RU2477177C2 - Method of preparing catalyst for decomposing nitrous oxide and process of decontaminating gas emissions containing nitrous oxide - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of decontaminating nitrous oxide, including low-concentration emissions of nitrous oxide, for example in exhaust gases from production of nitric acid, using a catalyst based on an iron-containing zeolite. Described is a method of preparing a catalyst for decomposing nitrous oxide by mixing a zeolite having a structure selected from the following: MFI, MEL, BEA, FER, MOR and having the composition: y·El₂O_n·SiO₂, where y = 10^-5-5·10^-2 , El is at least aluminium and one element from periods 2, 3, 4 and 5 of the periodic table of elements, n is valence of the element, with iron-modified binder, the binder being aluminium oxide with additives selected from the following oxides: silicon oxide, titanium oxide, zirconium oxide, iron oxide, cobalt oxide, copper oxide, lanthanum oxide, phosphorus oxide, with weight ratio of aluminium oxide to any of the listed oxides ranging from 0.01:100 to 10:100, with weight ratio of the zeolite to binder ranging from 1:9 to 9:1, where the modifying iron in the catalyst is x·Fe₂O₃, where x=10^-5-5·10^-2; modification is carried out by adding to the binder a dry or hydrated salt and/or solution of an iron salt with subsequent formation and activation of the catalyst to obtain a catalyst, wherein at least 0.5-50% of the contained iron and not less than 5·10¹⁷ iron atoms per gram catalyst are in reduced form in the form of special complexes of α-centres which are detectable and measurable using a special technique, involving determination of the amount of surface oxygen deposited from nitrous oxide at temperature of 100-300°C on the surface of the catalyst. A method of decontaminating gaseous emissions is also described.

EFFECT: simple method of producing a highly efficient catalyst for decomposing nitrous oxide.

6 cl, 1 tbl, 19 ex

Description

The invention relates to a method for neutralizing nitrous oxide, including low-concentration nitrous oxide emissions, for example, in exhaust gases from nitric acid production using an iron-based zeolite catalyst. Among the numerous catalysts suitable for the reduction and decomposition of nitrous oxide (F. Kapteijn, J. Rodriguez-Mirasol, JAMoulijn, Appl. Catal. B: Env. 9 (1996) 25-64), pentasil type zeolites ( structures MFI, MEL, BEA). Unlike zeolites containing other transition metals (Co, Cu, etc.), the activity of iron-containing zeolites is not inhibited, but rather increases in the presence of appreciable amounts of nitric oxide (II). This is an important advantage, since the exhaust gases of nitrogen production, as a rule, contain various nitrogen oxides, including nitric oxide (II). The activity of the catalyst is known to depend on the method of introducing iron into the zeolite (J. Perez-Ramirez, F. Kapteijn, K. Schoffel, J. Moulijn, Appl. Catal. B: Env. 44 (2003) 117-151). Moreover, for the introduction of iron into zeolite, a wide variety of methods are used.

Kapteijn et al. (F. Kapteijn, J. Rodriguez-Mirasol, JAMoulijn, J. Catal. 167 (1997) 256-265) studied nitrous oxide decomposition catalysts based on iron-containing zeolites obtained by ion exchange in aqueous solutions of salts gland. The use of this method is associated with the presence of a large amount of wastewater, loss of zeolite during the multi-stage process of ion exchange. Ion exchange is the basic method of zeolite modification for the synthesis of nitrous oxide decomposition catalysts based on the Beta, MFI, MEL, FER, and MOR modified noble and transition metal zeolites described in a number of patents (US 5171553, 1991; US 2008/0044334 A1). The ion exchange method is also used for the synthesis of the Fe-FER catalyst (US 6682710), which is highly active in the decomposition of nitrous oxide in the presence of NO, water and oxygen. In patents RU 2071817, B01D 53/86, 01.20.97; 2297278, B01J 29/46, 04/20/07, zeolites are described in which iron is introduced in another way: by adding an iron salt at the stage of hydrothermal synthesis. This method has its technological disadvantages: it is poorly reproducible and does not allow the use of ready-made commercial zeolites of aluminosilicate composition (iron content at the level of 0.05-0.1 wt.%) For the production of a molded catalyst.

Method for applying iron by precipitation (sublimation) of a volatile salt of iron from the gas phase (the so-called CVD method, HYChen, WMSachtler, Catal. Today 42 (1998) 73; HYChen, WMSachtler, Catal. Lett. 50 (1998) 125; PKRoy, GDPirngruber, J. Catal. 227 (2004) 164) is used mainly for preparatory and research purposes, as it requires special equipment for dosing the volatile iron salt. Mainly for this purpose, iron chlorides are used, which have an extremely high corrosion activity. When applying iron by the CVD method, special precautions are required to prevent the deposition (sublimation) of the iron salt outside the zeolite surface, for example, on the walls of the reactor. The most technologically advanced method today is solid-state ion exchange (M. Rauscher, K. Kesore, R. Mönnig, W. Schwieger, A. Tißler, T. Turek., Appl. Catal. 184 (1999) 249; application EP 0955080; US 2003/0143141 A1). Its disadvantage is multi-stage. For its implementation, several stages of processing a mixture of zeolite with an iron salt are necessary: intensive mixing in a ball mill, removing excess iron from the zeolite by washing with water, drying and calcining the zeolite before molding. All these methods, although they make it possible to obtain an active catalyst for the decomposition of nitrous oxide, are quite laborious and multistage.

