KR20040105883A - Method for recovering toluene diamine from solid wastes of toluene diisocyanate plant - Google Patents

Abstract

PURPOSE: Provided is a process for recovering toluene diamine from solid waste discharged from a toluene diisocyanate production process, which reduces the generation of waste water and waste product, and increases reutilization efficiency during the process. CONSTITUTION: The process for recovering toluene diamine from solid waste(10) discharged from a toluene diisocyanate production process comprises the steps of: pulverizing and screening the solid waste; mixing the treated solid waste with water(11) and a catalyst(12) to form slurry; pressurizing the slurry, introducing it continuously into a heat exchanger(22) and heating the slurry with a treating liquid discharged from a reactor(24) while cooling the treating liquid; warming the slurry to a liquid phase zone having a temperature of 200-370 deg.C less than the critical point of water to hydrolyze the organic particles in the slurry; cooling the hydrolyzed slurry by the heat exchange with the treating liquid discharged from the reactor and reducing the internal pressure; introducing the treating liquid into a distillation tower(31) to discharge a mixed gas(34) at the top and a mixture(35) of toluene diamine, the catalyst and high-boiling tar at the bottom; and introducing the mixture into a depressurization evaporator(41) to recover toluene diamine(42) at the top and to discharge a mixture of the catalyst and tar as waste products(43) at the bottom.

Description

Method for recovering toluene diamine from solid wastes of toluene diisocyanate plant}

The present invention relates to a method for recovering toluene diamine from the solid waste discharged from the toluene diisocyanate manufacturing process, more specifically, contained in the high-boiling tar waste discharged from the bottom of the distillation column in the production process of toluene diisocyanate. After toluene diisocyanate is recovered again by vacuum evaporation or thin film evaporation process, the solid waste which is finally discarded is pulverized and composed of alkali metal carbonate and alkali metal hydroxide at the temperature near the critical point of water and the pressure above the vapor pressure of water of the temperature. A method for recovering toluene diamine from solid wastes discharged from the toluene diisocyanate manufacturing process of recovering toluene diamine in high yield by hydrolysis by using at least one mixture selected from the group as a catalyst and recycling the wastewater and catalyst discharged will be.

Landfill and offshore dumping are the most economically preferred methods for treating liquid or solid waste from industrial sites. However, these methods are causing serious marine pollution and soil pollution problems, and as the scale of the industry expands, regulations are being tightened. In addition, international treaties and industrial waste landfill limits are expected to be banned in the coming years.

Incineration is the most preferred alternative to landfill and dumping at sea. Incineration is a method of burning waste above a proper temperature to decompose it. However, since incineration requires the installation of additional devices to remove secondary pollutants such as nitrogen oxides (NOx), sulfur oxides (SOx), and dioxins generated by high temperatures, an increasing investment is required. Since the temperature is maintained above 1000 ℃, a lot of energy is consumed, the operating costs are gradually increased.

Therefore, the development of technology to recover the maximum amount of recyclable materials or to convert the waste into new raw materials through some chemical reaction, instead of disposing or incinerating the waste in the conventional manner, can maximize the use of raw materials as well as environmental protection. In this regard, it is the most actively studied field in recent years.

Toluene diisocyanate is used as a raw material for producing polyurethanes. Toluene diisocyanate is prepared through the phosgenation reaction of toluenediamine, and the reaction mixture produced by the phosgenation reaction includes a process solvent and reaction intermediates, toluene diisocyanate, hydrogen chloride, phosgene, and side reaction products.

A distillation column is used to separate and purify toluene diisocyanate from the reaction mixture, and a high-boiling residue is discharged from the bottom of the distillation column. This high boiling residue is a tar with some fluidity even at room temperature and contains a significant amount of toluene diisocyanate, side reactants and various impurities. When a considerable amount of toluene diisocyanate remaining in the tar is recovered by vacuum evaporation or thin film evaporation, the tar waste becomes a solid waste. The main component of this waste is toluene diisocyanate oligomer in the form of two or more molecules bonded together, and hydrolyzing it can obtain a significant amount of toluenediamine.

