JPS6377548A - Catalyst and precursor thereof and manufacture thereof - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to catalysts, and in particular to catalyst strips containing catalytically active substances or precursors thereof. The term "catalyst" here refers not only to substances that catalyze chemical reactions, but also to substances that are used as absorbents or adsorbents, and in some cases react with components (e.g. impurities) of a fluid passing through a bed of catalyst particles. Also used in an inclusive sense are substances that may (possibly irreversibly) be present, such as zinc oxide or zeolites.

For processes where diffusion is not the limiting factor, catalyst activity depends on the surface area of the active material in the catalyst bed. For processes where diffusion is the limiting factor, catalytic activity is increased by increasing the geometric surface area per unit volume of the catalyst (or its precursor) forming the bed. Although reducing the size of the catalyst pieces has the effect of increasing the geometric surface area per unit volume of the catalyst pieces, the reactants in the bed (
In some cases, it is a liquid reactant, but more commonly it is a gas. (preferably). Catalytic reactions also generally involve the absorption or generation of heat, and geometry often affects heat transfer to and from the reactants. The ease of access of the reactants to or escape from the catalytic active sites may also be significantly affected.

For catalysts made by co-precipitation of catalytically active substances or their precursors (possibly also with stabilizing oxidic substances), the geometry of the catalyst pieces is generally relatively simple. For example, such compositions may be pelletized, compressed, or extruded and cut into shaped bodies, such as short cylinders. Preformed carrier (
(which is then coated or impregnated with the active substance, or its precursor, and optionally with a stabilizing substance), the carrier may have a more complex shape, e.g. They can be cylinders with axial passages, hollow cylinders with partition walls (e.g. spoked wheels), saddle shapes, monolithic bodies and honeycombs, etc., which provide desirable pressure drop and heat transfer properties and which also It also provides a large geometrical surface area, thus providing a significantly large surface area of catalytically active material per unit volume of catalyst bed after impregnation or coating and after activation (if necessary, such as reduction). However, it is often difficult to manufacture carriers with such complex shapes.

In the present invention, the carrier is in the form of a piece with a special open pore structure.

British Patent No. 1,349,400 discloses that a polyolefin composition containing a ceramic filler is formed, the polyolefin is incinerated away, and the remaining ceramic material is then fired to form a free-standing ceramic body. It has been proposed to produce porous carriers with complex shapes.

With the present invention, molded articles of relatively complex geometry (if desired) can be readily produced and have significantly greater porosity, thus allowing the reactive agent to be absorbed into the active substance impregnated into the carrier. A different catalyst preparation method is used to obtain good access to K. The increased porosity may allow reactants and products to enter and exit the catalyst chips by convection rather than by slow diffusion into and out of the catalyst chips.

GB 2,070,957 proposes the use of ceramic foams as carriers for catalytically active substances. Traditionally, ceramic foams are produced by impregnating an open cell foam of an organic plastic material such as polyurethane with a relatively low viscosity aqueous slurry of ceramic material such as alumina, and then blowing air through the impregnated foam. Excess slurry is removed by soaking or compressing the foam in one or more stages (see eg GB 1537549 and GB 2027688), drying and then calcination. It has been manufactured by removing organic materials and sintering ceramic particles. In such a method,
The ceramic material forms a coating on the organic plastic foam, so that when the organic material is removed during the firing process, the resulting ceramic foam is essentially a skeleton of the plastic foam. Ceramic copies (their filaments often have a hollow "core").

Such ceramic foams are characterized by relatively low bulk densities and high porosity, which is typically 70 to 95 inches of the volume of the ceramic foam unit.

Although such ceramic foams are satisfactory as catalyst supports for some applications, e.g. exhaust gas purification, most use random packed beds of ceramic foam units with active material coatings. For catalytic applications, the amount of active material in a given catalyst bed volume is generally inadequate because of the low bulk density and high porosity of the foam. Also, the ceramic foam often lacks the mechanical strength necessary to withstand the destructive forces encountered in catalyst beds of the volumes typically used in large scale catalytic processes.

We have here devised a different ceramic foam carrier. In the present invention, the carrier is made as described above, but is impregnated with a stale plastic foam, the pores of which are substantially filled with a relatively highly concentrated thixotropic slurry, and thus dried. The ceramic material is then carried out so that it remains in the pores of the foam; when fired, the plastic material is burned out and the resulting structure is a "negative" of the original plastic foam.
negative) J; therefore, in the present invention, the foam is not compressed or air is blown into the plastic foam to drive the slurry out of the foam. The ceramic material forms only a coating on the walls of the foam, so that when the plastic material is removed, the passages in the ceramic foam substantially correspond to the passages in the original plastic foam. In contrast to the ceramic foams of the present invention, the channels within the ceramic foam unit of the present invention correspond to the plastic material portion of the plastic foam rather than the pores of the plastic foam. The ceramic foam units of the present invention are characterized by small average pore sizes, relatively high bulk densities, and low total porosity (compared to those made by the prior art).

