A method for hydrolysis of ethylene carbonate to synthesize ethylene glycol

Abstract

The present application relates to a method for preparing ethylene glycol by catalytic hydrolysis of ethylene carbonate, which uses hydrotalcite-like compounds prepared by coprecipitation as catalyst, ethylene carbonate and water as raw materials, under the conditions of reaction temperature of 80-100 DEG C, molar ratio of water to ethylene carbonate of 1:1-1:5, mass fraction of catalyst relative to substrate ethylene carbonate of 5%wt-8%wt, and reaction time of 3-4 hours, to generate ethylene glycol. The method has the characteristics of mild reaction conditions, cheap and easy-to-prepare catalyst and good stability, and can be recycled multiple times after simple treatment while maintaining excellent catalytic effect.

Description

Technical Field

[0001] This invention relates to a method for the catalytic hydrolysis of ethylene carbonate to prepare ethylene glycol. Background Technology

[0002] Ethylene glycol is an important organic chemical raw material, mainly used to produce polyester fibers, antifreeze, lubricants, plasticizers, coatings, unsaturated polyester resins, nonionic surfactants, ethanolamine, and explosives. Currently, domestic ethylene glycol production processes mainly include coal-based ethylene glycol, petroleum-based ethylene glycol, and the emerging biomass-based ethylene glycol. However, the coal-based ethylene glycol process produces a large number of small-molecule byproducts during hydrogenation, resulting in poor product quality. While the emerging biomass-based ethylene glycol process shows good development prospects, the technology is not yet mature and requires further in-depth research before large-scale industrialization. Compared to other ethylene glycol production processes, the petroleum-based ethylene glycol process has wider industrial applications.

[0003] The main ethylene production technology involves oxidizing ethylene to obtain ethylene oxide, which is then hydrated to produce ethylene glycol. The hydration process is further divided into direct hydration of ethylene oxide and catalytic hydration of ethylene oxide. Direct hydration involves the direct reaction of ethylene oxide with water under high temperature and pressure to produce ethylene glycol. Although no catalyst is used, this method requires very high reaction temperatures (150–200°C), high pressures (1–2 MPa), and a large water-to-water ratio (greater than 20) to ensure a high ethylene glycol yield. Furthermore, the generated ethylene glycol undergoes side reactions with ethylene oxide to produce polyethylene glycols, resulting in low selectivity. The purification process, involving the evaporation of large amounts of excess water and ethylene glycol, is also energy-intensive, which is inconsistent with current green development principles.

[0004] The catalytic hydration method for ethylene oxide includes direct catalytic hydration and the ethylene carbonate route. For the direct catalytic hydration method, according to patents CN02112037.4, CN03141453.2, CN02112038.2, and CN200310108695.7 reported by Sinopec Corporation and the Shanghai Research Institute of Petrochemical Technology, the catalytic hydration method significantly reduces the water ratio (approximately 5-10) and produces milder reaction conditions compared to the direct hydration method for ethylene oxide. However, it still requires the evaporation and removal of a large amount of water and does not solve the problem of side reactions between ethylene oxide and ethylene glycol. In contrast, the ethylene carbonate route can significantly improve the selectivity of ethylene glycol. The patent CN96121781.2 reported by Mitsubishi Chemical Corporation of Japan and the literature reported by Kazuki Kawabe (Catal Surv Asia (2010) 14:111–115) provide detailed information on this process. First, ethylene oxide is used as a raw material and reacts with CO2 under the action of a catalyst to undergo a carbonylation reaction to produce ethylene carbonate (EC). Then, ethylene carbonate is used as an intermediate product for hydrolysis to produce ethylene glycol. Due to its near 100% selectivity for ethylene glycol, this process is called the OMEGA process (Only Mono Ethylene Glycol Advantage). Furthermore, the theoretical ester-to-water ratio in this process is close to the stoichiometric ratio of 1, further reducing water consumption. Compared with other methods, this route has advantages such as extremely high ethylene glycol selectivity, lower water consumption, and milder reaction conditions, making it a promising industrial direction for the production of ethylene glycol from ethylene oxide.

[0005] Currently, the catalysts used for the hydrolysis of ethylene carbonate mainly include: alkali (earth) metal carbonates (US4524224, 1985), compounds of Mo and W (JP822106631, 1982; W02009071651, 2009), quaternary ammonium salts, and ion exchange resins (EP0133763, 1989; US6080897, 2000; US200901568). 67, 2009), various imidazole resins (CN201410314342.0; CN201410498200.4; CN201410202046.1), ionic salts or ionic liquids (GreenChem., 2014, 16, 3297–3304; Chin.J.Chem.Eng., 2010, 18(6), 962-966; Green Chem., 2018, 20, 1594–1601), heteropolyacid crystals or supported materials (CN201810291181.6; CN200910311603.2; CN201610877515.9; Appl.Catal.A, 471(2014)50–55), etc. However, these catalytic systems have some problems, such as the difficulty in separating homogeneous catalysts; the low activity of ionic salts or ionic liquids; the low stability of resin catalysts and the swelling problem; and the cumbersome synthesis steps and high cost of heteropolyacid catalysts. These problems need to be solved for the hydrolysis route of ethylene carbonate.

