JPH08155295A - Carbon body and preparation thereof - Google Patents

Abstract

PURPOSE: To manufacture a carbon body having a sufficient strength in a state as it is formed and after heat treatment. CONSTITUTION: An aqueous mixture consisting of an active carbon particle, an organic binder of about 4 to about 25% expressed in weight percent based on the carbon content, a bentnite clay of from about 5 about 25% as an inorganic binder, a colloidal alumina of about 5 to about 35%, a silica in a water dispersed silica precursor form of about 0 to about 10%, and a chopped cellulose of about 0 to about 10% is prepared. The aqueous mixture is formed into a body and dried. Then, the dried body is subjected to heat treatment at a sufficient temperature and for a sufficient time for reacting the inorganic binder to manufacture the objective carbon body.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an activated carbon body containing bentonite clay, colloidal alumina, and optionally silica as an inorganic binder, and / or shredded cellulose, and a process for producing the same. . By combining an inorganic binder, the body to which the combination is added has high temperature strength. More specifically, the body is a honeycomb structure formed by extrusion.

[0002]

BACKGROUND OF THE INVENTION Activated carbon materials are commonly used to adsorb hydrocarbons and other impurities in gases (usually air) and liquids. For these applications, carbon is commonly used in the form of granules. Although granular shaped activated carbon can perform the desired adsorption in many applications, there are some applications where granules are a drawback. If the fluid must flow through a tortuous path, the back pressure created by the particles can be a problem. In some applications, due to the friction that causes the material or bed to fill less,
Granules may wear out significantly. In addition, the particles produced as a result of friction can block the flow passages.

Another method is to extrude activated carbon into the shape of a cellular honeycomb. A honeycomb can be easily formed by extruding a fine powder of activated carbon together with an appropriate binder. By having such a shape, the airflow can easily pass through the honeycomb in a state where there is almost no back pressure. It can also be shaped so that the gas easily contacts all carbon to adsorb the species to be removed. In addition, since the honeycomb is a solid piece, there is little or no carbon wear.

In the case of evaporative substances, the steam released from the fuel system while the vehicle is not moving, such as the steam released by the expansion and contraction of the gas in the fuel tank due to the temperature fluctuation, is activated carbon. Adsorbs. The air pushed out of the fuel tank during refueling carries together with it a large amount of fuel as vapor. This fuel must be captured to meet future air pollution standards. The adsorbed species desorb during engine operation and are recirculated to the engine inlet and burned. Most automobiles today are equipped with granular-filled activated carbon canisters to process the steam emitted from a steam source. However, this alone is not sufficient to meet future needs.

In order to use the honeycomb structure composed of activated carbon for the purpose of capturing the vapors emitted, it is desirable to maximize the adsorption capacity on a volume basis. This means maximizing the amount of carbon in that volume. If the velocity of the gas carrying the hydrocarbon vapor is slow,
Due to little or no pressure drop or flow restriction, the ratio of open frontal area to total cross-sectional area can be small. To achieve this, a cell having a small cell density due to a large wall thickness may be used. Those with an open front area of 25% are easy to manufacture. This has a carbon packing density of 75% in the assigned volume
Equal to that of This is greater than the packing density that would be found in the granules used today.

In cold start applications, activated carbon adsorbs hydrocarbons released during the first 90 to 120 seconds after the engine is started. During this start-up period, the catalytic converter has not reached the temperature at which it converts the hydrocarbons being released from the engine. Once the catalytic converter has reached that temperature, activated carbon can be removed from the exhaust system during bypass mode. The adsorbed hydrocarbon is desorbed from the activated carbon and converted into a harmless substance. Thus, the activated carbon is ready for hydrocarbon adsorption in the next cold start cycle.

Honeycomb structures used for cold start applications need to be of special geometry. The geometric surface area must be as large as possible, as the adsorption must be carried out quickly and efficiently. At the same time, make the open front area as wide as possible,
That is, the back pressure created by the high velocity flow of the exhaust gas must be minimized. In order to achieve this, a honeycomb structure with a thin wall and a high cell density is desirable. This honeycomb structure maximizes the adsorption efficiency of hydrocarbons contained in the exhaust gas while minimizing the back pressure. The open front area can easily cover 65% of the total front area.

Biofiltratio
In n), microorganisms attached to the activated carbon biofilter are used to convert VOC pollutants into end products such as carbon dioxide and water. Although granular activated carbon can be used, honeycomb-shaped ones are easier to recycle. Regeneration is performed by flushing the biofilter with water to remove innocuous products and accumulated dead biomass. Therefore, this operation can prolong the life of the filter. Activated carbon honeycombs in this application must be stable when in contact with water.
Biofiltration can be used to clean the air stream generated during operation and convert toxic vapors resulting from hazardous substances such as, for example, landfills and chemical processes.

Although the use of activated carbon has been described above,
There are many other uses. For example, activated carbon can be used to remove even organic pigments and ozone contained in air (VOC). Activated carbon can be used in wastewater treatment and removal of heavy metals contained in fluids and other separation applications, as well as in test methods such as, for example, the radon test.

In order to form an activated carbon honeycomb by extrusion, the carbon must be in the form of fine powder. Such carbons can also be mixed with liquids such as water and suitable plasticizers and binders. The thus plasticized mixture is extruded into a honeycomb shape through a die and dried.

