Method for producing N-vinylacetamide and pyrolysis device

Abstract

Provided is a method for producing N-vinylacetamide, which prevents liquefaction of a raw material gas (gasification raw material) due to re-condensation, suppresses clogging problems caused by aggregates in a pyrolysis reactor, and can be stably and continuously operated for a long period of time. A method for producing N-vinylacetamide, comprising: a supply step for supplying a raw material containing N-(1-methoxyethyl) acetamide (MEA) to an evaporator; an evaporation step for evaporating the raw material into a vaporized raw material in the evaporator; a superheating step in which the vaporized raw material is superheated so that the superheating temperature of the vaporized raw material is 5 DEG C higher than the boiling point of the N-(1-methoxyethyl) acetamide (MEA) under the pressure in the superheater (the boiling point of the N-(1-methoxyethyl) acetamide under the pressure in the superheater + 5 DEG C) and 200 DEG C inclusive, said superheating temperature being 5 DEG C higher than the boiling point of the N-(1-methoxyethyl) acetamide (MEA) under the pressure in the superheater (the boiling point of the N-(1-methoxyethyl) acetamide under the pressure in the superheater + 5 DEG C); and a pyrolysis step in which the vaporized raw material, which has been superheated, is supplied to a pyrolysis reactor for pyrolysis. The content of the N-(1-methoxyethyl) acetamide in the raw materials is 80 to 100 mass percent.

Description

[0001] This application is a divisional application of a patent application with an application date of December 7, 2020, application number 202080084509.2, and invention name “Method for producing N-vinyl acetamide and pyrolysis device”. Technical Field

[0002] The present invention relates to a method for producing N-vinylacetamide and a pyrolysis device. Background Art

[0003] Various methods have been proposed so far for the production of N-vinylcarboxylic acid amide (for example, see Patent Document 1). The production method described in Patent Document 1 discloses a method for producing N-vinylcarboxylic acid amide by evaporating a raw material of N-(2-alkoxyethyl)carboxylic acid amide and performing pyrolysis. In such a method for producing N-vinylcarboxylic acid amide by pyrolysis, the following situations may occur: due to factors such as heat dissipation to the atmosphere, heat absorption in a pyrolysis reactor (pyrolysis step), pressure changes due to mechanical failure, and stoppage of the supply of a heat source, the raw material gas (gasified raw material) is liquefied by recondensation in the evaporator, in the pipe connecting the evaporator and the pyrolysis reactor, or in the pyrolysis reactor, and the liquefied raw material flows into the high-temperature pyrolysis reactor. As a result, (i) the liquefied raw material flows into the inner wall of the hose of the pyrolysis reactor, and (ii) the liquefied raw material is polymerized before reevaporation on the inner wall of the hose of the pyrolysis reactor to produce asphalt-like or solid agglomerates (also called harz), which causes the hose of the pyrolysis reactor to be blocked, making it difficult to operate stably.

[0004] [Prior art literature]

[0005] [Patent Document]

[0006] Patent Document 1: International Publication No. 2017 / 002494 Summary of the invention

[0007] [Problems to be Solved by the Invention]

[0008] An object of the present invention is to solve the above-mentioned problems and to provide a method for producing N-vinylacetamide which can be operated stably and continuously for a long period of time by preventing the raw material gas (gasified raw material) from being liquefied due to recondensation, thereby suppressing the clogging problem of the pyrolysis reactor due to condensates.

[0009] [Methods to solve the problem]

[0010] The inventors of the present invention have conducted in-depth research to solve the aforementioned problems, and as a result, have found that by providing a superheater (superheating step) between the evaporator (evaporation step) and the pyrolysis reactor (pyrolysis step), and by satisfying at least one of the following conditions through the superheater (superheating step), the raw gas (gasified raw material) can be prevented from being liquefied due to recondensation, thereby completing the present invention.

[0011] (i) superheating the raw material gas (gasified raw material) so that the superheat temperature is higher than the boiling point of N-(1-methoxyethyl)acetamide at the superheater internal pressure by a specific temperature (5°C) (i.e., the boiling point of N-(1-methoxyethyl)acetamide at the superheater internal pressure + 5°C) and is 200°C or less, and,

[0012] (ii) A specific amount of heat is applied to the raw material gas (gasified raw material).

[0013] That is, the present invention provides the following [1] to

[15] .

[0014] [1]. A method for producing N-vinylacetamide, comprising:

[0015] a supply step of supplying a raw material containing N-(1-methoxyethyl)acetamide (MEA) to an evaporator,

[0016] an evaporation step of evaporating the raw material into a gasified raw material in the evaporator,

[0017] The gasification raw material is supplied to a superheater, and the gasification raw material is superheated so that the superheat temperature of the gasification raw material becomes a temperature 5°C higher than the boiling point of N-(1-methoxyethyl)acetamide at the superheater internal pressure (the boiling point of N-(1-methoxyethyl)acetamide at the superheater internal pressure + 5°C) and 200°C or less; and

[0018] A pyrolysis step of supplying the superheated gasified raw material to a pyrolysis reactor for pyrolysis;

[0019] The content of the N-(1-methoxyethyl)acetamide in the raw material is 80 to 100% by mass.

[0020] [2]. A method for producing N-vinylacetamide, comprising:

[0021] a supply step of supplying a raw material containing N-(1-methoxyethyl)acetamide (MEA) to an evaporator,

[0022] an evaporation step of evaporating the raw material into a gasified raw material in the evaporator,

[0023] a superheating step of supplying the gasification raw material to a superheater to apply a heat of 1.0 kJ / mol or more to the gasification raw material to superheat the gasification raw material, and

[0024] A pyrolysis step of supplying the superheated gasified raw material to a pyrolysis reactor for pyrolysis;

[0025] The content of the N-(1-methoxyethyl)acetamide in the raw material is 80 to 100% by mass.

[0026] [3] The method for producing N-vinylacetamide according to [1] or [2] above, wherein the evaporation step is carried out under reduced pressure.

[0027] [4] The method for producing N-vinylacetamide according to any one of [1] to [3] above, wherein the thermal decomposition step is carried out under reduced pressure.

[0028] [5]. The method for producing N-vinylacetamide according to any one of [1] to [4] above, wherein the evaporator is a falling film evaporator.

