CN109761772B - Method and device for separating and refining polymethoxy dimethyl ether - Google Patents

Abstract

_The invention relates to a method and a device for separating and purifying polymethoxydimethyl ether. Multistage rectification is adopted, and supplementary water, formaldehyde The aqueous solution and trioxymethylene are extracted from the tower kettle to achieve the purpose of separating formaldehyde and trioxymethylene. After separation by this process, formaldehyde will not polymerize to block condensers and pipelines, improve the continuity of equipment use, and can effectively recover unreacted raw material formaldehyde, reaction by-products such as methyl formate and PODE ₂ .

Description

Method and device for separating and refining polymethoxydimethyl ether

technical field

The invention belongs to the technical field of chemical engineering, and relates to the technology of adopting multistage rectification to separate the synthesis product mixture of methanol and aqueous formaldehyde to synthesize polymethoxydimethyl ether, in particular to a method and device for separating and refining polymethoxydimethyl ether.

Background technique

Polymethoxy dimethyl ether is a new type of diesel fuel additive, the chemical formula is CH ₃ O(CH ₂ O)nCH ₃ (where n is greater than 1, generally less than 10), and has a relatively high oxygen content (42 %～51%) and cetane number (up to 76 on average), among them, PODE _3-5 is the most ideal diesel additive, adding PODE _3-5 to diesel can effectively reduce the soot and particulate matter (PM) emissions of diesel engines , Improve fuel economy. PODEn is a homologous component formed by acid-catalyzed polycondensation of raw materials providing etherate end groups and raw materials providing methoxy groups. Compounds that provide end groups include methanol, dimethyl ether, and methylal, and compounds that provide methoxy groups include formaldehyde, trioxymethylene, and paraformaldehyde.

Over the years, domestic and foreign research teams led by BASF have carried out a lot of research on the synthesis and separation process of PODEn. The main reports are the methylal and trioxymethylene routes of BASF (US 20070260094), Tsinghua University and Jade The methylal and paraformaldehyde route (CN104974025A) of the cooperation of Huang Chemical Industry Co., Ltd. but because its reaction raw materials are anhydrous trioxymethylene and paraformaldehyde, the reaction product is simple in composition, and its separation process cannot be applied to the synthesis product of methanol and formaldehyde solution. In addition, there is the reaction and separation process of methanol and formaldehyde solution of BASF company (US 2008207954, US20080221368, US 7671240, US 7700809), its single-pass conversion rate is low, the separation process is complicated, the material is repeatedly heated and separated, and the energy consumption is large, and the equipment is corroded Seriously, it greatly limits the industrialization of its technological process.

SUMMARY OF THE INVENTION

The synthetic process of preparing PODEn with methanol and formaldehyde aqueous solution as raw materials is divided into two steps. The first step is a reaction stage in which formaldehyde and methanol react to form methylal, and the second step is a reaction stage in which methylal and formaldehyde react with formaldehyde to form PODEn.

The object of the present invention is to provide a method for separating and purifying polymethoxydimethyl ether (PODEn) by introducing supplementary water in a rectifying tower whose feed is methanol, formaldehyde, water, trioxymethylene and PODE ₂ mixture. and device. The synthetic product of PODEn made from methanol and aqueous formaldehyde solution is separated by distillation, and PODEn suitable for diesel components is obtained by refining.

In the present invention, supplementary water is introduced into the rectification column whose feed is methanol, formaldehyde, water, trioxymethylene and PODE ₂ mixture, and the method and device for realizing the separation and purification of polymethoxydimethyl ether include six rectification columns. and a dehydration unit.

The technical scheme of the present invention is as follows:

A method for separating and purifying polymethoxydimethyl ether, which adopts multistage rectification, and introduces supplementary water, formaldehyde aqueous solution and triacetate into a rectifying tower whose feed is a mixture of methanol, formaldehyde, water, trioxymethylene and PODE ₂ . The polyoxymethylene is extracted from the tower kettle to achieve the purpose of separating formaldehyde and trioxymethylene.

Moreover, the added amount of the supplementary water is in a mass ratio of 0.3:1 to 1:1 in terms of weight to the feed.

Also, make-up water is added from the same feed port as the feed or separately from two feed ports.

A device for introducing supplementary water to separate PODE in a rectifying column whose feed is methanol, formaldehyde, water, trioxymethylene and _PODE The outlet is connected to the feed port of the second rectification tower through a pipeline, the top outlet of the second rectification tower is connected to the feed port of the fourth rectification tower through a pipeline, and the tower still outlet of the second rectification tower is connected to the third rectification tower through a pipeline. The feed port of the rectifying tower, the tower bottom discharge port of the fourth rectifying tower is connected to the feed port of the fifth rectifying tower, and the top discharge port of the fifth rectifying tower is connected to the feed port of the dehydration unit through a pipeline , the outlet of the dehydration unit is connected to the feed port of the sixth rectifying tower, and it is characterized in that: the supplementary water is introduced into the fifth rectifying tower, and the supplementary water is added from the feeding port of the fifth rectifying tower or added in the fifth rectifying tower. A make-up water inlet is set on the distillation column.

