CN114436806B - Method for preparing disodium terephthalate and hydrogen by converting PET (polyethylene terephthalate) polyester waste plastics at low temperature by one-step method - Google Patents
Method for preparing disodium terephthalate and hydrogen by converting PET (polyethylene terephthalate) polyester waste plastics at low temperature by one-step method Download PDFInfo
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- CN114436806B CN114436806B CN202210013213.2A CN202210013213A CN114436806B CN 114436806 B CN114436806 B CN 114436806B CN 202210013213 A CN202210013213 A CN 202210013213A CN 114436806 B CN114436806 B CN 114436806B
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- PWKNBLFSJAVFAB-UHFFFAOYSA-N 1-fluoro-2-nitrobenzene Chemical compound [O-][N+](=O)C1=CC=CC=C1F PWKNBLFSJAVFAB-UHFFFAOYSA-N 0.000 title claims abstract description 131
- 238000000034 method Methods 0.000 title claims abstract description 124
- 239000004033 plastic Substances 0.000 title claims abstract description 122
- 229920003023 plastic Polymers 0.000 title claims abstract description 122
- 229910052739 hydrogen Inorganic materials 0.000 title claims abstract description 108
- 239000001257 hydrogen Substances 0.000 title claims abstract description 102
- 229920000728 polyester Polymers 0.000 title claims abstract description 101
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims abstract description 100
- 239000002699 waste material Substances 0.000 title claims abstract description 96
- 229920000139 polyethylene terephthalate Polymers 0.000 title description 156
- 239000005020 polyethylene terephthalate Substances 0.000 title description 156
- -1 polyethylene terephthalate Polymers 0.000 title description 5
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 283
- 238000006243 chemical reaction Methods 0.000 claims abstract description 120
- 239000003054 catalyst Substances 0.000 claims abstract description 91
- 238000004064 recycling Methods 0.000 claims abstract description 31
- 238000011065 in-situ storage Methods 0.000 claims abstract description 11
- 239000000203 mixture Substances 0.000 claims abstract description 10
- 239000013078 crystal Substances 0.000 claims abstract description 7
- 238000007670 refining Methods 0.000 claims abstract description 6
- 238000002156 mixing Methods 0.000 claims abstract description 4
- 238000006057 reforming reaction Methods 0.000 claims abstract description 4
- 238000012719 thermal polymerization Methods 0.000 claims abstract description 4
- 230000008878 coupling Effects 0.000 claims abstract description 3
- 238000010168 coupling process Methods 0.000 claims abstract description 3
- 238000005859 coupling reaction Methods 0.000 claims abstract description 3
- KKEYFWRCBNTPAC-UHFFFAOYSA-N Terephthalic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-N 0.000 claims description 112
- 239000000047 product Substances 0.000 claims description 78
- 239000007791 liquid phase Substances 0.000 claims description 65
- 239000011949 solid catalyst Substances 0.000 claims description 63
- 239000007864 aqueous solution Substances 0.000 claims description 53
- 238000002407 reforming Methods 0.000 claims description 47
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 40
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 37
- 239000000243 solution Substances 0.000 claims description 30
- 238000001914 filtration Methods 0.000 claims description 28
- 239000008367 deionised water Substances 0.000 claims description 27
- 229910021641 deionized water Inorganic materials 0.000 claims description 27
- 238000001035 drying Methods 0.000 claims description 8
- 229910052751 metal Inorganic materials 0.000 claims description 8
- 239000002184 metal Substances 0.000 claims description 8
- 229910000510 noble metal Inorganic materials 0.000 claims description 7
- 235000013361 beverage Nutrition 0.000 claims description 6
- 239000003153 chemical reaction reagent Substances 0.000 claims description 5
- 239000004744 fabric Substances 0.000 claims description 5
- 239000000413 hydrolysate Substances 0.000 claims description 4
- 229910052707 ruthenium Inorganic materials 0.000 claims description 3
- 230000008569 process Effects 0.000 abstract description 27
- 238000002425 crystallisation Methods 0.000 abstract description 25
- 230000003197 catalytic effect Effects 0.000 abstract description 4
- 230000008025 crystallization Effects 0.000 abstract description 4
- 239000007789 gas Substances 0.000 description 67
- 239000011734 sodium Substances 0.000 description 29
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 23
- 239000002245 particle Substances 0.000 description 23
- 238000001704 evaporation Methods 0.000 description 22
- 230000008020 evaporation Effects 0.000 description 22
- 239000007787 solid Substances 0.000 description 22
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 12
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 12
- 238000004587 chromatography analysis Methods 0.000 description 12
- 238000003756 stirring Methods 0.000 description 12
- 238000004817 gas chromatography Methods 0.000 description 11
- 230000002829 reductive effect Effects 0.000 description 10
- 239000011541 reaction mixture Substances 0.000 description 9
- 239000002253 acid Substances 0.000 description 7
- 238000005470 impregnation Methods 0.000 description 7
- 239000001569 carbon dioxide Substances 0.000 description 6
- 229910002092 carbon dioxide Inorganic materials 0.000 description 6
- 239000002243 precursor Substances 0.000 description 6
- 238000002360 preparation method Methods 0.000 description 6
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- KDLHZDBZIXYQEI-UHFFFAOYSA-N palladium Substances [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 5
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- 239000002351 wastewater Substances 0.000 description 5
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 4
- 238000005260 corrosion Methods 0.000 description 4
- 230000007797 corrosion Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 150000001335 aliphatic alkanes Chemical class 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 238000002309 gasification Methods 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 238000011068 loading method Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 238000000655 nuclear magnetic resonance spectrum Methods 0.000 description 3
- 239000013502 plastic waste Substances 0.000 description 3
- 238000000197 pyrolysis Methods 0.000 description 3
- 239000002910 solid waste Substances 0.000 description 3
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 238000000862 absorption spectrum Methods 0.000 description 2
- 239000003513 alkali Substances 0.000 description 2
- 239000012670 alkaline solution Substances 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 229910002091 carbon monoxide Inorganic materials 0.000 description 2
- VIQSRHWJEKERKR-UHFFFAOYSA-L disodium;terephthalate Chemical compound [Na+].[Na+].[O-]C(=O)C1=CC=C(C([O-])=O)C=C1 VIQSRHWJEKERKR-UHFFFAOYSA-L 0.000 description 2
- 239000007772 electrode material Substances 0.000 description 2
- 150000002431 hydrogen Chemical class 0.000 description 2
- 230000007062 hydrolysis Effects 0.000 description 2
- 238000006460 hydrolysis reaction Methods 0.000 description 2
- 230000003301 hydrolyzing effect Effects 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 230000003472 neutralizing effect Effects 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- 239000010948 rhodium Substances 0.000 description 2
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- LYCAIKOWRPUZTN-NMQOAUCRSA-N 1,2-dideuteriooxyethane Chemical compound [2H]OCCO[2H] LYCAIKOWRPUZTN-NMQOAUCRSA-N 0.000 description 1
- QXNVGIXVLWOKEQ-UHFFFAOYSA-N Disodium Chemical compound [Na][Na] QXNVGIXVLWOKEQ-UHFFFAOYSA-N 0.000 description 1
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 1
- 238000001157 Fourier transform infrared spectrum Methods 0.000 description 1
- 229920000426 Microplastic Polymers 0.000 description 1
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000006136 alcoholysis reaction Methods 0.000 description 1
- 238000005904 alkaline hydrolysis reaction Methods 0.000 description 1
- 238000005915 ammonolysis reaction Methods 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 239000003610 charcoal Substances 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 239000012634 fragment Substances 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 210000003041 ligament Anatomy 0.000 description 1
- 230000000670 limiting effect Effects 0.000 description 1
- 239000012263 liquid product Substances 0.000 description 1
- 239000002923 metal particle Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 238000005580 one pot reaction Methods 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- GPNDARIEYHPYAY-UHFFFAOYSA-N palladium(ii) nitrate Chemical compound [Pd+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O GPNDARIEYHPYAY-UHFFFAOYSA-N 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 229910052703 rhodium Inorganic materials 0.000 description 1
- SONJTKJMTWTJCT-UHFFFAOYSA-K rhodium(iii) chloride Chemical compound [Cl-].[Cl-].[Cl-].[Rh+3] SONJTKJMTWTJCT-UHFFFAOYSA-K 0.000 description 1
