Polymethoxy dimethyl ether rectification system
By using a five-stage distillation column system and pressure swing distillation technology, the problem of separating by-products in DMMn production has been solved, achieving high purity of DMMn products and effective recycling of by-products, thereby improving production efficiency and product quality.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-25
- Publication Date
- 2026-03-31
AI Technical Summary
In existing DMMn production facilities, the separation and recycling of by-products are difficult, especially the separation of the azeotrope between DMM1 and methanol, which is extremely difficult and affects the reaction process and product quality.
A five-stage distillation column system is adopted, including first-stage, second-stage, third-stage, fourth-stage and fifth-stage distillation columns. Combined with pressure swing distillation technology, it processes components such as DMM3-6, DMM7-13 and methanol respectively, and pre-treats them through an alkaline washing and dehydration device to achieve efficient separation and recycling of DMMn reaction products.
This improved the purity of DMMn products, made full use of by-product components, reduced raw material consumption, and enhanced production efficiency and product quality.
Smart Images
Figure CN224056699U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the technical field of chemical production equipment, and specifically relates to a polyoxymethylene dimethyl ether distillation system. Background Technology
[0002] Polyoxymethylene dimethyl ether (DMMn) (as a diesel additive, n is generally 3-8) has similar physicochemical properties to diesel fuel, with advantages such as high cetane number and oxygen content, and good miscibility with diesel fuel. When blended with diesel fuel in a certain proportion, it can significantly reduce the content of nitrogen oxides and particulate matter in exhaust emissions while maintaining the high cetane number and combustion performance of diesel fuel. It does not require modification of vehicle engines and is an ideal green diesel fuel additive, playing an important role in energy conservation and emission reduction, which meets the current global demand for environmentally friendly energy additives.
[0003] The raw materials for DMMn synthesis can be mainly divided into two parts according to their functions: one part is compounds that provide oligooxymethylene, including formaldehyde solution, trioxymethylene, and paraoxymethylene; the other part is end-capping agents, including methanol and methylal. However, regardless of the raw material and technology route used to produce polyoxymethylene dimethyl ether, a significant amount of byproducts are generated. In addition to DMMn with different degrees of polymerization, unreacted methanol, formaldehyde, and methylal are also produced. The separation methods of these byproducts and impurities, as well as the recycling of intermediate materials, have become key factors restricting DMMn production. On the one hand, to improve raw material utilization, long-chain molecules of DMM2 and above (mainly DMM7-13) need to be separated and recycled. On the other hand, unreacted DMM1 and byproduct methanol form an azeotrope, which is extremely difficult to separate. If DMM1 is returned to the reaction system without removing methanol, the methanol will participate in the reaction to produce water. In an acidic environment, this will not only lead to product hydrolysis but also further form an azeotrope, increasing the separation difficulty and seriously affecting the reaction process and product quality.
[0004] Several publicly reported DMMn demonstration-level industrial plants exist, but their actual effective production capacity is very limited. In terms of process technology, especially DMMn separation technology, many problems remain to be solved, and the technology has not yet reached a mature application stage. This makes it difficult to improve the production efficiency and product quality of existing plants, and plants under construction also face many uncertainties due to technological bottlenecks. Therefore, there is an urgent need for a distillation system to separate DMMn byproducts to improve the purity of the final product. Utility Model Content
[0005] The purpose of this invention is to provide a polyoxymethylene dimethyl ether (DMMn) distillation system that addresses the aforementioned shortcomings, solving the problems of current DMMn production equipment and enabling the separation and recycling of byproducts generated after the DMMn synthesis reaction, particularly the separation of methanol. To achieve the above objective, this invention provides the following technical solution:
[0006] A polyoxymethylene dimethyl ether (POM) distillation system includes a first distillation column assembly and a second distillation column assembly; the first distillation column assembly is connected to the second distillation column assembly; the first distillation column assembly is used to separate DMM3-6 from other products in the DMMn reaction products; the second distillation column assembly is used to separate methanol from the other products.
[0007] Furthermore, the outlet of the first distillation column assembly is connected to the inlet of the reaction device and the inlet of the second distillation column assembly (3), respectively, to send the separated DMM2, DMM7-13 and paraformaldehyde back to the inlet of the reaction device, and to send DMM1 and methanol into the second distillation column assembly; the outlet of the second distillation column assembly is connected to the inlet of the reaction device, to send the separated methanol DMM1 back to the reaction device.
