Process for the dechlorination of organic chlorosilane hydrolysate
By combining a hydrolysis reactor, a separator, and an electrostatic device, a highly efficient dechlorination process for organochlorosilane hydrolysates was achieved, solving the problem of high residual Cl ion concentration and realizing low-energy consumption and environmentally friendly production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG UNIV OF TECH
- Filing Date
- 2025-06-30
- Publication Date
- 2026-06-02
AI Technical Summary
Existing technologies result in a high concentration of residual Cl ions in organochlorosilane hydrolysates, leading to a decline in the quality of the hydrolysate siloxanes. Furthermore, traditional dechlorination methods suffer from problems such as high water consumption, excessive use of alkali solutions, and the generation of wastewater and waste salts.
The process employs a combination of a two-stage hydrolysis reactor, a hydrolysis phase separator, a hydrolysis electrostatic device, a water washing stirred tank, a water washing phase separator, and a water washing electrostatic device. By coupling coalescence sedimentation technology and a high-voltage electrostatic device, dual coalescence-sedimentation is achieved. Combined with the water washing dechlorination section, the use of alkali solution is avoided.
It significantly reduces the concentration of residual Cl ions in the hydrolysate, reduces water consumption and energy consumption, avoids the generation of waste liquid and waste salt, and makes the production process green and environmentally friendly, yielding high-quality siloxane products.
Smart Images
Figure CN120757582B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of organosilicon, and more specifically to a novel process for washing and dechlorinating organochlorosilane hydrolysates. Background Technology
[0002] Organochlorosilanes, through hydrolysis and condensation, produce intermediate oligomeric siloxanes with linear or cyclic structures, which are essential for the synthesis of silicone oils, silicone rubbers, and silicone resins. Typically, organochlorosilanes undergo hydrolysis under acidic conditions to produce hydrolysate oligomeric siloxanes and the byproduct HCl. However, HCl readily dissolves in the aqueous phase entrained in the hydrolysate, resulting in a high concentration of residual Cl ions in the hydrolysate siloxanes, directly impacting their quality and subsequent application development.
[0003] (CH3)2SiCl2+2H2O→(CH3)Si(OH)2+2HCl
[0004]
[0005] Currently, methods for removing residual Cl ions from hydrolyzed siloxanes mainly include setting up multi-stage water washing and alkali washing processes, or designing special steam towers or distillation towers. Patent CN101817505A discloses a water washing, alkali neutralization, and water washing method for dechlorination, in which the alkali solution used is a 5%–30% soda ash solution or a 2%–10% caustic soda solution. Although this process can effectively remove free chlorine from the hydrolysate, it suffers from problems such as large water and alkali consumption, wastewater and waste salt production in the water washing section, and high environmental treatment costs. Patents CN103214508A, CN102174200A, and CN1099435C employ multi-stage water washing and alkali washing for dechlorination, but also suffer from problems such as large amounts of wastewater and waste salt, and high treatment costs. To overcome the above problems, patent CN101323666A uses a steam tower to dechlorinate the crude hydrolysate. This process avoids the use of alkali and the generation of waste salt, but it still has problems such as large steam consumption and high energy consumption. Summary of the Invention
[0006] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a highly efficient washing and dechlorination method for organochlorosilane hydrolysates.
[0007] The technical solution adopted in this invention is as follows:
[0008] The aforementioned organochlorosilane hydrolysate washing and dechlorination process includes a hydrolysis dechlorination section and a water washing dechlorination section. After the raw organochlorosilane is processed through the hydrolysis dechlorination section and the water washing dechlorination section, a high-quality low-chlorinated siloxane product is obtained.
[0009] (1) The hydrolysis dechlorination section includes a two-stage hydrolysis reactor, a hydrolysis phase separator, and a hydrolysis electrostatic device. The raw material organochlorine silane (dichlorodimethylsilane) and process water are continuously fed to the two-stage hydrolysis reactor for hydrolysis reaction. Under acidic conditions, hydrolysate siloxane and by-product HCl are generated. The by-product HCl gas is collected from the top of the hydrolysis reactor for subsequent treatment. The hydrolysate siloxane and acid water mixture generated in the hydrolysis reactor are transported to the hydrolysis phase separator for coalescence dehydration and dechlorination. The oil phase hydrolysate obtained from the upper outlet after dehydration and dechlorination by the hydrolysis phase separator is sent to the hydrolysis electrostatic device for further dehydration and dechlorination. The oil phase hydrolysate from the upper outlet after dehydration and dechlorination by the hydrolysis electrostatic device is sent to the water washing dechlorination section for further dechlorination treatment. The water phase collected from the lower layer of the hydrolysis phase separator and the hydrolysis electrostatic device can be recycled for the hydrolysis reaction process in the two-stage hydrolysis reactor.
