JP2006307373A - Method for preparing active carbon fiber for desulfurization catalyst and active carbon fiber for desulfurization catalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for preparing an active carbon fiber for a desulfurization catalyst having high desulfurization efficiency and long activity life and to provide the active carbon fiber for the desulfurization catalyst obtained by the method. <P>SOLUTION: The method for preparing the active carbon fiber for the desulfurization catalyst is characterized as follows. The active carbon fiber is dipped in a metal solution controlled at a low pH value and sufficiently impregnated with the metal solution. The active carbon fiber is then washed and dried to thereby afford the active carbon fiber for the desulfurization catalyst in which the amount of the discharged metal is reduced in use as the catalyst without reducing the surface area of the active carbon fiber. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to sulfur oxide (SOx) contained in exhaust gas discharged from various incinerators such as municipal waste incinerators, industrial waste incinerators, sludge incinerators, melting furnaces, boilers, gas turbines, engines and the like. The present invention relates to a method for preparing activated carbon fibers for a desulfurization catalyst for removing water and the activated carbon fibers for a desulfurization catalyst obtained by the method.

Conventionally, as an apparatus for removing SOx in exhaust gas, SOx in exhaust gas is adsorbed on activated carbon fiber, and the sulfur component is oxidized by oxygen contained in the exhaust gas by utilizing the catalytic action of the activated carbon fiber. It has been proposed to remove the activated carbon fiber from the activated carbon fiber by absorbing it into moisture (Patent Document 1). In the exhaust gas treatment apparatus using activated carbon fiber, an activated carbon fiber tank for adsorbing SOx in the exhaust gas is disposed in the adsorption tower, and the exhaust gas is supplied from below to make SO ₂ on the surface of the activated carbon fiber. The SO ₃ is oxidized to SO ₃ and the generated SO ₃ reacts with the water supplied into the tower to produce sulfuric acid (H ₂ SO ₄ ).

  Considering the case where exhaust gas from a boiler that burns fuel such as coal or heavy oil is processed by the exhaust gas processing device, the amount of these exhaust gases is enormous, and therefore it is necessary to improve the desulfurization efficiency of the exhaust gas processing device. In order to increase the desulfurization efficiency, it is necessary not only to increase the size of the apparatus but also to improve the desulfurization efficiency of the activated carbon fiber itself used as a catalyst.

  On the other hand, a method for improving the desulfurization efficiency of the activated carbon fiber by adding a metal material to the activated carbon fiber has been proposed (Patent Document 2). In this method, the method of adding the metal material to the activated carbon fiber is not limited. For example, the method of impregnating the activated carbon fiber with a metal raw material as a solution, the method of adding the metal powder to the activated carbon fiber by spraying, etc. Examples include a method of firing together with a bulk body (solid) of a metal or a metal compound at the time of heat treatment, a method consisting of a metal added with a container or a furnace part, and a method of transferring a metal to a fiber at the time of heat treatment of activated carbon fiber. Yes. In this document 2, as a specific example of a method for adding a metal material to the activated carbon fiber, the activated carbon fiber is immersed in an aqueous solution of each metal of Cr, Fe, Ag, Pt, Ir, Pd, Mn, and Ni. After that, an example in which the desulfurization efficiency is almost doubled by firing in a nitrogen atmosphere is disclosed.

  In addition, activated carbon fibers used for the purpose of removing nitrogen oxides (NOx) from gases such as the atmosphere instead of desulfurization have been proposed (Patent Document 3). A copper compound composed of metallic copper and copper oxide is attached to the activated carbon fiber. As a method for preparing this activated carbon fiber, activated carbon fiber is immersed in an aqueous solution of copper salt, and a basic aqueous solution is added to the aqueous solution of copper salt to attach copper hydroxide to the activated carbon fiber. A method of treating carbon fiber at a temperature of 600 to 800 ° C. in an inert gas atmosphere is disclosed.

JP 11-347350 A JP 2004-66009 A JP-A-5-103986

  The method for preparing activated carbon fibers disclosed in Patent Document 2 discloses a method in which activated carbon fibers are immersed in a metal aqueous solution and then heat-treated. However, more detailed treatment conditions are not disclosed, and the method is simple. In addition, the desulfurization efficiency of the activated carbon fiber obtained according to this method varies from product to product and lacks performance stability. Therefore, an improved method for preparing activated carbon fibers capable of obtaining stable desulfurization efficiency characteristics is desired.

