JP2008272584A - Method of treating catalyst with degraded resolution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of treating a catalyst capable of reusing a catalyst supporting noble metal with a degraded resolution used in decomposition of a high concentration organic chlorine compound free of deterioration oil. <P>SOLUTION: The method of treating catalyst capable of reusing the catalyst with degraded resolution in decomposition processing of circulating a mixed liquid of organic chlorine compound, alkali metal hydroxide and isopropyl alcohol in a catalyst column, and making the liquid contact with the catalyst supporting noble metal to decompose the organic chlorine compound, includes the step of cleaning the catalyst with degraded resolution with isopropyl alcohol and of cleaning the cleaned catalyst with water, and is characterized by drying the catalyst after cleaning with water. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is a method for treating a catalyst that enables the reuse of a catalyst with reduced resolution, and in particular, by the decomposition of high-concentration organochlorine compounds (ie, low-concentration organochlorine compounds in oil do not apply). The present invention relates to a method for treating a catalyst capable of reusing a noble metal-supported catalyst having a reduced resolution.

  Among various organic chlorine compounds, polychlorinated biphenyl (hereinafter sometimes abbreviated as PCB) is extremely harmful to living organisms including the human body. Therefore, it was designated as a specified chemical substance in 1973, and its production, importation, Use is prohibited. However, after that, tens of thousands of tons of PCBs are left untreated without determining an appropriate disposal method. In view of the fact that PCB is a by-product of chlorinated dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF) which are highly toxic dioxins in high temperature decomposition, it is difficult to technically decompose PCB safely. A safe and efficient method for disassembling PCBs is desired.

  Against this background, many methods for dechlorinating organochlorine compounds such as PCB are known. Among them, as a method that can be decomposed at a low temperature and in a short time, microwaves are added in the presence of a catalyst in which a hydrogen donor and an alkali compound are added to an insulating oil containing PCB or low-concentration PCB, and palladium is supported on activated carbon. A method for efficiently decomposing PCB by irradiation is disclosed (Patent Documents 1, 2, etc.).

  However, repeated decomposition degrades the catalyst and decreases its activity. On the other hand, regeneration of degraded carbon-based noble metal catalysts has proven difficult. In particular, in the case of a catalyst used for the decomposition treatment of PCB contained in insulating oil, deteriorated oil, insulating oil additives (oxidizer, etc.) and their decomposition products adhere to the surface and block the active site of the catalyst. Therefore, the regeneration method is limited to a method such as washing the catalyst surface by liquid treatment.

  Conventionally, various methods have been proposed as a method for regenerating a carbon-based catalyst on which a noble metal is supported (Patent Documents 3 to 7), but these methods are used in the case of a general hydrogenation catalyst (Patent Documents 3 to 5). ) And PCB dechlorination catalysts (Patent Documents 6 to 7) are mainly treated by washing the catalyst by liquid treatment.

  In Patent Document 3, the activity decreasing catalyst used for hydrogenating diacetoxybutene to produce diacetoxybutane is treated with steam or warm water at 40 to 150 ° C.

  In Patent Document 4, a hydrogenation catalyst for hydrocracking trialkoxypropane is treated in a medium composed of an acid having a pKa value of less than 6, and it is washed with water, methanol or ethanol.

  In patent document 5, the deterioration catalyst used at the time of carboxylic acid ester manufacture is processed at the temperature of 0-100 degreeC for 0.1 to 50 hours in presence of reducing agents, such as methanol, ethanol, and hydrazine.

In Patent Document 6, the activity-reducing catalyst used in the PCB dechlorination treatment in the insulating oil is washed with a cleaning agent to remove the neutralized salt between the detached chlorine and alkali, thereby increasing the catalytic activity. I am returning. Moreover, in patent document 7, after wash | cleaning the activity fall catalyst used for the dechlorination process of PCB in insulating oil, solvent extraction is performed, and the catalytic activity is returned by further reducing.
Japanese Patent No. 3678740 Japanese Patent No. 3678738 JP-A-10-202106 (Claim 1 etc.) JP-A-9-141094 (Claim 1 etc.) Japanese Patent Laid-Open No. 9-253489 (Claim 1 etc.) JP 2005-270837 A (Claim 1 etc.) Japanese Patent Application No. 2005-307587 (Claims 1-2)

  However, the catalyst regenerated by the above method, for example, the catalyst regenerated by the method proposed in Patent Document 6, showed good results in the simulated oil test, but was subjected to a cracking test of real oil containing low-concentration PCB. The recovery degree of the resolution of the activity-reducing catalyst was up to about 70% of the new product. As described above, the catalyst used for the low-concentration PCB decomposition treatment contained in the insulating oil is affected by the oil, so that it is extremely difficult to recover the resolution to 100%.