Hydrolysis of tar wastes generated in toluene diisocyanate manufacturing processes is well known. As a method for promoting the hydrolysis, a gas or liquid coexists at a temperature of 350 ° C. or lower, or an aqueous solution state by adding an aqueous solution containing an acid or a base such as an aqueous ammonia solution, an alkaline earth metal hydroxide, an inorganic acid or an organic acid, or the like. A method of advancing a hydrolysis reaction is known. In addition, a low boiling point component such as toluene diisocyanate and the like is reacted using only superheated steam in a temperature range of 200 to 400 ° C. under a low pressure of 1 to 5 atmospheres. There is a method of decomposing the tar using a limited amount of supercritical water or subcritical water near the critical point with respect to the tar contained in a large amount and fluidity at medium or low temperature below 100 ℃.

German Patent Publication No. 2942678, Japanese Patent Application Laid-Open No. 58-201751, and German Patent Publication No. 1962598 disclose that toluene diisocyanate residues and water are preferentially formed in the solid phase very rapidly, and then the reaction proceeds. A batch process is therefore described in which this solid phase is slowly reliquefied. However, the formation of such solid phases can lead to problems that interrupt the continuous operation of the process in carrying out the reaction. In addition, converting the toluenediisocyanate produced through the phosgenation reaction to toluenediamine reduces the economic benefit effect, since the flowable residue containing a large amount of free toluene diisocyanate is used as a raw material.

Korean Patent Laid-Open Publication No. 2001-052948 describes a method of hydrolyzing at a temperature of 170 to 230 ° C. and 25 to 50 atm using a reverse mixing reactor of continuous or semi-continuous type. Hydrolysis reactions under such low and low pressure reaction conditions are undesirable. This is because the mass transfer characteristics such as the penetration and diffusion rate of the decomposition medium are very limited for the solid waste under low and low pressure conditions, and thus the processing time is long and the processing equipment is also enlarged.

U.S. Patent No. 6,255,529 and Korean Laid-Open Patent Publication No. 2001-01488 describe a method using supercritical water or near critical water at high temperature and high pressure conditions close thereto as a medium for hydrolysis reaction.

US Pat. No. 6,255,529 describes a method for hydrolysis of toluene diisocyanate residues using hot water, but according to this method, the economic benefit is inferior since it is a hydrolysis of flowable tar having a high content of free toluene diisocyanate and a catalyst. When not applied to the tar is removed by the thin film evaporation apparatus, such as toluene diisocyanate, such as low boiling point material, there is a disadvantage that the conversion yield to toluene diamine is very low.

Korean Patent Laid-Open No. 2001-01488 describes a method of hydrolyzing under supercritical water at 350-600 ° C. and 218-400 atm using ammonia water as a catalyst, but a part of the toluenediamine produced under high temperature conditions is pyrolyzed. Alternatively, there is a problem in that impurities such as benzenediamine are formed by oxidative decomposition, and since a large amount of ammonia, which is twice the weight of tar, is used as a catalyst, a large amount of catalyst is required, and bicarbonate produced by combining ammonia and carbon dioxide generated during hydrolysis. Ammonium, ammonium carbonate, organic polyamine salts, etc. form complex salt hydrates that can interfere with the continuous operation of the process, contaminate the product during the recovery of toluenediamine, or mix and discharge into the final waste. There is a problem that needs to be removed because it causes secondary environmental pollution. The use of water has the disadvantage that the device becomes larger. In addition, the use of ammonia solution that requires high temperature and high pressure makes it impossible to use expensive special equipment, and plugging due to corrosion caused by using supercritical water and reduced solubility in salts of supercritical water. There is a problem. In particular, the use of ammonia may include ammonia or ammonium salts in wastewater and wastes, which increase the total nitrogen concentration in wastewater and leachate, resulting in environmental pollution.

Apart from the above-mentioned method, the flowable tar containing free toluene diisocyanate is retreated with a thin film evaporation apparatus or a rotary evaporation granulation apparatus at 250 ° C. and 10 mmHg at a high temperature vacuum condition to recover toluene diisocyanate as much as possible. Although there is a method of disposing solid waste by landfilling, incineration, etc., this solid waste may not be a preferable solution because it contains a large amount of useful components that can be converted into toluenediamine by hydrolysis. In particular, industrial waste landfill facilities for landfilling solid wastes are limited, and new disposal technologies are required because ocean dumping is also prohibited internationally.