Closest to the technological essence of the claimed method is the catalyst synthesis method described in US 20100150801 A1, June 17, 2010, in which a silver-containing molded catalyst consisting of 1) Ag-modified porous material, 2) zeolite, is proposed for the selective NO _x hydrocarbon reduction reaction. free of metal and in H-form, and 3) an unmodified binder - pseudoboehmite. In the proposed method, the effect of isolation of zeolite from metal cations is achieved in order to preserve it in the H-form. This method is obviously suitable for catalysts containing such metal cations that readily penetrate and deactivate zeolite channels. For catalysts for the decomposition of nitrous oxide and, consequently, for iron-containing catalysts, this method requires serious changes that would lead to the opposite effect - facilitating the penetration of iron cations into zeolite channels.

All methods of preparing iron-containing catalysts have one peculiarity: despite the fact that it is iron that provides catalytic activity, the activity does not correlate well with the amount of iron introduced. This is due to the fact that the iron in the zeolite can be in a different state: from mononuclear centers in the microporous space of the zeolite to microparticles of the oxide phase on the outer surface. The ratio between the fractions of iron in various states is determined by the method of its introduction and activation of the catalyst (K.A. Dubkov, N.S. Ovanesyan, A.A. Shteinman, E.V. Starokon, G.I. Panov, J. Catal. 207 (2002) 341-352). All these forms exhibit different levels of activity in the decomposition of nitrous oxide. The task is further complicated by the fact that the quantitative assessment of various states of iron, as a rule, is difficult, which makes it impossible to reliably compare them with catalytic activity. In this regard, it is difficult to evaluate in advance the activity of each particular catalyst based only on the amount of iron introduced into it.

The invention solves the problem of developing a simple method for producing a highly efficient catalyst for the decomposition of nitrous oxide.

The problem is solved by the proposed method for preparing a catalyst for the decomposition of nitrous oxide, which is carried out by mixing a zeolite structure selected from the following series: MFI, MEL, BEA, FER, MOR, and having the composition: y · El ₂ O _n · SiO ₂ , where y = 10 ^-5 ÷ 5 · 10 ^-2 , El - at least aluminum and one of the elements 2, 3, 4, 5 of the Periodic table of the elements, n - valency of the element, with a binder modified with iron, aluminum oxide with additives is used as a binder, selected from the series of the following oxides: silicon oxide, titanium oxide, zirconium oxide, oxides d iron, cobalt oxide, copper oxide, lanthanum oxide, phosphorus oxide, in the mass ratio: alumina / any other of the listed oxides, varying from 0.01: 100 to 10: 100, in the mass ratio of zeolite / binder from 1 : 9 to 9: 1, where the modifying iron in the composition of the catalyst corresponds to x · Fe ₂ O ₃ , where x = 10 ^-5 ÷ 5 · 10 ^-2 , the modification is carried out by introducing into the binder a dry or hydrated salt and / or solution of an iron salt with subsequent molding and activation of the catalyst to obtain a catalyst in which, at least f, from 0.5 to 50% of the contained iron and not less than 5 · 10 ¹⁷ iron atoms per gram of catalyst is in reduced form in the form of special complexes - α centers, recorded and measured by a special method, which consists in determining the amount of surface oxygen deposited from nitrous oxide nitrogen at a temperature of from 100 to 300 ° C on the surface of the catalyst.

The amount of oxygen deposited, and therefore the number of α centers, is determined either by desorption of this oxygen with increasing temperature to 350 ° C and above, or by means of low-temperature isotope exchange with oxygen in the gas phase (GIPanov, A.K.Uriarte, M.A. Rodkin, VISobolev, Catal. Today 41 (1998) 365-385). For the manifestation of catalytic activity, the number of these centers should be at least 5 · 10 ¹⁷ atoms per gram of catalyst.

Salts of ferrous and / or ferric iron may be added to the binder.

The activation of the catalyst can be carried out in an environment of dry air and / or water vapor and / or a reducing agent and / or gas-vapor medium containing all of these components.

The element El can be specially added during the synthesis of zeolite (for example, from the second period B; from the third Na, Mg, Al; from the fourth Ca, Fe, Ti; from the fifth Pd) or be present in it as impurities. For example, all commercial zeolites contain impurities of iron, calcium, magnesium and other metals at a level of not less than 0.01 wt.%. This value corresponds to the value y = 6 · 10 ^-4 in the above formula.

The content of α centers in the catalyst is in the range from 5 · 10 ¹⁷ to 1 · 10 ²⁰ centers per gram of catalyst.

The problem is also solved by a method of neutralizing exhaust gases of industrial production from nitrous oxide N ₂ O without the formation of harmful by-products, in which the decomposition of nitrous oxide is carried out on a catalyst prepared as described above. Neutralization is carried out at a temperature of 400-750 ° C and a contact time of 0.1-5.0 s.

The degree of neutralization of industrial exhaust gas from N ₂ O is from 30 to 99.9% at the stated temperatures.

The procedure for molding the catalyst consists in homogenizing with prolonged stirring (20-40 min) a mechanical mixture of zeolite and an iron-modified binder in a mixer with Z-shaped blades, adding the required amount of water to the catalyst mass and extruding the mass through a die of the required diameter.

