A method for preparing propylene base ethyl ether by liquid phase cleavage of propionaldehyde diethyl acetal

Abstract

The application provides a method for preparing propylene ethyl ether by liquid phase cleavage of propionaldehyde diethyl acetal, and realizes low-cost and efficient preparation of high-purity propylene ethyl ether through sequentially conducted liquid phase cleavage reaction, rectification and extraction. The propylene ethyl ether content of the finished product propylene ethyl ether is greater than or equal to 98.0 wt%, the ethanol content is less than 1.0 wt%, and the quality of the finished product propylene ethyl ether is higher than that of propylene ethyl ether produced by a Rapaph process.

Description

Technical Field

[0001] This invention relates to the field of propylene diethyl ether preparation technology, specifically to a method for preparing propylene diethyl ether by liquid-phase pyrolysis of propionaldehyde diethanol. Background Technology

[0002] Propylene ethyl ether, also known as 1-ethoxy-1-propene, with the molecular formula CH3-CH=CH-O-CH2-CH3, is an organic solvent belonging to the ether class of compounds. It is usually a colorless and odorless liquid with good solubility, soluble in water and many organic solvents. Propylene ethyl ether is mainly used as an industrial solvent and is widely used in paints, varnishes, inks, adhesives, coatings, cleaning agents, and other fields. Its main function in these applications is to provide good solubility, which helps to dissolve and dilute other chemicals.

[0003] However, alkenyl ethers cannot be prepared using conventional ether preparation methods. This is because allyl alcohol is not available, making it impossible to react potassium / sodium allyl alcohol with haloalkanes. Furthermore, haloalkenes exhibit almost no nucleophilic substitution activity, and allyl chloride and sodium alkoxides cannot be used for preparation. Currently, the main methods for preparing allyl ethyl ethers are the Rapa process and acetal pyrolysis. The synthesis of allyl ethyl ethers using propyne and ethanol under a strongly basic catalyst suffers from short catalyst lifetime and poor safety. Regarding acetal liquid-phase pyrolysis, KCDrannock, Soc 81.3382.1959 proposed using a small amount of 85% phosphoric acid as a catalyst to heat the acetal, yielding alkenyl ethers during fractional distillation. Under these conditions, large amounts of black tar-like substances are produced in the reactants, resulting in consistently low alkenyl ether yields. Existing technology proposes a solution that uses heptanal diethyl acetal as raw material, a high-boiling-point, highly chemically stable liquid silane ether compound as the liquid phase medium, p-toluenesulfonic acid as a catalyst, and a nitrogen-containing heterocyclic compound as a retarder. The reaction temperature is 200℃~280℃. Heptanal diethyl acetal is decomposed in the liquid phase to obtain 1-n-pentyl-2-ethoxyethylene with a conversion rate of 96% and a selectivity of 85%. The catalyst used in the liquid phase cracking method is relatively simple and the conditions are easy to control; however, the post-processing is troublesome and the environmental pressure is high.

[0004] It is evident that the preparation of propylene ethyl ether still suffers from problems such as low catalyst efficiency, high energy consumption, high cost, environmental unfriendliness, poor process stability, or insufficient product purity. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention provides a method for preparing propylene ethyl ether by liquid-phase pyrolysis of propionaldehyde diethanol. Through sequential liquid-phase pyrolysis reaction, distillation and extraction, high-purity propylene ethyl ether is prepared at low cost and high efficiency. The finished propylene ethyl ether has a propylene ethyl ether content ≥98.0wt% and an ethanol content <1.0wt%. The quality of the finished propylene ethyl ether is higher than that of propylene ethyl ether produced by the Rapa process.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] The purpose of this invention is to provide a method for preparing propylene diethyl ether by liquid-phase pyrolysis of propionaldehyde diethanol, wherein the method comprises the following steps:

[0008] (1) Add propionaldehyde diethanol and catalyst into the reactor to carry out liquid-phase pyrolysis reaction;

[0009] (2) The gas-phase reaction system from the top of the reactor enters the distillation column with a condenser at the top for distillation. Uncondensed gas and condensate are collected from the top of the distillation column.

