A method for refining bio-based crude ethylene glycol

Abstract

The method for refining bio-based crude ethylene glycol comprises taking bio-based crude ethylene glycol as raw material, diluting it with water to an ethylene glycol concentration of 1-95% by weight, and continuously passing the diluted ethylene glycol aqueous solution through an adsorption bed filled with one or more macroporous adsorption resins and optional ion exchange resins at a temperature of 0-100° C. and a volume space velocity of 0.01-20 BV / hr to obtain a purified ethylene glycol aqueous solution, and then dehydrating it to obtain ethylene glycol.

Description

Technical Field

[0001] The present invention relates to a bio-based crude ethylene glycol, in particular to a bio-based crude ethylene glycol comprising butanediol, pentanediol, hexanediol and optionally A method for purifying bio-based crude ethylene glycol that contains hydroxy impurities with a boiling point close to that of ethylene glycol and trace amounts of acids, ethers, aldehydes, ketones, compounds containing double bonds and / or alcohols that affect the ultraviolet transmittance of ethylene glycol. Background Art

[0002] In recent years, due to the uncertainty of oil prices and people's emphasis on sustainable development, the technology of producing ethylene glycol using biomass as raw materials has developed rapidly. However, due to the different synthetic routes, the biological route to produce ethylene glycol produces hydroxyl-containing byproducts that are different from ethylene glycol produced by the petroleum route or coal-based ethylene glycol, as well as trace amounts of acids, ethers, aldehydes, ketones and / or alcohols that affect the ultraviolet transmittance of ethylene glycol, which are even lower than the detection limit of gas chromatography. The traditional means of purifying liquid compounds is a distillation process that uses different boiling points to separate substances. However, since these impurities are close to the boiling point of ethylene glycol, and the impurities such as acids, ethers, aldehydes, ketones and / or alcohols that affect the ultraviolet transmittance of ethylene glycol are similar to the physical properties of ethylene glycol, and the boiling points are very close, the separation of ethylene glycol from these alcohol impurities by direct distillation will result in low ethylene glycol distillation yield and high energy consumption. In addition, since the ethylene glycol obtained by distillation still contains some trace impurities, the ultraviolet transmittance of ethylene glycol cannot directly meet the requirements of fiber-grade and bottle-grade polyester.

[0003] US4935102, US4966658, US5423955, US8906205 all describe the technology of using different entrainers to separate ethylene glycol and butanediol. Entrainers and ethylene glycol have azeotropic points. Generally, the temperature of the azeotropic point is significantly lower than the boiling point of ethylene glycol. In this way, the boiling point of the azeotrope of ethylene glycol and entrainer and the boiling point of impurities such as butanediol produce a significant temperature difference, and the separation of ethylene glycol and butanediol can be achieved economically by distillation.

[0004] The process of producing ethylene glycol by biological route will produce other glycols besides butanediol such as pentanediol, hexanediol, optional Alcohol impurities with boiling points very close to those of ethylene glycol, and trace amounts of acids, ethers, aldehydes, ketones and / or alcohols that affect the ultraviolet transmittance of ethylene glycol and are even below the detection limit of gas chromatography. The above patent applications do not state that the technology therein can effectively separate these impurities.

[0005] CN106946654A describes a method of using an adsorption bed equipped with a porous carbon adsorbent to adsorb impurities in biomass ethylene glycol to achieve the effect of refining ethylene glycol. This technology only describes the improvement of the ultraviolet transmittance of ethylene glycol, but does not describe the ability to separate butanediol, such as the following molecular formula: Alcohol impurities such as pentanediol and hexanediol.

[0006] CN201010200038.5 describes a method for refining ethylene glycol using zeolite and silica-alumina as adsorbents. However, this method only describes that the adsorbent can effectively remove 1,2-butanediol, and does not explain that the adsorbent can improve ultraviolet transmittance or other hydroxyl impurities.

[0007] CN201110047173.5 describes a method for improving the ultraviolet transmittance of ethylene glycol by passing a fixed bed containing an adsorbent and contacting the adsorbent so that a substance affecting the ultraviolet transmittance of ethylene glycol remains in the solid bed. However, this method only describes the improvement of the ultraviolet transmittance by the adsorption bed, and does not describe its effect of adsorbing alcohol hydroxy impurities such as butanediol, pentanediol, and hexanediol.

