EP4680592A1 - A continuous process for purification of bisphenol ? a - Google Patents

A continuous process for purification of bisphenol ? a

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Publication number
EP4680592A1
EP4680592A1 EP24770170.9A EP24770170A EP4680592A1 EP 4680592 A1 EP4680592 A1 EP 4680592A1 EP 24770170 A EP24770170 A EP 24770170A EP 4680592 A1 EP4680592 A1 EP 4680592A1
Authority
EP
European Patent Office
Prior art keywords
bisphenol
bpa
phenol
water
acetone
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP24770170.9A
Other languages
German (de)
French (fr)
Inventor
Sanjay Pandurang KAMBLE
Sunil Sitaram Bhongale
Kapil Dnyaneshwar DHOTRE
Narendra Balwant BODAWAR
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Council of Scientific and Industrial Research CSIR
Original Assignee
Council of Scientific and Industrial Research CSIR
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Council of Scientific and Industrial Research CSIR filed Critical Council of Scientific and Industrial Research CSIR
Publication of EP4680592A1 publication Critical patent/EP4680592A1/en
Pending legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C37/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring
    • C07C37/68—Purification; separation; Use of additives, e.g. for stabilisation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
    • B01J31/06—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides containing polymers
    • B01J31/08—Ion-exchange resins
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C37/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring
    • C07C37/68—Purification; separation; Use of additives, e.g. for stabilisation
    • C07C37/70—Purification; separation; Use of additives, e.g. for stabilisation by physical treatment
    • C07C37/84—Purification; separation; Use of additives, e.g. for stabilisation by physical treatment by crystallisation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2231/00—Catalytic reactions performed with catalysts classified in B01J31/00
    • B01J2231/30—Addition reactions at carbon centres, i.e. to either C-C or C-X multiple bonds
    • B01J2231/34—Other additions, e.g. Monsanto-type carbonylations, addition to 1,2-C=X or 1,2-C-X triplebonds, additions to 1,4-C=C-C=X or 1,4-C=-C-X triple bonds with X, e.g. O, S, NH/N
    • B01J2231/341—1,2-additions, e.g. aldol or Knoevenagel condensations
    • B01J2231/347—1,2-additions, e.g. aldol or Knoevenagel condensations via cationic intermediates, e.g. bisphenol A type processes

Definitions

  • the present invention generally relates to a purification of bisphenol and/or its analogues and isomers. Specifically, the present invention relates to a continuous process for the purification of bisphenol-A (BPA) utilizing agitated thin film evaporator (ATFE) /agitated thin film dryer (ATFD) wherein unreacted phenol and traces of acetone are recovered and recycled in the process. Further, the resultant crude Bisphenol-A purified by extraction technique using toluene and water as a solvent. The present invention provides highly pure and colourless bisphenol-A.
  • BPA bisphenol-A
  • ATFE agitated thin film evaporator
  • ATFD agitated thin film dryer
  • Bisphenol-A or “p,p'-bisphenol-A” are well-known names for 2,2-bis(4-hydroxyphenyl)- propane which is a condensation product of phenol and acetone.
  • Bisphenol-A is a product of high technical and commercial importance for the manufacturing of many commercial products, such as polycarbonates and epoxy resins.
  • the global BPA market value is USD 10.92 billion (2020). Due to increased demand for BPA in the automotive industry, the market is projected to further reach USD 30.62 billion by 2026 at a CAGR of 7.8% (2021- 2026).
  • High quality epoxy resins, and particularly polycarbonates, require bisphenol-A of high purity for use in their preparation.
  • Bisphenol-A is prepared according to various known processes by the condensation reaction of an acetone and a stoichiometric excess of phenol in the presence of a catalyst. These known processes produce bisphenol-A and certain impurities including isomers, analogs and homologues, such as 2-(2-hydroxyphenyl)-2-(4-hydroxyphenyl)propane (hereafter referred to as o,p'-bisphenol-A), 2,2,4-trimethyl-4-(4-hydroxyphenyl)chroman, trisphenol, polyphenol and unfavorably colored substances.
  • o,p'-bisphenol-A 2-(2-hydroxyphenyl)-2-(4-hydroxyphenyl)propane
  • 2,2,4-trimethyl-4-(4-hydroxyphenyl)chroman trisphenol, polyphenol and unfavorably colored substances.
  • U.S. Pat. No. 3,326,986 discloses mixing crude bisphenol-A with water and heating the mixture to a temperature of 100° C resulting in an aqueous phase containing solid slurry. The mixture is cooled slowly to crystallize bisphenol-A. Any isomeric diphenols or other organic impurities remaining in the crystals are removed by washing with a chlorinated solvent, such as chloroform, methylene chloride, ethylene dichloride, propylene dichloride or chlorobenzene.
  • a chlorinated solvent such as chloroform, methylene chloride, ethylene dichloride, propylene dichloride or chlorobenzene.
  • U.S. Pat. No. 4,461,915 suggests mixing water-crystallized bisphenol-A in the presence of water with a water-immiscible organic solvent, such as toluene, agitating the mixture and forming three phases in the agitated mixture. The phase containing mainly the organic solvent is removed and purified bisphenol-A is recovered from the remaining two phases.
  • a water-immiscible organic solvent such as toluene
  • U.S. Pat. No. 4,740,635 discloses a process for crystallizing bisphenol-A wherein water is added to a mixture of a phenol-free mixture of bisphenol-A, 0.5 to 15 wt. -percent diphenol isomers and impurities. Water and the crude bisphenol-A mixture are heated to 95-105° C. at ambient-pressure to melt all the solid material. Then it is adiabatically cooled, while stirring, by reducing the pressure. The temperature is reduced to below 90° C. The crystallized bisphenol-A may be washed to further increase its purity. Unfortunately, the maximum purity of the crystallized bisphenol-A, even after several washing operations, does not exceed 99.2 percent.
  • U.S. Pat. No. 4,533,764 discloses a process for removing occluded organic solvent from bisphenol crystals.
  • the crystals are placed in water which is maintained at a temperature of 100° C or above to produce a molten water-bisphenol phase.
  • the water-bisphenol phase separates from the excess water and the solvent occluded by the bisphenol crystals can diffuse into the water phase from where it can be flash distilled.
  • U.S. Pat. No. 4,141,924 discloses a process for purifying a crude crystalline aromatic compound, such as bisphenol-A, wherein a dispersion of the liquefied crude material in an aqueous liquid is formed by agitating the mixture at ambient pressure and at a temperature sufficient to melt the crude material. Agitation is then reduced to permit formation of three phases, a solid crystalline phase, an aqueous liquid phase and a mother liquor phase.
