CN109761766B

CN109761766B - Separation process of polyoxymethylene dimethyl ether system containing formaldehyde

Info

Publication number: CN109761766B
Application number: CN201910095539.2A
Authority: CN
Inventors: 李鑫钢; 任远洋; 廉景燕; 韩振为
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: 2022-07-15
Anticipated expiration: 2039-01-31
Also published as: CN109761766A

Abstract

The invention provides a separation process of a polyoxymethylene dimethyl ether system containing formaldehyde, which adopts multi-stage rectification, introduces water into a rectifying tower containing formaldehyde at any stage, and enables the formaldehyde to be extracted from a tower kettle in the form of aqueous solution, thereby realizing the purpose of separating the formaldehyde. The process may employ different separation sequences. The formaldehyde separated by the process can not be polymerized to block condensers and pipelines, the use continuity of equipment is improved, and unreacted raw materials of formaldehyde, and reaction byproducts of methyl formate and PODE (dimethyl formiate) can be effectively recovered₂And the like.

Description

Separation process of polyoxymethylene dimethyl ether system containing formaldehyde

Technical Field

The invention belongs to the technical field of chemical engineering, relates to a separation technology for a synthetic product mixture of polyoxymethylene dimethyl ethers synthesized by using multistage rectification to separate methanol and formaldehyde water solution, and particularly relates to a separation process of a polyoxymethylene dimethyl ether system containing formaldehyde.

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 and generally less than 10), has higher oxygen content (42-51%) and cetane number (average value is up to 76), and PODE (peroxidase)_3-5Is the most ideal diesel oil additive, and PODE is added into the diesel oil_3-5Can effectively reduce the emission of soot and Particulate Matters (PM) of the diesel engine and improve the fuel economy. PODEn is a homologue component formed from the etherification end group-providing starting material and the methoxy group-providing starting material via polycondensation under acid catalysis. The compounds providing the terminal group include methanol, dimethyl ether, methylal, etc., and the compounds providing the methoxy group include formaldehyde, trioxane, 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, US 20080221368, US 7671240 and US 7700809) of BASF company have the disadvantages of low single-pass conversion rate, complex separation process, large 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 separation process of a polyoxymethylene dimethyl ether system containing formaldehyde. Separating the synthetic 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 to the first and second stage reaction processes.

A separation process of a polyoxymethylene dimethyl ether system containing formaldehyde adopts multi-stage rectification, water is introduced into a rectification tower containing formaldehyde at any stage, and the formaldehyde is extracted from a tower kettle in the form of aqueous solution, thereby realizing the purpose of separating the formaldehyde.

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

And the mass ratio of the addition amount of the make-up water to the feeding is 0.2: 1-1: 1.

A multi-stage separation device for polymethoxy dimethyl ether comprises a multi-stage rectifying tower, wherein a make-up water inlet is arranged on the rectifying tower of which any stage material contains formaldehyde.

And the dehydration unit comprises membrane dehydration, molecular sieve dehydration and adsorption dehydration.

The separation process of the polyoxymethylene dimethyl ether system containing formaldehyde comprises six rectifying towers and a dehydration unit.

The scheme comprises the following 4 parallel schemes:

the first scheme is as follows: introducing make-up water (1-10) into a fifth rectifying tower (1-E), and extracting materials (1-12) of formaldehyde water solution and trioxymethylene from the tower bottom of the fifth rectifying tower (1-E); materials (1-11) at the top of the fifth rectifying tower (1-E) enter a dehydration unit (1-F), and moisture (1-13) is removed; the materials (1-14) after water removal enter a sixth rectifying tower (1-G), the materials (1-15) of methanol are extracted from the tower top and PODE is extracted from the tower bottom₂The material (1-16);

the scheme comprises the following 3 separation processes:

scheme 1: feeding PODEN raw material (1- (1) -1) into a first rectifying tower (1- (1) -A), and collecting a material (1- (1) -2) of methyl formate at the tower top of the first rectifying tower (1- (1) -A); the tower bottom material (1- (1) -3) of the first rectifying tower (1- (1) -A) enters a second rectifying tower (1- (1) -B), and methylal, methanol, water, formaldehyde, trioxymethylene and PODE are extracted from the tower top of the second rectifying tower (1- (1) -B)₂The materials (1- (1) -4); the tower bottom materials (1- (1) -5) of the second rectifying tower (1- (1) -B) enter a third rectifying tower (1- (1) -C), and PODE is extracted from the top of the third rectifying tower (1- (1) -C)_3-5The material (1- (1) -6) and the tower bottom are PODE_6-10The materials (1- (1) -7); the material (1- (1) -4) at the top of the second rectifying tower (1- (1) -B) enters a fourth rectifying tower (1- (1) -D), and the material (1- (1) -8) of methylal and methanol is extracted from the top of the fourth rectifying tower (1- (1) -D); feeding tower bottom materials (1- (1) -9) of the fourth rectifying tower (1- (1) -D) into a fifth rectifying tower (1-E);

and (2) a flow scheme: PODEN raw material (1- (2) -1) enters a first rectifying tower (1- (2) -A), and methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE are extracted from the top of the first rectifying tower (1- (2) -A)₂The material (1- (2) -2); the material (1- (2) -3) at the bottom of the first rectifying tower (1- (2) -A) enters a second rectifying tower (1- (2) -B), and PODE is extracted from the top of the second rectifying tower (1- (2) -B)_3-5The material (1- (2) -4) and the tower bottom are PODE_6-10The materials (1- (2) -5); the material (1- (2) -2) at the top of the first rectifying tower (1- (2) -A) enters a third rectifying tower(1- (2) -C), and collecting materials (1- (2) -6) of methyl formate, methylal and methanol from the top of the third rectifying tower (1- (2) -C); materials (1- (2) -6) at the top of the third rectifying tower (1- (2) -C) enter a fourth rectifying tower (1- (2) -D), materials (1- (2) -8) of methyl formate and materials (1- (2) -9) of methylal and methanol are extracted from the top of the fourth rectifying tower (1- (2) -D); the tower bottom materials (1- (2) -7) of the third rectifying tower (1- (2) -C) enter a fifth rectifying tower (1-E);

and (3) a flow path: PODEN raw material (1- (3) -1) enters a first rectifying tower (1- (3) -A), and methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE are extracted from the top of the first rectifying tower (1- (3) -A)₂The material (1- (3) -2); the material (1- (3) -3) at the bottom of the first rectifying tower (1- (3) -A) enters a second rectifying tower (1- (3) -B), and PODE is extracted from the top of the second rectifying tower (1- (3) -B)_3-5The material (1- (3) -4) and the tower bottom are PODE_6-10The materials (1- (3) -5); the material (1- (3) -2) at the top of the first rectifying tower (1- (3) -A) enters a third rectifying tower (1- (3) -C), and the material (1- (3) -6) which is methyl formate is extracted from the top of the third rectifying tower (1- (3) -C); feeding the tower bottom material (1- (3) -7) of the third rectifying tower (1- (3) -C) into a fourth rectifying tower (1- (3) -D), and collecting a material (1- (3) -8) of methylal and methanol at the tower top of the fourth rectifying tower (1- (3) -D); the tower bottom materials (1- (3) -9) of the fourth rectifying tower (1- (3) -D) enter a fifth rectifying tower (1-E);

scheme II: PODEN raw material (2-1) enters a first rectifying tower (2-A), and a material (2-2) of methyl formate is extracted from the top of the first rectifying tower (2-A); the tower bottom material (2-3) of the first rectifying tower (2-A) enters a second rectifying tower (2-B), and methylal, methanol, water, formaldehyde, trioxymethylene and PODE are extracted from the tower top of the second rectifying tower (2-B)₂2-4); the tower bottom material (2-5) of the second rectifying tower (2-B) enters a third rectifying tower (2-C), and PODE is extracted from the tower top of the third rectifying tower (2-C)_3-5The material (2-6) and the tower bottom are PODE_6-102-7); the material (2-4) at the top of the second rectifying tower (2-B) enters a fourth rectifying tower, and the fourth rectifying tower introduces supplementary water (2-8); the top or bottom liquid of the fifth rectifying tower enters a membrane dehydration unit (2-F), and the moisture (2-13) is removed; the material (2-14) after water removal enters a sixth rectifying tower (2-G), the material (2-15) of methanol is extracted from the tower top and PODE is extracted from the tower bottom₂2-16 of (A))；

