The platinum catalyst in the form of wire mesh

 

The invention relates to a device the platinum catalyst made in the form of metal-fiber wire mesh. The use of the proposed catalyst includes nitric acid and nitrogen fertilizers, the production of hydrocyanic acid, the production of nitrites and nitrates and other productions containing technological scheme of the catalytic conversion of ammonia to oxides of nitrogen. Offered the platinum catalyst in the form of a wire mesh, is woven from wires with a diameter of 0.06 to 0.1 mm and containing alloys of platinum with rhodium, palladium, ruthenium, and other metals of the platinum group, characterized in that the woven cell has a rectangular shape with an aspect ratio of 1.1-5. The optimal value of the density of wires in the grid on one centimeter is one direction of the woven structure on a duck or on the basis of 10-30 threads, and a different woven patterns - in basis or on a duck 50-34 thread. Woven grid structure in the direction with a smaller number of threads can be formed by wires of replacenode alloys, for example of heat-resistant steels. To achieve the greatest level of effectiveness of the proposed platinum catalyst in the Assembly to be perpendicular to the direction of the fundamentals of each previous layer of the grid. 3 C.p. f-crystals, 1 Il.

The invention relates to a device the platinum catalyst made in the form of metal-fiber wire mesh. The use of the proposed catalyst includes nitric acid and nitrogen fertilizers, the production of hydrocyanic acid, the production of nitrites and nitrates and other productions containing technological scheme of the catalytic conversion of ammonia to oxides of nitrogen.

Widely known and widely used for many decades the platinum catalysts in the form of wire netting, made of alloys of platinum with rhodium, palladium, ruthenium, and other metals of the platinum group and which is weaved by the filaments (wires) with a diameter of 0.06 to 0.1 mm (see, for example, Atroshchenko, Kargin "Technology of nitric acid", M: GENTIL, 1962, page 37; Karavaev "Catalytic oxidation of ammonia, M.: Chemistry, 1983, page 41, 55). Described in these sources and used in practice, the platinum catalysts in the form of woven wire mesh simple weave have a symmetrical structure, i.e. a structure characterized by a square woven mesh. In this geometry patterns the number of threads per unit length on both vzaimnostiu in the form of a wire mesh square woven cell characterized by the significant deficiencies, despite their wide use in industry for almost a century. This conclusion about the shortcomings of square woven cell was made by us on the basis of the analysis of the results of the macro-kinetics and mechanism of oxidation of ammonia on platinum single catalytic filament-wire shown in the works: centuries of Barelko, P. I. Halzov, C. N. Doronin "Study of dynamic characteristics of the processes of reconstruction of the surface of the monolithic platinum-driven heterogeneous catalytic reaction Surface (physics, chemistry and mechanics), 1982, N6, S. 91-97; centuries of Barelko, P. I. Halzov, C. I. Chernyshov "Dynamic characteristics of the reaction of oxidation of ammonia on platinum alloys in Chemical industry, 1987, N8, S. 506. The analysis showed that the efficiency of conversion of ammonia to nitrogen oxides largely depends (of course, the identity of the other parameters) from the density of crisscrossed wires (nodes) in the woven structure of the platinum wire catalyst. This circumstance is due to the fact that the nodes of the grid woven patterns and parts of the wires adjacent to the nodes are characterized by a significant loss of catalytic activity due to the reduction of intense limited diffusion factor the decrease in the rate of mass transfer to the catalytic surface of the grid leads to a proportional decrease in the efficiency of the catalytic grid. In other words, the removal of nitrogen oxides per unit mass of platinum catalyst decreases with increasing density of nodes in the woven structure of the catalytic grid. This set the pattern allowed us to propose a hypothesis, according to which it was argued that the platinum catalyst in the form of a wire mesh with square cell has no optimal structure, since it is not possible to independently vary so important for the efficiency of the process parameter, as the node density woven patterns. Namely, when the decrease of the density of nodes (by an equivalent reduction of the number of threads and "duck" and "basis" in the woven grid structure) increase the efficiency of the platinum catalyst does not compensate for loss of activity due to an increase in cell size and related factors increased leakage of ammonia; on the other hand, the growth of activity of the platinum wire catalyst with high density textile does not compensate for the efficiency loss of the catalyst due to the increased density of the weave.

