WO2021073199A1

WO2021073199A1 - Continuous production method for hydroxyethylene diphosphonic acid crystals

Info

Publication number: WO2021073199A1
Application number: PCT/CN2020/105782
Authority: WO
Inventors: 程终发; 王燕平; 齐晓婧; 宋盟盟; 王宁宁; 刘全华
Original assignee: 山东泰和水处理科技股份有限公司
Priority date: 2019-10-17
Filing date: 2020-07-30
Publication date: 2021-04-22
Also published as: CN110642887A; CN110642887B

Abstract

A continuous production method for hydroxyethylene diphosphonic acid crystals, the specific operation method comprising: performing preheating and gas-liquid separation on a liquid product of hydroxyethylene diphosphonic acid with an active content of 50-65% and then continuously pumping same into a distilling still at a constant speed; when the active content of the material is greater than or equal to 70% after being concentrated by distillation, condensing the high-temperature material and automatically transferring the material sequentially from the first stage to n-th stage crystallization kettles connected in series; under the conditions of stirring and natural cooling, performing crystallization stage by stage; then, lowering the temperature by circulating condensation in the n-th stage crystallization kettle and keeping the system temperature at 20±2 degrees Celsius; and after fully crystallizing, separating and drying crystals to obtain hydroxyethylene diphosphonic acid crystal products with an active content greater than or equal to 98%.

Description

Continuous production method of hydroxyethylene diphosphonic acid crystals

Technical field

The invention belongs to the technical field of fine chemical production, and specifically relates to a continuous production method of hydroxyethylene diphosphonic acid crystals.

Background technique

Hydroxyethylidene diphosphonic acid (HEDP for short), because of its extremely stable CP bond in its molecule, the bond energy is 246kJ/mol, high temperature resistance, and has a good scale inhibitory effect on calcium carbonate, hydrated iron oxide and calcium phosphate in water , Is an important scale inhibitor and dispersant. Because HEDP can form stable complexes with iron, copper, zinc and other metal ions, and can dissolve oxides on the metal surface, it can be used as a complexing agent in the non-cyanide electroplating industry; in addition, because HEDP has better corrosion inhibition Anti-scaling effect and passivation effect on metal surfaces, high-purity HEDP products can be used for cleaning circuit boards in the electronics industry and metal surface treatment.

Conventional commercial HEDP liquid products with 50% or 60% specifications are mostly synthesized using phosphorus trichloride as one of the starting materials. The various impurities in the raw materials greatly limit its use in electronic cleaning, medicine and daily chemical industry. The application of the industry, therefore, the research and production of HEDP crystals or solid products with higher purity, to improve the added value of the products, has always become a technical hot spot for researchers in this field. Chinese patent CN1312163C discloses a kind of 50-60% liquid hydroxyethylene diphosphonic acid as raw material, adding crystal nucleus sodium acetate and crystal promoter anhydrous ethanol to slowly stir and crystallize in a reaction kettle, and then stand for aging. , Centrifugation and drying to prepare a solid product of hydroxyethylene diphosphonic acid with a content of ≥90%. The patent of CN101597305B discloses a process for preparing high-purity solid amino trimethylene phosphonic acid or hydroxyethylene diphosphonic acid. The process combines amino trimethylene phosphonic acid or hydroxyethylene diphosphonic acid with an effective substance content of 68-85%. The liquid temperature of the diphosphonic acid is controlled at 30-90°C, then ice crystal particles are added to the liquid system to precipitate crystals, and the corresponding solid products are obtained by centrifugal dehydration and drying at 60-120°C. CN107522740A relates to a production process of low-arsenic solid hydroxyethylene diphosphonic acid. Specifically, in a reactor, a dearsenic agent, phosphorus pentasulfide, is used to perform cyclic dearsenic treatment on a hydroxyethylene diphosphonic acid liquid, and then the material liquid is subjected to Concentrate, heat, and gradually increase the temperature to remove water. By adding a nucleating agent to the discharging tank, the material temperature is gradually reduced, and the HEDP solid product with activity ≥98% is prepared by natural crystallization. The inventor disclosed a preparation process suitable for electronic grade solid hydroxyethylene diphosphonic acid in CN100478347C.

