RU2106197C1 - Catalyst for cleaning gases from nitric oxides - Google Patents

Abstract

FIELD: environmental control; power engineering, chemical, metallurgical and other industries which activities result in gas discharges containing nitric oxides. SUBSTANCE: catalyst is supported by carrier containing titanium dioxide, and comprises at least one active component selected from among vanadium and copper compounds, and tremolite or wallastonite minerals or mixture thereof. These components are present in catalyst in the following ratio, wt. -% (contents of V and/or Cu compounds are given on basis of metal content): V, not more 1; Cu, not more 2; tremolite and/or wallastonite, 2-12; carrier, the balance. EFFECT: higher mechanical strength and catalytic activity; partial or full substitution of vanadium component by copper-containing component. 8 cl, 1 tbl

Description

 The invention relates to catalysts for the protection of the environment from toxic nitrogen emissions and can be used in energy, chemical, metallurgical and other industries having exhaust gases that contain nitrogen oxides.

 As the active components of the catalysts used in the process of selective catalytic reduction (SCR) of nitrogen oxides with ammonia, vanadium, copper, iron, manganese, tungsten, molybdenum, nickel, titanium oxides and their various combinations are used.

 One of the challenges arising in the development of SCR catalysts is to increase their service life by creating catalytic systems with high specific catalytic activity and increased mechanical strength. A problem is the selection of catalytic systems with partial or complete replacement of toxic and expensive vanadium compounds.

 A known catalyst with increased mechanical strength for the SLE process, including a solid carrier based on aerosilogel and refractory clay and alternately deposited layers of titanium oxide and vanadium oxide [1].

 The disadvantages of this catalyst are the complex technology of layer-by-layer deposition of titanium and vanadium oxides, waste water disposal and the impossibility of its operation in gas emissions containing large amounts of soot and dust due to abrasion of the active catalyst layer.

 A known catalyst comprising a titanium-containing agent and active components - transition metal oxides, as well as clay with a particle size of 100 - 500 μm with a mass ratio of titanium-containing agent and clay 4.5 - 1: 1 [2].

 The disadvantage of this catalyst is a decrease in mechanical strength in environments containing moisture due to clay swelling.

 A known method of increasing the mechanical strength of the catalyst by introducing into the composition of the extracted mass of aluminosilicate, mullite-siliceous fibers [3]. The composition of the catalyst includes titanium oxide and one oxide of an element such as vanadium, molybdenum and / or tungsten and an inorganic fiber, the gaps between the fibers being filled with said catalyst composition. The ratio by weight of the catalytic composition and fiber is at least 3.

 The disadvantage of this catalyst is the dilution of the active component and, consequently, a decrease in the activity of the catalyst, as well as the limited ability to prepare catalysts of various geometries.

Closest to the invention in technical essence and the achieved result is a catalyst containing at least 1 to 3 wt.% From the group of oxides Cu, Ni, Co and V, 7 to 8 wt.% WO ₃ , 15 wt.% Clay , the rest is a carrier based on titanium dioxide. The catalyst is obtained in the form of blocks with a cross section of 150 x 150 mm, a cell size of 7 x 7 mm and a partition thickness of 1.5 mm. For hardening, the end part of the blocks is shielded with a glassy cladding based on glaze. Additionally, a metal grate is stamped in front of the front catalyst bed, stamped according to the sectional dimensions of the catalyst block. The specific surface area of the obtained catalyst is 10-150 m ² / g with a pore volume of 0.2-0.6 cm ³ / g. The degree of conversion of NO _x at 350 - 380 ^o C does not exceed 89% [4].

 The disadvantages of this catalyst are the high energy consumption of the method of its preparation and multi-stage.

 The objective of the invention is the development of a catalyst for the purification of gases from nitrogen oxides with increased mechanical strength while maintaining high catalytic activity.

The problem is solved by using a catalyst containing a carrier comprising titanium dioxide containing at least one active component selected from the group of vanadium and copper compounds and tremolite and / or wollastonite with the following components in the catalyst, wt.%:
The content of compounds V and / or Cu in terms of metal
V - Not more than 1
Cu - Not more than 2
Tremolite and / or wollastonite - 2 - 12
Media - Other
The catalyst has the following composition, wt.%:
The content of compounds V in terms of metal
V - 0.16-1
Tremolite and / or wollastonite - 2 - 12
Media - Other
The catalyst has the following composition, wt.%:
The content of Cu compounds in terms of metal
Cu - 0.2 - 2
Tremolite and / or wollastonite - 2 - 12
Media - Other
The catalyst has the following composition, wt.%:
The content of compounds V and Cu is 0.2 - 1
Tremolite and / or wollastonite - 2 - 12
Media - Other
The catalyst may additionally contain tungsten oxide in an amount of not more than 10 wt. %, fiberglass - not more than 5 wt.%, clay - not more than 10 wt.%.

