CN112126030B - Control method for organic amine in waste brine formed by MDA preparation - Google Patents
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G12/00—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen
- C08G12/02—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes
- C08G12/04—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with acyclic or carbocyclic compounds
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- G01D21/02—Measuring two or more variables by means not covered by a single other subclass
Abstract
The invention provides a method for controlling organic amine in waste brine formed by preparing MDA. The method aims at the problems that in the MDA preparation process, especially under the process condition of high formaldehyde ratio, the content of organic amine in the formed waste brine is high, and the waste brine cannot be directly discharged to the sea or recycled in the chlor-alkali industry. The method is controlled from the source of organic amine formation, controls the turbidity of the reaction liquid after the condensation reaction of the aniline acid salt and the formaldehyde to control the organic amine in the final waste brine, and preferably adjusts the turbidity through the content of macromolecular polyamine in the condensation reaction liquid according to the main source of the turbidity. The method is visual, convenient and accurate in result, and the control means is convenient for industrial implementation.
Description
Technical Field
The invention belongs to the field of synthesis industry, and particularly relates to a method for controlling organic amine in waste brine formed by MDA preparation.
Technical Field
Diamines and polyamines of diphenylmethane are compounds and mixtures thereof, also referred to as polymethylene polyphenyl polyamines, hereinafter referred to as polyamines or MDA, having the following structure:
wherein n is a natural number.
The preparation of MDA by the reaction of aniline (or aniline salt) and formaldehyde in the presence of an acidic catalyst, and the synthesis of MDI (diphenylmethane diisocyanate) by the reaction of MDA and phosgene are well known in the industry, and MDI is one of the main raw materials in the polyurethane industry. In the art, MDA production is described in A number of published documents, for example U.S. Pat. No. 4,053,0077, EP-A-451442 and WO-A-99/40059, MDA is produced by continuous, semicontinuous or discontinuous reaction processes, aniline is reacted with hydrochloric acid to form aniline acid salt, formaldehyde is added to the reactor to form MDA acid salt, caustic sodA is added for neutralization, the brine layer and the polyamine layer are separated, and the polyamine layer is washed with water and then refined to obtain polyamine, which is one of the key elements of the MDI production process. In the process of preparing MDA from aniline and formaldehyde, a reaction solution obtained by reaction is neutralized by caustic soda, and a large amount of brine is generated. Aniline, MDA and other impurities usually remain in brine, and in the disclosed technology, MDA is usually removed by means of aniline extraction, and aniline is removed by means of rectification, so that the purpose of brine purification is achieved.
The brine treated by the method usually has a certain amount of organic matters remained, so that the organic amine is too high and exceeds the national sea discharge (TOC and aniline) index and the reuse standard of the chlor-alkali industry, and when the waste brine produced by the production device cannot be discharged to the sea or is treated in time, the production device is forced to reduce the load and even stop.
US6673970B1 discloses a condensation process that reduces or reduces the impurities in MDA and the influence on the color of the final MDI product: in the first step of the process, aniline hydrochloride is formed; secondly, adding reactants step by step to fully form a reaction intermediate; the third step is partial neutralization during molecular rearrangement by addition of a base in a molar amount of about 70-80% hydrochloric acid. USP3517062 discloses a process for continuous manufacture of MDA, aniline and hydrochloric acid are salified in a continuous flow tank reactor, and then enter another reactor to be continuously fed with formaldehyde, condensed therein, and then enter a tubular reactor to perform a rearrangement reaction. CN200710138065.2 discloses a method for brine treatment from the rear end, which removes organic matters in waste brine by combining catalytic oxidation with ultrasonic deep oxidation treatment to meet the requirements of chlor-alkali production.
In summary, the existing method for controlling organic amine in waste brine formed during preparation of MDA mainly aims at low molecular weight MDA and raw material aniline, and the adopted methods mainly include extraction, rectification, change of feeding mode, addition of a reaction kettle and the like, and specific factors causing increase of organic amine lack sufficient understanding and effective treatment means, so that effective control from the source is difficult, and the problem that waste brine cannot be directly discharged to the sea or recycled in chlor-alkali industry cannot be solved. In particular, the inventors have found that when the formaldehyde ratio in the condensation reaction for preparing MDA is high (usually 0.5 or more), the organic amine in the waste brine is further increased and the difficulty of treatment is further increased.
Disclosure of Invention
In view of the above problems in the art, it is an object of the present invention to provide a more efficient method for controlling organic amines in the waste brine formed in the preparation of MDA. The method is different from the prior art, and is based on new knowledge of organic amine cause and corresponding process control means, and the source formed by the organic amine is controlled from the front end, so that the waste brine which can be directly discharged into the sea or recycled for the chlor-alkali industry is obtained.
The inventor discovers that organic amine in the waste brine has a certain positive correlation with the turbidity of MDA condensation reaction liquid through long-term research on the waste brine formed by preparing MDA, the turbidity determines the size of the organic amine to a certain extent, and the organic amine in the waste brine can be indirectly controlled through the turbidity of the condensation reaction liquid. Further studies by the inventors have found that the cause of the turbidity as an index of control is that the main source of turbidity is not low molecular weight MDA and the raw material aniline, but rather the production of macromolecular polyamines formed during the MDA condensation reaction, wherein the proportion of macromolecular polyamines having a repeating unit number n > 10 is important, and the main cause of high proportion of macromolecular polyamines is: (1) macromolecular polyamine (n is more than 10) is insoluble in aniline and other organic solvents and is difficult to remove by an extraction mode; (2) the high boiling point of the macromolecular polyamines (n > 10) (e.g. boiling point > 300 ℃ with n = 10) cannot be removed by rectification. I.e., such materials are difficult to remove by conventional "extraction + rectification" means. Particularly, when the operation condition with high formaldehyde ratio (formaldehyde aniline molar ratio > 0.50) is adopted, the proportion of macromolecular polyamine in the prepared MDA is further increased remarkably, and the content of macromolecular polyamine in the drainage brine is increased to more than 10mg/L from the common 0.5-2 mg/L.