The scheme comprises the following 2 separation processes:

scheme 1: materials (2- (1) -10) which are formaldehyde aqueous solution and trioxymethylene are extracted from the tower bottom of the fourth rectifying tower (2- (1) -D); materials (2- (1) -9) at the top of the fourth rectifying tower (2- (1) -D) enter a fifth rectifying tower (2- (1) -E), materials (2- (1) -11) of methylal and methanol are extracted from the top of the fifth rectifying tower (2- (1) -E), and tower bottoms (2- (1) -12) of the fifth rectifying tower enter a dehydration unit (2-F);

and (2) a process: the top of the fourth rectifying tower (2- (2) -D) is extracted to be a material (2- (2) -9) of methylal and methanol; feeding the materials (2- (2) -10) at the bottom of the fourth rectifying tower (2- (2) -D) into a fifth rectifying tower (2- (2) -E), and extracting materials (2- (2) -12) of formaldehyde water solution and trioxymethylene from the bottom of the fifth rectifying tower (2- (2) -E); feeding the tower top material (2- (2) -11) of the fifth rectifying tower (2- (2) -E) into a dehydration unit (2-F);

the third scheme is as follows: 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, and the third rectifying tower introduces make-up water (3-6); the top or bottom liquid of the fifth rectifying tower enters a membrane 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), the materials (3-15) of methanol are extracted from the tower top and PODE is extracted from the tower bottom₂The material (3-16);

the scheme comprises the following 5 separation processes:

scheme 1: the tower bottom of the third rectifying tower (3- (1) -C) extracts materials (3- (1) -8) of formaldehyde water solution and trioxymethylene; feeding the materials (3- (1) -7) at the top of the third rectifying tower (3- (1) -C) into a fourth rectifying tower (3- (1) -D), and collecting the materials (3- (1) -9) which are methyl formate at the top of the fourth rectifying tower (3- (1) -D); feeding the tower bottom material (3- (1) -10) of the fourth rectifying tower (3- (1) -D) into a fifth rectifying tower (3- (1) -E), and collecting a material (3- (1) -11) of methylal and methanol from the tower top of the fifth rectifying tower (3- (1) -E); feeding tower bottom materials (3- (1) -12) of the fifth rectifying tower (3- (1) -E) into a dehydration unit (3-F);

and (2) a flow scheme: materials (3- (2) -8) which are formaldehyde aqueous solution and trioxymethylene are extracted from the tower bottom of the third rectifying tower (3- (2) -C); materials (3- (2) -7) at the top of the third rectifying tower (3- (2) -C) enter a fourth rectifying tower (3- (2) -D), and materials (3- (2) -9) of methyl formate, methylal and methanol are extracted from the top of the fourth rectifying tower (3- (2) -D); materials (3- (2) -9) at the top of the fourth rectifying tower (3- (2) -D) enter a fifth rectifying tower (3- (2) -E), materials (3- (2) -11) which are methyl formate and materials (3- (2) -12) which are methylal and methanol at the bottom of the fifth rectifying tower (3- (2) -E) are extracted from the top of the fifth rectifying tower (3- (2) -E); the tower bottom material (3- (2) -10) of the fourth rectifying tower (3- (2) -D) enters a dehydration unit (3-F);

and (3) a flow path: the top of the third rectifying tower (3- (3) -C) produces materials (3- (3) -7) of methyl formate, methylal and methanol; the material (3- (3) -7) at the top of the third rectifying tower (3- (3) -C) enters a fourth rectifying tower (3- (3) -D), and the material (3- (3) -9) which is methyl formate and the material (3- (3) -10) which is methylal and methanol at the bottom of the fourth rectifying tower (3- (3) -D) are extracted from the top of the fourth rectifying tower (3- (3) -D); feeding the tower bottom materials (3- (3) -8) of the third rectifying tower (3- (3) -C) into a fifth rectifying tower (3- (3) -E), and extracting materials (3- (3) -12) of formaldehyde water solution and trioxymethylene from the tower bottom of the fifth rectifying tower (3- (3) -E); the tower top material (3- (3) -11) of the fifth rectifying tower (3- (3) -E) enters a dehydration unit (3-F);

and (4) a flow chart: a material (3- (4) -7) of methyl formate is extracted from the top of the third rectifying tower (3- (4) -C); feeding the tower bottom material (3- (4) -8) of the third rectifying tower (3- (4) -C) into a fourth rectifying tower (3- (4) -D), and collecting a material (3- (4) -9) of methylal and methanol from the tower top of the fourth rectifying tower (3- (4) -D); feeding the tower bottom materials (3- (4) -8) of the fourth rectifying tower (3- (4) -D) into a fifth rectifying tower (3- (4) -E), and extracting materials (3- (4) -12) of formaldehyde water solution and trioxymethylene from the tower bottom of the fifth rectifying tower (3- (4) -E); the material (3- (4) -11) at the top of the fifth rectifying tower (3- (4) -E) enters a dehydration unit (3-F);

scheme 5: a material (3- (5) -7) of methyl formate is extracted from the top of the third rectifying tower (3- (5) -C); feeding the tower bottom materials (3- (5) -8) of the third rectifying tower (3- (5) -C) into a fourth rectifying tower (3- (5) -D), and extracting materials (3- (5) -10) of formaldehyde water solution and trioxymethylene from the tower bottoms of the fourth rectifying tower (3- (5) -D); feeding the tower top material (3- (5) -9) of the fourth rectifying tower (3- (5) -D) into a fifth rectifying tower (3- (5) -E), and collecting a material (3- (5) -11) of methylal and methanol from the tower top of the fifth rectifying tower (3- (5) -E); feeding tower bottom materials (3- (5) -12) of the fifth rectifying tower (3- (5) -E) into a dehydration unit (3-F);

and the scheme is as follows: PODEN raw material (4-1) enters a first rectifying tower (4-A), make-up water (4-2) is introduced into the 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)₂4-3); the material (4-4) 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 (4-5) and the tower bottom are PODE_6-104-6); the material (4-3) at the top of the first rectifying tower (4-A) enters a third rectifying tower; the top or bottom liquid of the fifth rectifying tower enters a membrane 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 is extracted from the top of the tower, and PODE is extracted from the bottom of the tower₂The material (4-16);

the scheme comprises the following 5 separation processes:

scheme 1: the tower bottom of the third rectifying tower (4- (1) -C) extracts materials (4- (1) -8) of formaldehyde water solution and trioxymethylene; the material (4- (1) -7) at the top of the third rectifying tower (4- (1) -C) enters a fourth rectifying tower (4- (1) -D), and the material (4- (1) -9) which is methyl formate is extracted from the top of the fourth rectifying tower (4- (1) -D); feeding the tower bottom materials (4- (1) -10) of the fourth rectifying tower (4- (1) -D) into a fifth rectifying tower (4- (1) -E), and extracting materials (4- (1) -11) of methylal and methanol from the top of the fifth rectifying tower (4- (1) -E); feeding tower bottom materials (4- (1) -12) of the fifth rectifying tower (4- (1) -E) into a dehydration unit (4-F);

and (2) a process: the tower bottom of the third rectifying tower (4- (2) -C) extracts materials (4- (2) -8) of formaldehyde water solution and trioxymethylene; the material (4- (2) -7) at the top of the third rectifying tower (4- (2) -C) enters a fourth rectifying tower (4- (2) -D), and the material (4- (2) -9) of methyl formate, methylal and methanol is extracted from the top of the fourth rectifying tower (4- (2) -D); materials (4- (2) -9) at the top of the fourth rectifying tower (4- (2) -D) enter a fifth rectifying tower (4- (2) -E), and a material (4- (2) -11) of methyl formate and a material (4- (2) -12) of methylal and methanol are extracted from the top of the fifth rectifying tower (4- (2) -E); the tower bottom material (4- (2) -10) of the fourth rectifying tower (4- (2) -D) enters a dehydration unit (4-F);

and (3) a flow path: the material (4- (3) -7) of methyl formate, methylal and methanol is extracted from the top of the third rectifying tower (4- (3) -C); the material (4- (3) -7) at the top of the third rectifying tower (4- (3) -C) enters a fourth rectifying tower (4- (3) -D), and the material (4- (3) -9) which is methyl formate and the material (4- (3) -10) which is methylal and methanol at the bottom of the fourth rectifying tower (4- (3) -D) are extracted from the top of the fourth rectifying tower (4- (3) -D); feeding the tower bottom materials (4- (3) -8) of the third rectifying tower (4- (3) -C) into a fifth rectifying tower (4- (3) -E), and extracting materials (4- (3) -12) of formaldehyde water solution and trioxymethylene from the tower bottom of the fifth rectifying tower (4- (3) -E); the tower top material (4- (3) -11) of the fifth rectifying tower (4- (3) -E) enters a dehydration unit (4-F);

and (4) a flow chart: a material (4- (4) -7) of methyl formate is extracted from the top of the third rectifying tower (4- (4) -C); feeding the tower bottom material (4- (4) -8) of the third rectifying tower (4- (4) -C) into a fourth rectifying tower (4- (4) -D), and collecting a material (4- (4) -9) of methylal and methanol at the tower top of the fourth rectifying tower (4- (4) -D); feeding the tower bottom material (4- (4) -10) of the fourth rectifying tower (4- (4) -D) into a fifth rectifying tower (4- (4) -E), and extracting a material (4- (4) -12) of formaldehyde water solution and trioxymethylene from the tower bottom of the fifth rectifying tower (4- (4) -E); feeding the tower top material (4- (4) -11) of the fifth rectifying tower (4- (4) -E) into a dehydration unit (4-F);