The addition of organic binders such as cellulose ethers and their derivatives renders the mixture plastic. Such a mixture is soft,
Difficult to handle when extruded before drying. Furthermore, the bodies formed from such mixtures have a relatively low strength at high temperatures, such as 250 ° C., which they are exposed to, especially in applications such as automotive exhaust purification. This is because the organic binder decomposes at such high temperatures.

There is a strong desire both to improve the strength of extruded honeycombs in the extruded state before further processing and handling and to improve the strength after drying and heat treatment.

It has been practiced to use clay as a binder in carbon mixtures to impart strength to carbon bodies formed therefrom.

US Pat. Nos. 4,259,299 and 4,518,704
And JP-A-57-122924 (1982), for example,
It relates to activated carbon bodies in which various inorganic binders such as clay binders are used.

In US Pat. No. 4,259,299,
A method of depleting ozone using an activated carbon product prepared from a mixture of activated carbon, zeolite and organic and / or inorganic binders is described. The organic binder may be lignin and the inorganic binder may be bentonite. Such products are heated to 350 ° C to increase their strength.

[0016]

There is a need to produce an activated carbon body that has improved strength and that functions effectively in high temperature applications such as cleaning automobile exhaust gases. Such bodies must be strong enough to be handled in the wet, as-molded condition so that they do not deform during handling. There is also a need to improve the handling and secondary molding suitability of molding mixes.

The present invention meets these needs.

[0018]

The present invention provides an activated carbon body made from activated carbon particles bound together by an inorganic binder consisting of bentonite clay and alumina, and optionally silica. Expressed in weight percent based on carbon content, bentonite content is about 5%
To 25% and the content of alumina is about 5% to 35%
%, And if silica is included, its content is up to about 25%.

The present invention is a method of making an activated carbon body as described above, comprising activated carbon particles, about 4% to 12% organic binder, expressed in weight percent based on carbon content, and inorganic binder. As about 5% to 25% bentonite clay and about 5% to 35% colloidal alumina,
An aqueous mixture of 0% to about 25% silica in the form of a water dispersible silica precursor and 0% to about 10% chopped (chopped) cellulose is prepared and the aqueous mixture is added to the body. And then dry the molded body,
There is provided a method comprising the steps of subjecting a dried body to a heat treatment for a time and time sufficient to react an inorganic binder to form an activated carbon body and subjecting it to heat treatment.

The present invention relates to a method of making a carbon body. This carbon body is typically an activated carbon honeycomb. This method prepares an aqueous starting mixture consisting of activated carbon particles, an inorganic reactive binder consisting of bentonite clay, colloidal alumina, and optionally colloidal silica, and optionally chopped cellulose. Including the step of The mixture is shaped into a body, for example by extrusion. Next, the molded body is dried and heat-treated.

An organic binder is included in the aqueous mixture to enhance the secondary moldability, especially the extrusion suitability. The mixture is plasticized by including an organic binder. This plasticization makes the mixture tough and cohesive.

When the honeycomb is extruded, a body having a good cell structure and a good skin structure can be extruded by adding the above-mentioned additives. The organic binder functions as an organic bond when dried.

The combination of colloidal alumina and bentonite clay, especially finely divided bentonite clay, and optionally inorganic binder of colloidal silica, imparts strength to the body, especially after heat treatment. The inorganic binders react with each other at least to some extent after heating to form a strong bond to bond and retain the activated carbon particles as the main component. The increased strength when heat-treated is maintained when the body is heated in air to a temperature of about 300 ° C-350 ° C, whereas a body containing only organic binder will not decompose or lose the organic binder. It becomes weaker (organic binder begins to burn by about 200 ℃). It is this strong bond that gives the body of the invention high temperature strength. When using only bentonite (or other clay), the final body becomes unstable when in contact with water due to the clay portion. High enough to dissociate water of crystallization from the clay, but with the plate-like properties of the original clay structure (platy
Even when heated to a temperature that is not high enough to destroy a character), such problems occur. The heat treatment temperature allowed in the present invention is not only sufficient to remove water of crystallization from the clay, but also the dissociation product of the clay, Si
The temperature is sufficient to react O ₂ and Al ₂ O _{3 with the} colloidal silica and alumina to form a bond. This bond is no longer susceptible to water splitting and the final body can withstand contact with water for a long time.

The inclusion of chopped cellulose in a wet mixture ready for extrusion can improve the toughness, cohesiveness and stiffness of the mixture. It has been found that this can improve the extrusion properties and the quality of the extruded product. In addition, the extruded product has a higher rigidity and can be more easily cut and handled without being deformed.

The combination of a reactive inorganic binder and cellulose provides excellent handleability and extrudability, and the body formed therefrom has a good tenacity in the wet as-molded state. Also, it has handleability, and the strength of the body after heat treatment increases, and the operating temperature increases.

The body can be used up to a temperature of about 350 ° C., above which the carbon itself begins to oxidize.

Types of carbon Activated carbon is a non-graphite microcrystalline form of carbon that is processed into porous carbon. Pores formed on activated carbon include macropores (eg, pores having a diameter greater than about 500 Å), mesopores (eg, pores having a diameter from about 20 Å to about 500 Å), Or there may be micropores (eg, pores having a diameter of less than about 20 Å). Activated carbon has a large specific surface area (eg 300 m ² / g to 2500 m
² / g) and is known for its large adsorption capacity.

