Method and device for continuously producing high-quality formate

Abstract

The invention discloses a method for continuously producing high-quality formate, the method for continuously producing high-quality formate can be applied to continuous large-scale production of formate, and the method comprises the following steps: premixing methyl formate obtained by methanol carbonylation as a raw material with a hydroxide aqueous solution; methyl formate is completely reacted in a rectifying tower in a reactive distillation mode, a methanol solution is obtained at the tower top, a formate solution is obtained at the tower kettle, and the formate solution can be further filtered, evaporated, centrifuged and dried to obtain high-quality formate.

Description

Technical Field

[0001] This invention belongs to the field of chemical production technology, specifically relating to a method and apparatus for the continuous production of high-quality formate. Background Technology

[0003] Formates are salts formed from formate ions (HCOO⁻) and cations. They typically possess good solubility and reducing properties, and are widely used in chemical synthesis as reducing agents and catalysts in ester preparation and aldehyde reduction reactions. They are also used as reducing agents to aid in the catalytic synthesis of dyes and bleaching agents. In the petroleum industry, they are used as water-reducing agents and acidifying agents to promote oil well production, and are widely applied in the chemical industry and other fields. Formate synthesis can be achieved mainly through traditional chemical synthesis methods, electrochemical reduction methods, and biomass conversion pathways. The sodium formate method, a traditional chemical synthesis method, is mature but faces serious pollution and high costs. The more advanced methyl formate hydrolysis method has become the mainstream industrial route. It synthesizes methyl formate through methanol carbonylation, followed by further hydrolysis to obtain formic acid. Formic acid reacts with carbonates to produce formates. This method uses simple raw materials and produces no byproducts, but the process is complex and requires a large initial investment. Due to the volatile nature of methyl formate, hydrolysis and acidolysis require the reaction to occur within a temperature range of -5 to 30°C. Since this temperature is below the boiling point of methyl formate (31.5°C), a long reaction time is necessary. However, methyl formate is still not completely hydrolyzed, resulting in the formation of formaldehyde-water solutions. This leads to formaldehyde volatilization and escape during subsequent processing. The carbon dioxide hydrogenation reduction method offers a green pathway, directly converting CO2 into formic acid / formate salts. However, this reaction presents significant thermodynamic challenges, requiring high pressure and highly efficient catalysts, and currently faces challenges in terms of both economy and efficiency.

[0004] Patent CN113248363A discloses a method for utilizing methyl formate waste liquid. The method involves hydrolyzing the methyl formate-containing waste liquid with a sulfuric acid solution, followed by neutralization with calcium hydroxide to obtain calcium formate. This method requires a specific concentration of sulfuric acid to inhibit methyl formate hydrolysis. The introduced sulfuric acid exists in solution form in the hydrolysate, but the patent does not specify a method for its removal, thus affecting the purity of the calcium formate product.

[0005] Patent CN115636746A discloses a process for the high-value comprehensive utilization of coal-derived methyl formate waste liquid. The process involves hydrolyzing the methyl formate waste liquid to obtain industrial calcium formate by adding inorganic calcium in batches. This method requires strict control of the reaction temperature, and the proportion of added methyl formate, water and inorganic calcium makes the reaction a solid-liquid reaction. The conversion rate of methyl formate is uncontrollable, and the solubility of inorganic calcium is low, which can easily lead to inorganic calcium entering the calcium formate product and affecting the purity of the calcium formate product. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for continuous production of high-quality formate. This method can be applied to the continuous large-scale production of formate. The process uses methyl formate obtained by methanol carbonylation as raw material and premixes it with an aqueous hydroxide solution. Then, the methyl formate is completely reacted in a distillation column by reactive distillation. A methanol solution is obtained at the top of the column, and a formate solution is obtained at the bottom. The formate solution can be further filtered, evaporated, centrifuged and dried to obtain high-quality formate.

