The catalytic element of the regular cell structure for high-temperature heterogeneous reactions

 

(57) Abstract:

The invention relates to the catalytic elements of the regular cell structure for high-temperature heterogeneous reactions. Described catalytic element of the regular cell structure for high-temperature heterogeneous reactions, such as conversion of ammonia, which is made in the form of a layer of the individual prisms connected side faces and having a cellular channels, separate prisms when laying them in a layer of the honeycomb structure have a gap between the side faces of 0.1 to 1.0 diameter cell channel. For laying around the perimeter of the layer are truncated under the diameter of the contact apparatus blocks of triangular and trapezoidal forms. For the second stage of the oxidation of ammonia using the catalyst composition, wt. % Fe2ABOUT3- 80-90; Cr2ABOUT3- 5-10; Al2ABOUT3- 5-10. Effect: the proposed catalytic element has a high strength and high durability. 2 C.p. f-crystals.

The invention relates to the catalytic elements of the regular cell structure for high-temperature heterogeneous reactions, for example for the conversion of ammonia, and can be used in the production of nitrogen, hydrocyanic acid, the element (RF patent 2128081, IPC B 01 J 35/04, 01 21/26, 1999), which is placed in the reactor vessel for supporting the device in a layer of the individual prisms of the coupled side edges without gaps. In case of using a catalytic element as a catalyst for the conversion of ammonia to the second stage, on top of it have a layer of platinum mesh, which is the catalyst for the first stage.

The lack of catalytic element is a low life, because the stacked without clearance individual prisms when thermal effects are destroyed, especially if they are located in the center of the layer.

Known monolithic catalyst carrier and method thereof (application Japan 62-191048, IPC B 01 J 35/04, B 01 D 53/36, 1987), derived from cordierite, which has a large number of pores, permeable to air and extending in the axial direction, and narrow the gaps between the pores. On the surface of the Central part of the inner wall to form the unfired base layer, which create pores permeable to air, and at the same time the pores of the microporous wall constituting the outer peripheral part of the carrier, insert the shell is able to expand when heated. The outer peripheral portion expands when retaliator allocation of nitrogen oxides from exhaust gases of combustion (application Germany 3430886, IPC B 01 J 35/04, 1986), consisting of separate molded ceramic blocks with a length of 10-50 cm with a porous surface and square channels for the flow of gases. Blocks on all 4 sides fastened with bars of square cross section with a Central protrusion on one side and a depression on the opposite. These protrusions and depressions serve for mounting layer blocks. On the sides of the blocks have projections passing through the block parallel to the channels.

The disadvantages of the described catalysts is a complex way of cooking.

Known catalytic device having a honeycomb cells (Japan's bid 53-137866, IPC B 01 D 53/34, 1978). To obtain catalysts with a honeycomb structure prepared honeycomb carrier in the form of cubic blocks with through drilled holes. These blocks after impregnating the catalytically active agents installed in the catalytic box with a gap between the layers of blocks. To maintain a given distance between layers of blocks establish strap, separating the layers.

The disadvantage is the time consuming method of manufacturing the drilled holes and catalytic boxes, and the gap existing between layers of blocks, only to some extent decides about alistar, installed in the cassette with mesh sides (Japan's bid 54-141382, IPC B 01 J 1/00, 1979). To prevent crushing of downstream units due to the weight of the upstream block net wall cassettes are supporting a solid lattice, upon which the honeycomb catalyst blocks. Support grid have some flexibility and are associated with catalytic cell blocks of the catalyst with a certain gap, whereby thermal expansion of the blocks does not produce the destruction of the tapes and their deformation.

However, the disadvantages described catalytic element should include the fact that the blocks are deformed not only in height but also in width, especially when large diameter reactor and, accordingly, the diameters of the layer of the catalytic unit.

The closest technical solution is a catalytic element for the conversion of ammonia based replacenode oxide catalyst made in the form of a layer of the individual prisms connected by edges without gaps, and having a cell channels (application EP 0260704, IPC B 01 J 21/04, 1988).

The disadvantage of the prototype is small, the service life of the catalytic element and the low strength when heated.

which has a high strength.

