JPS5915026B2 - Processing method of carbon material for SO↓3/SO↓2 conversion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to carbon for 503/502 conversion, which is used as a reduction catalyst when selectively converting the 503 component contained in various gases such as environmental air and exhaust gas into 502. Concerning material processing methods.

Various exhaust gases such as combustion exhaust gas from a flue and automobile exhaust gas contain sulfur oxides such as 502 and 503 (hereinafter referred to as SOx).

), NO, NO2, and other nitrogen oxides (hereinafter referred to as NOx
That's what it means. ), etc., and so if they were released into the atmosphere without limit, the ambient air would become increasingly polluted. For this reason, the discharge of the exhaust gas into the atmosphere is currently subject to strict legal regulations from the standpoint of preventing air pollution. Therefore, before the exhaust gas is discharged into the atmosphere, it is necessary to measure and control the amount of these harmful components using an analyzer such as a 502 meter or a NO2 meter.

Furthermore, as mentioned above, it is necessary to constantly control the environmental atmosphere by eliminating the amount of harmful components. In particular, the SO3 component reacts with coexisting moisture to form a fine sulfuric acid mist, but this sulfuric acid mist has a high dew point and is corrosive.
When measuring a gas containing an O3 component using various analyzers, various damages occur, such as corrosion of the pipes in the analyzer and a decrease in sensitivity due to contamination of the detection section. For this reason,
SO from various gases to be measured such as ambient air, exhaust gas, etc.
It is an important problem to remove the SOx component or to measure the SOx component in the gas. Conventionally, filters such as glass fiber filter paper or adsorbents such as perlite have been used to remove the SO3 component in the gas, that is, to remove sulfuric acid mist, but it is impossible to completely remove the fine sulfuric acid mist. In addition, when attempting to increase removal efficiency, pressure loss increases, resulting in disadvantages such as impracticality. In addition, S in gases, especially exhaust gas
Conventionally, infrared SO2 gas analyzers have been used to measure Ox components, but SO3, which is said to account for several percent of the SOx components (most of which is thought to exist as sulfuric acid mist), The disadvantage is that no measurements can be taken. (In addition, S in the environmental atmosphere
Infrared analysis is not suitable for measuring O2 components;
Rosaniline formalin method etc. will be used. ) In order to improve these drawbacks, the present inventors have developed a method for removing SO3 components from gases by selectively and highly efficiently converting SO3 components in gases such as environmental air and various exhaust gases into SO2. Developed a SOV/SO2 conversion method that can measure components or SO components - a patent application is pending by the same applicant as this case.

(Patent Application No. 53-105393 (Japanese Unexamined Patent Application No. 55-3275)
(See Publication No. 8)) According to the invention of this earlier application, SO
A gas containing the three components is brought into contact with a carbon-based material heated to a temperature of 320°C to 500°C to selectively remove the SO3 component in the gas and convert SO2 with high efficiency.
The purpose of the present invention is to remove the SO3 component from the gas or measure the SOx component or SO3 component. Materials as ingredients,
That is, the object of the present invention is to provide a processing method for making carbon materials highly flame retardant and highly active.

In other words, an object of the present invention is to obtain a carbon catalyst for SO3/SO2 conversion that has high flame retardancy, that is, high durability (long life), and high SO3/SO2 conversion activity. In order to achieve the above object, according to the present invention, SO. /SO2 conversion carbon material is subjected to the following two steps (a) and (x). (b) The carbon material is impregnated with a mixture of phosphoric acid and a water-soluble metal salt that can react with the phosphoric acid to produce a highly heat-resistant inorganic compound, and then the impregnated carbon material is placed in an inert gas atmosphere. A process of performing heat treatment at a temperature of 500°C to 1000°C.

(Flame retardant treatment step) (b) After treating the carbon material with an oxidizing acid, the carbon material is heated to 300°C in an inert gas atmosphere.
A process of performing heat treatment at a temperature of ~700°C.

(Activation treatment process) In the present invention, as will be explained later using experimental results, it is better to perform the flame retardant treatment after the activation treatment to increase durability without impairing the activation. can improve sex.

On the other hand, it has been found that when activation is performed after flame retardation, activation is improved but durability is impaired. Hereinafter, the present invention will be specifically explained in detail.

First, SO. V/
The SO2 conversion method will be explained using FIG. FIG. 1 shows an experimental apparatus for carrying out the SO3/SO2 conversion method. In this device, first, a gas (
A test gas) is prepared, and then the SO3 component in this test gas is converted to SO2. 1 is for SO', standard mixed gas cylinder 2 is an oxygen gas cylinder, and 3 is a nitrogen gas cylinder.