and (5) a flow chart: a material (4- (5) -7) of methyl formate is extracted from the top of the third rectifying tower (4- (5) -C); feeding the tower bottom materials (4- (5) -8) of the third rectifying tower (4- (5) -C) into a fourth rectifying tower (4- (5) -D), and extracting materials (4- (5) -10) of formaldehyde water solution and trioxymethylene from the tower bottoms of the fourth rectifying tower (4- (5) -D); feeding the tower top material (4- (5) -9) of the fourth rectifying tower (4- (5) -D) into a fifth rectifying tower (4- (5) -E), and collecting a material (4- (5) -11) of methylal and methanol from the tower top of the fifth rectifying tower (4- (5) -E); feeding tower bottom materials (4- (5) -12) of the fifth rectifying tower (4- (5) -E) into a dehydration unit (4-F);

in the first scheme, the operating pressure of a fifth rectifying tower (1-E) is 80-120KPa, the tower top operating temperature is 70-120 ℃, the mass ratio of the content of the make-up water (1-10) to the feed of the fifth rectifying tower (1-E) is 0.3: 1-1: 1 by weight, a dehydration unit (1-F) can be membrane dehydration, molecular sieve dehydration and adsorption dehydration, the operating pressure of a sixth rectifying tower (1-G) is 100-200KPa, and the tower top operating temperature is 60-90 ℃;

in the process 1, the operation pressure of the first rectifying tower (1- (1) -A) is 100-200KPa, the operation temperature of the tower top is 30-60 ℃, the operation pressure of the second rectifying tower (1- (1) -B) is 80-120KPa, the operation temperature of the tower top is 70-100 ℃, the operation pressure of the third rectifying tower (1- (1) -C) is 1-50KPa, the operation temperature of the tower top is 50-150 ℃, the operation pressure of the fourth rectifying tower (1- (1) -D) is 100-200KPa, and the operation temperature of the tower top is 35-70 ℃;

in the process 2, the operation pressure of the first rectifying tower (1- (2) -A) is 80-120KPa, the operation temperature of the tower top is 70-100 ℃, the operation pressure of the second rectifying tower (1- (2) -B) is 1-50KPa, the operation temperature of the tower top is 50-150 ℃, the operation pressure of the third rectifying tower (1- (2) -C) is 100-200KPa, the operation temperature of the tower top is 35-70 ℃, the operation pressure of the fourth rectifying tower (1- (2) -D) is 100-200KPa, and the operation temperature of the tower top is 30-60 ℃;

in the process 3, the operation pressure of the first rectifying tower (1- (3) -A) is 80-120KPa, the operation temperature of the tower top is 70-100 ℃, the operation pressure of the second rectifying tower (1- (3) -B) is 1-50KPa, the operation temperature of the tower top is 50-150 ℃, the operation pressure of the third rectifying tower (1- (3) -C) is 100-200KPa, the operation temperature of the tower top is 30-60 ℃, the operation pressure of the fourth rectifying tower (1- (3) -D) is 100-200KPa, and the operation temperature of the tower top is 35-70 ℃;

in the second scheme, the operating pressure of the first rectifying tower (2-A) is 100-200KPa, the tower top operating temperature is 30-60 ℃, the operating pressure of the second rectifying tower (2-B) is 80-120KPa, the tower top operating temperature is 70-100 ℃, the operating pressure of the third rectifying tower (2-C) is 1-50KPa, the operating temperature of the tower top is 50-150 ℃, the mass ratio of the content of the supplementary water (2-8) to the material (2-4) is 0.2: 1-0.8: 1 by weight, the dehydration unit (2-F) can be membrane dehydration, molecular sieve dehydration and adsorption dehydration, the operating pressure of the sixth rectifying tower (2-G) is 100-200KPa, and the tower top operating temperature is 60-90 ℃;

in the process 1, the operating pressure of the fourth rectifying tower (2- (1) -D) is 80-120KPa, the tower top operating temperature is 70-120 ℃, the operating pressure of the fifth rectifying tower (2- (1) -E) is 100-200KPa, and the tower top operating temperature is 35-70 ℃;

in the process 2, the operating pressure of the fourth rectifying tower (2- (2) -D) is 100-200KPa, the tower top operating temperature is 35-70 ℃, the operating pressure of the fifth rectifying tower (2- (2) -E) is 80-120KPa, and the tower top operating temperature is 70-120 ℃;

in the third scheme, the operating pressure of the first rectifying tower (3-A) is 80-120KPa, the operating temperature of the tower top is 70-100 ℃, the operating pressure of the second rectifying tower (3-B) is 1-50KPa, the operating temperature of the tower top is 50-150 ℃, the mass ratio of the content of the supplementary water (3-6) to the material (3-2) in weight percent is 0.2: 1-1: 1, the dehydration unit (3-F) can be membrane dehydration, molecular sieve dehydration and adsorption dehydration, the operating pressure of the sixth rectifying tower (3-G) is 100-200KPa, and the operating temperature of the tower top is 60-90 ℃;

in the process 1, the operation pressure of the third rectifying tower (3- (1) -C) is 80-120KPa, the operation temperature of the tower top is 70-120 ℃, the operation pressure of the fourth rectifying tower (3- (1) -D) is 100-200KPa, the operation temperature of the tower top is 30-60 ℃, the operation pressure of the fifth rectifying tower (3- (1) -E) is 100-200KPa, and the operation temperature of the tower top is 35-70 ℃;

in the process 2, the operation pressure of the third rectifying tower (3- (2) -C) is 80-120KPa, the operation temperature of the tower top is 70-120 ℃, the operation pressure of the fourth rectifying tower (3- (2) -D) is 100-200KPa, the operation temperature of the tower top is 35-70 ℃, the operation pressure of the fifth rectifying tower (3- (2) -E) is 100-200KPa, and the operation temperature of the tower top is 30-60 ℃;

in the flow 3, the operation pressure of the third rectifying tower (3- (3) -C) is 100-200KPa, the operation temperature of the tower top is 35-70 ℃, the operation pressure of the fourth rectifying tower (3- (3) -D) is 100-200KPa, the operation temperature of the tower top is 30-60 ℃, the operation pressure of the fifth rectifying tower (3- (3) -E) is 80-120KPa, and the operation temperature of the tower top is 70-120 ℃;

in the flow 4, the operation pressure of the third distillation column (3- (4) -C) is 100-200KPa, the tower top operation temperature is 30-60 ℃, the operation pressure of the fourth distillation column (3- (4) -D) is 100-200KPa, the tower top operation temperature is 35-70 ℃, the operation pressure of the fifth distillation column (3- (4) -E) is 80-120KPa, and the tower top operation temperature is 70-120 ℃;

scheme 5: the operation pressure of the third rectifying tower (3- (5) -C) is 100-200KPa, the tower top operation temperature is 30-60 ℃, the operation pressure of the fourth rectifying tower (3- (5) -D) is 80-120KPa, the tower top operation temperature is 70-120 ℃, the operation pressure of the fifth rectifying tower (3- (5) -E) is 100-200KPa, and the tower top operation temperature is 35-70 ℃;

in the fourth scheme, the operating pressure of the first rectifying tower (4-A) is 80-120KPa, and the mass ratio of the content of the make-up water (4-2) to the material (4-1) is 0.2: 1-1: 1, the operation temperature of the top of the tower is 70-100 ℃, the operation pressure of a second rectifying tower (4-B) is 1-50KPa, and the operation temperature of the top of the tower is 50-150 ℃; the dehydration unit (4-F) can be membrane dehydration, molecular sieve dehydration and adsorption dehydration, the operation pressure of the sixth rectifying tower (4-G) is 100-200KPa, and the operation temperature of the tower top is 60-90 ℃;

in the process 1, the operation pressure of the third rectifying tower (4- (1) -C) is 80-120KPa, the operation temperature of the tower top is 70-120 ℃, the operation pressure of the fourth rectifying tower (4- (1) -D) is 100-200KPa, the operation temperature of the tower top is 30-60 ℃, the operation pressure of the fifth rectifying tower (4- (1) -E) is 100-200KPa, and the operation temperature of the tower top is 35-70 ℃;

in the process 2, the operation pressure of the third rectifying tower (4- (2) -C) is 80-120KPa, the operation temperature of the tower top is 70-120 ℃, the operation pressure of the fourth rectifying tower (4- (2) -D) is 100-200KPa, the operation temperature of the tower top is 35-70 ℃, the operation pressure of the fifth rectifying tower (4- (2) -E) is 100-200KPa, and the operation temperature of the tower top is 30-60 ℃;

