Preparation method of degradable polyether amine

Abstract

The invention relates to a preparation method of degradable polyether amine. Comprising the following steps: mixing ethyl acetoacetate and isopropanolamine, and reacting under the action of a rare earth modified solid acid catalyst to obtain 3-oxobutyric acid-2-aminopropyl ester; the preparation method comprises the following steps: mixing 3-oxobutyric acid-2-aminopropyl ester with polyether amine, and reacting under the action of an imidization catalyst to prepare the degradable polyether amine. The solid acid catalyst is modified by rare earth, the reaction activity of the solid acid catalyst is improved, the imidization catalyst is modified by Lewis acid, and the conversion rate and selectivity of the product degradable polyether amine are improved. The catalyst provided by the invention can show high activity and high selectivity in application, the production process is environment-friendly, and less three wastes are generated.

Description

Technical Field

[0001] This invention relates to the field of catalysis technology, and more specifically to a method for preparing a biodegradable polyetheramine. Background Technology

[0002] Currently, mainstream biodegradable materials include bio-based polyesters such as polylactic acid (PLA) and polycaprolactone (PCL), as well as starch-based composite materials. Among them, polylactic acid (PLA) has attracted much attention because its raw materials are renewable (such as corn and cassava) and its degradation products are harmless (ultimately decomposing into water and carbon dioxide). However, its heat resistance and toughness still need to be optimized through copolymerization, blending, or the addition of modifiers.

[0003] Existing biodegradable materials still face challenges such as a mismatch between degradation rates and usage requirements, and insufficient mechanical properties. Against this backdrop, biodegradable polyetheramines (PEAs) have emerged as a promising new type of functional material. PEAs are polymers with ether bonds in their main chain and amino groups in their side chains. Their molecular structure can be flexibly controlled through monomer selection and synthetic pathways, endowing the materials with excellent flexibility, biocompatibility, and biodegradability. For example, by introducing dynamic covalent bonds (such as imine bonds) or hydrolyzable groups (such as ester bonds), controlled degradation of the material under specific environments (such as acidic or enzyme-catalyzed conditions) can be achieved.

[0004] CN114195984B discloses a method for preparing a bisphenol A-type epoxy curing agent containing dynamic enamine bonds and a biodegradable epoxy resin. The patent describes a method where hydroxylated bisphenol A monomers and ethyl acetoacetate compounds are reacted in an acidic solution to generate bisphenol A-type epoxy monomers, which are then reacted with the epoxy curing agent to prepare the biodegradable epoxy resin. The drawbacks of this method are that it uses an inorganic strong acid as a catalyst, generating a large amount of waste acid during the production process, which does not conform to the concept of green environmental protection. Furthermore, the acidic catalyst used has relatively weak acid strength, resulting in a low conversion rate.

[0005] CN118240195A discloses a method for preparing an amine-based curing agent containing dynamic enamine bonds and a biodegradable epoxy resin. The patent describes a method of preparing an amine-based curing agent by reacting it with an amine compound esterified with monoacetoacetic acid, and then mixing the curing agent with epoxy resin to prepare a biodegradable epoxy resin. A drawback of this method is that it also uses an inorganic strong acid as a catalyst, resulting in a large amount of waste.

[0006] In summary, existing technologies mainly use inorganic strong acids as catalysts, which generate a large amount of waste acid during the production process. The process does not conform to the concept of green environmental protection, and the acidic catalysts used have relatively weak acid strength, resulting in low conversion rate and selectivity of the reaction. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a method for preparing biodegradable polyetheramine.

[0008] 3-O-butanoic acid-2-aminopropyl ester is prepared by reacting ethyl acetoacetate with isopropanolamine, and then reacting 3-oxobutanoic acid-2-aminopropyl ester with polyetheramine to prepare biodegradable polyetheramine. This process uses a solid acid as a catalyst, abandoning the use of inorganic strong acids as catalysts in existing mainstream processes. It also avoids the generation of large amounts of waste acid during production, and offers advantages such as high product purity, simple process flow, and low emissions of waste gas, wastewater, and solid waste.

