Solid base catalyst and preparation method thereof, and carbamate synthesis method

Abstract

The invention provides a solid base catalyst, a preparation method and a carbamate synthesis method, and the preparation method of the solid base catalyst comprises the following steps: dispersing an alkali precursor in a solvent, then mixing with boron nitride, and drying to obtain a pre-loaded product; and roasting and activating the preloaded product to obtain the solid base catalyst. The solid base catalyst provided by the invention is simple in preparation method, good in active site dispersity and good in stability, and is used for efficient catalytic synthesis of aliphatic carbamate, the conversion rate of raw material amine reaches 80% or above, the yield of an aliphatic carbamate product reaches 70% or above, and the selectivity of aliphatic carbamate is 86% or above.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts and relates to a solid base catalyst, in particular to a solid base catalyst and a preparation method thereof and a method for synthesizing carbamate. Background Art

[0002] Aliphatic carbamates are an important class of organic synthesis intermediates, which are widely used in the manufacture of agricultural pesticides, herbicides and drug synthesis. In industry, they can also be used as important precursors for the synthesis of polyurethane by non-phosgene methods. The traditional synthesis method of aliphatic carbamates mainly uses phosgene as a raw material, and is obtained by alcoholysis and aminolysis. Phosgene is highly toxic and flammable, and is used in large quantities. It usually needs to be used in excess of 50-200%. A large amount of chlorine-containing substances is produced during the reaction, which seriously corrodes equipment and pollutes the environment. Therefore, it is imperative to use non-phosgene methods to produce carbamate compounds.

[0003] Using carbonate compounds to replace phosgene and reacting with amine compounds or urea compounds to obtain corresponding carbamate substances is a non-phosgene route with great development prospects. The method has mild reaction conditions, is environmentally friendly, and is safe to operate, but the method requires effective conversion of the reaction under catalytic conditions. For example, CN114957045A discloses a method for preparing pentamethylenedicarbamate, which uses an organic base catalyst to catalyze the synthesis of pentamethylenedicarbamate. Using organic compounds as catalysts still has the problems of being environmentally unfriendly and difficult to separate the catalyst. CN116474761A, CN111971119A, CN112898184A, etc. disclose methods for synthesizing carbamate compounds, in which catalysts containing rare earth or precious metal components are used. Catalysts containing rare earth or precious metal components generally can produce good catalytic effects, but their costs are high and the preparation process is relatively complicated.

[0004] In recent years, solid base catalysts have received much attention in the field of environmentally friendly chemical processes. Solid base catalysts have the advantages of easy separation from the reaction solution, mild reaction conditions, high activity and easy recycling. From the perspective of actual chemical production, solid base catalysts have low corrosion to equipment, enhance production continuity and simplify the production process. However, solid base catalysts currently have problems such as low utilization of active sites due to the aggregation of basic sites and poor cyclic stability due to the loss of basic sites, which limits their application.

[0005] Therefore, based on the deficiencies of the prior art, the present invention provides a solid base catalyst and a preparation method and a method for synthesizing carbamate. Summary of the invention

[0006] The purpose of the present invention is to provide a solid base catalyst and a preparation method and a method for synthesizing carbamate. The preparation method of the solid base catalyst is simple, the basic site has good dispersibility and good stability, and the solid base catalyst is used to catalyze the synthesis of aliphatic carbamates, thereby improving the reaction efficiency of the carbonyl esterification reaction, thereby improving the efficiency of the entire carbamate synthesis process.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing a solid base catalyst, the preparation method comprising the following steps:

[0009] (1) dispersing a base precursor in a solvent, then mixing it with boron nitride, and drying it to obtain a preloaded product;

[0010] (2) calcining and activating the preloaded product obtained in step (1) to obtain the solid base catalyst.

[0011] The solid base catalyst provided by the present invention uses boron nitride as a carrier material, and is prepared by loading and calcining an activation step through two steps: loading an alkali precursor and boron nitride. The alkali precursor is loaded on the surface of the boron nitride, and the precursor has high dispersibility in the carrier. Then, during the calcination process, more vacancies are generated on the carrier, and the alkali precursor is converted into an alkaline site. The alkaline site and the carrier have an interaction force, and the site is firmly anchored on the carrier, and the site is not easy to be lost. The active site of the catalyst has good dispersibility and good stability. The preparation process is simple and efficient, easy to operate, and no other organic solvents or toxic reagents need to be added, so the catalyst is environmentally friendly.