  Further, in the method for preparing activated carbon fibers disclosed in Patent Document 3, copper hydroxide fine particles formed by adding alkali to an acidic copper aqueous solution are precipitated on the activated carbon fibers, and the copper hydroxide fine particles are obtained. Therefore, copper does not enter the fiber micropores, but is attached to the fiber surface, and the copper hydroxide particles added by precipitation may block the fiber micropores. There is a risk of reducing the fiber surface area, which is an important requirement. As a result, the copper compound particles are easily peeled off from the activated carbon fibers, and the effect of the adhering metal (in this case, the denitration efficiency) is lowered relatively early, and the denitration efficiency is lowered due to the reduction in the surface area. In some cases.

  The present invention has been made in view of the above circumstances, and its purpose is to further improve the desulfurization efficiency and extend the active life in the activated carbon fiber in which the desulfurization efficiency is improved by adding metal. There is to plan. That is, an object of the present invention is to provide a method for preparing activated carbon fibers for a desulfurization catalyst having a high desulfurization efficiency and a long active life, and an activated carbon fiber for a desulfurization catalyst obtained by the method.

In order to solve the above-described problems and achieve the object, the method for preparing activated carbon fibers for a desulfurization catalyst according to claim [1] of the present invention immerses the activated carbon fibers in a metal solution controlled to a low pH value. Then, after the activated carbon fiber is sufficiently impregnated with the metal solution, the activated carbon fiber is washed and dried to reduce the surface area of the activated carbon fiber without reducing the surface area of the activated carbon fiber. It is characterized by obtaining an activated carbon fiber for a desulfurization catalyst whose amount is reduced.
The dried activated carbon fiber is preferably further heat-treated in an inert atmosphere. By the heat treatment (baking) in the inert atmosphere, the adhesion of the adhered metal to the fibers can be enhanced.

  The method for preparing activated carbon fibers for a desulfurization catalyst according to claim [2] of the present invention is the method for preparing activated carbon fibers for a desulfurization catalyst according to claim [1], wherein the metal solution is sufficient for the activated carbon fibers. After impregnating with the activated carbon fiber, an alkali is added to the metal solution to precipitate and settle a metal compound in the solution, and then the activated carbon fiber is washed and dried, thereby further supporting the amount of metal on the activated carbon fiber. It is characterized by increasing.

  The method for preparing activated carbon fibers for a desulfurization catalyst according to claim [3] of the present invention adjusts the metal content of the metal solution in the method for preparing activated carbon fibers for a desulfurization catalyst according to claim [2]. Thus, the amount of the metal compound supported on the activated carbon fiber is controlled.

  The method for preparing activated carbon fibers for desulfurization catalyst according to claim [4] of the present invention is the method for preparing activated carbon fibers for desulfurization catalyst according to any one of claims [1] to [3]. After immersing the activated carbon fiber in the metal solution, the activated carbon fiber is sufficiently immersed in the activated carbon fiber by placing the metal solution in a reduced pressure environment while immersing the activated carbon fiber. It is characterized by making it.

  The method for preparing activated carbon fiber for desulfurization catalyst according to claim [5] of the present invention is the method for preparing activated carbon fiber for desulfurization catalyst according to claim [2] or [3], wherein alkali is added to the metal solution. In addition, after depositing and precipitating the metal compound in the solution, the metal solution is placed in a reduced pressure environment while the activated carbon fiber is immersed, whereby the deposited particles of the metal compound are applied to the activated carbon fiber. It is characterized by ensuring attachment.

  The method for preparing activated carbon fibers for a desulfurization catalyst according to claim [6] of the present invention is the method for preparing activated carbon fibers for a desulfurization catalyst according to any one of claims [1] to [5]. The metal supported on the activated carbon fiber is Fe.

  Claim [7] of the present invention relates to activated carbon fiber for desulfurization catalyst, and this activated carbon fiber for desulfurization catalyst is activated carbon for desulfurization catalyst according to any one of claims [1] to [6]. It was obtained by the fiber preparation method.

