JPH07165407A - Small spherical activated carbon made of ion exchanger - Google Patents

Abstract

PURPOSE: To obtain an activated carbon microsphere from a gel-type inexpensive ion exchanger by carbonizing a granular org. gel ion exchanger in an inert atmosphere and then activating.

CONSTITUTION: A granular org. gel ion exchanger is carbonized in an inert atmosphere at 600 to 900°C, and then activated in an oxidative atmosphere at 800 to 900°C to obtain the activated carbon of the purpose. The carbonizing temp. is preferably 750 to 875°C. As for the exchanger, both of cation and anion exchangers can be used. The cation exchanger is especially a sulfonated styrene- divinylbenzene copolymer or styrene-acrylic acid copolymer. The cation exchanger is preferably a H type one. As for a preferable anion exchanger, especially, a polyacryl resin or polystyrene resin having tertiary or quaternary ammonium groups are used. Before carbonizing, the gel-type ion exchanger is preferably oxidized in an oxidative atmosphere up to 400°C.

COPYRIGHT: (C)1995,JPO

Description

Detailed Description of the Invention

Activated carbon is the most commonly used adsorbent. This fact makes it a “major” (ma) in the adsorption process.
It can be found by its non-specific adsorption properties that make it an “id of all work).” Increased demands on environmental obligations and limited legislation have led to increased demands on activated carbons. It is made by carbonizing and activating a compound containing OH. In fact, volatilization of some components during the carbonization process and combustion during activation can result in significant weight loss, thus allowing adequate yields. These compounds are preferred.

Further, the type of activated carbon can be of fine or coarse pores, depending on the solid or fragment treated base material. Useful raw materials include coconut shell, wood chips, peat, pit coal, tar, as well as special polymers that play a key role in the production of activated carbon fabrics, among others. Activated carbon has been used in various forms, powdered carbon, granular carbon, shaped carbon, and spherical carbon since the end of 1970. Due to its special shape on the one hand and, on the other hand, its extremely high wear resistance, such spherical shapes in special fields, such as the production of protective clothing against chemical poisons and filters for low pollutant concentrations in large air volumes. There are great demands on the use of carbon.

Even today, high quality spherical carbon has already been produced by carbonization and activation of polysulfonated macroporous ion exchangers based on styrene and divinylbenzene, but most of the spherical carbon is It is made by a multi-step process using tar-like distillate residues and is therefore complicated and expensive.

A related patent states that macroporous resins should form the base material, and that gel-type resins are not suitable because they are active because "inert surfaces" are not formed. Because it cannot be converted.
In most cases, macroporous ion exchanger resins have a more strongly cross-linked structure than gel type ones and usually require a high proportion of expensive divinylbenzene.

As a result of the considerable weight loss during carbonization and activation, the cost of manufacturing the base material is essentially significant. This provides a rationale for the fact that activated carbon microspheres made from macroporous ion exchangers only have a small market share. The object of the present invention was therefore to find a suitable process for the production of activated carbon globules from gel-type inexpensive ion exchangers.

Surprisingly, the granular organic gel type ion exchanger is mainly used in an inert atmosphere at 600 to 900 ° C.
Carbonized at temperatures of
It has been found that it can be made from granular organic gel type ion exchangers by activation at temperatures up to 900 ° C. The carbonization temperature is preferably 750 to 875 ° C.

Both cation or anion exchangers can be used. The cation exchanger comprises in particular a sulphonated styrene-divinylbenzene copolymer or a styrene-acrylic acid copolymer. The cation exchanger is preferably used in the H ⁺ form.

Suitable anion exchangers are based in particular on polyacrylic or polystyrene resins having tertiary or quaternary ammonium groups.

Prior to carbonization, the gel-type ion exchanger is preferably subjected to oxidation in an oxidizing atmosphere at temperatures up to 400 ° C.

In general, the oxidation phase is preceded by a drying step so that an amount of moisture of less than 55% is expelled. Such a drying process can be performed in air. However, as the temperature is raised in the oxidation process, the oxygen content must be reduced. 1 ~ 5 when the temperature reaches 300 ℃
To% it should be decreasing. The oxidation phase lasts 20 minutes to 6 hours, depending on the agglomerates used (fluidized bed / rotating tube). Oxygen plays a crucial role during the oxidation process, similar to what the sulphonic acid groups of cation exchangers do, which reduces the amount of volatile constituents and reduces oxygen cross-linking, reactive functional group positions that increase the softening temperature. Form.

