KR100431688B1 - Process for recovering trimellitic acid and catalysts, and apparatus thereof - Google Patents

Abstract

The present invention relates to a method and apparatus for recovering trimellitic acid, which is a catalyst and an intermediate reactant used in an oxidation reaction in trimellitic anhydride manufacturing plant.

According to the present invention, after dissolving the solid trimellitic acid and trimellitic anhydride in water, the impurities are removed by using a filter, and the trimellitic acid is crystallized and the trimellis are separated through solid / liquid separation. The acid and the catalyst can be recovered separately. The recovered trimellitic acid and the catalyst can be recycled to the trimellitic anhydride production process to increase the yield of trimellitic anhydride and reduce the catalyst consumption.

Description

Process and apparatus for recovering trimellitic acid and catalyst {PROCESS FOR RECOVERING TRIMELLITIC ACID AND CATALYSTS, AND APPARATUS THEREOF}

The present invention relates to a method and apparatus for recovering trimellitic acid and a catalyst. More specifically, a method and apparatus for separately recovering and recycling the trimellitic acid, trimellitic anhydride, and catalyst remaining in a solvent evaporator effluent, which is an industrial waste generated in the trimellitic anhydride production process, are recycled. will be.

Oxidation reaction of pseudocumene with oxygen in air under a catalyst such as cobalt, manganese, bromine, and the like to prepare trimellitic acid is disclosed in Korean Patent Publication No. 1992-0009976, US Patent No. 2,833,816, and 4,398,040. No. 4,537,978, 4,835,308, and the like are already disclosed in various patents. Trimellitic anhydride is produced from the reaction intermediate trimellitic acid through additional processes such as solid / liquid separation and dehydration, and acetic acid, which is a solvent, is separated and recovered through evaporation and distillation. However, catalysts do not have an economical and efficient recovery method and are sent to incinerators or wastes with the polymer impurities produced during the oxidation reaction. Since this waste contains a considerable amount of trimellitic acid and trimellitic anhydride, there is a problem that the trimellitic acid yield is lowered.

U.S. Patent No. 4,876,752 discloses a method of dissolving the extract of the lower part of trimellitic anhydride in water, and then recovering the precipitate by precipitating the catalyst. have.

U.S. Patent No. 4,816,601 discloses a method for recovering cobalt and manganese by using oxalic acid from a pseudocumene oxidizer extract, but the recovery of manganese is very low at 47.6% and no bromine is recovered. There is a disadvantage. In addition, when the recovered catalyst is returned to the oxidation reactor, the concentration of oxalic acid in the system is increased to generate various impurities, and also cause serious corrosion problems.

Korean Patent Publication No. 96-28971 and US Patent No. 5,840,643 make a liquid state by adding water to a pseudocumene oxidant extract, and then using a ion exchange resin column filled with a cation resin and an anion resin to prepare a catalyst. It discloses how to collect. In order to recover and recycle the catalyst, the catalyst adsorbed on the cationic and anionic resin has to be withdrawn using hydrochloric acid or sulfuric acid and sodium hydroxide or potassium hydroxide solution, respectively. It is complicated and expensive to separate the catalyst from these strong acid and strong base compounds. This takes In addition, strong acids and strong bases remaining in the separated and recovered catalyst may be concentrated in the trimellitic anhydride manufacturing process system, which may cause many problems.

As described above, the already disclosed prior art has not been put to practical use in commercial production trimellitic acid plants due to lack of technical complexity and economy. In addition, techniques for recovering trimellitic acid and trimellitic anhydride from wastes sent to incinerators or wastewater treatment plants to remove polymer impurities have not been disclosed.

The present invention provides a method for effectively recovering and recycling trimellitic acid, trimellitic anhydride, and catalyst materials from industrial waste containing polymer impurities generated during trimellitic anhydride manufacturing process.

An object of the present invention is to efficiently recover the catalyst used for the pseudocumene oxidation reaction in the trimellitic anhydride production plant and to recover trimellitic acid and trimellitic anhydride contained in the waste.

Another object of the present invention is to provide a new technique which significantly reduces the catalyst consumption in the production of trimellitic anhydride and increases the trimellitic anhydride yield.

1 is a schematic configuration diagram of an apparatus of the present invention.

