Method for preparing glycollic acid through ethylene glycol oxidation

Abstract

The invention provides a method for preparing glycollic acid through ethylene glycol oxidation, which comprises the following steps: carrying out oxidation reaction on ethylene glycol under the action of a catalyst to obtain glycollic acid, the pressure of the oxidation reaction is 1.0-2.0 MPa, the temperature is 60-80 DEG C, and the dosage ratio of the catalyst to the ethylene glycol is 1g: (10-20) mol; a carrier of the catalyst comprises a mesoporous molecular sieve, an active component of the catalyst comprises Pt, and auxiliary active components of the catalyst comprise Mn, Sn and Bi; based on 100% of the mass of the catalyst, the content of Pt is 0.8%-1.6%, and the total content of Sn, Bi and Mn is 1.0%-3.5%. According to the method, the selectivity of glycollic acid and the yield of ethylene glycol are remarkably improved by adopting the catalyst which takes Pt as an active component and Mn, Sn and Bi as auxiliary active components and combining parameters such as limited catalyst dosage, reaction pressure and temperature.

Description

Technical Field

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

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

[0003] In 1940, DuPont successfully produced glycolic acid by 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 at home and abroad. There are roughly 6 existing glycolic acid preparation processes: (1) a method of reacting carbon monoxide, formaldehyde and water under high temperature and high pressure in the presence of a strong acid catalyst; (2) a method of reacting with chloroacetic acid and sodium hydroxide; (3) a method of reacting glyoxal obtained by oxidation of ethylene glycol with a strong base to form glycolate by Cannizzaro reaction, and then adding acid to separate glycolic acid; (4) a method of reacting glyoxal obtained by oxidation of ethylene glycol with water in the presence of an inorganic catalyst in a liquid phase; (5) a method of contact oxidation of ethylene glycol in the presence of a noble metal catalyst and oxygen; (6) a method of oxidative esterification of ethylene glycol with methanol and oxygen to form methyl glycolate and then hydrolyzing it to produce glycolic acid. Among them, the method of preparing glycolic acid by selective oxidation of ethylene glycol has attracted widespread attention from all parties because of its single and readily available raw materials and simple process.

[0004] However, most of the existing methods for selective oxidation of ethylene glycol to prepare glycolic acid have a need to improve their selectivity or conversion rate. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing glycolic acid by oxidizing ethylene glycol. The method adopts a catalyst with Pt as an active component and Mn, Sn and Bi as co-active components, combined with limited parameters such as catalyst dosage, reaction pressure and temperature, to significantly improve the selectivity of glycolic acid and the yield of ethylene glycol.

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

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

[0008] Ethylene glycol undergoes oxidation reaction under the action of a catalyst to obtain glycolic acid; the pressure of the oxidation reaction is 1.0-2.0 MPa, the temperature is 50-80° C., and the amount ratio of the catalyst to the ethylene glycol is 1 g: (10-20) mol;

[0009] The catalyst carrier comprises a mesoporous molecular sieve, the active component comprises Pt, and the auxiliary active components comprise Mn, Sn and Bi;

[0010] Based on 100% of the mass of the catalyst, the content of Pt 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 oxidizing ethylene glycol provided by the present invention, the ethylene glycol comes 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 oxidation of ethylene glycol 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 oxidation of ethylene glycol provided by the present invention, the method for preparing the catalyst comprises the following steps:

[0014] The impregnation solution containing Pt salt, Mn salt, Sn salt and Bi salt is impregnated into the mesoporous molecular sieve in equal volumes, and the catalyst is obtained through aging, drying, calcining and reduction.

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

[0016] The drying temperature is 100-120°C and the drying time is 2-4h;

[0017] The calcination temperature is 400-600° C. and the calcination time is 4-6 hours.

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

[0019] Optionally, in the method for preparing the catalyst provided by the present invention, the mesoporous molecule is selected from MCM-41; preferably, the specific surface area of ​​the MCM-41 is 650-750m 2 / g, pore volume is 0.7-0.9cm 3 / g.

