A method for recovering industrial acetonitrile waste liquid

Abstract

The present invention relates to the technical field of organic waste liquid recovery, and particularly relates to a method for recovering industrial acetonitrile waste liquid. The method for recovering the industrial acetonitrile waste liquid includes the following steps: configuring the addition amounts of organic solid acid, catalyst, and calcium oxide; adding the acetonitrile waste liquid, organic solid acid, and catalyst into a first reaction kettle; adding the acetonitrile waste liquid and calcium oxide into a second reaction kettle; simultaneously heating the first reaction kettle and the second reaction kettle to 85-90 °C and performing cross reflux reaction until the mass percentage of residual ethanol in the second reaction kettle < 0.50% and the mass percentage of residual water < 0.10%, and performing atmospheric distillation to obtain a qualified acetonitrile fraction. By using the method for recovering the industrial acetonitrile waste liquid provided by the present invention, it has low cost, high efficiency, simple operation, strong versatility, and has great industrial application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of organic waste liquid recovery, and particularly relates to a method for recovering industrial acetonitrile waste liquid. Background Art

[0002] Acetonitrile is an important organic auxiliary agent and solvent, which is widely used in fields such as chemical industry, medicine, light textile, and national defense. Ethanol, water, and acetonitrile are miscible because they directly or indirectly participate in the same production process. Therefore, it is necessary to separate the three. However, because ethanol, water, and acetonitrile are azeotropic with each other, it is difficult to obtain relatively pure acetonitrile by ordinary distillation or rectification. Currently, the main methods for refining acetonitrile in industry are as follows:

[0003] (1) Variable pressure rectification: Utilize the relationship between the azeotropic points of ethanol, water, and acetonitrile and the change in pressure, and adopt two rectification towers with different operating pressures to achieve the effects of removing alcohol and water; (This method requires the coordinated adjustment of two towers, with complex operations, high working pressure, and large equipment investment.

[0004] (2) Azeotropic rectification method: Add an azeotropic agent to the top of the tower to change the relative volatility between components to achieve the separation purpose and obtain high-content acetonitrile; This method has a long full reflux water separation time, complex operations, and difficult control of the acetonitrile refining effect;

[0005] (3) Salting-out method: Add saturated brine to the acetonitrile waste liquid for phase separation and concentration, so that the acetonitrile composition in the organic phase bypasses the azeotropic point and is refined through a rectification tower to obtain high-purity acetonitrile; This method has cumbersome operations and is difficult to treat acetonitrile waste liquid with relatively complex components;

[0006] These refining methods each have their own characteristics, but they all have certain deficiencies and drawbacks. They not only require rectification means, but also have complex equipment, high costs, cumbersome operations, and poor versatility. Therefore, there is an urgent need to develop a new method with low cost, high efficiency, simple operation, strong versatility, and suitable for industrial production. Summary of the Invention

[0007] The purpose of the present invention is to overcome the above-mentioned deficiencies in the prior art and provide a method for recovering industrial acetonitrile waste liquid.

[0008] To solve the above technical problems, the present invention provides a method for recovering industrial acetonitrile waste liquid, including the following steps:

[0009] Configure the addition amounts of organic solid acid, catalyst, and calcium oxide;

[0010] Add acetonitrile waste liquid, organic solid acid, and catalyst to the first reaction kettle;

[0011] In the present invention, by using an acidic catalyst, ethanol present in the waste liquid can be esterified with a solid acid to form an ester. Since the boiling points of the ester and acetonitrile differ significantly, acetonitrile can be distilled out for separation.

[0012] Add acetonitrile waste liquid and calcium oxide to the second reaction kettle.

[0013] Heat the first reaction kettle and the second reaction kettle to 85 - 90 °C simultaneously and carry out cross - reflux reaction until the mass percentage of residual ethanol in the second reaction kettle is < 0.50% and the mass percentage of residual water is < 0.10%, then perform atmospheric distillation to obtain a qualified acetonitrile fraction.

[0014] In the present invention, a cross - reflux method is particularly adopted to enable ethanol that is distilled out before being esterified in the first reaction kettle to return to the kettle for esterification until the mass percentage of residual ethanol detected in the second reaction kettle is < 0.50%, thereby enabling acetonitrile to be distilled out from the second reaction kettle.

