A process for the preparation of ethylene glycol monobutyl ether

Abstract

The application provides a preparation method of ethylene glycol monobutyl ether, comprising preparing the ethylene glycol monobutyl ether by a double-effect rectification process. The preparation method of the ethylene glycol monobutyl ether in an embodiment of the application effectively reduces energy consumption, is safe and reliable in process, simple and easy to operate, and easy to implement.

Description

Technical Field

[0001] This invention relates to ethylene glycol monobutyl ether, specifically a method for preparing ethylene glycol monobutyl ether. Background Technology

[0002] Ethylene glycol monobutyl ether (EDGME) is an important derivative of ethylene oxide and a high-performance, environmentally friendly solvent widely used in industries such as inks, coatings, leather, and brake fluids. Industrially, EEGME is mainly synthesized from ethylene oxide and n-butanol via an ethoxylation reaction under the action of a catalyst. Taking the reaction of an alcohol (represented by ROH) and ethylene oxide (EO) as an example, the ethoxylation reaction can be represented as follows:

[0003] ROH + EO → RO(EO)1H

[0004] RO(EO)1H + EO → RO(EO)2H

[0005] RO(EO)₂H + EO → RO(EO)₃H

[0006] ······

[0007] ROH + nEO → RO(EO) n H

[0008] The three key characteristics of the above ethoxylation reaction are: (1) It has the characteristics of irreversible and parallel series reaction. The reaction will generate a series of ethoxylated homologues. However, from the perspective of the use of the reaction products, the target products needed in industry are often only the low addition products, while other high addition products become useless by-products. Therefore, how to improve the selectivity of the target product has become an important aspect of various process considerations. (2) The ring-opening addition reaction of ethylene oxide is strongly exothermic. The heat released by each mole of ethylene oxide ring opening is about 100kJ. How to effectively utilize the heat of reaction is also an important indicator of the advancement of the process and technology. (3) The reactant ethylene oxide is chemically very active and flammable and explosive. The design of any ethoxylation device must take into account its safety issues and achieve inherent safety.

[0009] Reactive distillation is a new chemical process intensification technology developed in the 1980s. This technology couples the two most critical processes in chemical engineering, reaction and separation, into the same equipment unit, becoming a representative technology for innovating traditional unit operations. For irreversible, parallel, and continuous reaction systems, coupling the reaction and product separation in a reactive distillation column allows for the timely removal of the high-boiling-point target product from the reaction zone through distillation, thereby improving the selectivity of low-boiling-point ethoxylated products. An Weizhong et al. reported a simulation study on the synthesis of ethylene glycol monobutyl ether by reactive distillation [Modern Chemical Industry, November 2007, Vol. 27, Supplement (2)]. This paper introduces the principle and simulation results of the synthesis of ethylene glycol monobutyl ether by reactive distillation column, but does not consider the utilization of reaction heat and the problem of system heat integration.

[0010] Theoretically, the reactive distillation process for synthesizing ethylene glycol monobutyl ether has energy-saving potential. On one hand, the ethoxylation reaction of ethylene oxide ring-opening is a strongly exothermic reaction. The heat of reaction is removed from the top of the column in the form of liquid vaporization. This results in the load on the top condenser being greater than the load on the bottom reboiler; that is, in terms of heat quantity, the heat carried by the vapor phase at the top of the column is greater than the heat required by the bottom reboiler. For this characteristic, industrial processes often use heat pump distillation technology to recover the condensation heat of the vapor phase at the top of the column. However, using traditional heat pump distillation technology faces a safety limitation. As is well known, ethylene oxide is a highly hazardous chemical, flammable and explosive. Engineering designs explicitly specify that the concentration of ethylene oxide in the compressor must be below 2000 ppm. Considering factors such as reactant deactivation or operational instability, it is highly likely that vapor phase material containing ethylene oxide will directly enter the compressor, which will be a constraint and hidden danger to the safety of the unit, significantly limiting the application of heat pump distillation technology in ethoxylation reactive distillation units. Summary of the Invention

[0011] A primary objective of this invention is to provide a method for preparing ethylene glycol monobutyl ether, comprising preparing the ethylene glycol monobutyl ether by a double-effect distillation process.

