CA1129397A - Hollow catalyst carrier and hollow catalyst made of transition-alumina and process for production thereof - Google Patents
Hollow catalyst carrier and hollow catalyst made of transition-alumina and process for production thereofInfo
- Publication number
- CA1129397A CA1129397A CA328,764A CA328764A CA1129397A CA 1129397 A CA1129397 A CA 1129397A CA 328764 A CA328764 A CA 328764A CA 1129397 A CA1129397 A CA 1129397A
- Authority
- CA
- Canada
- Prior art keywords
- alumina
- catalyst carrier
- hollow
- less
- hollow catalyst
- 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
Links
Landscapes
- Catalysts (AREA)
Abstract
HOLLOW CATALYST CARRIER AND HOLLOW CATALYST MADE OF
TRANSITION-ALUMINA AND PROCESS FOR PRODUCTION THEREOF
Abstract of the Disclosure:
The invention relates to a hollow catalyst carrier and hollow catalyst made of a transition-alumina (e.g. y-alumina). The catalyst carrier is a calcined product having a pipe-like or multi-cell structure and having a very large void ratio (i.e. not less than 3 %), a very large specific surface area (i.e. not less than 5 m2/g), a bulk density of 0.8 to 1.8 g/cm3, a compressive strength in the extrusion direction of not less than 20 kg/cm2, and at least one hole in the ex-trusion direction. The carrier is produced by subjecting a powder containing a rehydratable alumina to an extrusion molding step, rehydrating the molded product and calcining it.
The hollow catalyst carrier has very good properties for carry-ing catalytically active components thereon and has very good mechanical strength.
TRANSITION-ALUMINA AND PROCESS FOR PRODUCTION THEREOF
Abstract of the Disclosure:
The invention relates to a hollow catalyst carrier and hollow catalyst made of a transition-alumina (e.g. y-alumina). The catalyst carrier is a calcined product having a pipe-like or multi-cell structure and having a very large void ratio (i.e. not less than 3 %), a very large specific surface area (i.e. not less than 5 m2/g), a bulk density of 0.8 to 1.8 g/cm3, a compressive strength in the extrusion direction of not less than 20 kg/cm2, and at least one hole in the ex-trusion direction. The carrier is produced by subjecting a powder containing a rehydratable alumina to an extrusion molding step, rehydrating the molded product and calcining it.
The hollow catalyst carrier has very good properties for carry-ing catalytically active components thereon and has very good mechanical strength.
Description
`` llZ93g~
The present invention relates to hollow catalyst carriers and to hollow catalysts made of a transition-alumina and a process for the production thereof.
It is well known that ceramic hollow products, particularly those having a multi-cell structure, have a number of uniform and parallel flow paths for gases, and hence, they have a low pressure drop and a uniform distribution of the gas flow rate within the structure. Also, they have a large effective surface area per unit weight because of their thin wàlls. Moreover, although the products are light in weight, they are very strong, and also have good heat resistance. Owing to these various advantages, ceramic hollow products have hitherto been used as catalyst carriers, supporting materials for various products, heat exchangers, heat insulating materials, sound insulating materials, and the like. In view of their very good impact strength and wear characteristics, ceramic hollow products have been investigated as catalyst carriers for the treatment of automobile exhaust gases and for the re-moval of nitrogen oxides.
The ceramic hollow products are usually produced from cordierite prepared by calcining a mixture of talc, bentonite, a-alumina, spodumene, titania, zirconia, mullite, calcined kaolin, or the like. The ceramic products obtained from cordierite, spodumene, a-alumina or mullite have partic-ularly good characteristics as catalyst carriers because of their high mechanical strength and low thermal expansion~
However, these ceramic hollow products usually have low specific surface areas e.g. less than 5 m2/g, and small pore volumes, e.g. less than 0.2 cm3/g, and hence, they are inferior in their `30 ability to carry catalytically active components and are not necessarily suitable as catalyst carriers.
In order to enhance the ability for carrying the ~A
. . .
3~7 catalyst components, the ceramic products are usually coated with an activated alumina having high catalyst component-carrying properties by conventional methods, such as dipping or spraying. However, the products are inferior in durability, because the coating of activated alumina adheres rather weakly to the surface of the ceramic and peels off easily during use of the catalyst.
As a result of the present inventors' intensive study of this problem, it has been found that an integral hollow product of a transition-alumina having a large pore volume and a large specific surface area has very good ability for carrying catalyst components and hence is useful as a catalyst carrier.
An object of th~ present invention is accordingly to provide an improved catalyst carrier.
According to one aspect of the invention there is provided a hollow catalyst carrier which comprises a calcined product.comprising predominantly a transition-alumina and which has a void ratio in the cross section of not less than 3 %, a specific surface area of not less than 5 m2/g, a bulk density of 0.8 to 1.8 g/cm3, a pore volume of 0.3 to 0.8 cm3/g, a compressive strength in the extrusion direction of not less than 20 kg/cm and at least one hole in the extrusion direction, said calcined product being prepared by subjecting a powder containing a rehydratable alumina to an extrusion molding step, rehydrating the molded product and then calcining it.
According to another aspect of the invention there is provided a process for the production of a hollow catalyst carrier having a void ratio in the cross section of not less than 3 %, a specific surface area of not less than 5 m /g, a bulk density of 0.8 to 1.8 g/cm3, a compressive strength in the extrusion direction of not less than 20 kg/cm2 and at
The present invention relates to hollow catalyst carriers and to hollow catalysts made of a transition-alumina and a process for the production thereof.
It is well known that ceramic hollow products, particularly those having a multi-cell structure, have a number of uniform and parallel flow paths for gases, and hence, they have a low pressure drop and a uniform distribution of the gas flow rate within the structure. Also, they have a large effective surface area per unit weight because of their thin wàlls. Moreover, although the products are light in weight, they are very strong, and also have good heat resistance. Owing to these various advantages, ceramic hollow products have hitherto been used as catalyst carriers, supporting materials for various products, heat exchangers, heat insulating materials, sound insulating materials, and the like. In view of their very good impact strength and wear characteristics, ceramic hollow products have been investigated as catalyst carriers for the treatment of automobile exhaust gases and for the re-moval of nitrogen oxides.
The ceramic hollow products are usually produced from cordierite prepared by calcining a mixture of talc, bentonite, a-alumina, spodumene, titania, zirconia, mullite, calcined kaolin, or the like. The ceramic products obtained from cordierite, spodumene, a-alumina or mullite have partic-ularly good characteristics as catalyst carriers because of their high mechanical strength and low thermal expansion~
However, these ceramic hollow products usually have low specific surface areas e.g. less than 5 m2/g, and small pore volumes, e.g. less than 0.2 cm3/g, and hence, they are inferior in their `30 ability to carry catalytically active components and are not necessarily suitable as catalyst carriers.
In order to enhance the ability for carrying the ~A
. . .
3~7 catalyst components, the ceramic products are usually coated with an activated alumina having high catalyst component-carrying properties by conventional methods, such as dipping or spraying. However, the products are inferior in durability, because the coating of activated alumina adheres rather weakly to the surface of the ceramic and peels off easily during use of the catalyst.
As a result of the present inventors' intensive study of this problem, it has been found that an integral hollow product of a transition-alumina having a large pore volume and a large specific surface area has very good ability for carrying catalyst components and hence is useful as a catalyst carrier.
An object of th~ present invention is accordingly to provide an improved catalyst carrier.
According to one aspect of the invention there is provided a hollow catalyst carrier which comprises a calcined product.comprising predominantly a transition-alumina and which has a void ratio in the cross section of not less than 3 %, a specific surface area of not less than 5 m2/g, a bulk density of 0.8 to 1.8 g/cm3, a pore volume of 0.3 to 0.8 cm3/g, a compressive strength in the extrusion direction of not less than 20 kg/cm and at least one hole in the extrusion direction, said calcined product being prepared by subjecting a powder containing a rehydratable alumina to an extrusion molding step, rehydrating the molded product and then calcining it.
According to another aspect of the invention there is provided a process for the production of a hollow catalyst carrier having a void ratio in the cross section of not less than 3 %, a specific surface area of not less than 5 m /g, a bulk density of 0.8 to 1.8 g/cm3, a compressive strength in the extrusion direction of not less than 20 kg/cm2 and at
- 2 -.
llZ939;5 least one hole in the extrusion direction, which process com-prises a step selected from the group consisting of: (i) coat-ing a rehydratable alumina or a rehydratable alumina-containing alumina powder with a rehydration preventing agent, mixing the coated alumina with water and/or a water-containing substance and optionally solid materials, and kneading the mixture to give a plastic mixture, and (ii) mixing a rehydratable alumina or a rehydratable alumina-containing alumina powder with a non-aqueous substance, and optionally a releasing agent, a binding agent and solid materials, kneading the mixture to give a plastic mixture; followed by (iii) eXtending the plastlc mixture to form a hollow shape, rehydrating the hollow product, and optionally drying it, and (iv) calcining the resulting product.
The hollow catalyst carrier of the present invention is thus an integral, calcined product which comprises predom-inantly a transition-alumina and has a void ratio of not less than 3 % in cross section, a specific surface area of not less than 5 m2/g, a bulk density of 0.8 to 1.8 g/cm3 (the bulk density is of the substantial part other than void part and is measured by the method as disclosed in JIS R-2205), a pore volume of 0.3 to 0.8 cm3/g, and a compressive strength in the extrusion direction of not less than 20 kg/cm2 and has at least one hole in the extrusion direction.
The hollow catalyst of the present invention can be 54~oport~;nq produced by aarrying-catalytically active components on the hollow catalyst carrier obtained as above.
The transition-aluminas used in the present invention may include those aluminas having a large specific surface area identified as the ~-, Y-~ X~, ~- and ~- forms by X-ray diffraction, and comprises predominantly ~-alumina.
The hollow product produced by the extrusion molding _ 3 _ A
~129~97 includes all products having various hole shapes, such as circular, rectangular, and the like, and the products may be pipe-like having a single opening, and also multi-cellular (honeycomb structure having 400 to 600 holes per a square inch).
The hollow cataylst carrier and hollow catalyst made of a transition-alumina is prepared by using a rehydratable alumina as the starting material. The rehydratable alumina includes all transition-aluminas other than a-alumina which are obtained by subjecting alumina hydrate to heat decomposition, for instance, p-alumina, amorphous alumina, or the like. The transition-alumina can be obtained industrially by contacting an alumina hydrate, such as alumina trihydrate which is obtained by the Bayer process, with a heated gas at about 400 to 1200C
for a fraction of a second to 10 seconds, or by heating the alumina hydrate under reduced pressure at about 250-- 900C
for about 1 minute to 4 hours. The loss on ignition of such a transition-alumina is about 0.5 to 15 % by weight.