[0015] In a more preferred embodiment, the molar ratio of the addition amount of the organic solid acid to the residual amount of ethanol in the acetonitrile waste liquid is (0.5 - 1.2):1.

[0016] In a more preferred embodiment, the mass ratio of the addition amount of the catalyst to the residual amount of ethanol in the acetonitrile waste liquid is 5% - 10%.

[0017] In a more preferred embodiment, the molar ratio of the addition amount of calcium oxide to the residual amount of water in the acetonitrile waste liquid is (1 - 3):1.

[0018] In a more preferred embodiment, the organic solid acid is selected from at least one of oxalic acid, succinic acid, citric acid, adipic acid, and phthalic acid.

[0019] In a more preferred embodiment, the catalyst is selected from at least one of concentrated sulfuric acid, p - toluenesulfonic acid, and phosphoric acid.

[0020] In a more preferred embodiment, the time of the cross - reflux reaction is 8 - 12 hours.

[0021] In a more preferred embodiment, the recovery rate of the acetonitrile fraction is above 85%.

[0022] In summary, the present application includes at least one of the following beneficial technical effects:

[0023] The method for recovering industrial acetonitrile waste liquid provided by the present invention has a recovery rate of the acetonitrile fraction above 85%, and has advantages such as low cost, high efficiency, simple operation, and strong versatility, and has great industrial application prospects.

[0024] Other features and beneficial effects of the present invention will be described in the subsequent specification, and in part, will become apparent from the specification or be understood by implementing the present invention. The objectives and other beneficial effects of the present invention can be achieved and obtained by the structures and / or components pointed out in the specification and claims. Brief Description of the Drawings

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings; in the following description of the positional relationship of the drawings, unless otherwise specified, the direction in which the components are shown in the drawings is taken as the reference.

[0026] Figure 1 It is a flowchart of a method for recycling industrial acetonitrile waste liquid provided by an embodiment of the present invention;

[0027] Figure 2 It is a schematic structural diagram of a device for recycling industrial acetonitrile waste liquid provided by an embodiment of the present invention.

[0028] Reference Numerals:

[0029] 10, charging tank; 20, first reaction kettle; 21, first tail gas outlet; 30, second reaction kettle; 31, second tail gas outlet; 40, switch valve; 50, recovery storage tank. Detailed Embodiments

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention; the technical features designed in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other; based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0031] In the description of the present invention, it should be noted that all terms (including technical terms and scientific terms) used in the present invention have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains, and should not be construed as a limitation of the present invention; it should be further understood that the terms used in the present invention should be understood as having a meaning consistent with their meaning in the context of this specification and the relevant art, and should not be understood in an idealized or overly formal sense, unless clearly defined as such in the present invention.

[0032] Please refer to Figure 1 , the present invention provides a method for recovering industrial acetonitrile waste liquid, comprising the following steps:

[0033] Configure the addition amounts of organic solid acid, catalyst and calcium oxide;

[0034] Add acetonitrile waste liquid, organic solid acid, and catalyst into the first reaction kettle;

[0035] In the present invention, by using an acidic catalyst, ethanol present in the waste liquid can be esterified with the solid acid to form an ester. Since the boiling points of the ester and acetonitrile are quite different, acetonitrile can be separated by distillation.

[0036] Add acetonitrile waste liquid and calcium oxide into the second reaction kettle;

[0037] Heat the first reaction kettle and the second reaction kettle to 85 - 90 °C simultaneously and carry out cross reflux reaction until the mass percentage of ethanol residue < 0.50% and the mass percentage of water residue < 0.10%, and then perform atmospheric distillation to obtain a qualified acetonitrile fraction.

[0038] Please refer to Figure 2 , based on the method for recovering industrial acetonitrile waste liquid provided by the present invention, an industrial acetonitrile waste liquid recovery device using this method is provided, comprising:

[0039] A feeding tank 10 filled with industrial acetonitrile waste liquid;

[0040] A first reaction kettle 20, a second reaction kettle 30, several switching valves 40 on the connecting pipeline between them, a first tail gas outlet 21 communicating with the first reaction kettle 20, and a second tail gas outlet 31 communicating with the second reaction kettle 30;

[0041] A recovery storage tank 50 for recovering acetonitrile.