  Claim [8] of the present invention relates to an activated carbon fiber for a desulfurization catalyst. The activated carbon fiber for a desulfurization catalyst is obtained by immersing the activated carbon fiber in a metal solution controlled to a low pH value. The activated carbon fiber is thoroughly impregnated with the metal solution, and the activated carbon fiber is washed and dried to obtain the desulfurized activated carbon fiber, which is formed on the inner surface of each activated carbon fiber. The amorphous fine particles of the metal are adhered without clogging.

  Claim [9] of the present invention relates to an activated carbon fiber for a desulfurization catalyst, and the activated carbon fiber for a desulfurization catalyst is obtained by immersing the activated carbon fiber in a metal solution controlled to a low pH value. After sufficiently impregnating the metal solution, desulfurization obtained by adding an alkali to the metal solution to precipitate and precipitate a metal compound in the solution, and then washing and drying the activated carbon fiber The activated carbon fiber is characterized in that at least a part of the inside of the fine pores of each activated carbon fiber is filled with crystalline particles of the metal.

  The method for preparing activated carbon fibers for a desulfurization catalyst according to the present invention achieves an improvement in desulfurization efficiency and a longer life of the activated carbon fibers for a desulfurization catalyst. Further, according to this method, it is possible to suppress the clogging of the fine pores of the activated carbon fiber caused by the addition of metal, and to maintain the high surface area of the fiber, thereby enabling the treatment performance of the activated carbon fiber as a desulfurization catalyst. Can be improved.

  As described above, in the method for preparing activated carbon fibers for a desulfurization catalyst according to the present invention, activated carbon fibers are immersed in a metal solution controlled to a low pH value, and the activated carbon fibers are sufficiently impregnated with the metal solution. Thereafter, the activated carbon fiber is washed and dried to obtain an activated carbon fiber for a desulfurization catalyst with reduced metal outflow when used as a catalyst without reducing the surface area of the activated carbon fiber. Features.

  Examples of the activated carbon fiber used in the present invention include, but are not limited to, pitch-based activated carbon fiber, polyacrylonitrile-based activated carbon fiber, phenol-based activated carbon fiber, and cellulose-based activated carbon fiber. is not.

  The metal used in the present invention is preferably a group 3 to group 12 metal element on the periodic table of elements such as Cr, Mn, and Fe, which is a metal that is not easily deteriorated by desulfurization reaction and produced sulfuric acid and has high oxidation activity. Among these, Fe is more preferable from the viewpoint of (cost) versus (performance).

  The method for preparing activated carbon fibers for a desulfurization catalyst according to the present invention is characterized in that a metal solution used for loading a metal on activated carbon fibers is adjusted to a low pH value at least initially. As this low pH value, pH 2 or less is preferable. By adjusting the metal solution within this range, the metal can be completely dissolved, and the metal can adhere to the inner surfaces of many fine pores of the activated carbon fiber. Become. As a result, it is possible to improve the desulfurization performance by supporting the metal while maintaining the high surface area value of the activated carbon fiber. In the activated carbon fiber used for the desulfurization catalyst, the improvement of the desulfurization performance by the metal loading is considered to be because the desulfurization reaction is activated in the portion where the activated carbon surface and the metal coexist. The diameter of the activated carbon fiber is 10 μm, and the diameter of the micropores formed on the surface of each fiber is −10 mm. With respect to the activated carbon fiber having a large number of such fine pores, the method of the present invention makes it possible to attach a metal to the inner surface of the activated carbon fiber without blocking the numerous fine pores of the activated carbon fiber. As a result, the activated carbon fiber obtained by the method of the present invention has a very wide area active in the desulfurization reaction, and can greatly improve the desulfurization efficiency. Moreover, since the metal adheres in the fine pores of the fiber, it is difficult for the metal to flow out, and the amount of metal flowing out from the activated carbon fiber during use as a catalyst is greatly reduced.

  The metal can be adhered to the inner surfaces of the plurality of micropores by impregnating the metal solution having the low pH value into the micropores of the fiber. For this purpose, it is possible to take a sufficient immersion time. Although it is one means, it is preferable to accelerate | stimulate the impregnation of a solution efficiently by excluding gas from a micropore by leaving a metal solution under reduced pressure with the activated carbon fiber immersed.