The invention discovers a method for controlling the turbidity of the MDA condensation reaction liquid as the organic amine in the waste brine by analyzing the relation between the organic amine in the waste brine and the turbidity of the MDA condensation reaction liquid; through the analysis of turbidity sources, macromolecular polyamine generated in the condensation reaction process of MDA preparation is further found and controlled, the method is a main way and a preferable means for controlling turbidity, organic amine in waste brine can be controlled from the source, the turbidity control is very visual and convenient, and the method is suitable for real-time online control.
Accordingly, the technical scheme adopted by the invention is as follows:
a method for controlling organic amine in waste salt water formed by diamine and polyamine (MDA) for preparing diphenylmethane, wherein the turbidity of reaction liquid after condensation reaction of aniline acid salt and formaldehyde is controlled from the front end to be 0.03-1NTU, preferably 0.05-0.5NTU.
In the present invention, the method for preparing MDA comprises the following steps:
s1: aniline reacts with hydrochloric acid to generate aniline hydrochloride, formaldehyde is added to carry out condensation reaction to obtain a reaction mixture containing diaminodiphenyl diamine salt and polyamine salt, and the temperature is increased to carry out transposition reaction;
s2: neutralizing the reaction mixture in the S1 with alkali, separating out an organic phase and a water phase, washing the organic phase with water, and purifying and refining to obtain MDA;
s3: and (3) extracting and stripping the water phase generated in the neutralization and water washing processes of S2 to form waste brine.
In the invention, the main component of the turbidity of the reaction solution is macromolecular polyamine generated in the condensation reaction process, and the macromolecular polyamine has the following structure:
wherein n is a natural number greater than 10.
According to the analysis of the turbidity source, the content of the macromolecular polyamine in the reaction liquid can be controlled from the source by controlling the content of the macromolecular polyamine in the reaction liquid after the condensation reaction of the aniline hydrochloride and the formaldehyde, so that as a preferable scheme of the invention, the content of the macromolecular polyamine in the reaction liquid after the condensation reaction is controlled to be 0.02-0.6mg/L. It will be appreciated by those skilled in the art that, according to the above-described embodiment, the content of the macromolecular polyamine can be controlled at different stages of the reaction, or other nitrogen-containing components can be controlled at the same time, but the method still controls the organic amine from the source.
Accordingly, the present invention further provides a method for controlling organic amine in waste brine formed by MDA preparation, wherein the method preferably controls the organic amine in the waste brine by controlling the content of macromolecular polyamine in condensation reaction liquid.
The inventor researches the condensation reaction of formaldehyde and aniline to find that the residence time of the aniline and formaldehyde reaction influences the composition, and the longer the reaction residence time, the higher the polycyclic content of the product. When we need to control the polycyclic content in the product, the residence time of the reaction should be reduced to prevent further chain extension of MDA with formaldehyde to form higher molecular weight macromolecular polyamines.
Further, when the reaction product polyamine settles into the system, which is equivalent to that the retention time of the reaction product polyamine is increased without limit, the polyamine can continue to react and extend chain to form macromolecular polyamine with higher molecular weight after settling, and finally enters the system and the brine discharge along with liquid flushing. In conventional equipment for condensation reactions, such as tank reactors and pipelines, settling and accumulation are generally less likely to occur due to the turbulent flow of the fluid. In some equipment, such as heat exchangers or pipeline reactors, the reaction solution is usually in a laminar flow state, and polyamine is easy to settle, so that the retention time is too long, chain extension occurs, and macromolecular polyamine is formed. On one hand, the macromolecular polyamine is suspended in the condensation liquid for further chain extension reaction or other side reactions, on the other hand, the macromolecular polyamine is subjected to neutralization, extraction and stripping processes along with the reaction liquid, but cannot be removed, and is finally discharged along with the discharged brine. In particular, when the formaldehyde ratio of the condensation reaction is high (usually above 0.5), the reaction itself produces a higher polycyclic polyamine content, and the aforementioned settling and chain extension phenomena will be more pronounced.
Furthermore, it should be noted that there is a synergy between controlling the reaction residence time and controlling the sedimentation: if the reaction residence time is not controlled, the reaction can generate macromolecular polyamine, and the quality of MDA and waste brine can be influenced without settling; if the sedimentation is not controlled, polyamine generated by the reaction is precipitated without limit, even small-molecular polyamine such as tricyclic, tetracyclic and the like can be remained in the reactor without limit, and finally, large-molecular polyamine is formed and enters the system.
Therefore, need on the one hand to reduce condensation reaction's dwell time, on the other hand controls simultaneously and reduces the material and subsides in equipment such as heat exchanger pipeline reactor, reduces the formation of macromolecule polyamine from the source to reduce the turbidity of reaction solution, and then reduce the organic amine in the waste brine.