  • a crude crystalline aromatic compound such as bisphenol-A
  • 5,512,700 discloses a process for the purification of a crude bisphenol which comprises the steps of ( 1) preparing a mixture of a crude bisphenol- A and water at a pressure above atmospheric and a temperature above 100° C, (2) crystallizing bisphenol-A at a pressure below atmospheric, (3) separating crystalline bisphenol from the mother liquor, (4) dividing at least a portion of the mother liquor into a bisphenol-rich organic phase and a water-rich phase, (5) preparing a mixture of the bisphenol-rich organic phase, water and optionally an additional amount of crude bisphenol at a pressure above atmospheric and a temperature of above 100° C, (6) cooling the mixture and crystallizing bisphenol and (7) separating crystalline bisphenol from the mother liquor.
  • BPA bisphenol-A
  • the existing processes for purification of bisphenol-A consists of batch as well as continuous operation.
  • the conventional patents describe the continuous process for purification of BPA using multiple unit operations.
  • the existing patents use phenolic water for purification of Bisphenol-A which further leads to generation of large amounts of wastewater.
  • the minimum water being used (crude BPA to water ratio wt 1 : 1 ) in the downstream processing of crude BPA and the wastewater generated was further treated using cavitation/adsorption/ advanced oxidation processes (AOPs) and hybrid AOPs techniques.
  • the purified water further can be used in the process or as plant utilities like cooling water, boiler water, plant cleaning water etc.
  • the main objective of the present invention is to provide a process for purification of bisphenol-A and/or its analogues and isomers.
  • Another objective of the present invention is to provide a continuous process for the purification of bisphenol-A utilizing agitated thin film evaporator (ATFE)/agitated thin film dryer (ATFD) wherein unreacted phenol and traces of acetone are removed.
  • ATFE agitated thin film evaporator
  • ATFD agitated thin film dryer
  • Another objective of the present invention is to provide highly pure and colourless BPA.
  • the footprint of downstream processing for the purification of BPA is smaller than conventional process.
  • Another objective of the present invention is use minimum quantity of water (crude BPA to water ratio wt 1 : 1) in the downstream processing of crude BPA and the wastewater generated was further treated using cavitation/adsorption/ advanced oxidation processes (AOPs) and hybrid AOPs techniques.
  • the purified water further can be used in the process or as plant utilities like cooling water, boiler water, plant cleaning water etc.
  • the present invention generally relates to a purification of bisphenol-A and/ or its analogues and isomers. Specifically, the present invention relates to a continuous process for the purification of bisphenol-A (BPA) utilizing agitated thin film evaporator (ATFE) /agitated thin film dryer (ATFD) wherein unreacted phenol and traces of acetone are removed. Further impurities present in the crude BPA were selectively removed by combination organic, aqueous solvent so that highly pure, colourless 95 to 99.8% BPA can be obtained.
  • BPA bisphenol-A
  • ATFE agitated thin film evaporator
  • ATFD agitated thin film dryer
  • the present invention relates to a process for purification of bisphenol-A (BPA), wherein the process comprising the steps of: a) continuously feeding a mixture of phenol and acetone to a fixed bed reactor (FBR) from a top of the fixed bed reactor; b) charging the fixed bed reactor with an ion exchange resin (IER) as a catalyst to obtain a reaction product mixture; c) feeding the reaction product mixture obtained in step b subsequently to an agitated thin film dryer (ATFD)/agitated thin film evaporator (ATFE) to recover unreacted phenol along with traces of acetone as a top product and crude bisphenol-A (BPA) as a bottom product, respectively; d) feeding the crude bisphenol-A as a bottom product obtained in step c into a crystallizer followed by water and toluene to obtain a plurality of streams selected from a organic layer, a aqueous layer and a solid layer having a plurality of white crystals of moist BPA;
  • the organic layer removes impurities present in the crude BPA.
  • the aqueous layer removes traces of the unreacted phenol from the plurality of white crystals of moist BPA to obtain the purified dry BPA.
  • the process provides purity of the dry BPA in a range of 99.2-99.8%.
  • the BPA is crystallized at a temperature in a range of 40 °C to 80 °C.
  • the mixture of the step a) comprises a mole ratio of phenol: acetone in a range of 6: 1 to.10:1.
  • the reaction of phenol and acetone in fixed bed reactor is carried out at a temperature ranging from 90 °C to 110 °C and N2 pressure ranging from 1 to 4 kg/cm 2 .
  • the IER is charged to the fixed bed reactor at step b) at a range of 200 to 500 gm (dry weight).
  • the IER is charged to the fixed bed reactor at step b) at an average feed flow rate ranging from 200-1000 gm/hour.
  • the process achieves an 80-90% selectivity of BPA and a 70-95% conversion of acetone at temperatures ranging from 90 °C to 110 °C, resulting in the production of colorless purified dry BPA.
  • Fig. 1 illustrates block diagram for BPA process.
  • Fig. 2 illustrates HPLC Chromatogram of Purified Bisphenol A sample (Sample name B-5) Full scale Chromatogram.
  • Fig.3 illustrates HPLC Chromatogram of Purified Bisphenol A sample (Sample name B-5) Zoomed scale Chromatogram.
  • Fig.4 illustrates HPLC Purity Analysis Report for Purified Bisphenol A sample (Sample name B- 5).
  • Fig. 5 illustrates LCMS Impurity Profiling for Purified Bisphenol A Sample.
  • Fig. 6 illustrates DSC analysis for melting point profile and sample heating conditions for Aldrich BPA sample.
  • Fig. 7 illustrates DSC analysis for melting point profile and sample heating conditions for synthesized BPA sample.
  • the “CSIR-NCL sample” or “CSIR-NCL Bisphenol A” means the Bisphenol A prepared and purified by the process of the present case.
  • the present invention relates to a purification of bisphenol-A and/ or its analogues and isomers. Specifically, the present invention relates to a continuous process for the purification of bisphenol-A (BPA) utilizing - agitated thin film evaporator (ATFE) /agitated thin film dryer (ATFD) wherein unreacted phenol and traces of acetone are removed.
  • BPA bisphenol-A
  • ATFE agitated thin film evaporator
  • ATFD agitated thin film dryer
  • Figure 1 shows the process flow sheet for the production of BPA.
  • the 99% pure phenol and acetone was continuously fed from the top of the fixed bed reactor (FBR) using a gear pump.
  • Fixed bed reactor was charged with 200-260 gm of IER and inert material (to reduce the pressure drop).
  • the N2 pressure across the FBR was mentioned around 2 to 4 bar via back pressure regulator.
  • the reaction product was subsequently fed to agitated thin film dryer (ATFD)/ agitated thin film evaporator (ATFE) where excess of unreacted phenol along with traces of acetone were recovered as top product.
  • the recovered phenol and acetone was recycled to the phenol tank without any further treatment.
  • the bottom product from ATFD/ATFE i.e.
