Preparation method of guanidine carbonate

Abstract

According to the preparation method, a nitrogen source and an ammonia source are taken as reaction substrates, a metal organic compound is taken as an auxiliary agent, and guanidine carbonate is obtained through reaction. The preparation method comprises the following steps: by taking a metal organic compound MFM-303 (Al) as an auxiliary agent, under the induction of carboxyl and hydroxyl in a pore channel of the MFM-303 (Al), adsorbing and storing ammonia gas released by heating and decomposing an ammonia source or ammonia gas of the ammonia source in the pore channel, and then reacting with a nitrogen source cyanamide, urea or dicyandiamide to obtain guanidine carbonate; high-temperature and high-pressure reaction conditions are not needed, and meanwhile, the use of a large amount of ammonia water in the traditional process is abandoned, so that the industrial production safety is high; the method has the advantages of mild reaction conditions, few side reactions and high product yield, and is beneficial to industrial large-scale production.

Description

Technical Field

[0001] The present invention relates to the technical field of organic compound synthesis, and particularly relates to a preparation method of guanidine carbonate. Background Art

[0002] Guanidine carbonate, chemically named guanidine carbonate, is a white crystalline powder. Guanidine carbonate is an organic fine chemical raw material with extremely wide uses: it can be used as an organic synthesis raw material and an analytical reagent, a strong ethylating agent, an esterifying reagent, a protein carboxyl modifier, etc.; it can also be used for pH regulators of amino resins, antioxidants, resin stabilizers and soaps; it can also be used for cement slurries, additives of surfactants, etc. At the same time, in synthetic detergents, guanidine carbonate can also be used as a moisture-resistant agent and a synergist; in the determination of the contents of zinc, cadmium, manganese and other ions, it is used as a precipitant, etc.

[0003] In the prior art, the preparation of guanidine carbonate mainly uses dicyandiamide and ammonium salts as raw materials, and then through steps such as concentration crystallization and purification to obtain guanidine carbonate. CN1286806C discloses a preparation method of guanidine carbonate. At room temperature, using guanidine hydrochloride, sodium hydroxide and ethanol as raw materials, the free guanidine group is obtained by reaction. Carbon dioxide gas is introduced into the ethanol mother liquor containing the free guanidine group until the pH is 9, and after centrifugation, dissolution, filtration, dehydration and crystallization, guanidine carbonate is obtained. In this method, pure guanidine hydrochloride needs to be used for feeding, and the cost of feeding pure guanidine hydrochloride is relatively large, and sodium hydroxide is used to adjust the pH, and the equivalent of sodium hydroxide is not easy to control.

[0004] "Research on the synthesis method of high-purity guanidine carbonate", Chemical Reagents, 2000, 22(5), 314 discloses that in an autoclave, using liquid ammonia, carbon dioxide and aminocyanide as raw materials, the temperature is raised to 140 °C within 20 minutes for reaction. After filtration, the filtrate is subjected to vacuum distillation, crystallization and drying to obtain guanidine carbonate. However, the reaction pressure of this route is relatively high, the process operation is dangerous, and liquid ammonia is easy to volatilize and has an irritating odor, which is not conducive to large-scale production.

[0005] CN1385418A discloses using dicyandiamide and ammonium chloride to synthesize guanidine hydrochloride, then using sodium hydroxide to adjust the pH to alkaline, then introducing carbon dioxide gas, and finally performing concentration crystallization and purification to obtain guanidine carbonate. However, this route needs to be carried out under high temperature conditions, with high cost and low yield.

[0006] "Production and application of guanidine carbonate - Wen Zhanxi" in the 5th issue of "Chemical Industry Friends" in 2001 discloses that first, dicyandiamide and ammonium nitrate are used to synthesize guanidine nitrate, then sodium hydroxide is used to adjust the pH to alkaline, then carbon dioxide gas is introduced, and finally concentration crystallization and purification are carried out to obtain guanidine carbonate. Although guanidine carbonate can be easily obtained by this route, it needs to be carried out under high temperature and high pressure conditions. At the same time, ammonium nitrate belongs to an explosive, and the reaction is relatively dangerous. At the same time, a large amount of methanol is used in the post-treatment process, and the cost is relatively high.