[0008] Furthermore, the first distillation column assembly includes a primary distillation column, a secondary distillation column, and a tertiary distillation column; the inlet of the primary distillation column is connected to the outlet of the reaction unit; the reboiler of the primary distillation column is connected to the inlet of the secondary distillation column, and the primary distillation column is used to separate DMM1 and methanol from the reaction products, and to send DMM2, DMM3-6, DMM7-13, and paraformaldehyde into the secondary distillation column; the reboiler of the secondary distillation column is connected to the inlet of the tertiary distillation column, and the top of the column is connected to the inlet of the reaction unit, and the secondary distillation column is used to separate DMM2 and paraformaldehyde and return them to the reaction unit, and to send DMM3-6 and DMM7-13 into the tertiary distillation column; the reboiler of the tertiary distillation column is connected to the inlet of the reaction unit, and the tertiary distillation column is used to separate DMM7-13 and return them to the reaction unit.
[0009] Furthermore, the second distillation column assembly includes a four-stage distillation column and a five-stage distillation column; the inlet of the four-stage distillation column is connected to the top of the first-stage distillation column, the top of the first-stage distillation column is connected to the inlet of the fifth-stage distillation column, and the reboiler is connected to the inlet of the reaction unit. The four-stage distillation column is used to separate DMM1 and return it to the reaction unit, and to send DMM1 and methanol into the fifth-stage distillation column; the top of the fifth-stage distillation column is connected to the inlet of the fourth-stage distillation column, and the fifth-stage distillation column is used to separate methanol, and to send the unseparated DMM1 and methanol back to the fourth-stage distillation column for further distillation.
[0010] Furthermore, an alkaline washing and dehydration device is provided between the reaction device and the distillation column device; condensers are provided at the top of the first-stage, second-stage, third-stage, fourth-stage, and fifth-stage distillation columns.
[0011] Furthermore, the operating pressure of the primary distillation column is atmospheric pressure to 0.1 MPaG, and the operating temperature is 40 to 120°C.
[0012] Furthermore, the operating pressure of the secondary distillation column is negative, and the operating temperature is 60–150°C.
[0013] Furthermore, the three-stage distillation column operates under negative pressure and at an operating temperature of 100–200°C.
[0014] Furthermore, the operating pressure of the four-stage distillation column is 0.3–0.5 MPaG, and the operating temperature is 80–100℃.
[0015] Furthermore, the operating pressure of the five-stage distillation column is 0–0.1 MPaG, and the operating temperature is 40–80°C.
[0016] The beneficial effects of this utility model are:
[0017] This invention discloses a polyoxymethylene dimethyl ether (POD) distillation system, comprising a first distillation column assembly and a second distillation column assembly. The outlet of the first distillation column assembly is connected to the inlet of the reaction apparatus and the inlet of the second distillation column assembly, respectively, to separate DMM3-6 from other products in the DMMn reaction products. The separated DMM2, DMM7-13, and paraformaldehyde are returned to the inlet of the reaction apparatus, while DMM1 and methanol are fed into the second distillation column assembly. The outlet of the second distillation column assembly is connected to the inlet of the reaction apparatus, returning DMM1 (after methanol separation) to the reaction apparatus. This POD distillation system achieves the separation and recycling of byproducts generated after the DMMn synthesis reaction, particularly the separation of methanol to obtain purified DMM3-6. This not only improves product purity but also fully utilizes the byproduct components, effectively reducing raw material consumption. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of the polyoxymethylene dimethyl ether distillation system of this utility model;
[0019] In the attached diagram: 1-Reaction apparatus, 2-First distillation column assembly, 21-First stage distillation column, 22-Second stage distillation column, 23-Third stage distillation column, 3-Second stage distillation column assembly, 31-Fourth stage distillation column, 32-Fifth stage distillation column. Detailed Implementation
[0020] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
[0021] It should be understood that the terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “described” as used herein may also mean including the plural forms. The terms “comprising,” “including,” “containing,” and “having” are inclusive and therefore indicate the presence of the stated features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not construed as requiring them to be performed in a particular order described or illustrated unless the order of performance is explicitly indicated. It should also be understood that additional or alternative steps may be used.
[0022] Although terms such as first, second, third, etc., may be used in this document to describe multiple elements, components, regions, layers, and / or segments, these elements, components, regions, layers, and / or segments should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or segment from another. Unless the context clearly indicates otherwise, terms such as "first," "second," and other numerical terms used herein do not imply order or sequence. Therefore, the first element, component, region, layer, or segment discussed below may be referred to as the second element, component, region, layer, or segment without departing from the teachings of the exemplary embodiments.
