Catalyst for oxidation of hydrocarbon gases and the method of its preparation

 

(57) Abstract:

The inventive catalyst contains platinum on the media, representing the oxidized stainless steel in a ratio of components (wt.%): Pt 0,02-0,11, the media-the rest. For the preparation of the catalyst, a metal carrier stainless steel pre-occiderit, and then put platinum by immersing the carrier in an aqueous solution containing 4,510-4-6,010-4mol/l [Pt(NH3)4]Cl2and 0.005 mol/l potassium hydroxide at 170-210oWith in a confined space within 150-180 min and the ratio of bulk volume of the medium to the volume of solution equal to 1:13-1:14. 2c.p. f-crystals, 2 tab.

The invention relates to the field of environmental protection from toxic components of exhaust gases, namely catalytic oxidative purification of exhaust gases containing hydrocarbons.

Known catalyst for purification of gas emissions from organic impurities containing palladium, deposited on a metal carrier, in the following ratio, wt.

Pd 0,10 0,25

steel NOT leave [1]

This catalyst was prepared by depositing palladium on a metal carrier from the electrolyte solution met the current of 1.0-1.2 a/DM2full of period 10, the cathode period 1, the anode period 9 and the second phase: the current density of 2.0-2, 5 a/DM2, cathodic period 9, the anode period of 1 sec.

Palladiana lead from aqueous electrolyte solution of the following composition, g/l: duplissy palladium, calculated on the metal of 1.5 1.8 disubstituted ammonium phosphate 10-16; disubstituted phosphate sodium 50-60; water to 1 L. the Degree of conversion of p-xylene on this catalyst is 92-95% at temperatures of 350-400oC and the concentration of p-xylene in the gas, equal to 1.0 g/m2. [1] the Disadvantages of this catalyst and method thereof - a high content of palladium (0.25 wt.) and the lack of catalytic activity. The closest in technical essence and the achieved effect is the catalyst for purification of exhaust gases from harmful organic impurities containing from 0.04 to 0.14 wt. PD on the metal carrier. As the carrier used alloys OH (wire) and 18CR10NITI. [2]

The method of preparation of the catalyst includes the steps of degreasing, etching, followed by deposition of 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/P> The degree of conversion of p-xylene catalyst containing 0.06% of Pd, are 54-98% at temperatures 250-320oC.

Oxidation of xylene on the catalysts, which are prepared by the above method and have media risks and without them, at temperatures of 250-350oC are 54-98% and 41-95%, respectively [2]

The disadvantages of this catalyst and method of its production are insufficient catalytic activity at temperatures of 25O-400oC. and the dependence of the activity of the catalyst from the norm of the media.

The basis of the invention is the development of a catalyst on a metal carrier for the oxidation of hydrocarbon gases and method of its preparation, providing a high activity at 250-400oAnd small (not more than 0.11 wt%) content of platinum group metal.

The task is solved in that in the process of oxidation of hydrocarbon gases used catalyst containing a platinum group metal on a metal carrier, characterized in that it contains platinum and stainless steel in the following ratio of components (% by weight):

PT 0,02 0,11

stainless steel stop

The method of preparation of the catalyst, including steel pre occiderit, as platinum is applied by immersing the carrier in an aqueous solution containing 4,510-4- - 6,010-4mol/l [Pt(NH3)4] Cl2and 0.005 mol/l potassium hydroxide, at a temperature of 170-210oWith in a confined space within 150-180 minutes and the ratio of bulk volume of the medium to the volume of solution equal to 1:13 1:14.

The method of preparation of the catalyst is carried out as follows. The media is a crushed chips of steel HNT or X18H1OT.

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

2 stage ultrasonic treatment. The carrier is treated with ultrasound frequency 18 KHz in distilled water for 1 -2 minutes, installing the TGS-0,25. stage 1 and 2 provide the necessary degree of purity of the medium surface.