[0006] To explore a low-cost, stable, and highly effective heterogeneous solid catalyst, hydrotalcite-like materials can be studied. Hydrotalcite compounds (HT) and hydrotalcite-like compounds (HTLcs) both belong to layered double hydroxides (LDHs), and their basic chemical composition is [M...]. II 1-x M III x (OH)2] x+ A n- x / n ·yH2O, where M II It consists of divalent metal ions (Mg, Zn, Mn, Fe, Co, Ni, Cu, Ca, Cd, etc.), M III It consists of trivalent metal ions (Al, Fe, Co, Mn, Cr, Ga, In, etc.), A n- For interlayer n-valent anions, x is M III / (M II +M IIIThe molar ratio of ) and y represents the amount of interlayer water of crystallization. LDH layers are composed of M(OH)6 octahedra, exhibiting a certain degree of basicity, while metal ions can act as Lewis acidic sites. The calcination products of LDH are called layered double oxides (LDO) or mixed metal oxides (MMO), which often exhibit larger specific surface areas and stronger basicity, making them suitable as excellent heterogeneous solid base catalysts. Researchers have used hydrotalcite compounds as base catalysts to catalyze various reactions, such as Michael addition (J. Mol. Catal. A, 2007, 278:135-144); aldol condensation (Green Chem., 2001, 3:257-260); transesterification (Appl. Catal. A, 2005, 287:183-190); Knoevenagel condensation (J. Mol. Catal. A, 1999, 146:279-284); and Claisen-Schmidt reaction (J. Catal., 2011, 279:196-204). Currently, there are no reports on the use of hydrotalcite catalysts in the catalytic hydrolysis of ethylene carbonate. This patent aims to find a suitable hydrotalcite catalyst with excellent catalytic performance for this system, building upon previous research. Summary of the Invention

[0007] This invention utilizes LDH or LDO as a heterogeneous solid base in the catalytic hydrolysis of ethylene carbonate. The technical challenges addressed are reducing reaction temperature, shortening reaction time, lowering catalyst synthesis costs, and improving catalyst stability. This invention provides a novel method for the hydrolysis of ethylene carbonate to prepare ethylene glycol. This method features mild reaction conditions, inexpensive and readily available catalysts with good stability, and the catalysts can be repeatedly recycled with minimal processing while maintaining excellent catalytic performance.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for preparing ethylene glycol by hydrolysis of ethylene carbonate, using ethylene carbonate and water as raw materials, under the conditions of a reaction temperature of 70-100℃, a molar ratio of water to ethylene carbonate of 1-5, a catalyst mass fraction of 1%wt-10%wt of the substrate ethylene carbonate, and a reaction time of 1-5 hours, to produce ethylene glycol. The catalyst is a hydrotalcite-based material, and its preparation method includes the following steps:

[0009] 1) M II and M III A solution A is prepared by dissolving a soluble salt in deionized water in a certain proportion; a solution B is prepared by dissolving a mixed alkali in water in a certain proportion; M... II MIII The soluble salt is selected from at least one of nitrates, sulfates, or halides; the mixed alkali is sodium hydroxide and sodium carbonate mixed in a certain proportion and dissolved in water;

[0010] Among them, M is expressed as a molar ratio. II With M III The molar ratio is 2-4, and the n(OH) of the mixed alkali is... - )=2n(M II +M III ), n(CO3) 2- )=n(M III M II and M III Choose one of the following: sulfate, nitrate, or halide.

[0011] 2) Using the co-precipitation method, slowly add solution A and solution B dropwise into a certain amount of base solution at room temperature, while stirring vigorously, and control the pH in the range of 9-10;

[0012] 3) After the addition is complete, stir vigorously for a certain period of time and then age at a certain temperature for a certain period of time;

[0013] 4) Centrifuge the obtained turbid liquid and wash it with deionized water until the washing liquid is neutral;

[0014] 5) The obtained solid is dried at 80℃ for 24h to obtain a hydrotalcite-like (LDH) structure. If it is calcined at 200-800℃ for a certain time, a mixed metal oxide (LDO) is obtained.

