Preparation method and application of catalyst for preparing glycollic acid through ethylene glycol oxidation

Abstract

The invention provides a preparation method of a catalyst for preparing glycollic acid by oxidizing ethylene glycol, which comprises the following steps: impregnating a carrier in an impregnation liquid containing active metal salt, auxiliary metal salt and a polyhydroxy compound in equal volume, drying, roasting and reducing to obtain the catalyst for preparing glycollic acid by oxidizing ethylene glycol, wherein the active metal salt is selected from Pt salt and Pd salt, or Pt salt and Ru salt; the auxiliary metal salts are selected from any two of Sn, Ce, Ga, Bi, La, Mn and Rb salts; the carrier is a mixture of a mesoporous molecular sieve and an amorphous inorganic porous material. The catalyst prepared by the method can be used for preparing glycollic acid by high-activity and high-selectivity oxidation of ethylene glycol under mild, green and alkali-free conditions under the condition of low catalyst dosage.

Description

Technical Field

[0001] The invention relates to the technical field of ethylene glycol oxidation, and in particular to a preparation method and application of a catalyst for preparing glycolic acid through ethylene glycol oxidation. Background Art

[0002] Glycolic acid is an important fine chemical raw material, which is widely used in organic synthesis, medicine, food industry and cosmetics, but there is no enterprise that can produce glycolic acid monomer on a large scale. The main methods for synthesizing glycolic acid include formaldehyde carbonylation, hydrolysis of chloroacetic acid or ethanedinitrile and electrolytic reduction of oxalic acid, but they all have disadvantages such as harsh production conditions, high catalyst cost and large amount of by-products. Therefore, it is necessary to develop a new route for synthesizing glycolic acid with mild reaction conditions, green reaction process and feasibility of application.

[0003] With the breakthrough of key catalysts for the hydrogenation of dimethyl oxalate (DMO) in China, the production process of coal-to-ethylene glycol has become increasingly mature. A large amount of ethylene glycol production capacity has not been effectively released. Directly oxidizing the excess cheap ethylene glycol at low temperature to produce high-value-added glycolic acid provides a green and efficient production process for glycolic acid.

[0004] The reaction of ethylene glycol oxidation to glycolic acid is carried out in a series coupling form on the catalyst surface. The process involves the activation of OH bonds, CH bonds, C=O bonds and CC bonds. Ethylene glycol is a symmetrical molecule with two identical primary hydroxyl groups. During the oxidation process, the activation of the OH bonds and CH bonds on a single primary hydroxyl group and the oxidation of the aldehyde group (-CHO) first occur. After further CH bond activation, glycolic acid molecules are obtained. During the reaction, the catalyst easily causes the deep oxidation of another primary hydroxyl group in the glycolic acid product (generating oxalic acid) and the breakage of the CC bond (generating formic acid and CO 2 ) and other side reactions. Therefore, the core of the reaction of ethylene glycol oxidation to glycolic acid is to prepare a catalyst to solve the selectivity problem of glycolic acid. At present, studies have shown that under alkaline conditions, noble metal catalysts, transition metal catalysts, etc. have good catalytic performance. However, the introduction of alkali will destroy the stability of the catalyst, resulting in low catalyst utilization efficiency, easy deactivation, high cost, and easy to cause environmental pollution, increased separation costs and other problems, which limits its further industrialization process.

[0005] For example, Chinese patent document CN114534723A discloses a catalyst for selective oxidation of ethylene glycol to prepare glycolic acid and a preparation method thereof, wherein the catalyst uses activated carbon as a carrier, metal palladium as a main catalytic component, bismuth and cerium dioxide as co-catalysts, the content of metal palladium is 0.1% to 1.5% of the weight of the carrier, the content of cerium dioxide is calculated as cerium content, and the total content of metal bismuth and cerium dioxide is 0.25% to 1.5% of the weight of the carrier. The Pd-Bi-CeO 2The / C catalyst, under the bimetallic catalytic action of bismuth and cerium dioxide, achieves the purpose of efficiently and selectively catalyzing the reaction of ethylene glycol to glycolic acid at a low metal Pd loading. However, the catalyst needs to be catalytically reacted under alkaline conditions, and the introduction of alkali will destroy the stability of the catalyst.