[0023] For ease of description, spatial relative terms may be used in the text to describe the relationship of one element or feature relative to another element or feature, as shown in the figure. These relative terms include, for example, "inside," "outside," "middle," "outer," "below," "below," "above," "over," etc. The meaning of such spatial relative terms includes different orientations of the device in use or operation, in addition to the orientation depicted in the figure. For example, if the device in the figure is flipped, then an element described as "below other elements or features" or "below other elements or features" will subsequently be oriented "above other elements or features" or "above other elements or features." Therefore, the example term "below" can include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or in other directions), and the spatial relative descriptors used in the text will be interpreted accordingly.
[0024] This invention relates to a polyoxymethylene dimethyl ether distillation system, primarily for the separation and purification of DMMn synthesized from paraformaldehyde and methyl acetal as raw materials and solid acid as a catalyst. The main products include DMM3-6, paraformaldehyde, DMM1, DMM2, DMM7-13, and methanol. The system mainly separates unreacted paraformaldehyde, byproducts DMM1, DMM2, DMM7-13, and methanol from the products, ultimately obtaining purified DMM3-6 products.
[0025] Example 1
[0026] See attached Figure 1A polyoxymethylene dimethyl ether (POD) distillation system includes a first distillation column assembly 2 and a second distillation column assembly 3. The inlet of the first distillation column assembly 2 is connected to the outlet of a reaction unit 1, and the outlet is connected to the inlet of the reaction unit 1 and the inlet of the second distillation column assembly 3, respectively. Paraformaldehyde and methylal are used as raw materials, and a solid acid is used as a catalyst to carry out a chemical reaction in the reaction unit 1. The main products after the reaction are DMM1 and DMM2, DMM3-6, DMM7-13, methanol, and unreacted paraformaldehyde. These products and the unreacted paraformaldehyde are then further processed... The product enters the first distillation column assembly 2, which is mainly used to separate DMM3-6 from other products, obtaining purified DMM3-6. DMM2, DMM7-13, and paraformaldehyde are returned to the reaction unit 1 to participate in the reaction again. DMM1 and methanol are sent to the second distillation column assembly 3 for further separation and purification. The outlet of the second distillation column assembly 3 is connected to the inlet of the reaction unit 1. After DMM1 is separated from methanol in the second distillation column assembly 3, it is returned to the reaction unit to participate in the reaction again. This utility model's polyoxymethylene dimethyl ether distillation system realizes the separation and recycling of by-products generated after the DMMn synthesis reaction, especially the separation of methanol to obtain purified DMM3-6. This not only improves product purity but also fully utilizes the by-product components, effectively reducing raw material consumption.
[0027] Specifically, the first distillation column assembly 2 includes a primary distillation column 21, a secondary distillation column 22, and a tertiary distillation column 23, and the second distillation column assembly 3 includes a quaternary distillation column 31 and a quinary distillation column 32, such as... Figure 1As shown, the first-stage distillation column 21, the second-stage distillation column 22, the third-stage distillation column 23, the fourth-stage distillation column and the fifth-stage distillation column 32 all use layered structured packing (such as plate corrugated packing), with a single layer of packing height of 3 to 5 meters, and a total of 3 to 6 layers in a single column, and each column is equipped with a condenser at the top. The outlet of reaction unit 1 is connected to the inlet of primary distillation column 21. The top and bottom of primary distillation column 21 are connected to the inlets of quaternary distillation column 31 and secondary distillation column 22, respectively. The operating pressure of primary distillation column 21 is atmospheric pressure to 0.1 MPaG, and the operating temperature is 40 to 120℃. The reaction product of reaction unit 1 enters primary distillation column 21 for separation and purification, separating DMM1, methanol, and small amounts of DMM2 and paraformaldehyde, etc. After condensation by the top condenser, it is sent to quaternary distillation column 31. DMM2, DMM3-6, DMM7-13, and paraformaldehyde collected from the bottom of the column are sent to secondary distillation column 22 for further separation. The bottom of secondary distillation column 22 is connected to the inlet of tertiary distillation column 23, and the top of the column is connected to the inlet of reaction unit 1. Under negative pressure and at an operating temperature of 60–150°C, DMM2, DMM3–6, DMM7–13, and paraformaldehyde enter a secondary distillation column 22 for separation and purification. The separated DMM2 and paraformaldehyde are condensed by the top condenser and returned to the reaction unit 1 to participate in the reaction again. The DMM3–6 and DMM7–13 collected from the bottom of the column are sent to a tertiary distillation column 23 for further separation. The bottom of the tertiary distillation column 23 is connected to the inlet of the reaction unit 1. Operating under negative pressure and at an operating temperature of 100–200°C, DMM3–6 and DMM7–13 enter the tertiary distillation column 23 for separation and purification. The top distillate DMM3–6 