The properties of the activated carbon such as particle size, surface area, hydrocarbon adsorption capacity, adsorption efficiency, porosity, pore size, etc. can be varied according to its application. The carbon used in a given mixture may be of one type or a mixture of multiple types, based on, for example, the source of the precursor, the pores, the porosity, and the like. There is no limitation on the type of activated carbon used when carrying out the present invention. For example, all fine carbon powder,
Alternatively, all coarse powders can be used, or a mixture of these two types can be used. The type of carbon used depends on the requirements of the particular application.

One of the sources of activated carbon suitable for the practice of the present invention
One is B available from Calgon Carbon Corp.
PL-F3 (trademark) granular activated carbon is mentioned. This activated carbon is available in several particle size ranges. Particularly useful types of activated carbons available from this supplier, "6 × 16" are of mesh size, this type has a surface area from about 1050 m ² / g to about 1300 m ² / g.

One suitable mixture of activated carbons having various particle sizes is a finely divided activated carbon powder having an average particle size in the range of about 3 micrometers to about 10 micrometers in diameter, and a coarse and diameter. And including activated carbon powder having an average particle size in the range of about 20 micrometers to about 50 micrometers. Particularly suitable for practicing the present invention is Calgon Carbon BPL-F3®, which is ground to an average particle size of about 4-12 micrometers in diameter when practicing the present invention, and in diameter. about
Activated carbon such as Nuchar® SN-20 (available from West Baco), which is a coarse powder with an average particle size of 30 micrometers, is mentioned.

Organic Binder The purpose of including an organic binder is to impart plasticity and some degree of green strength after drying. Organic binders used in the practice of the present invention refer to cellulose ether type binders and / or their derivatives, some of which are heat-gelable. Examples of common organic binders that can be used in the present invention include methyl cellulose, ethyl cellulose, hydroxybutyl cellulose,
Hydroxybutyl methyl cellulose, hydroxyethyl cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, sodium carboxymethyl cellulose, and mixtures thereof. In practicing the present invention, methylcellulose and / or methylcellulose derivatives are generally used. Methylcellulose, hydroxypropylmethylcellulose, and combinations thereof are especially preferred. Preferred sources of cellulose ethers and / or their derivatives include Methocel® A4M, 20-333, F4M and F40M available from Dow Chemical Company. Methocel A4M has a gelation temperature of 50 ° C to 55 ° C and a gel strength of 5000 g / cm ² (65
(Based on a 2% solution at 0 ° C.). Methocel 20-333, F4M, and F4
0M is hydroxypropyl methylcellulose.

Bentonite Clay Bentonite refers to a group of clays containing montmorillonite as an essential mineral. This type of clay is about 3-4
It contains aluminum silicate together with wt% MgO. It is a very fine clay that imparts plasticity to the mixture and can provide cohesive strength to both as-molded and dried bodies. Different grades of bentonite are available from different suppliers, and depending on the deposits they were taken from and the degree of processing, the bentonites may vary somewhat with respect to particle size and impurities. Bentonite clay is particularly suitable for uniform distribution in the mixture due to its fine particle size. The average particle size of bentonite is generally less than 1 micrometer in diameter. Suitable bentonite clays, especially with regard to fine particle size, are comparable to the clays previously supplied by Southern Clay Products under the name Bentrite L®. Another suitable bentonite clay is G-129 available from Kaoporite.

Colloidal Alumina Several types of colloidal alumina are suitable for practicing the present invention, the colloidal alumina being in a powder form or as a colloidal suspension, which is usually acidic for their preferred suspension. Can be used. These are generally temporary boehmite, ie aluminum monohydrate. The powder morphology may change, eg HC
It should have adsorbed species such as 1 or HNO ₃ that make it easier to disperse in water during use. Without limiting the invention, one of a particularly useful class of colloidal aluminas
One is Al ₂ O ₃ having an average particle size of about 50 nanometers in diameter, such as that supplied by Niacor Products Co. under the name Niacor Al-20.
% Solids.

Colloidal Silica Precursor A water-dispersible colloidal silica precursor means a species that forms a dispersion in water and produces colloidal silica upon heat treatment or drying. The term preferably means colloidal silica itself or other species such as silicates.

One useful source of colloidal silica is a stabilized ammonium such as that supplied by DuPont under the name Ludox AS-40, such as SiO _{2 in} a basic aqueous medium. Approximately 40% solid dispersion is included. Other grades of colloidal silica can also be used. A suitable colloidal silica precursor is tetraethylorthosilicate (TEOS). The TEOS used is itself a liquid and contains about 4% alcohol from the production process. TEOS contains about 26% -28% of SiO _2. Other SiO ₂
Examples of the generated material include Silestar (registered trademark) OS, which is a product of Remet Chemical Company. This is TEOS
And a mixture of ethyl polysilicate. It is also possible to use pre-hydrolyzed ethyl silicate material supplied by Remet Chemical Company.

Chopped Cellulose Cellulose is a material that is shredded from wood and ground.
Cellulose is highly pure and in the form of fibers. This fiber is
It is insoluble in water, unlike other cellulose-based materials such as thimerucellulose made from similar fibers. The fibers must be short enough so that they do not cause problems such as plugging the extrusion die during the extrusion process. Generally, the fiber is 100 mesh (US standard). One particularly suitable cellulose is that marketed by International Filler Corporation under the name Alphacel C-100.

