A process for the oxidation of ethylene glycol to glycolic acid

Abstract

The application provides a method for preparing glycolic acid through oxidation of ethylene glycol, comprising the following steps: ethylene glycol is subjected to oxidation reaction under the action of a catalyst to obtain glycolic acid; the oxidation reaction is carried out at a pressure of 1.0-2.0 MPa and a temperature of 60-80 DEG C; the dosage ratio of the catalyst to the ethylene glycol is 1g:(10-20)mol; the carrier of the catalyst comprises a mesoporous molecular sieve, the active component comprises Pt, and the auxiliary active component comprises Mn, Sn and Bi; the content of Pt is 0.8%-1.6% and the total content of Sn, Bi and Mn is 1.0%-3.5% based on 100% of the mass of the catalyst. The method significantly improves the selectivity of glycolic acid and the yield of ethylene glycol by using a catalyst with Pt as the active component and Mn, Sn and Bi as the auxiliary active component, and by combining the parameters such as the dosage of the catalyst, the reaction pressure and the temperature.

Description

Technical Field

[0001] This invention relates to the field of ethylene glycol oxidation technology, and in particular to a method for preparing glycolic acid by ethylene glycol oxidation. Background Technology

[0002] Glycolic acid (also known as glycolic acid) is an important raw material for organic synthesis and a chemical product. It is widely used in organic synthesis, printing and dyeing, cosmetics, electroplating and petroleum industry. Its polymers can also be used as biodegradable materials in medical, packaging and many other fields.

[0003] In 1940, DuPont in the United States successfully produced glycolic acid using chemical synthesis. Later, Japan, Germany, and other countries also developed corresponding production technologies. After decades of development, a series of glycolic acid synthesis methods have been developed both domestically and internationally. There are roughly six existing glycolic acid preparation processes: (1) a method in which carbon monoxide, formaldehyde, and water react under high temperature and high pressure conditions in the presence of a strong acid catalyst; (2) a method using chloroacetic acid and sodium hydroxide; (3) a method in which glyoxal obtained from the oxidation of ethylene glycol undergoes a Carnicarro reaction with a strong base to form glycolate, and then glycolic acid is separated by adding acid; (4) a method in which glyoxal obtained from the oxidation of ethylene glycol undergoes a liquid-phase reaction with water in the presence of an inorganic catalyst; (5) a method in which ethylene glycol is contact-oxidized in the presence of a noble metal catalyst and oxygen; and (6) a method in which ethylene glycol is oxidized and esterified with methanol and oxygen to form methyl glycolate, which is then hydrolyzed to produce glycolic acid. Among these, the method of selective oxidation of ethylene glycol to prepare glycolic acid has received widespread attention due to the single and readily available raw materials and the simple process.

[0004] However, most existing methods for the selective oxidation of ethylene glycol to prepare glycolic acid have limitations in terms of selectivity or conversion rate. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing glycolic acid by oxidizing ethylene glycol. This method significantly improves the selectivity of glycolic acid and the yield of ethylene glycol by using a catalyst with Pt as the active component and Mn, Sn and Bi as co-active components, combined with limiting parameters such as catalyst dosage, reaction pressure and temperature.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing glycolic acid by ethylene glycol oxidation includes the following steps:

[0008] Ethylene glycol undergoes an oxidation reaction in the presence of a catalyst to yield glycolic acid; the oxidation reaction is carried out at a pressure of 1.0-2.0 MPa and a temperature of 50-80 °C, and the ratio of the catalyst to the ethylene glycol is 1 g:(10-20) mol.

[0009] The catalyst support includes a mesoporous molecular sieve, the active component includes Pt, and the co-active components include Mn, Sn and Bi.

[0010] Based on the mass of the catalyst, the Pt content is 0.8%-1.6%, and the total content of Sn, Bi and Mn is 1.0%-3.5%.

[0011] Optionally, in the method for preparing glycolic acid by ethylene glycol oxidation provided by the present invention, the ethylene glycol is derived from an ethylene glycol solution, and the concentration of the ethylene glycol solution is 0.2-0.6 mol / L.

[0012] Optionally, in the method for preparing glycolic acid by ethylene glycol oxidation provided by the present invention, the mass ratio of Mn, Sn and Bi is (0.4-1.0):(0.1-0.7):(0.1-0.5).

