Method of obtaining oxide catalysts on a substrate

FIELD: chemistry.

SUBSTANCE: invention pertains to the method of obtaining porous substances on a substrate for catalytic applications, to the method of obtaining porous catalysts for decomposition of N₂O and their use in decomposing N₂O, oxidising ammonia and reforming methane with water vapour. Description is given of the method of obtaining porous substances on a substrate for catalytic applications, in which one or more soluble precursor(s) metal of the active phase is added to a suspension, consisting of an insoluble phase of a substrate in water or an organic solvent. The suspension undergoes wet grinding so as to reduce the size of the particles of the substrate phase to less than 50 mcm. The additive is added, which promotes treatment before or after grinding. A pore-forming substance is added and the suspension, viscosity of which is maintained at 100-5000 cP, undergoes spray drying, is pressed and undergoes thermal treatment so as to remove the pore-forming substance, and is then baked. Description is also given of the method of obtaining porous catalysts on a substrate for decomposing N₂O, in which a soluble cobalt precursor is added to a suspension of cerium oxide and an additive, promoting treatment, in water. The suspension is ground to particle size of less than 10 mcm. A pore-forming substance, viscosity of which is regulated to approximately 1000 cP, is added before the suspension undergoes spray drying with subsequent pressing. The pore-forming substance is removed and the product is baked. Description is given of the use of the substances obtained above as catalysts for decomposition of N₂O, oxidation of ammonia and reforming of methane with water vapour.

EFFECT: obtaining catalysts with homogenous distribution of active phases and uniform and regulated porosity for optimisation of characteristics in catalytic applications.

The scope of the invention

The present invention relates to a universal method for producing a granular catalysts with different distribution of the active phase and an adjustable porosity. Requirements distribution of active phases and controlled porosity are determined by the characteristics inherent in the catalytic reaction (application), and may vary in accordance with the proposed method.

Description of the prior art,

The manufacture of the catalyst is carried out in some pretty difficult stages that depend on a large number of variables that are difficult to regulate at the same time.

Traditionally, large-scale manufacture of the catalyst includes two main approaches. The first is the method of co-precipitation. The second includes the impregnation of prior carrier (substrate) a precursor of the active phase or by the method of initial moisture content, or by an ion exchange method.

In the manufacture of the catalyst by coprecipitation of the components of the catalyst was prepared in the form of a solution and mixed in the appropriate ratios and concentrations. Phase catalyst precursor, typically a carbonate, hydroxide or oxide, is produced by adding a precipitating agent to the solution of the catalyst. Usually as a precipitator use the hydroxides or carbonates of alkali metals. Cree is practical parameters are the mixing, the regulation of pH and temperature. The suspension of catalyst precursor maintain that it has become more favorable morphology or structure. To facilitate filtration or centrifugation can add flocculants, and the solid precursor is separated from the liquid phase.

The precursor is washed to remove undesirable cations or anions. You may need to re-suspendirovanie and conduct ion exchange for the removal of adsorbed ions of alkali metals. The precursor is dried and then calcined to obtain the oxide phase. At this stage, the catalyst can be re-suspended for the deposition of additional phases.

If the pellets have to be formed by extrusion in the form of the oxide granularit to obtain a flowable powder, for example, by re-suspension and spray drying or fluidized bed or in a rotary granulator. Add additives for processing, for example lubricants, and then the granules formed into pellets, followed by heat treatment to obtain granules of the required strength.

Typical receive operation catalyst impregnation are the following.

Impregnation by the initial moisture content:

Prepare the substrate for the catalyst. This process involves a lot of individual operations, the including or extrusion and heat treatment paste the substrate, or granulation, tableting and heat treatment paste the substrate. Active phase receive in the form of a solution. Phase substrate is impregnated with a solution of the active phase. The impregnated granules are dried and subjected to heat treatment.

The loading of the active metal can be adjusted by adjusting the concentration of the metal precursor in the solution. If you want a high concentration of the active phase or if the solubility of the precursor is low, you may need several cycles of impregnation - treatment. In addition, it is difficult to specify the content of the metal. Several cycles may also be required when it is necessary to obtain bimetallic catalysts. The most important stage of this method is the drying process. If it is desirable to achieve uniform distribution of the active phase, the necessary quick drying. It is difficult to implement in large-scale way. Slow drying leads to segregation of the active phase on the outside of the granules and the uneven distribution of the active phase. This can have a negative effect on the catalytic properties of this substance.

Ion exchange:

Prepare the substrate for the catalyst. The substrate is dipped in a dilute solution of the active phase. Establish such a pH that the ion exchange of the active phase occurs with surface groups on the surface of the substrate. The pellets p is washed to remove ions of the active phase, not adsorbed on the surface of the substrate, and then thermally treated. The active phase will tend evenly distributed in the pellet, but its concentration is low. The maximum concentration of the active phase, which can be obtained will be limited ion exchange capacity of the phase of the substrate and/or solubility of a saturated solution of the active phase.

There are also other ways of obtaining oxide catalysts.

From US patent No. 6107238 a method of producing a catalyst with high resistance to abrasion, containing enriched oxide surface layer, comprising obtaining a suspension containing particles of the catalyst, catalyst precursor or substrate to catalyst (for example, transition metal oxides), colloidal Sol of oxide (for example, colloidal silicon dioxide) and a solution of solvent and solute, in which the dissolved substance consists essentially of the predecessor specified enriched oxide surface with a particle size of not greater than 5 nm (e.g., aqueous silicic acid or polysilicon acid) and then spray drying the suspension with the formation of porous microspheres catalyst, abrasion resistant, and calcining the microspheres after spray drying. This catalyst is particularly climbed the n in the processes of oxidation, in which the oxidation is conducted by the oxidized form of the catalyst and obtained the recovered form of the catalyst is separately recovered (for example, the two-stage vapor-phase methods, carried out in reactors with recirculating solids reactor with the transfer layer or circulating fluidized bed reactor and the like).