[0007] With the continuous development of industry, the consumption of guanidine carbonate is increasing day by day. There is an urgent need for a suitable route and lower cost for the large-scale industrial production of guanidine carbonate to meet the existing demand. Summary of the Invention

[0008] The object of the present invention is to provide a method for preparing guanidine carbonate, which does not require high-temperature and high-pressure reaction conditions, and at the same time abandons the use of a large amount of ammonia water in the traditional process, with high industrial production safety; the reaction conditions are mild, the side reactions are few, the product yield is high, and it is conducive to large-scale industrial production.

[0009] To achieve the object of the present invention, the following technical solutions are adopted:

[0010] The present invention provides a method for preparing guanidine carbonate, using a nitrogen source and an ammonia source as reaction substrates and a metal-organic compound as an auxiliary agent to react to obtain guanidine carbonate.

[0011] Specifically, the nitrogen source is one selected from cyanamide, urea and dicyandiamide, and the ammonia source is at least one selected from ammonium carbonate, ammonium bicarbonate and ammonia gas.

[0012] Preferably, when the ammonia source is ammonia gas, carbon dioxide also needs to be introduced into the reaction system;

[0013] Preferably, the mass of the ammonia gas is not less than the mass of the carbon dioxide;

[0014] More preferably, the mass ratio of the ammonia gas to the carbon dioxide is (2-10):1, for example, it can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0015] Specifically, the metal-organic compound is MFM-303(Al), that is, [Al(OH)(C 16 O8H8)](H2O)2.

[0016] Preferably, the preparation method of the metal-organic compound includes the following steps: adding biphenyl-3,3,5,5-tetracarboxylic acid, aluminum chloride, 2% hydrochloric acid and water into a hydrothermal reactor, heating and reacting at 200-220 °C for 65-80 h, filtering, washing and drying to obtain the metal-organic compound.

[0017] More preferably, for example, the heating reaction can be carried out at 200°C, 202°C, 204°C, 206°C, 208°C, 210°C, 212°C, 214°C, 216°C, 218°C or 220°C, etc. for, for example, 65 h, 66 h, 67 h, 68 h, 69 h, 70 h, 71 h, 72 h, 73 h, 74 h, 75 h, 76 h, 77 h, 78 h, 79 h or 80 h, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0018] Specifically, the reaction temperature is 25 - 70°C, and the reaction time is 10 - 14 h; preferably, the reaction temperature can be 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C or 70°C, etc., and the reaction time can be 10 h, 11 h, 12 h, 13 h or 14 h, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0019] In the present invention, increasing the temperature can promote the decomposition of the nitrogen source, thereby shortening the reaction time and increasing the yield.

[0020] Preferably, the reaction temperature is 40 - 70°C; more preferably, the reaction temperature can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C or 70°C, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0021] Specifically, the mass ratio of the nitrogen source to the metal organic compound is (2 - 8):1, for example, the mass ratio can be 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0022] Specifically, the feeding molar ratio of the nitrogen source to the ammonia source is 1:(1 - 8), for example, the molar ratio can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7 or 1:8, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0023] Specifically, a solvent needs to be added in the reaction, and the solvent is at least one selected from water and ammonia water;

[0024] Preferably, the mass ratio of the solvent to the nitrogen source is (0.5 - 5):1, for example, the mass ratio can be 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1 or 5:1, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0025] Specifically, after the reaction, the metal-organic compound is filtered and recovered, and the mother liquor is concentrated and then crystallized by gradient cooling. The guanidine carbonate crystals are obtained after multiple crystallizations.

[0026] Preferably, the cooling gradient of the gradient cooling is 5-10 °C per 30 min, and the temperature is reduced from the mother liquor concentration temperature to 30-50 °C until solids precipitate from the concentrated solution. For example, the cooling gradient of the gradient cooling can be 5 °C, 6 °C, 7 °C, 8 °C, 9 °C or 10 °C per 30 min, etc., but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention provides a method for preparing guanidine carbonate, using the metal-organic compound MFM-303(Al) as an auxiliary agent. Under the induction of carboxyl and hydroxyl groups in the pores of MFM-303(Al), the ammonia released by heating and decomposing the ammonia source or the ammonia itself is adsorbed and stored in the pores, and then reacts with the nitrogen sources cyanamide, urea or dicyandiamide to obtain guanidine carbonate; there is no need for high-temperature and high-pressure reaction conditions, and at the same time, the use of a large amount of ammonia water in the traditional process is abandoned, and the industrial production safety is high; the reaction conditions are mild, the side reactions are few, the product yield is high, and it is beneficial to industrial scale production. Specific Embodiments