The problem is solved by using a catalytic element of a regular cell structure for high-temperature heterogeneous reactions, which is made in the form of layers of the individual prisms connected side faces and having a cellular channels, separate prisms when laying them in a layer of the honeycomb structure have a gap between the side faces of 0.1 to 1.0 diameter cell channel. For laying around the perimeter of the layer are truncated under the diameter of the contact apparatus blocks of triangular and trapezoidal forms, which leads to additional increase resistance to thermal expansion along the perimeter of the layer of sorbent and catalyst.

For the second stage of the conversion of ammonia using the catalyst composition, wt.%: Fe2O3- 80-90; CR2O3- 5-10; Al2O3- 5-10.

A catalytic element for the conversion of ammonia and synthesis of hydrocyanic acid is made from a material having a composition, wt.%: 2MgO2l2ABOUT35SiO2- 80-85; Pt - 1,0; binding - rest.

It is preferable to use around the perimeter of the blocks having a cross-section of a rectangular triangle with convex hypotenuse. The radius of convexity of the hypotenuse corresponds to the radius of the contact unit cell structure, an additional layer of thermostable ceramic media having a regular cell structure and size, preferably similar to that used block catalyst with a regular cell structure. Sorbent honeycomb structure is placed in a layer with the same gap of 0.1 to 1.0 diameter cell channel sorbent.

In the catalytic element in the gaps between the individual blocks of catalyst and sorbent may vary depending on the composition.

Laying of individual prisms in the layer with a gap between the side edges of 0.1 to 1.0 diameter cell channel is optimal for conducting high temperature reactions and increases the service life of the catalysts.

The proposed catalytic element can be used in various high-temperature processes, for example, oxidation of ammonia to nitric oxide (II), oxidative ammonolysis of natural gas (methane) methane conversion.

The proposed catalytic element was tested in two high-temperature reactions: the oxidation of ammonia to nitric oxide (II) and oxidative ammonolysis of natural gas.

The following examples illustrate the proposed solution.

Example 1.

In the contact device UKL-7 on the grate of wammako to NO composition, wt.%: Fe2O3- 80-85, CR2O3- 5-10, binder based on Al2ABOUT3- other, having a square cross section. The height of the blocks 25-50 mm side of the block 70 mm, wall thickness 1.5 mm, pipe size 5x5 mm clearance between the side faces 5 mm, which is 1.0 in diameter cell channel. For dolldivine around the perimeter of the layer of catalyst blocks are used that have a triangular shape with convex hypotenuse. The radius of convexity of the hypotenuse is 800 mm Above the catalyst stack package of nine standard platinum mesh. The operating temperature of the contact apparatus 900-910oC. the Concentration of ammonia in the ammonia-air mixture of 11.5%. The conversion of ammonia to NO was 93.5%. The lifetime of the catalytic system is not less than 4,000 hours with maintaining the norm of the deadweight loss of platinum. The number of destroyed blocks of the catalyst honeycomb structure does not exceed 5% of the total number of downloaded blocks.

Example 2.

In the reactor for the synthesis of hydrogen cyanide 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 binding - rest height is between the side faces 1 mm, that is 0.25 of the diameter of the cell channel. For dolldivine around the perimeter of the layer of catalyst blocks are used that have a triangular shape with convex hypotenuse. The radius of convexity of the hypotenuse is 600 mm Further to the catalyst layer stack four platinum mesh of alloy 5. The source gas mixture contained 9-13% methane, 9-12% ammonia, 14-16% oxygen. At the operating temperature of 950-1050oWith the conversion to ammonia 60-65% of the HCN content 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 degree of destruction of the bulk catalyst is 3%.

Example 3.