<Description of Symbols for Main Parts of Drawings>

1, 9: stirrer 2: dissolution tank

3, 7, 11: pump 4, 12: heater

5: 1st filter 6: 2nd filter

8: condenser 10: crystal bath

13 solid / liquid separator 14 catalyst recovery liquid storage tank

The present invention dissolves solid trimellitic acid and trimellitic anhydride in water, and then removes impurities using a filter, and then precipitates trimellitic acid in a crystal bath and solid phase through solid / liquid separation. The present invention relates to a method and a device for separately recovering and recycling a trimellitic acid and a liquid catalyst.

The apparatus of the present invention is a dissolution tank for dissolving trimellitic acid and trimellitic anhydride, one or more filters equipped with an adsorbent for removing impurities, a crystal bath for evaporating the purified solution to precipitate trimellitic acid, and It consists of a centrifuge for separating / liquid.

According to the present invention, the trimellitic acid and the catalyst are separated and recovered by using the above apparatus. In the dissolution tank, water is used as a solvent, and activated carbon is used as an adsorbent of the filter. At this time, it is good to add water to trimellitic anhydride and trimellitic acid based on the mass ratio of 1 to 20: 1. When the input ratio is 1: 1 or less, high temperature and large amount to completely dissolve trimellitic anhydride and trimellitic acid. If energy of 20: 1 or more is required, the size of the dissolution tank becomes large and excessive energy is required to evaporate the solvent in the crystal bath, which is inefficient. In addition, it is preferable to set the concentration ratio of the solvent of the crystal bath [(the amount of solvent introduced into the crystal bath) / (the amount of solvent introduced into the solid / liquid separator)] to 2 to 30: 1. The catalyst is re-introduced into the oxidation reactor and adversely affects the oxidation reaction. If it is 30: 1 or more, the solid concentration becomes high, so that it does not flow well and may cause problems in solid / liquid separation. Hereinafter, the method and apparatus of the present invention will be described in detail with specific examples.

This embodiment will describe a process that uses a particular device and a particular stream of trimellitic anhydride production plant, but this embodiment is not intended to limit the scope of the invention to a particular device and stream. It is added to help the understanding of the present invention. For example, we will describe how to use activated carbon beds and centrifuges for solid / liquid separation, but other types of filters, such as leaf filters, press filters, and belt filters ( Belt Filter or Rotary Vacuum Filters can be used, and it can be replaced by a crystal tank without a stirrer. In addition, although the present invention has been applied to the case of treating the bottom eluate of the Solvent Evaporator in the trimellitic anhydride production process, the present invention can also be used to treat the pseudocumene oxidizer eluate, In addition, various modifications are possible to those skilled in the art.

Some of the devices of the present invention are well known in the art, and a detailed description thereof will be omitted. Hereinafter, the present invention will be described in detail with reference to the drawings.

Referring to Figure 1, the main apparatus of the present invention is composed of a dissolution tank (2), a first filter (5), a second filter (6), a crystal bath (10), a solid / liquid separator (13), 2) and crystal bath 10 are provided with agitators 1 and 9 and heaters 4 and 12, respectively. A transfer pump 3 is connected between the dissolution tank 2, the first filter 5, and the second filter 6, and part of the flow rate of the transfer pump line is recycled to the dissolution tank 2. The first filter 5 and the second filter 6 were operated alternately to allow continuous operation. The first filter 5 and the second filter 6 are connected to the crystal bath 10, the heater 10 is installed in the crystal bath 10 to adjust the temperature. A transfer pump 11 is connected between the crystallization tank 10 and the solid / liquid separator 13 to recycle a portion of the flow rate of the transfer pump line to the crystallization tank 10. The recovery catalyst storage tank 14 is connected to the solid / liquid separator 13 by a pipeline.

Referring to the operation method of the device of the present invention configured as described above are as follows. The bottom extract (A) and water (B) of the solvent evaporator of the trimellitic anhydride manufacturing plant are injected into the dissolution tank (2). The flow rate of water (B) and the temperature of the dissolution tank 2 are adjusted to dissolve the trimellitic acid and trimellitic anhydride in the solid state. The temperature of the dissolution tank 2 is maintained at 50 ° C to 120 ° C using the heater 4. The dissolved solution is injected into the upper portion of the first filter (5), in which undissolved solid polymer impurities and some liquid impurities are removed by the activated carbon layer. The first filter (5) and the second filter (6) is designed in the same way, and filled with activated carbon and the support screen (Support Screen) is mounted on the bottom is designed so that the activated carbon does not leak. The solution from which impurities are removed is sent to the crystal bath 10. When the impurity removal capability of the first filter 5 is lowered, the feed line injected into the upper portion of the first filter 5 is locked and injected into the second filter 6 to be treated. During this time, the first filter 5 is processed. Regeneration of activated carbon As such, two filters are used alternately to proceed continuously. One filter is regenerated while the other adsorbs the impurities. The regeneration method is regenerated using basic aqueous solution (NaOH, KOH or NH 4 OH), water and steam, and the water used for regeneration is sent to a wastewater treatment plant.