[0013] Optionally, in the method for preparing glycolic acid by ethylene glycol oxidation provided by the present invention, the preparation method of the catalyst includes the following steps:

[0014] The catalyst is obtained by impregnating mesoporous molecular sieves with an equal volume of impregnation solution containing Pt salt, Mn salt, Sn salt and Bi salt, followed by aging, drying, calcination and reduction.

[0015] Optionally, in the catalyst preparation method provided by the present invention, the aging temperature is 20-40℃ and the time is 2-4h;

[0016] The drying temperature is 100-120℃, and the time is 2-4 hours;

[0017] The roasting temperature is 400-600℃ and the time is 4-6 hours.

[0018] Optionally, in the catalyst preparation method provided by the present invention, the reduction atmosphere is a mixture of H2 and Ar, the volume content of H2 in the mixture is 10%-20%, the reduction temperature is 300-450℃, and the time is 3-6h.

[0019] Optionally, in the catalyst preparation method provided by the present invention, the mesoporous molecules are screened from MCM-41; preferably, the specific surface area of ​​the MCM-41 is 650-750 m². 2 / g, pore volume 0.7-0.9cm³ 3 / g.

[0020] Optionally, in the preparation method of the catalyst provided by the present invention, the Pt salt is selected from at least one of chloroplatinic acid (H2PtC16·6H2O), tetraammineplatinum, and platinum nitrate;

[0021] The Sn salt is selected from at least one of stannous chloride, stannous nitrate, and stannous sulfate;

[0022] The Bi salt is selected from at least one of bismuth nitrate, bismuth sulfate, and bismuth chloride;

[0023] The Mn salt is selected from at least one of manganese nitrate, manganese sulfate, and manganese chloride.

[0024] Optionally, in the method for preparing the catalyst provided by the present invention, the impregnation solution containing Pt salt, Mn salt, Sn salt and Bi salt is prepared by the following method:

[0025] The platinum salt and Mn salt were completely dissolved in deionized water to obtain a mixed solution of platinum salt and Mn salt.

[0026] Sn salt and Bi salt are dissolved in deionized water to obtain a mixed solution of Sn salt and Bi salt;

[0027] The mixed solution of the platinum salt and Mn salt is mixed with the mixed solution of the Sn salt and Bi salt to obtain the impregnation solution containing Pt salt, Mn salt, Sn salt and Bi salt.

[0028] Optionally, the preparation method of MCM-41 recommended by this invention includes the following steps:

[0029] (1) Dissolve the template agent (such as hexadecyltrimethylammonium bromide (CTAB)) in deionized water to obtain a template agent solution; if necessary, heat and stir to completely dissolve the template agent in deionized water;

[0030] (2) While stirring, adjust the pH of the template agent solution to about 11 with ammonia water;

[0031] (3) The silicon source is slowly added dropwise to the solution in step (2) while the temperature is maintained at 10-50℃. After the addition is complete, the mixture is stirred at this temperature for 0.2-0.5h to form a latex solution. The solution is then transferred to a crystallization vessel and crystallized at 100-120℃ for 40-55h. The solid obtained after separation is washed with deionized water until pH≈7. The solid is then dried at 80-150℃ for 2-4h to obtain a white powder sample. The sample is then placed in a muffle furnace and calcined at 400-600℃ for 4-6h to obtain mesoporous molecular sieve MCM-41.

[0032] The silicon source is selected from at least one of tetraethyl orthosilicate (TEOS), silica sol, or fumed silica.

[0033] Compared with the prior art, the advantages of the present invention are as follows:

[0034] The method for preparing glycolic acid by oxidizing ethylene glycol provided by the present invention uses a specific ratio of Mn, Sn and Bi and active metal Pt supported on a support. By limiting the oxidation reaction pressure, temperature and the ratio of catalyst to ethylene glycol, ethylene glycol is oxidized to glycolic acid with high selectivity, producing glycolic acid with high yield. The reaction conditions are milder and free from alkali corrosion, while the reaction time is shortened.