[0010] (3) Extract water and the condensate to obtain the finished product propylene ether and ethanol solution.

[0011] The method described in this invention includes sequential liquid-phase pyrolysis reaction, distillation, and extraction, achieving low-cost and high-efficiency preparation of high-purity propylene ethyl ether. The finished propylene ethyl ether has a propylene ethyl ether content ≥98.0 wt% and an ethanol content <1.0 wt%, and the quality of the finished propylene ethyl ether is higher than that of propylene ethyl ether produced by the Rapa process.

[0012] It should be noted that the distillation column is located above the reactor. The gas phase outlet at the top of the reactor is directly connected to the inlet at the bottom of the distillation column, so that the gas phase reaction system from the top of the reactor enters the distillation column for distillation. Uncondensed gas and condensate are collected from the top of the distillation column, while part of the condensate in the distillation column is returned to the reactor. In other words, the distillation column is connected to the reactor for reaction distillation.

[0013] It should be noted that the purity of propionaldehyde diethanol condensed in the method of the present invention is ≥95%, preferably ≥98%.

[0014] As a preferred technical solution of the present invention, in step (1), the temperature of the liquid phase pyrolysis reaction is 100~140℃, such as 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃ or 140℃, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0015] It should be noted that the liquid phase pyrolysis reaction begins when the temperature inside the reactor rises above 100℃, for example, by raising the temperature to 100~105℃. As the reaction proceeds, the temperature inside the reactor gradually increases. The temperature of the liquid phase pyrolysis reaction is 100~140℃. When the temperature inside the reactor is greater than 140℃, it indicates that the raw materials have been basically completely pyrolyzed. The reaction is then stopped, and the temperature is lowered to 40℃ to remove the high boiling point.

[0016] As a preferred technical solution of the present invention, in step (1), the catalyst is an organic acid catalyst, which includes a main component and an auxiliary agent.

[0017] As a preferred embodiment of the present invention, the main component is a high-boiling-point acid, including p-toluenesulfonic acid and / or methanesulfonic acid; the auxiliary agent is a high-boiling-point amine, including diisooctylamine; the mass ratio of the main component to the auxiliary agent in the organic acid catalyst is 10:(3~8), for example 10:3, 10:4 (i.e. 5:2), 10:5 (i.e. 2:1), 10:6 (i.e. 5:3), 10:7 or 10:8 (i.e. 5:4), etc., but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0018] As a preferred technical solution of the present invention, in step (1), the mass ratio of propionaldehyde diethanol and catalyst is 1:(0.003~0.01), that is, the mass of catalyst accounts for 0.3~1.0% of the mass of propionaldehyde diethanol, for example 1:0.003, 1:0.004, 1:0.005, 1:0.006, 1:0.007, 1:0.008, 1:0.009 or 1:0.01, etc., but not limited to the listed values, other unlisted values ​​within the above range are also applicable.

[0019] As a preferred technical solution of the present invention, in step (2), the top temperature of the distillation column is controlled to be 70~75℃, for example 70℃, 70.5℃, 71℃, 71.5℃, 72℃, 72.5℃, 73℃, 73.5℃, 74℃, 74.5℃ or 75℃, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0020] As a preferred technical solution of the present invention, in step (2), the distillation column is a packed column with a theoretical number of plates ≥30.

[0021] As a preferred technical solution of the present invention, in step (3), the extraction is carried out in an extraction tower, which is a packed tower with a theoretical number of plates ≥20. Preferably, the condensate from the upper part of the distillation tower is first buffered in a transfer tank before entering the extraction tower.

[0022] As a preferred technical solution of the present invention, in the extraction step (3), the flow rate ratio of condensate to water is 1:(0.5~2.0), for example 1:0.5, 1:0.7, 1:0.9, 1:1.0, 1:1.1, 1:1.3, 1:1.5, 1:1.7, 1:1.8 or 1:2.0, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0023] As a preferred technical solution of the present invention, in step (3), the content of the propylene ethyl ether in the finished product is ≥98.0wt% and the content of ethanol is <1.0wt%.

