JPS6388036A - Decolorizing adsorbing material - Google Patents

Abstract

PURPOSE:To especially enhance the decolorizing adsorbing property of melanoidin in liquid phase adsorption, by forming the decolorizing adsorbing material from an acrylonitrile type activated carbon fiber wherein a BET specific surface area, an entire pore area and ash component are within a specific range. CONSTITUTION:After an acrylonitrile fiber is oxidized in an oxidative atmosphere, the oxidized fiber is activated in activating gas to obtain a decolorizing adsorbing agent composed of an acrylonitrile type carbon fiber. This decolorizing adsorbing agent has characteristic values such that a BET specific surface area is 1,000-2,000m<2>/g, an entire pore volume (Va) is 0.70-2.50cm<2>/g, the percentage Vt/Va of the volume (Vt) occupied by transitional pores with a pore size of 40-2,000Angstrom to Va is 25% or more and ash is 2.0wt% or less. This decolorizing adsorbing agent can be suitably used in liquid phase adsorption centering around a food industry, especially, in the decolorizing adsorption of melanoidin.

Description

[Detailed description of the invention] (Industrial application field) Many foods such as sake! It is used in related food manufacturing fields for the purpose of decolorizing and adsorbing amino carbonyl reaction pigment components (melanoidins) produced during the lithium manufacturing process.

(Prior art and its problems) Powdered activated carbon has been used as an adsorbent in various fields in gas phase and liquid phase systems.Generally, the field of liquid phase adsorption is closely related to the food industry. In other words, activated carbon has traditionally been used to decolorize and remove coloring components generated in the manufacturing process of many foods such as sugar solutions, pepper oil, lactic acid drinks, and sake.This is a problem in the food industry. Coloring substances vary depending on the type of food and are extremely diverse, but the common problem in many foods is amino-carbonyl reaction-based coloring components, ie, melanoidins.

This melanoidin is a colored macromolecular substance, and its molecules range in a very wide range from several thousand to several million.

Therefore, activated carbon with large pores is required to remove melanoidin. Furthermore, since activated carbon is used for food, the amount of ash in activated carbon is usually severely limited. Currently, powdered activated carbon produced by chemical activation method is widely used for these food industry applications, but its powdery form makes it difficult to handle, recycling is almost impossible, and decolorization speed is slow. There are many problems, including the difficulty of separating activated carbon after decolorization.

On the other hand, recently developed activated carbon fiber (same as fibrous activated carbon, hereinafter abbreviated as rACFJ) is manufactured from rayon fiber, phenol fiber, acrylic fiber, etc. It is attracting attention as a new type of adsorption material because it has excellent processability that is not found in granular activated carbon, and excellent adsorption and desorption properties such as an extremely fast adsorption and desorption rate. This ACF has already been put into practical use in the fields of solvent recovery and air purification, and is being applied to various other fields. However, current application development is centered on the field of gas phase adsorption, and application development in the field of liquid phase adsorption has not progressed much.

The reason for this is thought to be mainly due to the size of the pores constituting the ACF. That is, the pore structure of ACF is significantly different from that of powdered activated carbon, in which micropores with a pore diameter of less than 40 pores occupy the majority of the pores, and pores with a pore diameter of 40 to 2
There are almost no transitional holes larger than 000 Å. Although these micropores are extremely effective for gas phase adsorption, they are not very effective for liquid phase adsorption in the food industry mentioned above. This is because in liquid phase adsorption, the molecules of the adsorbed substance often have a larger molecular diameter than in gas phase adsorption; This is because in liquid phase adsorption, the apparent molecular diameter of the adsorbed substance in the liquid phase becomes larger than it actually is due to the effects of solvent effects, etc., and as a result, it is almost impossible to enter the micropores of the adsorbent. .

Therefore, ACF for use in liquid phase adsorption needs to have a large number of transitional pores rather than micropores. Conventionally, ACF with enlarged pores has a specific An ACF has been proposed in which water-soluble salts, etc. are impregnated into 80F, which has structural characteristics, and then treated with an activating gas (Japanese Unexamined Patent Publication No. 5818418). However, the ACF according to this proposal has enlarged pores. However, the fiber strength is low and the ash content h1 in ACF is high, making it unsuitable for the purpose of liquid phase adsorption in the food industry.
In the case of ACF made from acrylic fibers, metal oxides such as titanium dioxide are added to the raw material polyacrylonitrile.
．． 10 to 1600% by weight, and this was mixed in air at 20% by weight.
Specific surface f14i obtained by oxidizing at 0 to 400°C and then activating at 800 to 1100°C in a mixed gas of water vapor and carbon dioxide gas.

ACFs with a large number of transitional holes in the range 00-2000 m'/(If) have also been proposed.

However, this ACF has extremely low fiber strength,
It is extremely easy to pulverize and has a high ash content, making it unsuitable for liquid phase adsorption in the food industry.

