CN118307389A - Method for recovering bisphenol A by catalyzing alcoholysis of polycarbonate - Google Patents
Method for recovering bisphenol A by catalyzing alcoholysis of polycarbonate Download PDFInfo
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- bisphenol
- polycarbonate
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- IISBACLAFKSPIT-UHFFFAOYSA-N bisphenol A Chemical compound C=1C=C(O)C=CC=1C(C)(C)C1=CC=C(O)C=C1 IISBACLAFKSPIT-UHFFFAOYSA-N 0.000 title claims abstract description 183
- 239000004417 polycarbonate Substances 0.000 title claims abstract description 68
- 238000006136 alcoholysis reaction Methods 0.000 title claims abstract description 45
- 238000000034 method Methods 0.000 title claims abstract description 45
- 229920000515 polycarbonate Polymers 0.000 title claims abstract description 36
- 239000003054 catalyst Substances 0.000 claims abstract description 65
- 150000004714 phosphonium salts Chemical class 0.000 claims abstract description 31
- 150000002148 esters Chemical class 0.000 claims abstract description 16
- 230000003197 catalytic effect Effects 0.000 claims abstract description 6
- 229920000402 bisphenol A polycarbonate polymer Polymers 0.000 claims abstract 3
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 75
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 37
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 claims description 24
- 238000002156 mixing Methods 0.000 claims description 17
- 238000004821 distillation Methods 0.000 claims description 16
- ZLLNYWQSSYUXJM-UHFFFAOYSA-N phenol tetraphenylphosphanium Chemical compound C1(=CC=CC=C1)O.C1(=CC=CC=C1)[P+](C1=CC=CC=C1)(C1=CC=CC=C1)C1=CC=CC=C1 ZLLNYWQSSYUXJM-UHFFFAOYSA-N 0.000 claims description 14
- 239000012265 solid product Substances 0.000 claims description 10
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 9
- 125000001997 phenyl group Chemical group [H]C1=C([H])C([H])=C(*)C([H])=C1[H] 0.000 claims description 8
- 125000003118 aryl group Chemical group 0.000 claims description 7
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 6
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 claims description 6
- ZXEKIIBDNHEJCQ-UHFFFAOYSA-N isobutanol Chemical compound CC(C)CO ZXEKIIBDNHEJCQ-UHFFFAOYSA-N 0.000 claims description 6
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 claims description 6
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 claims description 6
- -1 tetramethyl phosphonium phenol Chemical compound 0.000 claims description 6
- 125000003710 aryl alkyl group Chemical group 0.000 claims description 5
- 239000012295 chemical reaction liquid Substances 0.000 claims description 5
- 125000000753 cycloalkyl group Chemical group 0.000 claims description 5
- 125000004432 carbon atom Chemical group C* 0.000 claims description 4
- WAGFXJQAIZNSEQ-UHFFFAOYSA-M tetraphenylphosphonium chloride Chemical compound [Cl-].C1=CC=CC=C1[P+](C=1C=CC=CC=1)(C=1C=CC=CC=1)C1=CC=CC=C1 WAGFXJQAIZNSEQ-UHFFFAOYSA-M 0.000 claims description 4
- 150000001298 alcohols Chemical class 0.000 claims description 3
- 150000004649 carbonic acid derivatives Chemical class 0.000 claims description 3
- 150000004820 halides Chemical class 0.000 claims description 3
- QAOWNCQODCNURD-UHFFFAOYSA-M hydrogensulfate Chemical compound OS([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-M 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 claims description 3
- 230000001681 protective effect Effects 0.000 claims description 3
- XVHQFGPOVXTXPD-UHFFFAOYSA-M tetraphenylphosphanium;hydroxide Chemical compound [OH-].C1=CC=CC=C1[P+](C=1C=CC=CC=1)(C=1C=CC=CC=1)C1=CC=CC=C1 XVHQFGPOVXTXPD-UHFFFAOYSA-M 0.000 claims description 3
- 230000035484 reaction time Effects 0.000 claims description 2
- 238000006243 chemical reaction Methods 0.000 abstract description 31
- 238000011084 recovery Methods 0.000 abstract description 14
- 230000008569 process Effects 0.000 abstract description 11
- 239000002699 waste material Substances 0.000 abstract description 9
- 239000002904 solvent Substances 0.000 abstract description 6
- 230000007613 environmental effect Effects 0.000 abstract description 4
- 238000000926 separation method Methods 0.000 abstract description 3
- 231100000086 high toxicity Toxicity 0.000 abstract description 2
- 239000002910 solid waste Substances 0.000 abstract description 2
- 239000000126 substance Substances 0.000 abstract description 2
- 239000000203 mixture Substances 0.000 description 33
- 239000007787 solid Substances 0.000 description 23
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 18
- 238000006731 degradation reaction Methods 0.000 description 15
- 230000015556 catabolic process Effects 0.000 description 14
- 229920000642 polymer Polymers 0.000 description 13
- 238000001035 drying Methods 0.000 description 12
- 238000001914 filtration Methods 0.000 description 12
- 239000008188 pellet Substances 0.000 description 11
- 239000007790 solid phase Substances 0.000 description 11
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 10
- 238000001816 cooling Methods 0.000 description 10