[0006] Chinese patent document CN112961046B discloses a method for synthesizing glycolic acid without alkali using waste biomass, comprising the following steps: 1) hydrolyzing and hydrogenating the waste biomass to obtain polyols; 2) adding a metal catalyst to the extracted polyols and mixing them evenly, wherein the molar ratio of the metal catalyst to the polyols is 1:50-200; 3) pouring the polyols added with the metal catalyst into a high-pressure reactor, and filling it with oxygen at a pressure of 0.5-8MPa, reacting at a temperature of 20-180°C for 1-50h to obtain glycolic acid, but the amount of catalyst used in the oxidation process is relatively large, the molar ratio of the catalyst to the polyols is 1:50-200, and the utilization efficiency of the catalyst is not high. Summary of the invention

[0007] In view of this, the present invention provides a method for preparing a catalyst for preparing glycolic acid by oxidation of ethylene glycol. The catalyst prepared by the method can achieve high-activity and high-selectivity oxidation of ethylene glycol to prepare glycolic acid under mild and green alkali-free conditions with low catalyst dosage.

[0008] To achieve the above object, the present invention provides a method for preparing a catalyst for preparing glycolic acid by oxidation of ethylene glycol, comprising the following steps:

[0009] After the carrier is impregnated with equal volumes of an impregnation solution containing active metal salt, auxiliary metal salt and polyhydroxy compound, the catalyst for preparing glycolic acid by oxidation of ethylene glycol is obtained through drying, roasting and reduction.

[0010] Wherein, the active metal salt is selected from Pt salt and Pd salt, or Pt salt and Ru salt; the auxiliary metal salt is selected from any two of Sn, Ce, Ga, Bi, La, Mn and Rb salts;

[0011] The carrier is a mixture of a mesoporous molecular sieve and an amorphous inorganic porous material.

[0012] Optionally, in the method for preparing a catalyst for preparing glycolic acid by oxidation of ethylene glycol provided by the present invention, the molar ratio of the sum of the active metal salt and the auxiliary metal salt to the polyhydroxy compound is 1:0.3-3, calculated as metal elements.

[0013] Optionally, in the method for preparing a catalyst for preparing glycolic acid by oxidation of ethylene glycol provided by the present invention, the polyhydroxy compound is selected from one or more of ethylene glycol, citric acid, ethylenediaminetetraacetic acid, cyclohexanediaminetetraacetic acid, and triethylene glycol.

[0014] Optionally, in the method for preparing a catalyst for preparing glycolic acid by oxidation of ethylene glycol provided by the present invention, the molar ratio of the active metal salt to the auxiliary metal salt is 1:0.3-2, calculated on the basis of metal elements.

[0015] Optionally, in the method for preparing a catalyst for preparing glycolic acid by oxidation of ethylene glycol provided by the present invention, the active metal salt is selected from Pt salt and Pd salt;

[0016] Calculated in terms of metal elements, the molar ratio of the Pt salt to the Pd salt is 1:(0.2-5).

[0017] Optionally, in the method for preparing a catalyst for preparing glycolic acid by oxidation of ethylene glycol provided by the present invention, the mesoporous molecular sieve is selected from one or more of MCM-41, SBA-15, and Al-MCM-41; the specific surface area of ​​the mesoporous molecular sieve is 500-800m 2 / g, pore volume is 0.5-0.9ml / g; MCM-41 is preferred. The metal loading has no obvious effect on the pore size distribution, pore volume and specific surface area of ​​the mesoporous molecular sieve, and will not block its pores. Moreover, the good porous structure in the mesoporous molecular sieve can eliminate mass transfer limitations and provide uniform active centers for the oxidation reaction of ethylene glycol.

[0018] The amorphous inorganic porous material is selected from one or more of titanium dioxide, aluminum oxide-silicon dioxide, zirconium oxide-silicon dioxide, titanium oxide-silicon dioxide, aluminum oxide-zirconia, zirconium oxide-titania, and aluminum oxide-titania.

