Catalyst for alcoholysis of glycolic acid oligomer and application thereof

Abstract

The invention relates to the field of chemical waste treatment, and discloses a catalyst for alcoholysis of glycolic acid oligomer and application of the catalyst. On the basis of the total weight of the catalyst, the catalyst is prepared from the following components in percentage by weight: 20 to 70 percent of zinc oxide, 10 to 35 percent of cadmium oxide, 10 to 35 percent of aluminum oxide and 0.1 to 15 percent of cerium oxide. The catalyst provided by the invention has good glycolic acid oligomer treatment performance, and by adopting a preferable implementation mode, the realization of continuous production of glycolic acid esters and ethylene glycol from the oligomer is facilitated, the production process is reduced, the defect that a traditional intermittent kettle is not beneficial to capacity expansion is overcome, and the catalyst has important significance for realizing large-scale industrial application.

Description

Technical Field

[0001] This invention relates to the field of chemical waste treatment, specifically to a catalyst for the alcoholysis of glycolic acid oligomers and its application. Background Technology

[0002] Plastics, synthetic rubber, and synthetic fibers are known as the three major modern polymer materials. With the development of society and the economy, the use of plastic products has brought great convenience to people's daily lives and production, and has become an indispensable material in daily life.

[0003] Polyglycolic acid (PGA), also known as polyglycolic acid, is a highly crystalline, biodegradable aliphatic polymer with advantages such as rapid degradation. It is mainly used in medical consumables and agricultural films. Currently, the main industrial production processes for methyl glycolate (MG) in China are chloroacetic acid hydrolysis and formaldehyde carbonylation followed by esterification. These routes are complex, lengthy, costly, and cause severe environmental pollution with low yields of the target product. Therefore, a new approach is to use coal-to-syngas to produce dimethyl oxalate (DMO), followed by hydrogenation of DMO to produce methyl glycolate and then polyglycolic acid (PGA). However, this route generates a large amount of oligomerizing byproducts, such as glycolate esters. If these byproducts can be fully recovered, it could bring considerable economic benefits.

[0004] Therefore, it is of great significance to develop a catalyst that can efficiently treat oligomers in fusel oil, a byproduct of the PGA process, and a method for recovering glycol esters. Summary of the Invention

[0005] The purpose of this invention is to overcome the aforementioned problems in the prior art and to provide a catalyst for the alcoholysis of glycolic acid oligomers and its application.

[0006] To achieve the above objectives, the present invention provides a catalyst for the alcoholysis of glycolic acid oligomers, wherein, based on the total weight of the catalyst, the catalyst comprises: 20-70% by weight of zinc oxide, 10-35% by weight of cadmium oxide, 10-35% by weight of aluminum oxide, and 0.1-15% by weight of cerium oxide.

[0007] A second aspect of the present invention provides a method for preparing glycolate esters from glycolic acid oligomers, the method comprising: contacting a glycolic acid oligomer raw material with a lower alcohol in the presence of a catalyst; wherein the catalyst is the catalyst provided in the first aspect of the present invention.

[0008] A third aspect of the present invention provides the application of the catalyst described above in the alcoholysis of glycolic acid oligomers.

[0009] The catalyst of this invention has excellent performance in treating glycolic acid oligomers. Furthermore, by adopting the preferred embodiment of this invention, it is beneficial to achieve continuous production of glycolate esters and ethylene glycol from these oligomers, reducing the production process and overcoming the drawbacks of traditional batch reactors that are not conducive to expanding production capacity. This is of great significance for realizing large-scale industrial applications. Detailed Implementation

[0010] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0011] The first aspect of the present invention provides a catalyst for the alcoholysis of glycolic acid oligomers, wherein, based on the total weight of the catalyst, the catalyst comprises: 20-70% by weight of zinc oxide, 10-35% by weight of cadmium oxide, 10-35% by weight of aluminum oxide and 0.1-15% by weight of cerium oxide.

[0012] According to the present invention, preferably, the catalyst comprises 30-60% by weight of zinc oxide, based on the total weight of the catalyst.

[0013] According to the present invention, preferably, the catalyst comprises 15-30% by weight of cadmium oxide, based on the total weight of the catalyst.

