JPH04290549A - Treatment to recover sulfuric acid-activated activated carbon fiber and treatment to remove no from no-containing gas - Google Patents

Abstract

PURPOSE:To reactivate a sulfuric acid-activated ACF having decreased NH3 adsorptivity at room temp. to about 100 deg.C, lower than a conventional method, and to remove NO from NO-contg. gas. CONSTITUTION:This recovering method for sulfuric acid-activated activated carbon fiber features in that a NO-contg. gas is brought into contact with the sulfuric acid-activated activated carbon fiber adsorbing NH3 to reactivate the carbon fiber. Also, this invention relates to the method of removing NO from NO-contg. gas. by the treatment above described.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for regenerating sulfuric acid-activated carbon fibers that have adsorbed NH3, which is one of the malodorous substances, and a method for removing NO from NO-containing gas.

0002

[Prior Art and its Problems] A simple method for removing ammonia, which is a source of bad odors, is desperately needed to improve the livability of modern high-density living spaces, and various methods are currently being developed.

It is known that activated carbon fiber (ACF) activated with sulfuric acid has ammonia adsorption (Moch
ida, Kawano, Fujitsu Chem.
Lett. , NO. 9, 1990, 1627-1630
). The present inventors previously reported that by bringing the sulfuric acid-activated ACF that has adsorbed ammonia into contact with air heated to a high temperature, the adsorbed ammonia can be recovered and the adsorption ability of activated carbon fibers can be regenerated.

However, according to the above method, in order to obtain a sufficient regeneration effect, treatment must be performed with heated air at a temperature of 185° C. or higher, which poses major problems in terms of cost and durability of the device.

[0005]

[Means for Solving the Problems] In view of the above-mentioned problems, an object of the present invention is to provide a method for efficiently reactivating sulfuric acid-activated ACF at a lower temperature. Another object is to provide a method for removing NO from an NO-containing gas.

That is, the present invention provides a method for regenerating sulfuric acid-activated carbon fibers, which comprises reactivating the sulfuric acid-activated carbon fibers by bringing NO-containing gas into contact with the sulfuric acid-activated carbon fibers that have adsorbed NH3. , and the N
The present invention relates to a method for removing NO from an NO-containing gas, which is characterized in that NO is removed from the O-containing gas.

According to the research conducted by the present inventor, it was found that when NO-containing gas is brought into contact with sulfuric acid-activated ACF that has adsorbed ammonia, ACF can be reactivated at temperatures ranging from room temperature to around 100°C. . Moreover, sulfuric acid activated ACF
NO is removed from the NO-containing gas used for reactivation. Therefore, the present invention aims to simultaneously reactivate the sulfuric acid-activated ACF that has adsorbed ammonia and simultaneously remove NO from the NO-containing gas.
Alternatively, with the former or latter treatment as the main purpose, the reactivation of the sulfuric acid-activated ACF or the removal of NO from the NO-containing gas can also be performed.

The method of the present invention will be explained in detail below.

First, the ACF used in the present invention is not particularly limited, and may be pitch-based, phenolic resin-based, PA
Commercially available products such as N-based ACFs can be used.
can be used in any form such as fiber, web, cloth, paper, etc. Sulfuric acid-activated ACF is obtained by activating the above ACF with sulfuric acid. The activation method and conditions are not limited as long as ACF exhibits ammonia adsorption ability, and can be selected as appropriate. For example, ACF is impregnated with sulfuric acid by immersing it in sulfuric acid, etc., and then heat treated. The sulfuric acid used is preferably concentrated sulfuric acid (37 wt%). Heat treatment is usually 200 to 3
The process is carried out at about 00°C for about 2 to 10 hours. In this way, an activated ACF having ammonia adsorption capacity is obtained. The amount of ammonia adsorbed by sulfuric acid-activated ACF is usually 2 to 3.
It is wt%.

