Method for preparing glycollic acid by catalyzing selective oxidation of ethylene glycol

Abstract

The invention discloses a method for preparing glycollic acid by catalyzing selective oxidation of ethylene glycol, which comprises the following steps of: sealing ethylene glycol serving as a substrate, water serving as a solvent and a transition metal catalyst A and an alkaline cocatalyst B serving as a catalytic system, and reacting at 40-160 DEG C in an oxygen atmosphere to obtain the glycollic acid, the transition metal catalyst A comprises a carrier and transition metal loaded on the carrier; the alkaline cocatalyst B comprises at least one of calcium oxide, sodium hydroxide, potassium hydroxide and strontium oxide. The method provided by the invention has the advantages of high glycollic acid selectivity, good catalyst stability, simple reaction process and the like.

Description

Technical Field

[0001] The present invention relates to the field of catalytic technology, and more specifically, to a method for preparing glycolic acid by catalyzing the selective oxidation of ethylene glycol. Background Art

[0002] As an important fine chemical raw material, glycolic acid is widely used in chemical cleaning, personal care, medical and pharmaceutical fields. Its current global market consumption is about 100,000 t / a, and it is expected to reach 160,000 t / a in 2028 (Yuan Caicai, Zhang Ping, Zang Kai, et al. Purification and application of glycolic acid reaction solution [J]. Applied Chemical Industry, 2019, 48(7): 1659-1662. DOI: 10.3969 / j.issn.1671-3206.2019.07.034.). Polyglycolic acid produced by condensation of glycolic acid is biodegradable and plays an important role in biomedicine, food packaging, oil and gas extraction and agricultural production. PLGA synthesized by copolymerization modification of polyglycolic acid is an ideal drug delivery material and has been widely used (Yue Su, Bolun Zhang, Ruowei Sun, Wenfang Liu, Qubo Zhu, Xun Zhang, Rongrong Wang & Chuanpin Chen (2021) PLGA-based biodegradable microspheres in drug delivery: recent advances in research and application, Drug Delivery, 28: 1, 1397-1418, DOI: 10.1080 / 10717544.2021.1938756).

[0003] At present, the main routes for producing glycolic acid are chloroacetic acid hydrolysis, formaldehyde cyanidation, formaldehyde carbonylation, and dimethyl oxalate hydrogenation (Tian Kesheng, Wang Baowei, Xu Genhui. Synthesis and Application of Glycolic Acid [J]. Natural Gas Chemical Industry, 2006, 31 (6): 60-63, 71. DOI: 10.3969 / j.issn.1001-9219.2006.06.014.). Among these mainstream methods, chloroacetic acid hydrolysis and formaldehyde cyanidation have problems such as highly toxic raw materials and serious environmental pollution. Formaldehyde carbonylation is technically difficult, requires a large one-time investment, and requires high-pressure equipment, which has high requirements for equipment. Dimethyl oxalate hydrogenation hydrolysis has abundant raw material sources, mild reaction conditions, and a green and environmentally friendly process. It has been widely studied in recent years and is a new technology route that the industry is more optimistic about. The key to the DMO hydrogenation hydrolysis method lies in the preparation of hydrogenation catalysts. The development of hydrogenation catalysts is difficult. At present, dozens of domestic units and enterprises have been involved in the research and development of this catalyst. The high requirements for product separation and refining are also a difficulty in its industrialization (Shang Kuanxiang, Zhang Dazhou, Lu Wenxin, et al. Analysis of market prospects and technological progress of glycolic acid [J]. Fertilizer Design, 2022, 60(4): 5-7, 35. DOI: 10.3969 / j.issn.1004-8901.2022.04.002.). Therefore, it is of great application value to invent an environmentally friendly reaction method with mild reaction conditions. Summary of the invention

[0004] The object of the present invention is to overcome the above-mentioned defects of the prior art and provide a method for catalyzing the selective oxidation of ethylene glycol to prepare glycolic acid, using environmentally friendly solvent water as the reaction medium, not requiring an organic solvent, using cheap and readily available oxygen as the only oxidant, having mild reaction conditions (<160° C.), using a transition metal catalyst A and an alkaline co-catalyst B that are easy to separate, a one-step catalytic reaction process that saves reaction time, and being easy to operate and having low energy consumption.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A method for preparing glycolic acid by catalyzing the selective oxidation of ethylene glycol, wherein ethylene glycol is used as a substrate, water is used as a solvent, a transition metal catalyst A and an alkaline co-catalyst B are used as a catalytic system, and after being sealed, the reaction is carried out in an oxygen atmosphere at 40° C. to 160° C. for 20 min to 12 h to obtain glycolic acid; the transition metal catalyst A comprises a carrier and a transition metal supported on the carrier; and the alkaline co-catalyst B comprises at least one of calcium oxide, magnesium oxide, calcium hydroxide, sodium hydroxide, potassium hydroxide, strontium oxide, sodium bicarbonate and potassium carbonate.

