A method for removing nitrogen dioxide from dimethyl sulfoxide

Abstract

The present invention belongs to the technical field of separating nitrogen dioxide from dimethyl sulfoxide, and specifically, is a method for removing nitrogen dioxide from dimethyl sulfoxide, the method comprising: a mixed solution of nitrogen dioxide and dimethyl sulfoxide continuously enters from the top of a nitrogen dioxide removal tower in a degassing tower device, and the nitrogen dioxide gas is continuously removed from the top of the tower; and a dimethyl sulfoxide liquid is continuously removed from the bottom of the tower. The nitrogen dioxide dissolved in dimethyl sulfoxide is continuously removed in a specific removal tower device. The temperature of the removal tower is controlled by a heat exchange facility in the removal tower, thereby reducing safety hazards and reducing the generation of side reactions of dimethyl sulfoxide generating dimethyl sulfone.

Description

Technical Field

[0001] The invention belongs to the technical field of separating nitrogen dioxide from dimethyl sulfoxide, and specifically relates to a method for removing nitrogen dioxide from dimethyl sulfoxide. Background Art

[0002] Dimethyl sulfoxide is a typical fine chemical product. It is an important intermediate in the fields of electronics, carbon fiber, medicine, pesticides, organic synthesis, etc., and has a wide range of uses. Dimethyl sulfoxide is a high-efficiency organic solvent and emerging extractant developed in the 1960s. The dimethyl sulfoxide molecule contains a semi-polar sulfur-oxygen group, which can effectively form a coordination complex or solvate with metal ions. Therefore, dimethyl sulfoxide can extract precious metals such as gold, silver, and platinum in hydrochloric acid and sulfuric acid media, and can also extract rare earth elements such as uranium and thorium. What is more valuable is that it is a polar organic solvent, which has good solubility and strong permeability for organic and inorganic substances. Therefore, it is widely used in the fields of electronics, carbon fiber, medicine, pesticides, organic synthesis, and precious metal extraction.

[0003] In the preparation process of dimethyl sulfoxide, an oxidation preparation method is used, which uses nitrogen dioxide as an oxidant, pure oxygen, and dimethyl sulfide as raw materials. In this method, during the oxidation of dimethyl sulfide to dimethyl sulfoxide, nitrogen dioxide will dissolve in dimethyl sulfoxide in large quantities. In the traditional process of removing nitrogen dioxide, alkali is added to the dimethyl sulfoxide mixed solution for neutralization to generate sodium nitrate waste salt. Then, in the dimethyl sulfoxide distillation process, evaporation is used to remove the sodium nitrate waste salt. There are great safety hazards in the evaporation desalination process; many safety accidents have occurred at home and abroad, and a large amount of dimethyl sulfoxide-containing sodium nitrate waste salt has been discharged. Therefore, the development of a new method that is safe, efficient, and has no "three wastes" discharge is of great significance in terms of both safety and environmental impact. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for removing nitrogen dioxide from dimethyl sulfoxide, thereby solving potential safety hazards and not generating nitrogen oxide tail gas emissions.

[0005] The present invention is achieved in this way.

[0006] A method for removing nitrogen dioxide from dimethyl sulfoxide comprises the following steps: a mixed solution of nitrogen dioxide and dimethyl sulfoxide continuously enters the top of a nitrogen dioxide removal tower in a degassing tower, and nitrogen dioxide gas is continuously removed from the top of the tower; and a method for separating the dimethyl sulfoxide liquid continuously removed from the bottom of the tower.

[0007] Furthermore, the removal conditions are pressure: 0.0MPa~0.3MPa, temperature: 15~180℃.

[0008] Furthermore, the temperature of the removal system is 20 to 120° C., and the pressure is 0.0 MPa to 0.2 MPa.

[0009] Furthermore, the flow rate of the mixed liquid into the removal tower is 0.01-10.0 t / h; the mass ratio of the corresponding treated nitrogen dioxide in dimethyl sulfoxide is 1%-40% of the mixed solution.

[0010] Furthermore, the removal tower equipment is a plate tower, and the removal tower has a length-to-diameter ratio in the range of (1-20):1, including a plurality of tower plates arranged along the vertical direction and a riser arranged in the axial direction of the removal tower. Nitrogen dioxide and dimethyl sulfoxide are separated in the tower plates, and the separated nitrogen dioxide is discharged from the riser of the tower to the top of the tower.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] 1. Nitrogen dioxide dissolved in dimethyl sulfoxide is continuously removed in a specific removal tower. The temperature of the removal tower is controlled by the heat exchange facilities in the removal tower, which reduces safety hazards and reduces the side reaction of dimethyl sulfoxide to dimethyl sulfone.