[0014] According to the present invention, preferably, the catalyst comprises 15-30% by weight of aluminum oxide, based on the total weight of the catalyst.

[0015] According to the present invention, preferably, the catalyst comprises 1-10% by weight of cerium oxide, based on the total weight of the catalyst.

[0016] In this invention, the type and content of the catalyst are within the above-mentioned range, which can further ensure the overall performance of the catalyst.

[0017] According to the present invention, preferably, the average particle size of the catalyst is 5-500 nm.

[0018] In this invention, the catalyst preparation method can be a conventional catalyst preparation method in the art. Preferably, the catalyst preparation method includes: mixing the above-mentioned metal precursor and / or metal oxide (preferably the metal precursor), followed by aging, solid-liquid separation, washing, drying, and calcination to obtain the catalyst. It is understood that the amount of metal precursor and / or metal oxide used ensures that the content of zinc oxide, cadmium oxide, aluminum oxide, and cerium oxide in the catalyst is as described above.

[0019] In this invention, the precursor of metallic zinc is selected from at least one of soluble zinc salts, preferably one of zinc nitrate, zinc sulfate, zinc chloride and zinc acetate, and more preferably zinc nitrate.

[0020] In this invention, the precursor of metallic cadmium is selected from at least one of soluble cadmium salts, preferably one of cadmium nitrate and cadmium bicarbonate, and more preferably cadmium nitrate.

[0021] In this invention, the precursor of metallic aluminum is selected from at least one of soluble aluminum salts, preferably aluminum nitrate.

[0022] In this invention, the precursor of metallic cerium is selected from at least one of soluble cerium salts, preferably one of cerium nitrate, cerium sulfate, cerium chloride and cerium acetate, and more preferably zinc nitrate.

[0023] Preferably, the aging conditions include: a temperature of 50-80°C, a pH of 6.8-8, and a time of 0.5-3 hours.

[0024] Preferably, the drying conditions include: a temperature of 100-140°C and a time of 6-15 hours.

[0025] Preferably, the roasting conditions include: a temperature of 300-400℃ and a time of 2-6 hours.

[0026] In a preferred embodiment of the present invention, the catalyst preparation method includes: dissolving nickel nitrate, cadmium nitrate, aluminum nitrate, and cerium nitrate in deionized water, stirring and heating to 40-90°C, adding an alkaline precipitant dropwise and adjusting the pH to 5-8, stirring until a precipitate is formed, and then aging at 40-90°C for 1-4 hours; filtering and washing the aged precipitate, and drying it at 100-120°C for 10-20 hours; and then calcining it at 350-400°C for 2-6 hours to obtain the catalyst. The alkaline precipitant is selected from at least one of ammonia, ammonium carbonate, and ammonium bicarbonate, preferably ammonium bicarbonate.

[0027] A second aspect of the present invention provides a method for preparing glycolate esters from glycolic acid oligomers, the method comprising: contacting a glycolic acid oligomer raw material with a lower alcohol in the presence of a catalyst; wherein the catalyst is the catalyst provided in the first aspect of the present invention.

[0028] The raw material for the glycolic acid oligomers in this invention is a fusel oil containing glycolic acid oligomers. Preferably, the fusel oil containing glycolic acid oligomers includes at least one of ethylene glycol, glycolic acid, and glycolate, as well as oligomers generated by polymerization of at least one of ethylene glycol, glycolic acid, and glycolate. The oligomers are homopolymers or copolymers produced by polymerization of glycolic acid, glycolate, and ethylene glycol, for example, the oligomers can be ethylene glycol glycolate, ethylene glycol diglycolate, and diglycolate.

[0029] According to the present invention, preferably, the weight-average molecular weight of the oligomer is 200-5000 g / mol. In this invention, the weight-average molecular weight of the oligomer is determined by high-performance permeation gel chromatography (GPC).

[0030] According to the present invention, preferably, the content of the oligomer in the raw material of the glycolic acid oligomer is 5 wt%, more preferably 10-80 wt%, and can be any two values ​​from 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 70 wt%, 75 wt%, 80 wt%, 82 wt%, forming a range or a value within that range.

[0031] In this invention, the raw materials for the glycolic acid oligomers also include at least one of ethylene glycol, glycolic acid, and glycolate.

