Method and apparatus for the continuous post-treatment of a synthetic benzotriazole fluid
Patent Information
- Authority / Receiving Office
- DE · DE
- Patent Type
- Patents
- Current Assignee / Owner
- JIANGSU YANGNONG CHEMICAL GROUP CO LTD
- Filing Date
- 2020-04-15
- Publication Date
- 2026-07-23
AI Technical Summary
Existing batch-type synthesis methods for benzotriazole (BTA) are inefficient, energy-intensive, and lack effective recovery processes for BTA in aqueous layers, leading to high environmental impact and operational costs.
A continuous process for BTA post-treatment involving acidification, water washing, extraction, back-extraction, dehydration, and distillation, utilizing solubility differences at varying pH values to achieve separation without excessive evaporation energy, with a system comprising an acidification reactor, water scrubber, dehydration device, distillation device, and shaping device.
The process achieves high product quality with reduced energy consumption, lower environmental impact, and improved efficiency, enabling easy industrialization with stable product quality and reduced wastewater treatment pressure.
Abstract
Description
Technical field
[0001] The present invention relates to the technical field of petrochemistry and concerns a process for the continuous post-treatment of a synthetic benzotriazole fluid (abbreviated BTA fluid). In particular, the present invention relates to a process for synthesizing BTA in which the synthetic BTA fluid is subjected to post-treatment steps such as continuous acidification, water washing, extraction, back-extraction, dehydration, distillation, and the like. background
[0002] Benzotriazole (CAS: 95-14-7) consists of white and light brown needle-like crystals and is an important fine chemical product. It has a wide range of uses and is primarily employed as a rust inhibitor and corrosion inhibitor for metals (silver, copper, lead, nickel, zinc, and the like), but can also be used as a dye additive, synthetic detergent preservative, anticoagulant, synthetic dye intermediate, and the like, with a wide range of downstream applications.
[0003] A Chinese patent application (CN105237488A) describes a boiler-type batch synthesis process for BTA, in which the BTA is synthesized in one step by a pressure process from o-phenylenediamine. This process is batch-based, the production efficiency is low, and a recovery method for BTA in an aqueous layer is not mentioned. Summary
[0004] The present invention provides a method for the continuous post-treatment of synthetic BTA fluid. In particular, the present invention relates to a method for synthesizing BTA in which the synthetic BTA fluid is subjected to post-treatment steps such as continuous acidification, water washing, extraction, back-extraction, dehydration, distillation, and the like. The method utilizes the varying solubility of BTA in water at different pH values to achieve separation by extraction without consuming a large amount of evaporation energy. The present invention is easy to operate, has a low environmental impact, is highly economical and energy-efficient, and is readily scalable.
[0005] A process for the continuous post-treatment of the synthetic BTA fluid includes the following steps: (1) The synthetic BTA fluid and an acidification reagent are continuously fed into an acidification reactor for continuous acidification and an acidified aqueous layer and an acidified oil layer are extracted. (2) The oil layer acidified in (1) is fed into a water washing device for continuous water washing and a water-washed oil layer and a water-washed aqueous layer are extracted. (3) The aqueous layer acidified in (1) and the aqueous layer water-washed in (2) are combined and fed into an extraction tower for continuous extraction and an extracted aqueous layer and an extraction oil layer are extracted. (4) The oil layer extracted in (3) is fed into a back-extraction tower for continuous back-extraction and a back-extracted oil layer and a back-extracted aqueous layer are extracted to achieve the reuse of extraction solvent and BTA in the aqueous layer. (5) The oil layer washed by water in (2) is subjected to continuous dehydration and continuous distillation to obtain a BTA product.
[0006] In step (1) the acidification conditions are as follows: an acidification reagent is one or more of a hydrochloric acid, sulfuric acid, nitric acid and acetic acid, the acidification temperature is 20~100°C, pH=3~8, preferably 3~7 or 3~6, and further preferably 4~6 or 3~5 or 5~6; and The dwell time is 1 min to 300 min.
[0007] Preferably the acidification temperature is 40∼100°C, 40∼90°C, 40∼80°C or 40∼70°C, or preferably 50∼100°C, 50∼90°C, 50∼80°C or 50∼70°C, or preferably 60∼100°C, 60∼90°C, 60∼80°C or 60∼70°C.
[0008] Preferably, the pH value of an acidification endpoint is 3~6 or the pH value of the acidification endpoint is 3, 4, 5 or 6.
[0009] Preferably, the residence time for acidification is 30 min to 300 min, more preferably 60 min to 300 min, 60 min to 200 min or 60 min to 100 min, or preferably 70 min to 300 min, 70 min to 200 min or 70 min to 100 min, or preferably 100 min to 300 min or 100 min to 200 min or 200 min to 300 min.