[0007] This invention is achieved through the following technical solution: A method for continuous production of high-quality formate includes the following steps: The raw material liquid is mixed with an inorganic alkaline solution to obtain a premixed liquid. The premixed liquid is subjected to reactive distillation. The distillate is used to obtain a methanol solution, and the residue is used to obtain a formate solution. The raw material liquid is methyl formate obtained by methanol carbonylation; The raw material solution contains methyl formate at a mass concentration of 90-99.9%, methanol at a mass concentration of 0.1-9.8%, and formaldehyde at a mass concentration of 0.01-0.2%. The inorganic alkaline solution is an aqueous solution of hydroxides, wherein the hydroxides are hydroxides of lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, and strontium; the formate is the formate of the corresponding hydroxide, namely lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, and strontium. The concentration of the inorganic alkaline solution is 100 g / L to 800 g / L, preferably 200 g / L to 600 g / L; the molar ratio of methyl formate to inorganic alkaline in the premixed solution is 0.95 to 2.05:1. The operating pressure of the reactive distillation process is 101~150 kPa (A absolute pressure), preferably 101~120 kPa (A). In the above technical solution, the temperature of the premixed liquid is 40~80℃, preferably 40~60℃.

[0008] In the above technical solution, during the reactive distillation process, the premixed liquid is fed at a theoretical plate number of 5 to 30 from bottom to top, preferably 10 to 20. In the reactive distillation process, the ratio of the distillate collected from the bottom of the vessel to the recycled residue returned to the reactive distillation process is 1:0.1~2.0. The position of the recycled residue in the tower needs to be 2~10 theoretical plates higher than the premixed liquid feed position, preferably 2~5. In the reactive distillation process, the reflux ratio is 1~6:1, preferably 1~3:1; In the reactive distillation process, the theoretical plate number is 15-60, preferably 25-40.

[0009] During the reactive distillation process, the pH of the formate solution in the distillate at the bottom of the vessel is 7-10, preferably 7-8.

[0010] In the reactive distillation process, the methanol content in the distillate is 99-99.5% by mass, which can be used as carbonylated methanol for reuse in the preceding methanol carbonylation process; In the reactive distillation process, the conversion rate of methyl formate is 99.9-100%.

[0011] The above technical solution also includes a crystallization process, in which the formate solution obtained from the distillate during the reactive distillation process is filtered, evaporated and crystallized, subjected to solid-liquid separation and drying processes to obtain high-quality formate. The high-quality formate has a formate content greater than 99% by mass.

[0012] In the above technical solution, the filtration process employs one or more of the following methods: plate and frame filtration, vacuum bag filtration, filter cartridge filtration, and membrane filtration. The evaporation crystallization operation temperature is 60℃~170℃, preferably 80℃~150℃; The solid-liquid separation is performed using a centrifugal separation method; The drying process is operated at a temperature of 100℃~180℃, preferably 110℃~140℃.

[0013] An apparatus for continuous production of high-quality formate includes a premixing vessel, a reactive distillation column, a reboiler, a condenser, and a condenser tank. The bottom outlet of the premixing vessel is connected to the inlet pipe of the reactive distillation column; the bottom outlet of the reactive distillation column is connected to the inlet pipe of the reboiler; the outlet of the reboiler is connected to the reboiler return pipe of the reactive distillation column; the bottom outlet of the reactive distillation column is connected to the distillate return pipe of the reactive distillation column; the top outlet of the reactive distillation column is connected to the inlet pipe of the condenser; the outlet of the condenser is connected to the inlet pipe of the condenser; and the outlet of the condenser is connected to the distillate return pipe of the reactive distillation column.

[0014] In the above technical solution, a feed pump is also installed on the pipeline between the bottom outlet of the premixing vessel and the inlet of the reactive distillation column; A bottom discharge pump is also installed on the pipeline between the bottom outlet of the reactive distillation column and the return outlet of the distillate of the reactive distillation column. A top-of-the-column pump is also installed on the pipeline connecting the outlet of the condenser to the return outlet of the distillate from the reactive distillation column.

[0015] The advantages and beneficial effects of this invention are as follows: This invention provides a method for the continuous production of high-quality formate via methanol carbonylation and alkaline hydrolysis. This method utilizes a combination of reactive distillation and alkaline hydrolysis with methyl formate (an intermediate product in formic acid production) and an aqueous hydroxide solution to continuously produce formate. This shortens the formate production process and reduces the material requirements of the equipment. Simultaneously, the combination of reactive distillation and alkaline hydrolysis creatively achieves a high-efficiency conversion of over 99.9% formate, improving the quality of formate and increasing its purity to over 99%. The methanol obtained from the reactive distillation can also be used as recycled methanol without affecting the preceding processes, thus optimizing and upgrading the process. This invention features a simple process, zero emissions of waste gas, wastewater, and solid waste, is environmentally friendly, and is easily implemented for large-scale continuous automated production, giving it strong market competitiveness.