in the process 3, the operation pressure of the third rectifying tower (4- (3) -C) is 100-200KPa, the tower top operation temperature is 35-70 ℃, the operation pressure of the fourth rectifying tower (4- (3) -D) is 100-200KPa, the tower top operation temperature is 30-60 ℃, the operation pressure of the fifth rectifying tower (4- (3) -E) is 80-120KPa, and the tower top operation temperature is 70-120 ℃;

in the process 4, the operation pressure of the third rectifying tower (4- (4) -C) is 100-200KPa, the tower top operation temperature is 30-60 ℃, the operation pressure of the fourth rectifying tower (4- (4) -D) is 100-200KPa, the tower top operation temperature is 35-70 ℃, the operation pressure of the fifth rectifying tower (4- (4) -E) is 80-120KPa, and the tower top operation temperature is 70-120 ℃;

in the flow 5, the operation pressure of the third rectifying tower (4- (5) -C) is 100-200KPa, the operation temperature of the tower top is 30-60 ℃, the operation pressure of the fourth rectifying tower (4- (5) -D) is 80-120KPa, the operation temperature of the tower top is 70-120 ℃, the operation pressure of the fifth rectifying tower (4- (5) -E) is 100-200KPa, and the operation temperature of the tower top is 35-70 ℃;

the invention has the following beneficial effects:

the invention provides a separation process of a polyoxymethylene dimethyl ether system containing formaldehyde aiming at the technical current situation that the catalytic synthesis of polyoxymethylene dimethyl ether (PODEN) by taking methanol and formaldehyde aqueous solution as raw materials is complex in product component, the formaldehyde is easy to polymerize in the rectification separation process, and the unreacted raw materials need to be respectively recovered, and the method is characterized in that:

1. although the amount of the methyl formate as a side reaction product is small, the accumulation of the methyl formate in the product can be reduced after purification and separation.

2. 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.

3. Unreacted methylal can be recycled and returned to a reaction device for synthesizing PODEN by catalyzing methylal and formaldehyde, unreacted raw materials are reasonably recycled, and the utilization rate of the raw materials is improved.

4. 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.

5. Material PODE₂Methanol and water are processed by a dehydration unit and a sixth rectifying tower to obtain PODE₂The byproduct product improves the economic benefit.

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 chart of the separation process of example 3;

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

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- (1) -A is a first rectifying tower, 1- (1) -B is a second rectifying tower, 1- (1) -C is a third rectifying tower, 1- (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 bottom outlet of the first rectifying tower 1- (1) -A is connected with the feed inlet of the second rectifying tower 1- (1) -B through a pipeline, the tower top outlet of the second rectifying tower 1- (1) -B is connected with the feed inlet of the fourth rectifying tower 1- (1) -D through a pipeline, the tower bottom outlet of the second rectifying tower 1- (1) -B is connected with the feed inlet of the third rectifying tower 1- (1) -C through a pipeline, the tower bottom discharge port of the fourth rectifying tower 1- (1) -D is connected with the feed inlet of the fifth rectifying tower 1-E, the tower top 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.

Make-up water can enter the fifth rectifying tower 1-E together with the tower bottom discharge of the fourth rectifying tower 1- (1) -D, or be added independently, if the make-up water is added independently, a make-up water feed inlet is additionally arranged on the fifth rectifying tower 1-E.

Materials 1- (1) -1 are PODEN raw materials to be refined, 1- (1) -2 are methyl formate, 1- (1) -3 are raw materials to be refined without methyl formate, and 1- (1) -4 are methylal, methanol, water, formaldehyde, trioxymethylene and PODE₂1- (1) -5 is PODE_3-10The material of (1) -6 is PODE_3-51- (1) -7 is PODE_6-101- (1) -8 is a material of methylal and methanol, and 1- (1) -9 is methanol, formaldehyde, water, trioxymethylene and PODE₂1-10 is pure water material, 1-11 is PODE₂Water and methanol materials, 1-12 is aqueous solution containing formaldehyde and trioxymethylene, 1-13 is water material, 1-14 is methanol and PODE₂Materials, 1-15 are methanol materials, 1-16 are PODE₂And (3) feeding.

Scheme 1: feeding PODEN raw material (1- (1) -1) into a first rectifying tower (1- (1) -A), and collecting a material (1- (1) -2) of methyl formate at the tower top of the first rectifying tower (1- (1) -A); the material (1- (1) -3) at the bottom of the first rectifying tower (1- (1) -A) enters a second rectifying tower (1- (1) -B)) The top of the second rectifying tower (1- (1) -B) is extracted from methylal, methanol, water, formaldehyde, trioxymethylene and PODE₂The materials (1- (1) -4); the tower bottom materials (1- (1) -5) of the second rectifying tower (1- (1) -B) enter a third rectifying tower (1- (1) -C), and PODE is extracted from the top of the third rectifying tower (1- (1) -C)_3-5The material (1- (1) -6) and the tower bottom are PODE_6-10The materials (1- (1) -7); materials (1- (1) -4) at the top of the second rectifying tower (1- (1) -B) enter a fourth rectifying tower (1- (1) -D), and materials (1- (1) -8) of methylal and methanol are extracted from the top of the fourth rectifying tower (1- (1) -D); and the tower bottom materials (1- (1) -9) of the fourth rectifying tower (1- (1) -D) enter a fifth rectifying tower (1-E). Introducing make-up water (1-10) into a fifth rectifying tower (1-E), and extracting materials (1-12) of formaldehyde water solution and trioxymethylene from the tower bottom of the fifth rectifying tower (1-E); materials (1-11) at the top of the fifth rectifying tower (1-E) enter a dehydration unit (1-F), and moisture (1-13) is removed; the materials (1-14) after water removal enter a sixth rectifying tower (1-G), the materials (1-15) of methanol are extracted from the top of the tower, and PODE is extracted from the bottom of the tower₂The materials (1-16).

1800t/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 (formol)	9.08
			5	Water (I)	1.17
6	Trioxymethylene	2.50
			7	PODE₂	20.96
8	PODE_3-5	20.03
			9	PODE_6-10	2.41

The separation is carried out by adopting the first flow 1 of the method scheme, wherein the operating pressure of a first rectifying tower (1- (1) -A) is 100KPa, the tower top operating temperature is 32 ℃, the operating pressure of a second rectifying tower (1- (1) -B) is 80KPa, the tower top operating temperature is 86 ℃, the operating pressure of a third rectifying tower (1- (1) -C) is 1KPa, the tower top operating temperature is 52 ℃, the operating pressure of a fourth rectifying tower (1- (1) -D) is 100KPa, the tower top operating temperature is 40 ℃, the operating pressure of a fifth rectifying tower (1-E) is 80KPa, the mass ratio of the quantity of the make-up water (1-10) to the mass of the materials (1- (1) -9) is 0.3:1, the tower top operating temperature is 80 ℃, a dehydration unit (1-F) adopts a molecular sieve for dehydration, the operating pressure of the sixth rectifying tower (1-G) is 100KPa, and the tower top operating temperature is 64 ℃.

Separating to obtain 32t/h of PODE (dimethyl Formate), 670t/h and 377t/h of methyl formate, methylal and methanol materials₂PODE of 360t/h_3-5Qualified products and the formaldehyde water solution with the mass fraction of about 50 percent of 327t/h 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- (1) -D is a fourth rectifying tower, 2- (1) -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 second rectifying tower 2-B is connected with the feed inlet of the fourth rectifying tower 2- (1) -D through a pipeline, the tower kettle outlet of the second rectifying tower 2-B is connected with the feed inlet of the third rectifying tower 2-C through a pipeline, the tower top discharge port of the fourth rectifying tower 2- (1) -D is connected with the feed inlet of the fifth rectifying tower 2- (1) -E through a pipeline, the tower kettle discharge port of the fifth rectifying tower 2- (1) -E 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.

The make-up water can enter the fourth rectifying tower 2- (1) -D together with the top discharge of the second rectifying tower 2-B or be added separately, if the make-up water is added separately, a make-up water feeding port is additionally arranged on the fourth rectifying tower 2- (1) -D.

Material 2-1 is PODEN raw material to be refined, 2-2 is methyl formate, 2-3 is raw material to be refined without methyl formate, 2-4 is methylal, methanol, water, formaldehyde, trioxymethylene and PODE₂2-5 is PODE_3-102-6 is PODE_3-52-7 is PODE_6-102-8 is pure water material, 2- (1) -9 is methylal, methanol, formaldehyde, water, trioxymethylene and PODE₂2- (1) -10 is a material of formaldehyde aqueous solution and trioxymethylene, 2- (1) -11 is a material of methylal and methanol, and 2- (1) -12 is PODE₂Water and methanol materials, 2-13 are water materials, 2-14 are methanol and PODE₂Materials 2-15 are methanol materials, 2-16 are PODE₂And (3) feeding.

