JPH0669883B2 - Molecular sieve carbon material using wood-based raw material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a molecular sieve carbon material which is useful as an adsorbent for PSA, using a wood-based raw material such as pine or lauan.

<Prior Art> Two types of air separation methods using a PSA method (pressure swing adsorption method) using a molecular sieve material are known: oxygen enrichment mainly using a zeolite-based adsorbent and nitrogen enrichment using a molecular sieve carbon material.

As a conventional molecular sieve carbon material, it is common to adjust the pore size by adding some treatment to carbon material or activated carbon from coal-based raw materials such as coal and coke, and a typical production method is as follows. There is something like this.

(1) Coke having a volatile content of up to 5% is treated with a carbon fissionable hydrocarbon at a temperature of 600 to 900 ° C. to deposit the fissioned carbon in the skeleton of the coke, and How to make holes even smaller
No. 52-18675) (2) A carbonaceous adsorbent having a pore size of 0.5 nm or more is adsorbed with a hydrocarbon having a molecular size of the above pore size, and then heated to generate a thermal decomposition product of the hydrocarbon. A method of improving performance as a molecular sieve carbon material by narrowing the pore size by precipitating at the entrance of the pores of the carbonaceous adsorbent (JP-A-56-130226).

(3) Add a binder to the palm shell charcoal powder and granulate.
Dry-distilled at 0-900 ° C, dry-distilled carbon is washed with a dilute mineral acid aqueous solution, washed with water, and then dried, and 1-3% of coal tar pitch and / or coal tar is added to impregnate at 200-400 ° C. After that, heat it up to 950-1000 ℃ and heat it,
A method of cooling in an inert gas (JP-A-59-45914).

Among the methods (1) and (2), the molecular sieve function is achieved by adjusting the pore size of the coke or the carbonaceous adsorbent by depositing carbon produced by thermal decomposition of gaseous hydrocarbons in the pores. It is necessary to heat in a gaseous hydrocarbon atmosphere or to preliminarily adsorb hydrocarbons before heat treatment.

Therefore, the process becomes complicated and it is difficult to obtain a stable quality molecular sieve carbon material. The method (3) requires complicated steps such as granulation, drying, dry distillation, washing with a dilute mineral acid aqueous solution, washing with water and drying, impregnation with coal tar pitch, and heat treatment. One of the characteristics is that coconut shell charcoal is used as a raw material, but at present, palm coconut shell coal relies entirely on imported products and requires a strong force for fine crushing. For the above reasons, it is desired to produce a molecular sieve carbon material from an easily available raw material by an easy process.

<Problems to be Solved by the Invention> An object of the present invention is to provide a high-performance molecular sieve carbon material of stable quality that can be produced by a simple process using a wood-based raw material that is easily available and easily crushed. And

<Means for Solving the Problem> The present inventors have conducted various studies on the production method of the molecular sieve carbon material using various raw materials for carbon material production, the performance of the obtained carbon material, etc., and as a result, wood such as pine and lauan. The present invention has been accomplished by finding that the system raw material exhibits extremely excellent performance as a raw material for the molecular sieve carbon material.

The molecular sieve carbon material of the present invention is obtained by preliminarily drying and coarsely crushing wood pieces cut into an appropriate size and then finely pulverizing the carbide obtained by carbonizing at 400 to 1000 ° C., and 5 to 20 parts by weight with respect to 100 parts by weight of the carbide. Part of the pitch-based binder and water are kneaded, mixed well, molded, dried, then dry-distilled at 600-1100 ° C in a non-oxidizing inert gas atmosphere, and cooled in an inert gas to obtain. To be

As the raw material of the carbonaceous material of the present invention, almost all kinds of wood pieces that are normally available can be used, but among them, pinewood and lauan wood are also easily available, and the fine pulverizability of carbonaceous material after primary carbonization is also good. Good and suitable for the purposes of the invention.

The raw wood pieces are pre-dried to an appropriate water content, coarsely crushed, and then carbonized by primary carbonization at 400-1000 ° C. If the dry distillation temperature at this time is less than 400 °, the removal of volatile components is insufficient, the specific surface area is small, and sufficient adsorption capacity cannot be obtained. Further, it is not necessary to exceed 1000 ° C. and the energy consumption increases, which is not preferable.

After finely pulverizing the obtained carbide to obtain a molded product which is as uniform and dense as possible, 5 to 20 parts by weight and an appropriate amount of water are added to a pitch-based binder such as coal tar pitch to 100 parts by weight of the carbide, and the mixture is added by a conventional method. Mix and mold. If the amount of binder exceeds 20 parts by weight, the pore size of the molecular sieve carbon material will be small and the oxygen / nitrogen separation will be good, but the amount of gas adsorption will decrease, while if it is less than 5 parts by weight the amount of gas adsorption will be sufficient. However, since the pores do not shrink and the pore diameters are not uniform, the separability of oxygen / nitrogen deteriorates. The pore size of the molecular sieve carbon material can be adjusted by the amount of the binder added and the dry distillation conditions (atmosphere and temperature) in the subsequent step. It is desirable that the grain size of the carbide is pulverized so that 200 mesh under is 80% or more.

The molding size (diameter and length) is preferably about 2 to 5 mm. This molding process has the effect of facilitating the subsequent handling operation and reducing the particle spacing of the obtained carbon material to have a dense and uniform property, and to give a product with a shape suitable for use in the PSA device. There is. The molded product is pre-dried so that the water content does not abruptly evaporate in the initial stage of the dry distillation and the performance of the product is not deteriorated, and then subjected to the dry distillation process. The predrying may be carried out usually at 50 to 150 ° C. for about 0.3 to 3 hours.