[0008] The direct adsorption process of adsorbents traditionally used in petroleum-based ethylene glycol or coal-to-ethylene glycol processes cannot effectively separate specific impurities in bio-based ethylene glycol. Summary of the invention

[0009] The present invention provides a method for refining bio-based crude ethylene glycol, so as to separate impurities having a boiling point close to that of ethylene glycol and containing hydroxyl groups, as well as trace acids, ethers, aldehydes, ketones, compounds containing double bonds and / or alcohols and other impurities that affect the ultraviolet transmittance of ethylene glycol in bio-based crude ethylene glycol with high yield and low cost, thereby improving the purity and ultraviolet transmittance of ethylene glycol at the same time.

[0010] The method for refining bio-based crude ethylene glycol of the present invention comprises taking bio-based crude ethylene glycol as raw material, diluting with water to an ethylene glycol concentration of 1-95% by weight, preferably 20-90% by weight, and more preferably 40-85% by weight, and continuously passing the diluted ethylene glycol aqueous solution through an adsorption bed filled with one or more, preferably one or two, macroporous adsorption resins and optional ion exchange resins at a temperature of 0-100° C., preferably 10-80° C., particularly preferably 10-50° C., and a volume space velocity of 0.01-20 BV / hr, preferably 0.01-10 BV / hr to obtain a purified ethylene glycol aqueous solution, and then dehydrating to obtain ethylene glycol. The purity and ultraviolet transmittance of the dehydrated ethylene glycol can reach the industry's high-quality polyester-grade ethylene glycol standard. The standard for high-quality polyester-grade ethylene glycol here refers to a purity of more than 99.9%, and ultraviolet transmittances at wavelengths of 220nm, 275nm and 350nm reaching 75%, 95% and 99% respectively.

[0011] The resin can remove trace acids, ethers, aldehydes, ketones, compounds containing double bonds and / or alcohols that affect the ultraviolet transmittance, as well as impurities that affect the purity of ethylene glycol and have a boiling point close to that of ethylene glycol and contain hydroxyl groups, such as butanediol, pentanediol, hexanediol and optional The alcohol impurities are separated from ethylene glycol, achieving the effect of improving the ultraviolet transmittance and purity of ethylene glycol with high yield and low cost.

[0012] Optionally, the bio-based crude ethylene glycol is pretreated by an ultraviolet lamp process, for example, the bio-based crude ethylene glycol is irradiated under ultraviolet light with a wavelength of not less than 100nm, preferably a wavelength of not less than 180nm, and more preferably 180-350nm. In some bio-based crude ethylene glycol raw materials, there are more impurities that affect the ultraviolet transmittance, resulting in a lower ultraviolet transmittance, which in turn shortens the regeneration cycle of the resin, increases the regeneration cost and the resin cost. Therefore, in order to extend the regeneration cycle of the resin and reduce the operating cost of the resin, it is possible to choose to add a controllable ultraviolet lamp process before the resin adsorption process to improve the ultraviolet transmittance of ethylene glycol. Controllable ultraviolet light can convert impurities of compounds containing double bonds that absorb suitable ultraviolet light (e.g., 180-350nm ultraviolet light) into compounds that do not contain double bonds without decomposing the ethylene glycol molecules, thereby achieving the effect of pre-improving the ultraviolet transmittance of ethylene glycol.

[0013] The UV lamp process pretreatment can be carried out as follows: using bio-based crude ethylene glycol as raw material, at a temperature of 0-170°C, preferably 10-120°C, more preferably 10-50°C, and a residence time of more than 0-2 hours, preferably 0.1-1 hours, a container with a UV lamp having a wavelength of not less than 100nm, preferably a wavelength of not less than 180nm, more preferably 180-350nm is introduced. The UV lamp is preferably a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an LED lamp, a xenon lamp, or a metal chloride lamp. After the UV transmittance of the discharge is initially improved, it can enter the resin adsorption process for further treatment.

[0014] The macroporous adsorption resin is preferably a macroporous adsorption resin with a skeleton of styrene and / or divinylbenzene, and more preferably has a specific surface area greater than 800 m 2 / g macroporous adsorption resin with a skeleton of styrene and / or divinylbenzene.

