CN109776288B

CN109776288B - Method and device for separating polymethoxy dimethyl ether

Info

Publication number: CN109776288B
Application number: CN201910095670.9A
Authority: CN
Inventors: 韩振为; 任远洋; 廉景燕; 李鑫钢; 安登超
Original assignee: Beiyang National Distillation Technology Engineering Development Co ltd; Tianjin University
Current assignee: Beiyang National Distillation Technology Engineering Development Co ltd; Tianjin University
Priority date: 2019-01-31
Filing date: 2019-01-31
Publication date: 2022-07-08
Anticipated expiration: 2039-01-31
Also published as: CN109776288A

Abstract

The invention relates to a method and a device for separating polymethoxy dimethyl ether, which adopt multi-stage rectification to feed methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE₂Make-up water is introduced into the rectifying tower of the mixed material, and the aqueous solution of formaldehyde and trioxymethylene are extracted from the tower kettle of the rectifying tower or the tower kettle of the subsequent rectifying tower, so that the aim of separating formaldehyde and trioxymethylene is fulfilled. The formaldehyde separated by the process can not be polymerized to block condensers and pipelines, the continuity of the use of equipment is improved, and the unreacted raw material formaldehyde, and reaction byproducts methyl formate and PODE (dimethyl formamide) can be effectively recovered₂And the like.

Description

Method and device for separating polymethoxy dimethyl ether

Technical Field

The invention belongs to the technical field of chemical engineering, relates to a technology for synthesizing a synthetic product mixture of polymethoxy dimethyl ether by adopting multistage rectification separation of methanol and formaldehyde aqueous solution, and particularly relates to a method for synthesizing polymethoxy dimethyl ether by using methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE (formaldehyde-peroxidase)₂The rectification tower of the mixed material introduces make-up water to realize the separation and refining of the polymethoxy dimethyl ether and the device thereof.

Background

The polymethoxy dimethyl ether is a novel diesel additive, and the chemical formula is represented as CH₃O(CH₂O)nCH₃(wherein n is more than or equal to 1, generally less than 10), has higher oxygen content (42-51%) and cetane number (average up to 76), and the PODE (peroxidase) is_3-5Is the most ideal diesel oil additive, and PODE is added into the diesel oil_3-5Can effectively reduce soot and particles of diesel engineAnd (5) emission of substances (PM) and improvement of fuel economy. PODEn is a homologue component formed by the condensation polymerization of a source providing an etherate end group and a source providing a methoxy group under acid catalysis. The compounds providing terminal groups include methanol, dimethyl ether, methylal, etc., and the compounds providing methoxy groups include formaldehyde, trioxymethylene, paraformaldehyde, etc.

For many years, a large amount of researches on the synthesis and separation processes of PODEN have been carried out by domestic and foreign research teams mainly based on BASF corporation, and mainly reported are a methylal and trioxymethylene route (US 20070260094) of BASF corporation and a methylal and paraformaldehyde route (CN104974025A) of Qinghua university and Yuhuang chemical cooperation, but because the reaction raw materials are anhydrous trioxymethylene and paraformaldehyde, the reaction product composition is simple, and the separation process cannot be suitable for the separation of the synthesis product of methanol and formaldehyde aqueous solution; in addition, the reaction and separation processes of methanol and formaldehyde aqueous solution (US 2008207954, US20080221368, US 7671240 and US 7700809) of BASF company have the advantages of low single-pass conversion rate, complex separation process, high energy consumption for repeated heating and separation of materials and serious equipment corrosion, and greatly limit the industrialization of the process flow.

Disclosure of Invention

The synthesis process of preparing PODEN by using methanol and formaldehyde aqueous solution as raw materials is divided into two steps, wherein the first step is a reaction stage of formaldehyde and methanol reacting to generate methylal, and the second step is a reaction stage of methylal and formaldehyde reacting to generate PODEN.

The invention aims to provide a method for preparing methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE (formaldehyde-containing ether)₂The rectification tower of the mixed material introduces make-up water to realize the separation and refining of the polymethoxy dimethyl ether and the device thereof. Separating the synthesized product of PODEN with methanol and formaldehyde solution as material by distillation, refining to obtain PODEN suitable for diesel oil component, and recovering part of the material for the first and second stage reaction.

The feed materials of the invention are methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE₂The rectification tower of the mixed material introduces make-up water to realize the separation of polyoxymethylene dimethyl ethersThe method and the device for separating and refining can adopt six rectifying towers and a dehydration unit.

Taking 6-grade rectification as an example, the technical scheme is as follows:

(a) scheme 1 (as shown in figure 1)

A separation device for polyoxymethylene dimethyl ethers comprises six rectifying towers and a dehydration unit, wherein a tower kettle outlet of a first rectifying tower 1-A is connected with a feed inlet of a second rectifying tower 1-B through a pipeline, a tower top outlet of the first rectifying tower 1-A is connected with a feed inlet of a third rectifying tower 1-C through a pipeline, a tower top outlet of the third rectifying tower 1-C is connected with a feed inlet of a fourth rectifying tower 1-D through a pipeline, a tower kettle discharge port of the fourth rectifying tower 1-D is connected with a feed inlet of a fifth rectifying tower 1-E through a pipeline, a tower kettle discharge port of the fifth rectifying tower 1-E is connected with a feed inlet of a dehydration unit 1-F through a pipeline, and a discharge port of the dehydration unit 1-F is connected with a feed inlet of the sixth rectifying tower 1-G. Make-up water may enter the third rectification column 1-C together with the overhead discharge of the first rectification column 1-a, or be added separately, if make-up water is added separately, a make-up water feed inlet is required to be additionally provided on the third rectification column 1-C.

PODEN raw material (1-1) enters a first rectifying tower (1-A), and methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE are basically extracted from the top of the first rectifying tower (1-A)₂The material (1-2); the material (1-3) at the bottom of the first rectifying tower (1-A) enters a second rectifying tower (1-B), and the PODE is basically extracted from the top of the second rectifying tower (1-B)_3-5The materials (1-4) and the tower bottom are basically PODE_6-10The material (1-5); the material (1-2) at the top of the first rectifying tower (1-A) enters a third rectifying tower (1-C), the third rectifying tower (1-C) introduces make-up water (1-6), and the material (1-8) which is basically formaldehyde water solution and trioxymethylene is extracted from the tower bottom of the third rectifying tower (1-C); the materials (1-7) at the top of the third rectifying tower (1-C) enter a fourth rectifying tower (1-D), and the materials (1-9) which are basically methyl formate are extracted from the top of the fourth rectifying tower (1-D); feeding the tower bottom materials (1-10) of the fourth rectifying tower (1-D) into a fifth rectifying tower (1-E), and extracting materials (1-11) which are basically methylal and methanol from the tower top of the fifth rectifying tower (1-E); feeding tower bottom materials (1-12) of a fifth rectifying tower (1-E) into a dehydration unit (1-F), and removing moisture (1-13); the materials (1-14) after water removal enterFeeding into a sixth rectifying tower (1-G), collecting material (1-15) which is basically methanol at the top of the tower and material (PODE) which is basically PODE at the bottom of the tower₂The material (1-16); wherein the operating pressure of the first rectifying tower (1-A) is 80-120KPa, the operating temperature of the top of the tower is 70-100 ℃, the operating pressure of the second rectifying tower (1-B) is 1-50KPa, the operating temperature of the top of the tower is 50-150 ℃, the operating pressure of the third rectifying tower (1-C) is 80-120KPa, the operating temperature of the top of the tower is 70-120 ℃, the mass ratio of the content of the make-up water (1-6) to the material (1-2) is 0.2: 1-1: 1, the operating pressure of the fourth rectifying tower (1-D) is 100-200KPa, the operating temperature of the top of the tower is 30-60 ℃, the operating pressure of the fifth rectifying tower (1-E) is 100-200KPa, the operating temperature of the top of the tower is 35-70 ℃, and the dehydrating unit (1-F) is membrane dehydration, molecular sieve dehydration and the dehydration, The adsorption dehydration is carried out, the operation pressure of the sixth rectifying tower (1-G) is 100-200KPa, and the operation temperature of the tower top is 60-90 ℃.