  • the present invention relates to a process for purification of bisphenol-A (BPA), wherein the process comprising the steps of: a) continuously feeding a mixture of phenol and acetone to a fixed bed reactor (FBR) from a top of the fixed bed reactor; b) charging the fixed bed reactor with an ion exchange resin (IER) as a catalyst to obtain a reaction product mixture; c) feeding the reaction product mixture obtained in step b subsequently to an agitated thin film dryer (ATFD)/agitated thin film evaporator (ATFE) to recover unreacted phenol along with traces of acetone as a top product and crude bisphenol-A (BPA) as a bottom product, respectively; d) feeding the crude bisphenol-A as a bottom product obtained in step c into a crystallizer followed by water and toluene to obtain a plurality of streams selected from a organic layer, a aqueous layer and a solid layer having a plurality of white crystals of moist BPA;
  • the mixture of the step a) comprises a mole ratio of phenol: acetone in a range of 6: 1 to.10:1.
  • the IER is charged to the fixed bed reactor at step b) at a range of 200 to 500 gm (dry weight).
  • the IER is charged to the fixed bed reactor at step b) at an average feed flow rate ranging from 200-1000 gm/hour.
  • the process achieves an 80-90% selectivity of BPA and a 70-95% conversion of acetone at temperatures ranging from 90 °C to 110 °C, resulting in the production of colorless purified dry BPA (colourless 4,4’ -BPA product).
  • the present invention provides agitated thin film dryer (ATFD)/ agitated thin film evaporator (ATFE) followed by treatment with water and toluene to further remove impurities i.e., two solvent washes to obtain 99.2-99.8% pure bisphenol -A or its analogues and isomers. Also, the usage of ATFD/ ATFE and two solvent washes for the purification and achieve 99.2-99.8% pure bisphenol-A is not known in the prior art.
  • ATFD agitated thin film dryer
  • ATFE agitated thin film evaporator
  • the present invention relates a continuous catalytic pilot scale process for the production of bisphenol-A using phenol and acetone as a reactant in the presence of ion exchange resin as a catalyst.
  • the process of the present invention provides complete recovery of unreacted phenol by Agitated Thin Film Dryer (ATFD)/Agitated Thin Film Evaporator (ATFE).
  • the present invention uses acidic water for removing the color bodies present in the crude bisphenol-A.
  • the aqueous stream generated after the crystallization of bisphenol-A can be recycled in the present process. Also, the present invention provides zero liquid discharge.
  • the unreacted phenol and acetone obtained from Agitated Thin Film Dryer (ATFD)/ Agitated Thin Film Evaporator (ATFE) can be recycled and used as starting material, i.e., feed for fixed bed reactor.
  • Table 1 shows the effect of operating parameters such as conversion of acetone, phenol conversion, BPA formation and BPA selectivity achieved by the process of present invention.
  • Another aspect of the present invention is use minimum quantity water (crude BPA to water ratio wt 1: 1) in the downstream processing of crude BPA and the wastewater generated was further treated using cavitation/adsorption/advanced oxidation processes (AOPs) and hybrid AOPs techniques.
  • the purified water further can be used in the process or as plant utilities like cooling water, boiler water, plant cleaning water etc.
  • Table 2 shows the effect of temperature and vacuum on ATFD/ATFE performance on the recovery of phenol.
  • Table 2 Effect of temperature and vacuum on ATFD/ATFE performance for the recovery of phenol
  • the footprint of downstream processing for the purification of BPA is smaller than conversional process.
  • the purity of BPA obtained after the crystallization is found to be in the range of 99.2-99.8% which is suitable for further production of epoxy grade resins and polycarbonates.
  • the Figure 1 shows the process flow sheet for the continuous production of BPA.
  • the 99% pure phenol and acetone was feed from the top of the fixed bed reactor (FBR) using gear pump.
  • Fixed bed reactor was charged with 260 & 500 gm of IER and inert material (to reduce the pressure drop).
  • the N2 pressure across the FBR was mentioned around 2 to 4 bar via back pressure regulator.
  • the reaction product was subsequently feed to agitated thin film dryer (ATFD)/ agitated thin film evaporator (ATFE) where excess of unreacted phenol along with traces of acetone were recovered as top product.
  • the recovered phenol and acetone was recycled to phenol tank without any further treatment.
  • the bottom product from ATFD/ATFE i.e.
  • Phenol and acetone reaction was carried out using IER as catalyst in fixed bed reactor (FBR) in continuous mode of operation.
  • the mole ratios of phenol and acetone 10: 1 to 6: 1 was feed with the flow rate in the range of 200 to 1000 gm/hr at 90 to 110 °C reaction temperature and 1 to 4 kg/cm 2 N2 pressure across the FBR.
  • FBR was loaded with 260 to 500 gm of activated IER.
  • the obtained acetone and phenol conversion is in the range of 70-95 % and 13-20 % respectively.
  • the achieved BPA formation rate and BPA selectivity is in the range of 16-20 wt% and 82-87 % respectively. This is shown in Table 1.
  • the distillate of ATFD/ATFE contain phenol, 4-4’BPAand impurities of 96.94%, 0.07% and 0.54% respectively.
  • the ATFD/ATFE bottom product obtained crude BPA was further purified using water and toluene extraction methods. Further BPA was purified using water and toluene as solvent and further crystallization at 40-80 °C gives moist BPA.
  • the moist BPA was further dried in a vacuum dryer at 90 °C at 500-800 mbarg, in order to achieve dried BPA having purity of 99.2- 99.8%.
  • the distillate of ATFD/ATFE contains phenol, 4-4’BPA and impurities of 98%, 0.12% and 4.21 % respectively.
  • the ATFD/ATFE bottom product obtained crude BPA was further purified using water and toluene extraction methods. Further BPA was purified using water and toluene as solvent and further crystallization at 40-80 °C gives moist BPA.
  • the moist BPA was further dried in a vacuum dryer at 90 °C at 500-800 mbarg, in order to achieve dried BPA having purity of 99.2-99.8%.
  • the distillate of ATFD/ATFE contains phenol, 4-4’BPA and impurities of 99.30%, 0.12% and 0.58% respectively
  • the ATFD/ATFE bottom product obtained crude BPA was further purified using water and toluene extraction methods. Further BPA was purified using water and toluene as solvent and further crystallization at 40-80 °C gives moist BPA.
  • the moist BPA was further dried in a vacuum dryer at 90 °C at 500-800 mbarg, in order to achieve dried BPA having purity of 99.2-99.8%.
  • the distillate of ATFD/ATFE contains phenol, 4-4’BPA and impurities of 99.35%, 0.12% and 4.45% respectively.
  • the ATFD/ATFE bottom product obtained crude BPA was further purified using water and toluene extraction methods. Further, BPA was purified using water and toluene as solvent and further crystallization at 40-80 °C gives moist BPA.
  • the moist BPA was further dried in a vacuum dryer at 90 °C at 500-800 mbarg, in order to achieve dried BPA having purity of 99.2-99.8%. This is shown in Table 2.
  • HPLC equipped with UV detector was used for evaluating impurities in process purified Bisphenol A samples.
  • HPLC technique equipped with UV detector is very versatile technique for both volatile and non-volatile compounds possessing chromogenic/chromophore groups present in aromatic ring compounds.