In contrast to the known multi-stage and costly methods for the synthesis of a nitrous oxide decomposition catalyst based on an iron-containing zeolite, the proposed method is easily feasible. The essence of the method is that iron is introduced at the stage of forming the catalyst and is initially deposited not on the surface of the zeolite, but on the surface of the binder, in particular aluminum oxide compounds, silicon oxides and aluminosilicates of various compositions. For this, the binder is mixed in a mixer-former with the required amount of a solution of ferrous and / or ferric salt until a homogeneous mass is obtained; then zeolite in the H and / or NH ₄ form is added to this mixture, the required amount of water and the mixture are mixed for a time sufficient to obtain a homogeneous plastic mass. The extruded granules are dried and calcined at temperatures of 500-900 ° C in an environment of dry air, nitrous oxide, water vapor or a reducing gas. The method allows to obtain up to 50% of the introduced iron in the composition of α-centers, and the absolute number of such centers can reach 5 · 10 ¹⁹ ÷ 9 · 10 ¹⁹ centers / gram of catalyst. On the catalyst obtained by the claimed method, complete conversion of nitrous oxide is achieved in the moderate temperature region of 400-600 ° C, even in the presence of molecular oxygen and water vapor in the reaction mixture.

It is known that compounds of aluminum (for example, pseudoboehmite) and silicon (aerosil, aluminosilicate), which are traditionally used as binders for the synthesis of catalysts, have a fairly developed external surface from 100 to 400 m ² / g and a high concentration of hydroxyl groups on the surface of the carrier 2 · 10 ¹⁸ ÷ 10 · 10 ¹⁸ groups / m ² (according to Ralph K. Euler "Colloidal chemistry of silica and silicates", M., 1959). We use these properties of the surface of the binder to evenly distribute and fix the hydroxo complexes of iron on the surface of the binder when they are applied, for example, from a salt solution of ferrous and / or ferric iron. The solution of the iron salt can be added to a solution of an inorganic acid (in particular, nitric or hydrochloric), in which it is usually necessary to withstand pseudoboehmite before molding to peptize and impart the necessary rheological properties. Thus, the step of modifying the binder with iron is combined with the step of peptizing the binder. This eliminates the stage of modification of zeolite with iron. The reduction in the number of stages of preparation of the catalyst is an additional advantage of the application of the proposed method for producing a catalyst.

The outer surface of zeolites, as a rule, is 30-70 m ² / g, which is 10 ÷ 20% of the total surface of the zeolite crystal (including the surface of the microporous space). Due to their large diameter, hydrated iron complexes (hydroxocomplexes) do not penetrate into the microporous zeolite space of the claimed structures BEA, MFI, MEL, FER and MOR, but chemically bind mainly to the hydroxyl groups of the outer surface of the zeolite or are physically adsorbed also, mainly on the outer surface. Obviously, the outer surface of the zeolite is able to retain a smaller amount of hydroxocomplexes of iron than the well-developed surface of the binder (100-400 m ² / g). During the heat treatment of the catalyst, iron compounds that are not fixed on the surface pass into oxide phases that are not involved in the formation of α centers active in the decomposition of nitrous oxide. Thus, for nitrous oxide decomposition catalysts containing a relatively large amount of iron (1 ÷ 5 wt.%), The deposition of iron on a binder is preferable in comparison with deposition on a zeolite. The catalyst proposed in the present invention is a mixture of an iron-modified binder with a zeolite (commercial zeolite can be used without special preparation).

When heated from 200 ° C and above, the dehydration of the surface of both the zeolite and the binder occurs. The water formed during this process facilitates the diffusion and redistribution of iron hydroxocomplexes between the surface of the zeolite and the binder, thus ensuring the optimal chemical composition of the surface of the zeolite. The chemistry of the process is similar to the coprecipitation method, but without the use of large volumes of solutions and laborious stages of filtering and washing the catalysts.

Existing methods for introducing iron into zeolite differ in the efficiency of introducing iron into the composition of active centers - α centers. As already noted, one of the advantages of our method is that it allows you to get up to 50% of iron in the composition of α-centers. This occurs due to the occurrence of processes of simultaneous and joint dehydration of the binder surface, the zeolite surface, and iron hydroxocomplexes deposited on the binder during calcination of the catalyst at temperatures of 500-900 ° C. The resulting water and high temperature facilitate the diffusion of iron complexes from the surface of the binder to the zeolite surface and the reduction of iron to the state of Fe ^{+ 2} in the composition of α centers.

Thus, we offer an iron-containing nitrous oxide decomposition catalyst based on zeolites of the MFI, MEL, BEA, FER, MOR structure, containing a high proportion of iron in the composition of active centers - α centers, obtained by the original method, which is distinguished by its simplicity, manufacturability, and efficiency of iron introduction in the composition of active centers. This method allows you to:

1. Completely replace industrially difficult, multi-stage and poorly controlled methods for introducing iron into the zeolite: solid-phase and liquid-phase ion exchange, hydrothermal synthesis in the presence of iron, deposition from the vapor phase, etc., with an easy to use and well reproducible way to add salt iron into the binder.

2. Combine the peptization step of the binder with the step of introducing iron into the catalyst by adding an iron salt to the peptizing acid solution.

3. To apply a sufficiently large amount of iron (1 ÷ 10 wt.%) Uniformly distributed over the surface of the catalyst with a high proportion of it in the reduced state, namely in the composition of α-centers.

The invention is illustrated by the following examples and table. The names of the catalysts in the examples and the table reflect the chemical composition of the calcined catalyst in the form of weight% of the components contained in them: iron oxide, zeolite and oxides that make up the binder.

