A method for preparing a monomethyl amine solution

Abstract

The application discloses a preparation method of monocyamine solution and belongs to the technical field of fine chemical industry. By optimizing the process conditions, especially adding new stabilizers of o-benzoquinone, 1,4-naphthoquinone and methylhydroquinone, the content of dicyandiamide in the monocyamine solution is reduced, and high-quality monocyamine with a concentration of 30% is produced at a lower temperature. The fine control technology of monocyamine low-temperature hydrolysis reaction developed by the application changes the prior art method, i.e. first hydrolyzing lime nitrogen in a hydrolysis kettle to produce monocyamine aqueous solution with a concentration of 18%, then concentrating through an evaporation system, and finally producing monocyamine finished product with a concentration of 30%. The application improves the product quality and reduces the product energy consumption through the "low-temperature one-step hydrolysis method" monocyamine production process without evaporation and concentration, so that the stable and green low-carbon production of high-grade monocyamine products is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fine chemical technology, and particularly relates to a preparation method of monocyamine solution. BACKGROUND

[0002] As a raw material for organic synthesis and pharmaceutical intermediates, monocyamine is mainly used for producing acyclovir hydrochloride, cyanuric acid amide, sodium dicyanamide, thiourea, methyl cyanoguanidinate, and is also a raw material for preparing organic guanidine. In addition, as an important pesticide intermediate, cyanamide can be used to prepare fungicides carbendazim, benomyl, methyl pyrimethanil, pyrimethanil, and insecticides pirimicarb, and is an essential raw material for the synthesis of pharmaceutical, health care products, feed additives and pesticide intermediates.

[0003] With the development of cyanamide industry towards green, clean and low-carbon production, higher requirements are put forward for the energy consumption index of monocyamine products, which must be tackled from the aspects of process technology improvement and equipment innovation. In the prior art, the production process of monocyamine with a concentration of 30% is "hydrolysis + evaporation", that is, a two-step process of "hydrolysis" in the first step and "evaporation" in the second step. This requires first hydrolyzing calcium cyanamide in a hydrolysis kettle to produce monocyamine aqueous solution with a concentration of 18%, and then concentrating it through an evaporation system to prepare monocyamine products with a concentration of 30% according to product requirements. The most energy-consuming step of this process is the evaporation process, and there is a risk of explosion. Therefore, developing a one-step process that does not require an "evaporation" step to obtain the product, using a short process and low-energy consumption monocyamine production new process can effectively reduce the energy consumption of monocyamine production, and is helpful to realize the sustainable development of monocyamine industry.

[0004] The application fields of cyanamide products with different concentrations are different. For example, cyanamide aqueous solution with a concentration of 20% can be used as a defoliant, cyanamide aqueous solution with a concentration of 30% is most widely used in the synthesis of medicines and pesticides, and can be used as a plant growth regulator, and cyanamide aqueous solution with a concentration of 50% can be used in the electronic industry or as a sleep disruptor. In the above cyanamide products, one of the most important indicators is that the content of dicyanamide cannot exceed the standard. Cyanamide is relatively active, and when the temperature is high, it is easy to undergo polymerization to generate dicyanamide, affecting the quality of the product. Taking cyanamide solution with a concentration of 20% as an example, when the content of dicyanamide is less than 0.3%, the selling price is nearly double that when the content of dicyanamide is 0.6%. Therefore, reducing the content of dicyanamide in cyanamide solution is the key to obtaining high-quality products. In industry, stabilizers are added to increase the stability of cyanamide during production and storage. The paper "Selection of Cyanamide Stabilizers" studies the conditions of hydrolysis and polymerization of cyanamide, finds that the hydrolysis and polymerization of cyanamide are closely related to the acidity and temperature of the solution, and proposes a scheme for adjusting the storage and transportation of cyanamide solution by using phosphoric acid and sodium dihydrogen phosphate as stabilizers. Patent CN 110606496B discloses a method for continuously producing cyanamide, which uses cuprous chloride, ferric chloride, sodium sulfate, sodium sulfide and thiocyanic acid as stabilizers to reduce the loss and explosion risk of cyanamide caused by polymerization. Although the above documents give a scheme for the selection of stabilizers, the effects of different stabilizers are different, and therefore it is still necessary to find more excellent stabilizers to realize the preparation of high-quality cyanamide solution. SUMMARY

[0005] In view of the above prior art, the purpose of the present application is to provide a preparation method of cyanamide solution. The present application reduces the content of dicyanamide in cyanamide solution by optimizing the process conditions, especially by selecting new stabilizers such as o-benzoquinone, 1,4-naphthoquinone and methylhydroquinone, and realizes the production of high-quality cyanamide with a concentration of 30% at a lower temperature. The present application develops a fine control technology for low-temperature hydrolysis of cyanamide, which changes the existing technology that needs to first hydrolyze lime nitrogen in a hydrolysis kettle to produce cyanamide aqueous solution with a concentration of 18%, and then concentrate it through an evaporation system to finally produce cyanamide product with a concentration of 30%. The present application improves the product quality and reduces the energy consumption by using the "low-temperature one-step hydrolysis method" cyanamide production process without evaporation and concentration, so as to realize the stable and green low-carbon production of high-grade cyanamide products.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0007] In the first aspect of the present application, a preparation method of cyanamide solution is provided, which comprises the following steps:

[0008] The water, the stabilizer, the CO2 gas, and the lime nitrogen are added into the reactor, the pH and the temperature of the solution are adjusted, and after 1-10 hours of reaction, the materials in the reactor are taken out, the filtrate and the black residue are separated by filtration, and the filtrate is transferred into the reactor; all the above steps are repeated 1-5 times; and the final filtrate is the cyanamide solution;

[0009] The stabilizer is composed of o-benzoquinone, 1,4-naphthoquinone, and methylhydroquinone in a molar ratio of (1-10):(1-10):(1-10).

[0010] Further, the number of step repetitions is 2.

[0011] Further, the amount of CO2 gas introduced is 0.1-10 Nm 3 / h.

[0012] Further, the volume / mass ratio of the water to the added lime nitrogen in the reactor is (1-5) L:1 kg.

[0013] Further, the pH is 6.0-10.

[0014] Further, the amount of the stabilizer added is 0.005%-2% of the mass of the lime nitrogen.

[0015] Further, the effective nitrogen content in the lime nitrogen is ≥18%.

[0016] Further, the reaction temperature is 6-14℃.

[0017] The present application has the following beneficial effects:

[0018] (1) The present application selects a new stabilizer of o-benzoquinone, 1,4-naphthoquinone, and methylhydroquinone, reduces the content of dicyandiamide in the cyanamide solution, and improves the quality of the cyanamide product.

[0019] (2) The present application develops a fine control technology for cyanamide low-temperature hydrolysis reaction, and through the “low-temperature one-step hydrolysis method” cyanamide production process without evaporation and concentration, the product quality is improved and the product energy consumption is reduced, so that the stable production and green low-carbon production of high-grade cyanamide products are realized.

[0020] (3) The fine control technology for cyanamide low-temperature hydrolysis reaction developed by the present application changes the prior art in which lime nitrogen is first hydrolyzed in a hydrolysis kettle to produce a cyanamide aqueous solution with a concentration of 18%, and then concentrated by an evaporation system to finally produce a cyanamide product with a concentration of 30%. The most energy-consuming step in the prior art process is the evaporation process. The short-flow and low-energy-consumption cyanamide production new process of the present application can effectively reduce the energy consumption of cyanamide production, which is helpful to realize the sustainable development of the cyanamide industry. DETAILED DESCRIPTION

[0021] It should be noted that the following detailed description is illustrative only and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0022] In order for those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in conjunction with specific embodiments.

[0023] The test materials not specifically described in the embodiments of the present application are all conventional test materials in the art and can be purchased through commercial channels. The effective nitrogen in the lime nitrogen used in the present application is 21%.

[0024] In the prior art, the production process of monocyamine with a concentration of 30% is "hydrolysis + evaporation". In the evaporation step, the prior art mostly uses a thin film evaporation system or a single-effect evaporation system; when the evaporation system concentrates monocyamine, there is a risk that the temperature is too high to cause a violent polymerization reaction of the monocyamine solution, which poses a safety hazard. It can be seen that a better solution to improve production safety is to use a one-step reaction without an evaporation step, to directly obtain a monocyamine product with a concentration of 30% by using a hydrolysis process by selecting a suitable stabilizer, thereby forming the following scheme.

[0025] Example 1

[0026] The stabilizer used is composed of o-benzoquinone, 1,4-naphthoquinone and methylhydroquinone in a molar ratio of 2:1:1.

[0027] The preparation steps of the monocyamine solution are as follows:

[0028] (1) 20 L of deionized water and 0.8 g of stabilizer are added to the reaction kettle, stirred and CO2 gas is introduced, the amount of CO2 gas introduced is 1 Nm 3 / h, lime nitrogen is slowly added at a speed of 1.75 kg / h, the pH of the solution is maintained at 7.0-9.0, the temperature in the reaction kettle is 11℃, the reaction time is 5 hours, after the reaction is completed, the black residue is filtered with a Buchner funnel, the filtrate is transferred into the reaction kettle again, the black residue after the reaction is washed with 5 L of water, and the wash is stored separately.

[0029] (2) 20 L of water is added to the reaction kettle to make up 20 L, 0.8 g of stabilizer is added, stirred and CO2 gas is introduced, the amount of CO2 gas introduced is 1 Nm 3 / h, lime nitrogen is slowly added at a speed of 1.75 kg / h, the pH of the solution is maintained at 7.0-9.0, the temperature in the reaction kettle is 11℃, the reaction time is 5 hours, after the reaction is completed, the black residue is filtered with a Buchner funnel, the filtrate is transferred into the reaction kettle again, the black residue after the reaction is washed with 5 L of water, and the wash is stored separately.

[0030] (3) To the reactor, add water to make up 20 L, add 0.8 g stabilizer, stir and introduce CO2 gas, the amount of which is 1 Nm 3 / h, slowly add lime nitrogen at a speed of 1.75 kg / h, keep the pH of the solution at 7.0-9.0, the temperature in the reactor is 11 ℃, the reaction time is 5 hours, after the reaction is completed, filter the black residue and collect the filtrate; wash the black residue with 10 L water, combine the washings of this step with those of steps (1)-(2), and transfer the combined washings to the reactor as the mother liquor for the next time.

[0031] Use a liquid chromatograph to detect the collected filtrate, in which the content of monocyamine is 30.7%, and the content of dicyandiamide is 0.28%.

[0032] Example 2

[0033] The stabilizer used is composed of o-benzoquinone, 1,4-naphthoquinone and methylhydroquinone at a molar ratio of 1:2:1.

[0034] The preparation steps of the monocyamine solution are as follows:

[0035] (1) To the reactor, add 20 L deionized water and 0.8 g stabilizer, stir and introduce CO2 gas, the amount of which is 1 Nm 3 / h, slowly add lime nitrogen at a speed of 1.75 kg / h, keep the pH of the solution at 7.0-9.0, the temperature in the reactor is 11 ℃, the reaction time is 5 hours, after the reaction is completed, filter the black residue with a Buchner funnel, transfer the filtrate to the reactor, wash the black residue after the reaction with 5 L water, and store the washings separately.

[0036] (2) To the reactor, add water to make up 20 L, add 0.8 g stabilizer, stir and introduce CO2 gas, the amount of which is 1 Nm 3 / h, slowly add lime nitrogen at a speed of 1.75 kg / h, keep the pH of the solution at 7.0-9.0, the temperature in the reactor is 11 ℃, the reaction time is 5 hours, after the reaction is completed, filter the black residue with a Buchner funnel, transfer the filtrate to the reactor, wash the black residue after the reaction with 5 L water, and store the washings separately.

[0037] (3) To the reactor, add water to make up 20 L, add 0.8 g stabilizer, stir and introduce CO2 gas, the amount of which is 1 Nm 3 / h, slowly add lime nitrogen at a speed of 1.75 kg / h, keep the pH of the solution at 7.0-9.0, the temperature in the reactor is 11 ℃, the reaction time is 5 hours, after the reaction is completed, filter the black residue and collect the filtrate; wash the black residue with 10 L water, combine the washings of this step with those of steps (1)-(2), and transfer the combined washings to the reactor as the mother liquor for the next time.

[0038] The collected filtrate is detected by liquid chromatograph, wherein the content of monocyamine is 33.4%, and the content of dicyandiamide is 0.23%.

[0039] Example 3

[0040] The stabilizer used is composed of o-benzoquinone, 1,4-naphthoquinone and methylhydroquinone in a molar ratio of 1:1:2.

[0041] The preparation steps of monocyamine solution are as follows:

[0042] (1) 20 L of deionized water and 0.8 g of stabilizer are added into a reaction kettle, stirred and CO2 gas is introduced at a flow rate of 1 Nm 3 / h, calcium cyanamide is slowly added at a speed of 1.75 kg / h, the pH of the solution is maintained at 7.0-9.0, the temperature in the reaction kettle is 11 ℃, the reaction time is 5 hours, after the reaction is completed, the black residue is filtered by a Buchner funnel, the filtrate is transferred into the reaction kettle again, the black residue after the reaction is washed with 5 L of water, and the washing solution is stored separately.

[0043] (2) 20 L of water is added into the reaction kettle to make up, 0.8 g of stabilizer is added, stirred and CO2 gas is introduced at a flow rate of 1 Nm 3 / h, calcium cyanamide is slowly added at a speed of 1.75 kg / h, the pH of the solution is maintained at 7.0-9.0, the temperature in the reaction kettle is 11 ℃, the reaction time is 5 hours, after the reaction is completed, the black residue is filtered by a Buchner funnel, the filtrate is transferred into the reaction kettle again, the black residue after the reaction is washed with 5 L of water, and the washing solution is stored separately.

[0044] (3) 20 L of water is added into the reaction kettle to make up, 0.8 g of stabilizer is added, stirred and CO2 gas is introduced at a flow rate of 1 Nm 3 / h, calcium cyanamide is slowly added at a speed of 1.75 kg / h, the pH of the solution is maintained at 7.0-9.0, the temperature in the reaction kettle is 11 ℃, the reaction time is 5 hours, after the reaction is completed, the black residue is filtered by a Buchner funnel, the filtrate is transferred into the reaction kettle again, the black residue after the reaction is washed with 5 L of water, and the washing solution is stored separately.

[0045] The collected filtrate is detected by liquid chromatograph, wherein the content of monocyamine is 31.6%, and the content of dicyandiamide is 0.27%.

[0046] Example 4

[0047] The stabilizer used is composed of o-benzoquinone, 1,4-naphthoquinone and methylhydroquinone in a molar ratio of 1:2:1.

[0048] The preparation steps of monocyamine solution are as follows:

[0049] (1) To the reactor, 20 L of deionized water and 0.8 g of stabilizer were added, stirred and CO2 gas was introduced at a rate of 1 Nm 3 / h, lime nitrogen was slowly added at a rate of 1.75 kg / h, the pH of the solution was maintained at 7.0-9.0, the temperature in the reactor was 9°C, the reaction time was 5 hours, after the reaction was completed, the black residue was filtered with a Buchner funnel, the filtrate was transferred to the reactor again, the black residue after the reaction was washed with 5 L of water, and the wash was stored separately.

[0050] (2) To the reactor, 20 L of deionized water and 0.8 g of stabilizer were added, stirred and CO2 gas was introduced at a rate of 1 Nm 3 / h, lime nitrogen was slowly added at a rate of 1.75 kg / h, the pH of the solution was maintained at 7.0-9.0, the temperature in the reactor was 9°C, the reaction time was 5 hours, after the reaction was completed, the black residue was filtered with a Buchner funnel, the filtrate was transferred to the reactor again, the black residue after the reaction was washed with 5 L of water, and the wash was stored separately.

[0051] (3) To the reactor, 20 L of deionized water and 0.8 g of stabilizer were added, stirred and CO2 gas was introduced at a rate of 1 Nm 3 / h, lime nitrogen was slowly added at a rate of 1.75 kg / h, the pH of the solution was maintained at 7.0-9.0, the temperature in the reactor was 9°C, the reaction time was 5 hours, after the reaction was completed, the black residue was filtered with a Buchner funnel, the filtrate was transferred to the reactor again, the black residue after the reaction was washed with 5 L of water, and the wash was stored separately.

[0052] The collected filtrate was detected by liquid chromatograph, wherein the content of monocyamine was 30.6%, and the content of dicyanamide was 0.22%.

[0053] Example 5

[0054] The stabilizer used was composed of o-benzoquinone, 1,4-naphthoquinone and methylhydroquinone at a molar ratio of 1:2:1.

[0055] The preparation steps of the monocyamine solution were as follows:

[0056] (1) To the reactor, 20 L of deionized water and 0.8 g of stabilizer were added, stirred and CO2 gas was introduced at a rate of 1 Nm 3 / h, lime nitrogen was slowly added at a rate of 1.75 kg / h, the pH of the solution was maintained at 7.0-9.0, the temperature in the reactor was 9°C, the reaction time was 5 hours, after the reaction was completed, the black residue was filtered with a Buchner funnel, the filtrate was transferred to the reactor again, the black residue after the reaction was washed with 5 L of water, and the wash was stored separately.

[0057] (2) To the reactor, 20 L of deionized water and 0.8 g of stabilizer were added, stirred and CO2 gas was introduced at a rate of 1 Nm 3 / h, lime nitrogen was slowly added at a speed of 1.75 kg / h, the pH of the solution was kept at 7.0-9.0, the temperature in the reactor was 13°C, the reaction time was 5 hours, after the reaction was completed, the black residue was filtered with a Buchner funnel, the filtrate was transferred into the reactor again, the black residue after the reaction was washed with 5 L of water, and the washing liquid was stored separately.

[0058] (3) 20 L of water was added to the reactor to make up, 0.8 g of stabilizer was added, stirring and CO2 gas was introduced, the amount of introduction was 1 Nm 3 / h, lime nitrogen was slowly added at a speed of 1.75 kg / h, the pH of the solution was kept at 7.0-9.0, the temperature in the reactor was 13°C, the reaction time was 5 hours, after the reaction was completed, the black residue was filtered with a Buchner funnel, the filtrate was transferred into the reactor again, the black residue after the reaction was washed with 5 L of water, and the washing liquid was stored separately.

[0059] The collected filtrate was detected by liquid chromatograph, wherein the content of monocyamine was 31.2%, and the content of dicyandiamide was 0.29%.

[0060] Example 6

[0061] The stabilizer used was composed of o-benzoquinone, 1,4-naphthoquinone and methylhydroquinone according to a molar ratio of 1:2:1.

[0062] The preparation steps of the monocyamine solution were as follows:

[0063] (1) 20 L of deionized water and 0.6 g of stabilizer were added to the reactor, stirring and CO2 gas was introduced, the amount of introduction was 1 Nm 3 / h, lime nitrogen was slowly added at a speed of 1.75 kg / h, the pH of the solution was kept at 7.0-9.0, the temperature in the reactor was 13°C, the reaction time was 5 hours, after the reaction was completed, the black residue was filtered with a Buchner funnel, the filtrate was transferred into the reactor again, the black residue after the reaction was washed with 5 L of water, and the washing liquid was stored separately.

[0064] (2) 20 L of water was added to the reactor to make up, 0.6 g of stabilizer was added, stirring and CO2 gas was introduced, the amount of introduction was 1 Nm 3 / h, lime nitrogen was slowly added at a speed of 1.75 kg / h, the pH of the solution was kept at 7.0-9.0, the temperature in the reactor was 13°C, the reaction time was 5 hours, after the reaction was completed, the black residue was filtered with a Buchner funnel, the filtrate was transferred into the reactor again, the black residue after the reaction was washed with 5 L of water, and the washing liquid was stored separately.

[0065] (3) 20 L of water was added to the reactor to make up, 0.6 g of stabilizer was added, stirring and CO2 gas was introduced, the amount of introduction was 1 Nm 3 / h, lime nitrogen was slowly added at a speed of 1.75 kg / h, the pH of the solution was kept at 7.0-9.0, the temperature in the reactor was 11 °C, the reaction time was 5 hours, after the reaction was completed, the black residue was filtered, the filtrate was collected; the black residue was washed with 10 L of water, the washing solution of this step was combined with the washing solutions of steps (1)-(2), and was transferred to the reactor as the mother liquor for the next time.

[0066] The collected filtrate was detected by liquid chromatograph, wherein the monosodium cyanamide content was 30.7%, and the dicyan diamine content was 0.33%.

[0067] Example 7

[0068] The stabilizer used was composed of o-benzoquinone, 1,4-naphthoquinone and methylhydroquinone according to a molar ratio of 1:2:1.

[0069] The preparation steps of the monosodium cyanamide solution were as follows:

[0070] (1) 20 L of deionized water and 1.0 g of stabilizer were added to the reactor, stirring and CO2 gas was introduced, the amount of CO2 gas introduced was 1 Nm 3 / h, lime nitrogen was slowly added at a speed of 1.75 kg / h, the pH of the solution was kept at 7.0-9.0, the temperature in the reactor was 11 °C, the reaction time was 5 hours, after the reaction was completed, the black residue was filtered, the filtrate was collected; the black residue was washed with 10 L of water, the washing solution of this step was combined with the washing solutions of steps (1)-(2), and was transferred to the reactor as the mother liquor for the next time.

[0071] (2) 20 L of water was added to the reactor to make up 20 L, 1.0 g of stabilizer was added, stirring and CO2 gas was introduced, the amount of CO2 gas introduced was 1 Nm 3 / h, lime nitrogen was slowly added at a speed of 1.75 kg / h, the pH of the solution was kept at 7.0-9.0, the temperature in the reactor was 11 °C, the reaction time was 5 hours, after the reaction was completed, the black residue was filtered, the filtrate was collected; the black residue was washed with 10 L of water, the washing solution of this step was combined with the washing solutions of steps (1)-(2), and was transferred to the reactor as the mother liquor for the next time.

[0072] (3) 20 L of water was added to the reactor to make up 20 L, 1.0 g of stabilizer was added, stirring and CO2 gas was introduced, the amount of CO2 gas introduced was 1 Nm 3 / h, lime nitrogen was slowly added at a speed of 1.75 kg / h, the pH of the solution was kept at 7.0-9.0, the temperature in the reactor was 11 °C, the reaction time was 5 hours, after the reaction was completed, the black residue was filtered, the filtrate was collected; the black residue was washed with 10 L of water, the washing solution of this step was combined with the washing solutions of steps (1)-(2), and was transferred to the reactor as the mother liquor for the next time.

[0073] The collected filtrate was detected by liquid chromatograph, wherein the monosodium cyanamide content was 29.7%, and the dicyan diamine content was 0.28%.

[0074] Comparative Example 1

[0075] The preparation procedure of monosodium cyanamide solution is as follows:

[0076] (1) Add 20 L of deionized water into the reactor, stir and introduce CO2 gas, the introduced amount is 1 Nm 3 / h, slowly add calcium cyanamide at a speed of 1.75 kg / h, keep the pH of the solution at 7.0-9.0, the temperature in the reactor is 11℃, the reaction time is 5 hours, after the reaction is completed, filter the black residue with a Buchner funnel, transfer the filtrate into the reactor again, wash the black residue after the reaction with 5 L of water, and store the washing solution separately.

[0077] (2) Add water to make up 20 L in the reactor, stir and introduce CO2 gas, the introduced amount is 1 Nm 3 / h, slowly add calcium cyanamide at a speed of 1.75 kg / h, keep the pH of the solution at 7.0-9.0, the temperature in the reactor is 11℃, the reaction time is 5 hours, after the reaction is completed, filter the black residue with a Buchner funnel, transfer the filtrate into the reactor again, wash the black residue after the reaction with 5 L of water, and store the washing solution separately.

[0078] (3) Add water to make up 20 L in the reactor, stir and introduce CO2 gas, the introduced amount is 1 Nm 3 / h, slowly add calcium cyanamide at a speed of 1.75 kg / h, keep the pH of the solution at 7.0-9.0, the temperature in the reactor is 11℃, the reaction time is 5 hours, after the reaction is completed, filter the black residue to collect the filtrate; wash the black residue with 10 L of water, combine the washing solution of this step with the washing solutions of steps (1)-(2), and transfer the combined solution to the reactor as the mother liquor for the next time of feeding.

[0079] Detect the collected filtrate with a liquid chromatograph, wherein the monosodium cyanamide content is 26.5%, and the dicyanamide content is 26%.

[0080] Comparative Example 2

[0081] The stabilizer used is composed of o-benzoquinone and 1,4-naphthoquinone at a molar ratio of 1:2.

[0082] The preparation procedure of monosodium cyanamide solution is as follows:

[0083] (1) Add 20 L of deionized water, 0.8 g of stabilizer into the reactor, stir and introduce CO2 gas, the introduced amount is 1 Nm 3 / h, slowly add calcium cyanamide at a speed of 1.75 kg / h, keep the pH of the solution at 7.0-9.0, the temperature in the reactor is 11℃, the reaction time is 5 hours, after the reaction is completed, filter the black residue with a Buchner funnel, transfer the filtrate into the reactor again, wash the black residue after the reaction with 5 L of water, and store the washing solution separately.

[0084] (2) To the reactor, add water to make up 20 L, add 0.8 g of stabilizer, stir and pass in CO2 gas, the amount of which is 1 Nm 3 / h, slowly add lime nitrogen at a speed of 1.75 kg / h, keep the pH of the solution at 7.0-9.0, the temperature in the reactor is 11 ℃, the reaction time is 5 hours, after the reaction is completed, filter the black residue, collect the filtrate, wash the black residue with 5 L of water, and store the washing liquid separately.

[0085] (3) To the reactor, add water to make up 20 L, add 0.8 g of stabilizer, stir and pass in CO2 gas, the amount of which is 1 Nm 3 / h, slowly add lime nitrogen at a speed of 1.75 kg / h, keep the pH of the solution at 7.0-9.0, the temperature in the reactor is 11 ℃, the reaction time is 5 hours, after the reaction is completed, filter the black residue, collect the filtrate; wash the black residue with 10 L of water, combine the washing liquid of this step with the washing liquid of steps (1)-(2), and transfer it to the reactor as the mother liquor for the next time.

[0086] Use a liquid chromatograph to detect the collected filtrate, wherein the monocyamine content is 27.1%, and the dicyanamide content is 2.3%.

[0087] Comparative Example 3

[0088] The stabilizer used is composed of o-benzoquinone and methylhydroquinone at a molar ratio of 1:1.

[0089] The preparation steps of the monocyamine solution are as follows:

[0090] (1) To the reactor, add 20 L of deionized water and 0.8 g of stabilizer, stir and pass in CO2 gas, the amount of which is 1 Nm 3 / h, slowly add lime nitrogen at a speed of 1.75 kg / h, keep the pH of the solution at 7.0-9.0, the temperature in the reactor is 11 ℃, the reaction time is 5 hours, after the reaction is completed, filter the black residue, collect the filtrate; wash the black residue with 5 L of water, and store the washing liquid separately.

[0091] (2) To the reactor, add water to make up 20 L, add 0.8 g of stabilizer, stir and pass in CO2 gas, the amount of which is 1 Nm 3 / h, slowly add lime nitrogen at a speed of 1.75 kg / h, keep the pH of the solution at 7.0-9.0, the temperature in the reactor is 11 ℃, the reaction time is 5 hours, after the reaction is completed, filter the black residue, collect the filtrate; wash the black residue with 5 L of water, and store the washing liquid separately.

[0092] (3) To the reactor, add water to make up 20 L, add 0.8 g of stabilizer, stir and pass in CO2 gas, the amount of which is 1 Nm 3 / h, lime nitrogen was slowly added at a speed of 1.75 kg / h, the pH of the solution was kept at 7.0-9.0, the temperature in the reactor was 11 °C, the reaction time was 5 hours, after the reaction was completed, the black residue was filtered, the filtrate was collected; the black residue was washed with 10 L of water, the washing solution of this step was combined with the washing solutions of steps (1)-(2), and was transferred to the reactor as the mother liquor for the next time.

