Product separation rectifying tower for preparing dimethyl carbonate from urea through two-step method
The two-step dimethyl carbonate preparation process using urea has solved the problem of propylene carbonate reacting with methanol to produce propylene glycol, thus achieving high-purity dimethyl carbonate production and efficient utilization of raw materials.
Patent Information
- Application Number
- CN202422899248.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-26
- Publication Date
- 2025-11-11
- Estimated Expiration
- 2034-11-26
AI Technical Summary
In the industrial preparation of dimethyl carbonate, propylene carbonate reacts with methanol to produce propylene glycol, which then polymerizes with methanol, leading to an increase in byproducts and affecting product purity.
A two-step dimethyl carbonate preparation method using urea is employed, comprising a synthesis distillation column and a recovery column. Through the combination of components such as reflux pipes, circulation pipes, and falling film evaporators, efficient separation and recovery of raw materials are achieved, avoiding alcohol polymerization caused by high-temperature heating.
It improves the purity of dimethyl carbonate, reduces the generation of by-products, makes full use of raw materials, and reduces material loss.
Smart Images
Figure CN223529959U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the technical field of dimethyl carbonate production equipment, and more specifically, to a distillation column for separating and rectifying products from a two-step method for preparing dimethyl carbonate from urea. Background Technology
[0002] The industrial process for preparing dimethyl carbonate using the urea method mainly consists of two steps: first, the raw material urea reacts with propylene glycol to produce propylene carbonate; second, propylene carbonate further reacts with methanol via transesterification to generate dimethyl carbonate. The reaction between propylene carbonate and methanol requires a catalyst, therefore, in industrial applications, the two steps are typically carried out separately in a continuous reaction vessel.
[0003] In the process of preparing dimethyl carbonate from propylene carbonate and methanol by catalysis, propylene glycol is generated in the reaction system. Propylene glycol is prone to polymerize with propylene glycol or with methanol in this reaction system, which forms a large number of by-products and affects the purity of the product. Utility Model Content
[0004] The purpose of this invention is to solve the problem that in the existing industrial process for preparing dimethyl carbonate from urea, the reaction between propylene carbonate and methanol produces propylene glycol, which, after polymerization with methanol, generates a byproduct. This application provides a two-step distillation column for separating and rectifying products from urea in the preparation of dimethyl carbonate. This avoids the material loss caused by alcohol polymerization due to poor material flowability and continuous high-temperature heating in traditional thermosiphon reboilers.
[0005] This utility model is achieved through the following technical solution:
[0006] This invention provides a two-step distillation column for separating dimethyl carbonate products from urea, comprising a synthetic distillation column, the bottom of which is connected to a recovery column, and the top of the recovery column is provided with a reflux pipe, the end of which away from the recovery column is connected to the side wall of the synthetic distillation column; the bottom of the recovery column is connected to a falling film evaporator, the top of which is connected to the side wall of the recovery column, and a feed pipe is provided at the bottom of the falling film evaporator.
[0007] Preferably, the synthetic distillation column is equipped with a methanol tube, a propylene carbonate tube, and a catalyst tube, and the methanol tube, the propylene carbonate tube, and the catalyst tube are arranged side by side through the side wall of the synthetic distillation column.
[0008] Preferably, the bottom of the synthetic distillation column is provided with a circulation pipe, the outlet end of the circulation pipe is connected to the side wall of the synthetic distillation column, and a reboiler is installed in the middle section of the circulation pipe.
[0009] Preferably, a recovery pipe is installed at the top of the synthetic distillation column.
[0010] Preferably, the pipeline between the synthetic distillation column and the recovery column is equipped with a feed pump, and the pipeline between the recovery column and the falling film evaporator is equipped with a circulation pump.
[0011] Preferably, the discharge end of the falling film evaporator is connected to a buffer tank, and the bottom of the buffer tank is connected to the head end of the feed pipe.
[0012] Preferably, a feed pump is provided at the head end of the feed pipe near the buffer tank.
[0013] The technical solution of this utility model has the following beneficial effects:
[0014] This invention relates to a two-step process for preparing dimethyl carbonate from urea, using a product separation and distillation column. The raw materials react in the synthetic distillation column, where the high-temperature gas phase mainly consists of dimethyl carbonate and unreacted methanol. This gas is collected via a recovery pipe and further purified to obtain a high-purity dimethyl carbonate product. The material pumped from the bottom of the synthetic distillation column to the recovery column mainly includes methanol, catalyst, and the generated propylene glycol. This material can be further separated and recovered through heating and evaporation, with the separated methanol returned to the synthetic distillation column as feedstock. This dimethyl carbonate production and separation system avoids the problems of alcohol polymerization and material loss caused by poor material flowability and continuous high-temperature heating in traditional thermosiphon reboilers. Attached Figure Description
[0015] Figure 1 This is a schematic diagram of the distillation column for separating the product of the two-step urea preparation of dimethyl carbonate in Example 1.
[0016] Figure reference numerals: 1-synthetic distillation column, 11-methanol pipe, 12-propylene carbonate pipe, 13-catalyst pipe, 14-circulation pipe, 15-reboiler, 16-recovery pipe, 17-feed pump, 2-recovery column, 21-reflux pipe, 22-circulation pump, 3-falling film evaporator, 31-feed pipe, 32-buffer tank, 33-feed pump. Detailed Implementation
[0017] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below. Where specific conditions are not specified in the embodiments, they are performed according to conventional conditions or conditions recommended by the manufacturer; where the manufacturers of instruments, equipment, reagents, or raw materials are not specified, they are all conventional products that can be purchased commercially. The following are specific embodiments in conjunction with the accompanying drawings.