[0010] (2) The water washing dechlorination section includes a water washing stirred tank, a water washing phase separator and a water washing electrostatic device. The oil phase hydrolysate collected from the upper outlet of the electrostatic device of the hydrolysis section (1) is transported to the water washing stirred tank of the water washing dechlorination section and mixed with the washing water for washing. The mixture of the hydrolysate siloxane and the washing water after washing in the water washing stirred tank is transported to the water washing phase separator for coalescence, dehydration and dechlorination. The oil phase hydrolysate overflowing from the upper outlet after dehydration and dechlorination in the water washing phase separator is sent to the electrostatic device for further dehydration and dechlorination. Finally, high-quality low-chlorinated siloxane product is collected from the upper outlet of the electrostatic device. The water phase collected from the lower outlet of the water washing phase separator and the electrostatic device can be reused in the hydrolysis reaction process in the two-stage hydrolysis reactor in the hydrolysis dechlorination section (1).
[0011] The aforementioned organochlorosilane hydrolysate washing and dechlorination process is characterized in that the temperature in the first-stage hydrolysis reactor is controlled at 40℃~60℃, the pressure at 0.1~0.3MPa, the saturated hydrochloric acid concentration at 39%~45%, and the residence time at 5~10min; the temperature in the second-stage hydrolysis reactor is controlled at 40℃~60℃, the pressure at 0.1MPa, the concentrated hydrochloric acid concentration at 12%~25%, and the residence time at 5~10min.
[0012] The aforementioned organochlorosilane hydrolysate washing and dechlorination process is characterized in that the electric field strength in the hydrolysis electrostatic device or the water washing electrostatic device is 20-100 kV / m, the temperature is 40-90℃, and the power supply is a positive high voltage DC power supply or a negative high voltage DC power supply.
[0013] The aforementioned organochlorosilane hydrolysate washing and dechlorination process is characterized in that the temperature of the hydrolysis phase separator is controlled at 40-90°C, and the residence time in the hydrolysis phase separator is 5-10 min.
[0014] The aforementioned organochlorosilane hydrolysate washing and dechlorination process is characterized in that the temperature of the water washing phase separator is controlled at 40-90°C, and the residence time in the water washing phase separator is 5-10 min.
[0015] The aforementioned organochlorosilane hydrolysate washing and dechlorination process is characterized in that the temperature of the water washing stirring tank in the water washing and dechlorination section is 40-90℃, the stirring speed is 50-150r / min, and the residence time is 5-10min.
[0016] The aforementioned organochlorosilane hydrolysate washing and dechlorination process is characterized in that the water washing and dechlorination section in step (2) is a two- or three-stage series process. The oil phase output from the hydrolysis and dechlorination section in step (1) flows from the first-stage water washing and dechlorination section to the last-stage water washing and dechlorination section. Fresh process water is first introduced into the water washing stirred tank of the last-stage water washing and dechlorination section. The water phase collected from the lower layer of the water washing phase separator and the water washing electrostatic device in the last-stage water washing and dechlorination section flows back to the water washing stirred tank of the adjacent previous-stage water washing and dechlorination section. Similarly, the water phase collected from the lower layer outlet of the water washing phase separator and the water washing electrostatic device in the first-stage water washing and dechlorination section flows back to the hydrolysis reaction process in the two-stage hydrolysis reactor of the hydrolysis and dechlorination section in step (1).
[0017] Compared with existing processes, the beneficial effects of the present invention through the above process are as follows:
[0018] 1) The process of this invention cleverly couples the primary coalescence sedimentation of the coalescing phase separator and the advanced coalescence sedimentation of the high-voltage electrostatic device, which are two different droplet scale coalescence sedimentation synergistic effects. Through the dual coalescence-sedimentation technology, the amount of acid water entrained in the crude hydrolysate of organochlorosilanes in the hydrolysis dechlorination section and the hydrolysate of organochlorosilanes in the water washing dechlorination section is effectively reduced, thereby significantly reducing the total water consumption of the process and avoiding the use of alkali solution.