[0035] Using Mn-modified mesoporous molecular sieve MCM-41, which has high specific surface area and high pore volume, as a support, Pt, Sn, and Bi are loaded onto the Mn-modified MCM-41 molecular sieve. Pt, Mn, Sn, and Bi metals can be uniformly distributed on the pore walls. Pt forms alloys with metals Mn, Sn, and Bi, which reduces the agglomeration of Pt on the MCM-41 molecular sieve and increases the metal dispersion of Pt. Pt at the active sites of the catalyst is hardly lost, which improves the stability of the catalyst. At the same time, the combination of Pt with Mn, Sn, and Bi elements promotes the improvement of ethylene glycol conversion and selectivity, increases the oxidation rate, and shortens the oxidation time. Detailed Implementation

[0036] The present invention will now be described in detail through embodiments. It should be noted that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0037] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0038] The conditions for high-performance liquid chromatography (HPLC) detection of ethylene glycol and glycolic acid are as follows:

[0039] The column brand is Rezex™ ROA-Organic AcidH + (8%), model number 00G-0138-E0; detector is RID-20A, mobile phase is 0.05mol / L sulfuric acid aqueous solution, flow rate is 0.17ml / min, time is 25min, temperature is 40℃.

[0040] Specific surface area of ​​a carrier tested using the BET method;

[0041] Pore ​​volume: The BJH method was used to test the pore volume of the carrier.

[0042] Metal content: Pt, Sn, Bi and Mn on the catalyst were determined by inductively coupled plasma atomic emission spectrometry (ICP).

[0043] Example 1

[0044] This embodiment provides a catalyst, and the method includes the following steps:

[0045] Carrier preparation:

[0046] Step (1): Dissolve 5.4g of cetyltrimethylammonium bromide (CTAB) in 250mL of deionized water, place it in a water bath, and heat it under magnetic stirring to completely dissolve the template agent CTAB, thus obtaining the template agent solution;

[0047] Step (2): Add ammonia water to the above template agent solution under magnetic stirring to make the solution pH around 11;

[0048] Step (3): Take 25.30 g of tetraethyl orthosilicate (TEOS) (calculated as SiO2, mass fraction of 28.4%) and slowly add it dropwise to the solution in step (2). Maintain the temperature at 30℃ and stir for 0.2 h. Transfer the resulting latex solution to a crystallization vessel and crystallize at 120℃ for 48 h. After crystallization is complete, filter the solid and wash it with deionized water until pH≈7. Dry it at 100℃ for 4 h. Place the resulting white powder sample in a muffle furnace and calcine at 500℃ for 5 h to obtain MCM-41 molecular sieve.

[0049] Catalyst preparation:

[0050] Step (a): Take 10.0 mL of a solution containing platinum nitrate and MnSO4 (Pt and Mn element concentrations are 0.02 g / mL and 0.037 g / mL, respectively), which is a mixed solution containing Pt and Mn;

[0051] Step (b): Take 5.0 ml of a solution containing SnSO4 and Bi2(SO4)3, where the Sn concentration is 0.04 g / ml and the Bi concentration is 0.02 g / ml, and mix it with a mixed solution containing Sn and Bi to form an impregnation solution;

[0052] Step (c): The impregnation solution is added dropwise to 20g of the above MCM-41 molecular sieve support and shaken continuously until complete impregnation is achieved to achieve equal volume impregnation. The paste-like solid obtained by complete impregnation is aged at 20°C for 4h, then dried at 100°C for 4h, crushed and placed in a muffle furnace and calcined at 500°C for 5h to obtain the catalyst precursor. The catalyst precursor is placed in a tube furnace in a mixed gas atmosphere of H2 and Ar (H2 volume content is 20%) and reduced at 400°C for 4h to obtain the Cat-A catalyst.

[0053] Example 2-3

[0054] The preparation methods of the catalysts provided in Examples 2-3 (i.e., Examples 2 and 3) are similar to those in Example 1, with the only difference being some parameters, as shown in the table below. The catalysts obtained in Examples 2 and 3 are Cat-B and Cat-C, respectively.

[0055] Table 1

[0056]

[0057]

[0058] The performance of the supports and the content of each metal in the catalysts prepared in the above embodiments are shown in Table 2.