Unless stated otherwise, the weight percentages of the components and water in the mixture are based on the carbon content. For example, determine the percentage of a component or water in a mixture from the formula:

[0038]

[Equation 1]

The aqueous mixture is formed from carbon particles and the binders and additives mentioned above. The mixture is about 4% to about
Up to 12% organic binder, about 5% to about 25% bentonite clay, 0% to about 25% silica in the form of a water-dispersible silica precursor, and 0% to about 10% chop. It consists of tocellulose.

The inorganic additives, ie bentonite, colloidal alumina and, optionally, silica precursor, are added to the activated carbon mixture to heat treat the shaped body to remove the organic binder and then to surround the carbon. A bond is formed at.

The content of inorganic binder must be sufficient, at least to some extent, to form bonds between the activated carbon particles which are continuous. The ratio of bentonite, colloidal alumina, and silica can vary somewhat,
The total content of these inorganic binder components must be sufficient to achieve the adhesion mentioned above. It is preferred that the total inorganic binder content be less than or equal to about 65%. About 35%
With a binder content of 1, the binding effect provided by the inorganic binder is evident, with a content of from about 35% to about 60% being preferred. Even with contents of about 45% to about 60%, the binding effect is improved.

The greater the content of the inorganic binder, the greater the strength. However, as the content of the inorganic binder increases, the adsorption capacity decreases. Therefore, the content of the inorganic binder can be adjusted according to the desired characteristics.

With respect to strength, a content of inorganic binder of at least about 45% is preferred, most preferably at least about.
50%, or at least 60%.

The content of bentonite is basically about 5
% To about 25%, preferably about 10% to 25%, more preferably about 15% to about 25%. In some embodiments, about 15% to 20% is particularly useful.

Overall, the colloidal alumina content is preferably from about 10% to about 30%, with about 15% to about 30% being particularly useful.

Some compositions containing bentonite and alumina contain at least about 15% bentonite and at least about 15% colloidal alumina. At a total bentonite and alumina content of at least about 35%, a compressive strength of at least about 500 psi could be achieved after aging in air at about 250 ° C to about 350 ° C for about 4 hours.

Preferably SiO ₂ or a SiO ₂ precursor is added so that the content of SiO _{2 in} the mixture is up to about 25%,
Preferably from about 5% to about 25%, more preferably about 10%
% To about 20%.

Useful compositions contain at least about 15% bentonite clay, at least about 15% alumina, and at least about 5% colloidal silica. For this composition, the total content of inorganic binders is at least about 45%, at least about 50% for increased strength.
% Is particularly preferable. At a total inorganic binder content of at least about 50%, the body aged in air at about 250 ° C to about 350 ° C for about 4 hours had a compressive strength of at least about 1000 psi. Similarly measured compressive strengths were at least about 1400 psi at a total inorganic binder content of at least about 60%.

It is preferred to include up to about 12% of organic binder, for example for particularly good shape quality in extrusion of honeycombs, for good cell and skin structure of the body and for further drying. Due to the very high water content used to extrude the activated carbon, it is difficult to dry the product without cracking. From a practical and economic point of view, the content of organic binder is preferably from about 6% to about 10%.

As the as-molded body, ie, the body before drying containing the organic binder, is soft and can be easily deformed during handling, chopped cellulose was added to the mixture to provide consistency and Secondary moldability can be improved. This is particularly suitable when the mixture is shaped by extrusion. At this time, since the mixture contains chopped cellulose to impart rigidity and extrudability, the extruded product can be handled without being deformed. The addition of chopped cellulose also aids in drying the body and prevents cracking due to some strengthening.

When added, chopped cellulose is included up to about 10%, preferably about 4% to about 10%, more preferably about 5% to about 8%.

Other ingredients such as lubricants and surfactants can also be included in the mixture.

A mixture is prepared by dry blending the solid ingredients and then mixing with water. Without limiting the invention, one mixing technique includes placing the dry blended ingredients in a mix muller or other type of mixer such as a sigma blade mixer or a double arm mixer. Add water while mixing solids. Once the water is added, run the Mahler or other mixer until the batch is compressed and plasticized.

Usually when the particular additive is an aqueous suspension, as is the case with colloidal silica and pre-suspended alumina, the suspension is added with water. In most cases, the high shear mixer is used to mix the colloidal aqueous suspension with water to obtain a homogenous mixture. The water content of the starting colloidal suspension is calculated as part of the total water content in the mixture. The mixture of water and colloidal suspension is added to the dry ingredients (premixed) in a mix muller or other type of mixer and the batch is milled as follows.

Predispersed SiO ₂ and Al ₂ O ₃
When using these colloidal materials, mixing these materials with the rest of the water can lead to gels that are difficult to handle. To avoid this, SiO ₂
The pH of the colloidal mixture of Al ₂ O ₃ and Al ₂ O ₃ with an acid, eg
Adjust the pH to about 3.5-4.0 by adding nitric acid. This colloidal suspension does not gel.