In the reactor for the synthesis of hydrogen cyanide load the block layer ceramic sorbent cellular structure in the form of parallelepipeds height 25 mm side of the block 65 mm, wall thickness 0.8 mm, cross-section of the channel 4x4 mm Single blocks of square cross section are placed with a gap between the side edges 1 mm relative to each other, that is 0.25 of the diameter of the cell channel. To further improve the resistance to thermal expansion along the perimeter of the layer of blocks are used, having a cross-section of a rectangular triangle with convex hypotenuse. The radius of convexity of gdny grid alloy 5, then have the block layer of the catalyst conversion of ammonia composition, wt.%: 2MgO2l2O35SiO2- 80-85, promoter and binding - rest, height 25 mm, the same size as the sorbent. The stacking order of block catalyst similar to the stacking order of the sorbent. The source gas mixture contained 9-13% methane, 9-12% ammonia, 14-16% oxygen. The operating temperature of 950-1050oC. 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 is not less than 2000 hours after this time, the content of platinum in the ceramic sorbent-catcher reaches of 0.7% wt. Sorbent and block the catalyst of changing places. The performance of the reactor conversion remain virtually unchanged. The lifetime of the catalytic system 2000 including the Destruction of blocks of the sorbent and the catalyst was not observed.

Example 4.

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 clearance between the side faces of the blocks 2 mm, which is 0,with a convex base. The radius of convexity of the bases of the trapezoid corresponds to the radius of the contact apparatus. On the layer of sorbent stack two platinum mesh and top mesh layer block catalyst honeycomb structure composition, wt.%: 2MgO2l2O35SiO2- 80-85, promoter and binding - rest, the same size as the sorbent. The gap is 2 mm to 0.4 of the diameter of the cell channel. The pressure drop across the catalytic system is no more than 20-25 mm of water column at a linear gas flow rate of 1.2 m/s and the operating temperature of 950-1050oC. the Source gas mixture contained 9-13% methane, 9-12% ammonia, 14-16% oxygen. The HCN content 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.% changing places. The lifetime of the catalytic system 2000 including the Figures have remained almost unchanged. The destruction of the blocks of the sorbent and the catalyst was not observed.

Example 5.

In the contact device UKL-7 on the grate is placed a layer of hexagonal blocks of ceramic sorbent cell article mm. The stacking order of a layer similar to example 4. The clearance between the side faces of the blocks 3 mm, which is 0.75 of the diameter of the cell channel. 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 of 40 mm side of the block is 60 mm, the wall thickness between the cylindrical channels of 2.0 mm, diameter 4 mm, the clearance between the side faces of the blocks 3 mm, which is 0.75 of the diameter of the cell channel. The pressure drop across the catalytic system is no more than 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 6.

In the contact device UKL-7 on the grate is placed a layer of blocks of sorbent cell is mm. The stacking order is similar to example 1 with a gap between the side edges 1 mm, which is 0.25 of the diameter of the cell channel. 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 with a gap of 4 mm between the side faces, which is 1.0 in diameter cell channel, and composition, wt.%: Fe2ABOUT3- 80-85, CR2ABOUT3- 5-10, binder based on Al2ABOUT3- other, having a square cross section and dimensions similar to the sorbent, again the distribution grid from heat-resistant steel, and on top of the pack 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%. The conversion of ammonia to NO was 93.5%. 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 mesh and the sorbent replaced by new, destroyed blocks of the catalyst is sent for recycling. The degree of destruction does not exceed 5%. The sorbent with a platinum content of 0.2 wt.% and is Alenia production of nitric acid.

Example 7 (the prototype).

Similar to example 1, except that the blocks are installed with no gaps between the side faces. Dokladnu around the perimeter of the layer used parts after cutting a square blocks. The degree of destruction through 4,000 hours of work is 35%.

As can be seen from the examples presented proposed catalytic element has a high strength and high durability.

1. The catalytic element of the regular cell structure for high-temperature heterogeneous reactions, made in the form of layers of the individual prisms connected side faces and having a cellular channels, characterized in that the individual prisms when laying them in a layer of the honeycomb structure have a gap between the side faces of 0.1 to 1.0 diameter cell channel.

2. The catalytic element according to p. 1, wherein storing the perimeter of the layer are truncated under the diameter of the contact apparatus blocks of triangular and trapezoidal forms.

3. The catalytic element according to p. 1, characterized in that it is designed for the second stage of the conversion of ammonia and is made of material having one of the following composition, wt.%:

Fe2ABOUT3- 80-90

CR2ABOUT3

 

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