The existing published preparation methods of hydroxyethylene diphosphonic acid solids or crystals all adopt the traditional intermittent single-pot operation, which is not conducive to the stability of product quality between batches; at the same time, because the crystallization process is affected by many factors The slow physical process of the impact and the long equipment occupancy cycle greatly limit the production capacity of such products and seriously affect the market application and promotion of the products.

Summary of the invention

In order to solve the problems and deficiencies in the prior art, the present invention provides a production method capable of continuously producing hydroxyethylene diphosphonic acid crystals. The method uses the natural cooling and crystallization of hydroxyethylene diphosphonic acid and adopts multi-stage crystallization, which can effectively stabilize product quality, improve equipment utilization and product productivity, save water and reduce emissions, generate no three wastes, is safe and environmentally friendly, and is beneficial to Realize automatic control and large-scale industrial production.

The present invention is specifically realized through the following technical solutions:

A continuous production method of hydroxyethylene diphosphonic acid crystals specifically includes the following steps:

(1) After preheating, gas-liquid separation, the liquid product of hydroxyethylene diphosphonic acid with an active content of 50-65% is continuously pumped into the still at a constant speed;

(2) When the material in the distillation kettle reaches one-third of the volume of the kettle body, turn on the stirring and rapidly increase the temperature, and the system establishes a negative pressure condition of -0.04～-0.06MPa for continuous concentration and purification;

(3) When the volume of the material in the thickening kettle is greater than or equal to three-quarters of the volume of the kettle body, and the active content of the material is ≥70%, the high-temperature material will be cooled and automatically completed step by step between the first and last crystallization kettles connected in series. Under the conditions of material transfer, stirring and natural cooling, continuous crystallization is carried out step by step;

(4) The mixture material is cooled in the nth-stage crystallization kettle again through cyclic condensation and the temperature of the system is maintained at 20±2℃. After the system is filled with analytical crystals, the mixture material is centrifuged and dried to obtain a hydroxyl suboxide with an active content of ≥98%. Ethyl diphosphonic acid crystal product, the mother liquor obtained from separation is collected and recycled.

The temperature of the liquid after preheating in the above step (1) ranges from 60 to 100°C. Preferably, the temperature after preheating is from 75 to 90°C.

The separation described in the above step (1) means that the preheated materials are separated by a gas-liquid separator to remove the low-boiling hydrogen chloride and a small amount of water vapor entrained in the product, and the high-boiling substances continuously enter the distillation concentration kettle through the bottom of the gas-liquid separator .

The concentration temperature mentioned in the above step (2) may be 110-150°C, preferably, the concentration temperature is 120-130°C.

The concentration and purification described in the above step (2) means that when the material is concentrated at a high temperature, the mixed gas in the kettle enters the gas-liquid separator again to separate and remove the water and impurity acetic acid contained in the product.

The lower boiling point components obtained from the separation and purification described in the above step (1) and step (2) can be recycled and used as the raw material for the production of liquid products after being cooled and recovered.

The temperature of the condensed material in the above step (3) is 60-70°C.

The mixture material described in the above step (3) realizes automatic material transfer through the PLC automatic interlocking device established between the level gauge set in the 1-n-level crystallization kettle, the feed valve at the top of the kettle, and the discharge valve at the bottom of the kettle.

The number of crystallization tanks connected in series in the above step (3) is 2≦n≦8, and preferably, n=3-5.

In the above step (3), the gradient range of the natural temperature drop in the 1-n-level crystallization kettle is 5-20°C/level, which is a preferred gradient range of 5-10°C/level in the 1-2-level crystallization kettle. , The gradient range of natural cooling in the 3-n-level crystallization kettle is 10-20℃/level.

Among them, the stirring speed in the first-stage crystallization tank is 80-150 revolutions/min, and the stirring speed in the 1-n crystallization tank is gradually reduced.