[0020] Optionally, in the method for preparing the catalyst provided by the present invention, the Pt salt is selected from at least one of chloroplatinic acid (H2PtC16·6H2O), tetraamineplatinum 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] Completely dissolving the platinum salt and the Mn salt in deionized water to obtain a mixed solution of the platinum salt and the Mn salt;

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

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

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

[0029] (1) dissolving a template agent (such as hexadecyltrimethylammonium bromide (CTAB)) in deionized water to obtain a template agent solution; if necessary, heating and stirring may be performed to completely dissolve the template agent in the deionized water;

[0030] (2) Under stirring, adjusting the pH of the template solution to about 11 with aqueous ammonia;

[0031] (3) Slowly adding the silicon source to the solution of step (2) at a temperature of 10-50°C. After the addition is completed, stirring is continued at the temperature for 0.2-0.5h to form a latex solution, and the solution is transferred to a crystallization kettle and crystallized at 100-120°C for 40-55h. The separated solid is washed with deionized water to a pH value of 7, and then dried at 80-150°C for 2-4h to obtain a white powder sample, which is placed in a muffle furnace and calcined at 400-600°C for 4-6h to obtain a 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 effects of the present invention are as follows:

[0034] The method for preparing glycolic acid by oxidizing ethylene glycol provided by the present invention adopts a specific ratio of Mn, Sn and Bi and an active metal Pt to be loaded on a carrier, and by limiting the oxidation reaction pressure, temperature, and the dosage ratio of the catalyst to ethylene glycol, ethylene glycol is highly selectively oxidized to glycolic acid, and a high yield of glycolic acid is produced. The reaction conditions are milder and alkali-corrosion-free, and the reaction time is shortened.

[0035] Mn-modified mesoporous molecular sieve MCM-41 with high specific surface area and high pore volume is used as a carrier, and Pt, Sn and Bi are loaded on the Mn-modified MCM-41 molecular sieve. Pt, Mn, Sn and Bi metals can be evenly distributed on the pore wall, and Pt forms alloys with metal Mn, Sn and Bi, which reduces the agglomeration of Pt on the MCM-41 molecular sieve and increases the metal dispersion of Pt. The active site of the catalyst is almost not 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 rate and selectivity, increases the oxidation rate, and shortens the oxidation time. DETAILED DESCRIPTION

[0036] 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.

[0037] 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.

[0038] The conditions for HPLC detection of ethylene glycol and glycolic acid are as follows:

[0039] The brand of the chromatographic column is RezexTMROA-OrganicAcidH + (8%), model 00G-0138-E0; 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.

[0040] Specific surface area: BET method tests the specific surface area of ​​the carrier;

[0041] Pore ​​volume: BJH method is used to test the pore volume of the carrier;

[0042] Metal content: Inductively coupled plasma emission spectroscopy (ICP) was used to test the Pt, Sn, Bi and Mn on the catalyst.

[0043] Example 1

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

[0045] Vector preparation:

[0046] Step (1): dissolving 5.4 g of hexadecyltrimethylammonium bromide (CTAB) in 250 mL of deionized water, placing the mixture in a water bath, and heating the mixture under magnetic stirring to completely dissolve the template CTAB to obtain a template solution;

[0047] Step (2): adding ammonia water to the template solution under magnetic stirring to adjust the pH of the solution to about 11;

[0048] Step (3): Take 25.30g of tetraethyl orthosilicate (TEOS) (28.4% by mass in terms of SiO2) and slowly add it dropwise to the solution of step (2), keep the temperature at 30°C and stir for 0.2h, transfer the formed latex solution to a crystallization kettle, crystallize at 120°C for 48h, filter after crystallization is completed, wash the obtained solid with deionized water to pH≈7, and dry at 100°C for 4h. The obtained white powder sample is placed in a muffle furnace and calcined at 500°C for 5h to obtain MCM-41 molecular sieve.

[0049] Catalyst preparation:

[0050] Step (a): taking 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) to obtain a mixed solution containing Pt and Mn;

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

[0052] Step (c): add the impregnation liquid dropwise to 20g of the above-mentioned MCM-41 molecular sieve carrier, and shake continuously until it is completely impregnated to achieve equal volume impregnation; age the completely impregnated paste solid at 20°C for 4h, then dry it at 100°C for 4h, crush it and place it in a muffle furnace to roast it at 500°C for 5h to obtain a catalyst precursor; place the catalyst precursor in a tubular furnace in a mixed gas atmosphere of H2 and Ar (the volume content of H2 is 20%) and reduce it at 400°C for 4h to obtain a Cat-A catalyst.

[0053] Example 2-3

[0054] The preparation method of the catalyst provided in Examples 2-3 (ie, Examples 2 and 3) is similar to that in Example 1, except that some parameters are different. The specific different parameters are shown in the following table. The catalysts obtained in Examples 2 and 3 are Cat-B and Cat-C, respectively.

[0055] Table 1

[0056]

[0057]

[0058] The properties of the carriers prepared in the above examples and the contents of various metals in the catalysts are shown in Table 2.