  • Equipment HPLC
  • Agilent 1260 Infinity Methanol: Water (60:40, V/V)
  • Mobile Phase Composition Methanol: Water (60:40, V/V)
  • Column Hypersil Gold Cl 8, 250 mm (L) x 4.6 mm(id), 5 /urn Particle Size', Sample Injection Volume: 10 pL; Flow rate: 1 mL/min; Run time: 60 min; Detector: UV 230 nm; and Sample Concentration: 1000 ppm(w/v).
  • the LCMS spectra confirms presence of minimum impurities presence (considering smaller peak heights), the impurities were namely 2 (2,4’- Bisphenol A), Impurity 3 (Chroman I compound), Impurity 4 (Chroman II compound), and Impurity 5 (Trisphenol), respectively.
  • Table 3 List of Impurities detected in LCMS Analysis.
  • Figs. 6 and 7 report graphical profiles of melting point and sample heating conditions for commercial Bisphenol-A sample (Aldrich Bisphenol-A standard), (M.P. 157.1 °C) and process purified Bisphenol-A sample (M.P. 156.7 °C). The melting point both samples were nearly same.
  • Fig.8 depicts superimposed images of XRD Profiles of commercial Bisphenol-A sample (Aldrich standard), and process purified bisphenol-A sample (CSIR-NCL) of the present disclosure.
  • Present invention discloses the use of acidic water for removing the color bodies present in the Crude Bisphenol-A.
  • the present invention provides highly pure and colorless BPA.
  • Another advantage present invention is use minimum quantity water (crude BPA to water ratio wt 1 : 1) in the downstream processing of crude BPA and the wastewater generated was further treated using cavitation/adsorption/ advanced oxidation processes (AOPs) and hybrid AOPs techniques.
  • the purified water further can be used in the process or as plant utilities like cooling water, boiler water, plant cleaning water etc.

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  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
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  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

The present invention relates to purification of bisphenol and/or its analogues and isomers. Specifically, the present invention relates to a continuous process for the purification of bisphenol-A (BPA) utilizing flash distillation and agitated thin film evaporator (ATFE) /agitated thin film dryer (ATFD) wherein unreacted phenol and traces of acetone are recovered and reused. Further impurities present in the crude BPA were selectively removed by combination of organic and aqueous solvent to obtain the highly pure and colorless BPA. Another advantage present invention is the use of minimum quantity water (crude BPA to water ratio wt 1: 1) in the downstream processing of crude BPA and the wastewater generated was further treated using cavitation/adsorption/ advanced oxidation processes (AOPs) and hybrid AOPs techniques. The purified water further can be used in the process or as plant utilities like cooling water, boiler water, plant cleaning water etc.

Description

A CONTINUOUS PROCESS FOR PURIFICATION OF BISPHENOL - A
TECHNICAL FIELD OF THE INVENTION
The present invention generally relates to a purification of bisphenol and/or its analogues and isomers. Specifically, the present invention relates to a continuous process for the purification of bisphenol-A (BPA) utilizing agitated thin film evaporator (ATFE) /agitated thin film dryer (ATFD) wherein unreacted phenol and traces of acetone are recovered and recycled in the process. Further, the resultant crude Bisphenol-A purified by extraction technique using toluene and water as a solvent. The present invention provides highly pure and colourless bisphenol-A.
BACKGROUND OF THE INVENTION
Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the present invention, or that any publication specifically or implicitly referenced is prior art.
“Bisphenol-A” or “p,p'-bisphenol-A” are well-known names for 2,2-bis(4-hydroxyphenyl)- propane which is a condensation product of phenol and acetone. Bisphenol-A is a product of high technical and commercial importance for the manufacturing of many commercial products, such as polycarbonates and epoxy resins. The global BPA market value is USD 10.92 billion (2020). Due to increased demand for BPA in the automotive industry, the market is projected to further reach USD 30.62 billion by 2026 at a CAGR of 7.8% (2021- 2026). High quality epoxy resins, and particularly polycarbonates, require bisphenol-A of high purity for use in their preparation.
Bisphenol-A is prepared according to various known processes by the condensation reaction of an acetone and a stoichiometric excess of phenol in the presence of a catalyst. These known processes produce bisphenol-A and certain impurities including isomers, analogs and homologues, such as 2-(2-hydroxyphenyl)-2-(4-hydroxyphenyl)propane (hereafter referred to as o,p'-bisphenol-A), 2,2,4-trimethyl-4-(4-hydroxyphenyl)chroman, trisphenol, polyphenol and unfavorably colored substances. In view of the high technical and commercial interest in providing highly pure bisphenol-A, much research effort has been spent on its purification.
There are many patents related to the purification of bisphenol-A; and the extent of the purification necessary is dependent on yield, crude bisphenol purity, and quality of final product desired. According to one known method a mixture of bisphenol-A and water is prepared, the mixture is heated and subsequently cooled to re-crystallize bisphenol-A.
U.S. Pat. No. 3,326,986 discloses mixing crude bisphenol-A with water and heating the mixture to a temperature of 100° C resulting in an aqueous phase containing solid slurry. The mixture is cooled slowly to crystallize bisphenol-A. Any isomeric diphenols or other organic impurities remaining in the crystals are removed by washing with a chlorinated solvent, such as chloroform, methylene chloride, ethylene dichloride, propylene dichloride or chlorobenzene.
U.S. Pat. No. 4,461,915 suggests mixing water-crystallized bisphenol-A in the presence of water with a water-immiscible organic solvent, such as toluene, agitating the mixture and forming three phases in the agitated mixture. The phase containing mainly the organic solvent is removed and purified bisphenol-A is recovered from the remaining two phases.
U.S. Pat. No. 4,740,635 discloses a process for crystallizing bisphenol-A wherein water is added to a mixture of a phenol-free mixture of bisphenol-A, 0.5 to 15 wt. -percent diphenol isomers and impurities. Water and the crude bisphenol-A mixture are heated to 95-105° C. at ambient-pressure to melt all the solid material. Then it is adiabatically cooled, while stirring, by reducing the pressure. The temperature is reduced to below 90° C. The crystallized bisphenol-A may be washed to further increase its purity. Unfortunately, the maximum purity of the crystallized bisphenol-A, even after several washing operations, does not exceed 99.2 percent.
U.S. Pat. No. 4,533,764 discloses a process for removing occluded organic solvent from bisphenol crystals. The crystals are placed in water which is maintained at a temperature of 100° C or above to produce a molten water-bisphenol phase. The water-bisphenol phase separates from the excess water and the solvent occluded by the bisphenol crystals can diffuse into the water phase from where it can be flash distilled.