As described above, the technique of producing toluenediamine using hydrolysis reaction to recycle tar generated in the existing toluene diisocyanate manufacturing process is low reactivity, inadequate due to mass transfer resistance at low temperatures of less than 250 ℃ Salt generation problems due to the use of catalysts, excessive water usage, secondary pollution by nitrogen components in wastewater and waste, prolonged reaction time, and pyrolysis of toluenediamine occurring at high temperatures above 400 ° C. . In addition, existing techniques require that some of the toluene diisocyanate produced in the manufacturing process be converted back to toluenediamine by hydrolysis without sufficiently removing the free toluene diisocyanate contained in the tar to maintain fluidity in the process. There is a waste.

Accordingly, in the present invention, in the process of producing toluene diisocyanate by phosgenating toluene diamine, the solid waste from which free toluene diisocyanate is almost completely removed from the high boiling point residue separated to the bottom of the distillation column by vacuum evaporation, etc. After pretreatment and hydrolysis process using alkali metal hydroxide and alkali metal carbonate as catalysts, toluene diamine used as a raw material of toluene diisocyanate is produced and purified and recovered in high yield to greatly reduce the amount of final waste. Could.

In addition, the present invention has been developed a method for re-recovering and recycling the useful components in the wastewater and waste discharged from the recovery process of toluene diamine to clean the toluene diisocyanate manufacturing process, the present invention was completed based on this.

Accordingly, it is an object of the present invention to provide a method for recovering toluenediamine, a toluene diisocyanate raw material, in a high yield from solid waste discharged from the toluene diisocyanate manufacturing process.

Another object of the present invention is to provide a method for recovering toluenediamine, which can recycle wastewater and catalyst generated in the process of recovering toluenediamine.

In order to achieve the above object, a method for recovering toluene diamine of the present invention may include recovering toluenediamine from solid waste discharged from a toluene diisocyanate manufacturing process, comprising: pulverizing and selecting the solid waste; Preparing a slurry by mixing water and a catalyst with the selected solid waste particles; Pressurizing the slurry to 40 to 250 atmospheres to continuously introduce the slurry into a heat exchanger, and simultaneously cooling the treatment liquid while heating the introduced slurry with the treatment liquid discharged from the reactor; Hydrolyzing the organic particles of the slurry by raising the slurry to a liquid region having an internal temperature of 200 to 370 ° C. or lower than a critical point of water; Cooling the hydrolyzed slurry by heat exchange with the treatment liquid discharged from the reactor, and then lowering the internal pressure to 1 to 30 atmospheres; Flowing the treatment liquid into a distillation column to discharge a mixed gas including gas and water vapor at the upper part thereof, and discharging a mixed liquid of toluenediamine, a catalyst and a high boiling tar to the lower part of the distillation column; And injecting the mixed solution into a reduced pressure evaporator to recover toluenediamine in the upper part and discharging the catalyst and tar mixture in the lower part as waste.

The recovery method of the present invention for achieving another object of the present invention comprises the steps of recovering toluene diamine from the solid waste discharged from the toluene diisocyanate manufacturing process, the step of pulverizing and sorting the solid waste; Preparing a slurry by mixing water and a catalyst with the selected solid waste particles; Pressurizing the slurry to 40 to 250 atmospheres to continuously introduce the slurry into a heat exchanger, and simultaneously cooling the treatment liquid while heating the introduced slurry with the treatment liquid discharged from the reactor; Hydrolyzing the organic particles of the slurry by raising the slurry to a liquid region having an internal temperature of 200 to 370 ° C. or lower than a critical point of water; Cooling the hydrolyzed slurry by heat exchange with the treatment liquid discharged from the reactor, and then lowering the internal pressure to 1 to 30 atmospheres; Introducing the treatment liquid into a distillation column to discharge a mixed gas including a low boiling point organic material, ammonia, and water vapor at the top thereof, and a mixture of toluenediamine, a catalyst, and a high boiling tar at the bottom of the distillation column; Reacting the mixed gas discharged to the top of the distillation column with oxygen in an oxidation catalyst reactor to oxidatively decompose the low boiling point organic material and ammonia contained in the mixed gas; Cooling the mixed gas from which the contaminants have been removed to discharge the separated condensate and gas components; The mixed liquid discharged from the lower part of the distillation column was introduced into a reduced pressure evaporator to recover toluene diamine in the upper part, and the mixed liquid of high boiling tar and catalyst was mixed with the condensate in the lower part, and the filtered solid material was discarded. Transferring to a catalyst mixer for use as a recycle catalyst; And mixing the recycled catalyst transported from the catalyst mixer with the replenished catalyst and water and recycling the catalyst.

