The catalyst for purification of gas emissions of oxides of nitrogen

 

(57) Abstract:

The invention relates to the protection of the environment from toxic industrial emissions, or rather to the catalysts for purification of exhaust gases of internal combustion engines from nitrogen oxides. Describes the catalyst for purification of gas emissions of oxides of nitrogen containing media on the basis of silicon dioxide in the form of highly dispersed synthetic material are presented with an average particle size (5-20)10-12mm, and the ratio of the applied components, calculated on the dry matter is: Nickel oxide of 5.3% and 6.6%, chromium oxide 7-10%. This catalyst has significant advantages and a higher activity and duration of work without loss of activity compared with the known. table 1.

The present invention relates to the means of protecting the environment from toxic industrial emissions, namely the catalysts for purification of exhaust gases of internal combustion engines from oxides of nitrogen.

Known catalyst for reduction of nitrogen oxides, representing faience media, which caused the oxides of Nickel and chromium in the following ratio of components, wt.%:

The oxide of the PR operates at a temperature of 400oC, flow rate of the gas stream 100.000 h-1and the degree of gas purification from nitrogen oxides in these conditions is 98%, the duration of operation of the catalyst is not more than 100 hours.

Closest to the proposed technical solution is the catalyst for purification of gas emissions from nitrogen oxides, including oxides of silicon, chromium and Nickel containing additional oxides of barium, iron in the following ratio, wt.%:

The chromium oxide - 16,0-18,0

Nickel oxide is 0.5 - 5,1

The barium oxide - 0,05 - 0,15

Iron oxide - 0,03-0,25

The silicon oxide - Rest

(EN 2068732 C1, 10.11.96).

This catalyst contains oxides of barium and iron in addition to the above-mentioned ratio of the components and uses as a carrier silica.

The catalyst is characterized by increased activity, especially when applied as a reducing agent aqueous solution of urea.

However complicated the process of obtaining media by precipitation of sodium metasilicate sulfuric acid requires additional costs for the removal of water, the sodium salt of sulfuric acid.

The necessary control over the content of sodium and sulfur as toxic catalysate is it Nickel (15-30%) and chromium (60-76%), as the concentration of precipitated oxides of chromium and Nickel on a carrier of silica gel remains low, which leads to increase of consumption of the catalytic mass.

The authors propose the catalyst for purification of gas emissions of oxides of nitrogen containing media on the basis of silicon dioxide, which is fine synthetic material-aerosol with an average particle size (5 to 20)10-12mm, and the ratio of the applied components, calculated on the dry matter is: Nickel oxide of 5.3% and 6.6%, the chromium oxide - 7 - 10%.

Distinctive features of the invention are used as media superfine synthetic material-aerosol with an average particle size (5 to 20)10-12mm and the ratio of the applied components in terms of dry substance, which is: Nickel oxide of 5.3% and 6.6%, chromium oxide 7-10%.

The catalyst operates in the presence of the reducing agent is an aqueous solution of ammonia at a temperature of 310-350oC and flow rate 15103h-1with less salt content of Nickel and chromium in the impregnated composition.

Aerosil - fine synthetic silica grades a-300. The average particle size of Aerosil (5-20)1tx2">

Example 1. Prepare media of Aerosil and polyvinyl acetate dispersion (in the ratio 1:10). The resulting mass is formed into granules of spherical shape with a diameter of 4 mm, dried at a temperature of 205oC for 24 hours and calcined at a temperature of 900oC for 30 minutes. The resulting carrier is treated with water vapor for 1 hour to saturate and impregnate alternately salt solutions: 10% Nickel nitrate Ni (NO3)2; 25% chromium nitrate Cr(NO3)3. The catalyst was dried for 24 hours at a temperature of 205oC and calcined at a temperature of 550oC for 2.5 hours.

The resulting catalyst has a composition in wt. %:

NiO 6,1; Cr2O37,8; silicon dioxide else.

Through the catalyst miss the combustion products of diesel fuel. As a reducing agent is applied ammonia dissolved in water. Testing is carried out at atmospheric pressure, the temperature 310-350oC, the volumetric gas flow rate 15-16103h-1.

The degree of purification of exhaust gases of the internal combustion engine nitrous oxide is 90%.

Example 2. Of Aerosil and polyvinyl acetate dispersions prepared media in the recipe of pre turn: 5% of Nickel nitrate Ni(NO3)2and 5% of chromium nitrate Cr(NO3)3. The catalyst was dried for 24 hours at a temperature of 205oC and calcined at a temperature of 550oC for 2.5 hours.

The resulting catalyst has a composition in wt.%: PIO 1,6; Cr2O34,6; the rest of silicon dioxide.

The degree of recovery of nitrogen oxide in the exhaust gas of the internal combustion engine is 80% at the temperature of the gas mixture 310oC, the volumetric gas flow rate 15-16103h-1, atmospheric pressure. As a reducing agent is applied ammonia dissolved in water.

Example 3. Prepare media of Aerosil and polyvinyl acetate dispersions for the formulation of example 1. Impregnation of the carrier is carried out with aqueous solutions of salts in the following sequence: chromium nitrate 5% Cr(NO3)3; nitrate Nickel - 5% Ni(NO3)2moreover , the impregnation with solutions of salts is carried out after saturation of the media with water vapor. The carrier coated with the catalyst mass is dried for 24 hours at a temperature of 205oC and calcined at a temperature of 550oC.

The resulting catalyst has a composition in mass profits: NiO 2,8%; Cr2O34.6%, the rest of silicon dioxide.

oC, the volumetric gas flow rate 15-16103h-1, atmospheric pressure.

Example 4. The carrier obtained in formulation example 1, was impregnated with solutions of salts, mixed in a 1:1 ratio by volume: of Nickel nitrate 10% Ni(NO3)2; nitrate chromium 25% Cr(NO3)3. A carrier coated with a catalyst mass is dried for 24 hours at a temperature of 205oC and calcined at a temperature of 550oC for 2.5 hours.

The resulting catalyst has a composition in wt.%: PIO 6,6; Cr2O310; the rest of silicon dioxide. Through the catalyst miss the combustion products of diesel fuel as a reductant use ammonia water. At a temperature of 310oC, flow rate of the gas stream 15103h-1and atmospheric pressure, the degree of reduction of nitrogen oxides is 90%.

As follows from the table that the catalysts produced in accordance with the invention:

- do not contain expensive materials and their compounds, as the main material of the carrier is an aerosol, sustainest to get more active components - oxides of Nickel and chromium on the media at a lower salt content of Nickel and chromium in the catalyst mass in comparison with the known;

- in the manufacture does not require complex chemical engineering processes (coprecipitation, filtering, multi-stage washing and equipment;

- provide a degree of purification of exhaust gases from nitrogen oxides in the range of 80-90% at least 120 hours at a temperature of 310-350oC without loss of activity.

Therefore, the catalyst has significant advantages and a higher activity compared with the known.

Sources of information

1. Author's certificate N 1447393, M CL 01 J 23/26, the Catalyst for purification of gases from nitrogen oxides, published. Bull. N 48, 30.12.88,

2. Patent N 2068732 "the Catalyst for purification of gas emissions from nitrogen oxides) class. B 01 J 23/86, published. 10.11.1996, bull. N 31.

The catalyst for purification of gas emissions of oxides of nitrogen containing media on the basis of silicon dioxide, characterized in that as the carrier used superfine synthetic material are presented with an average particle size (520)10-12mm, and the ratio of the applied components in terms of dry ve the

 

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