[0019] Optionally, in the method for preparing a catalyst for preparing glycolic acid by oxidation of ethylene glycol provided by the present invention, the immersion temperature is 20-30° C. and the time is 1-3 h;

[0020] The drying temperature is 80-150° C. and the time is 2-6 hours. The calcination temperature is 400-500° C. and the time is 4-8 hours.

[0021] Optionally, in the method for preparing a catalyst for preparing glycolic acid by oxidation of ethylene glycol provided by the present invention, the reducing atmosphere is H 2 The reduction temperature is 300-500°C and the time is 3-8h.

[0022] Optionally, the metal salt in the method for preparing the catalyst for preparing glycolic acid by oxidation of ethylene glycol provided by the present invention is selected from soluble metal salts, such as the Pt salt selected from H 2 PtC1 6 6H 2 O, tetraamine platinum and platinum nitrate, etc.; the Pd salt can be selected from PdCl 2 , the Ru salt is selected from RuCl 3, Sn, Ce, Ga, Bi, La and Rb salts are respectively selected from nitrates and the like.

[0023] Optionally, in the method for preparing a catalyst for preparing glycolic acid by oxidation of ethylene glycol provided by the present invention, based on the mass of the catalyst for preparing glycolic acid by oxidation of ethylene glycol as 100%, the content of the active metal element is 0.2% to 2.5%, the content of the co-metal element is 0.3%-2%, the content of the mesoporous molecular sieve is 40%-70%, and the remainder is amorphous inorganic porous material.

[0024] The present invention also provides a method for preparing glycolic acid by oxidation of ethylene glycol, comprising the following steps: in an alkali-free condition and in an oxygen-containing atmosphere, ethylene glycol is subjected to an oxidation reaction under the action of a catalyst to obtain glycolic acid; preferably, the oxidation reaction is carried out at a pressure of 1-2 MPa, a temperature of 60-100° C., and a time of 6-10 h;

[0025] Wherein, the catalyst is selected from the catalyst prepared by the above-mentioned method for preparing the catalyst for preparing glycolic acid by oxidation of ethylene glycol; the ratio of the mass of the catalyst to the molar amount of the ethylene glycol is 1g:(200-350)mol.

[0026] Compared with the prior art, the effects of the present invention are as follows:

[0027] The invention provides a method for preparing a catalyst for preparing glycolic acid by oxidizing ethylene glycol. By adding a polyhydroxy compound to an impregnation solution containing an active metal salt, agglomeration of the active metal during carrier impregnation (affecting the stability and activity of the catalyst) can be effectively prevented. By further adding an auxiliary metal to the impregnation solution, the auxiliary metal and the active metal can form small-sized nano alloy particles, further inhibiting the agglomeration of the active metal, and finally obtaining a supported catalyst with high dispersion and high activity (small amount of catalyst). In addition, under alkali-free conditions, when the catalyst catalyzes the oxidation of ethylene glycol to prepare glycolic acid, the glycolic acid has high selectivity, mild process conditions, a green reaction process, and is environmentally friendly and pollution-free. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 TEM (transmission electron microscope) image of the catalyst obtained in Example 5 of the present invention;

[0029] Figure 2 This is a TEM (transmission electron microscope) image of the catalyst prepared in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0030] The present invention is described in detail below by way of examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art in this field can make some non-essential improvements and adjustments to the present invention based on the above content of the present invention.

[0031] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0032] MCM-41, SBA-15 and Al-MCM-41 were purchased from Beijing Sanju Environmental Protection New Materials Co., Ltd.

[0033] Among them, the specific surface area of ​​MCM-41 is 731.5m 2 / g, and the pore volume is 0.82ml / g.

[0034] The specific surface area of ​​SBA-15 is 562.3m 2 / g, and the pore volume is 0.54ml / g.

[0035] The specific surface area of ​​Al-MCM-41 is 680.4m 2 / g, and the pore volume is 0.62ml / g.

