N2o decomposition catalyst, use and a method for preparation thereof
FIELD: nitric acid production.
SUBSTANCE: invention relates to decomposition of N2O from nitric acid production emission gases. N2O is decomposed by contacting N2O-containing emission gas escaping absorption column with catalyst containing at least one cobalt oxide compound and at least one magnesium oxide compound under conditions favoring formation of N2O into nitrogen and oxygen gases, content of said cobalt oxide compounds ranging between 0.1 and 50% and that of magnesium oxide compounds between 50 and 99.9% based on the total weight of catalyst. At least 30% of cobalt in catalyst are in trivalent state. Preparation of catalyst envisages dry mixing of cobalt oxide and magnesium oxide compounds or corresponding precursors followed by compaction of the mixture under anhydrous conditions such that resulting catalyst has desired volume density.
EFFECT: enabled high degree of N2O decomposition at low temperatures and without disadvantages for nitric acid production process.
20 cl, 2 dwg
The present invention relates to a method of decomposition of N2O during the manufacture of nitric acid catalyst for the decomposition of N2O, and how to obtain it.
The oxidation of ammonia to nitric acid production along with desired nitric monoxide NO is formed as undesirable laughing gas N2O. the Latter in small quantities leads to the destruction of stratospheric ozone and greenhouse effect. After the reduction of emissions of laughing gas adipic acid production nitric acid represents the largest source of industrial emissions of laughing gas. Therefore, from the point of view of environmental protection, there is an urgent need for technical solutions to reduce emissions of laughing gas in the production of nitric acid. An overview of the processes nitric acid production and its various options are shown in Ullmann''s Encyclopedia of Industrial Chemistry, volume 17, VCH Weinheim (1991).
Promising the possibility of removal of N2O from industrial off-gases consists in the decomposition of N2O elemental nitrogen and oxygen using a suitable catalyst.
For the removal of N2O in the production of HNO3there are numerous suggestions, which are mainly based on the catalytic decomposition of N2About between Pt-nets and the first taproom what nicom.
Thus, the application US-A-4973457 described method of removing the dinitrogen oxide, which is formed during the combustion of NH3by holding gas for 0.1 to 3 seconds before cooling. As described here the way up to 90% N2O should rot in N2and O2. Alternatively stated that the gases for selective decomposition and reduce the retention time can jointly enter into contact with a catalyst based on a metal or metal oxide.
In the application DE-A-19805202 method for obtaining nitric acid, whereby to reduce the release of laughing gas reaction gases flow down along the platinum mesh pass before cooling on heat-resistant catalyst for the conversion of N2O contained in the reaction gases. The catalyst is heated to extreme temperatures from 800 to 1000°, which is supported directly after exiting the reaction gases from the catalyst gauze. As catalysts it is preferable to use a noble metal or ceramics.
In the application DE-A-19819882 also provides a method for the catalytic decomposition of N2O, in which the reaction gases from the combustion of ammonia prior to cooling, that is, before contacting with the heat exchanger, is passed over the catalyst, which preferably consists of 8 wt.% CuO, 30% wt. ZnO and 62 ve is.% Al 2O3. The duration of treatment before the decomposition of N2O is preferably <0.1 seconds.
In the application US-A-5478549 method for obtaining NO oxidation of ammonia on the catalyst of the platinum group metals, which is undesirable formed N2O together with the reaction gas is first passed through a system of traps for the regeneration of volatile metals of the platinum group and then for the decomposition of N2About passed over the catalyst layer of the oxide of zirconium. The temperature of the layer should be ≥600°C.
Accommodation directly for a Pt-net is desirable, as this should only replace the following after the Pt-grid load Raschig rings on the loose mass of the corresponding catalyst or a simple device for placement of the catalyst inside the grid. Disadvantages are extreme conditions. At temperatures around 900°With a water content of about 17% and the content of NO 10% high demands are made not only to the activity and selectivity of the catalyst, but also to its mechanical and thermal stability. In addition, granular mass of catalyst may be deposited scale Pt from Pt-nets and to reduce the selectivity of the decomposition of N2O, in which there is also a decomposition of the desired oxidation product of NO (Boudart and other Journal of Catalysis 39(1975), 383-394).
When placing the respective catalysts in the residual gas, which leaves the absorption column at a temperature of 20-30°s, water content depending on the variant of the method is limited to approximately 0.2-2%, the content of NOxapproximately 200-1000 nm Maximum temperature for this catalyst is set every time the temperature entering the turbine residual gas, which greatly limits the choice of suitable catalysts.
Among the many catalysts, the fundamental suitability for the decomposition and recovery of laughing gas proved (Kapteijn and others; Appl. Cat. In: Environmental 9 (1996), 25-64)should be called, among other zeolite catalysts loaded transition metals (US-A-5171553), the potential applicability of which to reduce N2About when nitric acid is also referred to Kapteijn.
In case of iron-containing zeolites, such as Fe-ZSM-5, their activity in the decomposition of N2O in the presence of appropriate amounts of NO increases, this is due to the reaction with the formation of NO2under NO+N2O→N2+NO2that is catalyzed by Fe-ZSM-5 (Kapteijn and other Journal of Catalysis 167 (1997), 256-265).
In accordance with this view is the possible introduction of such catalysts for the removal of N2O from the residual gas production is as nitric acid, which contains approximately equal parts NO and N2O. the Practical use of this kind of iron-and copper-containing zeolites can be, of course, problematic, specially made to their de-activated under hydrothermal conditions.
Iron-containing zeolites on the basis of ferrierite for recovery of N2O-containing gases are the subject of the application WO 99/34901. Used catalysts contain 80-90% ferrierite, as well as additional binder components. The proportion of water in the recovered gas is in the range from 0.5 to 5 vol.%. Compared to zeolites of different types of zeolite FER (ferrierite) type decomposition of N2O provide the best results (decomposition 77% N2O at 400°in the presence of 1000 nm NO and 3% N2O).
