A catalytic element for the conversion of ammonia and a method of catalytic conversion of ammonia

 

(57) Abstract:

The invention relates to a method of conversion of ammonia to two-stage catalytic systems and can be used mainly in the production of nitrogen and hydrocyanic acid, and has synthesis. A catalytic element for the conversion of ammonia includes the step of layers of the platinum mesh and the degree of catalyst a regular cell structure and includes the additional third level layer of thermostable ceramic media - catcher platinum regular cell structure, in which the step of incorporating the catalyst regular cell structure, have a prior stage of layers of platinum mesh or after it. Method of catalytic conversion of ammonia comprises passing the reaction gas mixture containing ammonia and oxygen-containing gas through a two-stage catalytic system comprising the step of layers of platinum mesh, the degree of catalyst a regular cell structure and catcher platinum - ceramic carrier having a honeycomb structure, which is periodically rotated with catalyst a regular cell structure. The implementation of the invention leads to reduce the CSO catalyst with simultaneous capture of platinum and subsequent return it to the manufacturing process, loss of platinum. 2 C. and 8 C.p. f-crystals.

The present invention relates to a method of conversion of ammonia to two-stage catalytic systems and can be used mainly in the production of nitrogen and hydrocyanic acid, and has synthesis.

During the manufacture of nitric acid by oxidation of ammonia with the use of platinum catalysts at high temperature ablation of the platinum in the oxidation of the filament mesh catalyst to oxides and subsequent evaporation of these oxides. All described in the literature as ways to capture platinum can be divided into two large groups: mechanical recovery and chemical capture.

However, neither the recovery of platinum mechanical filters of various designs or absorption catching oxide masses did not receive a distribution due to a number of shortcomings (Karavaev M. M. and other Catalytic oxidation of ammonia. - M.: Chemistry, 1983).

Only recently started production of catching platinum grids based on palladium and a method of operation of the contact device (patent RF 2154020, IPC 01 21/26, 2000).

The main disadvantage of this method is the efficiency of the allocation of platinum from the catcher.

Know the use of a layer of regular cellular structure formed cell block catalyst (patent RF 2100068, IPC B 01 J 23/78, 1997). This layer is located directly after the platinum layer grids, allows to reduce the attachment of platinum by reducing the number of nets in the first stage.

The disadvantage of this method is that it does not solved the problem of reducing losses of platinum due to their ash.

Known catalytic element for the conversion of ammonia (RF patent 2024294, IPC B 01 J 23/42, 1994) in the form of a package platinum-rhodium wire mesh with partial or complete separation of the grids of the gas-permeable heat-resistant and inert to the process of conversion strips in sequential alternation of strips and grids. To reduce losses platinum strip made of a material based on alumina and/or silicon and each strip has a thickness, 4-100 times the diameter of the wire mesh. The reduction of platinum is provided by optimizing the way of conversion of ammonia.

The lack of catalytic element is also sufficiently high number of irrecoverable losses of platinum.

The closest technikmesse, including ammonia and oxygen-containing gas through a two-stage catalytic system in which the first step along the gas mixture is a layer of platinum mesh, and the second step - oxide layer replacenode a catalyst having a honeycomb structure. At the first stage after the platinum grids establish safety net of the alloy, wt.%: palladium - 95 Ni - 5.

The main disadvantage is the use for catching platinum precious metal palladium and complex technology selection of platinum from catching grid.

The objective of the invention is to develop a catalytic element for the conversion of ammonia and a method of catalytic conversion of ammonia, which

- lead to a reduction in investment platinum by reducing the amount of platinum grids;

- increase the service life of the platinum catalyst with simultaneous capture of platinum and subsequent return it to the manufacturing process;

- reduce deadweight losses platinum.

The problem is solved by using a catalytic element for the conversion of ammonia, comprising the step of layers of the platinum mesh and the degree of catalyst a regular cell Stela platinum regular cell structure.

The stage that includes the catalyst for a regular cell structure, have a prior stage of layers of platinum mesh or after it.

The catalyst regular cell structure and media - catcher platinum contain from 0 to 0.7 wt.% platinum and media third stage extractor platinum has a structure similar to the catalyst carrier regular cell structure.

The problem is solved by a method of catalytic conversion of ammonia which comprises passing the reaction gas mixture containing ammonia and oxygen-containing gas through a two-stage catalytic system comprising the step of layers of platinum mesh, the degree of catalyst a regular cell structure and catcher platinum, which impose additional third level of thermostable ceramic carrier having a regular cell structure, which is periodically rotated with catalyst a regular cell structure.

The degree of catalyst a regular honeycomb structure include a prior step of the layers of the platinum mesh or after it.

The carrier of the third stage catcher platinum area of the third stage of the carrier - catcher of platinum is preferably less than 850oWith, and its mass number is bigger than the mass of catalyst a regular cell structure 10-50 wt.%.

The catalyst regular cell structure and thermostable ceramic media - catcher platinum contain from 0 to 0.7 wt.% platinum.

Media - catcher platinum with a platinum content of 0.2 wt.% and more is used as the catalyst for the second stage of the same process.