A method for introducing supplementary water to separate PODE in a rectifying column whose feed is methanol, formaldehyde, water, trioxymethylene and PODE ₂ mixture, the process is as follows: PODEn raw material enters the first rectifying column, and the first rectifying column tower top The material of methyl formate is extracted; the material of the first rectifying tower tower reactor enters the second rectifying tower, and the top of the second rectifying tower is extracted as methylal, methanol, water, formaldehyde, trioxymethylene and PODE ₂ The mixture material; the second rectifying tower tower still material enters the third rectifying tower, and the third rectifying tower top extraction is the material of PODE _3-5 , and the tower still is the material of PODE _6-10 ; the second rectifying tower The material at the top of the tower enters the fourth rectifying tower, and the material of methylal and methanol is extracted from the top of the fourth rectifying tower; the material in the bottom of the fourth rectifying tower enters the fifth rectifying tower, and the fifth rectifying tower Introduce supplementary water, and the fifth rectifying tower tower kettle extracts materials as formaldehyde aqueous solution and trioxymethylene; the fifth rectifying tower top material enters the dehydration unit, and the water is removed; the material after removing water enters the sixth rectifying tower. Distillation tower, the material from the top of the sixth rectifying tower is methanol, and the material from the tower bottom is PODE ₂ . The operating pressure of the first rectifying tower is 100-200KPa, the operating temperature of the tower top is 30-60 ℃, the operating pressure of the second rectifying tower is 80-120KPa, the operating temperature of the tower top is 70-100 ℃, the third rectifying tower The operating pressure of the tower is 1-50KPa, the operating temperature of the tower top is 50-150°C, the operating pressure of the fourth rectifying tower is 100-200KPa, the operating temperature of the tower top is 35-70°C, and the operation of the fifth rectifying tower The pressure is 80-120KPa, the operating temperature at the top of the tower is 70-120°C, the mass ratio of the supplementary water content to the material is 0.3:1 to 1:1 by weight, and the operating pressure of the sixth rectifying tower is 100-200KPa. The top operating temperature is 60-90°C.

A device for separating PODE by introducing supplementary water into a rectifying column with a mixture of methanol, formaldehyde, water, trioxymethylene and PODE ₂ as the feed, comprising six rectifying columns and a dehydration unit, and the top of the first rectifying column The outlet is connected to the feed port of the third rectification tower through a pipeline, the outlet of the tower reactor of the first rectification tower is connected to the feed port of the second rectification tower through a pipeline, and the top outlet of the third rectification tower is connected to the fourth rectification tower through a pipeline. The feed port of the rectifying tower, the tower still outlet of the third rectifying tower is connected to the feed port of the fifth rectifying tower through pipelines, and the top discharge port of the fifth rectifying tower is connected to the feed port of the dehydration unit, and the dehydration The discharge port of the unit is connected to the feed port of the sixth rectifying tower, and it is characterized in that: the supplementary water is introduced into the fifth rectifying tower, and the supplementary water is added from the feeding port of the fifth rectifying tower or added to the fifth rectifying tower. A make-up water inlet is set on the tower.

A method for introducing supplementary water to separate PODEn in a rectifying tower whose feed is methanol, formaldehyde, water, trioxane and PODE ₂ mixture, the process is as follows: PODEn raw material enters the first rectifying tower, and the first rectifying tower tower top The mixed material of methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE ₂ is extracted; the material of the first rectifying tower still enters the second rectifying tower, and the top of the second rectifying tower is collected. The material of PODE _3-5 and the tower still are the material of PODE _6-10 ; the material at the top of the first rectifying tower enters the third rectifying tower, and the top of the third rectifying tower is extracted as methyl formate, methyl formate The mixture material of aldehyde and methyl alcohol; The 3rd rectifying tower top material enters the 4th rectifying tower, and the 4th rectifying tower tower top extraction is the material of methyl formate, and the tower still is the mixture material of methylal and methanol; The material of the third rectifying tower tower kettle enters the fifth rectifying tower, and at the same time the fifth rectifying tower introduces supplementary water, and the fifth rectifying tower tower kettle extracts a mixture of formaldehyde aqueous solution and trioxymethylene; the fifth rectifying tower The material at the top of the tower enters the dehydration unit, and the water is removed; the material after the removal of water enters the sixth rectifying tower, and the material at the top of the sixth rectifying tower is methanol, and the tower bottom is the material of PODE ₂ . The operating pressure of the first rectifying tower is 80-120KPa, the operating temperature of the tower top is 70-100 ℃, the operating pressure of the second rectifying tower is 1-50KPa, the operating temperature of the tower top is 50-150 ℃, the third rectifying tower The operating pressure of the distillation tower is 100-200KPa, the operating temperature of the tower top is 35-70°C, the operating pressure of the fourth rectifying tower is 100-200KPa, the operating temperature of the tower top is 30-60°C, and the operation of the fifth rectifying tower The pressure is 80-120KPa, the operating temperature at the top of the tower is 70-120°C, the mass ratio of the supplementary water content to the material is 0.3:1 to 1:1 by weight, and the operating pressure of the sixth rectifying tower is 100-200KPa. The top operating temperature is 60-90°C.