. Волластонит - минерал из класса цепочечных силикатов, формулы [CaSiO₃]_n, образуется при метаморфизме известняков. Тремолит - минерал из класса цепочечных силикатов группы моноклинных амфиболов, формула [Ca₃Mg₅[Si₄O₁₁](OH)₂]_n.To obtain a catalyst, a thermostable fibrous material is used - wollastonite or tremolite, exhibiting a reinforcing effect, which leads to hardening of the catalyst, and contributing to an increase in the share of transport macropores with a size of more

. Wollastonite is a mineral from the class of chain silicates, of the formula [CaSiO ₃ ] _n , formed during the limestone metamorphism. Tremolite is a mineral from the class of chain silicates of the monoclinic amphibole group, the formula [Ca ₃ Mg ₅ [Si ₄ O ₁₁ ] (OH) ₂ ] _n .

 The proposed catalyst has increased mechanical strength and high catalytic activity compared with the known solution.

The process of preparation of the catalysts includes the following stages:
mixing of the starting bulk components: titanium dioxide, wollastonite and / or tremolite, with and without tungsten oxide, clay and fiberglass;
adding an aqueous solution of salts of copper and / or vanadium;
prolonged mixing of the resulting mass with the addition of an organic plasticizer and water;
extrusion or molding of the catalyst mass;
drying, drying, calcination.

 In the preparation of the catalysts, wollastonite and tremolite powders of natural origin with a particle size of 60-100 μm were used.

 The characteristics of the catalysts, the test results are shown in the table. The content of active components of Cu and / or V is given in terms of metal, since according to physicochemical studies, the catalysts lack pure phases of oxides or sulfates of copper and vanadium.

Examples 1-4 use TiO ₂ (anatase modification) obtained by vapor-phase hydrolysis of titanium chloride with a specific surface area of 15 m ² / g and a pore volume of 0.34 ml / g.

Example 1. In a Z-shaped mixer, 9.38 kg of TiO ₂ , 0.5 kg of WO ₃ are mixed, then a solution of vanadyl sulfate (0.298 kg of VOSO ₄ • 3H ₂ O in 1.5 l of water) is added to create the necessary molding properties pour a solution of polyethylene oxide (PEO) [0.1 kg PEO in 1 l of H ₂ O]. The components are thoroughly mixed for one hour until a homogeneous plastic mass is obtained. From the obtained mass, model fine-mesh blocks with a diameter of 10 mm, a channel size of 1.2 x 1, 2 mm, a wall thickness of 0.4 mm, section blocks 24 mm, a channel size of 6 x 6 mm and a wall thickness of 1.5 mm were extruded on laboratory equipment rings with an outer diameter of 6 mm and an inner diameter of 2 mm to determine mechanical strength. On a vacuum screw press, honeycomb blocks are extracted in the form of a square prism of 75 x 75 mm or 150 x 150 mm, channel size 2 x 2 mm, 5.6 x 5.6 mm, wall thickness 0.8 - 1.4 mm , block length 150 - 500 mm. The catalyst is dried, dried and calcined in air with a gradual increase in temperature to 500 ^o C and forced circulation of the coolant along the channels, kept at 500 ^o C for 4 hours

Example 2. In a Z-shaped mixer mix 8.68 kg of TiO ₂ , 1 kg of WO ₃ , 0.2 kg of tremolite, then add a solution of vanadyl sulfate (0.298 kg of VOSO ₄ • 3H ₂ O in 1.5 l of water), add a solution of polyethylene oxide (0.1 kg PEO in 0.96 l of H ₂ O). Further, as in example 1.

Example 3. In a Z-shaped mixer, 8.58 kg of TiO _2, 0.1 kg of WO ₃ , 1.2 kg of tremolite are mixed, a solution of vanadyl sulfate (2.298 kg of VOSO ₄ • 3H ₂ O in 1.5 l of water) is added, and a solution of polyethylene oxide (0.1 kg PEO in 0.96 l of H ₂ O). Further, as in example 1.

