Preparation method of anhydrous sodium formate

Abstract

The invention relates to the field of preparation of sodium formate, in particular to a preparation method of anhydrous sodium formate. The anhydrous sodium formate provided by the invention is prepared from formic acid and sodium hydroxide as raw materials. The preparation method comprises the following steps: S1, preparing a synthetic solution; s2, concentrating and crystallizing; s3, dewatering and drying. The preparation method provided by the invention is simple to operate, green and environment-friendly; the sodium formate finished product prepared by the preparation method provided by the invention is high in purity, low in water content and easy to separate from byproducts.

Description

Technical Field

[0001] The invention relates to the field of sodium formate preparation, and in particular to a method for preparing anhydrous sodium formate. Background Art

[0002] Sodium formate, molecular formula: HCOONa, molecular weight: 68.01, white granular or crystalline powder, easily soluble in water and glycerin. It has a slight formic acid odor and is hygroscopic. It decomposes into sodium oxalate and hydrogen when heated, and then generates sodium carbonate. Sodium formate is mainly used to produce sodium hydrosulfite, oxalic acid and formic acid. In the leather industry, it is used as a camouflage acid in the chrome tanning process, used as a catalyst and stabilizer, and a reducing agent in the printing and dyeing industry. At present, the main methods for producing sodium formate are synthesis method and polyol by-product method.

[0003] The process of synthesizing sodium formate is to use coal as raw material, and obtain the carbon monoxide gas required for the process through gasification, desulfurization, decarbonization and other processes, and then react with sodium hydroxide to generate sodium formate solution through heating and pressurization, and then generate solid product sodium formate through evaporation, separation and drying. The process has the following problems: the reaction conditions of carbon monoxide and sodium hydroxide are temperature 160-200°C and pressure 1.5-2.5Mpa, and the corrosiveness of sodium hydroxide at this temperature varies greatly with the increase of concentration. When the concentration of sodium hydroxide is greater than 20%, the corrosiveness of the equipment is greatly increased, but the upper limit of the sodium formate content of the sodium formate solution produced by sodium hydroxide with a concentration of 20% is only 425g / L; coal gas contains a small amount of carbon dioxide, and a small amount of impurities such as sodium carbonate and sodium chloride will be generated when the coal gas is synthesized with caustic soda. In the subsequent evaporation stage, these impurities are not easy to separate.

[0004] However, the sodium formate contained in the organic phase of the polyol by-product method promotes the decomposition of the polyol when heated during the subsequent polyol separation process, affecting the product quality of the polyol. Summary of the invention

[0005] In view of the above existing technical problems, the present invention aims to invent a method for preparing anhydrous sodium formate to solve the problems of the existing preparation method such as many by-products, difficult separation, high energy consumption and serious pollution. The sodium formate prepared by the present invention has high purity, low water content and low drying loss.

[0006] The invention discloses a method for preparing anhydrous sodium formate, comprising the following steps:

[0007] S1 Preparation of synthetic liquid: Deionized water is added to an enamel reactor, and then formic acid is added to obtain a mixed liquid, and then sodium hydroxide is added to the mixed liquid while stirring to react, and after the reaction is completed, a synthetic liquid is obtained;

[0008] S2 Concentration and crystallization: After the pH value of the synthetic liquid obtained in step S1 is tested to be up to standard, the synthetic liquid is filtered while hot, the filtrate is collected, the collected filtrate is concentrated under reduced pressure to obtain a concentrated synthetic liquid, and the concentrated synthetic liquid is cooled and crystallized to obtain a crystal;

[0009] S3 dehydration and drying: the crystals obtained in step S2 are placed in a centrifuge for dehydration, the speed of the centrifuge and the dehydration time are controlled, and then after the centrifugal dehydration is completed, the dehydrated crystals are pumped into a double cone dryer for drying, and the speed, vacuum degree, water bath temperature and drying time of the double cone dryer are adjusted. After the drying is completed, the dried crystals are collected to obtain anhydrous sodium formate.

[0010] Preferably, in the S1 synthetic liquid preparation step, the mass ratio of formic acid to sodium hydroxide is 1:(0.67-0.83).

[0011] Preferably, in the S2 concentration and crystallization step, the concentration of the concentrated synthetic solution is 35-40° Bé.

[0012] Preferably, in the step of preparing the S1 synthetic solution, when adding sodium hydroxide, the temperature of the mixed solution is controlled to be 60-90°C.

[0013] Preferably, in the S2 concentration and crystallization step, the pH value of the synthetic liquid is measured to be 6.0 to 6.5.

[0014] Preferably, in the S2 concentration and crystallization step, the filter used in the filtration process has a mesh size of 150 to 200.

[0015] Preferably, in the S2 concentration and crystallization step, the cooling and crystallization temperature of the concentrated solution is 18 to 21° C.; and the cooling and crystallization time is 9 to 11 hours.

[0016] Preferably, in the dehydration and drying step S3, the centrifuge speed is 500-800 rpm; and the dehydration time is 20-30 min.

[0017] Preferably, in the dehydration and drying step S3, the rotation speed of the double-cone dryer is 30 to 50 r / min; and the vacuum degree of the double-cone dryer is -0.08 to 0.1 MPa.

[0018] Preferably, in the dehydration and drying step S3, the water bath temperature during the drying process is 80-100° C.; and the drying time is 20-24 hours.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention provides a method for preparing anhydrous sodium formate, wherein formic acid is used as a raw material instead of coal to react with sodium hydroxide to generate a sodium formate solution, thereby reducing impurities generated during production and improving the purity of the sodium formate; in the preparation process, the temperature, time and other parameters of cooling crystallization and drying are controlled, thereby effectively improving the purity of the finished sodium formate product and reducing the water content of the finished sodium formate product. The preparation method provided by the present invention is simple to operate, green and environmentally friendly, and the obtained product has high purity, low water content, and is easy to separate from by-products. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 :Process flow chart of anhydrous sodium formate DETAILED DESCRIPTION

[0022] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0023] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0024] Embodiment 1: A method for preparing anhydrous sodium formate comprises the following steps.

[0025] Preparation of S1 synthetic liquid: add 300L of deionized water into an enamel reactor, then add 750kg of formic acid to obtain a mixed liquid, and then add 500kg of sodium hydroxide into the mixed liquid while stirring for reaction, wherein the mass ratio of formic acid to sodium hydroxide is 1:0.67, and the temperature of the mixed liquid is always controlled to be maintained at 60°C. After the reaction is completed, a synthetic liquid is obtained.

[0026] S2 Concentration and crystallization: After the pH value of the synthetic liquid obtained in step S1 is detected to be 6.0, the synthetic liquid is filtered while hot, and the filtrate is collected by a filter with a mesh number of 150. The collected filtrate is concentrated under reduced pressure. The concentration of the concentrated synthetic liquid is 35°Bé. The concentrated synthetic liquid is transferred to a crystallization kettle, and the temperature of the crystallization kettle is controlled to 15°C. Cooling crystallization is started, and crystallization is performed for 9 hours to obtain crystals.

[0027] S3 dehydration and drying: the crystals obtained in step S2 are placed in a centrifuge for dehydration, the centrifuge speed is controlled to be 500 rpm, the dehydration time is 20 min, and then after the centrifugal dehydration is completed, the dehydrated crystals are vacuum pumped into a double cone dryer for drying, the rotation speed of the double cone dryer is 30 r / min, the vacuum degree of the double cone dryer is -0.09 MPa, the water bath temperature is 80°C, the drying time is 18 h, and after the drying is completed, the dry crystals are collected, which are anhydrous sodium formate.

[0028] Embodiment 2: A method for preparing anhydrous sodium formate comprises the following steps.

[0029] Preparation of S1 synthetic liquid: 300L of deionized water was added to an enamel reactor, and then 750kg of formic acid was added to obtain a mixed liquid. Then 525kg of sodium hydroxide was added to the mixed liquid while stirring for reaction, wherein the mass ratio of formic acid to sodium hydroxide was 1:0.70. The temperature of the mixed liquid was always controlled to be maintained at 65°C. After the reaction was completed, a synthetic liquid was obtained.

[0030] S2 Concentration and crystallization: After the pH value of the synthetic liquid obtained in step S1 is detected to be 6.1, the synthetic liquid is filtered while hot, and the filtrate is collected by a filter with a mesh number of 160. The collected filtrate is concentrated under reduced pressure. The concentration of the concentrated synthetic liquid is 39°Bé. The concentrated synthetic liquid is transferred to a crystallization kettle, and the temperature of the crystallization kettle is controlled to 24°C. Cooling crystallization is started, and crystallization is performed for 9.5 hours to obtain crystals.

[0031] S3 dehydration and drying: the crystals obtained in step S2 are placed in a centrifuge for dehydration, the speed of the centrifuge is controlled to be 550rpm, the dehydration time is 22min, and then after the centrifugal dehydration is completed, the dehydrated crystals are vacuum pumped into a double-cone dryer for drying, the rotation speed of the double-cone dryer is 35r / min, the vacuum degree of the double-cone dryer is -0.08MPa, the water bath temperature is 85°C, the drying time is 20h, and after the drying is completed, the dry crystals are collected, which are anhydrous sodium formate.

[0032] Embodiment 3: A method for preparing anhydrous sodium formate comprises the following steps.

[0033] Preparation of S1 synthetic liquid: add 300L of deionized water into an enamel reactor, then add 750kg of formic acid to obtain a mixed liquid, and then add 550kg of sodium hydroxide into the mixed liquid while stirring for reaction, wherein the mass ratio of formic acid to sodium hydroxide is 1:0.73, and the temperature of the mixed liquid is always controlled to be maintained at 70°C. After the reaction is completed, a synthetic liquid is obtained.

[0034] S2 Concentration and crystallization: After the pH value of the synthetic liquid obtained in step S1 is detected to be 6.2, the synthetic liquid is filtered while hot, and the filtrate is collected by a filter with a mesh number of 170. The collected filtrate is concentrated under reduced pressure. The concentration of the concentrated synthetic liquid is 38°Bé. The concentrated synthetic liquid is transferred to a crystallization kettle, and the temperature of the crystallization kettle is controlled to 21°C. Cooling crystallization is started, and crystallization is performed for 10 hours to obtain crystals.

[0035] S3 dehydration and drying: the crystals obtained in step S2 are placed in a centrifuge for dehydration, the centrifuge speed is controlled to be 600 rpm, the dehydration time is 24 min, and then after the centrifugal dehydration is completed, the dehydrated crystals are vacuum pumped into a double cone dryer for drying, the rotation speed of the double cone dryer is 40 r / min, the vacuum degree of the double cone dryer is -0.10 MPa, the water bath temperature is 90°C, the drying time is 22 h, and after the drying is completed, the dry crystals are collected, which are anhydrous sodium formate.

[0036] Embodiment 4: A method for preparing anhydrous sodium formate comprises the following steps.

[0037] Preparation of S1 synthetic liquid: 300L of deionized water was added to an enamel reactor, and then 750kg of formic acid was added to obtain a mixed liquid. Then 575kg of sodium hydroxide was added to the mixed liquid while stirring for reaction. The mass ratio of formic acid to sodium hydroxide was 1:0.76. The temperature of the mixed liquid was always controlled to be maintained at 75°C. After the reaction was completed, a synthetic liquid was obtained.

[0038] S2 Concentration and crystallization: After the pH value of the synthetic liquid obtained in step S1 is detected to be 6.3, the synthetic liquid is filtered while hot, and the filtrate is collected by a filter with a mesh number of 180. The collected filtrate is concentrated under reduced pressure. The concentration of the concentrated synthetic liquid is 37°Bé. The concentrated synthetic liquid is transferred to a crystallization kettle, and the temperature of the crystallization kettle is controlled to 18°C. Cooling crystallization is started, and crystallization is performed for 10.5 hours to obtain crystals.

[0039] S3 dehydration and drying: the crystals obtained in step S2 are placed in a centrifuge for dehydration, the centrifuge speed is controlled to be 650rpm, the dehydration time is 26min, and then after the centrifugal dehydration is completed, the dehydrated crystals are vacuum pumped into a double cone dryer for drying, the rotation speed of the double cone dryer is 45r / min, the vacuum degree of the double cone dryer is -0.11MPa, the water bath temperature is 95°C, the drying time is 24h, and after the drying is completed, the dry crystals are collected, which are anhydrous sodium formate.

[0040] Embodiment 5: A method for preparing anhydrous sodium formate comprises the following steps.

[0041] Preparation of S1 synthetic liquid: add 300L of deionized water into an enamel reactor, then add 750kg of formic acid to obtain a mixed liquid, and then add 600kg of sodium hydroxide into the mixed liquid while stirring for reaction, wherein the mass ratio of formic acid to sodium hydroxide is 1:0.80, and the temperature of the mixed liquid is always controlled to be maintained at 80°C. After the reaction is completed, a synthetic liquid is obtained.

[0042] S2 Concentration and crystallization: After the pH value of the synthetic liquid obtained in step S1 is detected to be 6.4, the synthetic liquid is filtered while hot, and the filtrate is collected by a filter with a mesh number of 190. The collected filtrate is concentrated under reduced pressure. The concentration of the concentrated synthetic liquid is 40°Bé. The concentrated synthetic liquid is transferred to a crystallization kettle, and the temperature of the crystallization kettle is controlled to 26°C. Cooling crystallization is started, and crystallization is performed for 11 hours to obtain crystals.

[0043] S3 dehydration and drying: the crystals obtained in step S2 are placed in a centrifuge for dehydration, the centrifuge speed is controlled to be 700 rpm, the dehydration time is 28 min, and then after the centrifugal dehydration is completed, the dehydrated crystals are vacuum pumped into a double cone dryer for drying, the rotation speed of the double cone dryer is 50 r / min, the vacuum degree of the double cone dryer is -0.12 MPa, the water bath temperature is 100 ° C, the drying time is 27 h, and after the drying is completed, the dry crystals are collected, which are anhydrous sodium formate.

[0044] Embodiment 6: A method for preparing anhydrous sodium formate comprises the following steps.

[0045] Preparation of S1 synthetic liquid: add 300L of deionized water into an enamel reactor, then add 750kg of formic acid to obtain a mixed liquid, then add 625kg of sodium hydroxide into the mixed liquid while stirring for reaction, wherein the mass ratio of formic acid to sodium hydroxide is 1:0.83, and the temperature of the mixed liquid is always controlled to be maintained at 90°C. After the reaction is completed, a synthetic liquid is obtained.

[0046] S2 Concentration and crystallization: After the pH value of the synthetic liquid obtained in step S1 is detected to be 6.5, the synthetic liquid is filtered while hot, and the filtrate is collected by a filter with a mesh number of 200. The collected filtrate is concentrated under reduced pressure. The concentration of the concentrated synthetic liquid is 41°Bé. The concentrated synthetic liquid is transferred to a crystallization kettle, and the temperature of the crystallization kettle is controlled to 28°C. Cooling crystallization is started, and crystallization is performed for 11 hours to obtain crystals.

[0047] S3 dehydration and drying: the crystals obtained in step S2 are placed in a centrifuge for dehydration, the speed of the centrifuge is controlled to be 800 rpm, the dehydration time is 30 min, and then after the centrifugal dehydration is completed, the dehydrated crystals are vacuum pumped into a double cone dryer for drying, the rotation speed of the double cone dryer is 50 r / min, the vacuum degree of the double cone dryer is -0.13 MPa, the water bath temperature is 100 ° C, the drying time is 30 h, and after the drying is completed, the dry crystals are collected, which is anhydrous sodium formate.

[0048] The anhydrous sodium formate obtained in Examples 1 to 6 was tested, and the test data are shown in Table 1 below:

[0049] Table 1

[0050]

[0051]

[0052] It can be seen from the above table that the anhydrous sodium formate prepared in Examples 2 to 5 has high purity, low loss on drying, and low contents of chloride, sulfate and phosphate, which meet the requirements.

[0053] Comparative Example 1: Investigate the effect of sodium hydroxide concentration on product purity.

[0054] Add 300L of deionized water to the enameled reactor, and add 750kg of formic acid while stirring. Slowly add different amounts of sodium hydroxide, ensuring that the reaction temperature does not exceed 90°C, and prepare reaction solutions with different solution concentrations. Use a 200-mesh filter to filter the reaction solution until it is clear. Transfer the filtered reaction solution to an enameled reactor for reduced pressure concentration, removing 300L of water until the material precipitates. Control the temperature in the crystallization kettle to 20-23°C and keep it for 10 hours. Put the crystallized material into a centrifuge for dehydration for 25 minutes. Use a double cone dryer for drying, with a rotation speed of 45r / min, a vacuum degree of -0.09MPa, a water bath temperature of 95°C, a drying time of 24 hours, and a product purity test. The experimental results are shown in Table 2.

[0055] Table 2

[0056]

[0057] From the experimental results in the table above, it can be seen that the concentration of sodium hydroxide has a significant effect on the product purity of sodium formate within a certain range. When the solution concentration is 37°Bé (experiment number 2), the product purity reaches the highest, which is 99.9%. When the solution concentration exceeds or falls below 37°Bé, the product purity decreases slightly. This shows that 37°Bé is the optimal solution concentration and can be used as a reference standard in the production process to obtain high-purity anhydrous sodium formate.

[0058] Comparative Example 2: Investigate the effect of different crystallization temperatures on product purity.

[0059] Add 300L of deionized water to the enameled reactor, and add 750kg of formic acid while stirring. Slowly add 525kg of sodium hydroxide, ensuring that the reaction temperature does not exceed 90°C and the solution concentration should be 37°Bé. Use a 200-mesh filter to filter the reaction solution until it is clear. Transfer the filtered reaction solution to an enameled reactor for reduced pressure concentration, remove 300L of water until the material precipitates, and conduct experiments according to different crystallization temperatures. Control the temperature in the crystallization kettle to the set value and maintain it for 10 hours. Place the crystallized material in a centrifuge for dehydration for 25 minutes. Use a double-cone dryer for drying, with a rotation speed of 45r / min, a vacuum degree of -0.09MPa, a water bath temperature of 95°C, a drying time of 24 hours, and a product purity test. The experimental results are shown in Table 3.

[0060] Table 3

[0061]

[0062] From the experimental results in the table above, it can be seen that the crystallization temperature has a significant effect on the product purity of sodium formate. When the crystallization temperature is 18°C ​​(experiment number 2), the product purity reaches the highest, which is 99.9%, and the inorganic salt impurities meet the regulations. When the crystallization temperature exceeds or is lower than 18°C, the product purity decreases and the inorganic salt impurities increase. This shows that 18°C ​​is the optimal crystallization temperature and can be used as a reference standard in the production process to obtain high-purity anhydrous sodium formate.

[0063] Comparative Example 3: Investigate the effect of different drying times on product purity and water content:

[0064] Add 300L of deionized water to the enameled reactor and add 750kg of formic acid while stirring. Slowly add 525kg of sodium hydroxide to ensure that the reaction temperature does not exceed 90°C and the solution concentration should be 343g / L. Use a 200-mesh filter to filter the reaction solution until it is clear. Transfer the filtered reaction solution to a 1500L enameled reactor for reduced pressure concentration, removing 300L of water until the material precipitates. Control the temperature in the crystallization kettle to 18°C ​​and keep it for 10 hours. Put the crystallized material into a centrifuge for dehydration for 25 minutes. Use a double cone dryer for drying, with a rotation speed of 45r / min, a vacuum degree of -0.09Mpa, and a water bath temperature of 95°C. Set different drying times for experiments to detect product purity. The experimental results are shown in Table 4.

[0065] Table 4

[0066]

[0067] It can be seen from the experimental results that the drying time has a significant effect on the product purity and water content of sodium formate. When the drying time is 22 hours and 24 hours (experimental numbers 3 and 4), the product purity reaches the highest, which is 99.9%, and the drying loss is 0.21% and 0.18% respectively. When the drying time is less than 22 hours or more than 24 hours, the product purity decreases slightly. Considering the product quality and energy consumption, 22 to 24 hours is the best drying time, which can be used as a reference standard in the production process to obtain anhydrous sodium formate with high purity and low water content.

[0068] In summary, the present invention uses formic acid instead of coal as a raw material, reduces impurities in the production process, and effectively improves the purity of sodium formate. During the preparation process, the purity and yield of sodium formate are improved by strictly controlling the reaction conditions. By adjusting the process parameters such as pH value and reaction temperature, the best combination is found to achieve the highest yield and purity. The filtration process and dehydration process are strictly controlled to ensure effective removal of impurities. The production process is simplified, the energy consumption is low, it meets environmental protection requirements, and the operation is safe. Through the above optimization, the present invention significantly improves the purity and production efficiency of anhydrous sodium formate, while achieving the goals of environmental protection and energy saving. The purity of the produced anhydrous sodium formate is as high as 99.9%, and can meet the reagent standards of HG / T 5390-2018 (Chemical Industry Standard of the People's Republic of China), ACS (American Chemical Society) and EP (European Pharmacopoeia).

[0069] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A method for preparing anhydrous sodium formate, characterized in that: The following steps are involved: S1 Preparation of synthetic liquid: Deionized water is added to an enamel reactor, and then formic acid is added to obtain a mixed liquid, and then sodium hydroxide is added to the mixed liquid while stirring to react, and after the reaction is completed, a synthetic liquid is obtained; S2 Concentration and crystallization: After the pH value of the synthetic liquid obtained in step S1 is tested to be up to standard, the synthetic liquid is filtered while hot, the filtrate is collected, the collected filtrate is concentrated under reduced pressure to obtain a concentrated synthetic liquid, and the concentrated synthetic liquid is cooled and crystallized to obtain a crystal; S3 dehydration and drying: the crystals obtained in step S2 are placed in a centrifuge for dehydration, the speed of the centrifuge and the dehydration time are controlled, and then after the centrifugal dehydration is completed, the dehydrated crystals are pumped into a double cone dryer for drying, and the speed, vacuum degree, water bath temperature and drying time of the double cone dryer are adjusted. After the drying is completed, the dried crystals are collected to obtain anhydrous sodium formate.

2. The method for preparing anhydrous sodium formate according to claim 1, wherein In the S1 synthetic liquid preparation step, the mass ratio of formic acid to sodium hydroxide is 1:(0.67-0.83).

3. The method for preparing anhydrous sodium formate according to claim 1, wherein In the S2 concentration and crystallization step, the concentration of the concentrated synthetic solution is 35-40° Bé.

4. The method for preparing anhydrous sodium formate according to claim 1, wherein In the S1 synthetic liquid preparation step, when sodium hydroxide is added, the temperature of the mixed liquid is controlled at 60-90°C.

5. The method for preparing anhydrous sodium formate according to claim 1, wherein: In the S2 concentration and crystallization step, the pH value of the synthetic liquid was measured to be 6.0-6.

5.

6. The method for preparing anhydrous sodium formate according to claim 1, characterized in that: In the S2 concentration and crystallization step, the filter used in the filtration process has a mesh size of 150 to 200.

7. The method for preparing anhydrous sodium formate according to claim 1, characterized in that: In the S2 concentration and crystallization step, the cooling and crystallization temperature of the concentrated solution is 18 to 21° C.; and the cooling and crystallization time is 9 to 11 hours.

8. The method for preparing anhydrous sodium formate according to claim 1, wherein In the S3 dehydration and drying step, the centrifuge speed is 500-800 rpm; the dehydration time is 20-30 min.

9. The method for preparing anhydrous sodium formate according to claim 1, characterized in that: In the S3 dehydration and drying step, the rotation speed of the double cone dryer is 30 to 50 r / min; the vacuum degree of the double cone dryer is -0.08 to 0.1 MPa.

10. The method for preparing anhydrous sodium formate according to claim 1, characterized in that: In the dehydration and drying step S3, the water bath temperature during the drying process is 80-100° C.; the drying time is 20-24 hours.

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