In the invention, in the S1, the residence time of the condensation reaction of aniline hydrochloride and formaldehyde and the flow characteristic of the reaction liquid in a synthesis system are controlled, so that the content of macromolecular polyamine is controlled; preferably, the residence time of the controlled condensation reaction is between 0.1 and 2 hours, preferably between 0.4 and 0.8 hour; the residence time can be calculated according to the formula (1), and the volume unit can also be L:
residence time = sum of condensation reactor volumes (m) 3 ) Flow of mixture (m) 3 /h) (1)
In the present invention, the flow characteristics of the reactants within the system are related to the following parameters: the length (l) over which the fluid flows, for example the length of a heat exchange tube in a heat exchanger; velocity (v) of fluid flow, for example within a heat exchanger tube; the hydrodynamic radius (r) of the fluid flow, for example the internal diameter of a heat exchange tube in a heat exchanger; sedimentation velocity (u) of polyamine. Preferably, the parameters of the flow characteristics of the reactants within the system conform to the relationship of equation (2):
746.95ul/vr＜1 (2)
wherein l is in the unit of m, v is in the unit of m/s, r is in the unit of m, and u is in the unit of m/s. For example, for a tube and tube heat exchanger with a tube inner diameter of d, d =4r; for n =10 polyamine, u =1.6 × 10 -6 m/s, the formula (3) is obtained after the reduction of the above formula:
l/vd＜209.2 (3)
namely, the inventor conducts experimental research on the condensation reaction, and finds that the residence time of the reaction product is in positive correlation with the polycyclic polyamine content, and the longer the reaction residence time is, the higher the polycyclic content of the product is. The production of polycyclic polyamines and macromolecular polyamines can be reduced from the source by reducing the reaction residence time, but the reaction residence time should not be reduced indefinitely and it is necessary to ensure that the condensation reaction proceeds to completion.
Through long-period systematic research on the actual production process, the settlement of polycyclic polyamine and macromolecular polyamine in equipment such as a heat exchanger, a pipeline reactor and the like is found to be the main reason for generating the macromolecular polyamine in the waste brine, and the mechanism is that the residence time distribution of reactants in a container coincides with the settlement residence time distribution. In particular, the residence time of all reactants can be considered uniform for heat exchanger tubes and tube reactors, but for the settling process, different molecules are at different distances from the bottom of the tubes resulting in different settling times, resulting in a distribution of actual settling times that can be characterized by the average settling time. The ratio of the retention time of the sediment in the container to the average settling time is less than a certain value N, wherein N is related to the settling ratio and is obtained by actual data regression. However, it should be noted that, in the process of fluid circulation, the reaction material always contacts the inner wall of the container, and the sedimentation of polyamine cannot be completely eliminated, so that the macromolecular polyamine in the waste brine cannot be zero, therefore, the preparation method provided by the invention has the lower limit of practical production significance.
Accordingly, the present invention still further provides a method for controlling an organic amine in a waste brine formed by preparing MDA, preferably by controlling the residence time of the condensation reaction of aniline hydrochloride and formaldehyde during the condensation reaction and controlling the flow characteristics of the reaction solution in the synthesis system.
In the present invention, the molar ratio of formaldehyde to aniline in S1, i.e., the formaldehyde ratio, is (0.01-0.7): 1. The process of the present invention can be applied to the above-mentioned range of the formaldehyde ratio, and particularly, can obtain a good effect even in a system in which the formaldehyde ratio is high (usually 0.5 or more) which is difficult to handle.
In one embodiment, the acidic catalyst in S1 may be hydrochloric acid and/or nitric acid. The reaction conditions in S1 are well known in the art.
In another embodiment, the base in S2 may be sodium hydroxide and/or potassium hydroxide. The processing methods in S2 and S3 are well known in the art.
The invention also aims to provide the application of the method for controlling the organic amine in the waste brine.
The application of the method for controlling the organic amine in the waste brine formed by preparing the MDA is used for controlling the organic amine in the waste brine formed by preparing the MDA under the condition of different formaldehyde ratios; preferably, the method is used to control the organic amines in the waste brine from the production of MDA at high formaldehyde ratios, preferably (0.5-0.7): 1.
It is a further object of the present invention to provide a brine effluent formed in the production of MDA.
Waste brine formed in the preparation of MDA, obtained by the method for controlling an organic amine in the waste brine formed in the preparation of MDA.
In the invention, the content of the organic amine in the waste brine is 0.01-0.5mg/L, preferably 0.01-0.3mg/L.
In the invention, the waste brine can be used for the reuse of chlor-alkali brine or the direct sea drainage.
Compared with the prior art, the invention has the following positive effects:
(1) Based on the new discovery of the research on the source of the organic amine in the waste brine, the organic amine of the waste brine is controlled by controlling the turbidity of the condensation reaction liquid, the organic amine of the waste brine can be controlled from the front end, the organic amine can be controlled to be 0.01-0.5mg/L, and the detection control method is visual, convenient and fast and can realize on-line control.
(2) Based on the discovery of the relation between the turbidity of the condensation reaction liquid and the content of the macromolecular polyamine in the reaction liquid, the preferable scheme controls the turbidity of the condensation reaction liquid by controlling the content of the macromolecular polyamine in the condensation reaction liquid, so that a more accurate control effect can be obtained.
(3) The control of the content of macromolecular polyamine in the condensation reaction liquid is further realized by controlling the retention time of the mixture of the reactant formaldehyde and the product MDA in the condensation stage and controlling the flow characteristic of the reactant in the synthesis system, and the two process control means are convenient for industrial implementation.