[0009] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0010] A method for preparing a biodegradable polyetheramine includes the following steps:

[0011] S1. Ethyl acetoacetate and isopropanolamine were mixed and reacted under the action of rare earth modified solid acid catalyst to obtain 3-oxobutyric acid-2-aminopropyl ester.

[0012] S2: Mix 3-oxobutyric acid-2-aminopropyl ester obtained in step S1 with polyetheramine and react them under the action of an imidization catalyst to obtain degradable polyetheramine.

[0013] The reaction formula is shown below:

[0014]

[0015] The rare earth-modified solid acid catalyst used in step S1 of this invention has an SO4 structure. 2- / M x O y -N x O y M includes, but is not limited to, La and / or Ce, and N includes, but is not limited to, one or more of Si, Zr, Cr, Al, Zn, Ti, Sn, Cr, Fe, and Mo.

[0016] The method for preparing the rare earth modified solid acid catalyst in step S1 of the present invention includes the following steps: first, adding the dry active metal oxide to a sulfate solution containing rare earth elements, stirring, standing, separating, drying, and calcining.

[0017] As a preferred embodiment, in the preparation method of the rare earth modified solid acid catalyst of the present invention, the drying includes: drying the active metal oxide at 100-180℃ for 1-12h, preferably at 120-150℃ for 4-10h.

[0018] As a preferred embodiment, in the method for preparing the rare earth modified solid acid catalyst of the present invention, the mass ratio of the active metal oxide to the sulfate solution containing rare earth elements is 1:(5-10).

[0019] As a preferred embodiment, in the preparation method of the rare earth modified solid acid catalyst of the present invention, stirring is performed for 1-6 hours.

[0020] As a preferred embodiment, in the preparation method of the rare earth modified solid acid catalyst of the present invention, the drying after separation is carried out at 100-150℃ for 1-8 hours, preferably at 120-140℃ for 3-6 hours.

[0021] As a preferred embodiment, in the preparation method of the rare earth modified solid acid catalyst of the present invention, the calcination is carried out at 250-450℃ for 1-6 hours, preferably at 300-400℃ for 2-5 hours.

[0022] As a preferred embodiment, in the method for preparing the rare earth modified solid acid catalyst of the present invention, the mass concentration of the rare earth element sulfate solution is 1-10%, preferably 3-5%.

[0023] As a preferred embodiment, in step S1 of the present invention, the amount of rare earth modified solid acid catalyst added is 0.1-3% of the mass of ethyl acetoacetate.

[0024] As a preferred embodiment, in step S1 of the present invention, the molar ratio of ethyl acetoacetate and isopropanolamine is 1:(1-1.5).

[0025] As a preferred embodiment, in step S1 of the present invention, the reaction pressure is atmospheric pressure.

[0026] As a preferred embodiment, in step S1 of the present invention, the reaction temperature is 100-150℃.

[0027] As a preferred embodiment, in step S1 of the present invention, the reaction time is 4-12 hours.

[0028] As a preferred embodiment, in step S1 of the present invention, the stirring speed is 200-800 rpm.

[0029] As a preferred embodiment, in step S1 of the present invention, 3-oxobutyric acid-2-aminopropyl ester is obtained after post-processing following the reaction. The post-processing includes: removing ethyl acetoacetate and isopropanolamine from the reaction solution under negative pressure at 150°C and 1 kPa absolute pressure to obtain the intermediate product 3-oxobutyric acid-2-aminopropyl ester.

[0030] The method for preparing the imidization catalyst in step S2 of the present invention includes the following steps:

[0031] SS1: The catalyst precursor is obtained by impregnating the support with Lewis acid ethanol solution and drying it.

[0032] SS2: Prepare an aqueous solution of metal salt by mixing soluble rhodium and copper salts. Add the catalyst precursor obtained in step SS1 into the aqueous solution of metal salt for impregnation, then dry and calcine to obtain the imidized catalyst.

[0033] As a preferred embodiment, in step SS1, the Lewis acid includes one or more of AlCl3, BF3, SbCl5, FeBr3, FeCl3, SnCl4, TiCl4, and ZnCl2, preferably one or more of AlCl3, FeCl3, and SnCl4.