The US patent No. 6130184 describes a method of obtaining a cobalt containing catalyst or catalyst precursor comprising (a) a process of mixing (1) titanium oxide or a precursor of titanium oxide, (2) liquid and (3) compounds of cobalt, which is at least partially insoluble in the amount of fluid with the formation of the mixture, (b) shaping and drying of the thus obtained mixture, and (C) calcining the resulting composition. The process of mixing can imagine mixing, grinding or kneading depending on the content of solids in the mixture. Forming catalyst may include tableting, granulation, extrusion, spray drying, or a method of putting hot oil. This method does not result in a catalyst with the desired properties, in particular, with adjustable metal distribution centers and porosity. Control of these parameters is essential for optimization of performance in catalytic applications.

On the target inventions

The object of the invention is to provide a simple method of obtaining catalysts generally suitable for industrial applications. The next object is to obtain an oxide catalyst on a substrate with a certain distribution of the active phase and an adjustable porosity. Another object is reproducible and simple method of producing catalysts for the decomposition of N₂O. Another object is the application of these catalysts in various catalytic processes.

These and other objects of the invention are realized by a method described below. In addition, the invention is characterized by the claims.

The invention will be further illustrated by figure 1-9 on which:

figure 1 shows a comparison of unit operations in the traditional method of co-precipitation to obtain an oxide catalyst on a substrate and method of application spray (SDM), described in this application.

Figure 2 shows a micrograph obtained by the method of transmission electron microscopy (FACT), catalysts With/CEO₂received by the SDM method, with different dispersion of the metal when using (A) a soluble precursor of cobalt (high dispersion) or (C) insoluble precursor of cobalt (low dispersion).

Figure 3 represents the porosity of the catalysts With/CEO_{2/sub> cylindrical pellets of 5 mm × 5 mm)obtained by the method of SDM, depending on the starch content (with respect to the contents CEO2after sintering in air for six hours at different temperatures.}

Figure 4 represents the influence of the porosity of the catalyst on the diffusion coefficient of the gas and the radial crushing strength of the catalyst With/CEO₂cylindrical pellets of 5 mm × 5 mm)obtained by the method of SDM.

Figure 5 shows the conversion of N₂O depending on the temperature in the laboratory testing of catalysts With/CEO₂(particle 125-200 μm), obtained by different methods: (a) SDM with soluble precursor of cobalt, (b) SDM with an insoluble cobalt precursor and (C) by the method of initial moisture content. Experimental conditions: flow = 3 mbar N₂O, 20 mbar NO_x, 80 mbar O₂, 50 mbar H₂Oh, total pressure = 2 bar, watch the volumetric rate of gas = 140000 h^-1.

6 represents the selectivity for NO and the formation of N₂O depending on the time during the oxidation of ammonia in the pilot testing of catalysts With/CEO₂cylindrical pellets of 3 mm × 3 mm)obtained by the method of SDM c soluble precursor of cobalt and insoluble cobalt precursor. Experimental conditions: flow = 10,5% vol. NH₃in the air, temperature = 900°C, total pressure = 5 bar, cha the new volumetric rate of gas = 60000 h ^-1.

Fig.7 represents the conversion of N₂O depending on the time in the pilot testing of catalysts for Co₂AlO₄/SEO₂cylindrical pellets of 5 mm × 5 mm), manufactured by the method of SDM with soluble precursor of cobalt by adding corn starch or without him. Experimental conditions: flow = 6.5 mbar N₂About 50 mbar NO_x, 30 mbar O₂, 80 mbar H₂Oh, temperature = 900°C, total pressure = 5 bar, watch the volumetric rate of gas = 100000 h^-1.

Fig represents the conversion of N₂O depending on the time in the pilot testing of catalysts for Co₂AlO₄/SEO₂cylindrical pellets of 5 mm × 5 mm), manufactured by the method of SDM c soluble Co-precursor and corn starch, as well as by coprecipitation. Experimental conditions: flow = 6.5 mbar N₂About 50 mbar NO_x, 30 mbar O₂, 80 mbar H₂Oh, temperature = 900°C, total pressure = 5 bar, watch the volumetric rate of gas = 100000 h^-1.

Fig.9 represents the catalytic activity of Ni/Al₂O₃made by the SDM method, the reforming reaction of methane with water vapor in laboratory tests and comparison with commercial catalyst based on Ni (G91-HGS, Sud-Chemie). The tests were carried out on the catalyst particles 300-500 μm. Experimental conditions: temperature = 650°C, supply = the hypoxia ratio of N ₂O/CO₂/CH₄total gas flow = 125 IO h^-1, 2 g of catalyst + 10 g α-Al₂O₃(diluent), total pressure = 25 bar, a mass hourly space velocity = 1000 nl h^-1g^-1pre-processing catalyst = net N₂at 600°C for 12 h.

Thus, the invention relates to a method for producing a porous substances on the substrate for catalytic applications in which one or more soluble(s) precursor(s) of the active phase is added to a suspension consisting of insoluble phase substrate in water or in an organic solvent. The suspension is milled to reduce particle size and phase of the substrate(carrier) to a value of less than 50 microns, before or after grinding add additives that facilitate the processing, add a pore-forming substance and the suspension is subjected to spray-dried, pressed and thermally treated to remove the pore-forming substance. After that, the substance is sintered and preferably subjected to a preliminary treatment with hydrogen gas is a reducing agent or an inert gas.