Drawings
FIG. 1 is a schematic diagram of the MDA condensation reaction scheme. Wherein, 1 is a reaction kettle and a stirrer, 2 is a delivery pump, and 3 is a circulating cooler. The circulators used water bath coils in the pilot plant and tube or plate heat exchangers in the industrial plant.
FIG. 2 is an example of the analytical spectrum of macromolecular polyamine liquid chromatograph.
Detailed Description
In order that the technical features and contents of the present invention can be understood in detail, embodiments of the present invention will be described in more detail below. While embodiments of the present invention have been described in the examples, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein.
Examples 6 and 7 are the actual plant operating data, the remainder being laboratory bench test data.
The main raw material sources are as follows:
aniline, wanhua chemistry, purity 99.9wt%;
hydrochloric acid, warfarin chemical, concentration 34wt%;
formaldehyde, wanhua chemistry, concentration 37wt%.
The detection method comprises the following steps:
organic amine determination, namely, a gas chromatography-mass spectrometer (GC-MS) of 7890B +5977B of Agilent company in the United states, and adopting a standard method HJ 822-2017 for determination;
turbidity test, american HACH2100Q turbidimeter, the sample is placed in a 25nm sample cell for measurement, and GB/T15893.1-1995 standard is adopted for measurement;
macromolecular polyamine content determination, agilent 1260S liquid chromatograph, agilent Poroshell 120 EC-C18.6 x 150mm,2.7 μm, and peak position shown in FIG. 2. Gradient:
| time(min) | 0.1% aqueous triethylamine solution (%) | Methanol (%) |
| 0 | 64 | 36 |
| 14 | 64 | 36 |
| 25 | 56 | 44 |
| 70 | 10 | 90 |
| 73 | 10 | 90 |
| 75 | 64 | 36 |
| 80(end) | 64 | 36 |
Sample injection amount: 20 μ L.
Examples 6 and 7 were carried out in a large scale, practical industrial plant, as shown in FIG. 1, with a reactor volume of 80m 3 The length of the heat exchanger tube is 3m, and the inner diameter is 15mm; the remaining examples were carried out in a laboratory bench scale apparatus using a 1L flask plus a stirring paddle as the reactor, and a peristaltic pump to draw material to an external circulation coil (coil bore 3 mm) and cool it to maintain the reaction temperature.
Example 1
S1: reacting hydrochloric acid with a molar ratio of 0.3;
wherein the volume of the condensation reactor is 0.1L, the flow of the condensation reaction liquid is controlled to be 0.25L/h, and the retention time is 0.4h according to the formula (1);
the condensation reaction solution was in a laminar flow state (Re = 249) in a heat exchanger, the coil length (l) was 0.3m, the flow velocity (v) in the tube was 1.51m/s, the coil inner diameter (d) was 3mm, and the sedimentation velocity (u) of the polyamine was n =10, i.e., u = 1.6X 10 of the polyamine -6 m/s, calculated according to equation (3), gives l/vd =66.2 < 209.2.
S2: the reaction mixture in S1 was neutralized with an excess of 50wt% aqueous NaOH solution (NaOH to S1 added hydrochloric acid molar ratio of 1.10), the neutralized mixture was passed into a layering vessel to separate organic and aqueous phases, the organic phase was once washed with water, water and aniline were preliminarily separated by flash evaporation at 10kPa, and MDA was refined by 8barg steam distillation.
S3: and (3) extracting the brine obtained after mixing the water phase generated in the neutralization and water washing processes in the S2 by using an aniline solvent (the mass ratio of aniline to the water phase is 0.2.
After the operation is carried out for 3 months, the content of macromolecular polyamine in the condensation reaction liquid is controlled to be 0.06mg/L, the corresponding turbidity of the condensation reaction liquid is controlled to be 0.08NTU, no obvious deposit is generated in the coil pipe, and the content of organic amine in the waste saline is 0.04mg/L.
Example 2
S1: reacting hydrochloric acid with a molar ratio of 0.3;
wherein the volume of the condensation reactor is 0.1L, the flow of the condensation reaction liquid is controlled to be 0.25L/h, and the residence time is calculated according to the formula (1) to be 0.4h;
the condensation reaction solution was in a laminar flow state (Re = 335) in the heat exchanger, the coil length (l) was 1.2m, the flow velocity (v) in the tube was 2.03m/s, the coil inner diameter (d) was 3mm, and the polyamine sedimentation velocity (u) was n =10 and was u = 1.6X 10 of polyamine -6 m/s, calculated according to equation (3), gives l/vd =66.2 < 209.2.
S2: the reaction mixture in S1 was neutralized with an excess of 50% w NaOH aqueous solution (1.10 mole ratio of NaOH to S1 added hydrochloric acid), the neutralized mixture was passed into a layering vessel to separate the organic and aqueous phases, the organic phase was washed once with water, water and aniline were initially separated by flash evaporation at 10kPa, and MDA was refined by 8barg steam distillation.
S3: and (3) extracting the brine obtained after mixing the water phase generated in the neutralization and water washing processes in the S2 by using an aniline solvent (the mass ratio of aniline to the water phase is 0.2.
After the operation is carried out for 3 months, the content of macromolecular polyamine in the condensation reaction liquid is controlled to be 0.34mg/L, the corresponding turbidity of the condensation reaction liquid is controlled to be 0.58NTU, no obvious deposit is generated in the coil pipe, and the content of organic amine in the waste saline is 0.28mg/L.
