TW201809095A - Method for manufacturing bis(2-hydroxyethyl) cyclohexane-1,4-dicarboxylate (BHCD) and derivatives thereof - Google Patents

Abstract

The instant disclosure provides a method for manufacturing bis(2-hydroxyethyl) cyclohexane-1,4-dicarboxylate(BHCD) and derivatives thereof. The method includes the following steps. A first reactant including bis-hydroxyethyl terephthalate (BHET) is provided. 2-(2-hydroxyethoxy)ethyl 2-hydroxyethyl terephthalate(BHEET) is added to the first reactant including BHET to form a second reactant. The hydrogenation is performed on the second reactant.

Description

Method for preparing cyclohexane ethylene glycol ester and derivatives thereof

The invention relates to a hydrogenation method of a benzene ring derivative, in particular to hydrogenation of bis-hydroxyethyl terephthalate (BHET) to prepare cyclohexane ethylene glycol ester (bis(2) -hydroxyethyl)cyclohexane-1,4-dicarboxylate, BHCD) method.

Polyethylene terephthalate (PET) is a kind of polymer commonly used in life. It has the advantages of good toughness, light weight and acid and alkali resistance. In recent years, it has become a common container for soda, juice and carbonated beverages. Due to the increase in social demand, the production of PET products has also increased, and because PET products are usually disposable consumables, they often cause a large amount of waste.

Because PET is chemically inert and cannot be degraded by microorganisms in a short time, which seriously jeopardizes the ecological environment, how to effectively recover PET to produce economic value of cyclohexane ethylene glycol ester (bis(2-hydroxyethyl)cyclohexane- 1,4-dicarboxylate, BHCD), to solve the ecological environment pollution Dyeing has become an important issue that needs to be resolved urgently.

CN104003840A discloses a method for hydrogenating waste PET degradation monomer diethylene terephthalate as a raw material, wherein the diethylene terephthalate single system is purified and has a purity of 99%. the above. The method comprises the reaction of diethylene terephthalate monomer under the catalysis of Pd/C catalyst at a reaction pressure of 1.5 to 7.0 MPa (corresponding to 217 to 1015 psi) and a reaction temperature of 120 to 300 ° C. ~6.0 hours to obtain diethylene glycol 1,4-cyclohexanedicarboxylate. The technical disadvantage is that the degradation products generally obtained from the degradation of waste PET usually contain 10 to 30% of the dimer in addition to the BHET monomer, so that a purification step is required to obtain a good hydrogenation conversion rate in this patent.

The US6766276B2 patent discloses a method for hydrogenating a polyester oligomer containing a terephthalic acid residue. The process reveals that the poly terephthalate-containing residue is polymerized in the presence of a supported or suspended catalyst at a hydrogen pressure of at least about 60 barg (equivalent to 870 psi) and a temperature of from about 180 to 280 °C. The ester oligomer is contacted with hydrogen to convert the terephthalic acid residue to a 1,4 cyclohexane dicarboxylic acid residue. Although no additional purification step of the starting material is required as compared to the above patent, the method can only convert about 10 to 50% of the terephthalic acid residue to the 1,4 cyclohexanedicarboxylic acid residue.

In summary, the prior art still has the following problems: it is necessary to use a diethylene terephthalate monomer as a reactant, if a diethylene terephthalate monomer is not used as a reactant, The hydrogenation conversion rate of the terephthalic acid residue in the oligomer is converted to a 1,4 cyclohexanedicarboxylic acid residue, and the hydrogenation conversion ratio is not high. In addition, the conventional method is almost impossible to hydrogenate a diethylene terephthalate monomer at a low temperature (<120 ° C) and in a solvent-free environment.