[0012] According to one embodiment of the present invention, the method includes preparing the ethylene glycol monobutyl ether through a first distillation column and a second distillation column, wherein the pressure in the first distillation column is lower than that in the second distillation column.

[0013] According to one embodiment of the present invention, the method includes using the top distillate of the second distillation column as a heat source for the first distillation column.

[0014] According to one embodiment of the present invention, the pressure of the first reactive distillation column is 0.1 to 0.2 MPa, and the pressure of the second reactive distillation column is 0.4 to 0.6 MPa.

[0015] According to one embodiment of the present invention, the ethylene glycol monobutyl ether is prepared using n-butanol and ethylene oxide as raw materials, wherein the feed molar flow ratio of n-butanol and ethylene oxide in the second reactive distillation column is lower than that in the first reactive distillation column.

[0016] According to one embodiment of the present invention, the reboiling ratio of the second reactive distillation column is greater than that of the first reactive distillation column.

[0017] According to one embodiment of the present invention, the reboiling ratio of the first reactive distillation column is 7 to 10, and the reboiling ratio of the second reactive distillation column is 11 to 15.

[0018] According to one embodiment of the present invention, the first reactive distillation column includes a column body, a first reboiler disposed at the bottom of the column body, and a first condenser disposed at the top of the column body; the first condenser and the top of the column body form a first reflux path; the first reboiler and the bottom of the column body form a second reflux path.

[0019] According to one embodiment of the present invention, the second reactive distillation column includes a column body, a second reboiler disposed at the bottom end of the column body, and a second condenser disposed at the top end of the column body; a third reflux path is formed between the second condenser, the first reboiler, and the column body of the second reactive distillation column.

[0020] According to one embodiment of the present invention, the first reboiler includes a shell and a heat exchange chamber disposed outside the shell. The first reboiler forms a second reflux path with the bottom of the first reactive distillation column through the shell, and the first reboiler forms a third reflux path with the second condenser and the top of the second reactive distillation column through the heat exchange chamber.

[0021] The method for preparing ethylene glycol monobutyl ether according to one embodiment of the present invention effectively reduces energy consumption, is safe and reliable, simple to operate, and easy to implement. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of an apparatus for preparing ethylene glycol monobutyl ether according to one embodiment of the present invention. Detailed Implementation

[0023] Typical embodiments embodying the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various variations in different embodiments without departing from the scope of the present invention, and the descriptions and illustrations herein are for illustrative purposes only and not intended to limit the present invention.

[0024] One embodiment of the present invention provides a method for preparing ethylene glycol monobutyl ether, comprising using double-effect distillation technology in a reactive distillation system for preparing ethylene glycol monobutyl ether.

[0025] One embodiment of the present invention utilizes a double-effect reactive distillation process to achieve thermal integration between the high-pressure tower condenser and the low-pressure tower reboiler, effectively reducing the consumption of system utilities.

[0026] In one embodiment, ethylene glycol monobutyl ether is synthesized by using two reactive distillation columns with different operating parameters, one of which is a low-pressure reactive distillation column (first distillation column) and the other is a high-pressure reactive distillation column (second distillation column). The top vapor stream of the high-pressure column is used as the heat source for the reboiler of the low-pressure column, and the two columns are thermally integrated.

[0027] In one embodiment, the raw materials for synthesizing ethylene glycol monobutyl ether can be ethylene oxide and n-butanol.

[0028] The present invention does not particularly limit the catalyst for the ethoxylation reaction of ethylene oxide and n-butanol. It can be a solid heterogeneous catalyst that fixes the catalyst in a reactive distillation column, or a homogeneous catalyst that makes the catalyst flow, such as sodium n-butoxide, triethylamine, etc.

[0029] like Figure 1 As shown, the apparatus for preparing ethylene glycol monobutyl ether according to one embodiment of the present invention includes a first reactive distillation column 10 and a second reactive distillation column 20.