[0015] The ion exchange resin may be a weakly basic anion exchange resin, preferably a weakly basic anion exchange resin having primary amine groups, secondary amine groups and / or tertiary amine groups on its surface.

[0016] The bio-based crude ethylene glycol refers to ethylene glycol produced from biomass (here, biomass preferably refers to edible first-generation biomass including corn, sugar cane, etc. and non-food second-generation biomass including straw, wood, bagasse, etc., which is agro-forestry waste and non-food), and includes but is not limited to butanediol, pentanediol and hexanediol in addition to ethylene glycol. Optionally, the bio-based crude ethylene glycol also includes a compound having the following molecular formula: The butanediol is preferably 1,2-butanediol, 2,3-butanediol, 1,4-butanediol. The pentanediol is preferably 1,2-pentanediol. The hexanediol is preferably 1,2-hexanediol. More preferably, the bio-based crude ethylene glycol includes but is not limited to: 88-100 wt% ethylene glycol, preferably 95-100 wt% ethylene glycol, more preferably 98-100 wt% ethylene glycol (except the endpoint of 100 wt%),

[0017] 0-5% by weight, preferably 0-1% by weight, more preferably 0-0.5% by weight, particularly preferably 0-0.1% by weight of butanediol (preferably 1,2-butanediol, 2,3-butanediol and / or 1,4-butanediol; except endpoint 0),

[0018] 0-5% by weight, preferably 0-1% by weight, more preferably 0-0.5% by weight, particularly preferably 0-0.1% by weight of pentanediol (preferably 1,2-pentanediol; except for endpoint 0),

[0019] 0-5 wt %, preferably 0-2 wt %, more preferably 0-1.5 wt % of hexanediol (preferably 1,2-hexanediol; except endpoint 0), and

[0020] Optionally 0-5% by weight, preferably 0-1% by weight, more preferably 0-0.5% by weight, particularly preferably 0-0.1% by weight

[0021] The bio-based crude ethylene glycol optionally further comprises:

[0022] 0-5% by weight, preferably 0-1% by weight, more preferably 0-0.1% by weight of 1,2-propylene glycol, and 0-5% by weight, preferably 0-1% by weight, more preferably 0-0.1% by weight of diethylene glycol.

[0023] Since bio-based crude ethylene glycol contains specific hydrophilic hydroxyl-containing impurities, the dilution with water is helpful for the adsorption of the impurities.

[0024] The water may be, for example, desalted water.

[0025] The dehydration can be performed, for example, by rectification.

[0026] Since trace acids, ethers, aldehydes, ketones, compounds containing double bonds and / or alcohols that affect the ultraviolet transmittance of ethylene glycol can absorb ultraviolet light at trace levels, these impurities cannot be detected by instruments such as gas chromatography, liquid chromatography or chemical methods. Therefore, only ultraviolet transmittance can be used to represent its content in the raw material. In the present application, the transmittance of the bio-based crude ethylene glycol raw material does not meet the standards of superior polyester-grade ethylene glycol at least one of the ultraviolet transmittances at wavelengths of 220nm, 275nm and 350nm due to the presence of the above-mentioned impurities. Its transmittance can be expressed as follows: 220nm ultraviolet transmittance is less than 75%, preferably less than 40%, more preferably less than 10%; 275nm ultraviolet transmittance is less than 95%, preferably less than 70%, more preferably less than 30%; and / or 350nm ultraviolet transmittance is less than 99%, preferably less than 97%, and more preferably less than 96%.

[0027] According to the method of the present invention, the purity of the ethylene glycol can be increased to more than 99.9% under the condition of a high recovery rate of ethylene glycol of more than 99.9%, and the ultraviolet transmittance at wavelengths of 220nm, 275nm and 350nm is increased to more than 75%, 95% and 99% respectively. Moreover, compared with the traditional pure distillation method, the cost of the present invention is significantly lower. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Attached Figure 1 This is a flow chart of Example 1.

[0029] Figure 2 is a graph showing the change in ultraviolet transmittance of the ethylene glycol product of Example 1 (see Figure 2). Figure 2a ) and the change chart of ethylene glycol content (attached Figure 2b ).