  On the other hand, since the noble metal-supported catalyst used for the decomposition treatment is expensive, it is practically indispensable to reuse the catalyst as many times as possible in order to reduce the decomposition treatment cost of the organic chlorine compound. Further, experience has shown that the PCB decomposition treatment is easier to decompose in the high concentration PCB than in the low concentration PCB contained in the oil.

  Therefore, in the case of high-concentration PCB decomposition treatment in which no deteriorated oil is present, it is necessary to study the reuse of the catalyst from a viewpoint different from the low-concentration decomposition treatment. However, since the concept of using a catalyst with a high activity as little as possible has been established, there have been many studies on improving the activity of the catalyst and reducing the amount of use, but the point of reusing it even once. Is currently not being considered.

  The present invention has been made in view of the above circumstances, and a method for treating a catalyst that enables reusability of a noble metal-supported catalyst with reduced resolution used in the decomposition of a high-concentration organochlorine compound that does not contain deteriorated oil. It is an issue to provide.

  The present inventors diligently studied to solve the above problems. As a result, unlike the decomposition treatment of low-concentration PCB mixed in insulating oil, there is no deteriorated oil that becomes a catalyst activity inhibiting factor in the decomposition treatment of specific high-concentration PCB. Therefore, PCB, biphenyl, inorganic matter, etc. on the catalyst surface It has been found that the catalyst can be reused as if it were a new product even by simply removing the catalyst.

  In addition, since the above-mentioned catalyst treatment method uses isopropyl alcohol and water, it is safe and can be used in the field; the liquid after washing is relatively easy to collect; Although it is expensive, the precious metal is reused, so even if a large amount of catalyst is used, there is no problem in economic efficiency, and there is an advantage that the decomposition process of PCB can be industrially advantageous. Based on this, the present invention has been completed.

That is, the present invention is as follows.
1) In a decomposition process in which a mixed liquid of an organic chlorine compound, an alkali metal hydroxide and isopropyl alcohol is passed through a catalyst column and brought into contact with a catalyst having a noble metal supported on a carrier to decompose the organic chlorine compound.
A method of treating a catalyst that enables reuse of a catalyst with reduced resolution,
Washing the catalyst with reduced resolution with isopropyl alcohol, and washing the washed catalyst with water,
A method for treating a catalyst, comprising drying the catalyst after washing with water.
2) The method for treating a catalyst according to 1) above, wherein a step of washing the catalyst after washing with isopropyl alcohol with a hydrocarbon solvent is provided.
3) The method for treating a catalyst according to 2) above, wherein a step of replacing the catalyst washed with the hydrocarbon solvent with an aqueous organic solvent is provided.
4) The method for treating a catalyst according to any one of 1) to 3), wherein in the washing step with isopropyl alcohol, water, and a hydrocarbon solvent, a washing treatment is performed to such an extent that the catalyst does not collapse.
5) The method for treating a catalyst according to any one of 1) to 4) above, wherein the temperature of the cleaning agent in the cleaning step is from room temperature to 60 ° C.
6) The method for treating a catalyst according to any one of 1) to 5) above, wherein the noble metal is palladium.
7) The method for treating a catalyst according to any one of 1) to 6) above, wherein the support is selected from the group consisting of carbon, a resin, and a combination thereof.
8) The catalyst according to any one of 1) to 7) above, wherein the organic chlorine compound is an organic chlorine compound selected from the group consisting of PCBs, dioxins, aromatic chlorine compounds, and mixtures of two or more thereof. Processing method.

  According to the catalyst treatment method of the present invention, a reusable catalyst having performance equivalent to or better than that of a new product can be obtained. Therefore, by reusing the catalyst, it is possible to reduce the cost of the catalyst, and thus the decomposition treatment cost of the high concentration organochlorine compound.

In the method for treating a catalyst according to the present invention, a mixed liquid of an organochlorine compound, an alkali metal hydroxide and isopropyl alcohol is passed through a catalyst column and brought into contact with a catalyst having a noble metal supported on a carrier to decompose the organochlorine compound. In the decomposition process,
A method of treating a catalyst that enables reuse of a catalyst with reduced resolution,
The method includes a step of washing the catalyst with reduced resolution with isopropyl alcohol and a step of washing the washed catalyst with water, and drying the catalyst after washing with water.

