A process for the treatment of waste material suitable for use in the one-step synthesis of siloxanes

Abstract

The application discloses a treatment process for waste in a one-step synthesis stage of siloxane synthesis, and the process is designed according to the characteristics of the waste in the one-step synthesis stage of siloxane synthesis. The liquid phase in the waste is gradually separated, and raw materials or auxiliary materials are extracted, so that solid waste which cannot react is obtained, and the obtained solid waste can be treated as common solid waste, so that the problem that there is no treatment process for the waste in the one-step synthesis stage of siloxane synthesis in the prior art, and the existing treatment process for waste liquid cannot treat the waste in the one-step synthesis stage of siloxane synthesis is solved.

Description

Technical Field

[0001] This invention relates to the field of waste treatment technology, and specifically to a waste treatment process applicable to the one-step synthesis of siloxanes. Background Technology

[0002] Currently, most siloxane products on the market are industrial byproducts (from industries such as polysilicon and organosilicon). Some companies also synthesize siloxane compounds, and the silicon waste generated during the synthesis stage is generally reused as a silicon source for their main processes, or the useful components are extracted and sold as products to downstream companies. However, the one-step siloxane synthesis process differs from existing siloxane synthesis technologies, resulting in significantly different compositions of the waste generated during the synthesis stage. Existing siloxanes on the market are mainly byproducts, and the waste generated from their synthesis processes is primarily a liquid mixture of various compounds, resulting in a mixed liquid waste liquid. Different components are typically extracted from these waste liquids through distillation, or a catalyst is added to react them into other products, which are then extracted through distillation.

[0003] However, these methods are unsuitable for handling the waste generated during the one-step siloxane synthesis process, as the waste produced in this stage is a mixture of solid and liquid phases, existing in a slurry state, and mainly originates from unreacted raw materials and catalysts. Existing distillation processes struggle to handle this type of waste. Because: First, the one-step siloxane synthesis process is an intermittent operation, while the distillation column is a continuous operation, meaning the synthesis process cannot continuously supply feed for the waste distillation process. Second, compared to traditional synthesis processes on the market, the one-step siloxane synthesis process has a higher conversion rate and selectivity, with relatively smaller types and quantities of byproducts. Simply using distillation to treat waste does not offer advantages in terms of cost control and energy consumption. Third, since the waste itself is a slurry with high viscosity and contains solids, the viscosity of the material in the distillation column bottom is even higher after distillation, easily clogging reboilers, pipes, valves, etc. Viscous substances may also accumulate in the column section or top, leading to decreased distillation efficiency and difficulty in cleaning equipment or pipes over long periods. Even if the solids in the slurry are filtered out, the remaining liquid waste is difficult to treat using distillation. Not only can the one-step process not provide a continuous supply of waste for the distillation column, but the remaining waste will still form highly viscous gel-like solids after extraction in the distillation column, making these substances even more difficult to handle. Therefore, traditional separation methods are not suitable for one-step siloxane synthesis processes. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies, the present invention aims to provide a treatment process for waste generated during the one-step synthesis of siloxanes. This process is designed specifically for the characteristics of the waste generated during this stage. The present invention progressively separates the liquid phase in the waste, extracting the raw materials or auxiliary materials separately, ultimately yielding non-reactive solid waste. This solid waste can be treated as ordinary solid waste, thus solving the problems of the lack of a treatment process for waste generated during the one-step synthesis of siloxanes in existing technologies, and the inability of existing waste liquid treatment processes to handle the waste generated during this stage.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A process for treating waste materials in the one-step synthesis stage of siloxanes is described below:

[0007] Step 1: The waste material is transported to tank I and heated to 60~100℃ under stirring. The components in tank I evaporate upon heating and are condensed by heat exchanger I. The condensate is collected by buffer tank I.

[0008] Step 2: When no more condensate is produced in Step 1, stop heating and stirring in Tank I and transfer the waste material therein to Tank II;

[0009] Step 3: Repeat steps 1-2. When the waste material in tank II accumulates to a certain height, adjust the pipeline to prevent the evaporated material in tank II from entering heat exchanger I. Stir tank II and heat it to 100-150℃. At the same time, adjust the pipeline so that the waste material in tank II evaporates and is condensed sequentially by heat exchanger II and heat exchanger III. The condensate produced by the two heat exchangers (i.e., the condensate produced by heat exchanger II and heat exchanger III) can only be collected by buffer tank I through the pipeline. The temperature of heat exchanger II is 20-40℃, and the temperature of heat exchanger III is 8-15℃.