In our proposed method, the ammonia conversion is proposed to use as a catcher platinum extra layer of thermostable ceramic carrier having a regular cell structure and size, preferably similar to that used in method block catalyst with a regular cell structure. The number of media - catcher platinum is preferable to take in a greater amount than the amount of catalyst regular cell structure that reduces the loss of platinum. The temperature in the zone of the third stage of the carrier - catcher platinum preferably should be less than 850oTo facilitate sorption of platinum.

In the process of catching plateau. The accumulation of platinum in the media - catcher him change places with the degree of catalyst a regular cellular structure, and the role of the media - catcher platinum catalyst has a regular cell structure. The catalyst of the regular honeycomb structure may be located before or after the platinum layer grids. As catalysts regular cell structure can be used any known and used catalysts.

The proposed method for catalytic conversion of ammonia was carried out in conditions of industrial production: for cyanide hydrogen in the reactor with a diameter of 1200 mm at a temperature of 1050-1100oIn the production of nitric acid in the reactor UKL-7 with a diameter of 1500 mm at a temperature of 870-920oC. the Study of the influence of the chemical composition and the geometrical sizes of blocks of cellular structure on the yield of target products was carried out on pilot plant reactor cross section square 75x75 mm as the platinum catalyst package was used for braided mesh density 1024 cells/cm2diameter wire 0,092 mm, made of alloy 5. Blocks of catalyst and sorbent honeycomb structure was parallel is, Uchenie single channel is a square with a side of 2-8 mm Hexagonal prism have side 45-60 mm and cylindrical channels with a diameter of 4-8 mm

The following examples illustrate the proposed solution.

Example 1.

In the reactor for the synthesis of hydrogen cyanide load layer ceramic blocks sorbent cell structure height 25 mm side of the block 65 mm, wall thickness 0.8 mm, cross-section of the channel 4x4 mm, bulk quantity of 10% more than the number of block catalyst. On the layer of sorbent stack six platinum mesh, and then have the block layer of the catalyst conversion of ammonia composition, wt.%: 2MgO2l2OC5SiO2- 80-85, promoter and binding - rest, height 25 mm, the same size as the sorbent. The source gas mixture contained 9-13% methane, 9-12% ammonia, 14-16% oxygen. The pressure drop across the catalytic system 5-15 mm of water column at a linear gas flow rate of 1.2-1.5 m/s and the operating temperature of 1000-1050oC. the Content of HCN at the outlet of the reactor of 6.5-7.5%. Conversion to ammonia in the range of 60-65%. Loss of platinum two times lower than the established norms. The lifetime of the catalytic system 2000 including Ceramic sorbent-catcher contains 0.7 wt.% platinum. Then change the information in a catalytic system 2000 hours

Example 2.

In the reactor for the synthesis of hydrogen cyanide load layer ceramic blocks sorbent cell structure height 25 mm side of the block 65 mm, wall thickness 0.8 mm, cross-section of the channel 4x4 mm, a mass amount of sorbent to 50% more than the number of block catalyst. Next, on the layer of sorbent stack separating the grid from heat-resistant steel, on which is placed a layer of bulk catalyst for the conversion of ammonia composition, wt.%: 2MgO2l2ABOUT35SiO2- 80-85, promoter and binder - other, of a height of 25 mm and of the same size as the sorbent, and four platinum mesh of alloy 5. In conditions similar to example 1, the content of HCN at the outlet of the reactor is maintained at the level of at least 6.5% over 2000 hours of continuous operation of the reactor. The sorbent contains 0.2 wt.%. platinum. Then swap the sorbent and block the catalyst. The lifetime of the catalytic system 2000 including the Figures have not changed.

Example 3.

In the reactor for the synthesis of hydrogen cyanide load layer hexagonal blocks of ceramic sorbent cell structure height 25 mm side of the block is 50 mm, the wall thickness between the cylindrical channels of 2.0 mm, diameter 5 mm, mass kolichestvo the block layer of the catalyst honeycomb structure of the composition, wt.%: 2MgO2l2ABOUT35SiO2- 80-85, promoter and binding - rest, the same size as the sorbent. The pressure drop across the catalytic system of 20-25 mm of water column at a linear gas flow rate of 1.2 m/s and the operating temperature of 1000-1050oC. the Content of HCN at the outlet of the reactor of 6.5-7.5% conversion to ammonia in the range of 60-65%. The lifetime of the catalytic system 2000 h without increasing the standards of the deadweight loss of platinum. After this time the platinum grids are replaced, and the catalyst and sorbent with a platinum content of 0.7 wt. % change places. The lifetime of the catalytic system 2000 including the Figures have remained almost unchanged.

Example 4.