Accordingly, the present invention provides a catalyst or a precursor thereof consisting of a ceramic material containing or being associated with an active catalyst or a substance convertible thereto: A foam having a network of channels, the channels having an average minimum dimension in the range of 20 to 300 μm, and the foam having a network of channels of 40 to 300 μm.
A catalyst or its precursor material is provided, characterized in that it has a total porosity of 85% and an apparent density of at least 0.7 g/cm3.

The apparent density of the ceramic material (i.e. its external dimensions and N
density (determined by measurement of quantity) is preferably 5 f
/- Below, especially 1 to 2. It is preferably within the range of sy/-. If the pieces of ceramic foam are irregularly shaped (e.g. granules obtained by crushing) and their volume cannot therefore be easily determined by measuring the external dimensions of the pieces, the shape and by assuming an appropriate packing fraction for the particle size distribution piece.

The apparent density can be determined from the bulk density of the bed of the pieces and the Wfi of the pieces. Alternatively, it may be appropriate to treat the pieces as approximating a certain geometric shape whose volume can be calculated from its dimensions. Alternatively, the volume of ceramic foam pieces can be measured by filling at least the outer pores of the ceramic foam with a suitable substance (e.g. wax) and displacing the volume with a suitable fluid. Volume can also be determined.

The ceramic foam used in the present invention is preferably 2-
/f or less, particularly within the range of 0.2 to 1.5σ3/2, most preferably within the range of 0.2 to 0.8 cm"/f. Herein, "total pore volume" shall mean the volume of the foam, determined by its external dimensions, minus the volume occupied by the ceramic material itself.

The volume of the ceramic material itself can be determined by measuring the helium density. Total pore volume is the difference between the reciprocal of helium density and the reciprocal of apparent density. In the ceramic foam of the present invention, a portion of the total pore volume is in the form of relatively large pores (hereinafter referred to as "mega pores"), while the remainder is in the form of pores with dimensions normally found in ceramic carriers. Conventionally, the pore volume of ceramic catalyst supports is determined from measurements of density in mercury and density in helium, both measured at atmospheric pressure. The pore volume thus determined (i.e. the difference between the reciprocal of the mercury method density and the reciprocal of the helium method density) is referred to as the "micropore volume", and this value is typically between 0.02 and 0.3. It is within the range of crtr'/f. It will be appreciated that the apparent density, total pore volume and micropore volume will of course depend to some extent on the type of ceramic material.

The total porosity (total pore volume x apparent density, expressed as a percentage) of the ceramic foam used in the present invention is in the range of 40 to 85 inches, preferably 50 to 80 inches, and is The total porosity is generally smaller than the total porosity of (prior art) ceramic foams made by removing excess ceramic dispersion from impregnated foams. Foams made in the prior art generally have a total porosity of about 85 cm or greater, about 1.6 cm.
Total pore volume greater than or equal to tl/f, and 0.6 f 7cm3
It has the following apparent density: From the aforementioned mercury density measurements, the megaporosity (ie the proportion of the total volume in the form of megapores, and thus the ratio of megaporosity:total porosity) can also be determined. Mega porosity is the ratio of "difference between mercury method density and apparent density" to "mercury method density". Megaporosity; the ratio of total porosity (expressed as a percentage) is typically 6
Ceramic foam materials made by methods (prior art) in which excess ceramic material is removed from the impregnated foam by squeezing or air blowing typically range from 0% to 90%. It has a megaporosity/total porosity ratio of about 90- or more, often about 95-inch or more.

The surface area of the ceramic foam, measured by the BET method using nitrogen, is preferably in the range from 0.1 to 10 m''/f.

As mentioned above, ceramic foam catalysts or supports can be manufactured using open-cell organic plastic foams; a particularly suitable plastic foam is a flexible open-cell polyurethane foam, preferably 1 cm ( !j Near) It also has 5 or more bubbles. A certain geometrical shape of the catalyst or support is usually required.

The plastic foam can be cut and machined (eg, stamped) from a sheet or block of material into the desired contour of the composite piece. Alternatively, the plastic foam pieces with the desired profile of the desired pieces can also be produced directly in the processing process (e.g. casting, molding or extrusion methods, which are used for the production of plastic foams). . Alternatively, sheets, ropes or blocks of plastic foam can be impregnated with a slurry of ceramic material and machined after drying (but before firing and sintering) into the desired shape. The plastic foam piece should generally be slightly larger than the desired sintered ceramic foam piece, since some shrinkage typically occurs during the firing and sintering process. For certain applications, catalysts or supports in irregularly shaped (eg granular) form are required. In this case, the plastic foam can be crushed to the desired dimensions before impregnation. Alternatively, the ceramic material used in the slurry, which may crush the dried impregnated foam or the ceramic foam made by firing the dried impregnated foam, will depend on the intended use of the catalyst. That will happen. Therefore, silica-free materials (i.e. silica content of 0.5% by weight)
), such as alumina (usually in the alpha form) or calcium aluminate cement, are particularly suitable when the catalyst is for steam reforming. However, silica-containing materials are often used for other applications. Other materials that may be used include, for example, magnesia, rare earths, zirconia and titania. Mixtures of ceramic materials can also be used. The ceramic material must have a particle size that allows it to be easily dispersed in the carrier liquid of the slurry (preferably water) and penetrate into the air voids of the plastic foam.

