The method of preparation of the catalyst for oxidation of hydrocarbon gases

 

(57) Abstract:

The invention relates to the protection of the environment from toxic components of exhaust gases, namely catalytic oxidative purification of hydrocarbon gases. Describes the method of preparation of the catalyst for oxidation of hydrocarbon gases by deposition of platinum on the pre-oxidized metal carrier stainless steel in an aqueous solution of [Pt(NH3)4]Cl2and 0.005 mol/l potassium hydroxide at 170-210C in a closed volume within 150-180 min, and the carrier is made of-metal material "Mr" and the deposition is conducted in aqueous solution containing 610-4- 1210-4mol/l [Pt(NH3)4]Cl2when the ratio of the volume of the medium to the volume of solution equal to 1:10-1:11. The density of the material "Mr" was 1.97-2,99 g/cm3. Technical result: the catalyst has high activity at 250 - 400C, a small gas-dynamic resistance of the reaction stream and the selected geometric shape, porosity media. 1 C.p. f-crystals, 2 tab.

The invention relates to the field of environmental protection from toxic components of exhaust gases, namely catalytic oxidative cleaning uglev the Reden organic impurities in industrial gas emissions, in particular for purifying exhaust gases of internal combustion engines [SU authorship, 1170676, class B 01 J 37/03, 1985]. The method of preparation of the catalyst includes the manufacture of media in the form of packages of corrugated and flat strips of alloy H or 18CR10NITI with pre-applied risk, operations, degreasing, etching media with subsequent deposition on it of 0.04 to 0.14 wt.%. palladium in the form of a film from a solution of the following composition, g/l: palladium chloride 0,3-1,4; Trilon B 2,4-12; 25% ammonia solution 40-170; 5% solution of hydrazine hydrate is added 3,6-11; sodium chloride 0.5 to 1.5. The process palladiana performed at room temperature or 70oC. Specific surface area of the proposed catalyst is 2700-3000 m2/m3. The degree of conversion of n-xylene catalyst containing 0.06% of Pd, is 54-48% at a temperature of 250-320oC. oxidation of n-xylene at such a catalyst without scratches is 41-95% at a temperature of 250-350oC.

The disadvantages of the method of receipt of such catalyst are insufficient catalytic activity at temperatures of 250-400oC, small specific surface of the carrier, the dependence on the shape of the carrier of the catalyst activity.

Order Uwe is some processing acids, salts or electrochemical oxidation or on the surface of the carrier is applied to the metal oxide, followed by the introduction of active components [Popova N. M. The catalysts for purification of gas emissions from industrial productions, M.: Chemistry. S. 49; alhazov T. G., Margolis L. J. Deep catalytic oxidation of organic substances. M.: Chemistry, 1985, S. 192].

Known methods of preparing catalysts for oxidation of hydrocarbon gases containing a platinum group metal deposited on the oxidized metal carrier [Popova N. M. The catalysts for purification of gas emissions from industrial productions, M.: Chemistry, S. 49; alhazov T. G., Margolis L. J. Deep catalytic oxidation of organic substances. M.: Chemistry, 1985, S. 192; SU, copyright certificate, 386659, class B 01 J 23/42, 1973; RU, patent N 2063804, class B 01 J 23/89, 37/03].

Closest to the present invention is a method of preparation of the catalyst containing platinum on the media, representing the oxidized stainless steel in a ratio of components (wt.%): Pt 0,02-0,11, media - rest [RU, patent N 2063804, class B 01 J 23/89, 37/03]. For the preparation of the catalyst metal carrier, representing the crushed chips in stainless steel, pre is UP> - 6,010-4mol/l [Pt(NH3)4]Cl2and 0.005 mol/l potassium hydroxide at a temperature of 170-210oC in the closed volume within 150-180 min and the ratio of bulk volume of the medium to the volume of solution equal to 1:13-1:14. The degree of conversion of xylene catalyst is 98-99,8% at temperatures of 250-400oC.