[0010] Step 4: When the liquid level in buffer tank I no longer changes, adjust the pipeline and start the vacuum pump so that it can only evacuate tank II. At the same time, adjust the temperature of tank II to 150~200℃. The waste in tank II continues to evaporate and is cooled sequentially by heat exchanger II and heat exchanger III. The condensate produced by the two heat exchangers (i.e., the condensate produced by heat exchanger II and heat exchanger III) can only be collected by buffer tank II through the pipeline. The temperature of heat exchanger II is 30~45℃, and the temperature of heat exchanger III is 10~20℃. When the liquid level in buffer tank II no longer changes, turn off the vacuum pump and wait for the material in tank II to cool to below 50℃ before discharging it.

[0011] Preferably, the waste is a mixture comprising solid silicon, low molecular weight alcohols, siloxanes, siloxane oligomers, and a liquid catalyst.

[0012] Preferably, in step 1, the temperature is controlled at 70~90℃.

[0013] Preferably, in step 3, the temperature is controlled at 120~140℃.

[0014] Preferably, in step 4, the temperature is controlled at 160~180℃.

[0015] Preferably, in step 2, after tank I has discharged the waste into tank II for the last time, the reaction material from the synthesis stage is added to tank I to flush out the remaining waste in tank I.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. This invention targets the waste generated by the one-step siloxane synthesis process. Based on the characteristics of this waste, a targeted treatment method is designed to gradually separate the liquid phase in the waste and extract the raw materials or auxiliary materials respectively, finally obtaining non-reactive solid waste that can be treated as ordinary solid waste.

[0018] 2. The processing technology described in this invention avoids unnecessary waste caused by material being discharged with waste. The collected materials can be recycled and reused in categories. The liquid and solid components obtained after processing are relatively simple, which is convenient for downstream processing. The toxic, volatile, flammable and explosive substances contained in the siloxane process are extracted as much as possible, and the harm of the remaining final waste to the environment and human body is effectively reduced.

[0019] 3. The processing technology described in this invention extracts as many useful substances as possible from the waste material based on its characteristics. While classifying and collecting the substances, it also reduces the final amount and complexity of the waste material, which facilitates downstream waste treatment and has good prospects for industrial application. Attached Figure Description

[0020] Figure 1 This is a flowchart of a waste treatment process applicable to the one-step synthesis of siloxanes according to the present invention.

[0021] In the diagram: Tank I 1, Heat Exchanger I 5, Buffer Tank I 3, Tank II 2, Heat Exchanger II 6, Heat Exchanger III 7, Vacuum Pump 8, Buffer Tank II 4, Valve a, Valve b, Valve c, Valve d. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the present invention are within the scope of protection of the present invention.

[0023] Unless otherwise specified in the specific circumstances, the numerical ranges listed herein include upper and lower limits, as well as all integers and fractions within that range, but are not limited to the specific values ​​listed when the range is defined.

[0024] I. A process for treating waste materials in the one-step synthesis stage of siloxanes.

[0025] Currently, in existing siloxane synthesis processes, siloxane compounds are produced as byproducts. Since the entire process is part of the company's main organosilicon (or other) process, both raw materials and waste flow within the main process. Furthermore, except for the one-step siloxane synthesis process where the waste contains a solid phase, the waste from other processes is mainly gaseous or liquid. Therefore, the waste generated in existing siloxane synthesis processes is characterized by its single phase and ease of separation, resulting in relatively simple waste treatment processes, such as simple distillation, fractional distillation or fractional distillation, filtration, and crystallization.

[0026] However, this invention takes into account the characteristics of waste from the one-step siloxane synthesis process, such as the presence of solid phases, viscous slurry-like consistency, and significant differences in component properties. Therefore, its treatment process cannot rely on a single method; it must consider factors such as the phase state, properties, and potential operational problems. Thus, this invention specifically designs a treatment process tailored to the characteristics of waste from the one-step siloxane synthesis process. This process enables simultaneous liquid-liquid and solid-liquid separation. During liquid-liquid separation, useful components are collected together for reuse or storage, while the remaining useless liquid components are prevented from mixing with the solid components, thereby achieving effective separation.

