CA1258450A - Process for the preparation of catalyst supports and materials produced thereby - Google Patents
Process for the preparation of catalyst supports and materials produced therebyInfo
- Publication number
- CA1258450A CA1258450A CA000500881A CA500881A CA1258450A CA 1258450 A CA1258450 A CA 1258450A CA 000500881 A CA000500881 A CA 000500881A CA 500881 A CA500881 A CA 500881A CA 1258450 A CA1258450 A CA 1258450A
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- CA
- Canada
- Prior art keywords
- catalyst support
- diatomite
- pellets
- minutes
- process according
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
- B01J37/0018—Addition of a binding agent or of material, later completely removed among others as result of heat treatment, leaching or washing,(e.g. forming of pores; protective layer, desintegrating by heat)
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
- B01J31/003—Catalysts comprising hydrides, coordination complexes or organic compounds containing enzymes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
Abstract
ABSTRACT
A method of preparation of catalyst supports is disclosed as well as supports made by the method. Diatomite or perlite, an inorganic binder, a solvent, and up to 12 wt.% of an organic burnout material are mixed, extruded, pelleted, dried and calcined to form porous catalyst supports comprising diatomite or perlite and an inorganic binder. The resulting catalyst support has a mean pore diameter of 1-25 microns and is very useful for immobilizing microbial cells thereon.
A method of preparation of catalyst supports is disclosed as well as supports made by the method. Diatomite or perlite, an inorganic binder, a solvent, and up to 12 wt.% of an organic burnout material are mixed, extruded, pelleted, dried and calcined to form porous catalyst supports comprising diatomite or perlite and an inorganic binder. The resulting catalyst support has a mean pore diameter of 1-25 microns and is very useful for immobilizing microbial cells thereon.
Description
1~25~
PROCESS FOR TXE PREPARATION OF CATALYST SUPPORTS AND
MATERIALS PRODUCED THER~BY
This invention relates to a process for the production of catalyst supports. It also relates to the catalyst supports produced by the above process. Additionally, it relates to catalyst supports containing catalytically active substances such as microbial cells immobilized thereon.
The use of various substances to support, and in some instances immobilize, catalytically active materials is well known to those skilled in the art. Since catalytically active substances help to make reactions proceed which would otherwise not be thermodynamically possible or economically practical in many instances, it has become increasingly important to look for ways to efficiently utilize and maintain such catalytically active materials. Furthermore, since the cost of the catalytically active materials must itself be an active consideration in deciding whether to commercialize a process using the catalyst, there is even more reason to look at utilizing the catalyst as desirably as possible.
One of the most important classes of catalytically active materials or agents currently being studied and utilized in both theoretical and commercial settings are enzymes. It is known that enzymes, which are proteinaceous in nature and which are commonly water soluble, act as biocatalysts which serve to regulate many and varied chemical reactions which occur in living organisms. The enzymes may also be isolated and used in analytical, medical, and industrial applications. For example, they find use in industrial applications in the preparation of food such as cheese or bread as well as being used in the preparation of alcoholic beverages. The enzyme glucose isomerase is extensively used to convert glucose to fructose in the manufacture of high fructose corn syrup.
Since enzymes are commonly water soluble as well as being generally unstable and, therefore, subject to deactivation, they are - difficult to remove for reuse from solutions in which they are utilized and they may not retain their catalytic activity over extended periods of time. These difficulties lead to an increased ~:~5~
cost in the use of enzymes in commercial scale operations due to the necessity for frequent replacement of the enzyme. In order to reduce the high cost of enzyme replacement, various methods to immobilize enzymes prior to their use have been devised. This immobilization of the enzyme permits its reuse, whereas it might otherwise undergo deactivation or be lost in the reaction medium in which it is used. These immobilized enzyme systems may be employed in various reactor systems, for example, in packed columns and stirred tank reactors, depending on the nature of the substrate which is being biochemically reacted.
Apsrt from immobilization of enzymes themselves, various substances and techniques have been put forward by which the enzymes could be immobilized without isolation. In psrticular, whole cells of micro-organisms can be immobilized, thus using the microbial cell as a carrier for the enzyme and obviating the need for extraction of the enzyme from the cell.
One commonly used support or entrapement material for microbial cell immobilization is a gel, usually an alginate gel.
Essentially the cells are trapped in a three-dimensional polymer network with relatively large interstitial spaces in the gel. The use of such gels has not been without problems though.
One problem with immobilizing microbial cells in a gel is their marked tendency to lose their activity during storage or other - periods of non-use, for instance during transportation. An accompanying difficulty during non-use is the tendency for contaminating micro-organisms to proliferate. It is a relatively routine matter to prepare gel-immobilized cells which have high activity upon immediate use, but the activity tends to decay relatively quickly if the gel-immobilized microbial cells are not used. A basic disadvantage of gel is that it has a high water activity and probably provides a good environment for growth of contaminant moulds, bacteria, and the like. Such gels, of course, are not reusable either.