is condensed by the top condenser to obtain the final desired product, while the DMM7–13 collected from the bottom is returned to the reaction unit 1 to participate in the reaction again.Because methanol and DMM1 form an azeotrope that is difficult to separate, and because returning methanol to the reaction system generates water, leading to more side reactions, a four-stage distillation column 31 and a five-stage distillation column 32 are installed to ensure the separation of methanol. The top of the four-stage distillation column 31 is connected to the inlet of the five-stage distillation column 32, and the bottom of the column is connected to the inlet of the reaction apparatus 1. The operating pressure is 0.3–0.5 MPaG, and the operating temperature is 80–100℃. After DMM1 and methanol enter the four-stage distillation column 31, under pressurized conditions, the azeotropic composition of DMM1 and methanol is altered, reducing the DMM1 content in the azeotrope. The distillate from the top of the column is the unseparated azeotrope of DMM1 and methanol. After condensation in the top condenser, the product is sent to the five-stage distillation column 32 for further separation. The DMM1 collected from the bottom of the column is returned to the reaction unit 1 to participate in the reaction again. The top of the five-stage distillation column 32 is connected to the inlet of the four-stage distillation column 31. Its operating pressure is 0-0.1 MPaG and its operating temperature is 40-80℃. The azeotrope of unseparated DMM1 and methanol enters the four-stage distillation column 31 and, under normal pressure, changes the azeotropic composition again, increasing the composition of DMM1 in the azeotrope. The distillate at the top of the column is the azeotrope of unseparated DMM1 and methanol. After condensation in the top condenser, it is sent back to the four-stage distillation column 31 for further separation. The above process is repeated, and the product collected from the bottom of the column is the separated methanol.
[0028] Specifically, an alkaline washing and dehydration device is provided between the reaction unit 1 and the distillation column unit. The alkaline washing and dehydration device is used to wash and dehydrate the reaction product in the reaction unit 1, and then send the reaction product into the subsequent distillation column unit.
[0029] The working process of this utility model:
[0030] After low-polymerization-degree paraformaldehyde and methylal undergo a chemical reaction in reaction unit 1, the resulting reaction liquid (DMM1, DMM2, DMM3-6, DMM7-13, methanol, and unreacted paraformaldehyde, etc.) is washed and dehydrated by an alkaline washing and dehydration unit and then enters the primary distillation column 21 for separation and purification. The separated DMM2, DMM3-6, DMM7-13, and paraformaldehyde enter the secondary distillation column 22 from the bottom of the column for further separation. The separated DMM1 and methanol are condensed by a condenser and then enter the quaternary distillation column 31 from the top of the column for further separation. After the separation and purification of DMM2, DMM3-6, DMM7-13, and paraformaldehyde in the secondary distillation column 22, DMM2 and paraformaldehyde are distilled from the top of the column, condensed by a condenser, and sent back to reaction unit 1 to participate in the reaction. The DMM3-6 and DMM7-13 collected from the bottom of the column are separated and purified. MM7-13 enters the three-stage distillation column 23 for further separation; after DMM3-6 and DMM7-13 are separated and purified by the three-stage distillation column 23, DMM3-6 is distilled from the top of the column and condensed by the condenser to become the final product, while DMM7-13 collected from the bottom of the column is sent back to the reaction unit 1 to participate in the reaction; after DMM1 and methanol are separated and purified by the four-stage distillation column 31, the bottom liquid collected from the bottom of the column is DMM1 and sent back to the reaction unit 1 to participate in the reaction, while the top distillate is unseparated DMM1 and methanol, which is condensed by the top condenser and sent to the five-stage distillation column 32 for further separation and purification; after unseparated DMM1 and methanol are separated and purified again by the five-stage distillation column 32, the top distillate is unseparated DMM1 and methanol, which is condensed by the top condenser and sent back to the four-stage distillation column 31 for further separation, while the bottom liquid is the separated methanol.
[0031] The polyoxymethylene dimethyl ether distillation system of this invention uses a five-stage distillation column 32 to separate DMM3-6 from other products. In particular, the use of a two-stage pressure swing distillation column ensures the separation of methanol from the by-products and the recycling of the methanol-free by-products. This not only improves product purity but also makes full use of the by-product components and effectively reduces raw material consumption.
[0032] All technical features in this embodiment can be freely combined according to actual needs. The above embodiments are only used to illustrate the technical solution of this utility model and are not intended to limit it. Although this utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of this utility model without departing from the spirit and scope of the technical solution of this utility model, and all such modifications and substitutions should be covered within the scope of the claims of this utility model. Technologies, shapes, and structural parts not described in detail in this utility model are all known technologies.
