RU2161533C1 - Catalyst for removing oxygen and nitrogen dioxide from nitrose gases and method of preparation thereof - Google Patents

Abstract

FIELD: gas treatment. SUBSTANCE: in particular, invention relates to cleaning nitrose gases in hydroxylamine sulfate production. Catalyst on alumina-based carrier containing, wt %: iron oxide 10-30, manganese dioxide 4-7, cobalt(II,III) oxide 2-10, and silver oxide 3.5-10 additionally contains 0.01 to 2% (on conversion to oxide) of one element from following group: Na, K, Fe, Si, Ba, Ca, Mg. EFFECT: increased strength, activity, and selectivity of catalyst. 9 cl, 1 tbl, 10 ex

Description

 The present invention relates to a catalyst and a method for its preparation for the selective purification of gas mixtures containing nitric oxide from oxygen and nitrogen dioxide. In particular, the invention relates to the purification of nitrous gases in the production of hydroxylamine sulfate.

 The production of concentrated nitric oxide is based on the catalytic binding of oxygen and nitrogen dioxide contained in nitrous gases to hydrogen.

One-component supported catalysts for this process are known, such as 0.1% Mn / Al ₂ O ₃ , 5% Mn / SiOz (Tylus Wlodzimier, Zabrzesk. "Preparation of pure nitric oxide by catalytic removal of oxygen from nitrous gases" // Przem chem / -1989. -68, N 9, -s. 403-404. -Pol.).

 The disadvantage of these catalysts is their relatively low selectivity and strength.

 A known catalyst for the purification of nitrous gases, containing platinum or palladium on alumina, which is obtained by impregnating alumina with an aqueous solution of palladium or platinum salt (C. Thomas. Industrial Catalytic Processes and Effective Catalysts, ed. Mir, M, 1973, p. 187 -188).

 The disadvantage of the catalyst is the lack of selectivity and low strength.

A known catalyst for the purification of nitrous gases from oxygen and nitrogen dioxide (German patent N 1542628, IPC B 01 J 23/84, 1972), containing silver oxide and manganese dioxide on a carrier - aluminum oxide, with the following components (wt.%): silver oxide - 4, manganese dioxide - 5-30, γ-Al ₂ O ₃ - the rest. The method of preparation of the catalyst includes two options.

According to the first embodiment, the catalyst is prepared by impregnation of a molded or powdery carrier (γ-Al ₂ O ₃ ) with aqueous solutions of nitrate salts of silver and manganese, followed by drying and calcination at 500-550 ^o C.

In the second embodiment, finely ground carrier is mixed with oxides or salts of silver and manganese, followed by molding and calcination at 500-550 ^o C.

The main disadvantage of the catalyst should be considered a fairly low activity of the catalyst at temperatures below 500 ^o C and close to stoichiometric amounts of hydrogen (or another reducing agent). Thus, the degree of purification from oxygen and nitrogen dioxide at temperatures of 492-510 ^o C is only 84-89% on a catalyst composition of 10% MnO ₂ , 4% Ag ₂ O, the rest is γ-Al ₂ O ₃ at 95-100% hydrogen from stoichiometric amount. The degree of purification from oxygen and nitrogen dioxide of 95-98% is achieved only at 550 ^o C and higher, when the content of manganese dioxide in the catalyst is 30% and the amount of reducing gas is 5-10% higher than the stoichiometric, with the degree of conversion of NO - 7% .

A known catalyst for denitrification of exhaust gases (US patent N 5049364, IPC B 01 J 8/00, 1991). The catalyst contains: a) oxides of alkali and alkaline earth metals; b) at least one of the oxides: Co ₃ O ₄ , Cu ₂ O, Cr ₂ O ₃ , Mn ₂ O ₃ , NiO, PbO, Bi ₂ O ₃ , MoO ₂ ; Al ₂ O ₃ , SiO ₂ , ZrO ₂ , Fe ₂ O ₃ , etc .; c) one of the metals or metal oxides: Ru, Rh, Pd, Ag, Pt, Au.

