CN102219760B - Method for preparing epichlorohydrin and white carbon black by coupling process - Google Patents

Abstract

The invention discloses a method for preparing epichlorohydrin and white carbon black by a coupling process. The method comprises the steps as follows: hydrolyzing silicon tetrachloride to obtain silica gel and a byproduct, namely, HCl (chlorine hydride); chlorinating the byproduct-HCl with glycerol under the participation of a catalyst to obtain glycerindichlorohydrin and a by-product, namely, water; hydrolyzing the silicon tetrachloride with the byproduct-water; and carrying out thermal treatment on the silica gel to obtain the white carbon black, and saponifying the glycerindichlorohydrin to obtain epoxy chloropropane. In the invention, through coupling of glycerol chlorination and SiCl4 hydrolysis process, the byproduct water during chlorination and the byproduct HCl during hydrolysis process are both utilized, thus being beneficial to energy conservation and emission reduction as well as clean production during the production processes of the epoxy chloropropane and the white carbon black. In addition, due to mutual utilization of the byproducts during the two processes, the cost of the products obtained from the coupling production process is greatly lowered; furthermore, the coupling production process is beneficial to popularization and application of glycerol epoxy chloropropane technology, as well as health development of polycrystalline silicon industry.

Description

A method for preparing epichlorohydrin and white carbon black by coupled process

technical field

The invention belongs to a method for preparing epichlorohydrin and white carbon black. Specifically, it relates to a method for preparing epichlorohydrin and white carbon black from glycerin and silicon tetrachloride by a coupled process.

Background technique

Epichlorohydrin is an important basic chemical widely used in the manufacture of epoxy resins and various fine chemicals. The main production method of epichlorohydrin is based on the high-temperature chlorination of propylene developed by Shell in 1948. That is, propylene first reacts with chlorine gas at about 500°C to generate chloropropene, and the generated chloropropene reacts with chlorine water at about 5°C to generate dichloropropanol, and the generated dichloropropanol is then saponified and cyclized with caustic soda or lime water to obtain Epichlorohydrin. Such a production process consumes a lot of energy, is dangerous, and produces a large amount of saline wastewater (40-50 tons of wastewater/ton of epichlorohydrin). The reaction process is as follows:

In recent years, the process of using biodiesel by-product glycerol to prepare epichlorohydrin has received great attention. The reaction process is that biological glycerol and HCl react under the action of a catalyst to form dichloroglycerin, and the produced dichloroglycerin reacts with alkali to form epichlorohydrin. The reaction process is as follows:

Such a reaction can be carried out in a stirred tank (CN1882522A) or in a tubular reactor (CN100509726C).

Compared with the propylene method, the glycerin method has obvious advantages. The specific performance is: the use of renewable resources, simple process, low energy consumption (about 1/3 of the propylene method), and a small amount of wastewater (about 1/30 of the propylene method). However, for the glycerol method, the main problem is that the source of the reaction raw material HCl is not as easy to obtain as _Cl2 in the propylene method, and the storage and transportation of HCl is far less convenient than _Cl2 , which is the main obstacle restricting the popularization and application of the glycerin method.

Silica is a multifunctional additive widely used in rubber, tire, paint, ink, medicine, machinery and other industries. At present, the methods of producing white carbon black mainly include gas phase method and liquid phase method. The gas-phase method is hydrolysis with chlorosilane, and the liquid-phase method is hydrolysis with water hyaluronic acid. The gas phase method will generate a large amount of waste gas, and the liquid phase method will generate a large amount of saline wastewater. The quality of the gas phase method is better, and the gas phase method is generally used to produce high-quality silica.

With the solar photovoltaic industry being valued all over the world, China's polysilicon industry is developing rapidly. By 2011, China's polysilicon production capacity reached about 200,000 tons. However, about 15 tons of silicon tetrachloride will be produced as a by-product per ton of polysilicon production. The scientific and rational utilization of silicon tetrachloride has become a major problem in the development of the polysilicon industry and needs to be resolved urgently.

At present, there are two main methods for processing silicon tetrachloride: one is to convert it into trichlorosilane (CN101941702), but such a process is very costly and lacks market competitiveness; the other method is to use it to prepare white Carbon black (CN101798088). Theoretically speaking, 2.43 tons of HCl dry gas should be produced by producing 1 ton of white carbon black by using silicon tetrachloride to prepare white carbon black, and 7.6 tons of hydrochloric acid (32%) will be produced after being absorbed by H ₂ O. Although silicon tetrachloride can be used to obtain high-quality white carbon black, the application of this process is inhibited due to the by-production of such a large amount of hydrochloric acid.

