Method and equipment for synthesizing n-propyl acetate

Abstract

The invention discloses a method and equipment for synthesizing n-propyl acetate, a reaction-extractive distillation technology is adopted, reactive distillation and extractive distillation technologies are combined, efficient esterification reaction and high-purity separation of a target product are achieved, the technology is composed of a reactive extractive distillation tower and an extraction agent recovery tower, ethylene glycol is used as an extraction agent, and the extraction agent is recycled. Through the extraction effect of ethylene glycol on water, the removal efficiency of water is improved, the high purity of the product ester is ensured, meanwhile, ethylene glycol is recycled, the extraction agent consumption is reduced, efficient n-propyl acetate production is achieved, and economic and environment-friendly benefits are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of synthesizing n-propyl acetate, and particularly relates to a method and equipment for synthesizing n-propyl acetate. Background Art

[0002] N-propyl acetate is a widely used solvent with a fruity aroma. It is slightly soluble in water and miscible with organic solvents such as alcohols and ethers. It is mainly used as a flavoring agent, food flavor, solvent for nitrocellulose, and also in the gravure printing industry, especially for printing polyolefin and polyamide films. Due to its stable market demand, a green, environmentally friendly and sustainable n-propyl acetate industry, as well as production technologies with lower energy consumption and less waste emissions, will bring stronger competitiveness to the product.

[0003] In industrial production, the synthesis of n-propyl acetate mainly uses the esterification reaction of n-propanol and acetic acid. The traditional process generally adopts the aqueous phase reflux method, which has the following technical defects: First, to maintain the reaction kinetic balance between the esterification tower and the reactor, a large-flow material circulation system needs to be established, resulting in a significant increase in energy consumption; Second, due to the formation of a ternary azeotrope of n-propanol - water - n-propyl acetate in the reaction system, a decanter is set at the top of the esterification tower in the process design to improve the utilization rate of raw materials. Although this device can achieve the circulating rectification of the aqueous phase raw materials, it directly leads to two technical problems: One is that the heat load of the reboiler is significantly increased due to the continuous circulation of the azeotrope; The other is that the subsequent crude ester dehydration and purification process requires additional multi-stage separation equipment due to the need to handle the azeotrope, greatly increasing the equipment investment cost. In view of the above technical bottlenecks, the present study proposes a method and equipment for synthesizing n-propyl acetate. Summary of the Invention

[0004] The purpose of the present invention is: To solve the problems mentioned in the above background art, the present invention provides a method and equipment for synthesizing n-propyl acetate.

[0005] The present invention specifically adopts the following technical solutions to achieve the above purpose:

[0006] An apparatus for synthesizing n-propyl acetate, comprising: an extractant condenser, a first top condenser, a second top condenser, a reactive extractive distillation column, an extractant recovery column, a first reboiler at the bottom of the column and a second reboiler at the bottom of the column. Wherein, feed inlets are provided above and below the left side of the reactive extractive distillation column. The first top condenser is arranged above the reactive extractive distillation column, and the gas-phase outlet at the top of the reactive extractive distillation column is connected to the hot-end inlet of the first top condenser. The inlet of the first reboiler at the bottom of the column communicates with the reactive extractive distillation column, and the outlet of the first reboiler at the bottom of the column communicates with the inlet of the extractant recovery column. The outlet of the extractant recovery column communicates with the inlet of the second reboiler at the bottom of the column. The outlet of the second reboiler at the bottom of the column is connected to the reactive extractive distillation column through the extractant condenser. The second top condenser is arranged above the extractant recovery column, and the gas-phase outlet at the top of the extractant recovery column is connected to the hot-end inlet of the second top condenser.

[0007] Further, the total number of trays of the extractant recovery column is 17, and the feed position is the 8th tray.

[0008] Further, the reactive extractive distillation column uses reactive distillation technology for esterification reaction, and the reaction section is 13 - 31.