~,Z~ L j~
Another type oE material used to immobilize catalytic agents such as enzymes and microbial cells i5 a porous pellet composed primarily of a high silica content or mixtures oE silica and alumina. The high silica content is derived from the addition of a high purity siliceous material to the reaction mixture in the process oE making the pellet. On the porous surfaces of the pellets are deposited small amounts of the catalytically active agent. In general, the use of such a support can be advantageous because it greatly increases the efficiency of the use of the catalyst. By spreading the catalyst material over a large support surface area much more of its catalytically active surface is exposed to the chemicals whose reaction it is to catalyze.
In selecting such a porous, inorganic material to immobilize micro-organisms careful consideration must be given to the pore diameter of the carrier. Production rates are greatly affected by concentration of the enzymes or microbial cells and by the ease of diffusion to them. It has been generally recognized that by maximizing the concentration of microbial cells and accepting the resulting diffusion rates gives the best performance~
The highest loading of microbial cells are obtained when the pore diameters are based upon the microbial cell diameters. Pores which are one to five times the size oE the largest microbial cell typically provide the highest production rates. In microbial cell immobilization, the pore diamaters are based upon the major cell dimensions. ~iving systems re~uire additional care to insure adequate space for cell reproduction.
A big disadvantage with the use of conventional high silica-based catalyst supports is that their average pore diameter is too small for accomodating microbial cells. Their typical average pore diameter is much less than 1 micron. Typically, diamaters of 1 to 25 microns are needed to accomodate the microbial cells. ~E course, when it becomes difficult to immobilize an efEective number of microbial cells on a typical silica-based catalyst support, the economic attractiveness of such a support in commercial processes is greatly reduced.
Because of the above limitations to both the gel and silica-based inorganic supports for immobilization of microbial cells, research was conducted to find a support which would overcome all the above disadvantages as well as offer other advantages.
S During the course of such research, it was discovered that an efficient catalyst support made by the process of formin~ a mixture comprising an inorganic binder~ an organic burnout material, a solvent, and either expanded perlite, calcined diatomite, or flux-calcined diatomite, followed by formin~ an extrudate from the above mixture and then drying and calcining the extrudate results in an extremely economical, efficient support for immobilizing catalytic agents, in particular microbial cells. In the present invention~ we believe that by eliminating a high purity silica source from the reaction mixture of the present invention, the average pore diameter is conveniently controlled so that it falls in the range of from 1-25 microns. This contrasts sharply with the more conventional catalyst supports wherein the resulting average pore diameter is much smaller and therefore difficult to immobilize microbial cells on. Thus our invention results in the production of a catalyst support whose average pore diameter is in a range which is neither too large or too small for efficiently immobilizing microbial cells as in the case of silica-based supports.
Our catalyst support also does not provide for an environment where a decline in microbial activity occurs and - 25 microbial contaminants proliferate as in the case of gels.
Furthermore our supports are inert, rigid, and are reusable which greatly enhances their economic attractiveness. Additionally, our supports are made by an inventive process which employs economical ingredients and is easy to conduct.
Therefore, it is an object of the present invention to provide a novel process for the production of an inorganic catalyst support especially useful in the immobilization of microbial cells.
It is another object of the present invention to provide a catalyst support made by the above novel process.
Other aspects, objects, and the several advantages of the present invention are apparent from the specification and the appended claims.
-5- 1 ~ 5 ~
In accordance with one embodiment of the present invention we have discovered a novel process ~or the production of an inorganic catalyst support which is especially useful for immobili2ing microbial cells. Our inventive process involves the steps of:
(a) forming an extrudable mixture comprising:
(i) 20-70 wt.% of one material selected from the ~roup consisting of calcined diatomite, flux calcined diatomite and expanded perlite;
(ii) 5-30 wt.~ inorganic binder;
(iii) 0-12 wt.~ organic burnout material; and (iv) 20-50 wt.% solvent;
(b) extruding the mixture through a die to form an extrudate and then separating the extrudate into a plurality oE
pellets;
(c) drying the pellets at a temperature in the range of about 200 to 500F for about 5-30 minutes; and thereafter (d) calcining the dried pellets at a temperature in the range of about 700 to 2,000F for about 10-45 minutes.
Preferably, the mixture in the inventive process will comprise 30 - 45 wt.% of the diatomite or perlite used, 10 - 15 wt.%
inorganic binder, O - 12 wt.% organic burnout material, and 35 - 50 wt.% solvent.
Diatomite is a chalky sedimentary material composed of the skeletal remains of single celled aquatic water plants called diatoms. Many modern diatomite deposits were laid down by sedimentation in shallow waters years ago. Subsequent geologic uplift has raised these beds to positions where they can be mined by conventional methods. Deposits are found in numerous parts of the world, with one of the largest and purest deposits being located on the central California coast. In other locations, there are currently shallow bodies of water where diatomite deposition has occurred and/or is currently occurrin~. Such deposits are presently mined by dredging. A typical dry diatomite analysis is shown in Table I below.
TABLE I
Component Wt.%
Si02 ( ) 86.0 A1203 3.6
PROCESS FOR TXE PREPARATION OF CATALYST SUPPORTS AND
MATERIALS PRODUCED THER~BY
This invention relates to a process for the production of catalyst supports. It also relates to the catalyst supports produced by the above process. Additionally, it relates to catalyst supports containing catalytically active substances such as microbial cells immobilized thereon.