The presence of NOxaccelerates the decomposition of N2O, so that this catalyst is suitable for high speed decomposition of N2O in the tail gas of nitric acid before possible DeNOx-the stage at which reduce the content of NOxin the exhaust gas. Stage in the DeNOx plant for nitric acid but preferably after SCR method (selective catalytic reduction) with appropriate catalysts and NH3as a reducing agent at temperatures in the range from 250 to 350°C. Prewar the positive inclusion of a catalyst for the decomposition of N 2O, which operates at a temperature of approximately 400°With, it is impractical from an economic point of view, since the exhaust gas, after which the absorber has a temperature of about 30°With, you should first heated to approximately 400°and then cooling to about 300°C.
Therefore, the catalysts for the decomposition of N2O that do not require NO activation, appear to be preferred for the introduction of exhaust gas of the nitric acid production.
Such materials are, for example, binary oxides, such as Co3About4or NiO, high activity for the decomposition of N2O installed Saito and others in Actes du 2ieme Congres International sur la Catalyse, Technip, Paris 1961, 1937-1953.
Accordingly, the full decomposition of N2O on Co3O4occurs already at about 360°C. However, the drawback is the high cost of these materials.
In Actes du 2ieme Congres International sur la Catalyse, Technip, Paris 1961, 1937-1953 described other binary oxides, such as Al2O3or MgO, and their suitability for the decomposition of N2O.
However, these oxides, cheap compared to Co3O4have only weak activity in the decomposition of N2O. So, the complete decomposition of N2O on MgO reach only at a temperature of about 730°C.
The literature also described the introduction of a special connection with the relevant budget matrix or coating on various substrates. These activities, however, significantly lower than that of pure Co-components.
So, when making described in Adv. Sci. Technol. (Faenza, Italy) (1999) 16, 585-592 LaCoO3in a ceramic matrix (with 30 %weight part of LaCoO3for complete decomposition of N2O the required temperature from 420°C to about 650°C.
In the application DE-A-19700490 proposed a catalyst for the decomposition of laughing gas, which consists of a mixture of Co3About4and La1-xCuxCoO3-δand which in its pure form reach full decomposition of N2O (based on 2000 CNM N2O in synthetic air) already at about 300°C. Making the specified active ingredient in not mentioned specifically ceramic matrix with 25%by mass of the active component shifts, however, the reaction temperature until complete decomposition of N2O approximately 600°C.
In the application US-A-5705136 described method of decomposition of nitrogen oxides based catalysts containing mixed oxides of MgO and COO, i.e. solid solutions Soo in MgO (for example, with the stoichiometric ratio of COO/5MgO) or contain COO supported on a carrier of MgO (e.g., MgO+10% MEO). Thanks to the method of obtaining the cobalt atoms fixed on MgO or embedded in it so that the cobalt is found exclusively in the divalent state, mentioned and confirmed in Appl. Catal B: Environmental 13 (1997) 69-79. The scope of these catalysts is between 500 and 700°C.
In view of the prior art there is the problem of design for the production of HNO3the method of reducing N2O, which could provide a high degree of decomposition of N2O at low temperatures and without technological disadvantages for the process HNO3could be integrated into it. This applies not only to the necessary hardware costs that are associated with the implementation of such a method of reducing N2O, but also to a possible deterioration in the production of HNO3which may occur at full load, process or when starting or stopping production.
The problem is solved by the invention, which relates to a method of decomposition of N2O during the manufacture of nitric acid by contacting N2O-containing flue gas leaving the absorber column with a catalyst that contains at least one oxide compound of cobalt and at least one oxide compound of magnesium, under such conditions that ensure the transformation of N2O in gaseous nitrogen and oxygen, and the content of oxide compounds of cobalt is in the range from 0.1 to 50 wt.% and the content of the oxide of magnesium compounds in the range of from 50 to 99.9 wt.% calculated on the total mass was pushing the congestion.
Further, the present invention relates to a catalyst for the decomposition of N2O, containing at least one oxide compound of magnesium and at least one oxide compound of cobalt. The content of the oxide compounds of cobalt is in the range from 0.1 to 50 wt.%, preferably from 5 to 35 wt.%, and the content of the oxide compounds of magnesium in the range of from 50 to 99.9 wt.%, preferably from 65 to 95 wt.%, calculated on the total weight of the catalyst. The catalyst preferably has a bulk density in the range from 0.5 to 2.5 g/cm3in the calculation of the individual grains of the catalyst.
In the case of the proposed catalyst we are talking about a large volume of catalyst ("bulk catalyst").
The proposed catalyst containing compounds of cobalt, in which at least 30%, preferably more than 50% of the Co atoms are chemically III-valent state. Oxide compounds of cobalt and magnesium are presented in largely separate phases, which is confirmed by relevant experiments x-ray diffraction (XRD). The oxidation state of cobalt can be determined using photoelectron spectroscopy (XPS).
Preferably oxidic compound of cobalt or if there are several oxide compounds of cobalt, at least one of them has a perovskite structure or a spinel. Example and used according to the invention compounds of cobalt are the Co 3About4or LaCoO3. The invention also includes the use of appropriate doped compounds, as, for example, CuxCo3-xO4or La1-xSrxCOO3. As of magnesium compounds preferably used MgO.
Significant components of the catalyst, i.e. the oxide compounds of magnesium and III-valent cobalt should have possibly a higher specific surface area, to provide the best possible high activity of the catalyst. The specific surface oxide compounds of cobalt, depending on the type and preparation is typically in the range of from 3 to 30 m2/g of oxide compounds of Mg in the range from 20 to 200 m2/g Specific surface area of the finished catalyst is preferably in the range from 5 to 150 m2/year
In the form of a cylindrical molded grains of the catalyst preferably has a radial strength in compression in the range from 0.5 to 10 MPa.