[0034] As a preferred embodiment, in step SS1, the mass concentration of the Lewis acid ethanol solution is 0.1-5%, preferably 0.5-2%.

[0035] As a preferred embodiment, in step SS1, the support is a porous oxide, which is one or more of γ-Al2O3, SiO2, TiO2 and ZrO2, with γ-Al2O3 porous support being preferred.

[0036] As a preferred embodiment, the specific surface area of ​​the γ-Al₂O₃ is 100-300 m². 2 / g, preferably 150-250m 2 / g; pore volume 0.2-3ml / g, preferably 1-2ml / g; pore size 2-20nm, preferably 5-10nm.

[0037] As a preferred embodiment, the γ-Al2O3 is in the shape of a sheet, a cylinder, a clover, or a four-leaf clover, with a clover shape being preferred.

[0038] As a preferred embodiment, in step SS1, the impregnation temperature is 50-80℃, preferably 55-75℃; the stirring speed during the impregnation process is 100-800 rpm; and the impregnation time is 1-12 hours.

[0039] As a preferred embodiment, in step SS1, the drying is carried out at 100-150°C, preferably 110-140°C; the drying time is 1-12 hours, preferably 2-10 hours.

[0040] As a preferred embodiment, in step SS2, the ratio of rhodium salt to copper salt is 1:(0.1-0.3) in terms of metal molar ratio.

[0041] As a preferred option, rhodium salt is preferably rhodium trichloride, and copper salt is preferably copper nitrate.

[0042] As a preferred embodiment, in step SS2, the impregnation temperature is 60-90℃, preferably 70-80℃; the stirring speed during the impregnation process is 100-800 rpm; and the impregnation time is 2-12 hours.

[0043] As a preferred embodiment, in step SS2, the drying is carried out at 100-150°C, preferably 110-140°C; the drying time is 2-24 hours, preferably 8-16 hours.

[0044] As a preferred embodiment, in step SS2, the calcination is performed at 350-500℃ for 2-24 hours.

[0045] As a preferred embodiment, the reaction in step S2 is carried out in a batch reactor.

[0046] As a preferred embodiment, in step S2, the catalyst needs to be reduced with hydrogen before use. The reduction temperature is 100-300℃, preferably 150-200℃, the absolute pressure is 2-10MPa, preferably 4-8MPa, and the time is 1-24h, preferably 4-16h.

[0047] As a preferred embodiment, in step S2, the molar ratio of 3-oxobutyric acid-2-aminopropyl ester to polyetheramine is (2-2.1):1, preferably (2-2.05):1.

[0048] As a preferred embodiment, in step S2, the reaction temperature is 120℃-180℃, preferably 130-160℃.

[0049] As a preferred embodiment, the reaction pressure in step S2 is atmospheric pressure.

[0050] As a preferred embodiment, in step S2, the reaction time is 1-12 hours, preferably 4-8 hours.

[0051] As a preferred embodiment, in step S2, the stirring speed is 300-900 rpm.

[0052] As a preferred embodiment, the amount of imidization catalyst added in step S2 is 1-5% of the mass of the polyetheramine.

[0053] As a preferred embodiment, in step S2, the polyetheramine molecule contains polyoxyethylene and / or polyoxypropylene units, with a weight-average molecular weight of 100-5000.

[0054] In this invention, in step S2, the post-treatment temperature is 150-200℃, preferably 160-190℃, the absolute pressure is 2-20kPa, preferably 6-12kPa, and the treatment time is 1-6h, preferably 2-4h.

[0055] In this invention, the purity of the biodegradable polyetheramine is greater than 99%.

[0056] The beneficial effects of this invention are:

[0057] (1) Solid acid catalysts and supported catalysts are used in the production process, which abandons the existing technology of using inorganic strong acid as catalyst. The process generates less waste and is more in line with the concept of green environmental protection.