What was invented:

The object of the present invention is to couple the process of preparing epichlorohydrin by glycerin chlorination with the process of preparing white carbon black by hydrolysis of silicon tetrachloride, utilize the water produced by glycerol chlorination to hydrolyze silicon tetrachloride, and then use silicon tetrachloride The HCl produced by hydrolysis is used to chlorinate glycerin, and two products are obtained at the same time, and the by-products are mutually utilized. The reaction equation is as follows:

Technical scheme of the present invention is:

A method for preparing epichlorohydrin and white carbon black, carried out according to the following steps:

(1) Dissolve the catalyst in glycerin, input it into the reactor with a metering pump, and slowly input SiCl ₄ into the glycerin containing the catalyst, and control a certain reaction temperature, time and pressure to react;

(2) After controlling a certain reaction time, filter and separate the reaction mixture;

(3) Wash the hydrolyzed silica gel filter cake obtained in step (2) with about 30% dilute glycerin and then filter; the washed silica gel is made into a 20-50% slurry with deionized water , the slurry is spray-dried at 400~1000°C to obtain white carbon black;

(4) After the filtrate produced by washing is combined with the reaction filtrate, dichloroglycerin, monochloroglycerin, glycerin and tar are obtained by vacuum distillation; among them, dichloroglycerin reacts with alkali to generate epichlorohydrin; monochloroglycerin And glycerin is circulated back to the feed system to continue the reaction; the tar is harmlessly treated.

Wherein the catalyst described in step (1) is fatty acid and/or inorganic acid, wherein said fatty acid refers to C ₂ ~C ₁₂ monobasic acid and polybasic acid, preferably C ₆ ~C ₈ dibasic acid.

Wherein the reaction temperature in step (1) is 60-160°C, preferably 70-120°C, preferably 70-90°C in the early stage of the reaction, and 100-120°C in the late stage of the reaction.

Wherein the SiCl ₄ described in step (1) can be fed in parallel with glycerin, or can be added in the form of multi-channel distribution. It is preferred to add SiCl ₄ in the form of multiple distribution, so that the reaction can be controlled smoothly and safety can be achieved. operate.

Wherein the feed molar ratio of glycerol to silicon tetrachloride in step (1) is 2.5-1.8:1, and the preferred molar ratio is 2.3-1.8:1.

Wherein the reaction time described in step (1) is 2.5-8 hours, preferably 3-6 hours.

Wherein the operating pressure described in step (1) is 0.03~1.0MPa, preferably 0.35~0.85MPa. Pressurization is beneficial to increase the reaction rate and product yield, but too high pressure is not conducive to safe operation.

Wherein the reaction mixture after the coupling reaction of chlorination and hydrolysis described in step (2) can be filtered by pressure or by suction.

The slurry concentration in step (3) is preferably 30-40% by mass; the drying temperature is preferably 550-700°C.

Wherein the alkali described in the step (4) is NaOH or milk of lime or KOH, and the obtained dichloroglycerin is saponified with the alkali to obtain epichlorohydrin.

The above-mentioned method process for preparing epichlorohydrin and white carbon black can be intermittent or continuous, and the preferred scheme is a continuous operation process. The form of the reactor used can be tube type, tank type, or tower type.

The effect of the invention :

The present invention couples the glycerol chlorination and the _SiCl4 hydrolysis process, so that both the water by-product in the chlorination process and the HCl by-product in the hydrolysis process can be utilized, which is beneficial to the production process of epichlorohydrin and the production process of white carbon black for energy saving and emission reduction, Clean manufacturing. Again, because the two processes utilize each other's by-products, the product cost obtained in the coupled production process is greatly reduced; furthermore, the coupled production process proposed by the present invention is conducive to the popularization and application of glycerol method epichlorohydrin technology, and also Conducive to the healthy development of the polysilicon industry.

Detailed ways

The glycerol content in the industrial product glycerol used in the present invention can be 80%-99% (mass ratio), preferably glycerin with a water content of 2-8%.

There is no special requirement for the content of SiCl ₄ in the industrial product SiCl ₄ used, as long as the content is greater than 90% (mass ratio).