The rehydratable alumina usually has a particle size of not more than about 50 ~ and is used in an amount of at least about 10 % by weight, i.e. 10 to 100 % by weight, pre-ferably not less than 20 % by weight, more preferably not less than about 30 % by weight,- based upon the total weight of the solid materials, i.e. the materials composing the hollow catalyst carrier and the hollow catalyst.
Other solid materials conventionally used in this type of product may be employed e.g. a-alumina, silica, alumina hydrate, clay, talc, bentonite, diatomaceous earth, zeolite, ~-cordierite, spodumene, titania, zirconia, silica sol, alumina sol, mullite, and also combustible materials and various catalytically active components.
These other solid materials present in the hollow catalyst carrier are used in an amount of less than about 90 %
~j' ' .
.
" 11293~7 by weight, i.e. D to less than 90 % by weight, preferably less than 80 % by weight, more preferably less than 70 ~ by weight, based upon the total weight of the solid materials. The com-bustible materials are used in order to increase the pore volume of the thin wall of the final hollow catalyst carrier or hollow catalyst, and may include all combustible materials whlch are usually used in the production of activated alumina having a large pore volume. Suitable examples of the com-bustible materials are wood scraps, cork particles, powdery coal, active carbon, charcoal, crystalline cellulose powder, methyl cellulose, carboxymethyl cellulose r starch, sucrose, gluconic acid, polyethylene glycol, polyvinyl alcohol, poly-acrylamide, polyethylene, polystyrene, and mixtures thereof.
The larger the ratio of the combustible materials, the larger the macropore volume in the thin wall of the final hollow catalyst carrier or hollow catalyst. However, when the amount of the combustible materials is too large, the strength of the final product is decreased. Accordingly, a suitable amount and kind of combustible materiaI should be selected in accordance with the intended uses of the catalyst carrier and also the catalyst. -The hollow catalyst carrier and hollow catalyst can be produced by using the rehydratable alumina and other solid materials as mentioned above as the starting materials in the following manner:
(1) The rehydratable alumina is partially or wholly coated with an agent for preventing rehydration, and is then mixed with water and/or a water-containing substance and optionally other solid materials and a binding agent, and the mixture is thoroughly kneaded to give a plastic mixture. The resulting plastic mixture is subjected to extrusion molding using a pipe or multi-cell forming dies. The extrusion-molded 11293~7 l!roduct thus obtained is subjected to rehydration and optionally followed by drying, and is then activated by calcining.
(2) Alternatively, the rehydratable alumina is mixed with a non-aqueous substance which is liquid at a temperature lower than 100C and optionally other solid materials and a binding agent, and the mixture is thoroughly kneaded to give a plastic mixture. The resulting plastic mixture is treated in the same manner as in (1) above, i.e. it is subjected to extrusion molding, rehydration, optionally drying, and finally calcination.
In order to produce an extrusion-molded product from a ceramic powder, water and/or a water-containing substance is usually added to the powder in order to give it plasticity.
However, when the rehydratable alumina is mixed with water and/or a water-containing substance, the alumina rehydrates and hence is exothermally cured during the extrusion molding step so that the extrusion molding cannot be accomplished properly a hollow catalyst carrier or hollow catalyst having good inner and outer walls (particularly, good inner walls) cannot be obtained. Accordingly, in the present invention, the rehydratable alumina is first coated with an agent for pre-venting rehydration before being mixed with water or a water-containing substance and other solid materials, or is mixed with a liquid non-aqueous substance without using water or a water-containing substance.
The agent for preventing rehydration can be any substance capable of preventing rehydration of the alumina during the extrusion molding step. Organic substances which are solid at room temperature and have a solubility of less than about 20 % by weight, preferably less than about 10 % by weight, in water at room temperature, and organic substances llZ93g7 which are liquid at room temperature and have a solubility of les~ than about 50 % by weight, preferably less than about 25 %
by weight, in water at room temperature are particularly suitable. Suitable examples of the rehydration preventing agent are fatty acids and their salts, e.g. caproic acid, palmitic acid, oleic acid, glycolic acid, capric acid, stearic acid, salicylic acid, trimethylacetic acid, lauric acid, cerotic acid, cinnamic acid, malonic acid, myristic acid, sebacic acid, benzoic acid, or maleic anhydride; sulfonic or phosphoric acid derivatives of these fatty acids; alcohols e.g.
t-butyl alcohol, lauryl alcohol, cetyl alcohol, stearyl alcohol, cyclohxanol, menthol, cholesterol,-or naphthol; amines e.g.
laurylamine, tetramethylenediamine, diethanolamine, or diphenyl-amine; alkanes e.g. n-heptadecane, n-octadecane, n-nonadecane, or n-eicosane; aromatic compounds e.g. naphthalene, diphenyl, or anthracene; waxes; natural high molecular weight compounds e.g. starches, casein, cellulose or its derivatives, or algi-nates; synthetic high molecular weight compounds e.g. poly-ethylene, polyvinyl alcohol, polyvinyl chloride, polypropylene, poly (sodium acrylate), polybutadiene, isoprene rubber, or urethane resin; paraffins e.g. liquid paraffin, soy bean oil, rape seed oil, light oil, or kerosene; carboxylic acids e.g.
caprylic acid, or pelargonic acid; aromatic hydrocarbons e.g.
benzene, toluene, xylene, or cumene; or the like.
The rehydration preventing agent is used in such an amount that the surface of the rehydratable alumina is at least partially coated therewith. This is achieved by mixing the agent directly with the alumina powder or by any other suitable means. For example, when the agent is solid and hence it is difficult to coat the alumina powder directly therewith, coating can be achieved by dissolving the agent in an appropriate solvent, e.g. an alcohol or ether. When the agent ~A
~........... . . ....................... .
- - . . . .
11293g7 is liquid, coating can be achieved by dipping the alumina powder into the rehydration preventing agent or by coating with the agent in vaporized form. A combination of these means can be employed, if desired.
A suitable amount of the rehydration preventing agent depends on the particle size distribution of the solid materials, the compositions, the conditions for extrusion and also the conditions for rehydration, but is usually in the range of 0.01 to 30 ~ by weight based on the weight of the rehydratable alumina. When the amount of the rehydration preventing agent is smaller than 0.01 % by weight, rehydration cannot be sufficiently prevented, and the product is exothermically cured during the extrusion mo~ding step. When the rehydration preventing agent ls also used as the binding agent as mentioned hereinafter, the amount may be increased up to the maximum amount of the binding agent.
The binding agent may be any of the conventional binding agents which are usually used for the production of alumina catalyst carriers, such as polyvinyl alcohol, starches, cellulosesj and the like. The amount of the binding agent depends on the kind and particle size of the solid starting materials, the conditions employed for extrusion molding and .
the conditions for rehydration, but is usually not more than 30 % by weight based on the weight of the solid materials.
When the binding agent is used in too large an amount, the molded product is distorted during the removal of the rehy-dration preventing agent after extrusion molding, and hence, the product has inferior dimension stability and reduced strength. When the rehydration preventing agent also functions as a binding agent, only the deficient amount of the binding agent may be supplemented.
The rehydration preventing agent and the binding ~ . . .
. ~ . . ; 1 ' ,... .
1~293g~
agent are preferably used in a total amount of at least 2.5 %
by weight based on the weight of the solid materials. When the starting alumina and the other solid materials are mixed together and kneaded with the non-aqueous substance, and if the non-aqueous substance functions as binding agent, no further binding agent is required, but if the non-aqueous substance does not have any binding effect, a binding agent should preferably be added in an amount of at least 1.5 % by weight.
The plastic mixture to be subjected to the extrusion moldlng may be prepared by subjecting the rehydratable alumina to the rehydration preventing treatment, mixing the resulting alumina with other solid materials and a binding agent, and then mixing and kneading the mixture with water or a water-containing substance, or when no rehydration preventing treat-ment is done, by mixing the rehydratable alumina with other solid materials and a binding agent and then mixing and knead-ing the mixture with a non-aqueous substance. The mixing and kneading of the mixture of solid materials with water or a water-containing substance or with a non-aqueous substance may be done prior to supplying the mixture to the extrusion molding machine, or when using an extrusion molding machine having a kneading function, the kneading may be carried out in such machine immediately prior to extrusion.
The water or water-containing substance may usually be used in an amount of about 20 to 70 ~ by weight based upon the weight of the solid materials. The amount of the non-aqueous substance may vary depending on the particle size distribution and components of the solid materials, the con-ditions for the extrusion molding and the conditions for therehydration, but is usually in the range of about 2 to 100 %
by weight based upon the weight of the rehydratable alumina.
-- g _ . ,~`",,~ .
~1293~7 Suitable water-containing substances include an aqueous solution of an acid, an alkali, a catalytically active component, a binding agent, or other additives. Suit-able non-aqueous substance include all substances which are liquid at a temperature lower than about 100C, for example, alcohols having 1 to 4 carbon atoms such as methanol, ethanol, or propanol; hydrocarbons such as hexane, or heptane; poly-valent alcohols such as ethylene glycol, or glycerin;
paraffins such as soy bean oil, rape seed oil, light oil, or kerosene; carboxylic acids such as caprylic acid, or pelargonic acid; esters such as ethyl silicate, or methyl acetate;
aromatic hydrocarbons such as benzene, toluene, xylene, or cumene; dioxane; or a mixture of these substances. Preferred non-aqueous substances are dioxane, ethanol, propanol, ethylene glycol, glycerin, and rape seed oil, which are liquid at the kneading temperature, i.e. at 10C higher than room temperature.
The extrusion molding does not necessarily require a releasing agent, but a saturated fatty acid or a salt thereof, such as stearic acid, calcium stearate or the like, may be added when the starting mixture is kneaded. These releasing agents are usually used in an amount of 0 to 5 %
by weight based upon the weight of the solid materials.
The extrusion molding can be carried out by any type of extrusion molding machine which can form a pipe-like or multi-cellular molded product having a void ratio in cross section of not less than 3 %, i.e. 3 to 95 %, preferably 20 to 90 %. For example, an extrusion molding machine which can give multi-cell structural molded products as disclosed in U.S. Patent 3,559,252, Japanese Patent Publication No.