[0007] Optionally, in the transition metal catalyst A, the mass percentage of the transition metal is 0.1wt%-50wt%, preferably, the mass percentage of the transition metal is 0.5wt%-5wt%.

[0008] Optionally, the transition metal includes one or more of Au, Ag, Cu, Mo, Co, Rh, Ir, Ni, Pd, Pt, and Ru.

[0009] Optionally, the carrier includes one or more of titanium dioxide, zirconium dioxide, silicon dioxide, aluminum oxide, hydroxyapatite, cerium oxide, activated carbon, carbon nanotubes, and graphene oxide. Preferably, the alkaline promoter B includes at least one of calcium oxide, sodium hydroxide, potassium hydroxide, and strontium oxide.

[0010] Optionally, the mass ratio of the transition metal catalyst A to the substrate is (0.1-10):1.

[0011] Optionally, the mass ratio of the alkaline promoter B to the transition metal in the transition metal catalyst A is (0.2-100):1; preferably, the mass ratio is (1-20):1.

[0012] Optionally, the concentration of the substrate is 0.1wt%-10wt%, preferably, the concentration is 0.1wt%-5wt%.

[0013] Optionally, the reaction temperature is 40°C-100°C, the reaction time is 0.5h-12h, and the oxygen pressure is 0.5MPa-2.0MPa.

[0014] Optionally, the preparation method of the transition metal catalyst A includes: mixing a soluble salt solution of a transition metal and a carrier with water, adding a precipitant to deposit the transition metal on the surface of the carrier, slowly precipitating at 45°C-100°C for 1h to 12h, and washing, drying at 60°C-100°C for 6h to 18h, then placing in a hydrogen atmosphere, and reducing at 200°C-600°C for 2h to 4h to obtain catalyst transition metal catalyst A.

[0015] Optionally, the soluble salt solution of the transition metal includes a nitrate solution of the transition metal and a chloride solution of the transition metal.

[0016] Optionally, the precipitant includes one or more of urea, sodium hydroxide, sodium carbonate and ammonium carbonate.

[0017] Optionally, the precipitation temperature is 60°C-90°C, and the precipitation time is 2h-6h.

[0018] Implementing the embodiments of the present invention will have the following beneficial effects:

[0019] The present invention provides a method for preparing glycolic acid by catalyzing the selective oxidation of ethylene glycol, wherein cheap and readily available oxygen is used as the only oxidant, and glycolic acid is prepared by reaction under the action of a transition metal catalyst A and an alkaline co-catalyst B, and has the following effects:

[0020] 1. The reaction process of the present invention is simple, and selective oxidation of ethylene glycol to glycolic acid can be achieved through only one step of reaction process.

[0021] 2. The reaction conditions are mild and environmentally friendly. Water is used as solvent and oxygen is used as oxidant. There is no need to add organic solvents or other oxidants.

[0022] 3. The catalyst preparation process is simple, convenient for industrial scale-up, and easy to recycle.

[0023] Taking the above factors into consideration, the method for selectively preparing glycolic acid from ethylene glycol of the present invention has significant technical advancement and good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 1% AuO in Example 13 of the present invention x / ZrO 2 Cyclic stability diagram of the catalyst. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited in any way.

[0026] Example 1

[0027] The Au / support catalyst was prepared by a deposition sedimentation method. The specific preparation method is as follows:

[0028] Step 1: Evenly diffuse Au soluble salt solution with titanium dioxide, silicon dioxide, activated carbon, zirconium dioxide, aluminum oxide, hydroxyapatite, cerium oxide, calcium oxide and molybdenum disulfide in water, add urea to deposit Au on the surface of the carrier, and slowly precipitate at 80°C for 4 hours.

[0029] Step 2: Wash the sample in step 1 with pure water for several times, place it in an oven at 60°C and dry it for 12 hours to obtain the catalyst AuOx / carrier.

[0030] Step 3: The catalyst AuOx / support was reduced at 500°C for 2 h in a hydrogen atmosphere and passivated overnight at room temperature to obtain Au / TiO with a loading of 1%. 2 , Au / SiO 2 , Au / C, Au / ZrO 2 , Au / Al 2 O 3 , Au / HAP, Au / CeO2 , Au / CaO, Au / MoS 2 .

