Catalyst for selective reduction of nitrogen oxides by ammonia and the method of its preparation

 

(57) Abstract:

Catalyst for selective reduction of nitrogen oxides by ammonia contains along with titanium oxide as A component at least oxide of W, Si, B, P, Zr, Ba, La, Ce, and at least an oxide of V, Nb, Mo, Fe, Cu as the components of B, and the atomic ratio between the elements of the components A and B is 1 : 0.001 to 1. The catalyst was prepared by mixing reactive titanium oxide with a high specific surface area of anatase with substances components B or pre-forms, with the addition of the processing means in a homogeneous mixed mass of extruded material, the drying of pressed products and annealed in air at 300 - 800oS. 2 S. and 6 C. p. F.-ly, 3 ill., 8 table.

The invention relates to heterogeneous catalysis and relates to a catalyst for selective reduction of nitrogen oxides by ammonia, and the method of preparation of the catalyst.

There are a large number of catalysts for reductive catalytic reduction of nitrogen oxides, in particular oxide catalysts containing a noble metal and noble metal containing.

Known catalyst [1] which state: B-1: iron and vanadium and/or group b-2: molybdenum, tungsten, Nickel, cobalt, copper, chromium, and uranium;

(C) tin oxide;

D) metal oxide from the group of beryllium, magnesium, zinc, boron, aluminum, yttrium, rare earths, silicon, niobium, antimony, bismuth and manganese.

Components are atomic relations A:B:C:D=1:(0.01 to 10) (0 to 0.2) (0 to 0.15).

The catalyst of this composition is used to restore oxygen and admixtures gas mixtures in the temperature range from 150 to 550aboutAnd at space velocities of 300-100, 000 and h-1.

These catalysts can be obtained by means of known events; they must always ensure that the components a and b and in case of need can be obtained as a thoroughly mixed mixture of oxides. As typical examples for such methods get called:

Ia: how homogeneous dissolution,

IB: the coprecipitation method.

2: simultaneous use of methods of dissolution and precipitation,

3: the method of the mixed precipitation.

As starting materials for the production of components a, b and C apply solutions and/or precipitated mass, as, for example, hydroxide or modusoperandi gel knead until thoroughly mixed mixture and then subjected to Prokaeva talities active oxides. The temperature of calcination should be between 300 to 800aboutC. Below 300aboutSince you cannot get a thoroughly mixed mixture of oxides and thereby the active catalyst; above 800aboutWith sintering occurs, which leads to the loss of active catalyst surface.

As starting substances for titanium as a component And is used, for example, various titanium acid, a hydroxide of titanium and various titanium salts, such as halides, titanium sulfate, titanyl sulphate, etc., as initial substances for titanium can be used as organic compounds of titanium, such as alcoholate titanium. Not applicable the titanium oxide in the calcined form of rutile or anatase.

The further development of these methods of preparation of the catalyst based catalyst [2] as the starting material for the preparation of the catalyst used titanium dioxide and the latter together with the vanadium oxide and one or more oxides of the elements tungsten, molybdenum, phosphorus, chromium, copper, iron, uranium from hollowed out and then at least subjected to heat treatment.

In the catalyst [3] as the titanium oxide is titanium oxide in calcined modification of anatase. To produce the e mills prefer mill with eccentric discs and mill with the annular chambers. The annealing occurs in the temperature range from 200 to 900aboutC.

For all known so far catalysts of this type it is essential that the components a and b (for example, Ti, B=W, Mo and others) in a thoroughly mixed mixture existed in the form of their oxides. The latter then subjected to the forming process of pressing or squeezing with obtaining a catalyst in the form of a granular material or monoliths in cellular form.

This means that the formation of a catalyst, such as extrusion molding, must be preceded by the preparation process thoroughly mixed mixture as the starting material. This conventional at the present time, the principle has the following disadvantages:

Technically necessary related costs, multi-step, energy-intensive process steps.

Obtaining a thoroughly mixed mixture in the catalyst [1] harm the environment; problems arise from the exhaust air and waste water.

The work of mills to activate refining is energy intensive and the cost of devices for protection against noise and dust.

Upstream process steps for the formation of a thoroughly mixed mixture Pavia by reducing the process steps in obtaining the so-called full catalysts (the latter consist entirely of catalytically active mass) for selective reduction of nitrogen oxides in oxygen-containing exhaust gases in the presence of ammonia to achieve a high ease and thus a certain reduction of the production of catalysts. In addition, the process should be straight and thin adjustable properties of the catalyst.

This problem is solved mainly by the selection of certain materials based on titanium oxide and their processing in the mixing process, and you can unsubscribe from known events to obtain a thoroughly stirred mixture of oxides.