 The disadvantage of the catalyst is the low strength and low activity of the catalyst in the purification of nitric oxide from oxygen and nitrogen dioxide.

The closest technical solution to the claimed is the catalyst and the method claimed in the patent (RF patent N 892763, IPC B 01 J 23/84, 1999), and the catalyst has the following composition, wt.%:
iron oxide - 10-30
manganese dioxide - 4-7
cobalt oxide (II, III) - 2-10
silver oxide - 3.5-10
γ-alumina - the rest
The catalyst is obtained by mixing compounds of iron oxide, manganese dioxide and cobalt (II, III) oxide with reprecipitated aluminum hydroxide or its mixture with technical aluminum hydroxide at a weight ratio of 1: 4 to 4: 1, followed by molding, drying and calcination at a temperature of 500- 550 ^o C followed by impregnation with silver nitrate, drying and calcination or a silver salt is made by mixing all the active components, followed by molding, drying, calcination.

 The disadvantage of the catalyst is the insufficiently high strength of the catalyst, which leads to a change in its porous structure, a decrease in the specific surface, and sintering of silver occurs with particle coarsening, which causes a decrease in the activity of the catalyst.

 The problem solved by the invention is the development of a catalyst having increased strength, high activity and selectivity and a method for its preparation.

 The problem is solved on a catalyst for the purification of nitrous gases from oxygen and nitrogen dioxide, which contains (wt.%): Iron oxide - 10-30, manganese dioxide - 4-7, cobalt oxide (II, III) - 2-10, oxide silver - 3.5-10 on a carrier based on alumina, the carrier further comprises at least one compound of an element from the group of Na, K, Fe, Si, Ba, Ca, Mg in an amount of 0.01-2 wt.% (in terms of oxide).

The problem is solved by the method of producing a catalyst for the purification of nitrous gases from oxygen and nitrogen dioxide, including the preparation of a catalyst mixture by mixing iron oxide, manganese dioxide, cobalt oxide (II, III) with a binder based on aluminum hydroxide in the presence of a plasticizer with the introduction of this catalyst a mixture of silver nitrate followed by molding, drying and calcining at a temperature of 400-550 ^o C or impregnation with silver nitrate granules obtained from a catalyst mixture after molding curing, drying and calcining at a temperature of 400-550 ^o C, as a binder use a hydrated aluminum compound of the formula Al ₂ O ₃ · nH ₂ O, where 1,1≅n≅2,0, containing at least one compound of an element from the group : Na, K, Fe, Si, Ba, Ca, Mg in an amount of 0.01-2 wt.%. (in terms of oxide) and add a plasticizer in an amount necessary to obtain a plastic mass.

As a plasticizer, nitric and / or acetic acid is selected in an amount of 3-20 wt.%. from the content of alumina in the hydrated compound Al ₂ O ₃ · nH ₂ O, where 0.1 ≅ n ≅ 2.0.

As the hydrated aluminum compound of the formula Al ₂ O ₃ · nH ₂ O, where 1.1 ≅ n ≅ 2.0, one of the compounds is used: the hydrated product of the thermochemical activation of aluminum hydroxide, the hydrated product of the fast partial dehydration of aluminum hydroxide, which contain at least one compound of an element from the group: Na, K, Fe, Si, Ba, Ca, Mg in an amount of 0.01-2 wt.%.

 Wood flour up to 5 wt.% Is added to the mixture. to improve forming properties.

 Up to 25 wt.% Of spent silver catalyst is added to the charge, which is subjected to grinding and treatment with nitric acid to harden the fresh catalyst and improve its catalytic properties.

To increase the strength of the catalyst, aluminum hydroxide of the formula Al ₂ O ₃ · 3H ₂ O in an amount of 20-80 wt. %., which is preferably used bayerite or hydrargillite.

 After molding the granules, they are dried at room temperature, followed by drying and calcination.

 The content of compounds of additional elements in an amount of less than 0.01 wt.% Is insufficient to obtain a catalyst with high strength and preserving activity and selectivity for a long time, and the range is 0.01-2.0 wt. % is sufficient to obtain catalysts with the desired properties.