[0058] (2) Rare earth-modified solid acid catalysts were used to catalyze the reaction of ethyl acetoacetate and isopropanolamine to produce 3-oxobutyric acid-2-aminopropyl ester. The introduction of rare earth metals improved the overall acidity of the catalyst and increased the conversion rate of the reaction. Lewis acid-modified imidization catalysts were used to catalyze the reaction of 3-oxobutyric acid-2-aminopropyl ester with polyetheramine to generate degradable polyetheramine, which improved the conversion rate and selectivity of the reaction and reduced the formation of by-products. Detailed Implementation

[0059] To facilitate understanding of the present invention, the following description, in conjunction with embodiments, will further illustrate the invention. It should be understood that the following embodiments are merely for a better understanding of the invention and do not imply that the invention is limited to these embodiments.

[0060] Product purity was analyzed by gas chromatography. The analytical conditions of the gas chromatograph were: Agilent 7890, and the detection conditions were as follows: column was DB-5; injector and detector temperature was 280℃; initial column temperature was 50℃; temperature was increased to 280℃ at a rate of 20℃ / min, and held for 10min.

[0061] The NMR characterization results of the product 3-oxobutyric acid-2-aminopropyl ester from step 1 are as follows:

[0062]

[0063] NMR (600MHz, CDCl3): δ1.12(CH3), 2.25(CH3), 3.41(CH2), 3.39(CH), 4.42(CH2), 4.17(CH2), 5.11(NH2).

[0064] The NMR characterization results of the degradable polyetheramine product from step 2 are as follows:

[0065]

[0066] NMR (600MHz, CDCl3): δ1.12(CH3), 2.26(CH3), 2.0(NH), 3.39(CH), 4.07(H), 4.25(CH2), 4.5(CH2), 5.11(NH2).

[0067] All polyetheramines were purchased from Huntsman Corporation. Series of products.

[0068] Example 1

[0069] (1) Preparation of rare earth modified solid acid catalysts

[0070] SiO2 was dried at 100℃ for 1 hour. 100g of the dried SiO2 was added to 500g of a solution containing 1% Ce(SO4)2 by mass. The mixture was stirred thoroughly for 1 hour, allowed to stand overnight, dried under vacuum, dried at 100℃ for 1 hour, and then calcined at 250℃ for 1 hour to obtain the Ce(SO4)2-SiO2 catalyst.

[0071] (2) Preparation of imidization catalyst

[0072] A 0.1% (w / w) ZnCl2 ethanol solution was prepared. 200g of γ-Al2O3 support was added to the solution in equal volumes for impregnation. The solution was stirred at 100 rpm for 1 hour at 50°C. After impregnation, the support was dried at 100°C for 1 hour to obtain the modified support. 26.2g of RhCl3·3H2O and 2.42g of Cu(NO3)2·3H2O were weighed and added to 200mL of deionized water to prepare an impregnation solution. 120g of the modified support was added to the above impregnation solution and impregnated at 100 rpm for 2 hours at 60°C. After filtration, the solid was dried at 100°C for 2 hours and then calcined at 350°C for 2 hours to obtain the imidization catalyst. Before use, the catalyst was activated in a hydrogen atmosphere at 100°C and 2MPa for 1 hour.

[0073] (3) Reaction

[0074] Ethyl acetoacetate and isopropanolamine were fed at a molar ratio of 1:1, along with the aforementioned rare-earth-modified solid acid catalyst, with the catalyst addition amount being 0.1% of the mass of ethyl acetoacetate. The reaction was carried out at 100℃ and atmospheric pressure for 4 hours with a stirring speed of 200 rpm. The product was then subjected to negative pressure removal of ethyl acetoacetate and isopropanolamine at 150℃ and 1 kPa absolute pressure to obtain the intermediate product 3-oxobutyric acid-2-aminopropyl ester, with a purity of 99.3%. 3-oxobutyric acid-2-aminopropyl ester was then reacted with polyetheramine... D230 was added at a molar ratio of 2.0:1, along with the activated imidization catalyst described above, at a catalyst addition rate of 1% of the polyetheramine mass. The reaction was carried out at 120°C and atmospheric pressure for 1 hour with a stirring speed of 300 rpm. The reaction solution was then treated at 150°C and 2 kPa absolute pressure for 1 hour to obtain the biodegradable polyetheramine product, with a purity of 99.2%.

