JPH07187658A - Method for producing molecular sieve carbon adsorbent - Google Patents

Abstract

(57) [Summary] [Object] To provide a method for producing a molecular sieve carbon adsorbent which has a large amount of oxygen adsorption and is excellent in the separation ability of oxygen and nitrogen. [Structure] A process in which a carbonized product obtained by treating a base material containing carbon as a main component by a conventional method is weakly activated by reacting with an oxidizing gas, and a carbonized product after the weak activation process is processed up to the preceding process. The step of performing reheat treatment at a temperature higher than the treatment temperature and the step of bringing the dry-distilled product after the reheat treatment step into contact with a thermally decomposable hydrocarbon to adjust the pores are sequentially performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a molecular sieve carbon adsorbent, and more particularly to a molecular sieve carbon adsorbent which is suitably used when adsorbing and separating oxygen and nitrogen in air to produce oxygen and nitrogen. Manufacturing method.

[0002]

2. Description of the Related Art As a method for producing a molecular sieve carbon (carbon molecular sieve) adsorbent, for example, Japanese Patent Publication No.
The method described in Japanese Patent No. 502743 is known. According to this method, it is said that a single-quality molecular sieve carbon adsorbent having good separation characteristics can be produced by treating a carbonized product under a specific condition using a specific furnace.

Other methods for producing a molecular sieve carbon adsorbent include, for example, JP-B-49-18555 and JP-A-6-18555.
No. 1-8004, JP-A-4-310209, etc.

[0004]

However, in these conventional methods, when the molecular sieve carbon adsorbent is produced by heat treatment, there is a peak of the treatment temperature at which the maximum adsorption amount is obtained depending on the base material. When heat treatment was carried out, the adsorption rate of oxygen and nitrogen became slow, and a large separation ability as a molecular sieve carbon adsorbent could not be obtained. For this reason, the fact is that the heat treatment temperature lower than the above-mentioned peak temperature is adopted by giving importance to the adsorption rate at the expense of the adsorption amount.

Further, in Japanese Patent Publication No. 49-18555, it is described that carbon tetrachloride is exemplified to improve the molecular sieving ability by heating after activation.
There is no mention of any means for improving the nitrogen separability, and in fact, such activation and heating alone cannot provide a molecular sieve carbon adsorbent having industrially satisfactory oxygen / nitrogen separability. It was

[0006] Therefore, it is an object of the present invention to provide a method for producing a molecular sieve carbon adsorbent which has a large amount of oxygen adsorption and is excellent in the ability to separate oxygen and nitrogen.

[0007]

In order to achieve the above-mentioned object, a method for producing a molecular sieve carbon adsorbent of the present invention is to oxidize a carbonized product obtained by treating a substrate containing carbon as a main component by a conventional method. Process of reacting with volatile gas to weakly activate, dry heat treatment after weak activation process to reheat treatment at a temperature higher than the treatment temperature up to the previous process, and heat molecular sieve carbon precursor after reheat treatment process It is characterized in that the step of adjusting the fine pores by bringing them into contact with a decomposable hydrocarbon is sequentially performed.

The weak activation step in the method of the present invention comprises:
A dry-distilled product obtained by treating a substrate containing carbon as a main component by a conventional method, for example, granulating a phenol resin by a conventional method,
It is a step of activating a dry-distilled product or the like that has been dry-distilled at 0 to 750 ° C. by reacting it with an oxidizing gas such as oxygen, water vapor, carbon dioxide, etc., and is a step for increasing the adsorption amount. The processing temperature and processing time in this step are usually 700 to 900 ° C.
However, the higher the treatment temperature and the longer the treatment time, the faster the adsorption rate can be.

Further, in this weak activation step, in order not to adversely affect the final pore adjusting step,
It is necessary to weakly activate the pores so as not to excessively widen them, and it is preferable to weakly activate by selecting the conditions so that the carbon yield is 99 to 90%. If the carbon yield, that is, the activation yield is too low, the amount of adsorption cannot be sufficiently increased, and if it is too high, the separation ability is lowered.

The next re-heat treatment step is a step of heat-treating the material activated in the above-mentioned step at a temperature higher than the temperature given in the carbonization step or the weak activation step so far to heat-shrink the pores. By performing this step, the equilibrium adsorption amount can be improved by 5 to 15%. The treatment temperature at this time is most suitable for oxygen / nitrogen separation in the range of 1000 to 1200 ° C. When the temperature is low, thermal contraction is not sufficient, and when it is too high, the adsorption amount is rather lowered.
The atmosphere gas may be nitrogen gas or the like, and the processing time is 0.
The range of 1 to 3 hours is suitable. If it is too short, there is almost no effect, and if it is long, the effect is hardly improved.