[0042] In the above - disclosed embodiments, the same reference numerals may be reused. These repetitions are for the purpose of simplification and clarity, and are not intended to limit a specific relationship between the different structures discussed.

[0043] The technical solutions of the present invention are further illustrated and described below through specific embodiments. However, the protection scope of the present invention is not limited thereto.

[0044] Example 1

[0045] (1) Detection before feeding, the mass fraction of ethanol residue in the acetonitrile waste liquid (1000.0 g) is 5.02%, and the water content is 1.03%.

[0046] (2) Add acetonitrile waste liquid (500.0 g), anhydrous citric acid (144.6 g), and p-toluenesulfonic acid monohydrate (2.5 g) into the first reactor; add acetonitrile waste liquid (500.0 g) and calcium oxide (115.0 g) into the second reactor. Then, heat up to 85°C - 90°C simultaneously and carry out cross reflux for 12 hours.

[0047] (3) Take a sample from the second reactor: Monitor the mass fraction of ethanol residue (0.41%) and water content (0.05%) by gas phase. Both are qualified. Start atmospheric distillation and distill out qualified acetonitrile fraction (863.0 g), with a yield of 86.3%.

[0048] Example 2

[0049] (1) Before feeding, detect that the mass fraction of ethanol residue in the acetonitrile waste liquid (1000.0 g) is 3.40% and the water content is 0.8%.

[0050] (2) Add acetonitrile waste liquid (500.0 g), succinic acid (98.0 g), and p-toluenesulfonic acid monohydrate (2.0 g) into the first reactor; add acetonitrile waste liquid (500.0 g) and calcium oxide (81.6 g) into the second reactor. Then, heat up to 85°C - 90°C simultaneously and carry out cross reflux for 10 hours.

[0051] (3) Take a sample from the second reactor: Monitor the mass fraction of ethanol residue (0.21%) and water content (0.04%) by gas phase. Both are qualified. Start atmospheric distillation and distill out qualified acetonitrile fraction (901.0 g), with a yield of 90.1%.

[0052] Example 3

[0053] (1) Before feeding, detect that the mass fraction of ethanol residue in the acetonitrile waste liquid (1000.0 g) is 5.40% and the water content is 2.20%.

[0054] (2) Add acetonitrile waste liquid (500.0 g), phthalic acid (155.5 g), and p-toluenesulfonic acid monohydrate (2.7 g) into the first reactor; add acetonitrile waste liquid (500.0 g) and calcium oxide (167.1 g) into the second reactor. Then, heat up to 85°C - 90°C simultaneously and carry out cross reflux for 12 hours.

[0055] (3) Take a sample from the second reactor: Monitor the mass fraction of ethanol residue (0.33%) and water content (0.05%) by gas phase. Both are qualified. Start atmospheric distillation and distill out qualified acetonitrile fraction (851.0 g), with a yield of 85.1%.

[0056] Example 4

[0057] (1) Before feeding, detect that the mass fraction of ethanol residue in the acetonitrile waste liquid (1000.0 g) is 4.31% and the water content is 3.12%.

[0058] (2) Add acetonitrile waste liquid (500.0 g), oxalic acid (130.0 g), and concentrated sulfuric acid (2.2 g) into the first reactor; add acetonitrile waste liquid (500.0 g) and calcium oxide (186.7 g) into the second reactor. Then heat up to 85°C - 90°C simultaneously and carry out cross reflux for 12 hours.

[0059] (3) Sampling inside the second reactor: Monitor the mass fraction of ethanol residue (0.43%) and water content (0.06%) by gas phase, both are qualified. Start atmospheric distillation and distill out qualified acetonitrile fraction (879.0 g), with a yield of 87.9%.

[0060] Example 5

[0061] (1) Before feeding, detect that the mass fraction of ethanol residue in acetonitrile waste liquid (1000.0 g) is 2.31% and the water content is 0.66%.

[0062] (2) Add acetonitrile waste liquid (500.0 g), adipic acid (66.5 g), and concentrated sulfuric acid (1.2 g) into the first reactor; add acetonitrile waste liquid (500.0 g) and calcium oxide (60.5 g) into the second reactor. Then heat up to 85°C - 90°C simultaneously and carry out cross reflux for 8 hours.