[0030] Attached Figure 3 This is a flow chart of Example 2.

[0031] Figure 4 is a graph showing the change in ultraviolet transmittance of the ethylene glycol product of Example 2 (see Figure 4). Figure 4a ) and the change chart of ethylene glycol content (attached Figure 4b ).

[0032] Attached Figure 5 This is a flow chart of Example 3.

[0033] Figure 6 is a graph showing the change in ultraviolet transmittance of the ethylene glycol product of Example 3 (see Figure 6). Figure 6a ) and the change chart of ethylene glycol content (attached Figure 6b ).

[0034] Attached Figure 7 This is a flow chart of Comparative Example 1.

[0035] Figure 8 is a graph showing the change in ultraviolet transmittance of the ethylene glycol product of Comparative Example 2 (see Figure 8). Figure 8a ) and the change chart of ethylene glycol content (attached Figure 8b ). DETAILED DESCRIPTION

[0036] Example

[0037] The present invention is further described by the following examples, but the present invention is not limited to the following examples.

[0038] Example 1

[0039] The resin column was filled with 200 ml of XA-1G macroporous adsorption resin purchased from Xi'an Lanxiao Technology New Materials Co., Ltd. as an adsorbent, whose skeleton is styrene-divinylbenzene and whose specific surface area is 1200m 2 / g.

[0040] The crude ethylene glycol product obtained by hydrogenating biomass and performing preliminary distillation to remove light and heavy components was used as the raw material. The raw material was analyzed using the analysis method in GB / T4649-2008, and the content of each component was as follows: ethylene glycol content was 99.700% by weight, 1,2-pentanediol content was 0.020% by weight, 1,2-hexanediol content was 0.250% by weight, 1,2-butanediol content was 0.010% by weight, The content of 0.010 wt % and the content of other components are 0.010 wt %. The UV transmittance of the raw material is 13.5% at 220 nm, 59.0% at 275 nm and 96.8% at 350 nm.

[0041] like Figure 1 The process flow shown in the figure is to mix the crude ethylene glycol raw material with desalted water in a mass ratio of 3:1 to obtain a crude ethylene glycol aqueous solution, which is continuously introduced into a resin bed at a temperature of 30°C and a volume space velocity of 0.5 BV / hour, and the resin bed output is dehydrated using a distillation tower. The ultraviolet transmittance and ethylene glycol purity of the ethylene glycol product after adsorption and dehydration treatment are shown in the attached figure. Figure 2a And attached Figure 2b shown.

[0042] After 14 hours, the ultraviolet transmittance at 275nm dropped below the index of superior products, and the adsorbent failed. A total of 1524.6 grams of crude ethylene glycol aqueous solution was processed, which contained 1140.0 grams of ethylene glycol; the final qualified ethylene glycol product obtained was 1139.7 grams. Therefore, the yield of qualified ethylene glycol after refinement was 99.97%.

[0043] Comparative Example 1

[0044] The crude ethylene glycol product obtained by hydrogenating biomass and performing preliminary distillation to remove light and heavy substances in Example 1 is used as a raw material. Figure 7The traditional distillation method shown in the figure is used for separation. The total theoretical plates of the distillation tower are 90, the reflux ratio is 15:1, and the operating pressure is 10 kPa (absolute). The raw material enters the distillation tower at a flow rate of 200 g / h from the 40th theoretical plate. The ethylene glycol product is produced from the top of the distillation tower at a flow rate of 195 g / h. The weight percentage of ethylene glycol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol and The compositions are: 99.920%, 0.010%, 0.020%, 0.040%, 0.010%. The UV transmittance is 20.8% at 220nm, 63.2% at 275nm, and 98.5% at 350nm. The total ethylene glycol distillation yield is 97.7%.

[0045] Experimental results show that traditional distillation separation can effectively separate 1,2-hexanediol from ethylene glycol to achieve an ethylene glycol purity of more than 99.90%, but its ethylene glycol yield is only 97.7%, and the high reflux ratio leads to high steam energy consumption, and the ultraviolet transmittance cannot be effectively improved; the method of the present invention can increase the purity of ethylene glycol to more than 99.90% under the conditions of high ethylene glycol yield and low cost, and the ultraviolet transmittance of the obtained ethylene glycol at wavelengths of 220nm, 275nm, and 350nm is increased to more than 75%, 95%, and 99%, respectively.

