Method for catalytically converting waste PET (Polyethylene Terephthalate) plastic into 1, 4-cyclohexanedimethanol by two-step method

Abstract

The invention provides a method for catalytically converting waste PET (Polyethylene Terephthalate) plastic into 1, 4-cyclohexanedimethanol by a two-step method, which comprises the following steps of: 1, hydrogenating the waste PET plastic dispersed in methanol under the action of a nickel-based catalyst to obtain dimethyl 1, 4-cyclohexane dicarboxylate; and 2, centrifugally separating the catalyst and the reaction liquid in the step 1, and hydrogenating the reaction liquid under the action of a CuMgAl catalyst to obtain the target product 1, 4-cyclohexanedimethanol. The 1, 4-cyclohexanedimethanol is a key raw material for producing high-end polyester, and has very high market requirements. Under the optimal reaction condition, the molar yield of the 1, 4-cyclohexanedimethanol can reach 83.8%, and the separation purity reaches up to 99.5%. According to the method, upgrading and recycling of the PET waste are achieved so as to cope with the threat of white pollution to the ecological environment and human health.

Description

Technical Field

[0001] The present application relates to the technical field of high-value conversion of waste plastics, and in particular to a two-step method for catalytically converting waste PET plastics into 1,4-cyclohexanedimethanol. Background Art

[0002] Polyethylene terephthalate (PET) is one of the most widely used synthetic polyester plastics, with an annual global production of nearly 70 million tons. However, used PET waste plastics are usually unable to degrade under natural conditions, which will seriously threaten the ecological environment and human health. At the same time, PET, as a petroleum-based plastic, contains rich carbon, hydrogen and oxygen resources. Therefore, whether from the perspective of environmental pollution or resource utilization, the recycling of PET waste plastics needs to be solved urgently.

[0003] Chemical recycling of PET waste plastics is considered to be the most promising strategy for recycling PET waste due to its high efficiency and sustainability. At present, researchers have developed a variety of chemical strategies to recycle PET waste, such as hydrolysis, methanolysis, glycolysis and hydrogenolysis (CN113444284A, CN118561687A, CN114426483B, CN109705985A). Through these strategies, PET can be depolymerized into small molecular compounds, such as terephthalic acid (TPA), dimethyl terephthalate (DMT), bis(2-hydroxyethyl) terephthalate (BHET) and p-xylene (PX), etc., which can be directly or first oxidized and then repolymerized back to PET. However, the above process only realizes the closed-loop recycling of PET waste. If PET waste can be converted into higher value products, it is more desirable to achieve the upgrading and recycling of PET waste. 1,4-cyclohexanedimethanol (CHDM) is a key chemical for producing high-end copolyester plastics. Considering the chemical structure of PET itself, converting PET waste into CHDM is feasible and more economically valuable. However, this process has problems such as complex reaction process, low product selectivity, and expensive catalysts (CN117563628A, CN104003840B, CN117181218A).

[0004] Therefore, a simpler and more economical method for catalytically converting PET waste into CHDM with high selectivity is urgently needed. Summary of the invention

[0005] In view of this, the purpose of this application is to propose a two-step method for catalytically converting waste PET plastics into 1,4-cyclohexanedimethanol, so as to achieve the upgrading and recycling of waste PET plastics.

[0006] Based on the above purpose, the present application provides a two-step method for catalytically converting waste PET plastic into 1,4-cyclohexanedimethanol, the method comprising:

[0007] Step 1: Discarded PET plastic dispersed in a methanol medium reacts at 150-180° C. under the action of a nickel-based catalyst and in the presence of hydrogen, firstly methanolyzing and depolymerizing to obtain dimethyl terephthalate, and then further hydrogenating to obtain dimethyl 1,4-cyclohexanedicarboxylate;

[0008] Step 2, centrifugally separating the catalyst and the reaction liquid in step 1, and then reacting the reaction liquid at 250° C. under the action of CuMgAl catalyst and hydrogenation conditions to obtain the target product 1,4-cyclohexanedimethanol.