- YBCAZPLXEGKKFM-UHFFFAOYSA-K ruthenium(iii) chloride Chemical compound [Cl-].[Cl-].[Cl-].[Ru+3] YBCAZPLXEGKKFM-UHFFFAOYSA-K 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- 229910001415 sodium ion Inorganic materials 0.000 description 1
- 239000002689 soil Substances 0.000 description 1
- 238000009987 spinning Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000004083 survival effect Effects 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- MHSKRLJMQQNJNC-UHFFFAOYSA-N terephthalamide Chemical compound NC(=O)C1=CC=C(C(N)=O)C=C1 MHSKRLJMQQNJNC-UHFFFAOYSA-N 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/083—Preparation of carboxylic acids or their salts, halides or anhydrides from carboxylic acid anhydrides
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
- C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
- C01B3/22—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by decomposition of gaseous or liquid organic compounds
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/62—Plastics recycling; Rubber recycling
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Health & Medical Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Combustion & Propulsion (AREA)
- Inorganic Chemistry (AREA)
- Separation, Recovery Or Treatment Of Waste Materials Containing Plastics (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention provides a method for preparing disodium terephthalate and high-purity hydrogen by converting PET polyester waste plastics at a low temperature by a one-step method, which comprises the steps of directly mixing PET polyester waste plastics with a catalyst according to a certain proportion, adding the mixture into a low-concentration NaOH solution, coupling the PET hydrothermal thermal polymerization reaction and the in-situ reforming reaction of PET depolymerization products under a specific low-temperature hydrothermal condition by taking the multiple functions of NaOH and the directional catalytic characteristics of the catalyst as ties, so that the PET is completely converted in one reaction system at a high efficiency, the high-purity hydrogen with the purity close to 99% and the crude disodium terephthalate solution are directly obtained by the one-step method, and then the high-purity disodium terephthalate crystal is obtained through simple refining and crystallization processes, thereby realizing the high-value recycling of the PET polyester waste plastics.
Description
Technical Field
The invention relates to the technical field of thermochemical conversion of waste plastics, in particular to a method for preparing disodium terephthalate and hydrogen by converting PET polyester waste plastics at a low temperature by a one-step method.
Background
Plastics have played an important role in industrial production and daily life in recent decades due to their low production costs and good durability and corrosion resistance. However, high-efficiency and safe disposal of waste plastics is paid attention, most of waste plastics are currently treated as solid waste in a centralized manner, and are mainly treated by landfill or incineration, while waste plastics which are not treated in a centralized manner enter an ecological environment. Because of the difficult natural degradability of waste plastics, the soil and water environment are endangered for a long time. A part of waste plastics enter the ocean to be crushed into micro plastics, which has serious influence on the ocean environment and the growth and survival of marine organisms. Therefore, the directional recycling and high-value utilization of waste plastics are important demands of China, and have great significance for improving ecological environment, optimizing energy structures of China and realizing double-carbon targets.
Due to the advantages of strong chemical stability, high mechanical strength, good processability and the like, polyethylene terephthalate (PET) is one of the most widely used thermoplastic polyester plastics, and has wider application in the fields of product packaging, beverage filling, cloth spinning and the like. Among the urban organic solid waste and the industrial organic solid waste, PET waste plastics are one of the main components. Because the repeated aromatic terephthalate units exist in the PET plastic framework, the PET waste plastic is extremely difficult to degrade in the natural environment, so that development of a new process for carrying out directional depolymerization and conversion on the PET plastic to prepare clean energy and high-value chemicals is needed, the environmental pollution can be reduced, and the utilization rate of the waste plastic can be improved.
At present, the existing thermochemical depolymerization process of PET waste plastics mainly comprises an alcoholysis method, a hydrolysis method, an ammonolysis method and the like, and mainly has the problems that the loss of glycol in a PET depolymerization product is not pure in the obtained target product, and a large amount of waste liquid is generated due to the high-concentration alkali solution used in the process. PET has the potential to be converted to hydrogen as a highly hydrogen-containing organic compound. Pyrolysis gasification can convert waste plastics into hydrogen-rich synthesis gas by a thermal cracking-reforming process. However, the gas phase products of pyrolysis and gasification of waste plastics have higher content of byproducts such as carbon dioxide, alkane and the like, and tar generated in the pyrolysis and gasification process is difficult to treat. In addition, because PET is a substance with definite structural characteristics, how to use the structural characteristics of PET and directionally convert the PET into high-value fuel and high-value chemicals in a simple and ingenious way is a necessary way for improving the comprehensive utilization value and quickly reducing the waste plastics of PET.
Disclosure of Invention
The invention aims to solve the problems in the prior art, and provides a method for preparing disodium terephthalate and hydrogen by converting PET (polyethylene terephthalate) waste plastics at low temperature by a one-step method, which can efficiently convert PET polyester plastics into disodium terephthalate and high-purity hydrogen in a low-temperature hydrothermal environment, has simple process flow and high economic benefit, realizes clean and high-value utilization of PET polyester waste plastics, and reduces potential negative influence on the environment caused by the disposal process of waste plastics.
In order to achieve the aim, the invention provides a method for preparing the disodium terephthalate and the hydrogen by converting PET polyester waste plastics at low temperature by a one-step method, wherein the PET polyester waste plastics and a reforming catalyst are mixed according to a certain proportion and added into a low-concentration NaOH solution, the multiple functions of NaOH in a reaction system and the directional catalytic property of the reforming catalyst are adopted as ties, and the PET hydrothermal thermal polymerization reaction and the in-situ reforming reaction of PET depolymerization products are coupled under the low-temperature hydrothermal condition, so that the PET is completely converted in one step in one reaction system, and the high-purity hydrogen with the purity close to 99% and the crude disodium terephthalate solution are directly obtained by one-step method.
In the reaction system for one-step conversion of PET polyester waste plastics, the alkaline environment created by NaOH promotes the hydrothermal depolymerization of the PET polyester waste plastics, so that the PET polyester waste plastics are firstly converted into disodium terephthalate and ethylene glycol. And the obtained glycol is subjected to in-situ liquid phase reforming in the same reaction system under the catalysis of a reforming catalyst. The reforming catalyst has a catalytic effect on C-C bond rupture of ethylene glycol and water gas reaction, and can convert the ethylene glycol into hydrogen, carbon dioxide, carbon monoxide and a small amount of alkane. More importantly, the generated carbon dioxide is removed by NaOH existing in the reaction system and is treated by CO 3 2- Form(s) stored in Na 2 CO 3 Is a kind of medium. The removal of carbon dioxide in turn promotes the water gas reaction to consume carbon monoxide, and also greatly reduces the methane yield by inhibiting the methanation reaction. Thus, the PET one-step conversion process yields a mixture containing only trace amounts of alkanes and no CO x High purity hydrogen with a purity approaching 99%. The obtained liquid product can obtain high-purity disodium terephthalate crystal and does not contain the disodium terephthalate crystal through simple refining and evaporative crystallization processesWater of any harmful impurities. The high-purity disodium terephthalate crystal is expected to be widely applied as an excellent electrode material due to its high sodium ion capacity, good cycle performance and high reversible capacity.