[0046] Comparative Example 2

[0047] The crude ethylene glycol product obtained by hydrogenating biomass and performing preliminary distillation to remove light and heavy components in Example 1 is used as a raw material, and the same type and volume of adsorbent is loaded into the resin column.

[0048] like Figure 1 In the process flow shown in the figure, the crude ethylene glycol raw material is not mixed with water, and is directly passed into the resin bed continuously at a temperature of 30°C and a volume space velocity of 0.5 BV / hour. The ultraviolet transmittance and ethylene glycol purity of the ethylene glycol product after adsorption treatment are shown in the attached figure. Figure 8a And attached Figure 8b shown.

[0049] The experimental results show that although the same raw materials, adsorbents and operating conditions as those in Example 1 were used in Comparative Example 2, since the bio-based crude ethylene glycol was not mixed with water, the special impurities in the bio-based crude ethylene glycol could not be effectively adsorbed by the adsorbent, and the purity and ultraviolet transmittance of the ethylene glycol in the output material were not improved to the qualified standards.

[0050] Example 2

[0051] A low-pressure mercury ultraviolet lamp with a wavelength of 254 nm and a power of 23 watts was inserted into a 30 ml ultraviolet lamp container. 750 ml of D303 weak base anion exchange resin purchased from Xi'an Lanxiao Technology New Materials Co., Ltd. was filled into resin column A as an adsorbent, and its skeleton was styrene-divinylbenzene with primary amine functional groups; 200 ml of L493 macroporous adsorption resin purchased from Dow Chemical Company was filled into resin column B as an adsorbent, and its skeleton was macroporous styrene polymer with a specific surface area of ​​1100 m 2 / g.

[0052] The crude ethylene glycol product obtained by hydrogenating biomass and performing preliminary distillation to remove light and heavy components was used as the raw material. The raw material was analyzed using the analysis method in GB / T4649-2008, and the content of each component was as follows: ethylene glycol content was 99.753% by weight, 1,2-pentanediol content was 0.036% by weight, 1,2-hexanediol content was 0.146% by weight, 1,2-butanediol content was 0.033% by weight, The content is 0.010% by weight, the content of 1,4-butanediol is 0.002% by weight, the content of diethylene glycol is 0.010% by weight, and the content of other components is 0.010% by weight; the ultraviolet transmittance of the raw material is 1.1% at 220nm, 25.0% at 275nm, and 95.0% at 350nm.

[0053] like Figure 3 According to the process flow shown, the crude ethylene glycol raw material is continuously introduced into the UV lamp container at a flow rate of 100 ml / hour and a temperature of 20°C. The output of the UV lamp container is mixed with desalted water in a mass ratio of 2:1 to obtain a crude ethylene glycol aqueous solution, which is continuously introduced into resin bed A at a temperature of 20°C and a volume space velocity of 0.2BV / hour; the output of resin bed A is continuously introduced into resin bed B at a volume space velocity of 0.75BV / hour while other conditions remain unchanged, and the output of resin bed B is dehydrated using a distillation tower. The UV transmittance and ethylene glycol purity results of the ethylene glycol product after UV lamp treatment, adsorption and dehydration treatment are shown in the attached table. Figure 4a And attached Figure 4b shown.

[0054] After 9.3 hours, the UV transmittance at 275nm dropped below the index of superior products, and the adsorbent failed. A total of 1038.8 grams of crude ethylene glycol was processed, of which 1036.2 grams of ethylene glycol was contained; the final qualified ethylene glycol product obtained was 1036.0 grams. Therefore, the yield of refined ethylene glycol was 99.98%.

[0055] Example 3

[0056] 40 ml of D303 weak base anion exchange resin purchased from Xi'an Lanxiao Technology New Materials Co., Ltd. was filled in resin column A as an adsorbent, and its skeleton was styrene-divinylbenzene with primary amine functional groups; 200 ml of XA-1G macroporous adsorption resin purchased from Xi'an Lanxiao Technology New Materials Co., Ltd. was filled in resin column B as an adsorbent, and its skeleton was styrene-divinylbenzene with a specific surface area of ​​1200 m 2 / g.