The disadvantage of the method of preparation of this catalyst is granular media, which does not preserves the relative spatial position of the elements of the structure (rigidity), a relatively low proportion of solid material in the reactor volume (high porosity). In the catalytic treatment of hydrocarbon waste gases are often used block of metal carriers [SU authorship, 1170676, class B 01 J 37/03, 1985; Popov N. M. The catalysts for purification of gas emissions from industrial productions, M.: Chemistry, S. 49; alhazov T. G., Margolis L. J. Deep catalytic oxidation of organic substances. M.: Chemistry, 1985, S. 192], including in the catalytic converters of exhaust gases of engines. Block metal carriers have a defined geometric shape, size, porosity and other parameters, i.e. adapted to the type rela provides the inability to move and damage the catalytic layer, more efficient use of the surface, the possibility of independent optimization parameters determining the efficiency of the reactor, i.e., porous structure and form of the catalyst.

The basis of the invention is to develop a method for the preparation of block catalyst for oxidation of hydrocarbon gases containing platinum on the carrier, providing a high activity at a temperature of 250-400oC, a small gas-dynamic resistance of the reaction stream and the selected geometric shape, porosity media.

The task is solved in that in the method of preparation of the catalyst for oxidation of hydrocarbon gases, including the deposition of platinum on the pre-oxidized metal carrier stainless steel in an aqueous solution of [Pt(NH3)4] Cl2and 0.005 mol/l potassium hydroxide at a temperature of 170-210oC in the closed volume within 150-180 min, according to the invention the carrier is made of material "Mr" ("metallorubber") and the deposition is conducted in aqueous solution containing 610-4- 1210-4mol/l [Pt(NH3)4]Cl2when the ratio of the volume of the medium to the volume of solution equal to 1:10-1:11. The density of the material "Mr" extending t">

I stage - production of media.

Media in blocks of cylindrical shape made of-metal material MP. The Mr material is a homogeneous porous mass, obtained by cold pressing dosed by weight and an elongated wire helix [SU authorship, 183174, CL 7 d 16, I960.; Chegodaev D. E., Muluken O. P., Kholtygin E. C. Construction of the working bodies of machinery and equipment from progovorennogo of Mr material. - Samara: Samara aerospace University, 1994. C. 15-20]. He has a high porosity, large specific surface, good stability on the material volume, high damping properties and relatively simple manufacturing techniques. The density of the Mr material is connected with the wire diameter and porosity (P), defined as the percentage of voids per unit volume ratio.

< / BR>
where Snla geometric surface, cm2;

mnl- unit weight, g;

pnl- density unit g/cm3;

dCR- wire diameter, cm;

P is the porosity of the block.

Steel grade is determined by the composition of the catalyst [RU, patent N 2063804, class B 01 J 23/89, 37/03].

Were samples of media from a wire diameter of 0.02 and respectively equal to 1.4; 1,97; 2,56; 2,99 g/cm3and 4000; 5197; 6382; 7632 m2/m3. Cylinder volume was 1.52 cm3.

II stage - etching. The carrier is placed in a 20% solution of hydrochloric acid for 10-15 minutes at a temperature of 30-40oC, and then washed with distilled water and boiled in distilled water for 10-15 minutes.

Stage III - ultrasonic treatment.

The carrier is treated with ultrasound with a frequency of 18 kHz in distilled water for 1-2 min on installing the TGS-0,25. Phase II and III provide the necessary degree of purity of the medium surface.

IV stage - oxidation.

This stage should provide education on the surface of stainless steel is well linked with the basis of the oxide layer, which has a catalytic activity [Popova N. M. The catalysts for purification of gas emissions from industrial productions, M. : Chemistry. S. 49; alhazov T. G., Margolis L. J. Deep catalytic oxidation of organic substances. M.: Chemistry, 1985, S. 192] and is required for the deposition of platinum by the autoclave method of thermolysis. It is known from literature [Oxidation of metals So 2 /Under the editorship of N. Benar - M.: metallurgy, 1969, - S. 444] that the oxidation of most stainless steels at temperatures below 500owho was kidirali in a tubular electric furnace at temperatures of 400 to 500oC for three or five hours. The working temperature was regulated with a precision of 10oC electronic potentiometer using a chromel-alumaloy thermocouple. Oxidation at 350-400oC for three or four hours leads to the formation of thin well-linked with the base oxide film. The temperature increase to 500-600oC and time oksidirovaniya leads to a noticeable oxidation media and the formation of an oxide layer, which easily crumbles.

