阅读说明：本技术 一种羟基亚乙基二膦酸晶体的连续化生产方法 (Continuous production method of hydroxyethylidene diphosphonic acid crystal ) 是由 程终发 王燕平 齐晓婧 宋盟盟 王宁宁 刘全华 于 2019-10-17 设计创作，主要内容包括：本发明提供一种羟基亚乙基二膦酸晶体的连续化生产方法。具体操作方法包括：将活性含量为50~65%的羟基亚乙基二膦酸液体产品经预热、气液分离后匀速连续打入蒸馏釜；经蒸馏浓缩至物料活性含量≥70%时,高温物料经冷凝后尾串联的结晶釜之间完成逐级自动转料,搅拌和自然降温的条件下,进行逐级连续结晶；最后在第n级结晶釜内经循环冷凝降温并维持体系温度在20±2℃。充分析晶后,经分离、干燥处理,得活性含量≥98%的羟基亚乙基二膦酸晶体产品。本发明将传统的单釜封闭结晶方法,改为更适合工业化的流水线结晶方法,制备的结晶粒度合适,结晶过程中不添加助晶剂和晶核,不爆析,适合工业化。(The invention provides a continuous production method of hydroxyethylidene diphosphonic acid crystals, which comprises the following specific operation steps of preheating a hydroxyethylidene diphosphonic acid liquid product with the activity content of 50 ~ 65%, carrying out gas-liquid separation, continuously pumping the hydroxyethylidene diphosphonic acid liquid product into a distillation kettle at a constant speed, carrying out distillation concentration until the activity content of the material is more than or equal to 70%, carrying out automatic material transfer step by step between crystallization kettles connected in series after the high-temperature material is condensed, carrying out continuous crystallization step by step under the conditions of stirring and natural cooling, carrying out circulating condensation cooling in an nth-stage crystallization kettle, maintaining the system temperature at 20 +/-2 ℃, carrying out full crystallization, separating and drying to obtain the hydroxyethylidene diphosphonic acid crystal product with the activity content of more than or equal to 98%.)

1. A continuous production method of hydroxyethylidene diphosphonic acid crystal is characterized by comprising the following steps:

preheating hydroxyethylidene diphosphonic acid liquid with the activity content of 50 ~ 65 percent, and continuously pumping the liquid into a distillation still at a constant speed after gas-liquid separation;

stirring and heating are started, and meanwhile, concentration and purification are continuously carried out under negative pressure;

(3) when the active content of the materials in the concentration kettle is more than or equal to 70 percent, the high-temperature materials are cooled and then sequentially transferred step by step between 1-n stages of crystallization kettles connected in series end to end, and are continuously crystallized under the conditions of stirring and cooling;

(4) cooling the mixed material in an nth-stage crystallization kettle, maintaining the temperature of the system at 20 +/-2 ℃ to fully crystallize the system, separating and drying the mixed material to obtain a hydroxyethylidene diphosphonic acid crystal product with the activity content of more than or equal to 98%, and collecting and recycling mother liquor obtained by separation.

2. The method of claim 1, wherein the temperature of the preheated liquid product in step (1) is in the range of 60 ~ 100 ℃.

3. The method of claim 1, wherein the external distillation concentration temperature in step (2) is 110 ~ 150 ℃.

4. The method of claim 1, wherein the temperature of the condensed material in step (3) is 60 ~ 70 ℃.

5. The method as claimed in claim 1, wherein the number of the crystallization kettle stages connected end to end in the step (3) is 2-8.

6. The method as claimed in claim 1, wherein the temperature gradient of the 1 ~ n-grade crystallization kettle in the step (3) is in the range of 5 ~ 20 ℃/grade.

7. The method as claimed in any one of claims 1 and 6, wherein in each stage of crystallization kettle, the temperature reduction gradient of the temperature of the crystallization kettle of 1-2 stages is 5-10 ℃/stage, the temperature gradient range of the crystallization kettle of 3 ~ n stages is 10-20 ℃/stage, the stirring speed of the crystallization kettle of 1-n stages is gradually reduced, and the nth stage is cooled to 20 +/-2 ℃ by circulation.