1232/1976 and Japanese Patent PubIication (unexamined) No.
55960/1973; that which can give multi-cell structural molded rAl , li293~
products having fins which extend from the thin wall toward the center of core in order to improve the contact efficiency of the gas to be treated which passes through the core of the catalyst carrier or catalyst, as disclosed in Japanese Patent Publication (unexamined) No. 127886/1975; that which can give multi-cell structural molded products wherein at least one direction of thin wall is bent in the extrusion direction in order to prevent cracking and distortion of the product due to expansion or shrinkage of the multi-cell forming materials during the drying or calcining of the product, as disclosed in Japanese Patent Publication (unexamined) No. 565/1976; and that which can give multi-cell structural products having a collaring on the surrounding thin wall or having a surrounding thick wall in order to improve the impact strength of the product.
The hollow products of the present invention can also be produced by injection molding and transfer molding.
The outer shape and the hole shape of the hollow products may be in any geometrical form such as square, rectangle, triangle~ hexagon, circle, or the like. Further-more, the number of holes, wall thickness of cells, length of the molded products, sectional area of each cell, and the total sectional area of the hollow product (outer shape) having the pipe-like or multi-cell structure may appropriately be determined depending on the intended use of the products.
The hollow products obtained by extrusion molding are subjected to the rehydration treatment in order to enhance the impact strength and mechanical strength. The rehydration treatment can give the hollow products sufficient strength without forming a ceramic bond by sintering.
The rehydration can be done by the conventional methods which are used in the production of activated alumina, ~.~
~ ~29397 and is usually carried out at a temperature of from room temperature to 150C, preferably by immersing in steam or a steam-containing gas having a temperature of 80 to 100C, or by immersing in water at room temperature or higher, more pre-ferably at higher than 80C. When the rehydration preventing agent is insoluble in water at the above temperature range for rehydration, such as polyvinyl chloride, the hollow products may be immersed in an appropriate solvent such as alcohols, ethers, or esters, by which the coating layer is destroyed or dissolved out and the hollow products are then rehydrated with water which is contained in the molded products. When a non-aqueous substance having a solubility of not less than 5 % by weight at room temperature is used, the rehydration may pre-ferably be carried out under mild conditions, for instance, by using WateL diluted with a hydrophilic solvent (e.g~ alcohols) or by carrying out the rehydration in steam. This assists in the shape retention of the products.
The rehydration is usually carried out for about one minute to one week. When the rehydration time is longer and the rehydration temperature is higher, the bonding reaction of the hollow products proceeds more thoroughly and hence products having a larger mechanical strength can be obtained. When the rehydration temperature is higher, the rehydration time can be made shorter. The rehydration may also be carried out by keep-ing the product in a sealed vessel at room temperature and under atmospheric pressure for a long period of time.
The rehydrated hollow products thus obtained are then dried by natural drying, hot-air drying, or vacuum drying, by which any moisture adhering to the products is removed. The products are then further heat-treated at about 100 to 1100C, by which any moisture included within the products is removed and the products are activated. The drying step is not 11293g7 essential, but the hollow products may be subjected directly to calcination with mildly raised temperatures, for example, the hollow products may be calcined at room temperature to 300C for 48 hours and then at 300 to 1100C for 6 to 12 hours.
When the hollow products contain a combustible material, the products are heated at higher than about 250C
during the calcination, by which the combustible material is removed. When the removal of the combustible material and the activation of the hollow products are to be simultaneously carried out, the hollow products containing the combustible material may be placed on a bed and hot air or combustion gas containing a sufficient amount of oxygen passed thereto.
The hollow catalyst carrier obtained above is com-posed of thè crystalline phase of transition-alumina compris-ing predominantly y-alumina and has a specific surface area of not less than 5 m /g, preferably 10 to S00 m2/g, a bulk density of 0.8 to.1.8 g/cm3, a pore volume of 0.3 to 0.8 cm3/g, a compressive strength of not less than 20 kg/cm , preferably 30 to 500 kg/cm , in the extrusion direction, and further has a multi-cell structure having wall thickness of less than 1 mm just like conventional multi-cell structural catalyst carriers made of ceramic.
The hollow catalyst carrier of the present invention is distinguished from the conventional spherical or cylindrical catalyst carrier made of an activated alumina in the fact that the hollow products of the present invention has a void ratio in cross section of not less that.3.~, and has a larger specific surface area and larger pore volume and hence can be used for the treatment of exhaust gases with less pressure drop than the conventional spherical or cylindrical catalyst carrier. Moreover, the mechanical strength, such as a com-pres^sive strength, of the hollow products is imparted by the A
,.,., ... . , ~, . . ............. ... . ...... . . . ..... . .
, . . . `
i~Z9397 rehydration treatment followed by calcination at 100 to 1100Cunlike conventional ceramic hollow products wherein the products are sintered at high temperature such as 1200 to 2000C and thereby the strength is due to ceramic bonding.
Thus, since the hollow catalyst carrier of the present in-vention can be produced by calcining at a lower temperature, the cost for calcination apparatus, maintenance of the apparatus and fuel is very low.
The hollow products obtained above may further be modified by incorporating a specific substance into the solid starting materials or by impregnating a specific substance into the hollow products in order to make them suitable for specific uses, such as catalyst carriers for automobiles, which require a great heat resistance and impact strength.
For instance, an organic silicon compound may be added to the solid materials composing the hollow products or may be carried on the hollow products before or after the rehydration treatment. The organic silicon compound incorporated into or carried on the hollow products is oxidized or heat-decom-posed during the subsequent calcination step and thus thehollow products show durable activity for a long period of time owing to the delayed transition of y-alumina to ~-alumina The organic silicon compound may be any compound which can release silicon dioxide by oxidation or heat-decom-position thereof, for example, organoacetoxysilanes such as acetoxytrimethylsilane, acetoxytriethylsilane, diacetoxydim-ethylsilane, or diacetoxydiethylsilane; organoalkoxysilanes such as methoxytriethylsilane, or dimethoxydimethylsilane;
organodisilanes such as hexamethyldisilanej or hexaethyldis-ilane; organo-silanols such as trimethylsilanol, dimethylphenyl-silanol, triethylsilanol, diethylsilanol, or triphenylsilanol, organosilanecarboxylic acids; organosilmethylene, 1~29397 organopolysiloxane; organohydrogenosilane; organopolysilane;silicone tetrachloride; or the like.
The organic silicon compound is preferably incorp-orated into or carried on the hollow products in an amount of 0.01 to 30 ~ by weight, preferably 0.1 to 10 % by weight, (converted into SiO2) based upon the weight of the alumina.
Use of the silicon compound in an amount of over 30 ~ by weight is not favorable from the economical view point, and on the other hand, use of less than 0.01 % by weight is not favorable from the viewpoint of the reduced effect on the improvement of heat resistance.
It is not clear why the catalyst carrier made of transition-alumina is maintained with less decrease of re-activity and ha$ excellent impact strength and heat resistance for a long period of time by incorporation or carrying of the organic silicon compound, it is assumed that silicon dioxide derived from the organic silicon compound is very fine and has an extremely high reactivity and hence the silicon dioxide is reacted with the activated alumina contained in the catalyst carrier to form an alumina-silicon dioxide reaction product on the surface of the activated alumina at a temperature at which the activated alumina does not convert into -alumina, and thereby the transition of y-alumina into -alumina is inhibited.
The hollow catalyst carrier made of a transition-alumina may further be contacted with a mineral acid after the activation treatment, washed with water and then dried, by a catalyst carrier having a larger macropore volume and having a high activity can be obtained. Suitable examples of the mineral acid are hydrochloric acid, nitric acid and sùlfuric acid, which are usually used in an aqueous solution having a concentration of about 0.1 to 10 N.
Contact of the catalyst carrier with the mineral acid ~ , . i .
is usually carried out by immersing the catalyst carrier in an aqueous solution of a mineral acid for about 10 minutes or longer. When the contact time is shorter than 10 minutes, the desired effect for enlarging the macropore volume can not be achieved. The contact temperature is not critical, but is pre-ferably not higher than 100C.
The hollow catalyst of the present invention can be produced by first mixing the catalytically active components with the solid materials composing the catalyst carrier or by carrying the catalytically active components on the hollow catalyst carrier by conventional methods, e.g. immersing or spraying. When the active component is first mixed with the solid materials, it is added to the mixture before or after treatment of tne rehydratable alumina with a rehydration pre-venting agent, or before or during the kneading of the mixture of solid materials and a non-aqueous substance.
The catalytically active components useful in the present invention include all components which are usually used for the conventional catalysts carried on an activated alumina carrier. For example, a hollow catalyst containing at least one of platinum (Pt), ruthenium (Ru), rhodium (Rh) and palladium (Pd) is used for non-selective removal of nitrogen oxides (NOx) from exhaust gases from various stationary origins such as factories, selective removal of NOx by reduction with NH3, oxidation of CO and hydrocarbons or reduction of NOx con-tained in exhaust gases of automobiles, and deodorizing of various industrial exhaust gases. A hollow catalyst containing at least one oxide of metals selected from copper (Cu), iron (Fe), cobalt (Co), nickel (Ni), manganese (Mn) and vanadium (V) is used for selective removal of NOx from exhaust gases by re-duction with NH3, oxidation of CO and hydrocarbons or reduction of NOx contained in exhaust gases of automobiles, deodorizing ~' llZ9397 of various industrial eXhaust gases, and decomposition of NO.
Moreover, a hollow catalyst containing at least one oxide of metals selected from vanadium ~V), molybdenum (Mo), tangsten (W), chromium (Cr), titanium (Ti), zinc ~Zn), zirconium (Zr), niobium (Nb), silver (Ag), cerium (Ce), tin (Sn), rhenium (Re), and tantalum (Ta) is used for' selective removal of NOx of exhaust gases by reduction with N~3, oxidation of CO and hydrocarbons or reduction of NOx contained in exhaust gases of automobiles.
The present invention is illustrated by the following Examples but is not limited thereto. In Examples, the term "part" means "part by weight" unless otherwise specified.
Exampie 1 Stearic acid (2 parts) was added to activated alumina powder (100 parts) which contained 30 parts of p-alumina (average particle size: about 6 ~) obtained by calcining a gibbsite type alumina hydrate. The mixture was thoroughly '~; mixed in a mixing machine for 2 hours, and as a result the , surface of the alumina was coated with the stearic acid.