[0009] Further, the extractant in the reactive extractive distillation column is selected as ethylene glycol.

[0010] A method for synthesizing n-propyl acetate, comprising the following steps:

[0011] Step 1, feeding raw materials, injecting the raw materials through the feed inlet of the reactive extractive distillation column;

[0012] Step 2, reactive extractive distillation, the reactive extractive distillation column carries out esterification reaction through reactive distillation technology, and injects an extractant using ethylene glycol;

[0013] Step 3, condensing the top of the distillation column, condensing the top of the reactive extractive distillation column through the first top condenser;

[0014] Step 4, heating the bottom of the distillation column, heating the bottom of the reactive extractive distillation column through the first reboiler at the bottom of the column to maintain the separation efficiency in the column;

[0015] Step 5, recovery, the bottom stream of the reactive extractive distillation column is sent to the extractant recovery column for ethylene glycol recovery;

[0016] Step 6, condensing the top of the recovery column, condensing the top of the extractant recovery column through the second top condenser;

[0017] Step 7, heating the bottom of the recovery column, heating and purifying the bottom of the extractant recovery column through the second reboiler at the bottom of the column.

[0018] Step 8: The ethylene glycol is refluxed. The purified ethylene glycol is condensed by the extractant condenser, causing the ethylene glycol to cool down, and then it is refluxed to the reactive extractive distillation column together with the supplementary ethylene glycol for loss.

[0019] Further, the condensation parameter of the extractant condenser is 333.15K, and the load is -655.47kW to

[0020] -214.87kW.

[0021] Further, the condensation parameter of the first top condenser is 374.18K to 374.2K, and the load is -371.26kW to -128.58kW. The condensation parameter of the second top condenser is 372.66K to 372.67K, and the load is -431.4kW to -145.43kW.

[0022] Further, the input flow rate of the reactive extractive distillation column is 10.2 kmol / h to 30 kmol / h, the temperature condition is 298.15K, the reflux ratio is 0.3 to 0.33, and the bottom flow rate of the reactive extractive distillation column is 41.89 kmol / h to 126.67 kmol / h.

[0023] Further, the reaction section temperature of the reactive extractive distillation column is 377 to 395K, the reflux ratio is 0.3 to 0.33, the bottom temperature of the extractant recovery column is 470K, and the reflux ratio is 0.25 to 0.26.

[0024] Further, the parameters of the first reboiler are 414.32K to 415.12K, and the load is 232.72kW to 695.38kW. The parameters of the second reboiler are 469.95K, 687.77kW.

[0025] The beneficial effects of the present invention are as follows:

[0026] 1. The present invention adopts a reactive-extractive distillation process, combining reactive distillation and extractive distillation technologies, to achieve efficient esterification reaction and high-purity separation of the target product. This process consists of a reactive extractive distillation column and an extractant recovery column. Using ethylene glycol as the extractant, through the extraction of water by ethylene glycol, the water removal efficiency is improved, ensuring the high purity of the product ester. At the same time, ethylene glycol is recovered to reduce the consumption of the extractant, realizing the efficient production of n-propyl acetate and achieving economic and environmental benefits.

[0027] 2. The present invention integrates the reaction, extraction, and rectification processes in one system, shortening the process flow, reducing equipment investment and operating costs, and having good process integration. Through the selective action of the extractant, the relative volatility between the target product and by-products is enhanced, the separation efficiency is improved, and the selectivity is effectively increased. It reduces energy consumption and solvent usage, and reduces environmental pollution, having the functions of energy conservation and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is the process flow chart of the present invention;

[0029] Figure 2 is the working flow chart of the present invention;

