A system and method for preparing formic acid

Abstract

The invention discloses a system for preparing formic acid, comprising a sublimation device, a decarboxylation device, a first condenser and an absorption tower, wherein the decarboxylation device is connected to the sublimation device, the first condenser is connected to the decarboxylation device, the absorption tower is connected to the first condenser, and a sampling port is arranged at the outlet of the first condenser. By using oxalic acid as a raw material to prepare formic acid, the yield of the product is effectively improved, the production cost is reduced, and large-scale production can be achieved; the formic acid product obtained has less impurities and good quality; the preparation process is easy to control and the safety risk is small; and there is almost no waste water, which is beneficial to environmental protection.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical industry, and in particular to a system and method for preparing formic acid. Background Art

[0002] Natural formic acid exists in some natural plants, and its esters are more widely found in various fruits and natural essential oils. Although natural formic acid exists in natural plants, its content is extremely low and difficult to extract. At present, natural formic acid rarely appears on the market, and its content is low (less than 80%). It is generally made by dissolving glucose into a certain concentration of aqueous solution, oxidizing it with hydrogen peroxide (concentration of about 30%) under stirring and acidic conditions, and then neutralizing it with sodium hydroxide to form salt, evaporating and concentrating it, acidifying it with sulfuric acid, and distilling it.

[0003] However, since the generated formic acid is easily decarboxylated and decomposed under the action of sulfuric acid and hydrogen peroxide, the yield is very low, the production cost is too high, and it is difficult to produce on a large scale; and there are many side reactions when glucose is oxidized, and decarboxylation reaction can occur during the distillation process after acidification, resulting in low product content, poor quality, and serious three wastes; at the same time, the reaction is violent when oxidized with hydrogen peroxide, which is difficult to control, prone to safety accidents, and has low safety. Summary of the invention

[0004] The object of the present invention is to provide a system and method for preparing formic acid to solve the technical problems mentioned in the background technology. The object of the present invention is achieved through the following technical solutions:

[0005] A formic acid preparation system comprises a sublimation device, a decarboxylation device, a first condenser and an absorption tower. The decarboxylation device is connected to the sublimation device, the first condenser is connected to the decarboxylation device, the absorption tower is connected to the first condenser, and a sampling port is arranged at the outlet of the first condenser.

[0006] Furthermore, the sublimation device comprises a sublimation kettle, the outer side of which is provided with a heating jacket, in which heat transfer oil flows; and the sublimation kettle is provided with a nitrogen inlet, a raw material inlet and a sublimation outlet.

[0007] Furthermore, the decarboxylation device includes a decarboxylation tank, wherein a decarboxylation inlet and a decarboxylation outlet are respectively provided at two ends of the decarboxylation tank, the decarboxylation inlet is connected to the sublimation outlet, baffles are respectively fixed at the decarboxylation inlet and the decarboxylation outlet, a tube array is arranged between the two baffles, two ends of the tube array are respectively connected to the decarboxylation inlet and the decarboxylation outlet, and heat transfer oil is arranged to flow between the outer wall of the tube array and the decarboxylation tank.

[0008] Furthermore, the tube array is filled with ceramic rings.

[0009] Furthermore, an absorption inlet and a water pool are arranged at the bottom of the absorption tower, and a water inlet and an exhaust port are arranged at the top of the absorption tower. The absorption inlet is connected to the decarboxylation outlet through the first condenser, and the water inlet is connected to the water pool through a circulation pump.

[0010] Furthermore, it also includes a distillation kettle and a second condenser. The distillation kettle is provided with a distillation inlet and a distillation outlet. The distillation inlet is connected to the water pool through a circulation pump, and the distillation outlet is connected to the second condenser.

[0011] The present application also discloses a method for preparing formic acid using any of the above systems, comprising the following steps:

[0012] Step S1: adding anhydrous oxalic acid into a sublimation device, closing the sublimation device and introducing nitrogen into the sublimation device, maintaining a nitrogen flow rate of 1-3㎥ / h;

[0013] Step S2: heating the decarboxylation device to 150-160° C.;

[0014] Step S3: heating the sublimation device to 110-125° C., sublimating the oxalic acid in the sublimation device and entering the decarboxylation device along with nitrogen for decarboxylation;

[0015] Step S4: introducing the decarboxylation gas into an absorption tower, the waste gas is discharged from the top of the absorption tower, and crude formic acid is obtained from the bottom of the absorption tower.

[0016] Furthermore, the method further comprises: Step S5: sending the crude formic acid obtained in Step S4 into a distillation kettle, discharging the finished formic acid from the top of the distillation kettle, and transferring the oxalic acid at the bottom of the distillation kettle to a sublimation kettle for reuse.