Preferably, the suspension is subjected to wet grinding and particle size is reduced to 0.1-10 μm, preferably 1 μm. The viscosity of the suspension support at the level of 100-5000 JV, preferably about 1000 CP. A pore-forming substance is preferably I have is cellulose, starch or polymer fiber, is removed at a pressure of 10-20 mbar O₂diluted with an inert gas at 300 to 400°C. the heating Rate is preferably chosen possibly low, usually 1°·min^-1.

Phase substrate (carrier) represents one or more components selected from Al₂O₃, SiO₂, ZrO₂, TiO₂, ZnO, MgO, MgAl₂O₄, CoAl₂O₄and CeO₂. The active metal phase selected from transition metals (for example, Co, Ni, Cu, Fe), noble metals (such as Pt, Rh, Ru), lanthanides (e.g. La, Ce), as well as other elements of the Periodic table, which can act as stabilizers and / or promoters (alkaline earth, for example, Na, Mg, K, Cs) or other trivalent neustanovivshiesya metals (such as Al, Ga). The precursor of the active phase is one or more compounds selected from acetates, nitrates, sulfates, oxalates, acetylacetonates, preferably acetates. Cations of the active phase before adding to the suspension substrate can be bound in complexes with organic phase. You can also make partial complexation of cations, which operate to prevent the formation of large crystals. Additives that facilitate the processing, can provide dispersing agents, binders, plasticizers, lubr the edges, the pH modifiers, etc.

The invention also relates to a method for production of porous catalysts on the substrate for decomposition of N₂O, in which the soluble precursor of cobalt is added to a suspension of cerium oxide and additives that processing in the water. After that, the suspension is milled to a particle size less than 10 microns, add a pore-forming agent, viscosity regulate to about 1000 SP before the suspension is subjected to spray-dried, and then pressed, remove the pore-forming substance and the product is sintered. You can add the zirconium oxide and/or a soluble compound of aluminum. It is preferable to use as the precursor of cobalt acetate.

The substance obtained according to the method, it is possible to use, for example, as a catalyst for the decomposition of N₂O, the ammonia oxidation or reforming of methane with water vapor.

Detailed description of the invention

The present invention discloses a new simple, inexpensive, reproducible, uniform way that is easy to use on a large scale, producing high quality porous substances on the substrate for catalytic applications. The authors called his method of spray application (SDM). Figure 1 presents a comparison of unit operations in the method SDM and conventional coprecipitation method.

The main novelty of the JV is soba SDM this introduction one of the basic operations, i.e. spray drying, for simultaneously carrying out a large number of operations on the production of the catalyst:

i) applying a precursor(s) of metal on the substrate evenly over one stage;

ii) drying the catalyst precursor (avoiding subsequent separation of solid - liquid, such as filtration, centrifugation);

iii) introduction of additives that contribute to the processing (dispersants, binders, plasticizers, lubricants, modifiers, pH and the like);

iv) the granulation powder to obtain easily pressable powder.

After selecting the active form (compounds) and substrates for her, the challenge is to build from the predecessors of these active forms of the catalytic structure with properties and characteristics that will meet the requirements of the industrial customer. It was shown that the large scale production of catalysts for the decomposition of N₂O by the method of spray application amounts to many tons. Methods such as coprecipitation and impregnation or ion exchange, lead to many serious technical problems when scaling compared to the SDM. Other methods, such as Sol-gel, inoculation (clutch), heterogenization complexes and deposition-precipitation is still used only in laboratory scale and only dlearning number of formulations. Catalysts synthesized by these methods are not produced on an industrial scale.

Soluble precursor of the active phase is first added to a suspension consisting of phase substrate in water or other organic solvent in appropriate quantities and concentrations. The slurry is subjected to wet grinding in the mill constantly stir environment, or a ball mill to reduce particle size and phase of the substrate, preferably to less than 1 μm, thus achieving a stable dispersion. To prepare the catalyst for forming additives that facilitate processing, such as dispersants, binders, plasticizers, lubricants and pH modifiers that can be added before or after grinding. After grinding to the suspension, you can add a pore-forming substance, such as starch, cellulose or polymer fibers. The suspension is subjected to spray drying to obtain granules, suitable for molding by extrusion in the form, i.e. with a size distribution from 50 to 400 microns.

Extremely fast drying, achieved when spray drying, allows to obtain the precursor of the active phase deposited on the surface of the phase of the substrate evenly over the entire spray dried granule. This stage plays a crucial role in the emergence of close contact between Akti is Noah phase and its predecessor, which leads to the uniform distribution of metal in the final catalyst. Then the substance is pressed. Removing a pore-forming substances should be conducted in a controlled atmosphere (10-20 mbar O₂diluted with an inert gas, such as N₂, He or Ar). Thermal decomposition of the pore-forming phase in an oxidizing atmosphere can kataliziruetsa metal of the active phase, leading to thermal destruction. This happens not only in the oxidation of starch and cellulose, which is ectothermic. Many polymer processing additives that decompose endothermically, even when heated in air, such as polymethylmethacrylate (emission spectra obtained for pure), decompose exothermically if heated by contact with a catalytic phases. The proposed method of removing a pore-forming substances is also considered as a new aspect of the present invention, which is generally applicable in the production of catalysts. After this process the substance is sintered at a high temperature and get the ultimate catalyst. The uniform distribution of the active phase in the granules, spray dried, preserved in the final product - the catalyst granules.