[0019] 2) The process of this invention uses a water washing and dechlorination section instead of the water washing and alkali washing sections of the traditional process, avoiding the use of alkali solution and generating no waste liquid or waste salt, making the production process green and environmentally friendly.
[0020] 3) The process of this invention can significantly reduce the water consumption required in the washing section while reducing the total amount of chlorine removal. The amount of water phase produced in the washing section is reduced accordingly. Furthermore, all the water phase collected in the washing and dechlorination section can be reused in the hydrolysis and dechlorination section to replace part of the water replenishment required for the hydrolysis reaction, thus achieving zero waste liquid discharge in the washing and dechlorination section.
[0021] 4) The process of this invention improves the dechlorination efficiency of crude organochlorosilane hydrolysate by using a dual coalescence-sedimentation technology that couples a coalescing phase separator and a high-voltage electrostatic device, significantly reduces dechlorination energy consumption, and can obtain high-quality siloxane products with a residual chloride ion content of less than 1 ppm, making it suitable for industrial production. Attached Figure Description
[0022] Figure 1 This is a process flow diagram for producing oligomeric siloxanes according to Example 1 of this application;
[0023] Figure 2 This is a process flow diagram of the new process for producing oligomeric siloxanes in Example 2 of this application;
[0024] Figure 3 This is a process flow diagram of the conventional process for producing oligomeric siloxanes according to Example 2 of this application;
[0025] Figure 4 This shows the particle size distribution at nine sampling points in Example 1. Detailed Implementation
[0026] To further illustrate the present invention, the following specific embodiments will be described in detail.
[0027] Example 1:
[0028] The process for preparing high-quality siloxane products in this embodiment includes a hydrolysis dechlorination stage and a two-stage water washing dechlorination stage, such as... Figure 1 As shown, the process for preparing high-quality low-chlorinated siloxane products includes the following steps:
[0029] 1) Hydrochlorination section:
[0030] Dichlorodimethylsilane (purity ≥ 99%) and fresh process water are fed into a two-stage hydrolysis reactor in series at feed rates of 273 kg / h and 37.5 kg / h, respectively, for hydrolysis. The operating conditions in the first-stage hydrolysis reactor are: temperature 50℃, pressure 0.3 MPa, saturated hydrochloric acid solution concentration controlled at 41%–42%, and residence time 10 min; the operating conditions in the second-stage hydrolysis reactor are: temperature 60℃, pressure 0.1 MPa, concentrated hydrochloric acid solution concentration controlled at 14%–15%, and residence time 10 min. During the two-stage hydrolysis process, HCl gas, a byproduct, continuously escapes from the dichlorodimethylsilane. This HCl gas is collected from the top of the two-stage hydrolysis reactor for further processing. After the two-stage hydrolysis reaction, the conversion rate of dichlorodimethylsilane is consistently above 99.5%.
[0031] The mixture of hydrolysate siloxane and acidic water generated by the two-stage hydrolysis reaction is sent to a hydrolysis phase separator for primary coalescence dehydration and dechlorination (the temperature inside the hydrolysis phase separator is stabilized at 80℃, and the residence time is about 10 minutes). The acidic water content of the upper outlet oil phase hydrolysate is measured to be approximately 3.2%. The upper outlet crude oil phase hydrolysate (158-160 kg / h) after coalescence dehydration in the hydrolysis phase separator is then transported to a hydrolysis electrostatic device for advanced coalescence sedimentation dehydration (within the hydrolysis electrostatic device...). The operating temperature is 80℃, the power supply is a negative high voltage DC power supply, the electric field strength is 60KV / m, and the residence time is 10min. After testing, the water content of the upper outlet oil phase hydrolysate is reduced to about 0.4%. Then, the hydrolysate siloxane (154-155kg / h) after dehydration by the hydrolysis electrostatic device is further sent to the primary water washing and dechlorination section for treatment. The aqueous phase collected from the lower outlet of the hydrolysis phase separator and the hydrolysis electrostatic device is collected and reused in the hydrolysis reaction process in the two-stage hydrolysis reactor.