The examples also show the molar composition of the zeolite used and the active part of the finished molded catalyst without taking into account the binder, where the x and y coefficients in accordance with the claims mean the number of moles of iron oxide and any of the elements El per 1 mol of SiO ₂ in the zeolite.

Example 1

Catalyst 3% Fe ₂ O ₃ - 67% MFI (12) -30% Al ₂ O ₃

The nitrous oxide decomposition catalyst is obtained by molding a synthetic zeolite of structure MFI (Si / Al = 12) with a molar composition of 0.042-Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ in the H form with an iron-modified binder - aluminum hydroxide of pseudoboehmite structure . For this, 16 g of pseudoboehmite is kept in 27 ml of a 0.65 M solution of FeCl ₃ containing 1 ml of concentrated nitric acid for 2 hours at 40 ° C. 30 g of zeolite are added to the resulting mass and mixed in an extruder for 40 minutes. After obtaining the plastic mass, the mixture is extruded through a die of the desired size. The obtained granules are dried in air at room temperature for 12 hours and at 110 ° C for 10 hours and activated in dry air at 800 ° C for 2 hours. The molar composition of the active part of the molded catalyst without taking into account the binder 0.018 · Fe ₂ O ₃ · 0.042 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ .

The process is carried out in a flow reactor, in which 10 g of the obtained catalyst are loaded, a reaction mixture of the composition: 5 mol% N ₂ O in helium is passed through the catalyst bed, the contact time is 2 s. At a temperature of 330 ° C, a complete conversion of nitrous oxide is observed, which persists with increasing temperature up to 800 ° C. The temperature of the half-conversion of nitrous oxide (50% conversion of nitrous oxide) -310 ° C.

Example 2

Catalyst 3% Fe ₂ O ₃ - 67% MFI (47) -30% Al ₂ O ₃

The nitrous oxide decomposition catalyst is obtained by molding a synthetic zeolite of structure MFI (Si / B = 47) with a borosilicate composition and a molar composition of 0.011 · B ₂ O ₃ · 10 ^-5 · Al ₂ O ₃ SiO ₂ (obtained by the method published in Verified Syntheses of Zeolitic Materials, Harry Robson, Editor, Elsevier, 2001, p.203) in the H-form with a modified iron binder - aluminum hydroxide pseudoboehmite structure. For this, 16 g of pseudoboehmite is incubated in 20 ml of a 0.65 M solution of FeCl ₃ containing 1 ml of concentrated nitric acid for 2 hours at 40 ° C. 30 g of zeolite are added to the resulting mass and mixed in an extruder for 40 minutes. After obtaining the plastic mass, the mixture is extruded through a die of the desired size. The granules obtained are dried in air at room temperature for 12 hours and at 110 ° C for 10 hours. The dried granules are activated in a vapor-gas medium (for example, 30 mol% H ₂ O, 5 mol% CO, the rest is air) at 700 ° C for 2 hours. The molar composition of the active part of the molded catalyst without taking into account the binder 0.017 · Fe ₂ O ₃ · 0.011 · B ₂ O ₃ · 10 ^-5 · Al ₂ O ₃ · SiO ₂ .

10 g of the obtained catalyst are loaded into a flow reactor, through the bed of which a reaction mixture of the composition: 5 mol% N ₂ O in helium is passed, the contact time is 2 s. At a temperature of 500 ° C, a complete conversion of nitrous oxide is observed, which persists with increasing temperature up to 800 ° C. The temperature of the half-conversion of nitrous oxide (50% conversion of nitrous oxide) -450 ° C.

Example 3

Catalyst 3% Fe ₂ O ₃ - 67% MFI - 30% Al ₂ O ₃

The nitrous oxide decomposition catalyst is obtained by molding a synthetic zeolite with an MFI structure of aluminotitanosilicate composition (Si / Ti = 75; Si / Al = 80) and a molar composition of 0.013 · TiO ₂ · 0.0063 · Al ₂ O ₃ · SiO ₂ (obtained by the procedure published in Verified Syntheses of Zeolitic Materials, Harry Robson, Editor, Elsevier, 2001, p.209) in the H-form with an iron-modified binder - aluminum hydroxide pseudoboehmite structure. For this, 16 g of pseudoboehmite is maintained for peptization in 20 ml of a 0.65 M solution of FeCl ₃ containing 1 ml of concentrated nitric acid for 2 hours at 40 ° C. 30 g of zeolite are added to the resulting mass and mixed in an extruder for 40 minutes. After obtaining the plastic mass, the mixture is extruded through a die of the desired size. The obtained granules are dried in air at room temperature for 12 hours and at 110 ° C for 10 hours and activated in dry air at 800 ° C for 2 hours. The molar composition of the active part of the molded catalyst without taking into account the binder 0.017 · Fe ₂ O ₃ · 0.013 · TiO ₂ · 0.063 · Al ₂ O ₃ · SiO ₂ .

The process is carried out in a flow reactor, 10 g of the obtained catalyst are loaded, through the bed of which a reaction mixture of the composition: 5 mol% N ₂ O in helium is passed, the contact time is 2 s. At a temperature of 450 ° C, a complete conversion of nitrous oxide is observed, which persists with increasing temperature up to 650 ° C. The temperature of the half-conversion of nitrous oxide (50% conversion of nitrous oxide) is 430 ° C.