The method of spray application requires 3-5 unit operations, i.e. less than traditional methods such as coprecipitation and impregnation (see figure 1). Few operas is tion in the new method are multi-purpose, that makes it very attractive (see above).

The method of spray application provides the ability to get a wide range of catalysts on the substrate. The only requirement is to have a soluble active phase and the insoluble substrate. There are many opportunities to find appropriate precursors of the metals. You can use metals of different nature from the Periodic table of elements, while other methods have large restrictions.

This requirement meets traditional substrates used in catalysis (e.g., Al₂O₃, SiO₂, ZrO₂, TiO₂, ZnO, CeO₂, MgO, MgAl₂O₄, CoAl₂O₄). The active phase is selected from transition metals (for example, Co, Ni, Cu, Fe), noble metals (such as Pt, Rh, Ru), lanthanides (e.g. La, Ce), as well as other elements of the Periodic table, which can act as stabilizers and / or promoters (alkaline earth, for example, Na, Mg or Al, Ga. It is preferable to use the acetates, nitrates, sulfates, oxalates or acetylacetonates. Another feature of the method of spray application is the possibility of obtaining polymetallic catalysts with high dispersion of the components. This makes it attractive, for example, bifunctional catalysis or promoted the reaction is rd. Classic joint or sequential impregnation impregnation of the two metal salts has been shown to be not effective to achieve close cooperation between the two metals. Tested and new methods. In all cases, looking for a way to get monometallic catalyst (i.e. the source of catalyst), which is then modified by the addition of a second metal. This modification is carried out through selective reaction which takes place only on monometallic particles of the original catalyst. How SDM offers through operations in a single tank is a simple way to overcome this difficult and time-consuming manufacturing process, reaching very close contact of the introduced metals.

For the synthesis of bimetallic phases on a substrate the method of synthesis of the spray application can be further improved by linking the complex cations of the active phase with the organic phase before adding to the suspension substrate. This is a modification of the well-known Pechini method to obtain mixed metal oxides, in which the cations are bound in complexes with organic molecules, which undergo polymerization process. This approach leads to the formation of phase precursor containing chaotic dispersion of metal ions, which is then applied to mean the ku during spray drying. This ensures the formation of a mixed phase oxides at low temperatures. Suitable complexing agents include citric acid, glycine, EDTA, etc.

At high concentration of the active phase during the drying process, the granules can be formed large crystals of the active phase. This can be avoided by adding a small amount of monodentate complexing agents, such as triethanolamine (tea). This number must be less than the amount sufficient for complete bonding in complexes of cations of the active phase, preferably sufficient to bind each cation only one molecule of the complexing agents. The result of this partial complexation of the cation is that it prevents the formation of large crystals of the precursor of the active phase due to interruption of the crystal lattice.

How SDM universal that can be continuous or periodic, which contrasts with the high requirements to make way coprecipitation continuous. Scaling from pilot plant to full-scale production is relatively easy to implement in the framework of the SDM way that was demonstrated. The most important single operation, the grinding slurry and spray drying are standard operations in the processing of ceramics and Ho is Osho studied.

The method of spray application is well suited to achieve a uniform distribution of the catalyst components or creating predecessors with a specific stoichiometry. The final catalyst consists of small and dispersed mixed crystallites components due to the good contact of the active phase (for example, in bimetallic systems) and the substrate before and after the stage spray drying/coating. The coprecipitation also leads to high dispersion, but the technological requirements are much higher here, as well as the difficulties the quality of the precipitated product and the challenges of maintaining a constant product quality during the entire deposition process. Excellent characteristics of the catalyst, deposited by sputtering, in comparison with other methods were shown for the decomposition of N₂O in the presence of catalysts based on Co.

How SDM also allows you to accurately design the macrostructure of the obtained catalyst (pore size and pore volume) for optimum performance. By this method were obtained solid granules with a porosity of 70%.

The method of producing catalyst

Further describes a method of producing catalyst, entitled "Method of spray application and disclosed in the claims. The method of obtaining described with reference to obtaining catalyst razloga the Oia N ₂O, containing a pore-forming phase. Also covered other catalytic applications. It also describes the influence of the pore-forming phase on the properties of the catalyst to transfer gas. Further detail of each unit of operation in the method SDM presented in figure 1 for the catalyst With-Al/CeO₂.

Suspension

Aqueous suspension of cerium oxide or other phase substrate is prepared by adding to water their powder of cerium oxide c size agglomerates d₅₀that usually lie in the range of 10-20 microns. For dispersion of the suspension and prevent sedimentation using vigorous stirring. To this suspension is added polyvinyl alcohol (PVA) in the form of 5-10 wt.% aqueous solution. As a rule, to dissolve the PVA PVA solution should be warmed. After adding PVA to its suspension is stirred for 12 hours. While PVA adsorbed on the surface of the cerium oxide. The role of PVA is twofold. In suspension it acts as a steric stabilizer cerium oxide, reducing the tendency to sedimentation. At a later stage of manufacture, it acts as a temporary binder for granules obtained by spray drying.

To a suspension of cerium oxide added with vigorous stirring cobalt acetate, hydroxyacetate aluminum and zirconium oxide. For some trains you can use nitrate or other is Oli. The suspension is milled using a ball mill or mills with continuous mixing media to reduce the size of agglomerates of cerium oxide, so that d₅₀reduced to 0.1 to 10 μm (preferably 1 μm). This allows you to get the suspension is resistant to sedimentation, which is a practical advantage, and can improve the characteristics of the catalyst due to the improved uniformity of the catalyst. The viscosity of the slurry should be maintained at the level of 100-5000 JV, preferably about 1000 SP.