  Moreover, in the method of this invention, you may provide the process of adding the alkali to a metal solution and promoting precipitation of a metal compound as an intermediate treatment process as needed. It is possible to increase the amount of the metal supported on the surface of the activated carbon fiber by adjusting the number of metal fine particles to be supported and the particle diameter in the direction of increasing the metal precipitation promotion step by adjusting the pH.

  Furthermore, in the method of the present invention, it is also possible to control the amount of the metal compound supported on the activated carbon fiber by adjusting the metal content of the metal solution. Specifically, the adjustment of the metal content of the metal solution can be realized by transferring the activated carbon fiber impregnated with the metal solution into a metal solution of another concentration prepared separately. Alternatively, it can be realized by reducing the amount of the metal solution after sufficiently impregnating the activated carbon fiber with the metal solution. In this case, the reduction of the metal solution may be performed at once or may be performed continuously little by little.

  The basic structure of the method for preparing activated carbon fibers for a desulfurization catalyst according to the present invention will be further described below with reference to the drawings, taking as an example the case where the metal is Fe.

As shown in FIG. 1, Fe (NH ₃ ) (SO ₄ ) ₂ is dissolved in an aqueous solution of H ₂ SO ₄ in a container 1 to prepare an aqueous iron solution 2 having a pH of 1.5, and activated carbon is contained in the aqueous iron solution 2. The fiber 3 is immersed. Fe (NH ₃ ) (SO ₄ ) ₂ can be completely dissolved by dissolving it in an acidic solution having a pH of 1.5. As a result, metallic iron can be fed into any minute space as long as the solution can enter and has a diameter larger than iron ions (Fe ³⁺ , ion radius: 0.67 mm). Once the aqueous iron solution can be adhered, the iron compound can be adhered to the fine space by performing a drying process thereafter.

  Next, in order to fully infiltrate the iron aqueous solution 2 into the numerous micropores of the activated carbon fiber 3 that is the fine space, the iron aqueous solution 2 and the activated carbon fiber 3 were filled as shown in FIG. Place container 1 under reduced pressure environment 4. During this time, the concentration of the aqueous iron solution 2 is preferably kept uniform by stirring. When the iron aqueous solution 2 permeates into a large number of micropores, the iron component in the iron aqueous solution 2 is adsorbed on the inner surfaces of the micropores.

After the activated carbon fiber 2 is sufficiently impregnated with the aqueous iron solution 2 in the container 1, the activated carbon fiber 3 is taken out and, as shown in FIG. 3, using a suction filtration device 5, pH 1.5 H ₂ SO _4. Wash with solution. As a result, the metal component not fixed on the surface of the activated carbon fiber 2 is washed away.

  The washed activated carbon fiber 2 is put in a vacuum dryer 6 and dried. As a result of drying, the iron component adsorbed in the fine pores of the activated carbon fiber 2 becomes fine particles and is fixed on the inner surface of the fine pores.

  Since the iron component is fixed, that is, adsorbed and supported on the inner surface of the fine pores of the activated carbon fiber, the area on which iron is adsorbed and supported is large, and the amount of iron supported is remarkably increased. Moreover, since the supported form is adsorption, the supported iron fine particles are not aggregated or crystallized to increase the particle size, and the fine pores are not blocked by the iron secondary particles. In addition, it is possible to prevent a decrease in activity of the metal particles themselves due to aggregation and crystal growth.

In the preparation method, an iron aqueous solution in which the iron component is completely dissolved is attached to the entire surface including the fine pores of the activated carbon fiber, and dried to adsorb and support the fine particles of the iron component on the surface of the activated carbon fiber. ing. In order to adjust the loading amount of the iron component to be increased, in the preparation method, after the step of promoting the penetration of the aqueous iron solution 2 into the micropores by placing it under the reduced pressure environment 4 described with reference to FIG. You may provide the precipitation promotion process of an iron component. In this iron component precipitation accelerating step, as shown in FIG. 5, an aqueous NH ₃ solution 7 is added to the aqueous iron solution 2 in the container 1 to adjust the pH value of the aqueous iron solution 2 to, for example, pH 4. 2 is promoted to precipitate the iron component, and the number and particle size of the metal component adhering to the surface of the activated carbon fiber 2 are both controlled to increase. In this case, since the fine particles of the metal component are easily crystallized, it is important to adjust the amount of alkali added. This is because if the amount of precipitation due to the addition of alkali increases, the adhering metal particles grow after crystallization to increase the particle size and close the fine pores of the activated carbon fiber.