  Here, examples of the organic chlorine compound include PCB; dioxins; aromatic chlorine compounds such as trichlorobenzene and dichlorobenzene, and organic chlorine compounds selected from the group consisting of a mixture of two or more thereof.

  Examples of organochlorine compounds include those that are filled or stored in pole transformers, large transformers, OF cable insulating oil tanks, ballasts, and the like.

  Alkaline is added to the mixed solution to capture chlorine desorbed from the organic chlorine compound, but it has high dechlorination efficiency, is available at low cost, is easy to handle, and dissolves in isopropyl alcohol. From the viewpoint of excellent properties, alkali metal hydroxides such as NaOH and KOH are used. An alkali metal hydroxide may be used independently and may use 2 or more types together.

  In addition, a hydrogen donor is added to the mixed solution, but it is highly safe, can be obtained at low cost, has high decomposition efficiency of the organic chlorine compound, is easy to control the reaction, and is hardly decomposed PCB. Isopropyl alcohol is preferably used because of its high decomposition efficiency.

  Any compound other than isopropyl alcohol can be used in combination with isopropyl alcohol as long as the effect of the present invention is not impaired as long as the compound can donate a hydrogen atom to a radical generated from an organic chlorine compound. Examples of such hydrogen donors include heterocyclic compounds, amine compounds, alcohol compounds, ketone compounds, and alicyclic compounds.

  The amount of alkali metal hydroxide and isopropyl alcohol used for the decomposition treatment is not limited, but usually alkali metal hydroxide is 1.0 to 1.5 equivalents in terms of chlorine to organochlorine compound, and isopropyl alcohol is organochlorine. It is preferable to use 5 to 50% by volume with respect to the compound. The alkali metal hydroxide is preferably used in an amount of 0.1 to 50% (wt / vol), more preferably 0.1 to 10% (wt / vol) with respect to isopropyl alcohol. If the amount of the alkali metal hydroxide is too small, the decomposition reaction does not proceed. On the other hand, if the amount is too large, the alkali metal hydroxide cannot be completely dissolved in isopropyl alcohol.

  As a decomposition method, a known method can be applied, for example, a method of leaving at normal temperature and normal pressure and decomposing at normal temperature to 80 ° C., a method of decomposing at 50 to 200 ° C. by irradiating with microwaves, and the like. Can be mentioned.

  The catalyst in which the noble metal is supported on the carrier is not particularly limited as long as it can accelerate the dechlorination reaction of the organic chlorine compound. The supported amount of the noble metal in the catalyst is preferably 1 to 20% by mass, more preferably 5 to 10% by mass with respect to the total amount of the catalyst. Examples of the noble metal to be supported include palladium, ruthenium, palladium, rhodium, iridium, osmium and platinum. In consideration of high dechlorination efficiency, palladium, ruthenium and platinum are preferable, and palladium is particularly preferable.

  Any carrier can be used as long as it is generally used as a carrier for a noble metal catalyst. Specifically, a carrier having excellent alkali resistance such as carbon such as activated carbon generally used as an adsorbent; resin such as silicone resin, polyethylene resin and polystyrene resin; metal oxide or composite metal oxide; It is done. Among these carriers, carbon and resin are preferable because of high microwave absorption, and carbon is particularly preferable.

  Specific examples of catalysts in which a metal is supported on a carbon support include Pd / C (palladium-supported carbon compound), Ru / C (ruthenium-supported carbon compound), Pt / C (platinum-supported carbon compound), and the like. .

  The catalyst may be granular or honeycomb. The catalyst particle diameter is preferably 75 μm to 5 mm, and if it exceeds 5 mm, handling becomes worse, and if it is less than 75 μm, clogging tends to occur when packed in a column or the like. More preferably, it is 150 μm to 3 mm.

  The catalyst to be treated is an organic chlorine compound decomposed by adding an alkaline substance and a hydrogen donor to a high-concentration organochlorine compound, passing the mixed solution through the catalyst column, and contacting the catalyst. It was used at the time. The timing of treating the catalyst can be grasped by occurrence of clogging of the catalyst column, or by a method such as measuring the concentration of the organochlorine compound in the reaction solution using a known organochlorine compound analyzer such as GC-MS.