A pore-forming substance

To stable suspensions add a pore-forming substance. Use corn starch with an average particle size of 10-15 µm. The pore size can be adjusted by choice of starch. Other starches, such as rice or potato can be used to obtain smaller or larger pores, respectively. You can also use other pore-forming substances, other than starch. In the manufacture of catalysts according to the method SDM successfully applied microcrystalline cellulose Avicel.

In principle, it is possible to use any substance which is insoluble and thermally decomposed, leaving the inorganic residue. In the past alternatively, the starch used microcrystalline cellulose, although it did not give special advantages. Mo is but also use polymer beads or fibers, but if they melt before thermal decomposition, it may cause difficulties during heat treatment. Starch is added after grinding, so that the structure of starch grains, which causes the pore size is maintained. The water content of the suspension is set so that the viscosity of the suspension was 1000 SP.

Spray drying

Spray drying was performed on a pilot plant using a two-fluid atomizer and centrifugal atomizers. Full-scale spray drying is performed with the use of centrifugal atomizers and sprayers high pressure. In each case, no serious problems, and always get a good flowing powder. Once in full production, it was found that when using a spray gun high pressure in counter-current mode is too high, the inlet temperature may cause ignition of the powder. In this case, use the temperature at the inlet above 400°C. Countercurrent model is not ideal for substances that are sensitive to heat. Therefore, either the inlet temperature should be lower, which will lead to a reduction in the rate of production, or it is necessary to use a model of dispersion in parallel threads.

In our pilot tests, the inlet temperature typically ranged from 250 to 180°in the W ill feed rate of the suspension, and the outlet temperature was usually in the range of 105-110°C. This led to a moisture content of 0.2-0.5% and the average grain size d₅₀60-80 microns.

Pressing

Before pressing the powder, spray dried, was added 0.5% of aluminum stearate and the water content is brought to 0.5-2%. This operation was performed in a Forberg mixer. Water acts as a plasticizer for PVA, and the optimum water content depends on the exact composition of the catalyst. The required amount of water depends on the surface area of cerium oxide and purity PVA. The extruded pellets by uniaxial pressing on the press PTX Pentronix 612. For pellets of 5 mm or less acceptable mold single actions, but for the manufacture of larger granules, such as 9 mm corrugated granules, you must use the operation of double pressing. The compression ratio (the ratio between the depth of fill and the height of the pressed pellets) is usually equal to 2.2.

Removing a pore-forming substance

After pressing, the pellets are subjected to heat treatment to remove the pore-forming phase, after which it is sintered to the final obtain pellets of the catalyst. Heat treatment to remove the pore-forming starch is the most critical and crucial stage in the manufacture of the catalyst. The heated air granules containing starch, Pref which leads to a rapid rise in temperature in the stratum granulosum and unregulated burning of starch, that adversely affects the integrity of the granules. Heating of the granules in the nitrogen, to which is added a small amount of air, regulates the removal of starch. The range of concentrations of oxygen in the initial stages is 0.1 to 0.5 vol.%. At all stages of the removal of the starch, the main decomposition products of starch are the CO₂and water vapor even when the oxygen content of 0.5%.

After removal of the weight of the starch, as evidenced by the lack of CO₂in the exhaust gas, the oxygen content increases to 20 vol.%. Starch consists of two polymers, one of them is decomposed 170°and another in the range of 250-300°C. the heating Rate should be as low as possible, usually 1°·min^-1. Pellets are loaded into a perforated basket and passed through a layer of granules from the bottom of the gas mixture of the nitrogen-oxygen. To purge through the granules gas heat. The temperature of the pellets regulate by means of gas temperature and oxygen concentration. During this operation the temperature of the layer is more sensitive to oxygen than the temperature of the inlet gas, so it is a means by which temperature can be regulated during decomposition. In the first stage, the pellets are heated to 170°With the gas stream containing 0.1 vol.% the oxygen. Once it reaches a stable temperature, the con is entrely oxygen is slowly increased. For the development of the reaction can be followed by the rise of temperature in baskets, arranged vertically in series. As soon as the first polymer of starch decompose, the oxygen concentration is reduced and the temperature was raised to 250°C. Upon reaching a stable temperature, the oxygen concentration again increased up until all baskets will not complete the second stage of decomposition. The temperature was raised to 300°and the oxygen concentration is increased to 20%, while the reaction will not stop. Baskets cooled overnight in a stream of oxygen. The total process time is typically 2.5 days.

After removal from the furnace for burning a pore-forming substance baskets are placed in a vertical tube furnace. They heat up in the air with a speed of 1°·min^-1up to 950-1000°C. After 6-12 h at a maximum temperature of the furnace is cooled. The sintering process usually takes 2 days. Sintered pellets represent the final product.

Hereinafter the invention will be illustrated in the following examples:

Example 1. Obtaining catalysts Co/CeO₂with different distribution of active phases and download metal method SDM

Example 1A. The catalyst with a high dispersion of cobalt oxide supported on cerium oxide

Aqueous suspension phase substrate of cerium oxide were prepared by adding 5 kg sogepa the scientists powder of cerium oxide (Rhodia HSA15) c size of the agglomerates d ₅₀usually in the range of 10-20 μm to 5 l of water containing 40 g of PVA (Rhodoviol 25/140). For dispersion of cerium oxide used vigorous stirring, and then it was stirred for 15 hours to allow the PVA to be adsorbed on the surface of the cerium oxide.

