A system for reducing the acid value of a hydrolyzate of a silicone

Abstract

The utility model discloses a system of reducing organic silicon hydrolysate acid value, it includes hydrolysate delivery pipeline, heat exchanger, falling film evaporator, condenser, waste acid tank and vacuum pump, hydrolysate delivery pipeline is linked with the cold medium import of heat exchanger, and the cold medium export of heat exchanger is linked with the liquid inlet of falling film evaporator top, and the exhaust port of falling film evaporator top is linked with the air inlet of condenser, and the liquid outlet of condenser is linked with waste acid tank through liquid delivery pipe, and the air outlet of condenser is linked with the air inlet of waste acid tank top, and the air outlet of waste acid tank top is linked with the air inlet of vacuum pump. Advantageous effects: the utility model connects simple relation, and easy implementation has reduced the acid value content in hydrolysate, reduced the alkalescent material amount in subsequent cleavage process, saved the cost, and furthermore, it is convenient to store and transport, avoids the corrosion equipment pipeline, improves the service life of equipment pipeline.

Description

Technical Field

[0001] This utility model relates to the technical field of reducing the acid value of organosilicon hydrolysates, and in particular to a system for reducing the acid value of organosilicon hydrolysates. Background Technology

[0002] The hydrolysate is a cyclic polysiloxane (Me2SiO) obtained by hydrolyzing dimethyldichlorosilane monomer. n (abbreviated as cyclic) and linear polysiloxanes [HO(Me2SiO] ] n The preparation process of the mixture of H] (abbreviated as linear) is as follows: silicon powder and chloromethane gas react in a fluidized bed reactor in the presence of a copper catalyst to produce a mixed monomer of methylchlorosilane. The mixed methylchlorosilane monomer is separated by distillation to obtain dimethyldichlorosilane and other various purified monomers. Dimethyldichlorosilane reacts with water or concentrated hydrochloric acid to generate hydrolysate and concentrated hydrochloric acid or HCl gas. Therefore, the hydrolysate contains impurities such as chloride ions, which leads to a high acid value of the hydrolysate. Secondly, the dimethyldichlorosilane monomer after distillation will also contain other silane monomers containing acidic groups such as carboxyl groups and sulfonic acid groups, as well as organic acids (formic acid, acetic acid, etc.). When the silane monomers containing carboxyl groups and sulfonic acid groups are hydrolyzed, the carboxyl groups and sulfonic acid groups will ionize to release hydrogen ions, which will make the acid value of the hydrolysate higher. Meanwhile, improper operation during hydrolysis can also produce byproducts that increase acid value. Specifically, when the hydrolysis temperature is too high, the silicon-oxygen bond (-Si-O-Si-) breaks, generating products containing silanol groups (-Si-OH) and acidic fragments. Some fragments will further decompose into silicic acid substances, namely oligosilanols generated after the polysiloxane chain breaks. At high temperatures, these oligosilanols may undergo partial dehydration to form metasilicic acid (H2SiO3). Although these inorganic acids are relatively weak, their accumulation to a certain extent will increase the acid value.

[0003] Organic groups (such as alkyl and alkenyl groups) in hydrolysis products are easily oxidized by oxygen in the air under high temperature or long reaction conditions, becoming peroxides. These peroxides are unstable and decompose to form carboxylic acids (such as acetic acid and propionic acid). Alkenyl groups undergo oxidative cleavage to form aldehydes, which are further oxidized to carboxylic acids. These oxidized organic acids directly increase the acid value of the hydrolysate, and their production increases with increasing reaction temperature and time. A high acid value affects the production of subsequent products and increases production costs. When such hydrolysates are used as raw materials for the cracking of DMC, it increases the consumption of the cracking catalyst KOH. Furthermore, it is detrimental to the storage and transportation of the hydrolysate; a high acid value can corrode equipment and pipelines, affecting the quality of subsequent products. Utility Model Content

[0004] The main objective of this invention is to provide a system for reducing the acid value of organosilicon hydrolysates, thereby reducing the acid content in the hydrolysates, decreasing the amount of alkaline substances used in subsequent pyrolysis processes, and saving costs. Furthermore, it facilitates storage and transportation, avoids corrosion of equipment and pipelines, and extends the service life of equipment and pipelines.