The softening or agglomeration of the ion exchanger during heating is
It can be largely prevented by sulfonation and preoxidation. However, some of the resin globules may nevertheless form agglomerates, especially during undesired shut-downs in a rotary tube furnace. Such agglomeration can be avoided by pulverizing the ion exchanger with a small amount of non-softening powder such as carbon powder, preferably 0.5 to 5% by weight of pitch coal powder or activated carbon powder.

Carbon powder is added when filling the rotary tube furnace. It distributes very quickly and gives the surface of the ion exchanger a dry coating if they become sticky. No agglomeration was observed in the fluidized bed, at least on a pilot plant scale.

In the subsequent carbonization, which can also be considered as a pyrolysis or smoldering process, first of all CO ₂ , SO
_{As well as 2} , H ₂ O and CO, hydrocarbons and partially oxidized hydrocarbons are volatilized. In the case of polysulfonated ion exchangers, which is the usual case, the sulfur content can reach values of 15% or higher, based on anhydrous material. Starting from the H ⁺ form, the sulfonic acid is SO ₂ and H
Separated as ₂ O, while some percentage of sulfur is introduced into the material, partially in the form of thioethers. Starting from the Na ⁺ form, sulphate is formed, the carbon being first sulphated before reducing it. Even if the considerable unpleasant odor is not taken into consideration, high ash content is nevertheless a problem. Therefore, it is recommended to change the Na ⁺ type to the H ⁺ type by pickling. In order to increase the material's receptivity to combustion in the subsequent activation step, it is advantageous to add some steam to carry out a pre-light activation during the pyrolysis (smoldering) step.

This smoldering is based on a dry matter of 4
It results in a weight loss of 0-60%. Given an additional loss of 10% by weight or more of sulfur, the weight loss based on carbon is about 30-50%. Depending on the respective technical equipment by hand, the smoldering step at temperatures of 350-900 ° C. may take from less than one hour to several hours.

Oxygen introduced during the course of the oxidation process volatilizes again initially in the form of CO ₂ during smoldering and subsequently as CO when high temperatures are reached. Without a doubt,
This method is comparable to the first activation, which actually has a positive effect when the true activation step is performed.

The activation is usually carried out at a temperature of 800 to 900 ° C. This step is carried out in the empty form or diluted with an inert gas to form C.
Includes combustion with O ₂ , H ₂ O, O ₂ or CO. The steam activation method is carried out by adding 3 to 50%, preferably 3 to 15% of steam in a main inert atmosphere. The diffusion of oxidizing gas into the interior of the globules must be faster than the burning reaction, otherwise burning will be mainly concentrated in the outer shell of the globules. This can be achieved by a suitable combination of temperature and concentration, which is known to those skilled in the production of activated carbon. According to the desired degree of activation, 30-50% of the carbon present after pyrolysis is additionally vaporized while the sulfur content is reduced to 1-2%. Suitable yields, based on dry matter, are 25-30%, BET surface area is 800 m ² / g and benzene adsorption is 30-35% (P / P ₀ = 0.9). 15
An internal area of 00 m ² / g will be obtained, however, in this case the yield is between 12 and 1 based on dry starting material.
Going down to 5%.

The first heat treatment results in an increase in density. Later shrinkage of the material and increasing porosity can be observed. The particle size and particle size distribution depends on the starting material. However, the diameter of the desired product should be considered to be 10-20% smaller. The bulk weight of the desired product is 430-650 g /
It changes with l.

Different heat treatments can be carried out in a rotary tube furnace or a fluidized bed. They allow the respective best conditions, which can be carried out in one and the same agglomerate. This is advantageous in view of the considerable mass difference between the starting material and the desired product. The carbonization and activation steps can not only be carried out in a fluidized bed, but can also be carried out in different stages, the carbonization being carried out in a rotary tube furnace while the activation can be carried out in a fluidized bed. As a result of poor heat transfer and gas exchange, the reaction times are considerably longer in rotary tube furnaces, especially for the activation process. However, this does not affect the quality of the final product. The difference depends more on the processing time than on the product quality.

The present invention provides highly stable activated carbon microspheres made by the method described above. Characteristically, the pore distribution structure of this microsphere activated carbon shows a small mesopore spectrum in the range of 100-300 Å and a few macropores.