To a suspension of cerium oxide was added 289 g of cobalt acetate (Fluka) with vigorous stirring. The suspension was ground in the mill continuously stir the environment to reduce the size of agglomerates of cerium oxide so that d₅₀is less than 1 micron.

The water content of the suspension was adjusted so that the viscosity of the suspension is 1000 SP. Typically, the moisture content in the suspension is between 40 and 50%.

Spray drying can be carried out in the dryer with a centrifugal atomizer. The inlet temperature was usually 180-400°depending on the speed of injection of the suspension, and the outlet temperature was usually equal 105-110°C. as a result, the moisture content was 0.2-0.5 wt.% and the granules have a size of d₅₀from 60 to 200 microns, depending on the type of spray.

Before pressing the powder, spray dried, was added 0.5 wt.% the aluminum stearate and the water content is brought to 0.5 wt.%. This operation was performed in a Forberg mixer. Water acts as a plasticizer for PVA, and the optimum water content depends on the exact composition of the catalyst. Not the required amount of water depends on the surface area of cerium oxide and purity PVA. The extruded pellets by uniaxial pressing on the press PTX Pentronix 612. Received the corrugated beads with seven channels (d_m=9 mm, d_h=1.7 mm). Can be obtained pellets of various shapes, from simple cylinders to a multilayer pellets. Pressed pellets were specaly in the air, using conventional muffle furnace. The pellets were heated at a rate of 1°·min^-1900-1000°and kept at the maximum temperature for 6-12 hours. The chemical composition of the final catalyst consisted of 1.9 wt.% Co₂About₃and to 98.1 wt.% SEO₂.

Example 1b. The catalyst with low dispersion of cobalt oxide supported on cerium oxide

Received a suspension of cerium oxide as described in example 1A, using 5 kg of cerium oxide (Rhodia HSA15) and 5 l of water containing 40 grams of dissolved PVA (Rhodoviol 25/140). To the aqueous slurry of cerium oxide was added to 93 g of cobalt oxide (Co₃About₄, Merck) with vigorous stirring. After 1 hour of stirring to ensure uniform dispersion of the cobalt oxide, the slurry was ground in a ball mill to reduce the size of agglomerates of cerium oxide to a value of d₅₀less than 1 micron. The water content of the suspension was adjusted so that the viscosity of the suspension was 1000 SP. For spray drying, the addition of lubricants, extrusion pellets and sintering was performed as opisanoj example 1A. The chemical composition of the final catalyst consisted of 2.0 wt.% Co₂About₃and 98,0 wt.% SEO₂.

Figure 2 shows the different composition of the catalyst relative to the active phase depending on the nature of the cobalt precursor used in the preparation. The use of a soluble precursor of cobalt (cobalt acetate, example 1A) leads to a highly dispersed catalyst (figa). In the micrograph, obtained by the method of transmission electron microscopy, high-resolution, are not visible particles of cobalt oxide, and it shows that the particles of cobalt oxide have a size of less than 1 nm. When using insoluble precursor of cobalt (Co₃About₄, example 1b) observed large agglomerates of cobalt oxide on the substrate SEO₂(pigv), indicating less dispersion of the active phase in the final catalyst. A different composition of cobalt will undoubtedly affect the catalytic properties of substances, as shown in examples 4 and 5.

Example 2. Obtaining catalyst Ni/Al₂O₃way SDM

The catalyst is Nickel oxide deposited on a gamma-alumina, can be obtained according to the method described in example 1A. In 5 l of water were dissolved 40 g of PVA (Rhodoviol 25/140). With vigorous stirring, was added 5 kg of gamma-aluminum oxide (Sigma-Aldrich). The suspension was stirred for 15 h and then suspensie of aluminum oxide was added 3,175 kg of Nickel nitrate (Fluka). After stirring for 1 hour the suspension was ground using a ball mill to a value of d₅₀equal to 1 μm. After grinding the moisture content in the suspension was 42.9% and the viscosity was equal to 960 SP that is suitable for spray drying. The suspension was subjected to spray-dried and granulated by the method described in example 1A. Pellets were specaly standard muffle furnace in air. The pellets were heated at a rate of 1°·min^-1up to 700°C and held at this temperature for 6 hours. The chemical composition of the final catalyst consisted of 16.6 wt.% NiO and of 83.4 wt.% Al₂O₃.

Example 3. Obtaining catalysts With/CEO₂with different porosity way SDM

How SDM preparation of catalysts allows to obtain catalysts with adjustable volume and pore sizes. This is achieved by introducing fugitive pore-forming phase, such as starch, cellulose or polymer, in a suspension of the catalyst prior to spray drying. After pressing, spray dried granules, pellets or tablets pore-forming phase is removed by means of controlled heat treatments.

Aqueous suspension of cerium oxide and cobalt acetate as described in example 1A, was prepared and crushed to the desired particle size. To the suspension was added with rapid stirring fugitive pore-forming the ABC - corn starch (Collamyl). The suspension containing phase catalyst and a pore-forming phase from corn starch, is subjected to spray drying by the method described in example 1b. After adding lube, aluminum stearate, and regulation of the moisture content of the granules, dried by spraying, got granules or pellets by uniaxial pressing in the form as described in example 1A.