[0017] The technical solution provided in the embodiments of the present application has at least the following technical effects or advantages:

[0018] By using oxalic acid as a raw material to prepare formic acid, the yield of the product is effectively improved, the production cost is reduced, and large-scale production can be achieved; the obtained formic acid product has fewer impurities and good quality; the preparation process is easy to control and has low safety risks; and there is almost no wastewater, which is beneficial to environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings in the specification, which constitute a part of this application, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0020] Figure 1 This is a schematic diagram of the structure of an embodiment of the present application.

[0021] The accompanying drawings show: 1. sublimation device; 2. decarboxylation device; 3. first condenser; 4. absorption tower; 41. circulation pump; 5. distillation kettle; 6. second condenser. DETAILED DESCRIPTION

[0022] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the drawings and specific implementation methods of the specification. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example 1

[0023] like Figure 1 A formic acid preparation system shown in the figure includes a sublimation device 1, a decarboxylation device 2, a first condenser 3, an absorption tower 4, a distillation kettle 5 and a second condenser 6. The decarboxylation device 2 is connected to the sublimation device 1, the first condenser 3 is connected to the decarboxylation device 2, the absorption tower 4 is connected to the first condenser 3, the distillation kettle 5 is connected to the absorption tower 4, the second condenser 6 is connected to the distillation kettle 5, and a sampling port is also provided at the outlet of the first condenser 3.

[0024] Specifically, the sublimation device 1 includes a sublimation kettle, a heating jacket is provided on the outer side of the sublimation kettle, a heat transfer oil inlet is provided on the lower side of the heating jacket, a heat transfer oil outlet is provided on the upper side of the heating jacket, and the heat transfer oil enters from the heat transfer oil inlet and flows out from the heat transfer oil outlet to heat the sublimation kettle. A spiral guide plate is also fixed in the heating jacket to improve the fluidity of the heat transfer oil and prevent the heat transfer oil from being retained in the heating jacket and causing uneven heating.

[0025] The sublimation kettle is provided with a nitrogen inlet, a raw material inlet and a sublimation outlet respectively, and the nitrogen inlet is communicated with a nitrogen gas source through a nitrogen inlet pipe, and is used to blast nitrogen into the sublimation kettle. The raw material inlet is used to add oxalic acid raw materials into the sublimation kettle, and a cover plate is installed at the raw material inlet, and the cover plate is closed during operation to ensure the airtightness of the sublimation kettle. The sublimation outlet is communicated with a decarboxylation device 2, and is used to introduce the sublimated oxalic acid gas into the decarboxylation device 2. Preferably, the outer spiral of the nitrogen inlet pipe is coated with a heat-conducting oil pipe, which is used to heat the nitrogen to avoid the entry of low-temperature nitrogen and cause oxalic acid to sublimate.

[0026] The decarboxylation device 2 comprises a decarboxylation tank, and a decarboxylation inlet and a decarboxylation outlet are respectively provided at the two ends of the decarboxylation tank, and the decarboxylation inlet is communicated with the sublimation outlet through a decarboxylation pipeline, and is used to introduce the sublimated oxalic acid gas into the decarboxylation tank, and the decarboxylation pipeline is coated with a thermal insulation layer to avoid the oxalic acid gas from condensing in the decarboxylation pipeline and causing the blockage of the decarboxylation pipeline. Baffles are respectively fixed at the decarboxylation inlet and the decarboxylation outlet, and a tube array is arranged between the two baffles, and the two ends of the tube array are respectively communicated with the decarboxylation inlet and the decarboxylation outlet.

[0027] A heat transfer oil inlet is provided at the lower side of the decarboxylation tank, and a heat transfer oil outlet is provided at the upper side of the decarboxylation tank. The heat transfer oil inlet and the heat transfer oil outlet are both located between two baffles. The heat transfer oil enters between the outer wall of the tube and the decarboxylation tank from the heat transfer oil inlet, and flows out from the heat transfer oil outlet to achieve heating of the tube. When in use, the sublimated oxalic acid gas enters the tube from the decarboxylation inlet, and decarboxylates at high temperature to obtain formic acid and carbon dioxide, and formic acid, carbon dioxide and residual oxalic acid gas flow out from the decarboxylation outlet. Preferably, the tube is filled with porcelain rings to reduce corrosion to the tube.