[0032] According to the present invention, preferably, the content of ethylene glycol in the raw material of the glycolic acid oligomer is 15-80 wt%, which can be any two values ​​formed by 15 wt%, 18 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 70 wt%, 75 wt%, and 80 wt%, or a value within that range.

[0033] According to the present invention, preferably, the content of glycolic acid in the raw material of the glycolic acid oligomer is 0-30 wt%, which can be any two values ​​formed by 0, 3 wt%, 5 wt%, 8 wt%, 10 wt%, 13 wt%, 15 wt%, 18 wt%, 20 wt%, 25 wt%, 28 wt%, and 30 wt%, or a value within that range.

[0034] According to the present invention, preferably, the content of the glycolate in the raw material of the glycolic acid oligomer is 0-10 wt%, which can be any two values ​​formed by 0, 1 wt%, 2 wt%, 3 wt%, 5 wt%, 7 wt%, 9 wt%, and 10 wt%, or a value within that range.

[0035] In this invention, when the raw material for the glycolic acid oligomer is a fusel oil containing glycolic acid oligomers produced by hydrogenation of dimethyl oxalate, it usually also contains heavy impurities, with a content of 5-15 wt%. The content can be any two values ​​from 5 wt%, 6 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, and 15 wt%, or any value within that range.

[0036] According to the present invention, preferably, the weight ratio of the glycolic acid oligomer raw material to the lower alcohol is 1:0.5-28, which can be any two values ​​formed by 1:0.5, 1:2, 1:5, 1:8, 1:10, 1:12, 1:15, 1:18, 1:20, 1:25, and 1:28, or values ​​within that range, preferably 1:1-7, wherein the weight of the glycolic acid oligomer raw material is based on the weight of the glycolic acid oligomer. Using the aforementioned preferred weight ratio of glycolic acid oligomer raw material to lower alcohol is beneficial for further improving the conversion rate of glycolate oligomers. An appropriate alcohol content can reduce costs without affecting the reaction process.

[0037] According to the present invention, preferably, the lower alcohol is at least one of C1-C5 alcohols, which may be methanol, ethanol and propanol, and reacts with glycolic acid oligomers to generate glycolate esters, namely methyl glycolate, ethyl glycolate and propyl glycolate, respectively, and more preferably methanol.

[0038] According to a preferred embodiment of the present invention, the methanol may further include a small amount of low-boiling-point esters with a boiling point of 50-90°C, such as methyl acetate and ethyl acetate. Preferably, the content of low-boiling-point esters in the alcohol is less than or equal to 20 wt%, more preferably less than or equal to 10 wt%. When the methanol does not contain low-boiling-point esters, the recovered methyl glycolate has a higher yield and purity.

[0039] In this invention, the amount of catalyst packed in the fixed bed per unit time is not particularly limited, as long as it allows for the complete alcoholysis of glycolic acid oligomers. Preferably, the amount of catalyst packed in the fixed bed results in a liquid hourly space velocity (LHSV) of 0.05-5 h⁻¹. -1 Preferably 0.2-2h -1 .

[0040] According to the present invention, preferably, the contact conditions include: a reaction temperature of 80-200°C, a reaction pressure of 0.1-6 MPa, and a reaction time of 10-120 min; more preferably, an inert atmosphere, a temperature of 110-170°C, a pressure of 1-3 MPa, and a reaction time of 15-60 min.

[0041] According to a preferred embodiment of the present invention, the reaction is carried out in a continuously fed apparatus, wherein the continuously fed apparatus may be a continuously fed fixed bed or a continuously stirred reactor, and is more preferably a continuously fed fixed bed.

[0042] This invention provides a method for the continuous preparation of glycolate esters. The process is simple, involving the transesterification reaction of glycolate oligomers with lower alcohols in the presence of a catalyst in a fixed bed to obtain glycolate ester products. This method enables the continuous conversion of high-boiling-point substances such as ester oligomers, reducing other impurities in fusel oils without generating new byproducts, and recovering glycolate esters and / or ethylene glycol. Furthermore, the fixed-bed design simplifies the production process and facilitates the efficient and continuous conversion of ester oligomers.