In the method of the present invention, sulfuric acid-activated ACF which has lost or decreased its ammonia adsorption ability by adsorbing ammonia
is brought into contact with NO-containing gas to regenerate the ACF. At this time, the reaction that occurs between the adsorbed NH3 and NO is thought to follow the following equation. NO+NH3+1/402 -> N2+3/2H
2O

According to the present invention, the sulfuric acid-activated ACF that has adsorbed ammonia is reactivated, and NO in the NO-containing gas used for the reactivation is removed. Therefore, the method of the present invention uses sulfuric acid-activated AC that has adsorbed ammonia.
AC can be used as a method to remove NO in NO-containing gas at the same time as F is reactivated, or for the former purpose only.
It can be applied as a method for reactivating F or for the latter purpose only as a method for removing NO from NO-containing gas.

In the present invention, contact between the NO-containing gas and the sulfuric acid-activated ACF adsorbing ammonia is carried out by passing the NO-containing gas through a layer of the ACF. The layer of sulfuric acid activated ACF may be a packed or stacked layer of the ACF, or may be a fiber, web, paper, etc. NO
The contained gas may cross the ACF layer or
The two may be brought into contact by any method such as passing parallel to the layer.

As the NO-containing gas in the method of the present invention, for the purpose of reactivating ACF, any NO-containing gas that does not interfere with the reactivation can be used. Most preferred is air containing NO. In this case, the NO content in the gas can vary over a wide range, but is usually between 300 and 500 ppm, especially between 350 and 450 ppm.
A range of ppm is preferred.

[0014] For the purpose of reactivating ACF and removing NO from NO-containing gas, it is possible to use various NO-containing gases that contain NO as a component to be removed and do not hinder reactivation of ACF. can.

The process of the present invention can advantageously be carried out efficiently at temperatures ranging from room temperature to as low as 100°C. In particular, according to the method of the present invention, the ammonia adsorption ability of ACF can be sufficiently increased even when treated at room temperature. For example, when reactivating using NO-containing air at room temperature, the ammonia adsorption capacity when reactivating with heated air at 185 ° C.
A recovery rate of 90% can be obtained. This effect is NO
This is remarkable compared to the fact that the adsorption capacity can only be recovered by 10 to 20% during reactivation at 185° C. with NO-containing room temperature air. Furthermore, as the reactivation treatment temperature increases, the regeneration effect increases and the breakthrough time of reactivated ACF becomes longer. For example, for pitch-based activated carbon fibers and PAN-based activated carbon fibers, reactivation treatment at 100°C provides almost the same reactivation effect as 185°C heated air reactivation treatment. Further, the lower the humidity of the NO-containing gas, the better, and it is particularly preferable to use a relative humidity of 60% or less. Of course, it is not impossible to use a NO-containing gas with a relative humidity of 100%, but the reactivation effect at room temperature is reduced, and if the treatment temperature is raised, a sufficient effect cannot be obtained. The effects of the processing temperature and humidity are the same when NO is removed from the NO-containing gas.

[0016]

Effects of the Invention According to the method of the present invention, sulfuric acid-activated ACF with reduced NH3 adsorption capacity can be easily reactivated at a temperature lower than that of the conventional method, from room temperature to around 100°C. The load on the device can be reduced, and energy and cost savings can be achieved. In particular, it has the characteristic that a high regeneration effect can be obtained at room temperature. The regeneration treatment of the sulfuric acid-activated ACF of the present invention can be repeated without reducing the regeneration effect. At the same time, NO, which is a harmful substance, can be converted into nitrogen, which is harmless to the human body, and NO can be removed from the NO-containing gas.

[0017]

EXAMPLES Examples are shown below to make the features of the present invention clearer.

[0018]

[Reference Example 1] Preparation of sulfuric acid-activated ACF PAN-based carbon fiber (FE-200, manufactured by Toho Rayon Co., Ltd.)
, ACF of pitch-based carbon fiber (OG-5A, manufactured by Osaka Gas Co., Ltd.) and phenolic resin-based carbon fiber (ACN-210-20, manufactured by Nippon Kynor Co., Ltd.) were used as raw materials, and these ACFs were immersed in 3 times the weight of sulfuric acid. 250℃ under nitrogen flow
It was heat-treated at ℃ for 5 hours and activated with sulfuric acid. The sulfuric acid-activated AFCs are abbreviated as PAN-FE-200, OG-5A, and ACN-210-20, respectively. These sulfuric acid activation A
Table 1 shows the characteristics of FC.