[0029] [6]. The method for producing N-vinylacetamide as described in any one of [1] to [4] above, wherein the evaporator is a forced liquid film type.

[0030] [7]. The method for producing N-vinylacetamide as described in any one of [1] to [6] above, wherein the downstream end of the evaporator and the upstream end of the superheater are connected via a first pipe, and the downstream end of the first pipe is located at the highest position in the first pipe.

[0031] [8] The method for producing N-vinylacetamide as described in any one of [1] to [7] above, wherein the downstream end of the superheater is connected to the upstream end of the pyrolysis reactor via a second pipe, and the upstream end of the second pipe is located at the highest position in the second pipe.

[0032] [9] The method for producing N-vinylacetamide according to any one of [1] to [8] above,

[0033] A recovery step of recovering the unvaporized liquid raw material in the raw material supplied to the evaporator and the liquid raw material liquefied from a part of the vaporized raw material is further included between the evaporation step and the pyrolysis step;

[0034] The recovery step is a step of recovering the liquid raw material by a raw material recovery device provided between the evaporator and the pyrolysis reactor.

[0035]

[10] . In the method for producing N-vinylacetamide as described in [9] above, the downstream end of the evaporator and the upstream end of the raw material recovery device are connected.

[0036]

[11] . The method for producing N-vinylacetamide as described in [9] or

[10] above, wherein the downstream end of the raw material recovery device and the upstream end of the superheater are connected.

[0037]

[12] . The method for producing N-vinylacetamide according to any one of [9] to

[11] above, wherein the gasified raw material is supplied to the pyrolysis reactor after passing through the raw material recovery device.

[0038]

[13] The method for producing N-vinylacetamide as described in any one of [9] to

[12] above,

[0039] The raw material recovery device comprises:

[0040] a cylinder for the gasification raw material to flow through,

[0041] a recovery unit for causing a part or all of the gasification raw material flow flowing in the cylinder to collide with the gasification raw material, and recovering the non-gasified liquid raw material in the raw material supplied to the evaporator and the liquid raw material liquefied from a part of the gasification raw material; and

[0042] A discharge pipe for discharging the liquid raw material recovered by the recovery unit to the outside of the cylinder.

[0043]

[14] . A pyrolysis device comprising:

[0044] An evaporator that can evaporate the raw material to produce gasified raw material,

[0045] a superheater connected to the evaporator and capable of superheating the gasified raw material to a temperature 5°C higher than the boiling point of N-(1-methoxyethyl)acetamide at the superheater internal pressure (the boiling point of N-(1-methoxyethyl)acetamide at the superheater internal pressure + 5°C) and not higher than 200°C, and

[0046] A pyrolysis reactor is connected to the superheater and can pyrolyze the superheated gasification raw material.

[0047] [Effects of the invention

[0048] According to the present invention, it is possible to provide a method for producing N-vinylacetamide which can prevent the raw material gas (gasified raw material) from being liquefied due to recondensation, suppress the clogging problem of the pyrolysis reactor due to condensates, and enable stable continuous operation for a long period of time. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a flow chart showing the method for producing N-vinylacetamide of the present invention.

[0050] Figure 2 This is a schematic overall view when the evaporator is a falling film evaporator in the method for producing N-vinylacetamide of the present invention.

[0051] Figure 3 This is a schematic overall view when the evaporator is a forced liquid film evaporator in the method for producing N-vinylacetamide of the present invention. DETAILED DESCRIPTION

[0052] In the present specification, preferred provisions can be arbitrarily selected, and it can be said that the preferred provisions are more preferred when combined with each other.

[0053] In this specification, the description of "XX to YY" means "XX or more and YY or less".

[0054] In this specification, regarding the preferred numerical range (such as the range of content, etc.), the lower limit and upper limit described in stages can be independently combined. For example, according to the description of "preferably 10 to 90, more preferably 30 to 60", the "preferable lower limit (10)" and the "preferable upper limit (60)" can also be combined to obtain a range of "10 to 60".

[0055] [Method for producing N-vinylacetamide]

[0056] The method for producing N-vinyl acetamide according to the embodiment of the present invention is as follows: Figure 1 As shown, it includes a supply step S1, an evaporation step S2, an optional recovery step S3, a superheating step S4, and a pyrolysis step S5. Hereinafter, the method for producing N-vinylacetamide according to the embodiment of the present invention will be described in detail.

[0057] (Supply Step S1)

[0058] The supply step S1 is a step of supplying a raw material containing N-(1-methoxyethyl)acetamide (MEA) to an evaporator.

[0059] The method for producing N-vinylacetamide according to the embodiment of the present invention uses N-(1-methoxyethyl)acetamide represented by the following structural formula (1) as a part or all of the raw material.

[0060]

[0061] The content of N-(1-methoxyethyl)acetamide in the raw material is not particularly limited as long as it is 80 to 100% by mass, but is preferably 90 to 100% by mass, and more preferably 95 to 100% by mass.

[0062] The other components in the raw material other than N-(1-methoxyethyl)acetamide are not particularly limited, and examples thereof include acetamide and methanol.

[0063] In the supply step S1, the supply rate of the raw material to the evaporator varies depending on the size and capacity of the evaporator, but from the viewpoint of stably evaporating the raw material, 5 to 350 kg / h is preferred, 10 to 150 kg / h is more preferred, and 15 to 80 kg / h is even more preferred.

[0064] (Evaporation Step S2)

[0065] The evaporation step S2 is a step of evaporating the raw material in an evaporator to form a gasified raw material.

[0066] The evaporator used in the evaporation step S2 is not particularly limited, but is preferably a falling film evaporator or a forced liquid film evaporator from the viewpoint of efficiently evaporating the raw material.

[0067] The evaporation step S2 may be performed under reduced pressure or normal pressure, but is preferably performed under reduced pressure. Specifically, the reaction pressure of the evaporation step S2 is preferably 1 to 30 kPa, more preferably 3 to 25 kPa, and even more preferably 5 to 22 kPa.

[0068] The evaporation step S2 needs to be performed at a temperature at which the vaporized raw material is heated and evaporated, and specifically, it is preferably performed at 100 to 200°C, more preferably at 110 to 190°C, and even more preferably at 120 to 180°C.