[0043] According to a preferred embodiment of the present invention, a method for treating fusel oil containing glycolic acid oligomers includes the following steps: The catalyst provided by the present invention is loaded into a fixed bed, with both ends fixed by inert packing; the fusel oil containing glycolic acid oligomers and lower alcohols are mixed and fed into the fixed bed from top to bottom or bottom to top to react with the catalyst, under the reaction conditions as described above. After the reaction, the reaction liquid is pressurized and removed from a gas-liquid separator, and the reaction liquid is separated into high-purity glycolic acid esters and ethylene glycol by a distillation system. The inert packing is conventionally selected in the art, preferably quartz sand.

[0044] According to the most preferred embodiment of the present invention, the method for preparing glycolate esters from glycolic acid oligomers includes:

[0045] Catalyst preparation: Nickel nitrate, cadmium nitrate, aluminum nitrate, and cerium nitrate are dissolved in deionized water, stirred, and heated to 60-80℃. An alkaline precipitant is added dropwise and the pH is adjusted to 7-8. The mixture is stirred until a precipitate is formed, and then aged at 60-80℃ for 1-1.5 hours. The aged precipitate is filtered, washed, and dried at 115-125℃ for 10-13 hours. Then, it is calcined at 350-370℃ for 3-5 hours to obtain the catalyst. The amounts of nickel nitrate, cadmium nitrate, aluminum nitrate, and cerium nitrate are such that the catalyst contains 47-52% by weight of ZnO, 17-23% by weight of CdO, 22-28% by weight of Al2O3, and 3-6% by weight of CeO2.

[0046] The continuous alcoholysis of glycolic acid oligomers is achieved under the action of a catalyst: the catalyst is added to a fixed bed, and fusel oil and methanol are contacted with the catalyst, wherein the weight ratio of fusel oil to methanol is 1:2.5-3.5. The pressure in the fixed bed, i.e., the reaction pressure, is 1.5-2.5 MPa, the reaction temperature is 145-165℃, the reaction time is 40-60 min, and the catalyst loading is such that the liquid hourly space velocity of the mixture of fusel oil and methanol is 0.8-1.3 h⁻¹. -1 .

[0047] The third invention provides the application of the catalyst as described above in the alcoholysis of glycolic acid oligomers. The amount of catalyst used, as well as the reaction method and conditions for the alcoholysis of glycolic acid oligomers, are as provided in the first and second aspects above, and will not be repeated here.

[0048] The present invention will be described in detail below through examples. Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0049] The composition of this invention was determined by gas chromatography using the normalization method; the type and content of each component were determined by chromatographic peaks. The specific molecular structures of heavy impurities and oligomers were difficult to determine. However, because their retention times in the chromatogram were fixed, and the content of oligomers changed significantly after the reaction, while the content of heavy impurities remained unchanged before and after the reaction, the type and content of each component could be determined accordingly.

[0050] Fusel oil composition: methyl glycolate 5wt%, ethylene glycol 22wt%, glycolate oligomer 63wt%, heavy impurities 10wt%;

[0051] Conversion rate of oligomers % = (weight of oligomers in fusel oil - weight of oligomers in reaction products) ÷ weight of oligomers in fusel oil × 100%;

[0052] Selectivity of glycolate esters % = (Weight of glycolate esters in reaction products - Weight of glycolate esters in fusel oil) ÷ (Weight of oligomers in fusel oil - Weight of oligomers in reaction products) × 100%;

[0053] The selectivity of ethylene glycol (%) = (weight of ethylene glycol in the reaction product - weight of ethylene glycol in the fusel oil) ÷ (weight of oligomers in the fusel oil - weight of oligomers in the reaction product) × 100%.

[0054] Example 1

[0055] Catalyst preparation:

[0056] Weigh appropriate amounts of nickel nitrate, cadmium nitrate, aluminum nitrate, and cerium nitrate and dissolve them in 2000 mL of deionized water. While stirring continuously, heat the prepared solution to 70°C. Add 10 wt% ammonium bicarbonate solution dropwise to the aforementioned solution until the pH reaches 7.2. Maintain the temperature and stir for 1 hour, filter, wash, dry at 120°C for 12 hours, and then calcine at 350°C for 4 hours. The resulting catalyst is then shaped and ready for use. The average particle size of this catalyst is 80 nm, denoted as S1. The amounts of nickel nitrate, cadmium nitrate, aluminum nitrate, and cerium nitrate are such that the catalyst contains 50 wt% ZnO, 20 wt% CdO, 25 wt% Al2O3, and 5 wt% CeO2.