Example 1. Continuous operation in a tubular reactor

Dissolve adipic acid (catalyst) in 95% industrial glycerin (mass ratio) to prepare a 5% (mass ratio) industrial glycerin solution. Use a metering pump to press industrial glycerin containing catalyst into a tubular reactor with a total volume of 50L at a rate of 11.75kg/h. The tubular reactor is divided into two parts, the front part of which has a volume of 30L (DN40mm The tube is 24m long), and the reaction temperature is controlled at 70°C; the volume of the latter part of the tubular reactor is 20L (DN40mm tube, 16m), and the reaction temperature is controlled at 130°C.

Use another metering pump to press SiCl ₄ with a content of 98.5% (mass ratio) into the above reactor at a rate of 8.5kg/h. The molar ratio of SiCl ₄ to glycerol is 2.3:1.0, and SiCl ₄ enters the reactor in a multiplexed manner. Among them, 50% enters the front part of the reactor in the form of three-way uniform distribution, and the other 50% enters the rear part of the reactor in the form of two-way uniform distribution. The residence time of the control material in the reactor is about 3h. The pressure inside the reactor is 0.45~0.55MPa.

The material flowing out from the tubular reactor is pumped into the filter press, the filtrate is crude chlorinated glycerin, and the filter cake is silica gel. After washing the filter cake with glycerin, use deionized water to make a 40% (mass ratio) slurry and send it to a spray drying tower with an air flow temperature of 700°C for dehydration to obtain a white carbon black product of 2.88kg/h with a specific surface area of 167m ² /g, the average particle size is 185nm, and the yield is about 98%.

The crude chlorinated glycerin is combined with the glycerol from washing the filter cake and sent to the chlorinated glycerin separation tower. The separated dichloroglycerin and milk of lime are mixed into the saponification tower for reaction, and the epichlorohydrin produced is extracted from the top of the tower, and the finished product of epichlorohydrin is finally obtained after further refining.

The heavy component (monochloroglycerin) separated from the chlorinated glycerol separation tower is recycled to the feed system for further chlorination and lightening into dichloroglycerin, and the tar is discharged from the tower kettle. After 8 hours of continuous operation, the whole reaction system is balanced, and finally the epichlorohydrin 8.87kg/h with a content of 99.5% can be obtained from the epichlorohydrin rectification tower, and its yield is 79.4%.

Example 2. Tank Reactor Batch Operation

Be 0.5 m in the ^external circulation reaction kettle that add content and be 99% refined glycerin 186kg, add 10 kg of glacial acetic acid, close the feeding port, start the circulation pump, first with the metering pump of 35kg/h through the feeding pipeline Press into SiCl ₄ at a high rate, and control the reaction temperature to 90°C through jacket water cooling. After reacting for 2 hours, change the pumping rate of _SiCl4 to 50kg/h, control the reaction temperature to 120°C, continue this operation for 2 hours, pump 170kg of _SiCl4 in total, and the molar ratio of glycerol to _SiCl4 is 2:1, The operating pressure is 0.3~0.8MPa, and the total reaction time is 4 hours.

After the reaction is over, the reaction product is sent to a rotary drum suction filter through an external circulation pump, and the filter residue is washed with 30% dilute glycerin.

The filter residue was made into a slurry containing 50% silicon gel with deionized water, and the slurry was pumped into a spray drying tower at 550°C to obtain 58.0 kg of a white carbon black product with a yield of 96.7%. It is 148 m ² /g, and the average particle size is 206 nm.

Combine the filtrate and filter residue washing liquid and carry out rectification to obtain dichloroglycerin, and saponify the obtained dichloroglycerin with NaOH with a concentration of 20% to obtain crude epichlorohydrin, which is refined to obtain cyclohexanol with a content of 99.8%. Oxychloropropane 164.6 kg, yield 88.5%.

Example 3. Column Reactor Continuous Operation

Dissolve silicomomolybdic acid in 82% crude glycerin to make a 3% solution. Use a metering pump to press the crude glycerin containing catalyst into the tower reactor at a rate of 217kg/h. The tower reactor consists of two parts connected in series with an external circulation pump, the volume of the first tower is 0.4m ³ , and the volume of the second tower is 0.6m ³ .