[0015] 6) Due to the “structural memory effect” of LDO, after a round of reaction, the structure will change because it tends to return to the layered structure of LDH, and the catalytic effect will decrease accordingly. The recovered catalyst needs to be simply regenerated and activated before it can be put into the next round of reaction.

[0016] In the above technical solution, preferably, the aqueous solution A in step 1) is a zinc-aluminum nitrate;

[0017] In the above technical solution, preferably, the reaction process in step 3) is to continue vigorous stirring at 25°C for 2 hours after the addition is completed, and then raise the temperature to 65°C and let it stand and age for 24 hours;

[0018] In the above technical solution, preferably, the reaction process in step 5) is to heat LDH to 500°C in an air atmosphere in a muffle furnace at a heating rate of 5°C / min and hold for 3 hours.

[0019] In the above technical solution, preferably, step 6) activation and regeneration process involves washing the recovered catalyst with anhydrous ethanol and then heating it to 300°C in an air atmosphere in a muffle furnace at a heating rate of 5°C / min, and holding it for 3 hours.

[0020] In the above technical solution, preferably, the reaction temperature is 100℃, the molar ratio of water to ethylene carbonate is 2:1, the weight ratio of catalyst to ethylene carbonate is 6.5%wt, and the reaction time is 4 hours. The yield of ethylene glycol is 99.2%. After each round of reaction, the catalyst can be recycled for at least 5 rounds after simple treatment, and the catalytic activity remains stable, achieving good technical results. Attached Figure Description

[0021] Figure 1 The images show scanning electron microscope (SEM) images of Zn3Al-CO3-LDH (left) and Zn3Al-500 calcined for 3 hours (right) in Example 29.

[0022] The present invention will be further illustrated below 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. Detailed Implementation

[0023]

Example 1

[0024] Prepare two mixed solutions, A and B. Solution A (mixed salt solution) consists of 0.06 mol Zn(NO3)2·6H2O and 0.02 mol Al(NO3)3·9H2O dissolved in 100 mL of deionized water. Solution B (mixed alkali solution) consists of 0.16 mol NaOH and 0.02 mol Na2CO3 dissolved in 100 mL of deionized water.

[0025] 200 mL of deionized water was added to a three-necked flask as the base solution. The mixture was stirred vigorously at 25°C (600 rpm) and liquids A and B were slowly added dropwise to the flask using a constant-pressure dropping funnel. The flow rates of liquids A and B were monitored with a pH meter to maintain the pH of the liquid in the flask between 9 and 10. A white turbid liquid was obtained during the dropwise addition. After the addition was complete, the mixture was stirred vigorously at 25°C for 2 hours, then the temperature was raised to 65°C, the stirring was stopped, and the mixture was allowed to stand for 24 hours. The resulting white solid was collected by centrifugation and washed with deionized water until neutral. It was then dried in an oven at 80°C for 24 hours to obtain a white, light, and brittle solid. This solid was ground in a mortar and pestle to obtain Zn3Al-CO3-LDH.

[0026] The obtained Zn3Al-CO3-LDH was placed in a crucible and heated in a muffle furnace from room temperature to 500°C at a heating rate of 5°C / min. The temperature was maintained for 6 hours. After cooling to 50°C, the crucible was removed to obtain a white powder, namely Zn3Al-LDO-500-6h.

[0027]

Example 2

[0028] Catalytic reaction: In a 25 mL round-bottom flask, 2 g (22.67 mmol) of ethylene carbonate and 1 g (56.675 mmol) of deionized water were weighed, i.e., the ester-to-water molar ratio was 1:2.5. 150 mg of Zn3Al-LDO-500-6h obtained in [Example 1] was added, and the mixture was heated in a 100 °C oil bath under reflux with stirring for 3 hours at a stirring speed of 400 r / min. After the reaction was completed, the reaction solution was analyzed by gas chromatography-mass spectrometry (GC-MS).

[0029] The catalyst after the reaction is collected by centrifugation and washed with anhydrous ethanol until no impurity peaks are observed on the gas chromatograph (washed 4 times). The catalyst is then dried under an infrared lamp to obtain the catalyst recovered in one reaction cycle for subsequent calcination activation cycle.

[0030] The catalytic reaction operation process and conditions are the same as described above, except that the catalyst is replaced with Zn3Al-CO3-LDH prepared in Example 1.

[0031] Comparative Example 1

[0032] Prepare two solutions, A and B. Solution A (mixed salt solution) consists of 0.06 mol Mg(NO3)2·6H2O and 0.02 mol Al(NO3)3·9H2O dissolved in 100 mL of deionized water; Solution B consists of 0.16 mol NaOH and 0.02 mol Na2CO3 dissolved in 100 mL of deionized water.