The first step in the recycling of PET by chemical recovery is to degrade PET into a first reactant comprising bis-hydroxyethyl terephthalate (BHET). At this time, the first reactant contains BHET monomers, dimers and oligomers, which must be purified by conventional techniques to obtain BHET monomers. If no solvent is used during the reaction, the subsequent reaction must be at a high temperature ( >120 ° C) hydrogenation reaction to obtain bis (2-hydroxyethyl) cyclohexane-1,4-dicarboxylate (BHCD), so the process is complicated and energy-consuming.

In view of the problems faced by the prior art, the present invention provides a method for preparing bis(2-hydroxyethyl)cyclohexane-1,4-dicarboxylate (BHCD) and derivatives thereof, which can directly utilize PET. BHCD and its derivatives can be obtained by subjecting the degraded first reactant to hydrogenation without first purifying.

The present invention provides a process for the preparation of cyclohexane ethylene glycol ester (BHCD) and its derivatives. The method comprises the steps of: providing a first reactant comprising ethylene terephthalate (BHET); adding 2-(2-hydroxyethyl)ethanolate 2-hydroxyethanol terephthalate (2 - (2-hydroxyethoxy)ethyl 2-hydroxyethyl terephthalate, BHEET) to a first reactant comprising BHET to form a second reactant; and subjecting the second reactant to a hydrogenation reaction.

In various embodiments of the invention, the BHETs in the first reactant comprising BHET are present as monomers, dimers, oligomers, or a combination thereof.

In various embodiments of the invention, the first reaction comprising BHET The monomer comprises a monomer and a dimer of BHET.

In various embodiments of the present invention, the BHET dimer is 0 to 100 parts by weight based on 100 parts by weight of the monomer of BHET in the first reactant containing BHET.

In a plurality of embodiments of the present invention, in the first reactant comprising BHET, the dimer of the BHET is from 0 to 80 parts by weight based on 100 parts by weight of the monomer of the BHET.

In a plurality of embodiments of the present invention, in the first reactant comprising BHET, the dimer of the BHET is from 0 to 60 parts by weight based on 100 parts by weight of the monomer of the BHET.

In various embodiments of the invention, the oligomer of BHET has the structure of formula (1): Wherein n is an integer from 3 to 10.

In various embodiments of the invention, the hydrogenation reaction is carried out in the absence of a solvent.

In various embodiments of the invention, the hydrogenation reaction has a reaction temperature between 80 ° C and 115 ° C.

In various embodiments of the invention, the hydrogenation reaction has a reaction temperature between 85 ° C and 110 ° C.

In various embodiments of the invention, in the second reactant, The monomer of BHET is 100 parts by weight, and BHEET is 0.5 to 100 parts by weight.

In various embodiments of the present invention, BHEET is 7 to 60 parts by weight based on 100 parts by weight of the monomer of BHET in the second reactant.

In some embodiments of the present invention, BHEET is 25 to 50 parts by weight based on 100 parts by weight of the monomer of BHET in the second reactant.

In various embodiments of the invention, the catalyst is further added to the second reactant prior to performing the hydrogenation reaction.

In various embodiments of the invention, the catalyst comprises ruthenium (Ru), rhodium (Rh), platinum (Pt), palladium (Pd), or a combination thereof.

In various embodiments of the present invention, the total weight of the second reactant is 100 parts by weight, wherein the catalyst is 0.1 to 1.0 part by weight.

In various embodiments of the invention, the hydrogenation reaction has a reaction pressure of from 500 to 1500 psi.

In various embodiments of the invention, the hydrogenation reaction has a reaction time of from 0.5 hours to 6 hours.

The method for preparing BHCD and the derivative thereof provided by the invention can directly obtain the hydrogenation reaction at a temperature lower than the conventional reaction temperature by using the first reactant which is degraded by PET without special purification of BHET. An economically valuable BHCD product. Therefore, the present invention can easily and efficiently recycle PET.

100‧‧‧ method

101‧‧‧Steps

103‧‧‧Steps

105‧‧‧Steps

The embodiments of the present invention can be best understood from the following detailed description and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart showing a method of preparing BHCD and its derivatives, in accordance with some embodiments of the present invention.