[0057] The crude ethylene glycol product obtained by hydrogenating biomass and performing preliminary distillation to remove light and heavy components was used as the raw material. The raw material was analyzed using the analysis method in GB / T4649-2008, and the content of each component was as follows: ethylene glycol content was 98.81% by weight, 1,2-pentanediol content was 0.10% by weight, 1,2-hexanediol content was 1.05% by weight, and 1,2-butanediol content was 0.02% by weight. The content is 0.01% by weight, and the content of other components is 0.01% by weight; the ultraviolet transmittance of the raw material is 6.6% at 220nm, 63.0% at 275nm, and 95.0% at 350nm.

[0058] As attached Figure 5 As shown, the crude ethylene glycol raw material was mixed with desalted water in a mass ratio of 3:1 to obtain a crude ethylene glycol aqueous solution, which was continuously introduced into resin bed A at a temperature of 30°C and a volume space velocity of 1.0 BV / hour; the output of resin bed A was continuously introduced into resin bed B at a volume space velocity of 0.2 BV / hour under the same other conditions, and the output of resin bed B was dehydrated using a distillation tower. The ultraviolet transmittance and ethylene glycol purity results after adsorption treatment are shown in the attached figure. Figure 6a And attached Figure 6b shown.

[0059] After 5 hours, the purity dropped below the premium grade index and the adsorbent failed. A total of 217.8 grams of crude ethylene glycol aqueous solution was processed, which contained 161.41 grams of ethylene glycol; the final qualified ethylene glycol product obtained was 161.38 grams. Therefore, the yield of ethylene glycol after purification was 99.98%.

[0060] As can be seen from the examples, the present invention can well separate impurities such as trace acids, ethers, aldehydes, ketones, compounds containing double bonds and / or alcohols that affect the ultraviolet transmittance, as well as impurities that affect the purity of ethylene glycol and have a boiling point close to that of ethylene glycol and contain hydroxyl groups from ethylene glycol, thereby achieving the effect of improving the ultraviolet transmittance and purity of ethylene glycol with high yield and low cost.

Claims

1. A method for refining bio-based crude ethylene glycol, comprising: using bio-based crude ethylene glycol as a raw material, diluting it with water to an ethylene glycol concentration of 1-95% by weight, and continuously passing the diluted ethylene glycol aqueous solution through an adsorption bed filled with one or more macroporous adsorption resins and optionally ion exchange resins at a temperature of 0-100° C. and a volume space velocity of 0.01-20 BV / hr to obtain a purified ethylene glycol aqueous solution, and then dehydrating it to obtain ethylene glycol. The macroporous adsorption resin has a specific surface area greater than 800 m 2 / g, a macroporous adsorption resin with a framework of styrene and / or divinylbenzene, and the ion exchange resin is a weakly basic anion exchange resin having primary amine groups, secondary amine groups and / or tertiary amine groups on the surface, The bio-based crude ethylene glycol mentioned herein refers to ethylene glycol produced from biomass. The bio-based crude ethylene glycol raw material has at least one ultraviolet transmittance at wavelengths of 220nm, 275nm and 350nm that does not meet the standards for high-quality polyester-grade ethylene glycol.

2. The method according to claim 1, wherein the bio-based crude ethylene glycol is diluted with water to an ethylene glycol concentration of 20-90 wt. %, and / or The diluted ethylene glycol aqueous solution is subjected to the adsorption treatment at a temperature of 10-80°C and / or a volume space velocity of 0.01-10 BV / hr, and / or The adsorption bed is filled with one or two macroporous adsorption resins and optionally ion exchange resins.

3. The method according to claim 2, wherein the bio-based crude ethylene glycol is diluted with water to an ethylene glycol concentration of 40-85 wt %, and / or The diluted ethylene glycol aqueous solution is subjected to the adsorption treatment at a temperature of 10-50°C.

4. The method according to claim 1, wherein the bio-based crude ethylene glycol is pretreated by an ultraviolet lamp process.

