CN103183827A - Method of continuous concentrated acid hydrolysis of organochlorosilane - Google Patents

Abstract

The invention relates to a method for continuous concentrated acid hydrolysis of organochlorosilane, comprising the steps of: (1) carrying out hydrolysis reaction between organochlorosilane and concentrated acid in a hydrolysis reactor to generate hydrochloric acid and crude hydrolyzate with higher concentration; (2) hydrolysis After the liquid generated after the reaction passes through the coarse separator, the concentrated acid enters the falling film evaporator, and heat exchange generates HCl gas to obtain HCl gas for the production of methyl chloride; the concentrated acid at the bottom of the tower enters the hydrolysis reactor for recycling; after rough separation The oil phase separated by the reactor enters the first-stage phase separation and the second-stage phase separation, and the separated acid liquid returns to the hydrolysis reactor for circulation, and the oil phase enters the subsequent water washing process; (3) The oil phase entering the water washing process first passes through two stages in series Water washing and phase separation, then into dilute alkaline solution cycle washing and phase separation, and finally into two-stage series water washing and phase separation; the oil phase after water washing is an oligomerized siloxane product.

Description

A kind of continuous concentrated acid hydrolysis method of organochlorosilane

technical field

The invention relates to the technical field of organosilicon production, in particular to a process for generating oligosiloxane and anhydrous hydrogen chloride by continuous concentrated acid hydrolysis of organochlorosilane.

Background technique

Organochlorosilanes are transformed into linear or cyclic intermediate oligomeric organosiloxanes through hydrolysis and polycondensation, which are the basis for the synthesis of silicone oil, silicone rubber, and silicone resin. In particular, dimethyldichlorosilane (hereinafter referred to as dimethyl) is considered to be the most suitable for hydrolysis and condensation reactions.

At present, most domestic dimethyl hydrolysis adopts azeotropic acid hydrolysis process. Since the product hydrogen chloride dissolves in the dilute acid, a large amount of heat is released. In order to keep the reaction temperature within the requirements of the process conditions, the heat needs to be removed. This part of the heat cannot be used in the subsequent process, thus consuming a lot of energy. In addition, to recover the hydrogen chloride in the acid to make it meet the requirements of methyl chloride synthesis, and to facilitate transportation also consumes a lot of energy. In the post-treatment process of the product oligosiloxane, a large amount of waste water and waste acid will be produced, which will pollute the environment.

French patent FR2518099 hydrolyzes organochlorosilanes with saturated hydrochloric acid with insufficient water, so that the generated hydrogen chloride gas is easy to handle. However, when the water is insufficient, the hydrolysis is not complete, that is, a linear polyorganosiloxane containing Cl at the end will be produced. The high chlorine content of the crude hydrolyzate makes the work-up of the product difficult.

U.S. Patent No. 4,382,145 uses water in hydrochloric acid with a minimum concentration of 35% (wt) as reaction water, and its dosage is 10 to 30 times (molar ratio) of organochlorosilane, which is recycled inside and outside the reactor; U.S. Patent No. 4,497,942 uses water in a certain Under pressure, water in hydrochloric acid with a concentration of 40-42% is used as reaction water, and the dosage is 10-50 times (molar ratio) of organochlorosilane, and the hydrochloric acid is recycled inside and outside the reactor. The advantage of the two patents is to directly obtain anhydrous hydrogen chloride, which saves energy, but there is a shortcoming of incomplete hydrolysis, and the data on the yield and purity of hydrolyzate and hydrogen chloride are not given.