The proposed composite catalysts exhibit very high activity in the decomposition of N2O, which is even higher than the activity of pure compounds of cobalt. This can be seen in figure 1.
Shown T90, that is, the temperature required for 90%decomposition of N2O, and also the starting point of the temperature jump (TA) decomposition of N2O by weight of catalyst based on Co3 O4. For comparison, the corresponding values for the decomposition of N2O over the net Co3O4and clean MgO (Actes du 2ieme Congres International sur la Catalyse, Technip, Paris 1961, 1937-1953).
For these examples should be taken as the exact conditions of obtaining and measuring.
As clearly shown (figure 1), the oxide compound III-valent cobalt and MgO show a synergistic effect with respect to the decomposition of N2O. Instead of the expected proportionality, i.e. the linear behavior of the curve (dashed line) for T90=715°for pure MgO (corresponding to 0% Co3O4and T90=350°for net Co3O4or TAnd=605°for pure MgO and TAnd=280°for net Co3O4the value of T90the catalyst according to the invention is at 30% Co3O4only 355°With the start point of the temperature jump of the proposed catalyst TAnd=185°even With clearly lower than for pure Co3About4.
This effect was not observed for solid solutions of oxides II-valence cobalt (CoO) in MgO and also when using MgO as a carrier. Necessary for the decomposition of N2O temperature is clearly higher than in the case of the proposed composite catalysts.
This high activity of the catalyst, which provides a decomposition of N2O>80%, and the minimum sensitivity is tatelnosti to the water can preferably be used for removal of laughing gas from the exhaust gas of the production of HNO 3. But the use of the catalyst is not limited to the production of nitric acid. The catalyst can be used where it is desirable decomposition of laughing gas in the flue and process gases at relatively low temperatures. The proposed catalysts can be placed, for example, for gas turbines.
Figure 2 clearly explains particularly preferred device decomposition of laughing gas in the production of nitric acid, which is especially preferred, since N2O-containing gas is passed over the catalyst under a pressure of from 4 to 12 bar and the required amount is restored to the catalyst and, on the other hand, the heat required to establish the desired reactor operating temperature, can be returned on subsequent expansion turbine.
The flue gas leaving the absorber column (30) the production of HNO3skip over the proposed catalyst, which is located in the reactor (DeN2O-reactor) (70) in the direction of the process before the expansion turbine (80), in particular before the expansion turbine (80) and DeNOx-stage (50).
If the flow of exhaust gas is introduced DeNOx stage to reduce NOx, the proposed catalyst include after this stage, because the presence of NOx has an inhibitory dei is the influence on the decomposition of N 2O over this catalyst. As DeNOx stage, which is usually after the SCR process (Selective Catalytic Reduction) with NH3as a reducing agent is carried out at temperatures between 200 and 350°With, at lower temperatures works as are necessary for the removal of N2O inclusion of the reactor for removal of N2O makes it possible temperature level of the exhaust gases, increasing from the exit of the absorber before entering the expansion turbine. This is from a technical point of view is particularly preferable.
The transmission of N2O-containing off-gas flow over the catalyst is carried out usually at temperatures in the range from 250 to 650°C, preferably in the range from 300 to 600°C.
Moreover, the temperature of the catalyst layer because it is not the whole process, and, for example, work consistently included residual gas turbines, is chosen so as to achieve at least 80%, preferably at least 90%, particularly preferably more than 95%, the decomposition of N2O N2and O2.
The necessary temperature is determined by the composition of the exhaust gas, which can vary depending on options production of HNO3. For example, in the gas stream molecules of N2O, NOx or O3have inhibitory effect on otlozhenii N 2O over cobalt containing catalysts. When high proportions of these substances temperature increases accordingly.
On the other hand, it is necessary for the decomposition of N2Temperature depends on the time of turning or flow rate, i.e. transformations per unit time and per unit volume of catalyst over which is passed a stream of N2O-containing gases. As is known to the specialist, increasing the load on the catalyst at the required constant decomposition of N2O due to the corresponding increase in temperature. The increase in pressure, which is in the range from 4 to 12 bar, at constant volume of catalyst prolongs the time of conversion in the catalyst bed. Preferably the space velocity is in the range of from 2000 to 200,000 h-1in particular in the range from 5000 to 100000 h-1.
To establish operating temperature DeN2O-reactor according to the invention uses the heat of oxidation of NH3and by heat coming in DeN2O-reactor off-gas flow of hot gases of oxidation of NH3as explained in the figure 2. It is a special advantage, because DeN2O-reactor in the process of production of HNO3you do not need to submit additional heat in the form of steam or electric h is water.
The advantages of the proposed catalyst are also evident at the start and the end of production of HNO3.
Its minimal sensitivity to water provides not only stable over a long period of time, the decomposition of N2O also of N2O-containing gases at operating temperature, i.e. at temperatures between 250-650°With, but also allow you to download the catalyst also at lower temperatures, below the working temperature, water-containing exhaust gas, which occurs when starting and stopping the production of HNO3without his deaktivirovana.
While the operating pressure of the device slowly increases or decreases, but without feed and oxidation of ammonia. Therefore, there is no heat of reaction to heat DeN2O-reactor.
The proposed method thus provides effective reduction of N2O in the production of HNO3without much needed to reduce N2O events, such as pre-heating to the working temperature or flushing with dry air when you start or stop production.