[0009] Wherein, the nickel-based catalyst in step 1 comprises a carrier and an active ingredient and an auxiliary agent supported on the carrier, wherein the carrier is at least one of cerium oxide, magnesium oxide, silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, and niobium oxide; the active ingredient is nickel; and the auxiliary agent is at least one of platinum, palladium, and ruthenium;

[0010] Wherein, the CuMgAl catalyst in step 2 is prepared by a coprecipitation method, the mass fraction of Cu in the total amount of the catalyst is 20%, the mass fraction of Mg in the total amount of the catalyst is 5%, and the mass fraction of Al in the total amount of the catalyst is 40%;

[0011] Preferably, the nickel-based catalyst carrier is at least one of cerium oxide, magnesium oxide, silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, and niobium oxide, preferably cerium oxide.

[0012] Furthermore, the promoter of the nickel-based catalyst is selected from at least one of platinum, palladium and ruthenium, preferably palladium.

[0013] Furthermore, the nickel loading in the nickel-based catalyst is 1% to 7%, preferably 5%.

[0014] Furthermore, the palladium loading of the nickel-based catalyst promoter is 0.2% to 2%, preferably 0.5%.

[0015] Furthermore, the reaction temperature of step 1 is 150-180°C, preferably 180°C.

[0016] Furthermore, the reaction time of step 1 is 2-12 hours, preferably 10 hours.

[0017] Furthermore, the reaction hydrogen pressure in step 1 is 2-6 MPa, preferably 6 MPa.

[0018] Furthermore, the mass concentration of the PET plastic tested in the step 1 is 2%-20%, preferably 10%.

[0019] Furthermore, the reaction conditions of step 2 are 250°C, 4h, 5MPa H 2 .

[0020] The key step in catalytic conversion of waste PET plastics to prepare CHDM is the conversion of PET to 1,4-cyclohexanedicarboxylic acid dimethyl ester (DMCD). This step has extremely high requirements for the catalyst. Not only does it require the catalyst to have the ability to depolymerize PET by methanolysis, but it also requires the catalyst to be able to dissociate hydrogen and achieve selective hydrogenation, so that PET can be highly selectively converted to DMCD. The present invention uses cerium oxide with certain methanolysis activity as a catalyst carrier, non-precious metal nickel as the active center for benzene ring hydrogenation, and a small amount of precious metal palladium to regulate the hydrogenation selectivity to avoid transitional hydrogenation, thereby achieving a process of highly selective conversion of waste PET plastics to DMCD, and the molar yield of DMCD can reach 86.5%. Furthermore, DMCD can be further converted into CHDM on a CuMgAl catalyst, and the molar yield can reach 83.8% (calculated based on PET). CHDM is a key raw material for producing high-end polyesters such as polyethylene terephthalate-1,4-cyclohexanedimethanol (PETG) and poly(1,4-cyclohexanedimethanol terephthalate) (PCT) and has high added value. Therefore, the process has good industrial value. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the present application or related technologies, the drawings required for use in the embodiments or related technical descriptions are briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 This is a schematic diagram of the process of catalytically converting waste PET plastic into 1,4-cyclohexanedimethanol using a two-step method according to an embodiment of the present application. DETAILED DESCRIPTION

[0023] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0024] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present application should have the usual meanings understood by people with ordinary skills in the field to which the present application belongs. "Include" or "comprising" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, but do not exclude other elements or objects.

[0025] See also Figure 1 A two-step method for catalytically converting waste PET plastic into 1,4-cyclohexanedimethanol comprises:

[0026] Step 1: Waste PET plastic dispersed in a methanol medium reacts at 150-180° C. under the action of a nickel-based catalyst and in the presence of hydrogen, firstly undergoes methanolysis and depolymerization to obtain dimethyl terephthalate, and then further undergoes hydrogenation to obtain dimethyl 1,4-cyclohexanedicarboxylate.

[0027] In this step, the mass ratio of waste PET to catalyst is 0.5-10:1, the reaction temperature is 150-180°C, the reaction time is 2-12 hours, and the hydrogen pressure is 2-6 MPa. The mass concentration of the reactants is the mass percentage of waste PET plastic to solvent, which can be 2-20%.