  In the catalyst treatment method of the present invention, the deteriorated catalyst with reduced resolution is washed with isopropyl alcohol at room temperature to 60 ° C., and an organic chlorine compound, alkali, inorganic salt (reaction product of chlorine and alkali: NaCl, KCl), Deposits on the catalyst surface such as biphenyl (reactive decomposition product of PCB) are removed. If the washing temperature is too low, the inorganic salt crystallizes and is difficult to remove. In addition, by washing with isopropyl alcohol, even when the undecomposed organochlorine compound is transferred to the cleaning liquid, it can be used as a reaction solvent when the cleaning liquid is decomposed, so that unnecessary separation and recovery operations are not required. .

  Then, water washing with water, warm water or steam is performed to remove inorganic salts and unreacted alkali attached to the catalyst. The water washing is preferably performed until the pH of the washing liquid becomes neutral in order to remove the alkali adhering to the catalyst surface.

  On the other hand, when isopropyl alcohol cleaning is performed after water cleaning, the catalyst cannot be treated to the extent that it can be reused. The reason for this is presumed to be that inorganic salts supplemented by decomposition products such as biphenyl remain. Furthermore, in the case of first water washing, the processing operation of the undecomposed organochlorine compound transferred to the washing liquid becomes complicated.

  On the other hand, in the case of only isopropyl alcohol cleaning, the catalyst cannot be treated to the extent that it can be reused. The reason is considered to be that the dechlorination reaction on the catalyst surface is inhibited because the effect of removing the inorganic salt adhering to the catalyst surface is not sufficient.

  After the isopropyl alcohol cleaning, in order to more effectively remove biphenyl adhering to the catalyst surface, it is preferable to perform cleaning with a hydrocarbon solvent such as n-hexane, cyclohexane, toluene, xylene, cumene and the like. An aqueous solvent such as acetone can be used for the purpose of replacing the hydrocarbon solvent on the surface of the catalyst before washing with water. When the cleaning with the hydrocarbon solvent is performed before the isopropyl alcohol cleaning, it is not optimal as a reaction solvent when decomposing the undecomposed organochlorine compound transferred to the cleaning liquid.

  The cleaning method includes a batch method and a continuous method, and is not particularly limited, and an appropriate method can be used. When washing in batch mode, a known method such as mixing and stirring the catalyst and the cleaning agent, and then separating the catalyst by decantation, centrifugation, or filtration can be used. In the case of washing in a continuous manner, a known method such as washing by circulating a cleaning agent through a catalyst column packed with a catalyst and circulating the cleaning agent can be used. At the time of washing, it is preferable to carry out washing by a method such as adding gentle stirring that does not cause the catalyst to collapse, or passing the washing agent through the column at a low flow rate.

  The amount of the cleaning agent used for cleaning the catalyst varies depending on the type of cleaning agent, the cleaning method, etc., but in each cleaning step, the cleaning agent (volume) / catalyst (weight) = 2/1 to 50/1, more preferably 2. It is better to use at a ratio of / 1 to 20/1. The washing time is not particularly limited, but is usually about 1 minute to 5 hours. In each cleaning step, cleaning may be performed only once, or may be performed in multiple steps.

  After washing with water, the catalyst is dried. Drying conditions are preferably conditions that allow moisture to be removed without altering the catalyst, and are usually dried at a temperature of 70 to 120 ° C. for 2 to 24 hours. If the drying temperature is too low, moisture removal is insufficient.

  The catalyst obtained by the treatment method of the present invention is obtained by contacting the above-described mixed liquid of an organic chlorine compound, an alkali metal hydroxide and isopropyl alcohol with a catalyst in which a noble metal is supported on a carrier through a catalyst column. It can be reused in the decomposition process for decomposing organochlorine compounds.

  In addition, by performing this decomposition treatment using at least two catalyst columns, the catalyst treatment can be performed in the other catalyst column while the organic chlorine compound is being decomposed in one catalyst column. Even if the decomposition reaction does not proceed, the decomposition process can be continued continuously without disassembling the apparatus.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely using an Example and a comparative example, this invention is not limited only to a following example.