The present invention relates further to a method for producing the above-described catalyst, which contains at least one oxide compound of cobalt and at least one oxide compound of magnesium for FS is the supply of N 2O in N2O-containing gas, characterized in that the receiving catalyst comprises dry mixing the oxide compounds of cobalt and oxide compounds of magnesium or their respective predecessors, who by effects of temperature is transferred to the oxide compounds, and the subsequent compaction of granular mixtures in the absence of water, so that the resulting catalyst has a desired bulk density is preferably in the range from 0.5 to 2.5 g/cm3in particular from 1 to 2 g/cm3in the calculation of the individual grains of the catalyst.
The proposed method for the preparation of catalysts on an industrial scale, in particular the mixing of the components and the seal or molding the mixture, provides long-lasting activity of the decomposition of N2O also in the water-containing waste gas of the nitric acid production, which, in particular, is important when starting and stopping production.
To obtain the proposed catalyst is used compounds of cobalt, in which at least 30%, preferably more than 50%of the Co atoms are chemically III-valent state, but also such compounds, which in the course of obtaining and/or use of the catalyst, for example by heat treatment in an oxygen-containing atmosphere, transformed into compounds of cobalt, which contain such share III-Valentinov the cobalt.
Obtaining Co - and Mg-components implement special methods known to the expert (see, for example, G.ErtI, .Knoezinger, J.Weitkamp: Handbook of Heterogeneous Catalysis, Vol.1, Chap.2, VCH Weinheim (1997)). This is the typical methods of deposition from solutions of salts containing ions With or Mg, of which the deposition is carried out by adding the main precipitating reagents. But in the scope of the invention includes obtaining a solid-phase reaction or a simple decomposition of the corresponding starting compounds, as well as obtaining flame hydrolysis or flame pyrolysis.
To obtain catalysts of the original components can also be recycled not in oxide form. So, can be directly processed relevant source materials, such as carbonates, hydroxides, hydrates, oxides, nitrates or acetates of Mg or. The obtained molded product then at the final stage of heat treatment thermostatic at temperatures in the range from 200 to 700°C, preferably from 400 to 600°and thus transferred to the oxide state.
To achieve the described properties upon receipt of the catalyst in each case, pay attention to the fact that the components of the proposed catalyst, i.e. an oxide compound of cobalt, on the one hand, and an oxide compound of magnesium, on the other hand, are separated from each other at p is slichnih chemical compounds that is to take place phase. For the decomposition of N2O phase contained in the composite must be flexible and available for gas space containing N2O. one phase may not cover or block the other, as is the case when the active component supported on a carrier, for example MgO, for example, by deposition or impregnation or mixing. In the case of the proposed catalyst we are talking about a large volume of catalyst. The presence of both active components (oxidic compounds of cobalt and oxide compounds of magnesium) is an essential for the activity of the catalyst.
Proven special preference of the offered technology of preparation of the catalyst for the development of synergistic action of both components of the catalyst and to reduce the sensitivity of the catalyst to water.
In particular, this has implications for the use as oxide compounds of magnesium MgO. MgO has primarily with high specific surface, which is preferable for catalytic purposes, pronounced tendency to hydration. The reaction of MgO with H2O that occurs according to the equation : MgO+H2O→Mg(OH)2on the surface of MgO, is connected with increase of volume, which on its part can lead to blocking of the pores of the catalyst, i.e. to decrease kataliticheski the th activity to mechanical destruction of the grains of the catalyst. Condensation of water on the catalyst surface, which depending on the porosity and size distribution of pores of the catalyst due to capillary condensation can occur at temperatures well above the dew point of the gas phase, enhances the effect.
This is, in particular, when obtaining a catalyst that is a mixture of oxide compounds of cobalt and MgO and subsequent curing and molding produced with the addition of water. In this case, the magnesium oxide in the processing of partially dissolved in water and placed in a finely powdered form on the surface of the cobalt component. Hydration of such dispersed MgO, which compared with crystalline MgO, where MgO relate atomic structure of larger size, is greatly facilitated, blocks the availability of the cobalt component and results in a higher sensitivity of the catalyst to water.
In the case of the thus obtained catalysts require special care and special precautions for use in water-containing exhaust gas.
Getting a classic way of making ceramics or/and molding, which typically involve mixing the components with the addition of water and subsequent water plasticization and molding by extrusion and industrial production, the catalyst is in are widely used for purification of exhaust gases, leads to catalysts, which are only conditionally applicable for use in the manufacture of nitric acid.
Therefore, when proposed, in particular in pre/industrial, the method of producing oxide catalyst compounds of cobalt and magnesium are mixed dry in the form of powders. The subsequent compaction of the mixture and molding the molded grain of the desired geometry are also carried out in the absence of water.
The mixing and compaction or molding the mixture is usually produced with the addition of appropriate excipients, such as binders or auxiliary agents pressing, which are known to the expert and which, when thermal load on the catalyst, for example at annealing added excipients or use of the catalyst will not release water or release only the amount of water that is not happening condensation of this water in the catalyst, as, for example, graphite or talc.
Received offer by way catalysts typically have a pore volume in the range from 0.1 to 0.8 ml/g, preferably from 0.2 to 0.65 ml/year
As molded products valid all types of normal geometry catalysts, preferably cylindrical molded grains, such as hollow cylinders, but also a star particle, three-bladed, etc. that sravnenie is their volume have a high geometric surface.
For dry compaction and molding can be involved in various ways that are known to the specialist. The preferred method is to dry the pressed with the plunger and the matrix, but in the scope of the invention includes a seal, for example, roller compactor with subsequent destruction and sort of compacted materials. Equally dry extrusion, for example, through a gear wheel or roller press. Especially preferable for industrial production using automatic presses.
The necessary pressure for sealing or molding is determined by the used aggregates, form oxide compounds cobalt and magnesium, added auxiliary substances, as well as the desired density or hardness of the grains of the catalyst. According to the invention preferably this seal, so that the finished catalyst had a bulk density of 0.5 to 2.5 g/cm3in particular from 1 to 2 g/cm3to separate the catalyst grain.