A device for introducing supplementary water to separate PODEn in a rectifying column whose feed is a mixture of methanol, formaldehyde, water, trioxymethylene and PODE ₂ , comprising six rectifying columns and a dehydration unit, and the top of the first rectifying column The outlet is connected to the feed port of the third rectification tower through a pipeline, the outlet of the tower still of the first rectification tower is connected to the feed port of the second rectification tower through a pipeline, and the outlet of the tower still of the third rectification tower is connected to the fourth rectification tower through a pipeline. The feed port of the rectifying tower, the outlet of the tower still of the fourth rectifying tower is connected to the feed port of the fifth rectifying tower through the pipeline, and the top discharge port of the fifth rectifying tower is connected to the feed port of the dehydration unit, and the dehydration The discharge port of the unit is connected to the feed port of the sixth rectifying tower, and it is characterized in that: the supplementary water is introduced into the fifth rectifying tower, and the supplementary water is added from the feeding port of the fifth rectifying tower or added to the fifth rectifying tower. A make-up water inlet is set on the tower.

A method for introducing supplementary water to separate PODEn in a rectifying tower whose feed is methanol, formaldehyde, water, trioxane and PODE ₂ mixture, the process is as follows: PODEn raw material enters the first rectifying tower, and the first rectifying tower tower top The mixed material of methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE ₂ is extracted; the material of the first rectifying tower still enters the second rectifying tower, and the top of the second rectifying tower is collected. It is the material of PODE _3-5 , and the material of the tower still is extracted as the material of PODE _6-10 ; material; the material of the third rectifying tower tower bottom enters the fourth rectifying tower, and the top of the fourth rectifying tower is extracted as a mixture of methylal and methanol; the fourth rectifying tower tower bottom material enters the fifth rectifying tower At the same time, the fifth rectifying tower introduces supplementary water, and the fifth rectifying tower tower still produces a mixture of formaldehyde aqueous solution and trioxymethylene; the fifth rectifying tower top material enters the dehydration unit, and the water is removed; The material after water enters the sixth rectifying tower, the material of methanol is extracted from the top of the sixth rectifying tower, and the material of PODE ₂ is extracted from the tower bottom. The operating pressure of the first rectifying tower is 80-120KPa, the operating temperature of the tower top is 70-100 ℃, the operating pressure of the second rectifying tower is 1-50KPa, the operating temperature of the tower top is 50-150 ℃, the third rectifying tower The operating pressure of the distillation tower is 100-200KPa, the operating temperature of the tower top is 30-60°C, the operating pressure of the fourth rectifying tower is 100-200KPa, the operating temperature of the tower top is 35-70°C, and the operation of the fifth rectifying tower is The pressure is 80-120KPa, the operating temperature at the top of the tower is 70-120°C, the mass ratio of the supplementary water content to the material is 0.3:1 to 1:1 by weight, and the operating pressure of the sixth rectifying tower is 100-200KPa. The top operating temperature is 60-90°C.

The above-mentioned dehydration units are membrane dehydration, molecular sieve dehydration, and adsorption dehydration.

The beneficial effects that the present invention has:

Aiming at the technical situation that the product of catalyzing synthesis of polymethoxydimethyl ether (PODEn) using methanol and aqueous formaldehyde solution as raw materials has complex components, formaldehyde is easy to polymerize in the process of rectification and separation, and unreacted raw materials need to be recovered separately, the present invention proposes a new method in the process of rectification and separation. The material is a method and a device for the separation and purification of polymethoxydimethyl ether by introducing supplementary water into a rectifying column of methanol, formaldehyde, water, trioxymethylene and PODE ₂ mixture. The uniqueness of the method is as follows:

1. Other intermediate components such as methylal are discharged together with formaldehyde, which reduces the concentration of easy polymers such as hemiacetal and methyl glycol, prevents their polymerization from clogging the pipeline, and improves the continuity of equipment use.