The water content in the mixture can be adjusted to optimize the plasticity and handleability of the mixture. When the mixture is mixed and water is added, it is time for the water to be sufficient to wet all the particles. Continued mixing compacts the powder, removes air, and the compacted powder begins to agglomerate. As a result of continued mixing, these masses become plastic. With excess water, these masses are too soft for the molding process. Good plasticity and handleability of the mixture when the water content is generally about 140% to about 200%, more usually about 145% to about 160%, based on the carbon content. . Since the activated carbon used varies significantly with respect to structure, porosity, and surface area, the amount of water required can vary depending on the type of activated carbon. The amount may be greater than the amount described above.

Once the mixture has been found to be preferably plasticized, as indicated by hand or torque rheometer, the mixture is molded into a body.

The body produced according to the present invention may be of any size and shape. For example, a preferred shape for cold start and evaporant applications is a cellular body such as a honeycomb structure.

Examples of honeycombs produced by the method of the present invention include, but are not limited to, about 94 cells / cell.
cm ² (about 600 cells / in ² ), about 62 cells / cm ² (about
400 cells / in ² ) or approximately 47 cells / cm ² (approximately 300
With about 31 cells / cm ² (about 20 cells / in ² )
0 cells / in ² ) or about 15 cells / c
One having m ² (about 100 cells / in ² ). Typical wall thicknesses for honeycombs produced according to the present invention are:
For example, for a honeycomb of about 62 cells / cm ² (about 400 cells / in ² ) it can be about 0.15 mm (about 6 mils).
Wall thicknesses range from about 0.1 mm to about 1.3 mm (about 4 mils to about 50 mils) for most applications, but the invention is not limited to this range. The outer dimensions and outer shape of the body can be controlled according to the application, and are not limited to the above-mentioned numerical values. For example, other combinations of cell density and wall thickness can be used.

Molding may be performed by any method as long as it is a method of molding the plasticized mixture. The preferred molding method is extrusion. A ram extruder is commonly used, although other equipment known to those skilled in the art such as a continuous two stage degassing auger or twin screw extruder can be used.

When molding the honeycomb structure, it is preferable to extrude the mixture through a honeycomb die.

If desired, the molded body can be cut into various sized parts, depending on the intended use or as needed to facilitate handling and processing.

The shaped body obtained is dried at a temperature below about 100 ° C. Care should be taken to dry the body slowly and evenly so that it does not crack, for the most part because the body contains a relatively large amount of water due to the porosity of the carbon particles.

A preferred drying technique is to wrap the body in aluminum foil and place it in a dryer set at about 100 ° C. or below, generally about 95 ° C., for a time sufficient to remove water. Is mentioned. The foil allows the extruded body to dry slowly and evenly, thus creating a moist atmosphere without cracking. The drying time can vary depending on the dimensions of the body. For example, the diameter is 2.54 cm (1 inch) and the length is 22.9 cm (9 inches).
For honeycombs (inch), the drying time is typically about 4 days.

After calcination, these bodies have a greater strength than bodies containing only organic binder. That is, when using a body containing only an organic binder, about 200
Heating to temperatures in the range of from 0 ° C to about 350 ° C decomposes the organic binders and extrusion aids to a loss of strength, resulting in low operating temperatures. Therefore, the purpose of adding the inorganic additive is to form a stable bond at use temperatures up to about 350 ° C.

Thus, the inorganic binder reacts to form a relatively strong bond which does not significantly affect when the body is heated in air to a temperature in the range 300 ° C. to 350 ° C. during use. The dried body is heat treated for a sufficient temperature and time. Typical heat treatment temperatures are at least about 900 ° C, preferably at least about 1000 ° C.
The heating time is generally at least about 30 minutes. The heat treatment is performed in a non-reactive atmosphere such as nitrogen.

In order to remove the organic binder and allow the inorganic material to react sufficiently to form a bond around the carbon particles,
Perform heat treatment. This bond strengthens the activated carbon substrate when exposed to a temperature in air. This strength is lost in substrates bonded only with organic binders. Organically bonded substrates begin to lose strength at about 200 ° C as the organic bonds decompose and become oxidized. On the other hand, the inorganic bond remains relatively strong until the carbon itself begins to oxidize when approaching about 400 ° C.

One particularly suitable heat treatment technique is described below. The carbon body is vacuum industry's "Super VII General Purpose Metallurgical Facility (Super VII General Purpose Metallurgi
cal Vaccum Facility) ”. Place the sample in a graphite box located in the center of the furnace, then place a graphite lid and close the box. The main door of the furnace is closed and sealed, and the water-cooled container is evacuated. A vacuum of less than 0.1 mmHg is created using a two-stage vane rotary pump (Triback-A). Pump times range from 30 to 90 minutes depending on sample type and furnace loading. Once the vacuum level is reached, switch off the vacuum pump and fill the vessel with nitrogen up to 1.5 times atmospheric pressure. At this point the operation of the furnace is started. Nitrogen is present throughout the entire firing cycle (including the cooling period).

The reaction of the inorganic additive starts near the maximum temperature and is completed during the holding period. Typical heat treatments can range from about 900 ° C to about 1200 ° C for a period of time depending on temperature but most commonly for up to about 4 hours. Once the furnace has cooled to room temperature, open it and
The heat-treated body can be taken out.

The strength, ie the dry strength and heat treated strength of the activated carbon bodies produced by the process of the invention, is greater than that of bodies containing only organic binder.