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 7
- 239000000047 product Substances 0.000 description 7
- 238000006116 polymerization reaction Methods 0.000 description 6
- 239000003513 alkali Substances 0.000 description 5
- 239000000178 monomer Substances 0.000 description 5
- 238000004064 recycling Methods 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 4
- 238000003786 synthesis reaction Methods 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 125000001931 aliphatic group Chemical group 0.000 description 3
- 150000001450 anions Chemical class 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 239000002608 ionic liquid Substances 0.000 description 3
- 125000004437 phosphorous atom Chemical group 0.000 description 3
- 238000001228 spectrum Methods 0.000 description 3
- 125000000094 2-phenylethyl group Chemical group [H]C1=C([H])C([H])=C(C([H])=C1[H])C([H])([H])C([H])([H])* 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-M Bicarbonate Chemical compound OC([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-M 0.000 description 2
- 238000001157 Fourier transform infrared spectrum Methods 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 2
- 125000000217 alkyl group Chemical group 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 125000001797 benzyl group Chemical group [H]C1=C([H])C([H])=C(C([H])=C1[H])C([H])([H])* 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 125000000113 cyclohexyl group Chemical group [H]C1([H])C([H])([H])C([H])([H])C([H])(*)C([H])([H])C1([H])[H] 0.000 description 2
- 125000001511 cyclopentyl group Chemical group [H]C1([H])C([H])([H])C([H])([H])C([H])(*)C1([H])[H] 0.000 description 2
- 230000006378 damage Effects 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- VILAVOFMIJHSJA-UHFFFAOYSA-N dicarbon monoxide Chemical compound [C]=C=O VILAVOFMIJHSJA-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229920006351 engineering plastic Polymers 0.000 description 2
- 125000001495 ethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 description 2
- 238000007327 hydrogenolysis reaction Methods 0.000 description 2
- 230000007062 hydrolysis Effects 0.000 description 2
- 238000006460 hydrolysis reaction Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 229910021645 metal ion Inorganic materials 0.000 description 2
- 125000001624 naphthyl group Chemical group 0.000 description 2
- 239000012038 nucleophile Substances 0.000 description 2
- 230000000269 nucleophilic effect Effects 0.000 description 2
- 239000012434 nucleophilic reagent Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 125000004344 phenylpropyl group Chemical group 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- 125000001436 propyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])[H] 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 238000005809 transesterification reaction Methods 0.000 description 2
- 125000000008 (C1-C10) alkyl group Chemical group 0.000 description 1
- 125000003837 (C1-C20) alkyl group Chemical group 0.000 description 1
- RNFJDJUURJAICM-UHFFFAOYSA-N 2,2,4,4,6,6-hexaphenoxy-1,3,5-triaza-2$l^{5},4$l^{5},6$l^{5}-triphosphacyclohexa-1,3,5-triene Chemical compound N=1P(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP(OC=2C=CC=CC=2)(OC=2C=CC=CC=2)=NP=1(OC=1C=CC=CC=1)OC1=CC=CC=C1 RNFJDJUURJAICM-UHFFFAOYSA-N 0.000 description 1
- 125000005915 C6-C14 aryl group Chemical group 0.000 description 1
- 241000282414 Homo sapiens Species 0.000 description 1
- 208000027418 Wounds and injury Diseases 0.000 description 1
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 125000003158 alcohol group Chemical group 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 125000000484 butyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])C([H])([H])[H] 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000004132 cross linking Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical group COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- 230000002124 endocrine Effects 0.000 description 1
- 125000004185 ester group Chemical group 0.000 description 1
- 229940011871 estrogen Drugs 0.000 description 1
- 239000000262 estrogen Substances 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 239000003063 flame retardant Substances 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000009396 hybridization Methods 0.000 description 1
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 208000014674 injury Diseases 0.000 description 1
- 239000000543 intermediate Substances 0.000 description 1
- 150000002605 large molecules Chemical class 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 150000002736 metal compounds Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000011943 nanocatalyst Substances 0.000 description 1
- 239000002159 nanocrystal Substances 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 238000003415 nucleophilic catalysis Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 125000005561 phenanthryl group Chemical group 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 230000036632 reaction speed Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 230000001502 supplementing effect Effects 0.000 description 1