[0059] Table 2

[0060]

[0061] Example 4

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

[0063] A 1000mL micro-high pressure reactor (Beijing Century Senlang SLM1000) was used to add 600mL of 0.4mol / L ethylene glycol solution (solvent is water), the ratio of catalyst Cat-A to ethylene glycol was 1g:15mol, the reaction pressure of the oxidant oxygen in the reactor was 1.5MPa, the reaction temperature was 70℃, the rotor speed was 200r / min, the reaction time was 10h, and the reaction liquid was analyzed by high performance liquid chromatography after the reaction was completed and cooled. The specific results are shown in Table 3.

[0064] Example 5

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

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

[0067] Example 6

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

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

[0070] Example 7

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

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

[0073] Example 8

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

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

[0076] Comparative Example 1

[0077] The method for preparing glycolic acid by oxidation of ethylene glycol 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 oxidation of ethylene glycol 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 oxidation of ethylene glycol 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 oxidation of ethylene glycol 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 oxidation of ethylene glycol provided in this comparative example is similar to that of Example 6, except that a different catalyst is used. The method for preparing the catalyst used in this comparative example is similar to that of Example 1, except that 5.0 ml of deionized water is used in place of SnSO4 and Bi2(SO4)3 solution in step (b) of the catalyst preparation. The specific results are shown in Table 3.

[0086] Table 3 Oxidation reaction results

[0087] Ethylene glycol conversion, % 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] From the data in the above table, it can be seen that with MCM-41 molecular sieve as the carrier, Pt as the main active metal, Mn, Sn and Bi as additives, in a low-pressure (1.0-2.0MPa) oxygen environment, alkali-free conditions, the relationship between the amount of catalyst and ethylene glycol is 1g:10-20mol, at 60-80°C, ethylene glycol can be converted into glycolic acid with high selectivity and high conversion rate, while reducing the reaction time of the entire oxidation reaction.

[0089] 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 glycolic acid by oxidation of ethylene glycol, characterized in that: The steps include: Ethylene glycol undergoes oxidation reaction under the action of a catalyst to obtain glycolic acid; the pressure of the oxidation reaction is 1.0-2.0 MPa, the temperature is 60-80° C., and the amount ratio of the catalyst to the ethylene glycol is 1 g:(10-20) mol; The catalyst carrier comprises a mesoporous molecular sieve, the active component comprises Pt, and the auxiliary active components comprise Mn, Sn and Bi; Based on 100% of the mass of the catalyst, the content of Pt is 0.8%-1.6%, and the total content of Sn, Bi and Mn is 1.0%-3.5%.

2. The method for preparing glycolic acid by oxidation of ethylene glycol according to claim 1, characterized in that: The ethylene glycol comes from an ethylene glycol solution, and the concentration of the ethylene glycol solution is 0.2-0.6 mol / L.

3. The method for preparing glycolic acid by oxidation of ethylene glycol according to claim 1, characterized in that: The mass ratio of Mn, Sn and Bi is (0.4-1.0):(0.1-0.7):(0.1-0.5).

4. The method for preparing glycolic acid by oxidation of ethylene glycol according to claim 1, characterized in that: The preparation method of the catalyst comprises the following steps: The impregnation solution containing Pt salt, Mn salt, Sn salt and Bi salt is impregnated into the mesoporous molecular sieve in equal volumes, and the catalyst is obtained through aging, drying, calcining and reduction.

5. The method for preparing glycolic acid by oxidation of ethylene glycol as claimed in claim 4, characterized in that: The aging temperature is 20-40°C and the time is 2-4h; The calcination temperature is 400-600°C and the calcination time is 4-6 hours.

6. The method for preparing glycolic acid by oxidation of ethylene glycol as claimed in claim 4, characterized in that: The reducing atmosphere is a mixed gas of H2 and Ar, the volume content of H2 in the mixed gas is 10% to 20%, the reducing temperature is 300 to 450°C, and the reducing time is 3 to 6 hours.

7. The method for preparing glycolic acid by oxidation of ethylene glycol according to claim 1, characterized in that: The mesoporous molecules are selected from MCM-41.

8. The method for preparing glycolic acid by oxidation of ethylene glycol as claimed in claim 7, characterized in that: The specific surface area of ​​MCM-41 is 650-750m 2 / g, pore volume is 0.7-0.9cm 3 / g.

9. The method for preparing glycolic acid by oxidation of ethylene glycol as claimed in claim 4, characterized in that: The Pt salt is selected from at least one of H2PtC16·6H2O, tetraamine platinum 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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