[0019]

[0020]

[Example 1] Sulfuric acid-activated ACF according to Reference Example 1 with saturated adsorption of NH3 contains 400 ppm of NO at a relative humidity of 60%.
of air at 25℃, flow rate 2 x 10-3 g・min・ml-
1 for 10 hours to remove NH3 and reactivate it. 0.2 g of the thus obtained recycled ACF was packed into a glass U-shaped reaction tube with an inner diameter of 8 mm, and using a fixed bed flow reactor, NH3 = 400 ppm (in helium),
With a flow rate of 2 x 10-3 g・min・ml-1, N at room temperature
The adsorption of H3 was investigated. Converts ammonia in the outlet gas to NO and uses a NOX meter (ECL-77A manufactured by Yanagimoto Seisakusho)
The amount of adsorption (wt%) up to breakthrough was calculated. PAN-FE-200, OG-5A and ACN-21
The measurement results for each ACF of 0-20 are shown in (4) in Figure 1.
), (5) and (6). The figure also shows the results of reactivation using only air under the same conditions as above (1) and (2).
And (3), the results of reactivation in the same manner as above except using only 185°C air are shown in (7), (
8) and (9) are listed together for comparison.

As shown in (7), (8) and (9) in FIG. 1, when each of the three types of ACF was repeatedly reactivated with air at 185°C, the reactivation process was repeated for 3.0 hours and 3. 6 hours and 3.
After 4 hours, NH3 was completely adsorbed and removed and breakthrough occurred. In addition, reactivation treatment was performed with room temperature air that does not contain NO (1)
, (2) and (3) are also able to adsorb NH3 again, but the breakthrough time at that time is 0.5 hours each.
0.7 hours and 0.3 hours, and the adsorption capacity is 185
It remained at 10-20% of that when reactivated at ℃.

In contrast, (4), (
5) and (6), their breakthrough times were significantly extended, reaching 2.3 hours, 3.2 hours and 1.4 hours, respectively;
Its adsorption capacity is 40-90% when reactivated at 185℃
was able to recover. This shows that the method of the present invention exhibits an excellent reactivation effect even at room temperature.

Table 2 also shows the effect of NO on the amount of NH3 adsorbed before breakthrough in dry air for each ACF reactivated under the same conditions as above. Note that the values for initial adsorption in Table 2 indicate the amount of NH3 adsorbed by the sulfuric acid-activated ACF before reactivation.

[0024]

[0025]

[Example 2] The results of investigating the influence of reactivation temperature on NH3 adsorption capacity using OG-5A are shown in (5) to (10) in Figure 2.
). The measurement of NH3 adsorption capacity was carried out in the same manner as in Example 1. The reactivation conditions are (5), (8), (9
) and (10) at 25°C and 50°C, respectively.
The same procedure as in Example 1 was conducted except that the temperature was 80°C, 80°C, and 100°C. In addition, (6) and (7) are at a temperature of 25°C.
These are the results of NH3 adsorption when the reactivation was repeated two and three times. In addition, (1), (2), (3), (4) and (11) are the results when reactivating only using air at 25°C, 50°C, 80°C, 100°C and 185°C. and (12) show the results of measuring ACF before reactivation.

From the results shown in Figure 2, the effect of the reactivation temperature is that the breakthrough time is prolonged when the reactivation temperature is high for both air and NO-containing air; The effect of the NH3 adsorption ability is more noticeable when it is added. Furthermore, NO at 100℃
Reactivation with contained air was comparable in effectiveness to reactivation at 185° C. with NO-free air.

[0027] From the results in Figure 2, it is clear that NO in reactivation
It is clear that the effect of the contained gas is large.

[0028]

[Example 3] The difference in NH3 adsorption amount when the reactivation temperature was changed was investigated for three types of ACF. The results are shown in FIG. The amount of NH3 adsorption was measured in the same manner as in Example 1. The reactivation conditions were the same as in Example 1 except that the temperature was changed. (1), (2) in Figure 3
) and (3) are PAN-FE-20 in NO-containing air.
0, OG-5A, and ACN-210-20. In addition, (4), (5) and (6) in Figure 3 are OG-5A, PAN-FE-200 and ACN-
This is the measurement result of 210-20. According to this result, for any ACF, the higher the reactivation temperature, the higher the NH
3.The amount of adsorption also increases, and by adding NO, the amount of N adsorption increases.
It can be seen that the amount of H3 adsorption increases significantly. In particular, P.A.
1 with NO-containing air for N-FE-200 and OG-5A.
It can be seen that when the reactivation treatment is performed at 00°C, the same effect as when reactivated at 185°C in air can be achieved.