- USFPINLPPFWTJW-UHFFFAOYSA-N tetraphenylphosphonium Chemical compound C1=CC=CC=C1[P+](C=1C=CC=CC=1)(C=1C=CC=CC=1)C1=CC=CC=C1 USFPINLPPFWTJW-UHFFFAOYSA-N 0.000 description 1
- 238000004227 thermal cracking Methods 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
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- 231100000419 toxicity Toxicity 0.000 description 1
- 230000001988 toxicity Effects 0.000 description 1
- 229910021655 trace metal ion Inorganic materials 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 238000002834 transmittance Methods 0.000 description 1
- 239000002912 waste gas Substances 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 239000011701 zinc Substances 0.000 description 1
Landscapes
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention relates to the technical field of solid waste recovery, and provides a method for recovering bisphenol A by catalyzing alcoholysis of polycarbonate. The invention adopts the phosphonium salt catalyst to catalyze the alcoholysis reaction of bisphenol A polycarbonate, the phosphonium salt catalyst has simple structure, low price, mild reaction condition, high catalytic activity and easy recovery; the invention does not use any extra solvent in the depolymerization process, has simple operation, economy and environmental protection, and the obtained depolymerization products bisphenol A and carbonic ester can be used for repolymerization to synthesize polycarbonate, thus realizing the green circulation of bisphenol A polycarbonate in a real sense. In conclusion, the invention solves the problems of insufficient temperature, high toxicity, high cost, difficult separation and the like of the catalyst system in the existing chemical recovery of bisphenol A type polycarbonate waste, and has wide application prospect.
Description
Technical Field
The invention relates to the technical field of solid waste recovery, in particular to a method for recovering bisphenol A by catalyzing alcoholysis of polycarbonate.
Background
Polycarbonates (PCs) are a general term for high molecular weight compounds containing a carbonate in the molecular main chain, and polycarbonates are classified into various types of aliphatic, aromatic, aliphatic-aromatic, etc. depending on the structure of the ester group. Wherein, the application of the aliphatic and aliphatic-aromatic polycarbonates in engineering plastics is limited due to the low mechanical properties of the aliphatic and aliphatic-aromatic polycarbonates, and only the aromatic polycarbonates are industrially produced. At present, bisphenol A type polycarbonate (BPA-PC) is the most widely used.
BPA-PC is a thermoplastic engineering plastic with excellent comprehensive performance, has good mechanical property, optical property, thermal property and flame retardant property, and is widely applied to various fields. The total consumption of the global BPA-PC exceeds 700 ten thousand tons, the waste is slowly degraded in the natural world, the slow degradation process not only causes the pollution problem of plastics, but also slowly migrates and releases bisphenol A (BPA) contained in the waste, and the BPA is identified as having slow toxic effect and estrogen effect, can cause endocrine dyscrasia, and harm to human beings and injury to natural organisms. The recycling of BPA-PC waste is an effective method for treating waste plastics, saving fossil energy and avoiding bad influence of BPA on organisms.
Traditional polycarbonate recovery methods include mechanical recovery methods, which tend to result in degradation of polycarbonate quality, and energy recovery methods; the energy recovery method burns and utilizes heat energy, which not only causes the loss of fossil energy, but also produces waste gas which is not beneficial to environmental protection. The chemical recovery method can convert PC waste into monomers or raw materials to form a sustainable green circular economy mode, and is more in line with the concept of environmental protection and sustainable development.
At present, the main methods for chemically recycling polycarbonate are as follows: thermal cracking, hydrolysis, hydrogenolysis and alcoholysis recovery. However, these methods also have problems such as: the pyrolysis reaction temperature is high, and the products are complex and difficult to separate; the hydrolysis method is unfavorable for environmental protection because of unstable carbon-based products and CO 2 generated by decomposition, and wastes carbon-based resources in PC; the hydrogenolysis process requires high pressure and high temperature and the catalyst is mainly noble metal and has high cost. The alcoholysis method can realize recovery of BPA and carbon groups in alcohol by PC, is an ideal PC recovery mode, particularly methanol decomposition, can realize degradation of PC into polymerized monomers and then polymerization, and forms a true green cycle, and the principle schematic diagram of the alcoholysis method for recovering polycarbonate is shown in figure 1.