[0093] The collected filtrate was detected by a liquid chromatograph, wherein the monosodium cyanamide content was 27.9%, and the dicyan diamine content was 1.8%.

[0094] Comparative Example 4

[0095] The stabilizer used was composed of 1,4-naphthoquinone and methylhydroquinone at a molar ratio of 2:1.

[0096] The preparation steps of the monosodium cyanamide solution were as follows:

[0097] (1) 20 L of deionized water and 0.8 g of stabilizer were added to the reactor, stirring and CO2 gas was introduced, the amount of CO2 gas introduced was 1 Nm 3 / h, lime nitrogen was slowly added at a speed of 1.75 kg / h, the pH of the solution was kept at 7.0-9.0, the temperature in the reactor was 11 °C, the reaction time was 5 hours, after the reaction was completed, the black residue was filtered, the filtrate was collected; the black residue was washed with 10 L of water, the washing solution of this step was combined with the washing solutions of steps (1)-(2), and was transferred to the reactor as the mother liquor for the next time.

[0098] (2) 20 L of water was added to the reactor to make up 20 L, 0.8 g of stabilizer was added, stirring and CO2 gas was introduced, the amount of CO2 gas introduced was 1 Nm 3 / h, lime nitrogen was slowly added at a speed of 1.75 kg / h, the pH of the solution was kept at 7.0-9.0, the temperature in the reactor was 11 °C, the reaction time was 5 hours, after the reaction was completed, the black residue was filtered, the filtrate was collected; the black residue was washed with 10 L of water, the washing solution of this step was combined with the washing solutions of steps (1)-(2), and was transferred to the reactor as the mother liquor for the next time.

[0099] (3) 20 L of water was added to the reactor to make up 20 L, 0.8 g of stabilizer was added, stirring and CO2 gas was introduced, the amount of CO2 gas introduced was 1 Nm 3 / h, lime nitrogen was slowly added at a speed of 1.75 kg / h, the pH of the solution was kept at 7.0-9.0, the temperature in the reactor was 11 °C, the reaction time was 5 hours, after the reaction was completed, the black residue was filtered, the filtrate was collected; the black residue was washed with 10 L of water, the washing solution of this step was combined with the washing solutions of steps (1)-(2), and was transferred to the reactor as the mother liquor for the next time.

[0100] The collected filtrate was detected by a liquid chromatograph, wherein the monosodium cyanamide content was 27.4%, and the dicyan diamine content was 2.1%.

[0101] In summary, by using the method of Example 2, the monocyanamide content reaches 33.4%, and the dicyanamide content is 0.23%. The present application uses the "low-temperature one-step hydrolysis method" without evaporation and concentration to produce monocyanamide, which improves the monocyanamide content to more than 30% and reduces the dicyanamide content to less than 0.3%, improves the product quality and reduces the product energy consumption, and realizes the stable production and green and low-carbon production of high-grade monocyanamide products.

[0102] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Those skilled in the art can make various modifications and changes to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a monosodium cyanamide solution, characterized by, It comprises the following steps: adding water, stabilizer, CO2 gas, calcium cyanamide into the reactor, adjusting pH and temperature of the solution, taking out all the materials in the reactor after 1-10 hours of reaction, separating filtrate and black residue by filtration, transferring the filtrate into the reactor; repeating all the above steps for 1-5 times; the final filtrate is cyanamide solution; The stabilizer is composed of o-benzoquinone, 1,4-naphthoquinone and methylhydroquinone according to the molar ratio of (1-10):(1-10):(1-10); The pH is 6.0-10; the added amount of stabilizer is 0.005%-2% of the mass of calcium cyanamide; the effective nitrogen content in calcium cyanamide is ≥18%; the reaction temperature is 6-14℃.

2. The method of claim 1, wherein the monosolvate solution is prepared by, The step is repeated for 2 times.

3. The method of claim 1, wherein the monosolvate solution is prepared by, The CO2 gas passing amount is 0.1-10 Nm 3 / h.

4. The method of claim 1, wherein the monosolvate solution is prepared by, The volume-mass ratio of water to added calcium cyanamide in the reactor is (1-5) L:1 kg.