[0024] It should be noted that those skilled in the art often use gas chromatography to detect the finished product propylene ethyl ether, and the detection result is generally recorded as mass percentage, i.e., wt%.

[0025] As a preferred embodiment of the present invention, the method for preparing propylene diethyl ether by liquid-phase pyrolysis of propionaldehyde diethanol comprises the following steps:

[0026] (1) A measured amount of propionaldehyde diethanol and catalyst are added to the reactor, stirring is started, and then low-pressure steam is used to heat the reactor through the jacket to 100~105℃. When the temperature reaches above 100℃, the liquid phase cracking reaction begins; wherein, the mass ratio of propionaldehyde diethanol to catalyst is 1:(0.003~0.01); the catalyst is an organic acid catalyst, which includes a main component and an auxiliary agent; the main component includes p-toluenesulfonic acid and / or methanesulfonic acid; the auxiliary agent includes diisooctylamine; the mass ratio of the main component to the auxiliary agent in the organic acid catalyst is 10:(3~8);

[0027] (2) The cracking products enter the distillation column in gaseous form. The circulating water at the top of the distillation column is turned on to control the top temperature. The temperature is controlled at 70~75℃ for distillation. Uncondensed gas and condensate are collected from the top of the distillation column. The uncondensed gas passes through the tail gas trap and is discharged. The recondensate and the condensate collected from the top of the column are collected in the transfer tank. The distillation column is a packed column with a theoretical number of plates ≥30. The cracking products enter from below the bottom plate in gaseous form. The condensate at the top of the distillation column is collected from the top plate.

[0028] (3) Turn on the feed pump and pump the material in the transfer tank into the extraction tower that has been filled with water (tap water) to the designated liquid level at a certain flow rate. At the same time, turn on the water inlet valve of the extraction tower and control the water flow rate. The flow rate ratio of material to water is 1:(0.5~2.0). The extraction tower is a packed tower with a theoretical number of trays ≥20. The extraction tower is numbered from top to bottom as tray 1, tray 2, ... Tap water is injected from tray 1 through the distributor. The material in the transfer tank is injected from the bottom of the last tray through the distributor. The material collected from the top of the extraction tower is the finished product propylene ethyl ether (propylene ethyl ether content ≥98.0wt%, ethanol content <1.0wt%). The material collected from the bottom of the extraction tower is an ethanol solution.

[0029] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0030] (1) The catalyst of the present invention has a simple preparation process, low cost, high catalytic activity, strong selectivity, few components of pyrolysis products, and the main components of pyrolysis products have large differences in water solubility, making them easy to separate.

[0031] (2) This invention combines pyrolysis and purification to achieve continuous production of the separation process;

[0032] (3) The preparation method of high-purity propylene ethyl ether of the present invention has the characteristics of good process stability, mild reaction conditions, continuous long-term production and operation, simple equipment, low investment, high product purity, less waste, and high energy efficiency, and has good application prospects. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the apparatus system for preparing propylene diethyl ether by liquid-phase pyrolysis of propionaldehyde diethanol in a specific embodiment of the present invention.

[0034] In the diagram, 1-reaction vessel; 2-distillation column; 3-condenser; 4-tail gas collector; 5-transfer tank; 6-feed pump; 7-extraction column; 8-finished product receiving tank. Detailed Implementation