[0012] Preferably, the base precursor in step (1) comprises an alkali metal salt and / or an alkaline earth metal salt.

[0013] Preferably, the alkali metal of the alkali metal salt includes any one or a combination of at least two of lithium, sodium or potassium. Typical but non-limiting combinations include a combination of lithium and sodium, a combination of sodium and potassium, a combination of lithium and potassium, or a combination of lithium, sodium and potassium, preferably Na and / or K.

[0014] Preferably, the alkaline earth metal of the alkaline earth metal salt includes any one or a combination of at least two of beryllium, magnesium, calcium or barium. Typical but non-limiting combinations include a combination of beryllium and magnesium, a combination of magnesium and calcium, a combination of calcium and barium, a combination of beryllium, magnesium and calcium, a combination of magnesium, calcium and barium, or a combination of beryllium, magnesium, calcium and barium, preferably Mg and / or Ca.

[0015] Preferably, the alkali precursor comprises any one of nitrates, chlorides, carbonates or acetates of alkali metals and / or alkaline earth metals, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of nitrates and chlorides, a combination of chlorides and carbonates, a combination of carbonates and acetates, a combination of nitrates, chlorides and carbonates, a combination of chlorides, carbonates and acetates, or a combination of nitrates, chlorides, carbonates and acetates.

[0016] Preferably, the solvent in step (1) comprises an organic solvent and / or an inorganic solvent.

[0017] Preferably, the solvent in step (1) comprises any one of ethanol, deionized water or methanol, or a combination of at least two of them. Typical but non-limiting combinations include a combination of ethanol and deionized water, a combination of deionized water and methanol, a combination of ethanol and methanol, or a combination of ethanol, deionized water and methanol.

[0018] Preferably, the mass ratio of the alkali precursor to boron nitride in step (1) is (0.02-0.15):1, for example, it can be 0.02:1, 0.05:1, 0.08:1, 0.10:1, 0.12:1 or 0.15:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0019] Preferably, the calcination activation in step (2) is carried out under an inert gas atmosphere.

[0020] Preferably, the inert gas comprises any one of helium, argon or nitrogen, or a combination of at least two of them. Typical but non-limiting combinations include a combination of helium and argon, a combination of argon and nitrogen, a combination of helium and nitrogen, or a combination of helium, argon and nitrogen.

[0021] Preferably, the temperature of the calcination activation in step (2) is 300-1200°C, for example, it can be 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C or 1200°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] Preferably, the calcination activation time in step (2) is 2-4 h, for example, 2 h, 2.5 h, 3 h, 3.5 h or 4 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0023] In a second aspect, the present invention provides a solid base catalyst, which is prepared by the preparation method described in the first aspect.

[0024] In a third aspect, the present invention provides a method for synthesizing an aliphatic carbamate, the method comprising the following steps:

[0025] The solid base catalyst described in the second aspect is used to catalyze the carbonylation reaction of the organic amine and the carbonylating agent to obtain aliphatic carbamate.

[0026] The synthesis method provided by the present invention adopts a solid base catalyst to catalyze the reaction, the basic site activates the organic base and the carbonylating agent, and the urethane bond is directionally constructed. The catalytic activity of the carbonyl esterification reaction is excellent, and the raw material conversion rate and product yield of the carbonyl esterification reaction are significantly improved.

[0027] Preferably, the organic amine includes any one of n-pentylamine, pentamethylenediamine, n-hexylamine or hexamethylenediamine, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of n-pentylamine and pentamethylenediamine, a combination of pentamethylenediamine and n-hexylamine, a combination of n-hexylamine and hexamethylenediamine, a combination of n-pentylamine, pentamethylenediamine and n-hexylamine, or a combination of pentamethylenediamine, n-hexylamine and hexamethylenediamine.