[0075] Comparative Example 1

[0076] The difference from Example 1 is that an active metal solution was impregnated with an unmodified support in the preparation of the imidization catalyst, while other conditions remained unchanged. Under the same reaction conditions as in Example 1, the selectivity of 3-oxobutyric acid-2-aminopropyl ester was 99.3%, and the purity of the degradable polyetheramine product was 96.4%.

[0077] Comparative Example 2

[0078] The difference from Example 1 is that the active metal oxide was not modified with rare earth elements, while other conditions remained unchanged. Under the same reaction conditions as in Example 1, the selectivity of 3-oxobutyric acid-2-aminopropyl ester was 92.5%, and the purity of the degradable polyetheramine product was 93.1%.

[0079] Example 2

[0080] (1) Preparation of rare earth modified solid acid catalysts

[0081] Al2O3 was dried at 180℃ for 12 hours. 100g of the dried Al2O3 was added to 1000g of a solution containing 10% by mass of La2(SO4)3. The mixture was stirred thoroughly for 6 hours, allowed to stand overnight, dried under vacuum, dried at 150℃ for 8 hours, and then calcined at 450℃ for 6 hours to obtain the La2(SO4)3-Al2O3 catalyst.

[0082] (2) Preparation of imidization catalyst

[0083] A 5% (w / w) AlCl3 ethanol solution was prepared. 200g of SiO2 support was added to the solution in equal volumes for impregnation. The solution was stirred at 800 rpm for 12 h at 80°C. After impregnation, the support was dried at 150°C for 12 h to obtain the modified support. 26.2g of RhCl3·3H2O and 7.26g of Cu(NO3)2·3H2O were weighed and added to 200mL of deionized water to prepare an impregnation solution. 120g of the modified support was added to the above impregnation solution and impregnated at 800 rpm for 12 h at 90°C. After filtration, the solid was dried at 150°C for 24 h and then calcined at 500°C for 24 h to obtain the imidization catalyst. Before use, the catalyst was activated in a hydrogen atmosphere at 300°C and 10MPa for 24 h.

[0084] (3) Reaction

[0085] Ethyl acetoacetate and isopropanolamine were fed at a molar ratio of 1:1.5, and the above-mentioned rare earth-modified solid acid catalyst was added, with the catalyst addition amount being 3% of the mass of ethyl acetoacetate. The reaction was carried out at 150℃ and atmospheric pressure for 12 h with a stirring speed of 800 rpm. The product was then subjected to negative pressure removal of ethyl acetoacetate and isopropanolamine at 150℃ and 1 kPa absolute pressure to obtain the intermediate product 3-oxobutyric acid-2-aminopropyl ester, with a purity of 99.7%. 3-oxobutyric acid-2-aminopropyl ester was then reacted with polyetheramine... D400 was added at a molar ratio of 2.1:1, along with the activated imidization catalyst described above, at a catalyst addition rate of 5% of the polyetheramine mass. The reaction was carried out at 180°C and atmospheric pressure for 1 hour with a stirring speed of 900 rpm. The reaction solution was then treated at 200°C and 20 kPa absolute pressure for 6 hours to obtain the biodegradable polyetheramine product, with a purity of 99.8%.

[0086] Example 3

[0087] (1) Preparation of rare earth modified solid acid catalysts

[0088] ZrO2 was dried at 140℃ for 6 hours. 100g of the dried ZrO2 was added to 800g of a solution containing 5% by mass of La2(SO4)3. The mixture was stirred thoroughly for 3 hours, allowed to stand overnight, dried under vacuum, dried at 130℃ for 5 hours, and then calcined at 350℃ for 3 hours to obtain the La2(SO4)3-ZrO2 catalyst.