In the contact device UKL-7 on the grate is placed a layer of hexagonal blocks of ceramic sorbent cell structure with a height of 40 mm side of the block is 60 mm, the wall thickness between the cylindrical channels of 2.0 mm, diameter 4 mm, on Top of the sorbent have six platinum grid distribution grid from heat-resistant steel, on which is placed a layer of thermostable catalyst honeycomb structure composition, wt.%: 2MgO2l2ABOUT35SiO2- 80-85, promoter and binding - rest. The layer height 40 mm, sides of the political system 60-65 mm of water column at a linear gas flow rate of 7 m/s and the operating temperature 900-910oC. Conversion of ammonia to NO was 93.8%. The lifetime of the catalytic system is not less than 4,000 hours with maintaining the norm of the deadweight loss of platinum. After this time the platinum grids are replaced, and the catalyst and sorbent with a platinum content of 0.4 wt.% changing places. After 4000 hours of operation are saved in the rate of irreversible loss of platinum.

Example 5.

In the contact device UKL-7 on the grate is placed a layer of blocks of sorbent honeycomb structure having a square cross section with a height of 25 mm side of the block is 70 mm, the wall thickness of 2.0 mm channel size 4x4 mm on Top of the sorbent have a distribution grid of heat-resistant steel, the block layer of the catalyst for selective oxidation of ammonia to NO composition, wt.%: Fe2O - 80-85, CR2O3- 3-15, promoter and binding - rest having a square cross section and dimensions similar to the sorbent, again the distribution grid from heat-resistant steel, and over - the package of eight platinum mesh. The pressure drop of the gas stream of the ammonia-air mixture (ABC) on the catalytic system 50-55 mm of water column at a linear gas flow rate of 7 m/s and the operating temperature 900-910oC. the Concentration of ammonia in the ABC of 11.5%. Conversion is Vratnik loss of platinum. After this time the platinum mesh and the sorbent replaced with the new, the spent catalyst is sent for recycling, and the sorbent with a platinum content of 0.2% wt. used as the catalyst of the second stage of oxidation of ammonia to NO contact devices of medium and high pressure production of nitric acid.

Thus, the proposed method of conversion of ammonia nitrogen production and hydrocyanic acid will allow a 15-20% increase in time of non-stop operation of the contact apparatus with preservation of the average performance, 25-30% reduction in attachment of platinum and 5-50% deadweight loss. It should be noted that as the recovery of platinum from the sorbent during the operation of the contact device is immediately obtained a catalyst of the same process, with double the number. All previously proposed methods platinum to be drawn from the filter, sorbent, or platinum-palladium alloy, which, in turn, is a technologically challenging task and its cost performance commensurate with obtaining platinum from traditional sources.

1. A catalytic element for the conversion of ammonia, comprising the step of layers platino the UNT further comprises a third stage - thermostable layer ceramic media - catcher platinum regular cell structure.

2. The catalytic element according to p. 1, characterized in that the step of catalyst a regular cellular structure located in front of the tread layer of the platinum mesh or after it.

3. The catalytic element according to p. 1, characterized in that the catalyst is a regular cell structure and media - catcher platinum contain from 0 to 0.7 wt.% platinum.

4. The catalytic element according to p. 1, characterized in that the carrier of the third stage extractor platinum has a structure similar to the catalyst carrier regular cell structure.

5. Method of catalytic conversion of ammonia, comprising passing the reaction gas mixture containing ammonia and oxygen-containing gas through a two-stage catalytic system comprising the step of layers of platinum mesh, the degree of catalyst a regular cell structure and catcher platinum, characterized in that as a catcher platinum install additional third level of thermostable ceramic carrier having a regular cell structure, which periodically change the Yan of the catalyst of the regular honeycomb structure include a prior step of the layers of the platinum mesh or after it.

7. The method according to p. 5, characterized in that the carrier of the third stage extractor platinum has a structure similar to the catalyst carrier regular cell structure.

8. The method according to p. 5, characterized in that the temperature in the zone of the third stage of the carrier - catcher of platinum is less than 850oWith, and its mass number is bigger than the mass of catalyst a regular cell structure 10-50 wt.%.

9. The method according to p. 5, characterized in that the catalyst is a regular cell structure and media - catcher platinum contain from 0 to 0.7 wt.% platinum.

10. The method according to p. 5, characterized in that the carrier - catcher platinum with a platinum content of 0.2 wt.% and more is used as the catalyst for the second stage of the same process.

 

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FIELD: chemical industry, in particular method for production of value products from lower alkanes.

SUBSTANCE: claimed method includes passing of gaseous reaction mixture containing at least one lower alkane and elementary chlorine through catalytic layer. Used catalyst represents geometrically structured system comprising microfiber with diameter of 5-20 mum. Catalyst has active centers having in IR-spectra of adsorbed ammonia absorption band with wave numbers in region of ν = 1410-1440 cm-1, and contains one platinum group metal as active component, and glass-fiber carrier. Carrier has in NMR29Si-specrum lines with chemical shifts of -100±3 ppm (Q3-line) and -110±3 ppm (Q4-line) in integral intensity ratio Q3/Q4 from 0.7 to 1.2; in IR-specrum it has absorption band of hydroxyls with wave number of ν = 3620-3650 cm-1 and half-width of 65-75 cm-1, and has density, measured by BET-method using argon thermal desorption, SAr = 0.5-30 m2/g, and specific surface, measured by alkali titration, SNa = 10-250 m2/g in ratio of SAr/SNa = 5-30.

EFFECT: method of increased yield.

3 cl, 4 ex

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