Example 4. In a Z-shaped mixer, 8.21 kg of TiO ₂ , 0.45 kg of tremolite, 0.18 kg of wollastonite are mixed, a solution of vanadyl sulfate (0.383 kg of VOSO ₄ • 3H ₂ O in 1.5 l of water) is added, add a solution of polyethylene oxide (0.09 kg in 0.74 l of H ₂ O). Further, as in example 1.

Example 5. For the preparation of the catalyst, a support was used, containing mainly TiO ₂ (anatase) obtained by hydrolysis of titanyl sulfate with a specific surface area of 132 m ² / g and a pore volume of 0.42 ml / g.

In a Z-shaped mixer, 8.74 kg of TiO ₂ , 1 kg of wollastonite are mixed, a solution of copper nitrate (0.759 kg Cu (NO ₃ ) ₂ • 3H ₂ O) is added, a solution of polyethylene oxide (0.1 kg PEO in 1.3 l is added H ₂ O). Further, as in example 1.

In examples 6 to 7, 9, 10, a carrier is used that contains mainly TiO ₂ (anatase) obtained by hydrolysis of titanium chloride, with a specific surface area of 190-200 m ² / g, pore volume of 0.5 - 0.6 ml / g, different contents of V as an impurity. For the preparation of the catalysts in examples 8, 11, a support is used that contains mainly TiO ₂ (anatase) obtained by hydrolysis of titanyl sulfate with a specific surface area of 74 m ² / g and a pore volume of 0.36 ml / g.

Example 6. In a Z-shaped mixer, 8.83 kg of a TiO ₂ -based carrier with a vanadium content of 0.34 wt.%, 0.9 kg of tremolite are mixed, a solution of copper sulfate (0.427 kg of CuSO ₄ • 5H ₂ O in 2 l is added H ₂ O), a solution of polyethylene oxide (0.1 kg PEO in 1.8 l of H ₂ O) is added. Further, as in example 1.

Example 7. In a Z-shaped mixer, 8.1 kg of a TiO ₂ -based carrier with a vanadium content of 0.86 wt.%, 1 kg of tungsten oxide, 0.9 kg of tremolite are mixed, a solution of polyethylene oxide (0.1 kg PEO in 3 6 L H ₂ O). Further, as in example 1.

Example 8. In a Z-shaped mixer, 7.96 kg of a carrier based on TiO ₂ 1 kg of tungsten, 0.9 kg of tremolite are mixed, a solution of copper nitrate (0.416 kg of Cu (NO ₃ ) ₂ • 3H ₂ O in 1.3 l is added H ₂ O), a solution of plylene oxide (0.1 kg PEO in 1 l of H ₂ O) is added. Further, as in example 1.

Example 9. In a Z-shaped mixer, 8.05 kg of a TiO ₂ -based carrier with a vanadium content of 0.37 wt.%, 0.5 kg of tremolite, 1 kg of clay are mixed, a solution of copper sulfate (0.699 CuSO ₄ • 5H ₂ O is added in 2.5 l of H ₂ O), a solution of polyethylene oxide (0.1 kg of PEO in 1 l of H ₂ O) is added. Further, as in example 1.

Example 10. In a Z-shaped mixer, 7.25 kg of a TiO ₂ -based carrier are mixed with a vanadium content of 0.22 wt.%, 1 kg of tungsten oxide, 0.5 kg of thermolite, 0.7 kg of clay, 0.5 kg of mulito -silica fiber, adding a solution of copper sulfate (0.078 kg CuSO ₄ • 5H ₂ O in 2.5 l of H ₂ O). Further, as in example 1.

Example 11. In a Z-shaped mixer, 8.08 kg of a TiO ₂ -based carrier, 0.5 kg of tremolite, 0.7 kg of clay, 0.5 kg of mulite-siliceous fiber are mixed, a solution of copper sulfate (0.350 kg CuSO ₄ • 5H ₂ O in 1 L H ₂ O), a solution of polyethylene oxide (0.1 kg PEO in 1.5 L H ₂ O) is added. Further, as in example 1.

Example 12. A D Z-shaped mixer mixes 9.07 kg of a TiO ₂ -based support, 0.9 kg of tremolite, adding a solution of vanadyl sulfate (0.067 kg of VOSO ₄ • 3H ₂ O in 1.5 L of water), add a solution of polyethylene oxide ( 0.1 kg in 1 liter of H ₂ O). Further, as in example 1.