Feeding PODEN raw material (2-1) into a first rectifying tower (2-A), and extracting a material (2-2) of methyl formate from the top of the first rectifying tower (2-A); the tower bottom material (2-3) of the first rectifying tower (2-A) enters a second rectifying tower (2-B), and methylal, methanol, water, formaldehyde, trioxymethylene and PODE are extracted from the tower top of the second rectifying tower (2-B)₂2-4); the tower bottom material (2-5) of the second rectifying tower (2-B) enters a third rectifying tower (2-C), and PODE is extracted from the tower top of the third rectifying tower (2-C)_3-5The material (2-6) and the tower bottom are PODE_6-102-7); the material (2-4) at the top of the second rectifying tower (2-B) enters a fourth rectifying tower, and the fourth rectifying tower introduces supplementary water (2-8); the tower bottom of the fourth rectifying tower (2- (1) -D) is used for extracting a material (2- (1) -10) of formaldehyde water solution and trioxymethylene; feeding the tower top material (2- (1) -9) of the fourth rectifying tower (2- (1) -D) into a fifth rectifying tower (2- (1) -E), collecting the material (2- (1) -11) of methylal and methanol from the tower top of the fifth rectifying tower (2- (1) -E), and feeding the tower bottom liquid (2- (1) -12) of the fifth rectifying tower into a dehydration unit (2-F); removing water (2-13); the material (2-14) after water removal enters a sixth rectifying tower (2-G), the material (2-15) of methanol is extracted from the tower top and PODE is extracted from the tower bottom₂2-16.

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

the separation is carried out by adopting the scheme 1 of the method, wherein the operating pressure of a first rectifying tower (2-A) is 200KPa, the operating temperature of the top of the tower is 52 ℃, the operating pressure of a second rectifying tower (2-B) is 120KPa, the operating temperature of the top of the tower is 98 ℃, the operating pressure of a third rectifying tower (2-C) is 50KPa, the operating temperature of the top of the tower is 144 ℃, the operating pressure of a fourth rectifying tower (2- (1) -D) is 120KPa, the mass ratio of the quantity of the make-up water (2-8) to the quantity of the materials (2-4) is 0.8:1, the operating temperature of the top of the tower is 96 ℃, the operating pressure of a fifth rectifying tower (2- (1) -E) is 200KPa, the operating temperature of the top of the tower is 61 ℃, the dehydrating unit (2-F) adopts adsorption dehydration, the operating pressure of a sixth rectifying tower (2-G) is 200KPa, and the operating temperature of the top of the tower is 82 ℃.

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 622t/h of about 35 percent are recovered.

Example 3

In FIG. 3, 3-A is a first rectifying tower, 3-B is a second rectifying tower, 3- (1) -C is a third rectifying tower, 3- (1) -D is a fourth rectifying tower, 3- (1) -E is a fifth rectifying tower, 3-F is a dehydration unit, and 3-G is a sixth rectifying tower.

The tower bottom 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- (1) -C through a pipeline, the tower top outlet of the third rectifying tower 3- (1) -C is connected with the feed inlet of the fourth rectifying tower 3- (1) -D through a pipeline, the tower bottom discharge port of the fourth rectifying tower 3- (1) -D is connected with the feed inlet of the fifth rectifying tower 3- (1) -E through a pipeline, the tower bottom discharge port of the fifth rectifying tower 3- (1) -E is connected with the feed inlet of the dehydrating unit 3-F through a pipeline, and the discharge port of the dehydrating unit 3-F is connected with the feed inlet of the sixth rectifying tower 3-G.

Make-up water may be fed to the third rectification column 3- (1) -C together with the overhead discharge from the first rectification column 3-a or separately, if make-up water is added separately, additional make-up water feed inlets may be provided in the third rectification column 3- (1) -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- (1) -7 is methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE₂3- (1) -8 is a formaldehyde aqueous solution and a trioxymethylene material, 3- (1) -9 is a methyl formate material, and 3- (1) -10 is methylal, methanol, water, formaldehyde, trioxymethylene and PODE₂3- (1) -11 is a material of methylal and methanol, and 3- (1) -12 is PODE₂Water and methanol, 3-13 is water, 3-14 is methanol and PODE₂Material(s)3-15 is methanol material, 3-16 is 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, and the third rectifying tower introduces make-up water (3-6); the tower bottom of the third rectifying tower (3- (1) -C) extracts materials (3- (1) -8) of formaldehyde water solution and trioxymethylene; feeding the materials (3- (1) -7) at the top of the third rectifying tower (3- (1) -C) into a fourth rectifying tower (3- (1) -D), and collecting the materials (3- (1) -9) which are methyl formate at the top of the fourth rectifying tower (3- (1) -D); feeding the tower bottom materials (3- (1) -10) of the fourth rectifying tower (3- (1) -D) into a fifth rectifying tower (3- (1) -E), and extracting materials (3- (1) -11) of methylal and methanol from the top of the fifth rectifying tower (3- (1) -E); the tower bottom materials (3- (1) -12) of the fifth rectifying tower (3- (1) -E) enter a dehydration unit (3-F), and moisture (3-13) is removed; the materials (3-14) after water removal enter a sixth rectifying tower (3-G), the materials (3-15) of methanol are extracted from the top of the tower, and PODE is extracted from the bottom of the tower₂3-16).

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

numbering	Components	Content%
				1	Formic acid methyl ester	1.80
2	Methylal compound	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

The method adopts a scheme 1 of three processes for separation, wherein 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 1KPa, the operating temperature of the top of the tower is 52 ℃, the operating pressure of a third rectifying tower (3- (1) -C) is 100KPa, the mass ratio of the amount of the supplementary water (3-6) to the material (3-2) is 0.4:1, the operating temperature of the top of the tower is 80 ℃, the operating pressure of a fourth rectifying tower (3- (1) -D) is 100KPa, the operating temperature of the top of the tower is 32 ℃, the operating pressure of a fifth rectifying tower (3- (1) -E) is 100KPa, the operating temperature of the top of the tower is 40 ℃, a dehydration unit (3-F) adopts a molecular sieve for 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 540t/h_3-5Qualified products and the recovered formaldehyde solution with the mass fraction of about 20 percent of 1225 t/h.

Example 4

In fig. 4, 4-a is a first rectifying tower, 4-B is a second rectifying tower, 4- (1) -C is a third rectifying tower, 4- (1) -D is a fourth rectifying tower, 4- (1) -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- (1) -C through a pipeline, the tower top outlet of the third rectifying tower 4- (1) -C is connected with the feed inlet of the fourth rectifying tower 4- (1) -D through a pipeline, the tower kettle discharge port of the fourth rectifying tower 4- (1) -D is connected with the feed inlet of the fifth rectifying tower 4- (1) -E through a pipeline, the tower kettle discharge port of the fifth rectifying tower 4- (1) -E is connected with the feed inlet of the dehydration unit 4-F through a pipeline, and the discharge port of the dehydration unit 4-F is connected with the feed inlet of the sixth rectifying tower 4-G.

Make-up water may be fed to the first rectification column 4-a together with the feed to be refined for PODEn, 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 first rectification column 4-a.

Material 4-1 is PODEN to-be-refined raw material, 4-2 is pure water material, 4-3 is material containing no PODE_3-104-4 is PODE_3-104-5 is PODE_3-54-6 is PODE_6-104- (1) -7 is methyl formate, methylal, methanol, water, and PODE₂4- (1) -8 is aqueous formaldehyde solution and trioxymethylene material, 4- (1) -9 is methyl formate, 4- (1) -10 is methylal, methanol, water, andPODE₂4- (1) -11 is a material of methylal and methanol, 4- (1) -12 is PODE₂Water and methanol, 4-13 is 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), make-up water (4-2) is introduced into the 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)₂4-3); the material (4-4) 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 (4-5) and the tower bottom are PODE_6-104-6); the material (4-3) at the top of the first rectifying tower (4-A) enters a third rectifying tower (4- (1) -C); materials (4- (1) -8) which are formaldehyde aqueous solution and trioxymethylene are extracted from the tower bottom of the third rectifying tower (4- (1) -C); the material (4- (1) -7) at the top of the third rectifying tower (4- (1) -C) enters a fourth rectifying tower (4- (1) -D), and the material (4- (1) -9) which is methyl formate is extracted from the top of the fourth rectifying tower (4- (1) -D); feeding the tower bottom materials (4- (1) -10) of the fourth rectifying tower (4- (1) -D) into a fifth rectifying tower (4- (1) -E), and extracting materials (4- (1) -11) of methylal and methanol from the top of the fifth rectifying tower (4- (1) -E); feeding tower bottom materials (4- (1) -12) of the fifth rectifying tower (4- (1) -E) into 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 is extracted from the top of the tower, and PODE is extracted from the bottom of the tower₂The material (4-16).