The mother liquor described in the above step (4) is continuously pumped into the distillation and concentration device to be concentrated and then recycled for successive recrystallization. When the mother liquor is continuously recycled until the chroma is ≥180 Hazen, the mother liquor can be used as a composite phosphorus-containing scale inhibitor Etching agent monomer.

The method of the invention concentrates and removes impurities at high temperature, and is cooled to 60-70°C to form a supersaturated solution. By changing the environmental parameters in the crystallization kettle, crystal nuclei are condensed with polar concentrations in the first and second reaction kettles to ensure no explosion. Do not block the pipeline. In the subsequent crystallization kettle, the environmental parameters are changed again to make the crystal grow instead of continuing to nucleate, and grow the small crystal nuclei that are not suitable for separation into crystal grains of moderate size. In the last-stage crystallization kettle, the cyclic condensation is reduced to low temperature, and the product in the water is separated out as much as possible to ensure the maximum yield.

The present invention changes the crystallization of the closed crystallization kettle in the prior art at a constant rate and adding seed crystals or even a crystal promoting agent to a continuous operation in a multi-crystallization kettle assembly line, without adding any additives and crystal nuclei, and passing different environmental parameters. The multi-crystallization kettle adjusts the crystal metastable zone to prevent explosion and obtain crystal grains of appropriate size without introducing impurities such as crystal nuclei and crystal promoters.

The beneficial effects of the present invention are:

(1) The present invention realizes the continuous crystallization of hydroxyethylene diphosphonic acid crystals and the continuous recycling of mother liquor through the control of the environmental parameters of the crystallization kettles connected in series at various levels, thereby improving production efficiency and stable product quality;

(2) This method uses gravity sedimentation to separate and purify the liquid products after preheating and distillation and concentration stages, and remove relatively low boiling impurities such as hydrogen chloride, acetic acid and excess water contained in the product, and effectively realize the material recovery. Fast separation and purification, shorten the production cycle;

(3) In the multi-stage continuous crystallization process, a temperature drop of 5-20°C/level is achieved, and the final stage of cooling is used to achieve full crystallization, and the product yield can reach more than 90%;

(4) No crystal nucleus and crystal promoting agent are used in the multi-stage continuous crystallization process, no new impurities are introduced, and the final product has high purity;

(5) The process of recycling the mother liquor helps to realize the heat exchange between the system materials and helps to reduce the temperature of the crystallization system;

(6) This method produces no "three wastes" in the production process, is safe and environmentally friendly, saves water and reduces emissions, and is conducive to the realization of automated mass production.

Detailed ways

In order to further illustrate the significance of the present invention, the content involved in the present invention will be explained below in conjunction with embodiments, but the content is not limited.

Example 1

The hydroxyethylene diphosphonic acid liquid with an active content of 51.34% was preheated to 82°C by a graphite heater, hydrogen chloride and a small amount of water vapor in the system were removed by gas-liquid separation, and then continuously pumped into the distillation kettle at a flow rate of 250kg/h. ; When the material is continuously fed for 1 hour until the volume of the material occupies about one-third of the volume of the kettle body, turn on the distillation kettle and stir, maintain the system temperature at 125±1℃, and quickly externally distill and concentrate under negative pressure of -0.06MPa; continuous feeding for 3 hours Afterwards, the active content of the material in the distillation kettle is 70.28% and the volume of the material in the distillation kettle reaches the set transfer level, the valve at the bottom of the distillation kettle and the transfer pump are automatically opened to continuously transfer the material cooled to 62°C at a flow rate of 282kg/h The crystallization of the first-stage crystallization kettle is controlled by the PLC automatic interlocking device established between the level gauges set in the crystallization kettles at all levels, the feed valve at the top of the kettle, and the discharge valve at the bottom of the kettle. The first to fourth levels are connected in series in sequence. Automatically transfer materials step by step between the crystallization kettles, control the stirring rate at 120 revolutions/min and the natural cooling gradient of 5-20℃/level, and carry out step-by-step continuous crystallization; among them, the solid-liquid mixture in the crystallization kettle is 1 to 4 The injection time from the lowest liquid level to the highest liquid level is 2.5 hours, 2.5 hours, 2.5 hours and 3 hours respectively; the temperature of the mixture after natural cooling in the 1-4 crystallization kettle is: 55℃, 48℃, 36℃ and 26℃, in the last stage, that is, the fourth stage crystallization kettle interlayer is passed through circulating cooling water to cool down to 20.5℃, and then slowly stirred for 2 hours to make the system fully crystallized. The mixture is centrifuged and dried to separate the hydroxyethylene dichloride. Phosphonic acid white transparent regular crystal products and centrifugal mother liquor; the centrifugal mother liquor is recycled to the concentration tank and used for continuous crystallization, and the mixed centrifugal mother liquor is recycled until the color is 190Hazen. One production cycle, 98.71% hydroxyethylene diphosphonic acid The total amount of white transparent crystal products is 7585kg, the chloride ion content (as Cl-) is 0.005%, the product yield is 91.38%, the separated mother liquor totals 957.44kg, the active content is 60.25%, and the total yield of hydroxyethylene diphosphonic acid is 98.31%. The particle size is suitable and uniform, does not block the pipeline and is convenient for centrifugation.