Methyl cellulose (5 parts) and water (50 parts) were added to the mixture which was then kneaded in a kneading machine for 30 minutes and thereafter extruded by a screw type extruder to obtain a multi-cell product ~size: about 100 mm x 100 mm x 150 mm length, void ratio: 69.4 ~) having a wall thickness of 0.4 mm and square cell unit (side of the square: 2 mm).
The multi-cell product thus obtained was subjected ~1 to rehydration in steam for 2 hours and heated to 700C by ~ raising the temperature at a rate of 100C/hour and was then `~ calcined at 700C for one hour.
,, .
The multi-cell structural catalyst carrier thus , obtained had a compressive strength of 60 kg/cm , a specific surface area of lS0 m /g, a pore volume of 0.6 cm3/g, a bulk ,~ - 17 - -., . ~ .. -. . ... .
~129397 density of 1.21 g/cm3 and the alumina composing the multi-cell comprised predominantly y-alumina according to x-ray diffraction.
Example 2 Sodium alginate (0.5 part) was added to a powdery mixture of activated alumina powder (70 parts) containing 50 parts of p-alumina (average particle size: about 5 ~) and 30 parts of -alumina powder (average particle size: about 5 ~).
The mixture was thoroughly mixed in a mixing machine for one hour and as a result the surface of the alumina powder was coated with the sodium alginate. Methyl cellulose (10 parts) and water (40 parts) were added to the resulting powder and the mixture was kneaded with a kneader for 30 minutes and thereafter was extruded by a screw type extruder to obtain a multi-cell product (size: 100 mm~ x 150 mm length, void ratio:
64 %) having a wall thickness of 1 mm and square cell unit (side of the square: 4 mm).
The multi-cell product thus obtained was put in a sealed room and was subjected to a rehydration reaction at room temperature for one week, and thereafter heated to 600C
by raising the temperature at a rate of 50C/hour and was then calcined at 600C for one hour.
The multi-cell structural catalyst carrier thus obtained comprised predominantly y-alumina according to X-ray diffraction and had a compressive strength of 55 kg/cm , a specific surface area of 160 m2/g, a pore volume of 0.45 cm3/g, and a bulk density of 1.25 g/cm3.
Example 3 Rape seed oil ( 1 part) was added to a powdery mixture (100 parts) of p-alumina (average particle size: about 5 ~, 40 parts), x-alumina (40 parts) and a-alumina (20 parts).
The mixture was thoroughly mixed i~ a mixing machine for one , -- 1~ --J~
~, 11293~
hour and as a result the surface of the alumina powder was coated with the rape seed oil. Methyl cellulose (8 parts), spodumene (15 parts) and water (60 parts) were added to the resulting alumina powder and the mixture was kneaded in a kneading machine for 30 minutes and thereafter was extruded by a screw type extruder to obtain a multi-cell product (size:
about 100 mm x 100 mm x 150 mm le.ngth, void ratio: 75.6 %) having a wall thickness of 0.3 mm and square cell unit side of the square: 2 mm).
The multi-cel.l product thus obtained was immersed - in water at 95C for 240 minutes to effect rehydration, and thereafter was dried with hot air at 80C, and then heated up to 700C by raising the temperature at a rate of 100C/hour and was calcined at 700C for one hour.
The multi-cell structural catalyst carrier thus :
obtained had a compressive strength of 90 kg/cm , a specific surface area of 120 m2/g, a pore volume of 0.47 cm3/g, a bulk ~.
density of 1.75 g/cm3, and the alumina composing the multi-cell comprised predominantly y-alumina according to X-ray diffraction.
Example 4 :~ Alumina hydrate obtained by the Bayer process wascalcined with a hot gas at 700 - ~00C instantaneously (about 10 secondsl to give rehydratable alumina.
Ethylene glycol (40 parts) and methyl cellulose (5 parts) were added to the alumina thus obtained (100 parts) and the mixture was kneaded in a kneading machine and there-after was extruded with a screw type extruder to obtain a multi-cell product (size: about 100 mm x 100 mm x 150 mm length, void ratio: 69.9%) having a wall thickness of 0.4 mm and a honeycomb section (side of the section: 2 mm).
The multi-cell product thus obtained was rehydrated . ~ 1 ' A
.; ~ i ~, ... . ` .. - . .
. , . , . . . .. , . .. , . ` , ;~....... .
:~ 293g7 in steam for 2 days and dried in a vessel of a constant temperature of 80C overnight, and thereafter, it was heated up to 300C by raising the temperature at a rate of 50C/hour and further up to 600C by raising at a rate of 100C/hour and was then calcined at 600C for S hours.
The multi-cell structural catalyst carrier thus ob-tained had a compressive strength of 50 kg/cm2, a specific surface area of 150 m2/g, a pore volume of 0.6 cm3/g, a bulk density of 1.23 g/cm3 and the alumina composing the multi-cell comprised predominantly y-alumina according to X-ray diffraction.
Example 5 Cordierite (50 parts), starch (10 parts) and glycerin (30 parts)were added to the same rehydratable alumina (100 parts) as prepared in Example 4. The mixture was kneaded in a kneading machine and then extruded with a screw type extruder to obtain a multi-cell product (size: about 100 ~n x 100 mm x 150 mm length, void ratio: 69.9 %) having a wall thickness of 0.4 mm and a square section (side of the square:
2 mm).
The multi-cell product thus obtained was rehydrated in steam for 2 days and dried in a vessel having a constant temperature of 80C overnight, and thereafter, the product was heated to 700C by raising the temperature at a rate of 100C/hour and was then calcined at 700C for one hour.
The multi-cell structural catalyst carrier thus obtained had a compressive strength of 50 kg/cm , a specific surface area of 120 m2/g, a pore volume of 0.35 cm3/g, a bulk density of 1.46 g/cm3 and the alumina composing the multi-cell comprised predominantly ~-alumina according to X-ray diffraction.
Example 6 The multi-cell product obtained by molding and -11~9397 rehydrating in the same manner as described in Example 1 was heated to 1100C by raising the temperature at a rate of 100C/
hour and was then calcined at 1100C for one hour.
The multi-cell structural catalyst carrier thus ob-tained had a compressive strength of 50 kg/cm2, a specific surface area of 20 m2/g, a pore volume of 0.4 cm3/q, a bulk density of 1.47 g/cm3, and the alumina composing the multi-cell comprised predominantly ~-alumina according to X-ray diffraction.
Reference Example 1 Methyl cellulose (4.5 parts) and water (25 parts) were added to cordierite powder (average particle size: about 8 ~, 100 parts) and the mixture was kneaded in a kneading machine for 30 minutes, and thereafter, it was extruded with the same extruder as used in Example 1, and then dried and subsequently it was heated to 1300C by raising the temperature at a rate of 100C/hour and was calcined at this temperature for 5 hours.
The ceramic multi-cell structural catalyst carrier thus obtained had a compressive strength of 250 kg/cm2, a specific surface area of 0.2 m /g, and a pore volume of 0.20 cm3/g Reference Example 2 Methyl cellulose (5 parts) and water (26 parts) were added to mullite powder (average particle size: about 5 ~, 100 parts) and the mixture was kneaded in a kneading machine '~
for 30 minutes, and thereafter, it was extruded with the same extruder as used in Example 1, and then it was dried and heated to 1450C by raising the temperature at a rate of 100C/
hour and was sintered at this temperature for 10 hours.
The multi-cell structural catalyst carrier thus obtained had a compressive strength of 300 kg/cm , a specific ; surface area of 0.3 m /g, and a pore volume of 0.15 cm /g.
, . . ~ .
.. . . . . .
112~3g7 Reference Example 3 -Crystalline cellulose (10 parts) was added to activated alumina powder (100 parts) containing 30 parts pf p-alumina (average particle size: about 6 ~) which was pre-pared by calcining gibbsite type alumina hydrate. While adding water (50 parts) thereto, the mixture was formed to a spherical product of 3 mm~ by a dish type granulating machine.
The spherical product thus obtained was rehydrated in steam for 2 days and dried, and thereafter, it was heated to 700C by raising the temperature at a rate of 100C/hour and was calcined at this temperature for one hour. The spherical product of activated alumina had a compressive strength of 10 kg/cm2, a specific surface area of 180 m2/g, and a pore volume of 0.7 cm3/g.
Reference Example 4 Stearic acid (0.5 part) was added to a mixture of the same activated alumina powder (50 parts) as used in Example 1 and ~-alumina (average particle size: 5 ~, 50 parts), and the mixture was thoroughly mixed in a mixing machine for 2 hours so that the surface of the alumina powder was coated with the stearic acid. Methyl cellulose (1.5 part) and water (35 parts) were added to the alumina powder and the mixture was kneaded in a kneading machine for 30 minutes. The kneaded mixture was subjected to extrusion by using the same extruder as used in Example 1, but it could not be extruded.
The above procedure was repeated except that water was used in an amount of 45 parts instead of 35 parts. As a result, the extrusion could be carried out, but the formed product had an extremely inferior shape retention.
Example 7 Vanadium oxide (V2O5) of 15 ~ by weight based upon the weight of the catalyst carrier was carried on the catalyst A`
.
, ,, ~ .
~ i 11293g7 carriers obtained in the above Examples 1 to 6 and ReferenceExamples 1 to 3. The catalyst thus obtained were each packed into a reactor, the inlet temperature of which was kept at 350C. A synthetic gas (NO: 100 ppm, NH3: 100 ppm, 2 1-2% by volume, H2O: 18.0 % by volume, the remainder: N2) was introduced into the reactor at a space velocity as shown in the following Table 1, and the removal rate of NOx and the pressure drop were measured. The results are shown in Table 1.
~; ' ' - ~ . - ,- , . . ~ , . .
11293g7 Table 1 .__ .__ . . _ . ~:
Catalyst Space velocity: 8000 hr 1 Space velocity: 2000i 1 carrier __ __ Ir Removal rate Pressure drop Removal rate Pressure of NOx (%) (mm, H O) of NOx (%) drop 2 (mm, H2O~
_ _. _ ., . . ._ - :.
Example 1 98 3 90 7 Example 2 90 2 80 5 Example 3 98 3 90 7 Example 4 98 - 3 90 7 Example 5 98 3 90 7 Example 6 78 3 72 7 ... . .
Ref. Ex. 1 25 3 20 7 Ref. Ex. 2 30 3 26 7 Ref. Ex. 3 , 30 90 200 It is clear from the above results in Table 1 that the multi-cell catalyst carrier of the present invention can give excellent catalysts having greater removal rate of nitrogen oxides in comparison with other multi-cell catalyst carriers, and further shows extremely lower pressure drop in comparison with the spherical product of activated alumina.