[0005] To achieve the above objectives, the technical solution adopted by this utility model is as follows: a system for reducing the acid value of organosilicon hydrolysate, comprising a hydrolysate delivery pipeline, a heat exchanger, a falling film evaporator, a condenser, a waste acid tank, and a vacuum pump; the hydrolysate delivery pipeline is connected to the cold medium inlet of the heat exchanger, the cold medium outlet of the heat exchanger is connected to the liquid inlet above the falling film evaporator, the exhaust port at the top of the falling film evaporator is connected to the air inlet of the condenser, the liquid outlet of the condenser is connected to the waste acid tank via a delivery pipeline, the air outlet of the condenser is connected to the air inlet above the waste acid tank, and the air outlet at the top of the waste acid tank is connected to the air inlet of the vacuum pump.

[0006] Furthermore, it also includes a steam pipeline, the outlet of which is connected to the heat medium inlet of the heat exchanger.

[0007] Furthermore, the outlet end of the infusion pipe is located inside the lower part of the waste acid tank.

[0008] This utility model has the following beneficial effects:

[0009] This invention features a simple and easy-to-implement connection. After being heated by a heat exchanger, the substance enters a vacuum-sealed falling film evaporator, effectively lowering the boiling point of acidic substances. This allows low-boiling-point acidic substances to evaporate and be removed. Some acidic substances undergo chemical reactions, transforming into other substances, further reducing the acid value content in the hydrolysate. This reduces the amount of alkaline substances used in subsequent pyrolysis processes, saving costs. Moreover, it facilitates storage and transportation, avoids corrosion of equipment and pipelines, and extends the service life of equipment and pipelines. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0011] Figure 1 This is a schematic diagram of the overall structure of a system for reducing the acid value of organosilicon hydrolysates according to the present invention.

[0012] In the diagram: 1. Hydrolysate transport pipeline; 2. Heat exchanger; 3. Falling film evaporator; 4. Condenser; 5. Waste acid tank; 6. Vacuum pump; 7. Steam pipeline; 8. Liquid delivery pipeline. Detailed Implementation

[0013] The following is in conjunction with the appendix Figure 1 The principles and features of this utility model are described, making the technical means, creative features, and achieved objectives of this utility model easy to understand, and further elaborating on this utility model.

[0014] In the description of this utility model, it should be noted that the terms "upper," "lower," "inner," "front end," "rear end," "both ends," "one end," and "the other end," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0015] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," and "connected," etc., should be interpreted broadly. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0016] like Figure 1 As shown, the technical solution adopted by this utility model is as follows: a system for reducing the acid value of organosilicon hydrolysate, comprising a hydrolysate conveying pipeline 1, a heat exchanger 2, a falling film evaporator 3, a condenser 4, a waste acid tank 5, a vacuum pump 6, and a steam pipeline 7; the hydrolysate conveying pipeline 1 is connected to the cold medium inlet of the heat exchanger 2, the cold medium outlet of the heat exchanger 2 is connected to the liquid inlet above the falling film evaporator 3, the exhaust port at the top of the falling film evaporator 3 is connected to the air inlet of the condenser 4, the liquid outlet of the condenser 4 is connected to the waste acid tank 5 through a liquid delivery pipe 8, the air outlet of the condenser 4 is connected to the air inlet above the waste acid tank 5, the air outlet at the top of the waste acid tank 5 is connected to the air inlet of the vacuum pump 6, and the air outlet of the steam pipeline 7 is connected to the hot medium inlet of the heat exchanger 2; the liquid outlet of the liquid delivery pipe 8 is located at the bottom inside the waste acid tank 5.

[0017] Working principle: The hydrolysate first passes through the newly added heat exchanger 2, is preheated to 100℃, and then enters the falling film evaporator 3. A vacuum is drawn at the top of the falling film evaporator 3, and the hydrolysate flows out through the lower pipe of the evaporator 3 to proceed to the next step of pyrolysis. In the falling film evaporator 3, the material flows in a film-like manner along the heating tube wall under the action of gravity, wherein:

[0018] Hydrochloric acid (HCl solution) has an extremely low boiling point (-85℃ at normal pressure), making it even more volatile in the vacuum environment of the falling film evaporator 3. The hydrolysate, preheated to 100℃ by heat exchanger 2, enters the falling film evaporator 3. The film-like flow of the material comes into full contact with the heating tube walls, rapidly increasing its temperature. Under the combined effects of high temperature and vacuum, hydrogen chloride molecules in the hydrochloric acid escape from the liquid phase into the gas phase, and are removed along with the water vapor extracted by vacuum pump 6, directly reducing the concentration of free hydrogen ions in the system.

