A catalyst for the preparation of 1,4-cyclohexanedicarboxylic acid dimethyl ester from polyethylene terephthalate and its use

Abstract

The present application relates to the technical field of polyester recovery and green conversion catalysis, and discloses a catalyst for preparing 1,4-cyclohexane dimethyl dicarboxylate from polyethylene terephthalate and application thereof, and a preparation method, which comprises the following steps: (1) TiO2-SiO2 carrier preparation: hexadecyl trimethyl ammonium bromide and sodium carbonate are added into water to prepare a mixed solution, tetraethyl orthosilicate and titanium isopropylate are mixed and then added dropwise into the mixed solution, constant temperature stirring reaction is carried out, centrifugal separation is carried out, the obtained solid is dried and calcined, and the TiO2-SiO2 carrier is obtained; (2) Ru / TiO2-SiO2 preparation: the TiO2-SiO2 carrier is dispersed in a solution containing RuCl3, impregnation stirring is carried out, drying and hydrogen reduction are carried out, and the Ru / TiO2-SiO2 catalyst is obtained. The catalyst has high catalytic activity and selectivity in the reaction of preparing DMCD from polyethylene terephthalate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polyester recycling and green conversion catalysis, and in particular to a catalyst for preparing 1,4-cyclohexanedicarboxylic acid dimethyl ester from polyethylene terephthalate and application thereof. BACKGROUND

[0002] 1,4-cyclohexanedicarboxylic acid dimethyl ester (DMCD) is an important organic chemical raw material, mainly used for the synthesis of 1,4-cyclohexanediol (CHDM) and copolyesters. Both DMCD and CHDM are widely used in the production of high-performance polyesters and copolyesters. At present, the global market demand for DMCD and CHDM is growing, but the domestic market mainly relies on imports.

[0003] DMCD can be obtained by the hydrogenation reaction of dimethyl terephthalate (DMT). This route has been realized on a large scale abroad, but it is still in its infancy in China, mainly because the raw material DMT relies on imports and is expensive. Currently, the catalysts that can be used for the production of DMCD by the hydrogenation of DMT are mainly noble metal catalysts based on Pd and Ru. Among them, Ru-based catalysts are relatively inexpensive and have high catalytic activity at relatively low temperatures and hydrogen pressures.

[0004] Patent application CN115532255A discloses a preparation method of Ru-based catalyst and its application. The method uses ammonia water or ammonium salt to treat the Ru precursor, and then adds alkali metal base or alkali metal salt as an additive to realize the high dispersion of Ru-based catalyst (Ru / Al2O3) on the carrier. In a system containing 0.5 g of DMT, 0.5 g of 0.202% Ru-0.138% Na / γ-Al2O3 catalyst and 15 mL of ethyl acetate, the hydrogen pressure is maintained at 3 MPa at 120°C until the reaction is completed when there is no hydrogen consumption. Under these conditions, 100% DMT conversion and 99.8% DMCD selectivity can be obtained. However, the catalyst preparation process needs to be treated with alkali multiple times, which is easy to cause pollution; and the hydrogen pressure needs to be maintained during the reaction, which is complicated to operate. +

[0005] Yu et al. (ACS Sustainable Chem. Eng. 2020, 8, 10, 4058-4068) prepared Ru / Al2O3 catalysts by a novel supercritical CO2 fluid chemical deposition method. The catalysts were prepared by impregnating RuCl3 in a solution of Al2O3 powder in supercritical CO2, and then the powder was heated to 400°C under a hydrogen atmosphere. The catalysts were tested for the hydrogenation of DMT to DMCD. The results showed that the catalyst prepared by this method had a DMT conversion of 100% and a DMCD selectivity of 99.8% under the conditions of 120°C and 3 MPa hydrogen pressure. However, the preparation process of the catalyst is complicated and the catalyst needs to be heated to 400°C under a hydrogen atmosphere, which is not suitable for industrial production. x ​SBA-15 catalyst, with water as solvent, in the mixed reaction system of 2.38 g DMT, 0.05 g catalyst, 100 ℃, 4.14 MPa (H2), the conversion rate of DMT is 100% after 1 h of reaction, and the selectivity of DMCD is 85.4%. The preparation method of the catalyst is environmentally friendly and has high atom utilization rate; and the catalyst can remain stable during the reaction, without metal leaching and aggregation. Unfortunately, the preparation process of the catalyst is harsh and tedious, and the reaction rate is limited when using water as the solvent, which is not suitable for large-scale production.