Obtained by the process according to the invention, for example, a cylindrical molded catalyst grain usually has a radial density compression in the range of from 0.5 to 10 MPa.
Very high compaction usually leads to increased strength of the grains of the catalyst, however, complicates the availability of individual components of the composite C is rnah catalyst. The proposed catalyst so in individual cases should be particularly effective due to the high open porosity, which ensures that the individual components of the composite for N2O-containing gases. Total pore volume of the catalyst should be in the range from 0.1 to 0.8 ml/g, in particular in the range from 0.20 to 0.65 ml/year
In the scope of the invention is also possible pre-compaction of the catalyst components, which is necessary, for example, to produce a free flowing powder with the purpose of the automated filling of the pressing device. In the scope of the invention is particularly applicable separate mixing and granulation by spraying, on the one hand, the oxidized compounds of cobalt and, on the other hand, the oxidized compounds of magnesium or their respective parent compounds. Equally they can be carried out with the addition of appropriate excipients, such as binders, plasticizers or diluents, which are known to the expert.
Joint preliminary seal oxide compounds cobalt and an oxide of magnesium compounds is also in the scope of the invention, and in this case it must be ensured the absence of water. Joint water mixing and granulation of the starting components, in particular, when using MgO is not applicable is to obtain water resistant catalysts.
Temperature control, for example, annealing of added excipients or to transfer processed as starting compounds cobalt and magnesium into the corresponding oxides is also an integral part of the proposed preparation of catalysts. Preferably, the temperature control is performed as the final stage of preparation of the catalyst after molding at temperatures in the range from 200 to 700°C, preferably in the range from 400 to 600°C.
The choice of temperature potential temperature carried out in such a way as not to cause significant harm to the activity of the catalyst during the subsequent operating temperature. Normally, when the temperature selection pay attention to the fact that in the dry pressed material have been considered there was little or no sintering processes, which lead to the formation of dry ceramic moulds.
The invention is illustrated by the following examples.
Getting a cobalt component
An aqueous solution of cobalt acetate was mixed with excess sodium lye. The resulting precipitate was filtered, washed and dried. After grinding the dried product was followed by kneading it with the addition of the corresponding auxiliary substances (solvents, stabilizers). Drying by spraying Messi received a granulate with an average particle size of 50 μm and a bulk density of 0.9 g/cm 3.
Obtaining magnesium component
Magnesium carbonate by multi-stage calcination was converted into magnesium oxide and then stirred with the addition of appropriate auxiliary substances (solvents, stabilizers). Granulation by spraying the mixture obtained granulate with an average particle size of 3 μm and a bulk density of 0.6 g/cm3.
The mixture of components
Obtained by the above methods, the source components are mixed in dry form with the addition of graphite in such proportions that after subsequent heat treatment, the mass ratio of the resulting oxides of Co3O4/MgO=3/7.
Pressing and heat treatment of the mixture
The mixture was then extruded on an automatic press in the cylindrical molded with a grain size of d=3.5 mm and h=2,6 mm
Was followed by a final heat treatment of the obtained molded grains in air at 600°annealing added auxiliary substances and for the conversion of the cobalt component in the Co3O4.
The achieved compaction (bulk density) was 1.4 g/cm3when the total pore volume 390 cm3/, the Radial compressive strength of the catalyst particles was 1.4 MPa.
The content of cobalt, expressed in mass% on the total weight of the catalyst, was 21%.
The use of such catalyst
The trial is brezec for measurement in the laboratory reactor was obtained according to the above method for producing grains of the catalyst. The sample is then brought into a heated flow reactor made of quartz glass and filled exhaust gas, which is typical for exhaust gas of the nitric acid production after the reduction of NOx. The exhaust gas had the following composition: 2000 obnm N2O, 2,5 vol.% About2, 0,5% vol. H2O, N2.
The content of N2O was measured at the inlet to the reactor and at the exit of the reactor by means of infrared spectroscopy with Fourier transform.
Vhsv was 10000 h-1per bulk volume of catalyst 16 cm3.
In these conditions at 300°reached 55%decomposition of N2O. At 400°With>99% arriving in reactor N2O was decomposed in N2and O2.
1. The method of decomposition of N2O during the manufacture of nitric acid by contacting N2O-containing flue gas leaving the absorber column with a catalyst that contains at least one oxide compound of cobalt and at least one oxide compound of magnesium in such conditions that ensure the transformation of N2O in gaseous nitrogen and oxygen, the content of oxide compounds of cobalt is in the range from 0.1 to 50%, and the content of the oxide of magnesium compounds in the range of from 50 to 99.9% based on the total weight of the catalyst and at least 30% contained in the catalyst of the Co atoms are trivalent.
2. The method according to claim 1, characterized in that at least one of the contained in the catalyst compounds of cobalt has the structure of a perovskite or spinel.
3. The method according to claim 1, characterized in that the transmission of gas over the catalyst is carried out at flow rate from 2000 to 200000. h-1.
4. The method according to claim 1, characterized in that the pressure by passing the gas over the catalyst is in the range from 4 to 12 bar.
5. The method according to claim 1, characterized in that when the direction of the exhaust gas in an expansion turbine catalyst placed in the reactor off-gas flow in the direction of the process before the expansion turbine.
6. The method according to claim 5, characterized in that the exhaust gas lower content of NOxon stage DeNOxand the catalyst is placed upstream from the expansion turbine and after DeNOxstage.
7. The method according to claim 1, characterized in that N2O-containing gas is passed over the catalyst at temperatures in the range from 250 to 650°C.
8. The method according to claim 1, characterized in that for setting the operating temperature of the reactor using heat of oxidation of NH3by heat entering the reactor off-gas flow from hot process gases oxidation of NH3.