From the above, ACF has many transitional pores with large pore diameters and has a low content of impurities such as ash.
If so, it is extremely useful as a liquid phase adsorbent in fields centered on the food industry.

(Objective of the invention) The present invention is a decolorizing adsorbent having a large number of transitional pores with a large pore diameter and a low ash content. The present invention provides a decolorizing adsorbent that can be suitably used for adsorption.

(Structure of the Invention) The present invention has a BET specific surface area of 1000 to 2000 m'.
/9, total pore volume (Va-) is 0.70 to 2.50 cm
”/Q, and the pore diameter for Va is 40 to 2000
Volume occupied by human transitional pores (Vt) This is a decolorizing adsorbent made of acrylonitrile-based activated carbon fiber.

The decolorizing adsorbent of the present invention has characteristics not found in conventional rayon-based F or phenol-based ACF. In other words, in rayon-based ACF and 71-nol-based ACF, ACF
The pores that make up the pores are mostly composed of micropores with a pore diameter of less than 40 Å, and there are almost no pores with a pore diameter of 40 Å or more. Therefore, although rayon-based ACF and phenol-based ACF exhibit good adsorption performance for gas phase adsorption of benbin vapor, toluene vapor, etc., adsorption in the liquid phase,
In particular, the liquid phase adsorption performance of high molecular weight substances such as melanoidin is extremely low.

On the other hand, the decolorizing adsorbent of the present invention has a pore diameter of 40 to 2
A large number of transitional pores of 0,000 people are made, and the volume (V) is 25% or more of the total pore volume (Va). Therefore, the decolorizing adsorbent of the present invention is a rayon-based A
It exhibits high adsorption ability for melanoidin, etc. in the liquid phase, which was difficult to adsorb with CF and phenol.

In addition, the decolorizing adsorbent of the present invention has an ash content of 2,
The O-car content is 1fi% or less, making it extremely suitable for decolorizing applications in the food industry, such as sake production, where the ash content is subject to restrictions.

The decolorizing adsorbent of the present invention is basically produced by a conventionally known method in which acrylonitrile fibers are oxidized in an oxidizing atmosphere and then activated in an active gas.

The raw material acrylonitrile fiber contains at least 80% by weight of acrylonitrile, preferably 90 to 99% by weight.
．． It is an acrylonitrile-based uA fiber with 1!7 ash molecules iO,001~0.100% by weight than a polymer or copolymer containing 5% by weight, and such acrylonitrile-based fiber strengthens the purification of acrylonitrile and comonomer. It can be obtained by washing the fibers after spinning. If the ash content in the maple blue exceeds o or ioo %, as mentioned above, it is undesirable because it causes a significant decrease in the fiber strength of the ACF after activation. As a comonomer,
Acrylic acid, methacrylic ll1 female, allyl sulfonic acid,
or their salts, esters, acid chlorides, acid amides, n-substituted derivatives of vinylamide, vinyl chloride,
Examples include vinylidene chloride, α-chloroacrylonitrile, vinylpyridines, vinylbenzenesulfonic acid, vinylsulfonic acid and its alkaline earth metal salts.

The fineness of the acrylonitrile-based W4 miscellaneous material is not particularly limited, but is preferably 0.5 d to 15 d1, particularly 1 d to 5 d. If it is thinner than 0.5d, the fiber strength is low and the fiber is likely to break.On the other hand, if it is thicker than 15d, the oxidation rate is slow, and when ACF is used, the strength and elasticity are low and the activation yield is reduced.

The oxidation treatment of acrylonitrile fibers is carried out by heat treating the fibers in an oxidizing atmosphere.

Examples of oxidizing atmosphere media include air, oxygen, hydrogen chloride,
Although sulfur dioxide gas, a mixed gas, or a mixed gas of these and an inert gas is used, mainly air and a mixed gas of air and nitrogen are most suitable from the point of view of economy and process stability.

The most effective oxygen concentration in the oxidizing atmosphere in flameproofing treatment, ie, oxidation treatment, is in the range of 0.2 to 35% by volume. The oxidation treatment is carried out in two stages, with the first stage oxidizing at 20°C
The subsequent oxidation is performed at an oxygen concentration of 0.5 to 30% by volume medium.
Preferably, a 9% volume medium is used.

The time required for the oxidation treatment is 0.5 to 30 hours, preferably 1.0 to 10 hours, and is continued until the amount of oxygen bonding reaches 15% by weight or more. If the amount of oxygen binding is lower than this value, the degree of flame resistance will be low, the tow will break during high temperature activation, and the activation yield will also decrease.

The amount of R cord binding is preferably 16.5% by weight or more,
It can be increased to about 23-25%.

The oxidation temperature is 200 to 400°C, and the optimum temperature varies somewhat depending on the type of oxidation medium and the state of phosphorus impregnation.
The temperature ranges from 25 to 350°C.