The use of various substances to support, and in some instances immobilize, catalytically active materials is well known to those skilled in the art. Since catalytically active substances help to make reactions proceed which would otherwise not be thermodynamically possible or economically practical in many instances, it has become increasingly important to look for ways to efficiently utilize and maintain such catalytically active materials. Furthermore, since the cost of the catalytically active materials must itself be an active consideration in deciding whether to commercialize a process using the catalyst, there is even more reason to look at utilizing the catalyst as desirably as possible.
One of the most important classes of catalytically active materials or agents currently being studied and utilized in both theoretical and commercial settings are enzymes. It is known that enzymes, which are proteinaceous in nature and which are commonly water soluble, act as biocatalysts which serve to regulate many and varied chemical reactions which occur in living organisms. The enzymes may also be isolated and used in analytical, medical, and industrial applications. For example, they find use in industrial applications in the preparation of food such as cheese or bread as well as being used in the preparation of alcoholic beverages. The enzyme glucose isomerase is extensively used to convert glucose to fructose in the manufacture of high fructose corn syrup.
Since enzymes are commonly water soluble as well as being generally unstable and, therefore, subject to deactivation, they are - difficult to remove for reuse from solutions in which they are utilized and they may not retain their catalytic activity over extended periods of time. These difficulties lead to an increased ~:~5~
cost in the use of enzymes in commercial scale operations due to the necessity for frequent replacement of the enzyme. In order to reduce the high cost of enzyme replacement, various methods to immobilize enzymes prior to their use have been devised. This immobilization of the enzyme permits its reuse, whereas it might otherwise undergo deactivation or be lost in the reaction medium in which it is used. These immobilized enzyme systems may be employed in various reactor systems, for example, in packed columns and stirred tank reactors, depending on the nature of the substrate which is being biochemically reacted.
Apsrt from immobilization of enzymes themselves, various substances and techniques have been put forward by which the enzymes could be immobilized without isolation. In psrticular, whole cells of micro-organisms can be immobilized, thus using the microbial cell as a carrier for the enzyme and obviating the need for extraction of the enzyme from the cell.
One commonly used support or entrapement material for microbial cell immobilization is a gel, usually an alginate gel.
Essentially the cells are trapped in a three-dimensional polymer network with relatively large interstitial spaces in the gel. The use of such gels has not been without problems though.
One problem with immobilizing microbial cells in a gel is their marked tendency to lose their activity during storage or other - periods of non-use, for instance during transportation. An accompanying difficulty during non-use is the tendency for contaminating micro-organisms to proliferate. It is a relatively routine matter to prepare gel-immobilized cells which have high activity upon immediate use, but the activity tends to decay relatively quickly if the gel-immobilized microbial cells are not used. A basic disadvantage of gel is that it has a high water activity and probably provides a good environment for growth of contaminant moulds, bacteria, and the like. Such gels, of course, are not reusable either.
~,Z~ L j~
Another type oE material used to immobilize catalytic agents such as enzymes and microbial cells i5 a porous pellet composed primarily of a high silica content or mixtures oE silica and alumina. The high silica content is derived from the addition of a high purity siliceous material to the reaction mixture in the process oE making the pellet. On the porous surfaces of the pellets are deposited small amounts of the catalytically active agent. In general, the use of such a support can be advantageous because it greatly increases the efficiency of the use of the catalyst. By spreading the catalyst material over a large support surface area much more of its catalytically active surface is exposed to the chemicals whose reaction it is to catalyze.
In selecting such a porous, inorganic material to immobilize micro-organisms careful consideration must be given to the pore diameter of the carrier. Production rates are greatly affected by concentration of the enzymes or microbial cells and by the ease of diffusion to them. It has been generally recognized that by maximizing the concentration of microbial cells and accepting the resulting diffusion rates gives the best performance~
The highest loading of microbial cells are obtained when the pore diameters are based upon the microbial cell diameters. Pores which are one to five times the size oE the largest microbial cell typically provide the highest production rates. In microbial cell immobilization, the pore diamaters are based upon the major cell dimensions. ~iving systems re~uire additional care to insure adequate space for cell reproduction.
A big disadvantage with the use of conventional high silica-based catalyst supports is that their average pore diameter is too small for accomodating microbial cells. Their typical average pore diameter is much less than 1 micron. Typically, diamaters of 1 to 25 microns are needed to accomodate the microbial cells. ~E course, when it becomes difficult to immobilize an efEective number of microbial cells on a typical silica-based catalyst support, the economic attractiveness of such a support in commercial processes is greatly reduced.
Because of the above limitations to both the gel and silica-based inorganic supports for immobilization of microbial cells, research was conducted to find a support which would overcome all the above disadvantages as well as offer other advantages.