5. The method according to claim 4, wherein the bio-based crude ethylene glycol is irradiated under ultraviolet light with a wavelength of not less than 100 nm.

6. The method according to claim 5, wherein the bio-based crude ethylene glycol is irradiated under ultraviolet light with a wavelength of not less than 180 nm.

7. The method according to claim 6, wherein the bio-based crude ethylene glycol is irradiated under ultraviolet light with a wavelength of 180-350 nm.

8. The method according to claim 4, wherein the UV lamp process pretreatment is carried out as follows: bio-based crude ethylene glycol is used as raw material, and is introduced into a container with an ultraviolet lamp with a wavelength of not less than 100 nm at a temperature of 0-170° C. and a residence time of more than 0-2 hours.

9. The method according to claim 8, wherein the UV lamp process pretreatment is carried out as follows: bio-based crude ethylene glycol is used as raw material, and is introduced into a container with a UV lamp with a wavelength of not less than 180 nm at a temperature of 10-120° C. and / or a residence time of 0.1-1 hour.

10. The method according to claim 9, wherein the ultraviolet lamp process pretreatment is carried out as follows: bio-based crude ethylene glycol is used as raw material, and a container with an ultraviolet lamp with a wavelength of 180-350nm is introduced at a temperature of 10-50°C.

11. The method according to any one of claims 1 to 10, wherein the bio-based crude ethylene glycol comprises butanediol, pentanediol and hexanediol in addition to ethylene glycol, and optionally, the bio-based crude ethylene glycol further comprises a compound having the following molecular formula:

12. The method according to claim 11, wherein the butanediol is 1,2-butanediol, 2,3-butanediol, 1,4-butanediol, and / or The pentanediol is 1,2-pentanediol, and / or The hexanediol is 1,2-hexanediol.

13. The method according to any one of claims 1 to 10, wherein the bio-based crude ethylene glycol comprises: 88-100 wt% of ethylene glycol, except for the endpoint of 100 wt%, 0-5% by weight of butanediol, except for endpoint 0, 0-5% by weight of pentanediol, except for endpoint 0, 0-5% by weight of hexylene glycol, excluding endpoint 0, and Optional 0-5 wt% 14. The method according to claim 13, wherein the bio-based crude ethylene glycol comprises: 95-100 wt% ethylene glycol, excluding the endpoint of 100 wt%, and / or 0-1% by weight of butanediol, except endpoint 0, and / or 0-1% by weight of pentanediol, except for endpoint 0, and / or 0-2% by weight of hexylene glycol, except for endpoint 0, and / or Optional 0-1 wt% 15. The method according to claim 14, wherein the bio-based crude ethylene glycol comprises: 98-100 wt% ethylene glycol, excluding the endpoint of 100 wt%, and / or 0-0.5 wt% of butanediol, except endpoint 0, and / or 0-0.5 wt% pentanediol, except for endpoint 0, and / or 0-1.5 wt% hexylene glycol, except endpoint 0, and / or Optional 0-0.5 wt% 16. The method according to claim 15, wherein the bio-based crude ethylene glycol comprises: 0-0.1 wt% butanediol, except endpoint 0, and / or 0-0.1 wt% of pentanediol, except for endpoint 0, and / or Optional 0-0.1 wt% 17. The method according to claim 16, wherein the bio-based crude ethylene glycol comprises: The butanediol is 1,2-butanediol, 2,3-butanediol and / or 1,4-butanediol, and / or The pentanediol is 1,2-pentanediol, and / or The hexanediol is 1,2-hexanediol.

18. The method according to any one of claims 1 to 10, wherein the bio-based crude ethylene glycol optionally further comprises: 0-5 wt% of 1,2-propylene glycol, and 0-5 wt% diethylene glycol.

19. The method according to claim 18, wherein the bio-based crude ethylene glycol optionally further comprises: 0-1% by weight of 1,2-propylene glycol, and / or 0-1 wt% diethylene glycol.

20. The method according to claim 19, wherein the bio-based crude ethylene glycol optionally further comprises: 0-0.1% by weight of 1,2-propylene glycol, and / or 0-0.1 wt% diethylene glycol.

21. The process according to any one of claims 1 to 10, wherein the dehydration is carried out by distillation.

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