Example 3
S1: reacting hydrochloric acid with a molar ratio of 0.3;
wherein the volume of the condensation reactor is 0.1L, the flow of the condensation reaction liquid is controlled to be 0.05L/h, and the residence time is 2h according to the formula (1);
the condensation reaction solution was in a laminar flow state (Re = 249) in the heat exchanger, the coil length (l) was 0.3m, the flow velocity (v) in the tube was 1.51m/s, the coil inner diameter (d) was 3mm, and the polyamine sedimentation velocity (u) was n =10 and was 1.6X 10 based on the polyamine (u = 10) -6 m/s, calculated according to equation (3), gives l/vd =66.2 < 209.2.
S2: the reaction mixture in S1 was neutralized with an excess of 50% w NaOH aqueous solution (1.10 mole ratio of NaOH to S1 added hydrochloric acid), the neutralized mixture was passed into a layering vessel to separate the organic and aqueous phases, the organic phase was washed once with water, water and aniline were initially separated by flash evaporation at 10kPa, and MDA was refined by 8barg steam distillation.
S3: and (3) extracting the brine mixed with the water phase generated in the neutralization and water washing processes in the S2 by using an aniline solvent (the mass ratio of the aniline to the water phase is 0.2: 1) to remove small-molecule MDA, and then stripping by using 2barg steam to remove aniline in the brine, so as to obtain waste brine.
After the operation is carried out for 3 months, the content of macromolecular polyamine in the condensation reaction liquid is controlled to be 0.27mg/L, the corresponding turbidity of the condensation reaction liquid is controlled to be 0.48NTU, no obvious sediment exists in a coil pipe, and the content of organic amine in the waste saline is 0.25mg/L.
Example 4
S1: reacting hydrochloric acid with a molar ratio of 0.3;
wherein the volume of the condensation reactor is 0.1L, the flow of the condensation reaction liquid is controlled to be 0.05L/h, and the residence time is calculated according to the formula (1) to be 0.4h;
the condensation reaction solution was in a laminar flow state (Re = 249) in a heat exchanger, the coil length (l) was 0.3m, the flow velocity (v) in the tube was 1.51m/s, the coil inner diameter (d) was 3mm, and the sedimentation velocity (u) of the polyamine was n =10, i.e., u = 1.6X 10 of the polyamine -6 m/s, calculated according to formula (3) to give l/vd =66.2 < (R)209.2。
S2: the reaction mixture in S1 was neutralized with an excess of 50% w/w aqueous NaOH solution (NaOH to S1 molar hydrochloric acid addition ratio 1.10), the neutralized mixture was passed through a delayer to separate the organic and aqueous phases, the organic phase was washed once with water, water and aniline were initially separated by flash evaporation at 10kPa, and MDA was obtained by 8barg steam distillation refining.
S3: and (3) extracting the brine obtained after mixing the water phase generated in the neutralization and water washing processes in the S2 by using an aniline solvent (the mass ratio of aniline to the water phase is 0.2.
After the operation is carried out for 3 months, the content of macromolecular polyamine in the condensation reaction liquid is controlled to be 0.03mg/L, the corresponding turbidity of the condensation reaction liquid is controlled to be 0.04NTU, no obvious deposit is generated in the coil pipe, and the content of organic amine in the waste saline is 0.02mg/L.
Example 5
S1: reacting hydrochloric acid with a molar ratio of 0.3;
wherein the volume of the condensation reactor is 0.1L, the flow of the condensation reaction liquid is controlled to be 0.05L/h, and the residence time is calculated according to the formula (1) to be 0.4h;
the condensation reaction solution was in a laminar flow state (Re = 249) in the heat exchanger, the coil length (l) was 0.3m, the flow velocity (v) in the tube was 1.51m/s, the coil inner diameter (d) was 3mm, and the polyamine sedimentation velocity (u) was n =10 and was 1.6X 10 based on the polyamine (u = 10) -6 m/s, calculated according to equation (3), gives l/vd =66.2 < 209.2.
S2: the reaction mixture in S1 was neutralized with an excess of 50% w/w aqueous NaOH solution (NaOH to S1 molar hydrochloric acid addition ratio 1.10), the neutralized mixture was passed through a delayer to separate the organic and aqueous phases, the organic phase was washed once with water, water and aniline were initially separated by flash evaporation at 10kPa, and MDA was obtained by 8barg steam distillation refining.
S3: and (3) extracting the brine obtained after mixing the water phase generated in the neutralization and water washing processes in the S2 by using an aniline solvent (the mass ratio of aniline to the water phase is 0.2.
After the operation is carried out for 3 months, the content of macromolecular polyamine in the condensation reaction liquid is controlled to be 0.47mg/L, the corresponding turbidity of the condensation reaction liquid is controlled to be 0.94NTU, no obvious deposit is generated in the coil pipe, and the content of organic amine in the waste saline is 0.46mg/L.
Example 6
S1: reacting hydrochloric acid with a molar ratio of 0.3;
wherein the volume of the condensation reactor is 80m 3 Controlling the flow rate of the condensation reaction liquid to be 160m 3 The residence time is 0.5h according to the formula (1);
the condensation reaction solution was allowed to flow in a laminar state in a heat exchanger (Re = 1510) by using a tubular heat exchanger, the tubular length (l) was 3m, the flow velocity (v) in the tube was 1.83m/s, the inner diameter (d) of the tubular tube was 15mm, and the sedimentation velocity (u) of the polyamine was n =10 for the polyamine of u =1.6 × 10 -6 m/s, calculated according to equation (3), gives l/vd =109.3 < 209.2.