[0029]

[Example 4] The influence of the reactivation humidity of PAN-FE-200 and OG-5A on the amount of NH3 adsorbed was investigated. The results are shown in FIGS. 4 and 5, respectively. The amount of NH3 adsorption was measured in the same manner as in Example 1. The reactivation conditions were the same as in Example 1 except that the relative humidity was changed. (1), (2), (3) and (4) in FIG.
In addition, (1), (2), (3), and (4) in FIG. 5 are the results of measuring the amount of NH3 adsorption under conditions of relative humidity of 0%, 60%, 80%, and 100%, respectively. From this result, the lower the relative humidity (especially below 60%), the more NH3
It can be seen that the adsorption capacity is improved.

[0030]

[Example 5] NO40 in three types of ACF that adsorbed NH3
Air with a relative humidity of 60% containing 0 ppm at a flow rate of 2 x 10
-3g·min·ml−1 and the NO conversion rate when flowing at room temperature (25°C) was investigated. The measurement results are shown in FIG. In FIG. 6, (1), (2) and (3) are PAN-
It is a measurement result about each ACF of FE-200, OG-5A, and ACN-210-20. In the case of OG-5A, immediately after distribution, the NO conversion rate showed 50% and then immediately decreased, but after 1 hour it reached a steady value of about 20%.
This conversion rate could be maintained for the next 10 hours. The initial conversion rates of the other two types of ACF also decreased with the passage of time, but remained constant thereafter.

[0031]

[Example 6] Production rate of carbon dioxide, etc. NO2, CO2 and CO observed in outlet gas during reactivation with NO-containing dry air at 25-100°C
The production rate and NO conversion rate were measured. The measurement results are shown in Table 3.

[0032] As a result, at 25°C, 47% of NO (population concentration 400 ppm) was converted at the initial stage of the reaction. The NO conversion rate reached 92% at 100°C as the reaction temperature increased, and remained at 50% or higher even after 1 hour. Furthermore, the NO2 production rate was 8.3% at 25°C in the initial stage of the reaction, and decreased as the temperature increased, and decreased to 2.7% at 100°C.

[0033] Regarding the production rate of CO and CO2, 25
No formation was observed at ~50°C, and the reactivation temperature was at ~80°C.
At 100℃, CO2 is 170-270pp in the outlet gas.
A trace amount of CO was observed at 100°C.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the breakthrough time of NH3 adsorption and each ACF at a reactivation temperature of 25°C.

FIG. 2 is a graph showing the relationship between the breakthrough time of NH3 adsorption and each ACF at each reactivation temperature.

FIG. 3 is a graph showing the amount of NH3 adsorbed by each ACF at each reactivation temperature.

[Figure 4] PAN-FE-200 at each reactivation humidity
It is a graph showing the amount of NH3 adsorption.

FIG. 5 is a graph showing the amount of NH3 adsorbed by OG-5A at each reactivation humidity.

FIG. 6 is a graph showing the NO conversion rate of each ACF at a reactivation humidity of 60%.

Claims (3)

[Claims] Claim 1: Sulfuric acid activation characterized in that by bringing NO-containing gas into contact with sulfuric acid-activated activated carbon fibers that have adsorbed NH3, the activated carbon fibers are reactivated and NO is removed from the NO-containing gas. A method for regenerating activated carbon fibers and removing NO from NO-containing gas. 2. A method for regenerating sulfuric acid-activated activated carbon fibers, which comprises reactivating the activated carbon fibers by bringing NO-containing gas into contact with the sulfuric acid-activated activated carbon fibers that have adsorbed NH3. 3. A method for removing NO from an NO-containing gas by bringing the NO-containing gas into contact with sulfuric acid-activated carbon fibers that have adsorbed NH3.
O removal treatment method.