Generally, ceramic particles with dimensions within the range of 0.1 to 10 μm are suitable. The slurry typically contains at least 20% by weight, especially from 30 to 80% by weight, of ceramic material. Additives such as wetting agents, dispersion stabilizers (eg polyvinyl alcohol), and viscosity modifiers may be incorporated into the slurry. The slurry used is preferably chickentrope and has a relatively high viscosity under low shear conditions, preferably above 1000 cp, especially 1500 cp.
and has a relatively low viscosity under high shear conditions, preferably less than 500 cp, especially less than 300 ep. In this case, the viscosity of the dispersion (slurry) was measured using a Haak@Rotovisco rotary vane viscometer using a shear rate of 24/sec for low shear conditions and 441/sec for high shear conditions. can be measured at room temperature. To obtain a reliable indication of the chickentrope nature of the dispersion, the viscometer should be run at the above high shear rate for 5 minutes before reading the reading.

Impregnation of the plastic foam is preferably carried out by dipping the plastic foam in a slurry, shearing the slurry to reduce its viscosity;
Air is then forced out of the foam (eg, by crushing or vibrating the foam while soaking).

The impregnated foam is then removed from the slurry bath and dried. In many cases, it is desirable to blot the surface of the impregnated plastic foam with an absorbent to prevent the formation of a ceramic skin on the surface of the impregnated plastic foam. Alternatively, excess slurry on the surface of the foam may simply be washed away. In contrast to the aforementioned prior art, which creates ceramic foam structures that are positive replicas of plastic foams,
The foam is not squeezed or air blown after impregnation. Drying of the foam is typically carried out at temperatures below 100°C and may be carried out under controlled humidity conditions.

The plastic material is then removed from the impregnated foam by heating in air. This heating may be performed as part of the firing process to sinter the ceramic particles.

Generally, firing temperatures of 1000° C. or higher are required to sinter the ceramic particles to give a product of adequate mechanical strength. However, the removal of organic plastic materials can be performed at significantly lower temperatures, e.g.
It can generally be carried out at 0-600°C. The temperature required for sintering depends on the type of ceramic material, the B required for the support.
It depends on the ET surface area and the desired mechanical strength, etc.

For alpha alumina ceramic foams, the firing temperature is preferably within the range of 1300-1400<0>C.

In a preferred process, a "lobe" of polyurethane foam is passed continuously through a bath of an aqueous dispersion of a ceramic material (e.g., alpha alumina) and air is passed through a nip between a pair of rolls in the bath. is removed, excess liquid is drained away, and then dried and fired. The lobes are cut to suitably sized lengths before or after drying (but preferably before firing). The lobes may be of any suitable cross-sectional shape, such as circular, square, hexagonal cross-sectional shapes, and the cross-section of the desired catalyst particles to accommodate the shrinkage that occurs during the calcination/sintering process. It should be somewhat thicker than that. The degree of volumetric shrinkage that occurs during the firing/sintering process is typically within the range of 20 to 60 inches. The overall dimensions of the ceramic foam pieces are preferably in the range 2-20 mm.

By this method it is possible to produce macroporous alpha alumina compacts of considerable length. A typical product has the following characteristics:

BET surface area 0.1 m"/f Helium method density 3.97 f 7cm" Mercury method density
3.05 f 7cm” Apparent density 1.35
f/α3 total pore volume 0.49 cy*3/
f Micropore volume 0.085+3/liter Total porosity
66% Megaporosity 56% After sintering, the ceramic foam pieces are treated with catalytically active substances or their precursors (i.e. substances that can be converted into active substances by heating and/or oxidation or reduction) and optionally other substances (e.g. impregnated with stabilizer or its precursor). For example, to make a catalyst precursor for use in a steam reforming process, the support may be nickel and/or
or with cobalt compounds (e.g. salts such as nitrates),
In some cases, it is common to impregnate with a salt (eg aluminum nitrate) which decomposes to provide a stabilizing oxide. Upon heating, these vitreous salts decompose to their respective oxides, and upon subsequent reduction in a hydrogen-containing stream (this reduction is usually carried out during steam reforming), nickel and/or the cobalt oxide is reduced to active metal.

The sintered ceramic foam pieces can be impregnated more than once if desired to achieve the desired loading of active material or its precursor. Preferably, the impregnated carrier is calcined, for example at 350 to 750°C, to convert the metal compound into an oxide between the impregnation steps.

Since the ceramic foam carrier is typically sintered to the extent that it has a low BET surface area for imparting the desired mechanical strength, the ceramic foam itself is typically sintered to the extent that the active material is present in use. It will not exert any significant stabilizing effect to prevent sintering of the active material when in the metallic state. For this reason, it is highly preferred to incorporate the stabilizer or its precursor into the medium used to impregnate the carrier with the active substance (or its precursor). Alternatively, the support may be impregnated alternately with the active substance (or its precursor) and with the stabilizer (or its precursor); the stabilizer may be chemically similar to the ceramic support. For example, the carrier may be alpha alumina and the stabilizer may also be alpha alumina.

However, the stabilizer does not harden into the ceramic foam and can generally be separated from the ceramic foam by leaching with a suitable leaching agent (sulfuric acid in the case of alumina).

When the active catalyst material is a metal, and it is made by reducing a precursor containing a reducible metal compound, the amount of stabilizer is determined to give an optimal combination of good catalyst activity and long catalyst life. 10 of its reducible metal compound
Preferably, the amount corresponds to 50% by weight.

The invention is particularly suitable for producing precursors for reforming catalysts. In such reforming processes, hydrocarbon feedstocks such as methane, natural gas, LPG, naphtha are reacted with steam and/or carbon dioxide in the presence of supported nickel and/or cobalt catalysts, with the The heat required for an endothermic reaction is supplied from the sensible heat of the reactants or from an external heat source. The reforming is preferably carried out at a pressure of 1 to 50 bar absolute and 70 bar absolute.
Homer exit temperatures of between 0 and 900°C are carried out; even higher exit temperatures, e.g. up to 1100'C, may be used. Such a high exit temperature is necessary if the reforming process is to produce hydrogen for iron ore reduction.
Alternatively, it is used in particular when the reforming step is followed by a partial oxidation step with an oxygen-containing gas (eg air), as in the case of secondary bombing used in the production of ammonia synthesis gas. Preferably, the reaction is carried out in the presence of excess steam and/or carbon dioxide. The amount of steam is preferably 1.5 to 1 g mol, particularly 2.0 to 5 g mol per gram atom afi of carbon in the raw material.

The present invention is also useful in other catalytic processes, such as those described below.

Methanation generally uses a supported nickel and/or cobalt catalyst; hydrodesulfurization generally uses a mixture of cobalt and molybdenum oxides and/or sulfides as active catalysts. Such mixtures are also effective as catalysts for hydrogenolyzing hydrocarbons such as fuel oils to shorter chain hydrocarbons.

Catalytic combustion: In this case, the active catalyst is generally a noble metal such as platinum, often mixed with nickel. Unique applications for such combustion catalysts are space heaters and hair curlers.

Ethylene oxidation: the active substance is generally silver.

Xylene oxidation: the active substance is generally vanadium pentoxide.

Oxidation of sulfur dioxide to sulfur trioxide: The active catalyst is vanadium pentoxide.

Hypochlorite decomposition: The active catalyst is usually supported nickel, cobalt and/or copper. In this case the reactants are usually in the form of an aqueous solution.

Another application of the materials of the invention is the removal of carbon particles from gas streams, for example in automobile exhaust gas purification.

Porous ceramic foams can therefore be used to scavenge carbon particles from a gas stream and facilitate their combustion at low temperatures to carbon dioxide. For this application, oxides of alkali metals and alkaline earth metals are active substances. In particular, the oxides of sodium, potassium and barium are used. The catalyst may be made by impregnating a ceramic foam with one or more precursors of such alkaline substances, such as alkali or alkaline earth nitrates, or alkali metal hydroxides or carbonates. Can be done. For this application, the ceramic foam is preferably alumina, in particular a dispersion or impregnated plastic foam (before firing) with one or more alkali or alkaline earth metal compounds (corresponding oxides). It is an alkalized alumina made by blending a compound that can decompose into The resulting catalytic alkali or alkaline earth metal oxide impregnant may also catalyze the removal of nitrogen oxides through the formation of alkaline (or alkaline earth) nitrates, and such nitrates then acts to oxidize the carbon. Furthermore, alkali (alkaline earth metal) will facilitate the establishment of equilibrium in the shift reaction described below.

CO+ H, O: CO2+ H2 The hydrogen produced in this reaction reduces nitrogen oxides. It may be advantageous to provide a combustion catalyst, for example a supported noble metal, downstream of the alkalizing ceramic foam filter.

As an alternative to simply having the active substance present as a layer on or in the surface of the ceramic foam carrier, in some cases it is possible to make the ceramic foam itself from the active substance or its precursor. For example, ceramic foams may be made from iron oxides, such as magnetite, and used as an ammonia synthesis catalyst precursor (in which case the ceramic composition may contain stabilizers such as alumina, and promoters such as lime, magnesia, and potash). (usually containing cobalt oxide, and may also contain cobalt oxide), or as a nitrile hydrogenation catalyst precursor. Upon reduction of the iron oxide in the ceramic foam, the resulting sintered iron foam typically has sufficient mechanical strength and surface area to be useful as a catalyst in applications such as those described above.

Another example is to make the foam from a fermented iron/chromia mixture. Such compositions are useful as precursors for high temperature shift catalysts. Yet another example is to make the ceramic foam from zinc oxide, where the resulting foam itself is useful as an absorbent for sulfur compounds such as hydrogen sulfide.

In yet another application, the ceramic foam is a zeolite, in which case the ceramic of the foam contains a precursor of the zeolite, e.g. It may be kaolin.

When the ceramic material is not just a carrier for the active substance, but is itself a catalyst or its precursor,
The ceramic material is present in a major amount (i.e. at least 5
0 weight t%) of 1 or more gold! (selected from iron, cobalt, nickel, copper, vanadium, molybdenum, tungsten, chromium, manganese and zinc) and optionally a small amount (by weight) of one or more other metals (e.g. aluminum, calcium,
barium, magnesium, zirconium, titanium, or an alkali metal) or an oxide of silicon (usually acting as a stabilizer or promoter).

The invention is further illustrated by the following examples.

Example 1 From a sheet of open pore polyurethane having a density of 0.02997 an" and a maximum pore size of about 1.5 fi,
Pellets in the form of cylinders with a length of 21.5 m and a diameter of 23 mm were made by punching. There were at least 7 pores per linear meter.

A thixotropic aqueous slurry of alpha alumina was made as follows. 100 parts by weight of alpha alumina with a particle size of less than 55 μm are dry mixed with 1 part of finely ground titania, followed by an aqueous solution containing 1.5 mt4'ih % of polyvinyl alcohol of molecular dilution 125,000 and 0.01 i of BDX wetting agent. About 40 parts by weight were gradually added to obtain a concentrated dispersion.

The viscosity of this dispersion (measured at room temperature with a Hague-Rotovisco rotor viscometer as described above) was 2200 cp at a shear rate of 24/sec, but 100 cp at a shear rate of 441/sec. Ta. The aqueous solution of polyvinyl alcohol and wetting agent described above exhibits Newtonian flow properties, and its viscosity (measured on a Brookfield rotating cylinder viscometer at 24°C) is measured over shear rates of 7.5/sec to 75/sec. It was 5 cp.

While stirring the slurry in the mixer, polyurethane foam pellets were added and the resulting mixture was kneaded for 5 minutes. The resulting impregnant foam pellets were then removed from the mixer into a tray with a screen bottom. The tray was shaken for 2 minutes.

The impregnated pellets were then dried at about 70°C for 2 hours, then heated to 1370°C over 24 hours and maintained at this temperature for 6 hours.

The resulting alpha alumina foam pellets had the following properties:

Length: 17 m Diameter: 17 Volume shrinkage: 56 Horizontal fracture strength: 260 m'9 Apparent density: 1.43 f/B3 mercury method density
3.28f/- helium method density 4.
02f/1BET surface area 0.20 m”/
t Micropore volume 0.06 cm37 f Total pore volume 0.45 crn”/ f Total porosity 64 Chimega porosity 56 % The alumina foam pellets were then mixed with hexahydric nickel nitrate 9909/l and anhydrous aluminum nitrate 534 f/!
, for 15 minutes, and then removed from the impregnating solution and allowed to flow down for 1 hour. The impregnated pellets were then calcined at 450°C for 4 hours. The following weight composition (9
After calcination at 00°C) catalyst precursor pellets were obtained.

Atz Os 88% (weight)'r
to, 1chiNi0
The 11% obtained catalyst precursor was then tested for steam reforming activity by the following sweep.

A number of impregnated foam pieces were loaded into a laboratory steam reformer. A mixture of natural gas and steam containing 91% methane (volume ratio of steam:natural gas: 3:
1) was flowed into the reactor at a flow rate of 100017 hours at atmospheric pressure,
The precursor pellets were then reduced by increasing the temperature of the reactor to about 760° C. over a period of 4 hours.

The outlet concentration of methane was monitored. Then increase the temperature to about 760℃
16 at a flow rate of 1000 t/h to a mixture of nitrogen and steam (steam:nitrogen volume ratio 3:1).
I changed the time. The reactor was then cooled to 450°C.

The steam/nitrogen mixture was then switched to the original natural gas/steam mixture, and the temperature was again reduced to about 760°C.
It was raised to . Finally, the reactor was cooled again. The methane concentration of the gas leaving the reactor at various temperatures was determined using a standard commercial steam reforming catalyst in the form of a cylinder, 17 m in diameter and 17 m in length, with a single through hole of 7 m in diameter, with a Kkel content of 1.
The results are shown in the table below along with the results obtained using 0wt%).

This example shows that the catalyst according to the invention has high activity and that its precursor is easily reduced to active catalyst.