V stage - ultrasonic treatment.

Oxidized carrier is placed in distilled water and treated with ultrasound frequency 18 kHz within 1-2 minutes, This stage provides descaling, which is poorly connected to the surface of the media.

VI stage - patinirovanie.

The metal carrier, prepared as described above, placed in a quartz or Teflon autoclave with an aqueous solution of ammonium complex containing 610-4- 1210-4mol/l [Pt(NH3)4]Cl2and 0.005-0.01 mol/l potassium hydroxide, with respect to the bulk volume of the medium to the volume of solution equal to 1: 10-1:11. The solution was purged for 20-30 min with argon or nitrogen to remove from the within 150-180 min in an autoclave with stirring. Platinized media is washed with distilled water. Removing oxygen from the system is a prerequisite for obtaining high-quality coatings, as in his presence when thermolysis along with metallic platinum is formed of poorly soluble compounds of variable composition of platinum (IV). Intervals of duration and temperature of the process, the concentration of potassium hydroxide in solution are the terms of the allocation of platinum from a solution of the complex and preservation of media. They are determined experimentally [RU, patent N 2063804, class B 01 J 23/89, 37/03].

It is shown that the quantitative selection of platinum and the formation of a coating of good quality occurs within 150-180 min from a solution containing 0.005 mol/l potassium hydroxide, at temperatures 170-210oC. it Should be noted that the decrease in concentration in the solution of a complex of platinum below 610-4mol/l and above 1210-4mol/l does not lead to the desired percentage of platinum in the catalyst with respect to the carrier volume to volume solution of 1: 10-1:11 (PL. 1).

Tests of the prepared samples was performed by gas chromatography installation: micromodules isothermal reactor (volume of the reaction zone catalysis of 1.5-3.5 cmthe I column 3 mm, stationary phase squalane, carrier gas - nitrogen, isothermal mode/. The raw material used p-xylene (purity - 99.2%, and the qualification "H"). The process conditions: 1.5 to 3.5 cm3the test contact was placed in the reactor, the reaction temperature is in the range of 200-400oC, the supply of raw steam-air mixture to 50 ml/min

The degree of oxidation of p-xylene was calculated as the ratio of the peak heights of the hydrocarbon on the chromatogram before and after the oxidation reaction and was expressed in %. The concentration of p-xylene in the initial air-steam mixture was 1,72 g/m3.

The results of the tests of the prepared catalysts in the oxidation of p-xylene are shown in table. 2.

Based on the data table. 2, we can say that the catalysts obtained by the above method, are active in the processes of complete oxidation of hydrocarbons (p-xylene) at temperatures of 250-400oC and on the composition and activity of the same catalyst prototype. The catalytic activity of the samples does not depend on the form of media (a unit of Mr material or crushed chips) stainless steel.

The catalytic activity of samples differing density of the Mr material increases in raitala, the catalytic activity of the catalyst developed much more than a catalyst of similar [SU authorship, 1170676, class B 01 J 37/03, 1985].

Gas-dynamic resistance blocks from the Mr material with a density of 2.56 and to 2.99 g/cm3when the gas flow rate of 100 m3/h is 736 and 882,9 PA. Analysis of the data shows that increasing the density of the material more MP to 2.99 g/cm3will lead to an increase in its gas-dynamic resistance without increasing the catalytic activity derived from the catalyst, which is impractical.

1. The method of preparation of the catalyst for oxidation of hydrocarbon gases, including the deposition of platinum on the pre-oxidized metal carrier stainless steel in an aqueous solution containing [Pt(NH3)4]Cl2and 0.005 mol/l potassium hydroxide, at 170-210C in a closed volume within 150-180 min, characterized in that the carrier is made of-metal - Mr material, and the deposition is conducted in aqueous solution containing 610-4- 1210-4mol/l [Pt(NH3)4]Cl2when the ratio of the volume of the medium to the volume of solution equal to 1:10-1:11.

2. The method according to p. 1, characterized in that the carrier of the material

 

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EFFECT: method of increased yield.

3 cl, 4 ex

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