[0057] Continuous alcoholysis of glycolic acid oligomers:

[0058] The S1 catalyst was loaded into a fixed-bed reactor, and fusel oil and methanol were pumped in using a top-in, bottom-out feed method. The weight ratio of fusel oil to methanol was 1:3, the reaction pressure was 2 MPa, the reaction temperature was 150 °C, and the S1 catalyst loading was such that the liquid hourly space velocity (LHSV) of the fusel oil and methanol mixture was 1 h⁻¹. -1 The reaction time was 50 min. After the reaction, the reaction liquid was pressurized and removed from the gas-liquid separator. The contents of oligomers, methyl glycol, and ethylene glycol in the liquid after the reaction were analyzed by chromatography, and the conversion rate of oligomers, the selectivity of methyl glycol, and the selectivity of ethylene glycol were calculated. The results are shown in Table 1.

[0059] Example 2

[0060] Catalyst preparation:

[0061] The S2 catalyst was prepared according to the method of Example 1, except that the average particle size of the catalyst was 95 nm, and the amounts of nickel nitrate, cadmium nitrate, aluminum nitrate and cerium nitrate were such that the content of ZnO in the catalyst was 40 wt%, the content of CdO was 30 wt%, the content of Al2O3 was 10 wt%, and the content of CeO2 was 10 wt%.

[0062] Continuous alcoholysis of glycolic acid oligomers:

[0063] The S2 catalyst was loaded into a fixed-bed reactor, and fusel oil and methanol were pumped in using a top-in, bottom-out feed method. The weight ratio of fusel oil to methanol was 1:5, the reaction pressure was 3 MPa, the reaction temperature was 120℃, and the S2 catalyst loading resulted in a liquid hourly space velocity (LHSV) of 1.5 h⁻¹ for the fusel oil and methanol mixture. -1 The reaction time was 40 min. After the reaction, the conversion rate of the oligomer, the selectivity of methyl glycolate, and the selectivity of ethylene glycol were calculated, and the results are shown in Table 1.

[0064] Example 3

[0065] Catalyst preparation:

[0066] The S3 catalyst was prepared according to the method of Example 1, except that the average particle size of the catalyst was 120 nm, and the amounts of nickel nitrate, cadmium nitrate, aluminum nitrate and cerium nitrate were such that the content of ZnO in the catalyst was 70 wt%, the content of CdO was 10 wt%, the content of Al2O3 was 7 wt%, and the content of CeO2 was 3 wt%.

[0067] Continuous alcoholysis of glycolic acid oligomers:

[0068] S3 catalyst was loaded into a fixed-bed reactor, and fusel oil and methanol were pumped in using a top-in, bottom-out feed method. The weight ratio of fusel oil to methanol was 1:1, the reaction pressure was 1 MPa, the reaction temperature was 170℃, and the S3 catalyst loading was such that the liquid hourly space velocity (LHSV) of the fusel oil and methanol mixture was 2 h⁻¹. -1 The reaction time was 60 min. After the reaction, the conversion rate of oligomers, the selectivity of methyl glycolate, and the selectivity of ethylene glycol were calculated, and the results are shown in Table 1.

[0069] Example 4

[0070] Catalyst preparation:

[0071] The S4 catalyst was prepared according to the method of Example 1, except that the average particle size of the catalyst was 89 nm, and the amounts of nickel nitrate, cadmium nitrate, aluminum nitrate and cerium nitrate were such that the content of ZnO in the catalyst was 30 wt%, the content of CdO was 30 wt%, the content of Al2O3 was 30 wt%, and the content of CeO2 was 10 wt%.