Example 4

Catalyst 3% Fe ₂ O ₃ - 67% MEL (50) -30% Al ₂ O ₃

Analogously to example 1, with the difference that a synthetic zeolite of structure MEL (Si / Al = 50) with a molar composition of 0.01 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ in H form also with modified iron binder - aluminum hydroxide pseudoboehmite structure. The dried granules are activated in dry air at 900 ° C for 2 hours. The molar composition of the active part of the molded catalyst without taking into account the binder 0.017 · Fe ₂ O ₃ · 0.01 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ .

10 g of the obtained catalyst are loaded into a flow reactor, through the bed of which a reaction mixture of the composition: 5 mol% N ₂ O in helium is passed, the contact time is 2 s. At a temperature of 340 ° C, a complete conversion of nitrous oxide is observed, which persists with increasing temperature up to 800 ° C. The temperature of the half-conversion of nitrous oxide (50% conversion of nitrous oxide) is 320 ° C.

Example 5

Catalyst 3% Fe ₂ O ₃ - 67% BEA (38) -30% Al ₂ O ₃

Analogously to example 1, with the difference that a synthetic zeolite of structure BEA (Si / Al = 38) with a molar composition of 0.0013 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ in H form also with modified iron binder - aluminum hydroxide pseudoboehmite structure. The dried granules are activated in dry air at 800 ° C for 2 hours. The molar composition of the active part of the molded catalyst without taking into account the binder 0.0017 · Fe ₂ O ₃ · 0.013 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ .

10 g of the obtained catalyst are loaded into a flow reactor, through the bed of which a reaction mixture of the composition: 5 mol% N ₂ O in helium is passed, the contact time is 2 s. At a temperature of 325 ° C, a complete conversion of nitrous oxide is observed, which persists with increasing temperature up to 800 ° C. The temperature of the half-conversion of nitrous oxide (50% conversion of nitrous oxide) is 310 ° C.

Example 6

Catalyst 1.5% Fe ₂ O ₃ - 67.5% FER (38) -31% Al ₂ O ₃

Analogously to example 1, with the difference that for the synthesis of the catalyst using synthetic zeolite structure FER (Si / Al = 38) molar composition 0.013 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ in H-form, and a binder - aluminum hydroxide structure pseudoboehmite - incubated in 20 ml of 0.25 M solution of FeCl ₃ . The dried granules are activated in dry air at 700 ° C for 2 hours. The molar composition of the active part of the molded catalyst excluding the binder 0.0083 · Fe ₂ O ₃ · 0.013Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ .

10 g of the obtained catalyst are loaded into a flow reactor, through the bed of which a reaction mixture of the composition: 5 mol% N ₂ O in helium is passed, the contact time is 2 s. At a temperature of 320 ° C, a complete conversion of nitrous oxide is observed, which persists with increasing temperature up to 800 ° C. The temperature of the half-conversion of nitrous oxide (50% conversion of nitrous oxide) is 300 ° C.

Example 7

Catalyst 6% Fe ₂ O ₃ - 67% MOR-27% Al ₂ O ₃

Analogously to example 1, with the difference that a synthetic zeolite of the MOR structure (Si / Al = 7) with a molar composition of 0.05Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ in H-form is used, and the binder is used aluminum hydroxide pseudoboehmite structure - incubated in 20 ml of a 1 M solution of FeCl ₃ . The dried granules are activated in dry air at 700 ° C for 2 hours. The molar composition of the active part of the molded catalyst excluding the binder 0.036 · Fe ₂ O ₃ · 0.05 · Al ₂ O ₃ · 10 ^-5 NaO · SiO ₂ .

10 g of the obtained catalyst are loaded into a flow reactor, through the bed of which a reaction mixture of the composition: 5 mol% N ₂ O in helium is passed, the contact time is 2 s. At a temperature of 450 ° C, a complete conversion of nitrous oxide is observed, which persists with increasing temperature up to 700 ° C. The temperature of the half-conversion of nitrous oxide (50% conversion of nitrous oxide) is observed at 400 ° C.

Example 8

Catalyst 4% Fe ₂ O ₃ - 67% PdMFI (12) -26% Al ₂ O ₃ -3% SiO ₂

Analogously to example 1, with the difference that before molding the synthetic zeolite of the MFI structure was subjected to ion exchange in a 0.01 M solution of PdCl ₂ salt and was subsequently used in the Pd form having a molar composition: 0.042 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · 0.006 · PdO · SiO ₂ , a mixture of 14 g of pseudoboehmite with 1.4 g of aerosil having a specific surface area of 150 m ² / g was subjected to iron modification. For this, a mixture of pseudoboehmite and Aerosil is kept in 22 ml of a 1 M solution of Fe (NO ₃ ) ₃ containing 1 ml of concentrated nitric acid. After adding the zeolite to the modified binder of the Pd form, mixing and plasticization, the procedure is continued as in Example 1. The dried granules are activated in dry air at 850 ° C for 2 hours. The molar composition of the active part of the molded catalyst excluding the binder 0.024 · Fe ₂ O ₃ 0.042 Al ₂ O ₃ · 10 ^-5 Na ₂ O 0.006 PdO SiO ₂ .

10 g of the obtained catalyst are loaded into a flow reactor, through the bed of which a reaction mixture of the composition: 5 mol% N ₂ O in helium was passed, the contact time is 2 s. At a temperature of 310 ° C, a complete conversion of nitrous oxide is observed, which persists with increasing temperature up to 800 ° C. The temperature of the half-conversion of nitrous oxide (50% conversion of nitrous oxide) is 300 ° C.