[0036] Example 1

[0037] This embodiment provides a method for preparing a catalyst for preparing glycolic acid by oxidation of ethylene glycol, comprising the following steps:

[0038] Vector preparation:

[0039] Take 40 g of MCM-41 molecular sieve and 59.4 g of alumina-silica, mix them evenly to obtain a carrier;

[0040] Catalyst preparation:

[0041] Step 1: Measure 35 ml of H 2 PtCl 6 and PdCl 2 A mixed aqueous solution, wherein the molar ratio of Pt to Pd is 5:1, and the mixed concentration (H 2 PtCl 6 and PdCl 2 The total concentration of) is 0.079mol / L;

[0042] Step 2: Add 15 mL of 0.184 mol / L EDTA solution to the solution in step 1 and stir evenly;

[0043] Step 3: Take 50 ml of an aqueous solution containing tin nitrate and cerium nitrate, add it to the solution obtained in step 2, stir evenly, and obtain an impregnation solution; wherein the total concentration of tin nitrate and cerium nitrate in the aqueous solution containing tin nitrate and cerium nitrate is 0.056 mol / L, and the molar ratio of tin nitrate to cerium nitrate is 2:1.

[0044] Step 4: uniformly drip the impregnation solution obtained in step 3 onto the above-mentioned carrier. After dripping, soak at 30° C. for 2 h, dry at 120° C. for 4 h, and calcine at 400° C. for 7 h to obtain a catalyst precursor.

[0045] Step 5: The catalyst precursor was reduced at 500° C. for 4 h in a tubular furnace under a hydrogen atmosphere to obtain a catalyst. The catalyst was tested by inductively coupled plasma emission spectroscopy (ICP). Based on the mass of the catalyst as 100%, the total loading of Pt and Pd in ​​the catalyst was 0.509%, and the total loading of tin and cerium was 0.352%.

[0046] Example 2

[0047] The preparation method of the catalyst for preparing glycolic acid by oxidation of ethylene glycol provided in this embodiment is similar to that in Example 1, except that in step 1 of this embodiment, the molar ratio of Pt to Pd is 1:5, and the mixed concentration is 0.059 mol / L.

[0048] According to an inductively coupled plasma emission spectroscopy (ICP) test, based on the mass of the catalyst being 100%, the total loading of Pt and Pd in ​​the catalyst is 0.248%, and the total loading of tin and cerium is 0.369%.

[0049] Example 3

[0050] This embodiment provides a method for preparing a catalyst for preparing glycolic acid by oxidation of ethylene glycol, comprising the following steps:

[0051] Vector preparation:

[0052] Take 20 g of SBA-15 molecular sieve, 20 g of Al-MCM-41 molecular sieve and 59.4 g of alumina-silica, mix them evenly to obtain a carrier;

[0053] Catalyst preparation:

[0054] Step 1: Measure 35 ml of H 2 PtCl 6 6H 2 O and RuCl 3 Mixed aqueous solution, wherein the molar ratio of Pt to Ru is 5:1, and the mixed concentration (H 2 PtCl 6 and RuCl 3 The total concentration of) is 0.12mol / L;

[0055] Step 2: Add 15 mL of 0.84 mol / L cyclohexaneethylenediaminetetraacetic acid solution to the solution in step 1 and stir evenly;

[0056] Step 3: Take 50 ml of an aqueous solution containing manganese nitrate and cerium nitrate, add it to the solution obtained in step 2, stir evenly, and obtain an impregnation solution; wherein the total concentration of manganese nitrate and cerium nitrate in the aqueous solution containing manganese nitrate and cerium nitrate is 0.084 mol / L, and the molar ratio of manganese nitrate to cerium nitrate is 2:1.

[0057] Step 4: uniformly drip the impregnation solution obtained in step 3 onto the above-mentioned carrier. After dripping, soak at 30° C. for 2 h, dry at 90° C. for 5 h, and calcine at 600° C. for 4 h to obtain a catalyst precursor.

[0058] Step 5: The catalyst precursor was reduced at 300° C. for 8 h in a tubular furnace under a hydrogen atmosphere to obtain a catalyst.

[0059] According to an inductively coupled plasma emission spectroscopy (ICP) test, based on the mass of the catalyst being 100%, the total loading of Pt and Ru in the catalyst is 0.753%, and the total loading of tin and cerium is 0.348%.