U.S. Pat. No. 4,141,924 discloses a process for purifying a crude crystalline aromatic compound, such as bisphenol-A, wherein a dispersion of the liquefied crude material in an aqueous liquid is formed by agitating the mixture at ambient pressure and at a temperature sufficient to melt the crude material. Agitation is then reduced to permit formation of three phases, a solid crystalline phase, an aqueous liquid phase and a mother liquor phase. U.S. Pat. No. 5,512,700 discloses a process for the purification of a crude bisphenol which comprises the steps of ( 1) preparing a mixture of a crude bisphenol- A and water at a pressure above atmospheric and a temperature above 100° C, (2) crystallizing bisphenol-A at a pressure below atmospheric, (3) separating crystalline bisphenol from the mother liquor, (4) dividing at least a portion of the mother liquor into a bisphenol-rich organic phase and a water-rich phase, (5) preparing a mixture of the bisphenol-rich organic phase, water and optionally an additional amount of crude bisphenol at a pressure above atmospheric and a temperature of above 100° C, (6) cooling the mixture and crystallizing bisphenol and (7) separating crystalline bisphenol from the mother liquor.
The existing processes for purification of bisphenol-A (BPA) consists of batch as well as continuous operation. The conventional patents describe the continuous process for purification of BPA using multiple unit operations. The existing patents use phenolic water for purification of Bisphenol-A which further leads to generation of large amounts of wastewater.
Therefore, there is an unmet need in the art to solve the aforementioned problems and provide BPA with high levels of purity. Also, there is a need to provide a method for purification of BPA involving lesser steps.
In the present invention, the minimum water being used (crude BPA to water ratio wt 1 : 1 ) in the downstream processing of crude BPA and the wastewater generated was further treated using cavitation/adsorption/ advanced oxidation processes (AOPs) and hybrid AOPs techniques. The purified water further can be used in the process or as plant utilities like cooling water, boiler water, plant cleaning water etc.
OBJECTIVES OF THE INVENTION
The main objective of the present invention is to provide a process for purification of bisphenol-A and/or its analogues and isomers.
Another objective of the present invention is to provide a continuous process for the purification of bisphenol-A utilizing agitated thin film evaporator (ATFE)/agitated thin film dryer (ATFD) wherein unreacted phenol and traces of acetone are removed.
Another objective of the present invention is to provide highly pure and colourless BPA. In another embodiment of the present invention, the footprint of downstream processing for the purification of BPA is smaller than conventional process.
Another objective of the present invention is use minimum quantity of water (crude BPA to water ratio wt 1 : 1) in the downstream processing of crude BPA and the wastewater generated was further treated using cavitation/adsorption/ advanced oxidation processes (AOPs) and hybrid AOPs techniques. The purified water further can be used in the process or as plant utilities like cooling water, boiler water, plant cleaning water etc.
SUMMARY OF THE INVENTION
The present invention generally relates to a purification of bisphenol-A and/ or its analogues and isomers. Specifically, the present invention relates to a continuous process for the purification of bisphenol-A (BPA) utilizing agitated thin film evaporator (ATFE) /agitated thin film dryer (ATFD) wherein unreacted phenol and traces of acetone are removed. Further impurities present in the crude BPA were selectively removed by combination organic, aqueous solvent so that highly pure, colourless 95 to 99.8% BPA can be obtained.
In an aspect, the present invention relates to a process for purification of bisphenol-A (BPA), wherein the process comprising the steps of: a) continuously feeding a mixture of phenol and acetone to a fixed bed reactor (FBR) from a top of the fixed bed reactor; b) charging the fixed bed reactor with an ion exchange resin (IER) as a catalyst to obtain a reaction product mixture; c) feeding the reaction product mixture obtained in step b subsequently to an agitated thin film dryer (ATFD)/agitated thin film evaporator (ATFE) to recover unreacted phenol along with traces of acetone as a top product and crude bisphenol-A (BPA) as a bottom product, respectively; d) feeding the crude bisphenol-A as a bottom product obtained in step c into a crystallizer followed by water and toluene to obtain a plurality of streams selected from a organic layer, a aqueous layer and a solid layer having a plurality of white crystals of moist BPA; and e) separating the plurality of white crystals of moist BPA obtained in step d followed by drying in a vacuum dryer at 90 °C and 500-800 mbarg to obtain the purified dry BPA.
In various embodiments, the organic layer removes impurities present in the crude BPA.
In certain embodiments, the aqueous layer removes traces of the unreacted phenol from the plurality of white crystals of moist BPA to obtain the purified dry BPA.
In certain embodiments, the process provides purity of the dry BPA in a range of 99.2-99.8%.
In various embodiments, the BPA is crystallized at a temperature in a range of 40 °C to 80 °C.
In certain embodiments, the mixture of the step a) comprises a mole ratio of phenol: acetone in a range of 6: 1 to.10:1.
In various embodiments, the reaction of phenol and acetone in fixed bed reactor is carried out at a temperature ranging from 90 °C to 110 °C and N2 pressure ranging from 1 to 4 kg/cm2.
In certain embodiments, the IER is charged to the fixed bed reactor at step b) at a range of 200 to 500 gm (dry weight).
In certain embodiments, the IER is charged to the fixed bed reactor at step b) at an average feed flow rate ranging from 200-1000 gm/hour.
In various embodiments, the process achieves an 80-90% selectivity of BPA and a 70-95% conversion of acetone at temperatures ranging from 90 °C to 110 °C, resulting in the production of colorless purified dry BPA.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 illustrates block diagram for BPA process.
Fig. 2 illustrates HPLC Chromatogram of Purified Bisphenol A sample (Sample name B-5) Full scale Chromatogram. Fig.3 illustrates HPLC Chromatogram of Purified Bisphenol A sample (Sample name B-5) Zoomed scale Chromatogram.
Fig.4 illustrates HPLC Purity Analysis Report for Purified Bisphenol A sample (Sample name B- 5).
Fig. 5 illustrates LCMS Impurity Profiling for Purified Bisphenol A Sample.
Fig. 6 illustrates DSC analysis for melting point profile and sample heating conditions for Aldrich BPA sample.
Fig. 7 illustrates DSC analysis for melting point profile and sample heating conditions for synthesized BPA sample.
Fig. 8 illustrates superimposed images of XRD profiles of Aldrich STD and purified Bisphenol A.
DETAILED DESCRIPTION OF THE INVENTION
Here, the “CSIR-NCL sample” or “CSIR-NCL Bisphenol A” means the Bisphenol A prepared and purified by the process of the present case.
In a general embodiment, the present invention relates to a purification of bisphenol-A and/ or its analogues and isomers. Specifically, the present invention relates to a continuous process for the purification of bisphenol-A (BPA) utilizing - agitated thin film evaporator (ATFE) /agitated thin film dryer (ATFD) wherein unreacted phenol and traces of acetone are removed. The present invention provides highly pure, colourless BPA having purity in a range of 99.2-99.8%.