[0033] 200 mL of deionized water was added to a three-necked flask as the base solution. The flask was kept in an oil bath at 25 °C with vigorous stirring (600 rpm). Solutions A and B were added dropwise using a constant pressure dropper, with pH monitored and the flow rates of solutions A and B controlled to maintain the pH of the liquid in the flask between 9 and 10. A white turbid liquid was produced during the dropwise addition. After the addition was complete, vigorous stirring continued for 2 hours, then the temperature was raised to 65 °C, stirring was stopped, and the mixture was allowed to stand for 24 hours. The resulting white solid was collected by centrifugation and washed with deionized water until neutral. It was then dried in an oven at 80 °C for 24 hours to obtain a white, light, and brittle solid. This solid was finely ground in a mortar to obtain Mg3Al-CO3-LDH. The obtained Mg3Al-CO3-LDH was placed in a crucible and heated to 500 °C in a muffle furnace at a heating rate of 5 °C / min, held for 6 hours, and then cooled to a suitable temperature to obtain a white powder, Mg3Al-LDO-500-6h.

[0034] The catalytic reaction operation process and conditions are the same as in [Example 2], except that the catalysts used are the prepared Mg3Al-CO3-LDH and Mg3Al-LDO-500-6h, respectively.

[0035] Comparative Example 2

[0036] Prepare two solutions, A and B. Solution A (mixed salt solution) consists of 0.06 mol of Co(NO3)2·6H2O and 0.02 mol of Al(NO3)3·9H2O dissolved in 100 mL of deionized water; Solution B consists of 0.16 mol of NaOH and 0.02 mol of Na2CO3 dissolved in 100 mL of deionized water.

[0037] 200 mL of deionized water was added to a three-necked flask as the base solution. The flask was kept in an oil bath at 25°C with vigorous stirring (600 rpm). Solutions A and B were added dropwise using a funnel under constant pressure. The pH was monitored with a pH meter, and the flow rates of solutions A and B were controlled to maintain the pH of the liquid in the flask between 9 and 10. A pink turbid liquid was produced during the dropwise addition. After the addition was complete, vigorous stirring continued for 2 hours. Then, the temperature was raised to 65°C, the stirring speed was reduced to 250 rpm, and the mixture was aged at a low speed for 24 hours. The resulting pink solid was collected by centrifugation and washed with deionized water until neutral. It was then dried in an oven at 80°C for 24 hours to obtain a light, hard, pink solid. This solid was finely ground in a mortar and pestle to obtain Co3Al-CO3-LDH. The obtained Co3Al-CO3-LDH was placed in a crucible and heated in a muffle furnace from room temperature to 500°C at a heating rate of 5°C / min, and held for 6 hours. After cooling to a suitable temperature, it was taken out to obtain a white powder, namely Co3Al-LDO-500-6h.

[0038] The catalytic reaction operation process and conditions are the same as in [Example 2], except that the catalysts used are the prepared Co3Al-CO3-LDH and Co3Al-LDO-500-6h.

[0039] Comparative Example 3

[0040] Prepare two solutions, A and B. Solution A (mixed salt solution) consists of 0.06 mol Ni(NO3)2·6H2O and 0.02 mol Al(NO3)3·9H2O dissolved in 100 mL of deionized water; Solution B consists of 0.16 mol NaOH and 0.02 mol Na2CO3 dissolved in 100 mL of deionized water.

[0041] 200 mL of deionized water was added to a three-necked flask as the base solution. The flask was kept in an oil bath at 25 °C with vigorous stirring (600 rpm). Solutions A and B were added dropwise using a constant pressure dropper, with pH monitored and controlled to maintain the pH of the liquid in the flask between 9 and 10. A blue-green turbid liquid was produced during the dropwise addition. After the addition was complete, the temperature was raised to 40 °C and vigorous stirring was continued for 4 hours. Then, the temperature was raised to 70 °C, stirring was stopped, and the mixture was allowed to stand for 24 hours. The resulting blue-green solid was collected by centrifugation and washed with deionized water until neutral. It was then dried in an oven at 80 °C for 24 hours to obtain a light, hard, blue-green solid. This solid was finely ground in a mortar and pestle to obtain Ni3Al-CO3-LDH. The obtained Ni3Al-CO3-LDH was placed in a crucible and heated in a muffle furnace from room temperature to 500°C at a heating rate of 5°C / min, and held for 6 hours. After cooling to a suitable temperature, it was taken out to obtain a white powder, namely Ni3Al-LDO-500-6h.

[0042] The catalytic reaction operation process and conditions are the same as in [Example 2], except that the catalysts used are the prepared Ni3Al-CO3-LDH and Ni3Al-LDO-500-6h.