[0006] Martin et al. (Angew. Chem. Int. Ed. 2022, 61, e202117205) synthesized a series of CuFeCr catalysts derived from layered double hydroxide precursors, with 1,4-dioxane as solvent, under the reaction conditions of 0.5 g PET, 0.5 g catalyst, 240 ℃, 3 MPa pressure (CO2 and H2 volume ratio of 1:1), 48 h, in-situ methanol synthesis, polyethylene terephthalate alcoholysis (to terephthalic acid dimethyl ester), and even further hydrogenation of terephthalic acid dimethyl ester to p-xylene and 1,4-cyclohexane dimethyl ester can be achieved; under the optimized reaction conditions, the conversion rate of PET is 88.6%, and 3.7% of DMT, 49.1% of p-xylene and 28.6% of DMCD can be detected in the product. The catalyst realizes one-pot catalytic conversion of PET and CO2, and realizes methanol synthesis and PET decomposition at the same time. Unfortunately, the catalyst has the problems of large amount of catalyst (PET / catalyst = 1 / 1 (mass ratio)), high amount of solvent 1,4-dioxane (100 mL), harsh reaction conditions (240 ℃, 3 MPa), long reaction time, and complex product composition.

[0007] In summary, the 1,4-cyclohexane dimethyl ester (DMCD) used in the industry at present is all prepared by direct hydrogenation of expensive intermediate (terephthalic acid dimethyl ester DMT), and there is no related literature or patent to refer to for the catalyst and reaction process for directly synthesizing DMCD from polyethylene terephthalate or waste polyethylene terephthalate products (waste silk, disposable plastic bottles and packaging boxes) which are cheap and abundant in source. Therefore, it is of great significance to develop a catalyst with simple preparation method, excellent activity and high stability to realize one-step synthesis of PET to DMCD.

[0008] The catalyst and reaction process designed in the present application are the first public report in the world that can directly convert polyethylene terephthalate and waste polyethylene terephthalate products into 1,4-cyclohexane dimethyl ester (DMCD) with high selectivity under mild conditions. SUMMARY

[0009] In order to solve the above technical problems, the application provides a catalyst for preparing 1,4-cyclohexane dimethyl dicarboxylate from polyethylene terephthalate and application thereof, the catalyst preparation method is simple and environment-friendly, when the catalyst is applied to the preparation of DMCD from polyethylene terephthalate and waste polyethylene terephthalate products, the degradation of polyethylene terephthalate is complete, the selectivity of DMCD is high, and the catalyst has good stability.

[0010] The object of the application is achieved by the following technical solutions.

[0011] In a first aspect, the application provides a preparation method of a catalyst for preparing 1,4-cyclohexane dimethyl dicarboxylate from polyethylene terephthalate, the catalyst is a Ru / TiO2-SiO2 catalyst, and the preparation method comprises the following steps:

[0012] (1) Preparation of TiO2-SiO2 carrier: hexadecyl trimethyl ammonium bromide and sodium carbonate are added to water to prepare a mixed solution, tetraethyl orthosilicate and titanium isopropylate are mixed and then added dropwise into the mixed solution, constant-temperature stirring reaction is carried out, centrifugal separation is carried out, the obtained solid is dried and calcined to obtain the TiO2-SiO2 carrier;

[0013] (2) Preparation of Ru / TiO2-SiO2: the TiO2-SiO2 carrier is dispersed in a solution containing RuCl3, impregnation stirring is carried out, then drying and hydrogen reduction are carried out to obtain the Ru / TiO2-SiO2 catalyst.