9. The way is about to claim 1, characterized in, that is, the decomposition of N2O to N2and O2at least 80%.
10. The catalyst for the decomposition of N2O, consisting mainly of at least one of the oxide compounds of magnesium and at least one of the oxide compounds of cobalt, and the content of oxide compounds of cobalt is in the range from 0.1 to 50%, and the content of the oxide of magnesium compounds in the range of from 50 to 99.9% based on the total weight of the catalyst and at least 30% contained in the catalyst of the Co atoms are trivalent.
11. The catalyst according to claim 10, characterized in that the catalyst has a bulk density in the range from 0.5 to 2.5 g/cm3in the calculation of the individual grains of the catalyst.
12. The catalyst according to claim 10, characterized in that the oxidic compounds of cobalt and oxide compounds of magnesium are presented in separate phases.
13. The catalyst according to claim 10, characterized in that the pore volume of the catalyst is in the range from 0.1 to 0.8 ml/year
14. The catalyst according to claim 10, characterized in that at least 50% is contained in the catalyst of the Co atoms are in III-valent state.
15. The catalyst according to claim 10, characterized in that at least one of the contained in the catalyst compounds of cobalt has the structure of a perovskite or spinel.
16. The catalyst according to claim 10, distinguish who I am, the catalyst has a specific surface area in the range from 5 to 150 m2/year
17. The catalyst according to claim 10, characterized in that the catalyst is cylindrical molded grain and has a radial compressive strength in the range of from 0.5 to 10 MPa.
18. A method of producing a catalyst containing at least one oxide compound of magnesium and at least one oxide compound of cobalt, and the content of oxide compounds of cobalt is in the range from 0.1 to 50%, and the content of the oxide of magnesium compounds in the range of from 50 to 99.9% based on the total weight of the catalyst and at least 30% contained in the catalyst of the Co atoms are trivalent, and oxide compounds of cobalt and oxide compounds of magnesium or related predecessors that the temperature control is transferred to the oxide compounds are mixed together in dry form to obtain a free-flowing mixture and dry mixture in the absence of water condense to obtain a molded grains of the desired bulk density.
19. The method of producing catalyst p, characterized in that the oxidic compounds of magnesium and/or oxide compounds of cobalt, and/or respective predecessors that the temperature control is transferred to the oxide compounds, before the dry seal translate separate mixing is or granulation by spraying in bulk powder which is suitable for the automatic filling of the sealing device.
20. The method of producing catalyst p, characterized in that the molded grain is subjected to heat treatment at temperatures in the range from 200 to 700°C.
FIELD: industrial organic synthesis.
SUBSTANCE: invention relates to preparation of hydroxylamine sulfate used in caprolactam production. Process consists in catalytic steam-oxygen oxidation of ammonia and synthesis of hydroxylamine sulfate both carried out under elevated pressure (above 0.25 MPa), pressure in the steam-oxygen oxidation stage being higher than then in hydroxylamine sulfate synthesis stage by a value equal to aerodynamic resistance of equipment and pipelines installed between the two stages. Nitrose gas obtained after steam-oxygen oxidation stage is concentrated by condensing water vapors and freed of nitrogen dioxide, after which mixed with hydrogen for synthesis of hydroxylamine sulfate in dilute sulfuric acid solution. Nitric acid concentrate with 7-8.5% nitric acid releasing during concentration of nitrose gas is subjected to liquid-phase hydrogenation on platinum catalyst. Thus obtained pure nitrogen dioxide in mixture with hydrogen is sent to hydroxylamine sulfate synthesis stage and hydrogenation product containing up to 0.45% nitric acid is used to dilute concentrated sulfuric acid thereby providing wasteless technology.
EFFECT: simplified process flowsheet and automated process control, and reduced investment expenses of ammonia oxidation stage (by 65-70%).
3 cl, 2 dwg, 1 tbl
FIELD: industrial inorganic synthesis.
SUBSTANCE: invention relates to preparation of hydroxylamine sulfate used in caprolactam production. Process consists in the steam-oxygen conversion of ammonia, stabilization of resulting nitrose gas by hydrogenation of excess oxygen, two-step condensation of steam in the nitrose gas concentration process, liquid-phase hydrogenation of nitric acid condensate from the second-step nitrose gas concentration process to produce pure nitrogen monoxide (mixed then with main nitrose gas stream) and hydrogenated condensate with platinum dissolved therein, after which follows direct hydroxylamine sulfate synthesis in 19% sulfuric acid medium. To produce 19% sulfuric acid, concentrated sulfuric acid is subjected to two-step dilution: it is first mixed with condensate from the second-step nitrose gas concentration process and desalted water to 21.1-22.3% concentration and purified on activated carbon in presence of oxygen and then mixed with product of hydrogenation of the second-step condensate hydrogenation process to obtain 19% acid used in the hydroxylamine sulfate synthesis stage. As a result, platinum dissolved in the second-step condensate hydrogenation process is precipitates in reductive medium on the hydroxylamine sulfate synthesis platinum catalyst and recycled into the process thereby providing wasteless technology.
EFFECT: considerably reduced process losses.
FIELD: industrial inorganic synthesis.
SUBSTANCE: invention is directed to manufacturing very hard thermo- and chemically stable products. In particular, ferrosilicium with 50-95% Si is ground to particle size not greater than 0.1 mm and then mixed with silicon nitride and/or with ammonium chloride, and/or group II metal fluoride, and/or partial ferrosilicium combustion product containing 50-90% silicon nitride, 30-50% iron silicides, 4-16% iron, and up to 5% silicon. When ammonium chloride and group II metal fluoride are used together with each other their ratio will be (1-3):(3-1), respectively. Resulting mix is ground to particle size not greater than 0.1 mm. Powder is placed into reactor, which is filled with nitrogen to pressure 1 to 20 MPa. Burning reaction is the locally initiated and, at the end of it, nitrogen pressure is lowered to 0.1-20 MPa and diazotation reaction is conducted for 0.1-0.5 h. Cooled product is disintegrated and subjected to magnet separation for 0.5-1.0 h to separate iron, after which dissolved in 15-30% HCl. Undissolved precipitate is separated, washed, and dried. Silicon nitride thus obtained represents β-Si3N4 or mixture of α- and β-Si3N4 with 39.0-39.5% nitrogen and not more than 0.03% iron impurities.