Example 9

Catalyst 3% Fe ₂ O ₃ - 10% MFI (12) -77% Al ₂ O ₃ -10% SiO ₂

The catalyst with a reduced zeolite content is obtained analogously to example 1, with the difference that a mixture of 45 g of pseudoboehmite with 5 g of aerosil having a specific surface area of 150 m ² / g is subjected to iron modification. For this, a mixture of pseudoboehmite and Aerosil is kept in 18 ml of a 1 M solution of Fe (NO ₃ ) ₃ containing 5 ml of concentrated nitric acid. After adding 5 g of zeolite, mixing and plasticization, the procedure is continued as in Example 1. The dried granules are activated in dry air at 900 ° C for 1 h. The molar composition of the active part of the molded catalyst excluding the binder 0.12 · Fe ₂ O ₃ · 0.042 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ .

10 g of the obtained catalyst are loaded into the flow reactor, through the bed of which a reaction mixture of the composition: 5 mol% N ₂ O in helium is passed, the contact time is 5 s. At a temperature of 400 ° C, a complete conversion of nitrous oxide is observed, which persists with increasing temperature up to 800 ° C. The temperature of the half-conversion of nitrous oxide (50% conversion of nitrous oxide) is 370 ° C.

Example 10

Catalyst 3% Fe ₂ O ₃ - 80% BEA (38) -17% Al ₂ O ₃

Analogously to example 1, with the difference that 30 g of a synthetic zeolite of structure BEA (Si / Al = 38) of molar composition are used for the synthesis of the catalyst: 0.013 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ in H-form also with a modified iron binder - aluminum hydroxide structure of psvedoboehmite. For modification, 7.5 g of pseudoboehmite and 20.6 ml of a 0.65 M solution of FeCl _{3 are used} . The dried granules are calcined in dry air at 800 ° C for 2 hours. The molar composition of the active part of the molded catalyst excluding the binder 0.014 · Fe ₂ O ₃ · 0.013 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ .

10 g of the obtained catalyst are loaded into a flow reactor, through the bed of which a reaction mixture of the composition: 5 mol% N ₂ O in helium is passed, the contact time is 2 s. At a temperature of 320 ° C, a complete conversion of nitrous oxide is observed, which persists with increasing temperature up to 800 ° C. The temperature of the half-conversion of nitrous oxide (50% conversion of nitrous oxide) is 300 ° C.

Example 11

Catalyst 4% Fe ₂ O ₃ - 67% MFI (12) -15% Al ₂ O ₃ -14% SiO ₂

Analogously to example 1, with the difference that a mixture of 8 g of pseudoboehmite with 6.7 g of aerosil having a specific surface area of 150 m ² / g is subjected to iron modification. For this, a mixture of pseudoboehmite and Aerosil is kept in 22 ml of a 1 M solution of FeCl ₃ containing 1 ml of concentrated nitric acid. After adding MFI zeolite (Si / Al = 12) with a molar composition of 0.042 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ , mixing and plasticization, the procedure is continued as in Example 1. The dried granules are calcined in dry air at 850 ° C for 2 hours. The molar composition of the active part of the molded catalyst without taking into account the binder 0.024 · Fe ₂ O ₃ · 0.042 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ .

10 g of the obtained catalyst are loaded into the flow reactor, through the bed of which a reaction mixture of the composition is passed: 5 mol% N2O in helium, contact time 2 s At a temperature of 310 ° C, a complete conversion of nitrous oxide is observed, which persists with increasing temperature up to 800 ° C. The temperature of the half-conversion of nitrous oxide (50% conversion of nitrous oxide) is 300 ° C.

Example 12

Catalyst 4% Fe ₂ O ₃ - 65% MFI (12) -26% Al ₂ O ₃ -5% TiO ₂

Analogously to example 1, with the difference that a mixture of 14 g of pseudoboehmite with 2.3 g of titanium oxide anatase structure having a specific surface area of 80 m ² / g is subjected to iron modification. For this, a mixture of pseudoboehmite and titanium oxide is kept in 22 ml of a 1 M solution of Fe (NO ₃ ) ₃ containing 1 ml of concentrated nitric acid. After adding MFI zeolite (Si / Al = 12) with a molar composition of 0.042 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ , mixing and plasticization, the procedure is continued as in Example 1. The dried granules are activated in water vapor (50 mol % water in helium) at 650 ° С for 2 h. The molar composition of the active part of the molded catalyst excluding the binder 0.025 · Fe ₂ O ₃ · 0.042 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ .

10 g of the obtained catalyst are loaded into a flow reactor, through the bed of which a reaction mixture of the composition: 5 mol% N ₂ O in helium is passed, the contact time is 1 s. At a temperature of 370 ° C, a complete conversion of nitrous oxide is observed, which persists with increasing temperature up to 700 ° C. The temperature of the half-conversion of nitrous oxide (50% conversion of nitrous oxide) is 340 ° C.