The subject of the invention is a catalyst for selective reduction of nitrogen oxides by ammonia containing components

A) titanium oxide;

IN1at least one oxide of tungsten, silicon, boron, aluminum, phosphorus, zirconium, barium, yttrium, lanthanum, cerium

IN2at least one oxide of vanadium, niobium, molybdenum, iron, copper,

with an atomic ratio between the elements of the components A: B1B2equal 1 (0,00348 0,383) (0,0055 0,0185), characterized in that as component And the catalyst contains reactive titanium oxide consisting of at least 70 wt. from anatase, with the magnitude of the surface according to BET 40-280 m2/,

Another object of the invention is also a method of preparation of the catalyst for selective reduction of NOx by ammonia, including shmesani ribaut the ratio of the components, providing atomic ratio between the elements of components a, b1and IN2in the catalyst equal to 1:(0,00348-0,383):(0,0055-0,0185); the method differs in that it is used as a component reactive titanium dioxide with a BET surface 40-280 m2/g comprising at least 70 wt. from the anatase modification, which is mixed in the mixer with oxides components1it is preferably pre-forms, and stirred at pH 10.8 dry followed by the addition of oxides of components2it is preferably pre-forms, together with the usual molding or extrusion of ceramic masses additives, humidifying means, reinforcing means, binding means, auxiliary means forming and pore until a homogeneous plastic mass, which is then ekstragiruyut in a molded product, which is dried at a slow temperature increase up to a maximum of 60aboutC and then annealed them at stepwise increasing temperature in air at finite temperatures in the range of 400-700aboutC.

Used according to the invention, the titanium oxide can be a commercial product or can be obtained by deposition or flame is narrow particle size distribution with an average size of primary particles of about 30 nm.

The individual elements of the group can be applied, for example, in the form of the following starting compounds: tungsten oxide, para - or metabolomic ammonium, silica, kremneva.liliya acid, silicic acid, boron oxide, boric acid, aluminum oxide, phosphorus oxide, ammonium phosphate, postwarranty acid, phosphomolybdic acid, zirconium dioxide, zirconium phosphate, barium oxide,yttrium oxide, lanthanum oxide, cerium acetate, cerium nitrate, cerium oxide, bartolinova acid, vanadium oxide, oxalate vanadyl, ammonium metavanadate, Anatolyevna acid, vanadomolybdate acid, canadianpharmacyonline acid, vospominaniia acid, a hydrate of oxide of niobium, niobium oxalate, neobihnaya acid, ammonium molybdate, molybdenum oxide, iron oxide, iron phosphate, iron hydroxide, organic salts of iron, as iron oxalate, copper acetate, copper oxide (II), si-, Ce-, La-containing heteroalicyclic etc.

These compounds can be used in the form of solutions or as solids.

When the production of the catalysts according to the invention along with its own catalyst weight you want some more conventional fillers.

As skachivat the ve substrates can be used, for example, fiberglass different size.

As the binder, which give the pasta after molding sufficient resistance, suitable derivatives of cellulose, such as carboxymethylcellulose or unsubstituted cellulose.

In addition, as a binder used polyethylene, polypropylene, polyvinyl alcohol, polyethylene oxide, polyacrylamide or polystyrene.

In order to facilitate the pressing or improve extrusion ability, add auxiliary means for forming and/or softeners, for example, bentonite, alumina, organic acids, paraffin, waxes, silicone oils.

Finally, the porosity (pore volume, pore size) full of catalysts reached by the addition of appropriate pore, can also be adjusted. Such substances are, for example, fine coal or wood pulp, which fade when used annealing temperatures.

For intensive mixing of the starting compounds to obtain homogeneous mixing of the mass use of the mixing units. While I prefer the mixer with Sigma-shaped blades or vanes of the plasticizer. The use according to the invention the mass brings significant advantages in contrast to conventional still getting, in particular reduce related costs, may have a harmful effect on the environment and therefore also other technological stage. The coprecipitation and the processes of grinding to obtain a thoroughly stirred mixture of oxides falling away. This leads to a certain decrease in the cost of production and at the same time eliminates the dependence on expensive starting materials.

Moreover, it turns out that target the regulation of shrinkage, the decisive parameter for the tendency of cracking and ultimate strength full catalysts, probably due to the application of the appropriate starting materials and by adapting the mixing process relative intensity, temperature and time, including intermediate stage included ignition.