[0043] Comparative Example 4

[0044] Prepare two solutions, A and B. Solution A (mixed salt solution) consists of 0.06 mol Mn(NO3)2·4H2O and 0.02 mol Al(NO3)3·9H2O dissolved in 100 mL of deionized water; Solution B consists of 0.16 mol NaOH and 0.02 mol Na2CO3 dissolved in 100 mL of deionized water.

[0045] 200 mL of deionized water was added to a three-necked flask as the base solution. The flask was kept in an oil bath at 25°C with vigorous stirring (600 rpm). Solutions A and B were added dropwise using a constant pressure dropper, with pH monitored and the flow rates of solutions A and B controlled to maintain the pH of the liquid in the flask between 9 and 10. A yellowish-brown turbid liquid was produced during the dropwise addition. After the addition was complete, the temperature was raised to 40°C and vigorous stirring was continued for 3 hours. Then, the temperature was raised to 65°C, the stirring speed was reduced to 250 rpm, and the mixture was aged at low speed for 24 hours. The resulting yellowish-brown solid was collected by centrifugation and washed with deionized water until neutral. It was then dried in an oven at 80°C for 24 hours to obtain a light, brittle, yellowish-brown solid. This solid was finely ground in a mortar and pestle to obtain Mn3Al-CO3-LDH. The obtained Mn3Al-CO3-LDH was placed in a crucible and heated in a muffle furnace from room temperature to 500℃ at a heating rate of 5℃ / min, and held for 6 hours. After cooling to a suitable temperature, it was taken out to obtain a white powder, namely Mn3Al-LDO-500-6h.

[0046] The catalytic reaction operation process and conditions are the same as in [Example 2], except that the catalysts used are the prepared Mn3Al-CO3-LDH and Mn3Al-LDO-500-6h.

[0047]

Example 3

[0048] Prepare two mixed solutions, A and B. Solution A (mixed salt solution) consists of 0.04 mol Zn(NO3)2·6H2O and 0.02 mol Al(NO3)3·9H2O dissolved in 100 mL of deionized water. Solution B (mixed alkali solution) consists of 0.12 mol NaOH and 0.02 mol Na2CO3 dissolved in 100 mL of deionized water.

[0049] 200 mL of deionized water was added to a three-necked flask as the base solution. The flask was kept in an oil bath at 25°C with vigorous stirring (600 rpm). Liquids A and B were slowly added dropwise to the flask using a constant-pressure dropping funnel. The flow rates of liquids A and B were monitored with a pH meter to maintain the pH of the liquid in the flask between 9 and 10. A white turbid liquid was obtained during the dropwise addition. After the addition was complete, the mixture was stirred vigorously at 25°C for 2 hours, then the temperature was raised to 65°C, the stirring was stopped, and the mixture was allowed to stand for 24 hours. The resulting white solid was collected by centrifugation and washed with deionized water until neutral. It was then dried in an oven at 80°C for 24 hours to obtain a white, light, and brittle solid. This solid was finely ground in a mortar and pestle to obtain Zn₂Al₃-LDH. The obtained Zn2Al-CO3-LDH was placed in a crucible and heated in a muffle furnace from room temperature to 500℃ at a heating rate of 5℃ / min, and held for 6 hours. After cooling to a suitable temperature, it was taken out to obtain a white powder, namely Zn2Al-LDO-500-6h.

[0050] The catalytic reaction operation process and conditions are the same as in [Example 2], except that the catalysts used are the prepared Zn2Al-CO3-LDH and Zn2Al-LDO-500-6h.

[0051]

Example 4

[0052] Prepare two mixed solutions, A and B. Solution A (mixed salt solution) consists of 0.08 mol Zn(NO3)2·6H2O and 0.02 mol Al(NO3)3·9H2O dissolved in 100 mL of deionized water. Solution B (mixed alkali solution) consists of 0.20 mol NaOH and 0.02 mol Na2CO3 dissolved in 100 mL of deionized water.

[0053] 200 mL of deionized water was added to a three-necked flask as the base solution. The flask was kept in an oil bath at 25°C with vigorous stirring (600 rpm). Liquids A and B were slowly added dropwise to the flask using a constant-pressure dropping funnel. The flow rates of liquids A and B were monitored with a pH meter to maintain the pH of the liquid in the flask between 9 and 10. A white turbid liquid was obtained during the dropwise addition. After the addition was complete, the mixture was stirred vigorously at 25°C for 2 hours, then the temperature was raised to 65°C, the stirring was stopped, and the mixture was allowed to stand for 24 hours. The resulting white solid was collected by centrifugation and washed with deionized water until neutral. It was then dried in an oven at 80°C for 24 hours to obtain a white, light, and brittle solid. This solid was finely ground in a mortar and pestle to obtain Zn4Al-CO3-LDH. The obtained Zn4Al-CO3-LDH was placed in a crucible and heated in a muffle furnace from room temperature to 500℃ at a heating rate of 5℃ / min, and held for 6 hours. After cooling to a suitable temperature, it was taken out to obtain a white powder, namely Zn4Al-LDO-500-6h.