[0010] In step (2) the conditions for water washing are as follows: a water washing temperature is 20∼100°C, a ratio of wash water volume flow rate is water: acidified oil layer = 0.1:1∼20:1, and a residence time is 1 min∼300 min.
[0011] Preferably, the temperature of the water washing is 40°C∼90°C, 40°C∼80°C, 40°C∼70°C, 40°C∼60°C or 40°C∼0°C; or preferably 50°C∼90°C, 50°C∼80°C, 50°C∼70°C or 50°C∼60°C; or preferably 60°C∼90°C, 60°C∼80°C, or 60°C∼70°C; or preferably 70°C∼90°C or 70°C∼80°C.
[0012] Preferably, the ratio of the wash water volume flow rate to the acidified oil layer is 0.5:1∼20:1, 1:1∼20:1, 5:1∼20:1 or 1:1∼10:1; or preferably 0.5:1∼10:1, 1:1∼10:1 or 5:1∼10:1.
[0013] Preferably, the residence time of the water washing process is 15 min to 300 min, 30 min to 300 min, 50 min to 300 min, 60 min to 300 min, 100 min to 300 min, or 200 min to 300 min; or preferably 15 min to 250 min, 30 min to 250 min, 50 min to 250 min, 60 min to 250 min, 100 min to 250 min, or 200 min to 250 min; or preferably 15 min to 200 min, 30 min to 200 min, 50 min to 200 min, 60 min to 200 min, or 100 min to 200 min; or preferably 15 min~100 min, 30 min~100 min, 50 min~100 min or 60 min~100 min.
[0014] In step (3) the extraction conditions are as follows: an extraction temperature is 20∼100°C, a ratio of an extraction volume flow rate is an extraction solvent: (the water-washed aqueous layer + the acidified aqueous layer) = 0.1:1—20:1, and a residence time is 1 min∼300 min.
[0015] Preferably, the extraction temperature is 50-100°C, 50-90°C, 50-80°C or 50-65°C; or 60-100°C, 60-90°C or 60-80°C; or 65-100°C, 65-90°C or 65-80°C; or 80°C-90°C.
[0016] Preferably, the ratio of the extraction volume flow rate to the extraction agent is: (the water-washed aqueous layer + the acidified aqueous layer) = 1:1-20:1, 1:1-15:1, 1:1-10:1, or 1:1-5:1; or preferably 5:1-20:1, 5:1-15:1, or 5:1∼10:1; or preferably 10:1-20:1, or 10:1∼15:1.
[0017] Preferably, the residence time is 5 min∼300 min, 5 min∼200 min, 5 min∼100 min, 5 min∼60 min, or 5 min∼50 min; or 50 min∼300 min, 60 min∼300 min, 100 min∼300 min, or 200 min∼300 min; or preferably 50 min∼200 min, 60 min∼200 min, or 100 min∼200 min.
[0018] In step (3) the extraction solvent is one or more mixtures of chlorobenzene, dichlorobenzene, nitrochlorobenzene, toluene, xylene, benzene, methyl isobutyl ketone (MIBK), dichloromethane, dichloroethane, chloroform, carbon tetrachloride and ethyl acetate.
[0019] In step (4) the conditions for back-extraction are as follows: a back-extraction temperature is 20∼100°C, a ratio of back-extraction volume flow rate is back-extraction solvent: extracted oil layer = 0.1:1∼20:1, a residence time is 1 min∼300 min, and under the better conditions the residual amount of BTA in the back-extracted oil layer is less than 0.5%.
[0020] Preferably, the re-extraction temperature is 40–90°C, 50–90°C, 60–90°C or 65–90°C; or preferably 40–80°C, 50–80°C, 60–80°C or 65–80°C; or preferably 40–70°C, 50–70°C, 60–70°C, or 65–70°C; or preferably 40–65°C, 50–65°C, or 60–65°C.
[0021] Preferably, the ratio of the back-extraction volume flow rate to back-extraction agent: extracted oil layer is 0.5:1∼20:1, 1:1∼20:1, 5:1∼20:1 or 10:1∼20:1 or preferably 0.5:1∼10:1, 1:1∼10:1 or 5:1∼10:1 or preferably 0.5:1∼15:1, 1:1∼15:1, 5:1∼15:1 or 10:1∼15:1.
[0022] In step (4) the back-extraction agent is the same as the acidification reagent in step (1) and is one or more of the hydrochloric acid, the sulfuric acid, the nitric acid and the acetic acid.