8. The method according to claims 1-7, wherein the lower boiling point component separated and purified in step (1) and step (2) is recycled for use as a raw material for producing liquid products after cooling; and (4) continuously pumping the mother liquor obtained in the step (4) into a distillation concentration device for concentration, and then circularly performing step-by-step recrystallization, wherein the mother liquor can be used as a compound phosphorus-containing scale and corrosion inhibitor monomer when the chroma is more than or equal to 180 Hazen.

Technical Field

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

Background

The hydroxyethylidene diphosphonic acid (HEDP for short) has extremely stable C-P bond in the molecule, the bond energy is 246kJ/mol, and the hydroxyethylidene diphosphonic acid has high temperature resistance, has good scale inhibition effect on calcium carbonate, hydrated iron oxide and calcium phosphate in water and is an important scale inhibition dispersant. Because HEDP can form stable complex with iron, copper, zinc and other metal ions, the HEDP can dissolve oxides on the surface of metal and can be used as a complexing agent in the cyanide-free electroplating industry; in addition, because the HEDP has better corrosion and scale inhibition effects and a passivation effect on the metal surface, the high-purity HEDP product can be used for cleaning circuit boards in the electronic industry and treating the metal surface.

The conventional 50% or 60% specification HEDP liquid product is synthesized by taking phosphorus trichloride as one of the starting raw materials, various associated impurities in the raw materials greatly limit the application of the HEDP liquid product in the industries of electronic cleaning, medicine and daily chemical industry, so that HEDP crystals or solid products with higher purity are researched and produced, the added value of the product is improved, and the added value of the product is always a technical hotspot concerned by researchers in the field.

The prior published preparation methods of hydroxyethylidene diphosphonic acid solid or crystal all adopt the traditional intermittent single kettle type operation, which is not beneficial to the stability of the product quality among batches; meanwhile, because the crystallization process is a slow physical process influenced by multiple factors, the equipment occupation period is long, the capacity scale of the product is greatly limited, and the market application and popularization of the product are seriously influenced.

Disclosure of Invention

In order to solve the problems and the defects in the prior art, the invention provides a production method capable of continuously producing hydroxyethylidene diphosphonic acid crystals. The method adopts a multistage crystallization mode through natural cooling and crystallization of the hydroxyethylidene diphosphonic acid, can effectively stabilize the product quality, improve the equipment utilization rate and the product yield, save water, reduce emission, avoid three wastes, is safe and environment-friendly, and is beneficial to realizing automatic control and large-scale industrial production.

The invention is realized by the following technical scheme:

a continuous production method of hydroxyethylidene diphosphonic acid crystals specifically comprises the following steps:

(1) preheating a hydroxyethylidene diphosphonic acid liquid product with the activity content of 50 ~ 65 percent, and continuously pumping the liquid product into a distillation still at a constant speed after gas-liquid separation;

(2) when the material in the distillation kettle reaches one third of the volume of the kettle body, starting stirring and rapidly heating, and continuously concentrating and purifying the material under the negative pressure condition of-0.04 ~ -0.06 MPa;

(3) when the volume of the materials in the concentration kettle is more than or equal to three-quarters of the volume of the kettle and the active content of the materials is more than or equal to 70 percent, the high-temperature materials are cooled and then sequentially and automatically transferred step by step between 1 ~ n crystallization kettles connected in series end to end, and are continuously crystallized step by step under the conditions of stirring and natural cooling;

(4) and (3) circularly condensing the mixed material in the nth-stage crystallization kettle again to reduce the temperature and maintain the system temperature at 20 +/-2 ℃ so that the system is fully crystallized, centrifuging and drying the mixed material to obtain a hydroxyethylidene diphosphonic acid crystal product with the activity content of more than or equal to 98%, and collecting and recycling mother liquor obtained by separation.

The preheated liquid temperature in the step (1) is 60 ~ 100 ℃ or more, preferably 75 ~ 90 ℃ or more.

The separation in the step (1) is to separate the preheated material by a gas-liquid separator to remove low-boiling-point hydrogen chloride and a small amount of water vapor carried in the product, and the high-boiling-point substance continuously enters the distillation concentration kettle through the bottom of the gas-liquid separator.