2. By introducing supplementary water, the tower still produces an aqueous solution containing formaldehyde, preventing formaldehyde polymerization from blocking the condenser and pipelines, improving the continuity of equipment use, and at the same time, the recovered formaldehyde-containing aqueous solution can be returned to formaldehyde and methanol. The reaction device can reasonably recover unreacted raw materials and improve the utilization rate of raw materials.

3. By introducing supplementary water into the rectification column whose feed is a mixture of methanol, formaldehyde, water, trioxymethylene and PODE ₂ , some light components only need to be heated and distilled once, and the energy consumption is low.

Description of drawings

Fig. 1 is the separation process schematic diagram of embodiment 1;

Fig. 2 is the separation process schematic diagram of embodiment 2;

FIG. 3 is a schematic diagram of the separation process flow of Example 3. FIG.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are only descriptive, not restrictive, and cannot limit the protection scope of the present invention.

Example 1

1-A is the first rectifying tower, 1-B is the second rectifying tower, 1-C is the third rectifying tower, 1-D is the fourth rectifying tower, and 1-E is the fifth rectifying tower Distillation tower, 1-F is dehydration unit, 1-G sixth rectification tower.

The column still outlet of the first rectifying tower 1-A is connected to the feed port of the second rectifying tower 1-B by pipeline, and the top outlet of the second rectifying tower 1-B is connected to the fourth rectifying tower 1- The feed port of D, the outlet of the tower still of the second rectifying tower 1-B is connected to the feed port of the third rectifying tower 1-C by pipeline, and the outlet of the tower still of the fourth rectifying tower 1-D is connected to the first The feed port of the fifth rectifying tower 1-E, the top outlet of the fifth rectifying tower 1-E are connected to the feed port of the dehydration unit 1-F through the pipeline, and the discharge port of the dehydration unit 1-F is connected to the first The feed port of six rectification towers 1-G.

The make-up water can enter the fifth rectifying tower 1-E together with the discharge of the tower bottom of the fourth rectifying tower 1-D, or add it separately, if the make-up water is added separately, it needs to be additionally added on the fifth rectifying tower 1-E. Set up the make-up water inlet.

Material 1-1 is the raw material to be refined for PODEn, 1-2 is methyl formate, 1-3 is the raw material to be refined without methyl formate, and 1-4 is methylal, methanol, water, formaldehyde, trioxymethylene and The material of PODE ₂ , 1-5 is the material of PODE _3-10 , 1-6 is the product material of PODE _3-5 , 1-7 is the material of PODE _6-10 , 1-8 is the material of methylal and methanol , 1-9 are methanol, formaldehyde, water, trioxane and PODE ₂ materials, 1-10 are pure water materials, 1-11 are PODE ₂ , water and methanol materials, 1-12 are formaldehyde-containing aqueous solutions and trimer Formaldehyde, 1-13 is water material, 1-14 is methanol and PODE ₂ material, 1-15 is methanol material, 1-16 is PODE ₂ material.

The PODEn raw material (1-1) enters the first rectifying tower (1-A), and the material (1-2) of methyl formate is extracted from the top of the first rectifying tower (1-A); the first rectifying tower (1-A) 1-A) The tower reactor material (1-3) enters the second rectifying tower (1-B), and the second rectifying tower (1-B) overhead extracts methylal, methanol, water, formaldehyde, trimer The material (1-4) of formaldehyde and PODE ₂ ; the second rectifying column (1-B) tower bottom material (1-5) enters the third rectifying column (1-C), the third rectifying column (1- C) The material (1-6) of PODE _3-5 produced at the top of the tower and the material (1-7) of PODE _6-10 in the column bottom; the second rectifying tower (1-B) top material (1-4) ) into the fourth rectifying tower (1-D), the material (1-8) of methylal and methanol extracted from the top of the fourth rectifying tower (1-D); the fourth rectifying tower (1-D) The tower bottom material (1-9) enters the fifth rectifying tower (1-E), and the fifth rectifying tower (1-E) introduces supplementary water (1-10) simultaneously, and the fifth rectifying tower (1-E) The material (1-12) of aqueous formaldehyde solution and trioxymethylene is extracted from the tower kettle; ) is removed; the material (1-14) after removing the water enters the sixth rectifying tower (1-G), and the material (1-15) of the methanol extracted from the top of the tower and the material (1-15) of the tower still are PODE ₂ -16).