[0016] The above effects are mainly reflected in the following aspects: 1. Unlike the raw materials used in existing technologies: Methyl formate is an ester organic compound, a colorless, odorous, volatile liquid, miscible with ethanol, soluble in methanol and diethyl ether, easily hydrolyzed, with a boiling point lower than methanol, and easier to distill than methanol. The methyl formate used in this application mainly comes from: methyl formate, an intermediate product of the methyl formate hydrolysis process for producing formic acid (i.e., methyl formate obtained by methanol carbonylation). This methyl formate contains methanol and a small amount of formaldehyde, and is easily volatile at low temperatures; formaldehyde does not hydrolyze, but can be converted into methanol under alkaline hydrolysis. However, the volatile nature of methyl formate makes its hydrolysis incomplete. This application uses alkaline hydrolysis + reactive distillation to achieve a complete reaction between methyl formate and formaldehyde.

[0017] 2. The difference between the alkaline hydrolysis + reactive distillation method used in this application and the hydrolysis and acid hydrolysis methods in the prior art: (1) Due to the volatile nature of methyl formate, hydrolysis and acid hydrolysis require methyl formate to react in the range of -5~30℃, which is lower than the boiling point of methyl formate at 31.5℃, and requires a long reaction time. However, methyl formate is still not completely hydrolyzed, and the presence of formaldehyde forms an aqueous solution of formaldehyde. In subsequent processing, there are problems such as formaldehyde volatilization causing formaldehyde escape. (2) When methyl formate is neutralized with an inorganic base after hydrolysis or acidolysis, the incomplete hydrolysis of methyl formate during hydrolysis is not changed; at the same time, the neutralization reaction of formic acid obtained after hydrolysis with the inorganic base inhibits the reaction of formaldehyde with the inorganic base; since the degree of hydrolysis of methyl formate is uncertain, the ratio of the corresponding inorganic base is difficult to control. Combined with the fact that methanol that meets the requirements cannot be obtained at the top of the column during distillation, the bottom results are difficult to control, and the purity of the formate product is not high. (3) The alkaline hydrolysis + reactive distillation method adopted in this application can promote the separation of methanol in the feed liquid through reactive distillation, which accelerates the alkaline hydrolysis efficiency and significantly shortens the reaction time; the volatile methyl formate can be further hydrolyzed under the action of reflux and then flow to the lower section to react with inorganic base; at the same time, the upward movement of volatile methyl formate makes the ratio of inorganic base in the feed section significantly exceed the amount required for alkaline hydrolysis, thereby achieving the complete reaction of formaldehyde; The combination of alkaline hydrolysis and reactive distillation overcomes the problem of low conversion rate after methyl formate volatilization. At the same time, the use of a partial excess of alkali achieves complete reaction of formaldehyde, allowing methyl formate and inorganic alkali to react fully under near stoichiometric conditions. The reaction is controllable and the results are stable.

[0018] 3. The reflux design of a reactive distillation column has the following advantages: (1) The raw material liquid in the alkaline hydrolysis process has been preheated to accelerate the volatilization of methyl formate, so that the premixed liquid has sufficient temperature when it arrives at the reactive distillation column to accelerate the alkaline hydrolysis reaction (heating accelerates the reaction). Through the volatilization of methyl formate, the methyl formate gas forms a forced contact with the premixed liquid, which promotes full contact between methyl formate and inorganic base in the premixed liquid during the alkaline hydrolysis process, further shortening the time required for alkaline hydrolysis. Compared with hydrolysis and acid hydrolysis, its reaction time is shortened. (2) When the premixed liquid is fed, due to the volatilization of methyl formate, the volatilized methyl formate gas phase separates into gas and liquid at the feed position, which reduces the methyl formate content in the premixed liquid and causes an excess of inorganic base. The excess inorganic base accelerates the reaction of formaldehyde at this point, promoting the complete reaction of formaldehyde. During the gas-liquid contact process in the reactive distillation column, the rising vapor phase in the column bottom and the liquid solid (some inorganic bases have low solubility and require time for the solid phase to change to the liquid phase) are fully contacted, which promotes the contact and collision time between methyl formate and the liquid solid phase, further shortening the reaction time. However, a certain packing height needs to be maintained. Therefore, the feed position is set 5 to 30 theoretical plates away from the column bottom, preferably 10 to 20 plates. When the number of plates is less than 5, the inorganic base cannot react completely during the production process, resulting in an increase in the pH of the column bottom and an excess of alkali content in the column bottom product, which has a significant impact on the purity of the formate product. (3) The reflux position of the bottom liquid should be 2 to 10 plates higher than the feed position. After the premixed liquid is preheated, the amount of methyl formate volatilized is not large compared with the methyl formate in the feed. However, after this proportion of methyl formate rises to the top of the column, it is enough to reduce the conversion rate of methyl formate and affect the mass content of methanol at the top of the column. By refluxing the bottom liquid to the upper part of the feed position, the gas-liquid entrainment can be effectively suppressed. At the same time, the returned liquid phase promotes the new dissolution or hydrolysis of the volatilized methyl formate in water. Considering the conventional single plate efficiency of 90%, two plates can increase the absorption efficiency of methyl formate to 99%. The newly dissolved methyl formate or the hydrolyzed formic acid and methanol react with the excess alkali below the feed position to ensure the complete reaction of methyl formate. Therefore, the bottom liquid reflux position should be ensured to be 2 to 10 theoretical plates higher than the feed position of the premixed liquid. Too high a position will increase the equipment cost and energy consumption, and the economic efficiency will be poor. Attached Figure Description