[0014] The catalyst is prepared by an impregnation method, and the specific process is as follows: firstly, titanium isopropylate and tetraethyl orthosilicate are mixed at a certain proportion, hydrolysis and calcination are carried out to obtain a carrier (TiO2-SiO2); then the carrier is dispersed in a solution containing a ruthenium salt for impregnation; the obtained solid is reduced in a hydrogen stream, and finally the Ru / TiO2-SiO2 catalyst is obtained. The catalyst preparation method is simple, safe and environment-friendly, the above-mentioned Ru / TiO2-SiO2 catalyst can obtain DMCD by one-step degradation of PET, has high activity and selectivity of the target product, and has mild reaction conditions, and the catalyst is easy to recover and can be recycled.

[0015] The mixed hydrolysis method in the preparation process of the TiO2-SiO2 carrier can uniformly precipitate Ti and Si, and only uniform precipitation can form Ti-O-Si-O-Ti-O-Si-O cross arrangement, so that the catalyst has acidity, high activity and product selectivity in the degradation reaction of polyethylene terephthalate, and the reaction conditions are mild, there is no metal ion residue, the catalyst is easy to recover and can be recycled. If the step-by-step hydrolysis and separate precipitation are adopted, the distribution of Ti and Si in the catalyst is not uniform, the catalyst has no or weak acidity, and the pre-experiment shows that the catalyst prepared by precipitating TiO2 first and then precipitating SiO2 or the catalyst prepared by precipitating SiO2 first and then precipitating TiO2 has poor catalytic activity in the degradation reaction of polyesters. In addition, the catalyst prepared by loading metal Ru on the TiO2-SiO2 carrier can obtain 1,4-cyclohexane dimethyl dicarboxylate (DMCD) through one-step reaction of polyethylene terephthalate, without the need for further preparation through intermediates (dimethyl terephthalate DMT) hydrogenation, the price of polyethylene terephthalate is low and the source is abundant, and the waste polyethylene terephthalate products (waste silk, disposable plastic bottles and packaging boxes) can also be directly used for synthesizing DMCD, so that the raw material cost is reduced, the process is more simplified, the reaction time is short, and the energy consumption is reduced.

[0016] Preferably, in step (1), the mass ratio of titanium to silicon in the TiO2-SiO2 carrier is 9 / 1 to 1 / 9.

[0017] Preferably, in step (1), the mass-volume ratio of sodium carbonate, cetyltrimethylammonium bromide and water is 0.74-1.84 g:1.52 g:50-150 mL; the constant temperature stirring reaction is stirring at a temperature of 60-140℃ for 6-12 h; the temperature of the solid drying is 60-160℃; and in the process of calcination, the temperature is raised to 500-700℃ at a temperature raising rate of 2-5℃ / min, and the calcination is carried out for 2-6 h, and after the calcination is completed, the temperature is naturally lowered to room temperature.

[0018] Preferably, in step (2), the mass ratio of metal Ru in the Ru / TiO2-SiO2 catalyst is 1-15%, preferably 10-15%, and more preferably 12.5-15%.

[0019] Preferably, in step (2), the Ru content in the RuCl3-containing solution is 0.01-0.1 g / mL; the time of the impregnation stirring is 6-24 h; and the temperature of the drying is 80-100℃.

[0020] Preferably, in step (2), in the process of reduction, the temperature is raised to 200-500℃ at a temperature raising rate of 2-5℃ / min, and the reduction is carried out for 0.5-4 h, and after the reduction is completed, the temperature is naturally lowered to room temperature.

[0021] In a second aspect, the present application also provides a use of the Ru / TiO2-SiO2 catalyst in a reaction of preparing dimethyl 1,4-cyclohexanedicarboxylate from polyethylene terephthalate.

[0022] As preferred, the use comprises the following steps: mixing polyethylene terephthalate, Ru / TiO2-SiO2 catalyst and methanol, filling hydrogen, and then heating to 100-220℃ for 0.5-16h.