The temperature of the crystal bath 10 is maintained at 40 ℃ to 120 ℃ using the heater 12, the pressure of the crystal bath within the range of 0.05 ~ 1.2 kg / ㎠ (a) depending on the temperature so that the solvent evaporates at an appropriate rate It is adjusted to evaporate the solvent water or acetic acid aqueous solution to precipitate trimellitic acid. The temperature of the crystal bath is 40 ° C. and the pressure is 0.05 kg / cm 2 (a) or less, so it is not preferable to maintain excessive vacuum pressure to evaporate the solvent. It is uneconomical because a lot of coolant is required to cool one solvent. The precipitated solution separates the solid and the liquid in the solid / liquid separator 13, and the separated solid material (C) is sent to the dehydration reactor or trimellitic acid crystal bath of the trimellitic anhydride production process. The liquid state catalyst (D) separated from the solid / liquid separator 13 is sent to the pseudocumene reactor through the catalyst recovery liquid storage 14 for recycling.

Hereinafter, the present invention will be described in detail through examples. This example is not intended to limit the scope of the invention as a preferred embodiment of the invention.

(Examples 1 and 2)

The concentration of trimellitic acid in the feed (A) of Example 1 was 75.2% by weight, the concentration of the catalyst was 7.7% by weight, the temperature of the dissolution tank 2 was 95 ° C, and the temperature of the crystal bath 10 was 105 ° C. The flow rate of water (B) relative to the trimellitic acid flow rate was maintained at 10.6: 1. The solvent concentration ratio in the crystal bath was 8.0: 1. Other detailed operating conditions are shown in Table 1.

In Example 2, the temperature of the dissolution tank 2 was 98 ° C., and the flow rate of the water B relative to the flow rate of trimellitic acid was 9.3: 1. The solvent concentration ratio in the crystal bath was 6.0: 1. Other conditions are the same as in Example 1.

The experimental results according to the example are shown in Table 2.

The total recovery of trimellitic acid was found to be 100 x (amount of total trimellitic acid recovered / amount of trimellitic acid introduced), and the catalyst recovery was 100 x [the sum of recovered catalysts (catalysts included in C and D) / Amount of catalyst introduced (catalyst included in A)] was calculated for the cobalt, manganese and bromine catalysts respectively. The impurity removal rate was determined by 100 x [(the amount of impurities contained in the feed (A)-the total amount of impurities in the products C and D) / the amount of the impurities contained in the feed (A)). The amount of solvent added) / (the amount of solvent added to the solid / liquid separator).

Examples Operating Conditions and Performance division Example 1 Example 2 Feed (A) Flow Rate (kg / hr) 11.4 11.4 TMLA ^* Concentration (% by weight) 75.2 75.2 Impurity concentration (% by weight) 17.1 17.1 Catalyst (total) concentration (% by weight) 7.7 7.7 Cobalt (Co) 2.9 2.9 Manganese (Mn) 0.7 0.7 Bromine (Br) 4.1 4.1 Water (B) flow rate (kg / hr) 91.4 80.0 Ratio of water to TMLA 10.6 9.3 Dissolution tank (2) temperature (℃) 95 98 Crystal bath 10 temperature (℃) 105.0 105.0 Solvent concentration ratio 8.0 6.0

TMLA: Trimellitic acid

division Example 1 Example 2 After solid / liquid separation Flow rate (kg / hr) 12.8 14.9 TMLA concentration (% by weight) 19.0 18.8 Catalyst (total) concentration (% by weight) 5.8 5.1 Impurity concentration (% by weight) 0.00 0.00 Solid (C) after solid / liquid separation Flow rate (kg / hr) 8.0 7.9 TMLA concentration (% by weight) 75.8 72.9 Catalyst (total) concentration (% by weight) 1.6 1.5 Impurity concentration (% by weight) 0.04 0.04 Total trimellitic acid recovery (%) 99.0 99.2 Impurity Removal Rate (%) 99.8 99.8 % Catalyst recovery Cobalt (Co) 99.1 99.2 Manganese (Mn) 97.9 98.1 Bromine (Br) 99.5 99.6

As shown in the Examples and Tables, the present invention removes 99.8% of impurities contained in the feed, recovers more than 99% of trimellitic acid, cobalt and bromine catalysts, and the manganese catalyst is about 98%. It can be seen that it can be recovered.