EFFECT: enhanced process efficiency.
13 cl, 1 tbl
FIELD: chemical technology.
SUBSTANCE: invention relates to a method for preparing hydroxylamine aqueous solutions, to methods for its preparing by neutralization of its salts and the following isolation of indicated solutions. Method for preparing hydroxylamine an aqueous solution is carried out by neutralization of hydroxyl ammonium with a base in aqueous medium followed by isolation of hydroxylamine aqueous solution. Firstly, equipment used for carrying out the process is treated with 1-3% aqueous solution of alkyl-substituted phosphonic acid and/or its salt for 0.5-1 h. Alkyl-substituted phosphonic acid and/or its salts taken in the amount 0.01-0.1% of hydroxyl ammonium sulfate mass is added to the parent hydroxyl ammonium sulfate solution feeding to neutralization stage, and alkyl-substituted phenol taken in the amount 0.01-0.3% of hydroxylamine mass is added to the flow feeding to the isolation stage. Oxyethylidene diphosphonic acid (1-hydroxyethane-1,1-diphosphonic acid) and/or its salts, for example, sodium salt is used preferably as alkyl-substituted phosphonic acid. Sodium sulfate precipitate removing from neutralization stage is washed out with water and prepared liquid phase is returned to flow feeding to neutralization stage. Method can be carried out in equipment made of stainless. As result of carrying out the method colorless and stable in storage hydroxylamine an aqueous solution is prepared being without using the additional addition of stabilizing agents. Analysis showed absence of ions SO4 2-. Atomic-absorption analysis showed that mass part of iron ions is 1.2 x 10-6% that allows using the end product in electronic industry.
EFFECT: improved method for preparing.
3 cl, 7 ex
FIELD: inorganic chemistry, chemical technology.
SUBSTANCE: invention relates to a method for preparing nitrogen trifluoride of the formula NF3. Method for preparing nitrogen trifluoride is carried out from elemental fluorine and ammonia in melt medium of ammonium salts acid fluorides of the general formula: NH4H1-xFx wherein x = 2.0-3.0 at temperature 120-160°C and under pressure 0.1-0.55 MPa. Synthesis of nitrogen trifluoride is carried out for two successive stages - amination reaction of acid ammonium bifluoride melt to the complete binding gaseous ammonia followed by fluorination reaction of acid ammonium bifluoride. Both stages are carried out in structurally separated zones. Invention provides enhancing specific output of the reaction volume and safety of the process. Nitrogen trifluoride is used in many branches of chemical and electronic industry, namely: in chemical industry as fluorinating agents, as oxidants of high-caloric fuels in rocket technique, in electronic industry: for treatment of chambers for chemical and vapor-phase precipitation, for dry etching large integral schemes and so on.
EFFECT: improved method for preparing.
3 tbl, 3 dwg, 3 ex
FIELD: inorganic chemistry, chemical technology, chemical industry.
SUBSTANCE: method involves preparing a mixture containing metal oxide for nitriding, metal powder for nitriding and alkaline metal azide. As nitriding metal Nb, Ti, Zr and Hf can be used, and sodium azide can be used as alkaline metal azide. Samples are molded from the prepared mixture and placed into reactor, subjected to vacuum effect, washed out with nitrogen, filled with nitrogen to required pressure and ignited by tungsten spiral. Product obtained after combustion is decomposed and metal nitride powder is prepared. The yield of metal nitride is 96%, not less, with nitrogen content 7.17%, not less. Residual nitrogen is absent. Invention can be used in making heat-resistant, resistant to wear, resistant to erosion and chemically resistant articles.
EFFECT: improved method for preparing.
FIELD: industrial inorganic synthesis.
SUBSTANCE: invention relates to production of nitrogen trifluoride used in chemical industry as fluorination agent and fluorine-containing raw material as well as oxidant for high-calorific fuels, as component of working media in high-emission power lasers, etc. Process consists in electrolysis of hydrogen fluoride solutions of ammonium fluoride in electrolysis cells with carbon anodes, including dehydration and basic electrolysis processes and replacement of consumed substances during electrolysis. Dehydration electrolysis is started at cell voltage 3.0 v and conducted while lowering anodic current density to 0.005 A/cm2 to produce anodic gas with volume fraction of nitrogen trifluoride no higher than 0.05%. Basic electrolysis is conducted while raising anodic current density to 0.1 A/cm2.
EFFECT: reduced formation of tetrafluoromethane in basic electrolysis and lowered power consumption of electrochemical nitrogen trifluoride synthesis process.
2 cl, 1 tbl, 3 ex
FIELD: methods of forming nitrogen-controllable atmospheres used for heat treatment of metals; metallurgy and mechanical engineering.
SUBSTANCE: proposed method includes incomplete combustion of hydrocarbon fuel, adsorption cleaning of combustion products from carbon dioxide at closed system of restoration of absorbent properties and adsorption cleaning from moisture vapor. Then regeneration and cooling of adsorbent are performed by blowing with hot and cold gas-shielded atmospheres, respectively. Mixture of hydrocarbon gas and commercial nitrogen is additionally delivered to combustion chamber. Commercial nitrogen is delivered is the amount of 20-40% of volume of controllable atmosphere. Hydrocarbon gas is delivered in the amount of 4-7% of initial volume of hydrocarbon fuel.