[0023] The Ru / TiO2-SiO2 catalyst has high catalytic activity at relatively low temperature and hydrogen pressure. More preferably, heating to 150-170℃ for 2-16h.

[0024] As preferred, the mass ratio of the Ru / TiO2-SiO2 catalyst to polyethylene terephthalate is 1:2-1:200; the mass ratio of the methanol to polyethylene terephthalate is 5:1-100:1; and the pressure of the hydrogen is 0.5-4MPa.

[0025] As preferred, the polyethylene terephthalate is polyethylene terephthalate powder, slice, melt or waste polyethylene terephthalate product.

[0026] The polyethylene terephthalate raw material used in the degradation process of the catalyst and polyethylene terephthalate prepared by the present application can be fresh polyethylene terephthalate, polyethylene terephthalate waste silk in the textile industry, waste bottles and packaging boxes and other polyester products used for packaging.

[0027] Compared with the prior art, the present application has the following beneficial effects:

[0028] (1) The catalyst preparation method provided by the present application is simple, the selected metal active component is relatively inexpensive ruthenium, which can effectively reduce the application production cost;

[0029] (2) The present application directly synthesizes DMCD from polyethylene terephthalate, polyethylene terephthalate waste silk in the textile industry, waste bottles and packaging boxes and other polyester products used for packaging, the raw material source is low, the reuse and emission reduction of waste plastics can be realized, the product has high added value, has high economic value and social benefits, and helps to achieve the "double carbon" goal;

[0030] (3) The catalyst provided by the present application is green and environmentally friendly, has high activity and good stability, has high catalytic activity and DMCD selectivity in the preparation of DMCD from various sources of polyethylene terephthalate, can be used repeatedly, and has very broad application prospects. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 X-ray powder diffraction pattern of 10% Ru / TiO2-SiO2-5 / 5 catalyst;

[0032] Figure 2 (a) high resolution electron microscopy image and (b) elemental line scan image of 10% Ru / TiO2-SiO2-5 / 5 catalyst. DETAILED DESCRIPTION

[0033] The technical solutions of the present application are illustrated below with specific examples, but the scope of protection of the present application is not limited thereto:

[0034] The conversion rate of polyethylene terephthalate and the yield of the degradation product catalyzed by the Ru / TiO2-SiO2catalyst are calculated according to formula (1) (2) respectively:

[0035] The conversion rate of polyethylene terephthalate = (W0-W1) / W0 x 100% (1)

[0036] The molar yield of the degradation product = (the amount of substance of the degradation product) / (the amount of substance of benzene ring in the theoretically degraded polyethylene terephthalate) x 100% (2)

[0037] Wherein, W0 is the initial mass of polyethylene terephthalate, and W1 is the mass of the un-degraded polyethylene terephthalate.

[0038] Example 1

[0039] Preparation of TiO2-SiO2-5 / 5 support (the molar ratio of added tetraisopropyl titanate and tetraethyl orthosilicate is 5:5):

[0040] 0.94 g of sodium carbonate, 1.52 g of hexadecyl trimethyl ammonium bromide and 100 mL of deionized water were added to a round-bottom flask, stirred at 80°C for 1 h to obtain a transparent solution.

[0041] A mixture solution of tetraisopropyl titanate (5.68 g, 0.02 mol) and tetraethyl orthosilicate (5.28 g, 0.02 mol) was added dropwise to the above mixed solution, hydrolyzed at 80°C for 9 h, and after cooling, centrifuged, and the obtained solid was dried in an oven at 80°C; the solid product was calcined (the heating rate was 5°C / min, calcined at 550°C for 4 h, and then naturally cooled to room temperature), and finally the TiO2-SiO2-5 / 5 support was obtained.