Example 2

The hydroxyethylene diphosphonic acid liquid with an active content of 60.29% is preheated to 90℃ by a graphite heater, and the hydrogen chloride and a small amount of water vapor in the system are removed by gas-liquid separation. After that, it is continuously pumped into the distillation kettle at a flow rate of 200kg/h. ; Continuous feeding for 1.5 hours until the volume of the material accounts for about one-third of the volume of the kettle body, turn on the distillation kettle and stir, maintain the system temperature at 130±1℃, and quickly externally distill and concentrate under negative pressure of -0.04MPa; continuous feeding for 4 hours Afterwards, the active content of the material in the distillation kettle is 70.04% and the volume of the material in the distillation kettle reaches the set transfer level, the valve at the bottom of the distillation kettle and the transfer pump are automatically opened to continuously transfer the material cooled to 65°C at a flow rate of 250kg/h The crystallization of the first stage crystallization kettle is controlled by the PLC automatic interlocking device established between the level gauges set in the crystallization kettles at all levels, the feed valve at the top of the kettle, and the discharge valve at the bottom of the kettle. The crystallization kettles complete step-by-step automatic material transfer, control the stirring rate at 150 revolutions/min and the natural cooling gradient of 5-20 ℃/level, and carry out step-by-step continuous crystallization; among them, the solid-liquid mixture in the 1-3 crystallization kettles The injection time from the lowest liquid level to the highest liquid level is 3 hours, 3 hours and 3.5 hours respectively; after the natural cooling in the 1-3 crystallization kettle, the temperature of the mixture is 58℃, 49℃ and 35℃ respectively. The third stage is the third stage of the crystallization kettle through circulating cooling water to cool down to 20 ℃, slowly stirring for 2 hours to fully crystallize the system, the mixture is separated by centrifugation and drying to obtain white transparent regular crystals of hydroxyethylene diphosphonic acid. Product and centrifugal mother liquor; the centrifugal mother liquor is recycled to the concentration tank and reused for continuous crystallization, and the mixed centrifugal mother liquor is recycled until the color is 180Hazen, and the production cycle is 98.23% hydroxyethylene diphosphonic acid white and transparent. The total crystal product is 5889kg, the chloride ion content (as Cl-) is 0.003%, and the product yield is 90.47%; the separated mother liquor totals 878kg, the active content is 60.17%, and the total yield of hydroxyethylene diphosphonic acid is 98.41%. The particle size is suitable and uniform, does not block the pipeline and is convenient for centrifugation.