[0030] Reference numerals: 1, extractant condenser; 2, first top condenser; 3, second top condenser; 4, reactive extraction distillation column; 5, extractant recovery column; 6, first reboiler at the bottom of the column; 7, second reboiler at the bottom of the column. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0032] Please refer to Figure 1 , the present invention provides a device for synthesizing n-propyl acetate, including: an extractant condenser 1, a first top condenser 2, a second top condenser 3, a reactive extraction distillation column 4, an extractant recovery column 5, a first reboiler at the bottom of the column 6, and a second reboiler at the bottom of the column 7. Among them, feed inlets are provided above and below the left side of the reactive extraction distillation column 4. The first top condenser 2 is arranged above the reactive extraction distillation column 4, and the gas-phase outlet at the top of the reactive extraction distillation column 4 is connected to the hot-end inlet of the first top condenser 2. The inlet of the first reboiler at the bottom of the column 6 communicates with the reactive extraction distillation column 4, and the outlet of the first reboiler at the bottom of the column 6 communicates with the inlet of the extractant recovery column 5. The outlet of the extractant recovery column 5 communicates with the inlet of the second reboiler at the bottom of the column 7. The outlet of the second reboiler at the bottom of the column 7 is connected to the reactive extraction distillation column 4 through the extractant condenser 1. The second top condenser 3 is arranged above the extractant recovery column 5, and the gas-phase outlet at the top of the extractant recovery column 5 is connected to the hot-end inlet of the second top condenser 3.

[0033] In this embodiment, preferably, the total number of trays of the extractant recovery column 5 is 17, and the feed position is the 8th tray.

[0034] In this embodiment, preferably, the reactive extraction distillation column 4 uses reactive distillation technology for esterification reaction, and the reaction section is 13 - 31.

[0035] In this embodiment, preferably, ethylene glycol is selected as the extractant in the reactive extractive distillation column 4.

[0036] Example 1

[0037] Please refer to Figure 2 , the present invention also provides a method for synthesizing n-propyl acetate, which includes the following steps:

[0038] Step 1, feeding raw materials: Acetic acid and n-propanol respectively enter the feed port of the reactive extractive distillation column 4 at a flow rate of 10.2 kmol / h under the condition of 298.15K, and the reflux ratio is 0.33;

[0039] Step 2, reactive extractive distillation: The reactive extractive distillation column 4 carries out an esterification reaction through reactive distillation technology: acetic acid + n-propanol → n-propyl acetate + water. Since the esterification reaction is reversible, in order to improve the yield of PrAC, water needs to be removed. An extractant of ethylene glycol is injected to enhance the separation of water and PrAC by changing the relative volatility of water, and a supplementary feed stream (0.061 kmol / h of ethylene glycol) is added to supplement the ethylene glycol lost in the system;

[0040] Step 3, condensing at the top of the distillation column: The top product mainly contains n-propyl acetate, trace amounts of n-propanol and ethylene glycol. The top of the reactive extractive distillation column 4 is condensed by the first top condenser 2 (the set parameters of the first top condenser 2 are 374.18K and the load is -128.58 kW);

[0041] Step 4, heating at the bottom of the distillation column: The bottom product mainly contains water, ethylene glycol and trace amounts of acetic acid. The bottom of the reactive extractive distillation column 4 is heated by the first reboiler 6 (the parameters of the first reboiler 6 are 414.32K and 232.72 kW) to maintain the separation efficiency in the column and ensure that ethylene glycol and water are enriched at the bottom;

[0042] Step 5, recovery: The bottom stream of the reactive extractive distillation column 4 (41.89 kmol / h, 0.756 ethylene glycol, 0.243 water) is sent to the extractant recovery column 5 for ethylene glycol recovery. The feed position is the 8th plate, the total number of plates is 17, and the reflux ratio is 0.25;

[0043] Step 6, condensing at the top of the recovery column: The top product mainly contains water, trace amounts of acetic acid and ethylene glycol. The top of the extractant recovery column 5 is condensed by the second top condenser 3 (the condensation parameters of the second top condenser 3 are 372.66K and -145.43 kW);

[0044] Step 7: Heat the bottom of the recovery column. The main component of the bottom product is ethylene glycol (purity 0.9999). The bottom of the extraction agent recovery column 5 is heated and purified by the second reboiler 7 (parameters of the second reboiler 7 are 469.95K, 687.77kW).