US Pat. No. 6,225,490 discloses a continuous organochlorosilane hydrolysis process. The hydrolysis process includes at least three stages of reaction in series, and each stage of reaction includes an independent reactor and a phase separator. The organochlorosilane is fed from the reactor in the first stage, and the reaction water is all provided by the feed water in the last stage, and the reaction in the first stage produces hydrogen chloride gas. The hydrolyzate produced in the previous stage enters the next stage for hydrolysis treatment, and the hydrochloric acid produced in the latter stage is sent to the previous stage for reaction, that is, the hydrolysis reaction is carried out in a three-stage countercurrent method. Although this process can produce hydrogen chloride gas, the pressure of gas phase hydrogen chloride is too low to be directly applied in the synthesis of methyl chloride. Moreover, because the process is operated in series, the operating flexibility is small, and the reaction of any stage is not up to standard, which will affect the final quality of the product.

U.S. Patent No. 6,326,452 discloses a method for the hydrolysis of organochlorosilanes, which mainly includes two steps: the first step is actually to use stoichiometric water to hydrolyze organochlorosilanes to generate some crude hydrolyzate and hydrogen chloride with Cl-terminated polyorganosiloxanes Gas; in the second step, the quantitative high-temperature steam is used to strip the crude hydrolyzate, reduce the chlorine content and generate hydrochloric acid, return to the first step to react and replenish water, and the excess hydrochloric acid is decomposed to produce low-pressure hydrogen chloride gas, which is not suitable for use In the synthesis of methyl chloride. And the crude product is treated with steam, and the viscosity of the hydrolyzate is finally difficult to control.

Based on the above-mentioned patents and documents, it can be seen that it is necessary to design a reasonable continuous organochlorosilane hydrolysis process. This process should be able to obtain sufficient pressure and dry HCl gas so that it can be directly used in the synthesis of methyl chloride, and this process should reduce as much as possible. The generation of waste liquid, the viscosity and chlorine content of the final organosiloxane meet the requirements, and can be operated and controlled stably.

Contents of the invention

The technical purpose of the present invention is to overcome the shortcomings and deficiencies in the above-mentioned process, and to provide a process for the concentrated acid hydrolysis of organochlorosilanes with stable operation, low energy consumption and continuous operation. The yield of hydrolyzate is 95-98% (wt%), and the yield of dry HCl gas is 94-98% (wt%).

In order to achieve the above object, the technical scheme adopted in the present invention is:

A continuous concentrated acid hydrolysis method for organochlorosilanes, comprising the steps of:

(1) The hydrolysis reaction of organochlorosilane and concentrated acid in the hydrolysis reactor produces hydrochloric acid and crude hydrolyzate with higher concentration. The molar ratio of water to organochlorosilane in the reaction system is 5:1~20:1, and the reaction temperature 20～50℃, the operating pressure is 0.1～0.5MPa gauge pressure, the residence time of organochlorosilane and concentrated acid in the hydrolysis reactor is 60～180s;

(2) After the liquid generated after the hydrolysis reaction passes through the rough separator, the concentrated acid enters the falling film evaporator, heat exchange generates HCl gas, and then enters the drying and impurity removal equipment through the top of the evaporator to remove impurities and moisture in the HCl gas , the pressure is 0.2-0.5MPa, and the HCl gas used for the production of methyl chloride is obtained; the concentrated acid at the bottom of the tower enters the hydrolysis reactor for recycling; the oil phase separated by the rough separator enters the primary phase separation and secondary phase separation, and the The acid solution is returned to the hydrolysis reactor for circulation, and the oil phase enters the subsequent water washing process;

(3) The oil phase entering the water washing process first undergoes two-stage serial washing and phase separation, the soft water used for washing is added quantitatively, the washing temperature is 50-90°C, and the volume ratio of water to oil phase is 0.5:1-3:1. The operating pressure is 0.1-0.3MPa; the dilute acid produced by water washing enters the hydrolysis reactor as a supplement to the water source;

(4) The oil phase after the two-stage water washing enters the dilute lye for circular washing and phase separation. The dilute lye is 4-20%wt sodium carbonate solution, and the volume ratio of the lye to the oil phase is 2:1-8:1 , to remove the acid and most of the free chlorine in the oil phase; the separated lye is recycled;

(5) The oil phase separated in step (4) enters the final two-stage series washing and phase separation, soft water is added quantitatively, most of the separated water phase is used to prepare dilute lye, and a small part enters the waste lye tank; The oily phase after water washing is the oligomeric siloxane product.