Example 3

The hydroxyethylene diphosphonic acid liquid with an active content of 60.57% is preheated to 75℃ by a graphite heater, and the hydrogen chloride and a small amount of water vapor in the system are removed by gas-liquid separation. Then, it is continuously fed into the distillation kettle at a flow rate of 300kg/h. ; When the material is continuously fed until the volume of the material accounts for about one-third of the volume of the kettle body, turn on the distillation kettle and stir, maintain the system temperature at 128±2°C, and rapidly externally vaporize and concentrate under negative pressure of -0.04MPa. After continuous feeding for 2.8 hours, The active content of the material in the distillation kettle is 70.08% and the volume of the material in the distillation kettle reaches the set transfer level, the valve at the bottom of the distillation kettle and the transfer pump are automatically opened, and the material cooled to 70℃ is continuously transferred to the first at a flow rate of 320kg/h Crystallization in the first-stage crystallization kettle is controlled by the PLC automatic interlocking device established between the level gauge set at each stage of the crystallization kettle, the feed valve at the top of the kettle, and the discharge valve at the bottom of the kettle. Automatically transfer materials step by step between the kettles, control the stirring rate at 80 revolutions/min and the natural cooling gradient of 5～20℃/level, and carry out step by step continuous crystallization; among them, the solid-liquid mixture in the crystallization kettle is the lowest The injection time from the liquid level to the highest liquid level is 2 hours, 2 hours, 2 hours, 2 hours and 3 hours; the temperature of the mixture after the natural cooling in the 1-5 crystallization kettle is: 65℃, 58℃, 44℃ , 32 ℃ and 24 ℃, in the last stage, the fifth stage crystallization kettle interlayer is passed into circulating cooling water to cool down to 19 ℃, slowly stirred for 2 hours to fully crystallize the system, the mixture was centrifuged, dried and separated to obtain hydroxyl sub-layers. Ethyl diphosphonic acid crystal products and centrifugal mother liquor; the centrifugal mother liquor is recycled to the concentration tank and reused for continuous crystallization, and the mixed centrifugal mother liquor is recycled until the color is 185Hazen, and a production cycle is calculated to produce ethylene glycol with an active content of 98.03% A total of 8787kg of white and transparent regular crystals of diphosphonic acid, the chloride ion content (in Cl ^- ) is 0.009%, and the product yield is 90.47%; the separated mother liquor totals 1334kg, and the active content is 59.33%. Hydroxyethylene diphosphine The total acid yield was 98.49%. The particle size is suitable and uniform, does not block the pipeline and is convenient for centrifugation.

Comparative example 1 (traditional single-pot concentration crystallization method)

Pump 2000 kg of hydroxyethylene diphosphonic acid liquid with an active content of 60.57% into the reaction vessel, and rapidly increase the temperature to 130°C under agitation. At the same time, the system is established -0.05MPa negative pressure is quickly evaporated and concentrated to an active content of 75.32%. Control the stirring rate to 120 rpm and add seed crystals, pass in circulating water for cooling, cool down to 20±2°C according to a gradient of 5-10°C/h, stand for 1 to 2 hours and then centrifuge and dry to obtain activity content of 97.41% of hydroxyethylidene-diphosphonic acid crystals 890.68kg, disposable crystallization yield was 75.48%, repeating the above steps mother liquid circulation recrystallized three times, a total yield of 87.92%, chloride content (Cl ^- Calculated) is 0.011%.

Comparative example 2

Other operating conditions and process parameters are the same as in Example 2. The hydroxyethylene diphosphonic acid liquid with an activity of 70.04% after distillation and concentration and a temperature of 120°C is directly transferred to the first step at a flow rate of 180kg/h without cooling down. Crystallization in the first-stage crystallization kettle is controlled by the PLC automatic interlocking device established between the level gauge set at each stage of the crystallization kettle, the feed valve at the top of the kettle, and the discharge valve at the bottom of the kettle. Step by step automatic material transfer is completed between the kettles, the stirring rate is controlled at 140 revolutions/min and the natural cooling gradient of 5-20℃/level, and continuous crystallization is performed step by step; among them, crystal explosion occurs in the 1-2 crystallization kettles. Phenomenon, the temperature of the mixture after the natural cooling of 1~3 levels are respectively: 103℃, 87℃ and 72℃. In the last stage, the third stage crystallization kettle interlayer, circulating cooling water is introduced to cool down to 20℃, and the mixture is slowly stirred for 2 hours. , The system is fully crystallized, the mixture is centrifuged and dried to obtain the hydroxyethylene diphosphonic acid crystal product and the centrifugal mother liquor, respectively, and the hydroxyethylene diphosphonic acid white crystal product with an active content of 93.01% is produced, totaling 1007.49kg, The chloride ion content ( ^{calculated as Cl -} ) is 0.015%, and the one-time crystallization yield is 78.24%; the mother liquor obtained after separation is 994.36 kg in total, and the active content is 69.83%.