[0089] (2) Preparation of imidization catalyst

[0090] A 3% (w / w) FeCl3 ethanol solution was prepared. 200g of TiO2 support was added to the solution in equal volumes for impregnation. The solution was stirred at 400 rpm for 6 hours at 65°C. After impregnation, the support was dried at 125°C for 6 hours to obtain the modified support. 26.2g of RhCl3·3H2O and 4.84g of Cu(NO3)2·3H2O were weighed and added to 200mL of deionized water to prepare an impregnation solution. 120g of the modified support was added to this solution and impregnated at 75°C for 6 hours with a stirring speed of 400 rpm. After filtration, the solid was dried at 125°C for 12 hours and then calcined at 400°C for 12 hours to obtain the imidization catalyst. Before use, the catalyst was activated in a hydrogen atmosphere at 200°C and 5MPa for 12 hours.

[0091] (3) Reaction

[0092] Ethyl acetoacetate and isopropanolamine were fed at a molar ratio of 1:1.2, along with the aforementioned rare-earth-modified solid acid catalyst, with the catalyst addition amount being 1.5% of the mass of ethyl acetoacetate. The reaction was carried out at 125℃ and atmospheric pressure for 8 hours with a stirring speed of 500 rpm. The product was then subjected to negative pressure removal of ethyl acetoacetate and isopropanolamine at 150℃ and 1 kPa absolute pressure to obtain the intermediate product 3-oxobutyric acid-2-aminopropyl ester, with a purity of 99.5%. 3-oxobutyric acid-2-aminopropyl ester was then reacted with polyetheramine... D2000 was added at a molar ratio of 2.08:1, along with the activated imidization catalyst described above, at a catalyst addition rate of 3% of the polyetheramine mass. The reaction was carried out at 150°C and atmospheric pressure for 12 hours with a stirring speed of 600 rpm. The reaction solution was then treated at 180°C and 10 kPa absolute pressure for 3 hours to obtain the biodegradable polyetheramine product, with a purity of 99.6%.

[0093] Example 4

[0094] (1) Preparation of rare earth modified solid acid catalysts

[0095] CrO3 was dried at 120℃ for 4 hours. 100g of the dried CrO3 was added to 700g of a Ce(SO4)2 solution with a mass concentration of 3%. The mixture was stirred thoroughly for 2 hours, allowed to stand overnight, dried under vacuum, dried at 120℃ for 3 hours, and then calcined at 300℃ for 2 hours to obtain the Ce(SO4)2-CrO3 catalyst.

[0096] (2) Preparation of imidization catalyst

[0097] A 0.5% (w / w) SnCl4 ethanol solution was prepared. 200g of ZrO2 support was added to the solution in equal volumes for impregnation. The solution was stirred at 200 rpm for 3 hours at 55°C. After impregnation, the support was dried at 110°C for 2 hours to obtain the modified support. 26.2g of RhCl3·3H2O and 3.63g of Cu(NO3)2·3H2O were weighed and added to 200mL of deionized water to prepare an impregnation solution. 120g of the modified support was added to the above impregnation solution and impregnated at 70°C with a stirring speed of 200 rpm for 4 hours. After filtration, the solid was dried at 110°C for 8 hours and then calcined at 350°C for 4 hours to obtain the imidization catalyst. Before use, the catalyst was activated in a hydrogen atmosphere at 150°C and 4MPa for 4 hours.

[0098] (3) Reaction

[0099] Ethyl acetoacetate and isopropanolamine were fed at a molar ratio of 1:1.1, along with the aforementioned rare-earth-modified solid acid catalyst, with the catalyst addition amount being 1% of the mass of ethyl acetoacetate. The reaction was carried out at 110℃ and atmospheric pressure for 6 hours with a stirring speed of 300 rpm. The product was then subjected to negative pressure removal of ethyl acetoacetate and isopropanolamine at 150℃ and 1 kPa absolute pressure to obtain the intermediate product 3-oxobutyric acid-2-aminopropyl ester, with a purity of 99.4%. 3-oxobutyric acid-2-aminopropyl ester was then reacted with polyetheramine... D230 was added at a molar ratio of 2.0:1, along with the activated imidization catalyst described above, at a catalyst addition amount of 2% of the polyetheramine mass. The reaction was carried out at 130°C and atmospheric pressure for 4 hours with a stirring speed of 400 rpm. The reaction solution was then treated at 160°C and 6 kPa absolute pressure for 2 hours to obtain the biodegradable polyetheramine product, with a purity of 99.3%.