[0028] Preferably, the carbonylating agent comprises any one of dimethyl carbonate, ethyl methyl carbonate or diethyl carbonate or a combination of at least two thereof, typical but non-limiting combinations comprising a combination of dimethyl carbonate and ethyl methyl carbonate, a combination of ethyl methyl carbonate and diethyl carbonate, a combination of dimethyl carbonate and diethyl carbonate, or a combination of dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate.

[0029] Preferably, the amount of the solid base catalyst is 1-35wt% of the organic amine, for example, it can be 1wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt% or 35wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] Preferably, the molar ratio of the carbonylating agent to the organic amine is (1-20):1, for example, 1:1, 5:1, 10:1, 15:1 or 20:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] Preferably, the temperature of the carbonyl esterification reaction is 15-100°C, for example, 15°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C or 100°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] Preferably, the pressure of the carbonylation reaction is 0.1-2 MPa, for example, 0.1 MPa, 0.5 MPa, 1 MPa, 1.5 MPa or 2 MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] Preferably, the carbonyl esterification reaction time is 1-30 h, for example, 1 h, 5 h, 10 h, 15 h, 20 h, 24 h or 30 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] Preferably, during the carbonyl esterification reaction, the generated small molecule alcohol compounds are removed from the reaction system.

[0035] Preferably, the method of removing the reaction system comprises introducing gas and / or distillation.

[0036] Preferably, the gas comprises nitrogen and / or an inert gas.

[0037] Preferably, after the carbonyl esterification reaction, the reaction solution is mixed with an anti-solvent and subjected to standing crystallization and solid-liquid separation.

[0038] Preferably, the volume ratio of the reaction solution to the anti-solvent is (1-10):1, for example, it can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] Preferably, the temperature of the static crystallization is -5°C to 60°C, for example, -5°C, 0°C, 10°C, 20°C, 30°C, 40°C, 50°C or 60°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0040] Preferably, the standing crystallization time is 1-2 hours, for example, 1 hour, 1.2 hours, 1.5 hours, 1.8 hours or 2 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0041] Preferably, the anti-solvent comprises distilled water.

[0042] As a preferred technical solution of the synthesis method provided by the present invention, the synthesis method comprises the following steps:

[0043] A solid base catalyst is used to catalyze an organic amine and a carbonylating agent for a carbonylation reaction, wherein the amount of the solid base catalyst used is 1-35wt% of the organic amine, and the molar ratio of the carbonylating agent to the organic amine is (1-20):1; the temperature of the carbonylation reaction is 15-100°C, the pressure of the carbonylation reaction is 0.1-2MPa, and the carbonylation reaction time is 1-30h. During the carbonylation reaction, the generated small molecule alcohol compounds are removed from the reaction system by introducing gas and / or distillation; after the carbonylation reaction is completed, the reaction solution is mixed with a solvent in a volume ratio of (1-10):1, and crystallized at -5°C to 60°C for 1-2h, and then solid-liquid separation is performed to obtain an aliphatic carbamate;

[0044] The solid base catalyst is prepared by the following method:

[0045] (1) dispersing the alkali precursor in a solvent, adding boron nitride under stirring, the mass ratio of the alkali precursor to boron nitride being (0.02-0.15):1, evaporating in a water bath and drying in an oven to obtain a preloaded product;

[0046] The alkali precursor includes an alkali metal salt and / or an alkaline earth metal salt, the alkali metal of the alkali metal salt includes Na and / or K, and the alkaline earth metal of the alkaline earth metal salt includes Mg and / or Ca;

[0047] (2) The preloaded product obtained in step (1) is calcined and activated in an inert gas atmosphere at a temperature of 300-1200° C. for a time of 2-4 hours.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The solid base catalyst provided by the invention has a simple preparation method, good active site dispersibility and good stability, and is used for the efficient catalytic synthesis of aliphatic carbamates, achieving a conversion rate of raw material amines of more than 80%, an aliphatic carbamate product yield of more than 70%, and an aliphatic carbamate selectivity of more than 86%. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a transmission electron micrograph of the solid base catalyst prepared in Example 1. DETAILED DESCRIPTION

[0051] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0052] Example 1

[0053] This embodiment provides a solid base catalyst, and the preparation method of the solid base catalyst is as follows:

[0054] (1) 0.01 g KNO3 was dissolved in 30 g of a mixed solvent, wherein the mixed solvent was a mixture of water and ethanol in a volume ratio of 1:1, and then 0.19 g of boron nitride was added, wherein the porosity of the boron nitride was 38.3%, the average pore diameter was 20 nm, and the mass ratio of the base precursor to the support material was 0.05:1. After stirring for 12 h, the mixture was evaporated at 75 ° C. The solid was dried at 80 ° C. for 24 h to obtain a preloaded product, which was recorded as KNO3 / BN;

[0055] (2) The preloaded product obtained in step (1) is heat treated in a nitrogen atmosphere at 800° C. for 3 hours to obtain the solid base catalyst.

[0056] The transmission electron microscopy image of the solid base catalyst prepared in this example is as follows Figure 1 As shown by Figure 1 It can be seen that no nanoparticles appear in the solid base catalyst and the K atoms have good dispersion.

[0057] Example 2

[0058] This embodiment provides a solid base catalyst, and the preparation method of the solid base catalyst is as follows:

[0059] (1) 0.01 g KCl was dissolved in 30 g of a mixed solvent, wherein the mixed solvent was a mixture of water and ethanol in a volume ratio of 1:1, and then 0.19 g of boron nitride was added, and the mass ratio of the base precursor to the support material was 0.05:1. After stirring for 12 h, the mixture was evaporated at 75 ° C. The solid was dried at 80 ° C. for 24 h to obtain a preloaded product, which was recorded as KCl / BN;

[0060] (2) The preloaded product obtained in step (1) is heat treated in a nitrogen atmosphere at 900° C. for 3 hours to obtain the solid base catalyst.

[0061] Example 3

[0062] This embodiment provides a solid base catalyst, and the preparation method of the solid base catalyst is as follows:

[0063] (1) 0.01 g KNO3 was dissolved in 30 g of a mixed solvent, wherein the mixed solvent was a mixture of water and ethanol in a volume ratio of 1:1, and then 0.5 g of boron nitride was added, and the mass ratio of the base precursor to the support material was 0.02:1. After stirring for 12 h, the mixture was evaporated at 75 ° C. The solid was dried at 80 ° C. for 24 h to obtain a pre-loaded product, which was recorded as KNO3 / BN;

[0064] (2) The preloaded product obtained in step (1) is heat treated in a nitrogen atmosphere at 300° C. for 4 hours to obtain the solid base catalyst.

[0065] Example 4

[0066] This embodiment provides a solid base catalyst, and the preparation method of the solid base catalyst is as follows:

[0067] (1) 0.01 g KNO3 was dissolved in 30 g of a mixed solvent, wherein the mixed solvent was a mixture of water and ethanol in a volume ratio of 1:1, and then 0.07 g of boron nitride was added, and the mass ratio of the base precursor to the support material was 0.15:1. After stirring for 12 h, the mixture was evaporated at 75 ° C. The solid was dried at 80 ° C. for 24 h to obtain a pre-loaded product, which was recorded as KNO3 / BN;

[0068] (2) The preloaded product obtained in step (1) is heat treated in a nitrogen atmosphere at 1200° C. for 2 hours to obtain the solid base catalyst.

[0069] Example 5

[0070] This embodiment provides a solid base catalyst.

[0071] The preparation method of the solid base catalyst is the same as that of Example 1, except that the mass of KNO3 is replaced by NaNO3, and the rest is the same as that of Example 1.

[0072] Example 6

[0073] This embodiment provides a solid base catalyst.

[0074] Compared with Example 1, the preparation method of the solid base catalyst is the same as Example 1, except that the mass of KNO3 is replaced by Mg(NO3)2.

[0075] Example 7

[0076] This embodiment provides a solid base catalyst.

[0077] Compared with Example 1, the preparation method of the solid base catalyst is that the mass of KNO3 is replaced by a mixture of KNO3 and NaNO3, the mass ratio of KNO3 to NaNO3 is 1:1, and the rest is the same as Example 1.

[0078] Example 8

[0079] This embodiment provides a solid base catalyst.