[0060] Example 4

[0061] This embodiment provides a method for preparing a catalyst for preparing glycolic acid by oxidation of ethylene glycol, comprising the following steps:

[0062] Vector preparation:

[0063] Take 70 g of MCM-41 molecular sieve and 28.6 g of alumina-titania, mix them evenly to obtain a carrier;

[0064] Catalyst preparation:

[0065] Step 1: Measure 40 ml of H 2 PtCl 6 6H 2 O and PdCl 2 A mixed aqueous solution, wherein the molar ratio of Pt to Pd is 2:1, and the mixed concentration (H 2 PtCl 6 and PdCl 2 The total concentration of) is 0.306mol / L;

[0066] Step 2: Add 17 mL of 0.72 mol / L ethylene glycol solution to the solution in step 1 and stir evenly;

[0067] Step 3: Take 46 ml of an aqueous solution containing bismuth nitrate and gallium nitrate, add it to the solution obtained in step 2, and stir evenly to obtain an impregnation solution; wherein the total concentration of bismuth nitrate and gallium nitrate in the aqueous solution containing bismuth nitrate and gallium nitrate is 0.266 mol / L, and the molar ratio of bismuth nitrate to gallium nitrate is 1:1.

[0068] Step 4: uniformly drip the impregnation solution obtained in step 3 onto the above-mentioned carrier. After the dripping is completed, soak at 20° C. for 3 h, dry at 140° C. for 2 h, and calcine at 450° C. for 4 h to obtain a catalyst precursor;

[0069] Step 5: The catalyst precursor was reduced at 400° C. for 6 h in a tubular furnace under a hydrogen atmosphere to obtain a catalyst.

[0070] According to an inductively coupled plasma emission spectroscopy (ICP) test, based on the mass of the catalyst being 100%, the total loading amount of Pt and Pd in ​​the catalyst is 2.029%, and the total loading amount of bismuth and gallium is 1.713%.

[0071] Example 5

[0072] This embodiment provides a method for preparing a catalyst for preparing glycolic acid by oxidation of ethylene glycol, comprising the following steps:

[0073] Vector preparation:

[0074] Take 50 g of MCM-41 molecular sieve and 48.2 g of alumina, mix them evenly to obtain a carrier;

[0075] Catalyst preparation:

[0076] Step 1: Measure 40 ml of H 2 PtCl 6 6H 2 O and PdCl 2 A mixed aqueous solution, wherein the molar ratio of Pt to Pd is 1:1, and the mixed concentration (H 2 PtCl 6 and PdCl 2 The total concentration of) is 0.166mol / L;

[0077] Step 2: Add 17 mL of 0.293 mol / L triethylene glycol solution to the solution in step 1 and stir evenly;

[0078] Step 3: Take 46 ml of an aqueous solution containing bismuth nitrate and lanthanum nitrate, add it to the solution obtained in step 2, stir evenly, and obtain an impregnation solution; wherein the total concentration of bismuth nitrate and lanthanum nitrate in the aqueous solution containing bismuth nitrate and lanthanum nitrate is 0.109 mol / L, and the molar ratio of bismuth nitrate to lanthanum nitrate is 1:2.

[0079] Step 4: uniformly drip the impregnation solution obtained in step 3 onto the above-mentioned carrier. After dripping, soak at 30° C. for 1 hour, dry at 120° C. for 3 hours, and calcine at 400° C. for 6 hours to obtain a catalyst precursor.

[0080] Step 5: The catalyst precursor was reduced at 350° C. for 8 h in a tubular furnace under a hydrogen atmosphere to obtain a catalyst.

[0081] According to an inductively coupled plasma emission spectroscopy (ICP) test, based on the mass of the catalyst being 100%, the total loading amount of Pt and Pd in ​​the catalyst is 1.082%, and the total loading amount of bismuth and lanthanum is 0.813%.