[0018] like Figure 1As shown, this embodiment provides a two-step distillation column for separating dimethyl carbonate products from urea, including a synthesis distillation column 1. The bottom of the synthesis distillation column 1 is connected to a recovery column 2, and a reflux pipe 21 is installed at the top of the recovery column 2. The end of the reflux pipe 21 away from the recovery column 2 is connected to the side wall of the synthesis distillation column 1. A falling film evaporator 3 is connected to the bottom of the recovery column 2, and the top of the falling film evaporator 3 is connected to the side wall of the recovery column 2. A feed pipe 31 is installed at the bottom of the falling film evaporator 3.
[0019] In this embodiment, the synthetic distillation column 1 is equipped with a methanol pipe 11, a propylene carbonate pipe 12, and a catalyst pipe 13, which are arranged side by side through the side wall of the synthetic distillation column 1. A circulation pipe 14 is arranged at the bottom of the synthetic distillation column 1, and the outlet end of the circulation pipe 14 is connected to the side wall of the synthetic distillation column 1. A reboiler 15 is installed in the middle section of the circulation pipe 14. A recovery pipe 16 is installed at the top of the synthetic distillation column 1.
[0020] In this embodiment, a feed pump 17 is installed in the pipeline between the synthesis distillation column 1 and the recovery column 2, and a circulation pump 22 is installed in the pipeline between the recovery column 2 and the falling film evaporator 3.
[0021] In this embodiment, the discharge end of the falling film evaporator 3 is connected to a buffer tank 32, and the bottom of the buffer tank 32 is connected to the head end of the feeding pipe 31; a feeding pump 33 is configured on the head end of the feeding pipe 31 near the buffer tank 32.
[0022] The dimethyl carbonate (DMC) production process described in this embodiment utilizes a two-step urea-based distillation column. Methanol and propylene carbonate, the reactants for DMC, are fed into a synthesis distillation column 1, with sodium methoxide as a catalyst to promote reaction. The reactants react in column 1, and the resulting gas phase at high temperature primarily consists of DMC and unreacted methanol. This gas is discharged through recovery pipe 16 and further purified to obtain a high-purity DMC product. The material pumped from the bottom of column 1 to recovery column 2 mainly includes methanol, catalyst, and generated propylene glycol. This material can be further processed by heating and evaporation for separation and recovery. The separated methanol is returned to column 1 as a feedstock. This DMC production and separation system fully utilizes the input raw materials and effectively separates and recovers unreacted raw materials and catalyst, avoiding the generation of large amounts of byproducts from impurities such as propylene glycol. The final product has higher purity, and the amount of byproducts is lower.
[0023] The above are merely preferred embodiments of this utility model and are not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.
Claims
1. A two-step distillation column for separating and rectifying products from urea in the preparation of dimethyl carbonate, characterized in that, The system includes a synthetic distillation column (1), the bottom of which is connected to a recovery column (2), and the top of the recovery column (2) is provided with a reflux pipe (21), the end of which is away from the recovery column (2) is connected to the side wall of the synthetic distillation column (1). The bottom of the recovery tower (2) is connected to a falling film evaporator (3), the top of the falling film evaporator (3) is connected to the side wall of the recovery tower (2), and a feeding pipe (31) is provided at the bottom of the falling film evaporator (3).
2. The distillation column for separating and rectifying products from urea in the two-step process for preparing dimethyl carbonate according to claim 1, characterized in that, The synthetic distillation column (1) is equipped with a methanol pipe (11), a propylene carbonate pipe (12) and a catalyst pipe (13), and the methanol pipe (11), the propylene carbonate pipe (12) and the catalyst pipe (13) are arranged side by side through the side wall of the synthetic distillation column (1).
3. The distillation column for separating and rectifying products from urea in the two-step process for preparing dimethyl carbonate according to claim 1, characterized in that, The bottom of the synthetic distillation column (1) is provided with a circulation pipe (14), the outlet end of the circulation pipe (14) is connected to the side wall of the synthetic distillation column (1), and a reboiler (15) is provided in the middle section of the circulation pipe (14).
4. The distillation column for separating and rectifying products from urea in the two-step process for preparing dimethyl carbonate according to claim 1, characterized in that, The top of the synthetic distillation column (1) is provided with a recovery pipe (16).
5. The distillation column for separating and rectifying products from urea in a two-step process for preparing dimethyl carbonate according to claim 1, characterized in that, A feed pump (17) is installed in the pipeline between the synthetic distillation column (1) and the recovery column (2), and a circulation pump (22) is installed in the pipeline between the recovery column (2) and the falling film evaporator (3).
6. The distillation column for separating and rectifying products from urea in a two-step process for preparing dimethyl carbonate according to any one of claims 1 to 5, characterized in that, The discharge end of the falling film evaporator (3) is connected to a buffer tank (32), and the bottom of the buffer tank (32) is connected to the head end of the feed pipe (31).
7. The distillation column for separating and rectifying products from urea in a two-step process for preparing dimethyl carbonate according to claim 6, characterized in that, A feed pump (33) is provided at the head end of the feed pipe (31) near the buffer tank (32).