S During the course of such research, it was discovered that an efficient catalyst support made by the process of formin~ a mixture comprising an inorganic binder~ an organic burnout material, a solvent, and either expanded perlite, calcined diatomite, or flux-calcined diatomite, followed by formin~ an extrudate from the above mixture and then drying and calcining the extrudate results in an extremely economical, efficient support for immobilizing catalytic agents, in particular microbial cells. In the present invention~ we believe that by eliminating a high purity silica source from the reaction mixture of the present invention, the average pore diameter is conveniently controlled so that it falls in the range of from 1-25 microns. This contrasts sharply with the more conventional catalyst supports wherein the resulting average pore diameter is much smaller and therefore difficult to immobilize microbial cells on. Thus our invention results in the production of a catalyst support whose average pore diameter is in a range which is neither too large or too small for efficiently immobilizing microbial cells as in the case of silica-based supports.
Our catalyst support also does not provide for an environment where a decline in microbial activity occurs and - 25 microbial contaminants proliferate as in the case of gels.
Furthermore our supports are inert, rigid, and are reusable which greatly enhances their economic attractiveness. Additionally, our supports are made by an inventive process which employs economical ingredients and is easy to conduct.
Therefore, it is an object of the present invention to provide a novel process for the production of an inorganic catalyst support especially useful in the immobilization of microbial cells.
It is another object of the present invention to provide a catalyst support made by the above novel process.
Other aspects, objects, and the several advantages of the present invention are apparent from the specification and the appended claims.
-5- 1 ~ 5 ~
In accordance with one embodiment of the present invention we have discovered a novel process ~or the production of an inorganic catalyst support which is especially useful for immobili2ing microbial cells. Our inventive process involves the steps of:
(a) forming an extrudable mixture comprising:
(i) 20-70 wt.% of one material selected from the ~roup consisting of calcined diatomite, flux calcined diatomite and expanded perlite;
(ii) 5-30 wt.~ inorganic binder;
(iii) 0-12 wt.~ organic burnout material; and (iv) 20-50 wt.% solvent;
(b) extruding the mixture through a die to form an extrudate and then separating the extrudate into a plurality oE
pellets;
(c) drying the pellets at a temperature in the range of about 200 to 500F for about 5-30 minutes; and thereafter (d) calcining the dried pellets at a temperature in the range of about 700 to 2,000F for about 10-45 minutes.
Preferably, the mixture in the inventive process will comprise 30 - 45 wt.% of the diatomite or perlite used, 10 - 15 wt.%
inorganic binder, O - 12 wt.% organic burnout material, and 35 - 50 wt.% solvent.
Diatomite is a chalky sedimentary material composed of the skeletal remains of single celled aquatic water plants called diatoms. Many modern diatomite deposits were laid down by sedimentation in shallow waters years ago. Subsequent geologic uplift has raised these beds to positions where they can be mined by conventional methods. Deposits are found in numerous parts of the world, with one of the largest and purest deposits being located on the central California coast. In other locations, there are currently shallow bodies of water where diatomite deposition has occurred and/or is currently occurrin~. Such deposits are presently mined by dredging. A typical dry diatomite analysis is shown in Table I below.
TABLE I
Component Wt.%
Si02 ( ) 86.0 A1203 3.6
2 3 1.3 Group I Oxides 1.2 Group II Oxides 1.1 Other 0-5 Water 3.0 Loss on Ignition 3.6 Note:
~a) predominantly in amorphous form Calcined diatomite is diatomite which is mined, dried, granulated, and passed through a kiln which is operated at a temperature in the range of about 1600F to 2400F. The calcinstion causes the diatomite particles to shrink and harden and, to a certain extent, to agglomerate themselves into larger clusters.
Flux calcined diatomite is produced by adding a flux to the diatomite. The flux can be added as a solution dissolved in a water spray or mixing water. Alternatively, dry flux powder can be incorporated into the mass of diatomite particles either during air conveying of the diatomite or by dry mixing of the flux and diatomite in conventional dry mixing devices such as tumblers.
Normally there will be from about 3 to about 10 weight percent flux - based on the weight of the dry diatomite. Typical fluxes include alkali metal salts such as sodium carbonate ('`soda ash"), sodium chloride, sodium hydroxide, and sodium silicate. Those skilled in the art will be well aware of the appropriate quantity of flux to use for any particular type of flux and diatomite.
t~
A commercially available form of expanded perlite may be used in the present invention. Perlite is a mineral of volcanic origin which generally alls into the rhyolitic class. The unique feature of perlite is that it contains several percent water of hydration. If the perlite is rapidly heated to a temperature on the order of 1600F (870C) the water is converted to steam and the perlite "pops", i.e. it rapidly expands to a much lower density.
The amount of expansion is usually on the order of 4 to 20 times the original volume. AEter expansion, the perlite is milled and classified to produce a specified particle distribution size.
Preferably the expanded perlite utilized in this invention will have a density o about 5 - 20 pcf, most preferably about 12 - 16 pcf.
Whatever perlite or diatomite is used in the present invention is one which preferably forms a cake having a permeability between about 10 and 2000 darcies. The cake is formed by flowing a slurry of 20 grams of the perlite or diatomite used mixed with 980 grams of water through a 325-mesh screen at a rate of 1.0 gallons per square foot per minute.