[0069] In the evaporation step S2, it is preferred to provide the minimum amount of heat required to evaporate the raw material from the viewpoint of making the heat transfer area of ​​the evaporator smaller and making the evaporator more compact.

[0070] When the heat provided in the evaporation step S2 exceeds the minimum heat required to evaporate the raw material, more sufficient heat should be provided to prepare for heat dissipation to the atmosphere or heat absorption in the pyrolysis reaction step.

[0071] (Recovery Step S3)

[0072] The recovery step S3 is an arbitrary step for recovering the liquid raw material that has not been vaporized and the liquid raw material that has been liquefied from a part of the vaporized raw material in the raw material supplied to the evaporator between the evaporation step S2 and the pyrolysis step S5. The vaporized raw material in a vaporized state is supplied to the pyrolysis step. In addition, it is preferred that the recovery step S3 be performed by a raw material recovery device between the evaporator and the pyrolysis reactor.

[0073] exist Figure 1 , which is the order of evaporation step S2, recovery step S3, and superheating step S4, but is not limited to this. For example, it can also be the order of evaporation step S2, superheating step S4, and recovery step S3.

[0074] Even if only a small amount of liquid raw material is introduced into the pyrolysis reactor, agglomerates (harz) will be generated, and the agglomerates will block the pyrolysis reactor and make it impossible to continue the operation. Even if the agglomerates do not block the entire volume of the pyrolysis reactor, the operation will not continue by blocking a small volume of the raw material introduction side of the pyrolysis reactor. By recovering the liquid raw material to a recovery tank outside the system of the manufacturing device in the recovery step S3, the introduction of the liquid raw material into the pyrolysis reactor can be more reliably suppressed, and as a result, continuous operation can be achieved for a long time.

[0075] When the manufacturing device is in operation, important reasons for the generation of liquid raw materials include heat dissipation to the atmosphere, heat absorption in the pyrolysis reactor (pyrolysis step), operating pressure fluctuations due to mechanical failure and operational negligence, stoppage or shortage of the evaporator heat source due to mechanical failure and operational negligence, the generation of scale (black scale) in the evaporator, poor evaporation due to reduction in heat transfer area, and introduction of raw materials when the device is not fully heated at the start of operation.

[0076] (Overheating Step S4)

[0077] The superheating step S4 is a step of supplying the gasified raw material to a superheater for superheating, and is a step of satisfying at least any one of the following conditions: (i) the superheating temperature of the gasified raw material is set to a temperature 5° C. higher than the boiling point of N-(1-methoxyethyl)acetamide at the superheater pressure (i.e., the boiling point of N-(1-methoxyethyl)acetamide at the superheater internal pressure + 5° C.) and 200° C. or less, and (ii) a heat amount of 1.0 kJ / mol or more is applied to the gasified raw material.

[0078] The superheating temperature of the gasified raw material in the superheating step S4 is not particularly limited as long as it is 5°C higher than the boiling point of N-(1-methoxyethyl)acetamide at the superheater internal pressure (i.e., the boiling point of N-(1-methoxyethyl)acetamide at the superheater internal pressure + 5°C) and 200°C or less, but is preferably 165 to 200°C, more preferably 170 to 195°C, and even more preferably 173 to 190°C. The upper limit of the superheating temperature of the gasified raw material does not mean the temperature obtained by adding the temperature to the boiling point, but simply means the temperature of the upper limit.

[0079] Here, in this specification, the "superheat temperature of the gasified raw material" means the "highest temperature of the gasified raw material in the superheater", and is usually the temperature of the gasified raw material at the downstream end of the superheater (exit gas temperature).

[0080] Furthermore, since the saturated steam temperature of the heat medium at 2.0 MPaG (gauge pressure) (the upper limit pressure of steam in industry) is 215°C, the upper limit of the superheat temperature is preferably 200°C from the viewpoint of cost.

[0081] The amount of heat provided to the gasified raw material in the superheating step S4 is not particularly limited as long as it is 1.0 kJ / moL or more, but is preferably 1.0 to 9.0 kJ / moL, more preferably 1.5 to 8.0 kJ / moL, and even more preferably 2.0 to 7.0 kJ / moL.

[0082] The superheat temperature of the gasification raw material and the lower limit of the amount of heat provided to the gasification raw material are determined as follows.

[0083] There are places that cannot be heated (such as the seams of the jacket and the tunnel of the pyrolysis device) in the hose from the outlet of the superheater to the pyrolysis device. The temperature of these places that cannot be heated will decrease due to the heat absorption of the pyrolysis step. The temperature drop caused by the heat absorption in the pyrolysis step can be calculated from the heat dissipation, reaction rate, reaction heat, and residence time. Considering the calculated temperature drop and the temperature error (threshold, margin), the superheat temperature of the gasification raw material and the lower limit of the heat provided to the gasification raw material are determined.

[0084] On the other hand, the superheat temperature of the gasification raw material and the upper limit of the amount of heat supplied to the gasification raw material are determined as follows.

[0085] In order to prevent the reaction from proceeding too far outside the pyrolysis device, it is necessary to control the pyrolysis reaction so that the reaction rate is reduced to a sufficiently lower level than the reaction rate in the pyrolysis device. Therefore, usually, from the viewpoint of controlling the pyrolysis reaction, the upper limit of the superheat temperature of the gasification raw material and the amount of heat provided to the gasification raw material are set, but there are cases where the upper limit of the superheat temperature of the gasification raw material and the amount of heat provided to the gasification raw material are set depending on the temperature of the heat medium that can be used.

[0086] The superheating step S4 may be performed under reduced pressure or normal pressure, but is preferably performed under reduced pressure. Specifically, the pressure of the superheating step S4 is preferably 1 to 30 kPa, more preferably 3 to 25 kPa, and even more preferably 5 to 22 kPa.

[0087] (Pyrolysis Step S5)

[0088] The pyrolysis step S5 is a step of supplying the superheated gasified raw material to the pyrolysis reactor for pyrolysis. The gas flow of the gasified raw material supplied to the pyrolysis reactor is not particularly limited as long as it is an air flow flowing into the pyrolysis reactor, and can be an upward flow or a downward flow.

[0089] The pyrolysis step S5 may be carried out under reduced pressure or normal pressure, but is preferably carried out under reduced pressure. Specifically, the reaction pressure of the pyrolysis step S5 is preferably 1 to 30 kPa, more preferably 3 to 25 kPa, and even more preferably 5 to 22 kPa.