At present, alcoholysis catalysts reported in the literature are mainly organic alkali, inorganic alkali, metal salt, nano oxide thereof and ionic liquid systems, and different systems have certain defects, such as concentrated alkali or super alkali NaOH (polymer, 2000, 41:6759-6753), DTU (polymer, 2018, 143:106-114) and TBD (Green chem,2017, 19:5422-5434), under the condition that solvents are not adopted, the addition amount reaches more than 10mol percent to achieve ideal conversion rate, the higher addition amount not only can lead to equipment corrosion, but also can waste a large amount of water in the post-treatment process, and trace residual concentrated alkaline catalyst systems can lead to cross-linking hybridization when BPA is repolymerized into PC, so that depolymerized product BPA is difficult to be used as PC polymerization monomer for repolymerization; solid nanocatalysts such as ZnO-NPs/NBuCl (JMol. Catalyst. A-Chem,2017, 426:107-116), ceO 2 nanocrystals (catalyst. Lett.2017, 147:2940-2949) require a large amount of solvent (toluene, THF, etc.) to increase the reaction rate, which not only pollutes the environment but also causes complicated subsequent treatment; the ionic liquid (J.Hazard. Mater.2011, 189:249-254) can obtain good conversion rate under the condition of not using a solvent, but the dosage of the ionic liquid is higher, the synthesis process is complex, and the cost is high; in addition, research has found that metal compounds such as an organic zinc catalyst (CN 113912477A) have good catalytic activity on PC alcoholysis, but metal ions have certain toxicity on the environment, and residual trace metal ions enter BPA, so that the light transmittance of a polymerized PC product of the BPA is possibly reduced due to the influence of the metal ions.
In summary, the existing method for catalyzing the alcoholysis of the PC has the problems that the catalyst is complex to operate and high in cost, and the recovered BPA is difficult to use as a PC polymerization monomer, so that the method for catalyzing the alcoholysis of the PC has low cost, low treatment cost and high product BPA quality.
Disclosure of Invention
In view of this, the present invention provides a method for recovering bisphenol A by catalytic alcoholysis of polycarbonate. The method provided by the invention is simple to operate, low in cost, high in quality of the recovered BPA, and capable of being used as a monomer to be polymerized to synthesize BPA-PC, so that the green cycle of the BPA-PC is truly realized.
In order to achieve the above object, the present invention provides the following technical solutions:
A method for recovering bisphenol a by catalytic alcoholysis of polycarbonate, comprising the steps of:
Mixing bisphenol A type polycarbonate, alcohol and phosphonium salt catalyst for alcoholysis reaction to obtain bisphenol A and carbonic ester; the structural formula of the phosphonium salt catalyst is shown as formula I:
In formula I: r 1～R4 is independently C 1-C10 -alkanyl, C 6-C14 -aryl, C 7-C15 -arylalkyl, or C 5-C6 -cycloalkyl; x n- is hydroxide, sulfate, bisulfate, bicarbonate, carbonate, halide and-OR 5,R5 is C 6-C14 aryl, C 7-C15 arylalkyl, C 5-C6 cycloalkyl OR C 1-C20 alkanyl, n is 1 OR 2.
Preferably, in formula I: r 1～R4 is independently methyl or phenyl; r 5 is phenyl.
Preferably, the phosphonium salt catalyst is one or more of tetraphenyl phosphonium hydroxide, tetraphenyl phosphonium phenol, tetraphenyl phosphonium chloride and tetramethyl phosphonium phenol.
Preferably, the mass of the phosphonium salt catalyst is 1-10% of the mass of the bisphenol A type polycarbonate.
Preferably, the alcohol has 1 to 4 carbon atoms.
Preferably, the alcohol comprises one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, ethylene glycol and glycerol.
Preferably, the mass ratio of the alcohol to the bisphenol A type polycarbonate is (0.25 to 5): 1.
Preferably, the temperature of the alcoholysis reaction is 80-160 ℃, and the reaction time is 1-30 h; the pressure of the alcoholysis reaction is normal pressure; the alcoholysis reaction is carried out under a protective atmosphere.
Preferably, after the alcoholysis reaction is finished, the method further comprises the step of carrying out reduced pressure distillation on the obtained reaction liquid to obtain a solid product and a fraction; the solid product is bisphenol A and phosphonium salt catalyst; the fractions are carbonates and alcohols.
Preferably, the temperature of the reduced pressure distillation is 50-70 ℃ and the pressure is-0.01-0.1 MPa.
The invention provides a method for recycling bisphenol A by catalyzing alcoholysis of polycarbonate, which comprises the following steps: mixing bisphenol A type polycarbonate, alcohol and phosphonium salt catalyst for alcoholysis reaction to obtain bisphenol A and carbonic ester; the structural formula of the phosphonium salt catalyst is shown as formula I. The invention adopts the phosphonium salt catalyst to catalyze the alcoholysis reaction of the polycarbonate, the phosphonium salt catalyst has simple structure, low price, mild required reaction condition and high catalytic activity, can play a good role in catalyst under low load, obtains extremely high yield, almost has no byproducts, can greatly shorten the production period, improves the production benefit and is suitable for industrialization; in addition, the phosphonium salt catalyst adopted by the invention is easy to recycle, even if a trace amount of the phosphonium salt catalyst remains in BPA, the phosphonium salt catalyst is also a main catalyst for producing PC by polymerization of an ester exchange process, so that the BPA repolymerization is not affected, and the industrial application is easy; the method does not use any extra solvent in the alcoholysis process, is simple to operate, is economical and environment-friendly, and can recycle all components of the system; the depolymerization products bisphenol A and carbonic ester obtained by the invention can be used for repolymerization to synthesize PC, and can truly realize the green cycle of BPA-PC.