The embodiments of the present invention are disclosed in the following drawings, and the details of However, it should be understood that these practical details are not intended to limit the invention. That is, in some embodiments of the invention, these practical details are not necessary. In addition, the chemical structural formulas shown in the text will be illustrated in a simple schematic manner.

In this document, "one" and "the" can be used to mean one or more, unless the article specifically defines the article. It will be further understood that the terms "comprising", "comprising", "having", and <RTIgt; One or more of its other features, regions, integers, steps, operations, elements, components, and/or groups thereof.

In order to solve the problems described in the prior art, the present invention provides a process for preparing bis(2-hydroxyethyl)cyclohexane-1,4-dicarboxylate (BHCD) and derivatives thereof without hydrogenation reaction The first purification step, which can directly hydrogenate the first reactant containing bis-hydroxyethyl terephthalate (BHET) monomer, dimer and oligomer obtained after PET degradation. In order to obtain BHCD, PET can be recycled simply and efficiently.

The PET described in the present invention includes, but is not limited to, pure PET (virgin PET), recycled PET (recycled PET), post-consumer PET (post cosumer PET). And PET precursors (PET precursor) and the like.

The BHCD prepared by the method is often added to PET or polyurethane (PU) to effectively reduce the crystallization rate and improve the yellowing phenomenon. In addition, BHCD can be used as a synthetic precursor of cyclohexanedimethanol (CHDM), while CHDM is a commonly used monomer in the polyester industry to synthesize 1,4 cyclohexane dimethyl terephthalate. (Poly 1,4-cyclohexylene dimethylene terephthalate, PCT), Polyethylene terephthalate glycol-modified (PETG) or glycol ester modified polyterephthalic acid 1,4 - Copolyester having high thermal stability, good processability and high transparency, such as poly 1,4-cyclohexylene dimethylene terephthalate glycol-modified (PCTG).

The BHCD derivatives described in the present invention include, but are not limited to, compounds containing the structure of formula (2) as follows: A compound containing the structure of formula (3), n is an integer from 1 to 10, as shown below: And a compound containing the structure of the formula (4), n is an integer from 1 to 10, as shown below:

Specifically, the BHCD derivative of the present invention, for example, bis(2-hydroxyethyl)cyclohexane-1,4-dicarboxylate, 1,4-cyclohexane Dicarboxylic acid, 1,1'-(1,2-ethyl) 4,4'-bis(2-hydroxyethyl) ester (1,4-cyclohexanedicarboxylic acid, 1,1'-(1,2-ethanediyl) 4,4'-bis(2-hydroxyethyl)ester) and 1,4-cyclohexanedicarboxylic acid, 2-(2-hydroxyethyl)ethanolate, 2-hydroxyethanoldicarboxylate (1,4-cyclohexanedicarboxylic acid, 2 -(2-hydroxyethoxy)ethyl 2-hydroxyethyl ester).

The present invention provides a process 100 for the preparation of cyclohexane ethylene glycol ester (BHCD) and its derivatives. The method comprises the steps of: providing a first reactant comprising ethylene terephthalate (BHET) (step 101); adding 2-(2-hydroxyethyl)ethanol ester-2-hydroxyl terephthalate 2-(2-hydroxyethoxy)ethyl 2-hydroxyethyl terephthalate (BHEET) to a first reactant comprising BHET to form a second reactant (step 103); and hydrogenating the second reactant (step 105) ).

Please refer to FIG. 1 first. FIG. 1 is a method 100 for preparing cyclohexane ethylene glycol ester (BHCD) and its derivatives. Step 101 is to provide terephthalic acid a first reactant of ethylene glycol ester (BHET), the first reactant comprising BHET is obtained by degradation of PET, and the BHET in the first reactant may be a monomer, a dimer, an oligomer or Its combination exists.