In order to investigate the pressure drop characteristics of this catalyst precursor pellet, approximately 3 tons of pellets were loaded into a cylindrical container, and the internal pressure (outlet pressure) air flow + observed pressure drop was measured using a water manometer at various air flow rates. It was measured using The results are shown in the table below.

This reveals that the catalyst of the present invention exhibits superior pressure drop characteristics compared to standard commercially available catalysts. Heat transfer coefficients were measured and found that the foam catalyst pellets according to the present invention had coefficients approximately 10% greater than standard commercially available catalysts.

Example 2 The operation of Example 1 was repeated by incorporating 6.4% by weight of potassium carbonate into the alumina slurry. The foam pieces used in this example were shorter, so the fired pellets were 10+
The length was s+. It has been found that only two impregnations of the fired foam are necessary to achieve adequate nickel loading.

The properties of this foam carrier were as follows.

Length 10 m Diameter 17 m Volumetric shrinkage rate 53 cm Horizontal breaking strength 115 Kf Apparent density 1.13 f/an"Mercury method density Z 28 f 7 cm"Helium method density 0.78 W/cnr" B E T Surface 9
0.69 m”/total pore volume
0.62 err? / f micropore volume 0
．． The catalyst precursor pellets had the following composition (900°C
% by weight after firing at ).

The reforming activity of this alkalizing foam-supported catalyst is shown in the table below, along with the steam reforming activity of a standard commercially available alkalizing steam reforming catalyst.

In another experiment, the stability of the foam-supported catalyst was investigated by steam reforming methane at atmospheric pressure with an exit temperature of about 760° C. and a steam/methane molar ratio of 3=1. The test was conducted for more than 2000 hours, during which the outlet methane concentration was 0.4 to 0.55 volume t% (
(on a dry basis) except for a brief period early in this experiment, during which the methane concentration dropped to 0.25 vol.

EXAMPLE 3 A length of 1 m is cut from a sheet of open pore polyurethane having a density of 0.18 f 7 cm" and a minimum pore size of approximately 1 m.
A cylindrical pellet with a diameter of 0 m and a diameter of 13 m was made by punching. There were at least 10 pores per crR (linear).

A thixotropic aqueous slurry of kaolin was made by dry mixing 100 parts by weight of kaolin having a particle size of 100 μm or less with about 15 parts by weight of an aqueous solution containing about 5 parts by weight of polyvinyl alcohol. Then 95 parts by weight of deionized water was gradually added to obtain a highly concentrated dispersion.

Pellets of polyurethane foam were added to this and the resulting mixture was kneaded. The resulting impregnated foam pellets were then placed on a coarse sieve and shaken to remove excess kaolin dispersion. The impregnated pellets were then dried at about 50° C. for 24 hours and then heated to 700° C. for 2 hours to burn out the polyurethane foam and convert the kaolin to metakaolin. After cooling, the resulting porous metakaolin pellets were converted to zeolite A by heating to 100° C. with a 10-fold US solution of sodium hydroxide. Samples of the pellets were taken from the alkaline solution after various times and washed thoroughly with deionized water to remove excess alkali. The resulting pellets had the following properties.

When the pellets were immersed for 3 hours and subjected to an X-ray test, it was found that zeolite A was mixed with illite (2 parts by weight of
b) A: A ratio of 1 part by weight of illite) was found to be mixed. This pellet has a total porosity of 55% and a total porosity of 0.
It had a total pore volume of 45 cm"/f. Megaporosity was about 42%.

The Zeolite A pellets were useful as adsorbents for pressure swing adsorption, for example.

Example 4 The polyurethane foam pieces used in this example were
It was the same as that of Aluminum nonahydrate 15.5F, 2
A concentrated chickentrope dispersion was prepared by mixing an aqueous solution containing 209/l of potassium nitrate with an aqueous solution of 45tj containing 14-15% by weight of polyvinyl alcohol, and 135PR1 of deionized water.

Polyurethane pellets were added to this dispersion (as in Example 3).
slurry), drained, dried, and then
Heating to 1300℃ at a rate of 100℃ per hour, 13
Sintered iron oxide pellets A suitable for use as an ammonia synthesis catalyst precursor were obtained by sintering by maintaining the temperature at 00° C. for 2 hours. The above operation was repeated using 24.59 ml of aluminum nonahydrate and 10 d of potassium nitrate solution (same as above) to obtain pellets B for similar use. Pellets A and B had the following properties.

The above procedure was repeated using a polyurethane foam disk approximately 15 cy in diameter and 25 cy in thickness in place of the polyurethane foam pellet in the above procedure. The disc was impregnated with hematite slurry by placing the disc on a vibrating tray and gradually pouring the hematite dispersion (slurry) onto the surface of the disc. This technique produced a sintered ferroammonium synthesis catalyst precursor in the form of a slab suitable for packing as a fixed bed (rather than a granular bed) into a tubular synthesis reactor.

Example 5 The procedure of Example 4 was repeated by substituting magnetite for hematite. 4 pieces of dry impregnated foam
The magnetite was sintered by firing in air at 00°C and then in argon at 1300°C.

The product had the following properties.

Length 10 Furrow diameter 6.5 ■ Horizontal breaking strength 49 to 2 Apparent density 102 / α3 Mercury method density 4.192 Cohelium method density 4.65 / -3 BET surface area
0.19 m2/f total pore volume 0.
280 cr/f Micropore volume 0.02 crt?
/f Total porosity 57% Megaporosity 52% Example 6 By following the procedure of Example 1, a cylindrical alpha alumina ceramic foam pellet (Sample A) having a diameter of 8 cm and a length of 8 cm was prepared.
) and a similar pellet (sample B) with a diameter of 11.2 m and a length of 13-m. However, the plastic foam pieces were squeezed between rollers to drive off the alumina slurry before they were dried and fired. Sample A was fired at 1300°C, while sample B was fired at 1400°C. For comparison, Sample C (same dimensions as Sample B) was made in the same manner, but the plastic foam pieces were not subjected to squeezing to expel the alumina slurry. The properties of these calcined products are shown in the table below.

Ceramic foams made according to the invention contain more material and are much stronger than those made by methods that provide a ceramic skeleton of polyurethane foams. I understand. Products made using methods that provide a ceramic skeleton do not have sufficient strength to be used as supports in actual industrial catalyst applications.

Example 7 This example demonstrates the use of a ceramic foam according to the invention for carbon particle removal.

Alpha alumina foam pieces were made as described in Example 1 and impregnated with an aqueous solution containing 100 f/l potassium carbonate after firing. After impregnation, the alumina foam pieces were dried at 120° C. for 3 hours.

To test such samples, natural gas was saturated with toluene vapor and combusted under air starvation to produce a polysmoky flame containing large numbers of carbon particles.

The specimen is suspended within the soot-forming region of the flame for 30 seconds, after which time the specimen is exposed to normal, fully combusted natural gas/
Place the specimen over an air flame for 60 seconds, then turn the specimen over.
The normal flame was then suspended again for an additional 60 seconds. The amount of carbon remaining on the specimen was visually inspected. For comparison, pieces not impregnated with alkali were similarly tested. The pieces made in Example 2 (in which alkali was incorporated before firing) were also tested. These samples were further impregnated with alkali and
or tested without impregnation.

The results were as follows.

Example 1 (Alkalinization): Soot was easily deposited by blowing a multi-smoke flame. Only trace amounts of soot remained after combustion in a normal flame.

Example 1 (no alkalization): Soot was easily deposited by using a multi-smoking flame. After combustion in a normal flame, the soot removal was incomplete and some carbon-containing regions remained.

Example 2 (no alkalization) 2 Less soot was deposited than in each of the above cases. Incomplete removal of soot after combustion in normal flame.

Example 2 (alkalization): Soot deposition similar to the non-alkalized sample. Soot removal after combustion in a normal flame was virtually complete.

Similar results were obtained when sodium carbonate was used instead of potassium carbonate. Perform the above operation (1) 0.19♂
(2) Calcium aluminate rings with a pore volume of 0.28 cyrr"/f were tested repeatedly using alkali-impregnated and non-alkali-impregnated test specimens. Similar results were obtained when the flame was removed, but no smoky flame was produced, and the degree of soot removal by combustion in a normal flame was more incomplete.

50% of the test piece uniformly covered with soot by the above procedure.
0- sample, 50m in diameter! An air oxidation apparatus consisting of 1 electrothermal stainless steel reactor was loaded and air was flowed through the apparatus at a flow rate of 25 t/h. The heater was adjusted such that the temperature of the exhaust gas rose to 600° C. over a period of 3 hours.

During this time the outlet gas was analyzed for carbon monoxide and carbon dioxide by gas chromatography.

The results were as follows: Sample Observation Results Example 1 (no alkalization): Outlet gas temperature was 200°C
Carbon dioxide was evolved when the temperature reached 300°C, reaching its maximum concentration at a temperature of 300°C. -No carbon oxide detected.

Example 1 (Alkalinization): Carbon dioxide 8 was produced from the sample at temperatures well below 200°C, and carbon dioxide evolution was essentially complete when the temperature reached 300°C.

- No carbon oxides were detected.

Calcium aluminate ring; temperature is 300-350℃
When the temperature reached , carbon dioxide began to be produced. The highest concentration of carbon dioxide was achieved at an outlet temperature of about 500°C. - No carbon oxides were detected.

*The amount of carbon dioxide mentioned is probably due to the carbon dioxide generated initially at relatively low temperatures (even when not sooted) as a result of the carbon dioxide releasing reaction between the alkaline carbonate impregnant and the alumina. There are also a remarkable number of yoυ.