In the hydrolysis method of the present invention, the hydrogen chloride gas obtained in step (2) is anhydrous and clean, and the pressure is 0.2-0.5 MPa.

In the hydrolysis method of the present invention, the drying and impurity removal equipment in step (2) is conventional equipment that can remove impurities and moisture in HCl gas, such as HCl freeze-drying system and circulation cyclone demister (also known as circulation demister) atomizer), etc.

In the hydrolysis method of the present invention, the amount of water used for washing in step (3) is at most to make this part of water fully participate in the hydrolysis reaction.

In the hydrolysis method of the present invention, wherein the hydrolysis reactor in step (1) is a reflection device capable of reacting organochlorosilane and concentrated acid, preferably a dispersion liquid membrane analysis tower with high efficiency, the dispersion liquid The membrane type desorption tower includes a shell, which has a support, an upper head and a lower cone, a flange, an outer cylinder, and is connected and sealed by fasteners; the inner cylinder is also included in the shell ; The top of the analytical tower has a liquid inlet, the bottom has a liquid outlet, and the gas outlet is opened on the side of the outer cylinder; a liquid distribution plate is fixedly installed between the upper head and the outer cylinder, and the liquid distribution plate The upper part is a splash screen, and the lower part of the liquid distribution plate is a neatly arranged film-forming plate. The film-forming plate is horizontally supported, with a total of 3 to 10 layers. The angle between the forming template and the horizontal plane is 15 to 75 degrees. , the film-forming plates are arranged in a staggered direction; all the film-forming plates are installed in the inner cylinder, and an annular gap is formed between the inner cylinder and the outer cylinder as a gas diversion path. The residence time is 60-120s.

The raw material organochlorosilane of the present invention is preferably dimethyldichlorosilane, but not specifically dimethyldichlorosilane.

One of the main technical effects of the method of the present invention is to make the HCl gas produced by hydrolysis have sufficient pressure through a suitable reaction pressure (0.1-0.5 MPa gauge pressure), and at the same time use a three-stage integrated HCl freeze-drying system and demister device The impurities and moisture in the HCl gas are removed to make the HCl gas dry and pure to meet the synthesis requirements of methyl chloride.

Another technical effect of this method is to use super-stoichiometric water (water in concentrated acid:organochlorosilane=5-20:1, molar ratio) and suitable reaction temperature (20-50°C) for hydrolysis, and By improving the structure of the reactor, the oil-water two-phase film-forming contact makes the hydrolyzed product free of Si-Cl residue as much as possible, so as to reduce the water consumption in the subsequent process and avoid the generation of dilute acid waste liquid.

The third technical effect of this method is to use strictly controlled metered water and dilute lye (water:polyorganosiloxane=2～8:1, volume ratio) to carry out five-stage washing treatment on the product, so that polyorganosiloxane Alkanes have low viscosity (≤16cP) and low free Cl content (≤6ppm), and the quality is stable and controllable. The discharge of spent caustic soda is minimized, and a small amount of dilute acid produced by washing is returned to the reactor as make-up water for the hydrolysis reaction.

Can show following excellent hydrolysis effect by the implementation of above-mentioned process scheme of the present invention:

1. The special structure of the hydrolysis equipment (dispersed liquid membrane type analysis tower) increases the residence time of hydrolysis, and the full contact between water molecules and organochlorosilane molecules makes the hydrolysis reaction complete.

2. The use of super-stoichiometric water reduces the formation of linear siloxanes containing chlorine at the end, increases the yield of hydrolyzate and reduces the aftermath

water used for treatment. And ensure that the temperature change in the reaction process is small, and improve the quality of the product organosiloxane.

The dilute acid generated in the water washing process is recycled to avoid the generation of a large amount of waste acid liquid and ensure the water consumption for the hydrolysis of chlorosilane.