[0045] Step 8: Ethylene glycol reflux. The purified ethylene glycol is condensed by the extraction agent condenser 1 (parameters of the extraction agent condenser 1 are 333.15K, -214.87kW), causing the ethylene glycol to cool down, and then it refluxes to the reactive extraction distillation column 4 together with the replenished ethylene glycol to compensate for the loss.

[0046] Example 2

[0047] Please refer to Figure 2 , the present invention also provides a method for synthesizing n-propyl acetate, which includes the following steps:

[0048] Step 1: Feed raw materials. Acetic acid and n-propanol respectively enter the feed port of the reactive extraction distillation column 4 at a flow rate of 30 kmol / h under the condition of 298.15K, and the reflux ratio is 0.3.

[0049] Step 2: Reactive extraction distillation. The reactive extraction distillation column 4 conducts an esterification reaction through reactive distillation technology: acetic acid + n-propanol → n-propyl acetate + water. Since the esterification reaction is reversible, to improve the yield of PrAC, water needs to be removed. An extraction agent of ethylene glycol is injected to enhance the separation of water and PrAC by changing the relative volatility of water, and a supplementary feed stream (0.2 kmol / h of ethylene glycol) is added to compensate for the loss of ethylene glycol in the system.

[0050] Step 3: Condense the top of the distillation column. The top product mainly contains the product n-propyl acetate, trace amounts of n-propanol and ethylene glycol. The top of the reactive extraction distillation column 4 is condensed by the first top condenser 2 (parameters set for the first top condenser 2 are 374.2K, load -371.26kW).

[0051] Step 4: Heat the bottom of the distillation column. The bottom product mainly contains water, ethylene glycol and trace amounts of acetic acid. The bottom of the reactive extraction distillation column 4 is heated by the first reboiler 6 (parameters of the first reboiler 6 are 415.12K, 695.38kW) to maintain the separation efficiency inside the column and ensure that ethylene glycol and water are concentrated at the bottom.

[0052] Step 5: Recovery. The bottom stream (26.67 kmol / h, 0.763 ethylene glycol, 0.236 water) of the reactive extraction distillation column 4 is sent to the extraction agent recovery column 5 for ethylene glycol recovery. The feed position is the 8th plate, the total number of plates is 17, and the reflux ratio is 0.25.

[0053] Step 6, condensation at the top of the recovery column. The top products mainly include water, trace acetic acid, and ethylene glycol. The top of the extractant recovery column 5 is condensed by the second top condenser 3 (the condensation parameters of the second top condenser 3 are 372.67 K and -431.4 kW).

[0054] Step 7, heating at the bottom of the recovery column. The main component of the bottom product is ethylene glycol (purity 0.9999). The bottom of the extractant recovery column 5 is heated and purified by the second reboiler 7 (the parameters of the second reboiler 7 are 469.95 K and 687.77 kW).

[0055] Step 8, ethylene glycol reflux. The purified ethylene glycol is condensed by the extractant condenser 1 (the parameters of the extractant condenser 1 are 333.15 K and -655.47 kW), causing the ethylene glycol to cool down, and then it refluxes to the reactive extractive distillation column 4 together with the supplementary ethylene glycol to compensate for the loss.