[0071]

The present invention will be described in detail below with reference to examples. All parts, portions, and percentages are by weight unless otherwise noted.

Compressive strength was measured using a compression tester manufactured by Tinius Olsen at a crosshead speed of about 2.54 mm (about 0.1 inch) / minute. The average value of 3-4 different pieces is shown for each sample number. Unless otherwise noted, sample strength was measured at room temperature after heat treatment in nitrogen at about 1100 ° C. for about 1 hour.

The butane adsorption capacity was measured by placing the test sample in a Biker® tube housed in a tubular furnace having an inlet and an outlet. A butane gas flow of 1500 ppm by volume in a nitrogen carrier was introduced into the sample at a flow rate of about 4,000 cc / min,
The amount of adsorption was measured by monitoring the discharged gas flow with a flame ionization detector. Adsorption at room temperature was considered complete when the calibrated detector reading reached approximately 95%. At this point, the inlet gas flow was changed to nitrogen and the butane desorption at room temperature was measured. When the detector reading reached a value of about 5%, the temperature of the sample was raised to about 100 ° C. by raising the temperature of the furnace to remove the rest of the butane adsorbed by the sample. The detector readings were plotted against time and the area of each curve was integrated to determine adsorption and desorption. The value shown as the amount of adsorption is the value obtained by dividing the adsorbed butane in milligrams by the mass of the sample after the test or the volume of the sample.

Example 1 The following example illustrates the effect of composition on the strength and adsorption capacity of carbon honeycombs.

A mixture of activated carbon containing the binder composition shown in Table 1 was prepared. The activated carbon contained 80% Calgon BPL-F3 with an average particle size of about 6 micrometers in diameter and about 20% West Baco Nuture SN20 with an average particle size of about 30 micrometers in diameter. The organic binder used was Methocel® F40M or A4
It was M. Bentonite is Bentonite (registered trademark)
L, colloidal alumina is Niacor AL-20
And the colloidal silica was Ludox AS-40. Each mixture was extruded into a honeycomb shape, dried, and heat-treated at about 1100 ° C for about 1 hour, then about 4
Aging was performed at about 300 ° C for a period of time to simulate a usage condition for a certain application. For each honeycomb
Compressive strength and adsorption capacity were measured. Table 1 shows the results.

[0076]

[Table 1]

[0077]

[Table 2]

Comparing the 1-1 sample and the 1-2 sample, when the total content of the inorganic binders was about 25%, the combination of bentonite and alumina exceeded the alumina alone in terms of strength. It can be seen that there is a significant increase. 1
This synergistic effect is seen when the -6 sample is compared to the 1-7, 1-8, and 1-3 samples for strength values. In order to achieve a given level of strength, the use of both bentonite and alumina (two component system) is more of an inorganic binder than the amount of binder required when using bentonite alone. You can see that the amount is small. For example, in samples 1-3, a total of 30% inorganic binder gives strengths close to those of samples 1-6 where only 43% bentonite is required. The 1-4 and 1-5 samples with less than 43% inorganic binder are significantly stronger than the 1-6 sample. Comparing the samples 1-9 to 1-16, a more remarkable synergistic effect is observed when SiO ₂ is added to the inorganic binder composition (three-component system). For example, comparing the 1-10 sample with the 1-6 sample, the strength is significantly greater when the content of inorganic binder is split into bentonite, alumina and silica as opposed to bentonite only. It can be clearly seen that in the three-component system, the greater the content of the inorganic binder, the greater the strength.

Table 1 shows that the samples prepared according to the invention retain their strength after heat treatment, so that the temperature range useful for activated carbon honeycombs is from room temperature to about 350.
It can be seen that it has spread up to ℃. The strength after heat treatment is maintained by the formation of inorganic bonds. The mixture of inorganic materials shown in Table 1 produces a honeycomb body having a strength greater than that achievable with a mixture containing only bentonite clay. Higher strength compositions are obtained by increasing the total amount of inorganic binder, which may result in a lower adsorption capacity.

The total amount of carbon that the activated carbon body can adsorb depends on the adsorption capacity of the body composition and the shape of the body. For example, for honeycomb, the adsorption capacity depends on the shape of the honeycomb cellular structure. In Table 1, the adsorption capacity of the composition is represented by the adsorption capacity expressed in mg of butane adsorbed per 1 g of the sample. As one might expect, as the total content of inorganic binder increases, the adsorption capacity of the composition decreases. However, by increasing the percentage of solids contained in the predetermined volume, the volume-based adsorption capacity expressed in mg of butane adsorbed per 1 cc of the honeycomb is maintained in a large state. The percentage of solids in a given volume can be increased by increasing the wall thickness.
And / or can be increased by increasing the cell density of the honeycomb. The percent solids in the honeycomb structure is equal to 1 minus the open front area of the honeycomb. The open front area of the honeycomb was characterized using image analysis techniques. The percent solids shown in Table 1 were calculated by taking the difference from 1.0.

Example 2 The following example shows the effect of heat treatment temperature on the compressive strength of carbon bodies.

About 8% methylcellulose (F40M),
About 15% bentonite clay (Bentlite G-12
A batch composition was prepared consisting of 9), about 20% alumina (Niacol Al-20), and about 15% silica (Ludox AS-40).

