CN-121975120-A - Method and system for preparing low-water-content sodium sulfide/NMP mixture through sodium sulfide dehydration and application

CN121975120ACN 121975120 ACN121975120 ACN 121975120ACN-121975120-A

Abstract

The invention belongs to the field of chemical raw materials, and discloses a method and a system for preparing a low-water-content sodium sulfide/NMP mixture by dehydrating sodium sulfide and application thereof. The method comprises the steps of continuously adding the sodium sulfide aqueous solution into NMP at a target dehydration temperature at a preset flow, removing part of materials containing water, NMP and hydrogen sulfide from a dehydration kettle in the process, wherein the adding flow of the sodium sulfide aqueous solution is equal to the water quantity removed from the dehydration kettle at the target dehydration temperature by the water quantity, returning the materials in the dehydration tower to the dehydration kettle after the sodium sulfide aqueous solution is added to obtain the low-water-content sodium sulfide/NMP mixture, and optionally repeating the steps. The method has the advantages of high dehydration efficiency, good stability, low water content, small difference of water content and sulfur source content in the low-water-content sodium sulfide/NMP mixture among different batches, stable quality and good raw material support for obtaining high-quality polyphenylene sulfide, wherein the water/sulfur mole ratio of the dehydrated sodium sulfide/NMP mixture is less than or equal to 1.

Inventors

QI YANWEI
ZHANG BAOZHONG
ZHANG ZHIQUAN
Xiong Qiqiang
YANG YUQIANG
ZHANG LEI
FU HUIJUAN

Assignees

中国石油化工股份有限公司
中石化(天津)石油化工有限公司
中石化上海工程有限公司
中石化（上海）石油化工研究院有限公司
天津工业大学

Dates

Publication Date: 20260505
Application Date: 20241030

Claims (10)