The synthetic product mixture of 1800t/h PODEn is composed as follows:

Numbering component content% 1 methyl formate 1.80 2 Methylal 36.66 3 methanol 5.19 4 formaldehyde 9.08 5 water 1.17 6 Trioxymethylene 2.50 7 PODE₂ 20.96 8 PODE_3-5 20.03 9 PODE_6-10 2.41

Separation using scheme 1 of this method, the operating pressure of the first rectifying tower (1-A) is 100KPa, the operating temperature of the tower top is 32°C, the operating pressure of the second rectifying tower (1-B) is 80KPa, the operating temperature of the tower top is 86°C, and the operating temperature of the second rectifying tower (1-B) is 80KPa. The operating pressure of the third rectifying tower (1-C) is 1KPa, the operating temperature of the tower top is 52°C, the operating pressure of the fourth rectifying tower (1-D) is 100KPa, the operating temperature of the tower top is 40°C, and the fifth rectifying tower (1-E) ) operating pressure 80KPa, supplementary water content (1-10) and material (1-9) mass ratio 0.3:1, tower top operating temperature 76 ℃, dehydration unit (1-F) adopts molecular sieve dehydration, the sixth rectifying tower ( 1-G) The operating pressure is 100KPa, and the tower top operating temperature is 64°C.

Separately obtained 32t/h of methyl formate, 670t/h of methylal and methanol materials, 377t/h of PODE ₂ , 360t/h of PODE _3-5 qualified products, and recovered 327t/h of 50% mass fraction of Formaldehyde solution.

Example 2

2-A is the first rectifying tower, 2-B is the second rectifying tower, 2-C is the third rectifying tower, 2-D is the fourth rectifying tower, and 2-E is the fifth rectifying tower Distillation tower, 2-F is dehydration unit, 2-G sixth rectifying tower;

The top outlet of the first rectifying tower 2-A is connected to the feed port of the third rectifying tower 2-C by pipeline, and the column still outlet of the first rectifying tower 2-A is connected to the second rectifying tower 2- The feed port of B, the top outlet of the third rectifying tower 2-C is connected to the feed port of the fourth rectifying tower 2-D through pipelines, and the column still outlet of the third rectifying tower 2-C is connected to the first rectifying tower 2-D through pipelines. The feed port of the fifth rectifying tower 2-E, the top discharge port of the fifth rectifying tower 2-E is connected to the feed port of the dehydration unit 2-F, and the discharge port of the dehydration unit 2-F is connected to the sixth rectifying unit 2-F. Feed inlet of distillation column 2-G.

The make-up water can enter the fifth rectifying tower 2-E together with the discharge of the tower bottom of the third rectifying tower 2-C, or be added separately, if the make-up water is added separately, it needs to be additionally added on the fifth rectifying tower 2-E. Set up the make-up water inlet.

Material 2-1 is the raw material to be refined for PODEn, 2-2 is the raw material to be refined without PODE _3-10 , 2-3 is the material of PODE _3-10 , 2-4 is the product material of PODE _3-5 , 2- 5 is the material of PODE _6-10 , 2-6 is the material of methyl formate, methylal, methanol, 2-7 is the material of methanol, water, formaldehyde, trioxymethylene and PODE ₂ , 2-8 is methyl formate Ester, 2-9 is the material of methylal and methanol, 2-10 is the material of pure water, 2-11 is the material of PODE ₂ , water and methanol, 2-12 is the material of formaldehyde solution and trioxymethylene, 2-13 is water feed, 2-14 is methanol and PODE ₂ feed, 2-15 is methanol feed, and 2-16 is PODE ₂ feed.

The PODEn raw material (2-1) enters the first rectifying tower (2-A), and methyl formate, methylal, methanol, water, formaldehyde and trioxymethylene are extracted from the top of the first rectifying tower (2-A). and the material (2-2) of PODE ₂ ; the first rectifying column (2-A) column bottom material (2-3) enters the second rectifying column (2-B), the second rectifying column (2-B) ) The material (2-4) that is basically PODE _3-5 and the material (2-5) that the column bottom is basically PODE _6-10 is extracted from the top of the column; the first rectifying column (2-A) column top material (2 -2) enter the 3rd rectifying tower (2-C), the material (2-6) that is basically methyl formate, methylal and methanol is extracted from the top of the 3rd rectifying tower (2-C); the third The rectifying tower (2-C) top material (2-6) enters the fourth rectifying tower (2-D), and the fourth rectifying tower (2-D) top extracts the material (2- 8) and tower still are the material (2-9) of methylal and methyl alcohol; The 3rd rectifying tower (2-C) tower still material (2-7) enters the fifth rectifying tower (2-E), simultaneously The fifth rectifying tower (2-E) introduces supplementary water (2-10), and the fifth rectifying tower (2-E) column still produces the material (2-12) of aqueous formaldehyde and trioxymethylene; The top material (2-11) of the distillation column (2-E) enters the dehydration unit (2-F), and the moisture (2-13) is removed; the material (2-14) after removing the water enters the sixth rectification Column (2-G), the material (2-15) of methanol produced at the top of the column and the material (2-16) of PODE ₂ in the bottom of the column.