[0031] Example 2

[0032] The difference between this embodiment and embodiment 1 is that the soluble salts of transition metals are rhodium nitrate, tetraammine platinum nitrate, palladium nitrate, ruthenium chloride, zinc nitrate, tetrachloroauric acid and manganese nitrate, and the carrier is zirconium dioxide. According to the method of embodiment 1, RhO with a loading of 1% is obtained. x / ZrO 2 , PtO x / ZrO 2 , PdO x / ZrO 2 , RuO x / ZrO 2 ,Zuo x / ZrO 2 , AuO x / ZrO 2 and MnO x / ZrO 2 catalyst.

[0033] Example 3

[0034] Method for preparing glycolic acid by catalytic selective oxidation of ethylene glycol: 20 ml of 1% ethylene glycol aqueous solution, 50 mg of catalyst A of Example 1 and 50 mg of calcium oxide were added to a 50 ml reactor, oxygen was introduced into the reactor to replace the oxygen and then the pressure was filled to 1.2 MPa, and the reaction was carried out under stirring at 80° C. for 2 h. The solution after the reaction was analyzed by liquid chromatography, and the reaction conversion rate and target product selectivity were calculated according to the following formula.

[0035] Ethylene glycol conversion rate (%) = (n 反应前的乙二醇 -n 反应后剩余乙二醇 ) / n 反应前的乙二醇 *100%

[0036] Glycolic acid selectivity (%) = n 产物中乙醇酸 / (n 反应前的乙二醇 -n 反应后剩余乙二醇 )*100%

[0037] Example 4

[0038] Analysis of AuO on different carriers in Example 1 x / Carrier catalyst performance evaluation, the reaction conditions are the same as in Example 3, and the results are shown in Table 1.

[0039] Table 1 Performance evaluation of AuOx / carrier catalysts on different carriers

[0040] catalyst Conversion rate / % Glycolic acid selectivity / % <![CDATA[1%Au / TiO 2 -P25]]> 40.8 80.57 <![CDATA[1%Au / TiO 2 -A]]> 37.0 80.30 <![CDATA[1%Au / TiO 2 -R]]> 41.8 85.52 <![CDATA[1%Au / SiO 2 ]]> 42.9 82.00 1%Au / C 13.2 80.24 <![CDATA[1%Au / ZrO 2 ]]> 42.0 87.00 <![CDATA[1%Au / γ-Al 2 THE 3 ]]> 44.4 65.78 1%Au / HAP 41.7 70.40 <![CDATA[1%Au / CeO 2 ]]> 40.1 72.97 1%Au / CaO 0.0 0.00 <![CDATA[1%Au / MoS 2 ]]> 0.0 0.00

[0041] Among them, TiO 2 -A, TiO 2 -R,TiO 2 -P25 are anatase, rutile and mixed crystal forms of titanium dioxide, Al 2 O 3 The γ crystal form is used. From the reaction results, it can be seen that the selectivity of the catalyst system used in the present invention in the reaction of ethylene glycol oxidation to glycolic acid is higher than 65%. 2 The best effect was achieved when used as a carrier, with a selectivity of 87% for glycolic acid. 2 When CaO is used as a carrier, the catalyst is inactive.

[0042] Example 5

[0043] Analysis of MO of different transition metals in Example 2 x / ZrO 2 Catalyst performance evaluation: The reaction conditions were the same as in Example 3. The results are shown in Table 2.

[0044] Table 2 Performance evaluation of MOx / ZrO2 catalysts with different transition metals

[0045] catalyst Conversion rate / % Glycolic acid selectivity / % <![CDATA[1%Au / ZrO 2 ]]> 42.0 87.00 <![CDATA[1%Pt / ZrO 2 ]]> 33.1 57.93 <![CDATA[1%Rh / ZrO 2 ]]> 1.6 26.73 <![CDATA[1%Zn / ZrO 2 ]]> 0.6 38.57 <![CDATA[1%Pd / ZrO 2 ]]> 35.9 34.93 <![CDATA[1%Mn / ZrO 2 ]]> 3.0 12.28

[0046] From the reaction results, it can be seen that ZrO 2 Loading Au, Pt, Rh, Pd, and Mn can all promote the selective oxidation of ethylene glycol to glycolic acid. x / ZrO 2 Catalysts work best.