In an embodiment of the present invention, Figure 1 shows the process flow sheet for the production of BPA. The 99% pure phenol and acetone was continuously fed from the top of the fixed bed reactor (FBR) using a gear pump. Fixed bed reactor was charged with 200-260 gm of IER and inert material (to reduce the pressure drop). The N2 pressure across the FBR was mentioned around 2 to 4 bar via back pressure regulator. The reaction product was subsequently fed to agitated thin film dryer (ATFD)/ agitated thin film evaporator (ATFE) where excess of unreacted phenol along with traces of acetone were recovered as top product. The recovered phenol and acetone was recycled to the phenol tank without any further treatment. The bottom product from ATFD/ATFE i.e. crude BPA was taken into the crystallizer where water was added at temperature 80 to 100 °C while toluene was added at temperature 40-50 °C for separation and purification. Crystallization of BPA was carried out in the temperature range of 40-80 °C. Three streams- organic layer, aqueous layer and solid layer moist BPA white crystals were obtained. These moist BPA crystals were dried in a vacuum dryer at 90 °C at 500-800 mbarg. Further organic layer was subjected for recovery of remaining traces of BPA using cooling crystallization at 5 to 20 °C.
In another embodiment, the present invention relates to a process for purification of bisphenol-A (BPA), wherein the process comprising the steps of: a) continuously feeding a mixture of phenol and acetone to a fixed bed reactor (FBR) from a top of the fixed bed reactor; b) charging the fixed bed reactor with an ion exchange resin (IER) as a catalyst to obtain a reaction product mixture; c) feeding the reaction product mixture obtained in step b subsequently to an agitated thin film dryer (ATFD)/agitated thin film evaporator (ATFE) to recover unreacted phenol along with traces of acetone as a top product and crude bisphenol-A (BPA) as a bottom product, respectively; d) feeding the crude bisphenol-A as a bottom product obtained in step c into a crystallizer followed by water and toluene to obtain a plurality of streams selected from a organic layer, a aqueous layer and a solid layer having a plurality of white crystals of moist BPA; and e) separating the plurality of white crystals of moist BPA obtained in step d followed by drying in a vacuum dryer at 90 °C and 500-800 mbarg to obtain the purified dry BPA.
In various embodiments, the organic layer removes impurities present in the crude BPA. The impurities present in the crude BPA are selectively removed by combination of organic and aqueous solvent so that highly pure, colourless moist BPA is achieved. The moist BPA is finally dried using a vacuum dryer at 90 °C under vacuum 500-800 mbarg. In certain embodiments, the aqueous layer removes traces of the unreacted phenol from the plurality of white crystals of moist BPA to obtain the purified dry BPA.
In certain embodiments, the process provides purity of the dry BPA in a range of 99.2-99.8%.
In various embodiments, the BPA is crystallized at a temperature in a range of 40 °C to 80 °C. Further organic layer was subjected for recovery of remaining traces of BPA using cooling crystallization at 5 to 20 °C.
In certain embodiments, the mixture of the step a) comprises a mole ratio of phenol: acetone in a range of 6: 1 to.10:1.
In various embodiments, the reaction of phenol and acetone in fixed bed reactor is carried out at a temperature ranging from 90 °C to 110 °C and N2 pressure ranging from 1 to 4 kg/cm2.
In certain embodiments, the IER is charged to the fixed bed reactor at step b) at a range of 200 to 500 gm (dry weight).
In certain embodiments, the IER is charged to the fixed bed reactor at step b) at an average feed flow rate ranging from 200-1000 gm/hour.
In various embodiments, the process achieves an 80-90% selectivity of BPA and a 70-95% conversion of acetone at temperatures ranging from 90 °C to 110 °C, resulting in the production of colorless purified dry BPA (colourless 4,4’ -BPA product).
In another embodiment, the present invention provides agitated thin film dryer (ATFD)/ agitated thin film evaporator (ATFE) followed by treatment with water and toluene to further remove impurities i.e., two solvent washes to obtain 99.2-99.8% pure bisphenol -A or its analogues and isomers. Also, the usage of ATFD/ ATFE and two solvent washes for the purification and achieve 99.2-99.8% pure bisphenol-A is not known in the prior art.
In another embodiment, the present invention relates a continuous catalytic pilot scale process for the production of bisphenol-A using phenol and acetone as a reactant in the presence of ion exchange resin as a catalyst. In another embodiment, the process of the present invention provides complete recovery of unreacted phenol by Agitated Thin Film Dryer (ATFD)/Agitated Thin Film Evaporator (ATFE).
In yet another embodiment, the present invention uses acidic water for removing the color bodies present in the crude bisphenol-A.
In another embodiment of the present invention, the aqueous stream generated after the crystallization of bisphenol-A can be recycled in the present process. Also, the present invention provides zero liquid discharge.
In another embodiment of the present invention, the unreacted phenol and acetone obtained from Agitated Thin Film Dryer (ATFD)/ Agitated Thin Film Evaporator (ATFE) can be recycled and used as starting material, i.e., feed for fixed bed reactor.
In another embodiment of the present invention, Table 1 shows the effect of operating parameters such as conversion of acetone, phenol conversion, BPA formation and BPA selectivity achieved by the process of present invention.
Another aspect of the present invention is use minimum quantity water (crude BPA to water ratio wt 1: 1) in the downstream processing of crude BPA and the wastewater generated was further treated using cavitation/adsorption/advanced oxidation processes (AOPs) and hybrid AOPs techniques. The purified water further can be used in the process or as plant utilities like cooling water, boiler water, plant cleaning water etc.
Table 1: Effect of various operational parameters on the continuous production of BPA
In another embodiment of the present invention, Table 2 shows the effect of temperature and vacuum on ATFD/ATFE performance on the recovery of phenol. Table 2: Effect of temperature and vacuum on ATFD/ATFE performance for the recovery of phenol
Nomenclatures:
F Feed Flow rate (gm/h)
T ATFD/ATFE temperature (°C)
B ATFD/ATFE bottom (gm)
D Distillate cut of ATFD/ATFE (gm)
V ATFD/ATFE vacuum (torr) t Operational time (hr)
4,4’-BPA: 4,4’-Bisphenol-A
2,4’-BPA: 2,4’-Bisphenol-A
PhOH: Phenol
01 Other impurities
In another embodiment of the present invention, the footprint of downstream processing for the purification of BPA is smaller than conversional process.
In another embodiment of the present invention, the purity of BPA obtained after the crystallization is found to be in the range of 99.2-99.8% which is suitable for further production of epoxy grade resins and polycarbonates.
The Figure 1 shows the process flow sheet for the continuous production of BPA. The 99% pure phenol and acetone was feed from the top of the fixed bed reactor (FBR) using gear pump. Fixed bed reactor was charged with 260 & 500 gm of IER and inert material (to reduce the pressure drop). The N2 pressure across the FBR was mentioned around 2 to 4 bar via back pressure regulator. The reaction product was subsequently feed to agitated thin film dryer (ATFD)/ agitated thin film evaporator (ATFE) where excess of unreacted phenol along with traces of acetone were recovered as top product. The recovered phenol and acetone was recycled to phenol tank without any further treatment. The bottom product from ATFD/ATFE i.e. crude BPA was taken into the crystallizer where water and toluene was added for separation and purification. Crystallization of BPA was carried out in the temperature range of 40 to 80 °C. Three streams organic layer, aqueous layer and solid layer moist BPA white crystals were obtained. These moist BPA crystals were dried in vacuum dryer at 90 °C at 500-800 mbarg.