[0029] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0030] Preparation Example 1

[0031] Synthesis of MFM-303(Al), i.e., [Al(OH)(C 16 O8H8)](H2O)2: Add biphenyl-3,3,5,5-tetracarboxylic acid (60 mg, 0.182 mmol), aluminum chloride (121.2 mg, 0.909 mmol), 2% hydrochloric acid (2 mL) and water (10 mL) into a stainless steel hydrothermal autoclave with a polytetrafluoroethylene inner liner. Heat and react at 210 °C for 3 days, filter to obtain a white crystalline product, wash with water, and then dry in air to obtain 48.26 mg of the product for standby.

[0032] Elemental analysis of [Al(OH)(C 16 O8H8)](H2O)2 (% calc / found): C 46.65 / 46.90, H 3.29 / 3.32, N 0.0 / 0.0.

[0033] Infrared IR (ATR): v / cm -1: 3085 (w), 1683 (m), 1615 (m), 1579 (s), 1409 (m), 1246 (m), 1167 (m), 1089 (m), 986 (s), 803 (m), 764 (s), 648 (m).

[0034] Example 1

[0035] This example provides a method for preparing guanidine carbonate, and the preparation method includes the following steps:

[0036] Add 140 g of aminonitrile solution (concentration 30%), 72 g of ammonium carbonate, and 31 g of ammonia water (concentration 25%-28%) into the reaction flask, then add 6 g of MFM-303(Al), heat up to 40 °C, and react for 12 h; cool down, filter, and recover MFM-303; during the concentration of the mother liquor, crystallize by stepwise cooling: slowly decrease from 70 °C to 30-50 °C, decreasing 5 °C every 30 min until solid precipitates; obtain white crystals, and a total of 43.6 g of guanidine carbonate is obtained after crystallization 3 times; the total yield is 72.0%.

[0037] Example 2

[0038] This example provides a method for preparing guanidine carbonate, and the preparation method includes the following steps:

[0039] Add 140 g of aminonitrile solution (concentration 30%), 72 g of ammonium carbonate, and 31 g of ammonia water (concentration 25%-28%) into the reaction flask, then add 14 g of MFM-303(Al), heat up to 40 °C, and react for 12 h; cool down, filter, and recover MFM-303; during the concentration of the mother liquor, crystallize by stepwise cooling: slowly decrease from 70 °C to 30-50 °C, decreasing 5 °C every 30 min until solid precipitates; obtain white crystals, and a total of 46.0 g of guanidine carbonate is obtained after crystallization 3 times; the total yield is 76.0%.

[0040] Example 3

[0041] This example provides a method for preparing guanidine carbonate, and the preparation method includes the following steps:

[0042] Add 140 g of aminonitrile solution (concentration 30%), 72 g of ammonium carbonate, and 31 g of ammonia water (concentration 25%-28%) into the reaction flask, then add 20 g of MFM-303(Al), heat up to 40 °C, and react for 12 h; cool down, filter, and recover MFM-303; during the concentration of the mother liquor, crystallize by stepwise cooling: slowly decrease from 70 °C to 30-50 °C, decreasing 5 °C every 30 min until solid precipitates; obtain white crystals, and a total of 49.4 g of guanidine carbonate is obtained after crystallization 3 times, and the total yield is 81.5%.

[0043] Example 4

[0044] This example provides a method for preparing guanidine carbonate. The preparation method includes the following steps: It is basically the same as Example 1, except that 8.4 g of MFM-303(Al) is added, and finally 45.4 g of guanidine carbonate is obtained, with a total yield of 75.0%.

[0045] Example 5

[0046] This example provides a method for preparing guanidine carbonate. The preparation method includes the following steps: It is basically the same as Example 4, except that 144 g of ammonium carbonate and 62 g of ammonia water (concentration 25%-28%) are added, and finally 47.5 g of guanidine carbonate is obtained, with a total yield of 78.5%.