[0090] The pyrolysis step S5 is preferably performed at 250 to 500°C, more preferably at 300 to 480°C, and even more preferably at 350 to 450°C, from the viewpoint of efficient pyrolysis.

[0091] The residence time in the pyrolysis step S5 is preferably 0.1 to 10 seconds, more preferably 0.2 to 9 seconds, and even more preferably 0.3 to 8 seconds from the viewpoint of surely performing pyrolysis.

[0092] From the viewpoint of efficiently performing pyrolysis, the pyrolysis reactor preferably has a multi-tube structure.

[0093] The raw material supplied to the pyrolysis reactor is preferably a gasified raw material after the recovery step. By supplying the gasified raw material after the recovery step to the pyrolysis reactor, it is possible to more reliably suppress the introduction of the liquid raw material into the pyrolysis reactor and further suppress the generation of agglomerates.

[0094] The N-vinylcarboxylic acid amide obtained through the above steps is represented by the following structural formula (2), and can be obtained from N-(1-methoxyethyl)acetamide represented by the structural formula (1) contained in the raw material.

[0095]

[0096] (First Manufacturing Apparatus)

[0097] The first production apparatus for carrying out the production method of N-vinylacetamide according to the embodiment of the present invention is as follows: Figure 2 As shown, it is equipped with: a raw material supply device 10 for implementing the supply step S1, an evaporator (falling film evaporator) 20A for implementing the evaporation step S2, a raw material recovery device 30A for implementing the recovery step S3, a superheater 40A for implementing the superheating step S4, a pyrolysis reactor 50 for implementing the pyrolysis step S5, a cooler 60 for cooling the reactant pyrolyzed in the pyrolysis step S5 to liquefy it, and a reaction liquid receiver 70 for storing the liquefied reactant in the cooler 60.

[0098] The downstream end of the raw material supply device 10 is connected to the upstream end of the evaporator 20A via the piping 12, the downstream end of the evaporator 20A is connected to the upstream end of the raw material recovery device 30A, the downstream end of the raw material recovery device 30A is connected to the upstream end of the superheater 40A, the downstream end of the superheater 40A is connected to the upstream end of the pyrolysis reactor 50, the downstream end of the pyrolysis reactor 50 is connected to the upstream end of the cooler 60, and the downstream end of the cooler 60 is connected to the upstream end of the reaction liquid receiver 70.

[0099] The falling film evaporator is an evaporator that allows the liquid raw material to flow down in a film-like manner while being conveyed on the inner surface of the evaporation tube to evaporate. For example, it is an evaporator with a structure in which a plurality of hoses are arranged inside the shell and the liquid flows down the inner walls of these hoses. The superheater 40A has the same structure as the distiller 20A.

[0100] The raw material recovery device 30A is provided with a recovery tank 42 for recovering the recovered liquid raw material.

[0101] The reaction liquid receiver 70 is provided with a pressure pump 71, and the pressure of the entire production apparatus can be adjusted by the pressure pump 71. The pressure of the entire production apparatus can be confirmed by a pressure gauge PI provided in the reaction liquid receiver 70.

[0102] The raw material recovery device 30A may be configured mainly not to introduce the liquid raw material into the superheater 40A and the pyrolysis reactor 50 .

[0103] The raw material recovery device 30A, for example Figure 2As shown, it is preferred that the structure comprises: a cylinder 32 through which the gasified raw material flows, a recovery section 33 for causing a part or all of the gasified raw material flowing in the cylinder 32 to collide with the recovery section 33, and recovering the liquid raw material that has not been vaporized in the raw material supplied to the evaporator and the liquid raw material liquefied from a part of the gasified raw material, and a discharge pipe 34 for discharging the liquid raw material recovered by the recovery section 33 to the outside of the cylinder 32. The raw material recovery device 30A is preferably structured to further have a flow suppression section 31 so that all of the gasified raw material flowing in the cylinder 32 collide with the recovery section 33.

[0104] The flow suppressing portion 31 preferably has a tapered shape that narrows the flow of the gasified raw material toward the downstream.

[0105] The recovery part 33 is in a dish shape capable of receiving the gasification raw material flow, and preferably has a collection part for collecting the liquid raw material.

[0106] By making the raw material recovery device 30A have the above structure, the liquid raw material that has not been vaporized and the liquid raw material formed by liquefying a part of the vaporized raw material among the raw materials supplied to the evaporator are recovered by colliding with the recovery part 33, and the liquid raw material is discharged to the outside of the cylinder 32 through the discharge pipe 34. The vaporized raw material that has collided with the recovery part 33 passes through the gap between the recovery part 33 and the flow suppression part 31 and heads toward the superheater 40A and the pyrolysis reactor 50. That is, by making the raw material recovery device 30A have the above structure, the vaporized raw material that has collided with the recovery part 33 and the liquid raw material is recovered is introduced into the superheater 40A and the pyrolysis reactor 50.

[0107] The liquid raw material recovered in the raw material recovery device 30A is sent to the recovery tank 42. The recovery tank 42 can control the liquid raw material through the conversion valves 35a and 35b. In addition, the recovery tank 42 can adjust the pressure of the recovery tank 42 through the pressure pump 36 and the conversion valves 35a to 35d. The pressure of the recovery tank 42 can be confirmed by the pressure gauge PI.

[0108] The liquid raw material recovered in the raw material recovery device 30A always flows into the recovery tank 42 through the switching valves 35a and 35b. The recovery amount of the recovery tank 42 can be confirmed by the liquid level gauge LI set in the liquid level confirmation window of the recovery tank 42. When the liquid raw material stored in the recovery tank 42 is to be recovered, after closing the switching valves 35b and 35c, the nitrogen valve 37a is opened to introduce nitrogen into the recovery tank 42 from the nitrogen supply device 37 until the normal pressure is restored, and the extraction valve 41 is opened. After the recovery, the extraction valve 41 and the nitrogen valve 37a are closed, and the switching valve 36a is opened to adjust the pressure to the same pressure as the entire manufacturing device, and then the switching valve 35c is opened, and then the switching valve 35b is opened to make it possible to recover the liquid raw material.