[0028] The nickel-based catalyst comprises a carrier and an active ingredient and an auxiliary agent supported on the carrier, wherein the carrier is at least one of cerium oxide, magnesium oxide, silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, and niobium oxide; the active ingredient is nickel; and the auxiliary agent is at least one of platinum, palladium, and ruthenium;

[0029] The preparation method of the nickel-based catalyst is a step-by-step method, that is, first preparing a carrier and then loading the metal, and the metal loading adopts an excess impregnation method, a deposition precipitation method, and an equal volume impregnation method, etc., preferably an equal volume impregnation method. It should be understood that the excess impregnation method, the deposition precipitation method, and the equal volume impregnation method are all existing methods, and the embodiments of this application do not involve improvements to specific methods.

[0030] Furthermore, the carrier of the nickel-based catalyst is at least one of cerium oxide, magnesium oxide, silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, and niobium oxide, preferably cerium oxide.

[0031] Furthermore, the promoter of the nickel-based catalyst is selected from at least one of platinum, palladium and ruthenium, preferably palladium.

[0032] Furthermore, the nickel loading in the nickel-based catalyst is 1% to 7%, preferably 5%.

[0033] Furthermore, the palladium loading of the nickel-based catalyst promoter is 0.2% to 2%, preferably 0.5%.

[0034] Next, in step 2, the catalyst and the reaction liquid in step 1 are separated by centrifugation, and then the reaction liquid is reacted at 250° C. under the action of CuMgAl catalyst and hydrogenation conditions to obtain the target product 1,4-cyclohexanedimethanol.

[0035] In this step, the reaction temperature is 250°C, the reaction time is 4h, and the hydrogen pressure is 5MPa. The CuMgAl catalyst is prepared by coprecipitation, the mass fraction of Cu in the total amount of the catalyst is 20%, the mass fraction of Mg in the total amount of the catalyst is 5%, and the mass fraction of Al in the total amount of the catalyst is 40%;

[0036] In some embodiments, the obtained catalyst can be reused, wherein the catalyst can be calcined first and then reduced, for example, the catalyst is first calcined at 500°C and then reduced at 400°C, so as to remove the carbon deposits on the catalyst surface, so that the catalyst can be regenerated, the service life of the catalyst is extended, the cost of the catalyst is reduced, and the use efficiency of the catalyst is improved.

[0037] The technical solution of the present invention is further described below in conjunction with specific implementation methods.

[0038] The experimental methods in the following examples are all conventional methods unless otherwise specified.

[0039] Unless otherwise specified, the test materials used in the following examples were purchased from conventional biochemical reagent stores.

[0040] Example 1

[0041] Test materials: waste PET plastic; waste PET plastic mass: 0.1 g; solvent: methanol; solvent mass: 5 g; substrate concentration: 2%;

[0042] Catalyst: 5Ni / CeO 2 , where the active center is nickel, the carrier is cerium oxide, and the catalyst mass is 0.1g;

[0043] Experimental conditions: using a batch reactor; nitrogen pressure: 4MPa; reaction temperature: 180℃; reaction time: 2h;

[0044] Test method: 0.1g of waste PET plastic was dispersed in 5g of methanol, and then the dispersion and 0.1g of 5Ni / CeO 2The catalyst was put into a 50 mL stainless steel autoclave, sealed, filled with 4 MPa hydrogen, and heated to the required temperature of 180 ° C under rapid stirring. The reaction was stopped after 2 hours. After cooling to room temperature, an appropriate amount of ethyl acetate and internal standard tridecane were added to the autoclave, and the catalyst was separated by centrifugation. The supernatant was qualitatively and quantitatively analyzed by GC-MS (Agilent 7890A) and GC (Agilent 7890B), respectively.

[0045] Example 2

[0046] The only difference from Example 1 is that the catalyst is 5Ni / MgO.

[0047] Example 3

[0048] The only difference from Example 1 is that the catalyst is 5Ni / SiO 2 .

[0049] Example 4

[0050] The only difference from Example 1 is that the catalyst is 5Ni / TiO 2 .