1. A method for preparing a low water content sodium sulfide/NMP mixture by dewatering sodium sulfide comprising: (1) Preheating to form an aqueous solution of sodium sulfide; (2) Preheating NMP in a dehydration kettle to a target dehydration temperature, wherein the molar ratio of sodium sulfide to NMP in the sodium sulfide aqueous solution is 1 (2-4); (3) Continuously adding the sodium sulfide aqueous solution into NMP obtained in the step (2) at a preset flow rate at a target dehydration temperature, wherein part of the water, NMP and material containing hydrogen sulfide are removed from a dehydration kettle in the process, and the adding flow rate of the sodium sulfide aqueous solution is equal to the water quantity removed from the dehydration kettle at the target dehydration temperature by the water quantity, wherein the removed material containing water, NMP and material containing hydrogen sulfide is separated in a dehydration tower, and at least part of the water is removed from the top of the dehydration tower; (4) After the sodium sulfide aqueous solution is added, when the water quantity removed in the dehydration tower is confirmed to be the target dehydration quantity of all materials, returning the materials in the dehydration tower to a dehydration kettle to obtain the low-water-content sodium sulfide/NMP mixture, wherein the molar ratio of water to sulfur in the low-water-content sodium sulfide/NMP mixture is less than or equal to 1; optionally, repeating steps (1) to (4).
2. The method according to claim 1, characterized in that: in step (1): the temperature of the preheated sodium sulfide aqueous solution is 80-130 ℃, preferably the operating temperature of the step (1) is constant, and/or, The step (1) is performed under a nitrogen atmosphere, preferably a positive pressure nitrogen atmosphere, more preferably a pressure of 0.02-0.05 MPa, and/or, The molar ratio of water to sodium sulfide in the sodium sulfide aqueous solution is 4-10, preferably 4.3-9.0, preferably, The sodium sulfide aqueous solution is derived from at least one of a solution obtained by crystallizing sodium sulfide and optional water and a solution prepared by preparing sodium hydrosulfide, sodium hydroxide and water, more preferably, the sodium sulfide aqueous solution is derived from a solution obtained by heating and dissolving crystalline sodium sulfide containing 3-9 crystal water, or adding water and heating and dissolving, or is prepared by reacting sodium hydrosulfide with an aqueous solution of sodium hydroxide.
3. The method according to claim 1, characterized in that: In the step (2): The step (2) is carried out under nitrogen atmosphere and/or, The target dehydration temperature is 135-205 ℃, and preferably the operation temperature of the step (2) is constant.
4. The method according to claim 1, characterized in that: In the step (3): in the dehydration balance stage, the adding flow of the sodium sulfide aqueous solution is equal to the water quantity removed from the dehydration kettle at the target dehydration temperature by a water quantity meter; and/or the absolute pressure of the system of the dehydration kettle and the dehydration tower is more than or equal to 10kPa and less than or equal to P and less than or equal to normal pressure; and/or the target dehydration temperature is 135-205 ℃, preferably constant temperature.
5. The method according to claim 1, characterized in that: In the step (3): In the dehydration process, the amount of water removed from the dehydration tank at the target dehydration temperature is preferably controlled by the addition flow rate of the sodium sulfide aqueous solution by the water amount, The online conductivity meter is contacted with the mixture containing sodium sulfide and NMP in the dehydration kettle, and is used for monitoring the change of the water content in the dehydration kettle through the reading of the online conductivity meter and judging whether the adding flow of the sodium sulfide aqueous solution is equal to the water amount removed from the dehydration kettle.
6. The method according to claim 1, characterized in that: The dehydration tower comprises a rectifying section and a stripping section, wherein the theoretical plate number of the rectifying section is preferably 5-10, and/or the theoretical plate number of the stripping section is 5-10, and the dehydration tower is fed in a gas phase mode, the reflux ratio is controlled to be 0.5-2, and/or the dehydration tower comprises a distillation section and a stripping section, The sodium sulfide aqueous solution is continuously added into the dehydration kettle at a preset flow rate, wherein the adding position is under the liquid level or above the liquid level of the dehydration kettle, preferably, the sodium sulfide aqueous solution is continuously added into the dehydration kettle at a preset flow rate, the adding position is on the liquid level of the dehydration kettle, and the sodium sulfide aqueous solution is added in a single-point or multi-point spraying or sprinkling mode, and/or, The water adding flow of the sodium sulfide aqueous solution is equal to the water amount removed from the top of the dehydration tower by the water amount meter.
7. The method according to claim 1, characterized in that: in the step (4): After the sodium sulfide aqueous solution is added, when the dehydration kettle material reaches the target dehydration amount after confirming the water amount removed in the dehydration tower, continuously maintaining the original dehydration condition for 30-60 minutes, and/or, The operating temperature of step (4) is constant, and/or, The material in the dehydration column contains recovered NMP and preferably, The recovered NMP is returned to the dehydration kettle in its entirety, more preferably, the water content of the recovered NMP is less than or equal to 0.1%, and still more preferably, the water content of the recovered NMP is less than or equal to 0.01%.
8. The method according to claim 1, characterized in that: during the dehydration process, the tail gas containing hydrogen sulfide separated from the dehydration tower is recycled back to the dehydration kettle material, preferably through at least one device selected from a hydrogen sulfide circulating fan, a circulating compressor and a vacuum pump, preferably, The discharge port of the top of the dehydration tower is communicated with a vacuum pump, and hydrogen sulfide circulation is directly formed between the outlet of the vacuum pump and the dehydration kettle, or if the pressure difference between the outlet of the vacuum pump and the dehydration kettle can not meet the requirement of hydrogen sulfide circulation, a hydrogen sulfide circulation fan and/or a circulation compressor are additionally arranged for circulation.
9. A system for the dehydration of sodium sulfide to produce a low water content sodium sulfide/NMP mixture superior to a system for the method of any one of claims 1-8 for the dehydration of sodium sulfide to produce a low water content sodium sulfide/NMP mixture comprising: the device comprises a sodium sulfide aqueous solution preparation kettle, an NMP source, a dehydration kettle, monitoring equipment, a dehydration tower, a water treatment device and a water treatment device, wherein the monitoring equipment is arranged at the lower part of the dehydration kettle and is used for monitoring whether the water content of mixed solution in the dehydration kettle is stable or not; the top discharge port of the dehydration kettle is communicated with the feed port of the dehydration tower; the bottom discharge port of the dehydration tower is communicated with the feed port of the dehydration kettle, and the top discharge port of the dehydration tower is optionally communicated with the outside; Preferably, the system also comprises a nitrogen source, a discharge port of the nitrogen source is communicated with other equipment of the system along the material flow direction, and/or, Preferably, the dehydration tower also comprises at least one device of a hydrogen sulfide circulating fan, a circulating compressor and a vacuum pump which are communicated with a top discharge hole of the dehydration tower, and/or, Preferably, the dehydration tower comprises a rectifying section and a stripping section, preferably, the theoretical plate number of the rectifying section is 5-10, and/or the theoretical plate number of the stripping section is 5-10, and/or, Preferably, the detection device is an on-line conductivity meter.
10. Use of a process for preparing a low aqueous sodium sulphide/NMP mixture by dehydration of sodium sulphide according to any one of claims 1 to 8 or of a system according to claim 9 for preparing polyphenylene sulphide.