[0047] Example 6

[0048] The difference between Example 6 and Example 1 is that the loading amount of the transition metal is changed. Except for the above differences, other operations are the same and will not be repeated here. According to Example 3, the specific loading amount of X% AuO x / ZrO 2 The catalyst performance evaluation results are shown in Table 3 below.

[0049] Table 3 Performance evaluation results of X% AuOx / ZrO2 catalysts with different loadings

[0050]

[0051]

[0052] From the reaction results, it can be seen that the gold loading within a certain range can effectively achieve high selectivity in the conversion of ethylene glycol to glycolic acid. The performance is best when the loading is 1%. The following examples all use 1% Au / ZrO 2 .

[0053] Example 7

[0054] The difference between Example 7 and Example 3 is that the reaction time is changed. Except for the above differences, other operations are the same and will not be repeated here. The performance evaluation results under different reaction times are shown in Table 4 below.

[0055] Table 4 Performance evaluation results at different reaction times

[0056] Reaction time (h) Conversion rate / % Glycolic acid selectivity / % 0.5 41.3 81.41 2 42.0 87.00 4 42.7 77.47 6 42.2 75.41 12 42.3 75.50

[0057] From the reaction results, it can be seen that the reaction conditions of 0.5h-2h have relatively good glycolic acid selectivity, and the glycolic acid selectivity reaches the highest when the reaction time is 2h. In addition, glycolic acid is stably present in the method of the present invention, and no obvious further reaction of glycolic acid occurs when the reaction time is extended to 12h.

[0058] Example 8

[0059] The difference between Example 8 and Example 3 is that the reaction temperature is changed. Except for the above differences, other operations are the same and will not be repeated here. The performance evaluation results at different reaction temperatures are shown in Table 5 below.

[0060] Table 5 Performance evaluation results at different reaction temperatures

[0061] Reaction temperature (℃) Conversion rate / % Glycolic acid selectivity / % 50 42.0 89.55 80 42.0 87.00 100 42.3 80.48 120 46.2 65.90 140 45.0 49.21 160 51.3 18.95

[0062] It can be seen from the reaction results that the method provided by the present invention can produce glycolic acid with high selectivity at the above-mentioned reaction temperature. Among them, when the reaction temperature is 80°C, the selectivity of glycolic acid is the highest.

[0063] Example 9

[0064] The difference between Example 9 and Example 3 is that the oxygen pressure is changed. Except for the above differences, other operations are the same and will not be repeated here. The performance evaluation results under different oxygen pressures are shown in Table 6 below.

[0065] Table 6 Performance evaluation results under different oxygen pressures

[0066] Reaction pressure (MPa) Conversion rate / % Glycolic acid selectivity / % 0.1 40.4 79.36 0.5 42.3 80.22 1.0 42.0 87.00 1.5 43.0 77.50 2 41.8 79.37 3 41.7 80.92

[0067] It can be seen from the reaction results that the present invention can obtain a very high selectivity for glycolic acid under the above-examined oxygen pressures. Among them, when the oxygen pressure is 1.0 MPa, the selectivity for glycolic acid is the highest.

[0068] Example 10

[0069] The difference between Example 10 and Example 3 is that the ethylene glycol concentration is changed. Except for the above differences, other operations are the same and will not be repeated here. The performance evaluation results under different ethylene glycol concentrations are shown in Table 7 below.

[0070] Table 7 Performance evaluation results at different ethylene glycol concentrations

[0071] Ethylene glycol concentration / wt% Conversion rate / % Glycolic acid selectivity / % 0.5 66.4 70.34 1 42.0 87.00 2 21.8 90.23 5 10.0 92.56 10 5.3 95.92

[0072] It can be seen from the reaction results that the present invention can obtain a higher selectivity of glycolic acid within the range of 0.5wt%-10wt%.

[0073] Embodiment 11

[0074] Compared with Example 3, Example 11 differs in that the molar ratio of calcium oxide to ethylene glycol is changed. Except for the above differences, other operations are the same and will not be repeated here. The performance evaluation results under different molar ratios of calcium oxide to ethylene glycol are shown in Table 8 below.

[0075] Table 8 Performance evaluation results under different molar ratios of calcium oxide to ethylene glycol

[0076]

[0077]

[0078] From the reaction results, it can be seen that the alkaline co-catalyst plays a decisive role in the highly selective catalytic conversion of ethylene glycol to glycolic acid. When the molar ratio of the co-catalyst to ethylene glycol is 5:1, the conversion rate is high. When the molar ratio of the co-catalyst to ethylene glycol is 0.2:1, the selectivity of glycolic acid can reach up to 85.49%. Without the alkaline co-catalyst, ethylene glycol is almost not converted.