[0080] In the preparation method of the solid base catalyst, compared with Example 1, the mass of KNO3 is replaced by a mixture of NaNO3 and Ca(NO3)2 of equal mass, the mass ratio of NaNO3 to Ca(NO3)2 is 1:1, and the rest is the same as Example 1.

[0081] Comparative Example 1

[0082] This comparative example provides a solid base catalyst.

[0083] Compared with Example 1, the preparation method of the solid base catalyst is the same as Example 1 except that the mass of boron nitride is replaced by CeO2.

[0084] Comparative Example 2

[0085] This comparative example provides a solid base catalyst.

[0086] Compared with Example 1, the preparation method of the solid base catalyst is the same as Example 1 except that the mass of boron nitride is replaced by TiO2.

[0087] Comparative Example 3

[0088] This comparative example provides a solid base catalyst.

[0089] Compared with Example 1, the preparation method of the solid base catalyst is the same as Example 1 except that the mass of boron nitride is replaced by ZIF-67.

[0090] Application Example 1

[0091] This application example provides a catalytic synthesis method for aliphatic carbamates, using the solid base catalyst prepared in Example 1, and the catalytic synthesis method comprises the following steps:

[0092] Dimethyl carbonate was mixed with a solid base catalyst, and then hexamethylenediamine was added. The molar ratio of dimethyl carbonate to hexamethylenediamine was 4:1, and the amount of the solid base catalyst was 3wt% of the hexamethylenediamine. The mixture was reacted at 85°C and 0.1MPa. Stirring was continued during the reaction, and nitrogen was introduced to remove the methanol produced by the reaction. The reaction time was 24h to obtain a hexamethylenediamine product.

[0093] Application Example 2

[0094] This application example provides a catalytic synthesis method for aliphatic carbamates, using the solid base catalyst prepared in Example 2, and the catalytic synthesis method comprises the following steps:

[0095] Dimethyl carbonate was mixed with a solid base catalyst, and then hexamethylenediamine was added. The molar ratio of dimethyl carbonate to hexamethylenediamine was 6:1, and the amount of the solid base catalyst was 10wt% of the hexamethylenediamine. The mixture was reacted at 80°C and 1MPa. Stirring was continued during the reaction, and nitrogen was introduced to remove the methanol produced by the reaction. The reaction time was 30h to obtain a hexamethylenediamine product.

[0096] Application Example 3

[0097] This application example provides a catalytic synthesis method for aliphatic carbamates, using the solid base catalyst prepared in Example 3, and the catalytic synthesis method comprises the following steps:

[0098] Dimethyl carbonate was mixed with a solid base catalyst, and then pentamethylenediamine was added. The molar ratio of dimethyl carbonate to pentamethylenediamine was 1:1, and the amount of the solid base catalyst was 20wt% of pentamethylenediamine. The reaction was carried out at 15°C and 2MPa. Stirring was continued during the reaction, and nitrogen was introduced to remove the methanol produced by the reaction. The reaction time was 1h to obtain pentamethylenediamine product.

[0099] Application Example 4

[0100] This application example provides a catalytic synthesis method for aliphatic carbamates, using the solid base catalyst prepared in Example 4, and the catalytic synthesis method comprises the following steps:

[0101] Dimethyl carbonate is mixed with a solid base catalyst, and then n-pentylamine is added. The molar ratio of dimethyl carbonate to n-pentylamine is 20:1, and the amount of the solid base catalyst is 35wt% of the n-pentylamine. The reaction is carried out at 100°C and 0.5MPa. Stirring is continued during the reaction, and nitrogen is introduced to remove the methanol produced by the reaction. The reaction time is 10 hours to obtain an n-pentylcarbamate product.

[0102] Application Example 5

[0103] This application example provides a catalytic synthesis method for aliphatic carbamates. Compared with Application Example 1, an equal mass of the solid base catalyst prepared in Example 5 is used, and the rest is the same as Application Example 1.

[0104] Application Example 6

[0105] This application example provides a catalytic synthesis method for aliphatic carbamates. Compared with Application Example 1, an equal mass of the solid base catalyst prepared in Example 6 is used, and the rest is the same as Application Example 1.

[0106] Application Example 7

[0107] This application example provides a catalytic synthesis method for aliphatic carbamates. Compared with Application Example 1, an equal mass of the solid base catalyst prepared in Example 7 is used, and the rest is the same as Application Example 1.