[0033] The above embodiments are preferred implementations of this utility model. In addition, other implementations are also included. Any obvious substitutions without departing from the concept of this technical solution are within the protection scope of this utility model.
Claims
1. A polyoxymethylene dimethyl ethers rectification system characterized by: The first rectification tower assembly (2) and the second rectification tower assembly (3) are connected; the first rectification tower assembly (2) is used for separating DMM3-6 from other products in the DMMn reaction product; and the second rectification tower assembly (3) is used for separating methanol from other products.
2. A polyoxymethylene dimethyl ethers rectification system according to claim 1, characterized in that: The outlet of the first rectification tower assembly (2) is connected with the inlet of the reaction device (1) and the inlet of the second rectification tower assembly (3) respectively, and the separated DMM2, DMM7-13 and paraformaldehyde are sent back to the inlet of the reaction device (1), and DMM1 and methanol are sent to the second rectification tower assembly (3); and the outlet of the second rectification tower assembly (3) is connected with the inlet of the reaction device (1), and the separated DMM1 is sent back to the reaction device (1).
3. A polyoxymethylene dimethyl ethers rectification system according to claim 2, characterized in that: The first rectification tower assembly (2) comprises a first-stage rectification tower (21), a second-stage rectification tower (22) and a third-stage rectification tower (23); the inlet of the first-stage rectification tower (21) is connected with the outlet of the reaction device (1); the tower kettle of the first-stage rectification tower (21) is connected with the inlet of the second-stage rectification tower (22), and the first-stage rectification tower (21) is used for separating DMM1 and methanol from the reaction product and sending DMM2, DMM3-6, DMM7-13 and paraformaldehyde into the second-stage rectification tower (22); the tower kettle of the second-stage rectification tower (22) is connected with the inlet of the third-stage rectification tower (23), and the top thereof is connected with the inlet of the reaction device (1), and the second-stage rectification tower is used for separating DMM2 and paraformaldehyde and sending them back to the reaction device (1), and sending DMM3-6 and DMM7-13 into the third-stage rectification tower (23); and the tower kettle of the third-stage rectification tower (23) is connected with the inlet of the reaction device (1), and the third-stage rectification tower (23) is used for separating DMM7-13 and sending them back to the reaction device (1).
4. A polyoxymethylene dimethyl ethers rectification system according to claim 3, characterized in that: The second rectification tower assembly (3) comprises a fourth-stage rectification tower (31) and a fifth-stage rectification tower (32); the inlet of the fourth-stage rectification tower (31) is connected with the top of the first-stage rectification tower (21), the top thereof is connected with the inlet of the fifth-stage rectification tower (32), and the tower kettle thereof is connected with the inlet of the reaction device (1), and the fourth-stage rectification tower (31) is used for separating DMM1 and sending them back to the reaction device (1), and sending DMM1 and methanol into the fifth-stage rectification tower (32); and the top of the fifth-stage rectification tower (32) is connected with the inlet of the fourth-stage rectification tower (31), and the fifth-stage rectification tower (32) is used for separating methanol and sending the unseparated DMM1 and methanol back to the fourth-stage rectification tower (31) for re-distillation.
5. A polyoxymethylene dimethyl ethers rectification system according to claim 4, characterized in that: An alkali washing and dehydration device is arranged between the reaction device (1) and the rectification tower device; and a condenser is arranged at the top of the first-stage rectification tower (21), the second-stage rectification tower (22), the third-stage rectification tower (23), the fourth-stage rectification tower and the fifth-stage rectification tower (32).
6. A polyoxymethylene dimethyl ethers rectification system according to claim 3, characterized in that: The operating pressure of the first-stage rectification tower (21) is normal pressure to 0.1 MPaG, and the operating temperature is 40-120℃.
7. A polyoxymethylene dimethyl ethers rectification system according to claim 3, characterized in that: The operating pressure of the second-stage rectification tower (22) is negative pressure, and the operating temperature is 60-150℃.
8. A polyoxymethylene dimethyl ethers rectification system according to claim 3, characterized in that: The operating pressure of the third rectification tower (23) is negative pressure, and the operating temperature is 100-200 DEG C.
9. A polyoxymethylene dimethyl ethers rectification system according to claim 4, characterized in that: The operating pressure of the fourth rectification tower (31) is 0.3-0.5 MPaG, and the operating temperature is 80-100 DEG C.
10. A polyoxymethylene dimethyl ethers rectification system according to claim 4, characterized in that: The operating pressure of the fifth rectification tower (32) is 0-0.1 MPaG, and the operating temperature is 40-80 DEG C.