To create a variable porosity while maintaining the mechanical integrity of the granules pore-forming phase, you must remove the regulated way. This is achieved by thermal oxidation of a pore-forming substance with a low partial pressure of oxygen. The atmosphere consists of air diluted with nitrogen so that the oxygen concentration is 0.1-2 vol.%. Corn starch is composed of two different polymers amylose and amylopectin. Amylose consists of linear chains of alpha-linked glucose, and amylopectin consists of a branched polymer of alpha-linked glucose. Usually corn starch consists of 75% amylopectin and 25% amylose. Both polymer decomposed at 240 and 380°respectively in contact with solids, for example, aluminum oxide. In the presence of the oxidation catalyst, the decomposition temperature can be reduced by 80-100°C. Burning corn starch from the catalyst cobal the t/cerium oxide, obtained by the method SDM involves slow heating of the surface layer of granules to 170°C. During the heating process through the layer of miss gas consisting of air diluted with nitrogen so that the oxygen concentration below 1 vol.%. Low oxygen concentration limit temperature rise in the layer of pellets due to oxidation of amylopectin, less than 50°C. After complete decomposition of amylopectin, as evidenced by the low level of carbon oxides in the exhaust gas, the temperature is slowly increased to 300°and maintain at this temperature until complete digestion of amylose. After removal of the starch granules are heated in air up to 900-1000°for sintering.

The starch content of the suspension was varied from 0 to 25 wt.% in the calculation of the mass of cerium oxide. It is possible to produce granules of the catalyst with a higher content of the pore-forming substance, but the mechanical properties of the pellets after removal of the pore-forming substance is very low.

Changing the amount of a pore-forming phase, it is possible to adjust the pore volume. Figure 3 shows the effect of starch content on the porosity of the granules in the system With/CEO₂(nominal composition: 2 wt.% Co₂About₃and 98% SEO₂) at different sintering temperatures. With increasing starch content in the composition is above 9%, the porosity of the granules increases. Dr. who and the properties of the critically determined by the porosity of the catalyst: the effective diffusion coefficient inside the granules compared with the diffusion coefficient of the gas in the free space, and the strength of the granules. These two properties for the system Co/CEO₂shown in figure 4. The increase in porosity leads to an increase of the effective diffusion coefficient in the grain with reduced strength. Therefore, the optimum depends on the specific application.

Upon receipt of the granules or pellets by extrusion or by extrusion in the absence of a pore-forming phase receive a porosity in the range of 40-55%, provided that the sintering temperature is not very high. Pore size is determined by the size of the primary particles, which depends on the degree of grinding. The more efficient the process of crushing, the smaller the size of the pores between the particles. However, if the particle size less than one micron, a large proportion of the porosity will be less than 0.1-0.2 μm. By introducing a pore-forming phase can be increased and the porosity and pore size.

Example 4. Characteristics of catalysts With/CEO₂in the direct decomposition of N₂O

Catalysts With/CEO₂(nominal composition: 2 wt.% Co₂About₃and 98% SEO₂in the form of particles with a size of 125-200 μm, manufactured by different methods, were tested in the decomposition of N₂O. the Results are shown in figure 5. Clearly the correlation between catalytic activity and the dispersion phase of cobalt. The catalyst obtained by the method SDM using cobalt acetate as a precursor for what it shows the highest activity due to the high degree of dispersion of cobalt in the catalyst. The catalyst obtained by the method SDM from cobalt oxide as the precursor, showed significantly less activity due to the low dispersion of the active phase, forming large agglomerates of cobalt oxide on the substrate SEO₂(see figv). The catalyst With/CEO₂obtained by the method of initial moisture content using cobalt acetate, lead to very low activity, which correlates with low dispersion obtained by this method.

Example 5. The influence of cobalt precursor on the characteristics of the catalysts With/CEO₂in the oxidation of ammonia

Catalysts With/CEO₂in the form of cylindrical pellets with a size of 3 mm × 3 mm, obtained by the method SDM using soluble and insoluble precursors of cobalt, were tested in the oxidation of ammonia (Fig.6). Both catalyst had chemical composition: 20 wt.% Co₂About₃and 80 wt.% SEO₂. The catalysts showed similar initial selectivity NO (˜85%). However, the initial formation of N₂O on the catalyst obtained with the use of cobalt acetate as a precursor, was significantly lower compared with the catalyst obtained with the use of cobalt oxide as the precursor. Moreover, both the catalyst vary greatly in stability. The catalyst With/CEO₂obtained and the use of insoluble precursor of cobalt, deactivated much faster, which leads to lower selectivity and NO increased formation of N₂O.

Example 6. The influence of the porosity of the granules on the characteristics of the catalysts of Co₂AlO₄/CeO₂in the decomposition of N₂O

Catalysts CoAl₂O₄/CeO₂were obtained by the method SDM using cobalt acetate as its predecessor with the addition of corn starch or without him. Both catalyst had chemical composition: 1 wt.% Co₂About₃, 0,3% vol. Al₂O₃and 98 wt.% SEO₂. Catalysts in the form of cylindrical pellets of 5 mm × 5 mm were tested in the direct decomposition of N₂O to evaluate the influence of the porosity of the granules on the activity of the decomposition of N₂O. the Results are shown in Fig.7. Adding starch has proven beneficial effect on performance; the catalyst starch (porosity pellets 65%) showed a slightly higher conversion of N₂O than the catalyst with 15 wt.% starch (porosity of granules 50%).