[0032] 2) Primary water washing and dechlorination section (primary water washing and dechlorination unit):
[0033] The oil-phase hydrolysate siloxane from step 1) of the hydrolysis dechlorination section, together with the aqueous phase collected from the secondary washing unit, flows into the primary washing dechlorination section's stirring tank for mixing and washing (temperature in the stirring tank 80℃, stirring speed 150r / min, residence time 10min). The washed siloxane and water mixture is then sent to the primary washing phase separator for coalescence sedimentation dehydration (temperature 80℃, residence time 10min). After phase separation, the water content of the oil-phase hydrolysate siloxane is approximately 2.9%. The upper effluent oil-phase hydrolysate siloxane (15...) after coalescence sedimentation dehydration in the primary washing phase separator... The flow rate (9-160 kg / h) is fed to the primary electrostatic precipitator for advanced coalescence sedimentation and dehydration treatment (the operating temperature inside the primary electrostatic precipitator is 80℃, the power supply is a negative high-voltage DC power supply, the electric field strength is 60KV / m, and the residence time is 10min). After testing, the water content of the hydrolysate siloxane in the upper outlet oil phase is reduced to about 0.2%. The hydrolysate siloxane after dehydration in the primary electrostatic precipitator (154-155 kg / h) is further sent to the subsequent secondary dechlorination section for treatment. The aqueous phase collected from the primary phase separator and the lower outlet of the primary electrostatic precipitator is collected in a storage tank for later use.
[0034] 3) Secondary water washing and dechlorination section (secondary water washing unit):
[0035] From step 2), the hydrolyzed siloxane from the primary water washing and dechlorination section flows together with process water (34 kg / h) into the secondary water washing stirred tank for washing and dechlorination (temperature in the stirred tank 80℃, stirring speed 150 r / min, residence time 10 min). The mixture of the oil phase hydrolyzed siloxane and wash water after the second washing is sent to the secondary water washing phase separator for coalescence sedimentation and dehydration (temperature 80℃, residence time 10 min). After phase separation, the water content of the oil phase hydrolyzed siloxane is approximately 3.1%. The upper effluent oil phase hydrolyzed siloxane after coalescence and dehydration in the secondary water washing phase separator (…) The water phase (158-160 kg / h) is fed to the secondary electrostatic washing unit for advanced coalescence sedimentation and dehydration treatment (the operating temperature of the secondary electrostatic washing unit is 80℃, the power supply is a negative high voltage DC power supply, the electric field strength is 70KV / m, and the residence time is 10min). After testing, the water content of the siloxane in the upper outlet oil phase hydrolysate is reduced to about 0.2%, and the final low-chlorinated siloxane product (154-155 kg / h) is collected with a chloride ion content of less than 1ppm. The aqueous phase collected from the lower outlet of the secondary water washing phase separator and the secondary electrostatic washing unit is collected and transported back to the primary water washing stirred tank.
[0036] The device operated continuously and stably for 24 hours, and the hydrolysis conversion rate of dichlorodimethylsilane remained stable at over 99.5%. The experimental results are shown in Table 1.
[0037] Table 1. Results of chlorine removal from crude hydrolysate of organochlorosilanes after 24 hours of continuous operation of the new continuous dechlorination process unit.
[0038]
[0039] After 24 hours of continuous operation, samples were taken from nine locations: the inlet of the hydrolysis phase separator, the upper outlet of the hydrolysis phase separator, and the upper outlet of the hydrolysis electrostatic device in the hydrolysis dechlorination section; the inlet of the primary water washing phase separator, the upper outlet of the primary water washing phase separator, and the upper outlet of the primary water washing electrostatic device in the primary water washing unit in the water washing dechlorination section; and the inlet of the secondary water washing phase separator, the upper outlet of the secondary phase separator, and the upper outlet of the secondary water washing electrostatic device in the secondary water washing unit. The droplet size distribution of the aqueous phase in the oil phase samples was then analyzed using a photomicrograph. The results are as follows: Figure 4 As shown in Table 2.