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

the method adopts a scheme of a four-flow 1 for separation, wherein the operating pressure of a first rectifying tower (4-A) is 100KPa, the mass ratio of the amount of supplemented water (4-2) to a material (4-1) is 0.8:1, 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- (1) -C) is 100KPa, the operating temperature of the top of the tower is 80 ℃, the operating pressure of a fourth rectifying tower (4- (1) -D) is 100KPa, the operating temperature of the top of the tower is 32 ℃, the operating pressure of a fifth rectifying tower (4- (1) -E) is 100KPa, the operating temperature of the top of the tower is 40 ℃, a dehydration unit (4-F) adopts adsorption 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 ℃.

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 a formaldehyde water solution with the mass fraction of about 35 percent at 622t/h are recovered.

The separation process of a polyoxymethylene-containing polymethoxy dimethyl ether system according to the present invention has been described with reference to preferred embodiments, and it will be apparent to those skilled in the art that the present technology can be implemented by modifying or appropriately changing and combining the structures and devices described herein without departing from the spirit, scope and spirit of the present invention. 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 process of a polyoxymethylene dimethyl ether system containing formaldehyde is characterized in that: the polymethoxy dimethyl ether is prepared by taking methanol and aqueous solution of formaldehyde as raw materials, water is introduced into a rectifying tower with any grade containing formaldehyde, and the formaldehyde is extracted from a tower kettle in the form of the aqueous solution, so that the aim of separating the formaldehyde is fulfilled, and the polymethoxy dimethyl ether comprises six rectifying towers and a dehydration unit;

the separation process comprises the following 4 parallel schemes:

the first scheme comprises the following steps: introducing make-up water (1-10) into a fifth rectifying tower (1-E), and extracting materials (1-12) of formaldehyde water solution and trioxymethylene from the tower bottom of the fifth rectifying tower (1-E); materials (1-11) at the top of the fifth rectifying tower (1-E) enter a dehydration unit (1-F), and moisture (1-13) is removed; the materials (1-14) after water removal enter a sixth rectifying tower (1-G), the materials (1-15) of methanol are extracted from the tower top and PODE is extracted from the tower bottom₂Of (1)-16)；

Scheme one comprises the following 3 separation schemes:

scheme 1 of scheme one: feeding PODEN raw material (1- (1) -1) into a first rectifying tower (1- (1) -A), and collecting a material (1- (1) -2) of methyl formate at the tower top of the first rectifying tower (1- (1) -A); the materials (1- (1) -3) in the tower bottom of the first rectifying tower (1- (1) -A) enter a second rectifying tower (1- (1) -B), and methylal, methanol, water, formaldehyde, trioxymethylene and PODE are extracted from the tower top of the second rectifying tower (1- (1) -B)₂The materials (1- (1) -4); the tower bottom materials (1- (1) -5) of the second rectifying tower (1- (1) -B) enter a third rectifying tower (1- (1) -C), and PODE is extracted from the top of the third rectifying tower (1- (1) -C)_3-5The material (1- (1) -6) and the tower bottom are PODE_6-10The materials (1- (1) -7); the material (1- (1) -4) at the top of the second rectifying tower (1- (1) -B) enters a fourth rectifying tower (1- (1) -D), and the material (1- (1) -8) of methylal and methanol is extracted from the top of the fourth rectifying tower (1- (1) -D); feeding tower bottom materials (1- (1) -9) of the fourth rectifying tower (1- (1) -D) into a fifth rectifying tower (1-E);

scheme 2 of scheme one: PODEN raw material (1- (2) -1) enters a first rectifying tower (1- (2) -A), and methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE are extracted from the top of the first rectifying tower (1- (2) -A)₂The materials (1- (2) -2); the material (1- (2) -3) at the bottom of the first rectifying tower (1- (2) -A) enters a second rectifying tower (1- (2) -B), and PODE is extracted from the top of the second rectifying tower (1- (2) -B)_3-5The material (1- (2) -4) and the tower bottom are PODE_6-10The materials (1- (2) -5); the material (1- (2) -2) at the top of the first rectifying tower (1- (2) -A) enters a third rectifying tower (1- (2) -C), and the material (1- (2) -6) of methyl formate, methylal and methanol is extracted from the top of the third rectifying tower (1- (2) -C); feeding the material (1- (2) -6) at the top of the third rectifying tower (1- (2) -C) into a fourth rectifying tower (1- (2) -D), and collecting a material (1- (2) -8) of methyl formate at the top of the fourth rectifying tower (1- (2) -D) and a material (1- (2) -9) of methylal and methanol at the bottom of the fourth rectifying tower (1- (2) -D); the tower bottom materials (1- (2) -7) of the third rectifying tower (1- (2) -C) enter a fifth rectifying tower (1-E);

scheme 3 of scheme one: PODEN raw material (1- (3) -1) enters a first rectifying tower (1- (3) -A), and methyl formate, methylal, methanol, water, formaldehyde, trioxymethylene and PODE are extracted from the top of the first rectifying tower (1- (3) -A)₂Materials (1- (3) -2)) (ii) a The material (1- (3) -3) at the bottom of the first rectifying tower (1- (3) -A) enters a second rectifying tower (1- (3) -B), and PODE is extracted from the top of the second rectifying tower (1- (3) -B)_3-5The material (1- (3) -4) and the column bottom are PODE_6-10The materials (1- (3) -5); the material (1- (3) -2) at the top of the first rectifying tower (1- (3) -A) enters a third rectifying tower (1- (3) -C), and the material (1- (3) -6) which is methyl formate is extracted from the top of the third rectifying tower (1- (3) -C); feeding the tower bottom material (1- (3) -7) of the third rectifying tower (1- (3) -C) into a fourth rectifying tower (1- (3) -D), and collecting a material (1- (3) -8) of methylal and methanol at the tower top of the fourth rectifying tower (1- (3) -D); feeding the tower bottom materials (1- (3) -9) of the fourth rectifying tower (1- (3) -D) into a fifth rectifying tower (1-E);

scheme II: feeding PODEN raw material (2-1) into a first rectifying tower (2-A), and extracting a material (2-2) of methyl formate from the top of the first rectifying tower (2-A); the tower bottom material (2-3) of the first rectifying tower (2-A) enters a second rectifying tower (2-B), and methylal, methanol, water, formaldehyde, trioxymethylene and PODE are extracted from the tower top of the second rectifying tower (2-B)₂2-4); the tower bottom material (2-5) of the second rectifying tower (2-B) enters a third rectifying tower (2-C), and PODE is extracted from the tower top of the third rectifying tower (2-C)_3-5The material (2-6) and the tower bottom are PODE_6-102-7); the material (2-4) at the top of the second rectifying tower (2-B) enters a fourth rectifying tower, and the fourth rectifying tower introduces supplementary water (2-8); the top or bottom liquid of the fifth rectifying tower enters a membrane dehydration unit (2-F), and moisture (2-13) is removed; the material (2-14) after water removal enters a sixth rectifying tower (2-G), the material (2-15) of methanol is extracted from the tower top and PODE is extracted from the tower bottom₂2-16);

scheme two comprises the following 2 separation processes:

scheme 1 of scheme two: materials (2- (1) -10) which are formaldehyde aqueous solution and trioxymethylene are extracted from the tower bottom of the fourth rectifying tower (2- (1) -D); feeding the tower top material (2- (1) -9) of the fourth rectifying tower (2- (1) -D) into a fifth rectifying tower (2- (1) -E), collecting the material (2- (1) -11) of methylal and methanol from the tower top of the fifth rectifying tower (2- (1) -E), and feeding the tower bottom liquid (2- (1) -12) of the fifth rectifying tower into a dehydration unit (2-F);

scheme 2 of scheme two: the top of the fourth rectifying tower (2- (2) -D) produces a material (2- (2) -9) of methylal and methanol; feeding the materials (2- (2) -10) at the bottom of the fourth rectifying tower (2- (2) -D) into a fifth rectifying tower (2- (2) -E), and extracting materials (2- (2) -12) of formaldehyde water solution and trioxymethylene from the bottom of the fifth rectifying tower (2- (2) -E); feeding the tower top material (2- (2) -11) of the fifth rectifying tower (2- (2) -E) into a dehydration unit (2-F);

scheme three comprises the following 5 separation schemes:

scheme 1 of scheme three: the tower bottom of the third rectifying tower (3- (1) -C) extracts materials (3- (1) -8) of formaldehyde water solution and trioxymethylene; feeding the materials (3- (1) -7) at the top of the third rectifying tower (3- (1) -C) into a fourth rectifying tower (3- (1) -D), and collecting the materials (3- (1) -9) which are methyl formate at the top of the fourth rectifying tower (3- (1) -D); feeding the tower bottom material (3- (1) -10) of the fourth rectifying tower (3- (1) -D) into a fifth rectifying tower (3- (1) -E), and collecting a material (3- (1) -11) of methylal and methanol from the tower top of the fifth rectifying tower (3- (1) -E); feeding tower bottom materials (3- (1) -12) of the fifth rectifying tower (3- (1) -E) into a dehydration unit (3-F);

scheme 2 of scheme three: materials (3- (2) -8) which are formaldehyde aqueous solution and trioxymethylene are extracted from the tower bottom of the third rectifying tower (3- (2) -C); feeding the material (3- (2) -7) at the top of the third rectifying tower (3- (2) -C) into a fourth rectifying tower (3- (2) -D), and collecting the material (3- (2) -9) of methyl formate, methylal and methanol at the top of the fourth rectifying tower (3- (2) -D); feeding the material (3- (2) -9) at the top of the fourth rectifying tower (3- (2) -D) into a fifth rectifying tower (3- (2) -E), and collecting a material (3- (2) -11) of methyl formate at the top of the fifth rectifying tower (3- (2) -E) and a material (3- (2) -12) of methylal and methanol at the bottom of the fifth rectifying tower; the tower bottom material (3- (2) -10) of the fourth rectifying tower (3- (2) -D) enters a dehydration unit (3-F);

scheme 3 of scheme three: the top of the third rectifying tower (3- (3) -C) produces materials (3- (3) -7) of methyl formate, methylal and methanol; the material (3- (3) -7) at the top of the third rectifying tower (3- (3) -C) enters a fourth rectifying tower (3- (3) -D), and the material (3- (3) -9) which is methyl formate and the material (3- (3) -10) which is methylal and methanol at the bottom of the fourth rectifying tower (3- (3) -D) are extracted from the top of the fourth rectifying tower (3- (3) -D); feeding the tower bottom materials (3- (3) -8) of the third rectifying tower (3- (3) -C) into a fifth rectifying tower (3- (3) -E), and extracting materials (3- (3) -12) of formaldehyde water solution and trioxymethylene from the tower bottom of the fifth rectifying tower (3- (3) -E); the tower top material (3- (3) -11) of the fifth rectifying tower (3- (3) -E) enters a dehydration unit (3-F);

scheme 4 of scheme three: a material (3- (4) -7) of methyl formate is extracted from the top of the third rectifying tower (3- (4) -C); feeding the tower bottom material (3- (4) -8) of the third rectifying tower (3- (4) -C) into a fourth rectifying tower (3- (4) -D), and collecting a material (3- (4) -9) of methylal and methanol from the tower top of the fourth rectifying tower (3- (4) -D); feeding the tower bottom materials (3- (4) -8) of the fourth rectifying tower (3- (4) -D) into a fifth rectifying tower (3- (4) -E), and extracting materials (3- (4) -12) of formaldehyde water solution and trioxymethylene from the tower bottom of the fifth rectifying tower (3- (4) -E); the material (3- (4) -11) at the top of the fifth rectifying tower (3- (4) -E) enters a dehydration unit (3-F);

scheme 5 of scheme three: a material (3- (5) -7) of methyl formate is extracted from the top of the third rectifying tower (3- (5) -C); feeding the tower bottom materials (3- (5) -8) of the third rectifying tower (3- (5) -C) into a fourth rectifying tower (3- (5) -D), and extracting materials (3- (5) -10) of formaldehyde water solution and trioxymethylene from the tower bottom of the fourth rectifying tower (3- (5) -D); materials (3- (5) -9) at the top of the fourth rectifying tower (3- (5) -D) enter a fifth rectifying tower (3- (5) -E), and materials (3- (5) -11) of methylal and methanol are extracted from the top of the fifth rectifying tower (3- (5) -E); feeding tower bottom materials (3- (5) -12) of the fifth rectifying tower (3- (5) -E) into a dehydration unit (3-F);

the scheme four is as follows: PODEN raw material (4-1) enters a first rectifying tower (4-A), make-up water (4-2) is introduced into the 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)₂4-3); the tower bottom material (4-4) of the first rectifying tower (4-A) enters a second rectifying tower (4-A)4-B), PODE is extracted from the top of the second rectifying tower (4-B)_3-5The material (4-5) and the tower bottom are PODE_6-104-6); the material (4-3) at the top of the first rectifying tower (4-A) enters a third rectifying tower; the top or bottom liquid of the fifth rectifying tower enters a membrane 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 is extracted from the top of the tower, and PODE is extracted from the bottom of the tower₂The material (4-16);

scheme four comprises the following 5 isolation schemes:

scheme four, scheme 1: the tower bottom of the third rectifying tower (4- (1) -C) extracts materials (4- (1) -8) of formaldehyde water solution and trioxymethylene; materials (4- (1) -7) at the top of the third rectifying tower (4- (1) -C) enter a fourth rectifying tower (4- (1) -D), and materials (4- (1) -9) of methyl formate are extracted from the top of the fourth rectifying tower (4- (1) -D); feeding the tower bottom materials (4- (1) -10) of the fourth rectifying tower (4- (1) -D) into a fifth rectifying tower (4- (1) -E), and extracting materials (4- (1) -11) of methylal and methanol from the top of the fifth rectifying tower (4- (1) -E); feeding tower bottom materials (4- (1) -12) of the fifth rectifying tower (4- (1) -E) into a dehydration unit (4-F);

scheme 2 of scheme four: materials (4- (2) -8) which are formaldehyde aqueous solution and trioxymethylene are extracted from the tower bottom of the third rectifying tower (4- (2) -C); materials (4- (2) -7) at the top of the third rectifying tower (4- (2) -C) enter a fourth rectifying tower (4- (2) -D), and materials (4- (2) -9) of methyl formate, methylal and methanol are extracted from the top of the fourth rectifying tower (4- (2) -D); materials (4- (2) -9) at the top of the fourth rectifying tower (4- (2) -D) enter a fifth rectifying tower (4- (2) -E), and a material (4- (2) -11) of methyl formate and a material (4- (2) -12) of methylal and methanol are extracted from the top of the fifth rectifying tower (4- (2) -E); the tower bottom material (4- (2) -10) of the fourth rectifying tower (4- (2) -D) enters a dehydration unit (4-F);

scheme 3 of scheme four: the material (4- (3) -7) of methyl formate, methylal and methanol is extracted from the top of the third rectifying tower (4- (3) -C); the material (4- (3) -7) at the top of the third rectifying tower (4- (3) -C) enters a fourth rectifying tower (4- (3) -D), the material (4- (3) -9) of methyl formate and the material (4- (3) -10) of methylal and methanol are extracted from the top of the fourth rectifying tower (4- (3) -D); feeding the tower bottom materials (4- (3) -8) of the third rectifying tower (4- (3) -C) into a fifth rectifying tower (4- (3) -E), and extracting materials (4- (3) -12) of formaldehyde water solution and trioxymethylene from the tower bottom of the fifth rectifying tower (4- (3) -E); the material (4- (3) -11) at the top of the fifth rectifying tower (4- (3) -E) enters a dehydration unit (4-F);

scheme 4 of scheme four: a material (4- (4) -7) of methyl formate is extracted from the top of the third rectifying tower (4- (4) -C); feeding the tower bottom material (4- (4) -8) of the third rectifying tower (4- (4) -C) into a fourth rectifying tower (4- (4) -D), and collecting a material (4- (4) -9) of methylal and methanol at the tower top of the fourth rectifying tower (4- (4) -D); feeding the tower bottom materials (4- (4) -10) of the fourth rectifying tower (4- (4) -D) into a fifth rectifying tower (4- (4) -E), and extracting materials (4- (4) -12) of formaldehyde water solution and trioxymethylene from the tower bottom of the fifth rectifying tower (4- (4) -E); feeding the tower top material (4- (4) -11) of the fifth rectifying tower (4- (4) -E) into a dehydration unit (4-F);

scheme four, scheme 5: a material (4- (5) -7) of methyl formate is extracted from the top of the third rectifying tower (4- (5) -C); feeding the tower bottom materials (4- (5) -8) of the third rectifying tower (4- (5) -C) into a fourth rectifying tower (4- (5) -D), and extracting materials (4- (5) -10) of formaldehyde water solution and trioxymethylene from the tower bottoms of the fourth rectifying tower (4- (5) -D); materials (4- (5) -9) at the top of the fourth rectifying tower (4- (5) -D) enter a fifth rectifying tower (4- (5) -E), and materials (4- (5) -11) of methylal and methanol are extracted from the top of the fifth rectifying tower (4- (5) -E); feeding tower bottom materials (4- (5) -12) of the fifth rectifying tower (4- (5) -E) into a dehydration unit (4-F);