Dry distillation is carried out at a maximum temperature of 600 to 1100 ° C. by using a normal dry distillation furnace such as a vertical type dry distillation furnace or a rotary kiln and gradually raising the temperature under an inert atmosphere of nitrogen or a non-oxidizing gas. By keeping the atmosphere in an inert atmosphere during this period, it is possible to prevent the performance of the product from being deteriorated due to the progress of oxidation and activation of the carbon material. Although it depends on other conditions, generally, if the carbonization temperature is lower than 600 ° C, sufficient molecular sieving performance cannot be imparted.
If the temperature exceeds ℃, the amount of adsorbed gas will decrease.

The dry distillation time depends on the raw materials, the conditions of the first dry distillation carbonization, the temperature pattern of the dry distillation, etc., but the holding time at the maximum temperature is usually in the range of 5 to 120 minutes. If the temperature is rapidly raised, the performance of the product will be deteriorated due to the rapid volatilization of volatile components. Therefore, it is desirable that the rate of temperature increase be 3 to 20 ° C / min. It may be appropriately determined according to the performance of the product to be processed. After the dry distillation, while maintaining it in an inert gas atmosphere, it is cooled to 200 ° C or lower to obtain a molecular sieve carbon material.

<Operations and Effects> The wood-based raw material used for the molecular sieve carbon material of the present invention is easily available, and has a property of giving a carbide having a large specific surface area over a wide temperature range when being made into a carbide.
That is, even if the carbonization temperature is increased, the specific surface area does not decrease, and a large specific surface area can be obtained.Therefore, it is not necessary to strictly control the heating rate during carbonization, and relatively high temperature and high temperature Carbonization and carbonization are possible. Therefore, the operation is easy, and since sufficient dry distillation can be performed, the specific surface area becomes large, and the amount of distillate in the secondary dry distillation after molding is small, so that there is an advantage that deformation due to burning is small.

Further, the pulverizability of carbides is much better than that of palm shells and the like, and a fine powder suitable for molding can be easily obtained.

The results of measuring the strength (microstrength) of the carbonaceous material, which is the raw material of the molecular sieve carbonaceous material, are shown in FIG. The measurement is carried out by the following method. The larger the value, the more difficult the fine pulverization is, and the smaller the value, the easier the fine pulverization is. That is, the pine carbon material is more easily pulverized than the coconut shell charcoal.

"Measurement method of micro strength" 1. Grind the sample into 840-2000μ in an iron mortar and weigh 2g of it into a cylindrical tester with an inner diameter of 25mm and a length of 305mm.

2. Put 12 steel balls into the tester and rotate them 800 times around the center line perpendicular to the long axis (25 rpm x 32 min).

3. Remove the steel balls and shake the sample with a 250μ sieve for 10 minutes.

4. Weigh a sample of 250μ or more The molecular sieve carbon material of the present invention will be described in more detail with reference to the following examples. The performance evaluation of the molecular sieve carbon material was performed as follows.

A carbon material is filled in an adsorption tower having an inner diameter of 8 mm and a length of 1000 mm, degassed from the lower part of the adsorption tower with a vacuum pump, and then air having a pressure of 5 kg / cm ² G is charged. Then about 40 ml / min from the upper part of the adsorption tower
Measure the oxygen concentration in the gas discharged at the speed of 2 minutes,
The measured value was used for the purpose of performance evaluation. The molecular sieve carbonaceous material selectively adsorbs oxygen in the air, and in this test, it can be said that the lower the oxygen concentration in the outflow gas, the better the performance of the carbonaceous material. A Beckman Model 0260 oxygen analyzer was used to measure the oxygen concentration.

The specific surface area was measured by BET method using CO ₂ .

Examples 1 to 8 Pine chips and lauan chips were dried, and 85 parts of carbonaceous material obtained by carbonizing at 750 ° C. for 25 minutes was finely pulverized so that 200 mesh under was 80% or more, and coal tar pitch was 15 parts. water
Twenty-five parts were added and mixed well, and then thoroughly mixed with a kneader. This was molded into a pellet type with a diameter of 2.4 mm by an extrusion molding machine. After the molded product is dried at 100 ° C for 3 hours, the temperature is gradually raised in a vertical drying furnace while flowing a small amount of nitrogen gas, and the temperature is maintained at the specified temperature (600 ° C, 750 ° C, 900 ° C and 1050 ° C) for 1 hour. It was carbonized. Then, the product was cooled to 200 ° C. and then left to cool to obtain a product. Table 1 shows the industrial analysis and processing conditions of pine and lauan raw materials, carbides and products, and the oxygen concentration in the evaluation test of the products. FIG. 1 shows the relationship between the carbonization temperature of various raw materials and the oxygen concentration during the evaluation test.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the dry distillation temperature when various raw materials are dry carbonized in an inert atmosphere and the evaluation test (oxygen concentration%) of the obtained carbide. FIG. 2 is a graph showing the relationship between the fine crushing strength of various raw materials and the carbonization temperature.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-55-100212 (JP, A) JP-A-51-77594 (JP, A) JP-A-59-164611 (JP, A) JP-B-52- 6955 (JP, B1)

Claims (1)

[Claims] 1. A piece of wood cut to an appropriate size is pre-dried, coarsely crushed, and then carbonized at 400 to 1000 ° C. to obtain finely ground carbide, and 5 to 20 parts by weight of 100 parts by weight of carbide is crushed. Wood obtained by adding pitch-based binder and water, kneading, mixing well, molding, drying, then dry-distilling at 600 to 1100 ° C in a non-oxidizing inert gas atmosphere, and cooling in an inert gas. Molecular sieve carbonaceous material using system raw material.