(b) Scheme 2 (as shown in figure 2)

A separation device for polymethoxy dimethyl ether comprises six rectifying towers and a dehydration unit, wherein a tower kettle outlet of a first rectifying tower 2-A is connected with a feed inlet of a second rectifying tower 2-B through a pipeline, a tower top outlet of the first rectifying tower 2-A is connected with a feed inlet of a third rectifying tower 2-C through a pipeline, a tower top outlet of the third rectifying tower 2-C is connected with a feed inlet of a fourth rectifying tower 2-D through a pipeline, a tower top discharge port of the fourth rectifying tower 2-D is connected with a feed inlet of a fifth rectifying tower 2-E through a pipeline, a tower kettle discharge port of the fourth rectifying tower 2-D is connected with a feed inlet of a dehydration unit 2-F through a pipeline, and a discharge port of the dehydration unit 2-F is connected with a feed inlet of a sixth rectifying tower 2-G. The make-up water can enter the third rectifying tower 2-C together with the top discharge of the first rectifying tower 2-A or be added separately, if the make-up water is added separately, a make-up water feed inlet is additionally arranged on the third rectifying tower 2-C.

PODEN raw material (2-1) enters a first rectifying tower (2-A), and methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE are basically extracted from the top of the first rectifying tower (2-A)₂The material (2-2); the tower bottom material (2-3) of the first rectifying tower (2-A) enters a second rectifying tower (2-B), and PODE (peroxidase) is extracted from the tower top of the second rectifying tower (2-B)_3-5The material (2-4) and the bottom of the column are basically PODE_6-10Material (2-5) (ii) a The material (2-2) at the top of the first rectifying tower (2-A) enters a third rectifying tower (2-C), the third rectifying tower (2-C) introduces make-up water (2-6), and the material (2-8) which is basically formaldehyde water solution and trioxymethylene is extracted from the tower bottom of the third rectifying tower (2-C); the material (2-7) at the top of the third rectifying tower (2-C) enters a fourth rectifying tower (2-D), and the material (2-9) which is basically methyl formate, methylal and methanol is extracted from the top of the fourth rectifying tower (2-D); feeding the material (2-9) at the top of the fourth rectifying tower (2-D) into a fifth rectifying tower (2-E), and collecting a material (2-11) which is basically methyl formate at the top of the fifth rectifying tower (2-E) and a material (2-12) which is basically methylal and methanol at the bottom of the fifth rectifying tower (2-E); the tower bottom material (2-10) of the fourth rectifying tower (2-D) enters a dehydration unit (2-F), and the moisture (13) is removed; the materials (2-14) after water removal enter a sixth rectifying tower (2-G), materials (2-15) which are basically methanol are extracted from the top of the tower, and materials (2-15) which are basically PODE is extracted from the bottom of the tower₂2-16); wherein the operation pressure of the first rectifying tower (2-A) is 80-120KPa, the operation temperature of the top of the tower is 70-100 ℃, the operation pressure of the second rectifying tower (2-B) is 1-50KPa, the operation temperature of the top of the tower is 50-150 ℃, the operation pressure of the third rectifying tower (2-C) is 80-120KPa, the operation temperature of the top of the tower is 70-120 ℃, the mass ratio of the content of the supplementary water (2-6) to the material (2-2) is 0.2: 1-1: 1, the operation pressure of the fourth rectifying tower (2-D) is 100-200KPa, the operation temperature of the top of the tower is 35-70 ℃, the operation pressure of the fifth rectifying tower (2-E) is 100-200KPa, the operation temperature of the top of the tower is 30-60 ℃, and the dehydration unit (2-F) is a membrane dehydration unit, a molecular sieve dehydration unit, The adsorption dehydration is carried out, the operation pressure of the sixth rectifying tower (2-G) is 100-200KPa, and the operation temperature of the tower top is 60-90 ℃.

(c) Scheme 3 (as shown in figure 3)

A separation device for polymethoxy dimethyl ether comprises six rectifying towers and a dehydration unit, wherein a tower kettle outlet of a first rectifying tower 3-A is connected with a feed inlet of a second rectifying tower 3-B through a pipeline, a tower top outlet of the first rectifying tower 3-A is connected with a feed inlet of a third rectifying tower 3-C through a pipeline, a tower top outlet of the third rectifying tower 3-C is connected with a feed inlet of a fourth rectifying tower 3-D through a pipeline, a tower kettle discharge port of the third rectifying tower 3-C is connected with a feed inlet of a fifth rectifying tower 3-E through a pipeline, a tower top discharge port of the fifth rectifying tower 3-E is connected with a feed inlet of a dehydration unit 3-F through a pipeline, and a discharge port of the dehydration unit 3-F is connected with a feed inlet of a sixth rectifying tower 3-G. The make-up water may be fed to the third rectification column 3-C together with the top discharge from the first rectification column 3-a, or may be fed separately, if the make-up water is fed separately, it is necessary to additionally provide a make-up water feed inlet in the third rectification column 3-C.

PODEN raw material (3-1) enters a first rectifying tower (3-A), and methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE are basically extracted from the top of the first rectifying tower (3-A)₂The material (3-2); the material (3-3) at the bottom of the first rectifying tower (3-A) enters a second rectifying tower (3-B), and the PODE is basically extracted from the top of the second rectifying tower (3-B)_3-5The material (3-4) and the bottom of the column are basically PODE_6-103-5); the material (3-2) at the top of the first rectifying tower (3-A) enters a third rectifying tower (3-C), the third rectifying tower (3-C) introduces make-up water (3-6), and the material (3-7) which is basically methyl formate, methylal and methanol is extracted from the top of the third rectifying tower (3-C); the material (3-7) at the top of the third rectifying tower (3-C) enters a fourth rectifying tower (3-D), and the material (3-9) which is basically methyl formate and the material (3-10) which is basically methylal and methanol at the bottom of the fourth rectifying tower (3-D) are extracted from the top of the fourth rectifying tower (3-D); feeding the tower bottom materials (3-8) of the third rectifying tower (3-C) into a fifth rectifying tower (3-E), and extracting materials (3-12) which are basically formaldehyde water solution and trioxymethylene from the tower bottom of the fifth rectifying tower (3-E); the material (3-11) at the top of the fifth rectifying tower (3-E) enters a dehydration unit (3-F), and the moisture (3-13) is removed; the materials (3-14) after water removal enter a sixth rectifying tower (3-G), materials (3-15) which are basically methanol are extracted from the top of the tower, and materials (3-15) which are basically PODE is extracted from the bottom of the tower₂The material (3-16); wherein the operating pressure of the first rectifying tower (3-A) is 80-120KPa, the operating temperature of the top of the tower is 70-100 ℃, the operating pressure of the second rectifying tower (3-B) is 1-50KPa, the operating temperature of the top of the tower is 50-150 ℃, the operating pressure of the third rectifying tower (3-C) is 100-200KPa, the operating temperature of the top of the tower is 35-70 ℃, the mass ratio of the content of the make-up water (3-6) to the material (3-2) is 0.2: 1-1: 1, the operating pressure of the fourth rectifying tower (3-D) is 100-200KPa, the operating temperature of the top of the tower is 30-60 ℃, the operating pressure of the fifth rectifying tower (3-E) is 80-120KPa, the operating temperature of the top of the tower is 70-120 ℃, and the dehydration unit (3-F) is a membrane dehydration unit, a molecular sieve dehydration unit, a distillation unit and a distillation unit, Operation of the sixth rectifying column (3-G) for adsorption dehydrationThe pressure is 80-120KPa, and the operation temperature at the top of the tower is 60-90 ℃.