Preferably, the amount of NaOH in the low concentration NaOH solution is the amount of terephthalic acid in the fully neutralized PET hydrolysate and the CO in the product of the in situ liquid phase reforming of ethylene glycol is completely removed 2 To ensure that the added NaOH reagent completely removes terephthalic acid and carbon dioxide produced by the one-step conversion of PET polyester waste plastics.
Preferably, the NaOH concentration value of the low-concentration NaOH solution is 1.2-4.8%, and compared with the traditional PET alkaline hydrolysis process requiring higher NaOH concentration (20-30%), the method greatly reduces the corrosion to operating equipment and simultaneously avoids the discharge of wastewater containing a large amount of alkali substances.
Preferably, the temperature of the low-temperature hydrothermal condition is 180-260 ℃ so as to realize the complete depolymerization of the PET in the low-concentration NaOH solution and the in-situ liquid phase reforming process of the glycol in the depolymerization product of the PET. Because the concentration value of NaOH in the invention is 1.2-4.8%, the complete depolymerization of PET can not be realized under the condition of lower than 180 ℃, and because the temperature required by in-situ liquid phase reforming of the depolymerization product ethylene glycol of PET in the one-step process is above 180 ℃, the operation temperature is controlled between 180-260 ℃ in order to realize the process of preparing high-purity hydrogen and disodium terephthalate by converting PET by one-step method.
Preferably, the mass ratio range of the low-concentration NaOH solution to the PET polyester waste plastic is as follows: 50:1-100:1.
Preferably, the mass ratio of the PET polyester waste plastic to the reforming catalyst is as follows: 10:1-20:1.
Preferably, the product of the one-step complete conversion of PET polyester waste plastics in one reaction system further comprises a liquid phase product and a solid catalyst, wherein the liquid phase product and the solid catalyst are used for recycling, and the method comprises the following steps: the PET polyester waste plastics and a certain amount of NaOH reagent are added into the liquid phase product containing the solid catalyst again, and the mixture is used for preparing the terephthalamide again Disodium terephthalate and Na in the liquid phase product obtained after each cycle 2 CO 3 Has no obvious influence on the one-step conversion reaction of the new round of PET polyester waste plastics.
Preferably, the PET polyester waste plastic further comprises the refining treatment of disodium terephthalate after one-step complete conversion, and specifically comprises the following steps: filtering the mixture of the solid catalyst and the crude disodium terephthalate water solution obtained after circulation to separate the crude disodium terephthalate water solution, adding a proper amount of terephthalic acid into the crude disodium terephthalate water solution, and removing residual Na 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution.
Preferably, the purified aqueous disodium terephthalate solution is crystallized by evaporation to obtain pure disodium terephthalate crystals.
Preferably, the reforming catalyst is a noble metal catalyst having an active metal content of 0.1 to 10wt.%, preferably a noble metal catalyst having an active metal content of 5 wt.%.
Preferably, the noble metal catalyst is a Ru, pt, pd, rh supported biochar-based catalyst, preferably a Ru supported biochar-based catalyst.
Preferably, the PET polyester waste plastic comprises PET product waste such as plastic beverage bottles, disposable tableware, polyester cloth and the like.
The invention has the beneficial effects that:
1. the invention develops a method for preparing the disodium terephthalate and the hydrogen by converting PET polyester waste plastics at low temperature by a one-step method, so that the disodium terephthalate and the hydrogen with the purity close to 99% can be finally obtained, the PET polyester waste plastics can be rapidly treated by a one-step method, and high-value products can be obtained;
2. the reaction condition of the invention is mild, naOH solution with the concentration of 1.2-4.8% is used in the process, and compared with the traditional high-concentration (20-30%) NaOH depolymerization PET process, the process provided by the invention can not cause serious corrosion to operation equipment. In addition, the invention is based on the use of low concentration NaOH solutionThe theoretical value is calculated by adopting NaOH, namely the amount of NaOH is the theoretical amount for completely neutralizing terephthalic acid in the PET hydrolysate and the CO in the product in situ liquid phase reforming of ethylene glycol is completely removed 2 So that the end of the one-step conversion reaction does not produce wastewater containing a large amount of strong base. And after the terephthalic acid disodium salt purification process, the obtained liquid does not contain any harmful impurities;
3. compared with the traditional process of 'PET alkaline hydrolytic depolymerization and strong acid substitution terephthalic acid', the invention truly realizes the one-step full utilization of PET depolymerization products, avoids the loss of glycol in PET depolymerization products and prevents industrial terminals from containing a large amount of Na 2 SO 4 The discharge of NaCl wastewater, and the disodium terephthalate salt obtained by the invention has higher market value than terephthalic acid;
4. the hydrogen prepared by the invention has high purity of approximately 99%, and the obtained crude disodium terephthalate solution can be obtained at the end of the process after simple refining and evaporative crystallization. And proved by nuclear magnetic resonance spectrum, fourier transform infrared spectrum and X-ray diffraction detection, the material has extremely high purity and almost no impurity, and can be used for preparing electrode materials in electrochemical processes;
5. the process is simple and ingenious, the operation is easy, the PET conversion rate is close to 100%, the process is environment-friendly, the liquid-phase product and the catalyst can be recycled for multiple times, and the process has extremely high industrial application value.
The features and advantages of the present invention will be described in detail by way of example with reference to the accompanying drawings.
Drawings
FIG. 1 is a process flow diagram of a process for preparing disodium terephthalate and hydrogen by one-step low temperature conversion of PET polyester waste plastics in accordance with the present invention;
FIG. 2 is a graph of results of liquid phase product cycle testing;
FIG. 3 is a graph of catalyst cycle versus test results;
FIG. 4 is a chart showing the comparison of Fourier transform infrared absorption spectra of disodium terephthalate produced from different PET plastic waste materials;
FIG. 5 is a graph showing the contrast of nuclear magnetic resonance spectra of disodium terephthalate produced from different PET plastic waste materials.