[0030] In one embodiment, the first reactive distillation column 10 includes a column body, a first reboiler 11 disposed at the bottom of the column body, and a first condenser 12 disposed at the top of the column body. A n-butanol inlet and an ethylene oxide inlet are respectively provided on the side wall of the column body.

[0031] In one embodiment, the first condenser 12 is connected to the top of the tower body and the side wall adjacent to the top, thereby forming a first reflux path at the top of the tower body.

[0032] In one embodiment, the first reboiler 11 is connected to the bottom of the column and the side wall adjacent to the bottom, thereby forming a second reflux path at the bottom of the column.

[0033] In one embodiment, the n-butanol inlet of the first reactive distillation column 10 is located at the top of the column, adjacent to the top of the column; the ethylene oxide inlet is located in the middle of the column, between the top and bottom of the column.

[0034] In one embodiment, the second reactive distillation column 20 includes a column body, a second reboiler 21 disposed at the bottom of the column body, and a second condenser 22 disposed at the top of the column body. A n-butanol inlet and an ethylene oxide inlet are respectively provided on the side wall of the column body.

[0035] In one embodiment, a third reflux path is formed between the second condenser 22, the first reboiler 11, and the column body of the second reactive distillation column 20, so that the top gaseous stream of the second reactive distillation column 20 serves as the heat source for the first reboiler 11 of the first reactive distillation column 10.

[0036] In one embodiment, the second condenser 22 is connected to the sidewalls of the first reboiler 11 and the second reactive distillation column 20 near the top of the column, and the first reboiler 11 is connected to the top of the second condenser 22 and the second reactive distillation column 20.

[0037] In one embodiment, the first reboiler 11 includes a shell and a heat exchange chamber disposed outside the shell. The shell is used for the flow of reactants, and the heat exchange chamber heats the shell through a heat medium to raise the temperature of the material therein. The first reboiler 11 is connected to the bottom of the first reactive distillation column 10 and the side wall adjacent to the bottom through the shell to form a second reflux path, and is connected to the second condenser 22 and the top of the second reactive distillation column 20 through the heat exchange chamber to form a third reflux path.

[0038] In one embodiment, the n-butanol inlet of the second reactive distillation column 20 is located at the top of the column, adjacent to the top of the column; the ethylene oxide inlet is located in the middle of the column, between the top and bottom of the column.

[0039] In one embodiment, the second reboiler 21 is connected to the bottom of the column and the side wall adjacent to the bottom, thereby forming a fourth reflux path at the bottom of the column.

[0040] In one embodiment, the apparatus for preparing ethylene glycol monobutyl ether includes a n-butanol feed line and an ethylene oxide feed line.

[0041] In one embodiment, the n-butanol feed line includes a feed line 101, a feed line 102, and a feed line 103 connected together. A feed splitter 13 is provided on the n-butanol feed line to split the flow. The feed line 101 is connected to the feed splitter 13, and the n-butanol feedstock enters the n-butanol feed line through the feed line 101. The feed line 102 is connected to the feed splitter 13 and the n-butanol inlet of the first reactive distillation column 10, respectively. The feed line 103 is connected to the feed splitter 13 and the n-butanol inlet of the second reactive distillation column 20, respectively.

[0042] In one embodiment, the ethylene oxide feed line includes a feed line 201, a feed line 202, and a feed line 203 connected together. A feed splitter 23 is provided on the ethylene oxide feed line to split the flow. The feed line 201 is connected to the feed splitter 23, and the ethylene oxide feedstock enters the ethylene oxide feed line through the feed line 201. The feed line 202 is connected to the feed splitter 23 and the ethylene oxide inlet of the first reactive distillation column 10, respectively. The feed line 203 is connected to the feed splitter 23 and the ethylene oxide inlet of the second reactive distillation column 20, respectively.

[0043] In one embodiment, a product mixer 30 is provided outside the first reactive distillation column 10 and the second reactive distillation column 20.