Example 8 Finely ground Sakai Aluminum 5002 was mixed with finely ground titanium dioxide 5F and then 250W&t of the polyvinyl alcohol/wetting agent solution used in Example 1 was added. While shearing and stirring the resulting dispersion, 500 ml of open-cell polyurethane foam granules prepared by crushing polyurethane foam pellets in a coffee mill for 2 minutes were added, and the resulting mixture was shear-stirred for 2 minutes. The impregnated foam granules were removed onto absorbent paper, dried in air for 24 hours, and then calcined at 1400° C. for 2 hours in air. The resulting ceramic foam granules were sieved to obtain 1-3 haze size pieces.

The sieved granules are then mixed with a solution containing aluminum nitrate, nickel nitrate and copper nitrate (1 atom of aluminum υ
(containing about 5 atoms of nickel and about 7 atoms of copper). The impregnated granules were then heated in a V at 350°C for 2 hours, then the temperature was increased to 475°C and maintained at that temperature for 3 hours. This impregnation and calcination operation was then repeated.

The resulting media contained a total of about 10.5% by weight of copper oxide, nickel oxide, and alumina from the impregnating solution.

100 Wlt of this catalyst granule was immersed in an oil bath with a diameter of 2.
The catalyst was tested for hypochlorite decomposition activity by loading it into a 5-inch reactor. 1500 ppm by weight
An aqueous solution containing hypochlorous acid (IJ) was passed through a preheating coil in the bath before being fed to the bottom of the reactor. The effluent from the reactor was analyzed.

This test procedure was repeated using various bath temperatures and liquid flow rates.

For comparison, bauxite chips were similarly impregnated and tested. The chips were subjected to three impregnation/calcination operations in order to obtain a comparable content of oxides resulting from the impregnation solution.

The results were as follows.

Agent patent attorney Kyozo Yuasa! Jj:,,,',',,,
,”1-Nini1 (4 others)

Claims (13)

[Claims] (1) A catalyst or a precursor thereof consisting of a ceramic material containing or supporting an active catalyst or a substance convertible thereto: an irregular passageway through which the ceramic material extends; It is a foam with a mesh, and their passages are 20 to 300
and the foam has a total porosity of 40-85% and at least 0.7 g/cm.
A catalyst or its precursor characterized by having an apparent density of ^3. (2) A catalyst or precursor according to claim 1, wherein the foam has an apparent density within the range of 1 to 2.5 g/cm^3. (3) The catalyst or precursor according to claim 1 or 2, wherein the foam has a total pore volume of 0.2 to 1.5 cm^3/g. (4) A catalyst or precursor according to any one of claims 1 to 3, wherein the foam has a megaporosity of at least 60%. (5) The catalyst or precursor according to any one of claims 1 to 4, wherein the mega porosity of the foam is 60 to 90% of the total porosity. (6) Ceramic materials include alumina, iron oxide, iron oxide/
A catalyst or precursor according to any one of claims 1 to 5, consisting of a chromia mixture, zinc oxide, or zeolite. (7) Any of claims 1 to 6 consisting of a ceramic foam carrier impregnated with a catalytically active substance or with a substance that can be converted into a catalytically active substance by heating and/or reduction or oxidation. Catalysts or precursors as described. (8) Claim 7 comprising a ceramic foam carrier impregnated with at least one alkali metal or alkaline earth metal oxide or with a substance convertible to such an oxide upon heating. Catalysts or precursors as described in Section. (9) A patent claim in which the ceramic material contains a major amount, by weight, of an oxide of one or more metals selected from iron, cobalt, nickel, copper, vanadium, molybdenum, tungsten, chromium, manganese, and zinc. The catalyst or precursor according to any one of items 1 to 5. (10) Nickel and/or cobalt supported on alpha alumina foam or nickel and/or cobalt;
or a reducible compound of cobalt, or a precursor thereof according to claim 6. (11) Impregnation by impregnating an open cell organic plastic foam with a thixotropic dispersion of particulate ceramic material in a carrier liquid to form a shadow replica of the foam by filling the pores of the foam with the dispersion. a catalyst or its precursor comprising drying the impregnated foam without removing the ceramic material from the pores of the foam and heating the foam in air to remove the organic plastic and sinter the ceramic particles. A method of manufacturing a substance. (12) making a fired ceramic shade replica of a plastic foam from a silica-free ceramic material, impregnating the ceramic foam replica with at least one metal nitrate including nickel and/or cobalt nitrate; 12. The method of claim 11 for making a steam reforming catalyst precursor comprising firing a ceramic foam replica to decompose nitrates to the corresponding oxides. (13) A catalyst consisting of nickel and/or cobalt supported on a molded piece of silica-free ceramic foam having a network of irregular channels extending therein, the average minimum diameter of the channels ranging from 20 to 300 μm. dimensions and the foam has a total porosity of 40-85% and a total porosity of at least 0.7
A steam reforming process characterized in that a catalyst having an apparent density of g/cm^3 is used.