[0047] Example 6

[0048] This example provides a method for preparing guanidine carbonate. The preparation method includes the following steps: It is basically the same as Example 4, except that 96 g of ammonium carbonate and 48 g of ammonia water (concentration 25%-28%) are added, and finally 49.1 g of guanidine carbonate is obtained, with a total yield of 81.0%.

[0049] Example 7

[0050] This example provides a method for preparing guanidine carbonate. The preparation method includes the following steps:

[0051] Add 140 g of aminonitrile solution (concentration 30%), 79 g of ammonium bicarbonate and 31 g of ammonia water (concentration 25%-28%) into the reaction flask, then add 21 g of MFM-303(Al), heat up to 50 °C, and react for 12 h; cool down, filter, and recover MFM-303. During the concentration of the mother liquor, crystallize by stepwise cooling: slowly lower the temperature from 70 °C to 30-50 °C, lower the temperature by 5 °C every 30 min until solids precipitate; obtain white crystals, and a total of 44.8 g of guanidine carbonate is obtained after crystallization 3 times; the total yield is 74.0%.

[0052] Example 8

[0053] This example provides a method for preparing guanidine carbonate. The preparation method includes the following steps:

[0054] Add 140 g of aminocyanide solution (concentration 30%), 120 g of ammonium carbonate, and 79 g of ammonium bicarbonate; add 150 ml of water to the reaction flask, then add 20 g of MFM-303(Al), and heat up to 50 °C; react for 10 h, cool down, filter, and recover MFM-303. During the concentration of the mother liquor, crystallize by stepwise cooling: slowly cool from 70 °C to 30 - 50 °C, decreasing by 5 °C every 30 min until solid precipitation occurs; obtain white crystals, and a total of 51.8 g of guanidine carbonate is obtained after 3 times of crystallization; the total yield is 85.5%.

[0055] Example 9

[0056] This example provides a method for preparing guanidine carbonate, and the preparation method includes the following steps:

[0057] Introduce 80 g of ammonia gas and 99 g of carbon dioxide gas into 140 g of aminocyanide solution (concentration 30%); add 150 ml of water to the reaction flask, then add 20 g of MFM-303(Al), and heat up to 50 °C; react for 10 h, cool down, filter, and recover MFM-303. During the concentration of the mother liquor, crystallize by stepwise cooling: slowly cool from 70 °C to 30 - 50 °C, decreasing by 5 °C every 30 min until solid precipitation occurs; obtain white crystals, and a total of 50.9 g of guanidine carbonate is obtained after 3 times of crystallization; the total yield is 84.0%.

[0058] Example 10

[0059] This example provides a method for preparing guanidine carbonate, and the preparation method includes the following steps: It is basically the same as Example 7, except that 127.3 g of urea is used as the nitrogen source, and finally 32.7 g of guanidine carbonate is obtained; the total yield is 54.0%.

[0060] Example 11

[0061] This example provides a method for preparing guanidine carbonate, and the preparation method includes the following steps: It is basically the same as Example 7, except that 42.0 g of dicyandiamide is used as the nitrogen source, and finally 41.5 g of guanidine carbonate is obtained; the total yield is 68.5%.

[0062] Example 12

[0063] This example provides a method for preparing guanidine carbonate, and the preparation method includes the following steps:

[0064] Add 140 g of aminocyanide solution (concentration 30%), 120 g of ammonium carbonate, 150 ml of water into the reaction flask, then add 20 g of MFM-303(Al), heat up to 70 °C; react for 12 h, cool down, filter, and recover MFM-303. During the concentration of the mother liquor, crystallize by stepwise cooling: slowly reduce the temperature from 70 °C to 30 - 50 °C, reduce the temperature by 10 °C every 30 min until solid precipitates; obtain white crystals, and a total of 50.3 g of guanidine carbonate is obtained after crystallization for 3 times; the total yield is 83.0%.