Example 1 4300 Kg of a gel-type ion exchanger (DOW HCRSEH ⁺ ) having a diameter of 0.4 to 0.8 mm was dried (weight loss is slightly greater than 50%) and a ratio of nitrogen / nitrogen of 2: 1. Precarbonization in a rotary furnace at 400 ° C. for 12 hours in an air mixture. The carbonization step was then completed at about 900 ° C. for 6 hours in a nitrogen atmosphere.

After the pre-carbonization step (400 ° C.), the yield was about 22% based on the (wet) raw material, but 9
After treatment at 00 ° C it fell to 17%.

The carbonized material has a small inner surface (approximately 200 m
² / g). Afterwards steam was added to activate it in a pilot plant (rotary furnace) for 8 hours at 900 ° C. As a result, an internal surface area of 1300 m ² / g could be achieved and the% combustion loss was 35. 1 hour pre-carbonization (4
After 00 ° C.) the apparent density of the material was 750 g / l. After the second step (900 ° C.) it reached a value of about 900 g / l, but fell to 650 g / l after the activation step. At the same time, the diameter of the microspheres dropped to 20%.

Example 2 Starting Material

DOW HCRSE with a water content of 52%
10 m ³ (= 7.8 in acid form commercially available as H ⁺
Gel type ion exchanger resin of t).

I. Smoldering process

1. Process (up to 400 ° C). About 5 in nitrogen
% Additional oxygen. Residence time in rotary furnace is about 1 hour. Yield: 1975 Kg, based on dry matter: 52.7.
%.

2. Process (up to 850 ° C). 20 in nitrogen
Add% steam. Residence time about 1/2 hour. Yield: 1663 Kg, on dry matter: 44%.

The smoldered material had a bulk density of 938 g / l and a BET surface area of 80 m ² / g.

II. activation

The activation was also carried out in a rotary furnace due to a fluidized bed failure.

Temperature: 875 ° C. Add 25% steam to nitrogen Residence time: 8 hours Yield: 1104 kg, based on dry substance: 27%. BET surface area is 1250 m ² / g, apparent density 634
It was g / l. The ash content was 0.4%.

Similar results were obtained in a very short time when the activation was carried out in a fluidized bed.

While the specification and claims have been set forth by way of illustration, it will be appreciated that they are not limiting and various modifications can be made without departing from the scope of the invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ernesto De Luiter, Federal Republic of Germany Day 51381 Lever Kusen, Hohenstraße 57

Claims (17)

[Claims] 1. A method for carbonizing a granular organic gel ion exchanger at a temperature of 600 to 900 ° C. in a substantially inert atmosphere, and thereafter activating it at a temperature of 800 to 900 ° C. in an oxidizing atmosphere. And a method for producing activated carbon. 2. The ion exchanger is sulfonated styrene-
3. The method of claim 2 which is a cation exchanger selected from the group consisting of divinylbenzene copolymer or styrene-acrylic acid copolymer. 3. The method of claim 1, wherein the cation exchanger is in the H ⁺ form. 4. The method according to claim 1, wherein the ion exchanger is an anion exchanger selected from the group consisting of polyacrylic resins or polystyrene resins having tertiary or quaternary ammonium groups. 5. The method of claim 1, wherein the ion exchanger resin is dried prior to carbonization. 6. The method of claim 1 wherein the carbonization temperature is in the range of 750-875 ° C. 7. A gel ion exchanger, 40 times prior to carbonization
Process according to claim 1, characterized in that it is subjected to oxidation in an oxygen-containing atmosphere at temperatures up to 0 ° C. 8. The method of claim 7, wherein the oxygen content in the atmosphere is progressively reduced and the temperature is progressively increased. 9. The method of claim 1, wherein 3 to 50% by volume of water vapor is added to the substantially inert atmosphere to activate the carbonized material. 10. The method of claim 1 wherein carbon dioxide is added during activation in a substantially inert atmosphere. 11. The method of claim 1, wherein air is added during activation during the activation in a substantially inert atmosphere. 12. The method of claim 1 wherein both carbonization and activation are carried out in a fluidized bed. 13. The method of claim 1 wherein carbonization and activation are performed in separate steps. 14. Process according to claim 13, characterized in that the carbonization is carried out in a rotary furnace and the activation is carried out in a fluidized bed. 15. The method of claim 1 wherein the gel ion exchanger resin is powdered with a non-softening powder prior to thermal decomposition. 16. Activated carbon produced by the method of claim 1. 17. Spherical activated carbon characterized in that it has a narrow mesopore distribution of mainly 100 to 300 angstroms and only a few macropores.