Method for synthesizing ethylene glycol from ethylene

Abstract

The invention provides a method for synthesizing ethylene glycol from ethylene, which comprises the following steps: in the presence of a free radical inhibitor, ethylene, hydrogen peroxide and a titanium silicalite molecular sieve are contacted in a mixed solution of water and an optional organic solvent to carry out oxidation-hydration one-step reaction, and the addition amount of the free radical inhibitor is 0.005-5wt% of the addition amount of the hydrogen peroxide. By introducing the efficient free radical inhibitor and selectively inhibiting a side reaction path, generation of acidic impurities is remarkably reduced, selectivity and product purity of ethylene glycol are improved, and the method is suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of chemical engineering and organic synthesis technology, specifically relating to a one-step method for the direct synthesis of ethylene glycol from ethylene. Background Technology

[0002] Ethylene glycol (EG) is an important chemical raw material, widely used in polyester fibers, antifreeze, and other fields. Global EG production technologies are mainly divided into two categories: the "petroleum route," using ethylene, a petroleum refining product, as feedstock, and the "syngas route," using natural gas and coal as feedstock. Due to its high product yield and mature technology, the "petroleum route," which uses the oxidation and hydration of ethylene to produce EG, accounts for a larger share. The petroleum-based ethylene oxide hydration method requires the addition of a large amount of water during the hydration reaction, with the water-to-EO molar ratio often exceeding 20:1. This excessive water content necessitates multiple stages of evaporation (typically using 3-6 effect evaporation) to remove a significant amount of water. Furthermore, this technology produces numerous byproducts, including approximately 9% diethylene glycol, 1% triethylene glycol, and polyethylene glycol, complicating subsequent separation processes. Therefore, the direct hydration method suffers from drawbacks such as a long process flow, high energy consumption, and poor economic efficiency. The coal-based "syngas route" technology has a long process flow, requires a large number of different catalysts, and incurs high costs due to the use of precious metals. Meanwhile, the CO coupling process contains many impurities such as fusel oils, ethers, and esters, resulting in lower EG purity than petroleum-based ethylene oxide hydration products. This makes most EG products obtained by the CO coupling method unsuitable for traditional PET applications.

[0003] In recent years, the one-step direct oxidation of ethylene to ethylene glycol has attracted much attention due to its high atom economy and short process flow. More and more scholars have recognized the development potential of the TS-1 / H2O2 catalytic system for the one-step oxidation of ethylene to ethylene glycol and have conducted in-depth research in this field. However, all of this research has focused on small-batch catalyst and process improvement in the laboratory, and the process still faces challenges in practical applications: the free radical chain oxidation during the reaction easily generates acidic substances such as formic acid, acetic acid, and glyoxylic acid, with contents typically reaching 5%-10%. These impurities not only corrode equipment (such as reactors and pipelines) but also increase the energy consumption of subsequent neutralization and distillation. In environments with high ethylene glycol content, the generation of acidic impurities leads to a decrease in ethylene glycol selectivity. Simultaneously, acidic substances adsorb onto the catalyst surface, poisoning active sites and shortening catalyst life. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing one-step oxidation technology for ethylene glycol by proposing a method that regulates the chain oxidation reaction pathway by adding free radical inhibitors. This method blocks the generation of acidic impurities at the source, thereby achieving both high-concentration ethylene glycol products and improved ethylene glycol selectivity.

[0005] This invention provides a method for synthesizing ethylene glycol from ethylene. The preparation method includes: in the presence of a free radical inhibitor, contacting ethylene, hydrogen peroxide and titanium silicate molecular sieve in a mixed solution of water and optionally an organic solvent to carry out an oxidation-hydration one-step reaction, wherein the amount of free radical inhibitor added is 0.005wt%-5wt% of the amount of hydrogen peroxide added.

[0006] In this invention, the range of free radical inhibitors is relatively wide, generally including one or more of phenolic free radical inhibitors, amine free radical inhibitors, nitroxide free radical inhibitors, quinone free radical inhibitors, natural antioxidants, and other free radical inhibitors. Preferably, it is one or more of 2,2,6,6-tetramethylpiperidine nitroxide radical (TEMPO), L-ascorbic acid, urea, 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide radical (4-OH-TEMPO), and tea polyphenols. More preferably, it is a mixture of 2,2,6,6-tetramethylpiperidine nitroxide radical (TEMPO) and L-ascorbic acid, wherein the content of each in the mixture is not less than 30 wt%, and preferably the content of each is 40-60 wt%.