3 phase 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 [3] and is required for the deposition of platinum by the autoclave method of thermolysis. From literature it is known that the oxidation Bo the oxidation increases rapidly and the metal is destroyed. The media was oxidisable in a tubular electric furnace at temperatures of 400 to 500oWith over three or five hours. The working temperature was regulated with a precision of + 10oC electronic potentiometer using a chromel-alumaloy thermocouple. Oxidation at 400 - 500oWith for three or four hours leads to the formation of thin well-linked with the base oxide film yellow-pink color. The increase in temperature and time of oxidation leads to a noticeable oxidation media and the formation of an oxide layer, which easily crumbles.

stage 4 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.

5 stage patinirovanie. The metal carrier, prepared as described above, placed in a quartz or Teflon autoclave with an aqueous solution of ammonium platinum complex [Pt(NH3)4]Cl2and potassium hydroxide. Maintenance of the complex in solution take in the range of 4.5-610-4mol/l with a ratio of bulk volume of the medium to the volume of solution Rin argon or nitrogen removal from the system of molecular oxygen, then, the autoclave is pressurized. Must also be conducted at a temperature of 170-210oWith over 150-180 min in an autoclave with stirring. Platinum media is washed with distilled water and dried.

Specific examples of the implementation of stage 5 preparation of the catalysts are shown in table 1.

Removing oxygen from the system is a prerequisite for obtaining high-quality coatings, as in his presence when thermolysis along with metallic platinum are formed of low-soluble compounds of variable composition of platinum (4). Intervals of duration and temperature of the process, the concentration of potassium hydroxide in solution conditions are close to 100% allocation of platinum from a solution of the complex. They established experimentally.

During the process consists of time indukcionnogo period (i.e. the time until the occurrence of visually observable metal in the process) and the time of separation of the metal. The temperature decrease and the concentration of potassium hydroxide in solution increases the induction period.

In the autoclave process of thermolysis is the destruction of the carriers from stainless steel at a concentration of hydroxide CA is setele for z0, 90 and 120 minutes at a temperature of 210oAnd the concentration of potassium hydroxide in the solution is from 0.005 mol/l (table. 1 N5, N6). 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 (PL.1). The lower temperature (below 170oC) and a decrease in the concentration of potassium hydroxide (less than 0,005 mol/l) increases the time of induction period and coverage for 180 min, is not formed. High temperature (above 210oC) is impractical because it leads to increased design requirements of equipment, sealing and so on, it Should be noted that the decrease in concentration in the solution of a complex of platinum below 4,510-4mol/l does not lead to the desired percentage of platinum in the catalyst with respect to the bulk volume of the medium to the volume of solution equal to 1:13 1:14.

Tests of the prepared samples was performed by gas chromatography installation: micromodules isothermal reactor (volume of the reaction zone catalysis of 2.5-3.5 cm3) with the diffusion cell input gas-hydrocarbon mixture, the device chromatograph "Color 5O0 M (steel Packed column (3 mm x 1 m, napadisylate 99,2% qualification "h"). The process conditions of 2.5-3,) cm3the test contact was placed in the reactor, the reaction temperature 25O-400oC, the supply of raw material vapor-air mixture 50 ml/min oxidation of p-xylene was calculated as the ratio of the peak heights of p-xylene 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 data from 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 25O-400oC and activity superior to catalysts and analog prototype.

The content of platinum in the prepared catalysts is less than the catalysts of the prototype. TTT TTT

1. Catalyst for oxidation of hydrocarbon gases containing a platinum group metal on the oxidized metal carrier, characterized in that it contains oxidized platinum and stainless steel in the following ratio, wt.

Platinum 0,02 0,11

Oxidized stainless steel is, including the deposition of platinum on the pre-oxidized metal carrier, characterized in that the platinum is applied by immersing the carrier of stainless steel in an aqueous solution containing 4.5 to 10-4-6,0-104mol/l [Pt(NH3)4]Cl2and 0.005 mol/l potassium hydroxide, at a temperature of 170-210oWith in a confined space within 150-180 min and the ratio of bulk volume of the medium to the volume of solution equal to 1:13-1:14.

 

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