In particular, the first reactant comprising BHET may comprise monomers and dimers of BHET. According to some embodiments, in the first reactant comprising BHET, the BHET dimer is from 0 to 100 parts by weight based on 100 parts by weight of the monomer of BHET; preferably, the dimer of BHET is 0. ~80 parts by weight; optimally, the dimer of BHET is 0 to 60 parts by weight.

In some embodiments, the BHET dimer is terephthalic acid, 1,1 '-(1,2-ethyl) 4,4'-bis(2-hydroxyethyl) ester (1,4-Benzenedicarboxylic acid) Acid, 1,1'-(1,2-ethanediyl) 4,4'-bis(2-hydroxyethyl)ester).

In some embodiments, the oligomer of BHET has the structure of formula (1): Wherein n is an integer from 3 to 10.

With continued reference to Figure 1, step 103 is the addition of BHEET to the first reactant comprising BHET to form a second reactant. In the first reactant, the monomer of BHET has a melting point of 110 ° C, and the melting point of the dimer is 170 to 174 ° C. However, by adding BHEET to the first reactant, the second reactant has the presence of BHEET. Subsequent hydrogenation of BHET monomers, dimers, and oligomers can be carried out at or near the melting point of the BHET monomer.

According to one embodiment, in the second reactant, BHEET is from 0.5 to 100 parts by weight based on 100 parts by weight of the monomer of BHET; preferably, BHEET is from 7 to 60 parts by weight; optimally, BHEET is 25 ~50 parts by weight.

According to another embodiment, in the second reactant, BHEET is from 0.5 to 100 parts by weight based on 100 parts by weight of the monomer of BHET; preferably, BHEET is from 7 to 60 parts by weight; optimally, BHEET is 25 to 50 parts by weight, and the BHET dimer is 0 to 100 parts by weight, preferably 0 to 80 parts by weight; most preferably 0 to 60 parts by weight.

Continuing with reference to Figure 1, step 105 is to hydrogenate the second reactant. In some embodiments, the second reactant contains only the first reactant and BHEET, and does not contain any solvent, so the hydrogenation reaction is carried out without solvent. According to some embodiments, the hydrogenation reaction may have a reaction temperature of from 80 ° C to 115 ° C, a reaction pressure of from 500 to 1500 psi, and a reaction time of from 0.5 hours to 6 hours. According to another embodiment, the hydrogenation reaction may have a reaction temperature of from 85 ° C to 110 ° C and a reaction pressure of from 800 to 1200 psi.

In some embodiments, because the chemical structure of BHEET is similar to that of BHET, BHEET can not only promote the hydrogenation of BHET during the hydrogenation reaction, but also can be hydrogenated into a valuable product.

In some embodiments, the second reactant comprises a monomer, a dimer, and a BHEET of BHET, which, after performing a hydrogenation reaction, respectively produce BHCD, 1,4-cyclohexanedicarboxylic acid, 1,1'-(1 ,2-ethyl) 4,4'-bis(2-hydroxyethyl) ester (1,4-cyclohexanedicarboxylic acid, 1,1'-(1,2-ethanediyl) 4,4'-bis(2-hydroxyethyl )ester) and 1,4-cyclohexanedicarboxylic acid, 2-(2-hydroxyethyl)ethanolate, 2-hydroxyethanol ester (1,4-cyclohexanedicarboxylic acid, 2-(2-hydroxyethoxy)ethyl 2-hydroxyethyl ester). Wherein 1,4-cyclohexanedicarboxylic acid, 1,1'-(1,2-ethyl)4,4'-bis(2-hydroxyethyl) ester and 1,4-cyclohexanedicarboxylic acid, 2-(2-Hydroxyethyl)ethanol ester, 2-hydroxyethanol ester also has the same applicability and economic value as BHCD.

In some embodiments, the catalyst is further added to the second reactant prior to performing the hydrogenation reaction. For example, the catalyst comprises ruthenium (Ru), rhodium (Rh), platinum (Pt), palladium (Pd), or a combination thereof.