[0007] According to a preferred embodiment of the present invention, the amount of free radical inhibitor added is 0.1%-1% (wt) of the amount of hydrogen peroxide added.

[0008] In this invention, the organic solvent is an ether solvent such as tetrahydrofuran and ethylene glycol monomethyl ether, a ketone solvent such as acetone, an alcohol solvent such as ethanol, and other polar and non-polar solvents miscible with water, preferably one or more of tetrahydrofuran, ethylene glycol monomethyl ether, and acetone.

[0009] In the ethylene glycol preparation step of this invention, the mass ratio of titanium silicate molecular sieve to water is (0.08-30):1, preferably (0.08-1):1.

[0010] In the ethylene glycol preparation step of this invention, the mass ratio of hydrogen peroxide to water is (0.01-10):1, preferably (0.01-0.5):1.

[0011] In the preparation of ethylene glycol in this invention, the mass ratio of organic solvent to water is (0-50):1, preferably (0-5):1.

[0012] In the ethylene glycol preparation step of this invention, the molar ratio of ethylene to hydrogen peroxide is (0.5-10):1, preferably (1-3):1.

[0013] In this invention, the mass of the water mentioned above does not include the water content carried by the hydrogen peroxide.

[0014] This invention can be carried out at low temperature and low pressure. In this invention, the reaction temperature is 20-95℃, preferably 20-50℃.

[0015] In this invention, the reaction time is 0.1-20 h, preferably 0.5-6 h.

[0016] In this invention, the reaction pressure is 0.1-6 MPa, preferably 0.5-4 MPa.

[0017] In this invention, the concentration of hydrogen peroxide in the hydrogen peroxide solution is 5%-80% by mass, preferably 40%-60% by mass.

[0018] In this invention, the titanium-silicon molecular sieve includes one or more of the following: MFI structure titanium-silicon molecular sieve, MEL structure titanium-silicon molecular sieve, BEA structure titanium-silicon molecular sieve, MWW structure titanium-silicon molecular sieve, two-dimensional hexagonal structure titanium-silicon molecular sieve, MOR structure titanium-silicon molecular sieve, TUN structure titanium-silicon molecular sieve, and titanium-silicon molecular sieve with other structures.

[0019] The main advantages of using the technology of this invention are as follows: 1. Capturing active free radicals: Hydrogen peroxide may decompose on the catalyst surface to generate oxygen and water, and at the same time generate highly active oxygen species such as ·OH. These active oxygen species will non-selectively oxidize organic matter, resulting in by-products other than the main product. Free radical inhibitors preferentially combine with active intermediates such as ·OH, terminating the chain reaction, preventing the ethylene carbon chain from breaking, and avoiding further over-oxidation of ethylene glycol, etc.; 2. Stabilizing reaction intermediates: Inhibitors can stabilize transition state free radicals, enhance the formation of ethylene oxide from ethylene, and cause it to favor the formation of ethylene glycol; 3. Protecting the catalyst surface: Free radical inhibitors will reduce the generation of acidic impurities, reduce the exposure of the catalyst active center in the acidic environment, reduce the number of acidic impurities adsorbed on the catalyst active center, reduce the poisoning of the catalyst by acidic substances, and significantly maintain the catalyst activity and extend the catalyst life.

[0020] This invention introduces a highly efficient free radical inhibitor to selectively suppress side reaction pathways, significantly reduce the generation of acidic impurities, improve the selectivity of ethylene glycol and the purity of the product, making it suitable for industrial production. Detailed Implementation

[0021] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] This invention does not have special requirements for specific operations. For example, in a batch reaction, first add weighed water to the reactor, then weigh the titanium-silicon molecular sieve and solvent according to their mass ratio with water, add them to the reactor, and stir for 5 minutes to ensure uniform mixing. Next, add weighed hydrogen peroxide source, and finally add weighed free radical inhibitor. Seal the reactor, start stirring, and begin heating the reactor. Once the reaction temperature is reached, introduce ethylene to the set pressure to begin the reaction. After a certain time, the reaction ends, the unreacted ethylene is vented, the reactor is rapidly cooled, and the supernatant is collected. Gas chromatography and liquid chromatography are used to analyze the ethylene glycol content and selectivity, as well as the content of acidic impurities.