Example 13. In a Z-shaped mixer, 9.05 kg of a TiO ₂ -based support are mixed, 0.9 kg of tremolite, a solution of copper sulfate (0.078 kg of CuSO ₄ • 5H ₂ O in 1.1 L of H ₂ O) is added, a solution is added polyethylene oxide (0.1 kg PEO in 1 l of H ₂ O). Further, as in example 1.

 Example 14 (prototype). At the same time, the catalyst components are mixed: 2 weight. including ammonium metavanadate, 8 wt. including ammonium paratungstate, 100 wt. including titanium oxide, 15 wt. including clay, 2 wt. including polyethylene oxide, 20 wt. including polyethylene glycol and 50 wt. parts of water. Further, as in example 1.

.The catalytic properties of the catalyst samples are studied in a flow-through installation using a gas mixture of NO _x composition - 0.05 vol.%, NH ₃ ) - 0.05 vol. %, O ₂ - 0.5 vol.%. The volumetric gas flow rate is equal to 27000 h ^-1 . The analysis of the gas mixture is carried out by chromatographic method. The degree of conversion of nitric oxide is determined by the following formula:

.

Testing of the catalyst is carried out in the temperature range 225 - 400 ^o C.

,
где
N - показания индикатора прибора в делениях;
A - калибровочный коэффициент, кг/дел;
S - площадь поперечного сечения кольца катализатора, см².To determine the mechanical strength, the mass is extruded in the form of rings of high equal to the outer diameter, which are then compressed to crush in the transverse direction. The essence of the method is to measure the fracture forces of a ring between two parallel plates. The strength of the catalyst is expressed in kilograms per square centimeter and calculated by the formula

,
Where
N - readings of the indicator of the device in divisions;
A - calibration factor, kg / div;
S is the cross-sectional area of the catalyst ring, cm ² .

 The porous structure was determined by mercury porosimetry on a Porosiger-9300 instrument.

с сохранением высокой механической прочности (пр. 2).As follows from the above examples, the optimal content of tremolite and / or wollastonite is in the range of 2-12 wt.% (Examples 1-3). The content of tremolite and / or wollastonite less than 2 wt.% Is not enough to achieve high mechanical strength. The increase in the content of more than 12 wt.% Significantly affects the plastic properties of the moldable mass, the introduction of tremolite and / or wollastonite in the catalyst mass provides its high molding properties and high mechanical strength of the catalyst. This allows you to get the catalyst without the use of fiberglass, clay and expensive organic plasticizers (example 5). At the same time, the use of tremolite and wollastonite increases the proportion of transport macropores (more

while maintaining high mechanical strength (pr. 2).

 It is possible to prepare an active strong catalyst with a low content of the active component (examples 10, 13 and 14) and partial or complete replacement of toxic expensive vanadium compounds with copper-containing compounds (examples 4, 5, 7, 9 and 10).

 Thus, the present invention can find application in the energy, chemical, metallurgical and other industries having off-gases in which nitrogen oxides are contained.

Claims (4)

1. The catalyst for the purification of gases from nitrogen oxides on the basis of a carrier comprising titanium dioxide containing at least one active component selected from the group of compounds of vanadium, copper, characterized in that it additionally contains tremolite and / or wollastonite with the following components in catalyst, wt.%:
The content of compounds V and / or Cu in terms of metal V - Not more than 1
Cu - Not more than 2
Tremolite and / or wollastonite - 2.0 - 12.0
Media - Other
2. The catalyst according to claim 1, characterized in that the content of the components is, wt.%:
The content of compounds V in terms of metal V - 0.16 - 1.0
Tremolite and / or wollastonite - 2.0 - 12.0
Media - Other
3. The catalyst according to claim 1, characterized in that the content of the components is, wt.%:
The content of Cu compounds in terms of metal Cu - 0.2 - 2.0
Tremolite and / or wollastonite - 2.0 - 12.0
Media - Other
4. The catalyst according to claim 1, characterized in that the content of the components is, wt.%:
The content of compounds V and Cu in terms of metal V - 0.16 - 0.5
Cu - 0.2 - 1.0
Tremolite and / or wollastonite - 2.0 - 12.0
Media - Other
5. The catalyst according to claims 1 to 4, characterized in that it further comprises tungsten oxide in an amount of not more than 10 wt.%.  6. The catalyst according to claims 1 to 5, characterized in that it further comprises fiberglass in an amount of not more than 5 wt.%.  7. The catalyst according to claims 1 to 6, characterized in that it further comprises clay in an amount of not more than 10 wt.%. 8. The catalyst according to claims 1 to 7, characterized in that the proportion of macropores with a size of more than 10000

is at least 23%.

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