Drawings
FIG. 1 is a schematic diagram of the principle of recovery of polycarbonate by an alcoholysis process;
FIG. 2 is a 1 HNMR spectrum of the recovered BPA and pure BPA of example 1;
FIG. 3 is a FTIR spectrum of BPA recovered in example 1 and pure BPA.
Detailed Description
The invention provides a method for recycling bisphenol A by catalyzing alcoholysis of polycarbonate, which comprises the following steps:
Mixing bisphenol A type polycarbonate, alcohol and phosphonium salt catalyst for alcoholysis reaction to obtain bisphenol A and carbonic ester; the structural formula of the phosphonium salt catalyst is shown as formula I:
In formula I: r 1～R4 is independently C 1-C10 -alkanyl, C 6-C14 -aryl, C 7-C15 -arylalkyl, or C 5-C6 -cycloalkyl; x n- is hydroxide, sulfate, bisulfate, bicarbonate, carbonate, halide and-OR 5,R5 is C 6-C14 aryl, C 7-C15 arylalkyl, C 5-C6 cycloalkyl OR C 1-C20 alkanyl, n is 1 OR 2.
In the present invention, in the R 1～R4, the C 1-C10 alkyl group is preferably a C 1-C5 alkanyl group, more preferably a straight-chain alkyl group, further preferably a methyl group, an ethyl group, a propyl group or a butyl group; c 6-C14 aryl is preferably phenyl, naphthyl, fistular or phenanthryl, and the C 7-C15 arylalkyl is preferably benzyl, phenethyl or phenylpropyl; c 5-C6 cycloalkyl is preferably cyclopentyl or cyclohexyl.
In the present invention, in the R 5, the C 6-C14 aryl group is preferably phenyl, naphthyl or fistular; c 7-C15 arylalkyl is preferably benzyl, phenethyl or phenylpropyl; c 5-C6 cycloalkyl is preferably cyclopentyl or cyclohexyl; the C 1-C20 alkyl group is preferably a straight chain alkyl group, more preferably methyl, ethyl or propyl.
Further, in formula I: r 1-R4 is independently preferably methyl or C 6-C14 aryl, more preferably methyl or phenyl; r 5 is preferably phenyl.
In the present invention, the phosphonium salt catalyst is preferably one or more of tetraphenylphosphonium hydroxide, tetraphenylphosphonium phenol, tetraphenylphosphonium chloride and tetramethylphosphonium phenol.
The phosphonium salt catalyst adopted by the invention has the advantages of simple structure, low price, no use of any extra solvent in the alcoholysis process, low catalyst consumption, mild alcoholysis reaction condition, easy recovery, and easy industrial application, even if trace amount of catalyst remains in BPA, and is also the main catalyst for producing PC by polymerization in the transesterification process, so that the polymerization of BPA is not influenced.
Taking tetraphenylphosphonium phenol as an example, the catalyst mechanism of the phosphonium salt catalyst used in the present invention is described: tetraphenylphosphonium phenol is used as a nucleophilic reagent and alkali to promote transesterification reaction, in the nucleophilic reagent process, the P atom in the cation center of the quaternary phosphonium salt is negatively charged, and positive charges of the cations are mainly concentrated on surrounding hydrogen atoms, so that anion binding sites can be formed around alkyl hydrogen atoms close to the center P atom, different anions, anion transition states and intermediates can be stabilized, and the P atom with negative charges is nucleophilic to attack carbonyl carbon on PC to promote depolymerization of the PC; the surrounding tetraphenylphosphonium is combined with phenoxy anions, the electronegativity of oxygen atoms on the phenoxy anions is strong, the oxygen anions form weak hydrogen bonds and activate nucleophiles through the hydrogen bonds, so that alcohol has stronger nucleophilic performance as the nucleophile, in this case, the initial negative charge of oxygen on carbonyl carbon can be stabilized by providing hydrogen bonds from another alcohol molecule or both, and nucleophilic catalysis is a main path of the reaction.
In the present invention, the mass of the phosphonium salt catalyst is preferably 1 to 10%, more preferably 2 to 8%, and even more preferably 3.4% of the mass of the bisphenol a type polycarbonate.