[0054] The catalytic reaction operation process and conditions are the same as in [Example 2], except that the catalysts used are the prepared Zn4Al-CO3-LDH and Zn4Al-LDO-500-6h.

[0055] The catalytic effects of Examples 1-4 and Comparative Examples 1-4 are shown in the table below:

[0056]

[0057]

Examples 5-11

[0058] The preparation method and conditions for LDH coprecipitation are the same as in [Example 1], except that the calcination temperature is changed. The obtained Zn3Al-CO3-LDH was placed in a crucible and heated in a muffle furnace at a rate of 5℃ / min from room temperature to 800℃, 700℃, 600℃, 500℃, 400℃, 300℃, and 200℃, respectively, and held for 6 hours. After cooling to a suitable temperature, the product was removed, yielding white powders, namely Zn3Al-LDO-800-6h, Zn3Al-LDO-700-6h, Zn3Al-LDO-600-6h, Zn3Al-LDO-500-6h, Zn3Al-LDO-400-6h, Zn3Al-LDO-300-6h, and Zn3Al-LDO-200-6h. Example 8 is equivalent to a repeat of Example 1, and no significant difference in catalytic effect was found, indicating good repeatability.

[0059] The catalytic reaction operation is the same as in [Example 2], except that the catalyst used is LDO calcined at 7 different temperature gradients, such as Zn3Al-LDO-800-6h.

[0060] The catalytic effects of Examples 5-11 are shown in the table below:

[0061] Example 5 150 mg catalyst, 100 °C, 3 h LDO: 44.3% Example 6 150 mg catalyst, 100 °C, 3 h LDO: 57.0% Example 7 150 mg catalyst, 100 °C, 3 h LDO: 79.2% Example 8 150 mg catalyst, 100 °C, 3 h LDO: 93.0% Example 9 150 mg catalyst, 100 °C, 3 h LDO: 92.3% Example 10 150 mg catalyst, 100 °C, 3 h LDO: 94.4% Example 11 150 mg catalyst, 100 °C, 3 h LDO: 91.9%

[0062] Examples 12-15

[0063] The preparation method and conditions for LDH coprecipitation are the same as in [Example 1], except that the calcination temperature is the same as in [Example 8], and the calcination time is changed. The obtained Zn3Al-CO3-LDH is placed in a crucible and heated to 500°C in a muffle furnace at a heating rate of 5°C / min, and held for 5h, 4h, 3h, and 2h respectively. After cooling to a suitable temperature, it is taken out to obtain white powder, namely Zn3Al-LDO-500-5h, Zn3Al-LDO-500-4h, Zn3Al-LDO-500-3h, and Zn3Al-LDO-500-2h.

[0064] The catalytic reaction operation process and conditions are the same as in [Example 2], except that the catalyst used is LDO with four different calcination times, such as Zn3Al-LDO-500-5h.

[0065]

Examples 16 and 17

[0066] The preparation method and conditions for LDH coprecipitation are the same as in [Example 14], except that the calcination temperature is changed. The obtained Zn3Al-CO3-LDH is placed in a crucible and heated to 400°C and 300°C respectively in a muffle furnace at a heating rate of 5°C / min, and held for 3 hours. After cooling to a suitable temperature, it is taken out to obtain white powder, namely Zn3Al-LDO-400-3h and Zn3Al-LDO-300-3h.

[0067] The catalytic effects of Examples 12-17 are shown in the table below:

[0068] Example 12 150 mg catalyst, 100 °C, 3 h LDO: 90.7% Example 13 150 mg catalyst, 100 °C, 3 h LDO: 91.2% Example 14 150 mg catalyst, 100 °C, 3 h LDO: 92.5% Example 15 150 mg catalyst, 100 °C, 3 h LDO: 74.2% Example 16 150 mg catalyst, 100 °C, 3 h LDO: 88.3% Example 17 150 mg catalyst, 100 °C, 3 h LDO: 84.6%

[0069] It can be seen that when calcining for the same 6 hours, the LDO catalytic effect obtained by calcination temperature is not much different between 200-500℃. However, after shortening the calcination time, it was found that 300℃ or 400℃ cannot achieve the effect of 500℃ at 3 hours. Therefore, the optimal calcination condition is 500℃ for 3 hours.