[0035] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0036] This invention provides a method for preparing propylene diethyl ether by liquid-phase pyrolysis of propionaldehyde diethanol, the apparatus of which is as follows: Figure 1As shown, a distillation column 2 is connected to the top of a stirred reactor 1, connecting the top of reactor 1 to the bottom of distillation column 2 to form a reactive distillation. A condenser 3 is installed at the top of distillation column 2 to collect uncondensed gas and condensate from the top of distillation column 2. The uncondensed gas enters a tail gas collector 4, and the resulting tail gas is discharged. The resulting recondensate and the condensate collected from the top of distillation column 2 are collected together in a transfer tank 5. The outlet of transfer tank 5 is connected to the lower inlet of extraction column 7 via a feed pump 6. Tap water is added through the upper inlet of extraction column 7, allowing the tap water to extract the material in transfer tank 5. The material collected from the top of extraction column 7 is the finished product propylene ethyl ether (propylene ethyl ether content ≥ 98.0 wt%, ethanol content < 1.0 wt%), which is stored in the finished product receiving tank 8. The material collected from the bottom of extraction column 7 is an ethanol solution. Specifically, the method for preparing propylene ethyl ether by liquid-phase cracking of propionaldehyde diethanol includes the following steps:

[0037] (1) A measured amount of propionaldehyde diethanol and catalyst are added to the reactor, stirring is started, and then low-pressure steam is used to heat the reactor through the jacket to 100~105℃. When the temperature reaches above 100℃, the liquid phase cracking reaction begins; wherein, the mass ratio of propionaldehyde diethanol to catalyst is 1:(0.003~0.01); the catalyst is an organic acid catalyst, which includes a main component and an auxiliary agent; the main component includes p-toluenesulfonic acid and / or methanesulfonic acid; the auxiliary agent includes diisooctylamine; the mass ratio of the main component to the auxiliary agent in the organic acid catalyst is 10:(3~8);

[0038] (2) The cracking products enter the distillation column in gaseous form. The circulating water at the top of the distillation column is turned on to control the top temperature. The temperature is controlled at 70~75℃ for distillation. Uncondensed gas and condensate are collected from the top of the distillation column. The uncondensed gas passes through the tail gas trap and is discharged. The recondensate and the condensate collected from the top of the column are collected in the transfer tank. The distillation column is a packed column with a theoretical number of plates ≥30. The cracking products enter from below the bottom plate in gaseous form. The condensate at the top of the distillation column is collected from the top plate.

[0039] (3) Turn on the feed pump and pump the material in the transfer tank into the extraction tower that has been filled with water (tap water) to the designated liquid level at a certain flow rate. At the same time, turn on the water inlet valve of the extraction tower and control the water flow rate. The flow rate ratio of material to water is 1:(0.5~2.0). The extraction tower is a packed tower with a theoretical number of trays ≥20. The extraction tower is numbered from top to bottom as tray 1, tray 2, ... Tap water is injected from tray 1 through the distributor. The material in the transfer tank is injected from the bottom of the last tray through the distributor. The material collected from the top of the extraction tower is the finished product propylene ethyl ether (propylene ethyl ether content ≥98.0wt%, ethanol content <1.0wt%). The material collected from the bottom of the extraction tower is an ethanol solution.

[0040] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0041] Example 1

[0042] This embodiment provides a method for preparing high-purity propylene diethyl ether by liquid-phase pyrolysis of propionaldehyde diethanol, including the following steps:

[0043] (1) Using an organic acid catalyst composed of p-toluenesulfonic acid (main component) and diisooctylamine (auxiliary agent) in a mass ratio of 2:1 as the catalyst, the mass ratio of propionaldehyde diethanolate to catalyst is 1:0.003, 1:0.005, 1:0.007, and 1:0.009, respectively. That is, the mass ratio of catalyst to propionaldehyde diethanolate is 0.3%, 0.5%, 0.7%, and 0.9%. A certain amount of 98% pure propionaldehyde diethanolate and a certain amount of catalyst are added to the reactor, stirring is started, the jacket steam valve is opened, and low-pressure steam is used to heat the reactor through the jacket. The temperature is slowly raised to 100°C. At the same time, the inlet and outlet valves of the circulating water at the top of the distillation column are opened to start the liquid phase cracking reaction.