In the present invention, the alcohol preferably has 1 to 4 carbon atoms, more preferably 1 to 2 carbon atoms; the alcohol preferably comprises one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, ethylene glycol and glycerol, more preferably methanol, ethanol or glycerol, most preferably methanol; in the present invention, according to the type of alcohol used, bisphenol A type polycarbonate is subjected to alcoholysis to obtain a carbonate of a corresponding structure, for example, methanol is used as an alcoholysis reagent, and the obtained carbonate is dimethyl carbonate.
In the present invention, the mass ratio of the alcohol to the bisphenol A type polycarbonate is preferably (0.25 to 5): 1, more preferably (0.5 to 3): 1. The invention can effectively control the reaction speed by controlling the alcohol dosage within the range.
In the present invention, the temperature of the alcoholysis reaction is preferably 80 to 160 ℃, preferably 110 ℃, and the time of the alcoholysis reaction is preferably 1 to 30 hours, more preferably 2 to 20 hours, still more preferably 5 to 10 hours; in embodiments of the present invention, FITR is preferably used to detect the end point of the reaction; the pressure of the alcoholysis reaction is preferably normal pressure; the alcoholysis reaction is preferably carried out under a protective atmosphere, which is preferably an inert gas; in the invention, too low reaction temperature can lead to too slow degradation speed or no reaction, is not suitable for industrial production, and too high temperature can lead to excessive side reactions and difficult separation.
In the specific embodiment of the present invention, it is preferable that bisphenol A type polycarbonate is placed in a pressure-resistant bottle, then a catalyst and alcohol are sequentially added, and then the temperature is raised to the temperature of the alcoholysis reaction, and the alcoholysis reaction is carried out under stirring.
After the alcoholysis reaction is completed, the present invention preferably further comprises: performing reduced pressure distillation on the obtained reaction liquid to obtain a solid product and a fraction; the solid product is bisphenol A and phosphonium salt catalyst; the fractions are carbonates and alcohols. In the embodiment of the present invention, it is preferable that the obtained reaction liquid is cooled to room temperature and then distilled under reduced pressure; the temperature of the reduced pressure distillation is preferably 50-70 ℃, and the pressure is preferably-0.01-0.1 MPa. In the present invention, the solid product is a mixture of bisphenol A and a phosphonium salt catalyst, and since the phosphonium salt catalyst is soluble in water and bisphenol A is insoluble in water, the catalyst can be separated and recovered by: mixing the solid product with water, filtering to obtain water phase as catalyst water solution, evaporating and drying the catalyst water solution to obtain the recovered phosphonium salt catalyst. Or in the specific embodiment of the invention, the phosphonium salt catalyst adopted by the invention can be used in the synthesis process of PC, the catalyst in the recovered solid product has no influence on the subsequent synthesis of PC, and the catalyst can be directly used for the synthesis of PC by calculating and properly supplementing the reaction raw materials, so that the step of recovering the catalyst is not needed.
The following description of the embodiments of the present invention will clearly and fully describe the technical solutions of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The PC pellets in the following examples are bisphenol A type polycarbonate (BPA-PC).
Example 1
5.0G of PC pellets were placed in a pressure-resistant bottle, 0.17g of tetraphenylphosphonium phenol and 2.5g of methanol were sequentially added, the temperature was raised to 110℃and the mixture was stirred for 2 hours, after which the polymer was completely dissolved, and the completion of the reaction was detected by FTIR. The reaction solution is completely cooled to room temperature, the degradation solution is distilled under reduced pressure at 50 ℃ and minus 0.1MPa, the fraction is a mixture of methanol and carbonic ester, the solid sample is a mixture of BPA and a catalyst, and the catalyst is separated from the solid product for calculating the yield of the BPA, specifically: mixing the solid sample with water, filtering, and drying the solid phase to obtain the pure BPA, wherein the yield of the BPA is 98.2%.
FIG. 2 is a 1 HNMR spectrum of recovered BPA versus pure BPA; FIG. 3 is a FTIR spectrum of recovered BPA versus pure BPA; as can be seen from FIGS. 2-3, the spectra of the recovered BPA according to the present invention are substantially identical to those of pure BPA. The results in FIGS. 2-3 show that the depolymerization products of the present invention, BPA, are pure and free of oligomers or impurities.
Example 2
5.0G of PC pellets were placed in a pressure-resistant bottle, 0.05g of tetraphenylphosphonium phenol and 2.5g of methanol were sequentially added, the temperature was raised to 110℃and the mixture was stirred for 6 hours, after which the polymer was completely dissolved, and the completion of the reaction was detected by FTIR. And (3) completely cooling the reaction solution to room temperature, carrying out reduced pressure distillation on the degradation solution at 50 ℃ and minus 0.1MPa, wherein the fraction is a mixture of methanol and carbonic ester, the solid sample is a mixture of BPA and a catalyst, mixing the solid sample with water, filtering, and drying the solid phase to obtain pure BPA, wherein the yield of the BPA is 94.3%.