[0042] Example 2

[0043] The preparation method is the same as in Example 1, except that the molar ratio of tetraisopropyl titanate to tetraethyl orthosilicate is 1:9, 3:7, 7:3, and 9:1. The resulting supports are labeled as TiO2-SiO2-1 / 9, TiO2-SiO2-3 / 7, TiO2-SiO2-7 / 3, and TiO2-SiO2-9 / 1, respectively.

[0044] Example 3

[0045] Preparation of 10% Ru / TiO2-SiO2-5 / 5 catalyst (the mass ratio of metallic Ru in the catalyst is 10%):

[0046] 1 g of the TiO2-SiO2-5 / 5 support prepared in Example 1 was dispersed in 5 mL of deionized water, and then 2 mL of RuCl3 solution (Ru content 0.05 g / mL) was added. The mixture was stirred at room temperature for 10 h, and then dried in an oven at 100 °C. The resulting solid powder was reduced in a hydrogen stream at 400 °C for 1 h, and the resulting catalyst was labeled as 10% Ru / TiO2-SiO2-5 / 5.

[0047] like Figure 1 The X-ray powder diffraction pattern of the 10% Ru / TiO2-SiO2-5 / 5 catalyst is shown. It can be seen that there are no obvious diffraction peaks of titanium oxide or ruthenium in the catalyst, which indicates that titanium oxide and silicon dioxide are uniformly mixed and ruthenium is highly dispersed in the catalyst.

[0048] like Figure 2 The image shown is a high-resolution electron microscope image and elemental line scan image of the 10% Ru / TiO2-SiO2-5 / 5 catalyst. It can be seen that the catalyst particles are uniform and have abundant pores. The Si, Ti and Ru elements in the catalyst are uniformly distributed, which further demonstrates that the titanium oxide and silicon dioxide are uniformly mixed and the metallic ruthenium is highly dispersed.

[0049] Example 4

[0050] The preparation method is the same as in Example 3, except for the volume of RuCl3 solution added.

[0051] Adding 1 mL of RuCl3 solution (Ru content is 0.05 g / mL) resulted in a catalyst labeled as 5%Ru / TiO2-SiO2-5 / 5 (the mass ratio of metallic Ru in the catalyst is 5%).

[0052] Add 1.5 mL of RuCl3 solution (Ru content is 0.05 g / mL), and the resulting catalyst is labeled as 7.5%Ru / TiO2-SiO2-5 / 5 (the mass ratio of metallic Ru in the catalyst is 7.5%).

[0053] The catalyst obtained is marked as 10% Ru / TiO2-SiO2-5 / 5.

[0054] Example 5

[0055] The catalyst obtained is marked as 10% Ru / TiO2-SiO2-5 / 5.

[0056] The catalyst obtained is marked as 10% Ru / TiO2-SiO2-5 / 5.

[0057] The catalyst obtained is marked as 10% Ru / TiO2-SiO2-5 / 5.

[0058] The catalyst obtained is marked as 10% Ru / TiO2-SiO2-5 / 5.

[0059] The catalyst obtained is marked as 10% Ru / TiO2-SiO2-5 / 5.

[0060] Application Example 1

[0061] The catalysts prepared in Example 3 and Example 4 are respectively weighed 0.05 g, 0.5 g of solid polyethylene terephthalate powder, 10 mL of methanol in a high-pressure reactor, 3 MPa of hydrogen is filled, the high-pressure reactor is placed in an electric heating magnetic stirring device, after the temperature rises to 150°C, the stirring is started and the timing is started, the reaction time is 2 h.

[0062] After the reaction is completed, the high-pressure reactor is cooled to room temperature, the reaction liquid and the solid catalyst are centrifuged and separated, the upper clear liquid is taken and determined by gas chromatography, and the reaction results are shown in Table 1.