[0056] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An apparatus for synthesizing n-propyl acetate, characterized in that, Including: An extractant condenser (1), a first top condenser (2), a second top condenser (3), a reactive extractive distillation column (4), an extractant recovery column (5), a first reboiler (6) and a second reboiler (7). Among them, feed inlets are provided above and below the left side of the reactive extractive distillation column (4). The first top condenser (2) is arranged above the reactive extractive distillation column (4), and the gas-phase outlet at the top of the reactive extractive distillation column (4) is connected to the hot-end inlet of the first top condenser (2). The inlet of the first reboiler (6) communicates with the reactive extractive distillation column (4), and the outlet of the first reboiler (6) communicates with the inlet of the extractant recovery column (5). The outlet of the extractant recovery column (5) communicates with the inlet of the second reboiler (7). The outlet of the second reboiler (7) is connected to the reactive extractive distillation column (4) through the extractant condenser (1). The second top condenser (3) is arranged above the extractant recovery column (5), and the gas-phase outlet at the top of the extractant recovery column (5) is connected to the hot-end inlet of the second top condenser (3).

2. The apparatus for synthesizing n-propyl acetate according to claim 1, wherein: The total number of trays of the extractant recovery column (5) is 17, and the feed position is the 8th tray.

3. An apparatus for synthesizing n-propyl acetate according to claim 1, characterized in that: The reactive extractive distillation column (4) uses reactive distillation technology for esterification reaction, and the reaction section is 13 - 31.

4. An apparatus for synthesizing n-propyl acetate according to claim 1, characterized in that: The extractant in the reactive extractive distillation column (4) is selected as ethylene glycol.

5. A method for synthesizing n-propyl acetate, characterized in that, Including the following steps: Step 1, feed raw materials, and inject the raw materials through the feed inlet of the reactive extractive distillation column (4); Step 2, reactive extractive distillation, the reactive extractive distillation column (4) performs esterification reaction through reactive distillation technology, and injects an extractant using ethylene glycol; Step 3, condense the top of the distillation column, and condense the top of the reactive extractive distillation column (4) through the first top condenser (2); Step 4, heat the bottom of the distillation column, and heat the bottom of the reactive extractive distillation column (4) through the first reboiler (6) to maintain the separation efficiency in the column; Step 5, recovery, the bottom stream of the reactive extractive distillation column (4) is sent to the extractant recovery column (5) for ethylene glycol recovery; Step 6, condense the top of the recovery column, and condense the top of the extractant recovery column (5) through the second top condenser (3); Step 7, heat the bottom of the recovery column, and heat and purify the bottom of the extractant recovery column (5) through the second reboiler (7); Step 8, ethylene glycol reflux, the purified ethylene glycol is condensed through the extractant condenser (1), so that the ethylene glycol cools down, and is refluxed to the reactive extractive distillation column (4) together with the supplemented ethylene glycol to make up for the loss.

6. A method for synthesizing n-propyl acetate according to claim 5, characterized in that: The condensation parameters of the extractant condenser (1) are 333.15K, and the load is -655.47 kW to -214.87 kW.

7. A method for synthesizing n-propyl acetate according to claim 5, characterized in that: The condensation parameters of the first top condenser (2) are 374.18K to 374.2K, and the load is -371.26kW to -128.58kW. The condensation parameters of the second top condenser (3) are 372.66K to 372.67K, and the load is -431.4kW to -145.43kW.

8. A method for synthesizing n-propyl acetate according to claim 5, characterized in that: The input flow rate of the reactive extractive distillation column (4) is 10.2 kmol / h to 30 kmol / h, the temperature condition is 298.15K, the reflux ratio is 0.3 to 0.33, and the bottom flow rate of the reactive extractive distillation column (4) is 41.89 kmol / h to 126.67 kmol / h.

9. A method for synthesizing n-propyl acetate according to claim 5, characterized in that: The reaction section temperature of the reactive extractive distillation column (4) is 377 to 395K, the reflux ratio is 0.3 to 0.33, the bottom temperature of the extractant recovery column (5) is 470K, and the reflux ratio is 0.25 to 0.

26.

10. A method for synthesizing n-propyl acetate according to claim 5, characterized in that: The parameters of the first bottom reboiler (6) are 414.32K to 415.12K, and the load is 232.72kW to 695.38kW. The parameters of the second bottom reboiler (7) are 469.95K, 687.77kW.

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