Example 7. The influence of the method of obtaining catalysts of Co₂AlO₄/CeO₂on the decomposition of N₂O

The catalyst CoAl₂O₄/CeO₂was obtained by the method SDM using cobalt acetate as a precursor and with the addition of corn starch (15 wt.% in calculating the masses SEO₂). The final catalyst and the ate chemical composition: 1 wt.% Co ₂About₃, 0,3% vol. Al₂O₃and 98 wt.% SEO₂. In addition, the catalyst CoAl₂O₄/CeO₂was obtained by coprecipitation from a solution of precursors of Co, Al and CE (soluble) solution of the base sodium hydroxide and sodium carbonate. Aoademy catalyst had chemical composition: 42 wt.% Co₂About₃, a 13.9 wt.% Al₂O₃and of 42.7 wt.% SEO₂. To assess activity in the decomposition of N₂O used catalysts in the form of cylindrical pellets of 5 mm × 5 mm Fig results were compared. The catalysts obtained by the method SDM, have a high initial activity and stability throughout the work. There is a significant decontamination (˜20% of the initial activity after 30 days) of the catalyst obtained by coprecipitation. High dispersion of the cobalt cerium oxide facilitates a strong interaction between the active phase and the substrate, which stabilizes the composition. This cannot be achieved by conventional methods such as coprecipitation, as shown in the figure.

Example 8. Characteristics of catalysts based on Ni in the reforming process of methane

The activity of the catalyst Ni/Al₂O₃obtained by the method SDM according to example 2, in the reforming of methane at different feed ratios of H₂O/CO₂/CH₄compared with the industrial activity of the catalyst is of forminga (G91-HGS, Süd-Chemie). Both catalyst contained similar amounts of Nickel: 16.6 wt.% NiO to Ni/Al₂O₃and 19 wt.% NiO in industrial catalysts. This catalyst also contains other promoters, such as K. the Catalytic tests were carried out on particles of 300-500 μm and obtained values of intrinsic activity. Activity apromotional catalyst Ni/Al₂O₃received by way of SDM, at 650°expressed as the mole fraction of the product (on dry basis), higher than the activity of modern industrial Ni-catalyst (Fig.9). Were obtained methane conversion 26% (SDM) and 23% (industrial). The activity of the catalyst SDM decreases with the increase of the relative content of CO₂in the feed mixture (dry reforming). The industrial activity of the catalyst in a mixture of N₂O/CO₂/CH₄=1/1/1 higher than that of the catalyst Ni/Al₂O, obtained by the method of SDM. This may be due to the presence of promoters in the industrial catalyst, which reduces the rate of formation of coke, while the composition of the catalyst SDM was not present other metals than Ni.

The method of spray application allows you to obtain catalysts with homogeneous distribution of the active phase and uniform and controlled porosity with some regulation of pore size. Excellent characteristics of the catalysts obtained the s-SDM way, compared to other traditional methods (coprecipitation or impregnation) have been proven in various applications, including direct decomposition of N₂O, ammonia oxidation and reforming of methane with water vapor.

1. The method of obtaining porous substances on the substrate for catalytic applications in which one or more soluble(x) predecessor(s) of the active metal phase is added to a suspension consisting of insoluble phase substrate in water or an organic solvent, the suspension is subjected to wet grinding to reduce particle size and phase of the substrate to less than 50 μm, add additives that facilitate processing before or after grinding, add a pore-forming substance and the suspension, the viscosity of which is supported at 100-5000 JV, is subjected to spray-dried, pressed and heat-treated to remove the pore-forming substance and bake.

2. The method according to claim 1, in which the particle size is reduced to 0.1-10 μm, preferably 1 μm.

3. The method according to claim 1, in which the viscosity of the suspension support at about 1000 SP.

4. The method according to claim 3, in which a pore-forming substance is removed at a pressure of 10-20 mbar O₂diluted with an inert gas at 300 to 400°C.

5. The method according to claim 4, in which the heating rate is low, usually 1°·min^-1.

6. The method according to claim 1, in which oterom phase substrate is one or more compounds selected from Al₂O₃, SiO₂, ZrO₂, TiO₂, ZnO, MgO, MgAl₂O₄, CoAl₂O₄and CeO₂.

7. The method according to claim 1, in which the active metal phase selected from transition metals such as Co, Ni, Cu, Fe, noble metals such as Pt, Rh, Ru, lanthanides such as La, CE, and other elements of the Periodic table, which can act as stabilizers and / or promoters - alkaline earth, such as Na, Mg, K, Cs, or other trivalent neustanovivshiesya metals such as Al, Ga.

8. The method according to claim 7, in which the precursor of the active phase is one or more compounds selected from acetates, nitrates, sulfates, oxalates, acetylacetonates, preferably acetates.

9. The method according to claim 1, which used a pore-forming substance is a cellulose, starch or polymer fibers.

10. The method according to claim 1, in which the additives that facilitate the processing, are dispersing agents, binders, plasticizers, lubricants, pH modifiers, etc.

11. The method of obtaining porous catalysts on the substrate for decomposition of N₂O, in which the soluble precursor of cobalt is added to a suspension of cerium oxide and additives that treatment, in water, the suspension is milled to a particle size less than 10 microns, add a pore-forming substance, the viscosity of the reg is irout to about 1000 SP before as the suspension is subjected to spray-dried, followed by pressing, remove the pore-forming substance and the product is sintered.

12. The method according to claim 11, in which add zirconium oxide and/or a soluble compound of aluminum.

13. The method according to claim 11, in which the predecessor's use of cobalt acetate.

14. The use of the substance obtained according to any one of § § 11-13, as a catalyst for the decomposition of N₂O.

15. The use of the substance obtained according to any one of claims 1 to 10, as a catalyst for the decomposition of N₂O.

16. The use of the substance obtained according to any one of claims 1 to 10, as catalyst for the oxidation of ammonia.

17. The use of the substance obtained according to any one of claims 1 to 10, as a catalyst for the reforming of methane with water vapor.