[0065] Example 13

[0066] This example provides a method for preparing guanidine carbonate, and the preparation method includes the following steps:

[0067] Add 140 g of aminocyanide solution (concentration 30%), 120 g of ammonium carbonate, 68 ml of ammonia water, and 82 ml of water into the reaction flask, then add 20 g of MFM-303(Al), heat up to 70 °C; react for 12 h, cool down, filter, and recover MFM-303. During the concentration of the mother liquor, crystallize by stepwise cooling: slowly reduce the temperature from 70 °C to 30 - 50 °C, reduce the temperature by 10 °C every 30 min until solid precipitates; obtain white crystals, and a total of 51.5 g of guanidine carbonate is obtained after crystallization for 3 times; the total yield is 85.0%.

[0068] Comparative Example 1

[0069] This comparative example provides a method for preparing guanidine carbonate. Add 140 g of aminocyanide solution (concentration 30%), 120 g of ammonium carbonate, and 79 g of ammonium bicarbonate, and 150 ml of water into the reaction flask, heat up to 70 °C; react for 12 h, cool down, and filter off the insoluble substances. During the concentration of the mother liquor, crystallize by stepwise cooling to obtain white crystals, and crystallize for 3 times; a total of 12.1 g of guanidine carbonate is obtained; the total yield is 20.0%.

[0070] Comparative Example 2

[0071] This comparative example provides a method for preparing guanidine carbonate. Add 120 g of ammonium carbonate, 79 g of ammonium bicarbonate, and 150 ml of water into a 500 ml high-pressure reaction kettle respectively, heat up to 140 °C, use a constant flow pump to pump in 140 g of aminocyanide solution (concentration 30%), and keep the temperature at 140 °C; react for 6 h, cool down, and filter. During the concentration of the mother liquor, crystallize by stepwise cooling to obtain white crystals, and crystallize for 3 times; a total of 36.3 g of guanidine carbonate is obtained; the total yield is 60.0%.

[0072] Prepare guanidine carbonate by using the preparation methods provided in Examples 1 - 13 and Comparative Examples 1 - 2, calculate the raw material conversion rate according to the input amount of aminocyanide; calculate the yield of guanidine carbonate according to the input amount of aminocyanide; determine the purity of guanidine carbonate by titrating the carbonate content, and the obtained results are shown in Table 1.

[0073] Table 1

[0074] Raw material conversion rate (%) Yield of guanidine carbonate (%) Purity of guanidine carbonate (%) Example 1 94 72.0 99.45 Example 2 96 76.0 99.25 Example 3 98 81.5 99.60 Example 4 95 75.0 99.01 Example 5 90 78.5 99.26 Example 6 98 81.0 99.48 Example 7 96 74.0 99.01 Example 8 92 85.5 99.15 Example 9 93 84.0 99.35 Example 10 94 54.0 99.26 Example 11 99 68.5 99.46 Example 12 96 83.0 99.46 Example 13 94 85.0 99.46 Comparative Example 1 80 20.0 96.00 Comparative Example 2 89 60.0 96.17

[0075] As can be seen from Table 1, the preparation method provided by the present invention does not require high-temperature and high-pressure reaction conditions, and at the same time abandons the use of a large amount of ammonia water in the traditional process, with high safety in industrial production; the reaction conditions are mild, the side reactions are few, the product yield is high, which is conducive to industrial scale production;

[0076] It can be known from the comparison of Examples 1-4 that within the defined range of the mass ratio of the nitrogen source to the metal organic compound of (2-8):1, with the increase of the amount of the metal organic compound, it is beneficial to the formation of free guanidine groups, and the conversion rate of the raw material aminonitrile and the yield of the target product can be improved.

[0077] It can be known from the comparison of Examples 4-6 that within the defined range of the feeding molar ratio of the nitrogen source to the ammonia source of 1:(1-8), within this range, with the increase of the ammonia source, the conversion rate of the nitrogen source will increase, but an excessive ammonia source will promote the formation of other organic impurities such as urea and / or melamine from the nitrogen source.

[0078] In Examples 1, 7-9, the type of the ammonia source was changed, and at the same time, the input amount of the ammonia source was also changed; within a certain range, the ammonia source promoted the conversion of the nitrogen source and formed guanidine groups; however, beyond the appropriate range, the formation rate of the target product would be reduced. Using the ammonia source with a compounding ratio also increased the formation of carbonate ions.