Another component of the present invention is an inorganic binder. Generally any commercially available inorganic binder may be used in the present invention. Of course, it must have the requisite strength to bind with the mixture ingredients, especially the diatomite or expanded perlite.
One class of inorganic binder which may be used in the present invention are clays. Examples include kaolin clays and bentonite clays. Kaolin clays, sometimes referred to as white or porcelain clays are a white-burning clay, which due to their great purity, have a high fusion point. Kaolin clays are also the most refractory of all clays.
Bentonite clays are a form of montmorillonite clays.
Bentonite clays are hydrous alumina silicates normally containing significant portions of sodium, magnesium, and calcium oxides.
Another class of inorganic binders which can be used are monovalent silicates. Examples of monovalent silicates include but are not limited to sodium silicate and potassium silicate with sodium silicate preferred.
Other inorganic binders which may be utilized include phosphoric acid based binders such as aluminum phosphate and colloidal suspensions including colloidal silica, colloidal alumina, and colloidal zirconia.
Suitable combinations of the above inorganic binders may be utilized. However, clay based binder systems are presently preferred.
Suitable organic burnout materials for use in the present invention include but are not limited to starches, cellulose fibers, corn meal, and powdered carbons. Examples of the cellulose fibers include kraft fiber, wood fiber, straw fibers, and others which are a well opened fiber. Short fiber lengths are preferred for ease in mixing and extrudin~.
Any commercially available solvent can be used in the present invention which will cause the mixture of the solid components to take on an extrudable consistency. These solvents may be organic or aqueous in nature however an aqueous solvent is presently preferred.
Examples of suitable organic solvents include but are not limited to kerosene, diesel fuels, and alcohols.
After the mixture of the solids and solvent is formed into the extrusion feed, it is extruded in conventional extrusion equipment through a die to form an extrudate from ~hich individual pellets may be separated. It is frequently desirable to incorporate a lubricant or similar extrusion aid into the mixture to facilitate the extrusion; such material will be burned out of the product during the subsequent drying and/or calcining. Most commonly the extrudate is an elongated rod-like material of circular, oval, or square cross-sections. Circular cross-sections are preferred to minimize attrition of the pellets in subsequent handling. Normally the extruded rod is appro~imately 0.06 to 0.25 inches in width or diameter and preferably approximately 0.115 to 0.135 inches.
The extruded rod is commonly severed at intervals approximately equal to the diameter or width of the rod such that generally cylindrical or cubical pellets having approximately equal dimensions in all dimensions are formed. Conventional severing equipment such as wire knives can be used.
~2~
After the extruded pellets are formed they are dried in conventional drying units such as continuous belt dryers. Quite satisfactory materials have been made using a three ~one dryer in which the temperature generally ranges between about 200 - 500F, preferably between about 250 - 450F. Drying will generally bP for about 5 - 30 minutes. preferably about 10 - 15 minutes. The time and temperature relationships must be such that during the drying period all moisture is removed. After drying has been completed the pellets may be allowed to cool and are screened to remove any pellets which are over or under the desired size range.
Thereafter the dried pellets are calcined or fired in calcining equipment such as a rotary kiln generally at a temperature in the range of about 700 - 2,000F for about 10 - 45 minutes, preferably at a temperature in the range of about 1,400 - 1,800F
Eor about 20 - 30 minutes. The calcining time will normally be at least about 10 minutes and more on the order of about 20 - 30 minutes Calcining in an oxygen containing atmosphere should continue until all the organic burnout material, if any is present, has been burned out of the pellets leaving a highly porous composite of diatomite or perlite and inorganic binder. If desired, additional air injection can be made at approximately the mid-point of the calcination ~iln to enhance the calcination: an air lance is quite suitable Eor such air injection. The pellets can then be screened to remove off-size material.
In accordance with another embodiment of the present invention, an inorganic catalyst support having a pore diameter very suitable for immobilizing microbial cells is provid0d. This inorganic catalyst support is made by the above described inventive process.
The average pore diameter of the inventive catalyst support will be between about 1 and 25 microns. The resulting catalyst support has a mean pore diameter which is ideal for immobilizing microbial cells.
Generally, the inventive catalyst support will have a surface area in the range of about 3-20 m /g, a pore volume in the range of about 0.6-1.2 cc/g, and a crush strength of about 1-10 kg.
S~ 5~
The catalyst supports of the present invention are useful for supporting any suitable catalytic substance. In particular, the inventive catalyst supports are useful for immobiliæing biocatalysts, especially microbial cells. A wide variety of microbial cells to include bacterial and fungus-like microbes can be immobilized on the support by any method known to those skilled in the art. Typically, the immobilization occurs by simply contacting the support with an aqueous suspension of microbial cells to be i~mobilized thereon. There is a natural attraction between the microbial cell walls ancl the carrier as produced.
EXAMPLE
This example illustrates the preparation of an inventive catalyst support.