[0020] Figure 1 This is a schematic flowchart of a method for continuous production of high-quality formate provided by the present invention.

[0021] Figure 2 A simplified process flow diagram of an apparatus for the continuous production of high-quality formate provided by the present invention.

[0022] in: 1-Premixing vessel, 2-Feed pump, 3-Reactive distillation column, 4-Reboiler, 5-Condenser, 6-Bottom pump, 7-Condenser tank, 8-Top pump.

[0023] For those skilled in the art, other related figures can be obtained from the above figures without any creative effort. Detailed Implementation

[0024] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described below with reference to specific embodiments.

[0025] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0026] Example 1 Unless otherwise specified, the following embodiments are carried out in an apparatus for the continuous production of high-quality formate, which includes a premixing vessel (jacketed premixing vessel), a reactive distillation column (stainless steel packed column), a reboiler, a condenser, and a condenser tank; The bottom outlet of the premixing vessel is connected to the inlet pipe of the reactive distillation column; the bottom outlet of the reactive distillation column is connected to the inlet pipe of the reboiler; the outlet of the reboiler is connected to the reboiler return pipe of the reactive distillation column; the bottom outlet of the reactive distillation column is connected to the distillate return pipe of the reactive distillation column; the top outlet of the reactive distillation column is connected to the inlet pipe of the condenser; the outlet of the condenser is connected to the inlet pipe of the condenser; and the outlet of the condenser is connected to the distillate return pipe of the reactive distillation column.

[0027] In particular, a feed pump is also installed on the pipeline between the bottom outlet of the premixing vessel and the inlet of the reactive distillation column; A bottom discharge pump is also installed on the pipeline between the bottom outlet of the reactive distillation column and the return outlet of the distillate of the reactive distillation column. A top-of-the-column pump is also installed on the pipeline connecting the outlet of the condenser to the return outlet of the distillate from the reactive distillation column.