From these cylinders, SO/N2 standard mixed gas,
Oxygen gas and nitrogen gas are taken out to prepare, for example, the test gases shown in Table 1, which are then introduced onto the oxidizer 6. The gas flow rate was 1.01/min (0°C). Nitrogen gas is humidifier 4
is passed through to produce humidified nitrogen gas. 5, 51, and 5I are all flowmeters.

The oxidation catalyst 6 is a platinum/alumina catalyst (GHS=20.00
0), and is heated to a temperature of around 650° C. by an electric furnace 7. 8 is a thermocouple.

At this time, a part of the SO2 component in the test gas is oxidized and changed to SO3 according to the formula.

Table 1 shows the composition of the test gas before and after passing through the oxidation catalyst. In Table 1, the amount of SO3 after passing through the oxidation catalyst is a value determined from the difference between the amount of SO2 before passing through the oxidation catalyst (200 ppIn) and the amount of SO2 after passing (100 PF). The above-mentioned test gas containing the SO3 component that has passed through the oxidation catalyst 6 is then heated through an electric furnace 7' (converter)
It is introduced onto a carbon material heated to a temperature of 20 to 500° C., for example activated carbon 9, and brought into contact therewith. Said activated carbon 9
For example, cylindrical activated carbon Shirasagi manufactured by Takeda Pharmaceutical Co., Ltd., which has been crushed to a particle size of 10 to 16 mesh, can be used. In addition to activated carbon, various carbon materials such as carbon graphite can be used as such carbon materials. At this time, the SO3 component in the test gas undergoes the reduction reaction of the formula and is converted to SO2.

The converted SO2 and other remaining SO2 are passed through a glass filter 10 and quantified by an SO2 detection tube 11. Note that, instead of the SO detection tube 11, for example, an infrared SO2 analyzer may be used to continuously analyze the amount of SO2. The present invention relates to a flame retardant and activation treatment for the Kanihon material used in the above-mentioned SO3/SO2 conversion method, and this treatment method will be described in detail below. first,
Regarding the SOVSO2 conversion A carbon material used in the present invention, various carbon materials are used to convert the SO3/SO2
Figures 2 to 4 show the results of measuring conversion activity. I showed this.

Figures 2 to 4 show the SO of various carbon materials. 7/SO2
It is a graph showing conversion activity. In addition, A in FIGS. 2 to 4. , Al, A2, BO, Bl, B2 and C,
D indicates the following carbon materials, respectively. A.O.
= Carbon black.

A1 = AO at 2300℃~24(
1) A2 = AO subjected to pseudographitization treatment for 2 to 3 hours at ゜ω temperature at 29000C in a reducing gas atmosphere
Graphitized for 1 to 2 hours at a temperature of ~3000°C〇B0 = activated carbon〇B1 = BO in a reducing gas atmosphere at 2300°C ~ 240°C
Pseudographitization treatment was performed at a temperature of 0°C for 2 to 3 hours.

B22B.

〇C, D, which was subjected to graphitization treatment at a temperature of 2900°C to 3000°C for 1 to 2 hours in a reducing gas atmosphere.
= Graphite.

The following can be seen from FIGS. 2 to 4.

(1) The crystalline form of the carbon material has a greater influence on the SOV/SO2 conversion activity than the specific surface area of the carbon material.

(2) The following two points can be considered as directions for improving carbon materials.

(A) Development of an activation treatment method that does not impair the flame retardancy of flame-retardant carbon materials.

03) Development of a flame retardant treatment method that does not impair the SO3//SO2 conversion activity of highly active carbon materials.

Based on these guidelines, the present inventor has developed a carbon material that has high flame retardancy (great durability) and high durability by subjecting the carbon material to a combination of two processes: a flame retardant treatment process and an activation treatment process. We succeeded in obtaining a carbon material with high SOVSO2 conversion activity and completed the present invention.

In addition, the definition of SO3//SO2 conversion activity and Figure 2~
The test conditions in FIG. 9 are as follows.

S.O. S//SO2 conversion activity test conditions: Gas = SO39
7ppm, SO2lO3pp[[1,025% by volume, N
2 left.

GHSV: 6,0000 The flame retardant treatment in the present invention involves impregnating the aforementioned carbon material with a mixture of phosphoric acid and a water-soluble metal salt that can react with the phosphoric acid to produce a highly heat-resistant inorganic compound, and then impregnating the carbon material with The processed carbon material is heated to 500℃ in an inert gas atmosphere.
This is done by heating at a temperature of 1000°C.