S2: the reaction mixture in S1 was neutralized with an excess of 50% w/w aqueous NaOH solution (NaOH to S1 molar hydrochloric acid addition ratio 1.10), the neutralized mixture was passed through a delayer to separate the organic and aqueous phases, the organic phase was washed once with water, water and aniline were initially separated by flash evaporation at 10kPa, and MDA was obtained by 8barg steam distillation refining.
S3: and (3) extracting the brine mixed with the water phase generated in the neutralization and water washing processes in the S2 by using an aniline solvent (the mass ratio of the aniline to the water phase is 0.2: 1) to remove small-molecule MDA, and then stripping by using 2barg steam to remove aniline in the brine, so as to obtain waste brine.
After running for 6 months, the content of macromolecular polyamine in the condensation reaction liquid is controlled to be 0.18mg/L, the corresponding turbidity of the condensation reaction liquid is controlled to be 0.41NTU, no obvious deposit is left in the tube nest, and the content of organic amine in the waste brine is 0.17mg/L.
Example 7
S1: reacting hydrochloric acid with a molar ratio of 0.3;
wherein the volume of the condensation reactor is 80m 3 Controlling the flow rate of the condensation reaction liquid to be 160m 3 H, the retention time is 0.5h according to the formula (1);
the condensation reaction solution was allowed to flow in a laminar state (Re = 1510) in a heat exchanger using a tubular heat exchanger, the length (l) of the tubular heat exchanger was 3m, the flow velocity (v) in the tubular heat exchanger was 1.83m/s, the inner diameter (d) of the tubular heat exchanger was 15mm, and the sedimentation velocity (u) of the polyamine was n =10, i.e., u =1.6 × 10 of the polyamine -6 m/s, calculated according to equation (3), gives l/vd =109.3 < 209.2.
S2: the reaction mixture in S1 was neutralized with an excess of 50% w NaOH aqueous solution (1.10 mole ratio of NaOH to S1 added hydrochloric acid), the neutralized mixture was passed into a layering vessel to separate the organic and aqueous phases, the organic phase was washed once with water, water and aniline were initially separated by flash evaporation at 10kPa, and MDA was refined by 8barg steam distillation.
S3: and (3) extracting the brine mixed with the water phase generated in the neutralization and water washing processes in the S2 by using an aniline solvent (the mass ratio of the aniline to the water phase is 0.2: 1) to remove small-molecule MDA, and then stripping by using 2barg steam to remove aniline in the brine, so as to obtain waste brine.
After running for 6 months, the content of macromolecular polyamine in the condensation reaction liquid is controlled at 0.07mg/L, the corresponding turbidity of the condensation reaction liquid is controlled at 0.14NTU, no obvious sediment exists in a tube nest, and the content of organic amine in the waste saline is 0.021mg/L.
Example 8
S1: reacting hydrochloric acid with a molar ratio of 0.3;
wherein the volume of the condensation reactor is 80m 3 Controlling the flow rate of the condensation reaction liquid to be 160m 3 The residence time is 0.5h according to the formula (1);
the condensation reaction liquid was allowed to flow in a laminar state (Re = 901) in a plate heat exchanger, the flow distance, i.e., the vertical height (l) of the plate heat exchanger was 1.8m, the flow velocity (v) in the tube was 2.73m/s, the hydrodynamic radius (r) was 1.5mm, and the sedimentation velocity (u) of the polyamine was n =10 and was determined to be u =1.6 × 10 of polyamine -6 m/s, calculated according to equation (3), 746.95ul/vr =0.525 < 1.
S2: the reaction mixture in S1 was neutralized with an excess of 50% w NaOH aqueous solution (1.10 mole ratio of NaOH to S1 added hydrochloric acid), the neutralized mixture was passed into a layering vessel to separate the organic and aqueous phases, the organic phase was washed once with water, water and aniline were initially separated by flash evaporation at 10kPa, and MDA was refined by 8barg steam distillation.
S3: and (3) extracting the brine obtained after mixing the water phase generated in the neutralization and water washing processes in the S2 by using an aniline solvent (the mass ratio of aniline to the water phase is 0.2.
After operation for 6 months, the content of macromolecular polyamine in the condensation reaction liquid is controlled at 0.15mg/L, the corresponding turbidity of the condensation reaction liquid is controlled at 0.37NTU, no obvious sediment exists in a tube nest, and the content of organic amine in the waste saline is 0.14mg/L.
Comparative example 1
In this comparative example, the residence time of the condensation reaction of aniline hydrochloride and formaldehyde was longer than in example 1, and the precipitation was not controlled.
S1: reacting hydrochloric acid with a molar ratio of 0.3;
wherein the volume of the condensation reactor is 0.1L, the flow rate of the condensation reaction liquid is controlled to be 0.01L/h, and the retention time is 10h according to the formula (1);
the condensation reaction solution was in a laminar flow state (Re = 249) in the heat exchanger, the coil length (l) was 10m, the flow velocity (v) in the tube was 1.51m/s, the coil inner diameter (d) was 3mm, and the polyamine sedimentation velocity (u) was n =10, i.e., u =1.6 × 10 of polyamine -6 m/s, calculated according to equation (3), l/vd =2208 > 209.2.