The synthetic product mixture of 2400t/h PODEn is composed as follows:

Numbering component content% 1 methyl formate 1.80 2 Methylal 36.66 3 methanol 5.19 4 formaldehyde 9.08 5 water 1.17 6 Trioxymethylene 2.50 7 PODE₂ 20.96 8 PODE_3-5 20.03 9 PODE_6-10 2.41

Separation using scheme 2 of this method, the operating pressure of the first rectifying tower (2-A) is 100KPa, the operating temperature of the tower top is 90°C, the operating pressure of the second rectifying tower (2-B) is 1KPa, the operating temperature of the tower top is 52°C, and the operating temperature of the second rectifying tower (2-B) is 1KPa. The operating pressure of the third rectifying tower (2-C) is 100KPa, the operating temperature of the tower top is 39°C, the operating pressure of the fourth rectifying tower (2-D) is 100KPa, the operating temperature of the tower top is 32°C, and the fifth rectifying tower (2-E) ) operating pressure 100KPa, supplementary water (2-10) content and material (2-7) mass ratio 0.5:1, tower top operating temperature 80°C, dehydration unit (2-F) adopts membrane dehydration, and the sixth rectifying tower ( 2-G) The operating pressure is 100KPa, and the tower top operating temperature is 64°C.

42t/h of methyl formate, 893t/h of methylal and methanol materials, 503t/h of PODE ₂ , 480t/h of PODE _3-5 qualified products were obtained, and 622t/h of 35% mass fraction was recovered. Formaldehyde solution.

Example 3

3-A is the first rectifying tower, 3-B is the second rectifying tower, 3-C is the third rectifying tower, 3-D is the fourth rectifying tower, and 3-E is the fifth rectifying tower Distillation tower, 3-F is dehydration unit, 3-G sixth rectifying tower;

The top outlet of the first rectifying tower 3-A is connected to the feed port of the third rectifying tower 3-C by pipeline, and the tower still outlet of the first rectifying tower 3-A is connected to the second rectifying tower 3- The feed port of B, the outlet of the tower still of the third rectifying tower 3-C is connected to the feed port of the fourth rectifying tower 3-D by pipeline, and the outlet of the tower still of the fourth rectifying tower 3-D is connected to the first rectifying tower 3-D by pipeline The feed port of the fifth rectifying tower 3-E, the top discharge port of the fifth rectifying tower 3-E is connected to the feed port of the dehydration unit 3-F, and the discharge port of the dehydration unit 3-F is connected to the sixth rectifying unit 3-F. The feed port of distillation column 3-G.

The make-up water can enter the fifth rectifying tower 3-E together with the column still discharge of the fourth rectifying tower 3-D, or add it separately, if the make-up water is added separately, it needs to be additionally added on the fifth rectifying tower 3-E. Set up the make-up water inlet.

Material 3-1 is the raw material to be refined for PODEn, 3-2 is the raw material to be refined without PODE _3-10 , 3-3 is the material of PODE _3-10 , 3-4 is the product material of PODE _3-5 , 3- 5 is the material of PODE _6-10 , 3-6 is methyl formate, 3-7 is the material of methylal, methanol, water, formaldehyde, trioxymethylene and PODE ₂ , 3-8 is the material of methylal and methanol Material, 3-9 is the material of methanol, water, formaldehyde, trioxane and PODE ₂ , 3-10 is the pure water material, 3-11 is the material of PODE ₂ , water and methanol, 3-12 is the formaldehyde solution and the three Polyoxymethylene material, 3-13 is water material, 3-14 is methanol and PODE ₂ material, 3-15 is methanol material, 3-16 is PODE ₂ material.

The PODEn raw material (3-1) enters the first rectification tower (3-A), and methyl formate, methylal, methanol, water, formaldehyde and trioxymethylene are extracted from the top of the first rectification tower (3-A). and the material (3-2) of PODE ₂ ; the first rectifying column (3-A) column bottom material (3-3) enters the second rectifying column (3-B), the second rectifying column (3-B) ) The material (3-4) of PODE _3-5 produced at the top of the tower and the material (3-5) of PODE _6-10 in the tower bottom; the first rectifying tower (3-A) tower top material (3-2) Enter the third rectifying tower (3-C), the material (3-6) of methyl formate is extracted from the top of the third rectifying tower (3-C); the third rectifying tower (3-C) tower reactor material (3-7) enter the 4th rectifying tower (3-D), the material (3-8) of methylal and methanol extracted from the top of the 4th rectifying tower (3-D); 3-D) tower still material (3-9) enters the fifth rectifying tower (3-E), and the fifth rectifying tower (3-E) introduces supplementary water (3-10) simultaneously, and the fifth rectifying tower (3-E) 3-E) the material (3-12) of formaldehyde aqueous solution and trioxane is produced in the tower reactor; The fifth rectifying tower (3-E) overhead material (3-11) enters the dehydration unit (3-F), and the moisture (3-13) is removed; the material (3-14) after removing the water enters the sixth rectifying tower (3-G), and the material (3-15) and the tower still of the methanol extracted from the top of the tower are PODE ₂ material (3-16).