[0109] The temperature of the raw material recovery device 30A is appropriately selected from a temperature range in which the vaporized raw material generated in the evaporator 20A does not condense. The temperature of the recovery tank 42 may be any temperature as long as the recovered liquid raw material does not solidify.

[0110] The liquid raw material recovered in the raw material recovery device 30A is preferably supplied to the evaporator 20A. Figure 2 In the first production apparatus shown, the liquid raw material recovered in the recovery tank 42 is supplied to the evaporator 20A. By supplying the recovered liquid raw material to the evaporator 20A again, efficient use of the raw material can be achieved.

[0111] like Figure 2 As shown, it is preferable that the downstream end of the evaporator 20A is connected to the upstream end of the raw material recovery device 30A. With the structure in which the downstream end of the evaporator 20A is connected to the upstream end of the raw material recovery device 30A, the vaporized raw material heated and evaporated by the evaporator 20A can be directly sent to the raw material recovery device 30A. That is, it is possible to prevent a part of the vaporized raw material from being liquefied between the evaporator 20A and the raw material recovery device 30A.

[0112] like Figure 2 As shown in FIG. 1 , it is preferable that the downstream end of the raw material recovery device 30A is connected to the upstream end of the superheater 40A. With the structure in which the downstream end of the raw material recovery device 30A is connected to the upstream end of the superheater 40A, the gasified raw material recovered in the raw material recovery device 30A can be directly sent to the superheater 40A. That is, it is possible to prevent a part of the gasified raw material from being liquefied between the raw material recovery device 30A and the superheater 40A.

[0113] like Figure 2 As shown, it is preferable to adopt a structure in which the downstream end of the superheater 40A is connected to the upstream end of the pyrolysis reactor 50. By adopting a structure in which the downstream end of the superheater 40A is connected to the upstream end of the pyrolysis reactor 50, the gasified raw material superheated by the superheater 40A can be directly sent to the pyrolysis reactor 50. That is, it is possible to prevent a part of the gasified raw material from being liquefied between the superheater 40A and the pyrolysis reactor 50.

[0114] like Figure 2 As shown, it is preferred that the downstream end of the pyrolysis reactor 50 is connected to the upstream end of the cooler 60. By adopting the structure in which the downstream end of the pyrolysis reactor 50 is connected to the upstream end of the cooler 60, the target product obtained by pyrolysis in the pyrolysis reactor 50 can be directly sent to the cooler 60.

[0115] like Figure 2As shown, it is preferred that the downstream end of the cooler 60 is connected to the upstream end of the reaction liquid receiver 70. By connecting the downstream end of the cooler 60 to the upstream end of the reaction liquid receiver 70, the target object cooled by the cooler 60 can be directly sent to the reaction liquid receiver 70.

[0116] (Second manufacturing device)

[0117] The second production apparatus for carrying out the production method of N-vinylacetamide according to the embodiment of the present invention is as follows: Figure 3 As shown, it is equipped with: a raw material supply device 10 for implementing the supply step S1, an evaporator (forced liquid film evaporator) 20B for implementing the evaporation step S2, a superheater 40B for implementing the superheating step S4, a raw material recovery device 30B for implementing the recovery step S3, a pyrolysis reactor 50 for implementing the pyrolysis step S5, a cooler 60 for cooling and liquefying the reactant pyrolyzed in the pyrolysis step S5, and a reaction liquid receiver 70 for storing the reactant liquefied by the cooler 60.

[0118] The downstream end of the raw material supply device 10 is connected to the upstream end of the evaporator 20B via the pipe 12, the downstream end of the evaporator 20B is connected to the upstream end of the superheater 40B via the first pipe 90, the downstream end of the superheater 40B is connected to the upstream end of the raw material recovery device 30B via the second pipe front section 100a, the downstream end of the raw material recovery device 30B is connected to the upstream end of the pyrolysis reactor 50 via the second pipe rear section 100b, the downstream end of the pyrolysis reactor 50 is connected to the upstream end of the cooler 60 via the pipe 13, and the downstream end of the cooler 60 is connected to the upstream end of the reaction liquid receiver 70 via the pipe 14.

[0119] Forced liquid film evaporator, the liquid raw material is transported along the inner surface of the evaporation tube in the form of a film, and at the same time, a motor (such as Figure 3 An evaporator in which a motor M) rotates a fan or the like to generate a propulsion force through the air flow in the evaporation tube, and the film-like raw material in the evaporation tube is forced to move forward by the propulsion force to evaporate.

[0120] The pipe 95 connecting the first pipe 90 and the second pipe 100 in the superheater 40B zigzags to provide a specific amount of heat to the gas raw material in the pipe 95 , thereby bringing the gas raw material to a specific temperature.

[0121] The raw material recovery device 30B is provided with a recovery tank 42 for recovering the recovered liquid raw material.

[0122] The reaction liquid receiver 70 is provided with a pressure pump 71, and the pressure of the entire production apparatus can be adjusted by the pressure pump 71. The pressure of the entire production apparatus can be confirmed by a pressure gauge PI provided on the reaction liquid receiver 70.

[0123] It is preferred that the evaporator 20B is provided with a recovery tank 21 for recovering the liquid raw material that has not been vaporized in the raw material supplied to the evaporator 20B and the liquid raw material liquefied from a part of the vaporized raw material. From the viewpoint of easily recovering the liquid raw material, it is preferred that the recovery tank 21 is arranged at a position lower than the evaporator 20B. The recovery tank 21 is provided with a switching valve 22a that separates the evaporator 20B and the recovery tank 21, and an extraction valve 22b that extracts the liquid raw material recovered by the recovery tank 21 to the outside of the system. The recovery tank 21 can control the liquid raw material by the switching valve 22a and the extraction valve 22b. When the liquid raw material that has not been vaporized in the raw material supplied to the evaporator 20B is to be recovered, the extraction valve 22b is closed and the switching valve 22a is opened. When the liquid raw material recovered in the recovery tank 21 is to be extracted, the switching valve 22a is closed and the extraction valve 22b is opened.