The catalyst is very important for the hydrogenation reaction, but a good reaction effect can be achieved by adding a certain amount of the catalyst. In one embodiment, the total amount of the second reactant is 100 parts by weight, wherein the catalyst is 0.1 to 1.0 part by weight. In another embodiment, the catalyst is from 0.25 to 0.75 parts by weight. In still another embodiment, the catalyst is 0.4 to 0.6 parts by weight. Preferably, the catalyst is 0.5 parts by weight.

It can be seen from the above that the method for preparing BHCD and its derivatives provided by the present invention can add a second reactant containing BHEET and BHET monomers, dimers, oligomers or a combination thereof by adding BHEET. The hydrogenation reaction is carried out without solvent and at a temperature close to the melting point of the BHET monomer or even below the melting point, and the purification step before the hydrogenation reaction may be omitted.

Hereinafter, the actual ratio of each component in the reactants of the hydrogenation step of the present invention (experimental group 1 to 10) and the hydrogenation conversion ratio of the benzene ring after hydrogenation will be more clearly explained in the following two examples, and the following examples are merely illustrative. It is not intended to limit the present invention, and those having ordinary knowledge in the technical field of the present invention should flexibly select an appropriate reactant composition ratio and catalyst type depending on actual needs. The calculation method of the hydrogenation conversion rate of the benzene ring is by Nuclear Magnetic Resonance Spectroscopy (NMR). The ratio of the integral area of the disappearance of the benzene ring signal in the product was analyzed. Dimethyl sulfoxide (DMSO) was used as the solvent. The chemical shift of 8.1 ppm on the NMR spectrum was the signal of the benzene ring, and the chemical shift was about 1.3~. The 1.9 ppm portion is a cyclohexane signal, which is a conversion of the benzene ring hydrogenation over the signal integral area of the two portions.

Preparation of reactants

300 g of PET ester granules were put into 1500 g of ethylene glycol, and then 3 g of zinc acetate catalyst was added thereto, and the temperature was raised to 190 to 200 ° C to carry out reflux and reacted for 3 hours, and then left to cool to room temperature, and subjected to suction filtration. The solid crude product was isolated. This crude product was purified by recrystallization to obtain a BHET monomer and its dimer, respectively.

Preparation of BHEET

10 g of diethylene terephthalate (BHET) was added to a 100 ml reaction flask, and 11.4 ml of diethylene glycol (DEG, diethylene glycol) and 7.4 mg of zinc acetate were added to react at 180 ° C. After a few hours, the reaction flask was moved to room temperature and extracted with ethyl acetate (EtOAc, Ethyl acetate) and water to remove ethylene glycol (EG, ethylene glycol) and DEG. After collecting the organic layer and concentrating, it was purified by column chromatography (eluent ratio of EtOAc: n-Hexane = 3:1). Finally, ethanol and water are used for recrystallization to remove solid impurities, and after concentration, BHEET is obtained.

Example 1:

The experimental groups 1 to 5 contained 20 g of the reactant and 0.1 g of the Ru catalyst (ie, 2 g of Ru/C catalyst), wherein the reactant contained BHET monomer and BHEET, and the weight of the BHET monomer was 100 parts by weight, and different weights were added. The BHEET is shown in Table 1. The Ru/C catalyst is based on carbon and the active metal Ru accounts for 5% by weight of the catalyst. First, the reactants were hydrogenated with a Ru/C catalyst at a reaction pressure of 800 psi and a different reaction temperature for 3 hours, and the conversion of the benzene ring hydrogenation was induced by the above method to represent the BHET monomer and BHEET via hydrogenation. After the product rate, the results are shown in Table 1:

Referring to Table 1, comparing experimental groups 1 to 3 with experimental group 4, it can be found that when there is no BHEET in the reaction (experimental group 4), at the same reaction temperature (100 ° C) and pressure (800 psi), the benzene ring The hydrogenation conversion rate is 0%, in other words, it means that no BHET monomer and BHEET hydrogenated product are formed. When BHEET is present in the reactant, the reactant can be hydrogenated at a reaction temperature lower than the melting point of the BHET monomer at 100 ° C, and the benzene ring hydrogenation conversion rate increases as the amount of BHEET added increases. From Table 1, it can be found that when BHEET is 5.2 parts by weight (experiment group 2), the reaction The benzene ring hydrogenation conversion rate of the product can reach 95%, and when the BHEET is 7.5 parts by weight (experiment group 1), the reactant has a better benzene ring hydrogenation conversion rate of >99%.

Continuing with reference to Table 1, comparing experimental group 4 with experimental group 5, it can be found that when there is no BHEET in the reactant, the benzene ring hydrogenation conversion rate of the reactant is 0% at a temperature lower than the melting point of the reactant (100 ° C). The reaction temperature must be raised to 160 ° C in order to increase the benzene ring hydrogenation conversion of the reactants to >99%.

From the above, it is known that when no BHEET is present in the reactant, BHET is converted to BHCD by a hydrogenation reaction at a reaction temperature of 160 °C. However, when BHEET is added to the reactant, BHET can be hydrogenated at 100 ° C to form BHCD. Therefore, the presence of BHEET in the reactants can reduce the reaction temperature of hydrogenation of BHET to reduce energy loss.

Example 2:

The experimental groups 6 to 10 contained 20 g of the reactant and 0.1 g of the Ru catalyst (ie, 2 g of Ru/C catalyst), wherein the reactant contained BHET monomer, dimer and BHEET, and the BHET monomer was 100 parts by weight. Add different weight parts of BHET dimer and BHEET as shown in Table 2. The Ru/C catalyst is based on carbon and the active metal Ru accounts for 5% by weight of the catalyst. First, the reactants were hydrogenated with a Ru/C catalyst at a reaction pressure of 800 psi and a reaction temperature of 100 ° C for 3 hours, and then the conversion of the benzene ring hydrogenation was carried out by the aforementioned method to represent the BHET monomer and BHEET via hydrogenation. After the product rate, the results refer to Table 2:

Since the degraded product of PET typically contains BHET monomers and dimers, it must be purified to obtain BHET monomers, which can be subsequently hydrogenated to give BHCD. However, the present invention omits the purification step, and the PET-degraded product (including BHET monomer and dimer) can be directly subjected to subsequent hydrogenation reaction, and has high Benzene ring hydrogenation conversion rate.

Please refer to Table 2, the weight fraction of BHET monomer and dimer in the reaction group 6~10 is simulated to reflect the possible ratio of PET degradation. Comparing experimental groups 6-9 with experimental group 10, it was found that when there was no BHEET in the reaction (experimental group 10), the hydrogenation conversion rate of the benzene ring was 0 at the same reaction temperature (100 ° C) and pressure (800 psi). %, in other words, represents the formation of a product without hydrogenation of the BHET monomer and the BHET dimer.

However, when BHEET is present in the reactant, the reactant can be hydrogenated at a reaction temperature lower than the melting point of the BHET monomer at 100 ° C, and the benzene ring hydrogenation conversion rate increases as the amount of BHEET added increases. From Table 2, it can be found that when BHEET is 28 parts by weight or more (experimental groups 7, 6), the benzene ring hydrogenation conversion ratio of the reactant can reach >99%.

It can be seen that even if BHET dimer is present in the reactants, after adding BHEET, BHET monomer and dimer can be hydrogenated at 100 ° C and 800 psi to form BHCD and 1,4-cyclohexanedicarboxylic acid, respectively. 1,1'-(1,2-ethyl)4,4'-bis(2-hydroxyethyl) ester, and has a high benzene ring hydrogenation conversion ratio.