While the foregoing describes various embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.
EXAMPLES
The present invention is further explained in the form of the following examples. However, it is to be understood that the following examples are merely illustrative and are not to be taken as limitations upon the scope of the invention.
Example 1: General process for the production and purification of Bisphenol - A (BPA)
The experiment of phenol and acetone was carried out for the production of BPA. Phenol and acetone reaction was carried out using IER as catalyst in fixed bed reactor (FBR) in continuous mode of operation. The mole ratios of phenol and acetone 10: 1 to 6: 1 was feed with the flow rate in the range of 200 to 1000 gm/hr at 90 to 110 °C reaction temperature and 1 to 4 kg/cm2 N2 pressure across the FBR. FBR was loaded with 260 to 500 gm of activated IER. The obtained acetone and phenol conversion is in the range of 70-95 % and 13-20 % respectively. The achieved BPA formation rate and BPA selectivity is in the range of 16-20 wt% and 82-87 % respectively. This is shown in Table 1.
Example 2
SN 1 : Experiment for recovery and recycling of phenol was done with the help of agitated thin film dryer (ATFD)/ agitated thin film evaporator (ATFE). The reaction product mixture was feeded to agitated thin film dryer (ATFD)/ agitated thin film evaporator (ATFE) to recover unreacted phenol along with traces of acetone as top product and crude BPA as bottom product. The operating temperature and vacuum of the ATFD/ATFE was 101-104 °C and 2-3 torr respectively. The crude BPA flow rate to ATFD/ATFE was 190-193 gm/hr and it gives bottom product containing 4-4’BPA, phenol and impurities of 82.35%, 2.05% and 3.53% respectively. The distillate of ATFD/ATFE contain phenol, 4-4’BPAand impurities of 96.94%, 0.07% and 0.54% respectively. The ATFD/ATFE bottom product obtained crude BPA was further purified using water and toluene extraction methods. Further BPA was purified using water and toluene as solvent and further crystallization at 40-80 °C gives moist BPA. The moist BPA was further dried in a vacuum dryer at 90 °C at 500-800 mbarg, in order to achieve dried BPA having purity of 99.2- 99.8%.
SN 2: Experiment for recovery and recycling of phenol was done with the help of ATFD/ATFE. The reaction product mixture was feeded to agitated thin film dryer (ATFD)/ agitated thin film evaporator (ATFE) to recover unreacted phenol along with traces of acetone as top product and crude BPA as bottom product. The operating temperature and vacuum of the ATFD/ATFE was 102-106 °C and 3-5 torr respectively. The crude flow rate to ATFD/ATFE was 400-404 gm/hr and it gives bottom product containing 4-4’BPA, phenol and impurities of 90.52%, 0.44% and 3.15% respectively. The distillate of ATFD/ATFE contains phenol, 4-4’BPA and impurities of 98%, 0.12% and 4.21 % respectively. The ATFD/ATFE bottom product obtained crude BPA was further purified using water and toluene extraction methods. Further BPA was purified using water and toluene as solvent and further crystallization at 40-80 °C gives moist BPA. The moist BPA was further dried in a vacuum dryer at 90 °C at 500-800 mbarg, in order to achieve dried BPA having purity of 99.2-99.8%.
SN 3 : Experiment for recovery and recycling of phenol was done with the help of ATFD/ATFE. The reaction product mixture was feeded to agitated thin film dryer (ATFD)/ agitated thin film evaporator (ATFE) to recover unreacted phenol along with traces of acetone as top product and crude BPA as bottom product.. The operating temperature and vacuum of the ATFD/ATFE was 106-111 °C and 3-5 torr respectively. The crude flow rate to ATFD/ATFE was 420-438 gm/hr and it gives bottom product containing 4-4’BPA, phenol and impurities of 87.65%, 0.49% and 3.98% respectively. The distillate of ATFD/ATFE contains phenol, 4-4’BPA and impurities of 99.30%, 0.12% and 0.58% respectively The ATFD/ATFE bottom product obtained crude BPA was further purified using water and toluene extraction methods. Further BPA was purified using water and toluene as solvent and further crystallization at 40-80 °C gives moist BPA. The moist BPA was further dried in a vacuum dryer at 90 °C at 500-800 mbarg, in order to achieve dried BPA having purity of 99.2-99.8%.
SN 4: Experiment for recovery and recycling of phenol was done with the help of ATFD/ATFE. The reaction product mixture was feeded to agitated thin film dryer (ATFD)/ agitated thin film evaporator (ATFE) to recover unreacted phenol along with traces of acetone as top product and crude BPA as bottom product. The operating temperature and vacuum of the ATFD/ATFE was 112-121°C and 3-5 torr respectively. The crude flow rate to ATFD/ATFE was 505-511 gm/hr and it gives bottom product containing 4-4’BPA, phenol and impurities of 88.25%, 2.55% and 2.94% respectively. The distillate of ATFD/ATFE contains phenol, 4-4’BPA and impurities of 99.35%, 0.12% and 4.45% respectively. The ATFD/ATFE bottom product obtained crude BPA was further purified using water and toluene extraction methods. Further, BPA was purified using water and toluene as solvent and further crystallization at 40-80 °C gives moist BPA.
The moist BPA was further dried in a vacuum dryer at 90 °C at 500-800 mbarg, in order to achieve dried BPA having purity of 99.2-99.8%. This is shown in Table 2.
A skilled artisan will appreciate that the quantity and each of the ingredients can be used in different combinations or singly. All such variations and combinations would be falling within the scope of present disclosure.
Example 3: Characterization of process purified Bisphenol-A samples by various techniques
1) Purity Analysis of Bisphenol A by HPLC method
HPLC equipped with UV detector was used for evaluating impurities in process purified Bisphenol A samples. HPLC technique equipped with UV detector is very versatile technique for both volatile and non-volatile compounds possessing chromogenic/chromophore groups present in aromatic ring compounds.
The Equipment details and parameters for the method of analysis are: Equipment (HPLC): Agilent 1260 Infinity; Mobile Phase Composition: Methanol: Water (60:40, V/V); Column: Hypersil Gold Cl 8, 250 mm (L) x 4.6 mm(id), 5 /urn Particle Size', Sample Injection Volume: 10 pL; Flow rate: 1 mL/min; Run time: 60 min; Detector: UV 230 nm; and Sample Concentration: 1000 ppm(w/v).