[0100] Example 5

[0101] (1) Preparation of rare earth modified solid acid catalysts

[0102] Fe2O3 was dried at 150℃ for 10 h. 100 g of the dried Fe2O3 was added to 900 g of a solution containing 5% mass concentration of La2(SO4)3. The mixture was stirred thoroughly for 5 h, allowed to stand overnight, dried under vacuum, dried at 140℃ for 6 h, and then calcined at 400℃ for 5 h to obtain the La2(SO4)3-Fe2O3 catalyst.

[0103] (2) Preparation of imidization catalyst

[0104] A 2% (w / w) BF3 ethanol solution was prepared. 200g of γ-Al2O3 support was added to the solution in equal volumes for impregnation. The solution was stirred at 600 rpm for 10 h at 75 °C. After impregnation, the support was dried at 140 °C for 10 h to obtain the modified support. 26.2g of RhCl3·3H2O and 6.05g of Cu(NO3)2·3H2O were weighed and added to 200mL of deionized water to prepare an impregnation solution. 120g of the modified support was added to the above impregnation solution and impregnated at 700 rpm for 8 h at 80 °C. After filtration, the solid was dried at 140 °C for 16 h and then calcined at 450 °C for 20 h to obtain the imidization catalyst. Before use, the catalyst was activated in a hydrogen atmosphere at 200 °C and 8 MPa for 16 h.

[0105] (3) Reaction

[0106] Ethyl acetoacetate and isopropanolamine were fed at a molar ratio of 1:1.4, along with the aforementioned rare-earth-modified solid acid catalyst, with the catalyst addition amount being 2% of the mass of ethyl acetoacetate. The reaction was carried out at 140℃ and atmospheric pressure for 10 h with a stirring speed of 700 rpm. The product was then subjected to negative pressure removal of ethyl acetoacetate and isopropanolamine at 150℃ and 1 kPa absolute pressure to obtain the intermediate product 3-oxobutyric acid-2-aminopropyl ester, with an analytical purity of 99.6%. 3-oxobutyric acid-2-aminopropyl ester was then reacted with polyetheramine... D400 was added at a molar ratio of 2.05:1, along with the activated imidization catalyst described above, at a catalyst addition rate of 4% of the polyetheramine mass. The reaction was carried out at 160°C and atmospheric pressure for 8 hours with a stirring speed of 800 rpm. The reaction solution was then treated at 190°C and 12 kPa absolute pressure for 4 hours to obtain the biodegradable polyetheramine product, with a purity of 99.5%.

[0107] Example 6

[0108] (1) Preparation of rare earth modified solid acid catalysts

[0109] ZnO was dried at 130℃ for 5 hours. 100g of the dried ZnO was added to 700g of a Ce(SO4)2 solution with a mass concentration of 4%. The mixture was stirred thoroughly for 3 hours, allowed to stand overnight, dried under vacuum, dried at 130℃ for 4 hours, and then calcined at 350℃ for 4 hours to obtain the Ce(SO4)2-ZnO catalyst.

[0110] (2) Preparation of imidization catalyst

[0111] A 1% (w / w) TiCl4 ethanol solution was prepared. 200g of γ-Al2O3 support was added to the solution in equal volumes for impregnation. The solution was stirred at 500 rpm for 8 hours at 60℃. After impregnation, the support was dried at 130℃ for 8 hours to obtain the modified support. 26.2g of RhCl3·3H2O and 4.84g of Cu(NO3)2·3H2O were weighed and added to 200mL of deionized water to prepare an impregnation solution. 120g of the modified support was added to the above impregnation solution and impregnated at 500 rpm for 7 hours at 65℃. After filtration, the solid was dried at 130℃ for 14 hours and then calcined at 400℃ for 14 hours to obtain the imidization catalyst. Before use, the catalyst was activated in a hydrogen atmosphere at 250℃ and 6MPa for 10 hours.