[0063] Table 1 Activity of catalysts with different Ru contents on TiO2-SiO2-5 / 5 carrier

[0064] Catalyst PET conversion (%) DMCD yield (%) 5% Ru / TiO2-SiO2-5 / 5 100 7.2 7.5% Ru / TiO2-SiO2-5 / 5 100 45.5 10% Ru / TiO2-SiO2-5 / 5 100 84.4 12.5% Ru / TiO2-SiO2-5 / 5 100 99.6

[0065] Conclusion: With the increase of Ru loading amount on the TiO2-SiO2-5 / 5 carrier, the activity of the catalyst is improved, and when the Ru loading amount is 12.5%, the yield of polyethylene terephthalate one-step degradation into DMCD by 12.5% Ru / TiO2-SiO2-5 / 5 is 99.6%.

[0066] Application Example 2

[0067] Take 0.05 g of the catalyst prepared in Example 3, 0.5 g of a solid powder of polyethylene terephthalate, 10 mL of methanol in a high-pressure reaction kettle, fill in 3 MPa of hydrogen, place the high-pressure reaction kettle in an electric heating magnetic stirring device, after the temperature rises to 130-170℃, start stirring and timing, the reaction time is 2 h.

[0068] After the reaction is completed, the high-pressure kettle is cooled to room temperature, the reaction liquid and the solid catalyst are centrifugally separated, the supernatant is taken and determined by gas chromatography, and the reaction results are shown in Table 2.

[0069] Table 2 Activity of 10% Ru / TiO2-SiO2-5 / 5 catalyst at different temperatures

[0070] Temperature (°C) PET conversion (%) DMCD yield (%) 130 95.0 25.1 140 100 64.0 150 100 84.4 160 100 97.3 170 100 97.4

[0071] Conclusion: The reaction temperature plays a crucial role in the preparation of DMCD from polyethylene terephthalate by using the 10% Ru / TiO2-SiO2-5 / 5 catalyst. As the reaction temperature increases, the yield of DMCD also gradually increases.

[0072] Application Example 3

[0073] Take 0.05 g of the catalyst prepared in Example 3, 0.5 g of a solid powder of polyethylene terephthalate, 10 mL of methanol in a high-pressure reaction kettle, fill in 3 MPa of hydrogen, place the high-pressure reaction kettle in an electric heating magnetic stirring device, after the temperature rises to 150℃, start stirring and timing, the reaction time is 0.5-4 h.

[0074] After the reaction is completed, the high-pressure kettle is cooled to room temperature, the reaction liquid and the solid catalyst are centrifugally separated, the supernatant is taken and determined by gas chromatography, and the reaction results are shown in Table 3.

[0075] Table 3 Activity of 10% Ru / TiO2-SiO2-5 / 5 catalyst at different times

[0076] Time (h) PET conversion (%) DMCD yield (%) 0.5 90.5 20.3 1 100 43.8 2 100 84.4 3 100 94.9 4 100 96.4

[0077] Conclusion: The 10% Ru / TiO2-SiO2-5 / 5 catalyst prepared by the present application has good initial activity, and as the reaction time increases, the yield of DMCD also gradually increases, and the highest can reach 96.4%.

[0078] Application Example 4

[0079] Take 0.05 g of the catalyst prepared in Example 3, 0.5 g of solid polyethylene terephthalate powder, 10 mL of methanol in a high-pressure reactor, fill 3 MPa of hydrogen, place the high-pressure reactor in an electric heating magnetic stirring device, wait for the temperature to rise to 150℃, then start stirring and timing, the reaction time is 2 h.

[0080] After the reaction is completed, the high-pressure reactor is cooled to room temperature, the reaction liquid and the solid catalyst are centrifuged and separated, the recovered solid is supplemented to 0.5 g of PET for the next cycle reaction, the upper clear liquid is taken and determined by gas chromatography, and the reaction results are shown in Table 4.

[0081] Table 4 Repeated use activity of 10% Ru / TiO2-SiO2-5 / 5 catalyst

[0082] Number of recycling times PET conversion (%) DMCD yield (%) 1 100 84.4 2 100 84.0 3 100 84.2 4 100 84.6 5 100 84.5

[0083] Conclusion: The 10% Ru / TiO2-SiO2-5 / 5 catalyst prepared in the application has good cycle use stability, and the catalyst activity does not decrease obviously after 5 cycles.