Description of drawings

Fig. 1 is a process flow diagram of the present invention; Wherein: 1: hydrolysis reactor; 2: rough separator; 3: falling film evaporator; 4: phase separator; 5: condenser; 6: circulation type demister; 7: Water washing mixing and separation equipment; 8: Alkali washing mixing and separation equipment; 9: Water washing mixing and separation equipment; 10: Waste alkali tank; 11: Chlorosilane inlet; 12: HCl outlet; 13: Steam inlet; 14: Low Silicone outlet.

Detailed ways

For further illustrating the present invention, specifically illustrate in conjunction with following examples:

The present invention will be further described below in conjunction with the process flow and embodiments of FIG. 1 , but is not limited thereto. The concentration of hydrochloric acid entering the hydrolysis reactor is 33%-38%wt, and the concentration of hydrochloric acid at the outlet of the hydrolysis reactor is 40%-50%wt.

Example 1: Dimethyldichlorosilane and concentrated acid enter the hydrolysis reactor 1 for hydrolysis reaction. The molar ratio of water to dimethyldichlorosilane in the reaction system is 5:1, and the water source comes from the hydrolyzed oligosiloxane In the water washing process, the concentrated acid is recycled between the hydrolysis reactor 1 and the falling film evaporator 3 . The reaction temperature is controlled at 30°C, the operating pressure is 0.4MPa, and the residence time is 60s. The volume ratio of water to oligosiloxane is 0.5:1, the operating temperature is 55°C, and the operating pressure is 0.1MPa for the first two stages of series washing. The volume ratio of dilute lye to oligosiloxane is 8:1 for alkali cleaning, the operating temperature is 55°C, and the operating pressure is 0.1MPa. The volume ratio of water to oligosiloxane is 1:1, the operating temperature is 70°C, and the operating pressure is 0.1MPa for the last two-stage series washing. The indicators of the obtained product are as follows: the acid content in the acidic hydrolyzate is 1.5-2.6%wt, and the viscosity is 6-9cP; 15±3cP (25°C), the yield of hydrolyzate is 97.5%wt, the content of cyclosiloxane is 40±5%wt, and the yield of hydrogen chloride is 97%wt. The quality of the hydrolyzate meets the requirements of subsequent processes.

Example 2: Dimethyldichlorosilane and concentrated acid enter the hydrolysis reactor for hydrolysis reaction, the molar ratio of water to dimethyldichlorosilane in the reaction system is 10:1, and the water source comes from the hydrolyzate oligosiloxane washing In the process, the concentrated acid is recycled between the hydrolysis reactor and the falling film evaporator. The reaction temperature is controlled at 20°C, the operating pressure is 0.3MPa, and the residence time is 90s. The volume ratio of water to oligosiloxane is 2:1, the operating temperature is 75°C, and the operating pressure is 0.2MPa for the first two stages of series washing. The volume ratio of dilute lye to oligosiloxane is 6:1 for alkali cleaning, the operating temperature is 65°C, and the operating pressure is 0.1MPa. The volume ratio of water to oligosiloxane is 1:1, the operating temperature is 60°C, and the operating pressure is 0.3MPa for the last two-stage series washing. The specifications of the product obtained did not change significantly.

Example 3: Dimethyldichlorosilane and concentrated acid enter the hydrolysis reactor for hydrolysis reaction, the molar ratio of water to dimethyldichlorosilane in the reaction system is 15:1, and the water source comes from the hydrolyzate oligosiloxane washing In the process, the concentrated acid is recycled between the hydrolysis reactor and the falling film evaporator. The reaction temperature is controlled at 40°C, the operating pressure is 0.2MPa, and the residence time is 1200s. The volume ratio of water to oligosiloxane is 3:1, the operating temperature is 60°C, and the operating pressure is 0.1MPa for the first two stages of series washing. The volume ratio of dilute lye to oligosiloxane is 4:1 for alkali cleaning, the operating temperature is 60°C, and the operating pressure is 0.2MPa. The volume ratio of water to oligosiloxane is 3:1 for the last two-stage series washing, the operating temperature is 70°C, and the operating pressure is 0.2MPa. The specifications of the product obtained did not change significantly.