(d) Scheme 4 (as shown in FIG. 4)

A separation device for polymethoxy dimethyl ether comprises six rectifying towers and a dehydration unit, wherein a tower kettle outlet of a first rectifying tower 4-A is connected with a feed inlet of a second rectifying tower 4-B through a pipeline, a tower top outlet of the first rectifying tower 4-A is connected with a feed inlet of a third rectifying tower 4-C through a pipeline, a tower kettle outlet of the third rectifying tower 4-C is connected with a feed inlet of a fourth rectifying tower 4-D through a pipeline, a tower kettle discharge port of the fourth rectifying tower 4-D is connected with a feed inlet of a fifth rectifying tower 4-E through a pipeline, a tower top discharge port of the fifth rectifying tower 4-E is connected with a feed inlet of a dehydration unit 4-F through a pipeline, and a discharge port of the dehydration unit 4-F is connected with a feed inlet of the sixth rectifying tower 4-G. The make-up water may be fed to the third rectification column 4-C together with the overhead discharge from the first rectification column 4-a, or may be fed separately, if the make-up water is fed separately, it may be necessary to provide an additional make-up water feed inlet in the third rectification column 4-C.

PODEN raw material (4-1) enters a first rectifying tower (4-A), and methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE are basically extracted from the top of the first rectifying tower (4-A)₂The material (4-2); the material (4-3) at the bottom of the first rectifying tower (4-A) enters a second rectifying tower (4-B), and the PODE is basically extracted from the top of the second rectifying tower (4-B)_3-5The material (4-4) and the bottom of the column are basically PODE_6-104-5); the material (4-2) at the top of the first rectifying tower (4-A) enters a third rectifying tower (4-C), the third rectifying tower (4-C) introduces make-up water (4-6), and the material (4-7) of methyl formate is extracted from the top of the third rectifying tower (4-C); feeding tower bottom materials (4-8) of the third rectifying tower (4-C) into a fourth rectifying tower (4-D), and collecting materials (4-9) of methylal and methanol from the tower top of the fourth rectifying tower (4-D); feeding the tower bottom material (4-10) of the fourth rectifying tower (4-D) into a fifth rectifying tower (4-E), and extracting a formaldehyde water solution and a trioxymethylene material (4-12) from the tower bottom of the fifth rectifying tower (4-E); the material (4-11) at the top of the fifth rectifying tower (4-E) enters a dehydration unit (4-F), and the moisture (4-13) is removed; the material (4-14) after water removal enters a sixth rectifying tower (4-G), the material (4-15) of methanol extracted from the tower top and the PODE in the tower bottom₂The material (4-16); wherein, the first rectifying tower (4-A)) The operation pressure of the second rectifying tower (4-B) is 80-120KPa, the operation temperature of the tower top is 70-100 ℃, the operation pressure of the second rectifying tower (4-B) is 1-50KPa, the operation temperature of the tower top is 50-150 ℃, the operation pressure of the third rectifying tower (4-C) is 100-200KPa, the operation temperature of the tower top is 30-60 ℃, the mass ratio of the content of the supplementary water (4-6) to the material (4-2) is 0.2: 1-1: 1, the operation pressure of the fourth rectifying tower (4-D) is 100-200KPa, the operation temperature of the tower top is 35-70 ℃, the operation pressure of the fifth rectifying tower (4-E) is 80-120KPa, the operation temperature of the tower top is 70-120 ℃, the dehydration unit (4-F) is membrane dehydration, molecular sieve dehydration, adsorption distillation dehydration, and the operation pressure of the sixth rectifying tower (4-G) is 80-120KPa, the operation temperature at the top of the tower is 60-90 ℃.

(f) Scheme 5 (as shown in FIG. 5)

A separation device for polymethoxy dimethyl ether comprises six rectifying towers and a dehydration unit, wherein a tower kettle outlet of a first rectifying tower 5-A is connected with a feed inlet of a second rectifying tower 5-B through a pipeline, a tower top outlet of the first rectifying tower 5-A is connected with a feed inlet of a third rectifying tower 5-C through a pipeline, a tower kettle outlet of the third rectifying tower 5-C is connected with a feed inlet of a fourth rectifying tower 5-D through a pipeline, a tower top discharge port of the fourth rectifying tower 5-D is connected with a feed inlet of a fifth rectifying tower 5-E through a pipeline, a tower kettle discharge port of the fifth rectifying tower 5-E is connected with a feed inlet of a dehydration unit 5-F through a pipeline, and a discharge port of the dehydration unit 5-F is connected with a feed inlet of the sixth rectifying tower 5-G. The make-up water can be fed into the third rectification column 5-C together with the top discharge of the first rectification column 5-A, or fed separately, if the make-up water is fed separately, an additional make-up water feed inlet is required to be arranged on the third rectification column 5-C.

PODEN raw material (5-1) enters a first rectifying tower (5-A), and methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE are basically extracted from the top of the first rectifying tower (5-A)₂The material (5-2); the material (5-3) at the bottom of the first rectifying tower (5-A) enters a second rectifying tower (5-B), and PODE is extracted from the top of the second rectifying tower (5-B)_3-5The material (5-4) and the tower bottom are PODE_6-105-5); the material (5-2) at the top of the first rectifying tower (5-A) enters a third rectifying tower (5-C), the third rectifying tower (5-C) introduces make-up water (5-6), and methyl formate is extracted from the top of the third rectifying tower (5-C)5-7); feeding the tower bottom material (5-8) of the third rectifying tower (5-C) into a fourth rectifying tower (5-D), and extracting a formaldehyde water solution and a trioxymethylene material (5-10) from the tower bottom of the fourth rectifying tower (5-D); feeding the tower top material (5-9) of the fourth rectifying tower (5-D) into a fifth rectifying tower (5-E), and collecting a material (5-11) of methylal and methanol from the tower top of the fifth rectifying tower (5-E); feeding tower bottom materials (5-12) of a fifth rectifying tower (5-E) into a dehydration unit (5-F), and removing moisture (5-13); the material (5-14) after water removal enters a sixth rectifying tower (5-G), the material (5-15) of methanol extracted from the tower top and the PODE in the tower bottom₂5-16); wherein the operating pressure of the first rectifying tower (5-A) is 80-120KPa, the operating temperature of the top of the tower is 70-100 ℃, the operating pressure of the second rectifying tower (5-B) is 1-50KPa, the operating temperature of the top of the tower is 50-150 ℃, the operating pressure of the third rectifying tower (5-C) is 100-200KPa, the operating temperature of the top of the tower is 30-60 ℃, the mass ratio of the content of the make-up water (5-6) to the material (5-2) is 0.2: 1-1: 1, the operating pressure of the fourth rectifying tower (5-D) is 80-120KPa, the operating temperature of the top of the tower is 70-120 ℃, the operating pressure of the fifth rectifying tower (5-E) is 100-200KPa, the operating temperature of the top of the tower is 35-70 ℃, and the dehydrating unit (5-F) is a membrane dehydration unit, a molecular sieve dehydration unit, a distillation unit, and a unit, wherein the distillation unit, and a distillation unit, and a, The adsorption dehydration is carried out, the operation pressure of the sixth rectifying tower (5-G) is 100-200KPa, and the operation temperature of the tower top is 60-90 ℃.