The water-soluble metal salts that can react with phosphoric acid to produce highly heat-resistant inorganic compounds are preferably aluminum salts such as aluminum nitrate and aluminum sulfate, but various other salts such as calcium salts and magnesium salts may also be used. It's okay to be hot. The mixed solution of these water-soluble metal salts and phosphoric acid is a mixed aqueous solution in which the molar ratio of water-soluble metal salt:phosphoric acid is in the range of 1:0.5 to 1:5. The carbon material is impregnated with such a mixed aqueous solution by adding the carbon material to the mixed aqueous solution and leaving it at room temperature for about 2 hours. Also,
The above heat treatment is performed in an inert gas atmosphere such as nitrogen gas.
It is necessary to carry out at a temperature of 00°C to 1000°C.
SO3 of carbon material obtained at temperatures below 500℃
/SO2 conversion activity decreases, and even if heated to 10,000C or higher, no further improvement in performance can be obtained, making it economically unsuitable.

Note that this heat treatment involves separating the aqueous solution after the above-mentioned impregnation,
It is preferable to carry out the drying process after drying at a temperature of about 150° C. for about 3 hours in an inert gas atmosphere such as nitrogen gas. moreover,
The activation treatment in the present invention involves treating the carbon material with an oxidizing acid, and then heating the carbon material at 300°C to 300°C in an inert gas atmosphere.
This is done by heating at a temperature of 700°C. The aforementioned acids having oxidizing properties include mixed acids (a mixture of nitric acid and sulfuric acid), nitric acid, hot concentrated sulfuric acid, and the like. Moreover, the above-mentioned heat treatment needs to be carried out at a temperature of 300° C. to 700° C. in an inert atmosphere such as nitrogen gas. At temperatures below 300°C, SO3H groups, etc. remain on the surface of the carbon material, and the effects of these SO, H groups, etc. appear to interfere with activation, which is undesirable.
Further, even if heated to 700° C. or higher, no further improvement in performance can be obtained, which is economically disadvantageous.

Note that this heat treatment can be carried out after treating the carbon material with the oxidizing acid, washing it with pure water, etc., and then drying it in an inert gas atmosphere at a temperature of about 150°C for about 3 hours. preferable. In the present invention, the above-described flame retardant treatment step (step (a)) and activation treatment step (step (b)) are combined to achieve flame retardant treatment and activation treatment of the carbon material. As mentioned above, this combination is preferably a combination of step (a) first and then step (b). The carbon material treated by the treatment method of the present invention has a high SOV/SO2 conversion activity, is flame retardant, that is, has high durability, and has a long life, and is extremely effective in practice. Next, experimental examples of flame retardant treatment and activation treatment in the treatment method of the present invention will be shown.

[Flame retardant treatment]

First, using commercially available reagents and pure water, 0.5 mol of Al (
An aqueous solution of 11 containing NO3)3 and 0.6 moles of H3PO4 is prepared.

Next, the above-mentioned carbon material B is added to this aqueous solution. 150
After adding 9 and allowing to stand at room temperature for 2 hours for impregnation treatment, the aqueous solution was separated. After the separation, the carbon material was placed in an electric furnace and dried at 150°C in a nitrogen stream for 3 hours, then further heated to 900°C and heat-treated for 3 hours to form AlPO4 on the pore surface of the carbon material. It precipitates heat-resistant substances such as, making it flame retardant. (BP) Note that the above-mentioned carbon material B1 is also subjected to the same treatment to make it flame retardant.

(BP) Carbon material B mentioned above.

, Bl and the carbon materials B and B (I, respectively, SO3//SO2
The conversion activity and flame retardancy were measured and the results are shown in FIGS. 5 and 6. The test conditions were as described above, and flame retardancy was expressed using the COx (=CO+CO2) concentration at the converter outlet. In other words, the lower the COx concentration at the converter outlet at the same temperature, the more flame retardant it is. From FIG. 5 and FIG. 6, it can be seen that by applying this flame retardant treatment, not only the flame retardance of the carbon material is improved but also the effect of activation. [Activation Treatment] First, a mixed solution of 0.51% of concentrated nitric acid and 0.51% of concentrated sulfuric acid (mixed acid solution) is prepared using a commercially available reagent.

Next, the aforementioned carbon material Bll5O9 was gradually added to this liquid while stirring, and the mixture was allowed to stand for 24 hours. Next, after separating the liquid, it was thoroughly washed with pure water, and the supernatant liquid was
Even if a Cl2 solution is added, white turbidity due to BasO4 should not occur. After filtration, the carbon material is placed in an electric furnace and dried under a nitrogen stream at a temperature of 150° C. for 3 hours, then further heated to 600° C. and heat-treated for 3 hours for activation. (B') Measuring the SO3//SO2 conversion activity and flame retardance of the carbon material B1 described above and the activated carbon material B', respectively;
The results are shown in Figure 7. The test conditions are as described above. From FIG. 7, it can be seen that by performing this activation treatment, a considerable activation effect can be obtained, although the flame retardance is somewhat impaired. Example carbon material B.