[0044] In one embodiment, the bottom end of the first reactive distillation column 10 is connected to the product mixer 30 via the discharge pipe 31, and the bottom end of the second reactive distillation column 20 is connected to the product mixer 30 via the discharge pipe 32.

[0045] In one embodiment, during operation, the raw material n-butanol enters the n-butanol feed line from the feed line 101, and after passing through the feed splitter 13, it is divided into two streams. One stream enters the first reactive distillation column 10 through the feed line 102, and the other stream enters the second reactive distillation column 20 through the feed line 103. Similarly, the raw material ethylene oxide enters the ethylene oxide feed line from the feed line 201, and after passing through the feed splitter 23, it is divided into two streams. One stream enters the first reactive distillation column 10 through the feed line 202, and the other stream enters the second reactive distillation column 20 through the feed line 203.

[0046] The raw materials n-butanol and ethylene oxide react in the first reactive distillation column 10 and the second reactive distillation column 20. The resulting products are discharged from the bottom of the two columns through the discharge pipes 31 and 32, respectively, and then enter the product mixer 30 for mixing. After that, the product is discharged from the product mixer 30 and enters the downstream separation unit for separation and purification. During the reaction process, the high-temperature gaseous material discharged from the top of the second reactive distillation column 20 enters the heat exchange chamber of the first reboiler 11 through the third reflux path, and is used as the heat source of the first reboiler 11 to save the amount of heat medium used.

[0047] In one embodiment, in order to achieve thermal integration and greater energy saving, the key design of the first reactive distillation column 10 and the second reactive distillation column 20 is as follows: the temperature of the vapor stream at the top of the high-pressure column 20 is more than 10°C higher than the liquid phase temperature at the bottom of the low-pressure column 10, and the condenser load of the high-pressure column is greater than the reboiler load of the low-pressure column. For example, the temperature difference between the vapor stream at the top of the second reactive distillation column 20 and the liquid phase at the bottom of the first reactive distillation column 10 can be 22.5°C, 22.7°C, etc.

[0048] In one embodiment, the temperature difference between the gaseous stream at the top of the second reactive distillation column 20 and the liquid phase at the bottom of the first reactive distillation column 10 can be adjusted by controlling the pressure inside the first reactive distillation column 10 and the second reactive distillation column 20 during the preparation process.

[0049] In one embodiment, the pressure inside the first reactive distillation column 10 is 0.1–0.2 MPa, for example, atmospheric pressure, 0.11 MPa, 0.12 MPa, 0.13 MPa, 0.15 MPa, 0.17 MPa, 0.18 MPa, 0.19 MPa, etc.; the pressure inside the second reactive distillation column 20 is 0.4–0.6 MPa, for example, 0.4 MPa, 0.45 MPa, 0.5 MPa, 0.55 MPa, 0.58 MPa, etc. When selecting the operating pressure within the above pressure range, the temperature of the vapor phase material at the top of the second reactive distillation column 20 should be higher than the temperature of the product at the bottom of the first reactive distillation column 10, and the temperature difference between the two should meet the minimum industrial heat transfer temperature difference.

[0050] In one embodiment, the feed molar flow rate ratio of n-butanol to ethylene oxide in the first reactive distillation column 10 is (1.0 to 2.0):1, for example, 1.1:1, 1.2:1, 1.4:1, 1.5:1, 1.8:1, 1.9:1, etc. The feed molar flow rate ratio of n-butanol to ethylene oxide in the second reactive distillation column 20 is lower than that in the first reactive distillation column 10. The feed molar flow rate ratio of n-butanol to ethylene oxide in the second reactive distillation column 20 can be (1 to 1.4):1, for example, 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1.

[0051] In one embodiment, the reboiling ratio of the first reactive distillation column 10 is 7 to 10, such as 8 or 9, and the reboiling ratio of the second reactive distillation column 20 is greater than that of the first reactive distillation column 10. The reboiling ratio of the second reactive distillation column 20 can be 11 to 15, such as 12, 13 or 14.