in the first scheme, the operating pressure of a fifth rectifying tower (1-E) is 80-120KPa, the tower top operating temperature is 70-120 ℃, the mass ratio of the content of the supplementing water (1-10) to the feed of the fifth rectifying tower (1-E) is 0.3: 1-1: 1 by weight, a dehydration unit (1-F) is membrane dehydration or molecular sieve dehydration, the operating pressure of a sixth rectifying tower (1-G) is 100-200KPa, and the tower top operating temperature is 60-90 ℃;

in the first scheme, the operation pressure of the first rectifying tower (1- (1) -A) is 100-200KPa, the operation temperature of the tower top is 30-60 ℃, the operation pressure of the second rectifying tower (1- (1) -B) is 80-120KPa, the operation temperature of the tower top is 70-100 ℃, the operation pressure of the third rectifying tower (1- (1) -C) is 1-50KPa, the operation temperature of the tower top is 50-150 ℃, the operation pressure of the fourth rectifying tower (1- (1) -D) is 100-200KPa, and the operation temperature of the tower top is 35-70 ℃;

in the first scheme, the operation pressure of the first rectifying tower (1- (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 (1- (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 (1- (2) -C) is 100-200KPa, the operation temperature of the top of the tower is 35-70 ℃, the operation pressure of the fourth rectifying tower (1- (2) -D) is 100-200KPa, and the operation temperature of the top of the tower is 30-60 ℃;

in the first scheme, the operation pressure of the first rectifying tower (1- (3) -A) is 80-120KPa, the operation temperature of the tower top is 70-100 ℃, the operation pressure of the second rectifying tower (1- (3) -B) is 1-50KPa, the operation temperature of the tower top is 50-150 ℃, the operation pressure of the third rectifying tower (1- (3) -C) is 100-200KPa, the operation temperature of the tower top is 30-60 ℃, the operation pressure of the fourth rectifying tower (1- (3) -D) is 100-200KPa, and the operation temperature of the tower top is 35-70 ℃;

in the second scheme, the operating pressure of the first rectifying tower (2-A) is 100-200KPa, the tower top operating temperature is 30-60 ℃, the operating pressure of the second rectifying tower (2-B) is 80-120KPa, the tower top operating temperature is 70-100 ℃, the operating pressure of the third rectifying tower (2-C) is 1-50KPa, the operating temperature of the tower top is 50-150 ℃, the mass ratio of the content of the make-up water (2-8) to the material (2-4) is 0.2: 1-0.8: 1, the dehydration unit (2-F) is membrane dehydration or molecular sieve dehydration, the operating pressure of the sixth rectifying tower (2-G) is 100-200KPa, and the tower top operating temperature is 60-90 ℃;

in the second scheme, the operation pressure of the fourth rectifying tower (2- (1) -D) in the flow 1 is 80-120KPa, the tower top operation temperature is 70-120 ℃, the operation pressure of the fifth rectifying tower (2- (1) -E) is 100-200KPa, and the tower top operation temperature is 35-70 ℃;

in the scheme 2 of the second scheme, the operating pressure of the fourth rectifying tower (2- (2) -D) is 100-200KPa, the tower top operating temperature is 35-70 ℃, the operating pressure of the fifth rectifying tower (2- (2) -E) is 80-120KPa, and the tower top operating temperature is 70-120 ℃;

in the third scheme, the operating pressure of the first rectifying tower (3-A) is 80-120KPa, the operating temperature of the tower top is 70-100 ℃, the operating pressure of the second rectifying tower (3-B) is 1-50KPa, the operating temperature of the tower top is 50-150 ℃, the mass ratio of the content of the supplementary water (3-6) to the material (3-2) in weight percent is 0.2: 1-1: 1, the dehydration unit (3-F) is membrane dehydration or molecular sieve dehydration, the operating pressure of the sixth rectifying tower (3-G) is 100-200KPa, and the operating temperature of the tower top is 60-90 ℃;

in the third scheme, in the flow 1, the operating pressure of the third rectifying tower (3- (1) -C) is 80-120KPa, the tower top operating temperature is 70-120 ℃, the operating pressure of the fourth rectifying tower (3- (1) -D) is 100-200KPa, the tower top operating temperature is 30-60 ℃, the operating pressure of the fifth rectifying tower (3- (1) -E) is 100-200KPa, and the tower top operating temperature is 35-70 ℃;

in the third scheme, the operation pressure of the third rectifying tower (3- (2) -C) in the flow 2 is 80-120KPa, the tower top operation temperature is 70-120 ℃, the operation pressure of the fourth rectifying tower (3- (2) -D) is 100-200KPa, the tower top operation temperature is 35-70 ℃, the operation pressure of the fifth rectifying tower (3- (2) -E) is 100-200KPa, and the tower top operation temperature is 30-60 ℃;

in the third scheme, the operation pressure of the third rectifying tower (3- (3) -C) in the flow 3 is 100-200KPa, the tower top operation temperature is 35-70 ℃, the operation pressure of the fourth rectifying tower (3- (3) -D) is 100-200KPa, the tower top operation temperature is 30-60 ℃, the operation pressure of the fifth rectifying tower (3- (3) -E) is 80-120KPa, and the tower top operation temperature is 70-120 ℃;

in the third scheme, the operation pressure of the third rectifying tower (3- (4) -C) in the flow 4 is 100-200KPa, the tower top operation temperature is 30-60 ℃, the operation pressure of the fourth rectifying tower (3- (4) -D) is 100-200KPa, the tower top operation temperature is 35-70 ℃, the operation pressure of the fifth rectifying tower (3- (4) -E) is 80-120KPa, and the tower top operation temperature is 70-120 ℃;

scheme 5 of scheme three: the operating pressure of the third rectifying tower (3- (5) -C) is 100-200KPa, the tower top operating temperature is 30-60 ℃, the operating pressure of the fourth rectifying tower (3- (5) -D) is 80-120KPa, the tower top operating temperature is 70-120 ℃, the operating pressure of the fifth rectifying tower (3- (5) -E) is 100-200KPa, and the tower top operating temperature is 35-70 ℃;

in the fourth scheme, the operating pressure of the first rectifying tower (4-A) is 80-120KPa, the mass ratio of the content of the supplementary water (4-2) to the material (4-1) is 0.2: 1-1: 1, the operation temperature of the top of the tower is 70-100 ℃, the operation pressure of the second rectifying tower (4-B) is 1-50KPa, and the operation temperature of the top of the tower is 50-150 ℃; the dehydration unit (4-F) is membrane dehydration or molecular sieve dehydration, the operation pressure of the sixth rectifying tower (4-G) is 100-200KPa, and the operation temperature of the tower top is 60-90 ℃;

in the scheme 1, the operation pressure of the third rectifying tower (4- (1) -C) is 80-120KPa, the tower top operation temperature is 70-120 ℃, the operation pressure of the fourth rectifying tower (4- (1) -D) is 100-200KPa, the tower top operation temperature is 30-60 ℃, the operation pressure of the fifth rectifying tower (4- (1) -E) is 100-200KPa, and the tower top operation temperature is 35-70 ℃;

in the scheme four, in the flow 2, the operating pressure of the third rectifying tower (4- (2) -C) is 80-120KPa, the tower top operating temperature is 70-120 ℃, the operating pressure of the fourth rectifying tower (4- (2) -D) is 100-200KPa, the tower top operating temperature is 35-70 ℃, the operating pressure of the fifth rectifying tower (4- (2) -E) is 100-200KPa, and the tower top operating temperature is 30-60 ℃;

in the scheme four, the operation pressure of the third rectifying tower (4- (3) -C) in the flow 3 is 100-200KPa, the tower top operation temperature is 35-70 ℃, the operation pressure of the fourth rectifying tower (4- (3) -D) is 100-200KPa, the tower top operation temperature is 30-60 ℃, the operation pressure of the fifth rectifying tower (4- (3) -E) is 80-120KPa, and the tower top operation temperature is 70-120 ℃;

in the scheme 4, the operation pressure of the third rectifying tower (4- (4) -C) is 100-200KPa, the tower top operation temperature is 30-60 ℃, the operation pressure of the fourth rectifying tower (4- (4) -D) is 100-200KPa, the tower top operation temperature is 35-70 ℃, the operation pressure of the fifth rectifying tower (4- (4) -E) is 80-120KPa, and the tower top operation temperature is 70-120 ℃;

in the fourth scheme, in the flow 5, the operation pressure of the third distillation column (4- (5) -C) is 100-200KPa, the operation temperature of the top of the column is 30-60 ℃, the operation pressure of the fourth distillation column (4- (5) -D) is 80-120KPa, the operation temperature of the top of the column is 70-120 ℃, the operation pressure of the fifth distillation column (4- (5) -E) is 100-200KPa, and the operation temperature of the top of the column is 35-70 ℃.