In the proposed solution, a hydrated aluminum compound of the formula Al ₂ O ₃ · nH ₂ O, where 1.1 ≅ n ≅ 2.0, which can be obtained by any known methods, for example, rehydration of the product of the fast dehydration of hydrargillite, bayerite, nordstrandite, boehmite, a diaspora containing in its composition additionally modifying compounds of Na, K, Fe, Si, Ba, Ca, Mg, which may be partially present in the initial products, or they are introduced into the initial aluminum hydroxide before rapid dehydration by any known method s, for example by impregnation or coprecipitation. During the heat treatment of catalyst granules based on such a hydrated aluminum compound, a catalyst is formed on the modified surface of the carrier, which ensures the formation of a strong bond between the carrier and the active component, which leads to a catalyst with high activity and stability.

The main reason for the deactivation of silver-manganese catalysts for the purification of nitrous gases during its operation is a change in the phase composition, since silver sintering with particle enlargement occurs and the phase of coarse-grained manganese oxide β-Mn ₂ O ₃ appears (R.V. Bunina, I.S. Sazonova, E.M. Moroz, N.E. Bogdanchikova, A.A. Davydov, G. . M. Alikina. "Deactivation of the active component of the supported silver-manganese catalyst for purification of nitrous gases from oxygen in the production of hydroxylamine sulfate" // Siberian Chemical Journal. - 1992. - Issue 4, - pp. 134-138). In addition to the phase transformation of the active component in the process of deactivation of the catalyst, its porous structure changes. In the proposed solution, all these negative processes are significantly slowed down, because the catalyst is obtained ~ twice as strong as the known one, while its high activity and selectivity are retained in the purification of nitrous gases from oxygen and nitrogen dioxide.

 The catalyst is prepared as follows.

To prepare the catalyst, a hydrated aluminum compound with the gross formula Al ₂ O ₃ · nH ₂ O, where 1.1 ≅ n ≅ 2.0, containing at least one compound of an element from the group Na, K, Fe, Si, Ba, Ca and Mg in an amount of 0.01-2.0 wt.%.

 This compound can be obtained by any known method, for example, according to RF patent N 2064435 (IPC C 01 F 7/44, 1996) or by reprecipitation of technical alumina hydrate (V. A. Dzysko. "Fundamentals of methods for the preparation of catalysts", ed. Nauka, Novosibirsk , 1983).

The catalyst mixture is prepared by mixing iron oxide, manganese dioxide, cobalt oxide (II, III) with the above hydrated oxygen-containing aluminum compound with a plasticizer (nitric and / or acetic acid) in an amount of 3-20% of the content of Al ₂ O ₃ in the hydrated aluminum compound . To improve ductility, wood flour is added to the catalyst charge in an amount of up to 5 wt.%.

After plasticization, the required amount of iron oxide (Fe ³⁺ ), manganese dioxide (Mn ⁴⁺ ), cobalt oxide (Co ²⁺ , Co ³⁺ ) is added, the mixture is stirred and silver nitrate is added with stirring and the granules are extruded, dried at room temperature temperature, dried and calcined at a temperature of 400-550 ^o C. The stage of drying provides a low rate of removal of free water from the pore space of the catalyst granules and thereby stabilizes the active component on the surface of the carrier throughout the depth of the granules.

Silver oxide in the catalyst can be introduced by impregnation with silver nitrate of the granules obtained from the catalyst mixture, as described above, by mixing iron oxide, manganese dioxide, cobalt oxide (II, III) with a hydrated aluminum compound of the formula Al ₂ O ₃ · nH ₂ O, where 1 , 1 ≅ n ≅ 2 after molding, drying and calcination at a temperature of 400-550 ^o C.

 The mechanical crushing strength along the generatrix is determined on an MP-2S or MP-9C instrument.

 The test of the catalytic activity of the catalyst is determined on a laboratory flow-through installation in the reaction of oxygen with hydrogen in a model mixture containing nitric oxide, oxygen, hydrogen, water and argon with gas chromatographic analysis.

 The characteristics of the obtained catalyst, the method of its preparation and properties are shown in the table.