,.
.
llZ939;5 least one hole in the extrusion direction, which process com-prises a step selected from the group consisting of: (i) coat-ing a rehydratable alumina or a rehydratable alumina-containing alumina powder with a rehydration preventing agent, mixing the coated alumina with water and/or a water-containing substance and optionally solid materials, and kneading the mixture to give a plastic mixture, and (ii) mixing a rehydratable alumina or a rehydratable alumina-containing alumina powder with a non-aqueous substance, and optionally a releasing agent, a binding agent and solid materials, kneading the mixture to give a plastic mixture; followed by (iii) eXtending the plastlc mixture to form a hollow shape, rehydrating the hollow product, and optionally drying it, and (iv) calcining the resulting product.
The hollow catalyst carrier of the present invention is thus an integral, calcined product which comprises predom-inantly a transition-alumina and has a void ratio of not less than 3 % in cross section, a specific surface area of not less than 5 m2/g, a bulk density of 0.8 to 1.8 g/cm3 (the bulk density is of the substantial part other than void part and is measured by the method as disclosed in JIS R-2205), a pore volume of 0.3 to 0.8 cm3/g, and a compressive strength in the extrusion direction of not less than 20 kg/cm2 and has at least one hole in the extrusion direction.
The hollow catalyst of the present invention can be 54~oport~;nq produced by aarrying-catalytically active components on the hollow catalyst carrier obtained as above.
The transition-aluminas used in the present invention may include those aluminas having a large specific surface area identified as the ~-, Y-~ X~, ~- and ~- forms by X-ray diffraction, and comprises predominantly ~-alumina.
The hollow product produced by the extrusion molding _ 3 _ A
~129~97 includes all products having various hole shapes, such as circular, rectangular, and the like, and the products may be pipe-like having a single opening, and also multi-cellular (honeycomb structure having 400 to 600 holes per a square inch).
The hollow cataylst carrier and hollow catalyst made of a transition-alumina is prepared by using a rehydratable alumina as the starting material. The rehydratable alumina includes all transition-aluminas other than a-alumina which are obtained by subjecting alumina hydrate to heat decomposition, for instance, p-alumina, amorphous alumina, or the like. The transition-alumina can be obtained industrially by contacting an alumina hydrate, such as alumina trihydrate which is obtained by the Bayer process, with a heated gas at about 400 to 1200C
for a fraction of a second to 10 seconds, or by heating the alumina hydrate under reduced pressure at about 250-- 900C
for about 1 minute to 4 hours. The loss on ignition of such a transition-alumina is about 0.5 to 15 % by weight.
The rehydratable alumina usually has a particle size of not more than about 50 ~ and is used in an amount of at least about 10 % by weight, i.e. 10 to 100 % by weight, pre-ferably not less than 20 % by weight, more preferably not less than about 30 % by weight,- based upon the total weight of the solid materials, i.e. the materials composing the hollow catalyst carrier and the hollow catalyst.
Other solid materials conventionally used in this type of product may be employed e.g. a-alumina, silica, alumina hydrate, clay, talc, bentonite, diatomaceous earth, zeolite, ~-cordierite, spodumene, titania, zirconia, silica sol, alumina sol, mullite, and also combustible materials and various catalytically active components.
These other solid materials present in the hollow catalyst carrier are used in an amount of less than about 90 %
~j' ' .
.
" 11293~7 by weight, i.e. D to less than 90 % by weight, preferably less than 80 % by weight, more preferably less than 70 ~ by weight, based upon the total weight of the solid materials. The com-bustible materials are used in order to increase the pore volume of the thin wall of the final hollow catalyst carrier or hollow catalyst, and may include all combustible materials whlch are usually used in the production of activated alumina having a large pore volume. Suitable examples of the com-bustible materials are wood scraps, cork particles, powdery coal, active carbon, charcoal, crystalline cellulose powder, methyl cellulose, carboxymethyl cellulose r starch, sucrose, gluconic acid, polyethylene glycol, polyvinyl alcohol, poly-acrylamide, polyethylene, polystyrene, and mixtures thereof.
The larger the ratio of the combustible materials, the larger the macropore volume in the thin wall of the final hollow catalyst carrier or hollow catalyst. However, when the amount of the combustible materials is too large, the strength of the final product is decreased. Accordingly, a suitable amount and kind of combustible materiaI should be selected in accordance with the intended uses of the catalyst carrier and also the catalyst. -The hollow catalyst carrier and hollow catalyst can be produced by using the rehydratable alumina and other solid materials as mentioned above as the starting materials in the following manner:
(1) The rehydratable alumina is partially or wholly coated with an agent for preventing rehydration, and is then mixed with water and/or a water-containing substance and optionally other solid materials and a binding agent, and the mixture is thoroughly kneaded to give a plastic mixture. The resulting plastic mixture is subjected to extrusion molding using a pipe or multi-cell forming dies. The extrusion-molded 11293~7 l!roduct thus obtained is subjected to rehydration and optionally followed by drying, and is then activated by calcining.
(2) Alternatively, the rehydratable alumina is mixed with a non-aqueous substance which is liquid at a temperature lower than 100C and optionally other solid materials and a binding agent, and the mixture is thoroughly kneaded to give a plastic mixture. The resulting plastic mixture is treated in the same manner as in (1) above, i.e. it is subjected to extrusion molding, rehydration, optionally drying, and finally calcination.
In order to produce an extrusion-molded product from a ceramic powder, water and/or a water-containing substance is usually added to the powder in order to give it plasticity.
However, when the rehydratable alumina is mixed with water and/or a water-containing substance, the alumina rehydrates and hence is exothermally cured during the extrusion molding step so that the extrusion molding cannot be accomplished properly a hollow catalyst carrier or hollow catalyst having good inner and outer walls (particularly, good inner walls) cannot be obtained. Accordingly, in the present invention, the rehydratable alumina is first coated with an agent for pre-venting rehydration before being mixed with water or a water-containing substance and other solid materials, or is mixed with a liquid non-aqueous substance without using water or a water-containing substance.
The agent for preventing rehydration can be any substance capable of preventing rehydration of the alumina during the extrusion molding step. Organic substances which are solid at room temperature and have a solubility of less than about 20 % by weight, preferably less than about 10 % by weight, in water at room temperature, and organic substances llZ93g7 which are liquid at room temperature and have a solubility of les~ than about 50 % by weight, preferably less than about 25 %
by weight, in water at room temperature are particularly suitable. Suitable examples of the rehydration preventing agent are fatty acids and their salts, e.g. caproic acid, palmitic acid, oleic acid, glycolic acid, capric acid, stearic acid, salicylic acid, trimethylacetic acid, lauric acid, cerotic acid, cinnamic acid, malonic acid, myristic acid, sebacic acid, benzoic acid, or maleic anhydride; sulfonic or phosphoric acid derivatives of these fatty acids; alcohols e.g.
t-butyl alcohol, lauryl alcohol, cetyl alcohol, stearyl alcohol, cyclohxanol, menthol, cholesterol,-or naphthol; amines e.g.
laurylamine, tetramethylenediamine, diethanolamine, or diphenyl-amine; alkanes e.g. n-heptadecane, n-octadecane, n-nonadecane, or n-eicosane; aromatic compounds e.g. naphthalene, diphenyl, or anthracene; waxes; natural high molecular weight compounds e.g. starches, casein, cellulose or its derivatives, or algi-nates; synthetic high molecular weight compounds e.g. poly-ethylene, polyvinyl alcohol, polyvinyl chloride, polypropylene, poly (sodium acrylate), polybutadiene, isoprene rubber, or urethane resin; paraffins e.g. liquid paraffin, soy bean oil, rape seed oil, light oil, or kerosene; carboxylic acids e.g.
caprylic acid, or pelargonic acid; aromatic hydrocarbons e.g.
benzene, toluene, xylene, or cumene; or the like.
The rehydration preventing agent is used in such an amount that the surface of the rehydratable alumina is at least partially coated therewith. This is achieved by mixing the agent directly with the alumina powder or by any other suitable means. For example, when the agent is solid and hence it is difficult to coat the alumina powder directly therewith, coating can be achieved by dissolving the agent in an appropriate solvent, e.g. an alcohol or ether. When the agent ~A
~........... . . ....................... .
- - . . . .
11293g7 is liquid, coating can be achieved by dipping the alumina powder into the rehydration preventing agent or by coating with the agent in vaporized form. A combination of these means can be employed, if desired.
A suitable amount of the rehydration preventing agent depends on the particle size distribution of the solid materials, the compositions, the conditions for extrusion and also the conditions for rehydration, but is usually in the range of 0.01 to 30 ~ by weight based on the weight of the rehydratable alumina. When the amount of the rehydration preventing agent is smaller than 0.01 % by weight, rehydration cannot be sufficiently prevented, and the product is exothermically cured during the extrusion mo~ding step. When the rehydration preventing agent ls also used as the binding agent as mentioned hereinafter, the amount may be increased up to the maximum amount of the binding agent.
The binding agent may be any of the conventional binding agents which are usually used for the production of alumina catalyst carriers, such as polyvinyl alcohol, starches, cellulosesj and the like. The amount of the binding agent depends on the kind and particle size of the solid starting materials, the conditions employed for extrusion molding and .
the conditions for rehydration, but is usually not more than 30 % by weight based on the weight of the solid materials.
When the binding agent is used in too large an amount, the molded product is distorted during the removal of the rehy-dration preventing agent after extrusion molding, and hence, the product has inferior dimension stability and reduced strength. When the rehydration preventing agent also functions as a binding agent, only the deficient amount of the binding agent may be supplemented.
The rehydration preventing agent and the binding ~ . . .
. ~ . . ; 1 ' ,... .
1~293g~
agent are preferably used in a total amount of at least 2.5 %
by weight based on the weight of the solid materials. When the starting alumina and the other solid materials are mixed together and kneaded with the non-aqueous substance, and if the non-aqueous substance functions as binding agent, no further binding agent is required, but if the non-aqueous substance does not have any binding effect, a binding agent should preferably be added in an amount of at least 1.5 % by weight.