[0124] like Figure 3 As shown, the downstream end of the evaporator 20B and the upstream end of the superheater 40B are connected via the first pipe 90, and it is preferable that the downstream end of the first pipe 90 is located at the highest position in the first pipe 90. By adopting the structure in which the downstream end of the first pipe 90 is located at the highest position in the first pipe 90, the unvaporized liquid raw material and the liquid raw material liquefied from a part of the vaporized raw material among the raw materials flowing through the first pipe 90 are prevented from being subjected to the heat history and generating condensate due to over-entering the superheater 40B and stagnating, and thus the operation can be performed without generating condensate.

[0125] like Figure 3 As shown, the downstream end of the evaporator 40B is connected to the upstream end of the raw material recovery device 30B via the front section 100a of the second pipe, and the upstream end of the front section 100a of the second pipe is preferably located at the highest position in the front section 100a of the second pipe. By adopting the structure in which the upstream end of the front section 100a of the second pipe is located at the highest position in the front section 100a of the second pipe, the liquid raw material formed by liquefying a part of the gasified raw material flowing through the front section 100a of the second pipe can be efficiently recovered by the raw material recovery device 30B.

[0126] like Figure 3 As shown, the downstream end of the raw material recovery device 30B is connected to the upstream end of the pyrolysis reactor 50 via the rear section 100b of the second pipe, and the upstream end of the rear section 100b of the second pipe is preferably the lowest structure in the rear section 100b of the second pipe. By adopting the structure in which the upstream end of the rear section 100b of the second pipe is the lowest structure in the rear section 100b of the second pipe, even if part of the gasified raw material flowing through the rear section 100b of the second pipe is liquefied, the liquefied liquid raw material can be efficiently recovered by the raw material recovery device 30B.

[0127] like Figure 3 As shown, the downstream end of the superheater 40B is connected to the upstream end of the pyrolysis reactor 50 via the second pipe 100 (the front section 100a and the rear section 100b of the second pipe), and it is preferable that the upstream end of the second pipe 100 is located at the highest position in the second pipe 100. By adopting the structure in which the upstream end of the second pipe 100 is located at the highest position in the second pipe 100, even if part of the gasified raw material flowing through the second pipe 100 is liquefied, the liquefied liquid raw material can be efficiently recovered by the raw material recovery device 30B.

[0128] The liquid raw material recovered by the raw material recovery device 30B is sent to the recovery tank 42. From the viewpoint of easy recovery of the liquid raw material, the recovery tank 42 is preferably arranged at a lower position than the raw material recovery device 30B. The recovery tank 42 can control the liquid raw material through the conversion valve 35e and the extraction valve 41. In addition, the recovery tank 42 can adjust the pressure of the recovery tank 42 through the pressure pump 36, the conversion valve 35e and the extraction valve 41. The pressure of the recovery tank 42 can be confirmed by the pressure gauge PI.

[0129] The liquid raw material recovered in the raw material recovery device 30B always flows into the recovery tank 42 through the switching valve 35e. The recovery amount of the recovery tank 42 can be confirmed by a liquid level gauge LI such as a liquid level confirmation window provided in the recovery tank 42. When the liquid raw material stored in the recovery tank 42 is to be recovered, after closing the switching valve 35e, the nitrogen valve 37a is opened to introduce nitrogen into the recovery tank 42 from the nitrogen supply device 37 until the normal pressure is restored, and the extraction valve 41 is opened. After recovery, the extraction valve 41 and the nitrogen valve 37a are closed, and the switching valve 36a is opened. After adjusting the pressure to the same pressure as the entire manufacturing device through the pressure pump 36, the switching valve 35e is opened to make it possible to recover the liquid raw material.

[0130] The temperature of the raw material recovery device 30B is appropriately selected from a temperature range in which the vaporized raw material generated in the evaporator 20B and superheated in the superheater 40B does not condense. The temperature of the recovery tank 42 may be any temperature as long as the recovered liquid raw material does not solidify.

[0131] The liquid raw material recovered in the raw material recovery device 30B is preferably supplied to the evaporator 20B. Figure 3 The second manufacturing apparatus shown in FIG. 4 supplies the liquid raw material recovered in the recovery tank 42 to the evaporator 20B. Figure 3 In the second production apparatus shown, it is preferable to also supply the liquid raw material recovered in the recovery tank 21 to the evaporator 20B. By supplying the recovered liquid raw material to the evaporator again, efficient use of the raw material can be achieved.

[0132] Figure 3The manufacturing apparatus shown is preferably configured such that the rear section 100b of the second pipe is connected to the side or top of the raw material recovery device 30B. By adopting a configuration such that the rear section 100b of the second pipe is connected to the side or top of the raw material recovery device 30B, the liquid raw material recovered by the raw material recovery device 30B can be prevented from flowing into the rear section 100b of the second pipe.

[0133] Figure 3 The second manufacturing apparatus shown may also be configured such that the downstream end of the raw material recovery device 30B is connected to the upstream end of the pyrolysis reactor 50. By adopting a configuration such that the downstream end of the raw material recovery device 30B is connected to the upstream end of the pyrolysis reactor 50, the gasified raw material after the liquid raw material is recovered by the raw material recovery device 30B can be directly sent to the pyrolysis reactor 50. That is, it is possible to prevent a part of the gasified raw material from being liquefied between the raw material recovery device 30B and the pyrolysis reactor 50.

[0134] also, Figure 3 The manufacturing apparatus shown in the figure may also be replaced by the raw material recovery device 30B, the switching valve 35e, the pressure pump 36, the recovery tank 42, and the extraction valve 41 instead of using the raw material recovery device 30B. Figure 2 The raw material recovery device 30A, the switching valves 35a~35d, the pressure pump 36, the recovery tank 42, and the extraction valve 41.

[0135] [Pyrolysis device]

[0136] The pyrolysis apparatus according to the embodiment of the present invention comprises: an evaporator capable of evaporating a raw material to generate a gasified raw material; a superheater connected to the evaporator capable of superheating the gasified raw material to a temperature 5° C. higher than the boiling point of N-(1-methoxyethyl)acetamide at the superheater internal pressure (i.e., the boiling point of N-(1-methoxyethyl)acetamide at the superheater internal pressure + 5° C.) and 200° C. or lower; and a pyrolysis reactor connected to the superheater capable of pyrolyzing the superheated gasified raw material. The apparatus may further comprise the above-mentioned raw material recovery device, a cooler, a reaction liquid receiving container, a recovery tank, a nitrogen supply device, a pressure pump, a switching valve, a nitrogen valve, an extraction valve, a first pipe, a second pipe, a liquid level gauge, a motor, a pressure gauge, etc., as required.