[0023] In continuous synthesis processes, such as in tubular reactors, weighed water, titanium silicate molecular sieves, solvents, and free radical inhibitors are first added sequentially to a feed tank and stirred for 5 minutes to ensure homogeneity. Weighed hydrogen peroxide is then added to another feed tank. The slurry is pumped into the reactor. Ethylene is first mixed with the slurry via a mass flow meter, followed by the hydrogen peroxide. The feedstock undergoes a three-phase reaction within the reactor. After a certain reaction time, the mixture is discharged from the reactor. Unreacted ethylene gas is separated and vented. The mixture is rapidly cooled, and the supernatant is collected. Gas chromatography and liquid chromatography are used to analyze the ethylene glycol content and selectivity, as well as the content of acidic impurities.

[0024] The following detailed description of the embodiments further illustrates the present invention. It should be noted that the following embodiments are illustrative, not limiting, and should not be construed as limiting the scope of protection of the present invention; rather, the scope should be defined by the claims.

[0025] The hollow titanium-silicon molecular sieve is used as an example in the embodiments to illustrate the advantages of the present invention. HTS is a hollow titanium-silicon molecular sieve (brand name ETG-1) produced by Hunan Jianchang Petrochemical Co., Ltd.

[0026] In this invention, the post-reaction solution is analyzed using an Agilent gas chromatograph (GC-7890B).

[0027] The mass fraction of ethylene glycol was determined by the external standard method. A 5% (w / w) ethylene glycol standard was prepared using analytical grade ethylene glycol and injected into the gas chromatograph via an autosampler to obtain the peak area S1 of the ethylene glycol standard. A sample of the reaction product was taken and injected into the gas chromatograph via an autosampler to obtain the peak area S2 of ethylene glycol in the sample. The mass concentration of ethylene glycol in the sample, w% = S2 / S1 * 5%.

[0028] The mass fraction of diethylene glycol was analyzed using the external standard method. A 0.5% (w / w) diethylene glycol standard was prepared from analytical grade diethylene glycol and injected into the gas chromatograph using an autosampler to obtain the peak area S1 of the diethylene glycol standard. A sample of the reaction product was taken and injected into the gas chromatograph using an autosampler to obtain the peak area S2 of diethylene glycol in the sample. The mass concentration of diethylene glycol in the sample, w% = S2 / S1 * 0.5%.

[0029] The hydrogen peroxide content was quantitatively analyzed using the indirect iodometric method. 20% sulfuric acid was added to an Erlenmeyer flask, the sample was accurately weighed, and then 1g of potassium iodide and 3-4 drops of ammonium molybdate solution were added. The flask was then placed in the dark for 10 minutes. Next, titration was performed using 0.1mol / L sodium thiosulfate solution on a Metrohm 916Ti-Touch potentiometric titrator.

[0030] Based on the results of gas chromatography and hydrogen peroxide titration, the utilization rate of hydrogen peroxide was... u (H2O2), ethylene glycol selectivity s (EG) is calculated using formulas (1) to (3) respectively.

[0031] (1) (2) (3) In the formula, n 0 (H2O2) and n (H2O2) represents the amount of hydrogen peroxide before and after the reaction, in mol; n (EG) and n (DEG) represent the amounts of ethylene glycol (EG) and diethylene glycol (DEG) produced after the reaction, in mol.

[0032] Example 1 The reaction was carried out in a reactor under the following conditions: 1 g hollow titanium-silicon molecular sieve (HTS) catalyst, 13 g water, 1 g acetone, 6 g 50 wt% hydrogen peroxide, 0.003 g 2,2,6,6-tetramethylpiperidine nitroxide radical (TEMPO), 30 °C, reaction pressure 2 MPa, ethylene:hydrogen peroxide molar ratio 3:1, 4 h. The ethylene glycol mass fraction was 23.1%, the ethylene glycol selectivity was 96.8%, and the hydrogen peroxide utilization rate was 94.9%. After the reaction, the catalyst was dried in an oven, and then the reaction was repeated under the above conditions for a total of 5 cycles. The product after the 5th reaction was analyzed, and the ethylene glycol mass fraction was 21.1%, the ethylene glycol selectivity was 93.3%, and the hydrogen peroxide utilization rate was 89.2%.