[0027] Step 1: The waste material is transported to tank I 1 and heated to 60~100℃ under stirring. The components in tank I are heated and evaporated, then transported to heat exchanger I 5 for condensation. The condensate is collected by buffer tank I 3.

[0028] Step 2: When no more condensate is produced in Step 1, stop heating and stirring in Tank I and transfer the waste material therein to Tank II 2; wherein, after Tank I 1 has discharged the waste material into Tank II 2 for the last time, add the reaction material of the synthesis stage into Tank I 1 and rinse the waste material remaining in Tank I 1.

[0029] Step 3: Repeat steps 1-2. When the waste material in tank II 2 accumulates to a certain height, adjust the pipeline to stir tank II 2 and heat it to 100-150℃. At the same time, adjust the pipeline so that the waste material in tank II 2 evaporates due to the heat and is sequentially transported to heat exchanger II 6 and heat exchanger III 7 for condensation. The condensate produced by the two heat exchangers can only be collected by buffer tank I 3 through the pipeline. The temperature of heat exchanger II 6 is 20-40℃, and the temperature of heat exchanger III 7 is 8-15℃.

[0030] Step 4: When the liquid level in buffer tank I 1 no longer changes, start vacuum pump 8 to evacuate tank II 2, and simultaneously adjust the temperature of tank II 2 to 150~200℃; the waste in tank II 2 continues to evaporate and is cooled sequentially by heat exchanger II 6 and heat exchanger III 7, and the condensate is collected by buffer tank II 4; the temperature of heat exchanger II 6 is 30~45℃, and the temperature of heat exchanger III 7 is 10~20℃; when the liquid level in buffer tank II 4 no longer changes, turn off vacuum pump 8, and wait for the material in tank II 2 to cool to below 50℃ before discharging it.

[0031] In practice, the waste materials include solid silicon, low molecular weight alcohols, siloxanes, siloxane oligomers, liquid catalysts, etc. In the one-step synthesis process of siloxanes, the types of these substances in different batches of waste materials are fixed, only the quality of each substance in each batch is different.

[0032] In some embodiments, step 1 primarily involves separating the residual low-molecular-weight alcohols in the waste material, with the temperature controlled between 60 and 100°C. Excessive temperature will cause some siloxanes to separate, which is detrimental to subsequent use; excessively low temperature will leave the low-molecular-weight alcohols in the waste material, which is also unfavorable for subsequent processing. A preferred temperature is 70 to 90°C, which allows for more precise extraction of the material, ensuring that the extracted low-molecular-weight alcohols have sufficiently high purity for direct use as raw materials. Therefore, the preferred temperature is 70 to 90°C, but can be 60°C, 70°C, 80°C, 90°C, 100°C, or any range and sub-range between these values. It should be understood that in embodiments, any of the above ranges can be combined with any other range.

[0033] In some embodiments, in step 3, the temperature is controlled at 100~150℃, mainly for separating siloxanes from the waste. Too low a temperature will prevent the siloxanes from being separated, while too high a temperature will cause other substances in the waste to be separated along with the siloxanes, thus affecting the subsequent use of the siloxanes. A preferred temperature is 120~140℃, which allows for more precise extraction of siloxanes and ensures sufficiently high purity. Therefore, the preferred temperature is 120~140℃, but can be 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, etc., as well as all ranges and sub-ranges between these values. It should be understood that in the embodiments, any of the above ranges can be combined with any other range.

[0034] In some embodiments, in step 4, the temperature is controlled at 150~200℃, mainly for separating the siloxane oligomers in the waste. Too low a temperature will prevent the complete separation of the siloxane oligomers from the waste, while too high a temperature will cause other substances in the waste to be separated along with the siloxane oligomers, thus affecting the subsequent use of the siloxanes. A preferred temperature is 160~180℃, which allows for precise extraction of the siloxane oligomers, enabling them to be used directly as raw materials for downstream products. Therefore, the preferred temperature is 160~180℃, but can be 150℃, 150℃, 170℃, 180℃, 190℃, 200℃, etc., as well as all ranges and sub-ranges between these values. It should be understood that in the embodiments, any of the above ranges can be combined with any other range.