Bisphenol A samples after downstream purification were subjected to HPLC analysis for purity testing as per chromatographic parameters described above. The runs were extended up to sufficient length of time (60 min) to detect every trace of impurities. A typical chromatogram depicting the separation of impurities in Bisphenol A sample is given in Fig.2 (Full scale chromatogram), and Fig.3 (Zoomed scale chromatogram), whereas the HPLC purity analysis report (Area% 99.89) is presented in Fig.4.
2) Impurity Profiling by LCMS (Agilent QTOF) The impurity profiling of process purified Bisphenol A sample was done using Agilent LCMS QTOF instrument. The samples were run with -ve ESI mode and spectral data was acquired using Agilent MassHunter software. Besides phenol (unreacted starting material), the other four impurities at trace levels were detected in LCMS analysis. Table 3 shows the list of Impurities detected in LCMS analysis along with its molar mass, and Eig. 5 represents the identified peaks of impurities along with Area% purity results. The LCMS spectra confirms presence of minimum impurities presence (considering smaller peak heights), the impurities were namely 2 (2,4’- Bisphenol A), Impurity 3 (Chroman I compound), Impurity 4 (Chroman II compound), and Impurity 5 (Trisphenol), respectively.
Table 3: List of Impurities detected in LCMS Analysis.
3) NMR Analysis
NMR and 13C NMR analyses were performed to compare process purified Bisphenol-A sample (CSIR-NCL) with that of Aldrich Bisphenol-A standard sample. The samples were found almost comparable, however, unlike LCMS (TOF), NMR could not detect of 2, 4’ isomer of BPA or other impurities present in samples. The 1 H NMR and 13C NMR spectra peak values of process purified Bisphenol-A sample of the present case, respectively, are:
’H NMR (400 MHz, DMSOd6): d 9.21 (s, 2H), 6.97 (d, 4H), 6.62 (d, 4H), 1.51 (s, 6H); and 13C NMR (125 MHz, DMSOd6): d 154.9, 141.2, 127.4, 114.8, 41.0, 30.9. These NMR peak values are in line with the standard Bisphenol-A sample (Aldrich Bisphenol-A standard) peak values.
4) Melting Point of process purified Bisphenol-A sample with standard commercial bisphenol-A sample
The melting points (°C) were determined by using DSC analysis. Figs. 6 and 7 report graphical profiles of melting point and sample heating conditions for commercial Bisphenol-A sample (Aldrich Bisphenol-A standard), (M.P. 157.1 °C) and process purified Bisphenol-A sample (M.P. 156.7 °C). The melting point both samples were nearly same.
5) Crystallinity by XRD Analysis
The XRD analysis was performed to compare crystallinity of commercial Bisphenol-A sample (Aldrich Bisphenol-A standard) and process purified bisphenol-A samples (CSIR-NCL). Fig.8 depicts superimposed images of XRD Profiles of commercial Bisphenol-A sample (Aldrich standard), and process purified bisphenol-A sample (CSIR-NCL) of the present disclosure.
The sharper peaks in all the XRD pattern indicate that the samples are crystalline in nature and it is evident that XRD profile of STD Aldrich sample is matching with that Process purified Bisphenol A sample of the present disclosure.
The foregoing examples are merely illustrative and are not to be taken as limitations upon the scope of the invention. Various changes and modifications to the disclosed embodiments will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the scope of the invention.
ADVANTAGES OF THE PRESENT INVENTION
1. Present invention describes the complete recovery of unreacted phenol by flash distillation / Agitated Thin Film Dryer (ATFD) 2. Impurities present in the crude BPA were selectively removed by combination organic, aqueous solvent along with activated carbon so that highly pure, colorless 95 to 99.8% BPA can be achieved.
3. Present invention discloses the use of acidic water for removing the color bodies present in the Crude Bisphenol-A.
4. The aqueous stream generated after the crystallization of Bisphenol-A can be recycled in the process.
5. The present invention provides highly pure and colorless BPA.
6. The present invention provides pure BPA which is suitable for further production of epoxy grade resins and polycarbonates .The present invention provides the process of purification of BPA wherein the complete recovery of unreacted phenol & acetone is achieved using Agitated Thin Film Dryer (ATFD)/ Agitated Thin Film Evaporator (ATFE).
7. The present invention provides a process having zero liquid discharge.
8. The present invention provides a process for which the footprint of downstream processing for the purification of BPA is smaller than conventional process.
9. Another advantage present invention is use minimum quantity water (crude BPA to water ratio wt 1 : 1) in the downstream processing of crude BPA and the wastewater generated was further treated using cavitation/adsorption/ advanced oxidation processes (AOPs) and hybrid AOPs techniques. The purified water further can be used in the process or as plant utilities like cooling water, boiler water, plant cleaning water etc.

Claims

WE CLAIM:
1. A process for purification of bisphenol-A BPA, wherein the process comprising the steps of: a) continuously feeding a mixture of phenol and acetone to a fixed bed reactor ; b) charging the fixed bed reactor with an ion exchange resin as a catalyst to obtain a reaction product mixture; c) feeding the reaction product mixture subsequently to an agitated thin film dryer /agitated thin film evaporator to recover unreacted phenol along with traces of acetone as a top product and crude bisphenol-A as a bottom product, respectively; d) feeding the crude bisphenol-A as a bottom product obtained in step c into a crystallizer followed by water and toluene to obtain a plurality of streams selected from a organic layer, a aqueous layer and a solid layer having a plurality of white crystals of moist bisphenol-A; and e) separating the plurality of white crystals of moist bisphenol-A obtained in step d and followed by drying in a vacuum dryer at 90 °C and 500-800 mbarg to obtain the purified dry bisphenol-A .
2. The process as claimed in claim 1 , wherein the organic layer removes impurities present in the crude bisphenol-A.
3. The process as claimed in claim 1, wherein the aqueous layer removes traces of the unreacted phenol from the plurality of white crystals of moist BPA to obtain the purified dry bisphenol-A.
4. The process as claimed in claim 1 , wherein the process provides purity of the dry bisphenol - A in a range of 99.2-99.8%.
5. The process as claimed in claim 1, wherein the bisphenol-A is crystallized at a temperature in a range of 40 °C to 80 °C.
6. The process as claimed in claim 1, wherein the mixture of the step a) comprises a mole ratio of phenol: acetone in a range of 6: 1 to.10: 1.
7. The process as claimed in claim 1 , wherein the reaction of phenol and acetone in fixed bed reactor is carried out at a temperature ranging from 90 °C to 110 °C and N2 pressure ranging from 1 to 4 kg/cm2.
8. The process as claimed in claim 1, wherein the ion exchange resin is charged to the fixed bed reactor at a range of 200 to 500 gm (dry weight).
9. The process as claimed in claim 1, wherein the ion exchange resin is charged to the fixed bed reactor at an average feed flow rate ranging from 200-1000 gm/hour.
10. The process as claimed in claim 1, wherein the process achieves an 80-90% selectivity of BPA and a 70-95% conversion of acetone at temperatures ranging from 90 °C to 110 °C, resulting in the production of colorless purified dry bisphenol-A.
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