As the activation method, either a batch method or a continuous method can be adopted, but a continuous method in which the oxidized fibers are continuously supplied into the activation furnace and activated is preferable.

In this case, the activation becomes faster as the temperature rises, and as a result, air is trapped from the introduction part of the oxidized fibers.
There is a risk of trial spots.

In order to avoid this, the pressure inside the furnace can be reduced to 0.00 by adjusting the opening of the slit in the introduction part, introducing nitrogen gas or steam, etc.
It is preferable to maintain the pressure within a range of 2 to 2 kq/cm' (gauge pressure, hereinafter the same). Furnace pressure is 0,002kg/c
If the pressure is less than n+' or negative pressure, significant activation spots will occur, making it impossible to produce a good product. On the other hand, if the internal pressure is made extremely high, water vapor condenses from the slit portions to the lower temperature portions, thereby clogging the slit portions and making activation spots more likely to occur.

As the activating gas, water vapor, carbon dioxide, etc. are used, but it is preferable to use a mixed gas of carbon dioxide and/or nitrogen, which is mainly water vapor. 3 water vapor to the total volume
It is desirable to use an activating gas containing 0% or more by volume. Gases that can be mixed with water vapor include nitrogen, helium,
Single gases or mixed gases such as argon, ammonia, -carbon oxide, and nitrogen dioxide gas are used.

Activation temperature is 800-1100℃, especially 900-1000℃
°C is preferred. Activation time varies depending on activation temperature, but from 1 minute
120 minutes is preferred.

The ACF of the present invention can be obtained by the method described above.

(Effect of the invention) Table 1 shows the effects of the decolorizing adsorbent of the present invention.

Here, N004 to N0.6 in Table 1 are examples of the present invention,
Nos. 011 to 3 are comparative examples outside the present invention.

Table 1 (Note) *: AC using tryptophan melanoidin solution
The decolorization rate was measured at F1 degree of 750 ppm. This method was based on the activated carbon decolorizing power test method for brewing.

O mark (NO, n to N0.6): According to the results in Table 1 of this R-light example, it can be seen that the product of the present invention has excellent decolorization and adsorption performance.

In other words, according to the activated carbon standard for brewing, the activated carbon concentration is 750p.
The decolorization rate of tryptophan melanoidin solution with P fat is 8
It is specified that the decolorizing adsorbent of the present invention, Nos. 4 to 4 to No. 016 in Table 1, of the present invention satisfies this standard and exhibits high decolorizing adsorption power for melanoidin.

(Examples and Comparative Examples) The present invention will be explained in more detail below using Examples and Comparative Examples.

Example 1 91.5% by weight of acrylonitrile, methyl methacrylate 8. Ofl 11%, acrylamide 0.5% by weight
Spinning a polymer with a copolymer composition consisting of 2.0% by weight
After washing with MA acid, the ash content was 0.005ff! f
A tow of 540,000 denier acrylic [1] (l yarn fineness 1.5 d) was obtained. This tow was heated in air at 240℃ for 2
time, and further 0.5 hours at 270°C with a free shrinkage rate of 75-8
When the oxidation treatment was carried out under a tension such that the tension became 0%, oxidized m-fibers with an oxygen bond ff of 118.5% by weight were obtained. Furthermore, this oxidized fiber was activated at a temperature of 920°C and a furnace pressure of 0.005 kg/am'.
Nite activation Msu (H20/COx /N2 = 5/
1/1) IcJ: '115 minutes/<y-time activation resulted in an ACF having the following properties.

Specific surface W4: 1320m'/g Va: 1,10cm''/QVt/
Va x 100: 35% Ash content: 066% by weight As a result of a decolorization test of melanoidin solution using this ACF, 80 F ml B for melanoidin solution
250ppm Te decolorization rate 45%, ACFm6750pp
The decolorization rate was 88% at m. This decolorization test was carried out in accordance with the activated carbon decolorization power test method for M advancement.

Comparative Example The characteristics of a commercially available phenol Ilt/fI ACF felt (trade name: F-15, manufactured by Kuraray Chemical Co., Ltd.) were determined, and the results shown below were obtained.

Specific surface &! : 1500i+'/gVa
: 0.5c1/g Vt /Va
When the ACFiR degree in the melanoidin solution was 250 ppm, the decolorization rate was 10%, and when the ACFiH melon was 750 ppm, the decolorization rate was 30%.

Claims (1)

[Claims] The BET specific surface area is 1000-2000 m^2/g, the total pore volume (Va) is 0.70-2.50 cm^3/g, and the volume occupied by transitional pores with a pore diameter of 40-2000 Å relative to Va ( Vt) percentage ((Vt/V
a) x 100) is 25% or more, and the ash content is 2
．． A decolorizing adsorbent made of acrylonitrile-based activated carbon fiber having a content of 0% by weight or less.