Then a new method of producing catalysts by eliminating several process steps ensures a more direct and at the same time more flexible control over the properties of the catalyst. Thus, the selection of the appropriate component of the stabilizer of a number of IN1to improve the stability of the catalysts for baking. This is confirmed by the fact that the high value of the surface by BET the finished catalyst in practical production OSs modification of anatase to the rutile modification. Of these properties follow directly a longer service life is obtained by the formula of the invention catalysts.

Fig. 1 (for example 13) clearly shows the decrease of decrease of activity with long-term use in flue gases of furnaces for burning coal with working temperatures up to 300aboutIf the catalyst is used as a stabilizer SiO2.

Physico-chemical properties of the original materials (TiO2-agnates, stabilizers from a number of IN1), activators of a number of IN2and the choice of further additives and processing according to the invention in the mixer can be controlled at a predetermined mixing the mass of empirical change in the content of moisture in it during the kneading process, the pore volume and the pore radii. The distribution of the pore radii may vary within wide limits within the scope of meso - and macropores, and mono -, di - and tri-modal distribution of pore radii and transitional forms of the latter can be specifically set. The correct choice of these parameters leads to a significant increase in catalytic activity. But the distribution of pore size and pore volume can also have a decisive influence on stoikosti special value RK is the value of a solid surface, RK is the value of the catalyst according to the invention can vary dramatically choice of stabilizers or activators. Here, in particular, should be called the application of heteropolyacids as activators and/or stabilizers. It was found that the catalysts derived from these substances, when used in the flue gas chamber furnaces with liquid slag removal coal have, for example, as compared with catalysts [1] is definitely less of a tendency to the concentration of arsenic and other impurities (catalyst poisons). This can be explained by improved resistance to poisoning due to reduced adsorption on the catalyst surface. This makes it possible to use catalysts in vysokopillia production chamber furnaces with liquid slag removal coal. Known comparative catalysts opposite subject to rapid deactivation, which is caused mainly available in the flue gas with heavy metals.

Fig. 2 and 3 show an unexpected large increase in the activity of the catalysts according to the invention compared with conventional manufactured in comparative example 1 catalyst.

The catalyst test was carried out as in containing no dust exhaust gases on a laboratory test rig and in the exhaust gas installation for SIG emenim coal.

Experiments with spent catalyst in the temperature range 200-500aboutC. At this flow rate was between 10000 and 40000 h-1. Accordingly applied found favorable molar ratio between the reducing agent ammonia and nitric oxide from 0.6 to 1.6, preferably between 0.8 and 1.2.

Comparative example. 35 kg made by the Federal Republic of Germany patent N 2458888 thoroughly mixed mixture of oxides TiO2and WO3in a weight ratio of 9:1 are mixed with 20 liters of desalinated water, 6 kg 15 wt.-aqueous solution of NH3, 1.8 kg of monoethanolamine and solution metavanadate ammonium, corresponding to 350 g V2O5. The mixture under varying moisture content and at temperatures between 70 and 90aboutWith intensively stirred. Then add the queue 620 g SiO2, 1.4 kg, not containing alkali clay and 3.5 kg of glass fibers (length 1-8 mm). The mixture is kneaded 6-8 h until a homogeneous mixing of the mass, and for the regulation necessary for the subsequent molding plasticity additionally added 410 g of polyethylene oxide, 410 g of carboxymethyl cellulose, 230 g of lactic acid and 11.5 kg fully desalinated water.

Using an extruder catalyst mass is extruded to a monolithic cellular products with channels the information for conditioning the rising temperature in the region of 20-60aboutAnd then, after a gradual increase in temperature calcined for 24 h at 620aboutC.

The following describes examples 1 to 31 according to the invention. Each of these examples is one of many like him. Specified in these experiments, residual moisture and accordingly pH values ranging from 3.5 to 11.5% respectively from pH 7.2 to pH to 10.8.

P R I m e R s 1-9. The composition of the catalyst are given in table. 1. For the preparation of the catalysts was done as follows.

35 kg TiO2-anatase surface according to BET 98 m2/g is mixed with 4,4 kg parabolicamara ammonium (W), 22 liters of desalinated water, 7.5 kg 15 wt.-aqueous solution of NH3, 1.8 kg of monoethanolamine and solution metavanadate ammonium relevant 390 g V2O5. Under intensive mixing in the temperature range of 60-90aboutTo add further along the queue 670 g of SiO22.5 kg of glass fibers (length 1-8 mm) and 1.5 kg, not containing alkali clay. The mixture is stirred for 5-7 hours until a homogeneous mixing of the mass (Werner R PfIeiclerer-mixer LUK 2,5), and for the regulation of plasticity additionally add 450 g of polyethylene oxide, 450 g of carboxymethyl cellulose, 250 g of lactic acid and 12.3 l of desalinated water. To fine tune vlahos is know water. Then using an extruder catalyst mass is made up of a monolithic cellular products with channels with a square cross-section (division of cells 3.4 mm). After drying, the rising temperature of 20-60aboutWith in a drying installation for conditioning the molded product is calcined after a gradual temperature increase 24 h at 620aboutC.

In examples 6-9 instead of TiO2-anatase or parabolicamara ammonium (W) or metavanadate ammonium (V) was used made flame hydrolysis of TiO2-P-25 (Degussa), containing about 70 wt. of anatase, the rest of the rutile or oxide of tungsten, an oxide of boron or Nb2O5last used as water-soluble niobium oxalate.

P R I m e R 10-13. 35 kg TiO2-anatase surface according to BET of 75 m2/g are mixed in a continuous mixer with 4,4 kg parabolicamara ammonium (W) and 10 kg 15 wt.-aqueous solution of NH3. Resulting slurry is kneaded at 80aboutC for 3 hours to dry (residual moisture content of 5-10 wt.). Then thus obtained mixture is mixed with 22 liters of desalinated water, 75 kg 15 wt.-aqueous ammonia solution, 1.8 kg of monoethanolamine and solution metavanadate ammonium (V) corresponding to 390 g V2O5

In example 11 and table. 2 the ammonium metavanadate was replaced by ammonium molybdate (AM), in examples 12 and 13 paraformat ammonium substituted through HLW or SiO2.

P R I m e R s 14-17. 35 kg TiO2-anatase surface according to BET of 40 m2/g is mixed with 4.0 kg of aluminum oxide and 12 kg 15 wt.-aqueous solution of NH3. The paste is kneaded at 80aboutWith 2-3 hours per FTE enough moisture between 5-10 wt. Then the powder is pre-calcined at 400aboutC for 2 h

Pre-calcined mixture of the oxides are mixed in the mixer with 22 liters of desalinated water, 75 kg 15 wt.-aqueous solution of NH3, 2, 0 kg of monoethanolamine, 210 g of pulp (coarse-fibered pulp) and only then with a solution of metavanadate ammonium relevant 390 g V2O5. With vigorous mixing at 60-90aboutWith optional add 2.3 kg does not contain alkali clay, 2.2 kg of glass fibers (length 1-8 mm), 200 g of polyethylene oxide, 200 g of carboxymethyl cellulose and 250 g of lactic acid. The mixture is kneaded 5-7 h until a homogeneous mixing of the mass, and to regulate plasticity add the rest of ammonia water. Finally, using an extruder catalyst mass is made up of cellular products with square channels konfigurierbare molded product after a gradual increase in temperature calcined for 24 h at 700aboutC.

In examples 15-17 instead of aluminum oxide in accordance with the table. 3 add paraformat ammonium or oxide of lanthanum in example 16 instead of metavanadate add ammonium dissolved in water copper acetate (11).

P R I m e R s 18-21. 35 kg TiO2-anatase surface according to BET of 280 m2/g is mixed with 4.0 kg of zirconium oxide, 390 g V2O5and 15 kg 15 wt.-aqueous solution of NH3. Fluid paste is kneaded at 80aboutWith 2-4 hours to a residual moisture content of 5-10 wt. Then the dry powder pre-calcined at 700aboutWith 2 hours

Pre-calcined mixture is mixed with 25 kg of completely desalinated water, 75 kg 15 wt.-aqueous solution of NH3and 2.0 kg of monoethanolamine and further processed analogously to examples 1-9. The finished catalyst weight ekstragiruyut to cellular products as in examples 14-17.

In examples 19-21 according to the table. 4 replace the zirconium oxide by parabolicamara ammonium or propeciacost phosphorus in example 20 replace V2O5iron oxide (III).

P R I m e R s 22-26. 35 kg TiO2-anatase surface according to BET 98 m2/g is mixed with 422 g ammonium-2-hydro-12-WindowState and with 28 l of desalinated water.

A lot intensively sameshima) and 6.0 kg does not contain alkali clay. In addition, to regulate plasticity add 450 g of polyethylene oxide, 900 g of carboxymethyl cellulose, 250 g of lactic acid and 15 liters of desalinated water.

The mixture is kneaded 5-7 h until a homogeneous mixing of mass and processed in accordance with examples 1-9 to cellular products.

According to the table. 5 in examples 23-26 ammonium-2-hydro-12-canadapost replace the following heteropolyacids:

P R I m e R s 27-31. 35 kg TiO2-anatase surface according to BET 98 m2/g is mixed with 4.3 kg of parabolicamara ammonium, 22 liters of desalinated water, 7.5 kg 15 wt.-aqueous solution of NH3and 1.8 kg of monoethanolamine. Mass in accordance with examples 1-9 provide additives (plasticizers, reference substances, and so on ), intensively kneaded (2-7 h at 60-90aboutC) and ekstragiruyut to cellular products, which here serve as a pre-stage catalyst. Last dried analogously to examples 1-9 and calcined, and after cooling (item 7) with 1.0 g of vanadium pentoxide per 100 g of the mixture of titanium dioxide/oxides of tungsten is applied with a saturated solution of ammonium-2-hydro-12-WindowState in the amount of water corresponding to the capacity of cellular products. Drying is produced by passing air at 150aboutC. Final of the Idro-12-WindowState used in accordance with those specified in the table. 6 quantitative relationship metabolomic ammonium, yttrium oxide, zirconium dioxide or silicon dioxide or V2O5(as aqueous solutions of vanadium oxalate), Amani-6-wolframate-6-Vanadate or 11 molybde-1-windowsphone acid.

The test is made catalysts.

Prepared in accordance with examples 1-31 catalysts were tested in the exhaust gas furnace for burning liquid fuel, which is regulated by the dosage of additional harmful components (NOxand SO2and required for the recovery of nitric oxide with ammonia under the following conditions of experience.

Conditions of experience:

The composition of the flue gas:

NOx800 ppm

NH3800 ppm

SO2500 ppm

ABOUT25,0 about.

H2About 11,0 about.

CO212,0 about.

N2the balance of

Experiments with the catalyst is carried out at a temperature of 250-500aboutAnd the spatial velocity of 20 000 h-1. Selected results of measurements and long-term experiments in furnaces for burning coal when the above mentioned conditions are shown in graphs of Fig. 1-3. Underlying the measurement values are summarized in table. 7 and 8.

1. Catalyst for selective is tungsten, silicon, boron, aluminum, phosphorus, zirconium, barium, yttrium, landata, cerium, IN2at least the oxide of vanadium, niobium, molybdenum, iron, copper atomic ratio between the elements a, b1and IN2equal 1 (0,00348 0,383) (0,0055 0,0185), characterized in that the quality of the components And the catalyst contains reactive titanium oxide consisting of at least 70 wt. anatase, with the magnitude of the surface according to BET of 40 280 m2/,

2. The preparation method of catalyst for selective reduction of nitrogen oxides with ammonia, comprising mixing the component titanium dioxide component IN1selected from the group comprising oxide of tungsten, silicon, boron, aluminum, phosphorus, zirconium, barium, yttrium, lanthanum, cerium, with component b2selected from the group comprising oxide of vanadium, niobium, molybdenum, iron, copper, drying, calcining, and the process is conducted at a ratio of components providing the atomic ratio between the elements of components a, b1and IN2in the catalyst equal to 1 (0,00348 0,383) (0,0055 - 0,0185), characterized in that as component And use reactive titanium dioxide, consisting of at least 70 wt. anatase, with the magnitude of the surface according to BET of 40 280 m2/g, mixing on the forms, followed by intensive stirring at a pH of 7.2 to 10.8 in dry form, the addition of oxides of components2preferably with their previous forms, along with the usual for forming or extrusion of ceramic masses additives, humidifier, reinforcing, binders, auxiliary means forming and pore until a homogeneous plastic mass, then the mass ekstragiruyut with the formation of molded products, which are dried at a slow temperature increase up to a maximum of 60oC, followed by calcination at step temperature increase at 400 700oC.

3. The method according to p. 2, characterized in that as starting material for components1and IN2use of hydroxide, oxide, salt or heteroalicyclic or their salts, mainly salts of ammonia.

4. The method according to p. 2, characterized in that the component a and the component IN the1mixed in the mixer at a pH of 7.2 to 10.8, mix in dry form to a residual moisture content of 3.2 to 11.5% and then add the component IN the2.

5. The method according to p. 4, wherein the pre-mixed dry blend of components a and b1pre-calcined at tenesmus, consisting of components a, b1and IN2pre-calcined at 400 - 700oC, then stirred until a homogeneous plastic mass.

7. The method according to PP.2 to 6, characterized in that the components1and IN2used in the form of heteroalicyclic or one of its salts, preferably ammonium salts, and available in heteroalicyclic metals from group1and IN2are in an atomic ratio of from 1 to 12 1 to 12.

8. The method according to p. 2, characterized in that the starting material for the component IN the2select from the mixing process in the form of a salt, or heteroalicyclic, or its salts, preferably ammonium salts in aqueous solution impregnation put on consisting of the components a and b1pre-calcined catalyst mixture.

 

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