[0013] 2. The separation products of the present invention are dimethyl sulfoxide and nitrogen dioxide. Nitrogen dioxide will be used again in the oxidation of dimethyl sulfide, and the separated dimethyl sulfoxide will be directly distilled to dimethyl sulfoxide. In comparison, the method of the present invention will not produce nitrogen oxide tail gas emissions; there will be no large amount of sodium nitrate waste salt containing organic matter produced in the process of separating dimethyl sulfoxide and nitrogen dioxide; and there are also safety hazards caused by separating sodium nitrate waste salt.

[0014] 3. The removal tower of the present invention is a removal tower equipment with a large aspect ratio. The position for introducing the dimethyl sulfoxide mixed solution containing nitrogen dioxide is located at the top of the removal tower, and the removed nitrogen dioxide gas is continuously discharged from the top of the tower through the gas riser; the dimethyl sulfoxide from which the nitrogen dioxide gas is removed is continuously discharged from the bottom of the tower through the downcomer. Avoiding the re-contact between nitrogen dioxide and dimethyl sulfoxide is conducive to the continuous removal of nitrogen dioxide and is conducive to large-scale and continuous industrial production.

[0015] 4. By controlling the temperature, pressure, liquid level and mixed liquid feed volume of the removal system, the removal process can always maintain a continuous and stable production state. The separated product nitrogen dioxide will be reused without being discharged. The nitrogen dioxide removal rate can reach more than 80%. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A process diagram of the method provided by the present invention;

[0017] Figure 2 This is a schematic diagram of the structure of some tower sections of the desulfurization tower used in the method of the present invention. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] See also Figure 1 As shown, the present invention provides a method for removing nitrogen dioxide from dimethyl sulfoxide, which includes a mixed solution of nitrogen dioxide and dimethyl sulfoxide continuously entering from the top of a nitrogen dioxide removal tower in a degassing tower device, and continuously removing nitrogen dioxide gas from the top of the tower; and a separation method for dimethyl sulfoxide liquid continuously removed from the bottom of the tower. The removal conditions are pressure: 0.0MPa~0.3MPa, temperature: 15~180℃. Preferably, the removal system temperature is: 20~120℃, and the pressure is: 0.0MPa~0.2MPa.

[0020] The flow rate of the mixed liquid into the removal tower is 0.01-10.0 t / h; the mass ratio of the corresponding treated nitrogen dioxide in dimethyl sulfoxide is 1%-40% of the mixed solution.

[0021] See also Figure 2 As shown, the removal tower equipment is a plate tower, and the length-to-diameter ratio of the removal tower is in the range of (1-20):1, including a plurality of tower plates arranged in the vertical direction and a gas riser 1 arranged in the axial direction of the removal tower. Nitrogen dioxide and dimethyl sulfoxide are separated in the tower plate 3, and the separated nitrogen dioxide is discharged from the tower gas riser 2 to the top of the tower. The removal tower has heat exchange pipes and jacket heating facilities 2, and has temperature measurement, pressure measurement, liquid level and other facilities.

[0022] The present invention performs continuous degassing in a degassing tower with a large aspect ratio under degassing conditions of pressure: 0.0MPa to 0.3MPa and temperature: 15 to 120°C. The nitrogen dioxide gas removed in the process is reused, and the dimethyl sulfoxide from which the nitrogen dioxide has been removed is subjected to rectification treatment. Continuous feeding and discharging are achieved by controlling the temperature, pressure and liquid level of the removal system. The nitrogen dioxide removal rate reaches more than 80%. The present invention is a method for establishing a continuous, efficient, safe and environmentally friendly method for removing nitrogen dioxide dissolved in dimethyl sulfoxide.

[0023] A nitrogen dioxide mixed liquid dissolved in dimethyl sulfoxide is continuously introduced into a degassing tower with a large aspect ratio (see a schematic diagram of a tower section). Under the pressure and temperature conditions specified in the present invention, nitrogen dioxide and dimethyl sulfoxide are separated in the tower tray, and the separated nitrogen dioxide is discharged from the tower riser to the top of the tower; the separated dimethyl sulfoxide is continuously discharged from the bottom of the tower through the downcomer tray; and the liquid level in the tower bottom is controlled to obtain a method for continuously removing nitrogen dioxide from dimethyl sulfoxide.

[0024] (1) Reaction mechanism of the present invention:

[0025] Control the reaction temperature and pressure to prevent dimethyl sulfoxide from being oxidized to dimethyl sulfone

[0026] C2H6SO+NO2→C2H6SO2+NO

[0027] (2) The nitrogen dioxide removal rate of the present invention is defined as:

[0028] Removal rate = (mass of nitrogen dioxide in dimethyl sulfoxide removed / mass of nitrogen dioxide in dimethyl sulfoxide before removal) * 100%.

[0029] (3) In combination with the method of the present invention and the accompanying drawings, a mixed solution with a dimethyl sulfoxide mass concentration of 50 to 90% is prepared in the removal tower using dimethyl sulfoxide and nitrogen dioxide as media, and a dimethyl sulfoxide mass concentration of 70 to 90% is more preferably prepared.