[0035] II. Examples and Comparative Examples Example

[0036] Step 1: The waste liquid is transferred to tank I 1 and heated to 60°C under stirring. The components in tank I evaporate upon heating and are then transferred to heat exchanger I 5 for condensation. The condensate is collected by buffer tank I 3. In this step, valve a is open, allowing the condensate in heat exchanger I to enter buffer tank I. During this step, a large amount of low-molecular-weight alcohols are evaporated and collected; however, due to the minimum evaporation temperature, a small amount of low-molecular-weight alcohols may remain in the waste liquid.

[0037] Step 2: When no more condensate is produced in Step 1, stop heating and stirring in Tank I, close valve a, and transfer the waste liquid in it to Tank II 4.

[0038] Step 3: Repeat steps 1-2. When the waste liquid in tank II accumulates to a certain height, stir tank II and heat it to 100℃. The waste liquid in tank II evaporates due to heating. Open valves b and d, and close valve c. The evaporated gas is then transported to heat exchangers II 5 and III 6 for condensation. The condensate is collected by buffer tank I 3. Different temperatures of refrigerant are introduced into heat exchangers II and III, maintaining the temperature of heat exchanger II at 25℃ and heat exchanger III at 8℃. At this point, the residual low-molecular-weight alcohols in the waste liquid are completely evaporated, and siloxanes and their low-boiling-point oligomers are also gradually evaporated. However, the liquid mixture collected by buffer tank I is free of impurities and can be completely recovered for use in the one-step siloxane synthesis process.

[0039] Step 4: When the liquid level in buffer tank I 3 no longer changes, first open valve c and close valve b, start vacuum pump 8 to evacuate tank II 2, and simultaneously adjust the temperature of tank II to 150℃; the waste liquid in tank II continues to evaporate, and the gas generated by evaporation is sent to heat exchangers II and III for cooling, and the condensate is collected by buffer tank II; the temperature of heat exchanger II is 20℃, and the temperature of heat exchanger III is 8℃; when the liquid level in buffer tank II no longer changes, turn off the vacuum pump, and discharge the material in tank II after it cools to below 50℃. The material collected in buffer tank II in this step is a catalyst with a purity >90%; the remaining solid waste in tank II may be in a "wet soil" state, which can be collected and treated as ordinary solid waste. Example

[0040] The following adjustments are made based on Example 1, with the following differences: In step 1, the heating temperature of tank I is 100°C; in step 3, the heating temperature of tank II is 150°C, the temperature of heat exchanger II is 35°C, and the temperature of heat exchanger III is 15°C; in step 4, the heating temperature of tank II is 200°C, the temperature of heat exchanger II is 40°C, and the temperature of heat exchanger III is 12°C. In this operation, the material composition in buffer tank II consists of low-molecular-weight alcohols, siloxanes, and siloxane oligomers, free of impurities, and can be completely reused; buffer tank III stores the catalyst, with a purity >98%; the remaining solid waste in tank II is dry and sandy, easy to collect, and can be treated as ordinary solid waste. Example

[0041] The following adjustments are made based on Example 1, with the following differences: In step 1, the heating temperature of tank I is 70°C; in step 3, the heating temperature of tank II is 130°C, the temperature of heat exchanger II is 30°C, and the temperature of heat exchanger III is 12°C; in step 4, the heating temperature of tank II is 170°C, the temperature of heat exchanger II is 35°C, and the temperature of heat exchanger III is 8°C. In this operation, the material composition in buffer tank II consists of low-molecular-weight alcohols, siloxanes, and siloxane oligomers, free of impurities, and can be completely reused; buffer tank III stores the catalyst, with a purity >90%; the remaining solid waste in tank II is dry and sandy, easy to collect, and can be treated as ordinary solid waste.

[0042] Comparative Example 1

[0043] The waste liquid is fed into a distillation column for fractional distillation, with the reboiler temperature raised to 180°C. From the top down, low-molecular-weight alcohols, siloxanes, siloxane oligomers, and catalysts are distilled out sequentially. However, as the waste liquid continues to be transported, solid waste accumulates in the reboiler, increasing viscosity and reducing heat transfer efficiency. This leads to a decrease in the stripping temperature, reduced yields of each material, and cross-contamination of low-boiling-point substances into higher-boiling-point collection points. Furthermore, the solid phase in the reboiler may solidify and clog the reboiler.