1 is a process diagram schematically showing a process for recovering toluenediamine from the solid waste discharged from the toluene diisocyanate manufacturing process according to the present invention.

Figure 2 is a process diagram schematically showing a process for recovering toluenediamine from the solid waste discharged from the toluene diisocyanate manufacturing process according to the present invention, recycling the catalyst and the waste water generated.

※ Explanation of code for main part of drawing ※

10 and 110: solid waste 11 and 111: water

12 and 112 catalyst 13 and 113 mill

14 and 114: sorter 15 and 115: slurry mixer

21 and 121: high pressure pumps 22 and 122: heat exchanger

23 and 123: heaters 24 and 124: reactor

25 and 125: pressure drop valves 31 and 131: distillation column

32 and 132: condenser 33 and 133: gas-liquid separator

34 and 134: exhaust gas 35: wastewater

136: oxygen 137: condensate recovery tank

138: oxidation catalyst reactor 41 and 141: vacuum evaporator

42 and 142: toluenediamine 43 and 143: waste

144 catalyst regenerator 145 catalyst mixer

146: sludge mixer

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

As described above, the present invention relates to a method for recovering toluene diamine, which is a toluene diisocyanate raw material, from the solid waste discharged from the manufacturing process of toluene diisocyanate.

More specifically, the present invention is to recover the toluene diisocyanate contained in the high-boiling tar waste discharged from the bottom of the distillation column in the manufacturing process of toluene diisocyanate again by vacuum evaporation or thin film evaporation process, and finally The solid waste to be discarded is pulverized and hydrolyzed with a catalyst at least one selected from the group consisting of alkali metal carbonates and / or alkali metal hydroxides at a temperature near the critical point of the water and at a pressure above the vapor pressure of the water at this temperature to produce a high yield. It relates to an environmentally friendly process for producing toluenediamine and recycling the generated wastewater and catalyst.

In the recovery method of toluene diamine of the present invention, the solid waste generated in the toluene diisocyanate process is pulverized and selected, mixed with a catalyst and water, etc. to prepare a slurry, pressurizing the prepared slurry, and then hydrolyzing by raising the temperature. Step, after hydrolysis, recovering the toluenediamine produced.

The hydrolysis process is composed of a device for pressurizing the slurry, a heat exchanger for heating the slurry and cooling the high temperature treatment liquid discharged from the reactor, a reactor, a pressure reducing valve, and the like.

The process of recovering toluenediamine produced through the hydrolysis reaction comprises a distillation column for removing gas, water and low-boiling organics, and a reduced pressure distillation column for discharging toluenediamine to the upper portion, and the organic material contained in the excess water It may be added after the removal by the catalytic oxidation reaction to recover, and to recover and reuse the catalyst component from the waste.

In general, in the distillation column of the toluene diisocyanate process, the high boiling tar component generated by the side reaction in the process is discharged from the bottom of the distillation column. This tar component contains from several percent to several ten percent toluene diisocyanate, so it has very low fluidity. Therefore, if the residual toluene diisocyanate is recovered by vacuum evaporation or thin film evaporation method before being discharged as a final waste, it is not solid. And are ground to solid particles having a size distribution of several mm to several cm for transport and landfill or incineration.

As such, the process of the present invention recovers a high yield of toluenediamine from the solid waste discharged from the toluene diisocyanate process.

Referring to FIG. 1, in order to efficiently hydrolyze the solid waste 10, the solid waste 10 is pulverized and sorted in the mill 13 and the sorter 14 to a particle size of 1000 μm or less, preferably 100 μm or less.

The sorted waste is mixed with the hydrolysis reactant water 11 and the catalyst 12 in the mixer 15 into a slurry state. The reaction catalyst is preferably used by selecting one or more from the group consisting of alkali metal hydroxides and alkali metal carbonates that can promote the hydrolysis reaction of organic matter in the solid waste and increase the reaction efficiency without significantly causing process corrosion. , The alkali metal is sodium or potassium. Preferred catalyst for the present invention is sodium carbonate.