 The following examples illustrate the invention.

Example 1
160 g of a hydrated compound Al ₂ O ₃ · 2H ₂ O, obtained by rehydration of a product of fast partial dehydration of aluminum hydroxide containing sodium oxide in an amount of 0.06 wt.%, Iron oxide in an amount of 0.1 wt. %., silicon oxide in an amount of 0.05 wt.%. add wood flour in an amount of 5.1 g, add a solution of nitric acid in an amount of 10.5 ml (57% concentration of HNO ₃ ) as a plasticizer, add water in an amount of 35 ml and carry out the plasticization step with vigorous stirring for 1 hours. Then add a mixture of iron oxide in an amount of 30.6 g, manganese dioxide in an amount of 7.8 g, cobalt oxide (II, III) in an amount of 8.2 g and silver nitrate in an amount of 14.2 g, dissolved in 15 ml of water, the catalyst mixture is formed by extrusion, dried, dried and calcined at a temperature of 500 ^o C.

Example 2
160 g of a hydrated product of thermochemical activation of gibbsite containing sodium oxide in an amount of 0.08 wt. Are poured into a 1-liter mixer. % , iron oxide in an amount of 0.05 wt.%. and calcium oxide in an amount of 1.0 wt. %., add 5.4 ml of acetic acid (concentration of 99 wt.%), add 10 ml of water, mix, add 32 g of iron oxide, 9.3 cobalt (II, III) oxide, 7.3 g of manganese dioxide, mixture mix and add the calculated amount of silver nitrate, the mixture is molded, dried, dried and calcined at a temperature of 500 ^o C.

Example 3
Similar to example 1, only acetic acid is used as a plasticizer, a mixture of iron oxide, manganese dioxide, cobalt oxide (II, III) is added, the mass is mixed, formed, dried at 110 ^° C, calcined at 400 ^° C, then dried and calcined granules impregnated with a solution of silver nitrate, dried and calcined at a temperature of 500 ^o C.

Example 4
Similar to example 1, only in the catalyst mixture add aluminum hydroxide in the form of bayerite in an amount of 20 wt.%. from the content of Al ₂ O ₃ in the hydrated aluminum compound containing sodium oxide in an amount of 0.06 wt. % , silicon oxide in an amount of 0.1 wt.%., calcium oxide in an amount of 0.05 wt.%., barium oxide in an amount of 0.01 wt.%.

Example 5
Similar to example 1, it only differs in that to the hydrated aluminum compound containing sodium, potassium, silicon and barium oxides in a different ratio after plasticization with nitric acid, a mixture of iron oxide, manganese dioxide and cobalt oxide (II, III) is added, then the mixture is mixed for 40 min, the mass is molded, dried at a temperature of 110 ^o C and calcined in a stream of air at a temperature of 500 ^o C. Dried and calcined granules are impregnated with a solution of silver nitrate. After impregnation, the granules are dried and calcined at a temperature of 550 ^o C.

Example 6
Similar to example 4, only in the catalyst mixture add aluminum hydroxide in the form of hydrargillite in an amount of 80 wt.%. from the content of Al ₂ O ₃ in the hydrated aluminum compound containing sodium oxide in an amount of 0.06 wt.%., iron oxide in an amount of 1.94 wt.%. As a plasticizer, a mixture of nitric and acetic acids is used.

Example 7
60 g of ground silver catalyst wastes are charged into the reactor, a solution of nitric acid in an amount of 13.8 ml is added (concentration 58 wt.%), 60 ml of water are added, stirred, and then a hydrated aluminum compound containing sodium oxide in an amount of 0.03 is added wt.%. , magnesium oxide 0.01 wt.%, a mixture of metal oxides (32 g of iron oxide, 9.3 g of cobalt oxide (II, III), 6.9 g of manganese dioxide). Then add a solution of silver nitrate (15 g of silver nitrate dissolved in 35 ml of water). Then the catalyst is prepared analogously to example 1.

Example 8
Similar to example 1, only differs in the composition of the active components and additional elements, and silver nitrate is introduced by impregnation.