[0033] Example 2 The reaction was carried out in a reactor under the following conditions: 1 g hollow titanium silicate molecular sieve (HTS) catalyst, 13 g water, 1 g acetone, 6 g 50 wt% hydrogen peroxide, 0.003 g L-ascorbic acid, 30 °C, reaction pressure 2 MPa, ethylene:hydrogen peroxide molar ratio 3:1, 4 h. The ethylene glycol mass fraction was 22.8%, the ethylene glycol selectivity was 97.0%, and the hydrogen peroxide utilization rate was 93.3%. After the reaction, the catalyst was dried at low temperature in an oven, and then the reaction was repeated under the above conditions, for a total of 5 cycles. The product after the 5th reaction was analyzed, and the ethylene glycol mass fraction was 20.1%, the ethylene glycol selectivity was 92.6%, and the hydrogen peroxide utilization rate was 89.8%.

[0034] Example 3 The reaction was carried out in a reactor under the following conditions: 1g hollow titanium-silicon molecular sieve (HTS) catalyst, 13g water, 1g acetone, 6g 50wt% hydrogen peroxide, 0.003g urea, 30℃, reaction pressure 2MPa, ethylene, ethylene:hydrogen peroxide molar ratio 3:1, 4h. The ethylene glycol mass fraction was 22.5%, the ethylene glycol selectivity was 96.2%, and the hydrogen peroxide utilization rate was 92.1%. After the reaction, the catalyst was dried at low temperature in an oven, and then the reaction was repeated under the above conditions, for a total of 5 cycles. The product after the 5th reaction was analyzed, and the ethylene glycol mass fraction was 19.7%, the ethylene glycol selectivity was 92.0%, and the hydrogen peroxide utilization rate was 89.0%.

[0035] Example 4 The reaction was carried out in a reactor under the following conditions: 1 g hollow titanium silicate molecular sieve (HTS) catalyst, 13 g water, 1 g acetone, 6 g 50 wt% hydrogen peroxide, 0.003 g 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide radical (4-OH-TEMPO), 30 °C, reaction pressure 2 MPa, ethylene:hydrogen peroxide molar ratio 2:1, 4 h. The ethylene glycol mass fraction was 22.6%, the ethylene glycol selectivity was 97.2%, and the hydrogen peroxide utilization rate was 92.5%. After the reaction, the catalyst was dried at low temperature in an oven, and then the reaction was repeated under the above conditions for a total of 5 cycles. The product after the 5th reaction was analyzed, and the ethylene glycol mass fraction was 19.9%, the ethylene glycol selectivity was 91.8%, and the hydrogen peroxide utilization rate was 89.5%.

[0036] Example 5 The reaction was carried out in a reactor. Specific reaction conditions were: 1g hollow titanium silicate molecular sieve (HTS) catalyst, 13g water, 1g acetone, 6g 50wt% hydrogen peroxide, 0.003g tea polyphenols, 30℃, reaction pressure 2MPa, ethylene:hydrogen peroxide molar ratio 2:1, 4h. The ethylene glycol mass fraction was 22.0%, the ethylene glycol selectivity was 96.6%, and the hydrogen peroxide utilization rate was 90.0%. After the reaction, the catalyst was dried at low temperature in an oven, and then the reaction was repeated under the above conditions, for a total of 5 cycles. Analysis of the product after the 5th reaction showed an ethylene glycol mass fraction of 19.6%, an ethylene glycol selectivity of 91.5%, and a hydrogen peroxide utilization rate of 89.1%.

[0037] Example 6 The reaction was carried out in a reactor using hollow titanium-silicon molecular sieve (HTS) as the catalyst. The specific reaction conditions were: 1 g HTS catalyst, 14 g water, 6 g 50 wt% hydrogen peroxide, 0.003 g 2,2,6,6-tetramethylpiperidine nitroxide radical (TEMPO), 30 °C, reaction pressure 2 MPa, ethylene:hydrogen peroxide molar ratio 2:1, 4 h. The ethylene glycol mass fraction was 21.5%, the ethylene glycol selectivity was 96.0%, and the hydrogen peroxide utilization rate was 87.7%. After the reaction, the catalyst was dried at low temperature in an oven, and then the reaction was repeated under the above conditions, for a total of 5 cycles. The product after the 5th reaction was analyzed, and the ethylene glycol mass fraction was 18.4%, the ethylene glycol selectivity was 90.7%, and the hydrogen peroxide utilization rate was 88.0%.