The plastic mixture to be subjected to the extrusion moldlng may be prepared by subjecting the rehydratable alumina to the rehydration preventing treatment, mixing the resulting alumina with other solid materials and a binding agent, and then mixing and kneading the mixture with water or a water-containing substance, or when no rehydration preventing treat-ment is done, by mixing the rehydratable alumina with other solid materials and a binding agent and then mixing and knead-ing the mixture with a non-aqueous substance. The mixing and kneading of the mixture of solid materials with water or a water-containing substance or with a non-aqueous substance may be done prior to supplying the mixture to the extrusion molding machine, or when using an extrusion molding machine having a kneading function, the kneading may be carried out in such machine immediately prior to extrusion.
The water or water-containing substance may usually be used in an amount of about 20 to 70 ~ by weight based upon the weight of the solid materials. The amount of the non-aqueous substance may vary depending on the particle size distribution and components of the solid materials, the con-ditions for the extrusion molding and the conditions for therehydration, but is usually in the range of about 2 to 100 %
by weight based upon the weight of the rehydratable alumina.
-- g _ . ,~`",,~ .
~1293~7 Suitable water-containing substances include an aqueous solution of an acid, an alkali, a catalytically active component, a binding agent, or other additives. Suit-able non-aqueous substance include all substances which are liquid at a temperature lower than about 100C, for example, alcohols having 1 to 4 carbon atoms such as methanol, ethanol, or propanol; hydrocarbons such as hexane, or heptane; poly-valent alcohols such as ethylene glycol, or glycerin;
paraffins such as soy bean oil, rape seed oil, light oil, or kerosene; carboxylic acids such as caprylic acid, or pelargonic acid; esters such as ethyl silicate, or methyl acetate;
aromatic hydrocarbons such as benzene, toluene, xylene, or cumene; dioxane; or a mixture of these substances. Preferred non-aqueous substances are dioxane, ethanol, propanol, ethylene glycol, glycerin, and rape seed oil, which are liquid at the kneading temperature, i.e. at 10C higher than room temperature.
The extrusion molding does not necessarily require a releasing agent, but a saturated fatty acid or a salt thereof, such as stearic acid, calcium stearate or the like, may be added when the starting mixture is kneaded. These releasing agents are usually used in an amount of 0 to 5 %
by weight based upon the weight of the solid materials.
The extrusion molding can be carried out by any type of extrusion molding machine which can form a pipe-like or multi-cellular molded product having a void ratio in cross section of not less than 3 %, i.e. 3 to 95 %, preferably 20 to 90 %. For example, an extrusion molding machine which can give multi-cell structural molded products as disclosed in U.S. Patent 3,559,252, Japanese Patent Publication No.
1232/1976 and Japanese Patent PubIication (unexamined) No.
55960/1973; that which can give multi-cell structural molded rAl , li293~
products having fins which extend from the thin wall toward the center of core in order to improve the contact efficiency of the gas to be treated which passes through the core of the catalyst carrier or catalyst, as disclosed in Japanese Patent Publication (unexamined) No. 127886/1975; that which can give multi-cell structural molded products wherein at least one direction of thin wall is bent in the extrusion direction in order to prevent cracking and distortion of the product due to expansion or shrinkage of the multi-cell forming materials during the drying or calcining of the product, as disclosed in Japanese Patent Publication (unexamined) No. 565/1976; and that which can give multi-cell structural products having a collaring on the surrounding thin wall or having a surrounding thick wall in order to improve the impact strength of the product.
The hollow products of the present invention can also be produced by injection molding and transfer molding.
The outer shape and the hole shape of the hollow products may be in any geometrical form such as square, rectangle, triangle~ hexagon, circle, or the like. Further-more, the number of holes, wall thickness of cells, length of the molded products, sectional area of each cell, and the total sectional area of the hollow product (outer shape) having the pipe-like or multi-cell structure may appropriately be determined depending on the intended use of the products.
The hollow products obtained by extrusion molding are subjected to the rehydration treatment in order to enhance the impact strength and mechanical strength. The rehydration treatment can give the hollow products sufficient strength without forming a ceramic bond by sintering.
The rehydration can be done by the conventional methods which are used in the production of activated alumina, ~.~
~ ~29397 and is usually carried out at a temperature of from room temperature to 150C, preferably by immersing in steam or a steam-containing gas having a temperature of 80 to 100C, or by immersing in water at room temperature or higher, more pre-ferably at higher than 80C. When the rehydration preventing agent is insoluble in water at the above temperature range for rehydration, such as polyvinyl chloride, the hollow products may be immersed in an appropriate solvent such as alcohols, ethers, or esters, by which the coating layer is destroyed or dissolved out and the hollow products are then rehydrated with water which is contained in the molded products. When a non-aqueous substance having a solubility of not less than 5 % by weight at room temperature is used, the rehydration may pre-ferably be carried out under mild conditions, for instance, by using WateL diluted with a hydrophilic solvent (e.g~ alcohols) or by carrying out the rehydration in steam. This assists in the shape retention of the products.
The rehydration is usually carried out for about one minute to one week. When the rehydration time is longer and the rehydration temperature is higher, the bonding reaction of the hollow products proceeds more thoroughly and hence products having a larger mechanical strength can be obtained. When the rehydration temperature is higher, the rehydration time can be made shorter. The rehydration may also be carried out by keep-ing the product in a sealed vessel at room temperature and under atmospheric pressure for a long period of time.
The rehydrated hollow products thus obtained are then dried by natural drying, hot-air drying, or vacuum drying, by which any moisture adhering to the products is removed. The products are then further heat-treated at about 100 to 1100C, by which any moisture included within the products is removed and the products are activated. The drying step is not 11293g7 essential, but the hollow products may be subjected directly to calcination with mildly raised temperatures, for example, the hollow products may be calcined at room temperature to 300C for 48 hours and then at 300 to 1100C for 6 to 12 hours.
When the hollow products contain a combustible material, the products are heated at higher than about 250C
during the calcination, by which the combustible material is removed. When the removal of the combustible material and the activation of the hollow products are to be simultaneously carried out, the hollow products containing the combustible material may be placed on a bed and hot air or combustion gas containing a sufficient amount of oxygen passed thereto.
The hollow catalyst carrier obtained above is com-posed of thè crystalline phase of transition-alumina compris-ing predominantly y-alumina and has a specific surface area of not less than 5 m /g, preferably 10 to S00 m2/g, a bulk density of 0.8 to.1.8 g/cm3, a pore volume of 0.3 to 0.8 cm3/g, a compressive strength of not less than 20 kg/cm , preferably 30 to 500 kg/cm , in the extrusion direction, and further has a multi-cell structure having wall thickness of less than 1 mm just like conventional multi-cell structural catalyst carriers made of ceramic.
The hollow catalyst carrier of the present invention is distinguished from the conventional spherical or cylindrical catalyst carrier made of an activated alumina in the fact that the hollow products of the present invention has a void ratio in cross section of not less that.3.~, and has a larger specific surface area and larger pore volume and hence can be used for the treatment of exhaust gases with less pressure drop than the conventional spherical or cylindrical catalyst carrier. Moreover, the mechanical strength, such as a com-pres^sive strength, of the hollow products is imparted by the A
,.,., ... . , ~, . . ............. ... . ...... . . . ..... . .
, . . . `
i~Z9397 rehydration treatment followed by calcination at 100 to 1100Cunlike conventional ceramic hollow products wherein the products are sintered at high temperature such as 1200 to 2000C and thereby the strength is due to ceramic bonding.
Thus, since the hollow catalyst carrier of the present in-vention can be produced by calcining at a lower temperature, the cost for calcination apparatus, maintenance of the apparatus and fuel is very low.
The hollow products obtained above may further be modified by incorporating a specific substance into the solid starting materials or by impregnating a specific substance into the hollow products in order to make them suitable for specific uses, such as catalyst carriers for automobiles, which require a great heat resistance and impact strength.
For instance, an organic silicon compound may be added to the solid materials composing the hollow products or may be carried on the hollow products before or after the rehydration treatment. The organic silicon compound incorporated into or carried on the hollow products is oxidized or heat-decom-posed during the subsequent calcination step and thus thehollow products show durable activity for a long period of time owing to the delayed transition of y-alumina to ~-alumina The organic silicon compound may be any compound which can release silicon dioxide by oxidation or heat-decom-position thereof, for example, organoacetoxysilanes such as acetoxytrimethylsilane, acetoxytriethylsilane, diacetoxydim-ethylsilane, or diacetoxydiethylsilane; organoalkoxysilanes such as methoxytriethylsilane, or dimethoxydimethylsilane;
organodisilanes such as hexamethyldisilanej or hexaethyldis-ilane; organo-silanols such as trimethylsilanol, dimethylphenyl-silanol, triethylsilanol, diethylsilanol, or triphenylsilanol, organosilanecarboxylic acids; organosilmethylene, 1~29397 organopolysiloxane; organohydrogenosilane; organopolysilane;silicone tetrachloride; or the like.
The organic silicon compound is preferably incorp-orated into or carried on the hollow products in an amount of 0.01 to 30 ~ by weight, preferably 0.1 to 10 % by weight, (converted into SiO2) based upon the weight of the alumina.
Use of the silicon compound in an amount of over 30 ~ by weight is not favorable from the economical view point, and on the other hand, use of less than 0.01 % by weight is not favorable from the viewpoint of the reduced effect on the improvement of heat resistance.
It is not clear why the catalyst carrier made of transition-alumina is maintained with less decrease of re-activity and ha$ excellent impact strength and heat resistance for a long period of time by incorporation or carrying of the organic silicon compound, it is assumed that silicon dioxide derived from the organic silicon compound is very fine and has an extremely high reactivity and hence the silicon dioxide is reacted with the activated alumina contained in the catalyst carrier to form an alumina-silicon dioxide reaction product on the surface of the activated alumina at a temperature at which the activated alumina does not convert into -alumina, and thereby the transition of y-alumina into -alumina is inhibited.
The hollow catalyst carrier made of a transition-alumina may further be contacted with a mineral acid after the activation treatment, washed with water and then dried, by a catalyst carrier having a larger macropore volume and having a high activity can be obtained. Suitable examples of the mineral acid are hydrochloric acid, nitric acid and sùlfuric acid, which are usually used in an aqueous solution having a concentration of about 0.1 to 10 N.
Contact of the catalyst carrier with the mineral acid ~ , . i .
is usually carried out by immersing the catalyst carrier in an aqueous solution of a mineral acid for about 10 minutes or longer. When the contact time is shorter than 10 minutes, the desired effect for enlarging the macropore volume can not be achieved. The contact temperature is not critical, but is pre-ferably not higher than 100C.