[0028] In the laboratory, methyl formate (95wt%, methanol 4.9wt%, formaldehyde 0.1wt%) was fed at a rate of 63.2 g / min, and lithium hydroxide solution (100 g / L) was fed at a rate of 240 ml / min. After premixing in a jacketed premixing vessel at 40℃, the mixture was fed into a DN40 stainless steel packed tower. This stainless steel packed tower was segmented, consisting of three sections, each filled with 500 mm of high-efficiency packing material. Each section had 5 theoretical plates, for a total of 17 theoretical plates. The premixed solution entered the third section of packing, while the bottom liquid was returned to the second section. A reflux ratio of 3:1 was used at the top of the tower to the first section of packing. The tower pressure was atmospheric pressure, the top outlet temperature was 40℃, the methanol content was 99.4 wt%, methyl formate and formaldehyde were undetectable, and the methyl formate conversion rate was 100%. The bottom outlet temperature was 100℃, and the pH was 7.2. After vacuum filtration, the filtrate was evaporated and concentrated to obtain white crystals, which were then dried at 110°C to obtain hydrated lithium formate crystals with a purity of 99.99%. Example 2 Using the apparatus of Example 1, a mixture of methyl formate (95 wt%, methanol approximately 5 wt%, formaldehyde 500 ppm) at a feed rate of 63.2 g / min and 800 g / L sodium hydroxide solution at a feed rate of 50 ml / min was premixed using a jacketed mixer at a temperature controlled at 40°C. A reflux ratio of 6:1 was used at the top of the column. The column pressure was atmospheric pressure, the top outlet temperature was 40°C, the methanol content was 99 wt%, the methyl formate content was <100 ppm, formaldehyde was not detected, and the methyl formate conversion rate was 99.9%. The bottom outlet temperature was 104°C, and the pH was 7.8. After vacuum filtration, the filtrate was evaporated and concentrated to obtain white crystals, which were then dried at 110°C to obtain sodium formate with a purity of 99%. Example 3 Using the apparatus of Example 1, a mixture of 90 wt% methyl formate (9.8 wt% methanol, 0.2 wt% formaldehyde) at a feed rate of 66.7 g / min and 700 g / L potassium hydroxide solution at a feed rate of 80 ml / min was premixed using a jacketed mixer at a temperature controlled at 40°C. A reflux ratio of 6:1 was used at the top of the column. The column pressure was 150 kPa(A), the top outlet temperature was 50°C, the methanol content was 99 wt%, the methyl formate content was <100 ppm, formaldehyde was not detected, and the methyl formate conversion rate was 99.9%. The bottom outlet temperature was 110°C, and the pH was 9. After vacuum filtration, the filtrate was evaporated and concentrated to obtain white crystals, which were then dried at 110°C to obtain potassium formate with a purity of 99.995%. Example 4 Using the apparatus of Example 1, a mixture of methyl formate (95 wt%, methanol approximately 5 wt%, formaldehyde 500 ppm) at a feed rate of 63.2 g / min and rubidium hydroxide solution (400 g / L) at a feed rate of 256 ml / min was premixed in a jacketed mixer at a temperature controlled at 45°C. A reflux ratio of 3:1 was used at the top of the column. The column pressure was atmospheric pressure, the top outlet temperature was 40°C, the methanol content was 99.9 wt%, methyl formate and formaldehyde were undetectable, and the methyl formate conversion rate was 100%. The bottom outlet temperature was 104°C, and the pH was 8. After vacuum filtration, the filtrate was evaporated and concentrated to obtain white crystals, which were then dried at 120°C to obtain rubidium formate with a purity of 99.992%. Example 5 Using the apparatus of Example 1, a mixture of methyl formate (96 wt%, methanol approximately 4 wt%, formaldehyde 420 ppm) at a feed rate of 62.5 g / min and cesium hydroxide solution (400 g / L) at a feed rate of 375 ml / min was premixed in a jacketed mixer at a temperature controlled at 50°C. A reflux ratio of 2:1 was used at the top of the column. The column pressure was atmospheric pressure, the top outlet temperature was 40°C, the methanol content was 99.9 wt%, methyl formate and formaldehyde were undetectable, and the methyl formate conversion rate was 100%. The bottom outlet temperature was 104°C, and the pH was 7.8. After vacuum filtration, the filtrate was evaporated and concentrated to obtain white crystals, which were then dried at 120°C to obtain cesium formate with a purity of 99.99%. Example 6 Using the apparatus of Example 1, an additional 500mm packing height was added, resulting in a total of 22 theoretical plates. A mixture of 98wt% methyl formate (2wt% methanol, 360ppm formaldehyde) at a feed rate of 61.3g / min and 100g / L magnesium hydroxide solution at a feed rate of 292ml / min was premixed using a jacketed mixer at a temperature controlled at 60°C. The premixed solution was then fed into the fourth packing section, while the bottom liquid was returned to the second packing section. A reflux ratio of 3:1 was used at the top of the column to the first packing section. The column pressure was atmospheric pressure, the top outlet temperature was 40°C, the methanol content was 99.9 wt%, methyl formate <100ppm, formaldehyde was undetectable, and the methyl formate conversion rate was 99.9%. The bottom outlet temperature was 104°C, and the pH was 8. After vacuum filtration, the filtrate was evaporated and concentrated to obtain white crystals. After drying at 120°C, magnesium formate hydrate was obtained with a purity of 99.999%. Example 7 Using the apparatus of Example 6, a mixture of methyl formate (99 wt% (1 wt% methanol, 100 ppm formaldehyde) at a feed rate of 60.7 g / min and a 100 g / L calcium hydroxide solution at a feed rate of 370 ml / min was premixed at 80°C using a jacketed mixer. A reflux ratio of 3:1 was used at the top of the column. The column pressure was atmospheric pressure, the top outlet temperature was 40°C, the methanol content was 99.9 wt%, the methyl formate content was <100 ppm, formaldehyde was not detected, and the methyl formate conversion rate was 99.9%. The bottom outlet temperature was 105°C, and the pH was 7. After vacuum filtration, the filtrate was evaporated and concentrated to obtain white crystals, which were then dried at 120°C to obtain calcium formate with a purity of 100%. Example 8 Using the apparatus of Example 6, a mixture of methyl formate (99.9 wt%, methanol 0.1 