The characteristics of the present invention as described above is to remove impurities by using only water as a solvent without adding chemicals, and to efficiently recover and recycle trimellitic acid and catalyst to reduce the consumption of catalyst and increase the yield of trimellitic anhydride. It works. Application of the present invention can recover expensive catalysts and trimellitic acid that have been discarded so far, thereby preventing environmental pollution as well as economic effects through resource recycling.

Claims (10)

A method for recovering trimellitic acid and a catalyst, comprising the following processes: (A) In the preparation of trimellitic anhydride, the ratio of water to trimellitic anhydride and trimellitic anhydride in a stream containing trimellitic anhydride and trimellitic anhydride and a catalyst is set at a mass ratio of 1 to 20: 1. Adding a step to dissolve trimellitic acid and trimellitic anhydride; (B) removing the impurities by passing the solution through a filter containing an adsorption layer; (C) a step of crystallizing trimellitic acid by adding the solution from which the impurities are removed to a crystal bath and evaporating the solvent at a concentration ratio of 2 to 30: 1 based on a mass ratio; (D) recovering the crystallized solid trimellitic acid and a liquid catalyst through solid / liquid separation, respectively. The method for recovering trimellitic acid and the catalyst according to claim 1, wherein activated carbon is used as an adsorbent for impurities. The method for recovering trimellitic acid and the catalyst according to claim 2, wherein the temperature of the dissolution tank (2) is maintained at 50 to 120 ° C and the temperature of the crystal bath (10) is 40 to 120 ° C. [4] The trimellitic acid and the catalyst according to claim 3, wherein the dissolution tank 2 uses water as a solvent and a ratio of water to trimellitic anhydride and trimellitic acid is 1-20: 1 by mass ratio. Recovery method. The method for recovering trimellitic acid and the catalyst according to claim 4, wherein the concentration ratio of the solvent in the crystal bath 10 is 2 to 30: 1 based on the mass ratio. The method according to any one of claims 1 to 5, wherein the recovered catalyst is sent to a pseudocumene oxidation reactor for reuse, and the recovered trimellitic acid is converted to a trimellitic acid crystal tank of a trimellitic anhydride production plant, or A method for recovering trimellitic acid and a catalyst, which is sent to a trimellitic acid dehydration reactor to increase the trimellitic acid yield. It consists of a dissolution tank (2), one or a plurality of filters (5, 6), a crystal bath (10), a solid / liquid separator (13), wherein the dissolution tank (2) has a stirrer (1) and a heater (4) The installed trimellitic acid is dissolved in water, and the dissolved trimellitic acid is filled with activated carbon through a transfer pump 3 connected to the lower part of the dissolution tank 2, or a first filter 5 or a second filter ( 6) is filtered, and the solution from which impurities are removed from the filter is transferred to a crystal bath 10 in which a stirrer 9 and a heater 12 are installed to evaporate water to precipitate trimellitic acid, and then the precipitate. The silver treatment tank recovering apparatus for trimellitic acid and catalyst characterized in that the transfer to the solid / liquid separator (13) using a transfer pump (11) in the lower part of the crystal tank to separate the solid and the liquid. 8. The treatment apparatus for recovering trimellitic acid and catalyst according to claim 7, wherein the dissolution tank (2) is omitted and the liquid reactant from the pseudocumene oxidation reactor is treated. The filter of claim 7, wherein the first filter 5 and the second filter 6 are designed in the same manner, and the bead is injected into the upper part of the first filter 5 when the impurity removal capability of the first filter 5 is lowered. (Feed) The first filter (5) and the second filter (6) are alternated by closing the (Feed) line, injecting it into the second filter (6) and treating it, and regenerating activated carbon of the first filter (5). Retrieval treatment apparatus for trimellitic acid and catalyst characterized in that the continuous operation to enable the operation. 8. The apparatus for recovering trimellitic acid and catalyst according to claim 7, wherein the solid / liquid separator (13) uses centrifuges or rotary vacuum filters.