  The pH adjustment value in the iron component precipitation promoting step is not limited to pH 4, but is arbitrary. By appropriately adjusting this pH value, it is possible to control the precipitation amount of the iron component and the particle size of the precipitated particles. As described above, when the amount of precipitation increases or the particle size of the precipitate increases, the fine pores may be clogged. In addition, the precipitated particles aggregate or become easy to grow after crystallization. The surface area in the whole precipitation amount tends to decrease. It is necessary to adjust the pH value within a range where such a negative effect does not occur.

  In conventional immersion and impregnation methods in metal aqueous solutions, usually, if the amount supported on the activated carbon fiber is set to exceed 10% by mass, the result is that the micropores of the activated carbon fiber are blocked. Thus, by first immersing the activated carbon fiber in a low pH metal aqueous solution and sufficiently impregnating the activated carbon fiber with the metal aqueous solution, by appropriately adjusting the pH of the metal aqueous solution closer to neutrality, The metal loading can be adjusted to an amount exceeding 10% by mass without clogging the fine pores of the activated carbon fiber.

After the precipitation promoting step, the cleaning step described with reference to FIG. 3 is performed. In this case, the NH ₃ aqueous solution 7 is used as a cleaning solution. After this cleaning step, the reduced-pressure drying process described above with reference to FIG. 4 is performed.

  Examples of the present invention will be described below. However, the examples described below are merely examples for suitably explaining the present invention, and do not limit the present invention.

Example 1
A first embodiment of the present invention will be described with reference to FIGS. Fe (NH ₃ ) (SO ₄ ) ₂ was dissolved in H ₂ SO ₄ aqueous solution to prepare pH 1.5 iron aqueous solution 2 in container 1. As the iron aqueous solution 2, iron aqueous solutions having eight concentrations from 1.5 to 500 mmol / L were prepared.

The activated carbon fiber 3 was immersed in 120 mL of each of the eight types of iron aqueous solutions having different concentrations. As this activated carbon fiber 3, 2.0 g each of activated carbon fibers (trade name A-15) manufactured by Adol Co., Ltd. were used. Even in an iron aqueous solution having the highest iron concentration of 500 mmol / L, the pH value was controlled to a low pH value of pH 1.5, so that Fe (NH ₃ ) (SO ₄ ) ₂ was completely dissolved.

  Next, as shown in FIG. 2, each container 1 was placed under a reduced pressure environment 4 in order to allow each of the iron aqueous solutions 2 to sufficiently enter the numerous fine holes of the activated carbon fiber 3. This decompression condition was ˜50 mmHg for 60 minutes. During this time, the concentration of the aqueous iron solution 2 was kept uniform by stirring.

Next, the activated carbon fibers 3 are taken out from the respective containers 1 having different concentrations of the iron aqueous solution, and washed with a pH 1.5 H ₂ SO ₄ solution to 360 mL using a suction filtration device 5 as shown in FIG. did. Then, as shown in FIG. 4, each activated carbon fiber 3 after washing was placed in a vacuum dryer 6 and dried. The conditions of decompression and drying were ˜50 mmHg, 70 ° C., and 18 hours.

  Each dried carbon fiber 3 was fired in an Ar atmosphere at a temperature of 1100 ° C. for 1 hour.

(Example 2)
In the same manner as in Example 1, Fe (NH ₃ ) (SO ₄ ) ₂ was dissolved in an H ₂ SO ₄ aqueous solution to prepare an aqueous iron solution 2 having a pH of 1.5 in the container 1. As the iron aqueous solution 2, iron aqueous solutions having four concentrations of 1.5 to 9 mmol / L were prepared. The activated carbon fibers 3 were immersed in 120 mL of each of the four types of iron aqueous solutions having different concentrations. The activated carbon fiber used here was the same as that used in Example 1. That is, 2.0 g each of activated carbon fibers (trade name A-15) manufactured by Adol Co. were used.