[0028] The bottom of the absorption tower 4 is provided with an absorption inlet and a water pool, and the absorption inlet is connected to the water pool; the top of the absorption tower is provided with a water inlet and an exhaust port, and the water inlet is connected to the water pool through a circulation pump 41. The decarboxylation outlet is connected to the inlet of the first condenser 3 through a pipeline, and the outlet of the first condenser 3 is connected to the absorption inlet of the absorption tower 4 through a pipeline. When in use, the formic acid and residual oxalic acid condensed by the first condenser 1 are dissolved in the water pool at the bottom of the absorption tower 4, and the circulation pump 41 pumps the water in the water pool at the bottom of the tower to the water inlet at the top of the absorption tower to flow down, absorb the remaining formic acid, and the nitrogen and carbon dioxide are discharged from the exhaust port at the top of the absorption tower 4.

[0029] A sampling port is provided at the outlet of the first condenser 3, and the oxalic acid content is detected at the sampling port. If the oxalic acid content at the sampling port exceeds 1%, the sublimation temperature is lowered to reduce the oxalic acid sublimation amount, so as to improve the conversion rate of formic acid. The water pool is also provided with a clean water inlet to adjust the concentration of formic acid.

[0030] A steam jacket is installed on the outside of the distillation kettle 5. A steam inlet is provided on the upper side of the steam jacket, and a condensate outlet is provided at the bottom of the steam jacket. High-temperature steam enters the steam jacket from the steam inlet to heat the interior of the distillation kettle 5, and condensate is discharged from the condensate outlet at the bottom. The distillation kettle 5 is provided with a distillation inlet and a distillation outlet. The distillation inlet is connected to the water tank through a circulation pump 41, and is used to pump the formic acid solution into the distillation kettle 5. The distillation outlet is connected to the inlet of the second condenser 6. The finished formic acid after distillation flows out from the outlet of the condenser 6. The bottom material of the distillation kettle 5 is mainly oxalic acid, which can be moved to the sublimation kettle for application. Example 2

[0031] A method for preparing formic acid using the above preparation system comprises the following steps:

[0032] Step S1: adding anhydrous oxalic acid into the sublimation reactor from the raw material inlet, closing the end cover at the raw material inlet, and introducing nitrogen into the sublimation device, maintaining the nitrogen flow rate at 1-3㎥ / h;

[0033] Step S2: heating the decarboxylation tank to 150° C. Heating the decarboxylation tank in advance can prevent the sublimated oxalic acid from condensing in the decarboxylation tank and causing blockage of the tube array;

[0034] Step S3: heating the sublimation kettle to 110° C., sublimating the oxalic acid in the sublimation kettle, and entering the decarboxylation tank along with nitrogen for decarboxylation;

[0035] Step S4: introducing the decarboxylation gas into an absorption tower, and the nitrogen and carbon dioxide generated by decarboxylation are discharged from the top of the absorption tower, and formic acid is dissolved in a water pool at the bottom of the absorption tower to obtain crude formic acid.

[0036] If the oxalic acid content of the raw material at the sampling port exceeds 1%, or the color of the formic acid extracted from the bottom of the absorption tower is unqualified, step S5 is executed: the crude formic acid obtained in step S4 is sent to the distillation kettle, the top of the distillation kettle is connected to the second condenser to output the finished formic acid, and the bottom of the distillation kettle is oxalic acid, which is moved to the sublimation kettle for application. Example 3

[0037] A method for preparing formic acid using the above preparation system comprises the following steps:

[0038] Step S1: adding anhydrous oxalic acid into the sublimation reactor from the raw material inlet, closing the end cover at the raw material inlet, and introducing nitrogen into the sublimation device, maintaining the nitrogen flow rate at 1-3㎥ / h;

[0039] Step S2: heating the decarboxylation tank to 160° C. Heating the decarboxylation tank in advance can prevent the sublimated oxalic acid from condensing in the decarboxylation tank and causing blockage of the tube array;

[0040] Step S3: heating the sublimation kettle to 125° C., sublimating the oxalic acid in the sublimation kettle, and entering the decarboxylation tank along with nitrogen for decarboxylation;

[0041] Step S4: introducing the decarboxylation gas into an absorption tower, and the nitrogen and carbon dioxide generated by decarboxylation are discharged from the top of the absorption tower, and formic acid is dissolved in a water pool at the bottom of the absorption tower to obtain crude formic acid.