[0084] Application Example 5

[0085] Take 0.05 g of the catalyst prepared in Example 5, 0.5 g of solid polyethylene terephthalate powder, 10 mL of methanol in a high-pressure reactor, fill 3 MPa of hydrogen, place the high-pressure reactor in an electric heating magnetic stirring device, wait for the temperature to rise to 150℃, then start stirring and timing, the reaction time is 0.5-4 h.

[0086] After the reaction is completed, the high-pressure reactor is cooled to room temperature, the reaction liquid and the solid catalyst are centrifuged and separated, the upper clear liquid is taken and determined by gas chromatography, and the reaction results are shown in Table 5.

[0087] Table 5 Activity of Ru catalysts with different titanium-silicon ratio supports

[0088] Catalyst PET conversion (%) DMCD yield (%) 10% Ru / TiO2-SiO2-1 / 9 97.8 80.2 10% Ru / TiO2-SiO2-3 / 7 98.5 82.3 10% Ru / TiO2-SiO2-5 / 5 100 84.4 10% Ru / TiO2-SiO2-7 / 3 95.4 78.3 10% Ru / TiO2-SiO2-9 / 1 90.0 75.2

[0089] Conclusion: With the increase of the titanium-silicon ratio in the catalyst, the activity of the catalyst first increases and then decreases, when the titanium-silicon ratio is 5 / 5, the 10% Ru / TiO2-SiO2-5 / 5 catalyst has the best reaction activity for PET, and the yield of DMCD can reach 84.4%.

[0090] Application Example 6

[0091] The catalyst prepared in Example 3 is weighed at 0.05 g, 0.5 g of polyethylene terephthalate waste silk, 10 mL of methanol in a high-pressure reaction kettle, 3 MPa of hydrogen is filled, the high-pressure reaction kettle is placed in an electric heating magnetic stirring device, after the temperature rises to 150 DEG C, the stirring is started and the timing is started, and the reaction time is 3 h.

[0092] After the reaction is completed, the high-pressure kettle is cooled to room temperature, the reaction liquid and the solid catalyst are centrifugally separated, the upper clear liquid is taken and determined by gas chromatography, and the external standard method is used for quantitative analysis. The PET conversion rate is 100%, and the yield of DMCD is 93.2%.

[0093] Conclusion: The Ru / TiO2-SiO2 catalyst prepared in the application also has good catalytic activity and high DMCD yield for polyethylene terephthalate waste silk.

[0094] Application Example 7

[0095] The catalyst prepared in Example 3 is weighed at 0.05 g, 0.5 g of polyethylene terephthalate waste bottle, 10 mL of methanol in a high-pressure reaction kettle, 3 MPa of hydrogen is filled, the high-pressure reaction kettle is placed in an electric heating magnetic stirring device, after the temperature rises to 150 DEG C, the stirring is started and the timing is started, and the reaction time is 3 h.

[0096] After the reaction is completed, the high-pressure kettle is cooled to room temperature, the reaction liquid and the solid catalyst are centrifugally separated, the upper clear liquid is taken and determined by gas chromatography, and the external standard method is used for quantitative analysis. The PET conversion rate is 100%, and the yield of DMCD is 94.3%.

[0097] Conclusion: The Ru / TiO2-SiO2 catalyst prepared in the application also has good catalytic activity and high DMCD yield for polyethylene terephthalate waste bottle.

[0098] Application Example 8

[0099] The catalyst prepared in Example 3 is weighed at 0.05 g, 0.5 g of polyethylene terephthalate waste packaging box, 10 mL of methanol in a high-pressure reaction kettle, 3 MPa of hydrogen is filled, the high-pressure reaction kettle is placed in an electric heating magnetic stirring device, after the temperature rises to 150 DEG C, the stirring is started and the timing is started, and the reaction time is 3 h.