[0051] Example 5

[0052] The only difference from Example 1 is that the catalyst is 5Ni / Al 2 O 3 .

[0053] Example 6

[0054] The only difference from Example 1 is that the catalyst is 5Ni / ZrO 2 .

[0055] Example 7

[0056] The only difference from Example 1 is that the catalyst is 5Ni / Nb 2 O 5 .

[0057] Example 1 - Example 7 Test results, as shown in Table 1,

[0058] Table 1 Performance of different catalysts for catalytic conversion of waste PET plastic methanol to DMT

[0059] Test example PET conversion rate % DMT molar yield% Example 1 99.9 93.7 Example 2 99.9 88.3 Example 3 61.3 44.1 Example 4 32.6 15.7 Example 5 27.1 11.9 Example 6 36.2 18.7 Example 7 44.9 31.2

[0060] The key step in catalytically converting waste PET plastics into CHDM is the one-pot conversion of PET to DMCD. This step first requires the methanol depolymerization of PET into a small molecule compound DMT, which can be further hydrogenated under the action of hydrogen to obtain DMCD. Therefore, the catalyst designed for this step needs to have a certain ability to depolymerize PET with methanol, thereby efficiently converting waste PET plastics into DMCD in one pot. As can be seen from the above table, in the process of methanol depolymerization of PET to DMT, when the carrier of the nickel-based catalyst is at least one of cerium oxide, magnesium oxide, silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, and niobium oxide, cerium oxide is preferably used as the catalyst carrier, which can efficiently depolymerize PET into DMT with a yield of up to 93.7%.

[0061] Example 8

[0062] Test materials: waste PET plastic; waste PET plastic mass: 0.1 g; solvent: methanol; solvent mass: 5 g; substrate concentration: 2%;

[0063] Catalyst: 0.5Pd5Ni / CeO 2 , where the active center is nickel, the auxiliary agent is palladium, the carrier is cerium oxide, and the catalyst mass is 0.1g;

[0064] Experimental conditions: intermittent reactor; hydrogen pressure: 6MPa; reaction temperature: 180℃; reaction time: 10h;

[0065] Test method: 0.1g of waste PET plastic was dispersed in 5g of methanol, and then the dispersion and 0.1g of 0.5Pd5Ni / CeO 2 The catalyst was put into a 50 ml stainless steel autoclave, sealed, filled with 6 MPa hydrogen, and heated to the required temperature of 180°C under rapid stirring. The reaction was stopped after 10 hours. After cooling to room temperature, an appropriate amount of ethyl acetate and internal standard tridecane were added to the autoclave, and the catalyst was separated by centrifugation. The supernatant was qualitatively and quantitatively analyzed by GC-MS (Agilent 7890A) and GC (Agilent 7890B), respectively.

[0066] Example 9

[0067] The only difference from Example 8 is that the catalyst is 5Ni / CeO 2 .

[0068] Example 10

[0069] The only difference from Example 8 is that the catalyst is 2Pt5Ni / CeO 2 .

[0070] Embodiment 11

[0071] The only difference from Example 8 is that the catalyst is 2Pd5Ni / CeO 2 .

[0072] Example 12

[0073] The only difference from Example 8 is that the catalyst is 2Ru5Ni / CeO 2 .

[0074] Example 13

[0075] The only difference from Example 8 is that the catalyst is 1Pt1Pd5Ni / CeO 2 .

[0076] Embodiment 14

[0077] The only difference from Example 8 is that the catalyst is 1Ru1Pd5Ni / CeO 2 .

[0078] Embodiment 15

[0079] The only difference from Example 8 is that the catalyst is 2Pd1Ni / CeO 2 .

[0080] Example 16

[0081] The only difference from Example 8 is that the catalyst is 2Pd3Ni / CeO 2 .

[0082] Embodiment 17

[0083] The only difference from Example 8 is that the catalyst is 2Pd4Ni / CeO 2 .

[0084] Embodiment 18

[0085] The only difference from Example 8 is that the catalyst is 2Pd7Ni / CeO 2 .