[0042] If the oxalic acid content of the raw material at the sampling port exceeds 1%, or the color of the formic acid extracted from the bottom of the absorption tower is unqualified, step S5 is executed: the crude formic acid obtained in step S4 is sent to the distillation kettle, the top of the distillation kettle is connected to the second condenser to output the finished formic acid, and the bottom of the distillation kettle is oxalic acid, which is moved to the sublimation kettle for application. Example 4

[0043] A method for preparing formic acid using the above preparation system comprises the following steps:

[0044] Step S1: adding anhydrous oxalic acid into the sublimation reactor from the raw material inlet, closing the end cover at the raw material inlet, and introducing nitrogen into the sublimation device, maintaining the nitrogen flow rate at 1-3㎥ / h;

[0045] Step S2: heating the decarboxylation tank to 155° C. Heating the decarboxylation tank in advance can prevent the sublimated oxalic acid from condensing in the decarboxylation tank and causing blockage of the tube array;

[0046] Step S3: heating the sublimation kettle to 120° C., sublimating the oxalic acid in the sublimation kettle, and entering the decarboxylation tank along with nitrogen for decarboxylation;

[0047] Step S4: introducing the decarboxylation gas into an absorption tower, and the nitrogen and carbon dioxide generated by decarboxylation are discharged from the top of the absorption tower, and formic acid is dissolved in a water pool at the bottom of the absorption tower to obtain crude formic acid.

[0048] If the oxalic acid content of the raw material at the sampling port exceeds 1%, or the color of the formic acid extracted from the bottom of the absorption tower is unqualified, step S5 is executed: the crude formic acid obtained in step S4 is sent to the distillation kettle, the top of the distillation kettle is connected to the second condenser to output the finished formic acid, and the bottom of the distillation kettle is oxalic acid, which is moved to the sublimation kettle for application.

[0049] The technical solution provided in the embodiments of the present application has at least the following technical effects or advantages:

[0050] By using oxalic acid as a raw material to prepare formic acid, the yield of the product is effectively improved, the production cost is reduced, and large-scale production can be achieved; the obtained formic acid product has fewer impurities and good quality; the preparation process is easy to control and has low safety risks; and there is almost no wastewater, which is beneficial to environmental protection.

[0051] The technical solutions in the above embodiments of the present application have at least the following technical effects or advantages:

[0052] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0053] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention: the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0054] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A system for preparing formic acid, characterized in that: It includes a sublimation device, a decarboxylation device, a first condenser and an absorption tower, wherein the decarboxylation device is connected to the sublimation device, the first condenser is connected to the decarboxylation device, the absorption tower is connected to the first condenser, and a sampling port is provided at the outlet of the first condenser; The sublimation device includes a sublimation kettle, the outer side of the sublimation kettle is provided with a heating jacket, a spiral guide plate is fixed in the heating jacket, and heat transfer oil flows in the heating jacket; the sublimation kettle is respectively provided with a nitrogen inlet, a raw material inlet and a sublimation outlet; The decarboxylation device includes a decarboxylation tank, wherein a decarboxylation inlet and a decarboxylation outlet are respectively provided at both ends of the decarboxylation tank, the decarboxylation inlet is connected to the sublimation outlet, baffles are respectively fixed at the decarboxylation inlet and the decarboxylation outlet, a tube array is arranged between the two baffles, the two ends of the tube array are respectively connected to the decarboxylation inlet and the decarboxylation outlet, and heat transfer oil flows between the outer wall of the tube array and the decarboxylation tank.

2. A formic acid preparation system according to claim 1, characterized in that: The tube array is filled with ceramic rings.

3. The system for preparing formic acid according to claim 1, wherein: An absorption inlet and a water pool are provided at the bottom of the absorption tower, and a water inlet and an exhaust port are provided at the top of the absorption tower. The absorption inlet is connected to the decarboxylation outlet through the first condenser, and the water inlet is connected to the water pool through a circulation pump.

4. A system for preparing formic acid according to claim 3, characterized in that: It also includes a distillation kettle and a second condenser. The distillation kettle is provided with a distillation inlet and a distillation outlet. The distillation inlet is connected to the water pool through the circulation pump, and the distillation outlet is connected to the second condenser.

5. A method for preparing formic acid using the system according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step S1: adding anhydrous oxalic acid to a sublimation device, sealing the sublimation device, and introducing nitrogen into the sublimation device at a nitrogen flow rate of 1-3㎥ / h; Step S2: heating the decarboxylation device to 150-160°C; Step S3: heating the sublimation device to 110-125° C., allowing the oxalic acid in the sublimation device to sublime and enter the decarboxylation device along with nitrogen for decarboxylation; Step S4: introducing the decarboxylation gas into an absorption tower, the waste gas is discharged from the top of the absorption tower, and crude formic acid is obtained from the bottom of the absorption tower.

6. A method for preparing formic acid according to claim 5, characterized in that, The method further comprises: step S5: feeding the crude formic acid obtained in step S4 into a distillation kettle, discharging the finished formic acid from the top of the distillation kettle, and transferring the oxalic acid obtained at the bottom of the distillation kettle to a sublimation kettle.

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