[0137] The method for producing N-vinylacetamide according to the embodiment of the present invention can be preferably carried out using the pyrolysis apparatus according to the embodiment of the present invention.

[0138] [Example]

[0139] Hereinafter, the present invention will be described in more detail based on examples. However, the present invention is not limited to the examples described below as long as it does not exceed the gist of the present invention.

[0140] (Example 1)

[0141] use Figure 2 The manufacturing device shown.

[0142] The evaporator is a falling film evaporator, which is a shell and tube type evaporator (tube diameter: 25.4 mm, tube length: 2500 mm, number of tubes: 22) having a structure in which a plurality of hoses are provided inside a shell and liquid flows down along the inner walls of these hoses.

[0143] Saturated steam of 0.7 MPaG (gauge pressure) (temperature 170°C) was introduced into the shell side of the evaporator, and the liquid raw material N-(1-methoxyethyl)acetamide was supplied to the hose side at a supply rate of 20 kg / h under a reduced pressure condition of 20 kPa (absolute pressure) set by a pressure reducing device (pressure pump) installed in the reaction liquid receiving container, so as to flow down along the inner wall of the hose and evaporate. At this time, the gas temperature at the outlet of the evaporator was 160°C (the boiling point of N-(1-methoxyethyl)acetamide at 20 kPa (absolute pressure)).

[0144] The raw material recovery device is provided with flanges with an outer diameter of 267.4 mm at the top and bottom, respectively connected to the evaporator and the superheater. Saturated steam of 0.7 MPaG (gauge pressure) is introduced into the cylinder (sleeve) of the raw material recovery device, and the vaporized raw material is heated in a manner that does not condense.

[0145] The superheater is a shell-and-tube type superheater (tube diameter: 25.4 mm, tube length: 390 mm, number of tubes: 22) with a plurality of hoses installed inside the shell, similar to the evaporator. Saturated steam of 1.85 MPaG (gauge pressure) (temperature 211°C) is introduced into the shell side of the superheater to superheat the process gas (gasified raw material) generated in the evaporator to provide 5.65 kJ / moL of heat. The gas temperature at the superheater outlet is 185°C (160°C + 25°C).

[0146] The hose of the pyrolysis reactor is heated to 440° C. by electromagnetic induction heating, and the gasified raw material introduced into the hose is pyrolyzed under reduced pressure to obtain N-vinylacetamide.

[0147] The above conditions were used for 90 days of continuous operation without any problems.

[0148] (Example 2)

[0149] Use the same method as in Example 1 Figure 2 The manufacturing apparatus shown superheats the process gas (gasified raw material) produced by the evaporator to provide 3.39 kJ / moL of heat in such a way that the process gas temperature at the superheater outlet becomes 175°C (160°C+15°C). Apart from this, continuous operation was continued for 90 days under the same operating conditions as in Example 1 without any problems.

[0150] (Example 3)

[0151] Use the same method as in Example 1 Figure 2 The manufacturing apparatus shown superheats the process gas (gasified raw material) produced by the evaporator to provide 7.91 kJ / moL of heat in such a way that the process gas temperature at the superheater outlet becomes 195°C (160°C+35°C). Apart from this, continuous operation was continued for 90 days under the same operating conditions as in Example 1 without any problems.

[0152] (Comparative Example 1)

[0153] In addition to making Example 1 Figure 2 The manufacturing apparatus shown was operated continuously with the same manufacturing apparatus and operating conditions as Example 1 except that the superheater was not provided. As a result, the temperature of the pyrolysis reactor was confirmed to be abnormal and uncontrollable on the 45th day from the start of operation, so the operation was stopped. When the manufacturing apparatus was opened for inspection, it was found that asphalt-like and solid coagulants (harz) were generated and blocked the inlet of the pyrolysis reactor.

[0154] (Comparative Example 2)

[0155] Use the same method as in Example 1 Figure 2 The manufacturing apparatus shown was continuously operated under the same operating conditions as Example 1 except that the process gas (gasified raw material) generated by the evaporator was superheated to provide 0.45 kJ / mol of heat so that the process gas temperature at the superheater outlet was 162°C (160°C+2°C). On the 54th day after the start of operation, it was confirmed that the temperature of the pyrolysis reactor was fluctuating and uncontrollable, so the operation was stopped. When the manufacturing apparatus was opened for inspection, it was found that asphalt-like and solid condensates (harz) were generated and blocked the inlet of the pyrolysis reactor.

[0156] Industrial Applicability

[0157] N-vinylacetamide obtained by the production method of the present invention can be used for the production of N-vinylacetamide-based polymers such as coagulants, liquid absorbents and thickeners, and is also a useful monomer in many industrial applications.

[0158] Description of the accompanying drawings

[0159] 10: Raw material supply device

[0160] 11: Switching valve

[0161] 12~14:Piping

[0162] 20A, 20B: Evaporator

[0163] 21: Recycling tank

[0164] 22a, 22b: Extraction valve

[0165] 30A, 30B: Raw material recovery device

[0166] 31: Circulation suppression unit

[0167] 32: barrel

[0168] 33: Recycling Department

[0169] 34: Discharge piping

[0170] 35a~35e: conversion valve

[0171] 36,71: Pressure pump

[0172] 36a: Switching valve

[0173] 37: Nitrogen supply device

[0174] 37a: Nitrogen valve

[0175] 40A, 40B: Superheater

[0176] 41: Extraction valve

[0177] 42:Recycling tank

[0178] 50: Pyrolysis reactor

[0179] 60: Cooler

[0180] 70: Reaction liquid receiver

[0181] 90: 1st piping

[0182] 95:Piping

[0183] 100: 2nd piping

[0184] 100a: Front section

[0185] 100b: rear section

[0186] LI: Liquid level gauge

[0187] M: Motor

[0188] PI: Pressure gauge

[0189] S1: Supply step

[0190] S2: Evaporation step

[0191] S3: Recycling Step

[0192] S4: Overheating step

[0193] S5: Pyrolysis step.