The invention has the following beneficial effects:

the invention provides a method for synthesizing polyoxymethylene dimethyl ethers (PODEN) by taking methanol and formaldehyde aqueous solution as raw materials, aiming at the technical current situation that the components of the product are complex, formaldehyde is easy to polymerize in the rectification separation process, and unreacted raw materials need to be respectively recovered₂The method and the device for separating and refining the polymethoxy dimethyl ether by introducing the make-up water into the rectifying tower of the mixed material have the following unique points:

1. other intermediate components such as methylal and the like and formaldehyde are discharged together, so that the concentration of easily-polymerized substances such as hemiacetal, methylene glycol and the like is reduced, the pipeline is prevented from being blocked by polymerization, and the use continuity of equipment is improved.

2. Through introducing make-up water, the aqueous solution that contains formaldehyde is adopted to the tower bottom, prevents that formaldehyde polymerization from blockking up condenser and pipeline, improves equipment and uses the continuity, and the aqueous solution that contains formaldehyde of retrieving simultaneously can return to formaldehyde and the synthetic reaction unit of methyl acetal of methyl alcohol catalysis, and the material utilization ratio is improved to the reasonable recovery unreacted.

3. By feeding methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE₂The rectification tower of the mixed material introduces make-up water, more methanol is taken out along with methylal at the tower top, and the energy consumption of a subsequent dehydration unit and the last stage of rectification tower is reduced.

Drawings

FIG. 1 is a schematic flow diagram of the separation process of example 1;

FIG. 2 is a schematic flow diagram of the separation process of example 2;

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

FIG. 4 is a schematic flow diagram of the separation process of example 4;

FIG. 5 is a schematic flow diagram of the separation process of example 5;

Detailed Description

The present invention will be described in further detail with reference to the following embodiments, which are illustrative only and not limiting, and the scope of the present invention is not limited thereby.

Example 1

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

The tower kettle outlet of the first rectifying tower 1-A is connected with the feed inlet of the second rectifying tower 1-B through a pipeline, the tower top outlet of the first rectifying tower 1-A is connected with the feed inlet of the third rectifying tower 1-C through a pipeline, the tower top outlet of the third rectifying tower 1-C is connected with the feed inlet of the fourth rectifying tower 1-D through a pipeline, the tower kettle discharge port of the fourth rectifying tower 1-D is connected with the feed inlet of the fifth rectifying tower 1-E through a pipeline, the tower kettle discharge port of the fifth rectifying tower 1-E is connected with the feed inlet of the dehydrating unit 1-F through a pipeline, and the discharge port of the dehydrating unit 1-F is connected with the feed inlet of the sixth rectifying tower 1-G.

The make-up water can enter the third rectifying tower 1-C together with the top discharge of the first rectifying tower 1-A or be added separately, if the make-up water is added separately, a make-up water feed inlet is additionally arranged on the third rectifying tower 1-C.

The material 1-1 is PODEN to-be-refined raw material, and 1-2 is PODE-free_3-101-3 is PODE_3-101-4 is PODE_3-51-5 is PODE_6-101-6 is pure water material, 1-7 is methyl formate, methylal, methanol, water and PODE₂1-8 of aqueous solution of formaldehyde and trioxymethylene, 1-9 of methyl formate, 1-10 of methylal, methanol, water and PODE₂1-11 is a material of methylal and methanol, 1-12 is PODE₂Water and methanol, 1-13 is water, 1-14 is methanol and PODE₂Materials, 1-15 are methanol materials, 1-16 are PODE₂And (3) feeding.

PODEN raw material (1-1) enters a first rectifying tower (1-A), and methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE are extracted from the top of the first rectifying tower (1-A)₂The material (1-2); the material (1-3) at the bottom of the first rectifying tower (1-A) enters a second rectifying tower (1-B), and PODE is extracted from the top of the second rectifying tower (1-B)_3-5The material (1-4) and the tower bottom are PODE_6-10The material (1-5); the material (1-2) at the top of the first rectifying tower (1-A) enters a third rectifying tower (1-C), the third rectifying tower (1-C) introduces make-up water (1-6), and the material (1-8) of the aqueous solution of formaldehyde and trioxymethylene is extracted from the tower bottom of the third rectifying tower (1-C); feeding the material (1-7) at the top of the third rectifying tower (1-C) into a fourth rectifying tower (1-D), and collecting the material (1-9) of methyl formate at the top of the fourth rectifying tower (1-D); feeding the tower bottom materials (1-10) of the fourth rectifying tower (1-D) into a fifth rectifying tower (1-E), and collecting materials (1-11) of methylal and methanol from the tower top of the fifth rectifying tower (1-E); feeding tower bottom materials (1-12) of a fifth rectifying tower (1-E) into a dehydration unit (1-F), and removing moisture (1-13); the materials (1-14) after water removal enter a sixth rectifying tower (1-G), the materials (1-15) of methanol extracted from the tower top and the PODE are taken as the tower bottom₂The materials (1-16).

1800t/h PODEN synthesis product mixture, composition as follows:

numbering	Components	Content%
			1	Formic acid methyl ester	1.80
2	Methylal	36.66
			3	Methanol	5.19
4	Formaldehyde (I)	9.08
			5	Water (W)	1.17
6	Trioxymethylene	2.50
			7	PODE₂	20.96
8	PODE_3-5	20.03
			9	PODE_6-10	2.41

By adopting the method scheme 1 for separation, the operating pressure of a first rectifying tower (1-A) is 100KPa, the operating temperature of the top of the tower is 90 ℃, the operating pressure of a second rectifying tower (1-B) is 1KPa, the operating temperature of the top of the tower is 52 ℃, the operating pressure of a third rectifying tower (1-C) is 100KPa, the mass ratio of the amount of the supplementing water (1-6) to the material (1-2) is 0.4:1, the operating temperature of the top of the tower is 80 ℃, the operating pressure of a fourth rectifying tower (1-D) is 100KPa, the operating temperature of the top of the tower is 32 ℃, the operating pressure of a fifth rectifying tower (1-E) is 100KPa, the operating temperature of the top of the tower is 40 ℃, a membrane dehydration unit (1-F) is adopted for dehydration, the operating pressure of a sixth rectifying tower (1-G) is 100KPa, and the operating temperature of the top of the tower is 64 ℃.