[0112] (3) Reaction

[0113] Ethyl acetoacetate and isopropanolamine were fed at a molar ratio of 1:1.3, along with the aforementioned rare-earth-modified solid acid catalyst, with the catalyst addition amount being 2.5% of the mass of ethyl acetoacetate. The reaction was carried out at 130℃ and atmospheric pressure for 5 hours with a stirring speed of 400 rpm. The product was then subjected to negative pressure removal of ethyl acetoacetate and isopropanolamine at 150℃ and 1 kPa absolute pressure to obtain the intermediate product 3-oxobutyric acid-2-aminopropyl ester, with an analytical purity of 99.5%. 3-oxobutyric acid-2-aminopropyl ester was then reacted with polyetheramine... D2000 was added at a molar ratio of 2.04:1, along with the activated imidization catalyst described above, at a catalyst addition rate of 3% of the polyetheramine mass. The reaction was carried out at 140°C and atmospheric pressure for 6 hours with a stirring speed of 500 rpm. The reaction solution was then treated at 170°C and 8 kPa absolute pressure for 3 hours to obtain the biodegradable polyetheramine product, with a purity of 99.4%.

Claims

1. A method for preparing a biodegradable polyetheramine, comprising the following steps: S1. Ethyl acetoacetate and isopropanolamine were mixed and reacted under the action of rare earth modified solid acid catalyst to obtain 3-oxobutyric acid-2-aminopropyl ester. S2: The 3-oxobutyric acid-2-aminopropyl ester obtained in step S1 is mixed with polyetheramine and reacted under the action of an imidization catalyst to obtain degradable polyetheramine.

2. The method according to claim 1, characterized in that, The rare earth-modified solid acid catalyst used in step S1 has an SO4 structure. 2- / M x O y -N x O y M includes La and / or Ce, and N includes one or more of Si, Zr, Cr, Al, Zn, Ti, Sn, Cr, Fe, and Mo.

3. The method according to claim 2, characterized in that, The method for preparing the rare earth modified solid acid catalyst in step S1 includes the following steps: first, adding the dried active metal oxide to a sulfate solution containing rare earth elements, stirring, letting stand, separating, drying, and calcining.

4. The method according to claim 3, characterized in that, The mass ratio of the active metal oxide to the sulfate solution containing rare earth elements is 1:(5-10).

5. The method according to claim 1, characterized in that, In step S1, the molar ratio of ethyl acetoacetate and isopropanolamine is 1:(1-1.5).

6. The method according to claim 1, characterized in that, The method for preparing the imidization catalyst in step S2 includes the following steps: SS1: The catalyst precursor is obtained by impregnating the support with Lewis acid ethanol solution and drying it. SS2: Prepare an aqueous solution of metal salt by mixing soluble rhodium and copper salts. Add the catalyst precursor obtained in step SS1 into the aqueous solution of metal salt for impregnation, then dry and calcine to obtain the imidized catalyst.

7. The method for preparing a biodegradable polyetheramine according to claim 5, characterized in that, The Lewis acid in step SS1 includes AlCl3, BF3, SbCl5, FeBr3, FeCl3, SnCl4, TiCl4, and ZnCl2, preferably AlCl3, FeCl3, and SnCl4. The mass concentration of the prepared Lewis acid ethanol solution is 0.1-5%, preferably 0.5-2%.

8. The method according to claim 7, characterized in that, In step SS1, the Lewis acid includes one or more of AlCl3, BF3, SbCl5, FeBr3, FeCl3, SnCl4, TiCl4, and ZnCl2, preferably one or more of AlCl3, FeCl3, and SnCl4.

9. The method according to claim 7, characterized in that, In step SS2, the ratio of rhodium salt to copper salt is 1:(0.1-0.3) in terms of metal molar ratio; and / or, rhodium salt is preferably rhodium trichloride, and copper salt is preferably copper nitrate.

10. The method according to claim 1, characterized in that, In step S2, the molar ratio of 3-oxobutyric acid-2-aminopropyl ester to polyetheramine is (2-2.1):1, preferably (2-2.05):1; and / or, the polyetheramine molecule contains polyoxyethylene and / or polyoxypropylene units, with a weight-average molecular weight of 100-5000.

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