[0023] In step (5), the temperature of a continuous dehydration vessel material is 100–200°C, preferably 150–180°C, particularly preferably 170°C, and the absolute pressure is 5–50 kPa, preferably 5–30 kPa, 5–20 kPa, or 5–10 kPa, particularly preferably 5 kPa. The absolute pressure of the continuous distillation is 0–2 kPa, preferably 1 kPa, and the corresponding gas phase temperature is 140–190°C, preferably 150–180°C, even more preferably 180°C.
[0024] The present invention further provides a system for the continuous post-treatment of the synthetic BTA fluid, wherein the system is successively connected to an acidification reactor, a water washing device, a dehydration device, a distillation device and a molding device; and the water washing device is also successively connected to an extractor 1 and an extractor 2 and, via the extractor 2, to the acidification reactor.
[0025] Furthermore, the acidification reactor is connected to extractor 1 via a line for acidified water.
[0026] Furthermore, extractor 2 is returned to extractor 1 via a re-extraction oil line.
[0027] Furthermore, the dehydration device is fed back to the water washing device via a line for evaporated water.
[0028] A scheme of the present invention is used, and a method for the continuous post-treatment of the synthetic BTA fluid is provided. The BTA is synthesized by subjecting the synthetic BTA fluid to post-treatment steps of continuous acidification, water washing, extraction, back-extraction, dehydration, distillation, and the like. The method utilizes the varying solubility of BTA in water at different pH values to achieve separation by extraction without consuming a large amount of evaporation energy. The present invention is easy to operate, has a low environmental impact, is highly economical and energy-efficient, and is readily scalable. Brief description of the drawings
[0029] Fig.1 is a flow diagram of a continuous post-treatment, 1 is an acidification reactor, 2 is a water washing device, 3 is a dehydration device, 4 is a distillation device, 5 is a molding device, 6 is an extractor 1 and 7 is an extractor 2. Detailed description of the exemplary implementations
[0030] The following embodiments illustrate the present invention in detail, but do not further limit it. Unless otherwise stated, "%" here stands for "mass %". Example 1
[0031] BTA synthesis: 295 kg of o-phenylenediamine, 213 kg of sodium nitrite, and 370 kg of water are placed in a 1000-liter autoclave and replaced with nitrogen. After continuous stirring, the temperature is raised to 260°C and maintained for 3 hours to allow the reaction to occur. The temperature is then lowered and the pressure is released, yielding 877 kg of a clear, brown liquid. Analysis shows that the conversion rate of o-phenylenediamine is 100% and the yield of BTA is 98.94%. This procedure is used to synthesize BTA, and the synthetic fluid undergoes continuous post-treatment. Example 2
[0032] Continuous acidification: The synthetic fluid from Example 1 and 25% hydrochloric acid are continuously fed into an acidification vessel in a weight ratio of approximately 2:1. The acidification temperature is regulated to 65 °C, the residence time is 1 hour, and an acidification endpoint is pH 5–6. The acidified liquid is continuously layered; a resulting acidified oil layer is continuously washed with water, and an acidified aqueous layer is continuously extracted.
[0033] Continuous water washing: The water washing temperature is regulated to 60°C, the feed volume flow rate is water:oil = 0.95:1 ∼ 1.05:1, and the residence time is 1 h. A water-washed aqueous layer is then subjected to a continuous extraction step, and a water-washed oil layer is subjected to a continuous dehydration step.
[0034] Continuous extraction: The water-washed aqueous layer and the acidified aqueous layer are combined and subjected to an extraction step. Chlorobenzene is used as the extraction solvent, the extraction temperature is regulated to 60°C, the feed volume flow rate ratio is water:oil = 1:0.45 to 1:0.55, and the residence time is 1 hour. An extracted oil layer undergoes continuous back-extraction, and an extracted aqueous layer is treated as wastewater.
[0035] Continuous back-extraction: 25% hydrochloric acid is used as the back-extraction solvent, the temperature is regulated to 65°C, and the residence time is 1 hour. The extracted oil layer and the 25% hydrochloric acid are back-extracted at a volume flow rate of hydrochloric acid:extracted oil layer = 0.2:1 ∼ 0.25:1, and the BTA content in the back-extracted oil layer obtained at this point is <0.1%. The back-extracted oil layer is used as the recovery extraction solvent and reused for the continuous extraction step, and a back-extracted aqueous layer is BTA hydrochloride and is reused for the continuous acidification step.
[0036] Continuous dehydration: The continuously water-washed oil layer is dehydrated, the absolute pressure is regulated to 5 kPa and the boiler temperature is 170°C, the water content of the boiler material is less than 0.1% at this point, the dehydration water is reused for the continuous water washing step and the dehydrated boiler material enters a continuous distillation step.