[0040] Table 2 Summary of Average Particle Size Changes at Different Sampling Locations During 24 Hours of Continuous Operation of the New Continuous Dechlorination Process
[0041]
[0042] As can be seen from the results of Example 1 above, both the phase separator and the electrostatic device achieved the coalescence-sedimentation effect in each process unit. Through the dual coalescence-sedimentation system composed of the phase separator and the electrostatic device, the water content of the oil phase hydrolysate siloxane decreased significantly within a limited time, thereby reducing the residual chloride ion concentration in the oil phase hydrolysate siloxane and achieving the purpose of efficient dechlorination of dichlorodimethylsilane hydrolysate.
[0043] Example 2:
[0044] This embodiment compares the dechlorination effect of the process of the present invention with that of the traditional process on organochlorine silane hydrolysates. The specific process is as follows:
[0045] The process for preparing high-quality low-chlorinated siloxane products according to this invention includes a hydrolysis dechlorination stage and a two-stage water washing dechlorination stage, such as... Figure 2 As shown, based on Example 1, the process of preparing high-quality low-chlorinated siloxane products by reusing all the aqueous phase collected in the water washing and dechlorination section in the hydrolysis reactor of the hydrolysis and dechlorination section includes the following steps:
[0046] 1) Hydrochlorination section:
[0047] Dichlorodimethylsilane (purity ≥ 99%) and fresh process water are fed into a two-stage hydrolysis reactor in series at feed rates of 273 kg / h and 3.5 kg / h, respectively, for hydrolysis. The operating conditions in the first-stage hydrolysis reactor are: temperature 50℃, pressure 0.3 MPa, saturated hydrochloric acid solution concentration controlled at 41%–42%, and residence time 10 min; the operating conditions in the second-stage hydrolysis reactor are: temperature 60℃, pressure 0.1 MPa, concentrated hydrochloric acid solution concentration controlled at 14%–15%, and residence time 10 min. During the two-stage hydrolysis process, HCl gas, a byproduct, continuously escapes from the dichlorodimethylsilane. This HCl gas is collected from the top of the two-stage hydrolysis reactor for further processing. After the two-stage hydrolysis reaction, the conversion rate of dichlorodimethylsilane is consistently above 99.5%.
[0048] The mixture of hydrolyzed siloxane and acidic water generated by the two-stage hydrolysis reaction is sent to a hydrolysis phase separator for primary coalescence dehydration and dechlorination (the temperature inside the hydrolysis phase separator is stabilized at 80℃, and the residence time is about 10 minutes). The water content of the upper oil phase hydrolysate is measured to be approximately 3.4%. The upper outlet oil phase hydrolysate siloxane (158-160 kg / h) after coalescence dehydration in the hydrolysis phase separator is then transported to a hydrolysis electrostatic device for advanced coalescence sedimentation dehydration (operated inside the hydrolysis electrostatic device). The operating temperature is 80℃, the power supply is a negative high voltage DC power supply, the electric field strength is 60KV / m, and the residence time is 10min. After testing, the water content of the upper oil phase hydrolysate at the outlet is reduced to about 0.4%. Then, the oil phase hydrolysate siloxane (154-155kg / h) after dehydration by the electrostatic hydrolysis device is further sent to the primary water washing and dechlorination section for treatment. The aqueous phase collected from the lower outlet of the hydrolysis phase separator and the electrostatic hydrolysis device is collected and reused in the hydrolysis reaction process in the two-stage hydrolysis reactor.
[0049] 2) Primary water washing and dechlorination section (primary water washing and dechlorination unit):
[0050] The oil-phase hydrolysate siloxane from step 1) of the hydrolysis dechlorination section, together with the aqueous phase collected from the secondary washing unit, flows into the primary washing dechlorination section's stirring tank for mixing and washing (tank temperature 80℃, stirring speed 150 r / min, residence time 10 min). The washed hydrolysate and water mixture is then sent to the primary washing phase separator for coalescence sedimentation dewatering (temperature 80℃, residence time 10 min). After phase separation, the water content of the oil-phase hydrolysate siloxane is approximately 3.0%. The upper effluent oil-phase hydrolysate siloxane (158-160 kg / kg) after coalescence sedimentation dewatering in the primary washing phase separator is also analyzed. h) The water is fed to the primary electrostatic washing unit for advanced coalescence sedimentation and dehydration treatment (the operating temperature inside the primary electrostatic washing unit is 80℃, the power supply is a negative high voltage DC power supply, the electric field strength is 60KV / m, and the residence time is 10min). After testing, the water content of the upper oil phase hydrolysate siloxane is reduced to about 0.2%. The oil phase hydrolysate siloxane (154~155kg / h) after dehydration by the primary electrostatic washing unit is further sent to the subsequent secondary water washing dechlorination section for treatment. The aqueous phase (34kg / h) collected from the lower layer of the primary water washing phase separator and the primary electrostatic washing unit is sent to the two-stage hydrolysis reactor of the hydrolysis dechlorination section.