[0038] Example 7 The reaction was carried out in a reactor using hollow titanium-silicon molecular sieve (HTS) as the catalyst. The specific reaction conditions were: 1 g HTS catalyst, 13 g water, 1 g acetone, 6 g 50 wt% hydrogen peroxide, 0.03 g 2,2,6,6-tetramethylpiperidine nitroxide radical (TEMPO), 30 °C, reaction pressure 2 MPa, ethylene:hydrogen peroxide molar ratio 1:1, 4 h. The ethylene glycol mass fraction was 23.0%, the ethylene glycol selectivity was 97.4%, and the hydrogen peroxide utilization rate was 94.5%. After the reaction, the catalyst was dried at low temperature in an oven, and then the reaction was repeated under the above conditions, for a total of 5 cycles. Analysis of the product after the 5th reaction showed an ethylene glycol mass fraction of 21.2%, an ethylene glycol selectivity of 92.8%, and a hydrogen peroxide utilization rate of 89.7%.

[0039] Example 8 The reaction was carried out in a reactor under the following conditions: 1 g hollow titanium silicate molecular sieve (HTS) catalyst, 13 g water, 1 g acetone, 1 g 50 wt% hydrogen peroxide, 0.005 g 2,2,6,6-tetramethylpiperidine nitroxide radical (TEMPO), 30 °C, reaction pressure 2 MPa, ethylene:hydrogen peroxide molar ratio 3:1, 0.5 h. The ethylene glycol mass fraction was 5.85%, the ethylene glycol selectivity was 99.0%, and the hydrogen peroxide utilization rate was 99.1%. After the reaction, the catalyst was dried at low temperature in an oven, and then the reaction was repeated under the above conditions, for a total of 5 cycles. The product after the 5th reaction was analyzed, and the ethylene glycol mass fraction was 5.5%, the ethylene glycol selectivity was 94.6%, and the hydrogen peroxide utilization rate was 92.9%.

[0040] Example 9 The reaction was carried out in a reactor under the following conditions: 6.5 g hollow titanium silicate molecular sieve (HTS) catalyst, 13 g water, 1 g acetone, 6 g 50 wt% hydrogen peroxide, 0.003 g 2,2,6,6-tetramethylpiperidine nitroxide radical (TEMPO), 30 °C, reaction pressure 2 MPa, ethylene:hydrogen peroxide molar ratio 3:1, 4 h. The ethylene glycol mass fraction was 23.7%, the ethylene glycol selectivity was 97.0%, and the hydrogen peroxide utilization rate was 95.5%. After the reaction, the catalyst was dried at low temperature in an oven, and then the reaction was repeated under the above conditions for a total of 5 cycles. The product after the 5th reaction was analyzed, and the ethylene glycol mass fraction was 21.5%, the ethylene glycol selectivity was 93.5%, and the hydrogen peroxide utilization rate was 90.6%.

[0041] Example 10 The reaction was carried out in a reactor under the following conditions: 13g hollow titanium silicate molecular sieve (HTS) catalyst, 13g water, 1g acetone, 6g 50wt% hydrogen peroxide, 0.003g 2,2,6,6-tetramethylpiperidine nitroxide radical (TEMPO), 30℃, reaction pressure 2MPa, ethylene:hydrogen peroxide molar ratio 3:1, 4h. The ethylene glycol mass fraction was 23.6%, the ethylene glycol selectivity was 97.1%, and the hydrogen peroxide utilization rate was 95.8%. After the reaction, the catalyst was dried at low temperature in an oven, and then the reaction was repeated under the above conditions, for a total of 5 cycles. The product after the 5th reaction was analyzed, and the ethylene glycol mass fraction was 22.1%, the ethylene glycol selectivity was 93.8%, and the hydrogen peroxide utilization rate was 91.2%.

[0042] Example 11 The reaction was carried out in a reactor under the following conditions: 1 g hollow titanium silicate molecular sieve (HTS) catalyst, 13 g water, 1 g acetone, 13 g 50 wt% hydrogen peroxide, 0.003 g 2,2,6,6-tetramethylpiperidine nitroxide radical (TEMPO), 30 °C, reaction pressure 2 MPa, ethylene:hydrogen peroxide molar ratio 3:1, 6 h. The ethylene glycol mass fraction was 27.2%, the ethylene glycol selectivity was 74.8%, and the hydrogen peroxide utilization rate was 71.8%. After the reaction, the catalyst was dried at low temperature in an oven, and then the reaction was repeated under the above conditions for a total of 5 cycles. The product after the 5th reaction was analyzed, and the ethylene glycol mass fraction was 23.6%, the ethylene glycol selectivity was 67.7%, and the hydrogen peroxide utilization rate was 66.0%.

