. The method of claim 5, wherein the refining is performed by a method comprising: The resin in step 2) is one or more of Seplite LX-160, AMBERLITE IR120 Na, and D001 resin; and / or, the feed rate of the resin treatment bed in step 2) is 1-2 BV / h.

7. The purification method according to any one of claims 1 to 4, wherein The water / oil ratio of the water washing tower in step 3) is 0.1-2, and the oil is one or more of isopropyl ether, methanol, ethanol, butanol, phenol, acetone, and MTBE; and / or, the water washing tower in step 3) is one or a combination of a plate tower and a packed tower.

8. The purification method according to any one of claims 1 to 4, wherein The rectifying tower in step 4) is selected from any one of a plate tower, a structured packed tower, and a random packed tower; and / or, the mass fraction of BPA in the phenol / BPA mixed solution is 20%-40%; and / or, the number of theoretical plates of the rectifying tower is 20-35, the reflux ratio is 0.2-2, the column bottom pressure is 10-30 kPa, and the column bottom temperature is 190-210℃.

9. The purification method according to any one of claims 1 to 4, wherein The mass fraction of BPA in the phenol / BPA mixed solution in step 4) is 28-35%; and / or, the number of theoretical plates of the rectifying tower is 28-32, the reflux ratio is 1-1.5, the column bottom pressure is 18-22 kPa, and the column bottom temperature is 196-205℃.

10. The purification method according to any one of claims 1 to 4, wherein In the crystallization step, the phenol / BPA solution enters a primary crystallizer, after the BPA is partially crystallized, the crystallized solution enters a secondary crystallizer for further crystallization, the slurry of crystals and crystallized solution in the secondary crystallizer is sent to a primary centrifuge, the primary mother liquor and primary crystals are separated, the primary crystals are washed with secondary crystallization mother liquor, and the primary mother liquor is sent to the resin reactor.

11. The method of claim 10, wherein the refining is performed by a method comprising: The primary washed crystals are melted at a temperature of 90-150°C, then enter a primary flash evaporator, then enter a secondary flash evaporator, the low-phenol BPA solution after flash evaporation enters a stripping column to obtain a BPA product.

12. The method of claim 11 wherein the refining is characterized by, The melting temperature is 120-140°C.

13. The method of claim 11 wherein the refining is performed by a method selected from the group consisting of: The primary crystallization temperature is 60-72°C, the pressure is 65-80 kPa, and the residence time is 2-4 h; and / or, the secondary crystallization temperature is 50-55°C, the pressure is 22-32 kPa, and the residence time is 2-4 h; and / or, the primary centrifuge pressure is 30-50 kPa, and the ratio of secondary crystallization mother liquor to primary crystals is 0.5-1.

1. ​ 14. The method of claim 13, wherein the refining is performed by a method comprising: The primary crystallization temperature is 64-70°C, the pressure is 72-78 kPa, and the residence time is 2.5-3 h; and / or, the secondary crystallization temperature is 53-54°C, the pressure is 27-30 kPa, and the residence time is 2.5-3 h; and / or, the primary centrifuge pressure is 40-45 kPa, and the ratio of secondary crystallization mother liquor to primary crystals is 0.6-0.

7.

15. The refining method as described in claim 11, characterized in that, The primary flash evaporation pressure is 10-25 kPa, and the temperature is 155-180°C; and / or, the secondary flash evaporation pressure is 1-3 kPa, and the temperature is 158-170°C; and / or, the stripping column is selected from any one of a plate column, a structured packing column, and a random packing column; and / or, the theoretical plate number is 15-25; and / or, the stripping column pressure is 8-15 kPa; the stripping temperature is 165-175°C; and the steam to stripping feed ratio is 0.08-0.

12.

16. The method of claim 15, wherein the refining is performed by a method comprising: The primary flash evaporation pressure is 15-20 kPa, and the temperature is 160-170°C; and / or, the secondary flash evaporation pressure is 2-2.5 kPa, and the temperature is 160-165°C; and / or, the theoretical plate number is 18-20; and / or, the stripping column pressure is 10-12 kPa; the stripping temperature is 168-170°C; and the steam to stripping feed ratio is 0.1-0.11.

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