[0072] Continuous alcoholysis of glycolic acid oligomers:

[0073] The S4 catalyst was loaded into a fixed-bed reactor, and fusel oil and methanol were pumped in using a top-in, bottom-out feed method. The weight ratio of fusel oil to methanol was 1:2, the reaction pressure was 2 MPa, and the reaction temperature was 110 °C. The S3 catalyst loading amount resulted in a liquid hourly space velocity (LHSV) of 0.2 h⁻¹ for the fusel oil and methanol mixture. -1 The reaction time was 70 min. After the reaction, the conversion rate of oligomers, the selectivity of methyl glycolate, and the selectivity of ethylene glycol were calculated, and the results are shown in Table 1.

[0074] Example 5

[0075] Catalyst preparation:

[0076] The S5 catalyst was prepared according to the method of Example 1, except that the average particle size of the catalyst was 97 nm, and the amounts of nickel nitrate, cadmium nitrate, aluminum nitrate and cerium nitrate were such that the content of ZnO in the catalyst was 60 wt%, the content of CdO was 19 wt%, the content of Al2O3 was 20 wt%, and the content of CeO2 was 1 wt%.

[0077] Continuous alcoholysis of glycolic acid oligomers:

[0078] The S5 catalyst was loaded into a fixed-bed reactor, and fusel oil and methanol were pumped in using a top-in, bottom-out feed method. The weight ratio of fusel oil to methanol was 1:4, the reaction pressure was 1.5 MPa, and the reaction temperature was 140 °C. The S3 catalyst loading amount resulted in a liquid hourly space velocity (LHSV) of 0.6 h⁻¹ for the fusel oil and methanol mixture. -1 The reaction time was 40 min. After the reaction, the conversion rate of the oligomer, the selectivity of methyl glycolate, and the selectivity of ethylene glycol were calculated, and the results are shown in Table 1.

[0079] Example 6

[0080] The method of Example 1 was followed to obtain glycolates and ethylene glycol by alcoholysis of fusel oil. The difference was that, during the alcoholysis of glycolate oligomers, the weight ratio of fusel oil to ethanol was 1:10, the reaction pressure was 5 MPa, the reaction temperature was 180°C, and the S1 catalyst loading was such that the liquid hourly space velocity of the mixture of fusel oil and methanol was 4 h⁻¹. -1 The reaction time was 40 min. After the reaction, the conversion rate of the oligomer, the selectivity of methyl glycolate, and the selectivity of ethylene glycol were calculated, and the results are shown in Table 1.

[0081] Comparative Example 1

[0082] The alcoholysis of fusel oil was carried out according to the method in Example 1 to obtain glycolate and ethylene glycol, except that no catalyst was added during the reaction. After the reaction, the conversion rate of oligomers, the selectivity of methyl glycolate, and the selectivity of ethylene glycol were calculated, and the results are shown in Table 1.

[0083] Comparative Example 2

[0084] The reaction of fusel oil with alcoholysis to obtain glycolate and ethylene glycol was carried out according to the method of Example 1. The difference was that the catalyst added in the reaction was a conventional catalyst in the art, and the catalyst composition contained 40% by weight of zinc oxide, 30% by weight of iron oxide, 25% by weight of aluminum oxide, and 5% by weight of lanthanum oxide. After the reaction, the conversion rate of oligomers, the selectivity of methyl glycolate, and the selectivity of ethylene glycol were calculated, and the results are shown in Table 1.

[0085] Comparative Example 3

[0086] The reaction was carried out according to the method in Example 1, reacting fusel oil to obtain glycolate and ethylene glycol, except that CdO in the catalyst was replaced with MgO. After the reaction, the conversion rate of oligomers, the selectivity of methyl glycolate, and the selectivity of ethylene glycol were calculated, and the results are shown in Table 1.

[0087] Comparative Example 4

[0088] The reaction of fusel oil with alcoholysis to obtain glycolate and ethylene glycol was carried out according to the method of Example 1, except that CeO2 in the catalyst was replaced with lanthanum oxide. After the reaction, the conversion rate of oligomers, the selectivity of methyl glycolate, and the selectivity of ethylene glycol were calculated, and the results are shown in Table 1.

[0089] Comparative Example 5

[0090] The reaction was carried out according to the method in Example 1, reacting fusel oil to obtain glycolate and ethylene glycol, except that Al2O3 was replaced with magnesium oxide in the catalyst. After the reaction, the conversion rate of oligomers, the selectivity of methyl glycolate, and the selectivity of ethylene glycol were calculated, and the results are shown in Table 1.