[0044] (2) The cracking products enter the distillation column in gaseous form from the reactor. The circulating water at the top of the distillation column is turned on to control the top temperature, which is controlled at 70~75℃, and distillation is carried out. The jacket steam valve is adjusted to maintain the temperature inside the reactor at no less than 100℃. After the product is discharged from the top of the distillation column, the circulating water inlet valve of the condenser at the top of the column is adjusted to maintain the top temperature at 70~75℃. At the same time, the inlet and outlet valves of the trapping condenser are opened. Uncondensed gas and condensate are collected from the top of the distillation column. The uncondensed gas is discharged after passing through the tail gas trap, and the recondensate and the condensate collected from the top of the column are collected together in the transfer tank. The distillation column is a packed column with a theoretical number of 30 plates. The cracking products enter from below the bottom plate in gaseous form, and the condensate at the top of the distillation column is collected from the top plate.

[0045] (3) Start the feed pump and pump the material in the transfer tank into the extraction tower that has been filled with water (tap water) to the designated liquid level (60%) at a certain flow rate. At the same time, open the water inlet valve of the extraction tower and control the water flow rate. The flow ratio of material to water is 1:1.0. The extraction tower is a packed tower with a theoretical number of 23 plates. The extraction tower is numbered from top to bottom as 1 plate, 2 plate, ... Tap water is injected from the 1 plate through the distributor. The material in the transfer tank is injected from the bottom of the last plate (23 plates) through the distributor. The material overflowing from the top of the extraction tower is the finished product propylene ether. The material collected from the bottom of the extraction tower is an ethanol solution. During this period, the liquid level at the interface of the extraction tower is controlled at the designated position through the collection valve.

[0046] (4) When the temperature of the reactor exceeds 140°C, close the steam valve. After the top of the distillation column stops discharging, turn on the jacket cooling water to cool the reactor, and then drain the high-boiling point.

[0047] The amount of catalyst added was adjusted, and different batches of finished propylene ethyl ether were collected and analyzed by gas chromatography. The results are shown in Table 1.

[0048] Table 1

[0049]

[0050] As shown in Table 1, as the amount of catalyst added gradually increases, the reaction activity increases significantly and the yield also increases. However, the impurities also gradually increase, resulting in a decrease in the content of propylene ethyl ether in the product.

[0051] Example 2

[0052] This embodiment provides a method for preparing high-purity propylene diethyl ether by liquid-phase pyrolysis of propionaldehyde diethanol. Compared with Example 1, the only difference is that the mass ratio of propionaldehyde diethanol to catalyst is fixed at 1:0.005, that is, the mass proportion of catalyst relative to propionaldehyde diethanol is 0.5%, and the number of trays (30) of the distillation column is adjusted to 40, 50, and 60 respectively. Different batches of finished propylene diethyl ether were collected and analyzed by gas chromatography. The analysis results are shown in Table 2.

[0053] Table 2

[0054]

[0055] As shown in Table 2, the separation efficiency of propylene ethyl ether and impurities improves significantly with the increase of the number of trays in the distillation column, resulting in an increase in product content. However, this also reduces the rate of propylene ethyl ether extraction, causing some product to be converted into high-boiling impurities, thus reducing the yield.

[0056] Example 3

[0057] This embodiment provides a method for preparing high-purity propylene diethyl ether by liquid-phase pyrolysis of propionaldehyde diethanol. Compared with Example 1, the only difference is that the mass ratio of propionaldehyde diethanol to catalyst is fixed at 1:0.005, that is, the mass proportion of catalyst relative to propionaldehyde diethanol is 0.5%. The ratio of feed and water flow rates corresponding to the extraction tower (1:1.0) is adjusted to 1:0.5, 1:1.5, and 1:2.0, respectively. Different batches of finished propylene diethyl ether were collected and analyzed by gas chromatography. The analysis results are shown in Table 3.

[0058] Table 3

[0059]

[0060] As shown in Table 3, during the extraction process in the extraction tower, the ethanol removal efficiency increases significantly with the increase of water consumption, and the product content increases; however, the product entrained in the water also gradually increases, leading to a decrease in product yield and an increase in wastewater volume.

[0061] Comparative Example 1

[0062] This comparative example provides a method for preparing propylene diethyl ether by liquid-phase cracking of propionaldehyde diethanol. The only difference from Example 1 is that the gaseous product taken from the top of the reactor is directly condensed, and the resulting condensate is directly fed into the extraction tower for extraction, without further distillation in the distillation tower.