Example 4: Dimethyldichlorosilane and concentrated acid enter the hydrolysis reactor for hydrolysis reaction, the molar ratio of water to dimethyldichlorosilane in the reaction system is 20:1, and the water source comes from the hydrolyzate oligosiloxane washing In the process, the concentrated acid is recycled between the hydrolysis reactor and the falling film evaporator. The reaction temperature is controlled at 50°C, the operating pressure is 0.3MPa, and the residence time is 60s. The volume ratio of water to oligosiloxane is 0.5:1, the operating temperature is 60°C, and the operating pressure is 0.1MPa for the first two stages of series washing. The volume ratio of dilute lye to oligosiloxane is 8:1 for alkali cleaning, the operating temperature is 60°C, and the operating pressure is 0.1MPa. The volume ratio of water to oligosiloxane is 2:1, the operating temperature is 60°C, and the operating pressure is 0.1MPa for the last two-stage series washing. The specifications of the product obtained did not change significantly.

The above-mentioned embodiments are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. All such modifications and improvements should fall within the scope of protection defined by the claims of the present invention.

Claims (4)

1. A continuous concentrated acid hydrolysis method for organochlorosilanes, comprising steps: (1) The hydrolysis reaction of organochlorosilane and concentrated acid in the hydrolysis reactor produces hydrochloric acid and crude hydrolyzate with higher concentration. The molar ratio of water to organochlorosilane in the reaction system is 5:1~20:1, and the reaction temperature 20～50℃, the operating pressure is 0.1～0.5MPa gauge pressure, the residence time of organochlorosilane and concentrated acid in the hydrolysis reactor is 60～180s; (2) After the liquid generated after the hydrolysis reaction passes through the rough separator, the concentrated acid enters the falling film evaporator, heat exchange generates HCl gas, and then enters the drying and impurity removal equipment through the top of the evaporator to remove impurities and moisture in the HCl gas , the pressure is 0.2-0.5MPa, and the HCl gas used for the production of methyl chloride is obtained; the concentrated acid at the bottom of the tower enters the hydrolysis reactor for recycling; the oil phase separated by the rough separator enters the primary phase separation and secondary phase separation, and the The acid solution is returned to the hydrolysis reactor for circulation, and the oil phase enters the subsequent water washing process; (3) The oil phase entering the water washing process first undergoes two-stage serial washing and phase separation, the soft water used for washing is added quantitatively, the washing temperature is 50-90°C, and the volume ratio of water to oil phase is 0.5:1-3:1. The operating pressure is 0.1-0.3MPa; the dilute acid produced by water washing enters the hydrolysis reactor as a supplement to the water source; (4) The oil phase after the two-stage water washing enters the dilute lye for circular washing and phase separation. The dilute lye is 4-20%wt sodium carbonate solution, and the volume ratio of the lye to the oil phase is 2:1-8:1 , to remove the acid and most of the free chlorine in the oil phase; the separated lye is recycled; (5) The oil phase separated in step (4) enters the final two-stage series washing and phase separation, soft water is added quantitatively, most of the separated water phase is used to prepare dilute lye, and a small part enters the waste lye tank; The oily phase after water washing is the oligomeric siloxane product. 2. The hydrolysis method according to claim 1, characterized in that: the hydrogen chloride gas obtained in step (2) is anhydrous and clean, and the pressure is 0.2-0.5 MPa. 3. The hydrolysis method according to claim 1, characterized in that: the amount of water used for washing in step (3) is at most such that this part of water completely participates in the hydrolysis reaction. 4. The hydrolysis method according to claim 1, characterized in that: the hydrolysis reactor in step (1) is a dispersed liquid film desorption tower, and the residence time is 60-120s.