[0070]

Examples 18-23

[0071] The hydrolysis catalysis experiment was conducted under the same procedures and conditions as in [Example 2], except that the catalyst used was Zn3Al-LDO-500-3h from [Example 14]. The same amounts of EC and catalyst were used, but the ester-to-water ratio was changed. 0.4 g, 0.6 g, 0.8 g, 1.2 g, 1.4 g, and 1.6 g of deionized water were added, resulting in ester-to-water ratios of 1:1, 1:1.5, 1:2, 1:3, 1:3.5, and 1:4, respectively. The reaction was carried out in a 100°C oil bath under reflux with stirring for 3 hours at a stirring speed of 400 r / min. After the reaction, the reaction solution was analyzed using gas chromatography-mass spectrometry (GC-MS).

[0072] The catalytic effects of Examples 18-23 are shown in the table below:

[0073]

[0074]

[0075]

Examples 24-26

[0076] The hydrolysis catalysis experiment was conducted under the same procedures and conditions as in [Example 2], except that the same amounts of EC, catalyst, and ester-to-water ratio were used. The catalyst used was Zn3Al-LDO-500-3h from [Example 14], and the oil bath temperatures were varied, using oil baths at 100℃, 90℃, 80℃, and 70℃ for 3 hours each, with a stirring speed of 400 r / min. After the reaction, the reaction solution was analyzed using gas chromatography-mass spectrometry (GC-MS).

[0077] The catalytic effects of Examples 24-26 are shown in the table below:

[0078] Example 14 150 mg catalyst, 100 °C, 3 h, ester-to-water ratio 2:1 LDO: 92.0% Example 24 150 mg catalyst, 90℃ for 3 hours, ester-to-water ratio 2:1 LDO: 63.3% Example 25 150 mg catalyst, 80℃ for 3 hours, ester-to-water ratio 2:1 LDO: 32.9% Example 26 150 mg catalyst, 70℃ for 3 hours, ester-to-water ratio 2:1 LDO: 20.4%

[0079]

Examples 27-32

[0080] The hydrolysis catalysis experiment was conducted under the same procedures and conditions as in [Example 2], using the same amount of EC, ester-to-water ratio, and oil bath temperature. The only difference was that the catalyst used was Zn3Al-LDO-500-3h from [Example 14], with varying amounts of catalyst: 160 mg, 150 mg, 140 mg, 130 mg, 120 mg, 110 mg, and 100 mg. The reaction was carried out in a 100°C oil bath under reflux for 3 hours with stirring at 400 rpm. After the reaction, the reaction solution was analyzed using gas chromatography-mass spectrometry (GC-MS).

[0081] The catalytic effects of Examples 27-32 are shown in the table below:

[0082] Example 27 160 mg catalyst, 100 °C, 3 h, ester-to-water ratio 2:1 LDO: 94.1% Example 14 150 mg catalyst, 100 °C, 3 h, ester-to-water ratio 2:1 LDO: 92.0% Example 28 140 mg catalyst, 100 °C, 3 h, ester-to-water ratio 2:1 LDO: 92.4% Example 29 130 mg catalyst, 100 °C, 3 h, ester-to-water ratio 2:1 LDO: 92.7% Example 30 120 mg catalyst, 100 °C, 3 h, ester-to-water ratio 2:1 LDO: 88.4% Example 31 110 mg catalyst, 100℃ for 3 hours, ester-to-water ratio 2:1 LDO: 86.7% Example 32 100 mg catalyst, 100 °C, 3 h, ester-to-water ratio 2:1 LDO: 82.1%

[0083]

Examples 33-41

[0084] The hydrolysis catalysis experiment was conducted under the same procedures and conditions as in [Example 2], using the same amount of EC, ester-to-water ratio, and oil bath temperature. The only differences were the catalyst used: Zn3Al-LDO-500-3h from [Example 14], and the catalyst dosage: 130 mg from [Example 31]. Different reaction times were observed: 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, and 5 h. The stirring speed was 400 r / min. After the reaction, the reaction solution was analyzed using gas chromatography-mass spectrometry (GC-MS).

[0085] The catalytic effects of Examples 33-41 are shown in the table below:

[0086]

[0087]

[0088]

Examples 42-46

[0089] Because hydrolysis can cause water poisoning of the catalyst, resulting in decreased activity, calcination activation is required before it can be used in the next round of reaction. The exploratory cycle experiment was conducted under the same procedures and conditions as in [Example 2]. The catalyst from [Example 29] was collected by centrifugation and washed with anhydrous ethanol until no impurity peaks were observed on the gas chromatograph (washed 4 times). It was then dried under an infrared lamp and placed in a muffle furnace, heated to 200°C, 300°C, 400°C, and 500°C at a heating rate of 5°C / min, and held for 3 hours for calcination regeneration and activation. The catalytic effect was evaluated at each stage.