[0082] Example 6

[0083] This embodiment provides a method for preparing a catalyst for preparing glycolic acid by oxidation of ethylene glycol, comprising the following steps:

[0084] Vector preparation:

[0085] Take 50 g of MCM-41 molecular sieve and 47.6 g of zirconium oxide-silicon dioxide, mix them evenly to obtain a carrier;

[0086] Catalyst preparation:

[0087] Step 1: Measure 40 ml of H 2 PtCl 6 6H 2 O and PdCl 2 A mixed aqueous solution, wherein the molar ratio of Pt to Pd is 1:2, and the mixed concentration (H 2 PtCl 6 and PdCl 2 The total concentration of) is 0.244mol / L;

[0088] Step 2: Add 20 mL of 0.489 mol / L citric acid solution to the solution in step 1 and stir evenly;

[0089] Step 3: adding 40 ml of an aqueous solution containing cerium nitrate and rubidium nitrate to the solution obtained in step 2, stirring evenly, to obtain an impregnation solution; wherein the total concentration of cerium nitrate and rubidium nitrate in the aqueous solution containing cerium nitrate and rubidium nitrate is 0.427 mol / L, and the molar ratio of cerium nitrate to rubidium nitrate is 1:1.

[0090] Step 4: uniformly drip the impregnation solution obtained in step 3 onto the above-mentioned carrier. After dripping, soak at 25°C for 2h, dry at 100°C for 4h, and calcine at 500°C for 3h to obtain a catalyst precursor.

[0091] Step 5: The catalyst precursor was reduced at 450° C. for 6 h in a tubular furnace under a hydrogen atmosphere to obtain a catalyst.

[0092] According to an inductively coupled plasma emission spectroscopy (ICP) test, based on the mass of the catalyst being 100%, the total loading amount of Pt and Pd in ​​the catalyst is 1.331%, and the total loading amount of cerium and rubidium is 1.937%.

[0093] Comparative Example 1

[0094] The preparation method of the catalyst for preparing glycolic acid by oxidation of ethylene glycol provided in this comparative example is similar to that in Example 5, except that: PdCl is omitted in step 1 of the catalyst preparation of this comparative example. 2 In step 1, 40 ml of H 2 PtCl 6 An aqueous solution of H 2 PtCl 6 The concentration is 0.125mol / L.

[0095] According to an inductively coupled plasma emission spectroscopy (ICP) test, based on the mass of the catalyst being 100%, the loading amount of Pt in the catalyst is 1.057%, and the total loading amount of bismuth and lanthanum is 0.813%.

[0096] Comparative Example 2

[0097] The preparation method of the catalyst for preparing glycolic acid by oxidation of ethylene glycol provided in this comparative example is similar to that in Example 5, the only difference is that in step 2 of the catalyst preparation in this comparative example, 17 mL of deionized water is used instead of triethylene glycol solution.

[0098] According to an inductively coupled plasma emission spectroscopy (ICP) test, based on the mass of the catalyst being 100%, the total loading of Pt and Pd in ​​the catalyst is 1.035%, and the total loading of bismuth and lanthanum is 0.819%.

[0099] Comparative Example 3

[0100] The preparation method of the catalyst for preparing glycolic acid by oxidation of ethylene glycol provided in this comparative example is similar to that in Example 5, the only difference is that step 3 of the catalyst preparation in this comparative example contains only bismuth nitrate but no lanthanum nitrate, and the concentration of bismuth nitrate in 46 ml of the aqueous solution containing bismuth nitrate is 0.109 mol / L.

[0101] According to an inductively coupled plasma emission spectroscopy (ICP) test, based on the mass of the catalyst being 100%, the total loading amount of Pt and Pd in ​​the catalyst is 1.072%, and the loading amount of bismuth is 1.058%.

[0102] Experimental Example 1

[0103] The catalysts prepared in Example 5 and Comparative Example 2 were characterized by transmission electron microscopy (TEM). Figure 1It can be seen that the active metals in the catalyst prepared in Example 5 are evenly dispersed without clustering, and the size of the formed alloy metal particles is less than 1 nm. Figure 2 It can be seen that in the catalyst prepared in Comparative Example 2, the active metals are dispersed on the catalyst surface in the form of clusters.

[0104] Experimental Example 2

[0105] The catalysts prepared in the examples and comparative examples were used to verify the effect of ethylene glycol oxidation to prepare glycolic acid according to the following method. The specific test method is as follows:

[0106] In a micro batch reactor with a stirring function (Beijing Century Senlang Experimental Instrument Co., Ltd., model SLM1000), 600 mL of ethylene glycol solution (solvent is water) and a catalyst were added, oxygen was introduced to the reaction pressure, and the reaction was carried out according to the set reaction conditions. The specific reaction conditions are shown in Table 1. After the reaction was completed and cooled, the reaction solution was subjected to high performance liquid chromatography (detector RID-20A, mobile phase 0.05 mol / L sulfuric acid aqueous solution, flow rate 0.17 ml / min, time 25 min, temperature 40°C, and the chromatographic column used was RezexTM ROA-Organic Acid H + (8%), model 00G-0138-E0) was analyzed, and the specific analysis results are shown in Table 2 below.