[0086] Embodiment 19

[0087] The only difference from Example 8 is that the catalyst is 1Pd5Ni / CeO 2 .

[0088] Embodiment 20

[0089] The only difference from Example 8 is that the catalyst is 0.2Pd5Ni / CeO 2 .

[0090] Embodiment 21

[0091] The only difference from Example 8 is that the reaction time is 2 h.

[0092] Embodiment 22

[0093] The only difference from Example 8 is that the reaction time is 4 h.

[0094] Embodiment 23

[0095] The only difference from Example 8 is that the reaction time is 6 h.

[0096] Embodiment 24

[0097] The only difference from Example 8 is that the reaction time is 8 h.

[0098] Embodiment 25

[0099] The only difference from Example 8 is that the reaction time is 12 h.

[0100] Embodiment 26

[0101] The only difference from Example 8 is that the reaction temperature is 150°C.

[0102] Embodiment 27

[0103] The only difference from Example 8 is that the reaction temperature is 165°C.

[0104] Embodiment 28

[0105] The only difference from Example 8 is that the hydrogen pressure is 2 MPa.

[0106] Embodiment 29

[0107] The only difference from Example 8 is that the hydrogen pressure is 4 MPa.

[0108] Embodiment 30

[0109] The only difference from Example 8 is that the mass of the waste PET plastic is 0.5 g and the substrate concentration is 10%.

[0110] Embodiment 31

[0111] The only difference from Example 8 is that the mass of the waste PET plastic is 0.75 g and the substrate concentration is 15%.

[0112] Embodiment 32

[0113] The only difference from Example 8 is that the mass of the waste PET plastic is 1 g and the substrate concentration is 20%.

[0114] The test results of Example 8 to Example 32 are shown in Table 2.

[0115] Table 2 Performance of different catalysts in catalytic conversion of waste PET plastics to DMCD

[0116]

[0117]

[0118] It can be seen from the above table that in Examples 8 to 32, the nickel-based catalyst carrier is cerium oxide, the active ingredient is nickel, and the auxiliary agent is selected from at least one of platinum, palladium, and ruthenium. Palladium is preferably used as the catalyst auxiliary agent, which can effectively inhibit the transition hydrogenation of CO bonds, and the DMCD selectivity can reach 96.4%.

[0119] Furthermore, when the nickel loading in the nickel-based catalyst is between 1% and 5%, preferably 5%, the DMCD yield can reach 86.3%.

[0120] Furthermore, when the palladium loading of the nickel-based catalyst promoter is 0.2% to 2%, preferably 0.5%, the DMCD yield can reach 86.5% and the selectivity is 97.4%.

[0121] Furthermore, in 0.5Pd5Ni / CeO 2 Under the action of, the preferred reaction time is 4 to 12 hours, the reaction temperature is 165 to 180°C, the hydrogen pressure is 4 to 6 MPa, and the substrate concentration is 2 to 10%.

[0122] Embodiment 33

[0123] Test materials: the reaction supernatant obtained in step 1 (centrifuge after the reaction in step 1 is completed, without adding ethyl acetate and tridecane);

[0124] Catalyst: CuMgAl, catalyst mass 0.05g;

[0125] Experimental conditions: intermittent reactor; hydrogen pressure: 5MPa; reaction temperature: 250℃; reaction time: 4h;

[0126] Experimental method: The reaction supernatant obtained in step 1 and 0.05 g CuMgAl catalyst were put into a 50 mL stainless steel high-pressure reactor, sealed, filled with 5 MPa hydrogen, and heated to the required temperature of 250°C under rapid stirring. The reaction was stopped after 4 hours. After cooling to room temperature, an appropriate amount of ethyl acetate and internal standard tridecane were added to the reactor, the catalyst was separated by centrifugation, and the supernatant was qualitatively and quantitatively analyzed by GC-MS (Agilent 7890A) and GC (Agilent 7890B), respectively.