Detailed Description
The purpose of the traditional PET hydrolytic depolymerization is to generate disodium terephthalate at a temperature lower than 180 ℃, and then to produce terephthalic acid by adding sulfuric acid/hydrochloric acid by utilizing the principle of preparing weak acid from strong acid. Since a higher NaOH concentration (20-30%) is required to achieve complete depolymerization of PET at lower hydrothermal temperatures, severe corrosion of equipment is likely to occur and significant salt (Na) is produced during terephthalic acid purification 2 SO 4 /NaCl) wastewater. In addition, ethylene glycol, another major product of PET hydrolysis, can be mixed with the wastewater during the process, making it difficult to recover, resulting in loss of ethylene glycol and lower conversion utilization of PET. In order to solve the problems, the method for preparing the disodium terephthalate and the hydrogen by converting PET polyester waste plastics at low temperature by a one-step method of the invention is shown in a process flow chart of fig. 1, and specifically comprises the following steps:
s1, mixing the recycled PET waste plastics with a reforming catalyst according to the mass ratio of the PET waste plastics to the reforming catalyst of 10:1-20:1, adding the mixture of the PET waste plastics and the reforming catalyst into the low-concentration NaOH solution according to the mass ratio of the low-concentration NaOH solution of 50:1-100:1, and under the conditions of the reaction temperature of 180-260 ℃ and the reaction pressure of 0.5-3MPa, coupling the PET hydrothermal thermal polymerization reaction and the in-situ reforming reaction of the PET depolymerization product under the specific low-temperature hydrothermal condition by taking the multiple action of NaOH and the directional catalytic characteristic of the catalyst as a ligament, so as to directly obtain the high-purity hydrogen, crude disodium terephthalate solution and the solid catalyst, wherein the purity of the high-purity hydrogen is close to 99%.
Wherein the NaOH concentration value of the low-concentration NaOH solution is 1.2-4.8%, the NaOH amount is the theoretical amount of completely neutralizing terephthalic acid in PET hydrolysate and completely removing CO in the product in-situ liquid phase reforming of ethylene glycol 2 To ensure that the added NaOH reagent completely removes PTerephthalic acid and carbon dioxide produced by one-step conversion of ET polyester waste plastics. The reforming catalyst is a biochar-based catalyst loaded by Ru, pt, pd and Rh and prepared by an impregnation method and having active metal content of 5 wt.%. The PET waste plastic is PET product waste such as plastic beverage bottles, disposable tableware, polyester cloth and the like.
S2, recycling the liquid-phase product and the solid catalyst: adding PET polyester waste plastics and a certain amount of NaOH reagent into a liquid-phase product containing a solid catalyst again, and carrying out one-step reaction at the reaction temperature of 180-260 ℃ and the reaction pressure of 0.5-3MPa, so as to prepare the disodium terephthalate and the high-purity hydrogen again. Disodium terephthalate and Na in the liquid phase product obtained after each cycle 2 CO 3 Has no obvious influence on the one-step conversion reaction of the new round of PET polyester waste plastics.
S3, refining treatment of disodium terephthalate: filtering the mixture of the solid catalyst and the crude disodium terephthalate water solution obtained after circulation to separate the crude disodium terephthalate water solution, adding a proper amount of terephthalic acid into the filtered crude disodium terephthalate water solution, and removing the residual Na in the solution 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution. The refined disodium terephthalate aqueous solution is evaporated and crystallized to obtain high-purity disodium terephthalate crystals.
Referring to examples 1 to 5, the effect of reaction temperature on the conversion of PET polyester waste plastics by one-step method is specifically as follows:
example 1:
the preparation method of the reforming catalyst comprises the following steps: adding a certain amount of biochar and precursor ruthenium chloride into absolute ethyl alcohol according to 5wt.% of theoretical Ru load by using an impregnation method, uniformly stirring and impregnating for 12 hours at room temperature, continuously stirring at 80 ℃ until the absolute ethyl alcohol is evaporated to dryness, and drying an obtained sample (Ru/C) in a 105 ℃ oven; at 500 ℃,10% H 2 -reduction in 90% ar for 5 hours.
One-step low-temperature conversion of PET polyester waste plastics in high-pressure reactorProcess for the production of disodium terephthalate and high purity hydrogen: 0.7g PET polyester plastic particles, 70ml deionized water, 0.07g Ru/C catalyst and 0.874g NaOH were weighed and run at 180℃for 120 minutes under a reaction pressure of 0.5MPa without an initial pressure. After the reaction, the reaction mixture is cooled down rapidly, and gas generated by gas bag collection is analyzed by gas chromatography to obtain the hydrogen yield of 8.47 mol/kg PET The hydrogen concentration was 99.27%. After recycling the liquid-phase product and the solid catalyst for 5 times, filtering the liquid-phase product and the solid catalyst; adding terephthalic acid to the filtered aqueous solution until terephthalic acid is insoluble to remove residual Na therefrom 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution, and finally obtaining pure disodium terephthalate solid by an evaporation crystallization method.
Example 2:
the reforming catalyst was prepared in the same manner as in example 1.
The method for preparing the disodium terephthalate and the high-purity hydrogen by converting PET polyester waste plastics at low temperature by a one-step method in a high-pressure reaction kettle comprises the following steps: 0.7g PET polyester plastic particles, 70ml deionized water, 0.07g Ru/C catalyst and 0.874g NaOH were weighed and run at 200℃for 120 minutes under 1MPa reaction pressure without initial pressure. After the reaction, the reaction mixture is cooled down rapidly, and gas generated by gas bag collection is analyzed by gas chromatography to obtain the hydrogen yield of 18.31mol/kg PET The hydrogen concentration was 98.77%. After recycling the liquid-phase product and the solid catalyst for 5 times, filtering the liquid-phase product and the solid catalyst; adding terephthalic acid to the filtered aqueous solution until terephthalic acid is insoluble to remove residual Na therefrom 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution, and finally obtaining pure disodium terephthalate solid by an evaporation crystallization method.
Example 3:
the reforming catalyst was prepared in the same manner as in example 1.
One-step low-temperature conversion of PET polyester waste plastics in high-pressure reactor to prepare disodium terephthalateAnd a method for high purity hydrogen: 0.7g PET polyester plastic particles, 70ml deionized water, 0.07g Ru/C catalyst and 0.874g NaOH were weighed and run at 220℃for 120 minutes under 1.5MPa reaction pressure without initial pressure. After the reaction is finished, the temperature is quickly reduced, gas generated by gas bag collection is used for gas chromatographic analysis, and the hydrogen yield is 22.45 mol/kg PET The hydrogen concentration was 97.99%. After recycling the liquid-phase product and the solid catalyst for 5 times, filtering the liquid-phase product and the solid catalyst; adding terephthalic acid to the filtered aqueous solution until terephthalic acid is insoluble to remove residual Na therefrom 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution, and finally obtaining pure disodium terephthalate solid by an evaporation crystallization method.
Example 4:
The reforming catalyst was prepared in the same manner as in example 1.
The method for preparing the disodium terephthalate and the high-purity hydrogen by converting PET polyester waste plastics at low temperature by a one-step method in a high-pressure reaction kettle comprises the following steps: 0.7g PET polyester plastic particles, 70ml deionized water, 0.07g Ru/C catalyst and 0.874g NaOH were weighed and run at 240℃for 120 minutes under a reaction pressure of 2MPa without an initial pressure. After the reaction, the reaction mixture is cooled down rapidly, and gas generated by gas bag collection is analyzed by gas chromatography to obtain the hydrogen yield of 23.7 mol/kg PET The hydrogen concentration was 98.31%. After recycling the liquid-phase product and the solid catalyst for 5 times, filtering the liquid-phase product and the solid catalyst; adding terephthalic acid to the filtered aqueous solution until terephthalic acid is insoluble to remove residual Na therefrom 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution, and finally obtaining pure disodium terephthalate solid by an evaporation crystallization method.
Example 5:
the reforming catalyst was prepared in the same manner as in example 1.