(PCB decomposition test)
To 3.9 ml of a mixed solution of polychlorobiphenyl tetrachloride (KC400) and trichlorobenzene (TCB) (mixing ratio 6: 4), 146.1 ml of isopropyl alcohol as a hydrogen donor and 5.98 g (1.2 equivalents) of an alkaline substance ) Was added to obtain a PCB 3% treatment solution. The column was filled with 24 g of new Pd / C (0.425 to 1.7 mm activated carbon carrying 5% palladium), and a simple microwave reactor (temperature control type ZMW-024) manufactured by Shikoku Keiki Kogyo Co., Ltd. The temperature was maintained at 60 ° C. while irradiating microwaves with a mold, and the reaction was conducted while circulating test oil at a rate of 10 ml / min. The time course of PCB concentration in the reaction oil was analyzed by GC-MS (QP5050A) manufactured by Shimadzu Corporation using DB5MS as a capillary column. The time required for the PCB concentration to reach 0.5 ppm was 8 hours.

  Further, when the above decomposition test was repeated, the catalyst was clogged in the third decomposition test, so the test was stopped halfway.

[Example 1]
(Washing process)
The above decomposition test was repeated three times, and 24 g of 5% Pd / C catalyst (hereinafter referred to as deteriorated catalyst) with clogging was sampled and washed in 12 g increments by the following method.
To 12 g of the deteriorated catalyst, 50 ml of isopropyl alcohol (IPA) was added and gently stirred at room temperature for 1 minute to wash the PCB adhering to the catalyst.
After removing IPA by suction filtration, 50 ml of hexane was added to the catalyst, and gently stirred at 40 ° C. for 1 minute to wash biphenyl. After removing hexane by suction filtration, 50 ml of acetone was added to the catalyst and stirred gently at room temperature for 1 minute to replace the hexane remaining on the catalyst with acetone. After removing acetone by suction filtration, the process of adding 50 ml of pure water and gently stirring and washing at room temperature for 1 minute was repeated 3 times. After removing pure water by suction filtration, it was dried at 80 ° C. for 5 hours.
By these operations, 11.7 g of a regenerated catalyst was obtained.

(PCB decomposition performance test)
Evaluation of PCB decomposition performance of the obtained regenerated catalyst (about 24 g) was performed under the same conditions as in the above PCB decomposition test. As a result, the arrival time until the PCB concentration of the first treatment liquid reached 0.5 ppm was 12 hours. Further, when the above decomposition test was repeated, the catalyst was clogged in the fourth decomposition test, so the test was stopped halfway.

  From the above test results, it was found that by regenerating a catalyst having decreased activity by the method of the present invention, the catalytic ability can be restored to the extent that it can be reused in the decomposition test of organochlorine compound (PCB). In particular, it was found that the cleaning method using the organic solvent and pure water in Example 1 can restore the catalytic ability to the same level as that of a new product.

  According to the method for treating a catalyst of the present invention, a new or higher catalyst can be obtained from a deteriorated catalyst, so that the cost for decomposing various PCBs and dioxins can be obtained by using them for decomposing high-concentration organochlorine compounds. To make it possible to use industrially.

Claims (8)

In a decomposition treatment in which a mixed liquid of an organic chlorine compound, an alkali metal hydroxide and isopropyl alcohol is passed through a catalyst column and contacted with a catalyst having a noble metal supported on a carrier to decompose the organic chlorine compound,
A method of treating a catalyst that enables reuse of a catalyst with reduced resolution,
Washing the catalyst with reduced resolution with isopropyl alcohol, and washing the washed catalyst with water,
A method for treating a catalyst, comprising drying the catalyst after washing with water.   The method for treating a catalyst according to claim 1, further comprising a step of washing the catalyst after washing with isopropyl alcohol with a hydrocarbon solvent.   The method for treating a catalyst according to claim 2, further comprising a step of replacing the catalyst washed with the hydrocarbon solvent with an aqueous organic solvent.   The method for treating a catalyst according to any one of claims 1 to 3, wherein in the washing step using isopropyl alcohol, water and a hydrocarbon solvent, a washing treatment is performed to such an extent that the catalyst does not collapse.   The processing method of the catalyst in any one of Claims 1-4 whose temperature of the cleaning agent in a washing | cleaning process is room temperature-60 degreeC.   The method for treating a catalyst according to any one of claims 1 to 5, wherein the noble metal is palladium.   The method for treating a catalyst according to any one of claims 1 to 6, wherein the support is selected from the group consisting of carbon, a resin, and a combination thereof.   The method for treating a catalyst according to any one of claims 1 to 7, wherein the organic chlorine compound is an organic chlorine compound selected from the group consisting of PCBs, dioxins, aromatic chlorine compounds, and mixtures of two or more thereof. .