[0059] Table 2

[0060]

[0061] Example 4

[0062] This embodiment provides a method for preparing glycolic acid by ethylene glycol oxidation, including the following steps:

[0063] A 0.4 mol / L ethylene glycol solution (water as solvent) was added to a 1000 mL micro high-pressure reactor (Beijing Century Senlang SLM1000). The ratio of catalyst Cat-A to ethylene glycol was 1 g:15 mol. The reaction pressure of the oxidant oxygen in the reactor was 1.5 MPa, the reaction temperature was 70 °C, the rotor speed was 200 r / min, and the reaction time was 10 h. After the reaction was completed and cooled, the reaction solution was analyzed by high-performance liquid chromatography. The specific results are shown in Table 3.

[0064] Example 5

[0065] This embodiment provides a method for preparing glycolic acid by ethylene glycol oxidation, including the following steps:

[0066] A 1000 mL micro high-pressure reactor (Beijing Century Senlang SLM1000) was used to add 600 mL of 0.2 mol / L ethylene glycol solution (water as solvent). The ratio of catalyst Cat-B to ethylene glycol was 1 g:10 mol. The reaction pressure of oxygen as the oxidant in the reactor was 1.0 MPa, the reaction temperature was 60 °C, the rotor speed was 500 r / min, and the reaction time was 10 h. After the reaction was completed and cooled, the reaction solution was analyzed by high-performance liquid chromatography. The specific results are shown in Table 3.

[0067] Example 6

[0068] This embodiment provides a method for preparing glycolic acid by ethylene glycol oxidation, including the following steps:

[0069] A 1000 mL micro high-pressure reactor (Beijing Century Senlang SLM1000) was used to add 700 mL of 0.6 mol / L ethylene glycol solution (water as solvent). The ratio of catalyst Cat-C to ethylene glycol was 1 g:10 mol. The reaction pressure of oxygen as oxidant in the reactor was 2.0 MPa, the reaction temperature was 80 °C, the rotor speed was 1000 r / min, and the reaction time was 10 h. After the reaction was completed and cooled, the reaction solution was analyzed by high-performance liquid chromatography. The specific results are shown in Table 3.

[0070] Example 7

[0071] This embodiment provides a method for preparing glycolic acid by ethylene glycol oxidation, including the following steps:

[0072] A 1000 mL micro high-pressure reactor (Beijing Century Senlang SLM1000) was used to add 600 mL of 0.6 mol / L ethylene glycol solution (water as solvent). The ratio of catalyst Cat-B to ethylene glycol was 1 g: 20 mol. The reaction pressure of oxygen as the oxidant in the reactor was 2.0 MPa, the reaction temperature was 80 °C, the rotor speed was 800 r / min, and the reaction time was 6 h. After the reaction was completed and cooled, the reaction solution was analyzed by high-performance liquid chromatography. The specific results are shown in Table 3.

[0073] Example 8

[0074] This embodiment provides a method for preparing glycolic acid by ethylene glycol oxidation, including the following steps:

[0075] 700 mL of 0.5 mol / L ethylene glycol solution (solvent: water) was added to a 1000 mL micro high-pressure reactor (Beijing Century Senlang SLM1000). The ratio of catalyst Cat-B to ethylene glycol was 1 g: 20 mol. The reaction pressure of the oxidant oxygen in the reactor was 1.5 MPa, the reaction temperature was 70 °C, the rotor speed was 300 r / min, and the reaction time was 8 h. After the reaction was completed and cooled, the reaction solution was analyzed by high performance liquid chromatography. The specific results are shown in Table 3.

[0076] Comparative Example 1

[0077] The method for preparing glycolic acid by ethylene glycol oxidation provided in this comparative example is similar to that in Example 6, except that the reaction pressure in this comparative example is 3.0 MPa and the reaction temperature is 100 °C. The specific results are shown in Table 3.

[0078] Comparative Example 2

[0079] The method for preparing glycolic acid by ethylene glycol oxidation provided in this comparative example is similar to that in Example 5, except that the reaction pressure in this comparative example is 3.0 MPa and the reaction temperature is 100 °C. The specific results are shown in Table 3.

[0080] Comparative Example 3

[0081] The method for preparing glycolic acid by ethylene glycol oxidation provided in this comparative example is similar to that in Example 6, except that the reaction pressure in this comparative example is 0.5 MPa and the reaction temperature is 50 °C. The specific results are shown in Table 3.