[0052] In this invention, the two reactive distillation columns have different operating parameters. The selectivity of ethylene glycol monobutyl ether, the conversion rate of n-butanol, and the flow rate and composition of the bottom products of the two columns are also different. The technical indicators referred to, such as the selectivity of the target product, are calculated based on the product composition after mixing the bottom products of the two columns.

[0053] The method for preparing ethylene glycol monobutyl ether according to one embodiment of the present invention uses ethylene oxide and n-butanol as raw materials. The ethoxylation reaction for synthesizing ethylene glycol monobutyl ether is carried out in two reactive distillation columns with different operating parameters. One is a low-pressure reactive distillation column and the other is a high-pressure reactive distillation column. The top vapor stream of the high-pressure column is used as the heat source for the reboiler of the low-pressure column, and the two columns are thermally integrated.

[0054] The method for preparing ethylene glycol monobutyl ether according to one embodiment of the present invention overcomes the difficulties in energy saving in the reactive distillation synthesis of ethylene glycol monobutyl ether, especially the limitations of heat pump distillation and inter-tower heat integration.

[0055] One embodiment of the present invention synthesizes ethylene glycol monobutyl ether by reactive distillation, which utilizes the process enhancement method of reactive distillation to reduce the occurrence of side reactions and achieve high selectivity of the target product.

[0056] The method for preparing ethylene glycol monobutyl ether according to one embodiment of the present invention can reduce the amount of cooling utilities by more than 40% and the amount of heating medium by about 50%, showing significant energy-saving advantages.

[0057] The method for preparing ethylene glycol monobutyl ether according to one embodiment of the present invention does not involve the compression of ethylene oxide, eliminates the safety hazards associated with traditional heat pump distillation technology, and is safe, reliable, simple to operate, and easy to implement.

[0058] The preparation method of ethylene glycol monobutyl ether according to an embodiment of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. All raw materials used are commercially available.

[0059] Example 1

[0060] Used Figure 1 The equipment parameters of the first reactive distillation column 10 and the second reactive distillation column 20 are the same: the number of trays of the first reactive distillation column 10 and the second reactive distillation column 20 is 17 (from top to bottom, excluding the condenser and reboiler), wherein the n-butanol inlet is set on the first tray and the ethylene oxide inlet is set on the twelfth tray.

[0061] The catalyst used is triethylamine, which is dissolved in n-butanol and enters the reactive distillation column together with the n-butanol.

[0062] The feedstocks, n-butanol and ethylene oxide, enter the splitter through their respective feed lines and are then delivered in two separate streams to two reactive distillation columns. The total flow rate of n-butanol is 2.97 kmol / h, and the total flow rate of ethylene oxide is 2.27 kmol / h, with a total feed alcohol-to-alkane ratio of 1.3. The split ratio of ethylene oxide entering the first reactive distillation column 10 and the second reactive distillation column 20 is 0.55. The feed flow rates of n-butanol and ethylene oxide entering the first reactive distillation column 10 are 1.93 kmol / h and 1.25 kmol / h, respectively, with an alcohol-to-alkane ratio of 1.5. The feed flow rates of n-butanol and ethylene oxide entering the second reactive distillation column 20 are 1.04 kmol / h and 1.02 kmol / h, respectively, with an alcohol-to-alkane ratio of 1.0.

[0063] The ethoxylation reaction for the synthesis of ethylene glycol monobutyl ether is carried out in two reactive distillation columns with different operating pressures. The operating pressure of the second reactive distillation column 20 is 0.4 MPa, and the operating pressure of the first reactive distillation column 10 is 0.1 MPa. Under these conditions, the temperature of the gaseous material at the top of the second reactive distillation column 20 is 161.9 °C, and the temperature of the product at the bottom of the first reactive distillation column 10 is 139.4 °C. The temperature difference between the two temperatures is 22.5 °C, which meets the heat transfer temperature difference requirements of thermal integration.