Separating to obtain 32t/h of methyl formate, methylal and methanol materials 670t/h and 377t/h of PODE₂PODE of 360t/h_3-5Qualified products and a formaldehyde water solution with the mass fraction of about 466t/h of about 35 percent are recovered.

Example 2

In fig. 2, 2-A is a first rectifying tower, 2-B is a second rectifying tower, 2-C is a third rectifying tower, 2-D is a fourth rectifying tower, 2-E is a fifth rectifying tower, 2-F is a dehydration unit, and 2-G is a sixth rectifying tower.

The tower kettle outlet of the first rectifying tower 2-A is connected with the feed inlet of the second rectifying tower 2-B through a pipeline, the tower top outlet of the first rectifying tower 2-A is connected with the feed inlet of the third rectifying tower 2-C through a pipeline, the tower top outlet of the third rectifying tower 2-C is connected with the feed inlet of the fourth rectifying tower 2-D through a pipeline, the tower top discharge port of the fourth rectifying tower 2-D is connected with the feed inlet of the fifth rectifying tower 2-E through a pipeline, the tower kettle discharge port of the fourth rectifying tower 2-D is connected with the feed inlet of the dehydration unit 2-F through a pipeline, and the discharge port of the dehydration unit 2-F is connected with the feed inlet of the sixth rectifying tower 2-G.

Make-up water may enter the third rectification column 2-C together with the overhead discharge of the first rectification column 2-a, or be added separately, if make-up water is added separately, a make-up water feed inlet may be provided additionally on the third rectification column 2-C.

The material 2-1 is PODEN to-be-refined raw material, and the material 2-2 is PODE-free_3-102-3 is PODE_3-102-4 is PODE_3-52-5 is PODE_6-102-6 is pure water material, 2-7 is methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE₂2-8 is a formaldehyde aqueous solution and a trioxymethylene material, 2-9 is a methyl formate, methylal and methanol material, and 2-10 is PODE₂Water and methanol, 2-11 is methyl formate, 2-12 is methylal and methanol, 2-13 is water, 2-14 is methanol and PODE₂Materials 2-15 are methanol materials, 2-16 are PODE₂And (3) feeding.

PODEN raw material (2-1) enters a first rectifying tower (2-A), and methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE are extracted from the top of the first rectifying tower (2-A)₂The material (2-2); the material (2-3) at the bottom of the first rectifying tower (2-A) enters a second rectifying tower (2-B), and PODE is extracted from the top of the second rectifying tower (2-B)_3-5The material (2-4) and the tower bottom are PODE_6-102-5); the material (2-2) at the top of the first rectifying tower (2-A) enters a third rectifying tower (2-C), the third rectifying tower (2-C) introduces make-up water (2-6), and the material (2-8) of the aqueous solution of formaldehyde and trioxymethylene is extracted from the tower bottom of the third rectifying tower (2-C); the material (2-7) at the top of the third rectifying tower (2-C) enters a fourth rectifying tower (2-D), and the material (2-9) of methyl formate, methylal and methanol is extracted from the top of the fourth rectifying tower (2-D); feeding the material (2-9) at the top of the fourth rectifying tower (2-D) into a fifth rectifying tower (2-E), and collecting the material (2-11) of methyl formate at the top of the fifth rectifying tower (2-E) and the material (2-12) of methylal and methanol at the bottom of the fifth rectifying tower (2-E); the tower bottom material (2-10) of the fourth rectifying tower (2-D) enters a dehydration unit (2-F), and moisture (13) is removed; the material (2-14) after water removal enters a sixth rectifying tower (2-G), the material (2-15) of methanol extracted from the tower top and the PODE (dimethyl ether dehydrogenase) at the tower bottom are₂2-16.

2400t/h PODEN synthesis product mixture, composition as follows:

numbering	Components	Content%
				1	Formic acid methyl ester	1.80
2	Methylal	36.66
			3	Methanol	5.19
4	Formaldehyde (formol)	9.08
			5	Water (W)	1.17
6	Trioxymethylene	2.50
			7	PODE₂	20.96
8	PODE_3-5	20.03
			9	PODE_6-10	2.41

By adopting the method scheme 2 for separation, the operating pressure of a first rectifying tower (2-A) is 100KPa, the operating temperature of the top of the tower is 90 ℃, the operating pressure of a second rectifying tower (2-B) is 1KPa, the operating temperature of the top of the tower is 52 ℃, the operating pressure of a third rectifying tower (2-C) is 100KPa, the mass ratio of the content of the supplementary water (2-6) to the material (2-2) is 0.3:1, the operating temperature of the top of the tower is 80 ℃, the operating pressure of a fourth rectifying tower (2-D) is 100KPa, the operating temperature of the top of the tower is 40 ℃, the operating pressure of a fifth rectifying tower (2-E) is 100KPa, the operating temperature of the top of the tower is 32 ℃, a dehydration unit (2-F) adopts a molecular sieve for dehydration, the operating pressure of a sixth rectifying tower (2-G) is 100KPa, and the operating temperature of the top of the tower is 64 ℃.

42t/h of methyl formate, methylal and methanol materials are obtained by separation, wherein 893t/h and 503t/h of PODE are obtained₂PODE of 480t/h_3-5Qualified products and the formaldehyde water solution with the mass fraction of about 33 percent at 660t/h are recovered.

Example 3

In FIG. 3, 3-A is a first rectifying tower, 3-B is a second rectifying tower, 3-C is a third rectifying tower, 3-D is a fourth rectifying tower, 3-E is a fifth rectifying tower, 3-F is a dehydration unit, and 3-G is a sixth rectifying tower.

The tower kettle outlet of the first rectifying tower 3-A is connected with the feed inlet of the second rectifying tower 3-B through a pipeline, the tower top outlet of the first rectifying tower 3-A is connected with the feed inlet of the third rectifying tower 3-C through a pipeline, the tower top outlet of the third rectifying tower 3-C is connected with the feed inlet of the fourth rectifying tower 3-D through a pipeline, the tower kettle discharge port of the third rectifying tower 3-C is connected with the feed inlet of the fifth rectifying tower 3-E through a pipeline, the tower top discharge port of the fifth rectifying tower 3-E is connected with the feed inlet of the dehydration unit 3-F through a pipeline, and the discharge port of the dehydration unit 3-F is connected with the feed inlet of the sixth rectifying tower 3-G.

The make-up water may be fed to the third rectification column 3-C together with the top discharge from the first rectification column 3-a, or may be fed separately, if the make-up water is fed separately, it is necessary to additionally provide a make-up water feed inlet in the third rectification column 3-C.

Material 3-1 is PODEN to be refined, and material 3-2 is PODE-free_3-103-3 is PODE_3-103-4 is PODE_3-53-5 is PODE_6-103-6 is pure water material, 3-7 is methyl formate, methylal and methanol material, 3-8 is methanol, formaldehyde, water, trioxymethylene and PODE₂3-9 is methyl formate, 3-10 is methylal and methanol, 3-11 is water and PODE₂And methanol, 3-12 are aqueous formaldehyde solution and trioxymethylene, 3-13 are aqueous materials, and 3-14 are methanol and PODE₂Materials, 3-15 are methanol materials, 3-16 are PODE₂And (3) feeding.