[0030] (4) The removal pressure of the present invention is 0.0 MPa to 0.3 MPa, and the temperature is 15 to 180°C; the temperature of the removal system is more preferably 20 to 120°C.

[0031] (5) The mixed solution of dimethyl sulfoxide and nitrogen dioxide diffuses from the top of the removal tower to each tray. In order to increase the residence time of the tray in the mixed solution, the height of the removal tower and the number of trays are adjusted. The feed flow rate of the mixed solution is adjusted. The optimal solution for the height and number of trays of the removal tower is selected. The optimal solution is a tower height of 6 meters and 10 trays.

[0032] (6) Control the temperature, pressure, liquid level and mixed liquid feed rate of the removal system. In the mixed liquid separation stage, the separated nitrogen dioxide and dimethyl sulfoxide are always kept out of contact, and dimethyl sulfoxide as an oxidation product no longer participates in the oxidation reaction. The pressure of the mixed solution added to the removal tower is 0.0 MPa to 0.3 MPa, more preferably 0.0 MPa to 0.2 MPa.

[0033] (7) The separation of dimethyl sulfoxide and nitrogen dioxide in mixed solutions of different concentrations proceeds rapidly under the influence of temperature, pressure and each tray. The separation time for destroying solubility is 0.01s to 100s.

[0034] Example

[0035] Example 1: Enter the removal tower at a flow rate of 100 mL / min. Maintain the removal temperature at 50°C and the pressure at 0.05 MPa, and continue the removal for 30 minutes. Detection and calculation: The nitrogen dioxide removal rate is 76.5%, and the dimethyl sulfone generation rate is 0.1%.

[0036] Example 2, in this example, a mixed reagent of dimethyl sulfoxide and nitrogen dioxide (mass ratio: 5:1) enters the removal tower at a flow rate of 100 mL / min. The removal temperature is maintained at 50°C and the pressure is 0.02 MPa, and the removal is continued for 30 minutes. Detection and calculation: The nitrogen dioxide removal rate is 79.1%, and the dimethyl sulfone generation rate is 0.08%.

[0037] Example 3, in this example, a mixed reagent of dimethyl sulfoxide and nitrogen dioxide (mass ratio: 5:1) enters the removal tower at a flow rate of 100 mL / min. The removal temperature is maintained at 80°C and the pressure is 0.05 MPa, and the removal is continued for 30 minutes. Detection and calculation: the nitrogen dioxide removal rate is 85.2%, and the dimethyl sulfone generation rate is 0.15%.

[0038] Example 4, in this example, a mixed reagent of dimethyl sulfoxide and nitrogen dioxide (mass ratio: 5:1) enters the removal tower at a flow rate of 100 mL / min. The removal temperature is maintained at 80°C and the pressure is 0.02 MPa, and the removal is continued for 30 minutes. Detection and calculation: The nitrogen dioxide removal rate is 93.4%, and the dimethyl sulfone generation rate is 0.12%.

[0039] Example 5, in this example, a mixed reagent of dimethyl sulfoxide and nitrogen dioxide (mass ratio: 5:1) enters the removal tower at a flow rate of 100 mL / min. The removal temperature is maintained at 120°C and the pressure is 0.05 MPa, and the removal is continued for 30 minutes. Detection and calculation: The nitrogen dioxide removal rate is 95.2%, and the dimethyl sulfone generation rate is 0.21%.

[0040] Example 6, in this example, a mixed reagent of dimethyl sulfoxide and nitrogen dioxide (mass ratio: 5:1) enters the removal tower at a flow rate of 100 mL / min. The removal temperature is maintained at 120°C and the pressure is 0.02 MPa, and the removal is continued for 30 minutes. Detection and calculation: The nitrogen dioxide removal rate is 96.6%, and the dimethyl sulfone generation rate is 0.16%.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for removing nitrogen dioxide from dimethyl sulfoxide, characterized in that: The method comprises the following steps: a mixed solution of nitrogen dioxide and dimethyl sulfoxide continuously enters from the top of a nitrogen dioxide removal tower in a removal tower device, and the nitrogen dioxide gas is continuously removed from the top of the tower; A separation method for dimethyl sulfoxide liquid continuously removed from the bottom of a tower; The removal conditions are pressure: 0.0MPa~0.3MPa, temperature: 15~180℃; The removal tower equipment is a plate tower, and the removal tower has an aspect ratio range of (1 to 20): 1, including a plurality of tower plates arranged along the vertical direction and a riser arranged in the axial direction of the removal tower. Nitrogen dioxide and dimethyl sulfoxide are separated in the tower plates, and the separated nitrogen dioxide is discharged from the riser of the tower to the top of the tower.

2. The method according to claim 1, characterized in that The flow rate of the mixed liquid into the removal tower is 0.01-10.0 t / h; the mass ratio of the corresponding treated nitrogen dioxide in dimethyl sulfoxide is 1%-40% of the mixed solution.

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