Example 13

Catalyst 4% Fe ₂ O ₃ - 68% MFI (12) -27% Al ₂ O ₃ -1% ZrO ₂

Analogously to example 1, with the difference that a mixture of 14 g of pseudoboehmite with 0.5 g of zirconium oxide obtained by precipitation from a solution of zirconium urea with a specific surface area of 25 m ² / g is subjected to iron modification. For this, a mixture of pseudoboehmite and zirconium oxide is kept in 22 ml of a 1 M solution of Fe (NO ₃ ) ₃ containing 1 ml of concentrated nitric acid. After adding MFI zeolite (Si / Al = 12) with a molar composition of 0.042 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ , mixing and plasticization, the procedure was continued as in Example 1. The dried granules were activated in dry air at 850 ° C for 3 hours. The molar composition of the active part of the molded catalyst without taking into account the binder 0.024 · Fe ₂ O ₃ · 0.042 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ .

10 g of the obtained catalyst are loaded into the flow reactor, through the bed of which a reaction mixture of the composition: 5 mol% N ₂ O in helium is passed, the contact time is 0.5 s. At a temperature of 330 ° C, a complete conversion of nitrous oxide is observed, which persists with increasing temperature up to 700 ° C. The temperature of the half-conversion of nitrous oxide (50% conversion of nitrous oxide) is 310 ° C.

Example 14

Catalyst 4% Fe ₂ O ₃ - 68% MFI (12) -27% Al ₂ O ₃ -1% (CoO + CuO)

Analogously to example 1, with the difference that pseudoboehmite is subjected to modification with iron, cobalt and copper. For this, a mixture of pseudoboehmite is kept in 22 ml of a 1 M solution of Fe (NO ₃ ) ₃ containing 1 ml of concentrated nitric acid, with 2 ml of a 2 M solution of Cu (NO ₃ ) ₂ and 2 ml of a 2 M solution of Co ( NO ₃ ) ₂ . After adding MFI zeolite (Si / Al = 12) with a molar composition of 0.042 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ , mixing and plasticization, the procedure is continued as in Example 1. The dried granules are activated in a medium of 5% hydrogen in argon at 700 ° С for 3 h. The molar composition of the active part of the molded catalyst excluding the binder 0.024 · Fe ₂ O ₃ · 0.042 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ .

10 g of the obtained catalyst are loaded into a flow reactor, through the bed of which a reaction mixture of the composition: 5 mol% N ₂ O in helium is passed, the contact time is 1 s. At a temperature of 400 ° C, a complete conversion of nitrous oxide is observed, which persists with increasing temperature up to 700 ° C.

Example 15

Catalyst 4% Fe ₂ O ₃ - 68% MFI (12) -27% Al ₂ O ₃ -1% La ₂ O ₃

Analogously to example 1, with the difference that pseudoboehmite is subjected to modification with iron and lanthanum. For this, the pseudoboehmite mixture is kept in 22 ml of a 1 M solution of Fe (NO ₃ ) ₃ containing 1 ml of concentrated nitric acid, with the addition of 7 ml of a 0.5 M solution of La (NO ₃ ) ₃ in iron nitrate solution. After adding MFI zeolite (Si / Al = 12) with a molar composition of 0.042 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ , mixing and plasticization, the procedure is continued as in Example 1. The dried granules are activated in dry air at 800 ° C for 3 hours. The molar composition of the active part of the molded catalyst without taking into account the binder 0.024 · Fe ₂ O ₃ · 0.042 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ .

10 g of the obtained catalyst are loaded into a flow reactor, through the bed of which a reaction mixture of the composition: 5 mol% N ₂ O in helium is passed, the contact time is 1 s. At a temperature of 330 ° C, a complete conversion of nitrous oxide is observed, which persists with increasing temperature up to 700 ° C. The temperature of the half-conversion of nitrous oxide (50% conversion of nitrous oxide) is 310 ° C.

Example 16

Catalyst 2% Fe ₂ O ₃ - 67% MFI (12) -26.5% Al ₂ O ₃ -4.5% P ₂ O ₅

The nitrous oxide decomposition catalyst is obtained by molding the zeolite of the MFI structure (Si / Al = 12) in the H-form with a phosphorus-modified binder - aluminum hydroxide of the pseudoboehmite structure. For this, 14 g of pseudoboehmite is maintained for peptization in 20 ml of a 0.65 M solution of FeCl ₃ containing 2 ml of concentrated nitric acid for 2 hours at 40 ° C. To the resulting mass was added 3.7 g (NH ₄ ) ₂ HPO ₄ and 30 g of MFI zeolite (Si / Al = 12) with a molar composition of 0.042 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ and mixed in an extruder within 40 minutes After obtaining the plastic mass, the mixture is extruded through a die of the desired size. The granules obtained are dried in air at room temperature for 12 hours and at 110 ° C for 10 hours and activated in dry air at 700 ° C for 2 hours. The molar composition of the active part of the molded catalyst without taking into account the binder 0.012 · Fe ₂ O ₃ · 0.042 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ .

10 g of the obtained catalyst are loaded into a flow reactor, through the bed of which a reaction mixture of the composition: 5 mol% N ₂ O in helium is passed, the contact time is 2 s. At a temperature of 450 ° C, a complete conversion of nitrous oxide is observed, which persists with increasing temperature up to 800 ° C. The temperature of the half-conversion of nitrous oxide (50% conversion of nitrous oxide) is 400 ° C.

Example 17

Catalyst 2% Fe ₂ O ₃ - 68% MFI (12) -30% Al ₂ O ₃

Analogously to example 1, with the difference that a 0.33 M solution of ferrous iron salt FeCl ₃ with the addition of 2 ml of concentrated nitric acid is used to modify pseudoboehmite. The dried granules are activated in dry air at 850 ° C for 4 hours. The molar composition of the active part of the molded catalyst without taking into account the binder 0.012 · Fe ₂ O ₃ · 0.042 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ .

10 g of the obtained catalyst are loaded into a flow reactor, through the bed of which a reaction mixture of the composition: 5 mol% N ₂ O in helium is passed, the contact time is 2 s. At a temperature of 350 ° C, a complete conversion of nitrous oxide is observed, which persists with increasing temperature up to 800 ° C. The temperature of the half-conversion of nitrous oxide (50% conversion of nitrous oxide) is 330 ° C.

Example 18

Catalyst 1.5% Fe ₂ O ₃ - 68.5% MFI (12) -30% Al ₂ O ₃

Analogously to example 1, with the difference that for the modification of pseudoboehmite, 20 ml of an equally equivalent mixture of 0.33 M solution of ferrous iron salt FeCl ₃ and 0.33 M solution of ferric iron salt FeCl ₃ with the addition of 2 ml of concentrated nitric acid are used. The dried granules are activated in an inert gas at 850 ° C for 4 hours. The molar composition of the active part of the molded catalyst excluding the binder 0.09 · Fe ₂ O ₃ · 0.042 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ .

10 g of the obtained catalyst are loaded into a flow reactor, through the bed of which a reaction mixture of the composition: 5 mol% N ₂ O in helium is passed, the contact time is 2 s. At a temperature of 340 ° C, a complete conversion of nitrous oxide is observed, which persists with increasing temperature up to 800 ° C. The temperature of the half-conversion of nitrous oxide (50% conversion of nitrous oxide) is 325 ° C.

Example 19

Catalyst 3% Fe ₂ O ₃ - 67% MFI-MEL-BEA (38) -30% Al ₂ O ₃

Analogously to example 1, with the difference that a mechanical mixture of zeolites of different structures in a weight ratio of 1: 1: 1 MFI: MEL: BEA (Si / Al = 38) with a molar composition of 0.013 · Al ₂ O ₃ · 10 ^{-5 is used} · Na ₂ O · SiO ₂ in the H-form also with an iron-modified binder - aluminum hydroxide pseudoboehmite structure. The dried granules are activated in dry air at 800 ° C for 2 hours. The molar composition of the active part of the molded catalyst without taking into account the binder 0.017 · Fe ₂ O ₃ · 0.013 · Al ₂ O ₃ · 10 ^-5 · Na ₂ O · SiO ₂ .

10 g of the obtained catalyst are loaded into a flow reactor, through the bed of which a reaction mixture of the composition: 5 mol% N ₂ O in helium is passed, the contact time is 2 s. At a temperature of 340 ° C, a complete conversion of nitrous oxide is observed, which persists with increasing temperature up to 800 ° C. The temperature of the half-conversion of nitrous oxide (50% conversion of nitrous oxide) is 320 ° C.

The main parameters of the catalysts and their catalytic properties are shown in the table.

The catalysts shown in the table differ in the type of binder, modifying element, amount of metal introduced, zeolite: binder ratios, activation modes.

The concentration of active sites and the catalytic activity of the catalysts were compared with the activity of unmodified and iron-modified zeolite and pseudoboehmite. These systems exhibit significantly lower activity in the decomposition of nitrous oxide compared with the claimed catalyst.

Claims (6)

1. A method of preparing a catalyst for the decomposition of nitrous oxide by mixing a zeolite structure selected from the following series: MFI, MEL, BEA, FER, MOR and having the composition: y · El ₂ O _n · SiO ₂ , where y = 10 ^-5 -5 · 10 ^-2 , El - at least aluminum and one of the elements 2, 3, 4, 5 of the Periodic table of the elements, n - the valency of the element, with a binder modified with iron, aluminum oxide with additives selected from the following series is used as a binder oxides: silicon oxide, titanium oxide, zirconium oxide, iron oxide, cobalt oxide, copper oxide, lanthanum oxide, about phosphorus seed at a mass ratio of alumina / any of the other oxides, ranging from 0.01: 100 to 10: 100, with a mass ratio of zeolite / binder from 1: 9 to 9: 1, where the modifying iron in the composition of the catalyst corresponds to x · Fe ₂ O ₃ , where x = 10 ^-5 -5 · 10 ^-2 , the modification is carried out by introducing into the binder a dry or hydrated salt and / or solution of an iron salt, followed by molding and activation of the catalyst to obtain a catalyst in which at least from 0.5 to 50% of iron and not less than 5 · 10 ¹⁷ atoms iron per gram of catalyst is in reduced form in the form of special complexes - α-centers, recorded and measured by a special method, which consists in determining the amount of surface oxygen deposited from nitrous oxide at a temperature of from 100 to 300 ° C on the surface of the catalyst. 2. The method according to claim 1, characterized in that salts of ferrous and / or ferric iron are introduced into the binder. 3. The method according to claim 1, characterized in that the activation of the catalyst is carried out in an environment of dry air and / or water vapor, and / or a reducing agent, and / or a vapor-gas medium containing all of these components. 4. The method of neutralization of industrial exhaust gas from nitrous oxide N ₂ O without the formation of harmful by-products, characterized in that the decomposition of nitrous oxide is carried out on a catalyst prepared according to any one of claims 1 to 3. 5. The method of neutralization according to claim 4, characterized in that the neutralization is carried out at a temperature of 400-750 ° C. 6. The method of neutralization according to claim 4, characterized in that the neutralization is carried out at a contact time of 0.1-5.0 s.