PODEN raw material (3-1) enters a first rectifying tower (3-A), and methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE are extracted from the top of the first rectifying tower (3-A)₂The material (3-2); the material (3-3) at the bottom of the first rectifying tower (3-A) enters a second rectifying tower (3-B), and PODE is extracted from the top of the second rectifying tower (3-B)_3-5The material (3-4) and the tower bottom are PODE_6-103-5); the material (3-2) at the top of the first rectifying tower (3-A) enters a third rectifying tower (3-C), the third rectifying tower (3-C) introduces make-up water (3-6), and the material (3-7) of methyl formate, methylal and methanol is extracted from the top of the third rectifying tower (3-C); feeding the material (3-7) at the top of the third rectifying tower (3-C) into a fourth rectifying tower (3-D), and collecting the material (3-9) of methyl formate at the top of the fourth rectifying tower (3-D) and the material (3-10) of methylal and methanol at the bottom of the fourth rectifying tower (3-D); feeding the tower bottom material (3-8) of the third rectifying tower (3-C) into a fifth rectifying tower (3-E), and extracting a formaldehyde water solution and a trioxymethylene material (3-12) from the tower bottom of the fifth rectifying tower (3-E); the material (3-11) at the top of the fifth rectifying tower (3-E) enters a dehydration unit (3-F), and the moisture (3-13) is removed; the material (3-14) after water removal enters a sixth rectifying tower (C)3-G), the material (3-15) of methanol extracted from the tower top and the PODE in the tower bottom₂3-16.

2700t/h PODEN synthesis product mixture, composition as follows:

number of	Components	Content%
				1	Formic acid methyl ester	1.80
2	Methylal compound	36.66
			3	Methanol	5.19
4	Formaldehyde (I)	9.08
			5	Water (W)	1.17
6	Trioxymethylene	2.50
			7	PODE₂	20.96
8	PODE_3-5	20.03
			9	PODE_6-10	2.41

By adopting the method scheme 3 for separation, the operating pressure of a first rectifying tower (3-A) is 100KPa, the operating temperature of the top of the tower is 90 ℃, the operating pressure of a second rectifying tower (3-B) is 50KPa, the operating temperature of the top of the tower is 144 ℃, the operating pressure of a third rectifying tower (3-C) is 100KPa, the mass ratio of the amount of the supplementing water (3-6) to the material (3-2) is 0.5:1, the operating temperature of the top of the tower is 80 ℃, the operating pressure of a fourth rectifying tower (3-D) is 200KPa, the operating temperature of the top of the tower is 51 ℃, the operating pressure of a fifth rectifying tower (3-E) is 100KPa, the operating temperature of the top of the tower is 80 ℃, the dehydrating unit (3-F) adopts adsorption dehydration, the operating pressure of a sixth rectifying tower (3-G) is 100KPa, and the operating temperature of the top of the tower is 64 ℃.

48t/h of methyl formate, methylal and methanol materials 1004t/h and 566t/h of PODE are obtained by separation₂PODE of 540t/h_3-5Qualified products and the formaldehyde water solution with the mass fraction of 875t/h about 28 percent are recovered.

Example 4

In FIG. 4, 4-A is a first rectifying tower, 4-B is a second rectifying tower, 4-C is a third rectifying tower, 4-D is a fourth rectifying tower, 4-E is a fifth rectifying tower, 4-F is a dehydration unit, and 4-G is a sixth rectifying tower.

The tower kettle outlet of the first rectifying tower 4-A is connected with the feed inlet of the second rectifying tower 4-B through a pipeline, the tower top outlet of the first rectifying tower 4-A is connected with the feed inlet of the third rectifying tower 4-C through a pipeline, the tower kettle outlet of the third rectifying tower 4-C is connected with the feed inlet of the fourth rectifying tower 4-D through a pipeline, the tower kettle discharge outlet of the fourth rectifying tower 4-D is connected with the feed inlet of the fifth rectifying tower 4-E through a pipeline, the tower top discharge outlet of the fifth rectifying tower 4-E is connected with the feed inlet of the dewatering unit 4-F through a pipeline, and the discharge outlet of the dewatering unit 4-F is connected with the feed inlet of the sixth rectifying tower 4-G.

The make-up water may be fed to the third rectification column 4-C together with the overhead discharge from the first rectification column 4-a, or may be fed separately, if the make-up water is fed separately, it may be necessary to provide an additional make-up water feed inlet in the third rectification column 4-C.

The material 4-1 is PODEN to-be-refined raw material, and the material 4-2 is PODE-free_3-104-3 is PODE_3-104-4 is PODE_3-54-5 is PODE_6-104-6 is pure water material, 4-7 is methyl formate material, 4-8 is methylal, methanol, formaldehyde, water, trioxymethylene and PODE₂4-9 is materials of methylal and methanol, 4-10 is materials of methanol, water, formaldehyde, trioxymethylene and PODE₂4-11 is water, PODE₂And methanol, 4-12 is a material of formaldehyde aqueous solution and trioxymethylene, 4-13 is a material of water, 4-14 is methanol and PODE₂Materials, 4-15 are methanol materials, 4-16 are PODE₂And (3) feeding.

PODEN raw material (4-1) enters a first rectifying tower (4-A), and methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE are extracted from the top of the first rectifying tower (4-A)₂The material (4-2); the material (4-3) at the bottom of the first rectifying tower (4-A) enters a second rectifying tower (4-B), and PODE is extracted from the top of the second rectifying tower (4-B)_3-5The material (4-4) and the tower bottom are PODE_6-104-5); the material (4-2) at the top of the first rectifying tower (4-A) enters a third rectifying tower (4-C), the third rectifying tower (4-C) introduces make-up water (4-6), and the material (4-7) of methyl formate is extracted from the top of the third rectifying tower (4-C); feeding tower bottom materials (4-8) of the third rectifying tower (4-C) into a fourth rectifying tower (4-D), and extracting materials (4-9) of methylal and methanol from the tower top of the fourth rectifying tower (4-D); feeding the tower bottom material (4-10) of the fourth rectifying tower (4-D) into a fifth rectifying tower (4-E), and extracting the material (4-12) which is basically formaldehyde water solution and trioxymethylene from the tower bottom of the fifth rectifying tower (4-E); the material (4-11) at the top of the fifth rectifying tower (4-E) enters a dehydration unit (4-F), removing water (4-13); the material (4-14) after water removal enters a sixth rectifying tower (4-G), the material (4-15) of methanol extracted from the tower top and the PODE in the tower bottom₂The material (4-16).

2400t/h PODEN synthesis product mixture, composition as follows:

By adopting the method scheme 4 for separation, the operating pressure of a first rectifying tower (4-A) is 100KPa, the operating temperature of the top of the tower is 90 ℃, the operating pressure of a second rectifying tower (4-B) is 1KPa, the operating temperature of the top of the tower is 52 ℃, the operating pressure of a third rectifying tower (4-C) is 100KPa, the mass ratio of the content of the supplementary water (4-6) to the material (4-2) is 0.3:1, the operating temperature of the top of the tower is 32 ℃, the operating pressure of a fourth rectifying tower (4-D) is 100KPa, the operating temperature of the top of the tower is 40 ℃, the operating pressure of a fifth rectifying tower (4-E) is 100KPa, the operating temperature of the top of the tower is 80 ℃, a dehydration unit (4-F) adopts a molecular sieve for dehydration, the operating pressure of a sixth rectifying tower (4-G) is 100KPa, and the operating temperature of the top of the tower is 64 ℃.