Method for preparing disodium terephthalate and high-purity hydrogen by converting PET (polyethylene terephthalate) polyester waste plastics at low temperature in one-step manner in high-pressure reaction kettle The method comprises the following steps: 0.7g PET polyester plastic particles, 70ml deionized water, 0.07g Ru/C catalyst and 0.874g NaOH were weighed and run at 260℃for 120 minutes under a reaction pressure of 2.5MPa without an initial pressure. After the reaction is finished, the reaction is cooled down rapidly, gas generated by gas bag collection is used for gas chromatographic analysis, and the hydrogen yield is 24.38mol/kg PET The hydrogen concentration was 98.42%. After recycling the liquid-phase product and the solid catalyst for 5 times, filtering the liquid-phase product and the solid catalyst; adding terephthalic acid to the filtered aqueous solution until terephthalic acid is insoluble to remove residual Na therefrom 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution, and finally obtaining pure disodium terephthalate solid by an evaporation crystallization method.
The experimental results of examples 1-5 are shown in Table 1:
referring to examples 6 to 10, the effect of reaction time on the one-step conversion of PET polyester waste plastics is specifically as follows:
example 6:
the reforming catalyst was prepared in the same manner as in example 1.
The method for preparing the disodium terephthalate and the high-purity hydrogen by converting PET polyester waste plastics at low temperature by a one-step method in a high-pressure reaction kettle comprises the following steps: 0.7g PET polyester plastic particles, 70ml deionized water, 0.07g Ru/C catalyst and 0.874g NaOH were weighed and run at 240℃for 20 minutes without initial pressure and 2MPa reaction pressure. After the reaction, the reaction mixture is cooled down rapidly, and gas generated by gas bag collection is analyzed by gas chromatography to obtain the hydrogen with the yield of 20.97mol/kg PET The hydrogen concentration was 98.61%. After recycling the liquid-phase product and the solid catalyst for 5 times, filtering the liquid-phase product and the solid catalyst; adding terephthalic acid to the filtered aqueous solution until terephthalic acid is insoluble to remove residual Na therefrom 2 CO 3 And a small amount of NaOH to obtain refined disodium terephthalate waterAnd finally, obtaining pure disodium terephthalate solid by an evaporation crystallization method.
Example 7:
the reforming catalyst was prepared in the same manner as in example 1.
The method for preparing the disodium terephthalate and the high-purity hydrogen by converting PET polyester waste plastics at low temperature by a one-step method in a high-pressure reaction kettle comprises the following steps: 0.7g PET polyester plastic particles, 70ml deionized water, 0.07g Ru/C catalyst and 0.874g NaOH were weighed and run at 240℃for 40 minutes without initial pressure and 2MPa reaction pressure. After the reaction is finished, the temperature is quickly reduced, gas generated by gas bag collection is used for gas chromatographic analysis, and the yield of hydrogen is 22.62mol/kg PET The hydrogen concentration was 98.54%. After recycling the liquid-phase product and the solid catalyst for 5 times, filtering the liquid-phase product and the solid catalyst; adding terephthalic acid to the filtered aqueous solution until terephthalic acid is insoluble to remove residual Na therefrom 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution, and finally obtaining pure disodium terephthalate solid by an evaporation crystallization method.
Example 8:
the reforming catalyst was prepared in the same manner as in example 1.
The method for preparing the disodium terephthalate and the high-purity hydrogen by converting PET polyester waste plastics at low temperature by a one-step method in a high-pressure reaction kettle comprises the following steps: 0.7g PET polyester plastic particles, 70ml deionized water, 0.07g Ru/C catalyst and 0.874g NaOH were weighed and run at 240℃for 60 minutes under a reaction pressure of 2MPa without an initial pressure. After the reaction is finished, the temperature is quickly reduced, gas generated by gas bag collection is used for gas chromatographic analysis, and the yield of hydrogen is 22.72 mol/kg PET The hydrogen concentration was 98.47%. After recycling the liquid-phase product and the solid catalyst for 5 times, filtering the liquid-phase product and the solid catalyst; adding terephthalic acid to the filtered aqueous solution until terephthalic acid is insoluble to remove residual Na therefrom 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution, and finally, passingThe pure disodium terephthalate solid is obtained by the evaporative crystallization method.
Example 9:
The reforming catalyst was prepared in the same manner as in example 1.
The method for preparing the disodium terephthalate and the high-purity hydrogen by converting PET polyester waste plastics at low temperature by a one-step method in a high-pressure reaction kettle comprises the following steps: 0.7g PET polyester plastic particles, 70ml deionized water, 0.07g Ru/C catalyst and 0.874g NaOH were weighed and run at 240℃for 80 minutes without initial pressure and 2MPa reaction pressure. After the reaction is finished, the temperature is quickly reduced, gas generated by gas bag collection is used for gas chromatographic analysis, and the hydrogen yield is 22.60mol/kg PET The hydrogen concentration was 98.44%. After recycling the liquid-phase product and the solid catalyst for 5 times, filtering the liquid-phase product and the solid catalyst; adding terephthalic acid to the filtered aqueous solution until terephthalic acid is insoluble to remove residual Na therefrom 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution, and finally obtaining pure disodium terephthalate solid by an evaporation crystallization method.
Example 10:
the reforming catalyst was prepared in the same manner as in example 1.
The method for preparing the disodium terephthalate and the high-purity hydrogen by converting PET polyester waste plastics at low temperature by a one-step method in a high-pressure reaction kettle comprises the following steps: 0.7g PET polyester plastic particles, 70ml deionized water, 0.07g Ru/C catalyst and 0.874g NaOH were weighed and run at 240℃for 100 minutes without initial pressure and 2MPa reaction pressure. After the reaction, the reaction mixture is cooled down rapidly, and gas generated by gas bag collection is analyzed by gas chromatography to obtain the hydrogen yield of 23.71mol/kg PET The hydrogen concentration was 98.31%. After recycling the liquid-phase product and the solid catalyst for 5 times, filtering the liquid-phase product and the solid catalyst; adding terephthalic acid to the filtered aqueous solution until terephthalic acid is insoluble to remove residual Na therefrom 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution, and finally, obtaining the disodium terephthalate aqueous solution by an evaporation crystallization methodPure disodium terephthalate solid.
The experimental results of examples 6-10 are shown in Table 2:
referring to examples 11 to 14, the application of the one-step conversion PET process to common PET polyester waste plastics is as follows:
example 11:
the reforming catalyst was prepared in the same manner as in example 1.
The method for preparing the disodium terephthalate and the high-purity hydrogen by converting PET polyester waste plastics at low temperature by a one-step method in a high-pressure reaction kettle comprises the following steps: 0.7g of clear beverage bottle chips (cola bottles, mineral water bottles, etc.), 70ml of deionized water, 0.07g of Ru/C catalyst and 0.874g of NaOH were weighed and run at 240℃for 100 minutes under a reaction pressure of 2MPa without an initial pressure. After the reaction is finished, the temperature is quickly reduced, gas generated by gas bag collection is used for gas chromatographic analysis, and the hydrogen yield is 21.68mol/kg PET The hydrogen concentration was 98.26%. After recycling the liquid-phase product and the solid catalyst for 5 times, filtering the liquid-phase product and the solid catalyst; adding terephthalic acid to the filtered aqueous solution until terephthalic acid is insoluble to remove residual Na therefrom 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution, and finally obtaining pure disodium terephthalate solid by an evaporation crystallization method.
Example 12:
the reforming catalyst was prepared in the same manner as in example 1.