[0127] Example 33 Test results are shown in Table 3

[0128] Table 3 Performance of CuMgAl catalyst for converting DMCD into CHDM

[0129]

[0130] From the above table, we can see that at 250℃, 5MPa H 2 Under the reaction conditions of 4 hours, under the action of CuMgAl catalyst, DMCD in the reaction supernatant obtained in step 1 can be highly selectively converted into high value-added CHDM, and the yield can reach 83.8%, realizing the value-added recovery of waste PET plastics.

[0131] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present disclosure (including the claims) is limited to these examples. Based on the concept of the present disclosure, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the embodiments of the present disclosure as described above, which are not provided in detail for the sake of simplicity.

[0132] While the disclosure has been described in conjunction with specific embodiments thereof, many alternatives, modifications and variations of these embodiments will be apparent to those skilled in the art in light of the foregoing description.

[0133] The embodiments of the present disclosure are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present disclosure should be included in the scope of protection of the present disclosure.

Claims

1. A two-step method for catalytically converting waste PET plastic into 1,4-cyclohexanedimethanol, characterized in that: The method comprises: Step 1: waste PET plastic dispersed in a methanol medium is first depolymerized by methanol under the action of a nickel-based catalyst under hydrogenation conditions to obtain dimethyl terephthalate, and then further hydrogenated to obtain dimethyl 1,4-cyclohexanedicarboxylate; Step 2: centrifugally separate the catalyst and the reaction liquid in step 1, and then hydrogenate the reaction liquid under the action of a CuMgAl catalyst under hydrogenation conditions to obtain the target product 1,4-cyclohexanedimethanol; Wherein, the nickel-based catalyst in step 1 comprises a carrier and an active ingredient and an auxiliary agent supported on the carrier, wherein the carrier is at least one of cerium oxide, magnesium oxide, silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, and niobium oxide; the active ingredient is nickel; and the auxiliary agent is at least one of platinum, palladium, and ruthenium; The CuMgAl catalyst in step 2 is prepared by a coprecipitation method, wherein the mass fraction of Cu in the total amount of the catalyst is 20%, the mass fraction of Mg in the total amount of the catalyst is 5%, and the mass fraction of Al in the total amount of the catalyst is 40%.

2. The method for catalytically converting waste PET plastic into 1,4-cyclohexanedimethanol by a two-step method according to claim 1, characterized in that: The nickel-based catalyst carrier is selected from at least one of cerium oxide, magnesium oxide, silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, and niobium oxide, preferably cerium oxide.

3. The method for catalytically converting waste PET plastic into 1,4-cyclohexanedimethanol by the two-step method according to claim 1, characterized in that The nickel-based catalyst promoter is selected from at least one of platinum, palladium and ruthenium, preferably palladium.

4. The method for catalytically converting waste PET plastic into 1,4-cyclohexanedimethanol by a two-step method according to claim 1, characterized in that: The nickel loading in the nickel-based catalyst is 1% to 7%, preferably 5%.

5. The method for catalytically converting waste PET plastic into 1,4-cyclohexanedimethanol by the two-step method according to claim 1, characterized in that The nickel-based catalyst promoter loading is 0.2% to 2%, preferably 0.5%.

6. The method for catalytically converting waste PET plastic into 1,4-cyclohexanedimethanol by a two-step method according to claim 1, characterized in that: The reaction temperature of step 1 is 150-180°C, preferably 180°C.

7. The method for catalytically converting waste PET plastic into 1,4-cyclohexanedimethanol by a two-step method according to claim 1, characterized in that: The reaction time of step 1 is 2-12 hours, preferably 10 hours.

8. The two-step method for catalytically converting waste PET plastic into 1,4-cyclohexanedimethanol according to claim 1, characterized in that: The reaction hydrogen pressure in step 1 is 2-6 MPa, preferably 6 MPa.

9. The method for catalytically converting waste PET plastic into 1,4-cyclohexanedimethanol by a two-step method according to claim 1, characterized in that: The mass concentration of the waste PET plastics tested in the reaction in step 1 is 2%-20%, preferably 10%.

10. The two-step method for catalytically converting waste PET plastic into 1,4-cyclohexanedimethanol according to claim 1, characterized in that: The reaction conditions of step 2 are 250° C., 4 h, 5 MPa H2.

Images