Example 3
5.0G of PC pellets were placed in a pressure-resistant bottle, 0.50g of tetraphenylphosphonium phenol and 2.5g of methanol were sequentially added, the temperature was raised to 110℃and the mixture was stirred for 1 hour, after which the polymer was completely dissolved, and the completion of the reaction was detected by FTIR. And (3) completely cooling the reaction solution to room temperature, carrying out reduced pressure distillation on the degradation solution at 50 ℃ and minus 0.1MPa, wherein the fraction is a mixture of methanol and carbonic ester, the solid sample is a mixture of BPA and a catalyst, mixing the solid sample with water, filtering, and drying the solid phase to obtain the pure BPA, wherein the yield of the BPA is 98.9%.
Example 4
5.0G of PC pellets were placed in a pressure-resistant bottle, 0.17g of tetraphenylphosphonium phenol and 2.5g of methanol were sequentially added, the temperature was raised to 80℃and the mixture was stirred for 27 hours, after which the polymer was completely dissolved, and the completion of the reaction was detected by FTIR. And (3) completely cooling the reaction solution to room temperature, carrying out reduced pressure distillation on the degradation solution at 50 ℃ and minus 0.1MPa, wherein the fraction is a mixture of methanol and carbonic ester, the solid sample is a mixture of BPA and a catalyst, mixing the solid sample with water, filtering, and drying the solid phase to obtain pure BPA, wherein the yield of the BPA is 87.3%.
Example 5
5.0G of PC pellets were placed in a pressure-resistant bottle, 0.17g of tetraphenylphosphonium phenol and 2.5g of methanol were sequentially added, the temperature was raised to 160℃and the mixture was stirred for 2 hours, after which the polymer was completely dissolved, and the completion of the reaction was detected by FTIR. And (3) completely cooling the reaction solution to room temperature, carrying out reduced pressure distillation on the degradation solution at 50 ℃ and minus 0.1MPa, wherein the fraction is a mixture of methanol and carbonic ester, the solid sample is a mixture of BPA and a catalyst, mixing the solid sample with water, filtering, and drying the solid phase to obtain the pure BPA, wherein the yield of the BPA is 98.8%.
Example 6
5.0G of PC pellets were placed in a pressure-resistant bottle, 0.17g of tetraphenylphosphonium phenol and 1.25g of methanol were sequentially added, the temperature was raised to 110℃and the mixture was stirred for 4 hours, after which the polymer was completely dissolved, and the completion of the reaction was detected by FTIR. And (3) completely cooling the reaction solution to room temperature, carrying out reduced pressure distillation on the degradation solution at 50 ℃ and minus 0.1MPa, wherein the fraction is a mixture of methanol and carbonic ester, the solid sample is a mixture of BPA and a catalyst, mixing the solid sample with water, filtering, and drying the solid phase to obtain the pure BPA, wherein the yield of the BPA is 90.6%.
Example 7
5.0G of PC pellets were placed in a pressure-resistant bottle, 0.17g of tetraphenylphosphonium phenol and 5.06g of methanol were sequentially added, the temperature was raised to 110℃and the mixture was stirred for 4 hours, after which the polymer was completely dissolved, and the completion of the reaction was detected by FTIR. And (3) completely cooling the reaction solution to room temperature, carrying out reduced pressure distillation on the degradation solution at 50 ℃ and minus 0.1MPa, wherein the fraction is a mixture of methanol and carbonic ester, the solid sample is a mixture of BPA and a catalyst, mixing the solid sample with water, filtering, and drying the solid phase to obtain the pure BPA, wherein the yield of the BPA is 98.3%.
Example 8
5.0G of PC pellets were placed in a pressure-resistant bottle, 0.17g of tetraphenylphosphonium phenol and 3.6g of ethanol were sequentially added, the temperature was raised to 110℃and the mixture was stirred for 5 hours, after which the polymer was completely dissolved, and the completion of the reaction was detected by FTIR. And (3) completely cooling the reaction solution to room temperature, carrying out reduced pressure distillation on the degradation solution at 50 ℃ and minus 0.1MPa, wherein the fraction is ethanol and carbonate mixture, the solid sample is mixture of BPA and catalyst, mixing the solid sample with water, filtering, and drying the solid phase to obtain pure BPA, wherein the yield of the BPA is 93.2%.