[0091] Comparative Example 6

[0092] The method of Example 1 was followed to react the fusel oil to obtain glycolate and ethylene glycol, except that only ZnO was present in the catalyst. After the reaction, the conversion rate of oligomers, the selectivity of methyl glycolate, and the selectivity of ethylene glycol were calculated, and the results are shown in Table 1.

[0093] Comparative Example 7

[0094] The reaction was carried out according to the method in Example 1, reacting fusel oil to obtain glycolate and ethylene glycol, except that Al2O3 and CeO2 in the catalyst were replaced with MgO. After the reaction, the conversion rate of oligomers, the selectivity of methyl glycolate, and the selectivity of ethylene glycol were calculated, and the results are shown in Table 1.

[0095] Table 1

[0096]

[0097]

[0098] As can be seen from the results in Table 1, the catalysts prepared in Examples 1-6 of this invention significantly improve the alcoholysis effect of glycolic acid oligomers and effectively recover glycolates and ethylene glycol. The preferred embodiments of this invention can achieve higher glycolic acid oligomer conversion rates and better selectivity for glycolates and ethylene glycol.

[0099] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A catalyst for the alcoholysis of glycolic acid oligomers, characterized in that, Based on the total weight of the catalyst, the catalyst comprises: 20-70% by weight of zinc oxide, 10-35% by weight of cadmium oxide, 10-35% by weight of aluminum oxide and 0.1-15% by weight of cerium oxide.

2. The catalyst according to claim 1, wherein, Based on the total weight of the catalyst, the catalyst comprises: 30-60% by weight of zinc oxide, 15-30% by weight of cadmium oxide, 15-30% by weight of aluminum oxide and 1-10% by weight of cerium oxide.

3. The catalyst according to claim 1, wherein, The catalyst has an average particle size of 5-500 nm.

4. A method for preparing glycolate esters from glycolic acid oligomers, characterized in that, The method includes: contacting a raw material of glycolic acid oligomers with a lower alcohol in the presence of a catalyst; The catalyst is the catalyst according to any one of claims 1-3.

5. The method according to claim 4, wherein, The raw material for the glycolic acid oligomers is fusel oil containing glycolic acid oligomers; Preferably, the fusel oil containing glycolic acid oligomers includes at least one of ethylene glycol, glycolic acid, and glycolate, as well as oligomers generated by polymerization of at least one of ethylene glycol, glycolic acid, and glycolate. Preferably, the weight-average molecular weight of the oligomer is 200-5000 g / mol.

6. The method according to claim 5, wherein, The content of the oligomer in the raw material of the glycolic acid oligomer is 5 wt% or more, preferably 10-80 wt%; Preferably, the content of ethylene glycol in the raw material of the glycolic acid oligomer is 15-80 wt%, the content of glycolic acid is 0-30 wt%, and the content of glycolate is 0-10 wt%.

7. The method according to claim 4, wherein, The weight ratio of the raw material to the lower alcohol of the glycolic acid oligomer is 1:0.5-28, preferably 1:1-7, and the weight of the raw material of the glycolic acid oligomer is based on the weight of the glycolic acid oligomer. And / or, the lower alcohol is at least one of C1-C5 alcohols, preferably methanol.

8. The method according to claim 4, wherein, The catalyst is packed in a continuously fed fixed bed or reactor, and the liquid hourly space velocity (LHSV) of the mixture of the glycolic acid oligomer and the lower alcohol is 0.05-5 h⁻¹. -1 Preferably 0.2-2h -1 .

9. The method according to claim 4, wherein, The contact conditions include: a temperature of 80-200℃, a pressure of 0.1-6MPa, and a time of 10-120min; Preferably, the contact conditions include: a temperature of 110-170°C, a pressure of 1-3 MPa, and a time of 15-60 min; And / or, the contact is carried out in a continuously fed apparatus, which includes a continuously fed fixed bed or a continuously stirred tank reactor, preferably a continuously fed fixed bed.

10. The use of the catalyst according to any one of claims 1-3 in the alcoholysis of glycolic acid oligomers.

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