wt%, formaldehyde 100 ppm) at a feed rate of 60 g / min and strontium hydroxide solution (400 g / L) at a feed rate of 152 ml / min was premixed at 40°C using a jacketed mixer. A reflux ratio of 4:1 was used at the top of the column. The column pressure was 150 kPa(A), the top outlet temperature was 50°C, the methanol content was 99 wt%, methyl formate <100 ppm, formaldehyde was not detected, and the methyl formate conversion rate was 99.9%. The bottom outlet temperature was 110°C, and the pH was 9. After vacuum filtration, the filtrate was evaporated and concentrated to obtain white crystals, which were then dried at 110°C to obtain strontium formate with a purity of 99.995%. Example 9 A 200,000-ton formic acid production unit using the methyl formate hydrolysis process has a side-stream unit. The methyl formate solution in the unit's methyl formate storage tank is used as the methyl formate source for the side-stream unit. This solution contains 95.8 wt% methyl formate, 4.17 wt% methanol, and 300 ppm formaldehyde. Methyl formate is pumped at a rate of 1254 kg / h and potassium hydroxide solution at a rate of 1604 kg / h (700 g / L concentration) to a heated pipeline mixer, preheated to 60°C, before entering the DN... A 500 m packed tower is constructed with three sections of regular packing material, each with heights of 3, 3, and 3 m, and theoretical plate numbers of 9, 9, and 9 respectively, totaling 27 plates. The total tower height is approximately 14 m. The premixed liquid feed is located 3 m above the bottom of the tower with structured packing material. The reflux from the bottom to the upper part of the feed section is also 3 m of structured packing material (this position is 9 theoretical plates higher than the premixed liquid feed position). The tower top pressure is atmospheric pressure, the top outlet temperature is 40°C, the methanol content is 99.2 wt%, methyl formate and formaldehyde are undetectable, and the methyl formate conversion rate is 100%. The bottom outlet temperature is 106°C, and the pH is 7. The bottom liquid is a potassium formate solution. After vacuum filtration, the filtrate is evaporated and concentrated to obtain white crystals. After drying at 110°C, potassium formate is obtained with a purity of 99.994%. Comparative Example 1 A three-necked flask was used to react 63.2 g of methyl formate (approximately 5 wt% methanol and 500 ppm formaldehyde) with 240 ml of a 100 g / L lithium hydroxide solution under stirring. The reaction was carried out at 30°C for 2 hours. After distillation, the resulting liquid contained 80 wt% methanol, 450 ppm formaldehyde, and 20 wt% methyl formate, with a methyl formate conversion rate of 93.85%. The bottom liquid had a pH of 14. The purity of the lithium formate after filtration, evaporation, and drying was 92%. Comparative Example 2 Using the apparatus of Example 1, a mixture of 65 wt% methyl formate (15 wt% methanol, 8% methyl nitrite, and 12 wt% formaldehyde) at a feed rate of 92.4 g / min and 800 g / L sodium hydroxide solution at a feed rate of 50 ml / min was premixed using a jacketed mixer at a temperature controlled at 40°C. A reflux ratio of 6:1 was used at the top of the column. The column pressure was atmospheric pressure, and the top outlet temperature was 40°C. The methanol content was 72 wt%, methyl formate 2 wt%, methyl nitrite 2 wt%, and formaldehyde 24 wt%, with a methyl formate conversion rate of 98.4%. The bottom outlet temperature was 104°C, and the pH was 5. After vacuum filtration, the filtrate was evaporated and concentrated to obtain white crystals. After drying at 110°C, sodium formate was obtained with a sodium formate content of 95 wt% and a sodium nitrate content of 5 wt%. Comparative Example 3 Using the apparatus of Example 1, the reboiler reflux to the upper part of the feed section was eliminated, and the reboiler was not refluxed. A feed ratio of 95wt% methyl formate (approximately 5wt% methanol, 500ppm formaldehyde) at 63.2 g / min and 800 g / L sodium hydroxide solution at 50 ml / min was used. After premixing at 40°C with a jacketed mixer, a reflux ratio of 6:1 was adopted at the top of the column. The column pressure was atmospheric pressure, the top outlet temperature was 40°C, the methanol content was 90 wt%, methyl formate 10 wt%, formaldehyde 240ppm, and the methyl formate conversion rate was 96.2%. The reboiler outlet temperature was 104°C, and the pH was 14. After vacuum filtration, the filtrate was evaporated and concentrated to obtain white crystals, which were then dried at 110°C to obtain sodium formate with a purity of 98% and sodium hydroxide 2%. By comparing Example 1 and Comparative Example 1, the method of mixing and stirring lithium hydroxide solution with methyl formate (first alkaline hydrolysis) and then distilling in Comparative Example 1 resulted in a methyl formate conversion rate of 93.85% after distillation, which was lower than that in Example 1. Furthermore, the pH of the bottom liquid in Comparative Example 1 was 14, which was significantly different from the 100% methyl formate conversion rate and 99% lithium formate purity obtained in Example 1. In Comparative Example 1, after mixing and stirring lithium hydroxide solution with methyl formate, the reaction rate slowed down near the endpoint according to reaction kinetics. In contrast, Example 1 enhanced the conversion efficiency by using multiple theoretical plates for efficient gas-liquid contact. Comparative Example 1, by simply increasing stirring and extending the reaction time, could not achieve complete reaction. Additionally, methyl formate and formaldehyde, due to their high volatility, were present in the gas phase during mixing. In Example 1, a bottom liquid circulation method was used in the reactive distillation process to further enhance the absorption and reaction of methyl formate and formaldehyde in the gas phase, promoting further reaction. In Comparative Example 1, no enhancement measures were taken, and the final methyl formate conversion rate was only 93.85%. Moreover, the lithium hydroxide originally added in the correct proportion was present as an excess in the bottom liquid of the distillation column due to the incomplete reaction of methyl formate, forming a strongly alkaline solution with a pH of 14. When the bottom liquid went through subsequent processes, lithium hydroxide mixed in with the lithium formate product, resulting in a lithium formate purity of 92%.