  Next, in the same manner as in Example 1, as shown in FIG. 2, each container 1 is placed under a reduced pressure environment 4 in order to sufficiently infiltrate each iron aqueous solution 2 into the numerous micropores of the activated carbon fiber 3. placed. This decompression condition was ˜50 mmHg for 60 minutes. During this time, the concentration of the aqueous iron solution 2 was kept uniform by stirring.

Next, unlike Example 1, as shown in FIG. 5, an aqueous NH ₃ solution 7 having a concentration of 2.5% is added to the aqueous iron solution 2 in each container 1, and the pH value of the aqueous iron solution 2 is adjusted to pH 4. Adjusted. As a result of adjusting the pH to 4, precipitation of iron hydroxide was confirmed in the aqueous iron solution 2. After adjusting to pH 4, the precipitate was supported on the activated carbon fiber 2 by stirring for 10 minutes.

Activated carbon fiber 3 was taken out from each container 1 after the precipitation promoting step, and washed with NH ₃ aqueous solution to 360 mL of pH 4.0 using a suction filtration device. Then, as shown in FIG. 4, each activated carbon fiber 3 after washing was placed in a vacuum dryer 6 and dried. The conditions of decompression and drying were ˜50 mmHg, 70 ° C., and 18 hours. Each dried carbon fiber 3 was fired in an Ar atmosphere at a temperature of 1100 ° C. for 1 hour.

(Comparative Example 1)
An activated carbon fiber 3 carrying iron was obtained in the same manner as in Example 1 except that the pH value of the aqueous iron solution 2 was adjusted to pH 4.0 in Example 1.

(Evaluation 1)
The iron loading (wt%) in the activated carbon fiber with respect to the iron aqueous solution concentrations in Examples 1 and 2 and Comparative Example 1 was calculated as follows.

An iron aqueous solution prepared by dissolving Fe (NH ₃ ) (SO ₄ ) ₂ in an H ₂ SO ₄ aqueous solution 2, and the Fe concentration in the filtrate and washing solution in the suction filtration step were measured by absorptiometry, and the following formula (1) As shown in Fig. 5, the Fe content decrease in the iron aqueous solution 2, that is, the Fe content A (g) in the iron aqueous solution 2, and the Fe content B (g) in the filtrate of the suction filtration step and the Fe content in the cleaning liquid Assuming that the amount obtained by subtracting the sum of the amount C (g) was supported on the ACF, the weight ratio with respect to the ACF weight W (g) was obtained, and was defined as the iron loading amount X (wt%).
X (wt%) = {[A− (B + C) / W]} × 100 (1)

The measurement of the Fe concentration by the spectrophotometric method was performed as follows. The Fe solution serving as a measurement sample was adjusted to pH 1.5 or less with concentrated sulfuric acid, and the absorbance of a specific absorption peak (290 nm) of Fe ³⁺ was measured. The Fe concentration was calculated from the measured value of the sample by using a calibration curve prepared using the measured value measured in advance with an Fe solution having a known concentration. The measurement results are shown in FIG.

(Evaluation 2)
Next, using the samples of Examples 1 and 2 and Comparative Example 1 and activated carbon fibers not loaded with iron, the amount of iron loaded in activated carbon fibers (wt%) and desulfurization using activated carbon fibers The relationship with the desulfurization rate in the treatment was measured using a glass reaction tube. Conditions, reaction temperature: 50 ° C., catalyst (activated carbon fiber) weight: 0.2 g, the process gas amount: 100 sccm, the inlet S0 ₂ concentration: 1000 ppm, oxygen concentration: 4%, water content: 13% equivalent, with nitrogen balance there were. The measurement results are shown in FIG.

(Evaluation 3)
Next, using each sample of Example 1 and Comparative Example 1, the effluent iron concentration (mmol / L) when used as a catalyst was measured. The iron carrying amount of the Example 1 sample at the start of measurement was 12.5 wt%, and the iron carrying amount of the Comparative Example 1 sample was 2.7 wt%. The measuring method measured the Fe density | concentration of the condensed water collected by the liquid reservoir provided in the glass reaction tube lower part by the method as described in said (evaluation 1), and computed the outflow iron density | concentration.