The synthetic product mixture of 2700t/h PODEn is composed as follows:

Numbering component content% 1 methyl formate 1.80 2 Methylal 36.66 3 methanol 5.19 4 formaldehyde 9.08 5 water 1.17 6 Trioxymethylene 2.50 7 PODE₂ 20.96 8 PODE_3-5 20.03 9 PODE_6-10 2.41

Adopt this method scheme 3 separation, the operating pressure of the first rectifying tower (3-A) is 100KPa, the operating temperature of the tower top is 90 ℃, the operating pressure of the second rectifying tower (3-B) is 50KPa, the operating temperature of the tower top is 144 ℃, The operating pressure of the third rectifying tower (3-C) is 200KPa, the operating temperature of the tower top is 51°C, the operating pressure of the fourth rectifying tower (3-D) is 200KPa, the operating temperature of the tower top is 61°C, and the operating temperature of the fifth rectifying tower (3-E) is 200KPa. ) operating pressure 100KPa, supplementary water (3-10) content and material (3-9) mass ratio 1:1, tower top operating temperature 80°C, dehydration unit (3-F) adopts adsorption dehydration, and the sixth rectifying tower ( 3-G) The operating pressure is 100KPa, and the tower top operating temperature is 64°C.

48t/h of methyl formate, 1004t/h of methylal and methanol materials, 566t/h of PODE ₂ , 540t/h of PODE _3-5 qualified products were obtained, and 1225t/h of 20% mass fraction was recovered. Formaldehyde solution.

The present invention proposes a method and a device for separating and purifying polymethoxydimethyl ether by introducing supplementary water into a rectifying column whose feed is a mixture of methanol, formaldehyde, water, trioxymethylene and PODE ₂ . The embodiments of the present invention have been described, and it is obvious that those skilled in the art can make changes or appropriate changes and combinations of the structures and devices described herein without departing from the content, spirit and scope of the present invention to realize the technology of the present invention. It should be particularly pointed out that all similar substitutions and modifications apparent to those skilled in the art are deemed to be included in the spirit, scope and content of the present invention.

Claims (1)