The same activated carbon as in Example 1 was used.

The batch was extruded into a honeycomb shape, dried and heat treated in nitrogen at the temperatures shown in Table 2 below. The compressive strength was measured and is shown in Table 2. It can be seen that the strength is high at the heat treatment temperature of 1100 ° C or higher.
There is an optimal time and temperature combination that shows the highest strength before the strength decreases.

[0085]

[Table 3]

Example 3 A large honeycomb composed of samples 1-11 having the composition shown in Table 1 had a size of about 535 cm ³ (diameter = 7 cm, length = 14 c
It can adsorb up to 11.7 g of butane in the volume occupying m). A salient feature of this large honeycomb with suitable adsorption capacity is that it maintains its strength up to about 350 ° C.

[0087]

Embodiment 1 A method of making a carbon body comprising: a) activated carbon particles, from about 4% to about 12% organic binder, expressed as a weight percentage based on carbon content, as an inorganic binder, About 5% to about 25% bentonite clay and about 5% to about 35% colloidal alumina;
Preparing an aqueous mixture consisting of about 0% to about 25% silica in the form of a water-dispersible silica precursor, and about 0% to about 10% chopped cellulose; b) adding the aqueous mixture to the body. Molding, c) drying the body, d) heat treating the dried body for a temperature and for a time sufficient to react the inorganic binder.

[0088]

Embodiment 2 The method according to embodiment 1, wherein the content of the inorganic binder is about 35% to about 60% based on the content of the carbon.

[0089]

Embodiment 3 The method according to embodiment 2, wherein the content of the inorganic binder is about 45% to about 60% based on the content of the carbon.

[0090]

Embodiment 4 The method of Embodiment 1 wherein the bentonite clay content is from about 15% to about 25% based on the carbon content.

[0091]

Embodiment 5 The method according to Embodiment 1, wherein the bentonite clay has an average particle diameter of about 1 micrometer or less in diameter.

[0092]

Embodiment 6 The method of Embodiment 1 wherein the colloidal alumina content is from about 15% to about 30% based on the carbon content.

[0093]

Embodiment 7 The inorganic binder comprises bentonite clay and alumina, wherein the content of bentonite clay is at least about 15% and the content of colloidal alumina is at least about 15%. The method according to embodiment 1.

[0094]

Embodiment 8 The method of Embodiment 7 wherein the total content of said bentonite clay and said alumina is at least about 35%.

[0095]

Embodiment 9 About 250 for about 4 hours in air.
The method of claim 8 wherein the body has a compressive strength of at least about 500 psi after aging at a temperature in the range of from 0 ° C to about 350 ° C.

[0096]

Embodiment 10 The method according to embodiment 1, characterized in that the silica precursor is present as colloidal silica in the aqueous mixture.

[0097]

Embodiment 11 The method of Embodiment 10 wherein the colloidal silica content is from about 5% to about 25% based on the carbon content.

[0098]

Embodiment 12 The bentonite clay content is at least about 15%, the alumina content is at least about 15%, and the silica content is at least about 5%. The method according to embodiment 10.

[0099]

Embodiment 13 The method of Embodiment 12 wherein the total inorganic binder content is at least about 45%.

[0100]

Embodiment 14 The method of Embodiment 13 wherein the total inorganic binder content is at least about 50%.

[0101]

Embodiment 15 About 25 for about 4 hours in air
15. The method of embodiment 14 wherein the body has a compressive strength of at least about 1000 psi after aging at a temperature in the range of 0 ° C. to about 350 ° C.

[0102]

Embodiment 16 The method of Embodiment 14 wherein the total content of inorganic binders is at least about 60%.

[0103]

Embodiment 17 About 25 for about 4 hours in air
17. The method of embodiment 16 wherein the body has a compressive strength of at least about 1400 psi after aging at temperatures ranging from 0 ° C to about 350 ° C.

[0104]

Embodiment 18 The chopped cellulose is present in the aqueous mixture and its content is from about 4% to about 10% based on the content of the carbon. Method.

[0105]

Embodiment 19 The method of embodiment 18, wherein the chopped cellulose content is from about 5% to about 8% based on the carbon content.

[0106]

Embodiment 20 The organic binder is methyl cellulose, ethyl cellulose, hydroxybutyl cellulose,
A method according to embodiment 1, characterized in that it is selected from the group consisting of hydroxybutylmethylcellulose, hydroxyethylcellulose, hydroxymethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, sodium carboxymethylcellulose, and mixtures thereof.

[0107]

Embodiment 21 The method according to Embodiment 20, wherein the content of the organic binder is from about 6% to about 10% based on the content of the carbon.

[0108]

Embodiment 22 The method according to Embodiment 1, wherein the body is a honeycomb structure.

[0109]

[Embodiment 23] The method according to Embodiment 1, wherein the step of molding is performed by extruding the aqueous mixture.

[0110]

Embodiment 24 The method according to embodiment 1, wherein the aqueous mixture is extruded in the shape of a honeycomb structure.

[0111]

Embodiment 25 A body made of carbon particles bonded together with an inorganic binder consisting of bentonite clay and alumina, wherein the content of said bentonite clay is about 5%, expressed in weight percent based on carbon. To about 25%, and the alumina content is about 5% to about 35%.