[0044] Comparative Example 2

[0045] The following adjustments were made based on Example 1, with the following differences: In step 1, the heating temperature of tank I is 100°C; in step 3, the heating temperature of tank II is 180°C, the temperature of heat exchanger II is 45°C, and the temperature of heat exchanger III is 15°C; in step 4, the heating temperature of tank II is 220°C, the temperature of heat exchanger II is 56°C, and the temperature of heat exchanger III is 18°C. This operation wastes excess energy; the material composition in buffer tank II consists of low-molecular-weight alcohols, siloxanes, and siloxane oligomers, but contains some catalyst impurities, which need to be further separated before reuse; buffer tank III stores the catalyst with a purity >98%; the remaining solid waste in tank II is dry and sandy, making it easy to collect.

[0046] Compared to the above embodiments, Comparative Example 1 has the problem of not considering the deposition and separation of solid components in the waste. The solid waste continuously deposits in the bottom of the distillation column throughout the operation, affecting heat transfer, leading to uneven heat transfer, unstable extraction, increased energy consumption, and blockage of pipes and valves. If the solid components are periodically discharged from the bottom, the liquid components in the waste will also be discharged, resulting in material waste and requiring additional equipment to treat the solid components. This is partly to recover the liquid phase and partly to treat the solid components so they can be treated as hazardous chemicals, which significantly increases processing costs. Comparative Example 2 has the problem of exceeding the upper limit of the controlled temperature. Exceeding the temperature causes high-boiling-point substances to evaporate along with low-boiling-point substances during the evaporation stage, leading to cross-contamination. This not only results in poor liquid phase separation but also fails to achieve precise liquid phase separation. Therefore, the advantage of this invention is that, based on solid-liquid separation, it achieves precise liquid-liquid separation by controlling an appropriate temperature, ultimately enabling the waste components to be collected according to their characteristics or requirements.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A process for treating waste materials in the one-step synthesis stage of siloxanes, characterized in that, The specific steps are as follows: Step 1: The waste material is transported to tank I (1) and heated to 60~100℃ under stirring. The components in tank I are heated and evaporated, and then condensed by heat exchanger I (5). The condensate is collected by buffer tank I (3). Step 2: When no more condensate is produced in step 1, stop heating and stirring in tank I and transfer the waste material in it to tank II (2); Step 3: Repeat steps 1 to 2. When the waste material in tank II accumulates to a certain height, stir tank II and heat it to 100 to 150°C. At the same time, adjust the pipeline. The waste material in tank II is heated and evaporated. It is condensed by heat exchanger II (6) and heat exchanger III (7) in sequence. The condensate produced by the two heat exchangers can only be collected by buffer tank I through the pipeline. The temperature of heat exchanger II is 20 to 40°C and the temperature of heat exchanger III is 8 to 15°C. Step 4: When the liquid level in buffer tank I no longer changes, adjust the pipeline and start the vacuum pump (8) to evacuate tank II. At the same time, adjust the temperature of tank II to 150~200℃. The waste in tank II continues to evaporate and is cooled by heat exchanger II and heat exchanger III. The condensate is collected through the pipeline in buffer tank II (4). The temperature of heat exchanger II is 30~45℃ and the temperature of heat exchanger III is 10~20℃. When the liquid level in buffer tank II no longer changes, turn off the vacuum pump and wait for the material in tank II to cool to below 50℃ before discharging it.

2. The processing method according to claim 1, characterized in that, The waste material is a mixture containing solid silicon, low-molecular-weight alcohols, siloxanes, siloxane oligomers, and liquid catalysts.

3. The processing method according to claim 1, characterized in that, In step 1, the temperature is controlled at 70~90℃.

4. The processing method according to claim 1, characterized in that, In step 3, the temperature is controlled at 120~140℃.

5. The processing method according to claim 1, characterized in that, In step 4, the temperature is controlled at 160~180℃.

6. The processing method according to claim 1, characterized in that, In step 2, after tank I has discharged the waste into tank II for the last time, the reaction materials from the synthesis stage are added to tank I to flush out the remaining waste in tank I.

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