The method for preparing the disodium terephthalate and the high-purity hydrogen by converting PET polyester waste plastics at low temperature by a one-step method in a high-pressure reaction kettle comprises the following steps: 0.7g of colored beverage bottle chips (Lev bottle etc.), 70ml of deionized water, 0.07g of Ru/C catalyst and 0.874g of NaOH were weighed and run at 240℃for 100 minutes under a reaction pressure of 2MPa without an initial pressure. After the reaction is finished, the gas is cooled down quickly, and the generated gas is collected by using a gas bag and is subjected to gas chromatographySeparating to obtain hydrogen yield of 23.96mol/kg PET The hydrogen concentration was 98.11%. After recycling the liquid-phase product and the solid catalyst for 5 times, filtering the liquid-phase product and the solid catalyst; adding terephthalic acid to the filtered aqueous solution until terephthalic acid is insoluble to remove residual Na therefrom 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution, and finally obtaining pure disodium terephthalate solid by an evaporation crystallization method.
Example 13:
the reforming catalyst was prepared in the same manner as in example 1.
The method for preparing the disodium terephthalate and the high-purity hydrogen by converting PET polyester waste plastics at low temperature by a one-step method in a high-pressure reaction kettle comprises the following steps: 0.7g of disposable PET plastic tableware fragments, 70ml of deionized water, 0.07g of Ru/C catalyst and 0.874g of NaOH are weighed, and the reaction is operated for 100 minutes at 240 ℃ without initial pressure and 2 MPa. After the reaction, the reaction mixture is cooled down rapidly, and gas generated by gas bag collection is analyzed by gas chromatography to obtain the hydrogen yield of 23.16mol/kg PET The hydrogen concentration was 98.22%. After recycling the liquid-phase product and the solid catalyst for 5 times, filtering the liquid-phase product and the solid catalyst; adding terephthalic acid to the filtered aqueous solution until terephthalic acid is insoluble to remove residual Na therefrom 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution, and finally obtaining pure disodium terephthalate solid by an evaporation crystallization method.
Example 14:
the reforming catalyst was prepared in the same manner as in example 1.
The method for preparing the disodium terephthalate and the high-purity hydrogen by converting PET polyester waste plastics at low temperature by a one-step method in a high-pressure reaction kettle comprises the following steps: 0.7g of polyester fabric chips, 70ml of deionized water, 0.07g of Ru/C catalyst and 0.874g of NaOH are weighed, and the mixture is operated for 100 minutes at 240 ℃ under the condition of no initial pressure and 2MPa of reaction pressure. After the reaction is finished, the gas is cooled down rapidly, the generated gas is collected by using an air bag and is analyzed by gas chromatography,the yield of hydrogen was 21.52mol/kg PET The hydrogen concentration was 96.16%. After recycling the liquid-phase product and the solid catalyst for 5 times, filtering the liquid-phase product and the solid catalyst; adding terephthalic acid to the filtered aqueous solution until terephthalic acid is insoluble to remove residual Na therefrom 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution, and finally obtaining pure disodium terephthalate solid by an evaporation crystallization method.
Fig. 4 and 5 are graphs showing comparison of infrared absorption spectrum and nuclear magnetic resonance spectrum of disodium terephthalate produced from different PET plastic waste materials. The higher purity of the disodium terephthalate produced by the present invention is demonstrated by comparison with commercial disodium terephthalate.
The experimental results of examples 11-14 are shown in Table 3:
referring to examples 10 and 15-16, the mass ratio of the low concentration NaOH solution to the PET polyester waste plastic and the effect of NaOH concentration on the one-step conversion of PET polyester waste plastic are specifically as follows:
example 15:
the reforming catalyst was prepared in the same manner as in example 1.
The method for preparing the disodium terephthalate and the high-purity hydrogen by converting PET polyester waste plastics at low temperature by a one-step method in a high-pressure reaction kettle comprises the following steps: 0.7g PET polyester plastic particles, 35ml deionized water, 0.07g Ru/C catalyst and 0.874g NaOH were weighed and run at 240℃for 100 minutes without initial pressure and 2MPa reaction pressure. After the reaction is finished, the temperature is quickly reduced, gas generated by gas bag collection is used for gas chromatographic analysis, and the hydrogen yield is 23.55 mol/kg PET The hydrogen concentration was 98.72%. After recycling the liquid-phase product and the solid catalyst for 5 times, filtering the liquid-phase product and the solid catalyst; adding terephthalic acid to the filtered aqueous solution until terephthalic acid is insoluble to remove the terephthalic acidResidual Na in 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution, and finally obtaining pure disodium terephthalate solid by an evaporation crystallization method.
Example 16:
the reforming catalyst was prepared in the same manner as in example 1.
The method for preparing the disodium terephthalate and the high-purity hydrogen by converting PET polyester waste plastics at low temperature by a one-step method in a high-pressure reaction kettle comprises the following steps: 0.7g PET polyester plastic particles, 18ml deionized water, 0.07g Ru/C catalyst and 0.874g NaOH were weighed and run at 240℃for 100 minutes without initial pressure and 2MPa reaction pressure. After the reaction is finished, the temperature is quickly reduced, gas generated by gas bag collection is used for gas chromatographic analysis, and the hydrogen yield is 23.55mol/kg PET The hydrogen concentration was 99.6%. After recycling the liquid-phase product and the solid catalyst for 5 times, filtering the liquid-phase product and the solid catalyst; adding terephthalic acid to the filtered aqueous solution until terephthalic acid is insoluble to remove residual Na therefrom 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution, and finally obtaining pure disodium terephthalate solid by an evaporation crystallization method.
Referring to examples 10 and 17, the mass ratio of PET polyester waste to reforming catalyst and the effect on the one-step conversion of PET polyester waste are as follows:
example 17:
the reforming catalyst was prepared in the same manner as in example 1.
The method for preparing the disodium terephthalate and the high-purity hydrogen by converting PET polyester waste plastics at low temperature by a one-step method in a high-pressure reaction kettle comprises the following steps: 0.7g PET polyester plastic particles, 70ml deionized water, 0.035g Ru/C catalyst and 0.874g NaOH were weighed out and run at 240℃for 100 minutes without an initial pressure, a reaction pressure of 2 MPa. After the reaction, the reaction mixture is cooled down rapidly, and gas generated by gas bag collection is analyzed by gas chromatography to obtain the hydrogen yield of 23.62 mol/kg PET The hydrogen concentration was 98.4%. Recycling the liquid phase product and the solid catalyst for 5 times, and then producing the liquid phaseFiltering the materials and the solid catalyst; adding terephthalic acid to the filtered aqueous solution until terephthalic acid is insoluble to remove residual Na therefrom 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution, and finally obtaining pure disodium terephthalate solid by an evaporation crystallization method.
Referring to examples 10, 18 and 19, the active metal loading and impact on the one-step conversion of PET polyester waste plastics are specifically as follows:
example 18:
the preparation method of the reforming catalyst comprises the following steps: adding a certain amount of biochar and precursor chloroplatinic acid into absolute ethyl alcohol according to 0.1wt.% of theoretical Ru load by using an impregnation method, uniformly stirring and impregnating for 12 hours at room temperature, continuously stirring at 80 ℃ until the absolute ethyl alcohol is evaporated to dryness, and drying an obtained sample (Pt/C) in a 105 ℃ oven; at 500 ℃,10% H 2 -reduction in 90% ar for 5 hours.