[0082] Comparative Example 4

[0083] The method for preparing glycolic acid by ethylene glycol oxidation provided in this comparative example is similar to that in Example 4, except that the concentration of the ethylene glycol solution in this comparative example is 0.1 mol / L, and the ratio of catalyst Cat-A to ethylene glycol is 1 g: 25 mol. The specific results are shown in Table 3.

[0084] Comparative Example 5

[0085] The method for preparing glycolic acid by ethylene glycol oxidation provided in this comparative example is similar to that in Example 6, except that the catalyst used is different. The preparation method of the catalyst used in this comparative example is similar to that in Example 1, except that in step (b) of catalyst preparation, 5.0 ml of deionized water is used instead of SnSO4 and Bi2(SO4)3 solution. The specific results are shown in Table 3.

[0086] Table 3 Results of oxidation reaction

[0087] Ethylene glycol conversion rate, % Glycolic acid selectivity, % Glycolic acid yield, % Example 4 75.45 83.27 62.79 Example 5 80.16 90.46 72.51 Example 6 80.94 86.35 69.89 Example 7 78.35 85.16 66.72 Example 8 74.24 86.78 64.43 Comparative Example 1 82.57 69.56 57.44 Comparative Example 2 85.28 64.84 55.30 Comparative Example 3 51.73 81.36 42.09 Comparative Example 4 74.52 66.23 50.02 Comparative Example 5 52.35 68.43 35.82

[0088] As shown in the table above, using MCM-41 molecular sieve as the support, Pt as the main active metal, and Mn, Sn and Bi as promoters, under low pressure (1.0-2.0 MPa) oxygen environment, without alkali, with a catalyst-to-ethylene glycol ratio of 1 g: 10-20 mol, and at 60-80℃, ethylene glycol can be converted to glycolic acid with high selectivity and high conversion rate, while reducing the overall oxidation reaction time.

[0089] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing glycolic acid by ethylene glycol oxidation, characterized in that, Includes the following steps: Ethylene glycol undergoes an oxidation reaction in the presence of a catalyst to yield glycolic acid; the oxidation reaction is carried out at a pressure of 1.0-2.0 MPa and a temperature of 60-80 °C, and the ratio of the catalyst to the ethylene glycol is 1 g:(10-20) mol. The catalyst support includes a mesoporous molecular sieve, the active component includes Pt, and the co-active components include Mn, Sn and Bi. Based on the mass of the catalyst, the Pt content is 0.8%-1.6%, and the total content of Sn, Bi and Mn is 1.0%-3.5%. The mass ratio of Mn, Sn, and Bi is (0.4-1.0):(0.1-0.7):(0.1-0.5); The preparation method of the catalyst includes the following steps: The catalyst is obtained by impregnating mesoporous molecular sieves with an equal volume of impregnation solution containing Pt salt, Mn salt, Sn salt and Bi salt, followed by aging, drying, calcination and reduction. The mesoporous molecules were screened from MCM-41.

2. The method for preparing glycolic acid by ethylene glycol oxidation as described in claim 1, characterized in that, The ethylene glycol is derived from an ethylene glycol solution with a concentration of 0.2-0.6 mol / L.

3. The method for preparing glycolic acid by ethylene glycol oxidation as described in claim 1, characterized in that, The aging temperature is 20-40℃, and the time is 2-4 hours; The roasting temperature is 400~600℃ and the time is 4-6 h.

4. The method for preparing glycolic acid by ethylene glycol oxidation as described in claim 1, characterized in that, The reduction atmosphere is a mixture of H2 and Ar, with the volume content of H2 in the mixture being 10%~20%, and the reduction temperature being 300~450℃ for 3-6 hours.

5. The method for preparing glycolic acid by ethylene glycol oxidation as described in claim 1, characterized in that, The specific surface area of ​​the MCM-41 is 650-750 m². 2 / g, pore volume 0.7-0.9cm³ 3 / g.

6. The method for preparing glycolic acid by ethylene glycol oxidation as described in claim 1, characterized in that, The Pt salt is selected from at least one of H2PtC16·6H2O, tetraammineplatinum and platinum nitrate; The Sn salt is selected from at least one of stannous chloride, stannous nitrate, and stannous sulfate; The Bi salt is selected from at least one of bismuth nitrate, bismuth sulfate, and bismuth chloride; The Mn salt is selected from at least one of manganese nitrate, manganese sulfate, and manganese chloride.

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