Claims

1. A method for producing N-vinylacetamide, which is a method for producing N-vinylacetamide using a pyrolysis device. The pyrolysis device includes an evaporator, a superheater connected to the evaporator, and a pyrolysis reactor connected to the superheater. The manufacturing method comprises: A step of supplying a raw material containing N-(1-methoxyethyl)acetamide to an evaporator, wherein the content of N-(1-methoxyethyl)acetamide in the raw material is 80 to 100% by mass. an evaporation step of evaporating the raw material into a gasified raw material in the evaporator, supplying the gasification raw material to a superheater to superheat the gasification raw material so that the superheat temperature of the gasification raw material is 200° C. or less; and A pyrolysis step of supplying the superheated gasified raw material to a pyrolysis reactor for pyrolysis; The continuous operation days of the pyrolysis device can be increased compared to the continuous operation days of a pyrolysis device having an evaporator and a pyrolysis reactor connected to the evaporator but not having a superheater.

2. The method for producing N-vinylacetamide according to claim 1, wherein the superheating step is performed under reduced pressure.

3. The method for producing N-vinylacetamide according to claim 1, wherein the pressure in the superheating step is 1 to 30 kPa. 4 . The method for producing N-vinylacetamide according to claim 1 , wherein in the superheating step, a heat of 1.0 kJ / mol or more is applied to the gasification raw material to superheat the gasification raw material.

5. The method for producing N-vinylacetamide according to claim 1, wherein in the superheating step, superheating is performed so that the superheating temperature of the gasified raw material becomes a temperature 5° C. or higher than the boiling point of N-(1-methoxyethyl)acetamide at the internal pressure of the superheater.

6. The method for producing N-vinylacetamide according to claim 1, wherein in the superheating step, superheating is performed so that the superheating temperature of the gasified raw material becomes a temperature that is 15° C. or higher than the boiling point of N-(1-methoxyethyl)acetamide at the internal pressure of the superheater.

7. The method for producing N-vinylacetamide according to claim 1, wherein the continuous operation days of the pyrolysis device exceed 45 days.

8. The method for producing N-vinylacetamide according to claim 1, wherein the continuous operation days of the pyrolysis device exceed 54 days.

9. The method for producing N-vinylacetamide according to claim 1, wherein the evaporation step is performed under reduced pressure.

10. The method for producing N-vinylacetamide according to claim 1, wherein the thermal decomposition step is performed under reduced pressure.

11. The method for producing N-vinylacetamide according to claim 1, wherein the downstream end of the evaporator and the upstream end of the superheater are connected via a first pipe, and the downstream end of the first pipe is located highest in the first pipe.

12. The method for producing N-vinylacetamide according to claim 1, wherein the downstream end of the superheater and the upstream end of the pyrolysis reactor are connected via a second pipe, and the upstream end of the second pipe is located highest in the second pipe.

13. The method for producing N-vinylacetamide according to any one of claims 1 to 12, A recovery step of recovering the unvaporized liquid raw material in the raw material supplied to the evaporator and the liquid raw material liquefied from a part of the vaporized raw material is further included between the evaporation step and the pyrolysis step; The recovery step is a step of recovering the liquid raw material by a raw material recovery device provided between the evaporator and the pyrolysis reactor.

14. A method for producing N-vinylacetamide, comprising: using a pyrolysis device to produce N-vinylacetamide. The pyrolysis device includes an evaporator, a superheater connected to the evaporator, and a pyrolysis reactor connected to the superheater, and the manufacturing method includes: A step of supplying a raw material containing N-(1-methoxyethyl)acetamide to an evaporator, wherein the content of N-(1-methoxyethyl)acetamide in the raw material is 80 to 100% by mass. an evaporation step of evaporating the raw material into a gasified raw material in the evaporator, a superheating step of supplying the gasification raw material to a superheater to apply a heat of 1.0 kJ / mol or more to the gasification raw material to superheat the gasification raw material, and A pyrolysis step of supplying the superheated gasified raw material to a pyrolysis reactor for pyrolysis; The continuous operation days of the pyrolysis device can be increased compared to the continuous operation days of a pyrolysis device having an evaporator and a pyrolysis reactor connected to the evaporator but not having a superheater.

15. The method for producing N-vinylacetamide according to claim 14, wherein the superheating step is performed under reduced pressure.

16. The method for producing N-vinylacetamide according to claim 14, wherein the pressure in the superheating step is 1 to 30 kPa. 17 . The method for producing N-vinylacetamide according to claim 14 , wherein in the superheating step, a heat of 1.5 kJ / mol or more is applied to the gasification raw material to superheat the gasification raw material.

18. The method for producing N-vinylacetamide according to claim 14, wherein in the superheating step, the gasified raw material is superheated so that the superheating temperature becomes a temperature 5°C or higher than the boiling point of N-(1-methoxyethyl)acetamide at the internal pressure of the superheater.

19. The method for producing N-vinylacetamide according to claim 14, wherein in the superheating step, superheating is performed so that the superheating temperature of the gasified raw material becomes a temperature that is 15° C. or higher than the boiling point of N-(1-methoxyethyl)acetamide at the internal pressure of the superheater.

20. The method for producing N-vinylacetamide according to claim 14, wherein the continuous operation days of the pyrolysis device exceed 45 days.

21. The method for producing N-vinylacetamide according to claim 14, wherein the continuous operation days of the pyrolysis device exceed 54 days.

22. The method for producing N-vinylacetamide according to claim 14, wherein the evaporation step is performed under reduced pressure.

23. The method for producing N-vinylacetamide according to claim 14, wherein the pyrolysis step is performed under reduced pressure.

24. The method for producing N-vinylacetamide according to claim 14, wherein the downstream end of the evaporator and the upstream end of the superheater are connected via a first pipe, and the downstream end of the first pipe is located highest in the first pipe.

25. The method for producing N-vinylacetamide according to claim 14, wherein the downstream end of the superheater and the upstream end of the pyrolysis reactor are connected via a second pipe, and the upstream end of the second pipe is located highest in the second pipe.

26. The method for producing N-vinylacetamide according to any one of claims 14 to 25, A recovery step of recovering the unvaporized liquid raw material in the raw material supplied to the evaporator and the liquid raw material liquefied from a part of the vaporized raw material is further included between the evaporation step and the pyrolysis step; The recovery step is a step of recovering the liquid raw material by a raw material recovery device provided between the evaporator and the pyrolysis reactor.

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