[0043] Example 12 The reaction was carried out in a reactor under the following conditions: 1 g hollow titanium-silicon molecular sieve (HTS) catalyst, 2.5 g water, 12.5 g acetone, 6 g 50 wt% hydrogen peroxide, 0.003 g 2,2,6,6-tetramethylpiperidine nitroxide radical (TEMPO), 30 °C, 2 MPa reaction pressure, ethylene:hydrogen peroxide molar ratio 3:1, 4 h. The ethylene glycol mass fraction was 20.4%, the ethylene glycol selectivity was 93.8%, and the hydrogen peroxide utilization rate was 91.5%. After the reaction, the catalyst was dried at low temperature in an oven, and then the reaction was repeated under the above conditions for a total of 5 cycles. The product after the 5th reaction was analyzed, and the ethylene glycol mass fraction was 18.6%, the ethylene glycol selectivity was 88.1%, and the hydrogen peroxide utilization rate was 86.2%.

[0044] Example 13 The reaction was carried out in a reactor under the following conditions: 1 g hollow titanium silicate molecular sieve (HTS) catalyst, 13 g water, 1 g acetone, 6 g 50 wt% hydrogen peroxide, 0.003 g 2,2,6,6-tetramethylpiperidine nitroxide radical (TEMPO), 20 °C, 2 MPa reaction pressure, ethylene:hydrogen peroxide molar ratio 3:1, 4 h. The ethylene glycol mass fraction was 23.4%, the ethylene glycol selectivity was 95.5%, and the hydrogen peroxide utilization rate was 93.4%. After the reaction, the catalyst was dried at low temperature in an oven, and then the reaction was repeated under the above conditions for a total of 5 cycles. The product after the 5th reaction was analyzed, and the ethylene glycol mass fraction was 20.6%, the ethylene glycol selectivity was 89.1%, and the hydrogen peroxide utilization rate was 87.2%.

[0045] Example 14 The reaction was carried out in a reactor under the following conditions: 1 g hollow titanium silicate molecular sieve (HTS) catalyst, 13 g water, 1 g acetone, 6 g 50 wt% hydrogen peroxide, 0.003 g 2,2,6,6-tetramethylpiperidine nitroxide radical (TEMPO), 50 °C, reaction pressure 2 MPa, ethylene:hydrogen peroxide molar ratio 3:1, 4 h. The ethylene glycol mass fraction was 21.8%, the ethylene glycol selectivity was 93.5%, and the hydrogen peroxide utilization rate was 91.1%. After the reaction, the catalyst was dried at low temperature in an oven, and then the reaction was repeated under the above conditions, for a total of 5 cycles. The product after the 5th reaction was analyzed, and the ethylene glycol mass fraction was 18.8%, the ethylene glycol selectivity was 88.3%, and the hydrogen peroxide utilization rate was 86.2%.

[0046] Example 15 The method is the same as in Example 1, except that the free radical compound used is a mixture of 2,2,6,6-tetramethylpiperidine nitroxide radical (TEMPO) and L-ascorbic acid, each in an amount of 0.0015 g.

[0047] The ethylene glycol mass fraction was 24.0%, the ethylene glycol selectivity was 98.8%, and the hydrogen peroxide utilization rate was 97.9%. The catalyst was dried at low temperature in an oven after the reaction, and then the reaction was repeated under the same conditions for a total of 5 cycles. Analysis of the product after the 5th reaction showed an ethylene glycol mass fraction of 22.6%, an ethylene glycol selectivity of 94.0%, and a hydrogen peroxide utilization rate of 93.2%.

[0048] Comparative Example 1 The reaction was carried out in a reactor under the following conditions: 1 g hollow titanium-silicon molecular sieve (HTS) catalyst, 13 g water, 1 g acetone, 6 g 50 wt% hydrogen peroxide, reaction pressure 2 MPa, ethylene:hydrogen peroxide molar ratio 3:1, 4 h. The ethylene glycol mass fraction was 18.8%, the ethylene glycol selectivity was 80.5%, and the hydrogen peroxide utilization rate was 76.6%. After the reaction, the catalyst was dried at low temperature in an oven, and then the reaction was repeated under the above conditions, for a total of 5 cycles. The product after the 5th reaction was analyzed, and the ethylene glycol mass fraction was 14.8%, the ethylene glycol selectivity was 71.2%, and the hydrogen peroxide utilization rate was 64.6%.