[0051] 3) Secondary water washing and dechlorination section (secondary water washing unit):
[0052] The oil-phase hydrolysate siloxane from the primary water washing and dechlorination section (step 2) flows together with process water (34 kg / h) into the secondary water washing stirred tank for mixing and washing (temperature in the stirred tank 80℃, stirring speed 150 r / min, residence time 10 min). The mixture of oil-phase hydrolysate siloxane and wash water after the second washing is sent to the secondary water washing phase separator for coalescence sedimentation and dewatering (temperature 80℃, residence time 10 min). After phase separation, the water content of the oil-phase hydrolysate siloxane is approximately 2.8%. The upper effluent from the secondary water washing phase separator after coalescence and dewatering is... The hydrolyzed siloxane in the oil phase is transported to a secondary electrostatic washing unit for advanced coalescence sedimentation and dehydration treatment (the operating temperature in the secondary electrostatic washing unit is 80℃, the power supply is a negative high voltage DC power supply, the electric field strength is 70KV / m, and the residence time is 10min). After testing, the water content of the low-chlorinated siloxane in the upper outlet oil phase is reduced to about 0.2%, and the final low-chlorinated siloxane product is collected (154~155kg / h), with a chloride ion content of less than 1ppm. The aqueous phase collected from the lower outlet of the secondary water washing phase separator and the secondary electrostatic washing unit is collected and transported back to the primary water washing stirred tank.
[0053] The device operated continuously and stably for 24 hours, and the hydrolysis conversion rate of dichlorodimethylsilane remained stable at over 99.5%. The experimental results are shown in Table 3.
[0054] Comparative Example 1: Traditional Technology: The traditional process for producing low-chlorinated siloxanes is as follows... Figure 3 As shown, the specific steps are as follows:
[0055] 1) Hydrolysis section: The raw material dichlorodimethylsilane (purity above 99%) and fresh process water are fed into a two-stage hydrolysis reactor at feed rates of 273 kg / h and 3.5 kg / h respectively for hydrolysis reaction (the operating conditions in the first-stage hydrolysis reactor are 50℃, 0.3 MPa, saturated hydrochloric acid solution concentration controlled at 41-42%, and residence time of 10 min; the operating conditions in the second-stage hydrolysis reactor are 60℃, 0.1 MPa, concentrated hydrochloric acid solution concentration controlled at 14%-15%, and residence time of 10 min). The raw material dichlorodimethylsilane undergoes a two-stage hydrolysis reaction to produce hydrolyzed siloxane and byproduct HCl. HCl gas is extracted from the top of the two-stage hydrolysis reactor for further processing. The conversion rate of dichlorodimethylsilane is consistently above 99.5%. The mixture of hydrolyzed siloxane and acid water is fed into a hydrolysis phase separator for stratification. The temperature inside the hydrolysis phase separator is stabilized at T = 80℃, and the residence time of the mixture is 10 min. The upper oil phase hydrolyzed siloxane (160-161 kg / h) from the hydrolysis phase separator is sent to the subsequent water washing and alkaline washing section, while the lower aqueous phase is returned to the two-stage hydrolysis reactor to participate in the hydrolysis reaction.