The method for preparing the disodium terephthalate and the high-purity hydrogen by converting PET polyester waste plastics at low temperature by a one-step method in a high-pressure reaction kettle comprises the following steps: 0.7g PET polyester plastic particles, 70ml deionized water, 0.07g Ru/C catalyst and 0.874g NaOH were weighed and run at 240℃for 100 minutes without initial pressure and 0.5MPa reaction pressure. After the reaction is finished, the temperature is quickly reduced, gas generated by gas bag collection is used for gas chromatographic analysis, and the yield of hydrogen is 22.32 mol/kg PET The hydrogen concentration was 98.51%. After recycling the liquid-phase product and the solid catalyst for 5 times, filtering the liquid-phase product and the solid catalyst; adding terephthalic acid to the filtered aqueous solution until terephthalic acid is insoluble to remove residual Na therefrom 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution, and finally obtaining pure disodium terephthalate solid by an evaporation crystallization method.
Example 19:
the preparation method of the reforming catalyst comprises the following steps: a catalyst was prepared using an impregnation method, and a quantity of biochar and precursor chloroplatinic acid were added to a 10wt.% theoretical Ru loadingSoaking in absolute ethanol under stirring at room temperature for 12 hr, stirring at 80deg.C until the absolute ethanol is evaporated, and drying the obtained sample (Pt/C) in a 105 deg.C oven; at 500 ℃,10% H 2 -reduction in 90% ar for 5 hours.
The method for preparing the disodium terephthalate and the high-purity hydrogen by converting PET polyester waste plastics at low temperature by a one-step method in a high-pressure reaction kettle comprises the following steps: 0.7g PET polyester plastic particles, 70ml deionized water, 0.07g Ru/C catalyst and 0.874g NaOH were weighed and run at 240℃for 100 minutes without initial pressure and 0.5MPa reaction pressure. After the reaction is finished, the temperature is quickly reduced, gas generated by gas bag collection is used for gas chromatographic analysis, and the hydrogen yield is 23.83 mol/kg PET The hydrogen concentration was 98.25%. After recycling the liquid-phase product and the solid catalyst for 5 times, filtering the liquid-phase product and the solid catalyst; adding terephthalic acid to the filtered aqueous solution until terephthalic acid is insoluble to remove residual Na therefrom 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution, and finally obtaining pure disodium terephthalate solid by an evaporation crystallization method.
Referring to examples 10 and 20-22, the different reactive metals and their impact on the one-step conversion of PET polyester waste plastics are specified as follows:
example 20:
the preparation method of the reforming catalyst comprises the following steps: adding a certain amount of biochar and precursor chloroplatinic acid into absolute ethyl alcohol according to 5wt.% of theoretical Pt load by using an impregnation method, uniformly stirring and impregnating for 12 hours at room temperature, continuously stirring at 80 ℃ until absolute ethyl alcohol is evaporated to dryness, and drying an obtained sample (Pt/C) in a 105 ℃ oven; at 500 ℃,10% H 2 -reduction in 90% ar for 5 hours.
The method for preparing the disodium terephthalate and the high-purity hydrogen by converting PET polyester waste plastics at low temperature by a one-step method in a high-pressure reaction kettle comprises the following steps: 0.7g PET polyester plastic particles, 70ml deionized water, 0.07g Pt/C catalyst and 0.874g NaOH were weighed and run at 240℃for 100 minutes without initial pressure and 0.5MPa reaction pressure. After the reaction is finished, the rapid cooling is carried outCooling, collecting the generated gas by using an air bag, and performing gas chromatography analysis to obtain hydrogen with a yield of 23.2 mol/kg PET The hydrogen concentration was 98.8%. After recycling the liquid-phase product and the solid catalyst for 5 times, filtering the liquid-phase product and the solid catalyst; adding terephthalic acid to the filtered aqueous solution until terephthalic acid is insoluble to remove residual Na therefrom 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution, and finally obtaining pure disodium terephthalate solid by an evaporation crystallization method.
Example 21:
the preparation method of the reforming catalyst comprises the following steps: adding a certain amount of biochar and precursor rhodium chloride into absolute ethyl alcohol according to the Rh loading amount of 5wt.% theory by using an impregnation method, uniformly stirring and impregnating for 12 hours at room temperature, continuously stirring at 80 ℃ until the absolute ethyl alcohol is evaporated to dryness, and drying the obtained sample (Rh/C) in a 105 ℃ oven; at 500 ℃,10% H 2 -reduction in 90% ar for 5 hours.
The method for preparing the disodium terephthalate and the high-purity hydrogen by converting PET polyester waste plastics at low temperature by a one-step method in a high-pressure reaction kettle comprises the following steps: 0.7g PET polyester plastic particles, 70ml deionized water, 0.07g Rh/C catalyst and 0.874g NaOH were weighed and run at 240℃for 100 minutes without an initial pressure, with a reaction pressure of 0.5 MPa. After the reaction, the reaction mixture is cooled down rapidly, and gas generated by gas bag collection is analyzed by gas chromatography to obtain the hydrogen yield of 22.9 mol/kg PET The hydrogen concentration was 98.2%. After recycling the liquid-phase product and the solid catalyst for 5 times, filtering the liquid-phase product and the solid catalyst; adding terephthalic acid to the filtered aqueous solution until terephthalic acid is insoluble to remove residual Na therefrom 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution, and finally obtaining pure disodium terephthalate solid by an evaporation crystallization method.
Example 22:
the preparation method of the reforming catalyst comprises the following steps: catalyst prepared using impregnation method, according to 5wt.% theory Pd, loading, namely adding a certain amount of charcoal and precursor palladium nitrate into absolute ethyl alcohol, uniformly stirring and impregnating for 12 hours at room temperature, continuously stirring at 80 ℃ until the absolute ethyl alcohol is evaporated to dryness, and drying the obtained sample (Pd/C) in a 105 ℃ oven; at 500 ℃,10% H 2 -reduction in 90% ar for 5 hours.
The method for preparing the disodium terephthalate and the high-purity hydrogen by converting PET polyester waste plastics at low temperature by a one-step method in a high-pressure reaction kettle comprises the following steps: 0.7g PET polyester plastic particles, 70ml deionized water, 0.07g Pd/C catalyst and 0.874g NaOH were weighed and run at 240℃for 100 minutes under a reaction pressure of 0.5MPa without an initial pressure. After the reaction, the reaction mixture is cooled down rapidly, and gas generated by gas bag collection is analyzed by gas chromatography to obtain the hydrogen yield of 23.3 mol/kg PET The hydrogen concentration was 98.5%. After recycling the liquid-phase product and the solid catalyst for 5 times, filtering the liquid-phase product and the solid catalyst; adding terephthalic acid to the filtered aqueous solution until terephthalic acid is insoluble to remove residual Na therefrom 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution, and finally obtaining pure disodium terephthalate solid by an evaporation crystallization method.
Example 23: liquid phase product recycling test
The reforming catalyst was prepared in the same manner as in example 1.