[0064] The overhead materials of both the first reactive distillation column 10 and the second reactive distillation column 20 operate in total reflux mode, with no product collected. The bottom products of both columns are discharged through outlet pipes 31 and 32, mixed in product mixer 30, and then discharged again to the downstream separation unit for separation and purification. The unit operates continuously. Samples are taken from the product discharged from product mixer 30, cooled, and their composition is analyzed by chromatography.

[0065] The operating parameters of the first reactive distillation column 10 and the second reactive distillation column 20 are listed in Table 1. The product analysis results, by mass percentage, are as follows: ethylene oxide not detected; n-butanol 21.9%; ethylene glycol monobutyl ether 71.2%; diethylene glycol monobutyl ether 6.2%; triethylene glycol monobutyl ether 0.7%; tetraethylene glycol monobutyl ether and ethoxylated products with higher addition numbers not detected. Calculations show that the ethylene oxide conversion rate is 99.96%, and the selectivity of ethylene glycol monobutyl ether for ethylene oxide is 83.36%.

[0066] Comparative Example 1

[0067] This example was conducted in a conventional single reactive distillation column, which has the same structure as the first reactive distillation column 10. The relevant equipment parameters and feed conditions are the same as in Example 1, but the operating conditions are different (operating pressure 0.2 MPa, reboiling ratio 9, liquid holdup 70 L), as detailed in Table 1.

[0068] The column operates under steady-state conditions, with n-butanol and ethylene oxide continuously fed as reactants. The bottom product is continuously collected from the bottom of the reactive distillation column, and its composition is basically the same as that of the dual-column process. The ethylene oxide conversion rate is 99.96%, and the selectivity of ethylene glycol monobutyl ether to ethylene oxide is 83.31%.

[0069] The data in Table 1 show that, compared with the conventional single catalytic distillation column of Comparative Example 1, the dual-effect (dual-tower) thermal integration process of Example 1 of the present invention can save 46.2% of the condenser load or cooling medium consumption and 51.3% of the reboiler load or heating medium consumption.

[0070] Table 1

[0071]

[0072] Example 2

[0073] The equipment parameters of the apparatus are the same as in Example 1. The total flow rate of n-butanol is 2.70 kmol / h, the total flow rate of ethylene oxide is 2.27 kmol / h, the total feed alcohol-to-alkane ratio is 1.2, the split ratio of ethylene oxide entering the first reactive distillation column 10 and the second reactive distillation column 20 is 0.5, the feed flow rates of n-butanol and ethylene oxide entering the first reactive distillation column 10 are 1.62 kmol / h and 1.135 kmol / h, respectively, and the alcohol-to-alkane ratio is 1.4, and the feed flow rates of n-butanol and ethylene oxide entering the second reactive distillation column 20 are 1.08 kmol / h and 1.135 kmol / h, respectively, and the alcohol-to-alkane ratio is 0.95.

[0074] The ethoxylation reaction for the synthesis of ethylene glycol monobutyl ether is carried out in two reactive distillation columns with different operating pressures. The operating pressure of the second reactive distillation column 20 is 0.4 MPa, and the operating pressure of the first reactive distillation column 10 is 0.1 MPa. Under these conditions, the temperature of the gaseous material at the top of the second reactive distillation column 20 is 162.1 °C, and the temperature of the product at the bottom of the first reactive distillation column 10 is 139.4 °C. The temperature difference between the two temperatures is 22.7 °C, which meets the heat transfer temperature difference requirements of thermal integration.

[0075] The overhead materials of both the first reactive distillation column 10 and the second reactive distillation column 20 are operated in total reflux mode, with no product collected. The bottom products of both columns are mixed in the product mixer 30 after passing through the discharge port and then enter the downstream separation unit for separation and purification. The unit operates continuously, and samples are taken from the products discharged from the total product outlet, cooled, and their composition is analyzed by chromatography.