[0056] 2) Water Washing and Alkali Washing Section: The water washing and alkali washing section consists of three water washing units and one alkali washing unit. Each water washing unit includes a water washing stirred tank and a water washing phase separator, while the first-stage alkali washing unit includes an alkali washing stirred tank and an alkali washing phase separator. The oil phase hydrolysate siloxanes sequentially pass through the first-stage water washing unit, the first-stage alkali washing unit, the second-stage water washing unit, and the third-stage water washing unit to remove chlorine, yielding the final low-chlorinated siloxane product. The specific operation process is as follows:
[0057] S1: The oil phase hydrolysate siloxane obtained in step 1) is fed into the water washing stirred tank of the primary water washing unit and mixed and stirred together with the secondary water washing aqueous phase collected in the secondary water washing unit. The temperature of the stirred tank is T = 80℃, the stirring speed is 150r / min, and the residence time is 10min. The stirred water washing mixture is sent to the primary water washing phase separator for stratification. The temperature inside the primary water washing phase separator is T = 80℃ and the residence time is 10min. The primary water washing siloxane (oil phase) flows out from the upper outlet of the primary water washing phase separator and is sent to the primary alkaline washing unit. About 40% of the aqueous phase of the primary water washing collected in the phase separator of the primary water washing unit is recycled for the hydrolysis reaction process in the two-stage hydrolysis reactor, and the remaining about 60% of the aqueous phase of the water washing is discharged as waste liquid.
[0058] S2: The oil phase hydrolysate siloxane in the primary alkaline washing unit is fed together with 5% NaOH alkaline solution (26 kg / h) into the alkaline washing stirred tank for mixing and washing. The temperature inside the stirred tank is 80℃, the stirring speed is 150 r / min, and the residence time is 10 min. The alkaline washing mixture is then passed into the alkaline washing phase separator for stratification. The temperature inside the primary alkaline washing phase separator is T = 80℃ and the residence time is 10 min. The oil phase hydrolysate siloxane (159-160 kg / h) from the upper outlet of the alkaline washing phase separator is sent to the secondary water washing unit, and the aqueous alkaline solution collected from the lower outlet is discharged as waste alkaline solution.
[0059] S3: The oil-phase hydrolysate siloxanes are washed and dechlorinated sequentially through a secondary and tertiary water washing unit. The operating conditions in the water washing stirred tanks and water washing phase separators of the secondary and tertiary water washing units are the same as those in the primary water washing unit. Fresh process water (80 kg / h) is introduced from the water washing stirred tank of the tertiary water washing unit and sent to the tertiary water washing phase separator along with the oil-phase hydrolysate siloxanes. The lower layer of aqueous phase is collected and countercurrently returned to the water washing stirred tank of the secondary water washing unit. Similarly, the secondary water washing phase is reused in the water washing stirred tank of the primary water washing unit. Finally, after dechlorination by the tertiary water washing unit and the primary alkaline washing unit, a low-chlorinated siloxane product with a chloride ion concentration of 2-4 ppm is obtained.
[0060] Table 3 shows a comparison of the results of preparing low-chlorinated siloxane products using the technology of this invention and traditional technologies.
[0061] Table 3 Comparison of dechlorination results of organochlorosilane hydrolysates between the novel process of this invention and the traditional process.
[0062]
[0063] As can be seen in the above Example 2, the water phase collected in the water washing and dechlorination section of the new process of the present invention is reused in the hydrolysis reactor of the hydrolysis dechlorination section, which has basically no impact on the dechlorination effect of organochlorosilane hydrolysates. At the same time, the reuse of the water phase collected in the water washing and dechlorination section can effectively replace part of the fresh process water consumed by the hydrolysis reaction, effectively reducing the total water consumption of the new process, and there is no excess wastewater discharge in the water washing and dechlorination section.
[0064] Comparing the dechlorination effects of the novel process of this invention with traditional processes on organochlorosilane hydrolysates, it can be seen that the novel process of this invention significantly improves the dechlorination efficiency of organochlorosilane hydrolysates through a dual coalescence-sedimentation technology that couples a coalescing phase separator and a high-voltage electrostatic device. The process water consumption during the washing and dechlorination process of organochlorosilane hydrolysates is reduced by 55% compared to traditional technologies. The novel process of this invention replaces the alkaline washing and dechlorination section in the traditional process with a multi-stage water washing and dechlorination section, avoiding the use of alkali and thus eliminating waste alkali discharge. Furthermore, the aqueous phase collected in the water washing and dechlorination section of the novel process of this invention can be completely reused in the hydrolysis section, resulting in no excess wastewater discharge compared to traditional processes. In summary, the novel process of this invention has significant advantages over traditional technologies for preparing low-chlorinated siloxane products.