Use a metering pump to press SiCl with a content of 98.5% _into the above-mentioned tower reactor at a rate of 170kg/h. The molar ratio of glycerol to _SiCl4 was 1.8:1. SiCl ₄ enters the tower reactor in two distribution ways, one of which sends 40% of SiCl ₄ into the first tower reactor, and the other sends the remaining 60% of SiCl ₄ into the second tower reaction device. The operating temperature of the first tower is controlled at 60°C and the operating pressure is 0.25~0.35MPa, and the operating temperature of the second tower is controlled at 110°C and the operating pressure is 0.5~0.6MPa. The total residence time of the material in the tower is about 3.5 hours.

The outflowing reaction solution is pumped into a filter press, and the filter cake is washed with 30% dilute glycerol. The washing liquid and the reactant filtrate are combined for separation and circulation.

After continuous feed reaction for 6 hours, the operation of the reaction system gradually stabilized. The filter cake was made into a 20% slurry with deionized water, and sent to a spray drying tower at 950°C for drying to obtain 57.1kg/h of white carbon black, with a yield of 95.2%. Its specific surface area is 219 m ² /g, and its average particle size is 147 nm.

The filtrate is separated by rectification, the heavy component (monochloroglycerin and glycerol) is recycled, and the light component is dichloroglycerin. The obtained dichloroglycerin was reacted with 25% KOH in a saponification tower to generate crude epichlorohydrin, and then rectified to obtain 153.5 kg/h of epichlorohydrin with a purity of 99.8%, with a yield of 91.7%.

Claims (7)

1. a method for preparing epichlorohydrin and white carbon black is characterized in that it is carried out according to the following steps: (1) Dissolve the catalyst in glycerin, input it into the reactor with a metering pump, and slowly input SiCl ₄ into the glycerin containing the catalyst, and control a certain reaction temperature, time and pressure to react; (2) After controlling a certain reaction time, filter and separate the reaction mixture; (3) Wash the hydrolyzed silica gel filter cake obtained in step (2) with about 30% dilute glycerin and then filter; the washed silica gel is made into a 20-50% slurry with deionized water , spray drying the slurry at 400-1000°C to obtain white carbon black; (4) After the filtrate produced by washing is combined with the reaction filtrate, dichloroglycerin, monochloroglycerin, glycerin and tar are obtained by vacuum distillation; among them, dichloroglycerin reacts with alkali to generate epichlorohydrin; monochloroglycerin and glycerin are circulated back to the feed system to continue the reaction; the tar is harmlessly treated; Wherein the alkali described in step (4) is NaOH or milk of lime or KOH, the catalyst described in step (1) is fatty acid and/or inorganic acid, wherein said fatty acid refers to C ₂ ~C ₁₂ monobasic acid and polyacids. 2. A method for preparing epichlorohydrin and white carbon black according to claim 1, characterized in that the reaction temperature in step (1) is 60~160°C, and the SiCl ₄ is mixed with glycerol flow feed, or added in the form of multiple distribution, the feed molar ratio of glycerin and silicon tetrachloride is 2.5~1.8:1, the reaction time is 2.5~8 hours, the operating pressure is 0.03~1.0MPa. 3. A method for preparing epichlorohydrin and white carbon black according to claim 1, characterized in that the reaction mixture after the coupling reaction of chlorination and hydrolysis in step (2) is filtered by pressure filtration or by pumping Filtration for separation. 4. A method for preparing epichlorohydrin and white carbon black according to claim 1, wherein the concentration of the slurry in step (3) is 30-40% by mass; the drying temperature is 550-700°C . 5. a kind of method for preparing epichlorohydrin and white carbon black according to claim 1 is characterized in that described method process is intermittent, or continuous, and the reactor form used is tubular, kettle type or tower type. 6. A method for preparing epichlorohydrin and white carbon black according to claim 2, wherein the catalyst described in step (1) is a C ₆ ~ C ₈ dibasic acid, and the reaction The temperature is 70-120°C, the early stage of the reaction is controlled at 70-90°C, and the late stage of the reaction is controlled at 100-120°C; the SiCl ₄ is added to SiCl ₄ in the form of multiple distribution, and the feed of glycerol and silicon tetrachloride The molar ratio is 2.3-1.8:1, the reaction time is 3-6 hours, and the operating pressure is 0.35-0.85 MPa. 7. a kind of method for preparing epichlorohydrin and white carbon black according to claim 6 is characterized in that described method process is continuous operation process.