[0063] The amount of catalyst added was adjusted, and different batches of finished propylene ethyl ether were collected and analyzed by gas chromatography. The results are shown in Table 4.

[0064] Table 4

[0065]

[0066] Comparing Table 1 and Table 4, it can be seen that without separation in the distillation column, the gaseous material will contain propionaldehyde diethanol, causing the raw material to enter the subsequent extraction stage. In the extraction stage, some of the acetal dissolves in water and is lost, while the rest dissolves in propylene ether, resulting in a decrease in product content and a significant reduction in yield.

[0067] In summary, the method of the present invention includes sequential liquid-phase pyrolysis reaction, distillation, and extraction, achieving low-cost and high-efficiency preparation of high-purity propylene ethyl ether. The finished propylene ethyl ether has a propylene ethyl ether content ≥98.0 wt% and an ethanol content <1.0 wt%, and the quality of the finished propylene ethyl ether is higher than that of propylene ethyl ether produced by the Rapa process.

[0068] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0069] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0070] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0071] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing propylene diethyl ether by liquid-phase pyrolysis of propionaldehyde diethanol, characterized in that, The method for preparing propenyl diethyl ether by liquid-phase pyrolysis of propionaldehyde diethanol comprises the following steps: (1) Add propionaldehyde diethanol and catalyst into the reactor to carry out liquid-phase pyrolysis reaction; (2) The gas-phase reaction system from the top of the reactor enters the distillation column with a condenser at the top for distillation. Uncondensed gas and condensate are collected from the top of the distillation column. (3) Extract water and the condensate to obtain the finished product propylene ether and ethanol solution.

2. The method for preparing propylene diethyl ether by liquid-phase pyrolysis of propionaldehyde diethanol according to claim 1, characterized in that, In step (1), the temperature of the liquid phase pyrolysis reaction is 100~140℃.

3. The method for preparing propylene diethyl ether by liquid-phase pyrolysis of propionaldehyde diethanol according to claim 1, characterized in that, In step (1), the catalyst is an organic acid catalyst, which includes a main component and an auxiliary agent.

4. The method for preparing propylene diethyl ether by liquid-phase pyrolysis of propionaldehyde diethanol according to claim 3, characterized in that, The main component includes p-toluenesulfonic acid and / or methanesulfonic acid; the auxiliary agent includes diisooctylamine; the mass ratio of the main component to the auxiliary agent in the organic acid catalyst is 10:(3~8).

5. The method for preparing propylene diethyl ether by liquid-phase pyrolysis of propionaldehyde diethanol according to claim 1, characterized in that, In step (1), the mass ratio of propionaldehyde diethanol condensation to catalyst is 1:(0.003~0.01).

6. The method for preparing propylene diethyl ether by liquid-phase pyrolysis of propionaldehyde diethanol according to claim 1, characterized in that, In step (2), the top temperature of the distillation column is controlled to be 70~75℃.

7. The method for preparing propylene diethyl ether by liquid-phase pyrolysis of propionaldehyde diethanol according to claim 1, characterized in that, In step (2), the distillation column is a packed column with a theoretical plate number ≥30.

8. The method for preparing propylene diethyl ether by liquid-phase pyrolysis of propionaldehyde diethanol according to claim 1, characterized in that, In step (3), the extraction is carried out in an extraction tower, which is a packed tower with a theoretical plate number ≥20.

9. The method for preparing propylene diethyl ether by liquid-phase pyrolysis of propionaldehyde diethanol according to claim 1, characterized in that, In step (3) of the extraction, the flow rate ratio of condensate to water is 1:(0.5~2.0).

10. The method for preparing propylene diethyl ether by liquid-phase pyrolysis of propionaldehyde diethanol according to claim 1, characterized in that, In step (3), the content of the propylene ethyl ether in the finished product is ≥98.0wt% and the content of ethanol is <1.0wt%.

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