S2: the reaction mixture in S1 was neutralized with an excess of 50% w NaOH aqueous solution (1.10 mole ratio of NaOH to S1 added hydrochloric acid), the neutralized mixture was passed into a layering vessel to separate the organic and aqueous phases, the organic phase was washed once with water, water and aniline were initially separated by flash evaporation at 10kPa, and MDA was refined by 8barg steam distillation.
S3: and (3) extracting the brine obtained after mixing the water phase generated in the neutralization and water washing processes in the S2 by using an aniline solvent (the mass ratio of aniline to the water phase is 0.2.
After the operation for 3 months, the content of macromolecular polyamine in the condensation reaction liquid is 20.9mg/L, the turbidity corresponding to the condensation reaction liquid is 23.8NTU, obvious deposits can be observed on the coil pipe, and the content of organic amine in the waste brine is 19.7mg/L.
Comparative example 2
In comparison with example 1, the residence time of the condensation reaction of aniline hydrochloride and formaldehyde is unchanged and the precipitation is not controlled.
S1: reacting hydrochloric acid with a molar ratio of 0.3;
wherein the volume of the condensation reactor is 0.1L, the flow of the condensation reaction liquid is controlled to be 0.25L/h, and the residence time is calculated according to the formula (1) to be 0.4h;
the condensation reaction solution was in a laminar flow state (Re = 249) in the heat exchanger, the coil length (l) was 10m, the flow velocity (v) in the tube was 1.51m/s, the coil inner diameter (d) was 3mm, and the polyamine sedimentation velocity (u) was n =10, i.e., u =1.6 × 10 of polyamine -6 m/s, according to formula(3) Calculated l/vd =2208 > 209.2.
S2: the reaction mixture in S1 was neutralized with an excess of 50% w NaOH aqueous solution (1.10 mole ratio of NaOH to S1 added hydrochloric acid), the neutralized mixture was passed into a layering vessel to separate the organic and aqueous phases, the organic phase was washed once with water, water and aniline were initially separated by flash evaporation at 10kPa, and MDA was refined by 8barg steam distillation.
S3: and (3) extracting the brine mixed with the water phase generated in the neutralization and water washing processes in the S2 by using an aniline solvent (the mass ratio of the aniline to the water phase is 0.2: 1) to remove small-molecule MDA, and then stripping by using 2barg steam to remove aniline in the brine, so as to obtain waste brine.
After the operation is carried out for 3 months, the content of macromolecular polyamine in the condensation reaction liquid is 13.5mg/L, the turbidity corresponding to the condensation reaction liquid is 15.4NTU, obvious deposits can be observed on the coil pipe, and the content of organic amine in the waste brine is 12.7mg/L.
Comparative example 3
In this comparative example, the residence time of the condensation reaction of aniline hydrochloride and formaldehyde was longer and the precipitation was controlled, as compared with example 1.
S1: reacting hydrochloric acid with a molar ratio of 0.3;
wherein the volume of the condensation reactor is 0.1L, the flow of the condensation reaction liquid is controlled to be 0.01L/h, and the residence time is 10h according to the formula (1);
the condensation reaction solution was in a laminar flow state (Re = 249) in a heat exchanger, the coil length (l) was 0.3m, the flow velocity (v) in the tube was 1.51m/s, the inner diameter (d) of the tube was 3mm, and the sedimentation velocity (u) of the polyamine was n =10, i.e., u = 1.6X 10 of the polyamine -6 m/s, calculated according to equation (3), gives l/vd =66 > 209.2.
S2: the reaction mixture in S1 was neutralized with an excess of 50wt% aqueous NaOH solution (NaOH to S1 added hydrochloric acid molar ratio of 1.10), the neutralized mixture was passed into a layering vessel to separate organic and aqueous phases, the organic phase was once washed with water, water and aniline were preliminarily separated by flash evaporation at 10kPa, and MDA was refined by 8barg steam distillation.
S3: and (3) extracting the brine mixed with the water phase generated in the neutralization and water washing processes in the S2 by using an aniline solvent (the mass ratio of the aniline to the water phase is 0.2: 1) to remove small-molecule MDA, and then stripping by using 2barg steam to remove aniline in the brine, so as to obtain waste brine.
After operation for 3 months, the content of macromolecular polyamine in the condensation reaction liquid is 11.8mg/L, the turbidity corresponding to the condensation reaction liquid is 13.4NTU, obvious deposits can be observed in a tube nest, and the content of organic amine in the waste brine is 11.0mg/L.
Comparative example 4
In this comparative example, the residence time of the condensation reaction of aniline hydrochloride and formaldehyde was increased and the precipitation was controlled, as compared with example 1, and the formaldehyde ratio was set to 0.4.
S1: reacting hydrochloric acid with a molar ratio of 0.3;
wherein the volume of the condensation reactor is 0.1L, the flow rate of the condensation reaction liquid is controlled to be 0.01L/h, and the retention time is 10h according to the formula (1);
the condensation reaction solution was in a laminar flow state (Re = 249) in the heat exchanger, the coil length (l) was 10m, the flow velocity (v) in the tube was 1.51m/s, the coil inner diameter (d) was 3mm, and the polyamine sedimentation velocity (u) was n =10, i.e., u =1.6 × 10 of polyamine -6 m/s, calculated according to equation (3), gives l/vd =2207 > 209.2.
S2: the reaction mixture in S1 was neutralized with an excess of 50wt% aqueous NaOH solution (NaOH to S1 added hydrochloric acid molar ratio of 1.10), the neutralized mixture was passed into a layering vessel to separate organic and aqueous phases, the organic phase was once washed with water, water and aniline were preliminarily separated by flash evaporation at 10kPa, and MDA was refined by 8barg steam distillation.