, Bl are first subjected to the above-mentioned flame retardant treatment, and then the above-mentioned activation treatment is successively applied to B?, B? Get β. Also, on the contrary, carbon material B. , Bl were first subjected to activation treatment, and then flame retardant treatment was sequentially applied to B'A and B'. 0 These carbon materials Br
β, B'(I, B(Iβ, B'. SO, /SO
2 conversion activity and flame retardancy were measured and the results are shown in FIGS. 8 and 9. (Comparison with measurement results for untreated carbon materials B., Bl) As is clear from Figures 8 and 9, the combination of both treatments takes advantage of their respective strengths, especially the reduction in flame retardancy due to activation. It can be seen that the defects are resolved.

However, from this experimental result, it is possible to improve durability without damaging the activation process by simultaneously performing flame retardant treatment after activation treatment; It has been found that if carried out after the oxidation treatment, activation is improved but durability is impaired.

Therefore, it is desirable to carry out the flame retardant treatment after the activation treatment. In this way, in the present invention, by applying a combination of flame retardant treatment and activation treatment to the carbon material, it is possible to improve the SOVSO2 conversion activity and flame retardancy of the carbon material.

In addition, in Figures 5 to 9, converter temperature-SO3/SO2 conversion activity characteristics and converter temperature-converter outlet COx concentration characteristics are shown simultaneously in each figure, but this distinction can be made as follows. It's been made to be. That is, for example, in FIG. 5, the characteristic line B is marked with a downward arrow and a leftward arrow. and a characteristic line B with a downward arrow and a rightward arrow. is shown, but characteristic line B with a leftward arrow
. shows the converter temperature-SOV/SO2 conversion activity characteristic line, while characteristic line B with a right-pointing arrow. is a converter temperature-converter outlet COx concentration characteristic line. This also applies to other characteristic lines. Therefore, in FIGS. 5 to 9, the characteristic line with the leftward arrow represents the converter temperature - SOy
/SO2 conversion activity characteristic line, and the characteristic line with a rightward arrow is a converter temperature-converter outlet COx concentration characteristic line.

[Brief explanation of drawings]

Figure 1 shows the experimental equipment for carrying out the SO3/SO2 conversion method, and Figures 2 to 4 show SO of various carbon materials.
FIGS. 5 to 6 are graphs showing 3/SO2 conversion activity.
The figure shows the SO of various carbon materials treated with flame retardant treatment. /
7 is a graph showing SO2 conversion activity and flame retardancy;
The figure shows SO〆S of various carbon materials that have been subjected to activation treatment.
This is a graph showing O2 conversion activity and flame retardancy, and Figures 8 to 9 show SO3/SO2 conversion activity and flame retardancy of various carbon materials that have been subjected to both flame retardant treatment and activation treatment. It is a graph. 1...SO2/N, standard mixed gas cylinder, 2.
... Oxygen gas cylinder, 3 ... Nitrogen gas cylinder, 6 ... Oxidation catalyst, 7 ... Electric furnace, 7t ... Electric furnace (converter) , 8... thermocouple, 9... activated carbon, 11... SO2
Detector tube.

Claims (1)

[Scope of Claims] 1. A flame retardant and activation treatment method for a carbon material, which comprises subjecting the carbon material for SO_3/SO_2 conversion to the following two steps (a) and (b). (b) The carbon material is impregnated with a mixture of phosphoric acid and a water-soluble metal salt that can react with the phosphoric acid to produce a highly heat-resistant inorganic compound, and then the impregnated carbon material is placed in an inert gas atmosphere. A process of performing heat treatment at a temperature of 500°C to 1000°C. (b) A step of treating the carbon material with an oxidizing acid and then subjecting it to heat treatment at a temperature of 300°C to 700°C in an inert gas atmosphere. 2. In the treatment method described in claim 1, after first treating in step (b),
A treatment method characterized in that the treatment is then carried out in step (a). 3. The treatment method according to claim 1, wherein the water-soluble metal salt that can react with phosphoric acid to produce a highly heat-resistant inorganic compound is an aluminum salt. 4. The treatment method according to claim 3, wherein the aluminum salt is aluminum nitrate or aluminum sulfate. 5. The treatment method according to claim 1, wherein the water-soluble metal salt that can react with phosphoric acid to produce a highly heat-resistant inorganic compound is a calcium salt or a magnesium salt. 6. The treatment method according to claim 1, wherein the oxidizing acid is a mixed acid, nitric acid, or hot concentrated sulfuric acid. 7. The processing method according to claim 1, wherein the heat treatment in the step (a) is carried out after impregnating the carbon material with the mixed liquid and drying it. 8. In the treatment method according to claim 1, the heat treatment in the step (b) is performed after the carbon material is treated with the oxidizing acid, washed, and then dried. Featured processing method. 9. The processing method according to claim 7 or 8, wherein the drying is performed by heating in an inert gas atmosphere.