Description

Method and system for preparing low-water-content sodium sulfide/NMP mixture through sodium sulfide dehydration and application Technical Field The invention relates to the field of chemical raw material preparation, in particular to a method and a system for preparing a low-water-content sodium sulfide/NMP mixture for polyphenylene sulfide by dehydrating sodium sulfide and application thereof. Background There are various synthetic methods for polyphenylene sulfide, wherein the sodium sulfide method is one of the methods for the industrialization of polyphenylene sulfide, and the existing industrialized device is mainly the sodium sulfide method. The water content of the polymerization system of the sodium sulfide method has great influence on polymerization, and various literature data and experimental data show that the optimal water content of the solvent system of the polymerization reaction exists, so that the effect and the product index of the polymerization reaction can be controlled by controlling the water content of the solvent system of the polymerization reaction to a certain extent. The water in the polymerization system is mainly derived from sodium sulfide raw material, and the water content of the water is far higher than the water content required by the polymerization solvent system, so that the dehydration of sodium sulfide and the control and regulation of the water content of the polymerization solvent system are necessary. For example, patent CN109563268a synthesizes sodium hydrosulfide, sodium hydroxide in the presence of sodium acetate, NMP and water, then dehydrates. PPS is polymerized to obtain PPS particles having a molecular weight of 34000-67000 g/mol (polyphenylene sulfide) when the water/NMP (molar ratio) is in the range of 0.54-0.85, only PPS particles having a molecular weight of <30000g/mol are obtained when the water/NMP (molar ratio) is greater than 0.85, and PPS particles are not obtained when the water/NMP (molar ratio) is less than 0.50. At present, the dehydration mode of sodium sulfide is mainly that dehydration is carried out in a kettle under normal pressure or vacuum. In general, crystalline sodium sulfide, NMP and a small amount of sodium hydroxide are added into a dehydration kettle, or sodium hydrosulfide, sodium hydroxide and NMP are reacted to generate sodium sulfide and then evaporated for dehydration. Along with the dehydration, water and NMP are continuously evaporated, the water and NMP in the dehydration kettle are continuously reduced, the water concentration in the kettle is gradually reduced, and the temperature of the dehydration kettle is continuously increased, so that the dehydration kettle and the dehydration tower are always in an unsteady state operation. For example, the dehydration process of CN110294844A sodium sulfide comprises the steps of adding NMP into a reaction kettle, then adding sodium sulfide, sodium hydroxide and nitrogen in sequence for protection, heating to 150-203 ℃ at a temperature rising rate of 0.8-2 ℃ per minute, and keeping the temperature for 10min to stop dehydration, adding sodium sulfide, NMP, an auxiliary agent and sodium hydroxide into the reaction kettle by CN110818898A, stirring, replacing nitrogen, heating to 120-170 ℃ at a vacuum degree of-0.03-0.08 MPa at a temperature rising rate of 1-5 ℃ per minute to perform dehydration, and synthesizing sodium sulfide and sodium hydroxide in the molar ratio of 1:1-1.2 by CN109563268A in the presence of sodium acetate, NMP and water, performing dehydration at 130-210 ℃ and keeping the molar ratio of water and sulfur in the rest mixture at 1.7-2.5. The common feature of the above documents is that the dehydration temperature is gradually increased and the content of the evaporation mixed liquid composition of the evaporation kettle is also changed along with the change of the water content in the dehydration kettle. The inventor of the present invention found that the current technology for recovering NMP in the dehydration process usually comprises directly condensing water and solvent evaporated from a dehydration kettle into a receiving tank and then into a solvent recovery system to recover the solvent, or recovering most NMP through internal reflux by an externally cooled reflux column, condensing uncondensed water and part of NMP into the receiving tank by a condenser and then into the solvent recovery system to recover NMP, or removing water by a dehydration tower with only a rectifying section, and directly returning a certain amount of recovered NMP to the dehydration kettle. The above process results in a significant reduction in NMP in the dehydration tank or reduced dehydration efficiency due to the fraction of water contained in the recovered NMP, while the overall system is always in an unstable operation. For example, CN102964599A adopts vacuum dehydration, the dehydrated liquid directly enters a dehydration storage tank, then enters a recovery dehydration pr