In addition, the solid waste content of the slurry is preferably 0.1 to 50% by weight, the catalyst content is 0.1 to 5.0% by weight, preferably 1.0 to 3.0% by weight. The pH of the slurry is preferably maintained at 7 or more, because the hydrolysis reaction is promoted when the hydroxide ion concentration is increased.

The slurry is elevated to a pressure (40 to 250 atm) where water does not become water vapor through the high pressure injection pump 21 and is injected into the hydrolysis process. The temperature of the slurry should be raised to 200 to 370 ° C. for sufficient hydrolysis reaction. For this purpose, the slurry is first heated while passing through the heat exchanger 22 and the final reaction temperature of 200 to 370 ° C. in the heater 23. Is raised. A large amount of thermal energy is required up to the reaction temperature, and energy efficiency can be reduced because heat energy generated from a high temperature treatment liquid discharged from the reactor can be recovered and used as the heat exchanger.

As the reactor for hydrolysis, a cylindrical reactor, a tower reactor, a tubular reactor, a stirred reactor and / or a fluidized bed reactor may be connected in parallel or in series. The said reaction temperature and pressure are 200-370 degreeC and 40-250 atmospheres, Preferably it is 280-320 degreeC and 100-200 atmospheres. The higher the reaction temperature, the faster the reaction rate by improving the mass transfer resistance between the reaction medium and the tar. However, when the temperature is too high, the methyl group of toluenediamine produced by the hydrolysis reaction is thermally decomposed to remove impurities such as benzenediamine. As a result, it may be a factor to lower the product purity of toluenediamine. The average reaction time or residence time of the hydrolysis reaction is 0.1 to 60 minutes, preferably 1 to 5 minutes.

Since the treatment liquid discharged from the reactor after the hydrolysis reaction is completed for a sufficient time in the reactor maintains a high reaction temperature, as described above, the slurry flowing into the heat exchanger 22 is cooled and then cooled and the pressure reducing valve 25 And then the pressure is lowered to the process to recover the toluenediamine produced. Preferably, the hydrolyzed slurry is cooled by heat exchange with the treatment liquid discharged from the reactor and the internal pressure is lowered to 1 to 30 atmospheres.

On the other hand, the toluene diamine recovery apparatus is composed of a distillation column 31 for removing the gas component and water generated in the reaction, and a low boiling point material generated by the side reaction, and a reduced pressure evaporator 41 for recovering toluene diamine. Gas components, water, and low boiling point organic matter to be removed are discharged in a gaseous state from the upper part of the distillation column 31, condensed by the condenser 32, separated into liquid and gas through the gas-liquid separator 33, and finally Discharged.

In addition, toluenediamine having a high boiling point discharged to the bottom of the distillation column 31 is recovered in a gaseous state through a reduced pressure evaporator 41 and commercialized. The catalyst and sludge components remaining after evaporation in the vacuum evaporator are solidified and treated as waste.

The internal pressure of the distillation column 31 is 1 to 5 absolute atmospheric pressure, the internal temperature of the distillation column 31 is preferably 100 to 150 ℃ upper portion, 180 to 250 ℃ lower portion. In addition, the internal pressure and temperature of the reduced pressure evaporator 41 are preferably 0.01 to 1.0 absolute atmospheric pressure and 100 to 320 ° C, which can prevent thermal decomposition of toluenediamine and increase the purification yield.

On the other hand, according to the present invention is shown in Figure 2 a process for recycling water and catalyst components in the wastewater and waste generated after recovering toluenediamine.

Referring to FIG. 2, the solid waste 110 generated in the manufacturing process of toluene diisocyanate is pulverized and sorted through the mill 113 and the sorter 114, and the particle size of the pulverized and sorted solid waste is 1000 μm. Below, Preferably it is 100 micrometers or less. The aqueous solution of the catalyst after the hydrolysis reaction for toluene diamine production is recovered by the catalyst mixer 145 and mixed with water 111 and the catalyst 112, and the selected solid waste is mixed with the catalyst mixture and the slurry mixer 115 In a slurry state. The reaction catalyst, the solid waste content of the slurry, the catalyst content and the pH of the slurry are as described above. Injecting conditions and hydrolysis conditions of the slurry reaction conditions are also the same as the process of recovering the toluenediamine.