[0079] Example 12

[0080] The difference between Example 12 and Example 3 is that the alkaline co-catalyst B is changed. Except for the above differences, other operations are the same and will not be repeated here. The performance evaluation results under different alkaline co-catalysts B are shown in Table 9 below.

[0081] Table 9 Performance evaluation results under different alkaline co-catalysts B

[0082] Catalyst Conversion rate / % Glycolic acid selectivity / % CaO 42.0 87.00 MgO 13.0 87.86 NaOH 36.6 76.59 KOH 24.8 78.84 SrO 23.6 96.75 <![CDATA[NaHCO 3 ]]> 1.4 99.21 <![CDATA[K 2 CO 3 ]]> 9.5 98.64

[0083] It can be seen from the reaction results that the alkaline co-catalysts used in the present invention can obtain higher glycolic acid selectivity.

[0084] Embodiment 13

[0085] The catalyst 1% AuO x / ZrO 2 The cyclic stability of the catalyst, the alkaline co-catalyst is calcium oxide, the reaction conditions are the same as in Example 3, and the cyclic method is: the catalyst AuO x / ZrO 2 After washing and drying, 50 mg of CaO was added and the next reaction was carried out. Figure 1 As shown, after four cycles, 1% AuO x / ZrO 2 The catalyst has stable performance, still maintains high catalytic activity, and the selectivity of glycolic acid is maintained at more than 85%.

[0086] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing glycolic acid by catalytic selective oxidation of ethylene glycol, characterized in that: The method uses ethylene glycol as a substrate, water as a solvent, a transition metal catalyst A and an alkaline co-catalyst B as a catalytic system, and reacts for 20 minutes to 12 hours at 40° C. to 160° C. in an oxygen atmosphere after sealing to obtain glycolic acid. The transition metal catalyst A comprises a carrier and a transition metal supported on the carrier; The alkaline promoter B includes at least one of calcium oxide, magnesium oxide, calcium hydroxide, sodium hydroxide, potassium hydroxide, strontium oxide, sodium bicarbonate, and potassium carbonate.

2. The method according to claim 1, characterized in that: In the transition metal catalyst A, the mass percentage of transition metal is 0.1wt%-50wt%; The transition metal includes one or more of Au, Ag, Cu, Mo, Co, Rh, Ir, Ni, Pd, Pt, and Ru; The carrier includes one or more of titanium dioxide, zirconium dioxide, silicon dioxide, aluminum oxide, hydroxyapatite, cerium oxide, activated carbon, nano carbon tubes, and graphene oxide.

3. The method according to claim 2, characterized in that In the transition metal catalyst A, the mass percentage of transition metal is 0.5wt%-5wt%.

4. The method according to claim 1, characterized in that The alkaline promoter B includes at least one of calcium oxide, sodium hydroxide, potassium hydroxide and strontium oxide.

5. The method according to claim 1, characterized in that The mass ratio of the transition metal catalyst A to the substrate is (0.1-10): 1; The mass ratio of the basic promoter B to the transition metal in the transition metal catalyst A is (0.2-100): 1; The concentration of the substrate is 0.1 wt%-10 wt%.

6. The method according to claim 5, characterized in that The reaction temperature is 40℃-100℃, the reaction time is 0.5h-12h, and the oxygen pressure is 0.5MPa-2.0MPa; The concentration of the substrate is 0.1wt%-5wt%; The mass ratio of the basic promoter B to the transition metal in the transition metal catalyst A is (1-20):

1.

7. The method according to claim 1, characterized in that The preparation method of the transition metal catalyst A comprises: mixing a soluble salt solution of a transition metal and a carrier with water, adding a precipitant to deposit the transition metal on the surface of the carrier, slowly precipitating at 45°C-100°C for 1h-12h, washing, drying at 60°C-100°C for 6h-18h, then placing in a hydrogen atmosphere, and reducing at 200°C-600°C for 2h-4h to obtain the catalyst transition metal catalyst A.

8. The method according to claim 7, characterized in that The soluble salt solution of the transition metal includes a nitrate solution of the transition metal and a chloride solution of the transition metal; The precipitant includes one or more of urea, sodium hydroxide, sodium carbonate and ammonium carbonate.

9. The method according to claim 7, characterized in that: The precipitation temperature is 60°C-90°C, and the precipitation time is 2h-6h.

Images