[0065] The foregoing description is not intended to limit the invention, nor is the invention limited to the examples given. Any changes, modifications, additions, or substitutions made by those skilled in the art within the scope of the invention should also be considered within the protection scope of the invention.
Claims
1. A process for washing and dechlorinating organochlorosilane hydrolysates, characterized in that... After the raw organochlorosilane is subjected to a hydrolysis dechlorination section and a water washing dechlorination section, high-quality low-chlorinated siloxane products are obtained. The process includes the following: (1) The hydrolysis dechlorination section includes a hydrolysis reactor, a hydrolysis phase separator and a hydrolysis electrostatic device; The raw material, organochlorosilane, and process water are continuously fed separately and sequentially to a two-stage hydrolysis reactor for hydrolysis. The hydrolysis reaction is carried out under acidic conditions. The byproduct HCl gas released during the reaction is collected for further treatment. The hydrolysate siloxane and acid water mixture generated by the reaction are sent to a hydrolysis phase separator for coalescence, dehydration, and dechlorination. After that, it enters a hydrolysis electrostatic device for further dehydration and dechlorination, and then is sent to a water washing and dechlorination section for further dechlorination treatment. The aqueous phase collected from the lower layers of both the hydrolysis phase separator and the hydrolysis electrostatic device is collected and reused in the hydrolysis reaction process in the hydrolysis reactor. (2) The water washing dechlorination section includes at least one stage. Each stage of the water washing dechlorination section includes a water washing stirred tank, a water washing phase separator and a water washing electrostatic device. The oil phase hydrolysate siloxane output from the water washing dechlorination section in step (1) enters the water washing stirred tank of the water washing dechlorination section and is mixed with the washing water for washing. The washing mixture is sent to the water washing phase separator for coalescence dehydration and dechlorination. Then it enters the water washing electrostatic device for further dehydration and dechlorination. Finally, high-quality low-chlorinated siloxane products are collected. The water phase collected from the lower layer of the water washing phase separator and the water washing electrostatic device can be recycled for the hydrolysis reaction process in the water washing dechlorination section in step (1). The hydrolysis reactor consists of two stages connected in series. The temperature in the first-stage hydrolysis reactor is controlled at 40℃~60℃, the pressure at 0.1~0.3MPa, the saturated hydrochloric acid concentration at 39%~45%, and the residence time at 5~10min. The temperature in the second-stage hydrolysis reactor is controlled at 40℃~60℃, the pressure at 0.1MPa, the concentrated hydrochloric acid concentration at 12%~25%, and the residence time at 5~10min. The temperature of the water washing agitator in the water washing and dechlorination section is 80~90℃, the stirring speed is 50~150 r / min, and the residence time is 5-10min; In step (2), the water washing and dechlorination section is a two- or three-stage series process.
2. The organochlorine silane hydrolysate washing and dechlorination process according to claim 1, characterized in that... The electric field strength in the electrostatic hydrolysis device or electrostatic washing device is 20~100kV / m, the temperature is 40~90℃, and the power supply is a positive high voltage DC power supply or a negative high voltage DC power supply.
3. The organochlorine silane hydrolysate washing and dechlorination process according to claim 1, characterized in that... The temperature of the hydrolysis phase separator is controlled at 40~90℃, and the residence time in the hydrolysis phase separator is 5~10min.
4. The organochlorine silane hydrolysate washing and dechlorination process according to claim 1, characterized in that... The temperature of the water washing phase separator is controlled at 40~90℃, and the residence time in the water washing phase separator is 5~10min.
5. The organochlorine silane hydrolysate washing and dechlorination process according to claim 1, characterized in that, In step (1), the oil phase output from the hydrolysis dechlorination section flows from the first-stage water washing dechlorination section to the last-stage water washing dechlorination section. Fresh process water is first introduced into the water washing stirred tank of the last-stage water washing dechlorination section. The water phase collected from the lower layer of the water washing phase separator and the water washing electrostatic device in the last-stage water washing dechlorination section flows back to the water washing stirred tank of the adjacent previous-stage water washing dechlorination section. Similarly, the water phase collected from the lower layer of the water washing phase separator and the water washing electrostatic device in the first-stage water washing dechlorination section flows back to the hydrolysis reaction process in step (1) hydrolysis dechlorination section.