300 lbs. of flux-calcined diatomite tCELITE HYFLO SUPER
CEL~ from ~anville Product Corporation) were mixed with 100 lbs. of bentonite clay, 100 lbs. of cellulose fiber, and 45 gallons of water and mixed thoroughly to produce an extrudable consistency. The mixture was then fed to a screw extruder with 0.13 inch holes in the die plate. The extruded rod was cut at 0.13 inch intervals into pellets. These pellets were then dried in a 350F oven for about 20 minutes and were thereafter calcined in a 1,450~F rotary kiln for approximately 20 minutes. The resulting calcined pellets were screened to obtain a uniform size. The physical properties of the pellets, useful as a support for immobilizing microbial cells, was as follows: mean pore diameter, 2.0 microns; surface area, /l.0 m /g; pore volume, 0.9 cm /g; and crush strengh, 1.5 kg.
Reasonable modifications and variations are possible from the foregoing without departing from the spirit or scope of the present invention.
~a) predominantly in amorphous form Calcined diatomite is diatomite which is mined, dried, granulated, and passed through a kiln which is operated at a temperature in the range of about 1600F to 2400F. The calcinstion causes the diatomite particles to shrink and harden and, to a certain extent, to agglomerate themselves into larger clusters.
Flux calcined diatomite is produced by adding a flux to the diatomite. The flux can be added as a solution dissolved in a water spray or mixing water. Alternatively, dry flux powder can be incorporated into the mass of diatomite particles either during air conveying of the diatomite or by dry mixing of the flux and diatomite in conventional dry mixing devices such as tumblers.
Normally there will be from about 3 to about 10 weight percent flux - based on the weight of the dry diatomite. Typical fluxes include alkali metal salts such as sodium carbonate ('`soda ash"), sodium chloride, sodium hydroxide, and sodium silicate. Those skilled in the art will be well aware of the appropriate quantity of flux to use for any particular type of flux and diatomite.
t~
A commercially available form of expanded perlite may be used in the present invention. Perlite is a mineral of volcanic origin which generally alls into the rhyolitic class. The unique feature of perlite is that it contains several percent water of hydration. If the perlite is rapidly heated to a temperature on the order of 1600F (870C) the water is converted to steam and the perlite "pops", i.e. it rapidly expands to a much lower density.
The amount of expansion is usually on the order of 4 to 20 times the original volume. AEter expansion, the perlite is milled and classified to produce a specified particle distribution size.
Preferably the expanded perlite utilized in this invention will have a density o about 5 - 20 pcf, most preferably about 12 - 16 pcf.
Whatever perlite or diatomite is used in the present invention is one which preferably forms a cake having a permeability between about 10 and 2000 darcies. The cake is formed by flowing a slurry of 20 grams of the perlite or diatomite used mixed with 980 grams of water through a 325-mesh screen at a rate of 1.0 gallons per square foot per minute.
Another component of the present invention is an inorganic binder. Generally any commercially available inorganic binder may be used in the present invention. Of course, it must have the requisite strength to bind with the mixture ingredients, especially the diatomite or expanded perlite.
One class of inorganic binder which may be used in the present invention are clays. Examples include kaolin clays and bentonite clays. Kaolin clays, sometimes referred to as white or porcelain clays are a white-burning clay, which due to their great purity, have a high fusion point. Kaolin clays are also the most refractory of all clays.
Bentonite clays are a form of montmorillonite clays.
Bentonite clays are hydrous alumina silicates normally containing significant portions of sodium, magnesium, and calcium oxides.
Another class of inorganic binders which can be used are monovalent silicates. Examples of monovalent silicates include but are not limited to sodium silicate and potassium silicate with sodium silicate preferred.
Other inorganic binders which may be utilized include phosphoric acid based binders such as aluminum phosphate and colloidal suspensions including colloidal silica, colloidal alumina, and colloidal zirconia.
Suitable combinations of the above inorganic binders may be utilized. However, clay based binder systems are presently preferred.
Suitable organic burnout materials for use in the present invention include but are not limited to starches, cellulose fibers, corn meal, and powdered carbons. Examples of the cellulose fibers include kraft fiber, wood fiber, straw fibers, and others which are a well opened fiber. Short fiber lengths are preferred for ease in mixing and extrudin~.
Any commercially available solvent can be used in the present invention which will cause the mixture of the solid components to take on an extrudable consistency. These solvents may be organic or aqueous in nature however an aqueous solvent is presently preferred.
Examples of suitable organic solvents include but are not limited to kerosene, diesel fuels, and alcohols.
After the mixture of the solids and solvent is formed into the extrusion feed, it is extruded in conventional extrusion equipment through a die to form an extrudate from ~hich individual pellets may be separated. It is frequently desirable to incorporate a lubricant or similar extrusion aid into the mixture to facilitate the extrusion; such material will be burned out of the product during the subsequent drying and/or calcining. Most commonly the extrudate is an elongated rod-like material of circular, oval, or square cross-sections. Circular cross-sections are preferred to minimize attrition of the pellets in subsequent handling. Normally the extruded rod is appro~imately 0.06 to 0.25 inches in width or diameter and preferably approximately 0.115 to 0.135 inches.
The extruded rod is commonly severed at intervals approximately equal to the diameter or width of the rod such that generally cylindrical or cubical pellets having approximately equal dimensions in all dimensions are formed. Conventional severing equipment such as wire knives can be used.