Example 5

In FIG. 5, 5-A is a first rectifying tower, 5-B is a second rectifying tower, 5-C is a third rectifying tower, 5-D is a fourth rectifying tower, 5-E is a fifth rectifying tower, 5-F is a dehydration unit, and 5-G is a sixth rectifying tower;

the tower kettle outlet of the first rectifying tower 5-A is connected with the feed inlet of the second rectifying tower 5-B through a pipeline, the tower top outlet of the first rectifying tower 5-A is connected with the feed inlet of the third rectifying tower 5-C through a pipeline, the tower kettle outlet of the third rectifying tower 5-C is connected with the feed inlet of the fourth rectifying tower 5-D through a pipeline, the tower top discharge port of the fourth rectifying tower 5-D is connected with the feed inlet of the fifth rectifying tower 5-E through a pipeline, the tower kettle discharge port of the fifth rectifying tower 5-E is connected with the feed inlet of the dehydrating unit 5-F through a pipeline, and the discharge port of the dehydrating unit 5-F is connected with the feed inlet of the sixth rectifying tower 5-G.

Make-up water may be fed to the third rectification column 5-C together with the overhead discharge from the first rectification column 5-a, or may be fed separately, if the make-up water is fed separately, it may be necessary to provide an additional make-up water feed inlet in the third rectification column 5-C.

Material 5-1 is PODEN to be refined raw material, 5-2 is PODE-free_3-105-3 is PODE_3-105-4 is PODE_3-55-5 is PODE_6-105-6 is pure water material, 5-7 is methyl formate material, 5-8 is methylal, methanol, formaldehyde, water, trioxymethylene and PODE₂5-9 of methylal, methanol, water and PODE₂5-10 of aqueous solution of formaldehyde and trioxymethylene, 5-11 of methylal and methanol, 5-12 of methanol, water and PODE₂5-13 is water material, 5-14 is methanol and PODE₂Material, 5-15 is methanol material, 5-16 is PODE₂And (3) feeding.

PODEN raw material (5-1) enters a first rectifying tower (5-A), and methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE are extracted from the top of the first rectifying tower (5-A)₂The material (5-2); the material (5-3) at the bottom of the first rectifying tower (5-A) enters a second rectifying tower (5-B), and PODE is extracted from the top of the second rectifying tower (5-B)_3-5The material (5-4) and the tower bottom are PODE_6-105-5); the material (5-2) at the top of the first rectifying tower (5-A) enters a third rectifying tower (5-C), and simultaneously, the third rectifying tower (5-C) introduces make-up water (5-6), and the material (5-7) of methyl formate is extracted from the top of the third rectifying tower (5-C); feeding the tower bottom material (5-8) of the third rectifying tower (5-C) into a fourth rectifying tower (5-D), and extracting a formaldehyde water solution and a trioxymethylene material (5-10) from the tower bottom of the fourth rectifying tower (5-D); the material (5-9) at the top of the fourth rectifying tower (5-D) enters a fifth rectifying tower (5-E), and the material (5-11) of methylal and methanol is extracted from the top of the fifth rectifying tower (5-E)(ii) a Feeding tower bottom materials (5-12) of a fifth rectifying tower (5-E) into a dehydration unit (5-F), and removing moisture (5-13); the material (5-14) after water removal enters a sixth rectifying tower (5-G), the material (5-15) of methanol extracted from the tower top and the PODE in the tower bottom₂5-16.

1800t/h PODEN synthesis product mixture, composition as follows:

By adopting the method scheme 5 for separation, the operating pressure of a first rectifying tower (5-A) is 100KPa, the operating temperature of the top of the tower is 90 ℃, the operating pressure of a second rectifying tower (5-B) is 1KPa, the operating temperature of the top of the tower is 52 ℃, the operating pressure of a third rectifying tower (5-C) is 100KPa, the mass ratio of the amount of the supplementing water (5-6) to the material (5-2) is 0.4:1, the operating temperature of the top of the tower is 32 ℃, the operating pressure of a fourth rectifying tower (5-D) is 100KPa, the operating temperature of the top of the tower is 80 ℃, the operating pressure of a fifth rectifying tower (5-E) is 100KPa, the operating temperature of the top of the tower is 40 ℃, a membrane dehydration unit (5-F) is adopted for dehydration, the operating pressure of a sixth rectifying tower (5-G) is 100KPa, and the operating temperature of the top of the tower is 64 ℃.

The invention provides a method for preparing methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE₂The method and the device for separating and refining the polymethoxy dimethyl ether by introducing the make-up water into the rectifying tower of the mixed material have been described by the preferred embodiments, and it is obvious for the related technical personnel to modify or change the structure and the equipment described in the text without departing from the content, the spirit and the scope of the inventionThe present technology can be implemented with appropriate modifications and combinations. It is expressly intended that all such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and content of the invention.

Claims

1. A separation method of polymethoxy dimethyl ether is characterized in that: the polyoxymethylene dimethyl ether is prepared by taking methanol and formaldehyde aqueous solution as raw materials, PODEN raw material enters a first rectifying tower, and methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE are extracted from the top of the first rectifying tower₂The mixed materials of (1); the material at the bottom of the first rectifying tower enters a second rectifying tower, and PODE is extracted from the top of the second rectifying tower_3-5The material and the tower bottom are PODE_6-10The material (2); feeding the material at the top of the first rectifying tower into a third rectifying tower, and introducing make-up water into the third rectifying tower;

the method specifically comprises five parallel technical schemes:

the first scheme is as follows: adopting six-stage rectification, feeding PODEN raw material into first rectification tower, and extracting methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE from tower top of first rectification tower₂The mixed materials of (1); the material at the bottom of the first rectifying tower enters a second rectifying tower, and PODE is extracted from the top of the second rectifying tower_3-5The material and the tower bottom are PODE_6-10The material (2); feeding the material at the top of the first rectifying tower into a third rectifying tower, introducing make-up water into the third rectifying tower, wherein the mass ratio of the added amount of the make-up water to the fed material is 0.2: 1-1: 1 by weight, and extracting a mixed material of a formaldehyde water solution and trioxymethylene from the tower kettle of the third rectifying tower; feeding the material at the top of the third rectifying tower into a fourth rectifying tower, and extracting the material which is methyl formate at the top of the fourth rectifying tower; feeding the tower bottom material of the fourth rectifying tower into a fifth rectifying tower, and extracting a mixed material of methylal and methanol from the tower top of the fifth rectifying tower; the tower bottom material of the fifth rectifying tower enters a dehydration unit, the material after water removal enters a sixth rectifying tower, the material of methanol is extracted from the tower top of the sixth rectifying tower, and PODE is extracted from the tower bottom₂Wherein the operating pressure of the first rectifying tower is 80-120KPa, and 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 operating pressure of the third rectifying tower is 80-120KPa, the operating temperature of the tower top is 70-120 ℃, the mass ratio of the supplementary water content to the materials in weight is 0.2: 1-1: 1, the operating pressure of the fourth rectifying tower is 100-;