Example 9
Adding 5.0g of PC granules into a pressure-resistant bottle, sequentially adding 0.17g of tetraphenylphosphonium phenol and 7.3g of glycerol, heating to 110 ℃, stirring for 30 hours, depolymerizing the polymer to 33%, completely cooling the reaction liquid to room temperature, carrying out reduced pressure distillation on the degradation liquid at 50 ℃ and minus 0.1MPa, wherein the fraction is glycerol and carbonate mixture, the solid sample is a mixture of BPA and a catalyst, mixing the solid sample with water, filtering after mixing, and drying the solid phase to obtain pure BPA, wherein the yield of the BPA is 15.6%. In example 9, glycerol is used as an alcoholysis reagent, and the yield of BPA is low because the glycerol has longer alcohol chain and larger steric hindrance, so that the alcoholysis effect is poor.
Example 10
5.0G of PC pellets were placed in a pressure-resistant bottle, 0.17g of tetraphenyl phosphonium chloride and 2.5g of methanol were added in this order, the temperature was raised to 110℃and the mixture was stirred for 2 hours, after which the polymer was completely dissolved, and the completion of the reaction was detected by FTIR. And (3) completely cooling the reaction solution to room temperature, carrying out reduced pressure distillation on the degradation solution at 50 ℃ and minus 0.1MPa, wherein the fraction is a mixture of methanol and carbonic ester, the solid sample is a mixture of BPA and a catalyst, mixing the solid sample with water, filtering, and drying the solid phase to obtain pure BPA, wherein the yield of the BPA is 90.1%.
Example 11
5.0G of PC pellets were placed in a pressure-resistant bottle, 0.17g of tetramethyl phosphonium phenol and 2.5g of methanol were added in this order, the temperature was raised to 110℃and the mixture was stirred for 2 hours, after which the polymer was completely dissolved, and the completion of the reaction was detected by FTIR. And (3) completely cooling the reaction solution to room temperature, carrying out reduced pressure distillation on the degradation solution at 50 ℃ and minus 0.1MPa, wherein the fraction is a mixture of methanol and carbonic ester, the solid sample is a mixture of BPA and a catalyst, mixing the solid sample with water, filtering, and drying the solid phase to obtain the pure BPA, wherein the yield of the BPA is 92.5%.
In summary, the invention solves the problems of insufficient mildness, high toxicity, high cost, difficult separation and the like of the existing catalyst system for chemically recycling the BPA-PC waste, realizes the efficient green depolymerization of the BPA-PC by using a commercially available simple and low-cost catalyst system, is easy to separate, and is suitable for industrialization.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (10)
1. A method for recovering bisphenol a by catalytic alcoholysis of polycarbonate, comprising the steps of:
Mixing bisphenol A type polycarbonate, alcohol and phosphonium salt catalyst for alcoholysis reaction to obtain bisphenol A and carbonic ester; the structural formula of the phosphonium salt catalyst is shown as formula I:
In formula I: r 1～R4 is independently C 1-C10 -alkanyl, C 6-C14 -aryl, C 7-C15 -arylalkyl, or C 5-C6 -cycloalkyl; x n- is hydroxide, sulfate, hydrogen carbonate, halide OR-OR 5,R5 is C 6-C14 aryl, C 7-C15 arylalkyl, C 5-C6 cycloalkyl OR C 1-C20 alkanyl, n is 1 OR 2.
2. The method according to claim 1, wherein in formula I: r 1～R4 is independently methyl or phenyl; r 5 is phenyl.
3. The method of claim 1, wherein the phosphonium salt catalyst is one or more of tetraphenyl phosphonium hydroxide, tetraphenyl phosphonium phenol, tetraphenyl phosphonium chloride, and tetramethyl phosphonium phenol.
4. The method according to claim 1, 2 or3, wherein the mass of the phosphonium salt catalyst is 1 to 10% of the mass of the bisphenol a polycarbonate.
5. The method according to claim 1, wherein the alcohol has 1 to 4 carbon atoms.
6. The method of claim 1 or 5, wherein the alcohol comprises one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, ethylene glycol, and glycerol.
7. The method according to claim 1 or 5, wherein the mass ratio of the alcohol to the bisphenol A type polycarbonate is (0.25 to 5): 1.
8. The method according to claim 1, wherein the alcoholysis reaction is carried out at a temperature of 80 to 160 ℃ for a reaction time of 1 to 30 hours; the pressure of the alcoholysis reaction is normal pressure; the alcoholysis reaction is carried out under a protective atmosphere.
9. The method according to claim 1, further comprising subjecting the obtained reaction liquid to reduced pressure distillation after the alcoholysis reaction is completed to obtain a solid product and a fraction; the solid product is bisphenol A and phosphonium salt catalyst; the fractions are carbonates and alcohols.
10. The method according to claim 9, wherein the reduced pressure distillation is carried out at a temperature of 50 to 70 ℃ and a pressure of-0.01 to 0.1MPa.
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