The hollow catalyst of the present invention can be produced by first mixing the catalytically active components with the solid materials composing the catalyst carrier or by carrying the catalytically active components on the hollow catalyst carrier by conventional methods, e.g. immersing or spraying. When the active component is first mixed with the solid materials, it is added to the mixture before or after treatment of tne rehydratable alumina with a rehydration pre-venting agent, or before or during the kneading of the mixture of solid materials and a non-aqueous substance.
The catalytically active components useful in the present invention include all components which are usually used for the conventional catalysts carried on an activated alumina carrier. For example, a hollow catalyst containing at least one of platinum (Pt), ruthenium (Ru), rhodium (Rh) and palladium (Pd) is used for non-selective removal of nitrogen oxides (NOx) from exhaust gases from various stationary origins such as factories, selective removal of NOx by reduction with NH3, oxidation of CO and hydrocarbons or reduction of NOx con-tained in exhaust gases of automobiles, and deodorizing of various industrial exhaust gases. A hollow catalyst containing at least one oxide of metals selected from copper (Cu), iron (Fe), cobalt (Co), nickel (Ni), manganese (Mn) and vanadium (V) is used for selective removal of NOx from exhaust gases by re-duction with NH3, oxidation of CO and hydrocarbons or reduction of NOx contained in exhaust gases of automobiles, deodorizing ~' llZ9397 of various industrial eXhaust gases, and decomposition of NO.
Moreover, a hollow catalyst containing at least one oxide of metals selected from vanadium ~V), molybdenum (Mo), tangsten (W), chromium (Cr), titanium (Ti), zinc ~Zn), zirconium (Zr), niobium (Nb), silver (Ag), cerium (Ce), tin (Sn), rhenium (Re), and tantalum (Ta) is used for' selective removal of NOx of exhaust gases by reduction with N~3, oxidation of CO and hydrocarbons or reduction of NOx contained in exhaust gases of automobiles.
The present invention is illustrated by the following Examples but is not limited thereto. In Examples, the term "part" means "part by weight" unless otherwise specified.
Exampie 1 Stearic acid (2 parts) was added to activated alumina powder (100 parts) which contained 30 parts of p-alumina (average particle size: about 6 ~) obtained by calcining a gibbsite type alumina hydrate. The mixture was thoroughly '~; mixed in a mixing machine for 2 hours, and as a result the , surface of the alumina was coated with the stearic acid.
Methyl cellulose (5 parts) and water (50 parts) were added to the mixture which was then kneaded in a kneading machine for 30 minutes and thereafter extruded by a screw type extruder to obtain a multi-cell product ~size: about 100 mm x 100 mm x 150 mm length, void ratio: 69.4 ~) having a wall thickness of 0.4 mm and square cell unit (side of the square: 2 mm).
The multi-cell product thus obtained was subjected ~1 to rehydration in steam for 2 hours and heated to 700C by ~ raising the temperature at a rate of 100C/hour and was then `~ calcined at 700C for one hour.
,, .
The multi-cell structural catalyst carrier thus , obtained had a compressive strength of 60 kg/cm , a specific surface area of lS0 m /g, a pore volume of 0.6 cm3/g, a bulk ,~ - 17 - -., . ~ .. -. . ... .
~129397 density of 1.21 g/cm3 and the alumina composing the multi-cell comprised predominantly y-alumina according to x-ray diffraction.
Example 2 Sodium alginate (0.5 part) was added to a powdery mixture of activated alumina powder (70 parts) containing 50 parts of p-alumina (average particle size: about 5 ~) and 30 parts of -alumina powder (average particle size: about 5 ~).
The mixture was thoroughly mixed in a mixing machine for one hour and as a result the surface of the alumina powder was coated with the sodium alginate. Methyl cellulose (10 parts) and water (40 parts) were added to the resulting powder and the mixture was kneaded with a kneader for 30 minutes and thereafter was extruded by a screw type extruder to obtain a multi-cell product (size: 100 mm~ x 150 mm length, void ratio:
64 %) having a wall thickness of 1 mm and square cell unit (side of the square: 4 mm).
The multi-cell product thus obtained was put in a sealed room and was subjected to a rehydration reaction at room temperature for one week, and thereafter heated to 600C
by raising the temperature at a rate of 50C/hour and was then calcined at 600C for one hour.
The multi-cell structural catalyst carrier thus obtained comprised predominantly y-alumina according to X-ray diffraction and had a compressive strength of 55 kg/cm , a specific surface area of 160 m2/g, a pore volume of 0.45 cm3/g, and a bulk density of 1.25 g/cm3.
Example 3 Rape seed oil ( 1 part) was added to a powdery mixture (100 parts) of p-alumina (average particle size: about 5 ~, 40 parts), x-alumina (40 parts) and a-alumina (20 parts).
The mixture was thoroughly mixed i~ a mixing machine for one , -- 1~ --J~
~, 11293~
hour and as a result the surface of the alumina powder was coated with the rape seed oil. Methyl cellulose (8 parts), spodumene (15 parts) and water (60 parts) were added to the resulting alumina powder and the mixture was kneaded in a kneading machine for 30 minutes and thereafter was extruded by a screw type extruder to obtain a multi-cell product (size:
about 100 mm x 100 mm x 150 mm le.ngth, void ratio: 75.6 %) having a wall thickness of 0.3 mm and square cell unit side of the square: 2 mm).
The multi-cel.l product thus obtained was immersed - in water at 95C for 240 minutes to effect rehydration, and thereafter was dried with hot air at 80C, and then heated up to 700C by raising the temperature at a rate of 100C/hour and was calcined at 700C for one hour.
The multi-cell structural catalyst carrier thus :
obtained had a compressive strength of 90 kg/cm , a specific surface area of 120 m2/g, a pore volume of 0.47 cm3/g, a bulk ~.
density of 1.75 g/cm3, and the alumina composing the multi-cell comprised predominantly y-alumina according to X-ray diffraction.
Example 4 :~ Alumina hydrate obtained by the Bayer process wascalcined with a hot gas at 700 - ~00C instantaneously (about 10 secondsl to give rehydratable alumina.
Ethylene glycol (40 parts) and methyl cellulose (5 parts) were added to the alumina thus obtained (100 parts) and the mixture was kneaded in a kneading machine and there-after was extruded with a screw type extruder to obtain a multi-cell product (size: about 100 mm x 100 mm x 150 mm length, void ratio: 69.9%) having a wall thickness of 0.4 mm and a honeycomb section (side of the section: 2 mm).
The multi-cell product thus obtained was rehydrated . ~ 1 ' A
.; ~ i ~, ... . ` .. - . .
. , . , . . . .. , . .. , . ` , ;~....... .
:~ 293g7 in steam for 2 days and dried in a vessel of a constant temperature of 80C overnight, and thereafter, it was heated up to 300C by raising the temperature at a rate of 50C/hour and further up to 600C by raising at a rate of 100C/hour and was then calcined at 600C for S hours.
The multi-cell structural catalyst carrier thus ob-tained had a compressive strength of 50 kg/cm2, a specific surface area of 150 m2/g, a pore volume of 0.6 cm3/g, a bulk density of 1.23 g/cm3 and the alumina composing the multi-cell comprised predominantly y-alumina according to X-ray diffraction.
Example 5 Cordierite (50 parts), starch (10 parts) and glycerin (30 parts)were added to the same rehydratable alumina (100 parts) as prepared in Example 4. The mixture was kneaded in a kneading machine and then extruded with a screw type extruder to obtain a multi-cell product (size: about 100 ~n x 100 mm x 150 mm length, void ratio: 69.9 %) having a wall thickness of 0.4 mm and a square section (side of the square:
2 mm).
The multi-cell product thus obtained was rehydrated in steam for 2 days and dried in a vessel having a constant temperature of 80C overnight, and thereafter, the product was heated to 700C by raising the temperature at a rate of 100C/hour and was then calcined at 700C for one hour.
The multi-cell structural catalyst carrier thus obtained had a compressive strength of 50 kg/cm , a specific surface area of 120 m2/g, a pore volume of 0.35 cm3/g, a bulk density of 1.46 g/cm3 and the alumina composing the multi-cell comprised predominantly ~-alumina according to X-ray diffraction.
Example 6 The multi-cell product obtained by molding and -11~9397 rehydrating in the same manner as described in Example 1 was heated to 1100C by raising the temperature at a rate of 100C/
hour and was then calcined at 1100C for one hour.
The multi-cell structural catalyst carrier thus ob-tained had a compressive strength of 50 kg/cm2, a specific surface area of 20 m2/g, a pore volume of 0.4 cm3/q, a bulk density of 1.47 g/cm3, and the alumina composing the multi-cell comprised predominantly ~-alumina according to X-ray diffraction.
Reference Example 1 Methyl cellulose (4.5 parts) and water (25 parts) were added to cordierite powder (average particle size: about 8 ~, 100 parts) and the mixture was kneaded in a kneading machine for 30 minutes, and thereafter, it was extruded with the same extruder as used in Example 1, and then dried and subsequently it was heated to 1300C by raising the temperature at a rate of 100C/hour and was calcined at this temperature for 5 hours.
The ceramic multi-cell structural catalyst carrier thus obtained had a compressive strength of 250 kg/cm2, a specific surface area of 0.2 m /g, and a pore volume of 0.20 cm3/g Reference Example 2 Methyl cellulose (5 parts) and water (26 parts) were added to mullite powder (average particle size: about 5 ~, 100 parts) and the mixture was kneaded in a kneading machine '~
for 30 minutes, and thereafter, it was extruded with the same extruder as used in Example 1, and then it was dried and heated to 1450C by raising the temperature at a rate of 100C/
hour and was sintered at this temperature for 10 hours.
The multi-cell structural catalyst carrier thus obtained had a compressive strength of 300 kg/cm , a specific ; surface area of 0.3 m /g, and a pore volume of 0.15 cm /g.
, . . ~ .
.. . . . . .
112~3g7 Reference Example 3 -Crystalline cellulose (10 parts) was added to activated alumina powder (100 parts) containing 30 parts pf p-alumina (average particle size: about 6 ~) which was pre-pared by calcining gibbsite type alumina hydrate. While adding water (50 parts) thereto, the mixture was formed to a spherical product of 3 mm~ by a dish type granulating machine.
The spherical product thus obtained was rehydrated in steam for 2 days and dried, and thereafter, it was heated to 700C by raising the temperature at a rate of 100C/hour and was calcined at this temperature for one hour. The spherical product of activated alumina had a compressive strength of 10 kg/cm2, a specific surface area of 180 m2/g, and a pore volume of 0.7 cm3/g.