~2~
After the extruded pellets are formed they are dried in conventional drying units such as continuous belt dryers. Quite satisfactory materials have been made using a three ~one dryer in which the temperature generally ranges between about 200 - 500F, preferably between about 250 - 450F. Drying will generally bP for about 5 - 30 minutes. preferably about 10 - 15 minutes. The time and temperature relationships must be such that during the drying period all moisture is removed. After drying has been completed the pellets may be allowed to cool and are screened to remove any pellets which are over or under the desired size range.
Thereafter the dried pellets are calcined or fired in calcining equipment such as a rotary kiln generally at a temperature in the range of about 700 - 2,000F for about 10 - 45 minutes, preferably at a temperature in the range of about 1,400 - 1,800F
Eor about 20 - 30 minutes. The calcining time will normally be at least about 10 minutes and more on the order of about 20 - 30 minutes Calcining in an oxygen containing atmosphere should continue until all the organic burnout material, if any is present, has been burned out of the pellets leaving a highly porous composite of diatomite or perlite and inorganic binder. If desired, additional air injection can be made at approximately the mid-point of the calcination ~iln to enhance the calcination: an air lance is quite suitable Eor such air injection. The pellets can then be screened to remove off-size material.
In accordance with another embodiment of the present invention, an inorganic catalyst support having a pore diameter very suitable for immobilizing microbial cells is provid0d. This inorganic catalyst support is made by the above described inventive process.
The average pore diameter of the inventive catalyst support will be between about 1 and 25 microns. The resulting catalyst support has a mean pore diameter which is ideal for immobilizing microbial cells.
Generally, the inventive catalyst support will have a surface area in the range of about 3-20 m /g, a pore volume in the range of about 0.6-1.2 cc/g, and a crush strength of about 1-10 kg.
S~ 5~
The catalyst supports of the present invention are useful for supporting any suitable catalytic substance. In particular, the inventive catalyst supports are useful for immobiliæing biocatalysts, especially microbial cells. A wide variety of microbial cells to include bacterial and fungus-like microbes can be immobilized on the support by any method known to those skilled in the art. Typically, the immobilization occurs by simply contacting the support with an aqueous suspension of microbial cells to be i~mobilized thereon. There is a natural attraction between the microbial cell walls ancl the carrier as produced.
EXAMPLE
This example illustrates the preparation of an inventive catalyst support.
300 lbs. of flux-calcined diatomite tCELITE HYFLO SUPER
CEL~ from ~anville Product Corporation) were mixed with 100 lbs. of bentonite clay, 100 lbs. of cellulose fiber, and 45 gallons of water and mixed thoroughly to produce an extrudable consistency. The mixture was then fed to a screw extruder with 0.13 inch holes in the die plate. The extruded rod was cut at 0.13 inch intervals into pellets. These pellets were then dried in a 350F oven for about 20 minutes and were thereafter calcined in a 1,450~F rotary kiln for approximately 20 minutes. The resulting calcined pellets were screened to obtain a uniform size. The physical properties of the pellets, useful as a support for immobilizing microbial cells, was as follows: mean pore diameter, 2.0 microns; surface area, /l.0 m /g; pore volume, 0.9 cm /g; and crush strengh, 1.5 kg.
Reasonable modifications and variations are possible from the foregoing without departing from the spirit or scope of the present invention.
Claims (13)
1. A process for the formation of a catalyst support useful for immobilizing microbial cells comprising the steps of:
(a) forming an extrudable mixture comprising:
(i) 20-70 wt.% of one material selected from the group consisting of calcined diatomite, flux calcined diatomite, and expanded perlite;
(ii) 5-30 wt.% inorganic binder;
(iii) 0-12 wt.% organic burnout material; and (iv) 20-50 wt.% solvent;
(b) extruding the mixture through a die to form an extrudate and then separating the extrudate into a plurality of pellets;
(c) drying the pellets at a temperature in the range of about 200° to 500°F for about 5 - 30 minutes;
and thereafter (d) calcining the dried pellets at a temperature in the range of about 700° to 2,000°F for about 10 -45 minutes.
(a) forming an extrudable mixture comprising:
(i) 20-70 wt.% of one material selected from the group consisting of calcined diatomite, flux calcined diatomite, and expanded perlite;
(ii) 5-30 wt.% inorganic binder;
(iii) 0-12 wt.% organic burnout material; and (iv) 20-50 wt.% solvent;
(b) extruding the mixture through a die to form an extrudate and then separating the extrudate into a plurality of pellets;
(c) drying the pellets at a temperature in the range of about 200° to 500°F for about 5 - 30 minutes;
and thereafter (d) calcining the dried pellets at a temperature in the range of about 700° to 2,000°F for about 10 -45 minutes.
2. A process according to Claim 1 wherein the extrudable mixture in 1(a) comprises:
(a) 30 - 45 wt.% of said material selected from the group consisting of calcined diatomite, flux calcined diatomite, and expanded perlite;
(b) 10 - 15 wt.% of said inorganic binder;
(c) 0 - 12 wt.% of said organic burnout material; and (d) 35 - 50 wt.% of said solvent.