[0063] (3) Sampling inside the second reactor: Monitor the mass fraction of ethanol residue (0.25%) and the mass fraction of water residue (0.03%) by gas phase, both are qualified. Start atmospheric distillation and distill out qualified acetonitrile fraction (913.0 g), with a yield of 91.3%.

[0064] Comparative Example 1

[0065] (1) Before feeding, detect that the mass fraction of ethanol residue in acetonitrile waste liquid (1000.0 g) is 5.02% and the water content is 1.03%.

[0066] (2) Add acetonitrile waste liquid (500.0 g), anhydrous citric acid (144.6 g), and p-toluenesulfonic acid monohydrate (2.5 g) into the first reactor; add acetonitrile waste liquid (500.0 g) and calcium oxide (115.0 g) into the second reactor. Then heat up to 85°C - 90°C simultaneously and carry out conventional series reflux for 12 hours. Specifically, the distillate from the first reactor directly enters the second reactor, and sampling is carried out after refluxing in the second reactor for 12 hours;

[0067] (3) Sampling inside the second reactor: Monitor the mass fraction of ethanol residue (2.35%) and the water content (1.19%) by gas phase, both are unqualified, and the yield is 82.5%.

[0068] It should be noted that the specific parameters or some common reagents in the above embodiments are specific embodiments or preferred embodiments under the concept of the present invention, rather than a limitation thereto; those skilled in the art can make adaptive adjustments within the concept and protection scope of the present invention. In addition, unless otherwise specified, the raw materials used can also be conventional commercially available products in the art or prepared by conventional methods in the art.

[0069] In addition, those skilled in the art should understand that although there are many problems in the prior art, each embodiment or technical solution of the present invention can be improved in only one or several aspects, and it is not necessary to solve all the technical problems listed in the prior art or the background art at the same time. Those skilled in the art should understand that the content not mentioned in a claim should not be regarded as a limitation to that claim.

[0070] Although terms such as first reaction kettle, second reaction kettle, organic solid acid, catalyst, etc. are used more frequently herein, the possibility of using other terms is not excluded. These terms are used only to more conveniently describe and explain the essence of the present invention; interpreting them as any additional limitation is contrary to the spirit of the present invention; the terms "first", "second", etc. (if any) in the description and claims of the embodiments of the present invention are used to distinguish similar objects and do not necessarily need to describe a specific order or sequence.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than a limitation thereto; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for recovering industrial acetonitrile waste liquid, characterized in that Comprising the following steps: Configuring the addition amounts of the organic solid acid, the catalyst, and calcium oxide; Adding the acetonitrile waste liquid, the organic solid acid, and the catalyst into the first reaction kettle; Adding the acetonitrile waste liquid and calcium oxide into the second reaction kettle; Simultaneously heating the first reaction kettle and the second reaction kettle to 85 - 90 °C and carrying out cross reflux reaction until the mass percentage of residual ethanol in the second reaction kettle < 0.50% and the mass percentage of residual water < 0.10%, and performing atmospheric distillation to obtain a qualified acetonitrile fraction; Wherein, the organic solid acid is selected from at least one of oxalic acid, succinic acid, citric acid, adipic acid, and phthalic acid, and the molar ratio of the addition amount of the organic solid acid to the residual amount of ethanol in the acetonitrile waste liquid is (0.5 - 1.2):1; The catalyst is selected from at least one of concentrated sulfuric acid, p-toluenesulfonic acid, and phosphoric acid, and the mass ratio of the addition amount of the catalyst to the residual amount of ethanol in the acetonitrile waste liquid is 5% - 10%; 2. The recovery method of industrial acetonitrile waste liquid according to claim 1, wherein: The molar ratio of the addition amount of calcium oxide to the residual amount of water in the acetonitrile waste liquid is (1 - 3):1; 3. The recovery method of industrial acetonitrile waste liquid according to claim 1, characterized in that: The time of the cross reflux reaction is 8 - 12 hours; 4. The recovery method of industrial acetonitrile waste liquid according to claim 1, characterized in that: The recovery rate of the acetonitrile fraction is above 85%.

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