Comparative example 3

Control the stirring rate in the 1-4 stage crystallization kettle to be 200 revolutions/min. Other operating conditions and process parameters are the same as those in Example 1. Serious explosion phenomenon occurs in the 1-2 stage crystallization kettle, and the precipitated crystal particles are small and the crystals are fine powder. As a result, the active content of hydroxyethylene diphosphonic acid crystals is 95.39%, the chloride ion content (calculated as Cl-) is 0.031%, and the one-time crystal yield is 80.24%.

Comparative example 4

Control the stirring rate in the 1~4 crystallization kettle to be 30 revolutions/min. Other operating conditions and process parameters are the same as in Example 1. The explosion phenomenon occurs in the 1 to 2 crystallization kettle, and the precipitated crystals are of different size and shape. Irregularity, the activity content of the hydroxyethylene diphosphonic acid crystals is 90.08%, the chloride ion content ( ^{calculated as Cl -} ) is 0.035%, and the one-time crystal yield is 81.02%.

Claims

A continuous production method of hydroxyethylene diphosphonic acid crystals is characterized in that it specifically includes the following steps:

The hydroxyethylene diphosphonic acid liquid with an active content of 50-65% is preheated, gas-liquid separated, and then continuously pumped into the distillation kettle at a constant speed; stirring is turned on and the temperature is raised, and at the same time, continuous concentration and purification under negative pressure;

(3) When the active content of the material in the concentration kettle is ≥70%, the high-temperature material is cooled down to complete the step-by-step transfer between the 1-n crystallization kettles in series, and the continuous crystallization is carried out under the conditions of stirring and cooling;

(4) The mixture material is cooled in the nth-stage crystallization kettle and the system temperature is maintained at 20±2℃. After the system is filled with analytical crystals, the mixture material is separated and dried to obtain a hydroxyethylene disulfide with an active content of ≥98%. Phosphonic acid crystal products, the mother liquor obtained from separation is collected and recycled.
The method according to claim 1, wherein the temperature of the liquid product after preheating in the step (1) ranges from 60 to 100°C.
The method according to claim 1, characterized in that, in the step (2), the temperature of steaming and concentrating outside is 110-150°C.
The method according to claim 1, wherein the temperature of the condensed material in the step (3) is 60-70°C.
The method according to claim 1, characterized in that, in the step (3), the number of crystallization tank stages connected in series end to end is 2≤n≤8.
The method according to claim 1, wherein the temperature gradient of the 1-n-level crystallization kettle in the step (3) is 5-20°C/level.
The method according to any one of claims 1 and 6, characterized in that, in the crystallization kettles at various levels, the temperature drop gradient of the 1-2 crystallization kettle temperature is 5-10°C/level, and the crystallization kettle temperature is 3 to n The gradient range is 10-20°C/level; the stirring speed of the 1-n crystallizer is gradually reduced; the nth stage is cooled to 20±2°C through circulation.
According to claims 1-7, characterized in that the lower boiling point components obtained from the separation and purification in the step (1) and step (2) can be recycled for the production of liquid products after being cooled and recovered; The mother liquor of step (4) is continuously fed into the distillation and concentration device to be concentrated and then recycled for step-by-step recrystallization. When the mother liquor is continuously recycled until the chroma is greater than or equal to 180 Hazen, the mother liquor can be used as a compound type phosphorus-containing scale and corrosion inhibitor monomer .