  As can be seen from FIG. 6, in Example 1, the amount of iron supported with respect to the increase in the concentration of the iron solution rapidly increased immediately after the activated carbon fiber was immersed in the iron solution, and then gradually changed. Even at a concentration of 0.0 mmol / L, the supported amount is a little less than 10.0 wt%. On the other hand, in Example 2 and Comparative Example 1 having a step of depositing and supporting an iron component, the supported amount continued to increase relatively rapidly in proportion to the concentration, and a 30.0 mmol / L aqueous iron solution. The loading amount has already reached 10.0 wt%.

  As can be seen from FIG. 7, the desulfurization rate increases in proportion to the increase in the iron loading amount only in the sample of Example 1, and in Example 2, although the increase tendency is recognized, the desulfurization rate is low. In Comparative Example 1, the desulfurization rate decreases as the loading amount increases.

  As can be seen from FIG. 8, in the sample of Example 1, the outflow of iron during use as a catalyst is constant over time and is suppressed to a very small amount of 0.1 mmol / L or less. On the other hand, in the sample of Comparative Example 1, the outflow amount is a relatively large value of 0.7 mmol / L, and the outflow amount is not reduced even when time passes. Therefore, the active life of Example 1 is high, but the active life of Comparative Example 1 is considerably short.

(Evaluation 4)
The samples of Example 1 and Example 2 were subjected to crystallinity analysis by X-ray diffraction, surface observation by a scanning electron microscope, and specific surface area measurement. The results are shown in Table 1 below.

  The following can be inferred from the results shown in Table 1 above. In other words, by preparing an iron solution at a low pH value, the activated carbon fiber of a solution having a high metal-dissolved concentration in which the iron component is completely dissolved is immersed, and the solution is sufficiently impregnated with the fiber, thereby the iron component is sufficiently impregnated. It can be adsorbed on the inner surface of fine pores of activated carbon fibers in the state of ions instead of particles, and after impregnation with the solution, it is washed and dried, so that the metal in the ionic state is amorphous and does not crystallize on the inner surface of the fine pores It is presumed that it does not easily peel off when supported. On the other hand, in Example 2 in which an alkali is added to generate iron precipitates in the remaining iron solution in the intermediate step, the precipitates due to the alkali crystallize into iron crystal particles having a relatively large particle size. Seems to adhere to the surface and micropores of the activated carbon fiber. In this case, although the amount carried on the fiber increases, the iron component having a particle shape after crystallization into the fine pores enters, so that the fine pores are at least partially blocked. Therefore, if the amount of alkali added is adjusted appropriately and the amount of precipitation is suppressed so as to avoid clogging of micropores, the surface area, which is an important factor for improving the desulfurization activity rate, is reduced by Example 2. It can be seen that the iron content contributing to the desulfurization reaction can be increased.

  From the above results, it can be concluded that according to the supporting method of Example 1, the iron component is adsorbed and supported in the micropores of the activated carbon fiber without clogging the micropores, so that the concentration of the iron solution increases. Although there is no sudden increase in the amount supported, the supported iron component is supported finely and evenly in an amorphous state. On the other hand, in Comparative Example 1, since the iron component deposited from the beginning is deposited and supported on the surface of the activated carbon fiber, there is an abrupt increase in the amount supported as the concentration of the iron solution increases. The supported iron component grows after aggregation or crystallization, becomes a bulk of secondary particles, and is unevenly supported. In Example 2, when the amount of precipitation due to alkali is increased, surface area reduction begins to occur. Therefore, by suppressing the amount of precipitation, it is possible to increase the amount of metal supported while maintaining the effects of Example 1. It is. Therefore, if activated carbon fibers are produced by the preparation method of the present invention, activated carbon fibers for a desulfurization catalyst having a long life and high activity characteristics can be obtained.

  As described above, the method for preparing an activated carbon fiber for a desulfurization catalyst according to the present invention further improves the desulfurization efficiency and prolongs the active life in the activated carbon fiber whose desulfurization efficiency is improved by adding metal. Can be planned. That is, according to the present invention, it is possible to provide a method for preparing activated carbon fibers for a desulfurization catalyst having a high desulfurization efficiency and a long active life, and activated carbon fibers for a desulfurization catalyst obtained by the method.