The concentration temperature in the above step (2) may be 110 ~ 150 deg.c, and preferably, the concentration temperature is 120 ~ 130 deg.c.

The concentration and purification in the step (2) refers to that the mixed gas in the kettle enters the gas-liquid separator again for separation to remove water and acetic acid impurities contained in the product when the material is concentrated at high temperature.

The lower boiling point component obtained by the separation and purification in the step (1) and the step (2) can be recycled to be used as a raw material for producing liquid products after being cooled and recovered.

The temperature of the condensed material in the step (3) was 60 ~ 70 ℃.

And (3) automatically transferring the mixed material through a PLC automatic interlocking device which is established among a liquid level meter arranged in the 1 ~ n-grade crystallization kettle, a kettle top feeding valve and a kettle bottom discharging valve.

The number of the crystallization kettles connected end to end in the step (3) is 2-8, preferably n = 3 ~ 5.

The gradient range of the natural cooling in the 1 ~ n-grade crystallization kettle in the step (3) is 5 ~ 20 ℃/grade, the preferred gradient range of the natural cooling in the 1-2-grade crystallization kettle is 5-10 ℃/grade, and the gradient range of the natural cooling in the 3-n-grade crystallization kettle is 10 ~ 20 ℃/grade.

Wherein the stirring speed in the 1 st-stage crystallization kettle is 80-150 rpm, and the stirring speed of the 1-n crystallization kettle is gradually reduced.

And (4) continuously pumping the mother liquor in the step (4) into a distillation concentration device for concentration and then circularly using for recrystallization step by step, wherein the mother liquor can be used as a compound phosphorus-containing scale and corrosion inhibitor monomer when the chroma is more than or equal to 180 Hazen.

The invention concentrates and removes impurities at high temperature, cools to 60-70 ℃ to form supersaturated solution, and coagulates crystal nucleus in the first and second reaction kettles by using the concentration of polar region by changing the environmental parameters in the crystallization kettle, thereby ensuring no sudden precipitation and no pipeline blockage. In the subsequent crystallization kettle, the environmental parameters are changed again, so that the crystal grows instead of continuously nucleating, and small crystal nuclei which are not easy to separate grow into crystal grains with proper size. In the last stage of crystallization kettle, the circulating condensation is reduced to low temperature, so that the product in water is separated out as much as possible, and the maximum yield is ensured.

The invention changes the constant-speed cooling and crystal seed adding even crystallization accelerator closed crystallization kettle crystallization in the prior art into multi-crystallization kettle assembly line continuous operation, does not add any auxiliary agent and crystal nucleus in the middle, adjusts a crystal metastable zone through the multi-crystallization kettle with different environmental parameters, prevents sudden precipitation and obtains crystal grains with proper size, and does not need to introduce impurities such as crystal nucleus, crystal accelerator and the like.

The invention has the beneficial effects that:

(1) according to the invention, through controlling the environmental parameters of the crystallization kettles connected in series at all levels, the industrial production line continuous crystallization and the mother liquor continuous cyclic utilization of the hydroxyethylidene diphosphonic acid crystal are realized, the production efficiency is improved, and the product quality is stable;

(2) the method utilizes the gravity settling effect to separate and purify liquid products in the preheating stage and the distillation concentration stage respectively, removes impurities with relatively low boiling points such as hydrogen chloride, acetic acid and the like and redundant moisture in the products, effectively realizes the rapid separation and purification of materials, and shortens the production period;

(3) the cooling gradient of 5 ~ 20 ℃/level is realized in the multi-level continuous crystallization process, the last level cooling is adopted to realize full crystallization, and the product yield can reach more than 90%;

(4) in the multistage continuous crystallization process, crystal nucleus and a crystal promoter are not used, new impurities are not introduced, and the final product has high purity;

(5) the heat exchange among the system materials is facilitated in the process of recycling the mother liquor, and the temperature of a crystallization system is facilitated to be reduced;

(6) the production process of the method does not generate three wastes, is safe and environment-friendly, saves water and reduces emission, and is beneficial to realizing automatic large-scale production.

Detailed Description

In order to further explain the meaning of the present invention, the following examples are given to explain the contents of the present invention, but the contents are not limited thereto.