1. a method for separating and purifying polymethoxy dimethyl ether, is characterized in that: described polymethoxy dimethyl ether is to take methanol and aqueous formaldehyde solution as raw material and obtain, in charging is methanol, formaldehyde, water, Make-up water is introduced into the rectifying tower of the mixture of trioxymethylene and PODE ₂ , and the formaldehyde aqueous solution and trioxymethylene are extracted from the tower kettle to realize the purpose of separating formaldehyde and trioxymethylene; Specifically, it includes three parallel technical solutions: Option 1: Six-stage rectification is adopted, including six rectification towers and one dehydration unit. The PODEn raw material enters the first rectification tower, and the material of methyl formate is extracted from the top of the first rectification tower; the first rectification tower The tower bottom material enters the second rectifying tower, and the top of the second rectifying tower is extracted as a mixture of methylal, methanol, water, formaldehyde, trioxymethylene and PODE ₂ ; the second rectifying tower tower bottom material enters the first Three rectifying towers, the material from the top of the third rectifying tower is PODE _3-5 , and the tower bottom is the material of PODE _6-10 ; the material at the top of the second rectifying tower enters the fourth rectifying tower, and the fourth rectifying tower The materials of methylal and methanol are extracted from the top of the distillation column; the material in the bottom of the fourth rectifying column enters the fifth rectifying column, and at the same time, the fifth rectifying column introduces supplementary water, and the amount of supplementary water added is based on the weight of the input. The mass ratio of the materials is 0.3:1 to 1:1, and the fifth rectifying tower column kettle is extracted as the material of formaldehyde aqueous solution and trioxymethylene; the fifth rectifying tower top material enters the dehydration unit, and the material after the water is removed Enter the sixth rectifying tower, the material of methanol extracted from the top of the sixth rectifying tower, and the material of PODE ₂ from the tower still; the operating pressure of the first rectifying tower is 100-200KPa, and the operating temperature at the top of the tower is 30 -60°C, the operating pressure of the second rectifying tower is 80-120KPa, the operating temperature of the tower top is 70-100°C, the operating pressure of the third rectifying tower is 1-50KPa, and the operating temperature of the tower top is 50-150°C , the operating pressure of the fourth rectifying tower is 100-200KPa, the operating temperature at the top of the tower is 35-70 ℃, the operating pressure of the fifth rectifying tower is 80-120KPa, the operating temperature at the top of the tower is 70-120 ℃, the supplementary water content The mass ratio to the material is 0.3:1 to 1:1 in terms of weight, the operating pressure of the sixth rectifying tower is 100-200KPa, and the operating temperature at the top of the tower is 60-90°C; Option 2: Six-stage rectification is adopted, including six rectifying towers and one dehydration unit. The PODEn raw material enters the first rectifying tower, and the top of the first rectifying tower is extracted into methyl formate, methylal, methanol, and water. , formaldehyde, trioxymethylene and PODE ₂ mixed material; the first rectifying tower tower still material enters the second rectifying tower, and the second rectifying tower top extraction is the material of PODE _3-5 , and the tower still is PODE _{6 -10} material; the first rectifying tower top material enters the third rectifying tower, and the third rectifying tower top is extracted as a mixture of methyl formate, methylal and methanol; the third rectifying tower top The material enters the fourth rectifying tower, the material from the top of the fourth rectifying tower is methyl formate, and the tower still is a mixture of methylal and methanol; the material from the third rectifying tower tower still enters the fifth rectifying tower At the same time, the fifth rectifying tower introduces supplementary water, and the mass ratio of the added amount of the supplementary water to the feed is 0.3:1 to 1:1 by weight, and the fifth rectifying tower still produces formaldehyde aqueous solution and trioxymethylene The mixed material; the material at the top of the fifth rectifying tower enters the dehydration unit, and the material after removing water enters the sixth rectifying tower, and the top of the sixth rectifying tower is extracted as the material of methanol, and the tower still is the material of PODE ₂ ; The operating pressure of the first rectifying tower is 80-120KPa, and the operating temperature at the top of the tower is 70-100 ℃, and the operating pressure of the second rectifying tower is 1-50KPa, and the operating temperature at the top of the tower is 50-150 ℃, and the third The operating pressure of the rectifying tower is 100-200KPa, the operating temperature at the top of the tower is 35-70 ℃, the operating pressure of the fourth rectifying tower is 100-200KPa, the operating temperature at the top of the tower is 30-60 ℃, and the operating temperature of the fifth rectifying tower is 30-60 ℃. The operating pressure is 80-120KPa, the operating temperature at the top of the tower is 70-120°C, the mass ratio of the supplementary water content to the material is 0.3:1 to 1:1 by weight, and the operating pressure of the sixth rectifying tower is 100-200KPa, The operating temperature at the top of the tower is 60-90℃; Option 3: Six-stage rectification is adopted, including six rectifying towers and one dehydration unit. The PODEn raw material enters the first rectifying tower, and the top of the first rectifying tower is extracted into methyl formate, methylal, methanol, and water. , the mixture of formaldehyde, trioxymethylene and PODE ₂ ; the first rectifying tower still material enters the second rectifying tower, the second rectifying tower top is extracted as the material of PODE _3-5 , and the tower still is extracted as The material of PODE _6-10 ; the material at the top of the first rectifying tower enters the third rectifying tower, and the material at the top of the third rectifying tower is extracted as methyl formate; the material in the bottom of the third rectifying tower enters the fourth rectifying tower Distillation tower, the top of the fourth rectifying tower is extracted as a mixture of methylal and methanol; the material in the fourth rectifying tower tower bottom enters the fifth rectifying tower, and at the same time the fifth rectifying tower introduces supplementary water, and the The mass ratio of the add-on to the feed is 0.3:1 to 1:1 by weight, and the fifth rectifying tower tower kettle is extracted as a mixture of aqueous formaldehyde and trioxymethylene; the fifth rectifying tower overhead material enters the dehydration unit, the moisture is removed; the material after the removal of water enters the sixth rectification tower, the material of methanol extracted from the top of the sixth rectification tower, and the material of PODE ₂ extracted from the tower; the material of the first rectification tower The operating pressure is 80-120KPa, the operating temperature at the top of the tower is 70-100°C, the operating pressure of the second rectifying tower is 1-50KPa, the operating temperature at the top of the tower is 50-150°C, and the operating pressure of the third rectifying tower is 100-200KPa, the operating temperature of the tower top is 30-60 ℃, the operating pressure of the fourth rectifying tower is 100-200KPa, the operating temperature of the tower top is 35-70 ℃, the operating pressure of the fifth rectifying tower is 80-120KPa, The operating temperature at the top of the tower is 70-120°C, the mass ratio of the supplementary water content to the material is 0.3:1 to 1:1 by weight, the operating pressure of the sixth rectifying tower is 100-200KPa, and the operating temperature at the top of the tower is 60- 90°C.

Images