[0090] The catalytic effects of Examples 42-46 are shown in the table below:

[0091]

[0092] It can be seen that re-calcining and activating at 300℃ for 3 hours can restore LDO to its original activity.

[0093]

Example 47

[0094] The cyclic experiment procedure and conditions were the same as in [Example 2]. The catalyst after the reaction in [Example 39] was collected by centrifugation and washed with anhydrous ethanol until no impurity peaks were observed on the gas chromatograph (washed 4 times). It was dried under an infrared lamp and then placed in a muffle furnace and heated to 300°C at a heating rate of 5°C / min, held for 3 hours, and then calcined to regenerate and activate it, thus obtaining Zn3Al-LDO-500-3 recalcined. This was then reacted under the same conditions as in [Example 39], which constituted the first round of the cyclic reaction. This cyclic reaction was repeated five times.

[0095] The catalytic effects of the five-cycle cycle are shown in the table below:

[0096] Example 39 130 mg catalyst, 100 °C, 4 h, ester-to-water ratio 2:1 LDO: 99.2% First round of cycles 130 mg catalyst, 100 °C, 4 h, ester-to-water ratio 2:1 LDO: 99.5% Second round of cycling 130 mg catalyst, 100 °C, 4 h, ester-to-water ratio 2:1 LDO: 99.3% Third round of cycling 130 mg catalyst, 100 °C, 4 h, ester-to-water ratio 2:1 LDO: 98.8% Fourth cycle 130 mg catalyst, 100 °C, 4 h, ester-to-water ratio 2:1 LDO: 97.5% Fifth cycle 130 mg catalyst, 100 °C, 4 h, ester-to-water ratio 2:1 LDO: 97.9%

Claims

1. A method for synthesizing ethylene glycol by hydrolysis of ethylene carbonate, characterized in that: Using LDO, a mixed metal oxide obtained by calcining zinc-aluminum hydrotalcite compound LDH at 200–800 °C for 2–6 h, as a catalyst, ethylene glycol is synthesized by hydrolysis of ethylene carbonate. Ethylene glycol is generated by reacting ethylene carbonate and water at a reaction temperature of 70–100 °C, a molar ratio of water to ethylene carbonate of 1–5, a catalyst mass fraction of 5% wt% to 8% wt% relative to the substrate ethylene carbonate, and a reaction time of 1–5 hours.

2. The method according to claim 1, characterized in that: The mixed metal oxide LDO obtained by calcining zinc-aluminum hydrotalcite compound LDH at 400-500℃ for 3-6 h was used as a catalyst.

3. The method according to claim 1, characterized in that: The preparation of hydrotalcite-based materials includes the following steps: 1) M II and M III Dissolve the soluble salt in water to prepare solution A; dissolve the mixed alkali in water to prepare solution B; M II Zn 2+ M III For Al 3+ ; The M II M III The soluble salts are selected from at least one or more of nitrates, sulfates, or halides; The mixed alkali is a mixture of sodium hydroxide and sodium carbonate dissolved in water; Among them, M is expressed as a molar ratio. II With M III The molar ratio is 2:1 to 4:1, and the molar relationship between the mixed salt and the mixed alkali is n(OH) - )=2n(M II +M III ), n(CO3) 2- )=n(M III ); 2) Using the co-precipitation method, add solutions A and B dropwise into the base solution water at room temperature while stirring, and control the pH in the range of 9-10; 3) After the addition is complete, age at 65℃ for one day; 4) Centrifuge the turbid liquid obtained in step 3) and wash with water until the washing liquid is neutral; 5) Dry the obtained solid to obtain zinc-aluminum hydrotalcite compound LDH.

4. The method according to claim 1 or 2, characterized in that, After recovering the catalyst from the previous reaction, it was washed with anhydrous ethanol until no impurity peaks were observed on the gas chromatograph. The catalyst was then dried under an infrared lamp and calcined in a muffle furnace for activation.

5. The method according to claim 1, characterized in that, The reaction also includes a catalyst activation and regeneration process, specifically, the recovered catalyst is washed with anhydrous ethanol and then calcined and activated in a muffle furnace at 200~500℃ for 2~5h in an air atmosphere.

6. The method according to claim 5, characterized in that, The catalyst activation and regeneration process specifically involves washing the recovered catalyst with anhydrous ethanol and then calcining it in a muffle furnace at 300-500°C for 3-5 hours in an air atmosphere.

7. The method according to claim 1, characterized in that, The reaction temperature is 90~100℃, the molar ratio of water to ethylene carbonate is 2~3, the weight ratio of catalyst to ethylene carbonate is 6%wt~8%wt, and the reaction time is 3~4 hours.

8. The method according to claim 7, characterized in that, The yield of ethylene glycol was 93.0–99.2%.

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