EFFECT: low cost of process; increased productivity; reduced specific consumption of hydrocarbon fuel.
1 tbl, 3 ex
FIELD: chemical industry; modernization of installations of nitric acid production according to a combined scheme.
SUBSTANCE: the invention is pertaining to the field of chemical industry, in particular, to the method of modernization of installations of nitric acid production. The method of modernizing of installation of production of the nitric acid providing for oxidation of ammonia with the help of air under a rarefaction, compression of the cooled nitrous gases in a nitrose supercharger, an absorption of nitric oxides in a tower absorber under pressure of 3.5-4.0 kg / cm2, expansion of the waste tail gases in the turbo-expander, consists in the fact that they increase the pressure of the nitrous gases at the inlet of the supercharger in the range from rarefaction up to the pressure of 1.02-1.05 kg / cm2, by installing a new or an additional gas blowers on the lines of the ammonia - air mixture or the nitrous gases or by decrease of hydraulic resistance of apparatuses and devices of pipelines at absorption inlet of the nitrose supercharger. At a pressure increase at the inlet of absorption of the nitrose gasses supercharger by decrease of the hydraulic resistance of the apparatuses and pipelines before absorption of the nitrose supercharger the increase of productivity of the installation will be much lower (~ up to 8 %). The method ensures an increase of productivity of the installation using the existing equipment at addition of small investments, which pay off less than for 1 year (from 0.6 up to 0.8 of a year) due to decrease of specific consumptions of raw material and power and a significant decrease of the conditionally-permanent expenses. Simultaneously the method allows to increase concentration of nitric acid and a degree of absorption, that may achieve its maximum at addition of pressure systems.
EFFECT: the invention ensures increased productivity of the installation at addition of small investments, which pay off less than for 1 year.
6 dwg, 1 ex
FIELD: initiating ammonia conversion reaction.
SUBSTANCE: proposed method is performed on reticular platinoid catalyst by passing the ammonia-containing gas mixture and oxygen-containing gas through it; local sections of catalyst surfaces are periodically heated to reaction initiating temperature by means of linear electric heating elements located directly on catalyst surface. Equivalent diameters of local sections of catalyst surface are selected between 1-5 of magnitude of external equivalent diameter of separate electric heating element; linear electric heating elements are connected to electric power source at duty factor from 20 to 1 s. Used as material for reticular platinoid catalyst are the following alloys: Pt-81, Pd-15, Rh-3.5 and Ru-0.5 mass-%; Pt-92,5, Pd -4.0 and Rh -3.5 mass-%; Pt-95 and Rh-5 mass-%; Pt-92.5 and Rh-7.5 mass-%. Initiating the ammonia conversion reaction by this method is performed in reactors for production of nitric and hydrocyanic acids and hydroxylamine sulfate.
EFFECT: reduction of time required for reaction over entire surface of catalyst; reduction of explosion danger.
2 cl, 10 ex
FIELD: catalyst manufacture technology.
SUBSTANCE: invention relates to carbon monoxide-water steam conversion to form nitrogen-hydrogen mixture that can be used in ammonia synthesis. Preparation of catalyst comprises precipitation of iron hydroxide from iron nitrate solution with ammonia-containing precipitator, washing of iron hydroxide to remove nitrate ions, mixing with copper compound, granulation, and drying and calcination of granules. Invention is characterized by that iron hydroxide is mixed with copper and calcium oxides at molar ratio Fe2O3/CuO/CaO = 1:(0.03-0.2):(1.0-2.0), after which mechanical activation is performed. Resulting catalyst is 1.8-2.0-fold stronger and by 11.0-15.4% more active than prototype catalyst.
EFFECT: increased strength and catalytic activity.
1 tbl, 3 ex
FIELD: chemical industry.
SUBSTANCE: the invention is pertinent to the field of chemical industry, in particular to production of a catalysts and processes of oxidation of ammonia in production of a weak nitric acid. The invention offers an ammonia conversion catalyst on the basis of the mixture of oxides of unitized structure and a method oxidation of ammonia in production of weak nitric acid. The catalyst represents a mixture of oxides of the over-all formula (AxByO3Z)k (MmOn)f, (NwPgvOv)r where: A - cation of Ca, Sr, Ba, Mg, Be, Ln or their mixtures; B - cations of Mn, Fe, Ni, Co, Cr, Cu, V, A1 or their mixtures; x=0-2, y=1-2, z=0.8-l.7; M - A1, Si, Zr, Cr, Ln, Mn, Fe, Co, Cu, V, Ca, Sr, Ba, Mg, Be or their mixtures; m=l-3, n=l-2; N - Ti, Al, Si, Zr, Ca, Mg, Ln, W, Mo or their mixtures, P - phosphorus, O - oxygen; w=0-2, g=0-2, v=l-3; k, f and r - mass %, at a ratio (k+f)/r=0-l, f/r=0-l, k/f = 0-100. The catalyst is intended for use in a composition of a two-stage catalytic system generated by different methods, also in a set with the trapping platinoid screens and-or inert nozzles. The technical result ensures activity, selectivity and stability of the catalyst to thermocycles at its use in two-stage catalytic system with a decreased loading of platinoid screens.
EFFECT: the invention ensures high activity, selectivity and stability of the catalyst to thermocycles at its use in two-stage catalytic system with a decreased loading of platinoid screens.
8 cl, 1 tbl, 5 ex
FIELD: petrochemical processes catalysts.
SUBSTANCE: fischer-Tropsch process catalyst constituted by cobalt deposited on granulated halumine may further contain promoters selected from oxides ZrO2 and HfO2 and metals Ru, Pd, and Pt.
EFFECT: increased selectivity and productivity.
2 cl, 3 tbl, 2 ex