[0037] Continuous distillation: The dehydrated boiler material is continuously fed into a distillation tower, the absolute pressure is regulated to 1 kPa, and the temperature of the tower head is approximately 180°C. A continuously extracted tower head fraction is a BTA product, and the product appears as a white solid after cooling. Examples 3-6
[0038] Based on Example 2, the extraction solvent is changed to MIBK, the back-extraction solvent and acid are changed to sulfuric acid, the other conditions remain unchanged, and the applications of the materials are carried out. The results are as follows: Table 1: Example number Application number Product coloring Product yield / % Example 3 First batch 20 81,2 Example 4 Quantity 1 20 97,4 Example 5 Quantity 2 15 97,8 Example 6 Quantity 3 15 98,1 Examples 7-17
[0039] Based on Example 2, the post-treatment conditions are changed and the results are as follows: Table 2: Contrast examples 1-4
[0040] The material from Example 2 of the present invention is treated using a prior art batch-type post-treatment process. The water washing conditions are the same as in Example 2; the water washing temperature is 60°C, the water-to-oil ratio is 1:1, and the heat preservation time is 1 hour. The treatment results are as follows: Table 3: Example number Treatment mode Acidification endpoint pH Total time from acidification to dehydration / h BTA yield / % Example 2 continuously 5 2 98,94 Example 15 continuously 8 2 50,61 Example 16 continuously 1 2 5,13 Example 17 continuously 5 2 98,96 Contrast example 1 Batch type 5 10 97,85 Contrast example 2 Batch type 5 5 95,56 Contrast example 3 Batch type 8 10 42,27 Contrast example 4 Batch type 1 10 5,05
[0041] The behavior of the products from examples 7-14 above and the contrast examples is determined. Product color, product purity, and product yield are all measured according to an HG / T 3824-2014 quality standard procedure, and the measurement results for product color, product purity, and wastewater are as follows: Table 4: Example number Product coloring Product purity / % Product yield / % Wastewater TOC / ppm Example 7 15 99,95 98,16 489 Example 8 13 99,91 98,54 455 Example 9 10 99,96 97,96 468 Example 10 12 99,89 98,33 473 Example 11 14 99,81 98,12 485 Example 12 15 99,79 98,59 476 Example 13 12 99,92 98,15 464 Example 14 10 99,9 98,21 433 Example 15 >150 98,12 50,61 - Example 16 >150 95,01 5,13 - Example 17 22 99,86 98,96 486 Contrast example 1 25 99,79 97,85 4325 Contrast example 2 30 99,52 95,56 5230 Contrast example 3 >150 97,96 42,27 - Contrast example 4 >150 94,89 5,05 -
[0042] Tables 3 and 4 show that the pH value at the acidification endpoint has the greatest influence on product quality and yield, with a pH value preferably being 5–6. The product quality of the continuous process is stable. Compared to the batch-type process, product coloration is reduced by 30–50%, the quality is improved, the total organic carbon (TOC) of the wastewater is reduced by approximately 90% compared to the previous year, and the wastewater treatment pressure is significantly reduced. Furthermore, the water-to-oil ratio of the water wash step also affects the product coloration. Compared to the batch-type process, the continuous post-treatment can achieve the desired effect with less water.
[0043] From the descriptions above, it is evident that all existing BTA post-treatment processes worldwide employ a batch-type treatment mode, primarily batch acidification, followed by batch water washing and BTA recovery from the water through cooling and crystallization. These processes require numerous devices and consume significant amounts of energy. However, the present invention provides for continuous post-treatment. The operating procedure is simple, the process reliability is high, and the efficiency is high. Before dehydration, the post-treated materials are at the same temperature, reducing heat exchange and energy consumption. Furthermore, continuous acidification, dehydration, and rectification produce high-quality BTA products.Compared to the batch-type post-treatment process, energy consumption is lower, there are no frequent temperature increases and decreases during crystallization, and there are no large number of solid-liquid separation processes in batch-type treatment. The TOC content of the wastewater from continuous treatment is below 500 ppm, and the wastewater treatment pressure is also significantly lower.
[0044] The content of the present invention is not limited to the content of the examples of the present invention.