Reference Example 4 Stearic acid (0.5 part) was added to a mixture of the same activated alumina powder (50 parts) as used in Example 1 and ~-alumina (average particle size: 5 ~, 50 parts), and the mixture was thoroughly mixed in a mixing machine for 2 hours so that the surface of the alumina powder was coated with the stearic acid. Methyl cellulose (1.5 part) and water (35 parts) were added to the alumina powder and the mixture was kneaded in a kneading machine for 30 minutes. The kneaded mixture was subjected to extrusion by using the same extruder as used in Example 1, but it could not be extruded.
The above procedure was repeated except that water was used in an amount of 45 parts instead of 35 parts. As a result, the extrusion could be carried out, but the formed product had an extremely inferior shape retention.
Example 7 Vanadium oxide (V2O5) of 15 ~ by weight based upon the weight of the catalyst carrier was carried on the catalyst A`
.
, ,, ~ .
~ i 11293g7 carriers obtained in the above Examples 1 to 6 and ReferenceExamples 1 to 3. The catalyst thus obtained were each packed into a reactor, the inlet temperature of which was kept at 350C. A synthetic gas (NO: 100 ppm, NH3: 100 ppm, 2 1-2% by volume, H2O: 18.0 % by volume, the remainder: N2) was introduced into the reactor at a space velocity as shown in the following Table 1, and the removal rate of NOx and the pressure drop were measured. The results are shown in Table 1.
~; ' ' - ~ . - ,- , . . ~ , . .
11293g7 Table 1 .__ .__ . . _ . ~:
Catalyst Space velocity: 8000 hr 1 Space velocity: 2000i 1 carrier __ __ Ir Removal rate Pressure drop Removal rate Pressure of NOx (%) (mm, H O) of NOx (%) drop 2 (mm, H2O~
_ _. _ ., . . ._ - :.
Example 1 98 3 90 7 Example 2 90 2 80 5 Example 3 98 3 90 7 Example 4 98 - 3 90 7 Example 5 98 3 90 7 Example 6 78 3 72 7 ... . .
Ref. Ex. 1 25 3 20 7 Ref. Ex. 2 30 3 26 7 Ref. Ex. 3 , 30 90 200 It is clear from the above results in Table 1 that the multi-cell catalyst carrier of the present invention can give excellent catalysts having greater removal rate of nitrogen oxides in comparison with other multi-cell catalyst carriers, and further shows extremely lower pressure drop in comparison with the spherical product of activated alumina.
,.
.
Claims (11)
EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS
FOLLOWS:
1. A hollow catalyst carrier which comprises a calcined product comprising predominantly a transition-alumina and which has a void ratio in the cross section of not less than 3 %, a specific surface area of not less than 5 m2/g, a bulk density of 0.8 to 1.8 g/cm3, a pore volume of 0.3 to 0.8 cm3/g, a compressive strength in the extrusion direction of not less than 20 kg/cm2 and at least one hole in the extrusion direction, said calcined product being pre-pared by subjecting a powder containing a rehydratable alumina to an extrusion molding step, rehydrating the molded product and then calcining it.
2. A hollow catalyst carrier according to claim 1, wherein the transition-alumina is .gamma.-alumina.
3. The hollow catalyst carrier according to claim 1, which has a multi-cell structure having 400 to 600 holes per square inch.
4. A hollow catalyst which comprises a catalytically active component carried on a calcined product comprising predominantly a transition-alumina and having a void ratio in the cross section of not less than 3 %, a specific surface area of not less than 5 m2/g, a bulk density of 0.8 to 1.8 g/cm3, a compressive strength in the extrusion direction of not less than 20 kg/cm2 and at least one hole in the extrusion . direction, said calcined product being prepared by subjecting a powder containing a rehydratable alumina to an extrusion molding step, rehydrating the molded product and then calcining it.
5. A process for the production of a hollow catalyst carrier having a void ratio in the cross section of not less than 3 %, a specific surface area of not less than 5 m2/g, a bulk density of 0.8 to 1.8 g/cm3, a compressive strength in the extrusion direction of not less than 20 kg/cm2 and at least one hole in the extrusion direction, which process comprises a step selected from the group consisting of:
(i) coating a rehydratable alumina or a rehydratable alumina-containing alumina powder with a rehydration preventing agent, mixing the coated alumina with water and/or a water-containing substance and optionally solid materials, and kneading the mixture to give a plastic mixture, and (ii) mixing a rehydratable alumina or a rehydratable alumina-containing alumina powder with a non-aqueous substance, and optionally a releasing agent, a binding agent and solid materials, kneading the mixture to give a plastic mixture;
followed by (iii) extending the plastic mixture to form a hollow shape, rehydrating the hollow product, and optionally drying it, and (iv) calcining the resulting product.
(i) coating a rehydratable alumina or a rehydratable alumina-containing alumina powder with a rehydration preventing agent, mixing the coated alumina with water and/or a water-containing substance and optionally solid materials, and kneading the mixture to give a plastic mixture, and (ii) mixing a rehydratable alumina or a rehydratable alumina-containing alumina powder with a non-aqueous substance, and optionally a releasing agent, a binding agent and solid materials, kneading the mixture to give a plastic mixture;
followed by (iii) extending the plastic mixture to form a hollow shape, rehydrating the hollow product, and optionally drying it, and (iv) calcining the resulting product.
6. A process for the production of a hollow catalyst carrier according to claim 5, wherein the starting rehydrat-able alumina is used in an amount of 10 to 100 % by weight.
based upon the total weight of the solid materials composing the hollow catalyst carrier.
based upon the total weight of the solid materials composing the hollow catalyst carrier.
7. A process for the production of a hollow catalyst carrier according to claim 5, step (i), wherein the rehy-dration preventing agent is used in an amount of 0.01 to 30 % by weight based upon the weight of the rehydratable alumina.
8. A process for the production of a hollow catalyst carrier according to claim 5, step (i), wherein the water and/or water-containing substance is used in an amount of 20 to 70 % by weight based upon the weight of the solid materials.
9. A process for the production of a hollow catalyst carrier according to claim 5, wherein the calcination is carried out at 100 to 1100°C.
10. A process for the production of a hollow catalyst carrier according to claim 5, step (ii), wherein the non-aqueous substance is used in an amount of 2 to 100 % by weight based upon the weight of the rehydratable alumina.
11. A process for the production of a hollow catalyst, which comprises supporting a catalytically active component on a hollow catalyst carrier produced by the process as set forth in any one of claims 5, 6 or 7.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA328,764A CA1129397A (en) | 1979-05-29 | 1979-05-29 | Hollow catalyst carrier and hollow catalyst made of transition-alumina and process for production thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA328,764A CA1129397A (en) | 1979-05-29 | 1979-05-29 | Hollow catalyst carrier and hollow catalyst made of transition-alumina and process for production thereof |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1129397A true CA1129397A (en) | 1982-08-10 |
Family
ID=4114316
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA328,764A Expired CA1129397A (en) | 1979-05-29 | 1979-05-29 | Hollow catalyst carrier and hollow catalyst made of transition-alumina and process for production thereof |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1129397A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115228453A (en) * | 2021-04-23 | 2022-10-25 | 中国石油化工股份有限公司 | Preparation method of carrier, catalyst with deoxidation function, preparation method and application |
-
1979
- 1979-05-29 CA CA328,764A patent/CA1129397A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115228453A (en) * | 2021-04-23 | 2022-10-25 | 中国石油化工股份有限公司 | Preparation method of carrier, catalyst with deoxidation function, preparation method and application |
| CN115228453B (en) * | 2021-04-23 | 2023-11-24 | 中国石油化工股份有限公司 | Preparation method of carrier, catalyst with deoxidizing function, preparation method and application |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4260524A (en) | Hollow catalyst carrier and hollow catalyst made of transition-alumina and process for production thereof | |
| KR930005311B1 (en) | Preparation of monolithic support structure containing high surface area agglomerates | |
| KR940000869B1 (en) | Preparation of monolithic catalyst supports having an integrated high surface area phase | |
| KR930005309B1 (en) | Preparation of monolithic catalyst support structures having an integrated high surface area phase | |
| EP0038705B1 (en) | Process for the production of a low density activated alumina formed product | |
| CA1304068C (en) | Ceramic foam catalysts, or catalyst supports, particularly for steam reforming | |
| EP2226308B1 (en) | Molded porous article, method for production thereof, catalyst carrier, and catalyst | |
| EP0355231B1 (en) | Heat-resistant catalyst carrier moldings and catalysts for combustion | |
| RU2005115060A (en) | METHOD FOR PRODUCING CARRIER FOR CATALYST WITH HIGH HYDROTHERMAL STABILITY (OPTIONS), CATALYST FOR SYNTHESIS OF HYDROCARBONS AND METHOD FOR SYNTHESIS OF HYDROCARBONS FROM SYNTHESIS-GAS | |
| KR20010089731A (en) | High strength/high surface area alumica ceramics | |
| US5580539A (en) | Process for making alumina agglomerates | |
| US7304013B2 (en) | Metal oxide catalysts | |
| GB2343675A (en) | Porous ceramic matrix; catalysts and heat exchangers | |
| US7244689B2 (en) | Method of producing alumina-silica catalyst supports | |
| EP0019674B1 (en) | Process for the production of a hollow catalyst carrier made of transition-alumina | |
| CA1129397A (en) | Hollow catalyst carrier and hollow catalyst made of transition-alumina and process for production thereof | |
| CA1081674A (en) | Control of physical properties of alumina extrudates | |
| RU2756660C1 (en) | Catalytic element of a regular cellular structure for heterogeneous reactions | |
| JP2003117400A (en) | Carrier, method for producing the same and hydrogen refining catalyst using the same | |
| KR820001901B1 (en) | Process for producing hollow catalyst carrier made of transition-alumina | |
| Kraushaar‐Czarnetzki et al. | Shaping of solid catalysts | |
| JPH0810619A (en) | Ozone decomposing catalyst and decomposing method | |
| CN112007625A (en) | Alpha-alumina carrier, preparation method thereof, silver catalyst and application | |
| JPH0275341A (en) | Heat-resistant catalyst carrier molding and catalyst prepared therefrom | |
| JP2003012303A (en) | Hydrogen refining unit, hydrogen refining catalyst and its carrier, and production method of the carrier |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |