The method of oxidation of ammonia using the oxide catalyst honeycomb structure and method of preparation of catalyst

 

(57) Abstract:

The invention is used in catalytic chemistry, in particular in the oxidation of ammonia to nitric oxide (II) in the dual oxide catalyst honeycomb structure. Describes how the oxidation of ammonia using a catalytic oxide composition produced in the form of honeycomb structures of composition in weight. %: 25-40 MnO2; 1-15 Fe2O3; 15-20 CeO; 5-15 La2O3; 0,1-0,5 SrO; 0,1-1 MgO; 0,1-0,5 BaO; 1.0 to 1.5 SiO2; Al2O3- the rest. Describes compounds of the formula I, which is obtained by mixing the components in the form of individual oxides or mixtures thereof, hydroxides or salts with subsequent dispersion, mixing with acetic acid, water, ethylene glycol and kaolin wool mass ratio 1: (0,042-0,044): (0,21-0,23): (0,014-0,016): (0,055-0,062), forming by extrusion, drying and heat treatment at 850-900oC. At atmospheric pressure, the conversion rate of ammonia is 98,7%, in the industrial unit under pressure 94,0-95,6 %. The advantage of this invention is its industrial applicability and simplification of the process. 2 c.p. f-crystals, 2 tab.

The invention relates to a method for oxidation of ammonia using an oxide rolled Miaka on a two-stage catalyst, in which the first step is the grid of the platinum metals, and the second oxide catalyst is promising? so how can significantly reduce the loading of the platinum catalyst and reduce the deadweight loss of platinum.

The known method the oxidation of ammonia to nitric oxide (II) in aggregates at atmospheric pressure using as the catalyst of the second step of the oxide zhelezohromovyh catalyst, and in aggregates under pressure zhelezoiridievykh catalyst and catalysts containing the oxides of iron, chromium, strontium and zirconium.

The catalysts are characterized by a specific surface area of 15-50 m2/g and are made in the form of tablets with a size of 4-6 mm zhelezohromovye the catalyst with ammonia concentrations of 10.5 to 11.3% and a temperature of 800oC degree of conversion of ammonia amounted to 93.3-98,4%; galatalikemal catalyst at a temperature of 890-900oC degree of conversion of ammonia for mileage averages 94,4%, which practically coincides with the degree of conversion on the platinum catalyst (alloy No. 5) (Atroshchenko Century. And. Catalysts in the nitrogen industry. Kharkov, 1977, S. 41).

Currently, almost all industrial units p is IACA is the use of the catalyst in the form of tablets, that significantly increases the hydraulic resistance complicates the loading and unloading oxide catalyst.

You know the oxidation of ammonia to oxides of Fe-Mg-Al catalyst in the second stage, which is prepared by sputtering in the plasma of an aqueous solution of iron-containing raw materials of magnesium nitrate and aluminum hydroxide, followed by pelletizing the obtained product and heat-treated at 800oC. At atmospheric pressure at a temperature of 800-900oC the degree of conversion of ammonia on the catalyst is 95,8-96,8% (USSR author's certificate N 1541833, 1995).

Known two-way oxidation of ammonia using the catalyst of the second stage composition (weight%): 0.1 TO 1.5% V2O5, 2-3,5% CeO2, Fe2O3- the rest, which in the temperature range of 900-930oC at atmospheric pressure, the conversion rate of ammonia is 89-92%. The catalyst is prepared by mixing a solution of oxalate vanadyl with solutions of the nitrates of iron and cerium, evaporation, heat treatment at 400oC, pelletizing and re-heat treatment at a temperature of 700oC (USSR author's certificate N 1383563, 1995).

The oxidation of ammonia can be carried out using cableconnector 850-900oC this catalyst is relatively high and is at atmospheric pressure 92,2-93,6% (USSR author's certificate N 856540, 1979).

The main disadvantage of these methods is the low degree of conversion of ammonia, the use of preformed catalysts and process only at atmospheric pressure.

In the author's certificate of the USSR N 771958, 1995 described the oxidation of ammonia to two-stage oxide catalyst containing the oxides of iron, magnesium and aluminum in the amount of: 0,3-1,7 MgO, 19,6-20% Al2O3and Fe2O3- the rest (better than 0.5% of MgO, 20% Al2O3, Fe2O3- else). The catalyst is made in the form of tablets. It is characterized by high mechanical strength and heat stability. In laboratory conditions in the presence of one of the platinum mesh and a layer of preformed catalyst height of 50 mm in the temperature range 850-920oC the conversion of ammonia is to 98.1-98.7 per cent. In the manufacturing apparatus under a pressure of 7.3 ATA containing 7 platinum grids, the conversion of ammonia was 94-95,2%.

Method of preparation of this catalyst consists in mixing at 170-250oC nitrate salts of iron, aluminum is P>oC. the Main disadvantage of this method is the use of preformed catalyst, which complicates the process.

The closest in technical essence and the achieved result is the way the ammonia oxidation on oxide catalyst honeycomb structure composition (weight%): the 58.9-69,2% Fe2O3, 14,83-17.4% of Al2O3, 0.37 to 0.4% of MgO, 13,0-25,9% cordierite and the method of its preparation, which consists in grinding using the balls of the mixture of iron oxide, nitrate, aluminum, magnesium and water for 1 hour at room temperature, then at a temperature of 400oC, mixing the resulting mass with petroleum butter, oleic acid, ethyl alcohol and cordierite mass ratio 1: (0,15-0,3): (0,02-0,04): (0,12-0,15): (0,15-0,35), forming by extrusion in cell structure and annealing at a temperature of 850-1100oC. using these catalysts at 850oC, flow rate 17000 h-1concentrations of ammonia in the air 10,5% vol. the conversion of ammonia is 98.3-98.6% of the (USSR author's certificate N 1676142, 1995).

The disadvantages of this method include conducting the ammonia oxidation process only at atmospheric pressure and the complexity of the method of synthesis of the catalyst honeycomb structure at a temperature of 850-900oC using the oxide catalyst of honeycomb structure and the method of preparing this catalyst.

To achieve this goal the proposed conduct of the ammonia oxidation process at a temperature of 850-900oC using multicomponent oxide catalyst containing the oxides of transition, alkaline earth, rare earth elements and oxides of silicon and aluminum composition (weight%): 25-40% MnO2, 1-15% Fe2O3, 15-20% CeO2, 5-15% of La2O3, 0.1 to 0.5% SrO, 0.1-1% of MgO, 0.1 to 0.5% BaO, 1.0 to 1.5 SiO2, Al2O3- the rest is up to 100%.

This catalyst is prepared in the form of a honeycomb structure by mixing, dispersion and extrusion of the mixture of the starting components, in which the mass ratio of powder catalyst, acetic acid, water, ethylene glycol and kaolin wool is 1: (0,042-0,044): (0,21-0,23): (0,014-0,016): (0,055-0,062).

Distinctive features of the proposed method for the oxidation of ammonia at a temperature of 850-900oC using the oxide catalyst honeycomb structure and method of its preparation are:

1. The chemical composition of the oxide catalyst, including, wt.%: 25-40% MnO2, 1-15% Fe2O3, 15-20% CeO2, 5-15% of La2O3, Telesfora cell structure on p. 1, which consists in mixing the elements included in the catalyst composition: Mn, Fe, La, Sr, Mg, Ba, Al, in the form of individual oxides or oxide compounds containing mixtures or hydroxides or salts, followed by drying, the dispersion in the planetary mill until the particle size of 1-5 microns, mixed with acetic acid, water, ethylene glycol and kaolin wool mass ratio 1: (0,042-0,044):(0,21-0,23):(0,014-0,016):(0,055-0,062), the molding in the form of a honeycomb structure of a given size by drying in air and then in an oven at 110oC and calcination in air at 850-900oC.

Significant distinctive features is that it is unknown how the oxidation of ammonia at a temperature of 850-900oC using the oxide catalyst described composition, made in the form of honeycomb structures and providing a high degree of conversion of ammonia. No known methods of preparing such catalysts in the form of honeycomb structures by dispersing a mixture of a catalytically active composition to a specified particle size and added to the mass before forming the above reagents in a certain ratio.

The samples were experienced in the installation of the oxidation of ammonia in atmospheres mesh of alloy No. 5 (81% Pt, 15% Pd, 3,5% Rh, 0.5% Of Ru, %, weight), the second oxide catalyst. The activity was characterized by the conversion of ammonia, X%. One of the catalysts of the optimal composition was described in an industrial unit at high pressure. The test conditions are shown below.

Example 1. To prepare 1 kg of the catalyst composition of 28.0% MnO2, 3,0% Fe2O3, 15,0% CeO2, 7,0% La2O3that 0.5% of SrO, 0.5% Of MgO, 0.1% of BaO, 1.2% of SiO2, 44,7% Al2O3- 280 g MnO230 g of Fe2O3150 g of CeO270 g of La2O35 g of SrO, 5 g of MgO, 1 g BaO, 400,4 g Al2O3thoroughly mixed and dispersed in a planetary mill until the particle size of 1-3 microns, and then mixed with 220 g of water, to 44.1 g of acetic acid, to 58.8 g of kaolin wool composition: 2Al2O3SiO22H2O, 14 ml of ethylene glycol and stirred for 30-40 minutes until a homogeneous plastic mass, in which the mass ratio of powder catalyst, acetic acid, water, ethylene glycol and kaolin wool is 1: 0,044:0,22:0,015:0,059. The resulting mass is molded in the form of a honeycomb structure, air-dried, then in a drying Cabinet at 110oC, calcined in air at 900oC for 6 hours. The conversion of ammonia to this kataliza - 25 kg/cm2.

Other examples that represent the essence of the present invention, are shown in table 1.

Examples 1-12 illustrate a method of oxidation of ammonia using oxide catalysts of different chemical composition, prepared according to example 1. The table also shows thermal stability and the mechanical strength of the catalysts of different chemical composition. Examples 13-17 illustrate the method of preparation of the catalyst.

When reducing the content of manganese and iron, respectively, to 24% MnO2and 0.7% Fe2O3there is a decrease in the degree of conversion of ammonia and reduction of thermal stability (examples 6, 7). The decrease of the concentration of lanthanum and cerium to 4.5% La2O3and 14.0% CeO2leads to a decrease in thermal stability and reduction of mechanical strength (example 8). Reduction of the concentration of alkaline-earth elements SrO, MgO and BaO to 0.05% also leads to a decrease in thermal stability and a slight decrease in the degree of conversion of ammonia (example 9). The increase in the content of manganese dioxide to 41.0% and iron oxide-16.0% also leads to lower conversion rate and lower mechanical strength (example 11). The increase in the content of La2O3up to 16% .%: 25-40% MnO2, 1-15% Fe2O3, 15-20% CeO2, 5-15 La2O3, 0.1 to 0.5% SrO, 0.1-1% of MgO, 0.1 to 0.5% BaO, 1.0 to 1.5% SiO2, Al2O3- the rest is up to 100% (examples 1-5).

Example 13. In example 13 the chemical composition of the catalyst is similar to example 2, the method of preparation of the catalyst is similar to example 1, the difference lies in the fact that the preparation of the catalyst as a source of compounds of manganese, iron, lanthanum, barium, using magnesium nitrate salts, which are dissolved in water and mixed with cerium oxide and strontium hydroxide, followed by evaporation of the mixture until dry and then the catalyst is prepared analogously to example 1.

Example 14. The chemical composition of the catalyst is similar to example 2, the method of preparation of the catalyst is similar to example 1, the difference is that as a parent compounds of iron, manganese, strontium, lanthanum and strontium use chlorides, magnesium and barium is used in the form of nitrate, silicon and aluminum is injected as in example 1. An aqueous solution of initial components of manganese, iron, cerium, lanthanum, strontium, barium and magnesium evaporated on a water bath, the residue is then dispersed in a planetary mill and mixed with other components similar to prima is what a mixture of oxides of manganese, iron, cerium, lanthanum, strontium, magnesium and barium is dispersed in a planetary mill until the particle size of 6-8 microns.

Example 16. The chemical composition of the catalyst and method of preparation similar to example 1, the difference lies in the fact that the finished catalyst calcined at 840oC.

Example 17. The chemical composition of the catalyst and method of preparation similar to example 1, the difference lies in the fact that the finished catalyst calcined at 920oC.

Examples 13 and 14 demonstrate the ability to use as a source of compounds of manganese, iron, lanthanum, magnesium, strontium and barium nitrate, chloride salts or hydroxides.

Example 15 demonstrates that the dispersion of the source components to the size of the particles greater than 5 microns leads to a decrease in catalyst activity and reduced mechanical strength. The reduction of particle size less than 1 μm is impractical due to the secondary aggregation particles.

Examples 16-17 show that temperature range 850-900oC by calcination of a mixture of original substances is the most optimal. During annealing of the finished catalyst at a temperature below 850oC does not olivine finished catalyst above 900oC leads to a decrease of specific surface area from 20 to 10 m2/g, which also affects the reduction in the degree of conversion of ammonia.

The mixture of powder catalyst with acetic acid, water, kaolin wool and ethylene glycol at concentrations other than those specified in the invention within leads to catalyst weight is not plastic, it is difficult to shape, and the resulting catalyst has a low mechanical strength. The lack of a stage of drying the molded catalyst leads to cracking of the product during the heat treatment.

The catalyst composition (in weight. %): 25% MnO2, 5,5% Fe2O3, 17.5% of CeO2, 7,0% La2O3to 0.25% of SrO, 0.25% Of MgO, 0.1% of BaO, 1.2% of SiO2, Al2O3- the rest prepared according to example 1 was tested in an industrial unit oxidation of ammonia at a pressure of 7.3 ATA. The concentration of ammonia was remaining 9.08-9,36%, the load of ammonia 5600-6000 m3/hour and a temperature of 850-900oC. the Catalyst in the amount of 100 DM3made in the form of rectangular blocks of honeycomb structure with the size of the footprint 70x70 mm and a height of 50 mm and a wall thickness of 2 mm and number of holes 100, was laid in a single row across the cross section of the apparatus on nichrome mesh, Pokrywa is oversee ammonia was 94,1-95,6%, which is 3% higher than the conversion rate on pure platinum catalyst under these conditions.

During operation of the catalyst during the 11 months he has retained a high initial activity and mechanical strength (table 2). The relative deadweight loss of platinum 0.12 g/t acid.

From tables 1 and 2 shows that described in the invention method, the oxidation of ammonia at a temperature of 850-900oC with the use of oxide catalysts of the proposed structure provides a high degree of conversion of ammonia, up to 98.6-98.7 per cent at atmospheric pressure and 95.6% at high pressure. The use of catalysts of honeycomb structure greatly simplifies the operation of the process and reduces abrasion. Proposed invention is a method of preparation of the catalyst greatly simplifies the procedure for the synthesis of the catalyst and, in addition, allows to prepare the catalyst on the existing industrial equipment.

The invention is industrially applicable as it can be used in chemical plants for the oxidation of ammonia to nitric oxide (II) in the manufacture of nitric acid on an industrial scale.

1. The method of oxidation of ammonia xidi iron, magnesium and aluminum, characterized in that it additionally contains an alkaline earth oxides and rare earth elements and oxides of manganese and silicon in the following content, wt.%:

MnO2- 25 - 40

Fe2O3- 1 - 15

CeO2- 15-20

Za2O3- 5 - 15

SrO - 0,1 - 0,5

MgO - 0,1 - 1,0

BaO - 0,1 - 0,5

SiO2- 1,0 - 1,5

Al2O3- The rest is up to 100

2. The method of preparation of the oxide catalyst honeycomb structure under item 1 for the oxidation of ammonia to nitric oxide (II), which consists in mixing the starting components, the dispersion in the planetary mill until the particle size of 1-5 microns, mixed with acetic acid, water, ethylene glycol and kaolin wool mass ratio 1 : (0,042-0,044) : (0,21-0,23) : (0,014-0,016) : (0,055-0,062), drying in air and at 110oC and annealing at 850-900oC.

 

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