[0029] In Examples 1 and 2, methyl formate from different sources was subjected to alkaline hydrolysis and reactive distillation using the process described in Example 1. The resulting reaction solution showed a methyl formate conversion rate of 98.4% after distillation. The bottom temperature was 104°C, the pH was 5, the sodium formate content was 95 wt%, and the sodium nitrate content was 5 wt%, which is lower than the 99% purity in Example 2. Therefore, the technical solution in this application specifically addresses the development of methyl formate from this particular source obtained by methanol carbonylation.

[0030] Through Example 1 and Comparative Example 3, Comparative Example 3, using a non-reflux method, achieved a methyl formate conversion rate of 96.2% after distillation; the pH of the bottom column was 14. The purity of sodium formate was 98%, and sodium hydroxide was 2%. The purity of sodium formate obtained in Example 3 was lower than that in Example 1. Preheating of the premixed liquid was used to utilize the high volatility of methyl formate. The vaporized methyl formate gas phase at the feed point underwent gas-liquid separation, reducing the methyl formate content in the premixed liquid and causing an excess of inorganic alkali. This excess inorganic alkali accelerated the formaldehyde reaction, promoting complete formaldehyde reaction. However, formaldehyde is also volatile, and flash evaporation occurred along with methyl formate during distillation. The technical solution in Example 1 utilized a bottom liquid circulation method, hydrolyzing the volatilized methyl formate and absorbing formaldehyde into an aqueous formaldehyde solution, which then reacted with the excess inorganic alkali at the bottom, achieving a complete reaction between methyl formate and formaldehyde. In Comparative Example 3, the bottom liquid reflux method mentioned in this patent was not used, and the volatilized methyl formate and formaldehyde were ignored. As a result, the methyl formate in Comparative Example 3 was not completely converted and the formaldehyde was not completely reacted. In addition, in Comparative Example 3, the sodium hydroxide that was originally added in the correct proportion was present as an excess substance in the bottom liquid of the column during distillation because the methyl formate did not react completely. This formed a strongly alkaline solution with a pH of 14. When the bottom liquid went through subsequent processes, the purity of sodium formate decreased to 98% and sodium hydroxide to 2%.