In the present invention, the toluene diamine recovery apparatus is composed of a distillation column 131 for removing the gas component and water generated in the reaction, and a low boiling point material generated by the side reaction, and a reduced pressure evaporator 141 for recovering toluene diamine. Gas components to be removed, water, low-boiling organic matter, etc. are discharged in a gaseous state from the top of the distillation column (131). Due to the high temperature of the exhaust gas, pollutants such as low-boiling organics and ammonia may be released together with water vapor and carbon dioxide. Therefore, contaminants of the condensed water can be reduced if a facility for oxidatively decomposing such low boiling point organic matter and ammonia is added.

According to the present invention, the vapor discharged from the top of the distillation column 131 is reacted with the oxygen 136 in the oxidation catalyst reactor 138 to remove the low boiling point organic matter and ammonia. The gaseous components from which the contaminants have been removed are condensed by the condenser 132, and water and gas are separated and discharged through the gas-liquid separator 133. The water condensed in the gas-liquid separator 133 may be used again in the process because the organics have been sufficiently removed. In addition, toluenediamine 142 having a high boiling point discharged from the bottom of the distillation column 131 is recovered in a gaseous state through a reduced pressure evaporator 141 and commercialized. The sludge component remaining after evaporation in the reduced pressure evaporator 141 includes a polymer material and a catalyst component which are not converted to toluenediamine by the hydrolysis reaction. After the residual sludge waste and the water recovered in the gas-liquid separator 133 are mixed in the sludge mixer 146, the catalyst component in the residual sludge is recovered by the catalyst regenerator 144. The recovered catalyst is sent to the catalyst mixer 145, and the remaining sludge component is treated as waste 143.

The internal pressure of the distillation column 131, the internal temperature of the distillation column and the internal pressure and temperature of the reduced pressure evaporator 141 are the same as the recovery process of the toluenediamine.

On the other hand, the oxidation catalyst reactor 138 is a reactor filled with an oxidation catalyst, the oxidation catalyst is an alumina phase on which one to four transition metal oxides are supported; An alumina phase in which at least one precious metal selected from the group consisting of platinum, silver, rhodium, palladium, ruthenium and gold is supported together with the oxide; Or these mixed catalyst can be used.

The present invention will be described in more detail through the following Comparative Examples and Examples, but the scope of the present invention is not limited to the following Examples.

Comparative Example 1

In the chemical process for producing toluene diisocyanate by phosgenating toluene diamine, tar generated as a side reaction was treated for about 1 hour in a rotary evaporation granulation apparatus maintained at 260 ° C. and 10 mmHg to include free toluene diisocyanate. The low boiling point material was removed. The high boiling point residue discharged at this time has a content of free toluene diisocyanate of 500 ppm or less, and is a solid without fluidity at room temperature.

This solid residue was triturated to 100mesh or less and 200g was taken up and dispersed in 600g of water. Water in which the solid residue is dispersed is injected into a continuous reaction apparatus consisting of a preheater and a tubular reactor as shown in FIG. 1, reacted for 1 minute at 400 ° C. and 250 atmospheres, and then quenched to recover a decomposed mixture. And analyzed. As a result, the yield of toluenediamine was 20%.

Comparative Example 2

The reaction was carried out by increasing the reaction time to 5 minutes under the same conditions as in the experiment of Comparative Example 1, and the decomposition mixture was analyzed. As a result, the yield of toluenediamine was 25%.

Comparative Example 3

Under the same conditions as in the experiment of Comparative Example 2, the reaction temperature was adjusted to 460 ° C., and the decomposition mixture was analyzed. As a result, the yield of toluenediamine was 21%, and 1,3-benzenediamine was produced 2%.

Comparative Example 4

Under the same conditions as in the experiment of Comparative Example 1, the reaction was carried out using an aqueous solution of 3% by weight of sodium hydroxide instead of water, and the decomposition mixture was analyzed. As a result, the yield of toluenediamine was 55%. As a result of analyzing the metal element of the decomposition mixture with an inorganic element analyzer, chromium and molybdenum were detected by 30 ppm and 50 ppm, respectively. After completion of the reaction, it was confirmed that salt was deposited in the reactor.