[0108] Application Example 8

[0109] This application example provides a catalytic synthesis method for aliphatic carbamates. Compared with Application Example 1, an equal mass of the solid base catalyst prepared in Example 8 is used, and the rest is the same as Application Example 1.

[0110] Comparative application example 1

[0111] This comparative application example provides a catalytic synthesis method for aliphatic carbamates. Compared with Application Example 1, no solid base catalyst is used, and the rest is the same as Application Example 1.

[0112] Comparative Application Example 2

[0113] This comparative application example provides a catalytic synthesis method for aliphatic carbamates. Compared with Application Example 1, an equal mass of the solid base catalyst prepared in Comparative Example 1 is used, and the rest is the same as Application Example 1.

[0114] Comparative Application Example 3

[0115] This comparative application example provides a catalytic synthesis method for aliphatic carbamates. Compared with Application Example 1, the solid base catalyst prepared in Comparative Example 2 of equal mass is used, and the rest is the same as Application Example 1.

[0116] Comparative Application Example 4

[0117] This comparative application example provides a catalytic synthesis method for aliphatic carbamates. Compared with Application Example 1, the solid base catalyst prepared in Comparative Example 3 of equal mass is used, and the rest is the same as Application Example 1.

[0118] The products after the reaction of the application example and the comparative application example were centrifuged to separate the catalyst, and the supernatant was analyzed by gas chromatography for composition. The calculation results are listed in Table 1.

[0119] The test conditions of gas chromatography are as follows: column model GsBP-1; column temperature initially 80°C, retained for 1 min, increased to 125°C at 10°C / min, retained for 2 min, then increased to 230°C at 20°C / min, retained at 230°C for 5 min; control mode is pressure control, pressure 50 kPa, purge flow rate 3 mL / min, split ratio 30; vaporization temperature 250°C.

[0120] Table 1

[0121]

[0122] It can be seen from Table 1 that:

[0123] The synthesis method of aliphatic carbamate provided by the present invention uses a solid base catalyst to carry out a catalytic reaction, has a good catalytic effect, an amine conversion rate of more than 80%, an aliphatic carbamate yield of more than 70%, and an aliphatic carbamate selectivity of more than 86%. In Application Examples 7 and 8, boron nitride is used as a carrier material, and when K and Na, or Na and Ca are used as two combined base precursors, the two base precursors cooperate with boron nitride to achieve an excellent catalytic effect, and the amine conversion rate is especially more than 85%, the aliphatic carbamate yield is more than 79%, and the aliphatic carbamate selectivity is more than 93%;

[0124] Compared with Application Example 1, in Comparative Application Example 1, without using a solid base catalyst, the conversion rate of hexamethylenediamine was only 55%, the yield of hexamethylenediamine was only 29%, and the purity of the hexamethylenediamine product was only 95%. In Comparative Application Examples 2-4, other metal oxides or metal organic framework materials were used as carriers, and the amine conversion rate, aliphatic carbamate yield and aliphatic carbamate selectivity were significantly reduced.

[0125] In summary, the solid base catalyst provided by the present invention has a simple preparation method, good active site dispersion and good stability, and is used for the efficient catalytic synthesis of aliphatic carbamates, achieving a conversion rate of the raw material amine of more than 80%, an aliphatic carbamate product yield of more than 70%, and an aliphatic carbamate selectivity of more than 86%.

[0126] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a solid base catalyst, characterized in that: The preparation method comprises the following steps: (1) dispersing a base precursor in a solvent, then mixing it with boron nitride, and drying it to obtain a preloaded product; (2) calcining and activating the preloaded product obtained in step (1) to obtain the solid base catalyst.

2. The preparation method according to claim 1, characterized in that: The base precursor in step (1) comprises an alkali metal salt and / or an alkaline earth metal salt; Preferably, the alkali metal of the alkali metal salt includes any one or a combination of at least two of lithium, sodium or potassium; Preferably, the alkaline earth metal of the alkaline earth metal salt includes any one or a combination of at least two of beryllium, magnesium, calcium or barium; Preferably, the alkali precursor in step (1) comprises any one or a combination of at least two of nitrates, chlorides, carbonates or acetates of alkali metals and / or alkaline earth metals; Preferably, the solvent in step (1) is any one of ethanol, deionized water or methanol, or a combination of at least two thereof; Preferably, the mass ratio of the alkaline precursor to boron nitride in step (1) is (0.02-0.15):

1.