[0100] After the reaction is completed, the high-pressure kettle is cooled to room temperature, the reaction liquid and the solid catalyst are centrifugally separated, the upper clear liquid is taken and determined by gas chromatography, and the external standard method is used for quantitative analysis. The PET conversion rate is 100%, and the yield of DMCD is 92.1%.

[0101] Conclusion: The Ru / TiO2-SiO2 catalyst prepared by the application has good catalytic activity and high DMCD yield for polyethylene terephthalate waste packaging boxes.

[0102] The above is only the preferred embodiment of the present application, and does not limit the patent scope of the present application, and any equivalent structure or equivalent process transformation made by the present application specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for the one-step reaction of polyethylene terephthalate to produce dimethyl 1,4-cyclohexanedicarboxylate, characterized in that, The method comprises the following steps: (1) Preparation of TiO2-SiO2 carrier: hexadecyl trimethyl ammonium bromide and sodium carbonate are added into water to prepare a mixed solution, tetraethyl orthosilicate and tetraisopropyl titanate are mixed and then added dropwise into the mixed solution, constant temperature stirring reaction is performed, centrifugal separation is performed, the obtained solid is dried and calcined to obtain the TiO2-SiO2 carrier, and the mass ratio of titanium to silicon is 9 / 1 to 1 / 9; (2) Preparation of Ru / TiO2-SiO2: the TiO2-SiO2 carrier is dispersed in a solution containing RuCl3, impregnation stirring is performed, then drying and hydrogen reduction are performed to obtain the Ru / TiO2-SiO2 catalyst, and the mass ratio of metal Ru in the Ru / TiO2-SiO2 catalyst is 10 to 15 %; The polyethylene terephthalate, the Ru / TiO2-SiO2 catalyst and methanol are mixed, the mass ratio of the Ru / TiO2-SiO2 catalyst to the polyethylene terephthalate is 1:2 to 1:200, the mass ratio of methanol to the polyethylene terephthalate is 5:1 to 100:1, hydrogen gas with a pressure of 0.5 to 4 MPa is filled, and then the temperature is increased to 140 to 220 DEG C and reaction is performed for 2 to 16 h.

2. The method of claim 1, wherein, In step (1), the mass ratio of titanium to silicon in the TiO2-SiO2 carrier is 9 / 1, 7 / 3, 5 / 5, 3 / 7 or 1 / 9.

3. The method according to claim 1 or 2, characterized in that In step (1), the mass-volume ratio of the hexadecyl trimethyl ammonium bromide, the sodium carbonate and the water is 1.52 g: 0.74 to 1.84 g: 50 to 150 mL; the constant temperature stirring reaction is stirring at a temperature of 60 to 140 DEG C for 6 to 12 h; the temperature for drying the solid is 60 to 160 DEG C; and in the process of calcination, the temperature is increased to 500 to 700 DEG C at a temperature increasing rate of 2 to 5 DEG C / min, and the calcination is performed for 2 to 6 h, and then the temperature is naturally decreased to room temperature after the calcination is completed.

4. The method of claim 1, wherein, In step (2), the mass ratio of metal Ru in the Ru / TiO2-SiO2 catalyst is 12.5 to 15 %.

5. The method of claim 1 or 4, wherein, In step (2), the Ru content in the solution containing RuCl3 is 0.01 to 0.1 g / mL; the time for impregnation stirring is 6 to 24 h; and the temperature for drying is 80 to 100 DEG C.

6. The method of claim 1 or 4, wherein, In step (2), in the process of reduction, the temperature is increased to 200 to 500 DEG C at a temperature increasing rate of 2 to 5 DEG C / min, and the reduction is performed for 0.5 to 4 h, and then the temperature is naturally decreased to room temperature after the reduction is completed.

7. The method of claim 1, wherein, The temperature is increased to 150 to 170 DEG C and reaction is performed for 2 to 16 h.

8. The method of claim 1, wherein, The source of the polyethylene terephthalate is polyethylene terephthalate powder, polyethylene terephthalate slice, polyethylene terephthalate melt or waste polyethylene terephthalate product.

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