Example 1

Using the same reaction apparatus and high boiling point residue as in Comparative Example 1, 200 g of the high boiling point residue was mixed with 600 g of 5% by weight aqueous sodium carbonate solution and reacted for 1 minute under conditions of 300 ° C and 100 atmospheres. As a result of analyzing the decomposition mixture, the toluenediamine yield reached 75%. As a result of analyzing the metal elements by the same method as that described in Comparative Example 4, metal chromium and molybdenum were detected by 5 ppm and 7 ppm, respectively.

Example 2

Using the same reaction apparatus and high boiling point residue as in Example 1, 200 g of the high boiling point residue was mixed with 600 g of a 3% by weight aqueous solution of sodium carbonate, and then reacted for 1 minute under the conditions of 300 ° C. and 100 atmospheres. Analysis of the degradation mixture yielded a toluenediamine yield of 78%.

Example 3

The decomposition mixture obtained in Example 2 was evaporated in a rotary vacuum evaporator to recover water. Sodium carbonate was added to the recovered water to 3% by weight, and the reaction was carried out in the same manner as in Example 2. However, the reaction time was maintained for 5 minutes, the analysis of the decomposition mixture after the reaction was completed, the toluenediamine yield reached 81%.

Example 4

Using the same reaction apparatus and high boiling point residue as in Example 1, 200 g of the high boiling point residue was mixed with 800 g of a 3% by weight aqueous solution of sodium carbonate, and then reacted for 1 minute under the conditions of 320 ° C. and 100 atmospheres. As a result of analyzing the decomposition mixture, the toluenediamine yield reached 85%. As a result of analyzing the metal elements in the same manner as in Comparative Example 4, metal chromium and molybdenum were detected by 3 ppm and 5 ppm, respectively.

Example 5

Using the same reaction apparatus and high boiling point residue as in Example 1, 200 g of the high boiling point residue was mixed with 800 g of 3% by weight aqueous potassium hydroxide solution, and then reacted for 1 minute under the conditions of 320 ° C. and 100 atmospheres. As a result of analyzing the decomposition mixture, the toluenediamine yield reached 75%.

Example 6

Using the same reaction apparatus and high boiling point residue as in Example 1, 200 g of the high boiling point residue was mixed with 800 g of 3% by weight aqueous solution of cerium carbonate, and then reacted for 1 minute under the conditions of 320 ° C. and 100 atm. As a result of analyzing the decomposition mixture, the toluenediamine yield reached 73%.

Example 7

The water obtained in Example 3 was subjected to a reaction of removing residual organic material and ammonia by oxidizing with oxygen using a fixed bed oxidation catalyst reactor as shown in FIG. 2 at 125 ° C. under atmospheric pressure. As a catalyst, a catalyst having a transition metal oxide supported on alumina was used. The initial concentration of organic matter was 3,000 mg / L on the basis of total organic carbon, and the concentration of ammonia was 2,000 mg / L, and the removal rate was 97% and 94%, respectively.

As described above, toluene diamine, which is a raw material for toluene diisocyanate, is produced from the solid waste generated in the toluene diisocyanate manufacturing process by using a hydrolysis reaction at a temperature and pressure condition near the critical point of water. It can be recovered to about 85% by weight, and recycled to the process can increase the production of toluene diisocyanate. In addition, the process of the present invention can recycle useful components in the wastewater and waste discharged from the process, and can reduce the amount of solid waste by 80 to 95% by weight. The method of the present invention uses alkali metals that do not cause environmental pollution and carbon dioxide generated during the hydrolysis reaction and alkali metal hydroxides that are neutralized and converted into carbonates as catalysts, and thus do not cause total nitrogen problems even in the leachate even when the residual wastes are buried. Furthermore, after removing low-boiling organic matter and nitrogen contained in the discharged waste water, the waste catalyst component discharged is recovered and recycled in the process, thereby fundamentally reducing the generation of harmful waste water and waste and expanding the process recycling rate. It works.