3. The preparation method according to claim 1 or 2, characterized in that: The calcination activation in step (2) is carried out under an inert gas atmosphere; Preferably, the inert gas includes any one of helium, argon or nitrogen, or a combination of at least two thereof; Preferably, the temperature of the calcination activation in step (2) is 300-1200°C; Preferably, the calcination activation time in step (2) is 2-4 hours.

4. A solid base catalyst, characterized in that The solid base catalyst is prepared by the preparation method according to any one of claims 1 to 3.

5. A method for synthesizing aliphatic carbamates, characterized in that: The synthesis method comprises the following steps: The solid base catalyst according to claim 4 is used to catalyze the carbonylation reaction of organic amine and carbonylating agent to obtain aliphatic carbamate.

6. The synthesis method according to claim 5, characterized in that The organic amine includes any one of n-pentylamine, pentamethylenediamine, n-hexylamine or hexamethylenediamine, or a combination of at least two thereof; Preferably, the carbonylating agent comprises any one of dimethyl carbonate, ethyl methyl carbonate or diethyl carbonate, or a combination of at least two thereof; Preferably, the molar ratio of the carbonylating agent to the organic amine is (1-20):1; Preferably, the solid base catalyst is used in an amount of 1-35 wt % of the organic amine.

7. The synthesis method according to claim 5 or 6, characterized in that: The temperature of the carbonyl esterification reaction is 15-100°C; Preferably, the carbonylation reaction pressure is 0.1-2 MPa; Preferably, the carbonyl esterification reaction time is 1-30 hours.

8. The synthesis method according to any one of claims 5 to 7, characterized in that During the carbonyl esterification reaction, the generated small molecule alcohol compounds are removed from the reaction system; Preferably, the method of removing the reaction system comprises introducing gas and / or distillation; Preferably, the gas comprises nitrogen and / or an inert gas.

9. The synthesis method according to any one of claims 5 to 8, characterized in that: After the carbonyl esterification reaction, the reaction solution is mixed with an anti-solvent, and then allowed to stand for crystallization and solid-liquid separation; Preferably, the volume ratio of the reaction solution to the anti-solvent is (1-10):1; Preferably, the temperature of the static crystallization is -5°C to 60°C; Preferably, the standing crystallization time is 1-2 hours.

10. The synthesis method according to any one of claims 5 to 9, characterized in that: The synthesis method comprises the following steps: A solid base catalyst is used to catalyze an organic amine and a carbonylating agent for a carbonylation reaction, wherein the amount of the solid base catalyst used is 1-35wt% of the organic amine, and the molar ratio of the carbonylating agent to the organic amine is (1-20):1; the temperature of the carbonylation reaction is 15-100°C, the pressure of the carbonylation reaction is 0.1-2MPa, and the carbonylation reaction time is 1-30h. During the carbonylation reaction, the generated small molecule alcohol compounds are removed from the reaction system by introducing gas and / or distillation; after the carbonylation reaction is completed, the reaction solution is mixed with a solvent in a volume ratio of (1-10):1, and crystallized at -5°C to 60°C for 1-2h, and then solid-liquid separation is performed to obtain an aliphatic carbamate; The solid base catalyst is prepared by the following method: (1) dispersing the alkali precursor in a solvent, adding boron nitride under stirring, the mass ratio of the alkali precursor to boron nitride being (0.02-0.15):1, evaporating in a water bath and drying in an oven to obtain a preloaded product; The alkali precursor includes an alkali metal salt and / or an alkaline earth metal salt, the alkali metal of the alkali metal salt includes Na and / or K, and the alkaline earth metal of the alkaline earth metal salt includes Mg and / or Ca; (2) The preloaded product obtained in step (1) is calcined and activated in an inert gas atmosphere at a temperature of 300-1200° C. for a time of 2-4 hours.

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