[0076] The operating parameters of the first reactive distillation column 10 and the second reactive distillation column 20 are listed in Table 2. The product analysis results, by mass percentage, are as follows: ethylene oxide not detected; n-butanol 16.9%; ethylene glycol monobutyl ether 75.0%; diethylene glycol monobutyl ether 7.2%; triethylene glycol monobutyl ether 0.9%; tetraethylene glycol monobutyl ether and ethoxylated products with higher addition numbers not detected. Calculations show that the ethylene oxide conversion rate is 99.95%, and the selectivity of ethylene glycol monobutyl ether for ethylene oxide is 82.45%.

[0077] Comparative Example 2

[0078] The equipment parameters and feed conditions were the same as in Example 2, but the operating conditions were different (operating pressure 0.2 MPa, reboiling ratio 9, liquid holdup 50 L), as detailed in Table 2. The column operated under steady-state conditions, with continuous feed of the reactants n-butanol and ethylene oxide, and continuous product collection from the bottom of the reactive distillation column.

[0079] The data in Table 2 show that the composition of the bottom product of Comparative Example 2 is basically the same as that of Example 2, with an ethylene oxide conversion rate of 99.95% and a selectivity of ethylene glycol monobutyl ether for ethylene oxide of 82.47%. Compared with the conventional single reactive distillation column of Comparative Example 2, the double-effect (double-tower) thermal integration process of Example 2 of this invention can save condenser load by 44.6% and reboiler load by 49.9%.

[0080] Table 2

[0081]

[0082]

[0083] Unless otherwise specified, the terms used in this invention have the meanings commonly understood by those skilled in the art.

[0084] The embodiments described in this invention are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Those skilled in the art can make various other substitutions, changes and improvements within the scope of this invention. Therefore, this invention is not limited to the above embodiments, but is only defined by the claims.

Claims

1. A method for preparing ethylene glycol monobutyl ether, comprising preparing the ethylene glycol monobutyl ether by a double-effect distillation process; The preparation of the ethylene glycol monobutyl ether includes using a first distillation column and a second distillation column, wherein the pressure in the first distillation column is lower than that in the second distillation column; The first reactive distillation column includes a column body, a first reboiler disposed at the bottom of the column body, and a first condenser disposed at the top of the column body; the first condenser and the top of the column body form a first reflux path; the first reboiler and the bottom of the column body form a second reflux path; The second reactive distillation column includes a column body, a second reboiler disposed at the bottom of the column body, and a second condenser disposed at the top of the column body; a third reflux path is formed between the second condenser, the first reboiler, and the column body of the second reactive distillation column; The n-butanol inlet of the first reactive distillation column is located at the top of the column, adjacent to the top of the column; the ethylene oxide inlet is located in the middle of the column, between the top and bottom of the column. The n-butanol inlet of the second reactive distillation column is located at the top of the column, adjacent to the top of the column; the ethylene oxide inlet is located in the middle of the column, between the top and bottom of the column. The temperature of the vapor stream at the top of the second reactive distillation column is more than 10°C higher than the temperature of the liquid stream at the bottom of the first reactive distillation column. The resulting products are discharged from the bottom of the first and second reactive distillation columns through the discharge pipelines and then enter the product mixer for mixing. After that, the products are discharged from the product mixer and enter the downstream separation unit for separation and purification. The pressure of the first reactive distillation column is 0.1–0.2 MPa, the pressure of the second reactive distillation column is 0.4–0.6 MPa, the reboiling ratio of the first reactive distillation column is 7–10, and the reboiling ratio of the second reactive distillation column is 11–15.

2. The method according to claim 1, comprising using the top distillate of the second distillation column as a heat source for the first distillation column.

3. The method according to claim 1, wherein, The ethylene glycol monobutyl ether is prepared using n-butanol and ethylene oxide as raw materials, wherein the molar flow ratio of n-butanol to ethylene oxide in the second reactive distillation column is lower than that in the first reactive distillation column.

4. The method according to claim 1, wherein, The first reboiler includes a shell and a heat exchange chamber disposed outside the shell. The first reboiler forms a second reflux path with the bottom of the first reactive distillation column through the shell. The first reboiler forms a third reflux path with the second condenser and the top of the second reactive distillation column through the heat exchange chamber.

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