scheme two is as follows: adopting six-stage rectification, feeding PODEN raw material into first rectification tower, and extracting methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE from tower top of first rectification tower₂The mixed material of (1); the material at the bottom of the first rectifying tower enters a second rectifying tower, and PODE is extracted from the top of the second rectifying tower_3-5The material and the tower bottom are PODE_6-10The material (2); feeding the material at the top of the first rectifying tower into a third rectifying tower, introducing make-up water into the third rectifying tower, wherein the mass ratio of the added amount of the make-up water to the fed material is 0.2: 1-1: 1 by weight, and extracting a mixed material of a formaldehyde water solution and trioxymethylene from the tower kettle of the third rectifying tower; the material at the top of the third rectifying tower enters a fourth rectifying tower, and the mixed material of methyl formate, methylal and methanol is extracted from the top of the fourth rectifying tower; feeding the material at the top of the fourth rectifying tower into a fifth rectifying tower, and extracting a material of methyl formate at the top of the fifth rectifying tower and a mixed material of methylal and methanol at the bottom of the fifth rectifying tower; feeding the tower bottom material of the fourth rectifying tower into a dehydration unit; the material after water removal enters a sixth rectifying tower, the material of methanol is extracted from the tower top of the sixth rectifying tower, and PODE is extracted from the tower bottom₂Wherein the operation pressure of the first rectifying tower is 80-120KPa, the operation temperature of the tower top is 70-100 ℃, the operation pressure of the second rectifying tower is 1-50KPa, the operation temperature of the tower top is 50-150 ℃, the operation pressure of the third rectifying tower is 80-120KPa, the operation temperature of the tower top is 70-120 ℃, the mass ratio of the supplementary water content to the materials is 0.2: 1-1: 1, the operation pressure of the fourth rectifying tower is 100-At 60 ℃, the dehydration unit is membrane dehydration or molecular sieve dehydration, the operation pressure of the sixth rectifying tower is 100-200KPa, and the operation temperature at the top of the tower is 60-90 ℃;

the third scheme is as follows: adopting six-stage rectification, feeding PODEN raw material into first rectification tower, and extracting methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE from tower top of first rectification tower₂The mixed materials of (1); the material at the bottom of the first rectifying tower enters a second rectifying tower, and PODE is extracted from the top of the second rectifying tower_3-5The material and the tower bottom are PODE_6-10The material (2); feeding the material at the top of the first rectifying tower into a third rectifying tower, introducing make-up water into the third rectifying tower, wherein the mass ratio of the addition amount of the make-up water to the feeding amount is 0.2: 1-1: 1, and extracting a mixed material of methyl formate, methylal and methanol from the top of the third rectifying tower; feeding the material at the top of the third rectifying tower into a fourth rectifying tower, and extracting a material of methyl formate at the top of the fourth rectifying tower and a mixed material of methylal and methanol at the bottom of the fourth rectifying tower; feeding the tower bottom material of the third rectifying tower into a fifth rectifying tower, and collecting the material of formaldehyde water solution and trioxymethylene from the tower bottom of the fifth rectifying tower; the material at the top of the fifth rectifying tower enters a dehydration unit, the material after water removal enters a sixth rectifying tower, the material of methanol is extracted from the top of the sixth rectifying tower, and PODE is adopted at the tower bottom₂The 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 operating pressure of the third rectifying tower is 100-200KPa, the operating temperature of the tower top is 35-70 ℃, the mass ratio of the supplementary water content to the materials is 0.2: 1-1: 1, the operating pressure of the fourth rectifying tower is 100-200KPa, the operating temperature of the tower top is 30-60 ℃, the operating pressure of the fifth rectifying tower is 80-120KPa, the operating temperature of the tower top is 70-120 ℃, the dehydrating unit is membrane dehydration or molecular sieve dehydration, the operating pressure of the sixth rectifying tower is 80-120KPa, and the operating temperature of the tower top is 60-90 ℃;

and the scheme is as follows: adopting six-stage rectification, feeding PODEN raw material into first rectification tower, and extracting methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE from tower top of first rectification tower₂The mixed materials of (1); first rectifying tower bottomFeeding the material into a second rectifying tower, and extracting PODE from the top of the second rectifying tower_3-5The material and the tower bottom are PODE_6-10The material (2); feeding the material at the top of the first rectifying tower into a third rectifying tower, introducing make-up water into the third rectifying tower at the same time, wherein the mass ratio of the addition amount of the make-up water to the feeding amount is 0.2: 1-1: 1, and extracting the material of methyl formate at the top of the third rectifying tower; the tower bottom material of the third rectifying tower enters a fourth rectifying tower, and a mixed material of methylal and methanol is extracted from the tower top of the fourth rectifying tower; feeding the tower bottom material of the fourth rectifying tower into a fifth rectifying tower, and collecting a mixed material of a formaldehyde water solution and trioxymethylene from the tower bottom of the fifth rectifying tower; feeding the material at the top of the fifth rectifying tower into a dehydration unit, feeding the material subjected to water removal into a sixth rectifying tower, collecting the material which is methanol at the top of the sixth rectifying tower, and feeding PODE (potassium iodide) at the tower bottom of the sixth rectifying tower₂The 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 operating pressure of the third rectifying tower is 100-200KPa, the operating temperature of the tower top is 30-60 ℃, the mass ratio of the supplementary water content to the materials is 0.2: 1-1: 1, 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 of the tower top is 70-120 ℃, the dehydrating unit is membrane dehydration or molecular sieve dehydration, the operating pressure of the sixth rectifying tower is 80-120KPa, and the operating temperature of the tower top is 60-90 ℃;

and a fifth scheme: adopting six-stage rectification, feeding PODEN raw material into first rectification tower, and extracting methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE from tower top of first rectification tower₂The mixed materials of (1); the material at the bottom of the first rectifying tower enters a second rectifying tower, and PODE is extracted from the top of the second rectifying tower_3-5The material and the tower bottom are PODE_6-10The material (2); feeding the material at the top of the first rectifying tower into a third rectifying tower, introducing make-up water into the third rectifying tower at the same time, wherein the mass ratio of the addition amount of the make-up water to the feeding amount is 0.2: 1-1: 1, and extracting the material of methyl formate at the top of the third rectifying tower; the material at the tower bottom of the third rectifying tower enters a fourth rectifying tower, and the material at the tower bottom of the fourth rectifying tower is formaldehyde aqueous solution anda mixed material of trioxymethylene; feeding the material at the top of the fourth rectifying tower into a fifth rectifying tower, and extracting a mixed material of methylal and methanol from the top of the fifth rectifying tower; the tower bottom material of the fifth rectifying tower enters a dehydration unit, the material after water removal enters a sixth rectifying tower, the material of methanol is extracted from the tower top of the sixth rectifying tower, and the tower bottom is PODE₂Wherein the operation pressure of the first rectifying tower is 80-120KPa, the operation temperature of the tower top is 70-100 ℃, the operation pressure of the second rectifying tower is 1-50KPa, the operation temperature of the tower top is 50-150 ℃, the operation pressure of the third rectifying tower is 100-200KPa, the operation temperature of the tower top is 30-60 ℃, the mass ratio of the supplementary water content to the materials is 0.2: 1-1: 1, the operation pressure of the fourth rectifying tower is 80-120KPa, the operation temperature of the tower top is 70-120 ℃, the operation pressure of the fifth rectifying tower is 100-200KPa, the operation temperature of the tower top is 35-70 ℃, the dehydration unit is membrane dehydration or molecular sieve dehydration, the operation pressure of the sixth rectifying tower is 100-200KPa, and the operation temperature of the tower top is 60-90 ℃.