[0107] Table 1 Reaction conditions

[0108]

[0109] Table 2 Oxidation reaction results

[0110]

[0111]

[0112] From the data in the above table, it can be seen that when a single active metal is used or polyhydroxy compounds are not added during the preparation process, the final catalyst has a significantly lower yield of glycolic acid under the same reaction conditions. This shows that the preparation method of the catalyst provided by the present invention can significantly improve the yield of ethylene glycol converted to glycolic acid under the condition of reducing the amount of catalyst used, by using two active metals and introducing polyhydroxy organic matter and co-metal during the preparation process, compared with the prior art.

[0113] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations based on the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a catalyst for preparing glycolic acid by oxidation of ethylene glycol, It is characterized in that The steps include: After the carrier is impregnated with equal volumes of an impregnation solution containing active metal salt, auxiliary metal salt and polyhydroxy compound, the catalyst for preparing glycolic acid by oxidation of ethylene glycol is obtained through drying, roasting and reduction. Wherein, the active metal salt is selected from Pt salt and Pd salt, or Pt salt and Ru salt; the auxiliary metal salt is selected from any two of Sn, Ce, Ga, Bi, La, Mn and Rb salts; The carrier is a mixture of a mesoporous molecular sieve and an amorphous inorganic porous material.

2. The preparation method according to claim 1, It is characterized in that The molar ratio of the active metal salt to the polyhydroxy compound is 1:0.3-3.

3. The preparation method according to claim 1, It is characterized in that The polyhydroxy compound is selected from one or more of ethylene glycol, citric acid, ethylenediaminetetraacetic acid, cyclohexanediaminetetraacetic acid, and triethylene glycol.

4. The preparation method according to claim 1, It is characterized in that The molar ratio of the active metal salt to the auxiliary metal salt is 1:0.3-2.

5. The preparation method according to claim 1, It is characterized in that The active metal salt is selected from Pt salt and Pd salt; Calculated in terms of metal elements, the molar ratio of the Pt salt to the Pd salt is 1:0.2-5.

6. The preparation method according to claim 1, It is characterized in that The mesoporous molecules are selected from one or more of MCM-41, SBA-15, and Al-MCM-41; The amorphous inorganic porous material is selected from one or more of titanium dioxide, aluminum oxide-silicon dioxide, zirconium oxide-silicon dioxide, titanium oxide-silicon dioxide, aluminum oxide-zirconia, zirconium oxide-titania, and aluminum oxide-titania.

7. The preparation method according to claim 1, It is characterized in that The immersion temperature is 20-30°C and the time is 1-3h; The drying temperature is 80-150° C. and the time is 2-6 hours. The calcination temperature is 400-600° C. and the time is 3-8 hours.

8. The preparation method according to claim 1, It is characterized in that The reducing atmosphere is H 2 The reduction temperature is 300-500°C and the time is 3-8h.

9. The preparation method according to claim 1, It is characterized in that Taking the mass of the catalyst for preparing glycolic acid by oxidation of ethylene glycol as 100%, the content of the active metal element is 0.2%-2.5%, the content of the auxiliary metal element is 0.3%-2%, the content of the mesoporous molecular sieve is 40%-70%, and the remainder is amorphous inorganic porous material.

10. A method for preparing glycolic acid by oxidation of ethylene glycol, It is characterized in that The steps include: Under alkali-free conditions and in an oxygen-containing atmosphere, ethylene glycol undergoes oxidation reaction under the action of a catalyst to obtain glycolic acid; Wherein, the catalyst is selected from the catalyst prepared by the method for preparing the catalyst for preparing glycolic acid by oxidation of ethylene glycol as described in any one of claims 1-9; the ratio of the mass of the catalyst to the molar amount of the ethylene glycol is 1g:(200-350)mol.

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