(a) 30 - 45 wt.% of said material selected from the group consisting of calcined diatomite, flux calcined diatomite, and expanded perlite;
(b) 10 - 15 wt.% of said inorganic binder;
(c) 0 - 12 wt.% of said organic burnout material; and (d) 35 - 50 wt.% of said solvent.
3. A process according to Claim 1 wherein said inorganic binder is bentonite clay.
4. A process according to Claim 1 wherein said organic burnout material is cellulose.
5. A process according to Claim 1 wherein said solvent is water.
6. A process according to Claim 1 wherein said drying is conducted at a temperature in the range of 250° to 450°F for about10 - 15 minutes.
7. A process according to Claim 1 wherein said calcining is conducted at a temperature in the range of 1,400° to 1,800°F for about 20 - 30 minutes.
8. A catalyst support made by the process of Claim 1.
9. A catalyst support made by the process of Claim 1 and having an average pore diameter of between about 1 and 25 microns.
10. A catalyst support according to Claim 8 having at least one catalytically active substance thereon.
11. A catalyst support according to Claim 10 wherein said catalytically active substance is a microbial cell.
12. A catalyst support according to Claim 9 having at least one catalytically active substance thereon.
13. A catalyst support according to Claim 12 wherein said catalytically active substance is a microbial cell.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US69693585A | 1985-01-31 | 1985-01-31 | |
| US06/696,935 | 1985-01-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1258450A true CA1258450A (en) | 1989-08-15 |
Family
ID=24799119
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000500881A Expired CA1258450A (en) | 1985-01-31 | 1986-01-31 | Process for the preparation of catalyst supports and materials produced thereby |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS61192287A (en) |
| CA (1) | CA1258450A (en) |
| DE (1) | DE3602822A1 (en) |
| FR (1) | FR2578448B1 (en) |
| GB (1) | GB2185908B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63155400U (en) * | 1987-03-30 | 1988-10-12 | ||
| EP0302965A3 (en) * | 1987-08-11 | 1989-08-02 | Manville Corporation | Novel porous extruded shape biocarrier materials |
| WO1990015136A1 (en) * | 1989-06-09 | 1990-12-13 | Biotech International Limited | A method of growing and preserving fungi and bacteria |
| DE4405876A1 (en) * | 1994-02-23 | 1995-10-05 | Sued Chemie Ag | Shaped catalyst or catalyst carrier bodies |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2423686A (en) * | 1942-10-08 | 1947-07-08 | Johns Manville | Siliceous contact material and process of manufacture |
| US3526602A (en) * | 1968-02-09 | 1970-09-01 | Shikishima Mui Bii Kk | Catalyst carrier and process of making the same |
| GB1586364A (en) * | 1976-06-17 | 1981-03-18 | Atomic Energy Authority Uk | Porous inorganic materials |
| US4213882A (en) * | 1976-08-09 | 1980-07-22 | Johns-Manville Corporation | Preparation method for catalyst support and materials produced thereby |
| CA1076095A (en) * | 1976-09-28 | 1980-04-22 | Charles E. Moyer (Jr.) | Olefin hydration process and catalyst |
| JPS5350391A (en) * | 1976-10-19 | 1978-05-08 | Agency Of Ind Science & Technol | Method for increasing activity of alpha-1,6-glucosidase |
| CA1102777A (en) * | 1977-03-04 | 1981-06-09 | Percy R. Kavasmaneck | Low-metal content olefin hydration catalyst and related process |
| JPS6013674B2 (en) * | 1977-04-19 | 1985-04-09 | 旭硝子株式会社 | insoluble bioactive |
| DE2912827A1 (en) * | 1979-03-30 | 1980-10-09 | Basf Ag | METHOD FOR IMMOBILIZING ENZYMATICALLY ACTIVE PREPARATIONS |
| US4253990A (en) * | 1979-09-11 | 1981-03-03 | Johns-Manville Corporation | Preparation method for catalyst supports and materials produced thereby |
| EP0035883B1 (en) * | 1980-03-08 | 1984-06-06 | Fuji Oil Company, Limited | Method for enzymatic interesterification of lipid and enzyme used therein |
| US4297241A (en) * | 1980-03-21 | 1981-10-27 | Union Carbide Corporation | Method of preparing an olefin hydration catalyst |
-
1986
- 1986-01-30 FR FR8601289A patent/FR2578448B1/en not_active Expired - Lifetime
- 1986-01-30 DE DE19863602822 patent/DE3602822A1/en active Granted
- 1986-01-31 JP JP1828486A patent/JPS61192287A/en active Pending
- 1986-01-31 CA CA000500881A patent/CA1258450A/en not_active Expired
- 1986-02-04 GB GB8602718A patent/GB2185908B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB2185908A (en) | 1987-08-05 |
| JPS61192287A (en) | 1986-08-26 |
| DE3602822C2 (en) | 1988-08-18 |
| FR2578448A1 (en) | 1986-09-12 |
| GB2185908B (en) | 1989-11-29 |
| DE3602822A1 (en) | 1986-08-14 |
| FR2578448B1 (en) | 1990-11-16 |
| GB8602718D0 (en) | 1986-03-12 |
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