[0045] This document uses specific examples to describe the structure and implementation methods of the present invention. The descriptions of the examples above serve only to illustrate the core concept of the present invention. It should be noted that, for the average person skilled in the art, a multitude of improvements and modifications to the present invention could be made without deviating from the principle of the present invention, and these improvements and modifications would also fall within the scope of protection of the claims of the present invention. QUOTES INCLUDED IN THE DESCRIPTION
[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature
[0000] CN 105237488 A
[0003]
Claims
[1] A method for the continuous post-treatment of a synthetic benzotriazole (BTA) fluid, the method comprising the following steps: (1) Continuous feeding of the synthetic BTA fluid and an acidification reagent into an acidification reactor for continuous acidification and extraction of an acidified aqueous layer and an acidified oil layer; (2) Feeding the acidified oil layer from (1) into a water washing device for continuous water washing and extraction of a water-washed oil layer and a water-washed aqueous layer; (3) Combining the acidified aqueous layer at (1) and the water-washed aqueous layer at (2) and feeding into an extraction tower for continuous extraction and extracting an extracted aqueous layer and an extracted oil layer; (4) Feeding the extracted oil layer from (3) into a re-extraction tower for continuous re-extraction and extracting a re-extracted oil layer and a re-extracted aqueous layer to achieve the reuse of an extraction solvent and the BTA in the aqueous layer; and (5) Subjecting the water-washed oil layer from (2) to continuous dehydration and continuous distillation and forming in a molding device to obtain a BTA product. [2] The method for the continuous post-treatment of the synthetic BTA fluid according to claim 1, wherein in step (1) the acidification reagent is one or more of a hydrochloric acid, sulfuric acid, nitric acid and acetic acid, preferably the temperature of the continuous acidification is 20~100°C; preferably the pH value of the continuous acidification is 3~8, more preferably 3~6, and further preferably 4~6 or 3~5 or 5~6; and Preferably, the residence time for continuous acidification is 1 min to 300 min. [3] The method for the continuous post-treatment of the synthetic BTA fluid according to claim 1, wherein in step (2) the conditions for the continuous water washing are as follows: a temperature of the continuous water washing is 20∼100°C, preferably a ratio of water washing volume flow rate water: acidified oil layer = 0.1:1∼20:1 is; preferably the residence time of the water washing is 1 min to 300 min; and Preferably, the water washing device is a water washing tower or a water washing boiler. [4] The method for the continuous post-treatment of the synthetic BTA fluid according to claim 1, wherein in step (3) the extraction conditions are as follows: The extraction temperature is 20~100°C; preferably a ratio of extraction volume flow rate to extraction solvent: (the water-washed aqueous layer + the acidified aqueous layer) = 0.1:1 ∼ 20:1; and preferably the residence time of the extraction is 1 min~300 min. [5] The process for the continuous post-treatment of the synthetic BTA fluid according to claim 1, wherein in step (3) the extraction agent is one or more mixtures of chlorobenzene, dichlorobenzene, nitrochlorobenzene, toluene, xylene, benzene, methyl isobutyl ketone (MIBK), dichloromethane, dichloroethane, chloroform, carbon tetrachloride and ethyl acetate. [6] The method for the continuous post-treatment of the synthetic BTA fluid according to claim 1, wherein in step (4) the conditions for the back-extraction are as follows: a back-extraction temperature is 20∼100°C; preferably a ratio of a re-extraction volume flow rate to re-extraction solvent: extracted oil layer = 0.1:1∼20:1; preferably the residence time of the back-extraction is 1 min to 300 min; and preferably the residual amount of BTA in the re-extracted oil layer is less than 0.5%. [7] The method for the continuous post-treatment of the synthetic BTA fluid according to claim 1, wherein in step (4) the re-extraction agent is one or more of a hydrochloric acid, sulfuric acid, nitric acid and acetic acid. [8] The method for the continuous post-treatment of the synthetic BTA fluid according to claim 1, wherein in step (5) the temperature of the continuous dehydration is 100∼200°C; preferably an absolute pressure of 5∼50 kPa; preferably an absolute pressure of continuous distillation of 0∼2 kPa; and preferably a corresponding gas phase temperature of 140~190°C. [9] A system for the continuous post-treatment process of the synthetic BTA fluid according to claim 1, wherein the system is successively connected to an acidification reactor (1), a water washing device (2), a dehydration device (3), a distillation device (4) and a molding device (5); and wherein the water washing device (2) is also successively connected to an extractor 1 (6) and an extractor 2 (7) and is connected to the acidification reactor (1) via the extractor 2 (7). [10] The system according to claim 9, wherein the acidification reactor (1) is connected to the extractor 1 (6) by a line for acidified water. [11] The system according to claim 9, wherein the extractor 2 (7) is returned to the extractor 1 (6) via a re-extraction oil line. [12] The system according to claim 9, wherein the dehydration device (3) is returned to the water washing device (2) via a line for evaporated water.