The final fine pore adjusting step is performed to adjust the fine pore diameter, and is a step of contacting with a thermally decomposable hydrocarbon such as toluene at 700 to 800 ° C., for example. In this step, the pore size of a desired size can be obtained by appropriately selecting the type of pyrolytic hydrocarbon, the treatment temperature, and the treatment time.

[0012]

EXAMPLES Examples and comparative examples of the present invention will be described below. A general dry-distilled product obtained by granulating a phenol resin and dry-distilling at 450 to 750 ° C. was used as carbon dioxide gas 20%, nitrogen 8
The mixture was treated at 800 ° C. for 0.5 to 3 hours in a 0% mixed gas atmosphere, and was weakly activated so that the carbon yield was 99 to 90%. Next, this was heat-treated in nitrogen gas in the range of 900 to 1300 ° C. for 0.1 to 3 hours while changing the treatment temperature. Furthermore, toluene is added to nitrogen gas at 700 to 800 ° C.
% Gas containing oxygen, the oxygen constant k is approximately 4.0 to 5.0.
Was carried pore adjusted to × become ^10-2. In addition, for comparison, those which were not subjected to the weak activation (Comparative Example 1),
Those that were not heat-treated (Comparative Example 2) were prepared, and the performance of each molecular sieve carbon adsorbent was compared under the conditions of atmospheric pressure and 25 ° C.

There are various evaluations of the performance of the molecular sieve carbon adsorbent, but in this case, the equilibrium adsorption amount of oxygen and the separation coefficient between oxygen and nitrogen were evaluated. There are various ways to express the separation factor, but the most common method was used. That is, the adsorption rate formula is expressed as dq / dt = k
(Q * -q) (where q is the adsorption amount at time t,
(q * is the equilibrium adsorption amount, k is a constant), and the constant k is calculated from the measured adsorption rate, and the ratio of the constants of oxygen and nitrogen is α = k.
The separation coefficient was O ₂ / kN ₂ .

Table 1 shows the measurement results of the oxygen equilibrium adsorption amount and the oxygen / nitrogen separation coefficient of each molecular sieve carbon adsorbent depending on the difference in carbon yield and reheat treatment temperature.

[0015]

[Table 1]

As is clear from Table 1, the molecular sieve carbon adsorbents produced by the method of the present invention are superior in oxygen adsorption amount and separation coefficient to those of Comparative Examples 1 and 2, and in particular,
When the carbon yield is 99 to 90%, the heat treatment temperature is 1000.
A significant difference is seen at ~ 1200 ° C.

The molecular sieve carbon adsorbent produced by the method of the present invention has improved performance mainly for the purpose of separating oxygen and nitrogen, but it also contains another gas mixture, for example, argon. It can also be effectively used for separation of mixed gas. The dry-distilled product obtained by the conventional method may be a vinylidene chloride resin or the like in addition to the phenol resin.

[0018]

Industrial Applicability As described above, the method for producing a molecular sieve carbon adsorbent of the present invention has a weak activation (activation) step, a reheat treatment step, and a pore adjusting step for a carbonized product obtained by a conventional method. By sequentially performing the above, the oxygen adsorption amount and the separation coefficient can be significantly improved. Therefore, by using this as an adsorbent for nitrogen production, a large amount of nitrogen is generated per unit amount of adsorbent, the nitrogen yield is increased, and the production cost of nitrogen can be reduced.

Claims (3)

[Claims] 1. A step of reacting a dry-distilled product obtained by treating a base material containing carbon as a main component by an ordinary method with an oxidizing gas to weakly activate, and a dry-distilled product after the weak activation step to a pre-process. The molecular sieve characterized by sequentially performing a step of reheat treatment at a temperature higher than the treatment temperature of up to and a step of adjusting the pores by contacting the molecular sieve carbon precursor after the reheat treatment step with a pyrolytic hydrocarbon. Method for producing carbon adsorbent. 2. The carbon yield in the weak activation step is 9
It is 9-90%, The manufacturing method of the molecular sieve carbon adsorbent of Claim 1 characterized by the above-mentioned. 3. The processing temperature of the reheat treatment step is 1000.
It is -1200 degreeC, The manufacturing method of the molecular sieve carbon adsorbent of Claim 1 characterized by the above-mentioned.