The method for preparing the disodium terephthalate and the high-purity hydrogen by converting PET polyester waste plastics at low temperature by a one-step method in a high-pressure reaction kettle comprises the following steps: 0.7g PET polyester plastic particles, 70ml deionized water, 0.07g gRu/C catalyst and 0.874g NaOH were weighed and run at 240℃for 100 minutes without an initial pressure, a reaction pressure of 2 MPa. And after the reaction is finished, rapidly cooling, collecting generated gas by using an air bag, performing gas chromatographic analysis, and filtering and separating the liquid phase and the solid catalyst. Then adding the liquid phase product obtained by filtration, 0.7g PET polyester plastic particles, 0.07g fresh Ru/C catalyst and 0.874g NaOH into a high-pressure reaction kettle to operate under the same working condition, circulating for 5 times, collecting the generated gas each time and analyzing by using a gas chromatograph to obtain a liquid phase product recycling influence rule, and according to figure 2, the disodium terephthalate and sodium carbonate in the liquid phase product have no obvious influence on the hydrogen yield, so that the method has recycling potential.
Example 24: modification evaluation test of Ru catalyst by NaOH solution
The reforming catalyst was prepared in the same manner as in example 1.
The method for preparing the disodium terephthalate and the high-purity hydrogen by converting PET polyester waste plastics at low temperature by a one-step method in a high-pressure reaction kettle comprises the following steps: 0.7g PET polyester plastic particles, 70ml deionized water, 0.07g Ru/C catalyst and 0.874g NaOH were weighed and run at 240℃for 100 minutes without initial pressure and 2MPa reaction pressure. And after the reaction is finished, rapidly cooling, collecting generated gas by using an air bag, performing gas chromatographic analysis, filtering and separating the liquid phase and the solid catalyst, and drying the used solid catalyst. Then, 0.07g of the dried solid catalyst, 0.7g of PET polyester plastic particles, 70ml of deionized water and 0.874g of NaOH are added into a high-pressure reaction kettle to operate under the same working condition, the circulation is carried out for 5 times, and generated gas is collected each time and analyzed by a gas chromatograph instrument, so that the stability analysis of the Ru catalyst in an alkaline solution is obtained.
For comparison, in this example, 0.226g of ethylene glycol (0.7 g of PET theoretical depolymerization yield), 70ml of deionized water, 0.07g of Ru/C catalyst was weighed out, run at 240℃without initial pressure, under a reaction pressure of 2MPa for 100 minutes, and catalyst recycling experiments were performed according to the above process flow. The experimental result is compared with the stability of the Ru catalyst in the alkaline solution, the comparison result is shown in figure 3, and the result shows that the modification of the Ru catalyst by the NaOH solution can obviously improve the stability of the Ru catalyst. Compared with the NaOH+glycol system, in the NaOH+PET+catalyst system, the average Ru active metal particles have lower particle size under the influence of NaOH solution, which proves that the metal agglomeration phenomenon is relieved, and the method has higher reference value for industrial application.
The above embodiments are illustrative of the present invention, and not limiting, and any simple modifications of the present invention fall within the scope of the present invention.
Claims (8)
1. The method for preparing the disodium terephthalate and the hydrogen by converting PET polyester waste plastics at low temperature by a one-step method is characterized by comprising the following steps: mixing PET polyester waste plastics and a reforming catalyst according to a certain proportion, adding the mixture into a low-concentration NaOH solution, coupling a PET hydrothermal thermal polymerization reaction and an in-situ reforming reaction of a PET depolymerization product under a low-temperature hydrothermal condition, so that PET is completely converted in one step in a reaction system, and hydrogen and a crude disodium terephthalate solution are directly obtained; the reforming catalyst is a noble metal catalyst with an active metal content of 0.1-10 wt.%; the noble metal catalyst is a Ru, pt, pd, rh-loaded biochar-based catalyst; the mass ratio range of the low-concentration NaOH solution to the PET polyester waste plastic is as follows: 50:1-100:1; the temperature of the low-temperature hydrothermal condition is 240-260 ℃; the NaOH concentration value of the low-concentration NaOH solution is 1.2-4.8%; the mass ratio range of the PET polyester waste plastic to the reforming catalyst is as follows: 10:1-20:1.
2. The method for preparing the disodium terephthalate and the hydrogen by converting PET polyester waste plastics at low temperature by a one-step method according to claim 1, which is characterized in that: the amount of NaOH in the low-concentration NaOH solution is the amount of terephthalic acid in the neutralized PET hydrolysate and the CO in the product in-situ liquid phase reforming of ethylene glycol is removed 2 Sum of the amounts of (3).
3. The method for preparing the disodium terephthalate and the hydrogen by converting PET polyester waste plastics at low temperature by a one-step method according to claim 1, which is characterized in that: the product of the one-step complete conversion of PET in one reaction system also includes a solid catalyst for recycling comprising the steps of: the method comprises the steps of filtering a mixture of a solid catalyst and a crude disodium terephthalate aqueous solution, separating the solid catalyst, drying the solid catalyst, mixing the dried solid catalyst, PET polyester waste plastics and deionized water according to a certain mass ratio, and adding a certain amount of NaOH reagent for preparing disodium terephthalate and hydrogen again.
4. The method for preparing the disodium terephthalate and the hydrogen by converting PET polyester waste plastics at low temperature by a one-step method according to claim 1, which is characterized in that: the product of the one-step complete conversion of PET in a reaction system also comprises a solid catalyst, and the one-step complete conversion further comprises the refining treatment of disodium terephthalate, and specifically comprises the following steps: filtering the mixture of the solid catalyst and the crude disodium terephthalate aqueous solution to separate the crude disodium terephthalate aqueous solution, adding a proper amount of terephthalic acid into the crude disodium terephthalate aqueous solution, and removing residual Na 2 CO 3 And a small amount of NaOH to obtain a refined disodium terephthalate aqueous solution.
5. The method for preparing the disodium terephthalate and the hydrogen by converting PET polyester waste plastics at a low temperature by a one-step method according to claim 4, which is characterized in that: the purified disodium terephthalate aqueous solution is evaporated and crystallized to obtain pure disodium terephthalate crystals.
6. The method for preparing the disodium terephthalate and the hydrogen by converting PET polyester waste plastics at low temperature by a one-step method according to claim 1, which is characterized in that: the reforming catalyst is a noble metal catalyst having an active metal content of 5 wt.%.
7. The method for preparing the disodium terephthalate and the hydrogen by converting PET polyester waste plastics at low temperature by a one-step method according to claim 1, which is characterized in that: the noble metal catalyst is a Ru-supported biochar-based catalyst.
8. The method for preparing the disodium terephthalate and the hydrogen by converting PET polyester waste plastics at low temperature by a one-step method according to claim 1, which is characterized in that: the PET polyester waste plastic comprises a plastic beverage bottle, a disposable tableware and polyester cloth.
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| PCT/CN2022/080073 WO2023130566A1 (en) | 2022-01-07 | 2022-03-10 | Method for preparing disodium terephthalate and high-purity hydrogen by one-step low-temperature conversion of pet polyester waste plastic |
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| CN114955993B (en) * | 2022-06-10 | 2023-10-27 | 天津大学 | Device for continuously producing hydrogen by photocatalytic degradation of polyester plastics |
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| JP2004277638A (en) * | 2003-03-18 | 2004-10-07 | Teijin Fibers Ltd | Collecting method of highly pure terephthalic acid from polyester wastes |
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| CN113401866B (en) * | 2021-05-29 | 2023-05-30 | 浙江大学 | Method for preparing hydrogen-rich synthetic gas by degrading polyolefin waste plastics at low temperature |
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| CN101857198A (en) * | 2010-05-27 | 2010-10-13 | 复旦大学 | One-step method for continuously preparing high-purity hydrogen through ethylene glycol aqueous-phase reforming |
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