[0112]

Embodiment 26 The body according to embodiment 25, wherein the content of the inorganic binder is from about 35% to about 60% based on the content of the carbon.

[0113]

Embodiment 27 The body according to embodiment 26, wherein the content of the inorganic binder is from about 45% to about 60% based on the content of the carbon.

[0114]

Embodiment 28 The body according to embodiment 27, wherein the bentonite clay content is from about 15% to about 25% based on the carbon content.

[0115]

Embodiment 29 The body according to embodiment 27, wherein the bentonite clay has an average particle size of about 1 micrometer or less in diameter.

[0116]

Embodiment 30 The body of Embodiment 27, wherein the alumina content is from about 15% to about 30% based on the carbon content.

[0117]

Embodiment 31 The body of Embodiment 25, wherein each of said bentonite clay content and said alumina content is at least about 15%.

[0118]

Embodiment 32 The body according to Embodiment 31, wherein the total content of said bentonite and said alumina is at least about 35%.

[0119]

Embodiment 33 About 25 for about 4 hours in air
33. A body according to embodiment 32, wherein the body has a compressive strength of at least about 500 psi after aging at temperatures ranging from 0 ° C to about 350 ° C.

[0120]

Embodiment 34 A body according to embodiment 25, comprising additional components selected from the group consisting of silica, chopped cellulose, and mixtures thereof.

[0121]

Embodiment 35. A body according to embodiment 34, characterized in that said additional component is silica as an inorganic binder.

[0122]

Embodiment 36 The body of embodiment 35, wherein the silica content is from about 5% to about 25% based on the carbon content.

[0123]

Embodiment 37. The embodiment characterized in that said bentonite clay content is at least about 15%, said alumina content is at least about 15%, and said silica content is at least about 5%. The body according to aspect 35.

[0124]

Embodiment 38 The body according to embodiment 37, wherein the total content of said inorganic binder is at least about 45%.

[0125]

Embodiment 39 The body according to embodiment 38, wherein the total content of said inorganic binder is at least about 50%.

[0126]

Embodiment 40 About 25 for about 4 hours in air
40. The body of embodiment 39, wherein the body has a compressive strength of at least about 1000 psi after aging at temperatures ranging from 0 ° C to about 350 ° C.

[0127]

Embodiment 41 The body according to embodiment 40, characterized in that the content of said inorganic binder is at least about 60%.

[0128]

Embodiment 42 About 25 for about 4 hours in air
42. The body of embodiment 41, wherein the body has a compressive strength of at least about 1400 psi after aging at a temperature in the range of 0 ° C to about 350 ° C.

[0129]

Embodiment 43 A body according to embodiment 34, characterized in that said additional ingredient is chopped cellulose.

[0130]

Embodiment 44 The body of embodiment 43, wherein the chopped cellulose content is from about 4% to about 10% based on the carbon content.

[0131]

Embodiment 45 The body of embodiment 43, wherein the chopped cellulose content is from about 5% to about 8% based on the carbon content.

[0132]

Embodiment 46 A body according to embodiment 25, which has a honeycomb structure.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location B01D 53/77 ZAB (72) Inventor Donald Lloyd Guile New York, USA 14845 Horseheads Stony Block Road East East 1245 (72) Inventor Kennis Elmer Zaun, New York, USA 14830 Corning Lee Road 3673

Claims (13)

[Claims] 1. A method of making a carbon body comprising: a) activated carbon particles, from about 4% to about 12% organic binder, inorganic binder, expressed in weight percent based on carbon content; About 5% to about 25% bentonite clay and about 5% to about 35% colloidal alumina;
Preparing an aqueous mixture consisting of about 0% to about 25% silica in the form of a water-dispersible silica precursor, and about 0% to about 10% chopped cellulose; b) adding the aqueous mixture to the body. Molding, c) drying the body, and d) heat treating the dried body for a time and at a temperature sufficient to react the inorganic binder. 2. The method of claim 1, wherein the content of the inorganic binder in the aqueous mixture is from about 35% to about 60% based on the carbon content. 3. The method of claim 1, wherein the bentonite clay has an average particle size of about 1 micrometer or less in diameter. 4. The method of claim 1 wherein the content of the colloidal alumina in the aqueous mixture is from about 15% to about 30% based on the carbon content. 5. The silica precursor is present as colloidal silica in the aqueous mixture.
The described method. 6. The method of claim 5, wherein the colloidal silica content is from about 5% to about 25% based on the carbon content. 7. The bentonite clay content is at least about 15%, the alumina content is at least about 15%, and the silica content is at least about 5%.
The method according to claim 5, wherein 8. The method of claim 7, wherein the total inorganic binder content is at least about 45%. 9. The method of claim 8 wherein the total inorganic binder content is at least about 50%. 10. The method of claim 1, wherein chopped cellulose is included in the aqueous mixture and its content is from about 5% to about 8% based on the carbon content. . 11. The method of claim 1, wherein the aqueous mixture is extruded into the shape of a honeycomb structure. 12. A body manufactured by the method according to any one of claims 1 to 11. 13. A body made from carbon particles bonded together with an inorganic binder consisting of bentonite clay and alumina, wherein the content of said bentonite clay is about 5 in weight percent based on carbon.
% To about 25% and the alumina content is about 5
Body characterized by being from 35% to about 35%.