Please refer to Table 1 and Table 2 at the same time. It can be found that when there is BHET dimer in the reactants, it is only necessary to increase the content of BHEET in the reactants at the same reaction temperature (100 ° C) and pressure (800 psi). Hydrogenation of BHET monomers and dimers to form BHCD and 1,4-cyclohexanedicarboxylic acid, 1,1'-(1,2-ethyl)4,4'-bis(2-hydroxyethyl), respectively ester. Accordingly, it can be confirmed that the present invention can omit the purification step after PET degradation, directly hydrogenate the product thereof, and has a high benzene ring hydrogenation conversion ratio.

It can be seen from the above embodiments of the present invention that the method for preparing BHCD and its derivatives provided by the present invention omits the purification step before the hydrogenation reaction, and can be straight The product degraded by PET is hydrogenated to obtain an economically valuable BHCD product. Therefore, the present invention can easily and efficiently recycle PET. In addition, the method for preparing BHCD and its derivatives of the present invention, by adding BHEET, can make the reactants containing BHEET and BHET monomers, dimers, oligomers or a combination thereof in the absence of solvent and close to the melting point, or even The hydrogenation reaction is carried out at a temperature lower than the melting point, and has a high benzene ring hydrogenation conversion ratio.

Although the embodiments of the present invention have been disclosed as above, it is not intended to limit the present invention, and any person skilled in the art can make some modifications and retouchings without departing from the spirit and scope of the present invention. The scope is defined as defined in the scope of the patent application.

Claims (17)

A method for preparing cyclohexane ethylene glycol ester (BHCD) and a derivative thereof, comprising: providing a first reactant comprising a pair of ethylene phthalate (BHET); adding a pair of phthalic acid 2- (2-hydroxyethyl)ethanol ester-2-hydroxyethanol ester (BHEET) to the first reactant comprising the BHET to form a second reactant; and subjecting the second reactant to a hydrogenation reaction. The method of claim 1, wherein the BHET system in the first reactant comprising the BHET is present as a monomer, a dimer, an oligomer, or a combination thereof. The method of claim 2, wherein in the first reactant comprising the BHET, the dimer of the BHET is from 0 to 100 parts by weight based on 100 parts by weight of the monomer of the BHET. The method of claim 2, wherein in the first reactant comprising the BHET, the dimer of the BHET is from 0 to 80 parts by weight based on 100 parts by weight of the monomer of the BHET. The method of claim 2, wherein in the first reactant comprising the BHET, the dimer of the BHET is from 0 to 60 parts by weight based on 100 parts by weight of the monomer of the BHET. The method of claim 2, wherein the oligomer of the BHET has the structure of the formula (1): Wherein n is an integer from 3 to 10. The method of claim 1, wherein the hydrogenation reaction is carried out without a solvent. The method of claim 1, wherein the reaction temperature of one of the hydrogenation reactions is between 80 ° C and 115 ° C. The method of claim 1, wherein the reaction temperature of the hydrogenation reaction is between 85 ° C and 110 ° C. The method of claim 1, wherein in the second reactant, the BHEET is from 0.5 to 100 parts by weight based on 100 parts by weight of the monomer of the BHET. The method of claim 1, wherein in the second reactant, the BHEET is 7 to 60 parts by weight based on 100 parts by weight of the monomer of the BHET. The method of claim 1, wherein in the second reactant, the BHEET is 25 to 50 parts by weight based on 100 parts by weight of the monomer of the BHET. For example, in the method of claim 1, the catalyst is further added to the second reactant before the hydrogenation reaction. The method of claim 13, wherein the catalyst comprises ruthenium (Ru), rhodium (Rh), platinum (Pt), palladium (Pd), or a combination thereof. The method of claim 13, wherein the total amount of the second reactant is 100 parts by weight, wherein the catalyst is 0.1 to 1.0 part by weight. The method of claim 1, wherein the hydrogenation reaction has a reaction pressure of 500 to 1500 psi. The method of claim 1, wherein the hydrogenation reaction has a reaction time of from 0.5 hours to 6 hours.