[0049] Comparative Example 2 The reaction was carried out in a reactor under the following conditions: 1 g hollow titanium silicate molecular sieve (HTS) catalyst, 14 g water, 6 g 50 wt% hydrogen peroxide, 30 °C, reaction pressure 2 MPa, ethylene:hydrogen peroxide molar ratio 3:1, 4 h. The ethylene glycol mass fraction was 17.2%, the ethylene glycol selectivity was 78.2%, and the hydrogen peroxide utilization rate was 69.8%. After the reaction, the catalyst was dried at low temperature in an oven, and then the reaction was repeated under the above conditions, for a total of 5 cycles. The product after the 5th reaction was analyzed, and the ethylene glycol mass fraction was 13.5%, the ethylene glycol selectivity was 69.4%, and the hydrogen peroxide utilization rate was 60.1%.

[0050] Comparative Example 3 The reaction was carried out in a reactor under the following conditions: 1g hollow titanium-silicon molecular sieve (HTS) catalyst, 13g water, 1g acetone, 13g 50wt% hydrogen peroxide, 30℃, reaction pressure 2MPa, ethylene:hydrogen peroxide molar ratio 3:1, 6h. The ethylene glycol mass fraction was 19.6%, the ethylene glycol selectivity was 57.4%, and the hydrogen peroxide utilization rate was 56.0%. After the reaction, the catalyst was dried at low temperature in an oven, and then the reaction was repeated under the above conditions for a total of 5 cycles. The product after the 5th reaction was analyzed, and the ethylene glycol mass fraction was 15.5%, the ethylene glycol selectivity was 44.7%, and the hydrogen peroxide utilization rate was 42.3%.

[0051] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A method for synthesizing ethylene glycol from ethylene, the preparation method comprising: In the presence of a free radical inhibitor, ethylene, hydrogen peroxide, and titanium silicate molecular sieve are contacted in a mixed solution of water and optionally an organic solvent to carry out an oxidative hydration one-step reaction, wherein the amount of free radical inhibitor added is 0.005wt%-5wt% of the amount of hydrogen peroxide added.

2. The method according to claim 1, wherein, The free radical inhibitors mentioned include one or more of the following: phenolic free radical inhibitors, amine free radical inhibitors, nitroxide free radical inhibitors, quinone free radical inhibitors, and natural antioxidant free radical inhibitors; Preferably, the free radical inhibitor is one or more of 2,2,6,6-tetramethylpiperidine nitroxide radical (TEMPO), L-ascorbic acid, urea, 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide radical (4-OH-TEMPO), and tea polyphenols; More preferably, the free radical inhibitor is a mixture of 2,2,6,6-tetramethylpiperidine nitrogenoxide radical (TEMPO) and L-ascorbic acid, wherein the content of each in the mixture is not less than 30 wt%, preferably 40-60 wt%.

3. The method according to claim 1, wherein, The amount of free radical inhibitor added is 0.1wt%-1wt% of the amount of hydrogen peroxide added.

4. The method according to claim 1, wherein, The organic solvent is a water-miscible solvent, preferably one or more of tetrahydrofuran, ethylene glycol monomethyl ether, and acetone; and / or the concentration of hydrogen peroxide in the hydrogen peroxide is 5%-80% by mass, preferably 40%-60% by mass.

5. The method according to claim 1, wherein, The mass ratio of titanium-silicon molecular sieve to water is (0.08-30):1, preferably (0.08-1):

1.

6. The method according to claim 1, wherein, The mass ratio of hydrogen peroxide to water is (0.01-10):1, preferably (0.01-0.5):

1.

7. The method according to claim 1, wherein, The mass ratio of organic solvent to water is (0-50):1, preferably (0-5):

1.

8. The method according to claim 1, wherein, The molar ratio of ethylene to hydrogen peroxide is (0.5-10):1, preferably (1-3):

1.

9. The method according to claim 1, wherein, The reaction temperature is 20-95℃, preferably 20-50℃; the reaction time is 0.1-20h, preferably 0.5-6h; the reaction pressure is 0.1-6MPa, preferably 0.5-4MPa.

10. The method according to claim 1, wherein, The titanium-silicon molecular sieve includes one or more of the following: MFI structure, MEL structure, BEA structure, MWW structure, two-dimensional hexagonal structure, MOR structure, and TUN structure.