It is for demonstrating Example 1 of this invention, and is a figure which shows the process in which activated carbon fiber is immersed in the solution of the metal which it is going to carry | support. It is for demonstrating Example 1 of this invention, and is a figure which shows the state which is performing the pressure reduction process in order to raise the impregnation to the activated carbon fiber of a metal solution. It is for demonstrating Example 1 of this invention, and is a figure which shows the state which carries out the vacuum washing | cleaning of the activated carbon fiber which impregnated the metal solution. It is for demonstrating Example 1 of this invention, and is a figure which shows the state which dried the activated carbon fiber after washing | cleaning under reduced pressure. FIG. 9 is a diagram for explaining a second embodiment of the present invention, and shows a process of precipitating a metal component by increasing the pH of the metal solution after once impregnating the activated carbon fiber with the metal solution. It is for demonstrating the effect of this invention, and is a figure which shows the relationship between the iron concentration of an iron solution, and the iron load in activated carbon fiber. It is for demonstrating the effect of this invention, and is a figure which shows the relationship between the iron carrying amount in activated carbon fiber, and the desulfurization rate using activated carbon fiber. FIG. 6 is a diagram for explaining the effect of the present invention, and is a view showing the amount of iron component carried over time on the activated carbon fiber depending on the carrying method.

Explanation of symbols

1 container 2 an aqueous solution of iron 3 activated carbon fibers 4 vacuum environment 5 suction filtration apparatus 6 vacuum dryer 7 NH ₃ aq

Claims (9)

  The activated carbon fiber is immersed in a metal solution controlled to a low pH value, and the activated carbon fiber is sufficiently impregnated with the metal solution, and then the activated carbon fiber is washed and dried to thereby obtain the activated carbon fiber. A method for preparing an activated carbon fiber for a desulfurization catalyst, comprising obtaining an activated carbon fiber for a desulfurization catalyst with a reduced metal outflow when used as a catalyst without reducing the surface area of the catalyst.   After sufficiently impregnating the activated carbon fiber with the metal solution, an alkali is added to the metal solution to precipitate and settle a metal compound in the solution, and then the activated carbon fiber is washed and dried. The method for preparing activated carbon fibers for a desulfurization catalyst according to claim 1, further comprising increasing the amount of metal supported on the activated carbon fibers.   The method for preparing activated carbon fibers for a desulfurization catalyst according to claim 2, wherein the amount of the metal compound supported on the activated carbon fibers is controlled by adjusting the metal content of the metal solution.   After immersing the activated carbon fiber in the metal solution, the metal solution is placed in a reduced pressure environment while the activated carbon fiber is immersed, so that the low pH metal solution is sufficiently contained in the activated carbon fiber. The method for preparing activated carbon fibers for a desulfurization catalyst according to any one of claims 1 to 3, wherein the impregnation is performed.   After adding an alkali to the metal solution and precipitating and precipitating the metal compound in the solution, the metal solution is placed in a reduced pressure environment while the activated carbon fiber is immersed, whereby the deposited particles of the metal compound 4. The method of preparing activated carbon fibers for a desulfurization catalyst according to claim 2, wherein the attachment to the activated carbon fibers is ensured.   The method for preparing an activated carbon fiber for a desulfurization catalyst according to any one of claims 1 to 5, wherein the metal supported on the activated carbon fiber is Fe.   An activated carbon fiber for a desulfurization catalyst obtained by the method for preparing an activated carbon fiber for a desulfurization catalyst according to any one of claims 1 to 6. For desulfurization obtained by immersing activated carbon fiber in a metal solution controlled to a low pH value, sufficiently impregnating the activated carbon fiber with the metal solution, washing the activated carbon fiber, and drying. Activated carbon fiber,
An activated carbon fiber for a desulfurization catalyst, characterized in that amorphous fine particles of the metal adhere to the inner surface of the fine pores of each activated carbon fiber without closing the fine pores. After immersing the activated carbon fiber in a metal solution controlled to a low pH value and sufficiently impregnating the activated carbon fiber with the metal solution, an alkali is added to the metal solution to deposit a metal compound in the solution, Activated carbon fiber for desulfurization obtained by settling and then washing and drying the activated carbon fiber,
An activated carbon fiber for a desulfurization catalyst, wherein at least a part of the inside of the fine pores of each activated carbon fiber is filled with crystalline particles of the metal.

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