[0079] In Examples 1, 10-11, the type of the nitrogen source was changed. Compared with using aminonitrile as the nitrogen source, when using urea and dicyandiamide as the nitrogen source, there would be more side reactions during the reaction (such as melamine and / or cyanuric acid, etc.), which was not conducive to the purification of guanidine carbonate; and the yield was lower than that when using aminonitrile solution as the nitrogen source.

[0080] In Examples 1, 12-13, the type of the solvent was changed. Changing the solvent had a relatively small impact on this reaction. When ammonia water was selected as the reaction solvent, the yield of guanidine carbonate was higher.

[0081] It can be known from the comparison of Example 1 and Comparative Example 1 that if the preparation method provided by the present invention is not adopted, it will cause a large waste of raw materials, the yield of guanidine carbonate is low, which is not conducive to industrial production.

[0082] It can be known from the comparison of Example 1 and Comparative Example 2 that compared with the method of the prior art, the preparation by MFM adsorption has higher safety, and the product yield and raw material conversion rate are higher. Using the MFM catalyst can improve the utilization rate of the ammonia source and the conversion rate of aminonitrile.

[0083] In summary, the present invention provides a method for preparing guanidine carbonate. Using the metal-organic compound MFM-303(Al) as an auxiliary agent, under the induction of carboxyl and hydroxyl groups in the pores of MFM-303(Al), the ammonia released by heating and decomposing the ammonia source or the ammonia itself is adsorbed and stored in the pores, and then reacts with the nitrogen sources cyanamide, urea or dicyandiamide to obtain guanidine carbonate; there is no need for high-temperature and high-pressure reaction conditions, and at the same time, the use of a large amount of ammonia water in the traditional process is abandoned, and the industrial production safety is high; the reaction conditions are mild, the side reactions are few, the product yield is high, which is conducive to industrial scale production.

[0084] The above are only specific embodiments 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 conceived by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A preparation method of guanidine carbonate, characterized in that, Using a nitrogen source and an ammonia source as reaction substrates and a metal-organic compound as an auxiliary agent, guanidine carbonate is obtained through a reaction.

2. The preparation method according to claim 1, characterized in that, The nitrogen source is one selected from aminocyanide, urea, and dicyandiamide, and the ammonia source is at least one selected from ammonium carbonate, ammonium bicarbonate, and ammonia gas.

3. The preparation method according to claim 2, characterized in that, When the ammonia source is ammonia gas, carbon dioxide also needs to be introduced into the reaction system; Preferably, the mass of the ammonia gas is not less than the mass of the carbon dioxide; More preferably, the mass ratio of the ammonia gas to the carbon dioxide is (2-10):

1.

4. The preparation method according to claim 1, characterized in that, The metal-organic compound is MFM-303(Al), namely [Al(OH)(C 16 O8H8)](H2O)2.

5. The preparation method according to claim 4, characterized in that, The preparation method of the metal-organic compound includes the following steps: adding biphenyl-3,3,5,5-tetracarboxylic acid, aluminum chloride, 2% hydrochloric acid, and water into a hydrothermal reactor, heating and reacting at 200-220 °C for 65-80 h, filtering, washing, and drying to obtain the metal-organic compound.

6. The preparation method according to claim 1, wherein The reaction temperature is 25-70 °C, and the reaction time is 10-14 h; Preferably, the reaction temperature is 40-70 °C.

7. The preparation method according to claim 1, characterized in that, The mass ratio of the nitrogen source to the metal-organic compound is (2-8):

1.

8. The preparation method according to claim 1, wherein The feeding molar ratio of the nitrogen source to the ammonia source is 1:(1-8).

9. The preparation method according to claim 1, wherein A solvent also needs to be added in the reaction, and the solvent is at least one selected from water and ammonia water; Preferably, the mass ratio of the solvent to the nitrogen source is (0.5-5):

1.

10. According to the preparation method described in claim 1, wherein After the reaction, the metal-organic compound is recovered by filtration, and the mother liquor is concentrated and then crystallized by gradient cooling. The crystallization is repeated multiple times to obtain guanidine carbonate crystals; Preferably, the cooling gradient for gradient cooling is to decrease by 5-10 °C every 30 min, from the mother liquor concentration temperature to 30-50 °C until solids precipitate out in the concentrated solution.