Claims (12)

In the method for recovering toluene diamine from the solid waste discharged from the toluene diisocyanate manufacturing process, Grinding and sorting the solid waste; Preparing a slurry by mixing water and a catalyst with the selected solid waste particles; Pressurizing the slurry to 40 to 250 atmospheres to continuously introduce the slurry into a heat exchanger, and simultaneously cooling the treatment liquid while heating the introduced slurry with the treatment liquid discharged from the reactor; Hydrolyzing the organic particles of the slurry by raising the slurry to a liquid region having an internal temperature of 200 to 370 ° C. or lower than a critical point of water; Cooling the hydrolyzed slurry by heat exchange with the treatment liquid discharged from the reactor, and then lowering the internal pressure to 1 to 30 atmospheres; Flowing the treatment liquid into a distillation column to discharge a mixed gas including gas and water vapor at the upper part thereof, and discharging a mixed liquid of toluenediamine, a catalyst and a high boiling tar to the lower part of the distillation column; And Toluene diamine from the solid waste discharged from the toluene diisocyanate manufacturing process comprising the step of introducing the mixed solution into a reduced-pressure evaporator to recover toluene diamine at the top, and discharge the catalyst and tar mixture as waste at the bottom. How to recover. In the method for recovering toluene diamine from the solid waste discharged from the toluene diisocyanate manufacturing process, Grinding and sorting the solid waste; Preparing a slurry by mixing water and a catalyst with the selected solid waste particles; Pressurizing the slurry to 40 to 250 atmospheres to continuously introduce the slurry into a heat exchanger, and simultaneously cooling the treatment liquid while heating the introduced slurry with the treatment liquid discharged from the reactor; Hydrolyzing the organic particles of the slurry by raising the slurry to a liquid region having an internal temperature of 200 to 370 ° C. or lower than a critical point of water; Cooling the hydrolyzed slurry by heat exchange with the treatment liquid discharged from the reactor, and then lowering the internal pressure to 1 to 30 atmospheres; Introducing the treatment liquid into a distillation column to discharge a mixed gas including a low boiling point organic material, ammonia, and water vapor at the top thereof, and a mixture of toluenediamine, a catalyst, and a high boiling tar at the bottom of the distillation column; Reacting the mixed gas discharged to the top of the distillation column with oxygen in an oxidation catalyst reactor to oxidatively decompose low-boiling point organic matter and ammonia contained in the mixed gas; Cooling the mixed gas from which the contaminants have been removed to discharge the separated condensate and gas components; The mixed liquid discharged from the lower part of the distillation column was introduced into a reduced pressure evaporator to recover toluene diamine in the upper part, and the mixed liquid of high boiling tar and catalyst was mixed with the condensate in the lower part, and the filtered solid material was discarded. Transferring to a catalyst mixer for use as a recycle catalyst; And A method of recovering toluene diamine from the solid waste discharged from the toluene diisocyanate manufacturing process comprising the step of mixing the recycle catalyst and the supplemented catalyst and water transported from the catalyst mixer to recycle the catalyst. The method of claim 1 or 2, wherein the solid waste is pulverized and screened to a particle size of 1000 mu m or less. The method of claim 1 or 2, wherein the catalyst is selected from the group consisting of alkali metal hydroxides and alkali metal carbonates. The method according to claim 4, wherein the alkali metal is sodium or potassium. The process of claim 1 or 2, wherein the solid waste content of the slurry is 0.1-50% by weight and the catalyst content is 0.1-5.0% by weight. The method of claim 1 or 2, wherein the pH of the slurry is at least 7. The method of claim 1 or 2, wherein the reactor is selected from the group consisting of a cylindrical reactor, a tower reactor, a tubular reactor, a stirred reactor and a fluidized bed reactor and connected in parallel or in series. The method according to claim 1 or 2, wherein the average residence time of the reaction liquid in the reactor is 0.1 to 60 minutes. According to claim 1 or 2, wherein the internal pressure of the distillation column is an absolute pressure of 1 to 5, the internal temperature of the top of the distillation column is maintained at 100 to 150 ℃, the internal temperature of the bottom of the distillation column is maintained at 180 to 250 ℃ How to feature. The method of claim 1 or 2, wherein the internal pressure of the reduced pressure evaporator is 0.01 to 1.0 absolute atmospheric pressure, and the internal temperature is 100 to 320 ° C. The oxidation catalyst of claim 2, wherein the oxidation catalyst of the reactor is an alumina phase on which one to four transition metal oxides are supported; An alumina phase on which at least one precious metal selected from the group consisting of platinum, silver, rhodium, palladium, ruthenium and gold is supported together with the oxide; Or a mixed catalyst thereof.