[0019] Formic acid (boiling point 100.8℃), acetic acid (boiling point 117.9℃), and other low-carbon chain organic acids have low boiling points and are somewhat volatile. In the falling film evaporator 3, the preheating temperature of 100℃ combined with a vacuum environment (pressure reduction lowers the boiling point) significantly increases the volatility of these organic acids. When the material flows in a film-like manner, the contact area with the gas phase is increased, making it easier for organic acid molecules to diffuse from the liquid phase to the gas phase, while the evaporated water is removed from the system. At the same time, the efficient heat transfer characteristics of the film flow ensure uniform material temperature and prevent local overheating that could lead to the decomposition of organic acids and the formation of new acidic substances.

[0020] When silane monomers containing carboxyl groups hydrolyze, the released carboxyl groups (-COOH) ionize into hydrogen ions, making the system acidic. In the falling film evaporator 3, the high temperature (around 100℃) and material concentration environment promote the decarboxylation reaction of carboxyl groups: -COOH → -H+ CO2↑. The generated carbon dioxide escapes rapidly under vacuum conditions, reducing the number of carboxyl groups. At the same time, the concentration of silanol groups (-Si-OH) in the concentrated material increases, making it more prone to condensation reactions (2-Si-OH → -Si-O-Si- + H2O). The water generated in the reaction is removed with evaporation, and the condensation process consumes hydrogen ions, indirectly reducing the acidity of the system.

[0021] The hydrogen ions from the ionization of the sulfonic acid group (-SO3H) are a strong source of acidity, and the corresponding sulfonic acid substances have high boiling points, making them difficult to volatilize directly. However, in the high-temperature environment of the falling film evaporator 3, the sulfonic acid group undergoes a desulfonation reaction: -SO3H → -H +SO3↑. Sulfur trioxide (SO3) has a low boiling point (44.8℃) and readily volatilizes away from the hydrolysate under vacuum, thus reducing the total amount of sulfonic acid groups. In addition, the high temperature promotes the condensation of silanol groups. The free hydrogen ions in the hydrolysate combine with the hydroxyl groups generated by the condensation reaction to form water, which is removed during evaporation, further reducing the acid value.

[0022] The inorganic acids such as metasilicic acid (H2SiO3) generated by the breaking of silicon-oxygen bonds are relatively weak, but their accumulation can lead to an increase in acid value. In the falling film evaporator 3, the high temperature and vacuum environment promote the dehydration reaction of metasilicic acid: H2SiO3 → SiO2 + H2O. The generated silicon dioxide (SiO2) is a stable solid that remains in the hydrolysate and no longer contributes to acidity. The water generated in the reaction is removed with evaporation, reducing the acidic components in the hydrolysate. At the same time, the film-flowing material is heated evenly, preventing the metasilicic acid from further decomposing due to localized overheating and producing other acidic substances.

[0023] The carboxylic acids produced by oxidation are similar in nature to the organic acids introduced from the raw materials, exhibiting low boiling points and high volatility. The falling film evaporator 3 promotes their volatilization through high temperature and vacuum, allowing them to be removed with the steam. Furthermore, the reduced oxygen content inhibits the continued oxidation reaction, preventing the formation of new organic acids. For already formed organic acids, the efficient heat transfer of the film flow ensures their full volatilization, minimizing residues in the hydrolysate.

[0024] The gas discharged from the top of the falling film evaporator 3 is condensed by the condenser 4, and the acid water enters the waste acid tank 5 and is discharged from the bottom for treatment. The uncondensed gas enters the waste acid tank 5 and is vented by the vacuum pump 6.

[0025] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. A system for reducing the acid value of organosilicon hydrolysates, characterized in that, It includes a hydrolysate delivery pipeline, a heat exchanger, a falling film evaporator, a condenser, a waste acid tank, and a vacuum pump; the hydrolysate delivery pipeline is connected to the cold medium inlet of the heat exchanger, the cold medium outlet of the heat exchanger is connected to the liquid inlet above the falling film evaporator, the exhaust port at the top of the falling film evaporator is connected to the air inlet of the condenser, the liquid outlet of the condenser is connected to the waste acid tank through a delivery pipeline, the air outlet of the condenser is connected to the air inlet above the waste acid tank, and the air outlet at the top of the waste acid tank is connected to the air inlet of the vacuum pump.

2. The system for reducing the acid value of organosilicon hydrolysates according to claim 1, characterized in that, It also includes a steam pipeline, the outlet of which is connected to the heat medium inlet of the heat exchanger.

3. The system for reducing the acid value of organosilicon hydrolysates according to claim 1, characterized in that, The outlet end of the infusion pipe is located inside the lower part of the waste acid tank.

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