S3: and (3) extracting the brine obtained after mixing the water phase generated in the neutralization and water washing processes in the S2 by using an aniline solvent (the mass ratio of aniline to the water phase is 0.2.
After the operation is carried out for 3 months, the content of macromolecular aniline in the condensation reaction liquid is 3.85mg/L, the turbidity corresponding to the condensation reaction liquid is 4.1NTU, obvious deposits can be observed on the coil pipe, and the content of organic amine in the waste saline is 2.07mg/L.
By comparing the above examples and comparative examples, it can be seen that the embodiments of the present invention, especially under the condition of high formaldehyde ratio, can achieve the goal of reducing polyamine and waste brine organic amine in the reaction liquid in the MDA preparation process. Taking the formaldehyde ratio of 0.6 as an example, when the scheme of the invention is not implemented, the highest polyamine content in the reaction liquid is 20.9mg/L, the turbidity is 23.8NTU, and the organic amine content in the waste brine is 19.7mg/L. After the method is implemented, polyamine in the reaction liquid is only 0.06mg/L, turbidity is 0.08NTU, and organic amine in the waste brine is 0.04mg/L, which are all obviously reduced, and the operation flexibility and stability of device production are greatly improved.
It will be appreciated by those skilled in the art that modifications and adaptations to the invention may be made in light of the teachings of the present disclosure. Such modifications or adaptations are intended to be within the scope of the present invention as defined by the claims.
Claims (12)
1. A method for controlling organic amine in waste salt water formed by diamine and polyamine (MDA) for preparing diphenylmethane is characterized in that the turbidity of reaction liquid is controlled to be 0.03-1.0NTU after aniline hydrochloride and formaldehyde are subjected to condensation reaction from the front end;
the method controls the residence time of the condensation reaction of aniline hydrochloride and formaldehyde in the condensation reaction process and controls the flow characteristic of the reaction liquid in a synthesis system;
wherein the residence time of the condensation reaction is controlled to be 0.1-2h;
wherein the flow characteristics of the reaction solution in the system are related to the parameters of the length (l) of the fluid flow, the velocity (v) of the fluid flow, the hydrodynamic radius (r) of the fluid flow and the settling velocity (u) of the polyamine, and the parameters of the flow characteristics of the reaction solution in the system conform to the following relations:
746.95ul/vr＜1
l is in the unit m, v is in the unit m/s, r is in the unit m, and u is in the unit m/s.
2. The method according to claim 1, wherein the turbidity of the reaction solution is 0.05 to 0.5NTU; the residence time of the condensation reaction is controlled to be 0.4-0.8h.
3. The process according to claim 1 or 2, wherein the process for preparing MDA comprises the following steps:
s1: aniline reacts with hydrochloric acid to generate aniline hydrochloride, formaldehyde is added to carry out condensation reaction to obtain a reaction mixture containing diaminodiphenyl diamine salt and polyamine salt, and the temperature is raised to carry out transposition reaction;
s2: neutralizing the reaction mixture in the S1 by using alkali, separating an organic phase and a water phase, washing the organic phase by using water, and purifying and refining to obtain MDA;
s3: and (3) extracting and stripping the water phase generated in the neutralization and water washing processes of S2 to form waste brine.
4. The method of claim 3, wherein the turbidity of the reaction solution is mainly composed of the macromolecular polyamine formed in the condensation reaction of S1, and the macromolecular polyamine has the following structure:
wherein n is a natural number greater than 10.
5. The method of claim 3, wherein the content of the macromolecular polyamine in the reaction solution is controlled to be 0.02-0.6mg/L after the condensation reaction of the S1 aniline hydrochloride and formaldehyde.
6. A method for controlling organic amine in waste brine formed by MDA preparation, which adopts the method of claim 4 or 5, and controls the organic amine in the waste brine by controlling the content of macromolecular polyamine in condensation reaction liquid.
7. The control method according to claim 6, wherein in S1, the residence time of the condensation reaction of aniline hydrochloride and formaldehyde and the flow characteristics of the reaction solution in the synthesis system are controlled, so as to control the content of macromolecular polyamine;
the residence time of the condensation reaction is controlled to be 0.1-2h;
the flow characteristics of the reaction liquid in the system are related to parameters such as the length (l) of the flowing fluid, the speed (v) of the flowing fluid, the hydraulic radius (r) of the flowing fluid and the sedimentation speed (u) of the polyamine;
the flow characteristics of the reaction liquid in the system are characterized by the following relations:
746.95ul/vr＜1
wherein, the unit of l is m, the unit of v is m/s, the unit of r is m, and the unit of u is m/s.
8. The control method according to claim 7, characterized in that the residence time of the condensation reaction is controlled between 0.4 and 0.8h.
9. The method according to claim 3, wherein the molar ratio of formaldehyde to aniline during the condensation reaction, i.e. the formaldehyde ratio, is (0.01-0.7): 1.
10. Use of the method for controlling organic amine in waste brine formed by MDA according to any of claims 1-8 for controlling organic amine in waste brine formed by MDA under different formaldehyde ratio conditions.
11. Use according to claim 10, characterized in that the process is used for controlling organic amines in waste brine for the production of MDA under high formaldehyde ratio conditions.
12. Use according to claim 11, characterized in that the high formaldehyde ratio is (0.5-0.7): 1.
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