[0031] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A method for continuous production of high-quality formate, characterized in that, Includes the following steps: The raw material solution is mixed with an inorganic alkaline solution to obtain a premixed solution. The premixed solution is subjected to reactive distillation. The distillate is used to obtain a methanol solution, and the residue is used to obtain a formate solution. The raw material liquid is methyl formate obtained by methanol carbonylation; The raw material solution contains methyl formate at a mass concentration of 90-99.9%, methanol at a mass concentration of 0.1-9.8%, and formaldehyde at a mass concentration of 0.01-0.2%. The inorganic alkaline solution is an aqueous solution of hydroxides, wherein the hydroxides are hydroxides of lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, and strontium; the formate is the formate of the corresponding hydroxide, namely lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, and strontium. The concentration of the inorganic alkaline solution is 100 g / L to 800 g / L, preferably 200 g / L to 600 g / L; the molar ratio of methyl formate to inorganic alkaline in the premixed solution is 0.95 to 2.05:

1. The operating pressure of the reactive distillation process is 101~150 kPa (A absolute pressure), preferably 101~120 kPa (A).

2. The method for continuous production of high-quality formate according to claim 1, characterized in that, The temperature of the premixed liquid is 40~80℃, preferably 40~60℃.

3. The method for continuous production of high-quality formate according to claim 1, characterized in that, In the reactive distillation process, the premixed liquid is fed at a position of 5 to 30 theoretical plates from bottom to top, preferably 10 to 20.

4. The method for continuous production of high-quality formate according to claim 1, characterized in that, In the reactive distillation process, the ratio of the distillate collected from the bottom of the vessel to the recycled residue returned to the reactive distillation process is 1:0.1~2.

0. The position of the recycled residue in the tower needs to be 2~10 theoretical plates higher than the premixed liquid feed position, preferably 2~5.

5. The method for continuous production of high-quality formate according to claim 1, characterized in that, In the reactive distillation process, the reflux ratio is 1~6:1, preferably 1~3:

1.

6. The method for continuous production of high-quality formate according to claim 1, characterized in that, In the reactive distillation process, the theoretical plate number is 15-60, preferably 25-40.

7. The method for continuous production of high-quality formate according to claim 1, characterized in that, It also includes a crystallization process, in which the formate solution obtained from the distillate residue during the reactive distillation process is filtered, evaporated and crystallized, and then subjected to solid-liquid separation and drying to obtain high-quality formate.

8. The method for continuous production of high-quality formate according to claim 7, characterized in that... The filtration process employs one or more of the following methods: plate and frame filtration, vacuum bag filtration, cartridge filtration, and membrane filtration. The evaporation crystallization operation temperature is 60℃~170℃, preferably 80℃~150℃; The solid-liquid separation is performed using a centrifugal separation method; The drying process is operated at a temperature of 100℃~180℃, preferably 110℃~140℃.

9. An apparatus for continuous production of high-quality formate, characterized in that, This includes premixing kettles, reactive distillation columns, reboilers, condensers, and condensers; The bottom outlet of the premixing vessel is connected to the inlet pipe of the reactive distillation column; the bottom outlet of the reactive distillation column is connected to the inlet pipe of the reboiler; the outlet of the reboiler is connected to the reboiler return pipe of the reactive distillation column; the bottom outlet of the reactive distillation column is connected to the distillate return pipe of the reactive distillation column; the top outlet of the reactive distillation column is connected to the inlet pipe of the condenser; the outlet of the condenser is connected to the inlet pipe of the condenser; and the outlet of the condenser is connected to the distillate return pipe of the reactive distillation column.

10. The apparatus for continuous production of high-quality formate according to claim 9, characterized in that, A feed pump is also installed on the pipeline between the bottom outlet of the premixing vessel and the inlet of the reactive distillation column; A bottom discharge pump is also installed on the pipeline between the bottom outlet of the reactive distillation column and the return outlet of the distillate of the reactive distillation column. A top-of-the-column pump is also installed on the pipeline connecting the outlet of the condenser to the return outlet of the distillate from the reactive distillation column.

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