Example 9 (prototype)
Prepared analogously to example 1, only as an aluminum hydroxide a mixture of precipitated and technical aluminum hydroxide is used and plasticization is carried out with 10% acetic acid and a mixture of iron oxide, manganese dioxide, cobalt (II, III) oxide and silver nitrate is added, then the mass is molded, dried and calcined.

Example 10 (prototype)
Prepared analogously to example 5, only a mixture of redeposited and technical aluminum hydroxide is used as aluminum hydroxide, a mixture of iron oxide, manganese dioxide, cobalt oxide (II, III) is added, the mass is molded, dried, calcined and impregnated with silver nitrate, dried and calcined at a temperature 500 ^o C.

From the above examples it follows that the use of a hydrated compound of the formula Al ₂ O ₃ · nH ₂ O, where 1.1 <n <2.0 and containing at least one compound of an element from the group Na, K, Fe , Si, Ba, Ca, Mg in an amount of 0.01-2.0 wt.%., Leads to the preparation of a catalyst having high strength while maintaining high activity and selectivity.

 The increased strength of the catalyst contributes to the preservation of the active ionic form of silver and slows down the formation of an inactive metal form and the service life of the catalysts is significantly increased.

Claims (9)

1. The catalyst for the purification of nitrous gases from oxygen and nitrogen dioxide, containing, wt.%:
Iron oxide - 10 - 30
Manganese Dioxide - 4 - 7
Cobalt oxide (II, III) - 2 - 10
Silver oxide - 3.5 - 10
on an alumina-based carrier, characterized in that the carrier further comprises at least one compound of an element from the group of Na, K, Fe, Si, Ba, Ca, Mg in an amount of 0.01 to 2 wt.% (in terms of on oxide). 2. A method of producing a catalyst for purifying nitrous gases from oxygen and nitrogen dioxide, comprising preparing a catalyst mixture by mixing iron oxide, manganese dioxide, cobalt oxide (II, III) with an aluminum hydroxide binder in the presence of a plasticizer with the introduction of silver nitrate into this catalyst mixture followed by molding, drying and calcining at a temperature of 400 - 550 ^o C or impregnation with silver nitrate granules obtained from the catalyst mixture after molding, drying and calcination at a temperature ature 400 - 550 ^o C, characterized in that a hydrated aluminum compound of the formula Al ₂ O ₃ · nH ₂ , where 1.1 ≅ n ≅ 2.0, containing at least one compound of an element from the group Na, K is used as a binder , Fe, Si, Ba, Ca, Mg in an amount of 0.01 to 2 wt.% (In terms of oxide) and add a plasticizer in an amount necessary to obtain a plastic mass. 3. The method of producing the catalyst according to claim 2, characterized in that as a plasticizer and use nitric and / or acetic acid in an amount of 3 to 20 wt. % of the content of alumina in the hydrated compound Al ₂ O ₃ · nH ₂ O, where 1.1 ≅ n ≅ 2.0. 4. The method according to p. 2, characterized in that as a hydrated aluminum compound of the formula Al ₂ O ₃ · nH ₂ O, where 1.1 ≅ n ≅ 2.0, use the hydrated product of the thermochemical activation of aluminum hydroxide, the hydrated product of partial partial dehydration of aluminum hydroxide.  5. The method according to claim 2, characterized in that wood flour is added to the catalyst mixture to 5 wt.% By weight of the catalyst mixture.  6. The method according to claim 2, characterized in that up to 25 wt.% Of spent silver catalyst is added to the catalyst charge, which is subjected to preliminary grinding and treatment with nitric acid.  7. The method according to claim 2, characterized in that after molding the granules are dried at room temperature, followed by drying and calcination. 8. The method according to claim 2, characterized in that aluminum hydroxide of the formula Al ₂ O ₃ · 3H ₂ O is added to the catalyst charge in an amount of 20 to 80 wt.% Of the Al ₂ O ₃ content in the hydrated aluminum compound. 9. The method according to claim 8, characterized in that the aluminum hydroxide of the formula Al ₂ · 3H ₂ O is bayerite or hydrargillite.

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