32 (i.e., 1024 node - weave on 1 cm2or 1024 holes on 1 cm2) when the diameter of the filaments 0,06-0,1 mm Platinum catalysts in the form of a wire mesh with these geometric parameters are predominant in practical use in industrial processes, including technological cycle of catalytic conversion of ammonia to nitrogen oxides. The use of platinum in catalytic grids with square cells with different density textile (more or less 1024 holes on cm2) led to the deterioration of the technological and economic characteristics of the process: the reduction in the conversion of ammonia to oxides of nitrogen, increased losses of platinum, the increase in the hydraulic resistance of the catalytic package during operation.

Attempts were made to overcome these disadvantages of the platinum wire catalyst symmetric (square) woven cell by differentiation of nets in the catalytic package by the number of twists per 1 cm: it was suggested in the catalytic package to use the first sing 1024, the density of the weave (see RF Patent 2065327, from 20.08.96, bull. 23; the Patent of the Russian Federation 2094118, from 27.10.97, bull. 30). However, these technical solutions protected by these patents, did not eliminate the above disadvantages of the platinum catalysts in the form of a wire mesh with a symmetric, square woven mesh.

As a prototype selects the platinum catalysts in the form of a wire mesh square woven cell, described in the monograph: M. M. Karavaev "Catalytic oxidation of ammonia, M.: Chemistry, 1983, page 41, 55. All of the above disadvantages of the platinum catalysts in the form of woven wire mesh with square cells inherent in the selected prototype.

The objective of the invention is to eliminate these disadvantages.

This goal is achieved by making the structure of the platinum catalyst in the form of woven wire mesh following distinctive characteristics, which are reflected in PP 1-4 claims: - woven cell platinum catalytic mesh is shaped in the form of a rectangle with an aspect ratio of 1.1-5; - textile mesh, the number of wires to one centimeter in one of the directions of the woven patterns ("duck" or "basis") is chosen in the range of 10 to 30 threads at the net in the direction with a smaller number of threads form the wires from replacenode alloys, for example, from heat-resistant steels; - when assembling grids in catalytic batch reactor the direction of the "basics" of each next layer grid oriented perpendicular to the direction of the "basics" of each previous layer of the grid.

Protected by the present invention, the technical solution, the main feature of which is a rectangular woven in the cell structure of the platinum catalyst in the form of a wire mesh, unexpectedly enabled to realize a number of benefits of technological and economic nature in comparison with the commonly used up to the present time the platinum catalysts with square woven cell adopted in this description of the invention for the prototype. The figure schematically presents the woven structure of the platinum catalyst, protected by the present invention in comparison with a woven structure of the platinum catalyst of the prototype.

Achieved benefits and distinguishing features reflected in the formula of the present invention are illustrated below, calculations and examples.

The use of the protected invention the platinum catalysts with rectangular woven cell allows humanised (to increase the removal of nitrogen oxides per unit mass scale and to increase the conversion rate of ammonia) without compromising other characteristics (in particular, such as loss of platinum, the hydraulic characteristics of the catalytic package). For example, if you compare the standard platinum grid with square cells 3232 threads per centimeter for "duck" and "basis" (1024 weave on 1 cm2with this invention are identical by weight of the platinum mesh with rectangular woven structure 4519 threads per cm (855 weaves 1 cm), it appears that the density of the weave in the proposed catalyst is reduced by 16.5% compared with the catalyst of the prototype. This means that approximately the same proportion should increase the efficiency of the platinum catalyst (removal of product per unit mass of platinum).

Example 1. Direct verification of this conclusion was carried out in conditions of the pilot reactor, the concentration of ammonia in the air 10 vol.%, the linear flow velocity of 0.5 m/s, inlet temperature 20oWith used to weave experienced mesh wire with cross-sectional diameter 0,092 mm made of standard alloy SP. 5 (an alloy of platinum with palladium, rhodium and ruthenium). Comparative experiments were performed on a single grid with a standard square weave (3232 threads on a duck iaeou catalytic grid with rectangular cell was higher than the grid prototype, more than 20%. Thus, the level of the realized effect exceeded the expected value. This is associated with additional intensification of the process of conversion of ammonia by reducing the diffusion resistance in the gap between contiguous threads in the proposed catalytic grid.

Example 2. Research on pilot reactor showed that the optimum aspect ratio rectangular woven cell platinum wire catalyst is in the range of 1.1-5. When the aspect ratio woven cell above the upper limit (>5) catalytic grid loses structural rigidity in the Assembly of the catalytic package geometrical uniformity of the mesh due to the mobility of the filaments is broken, causing the reactor hydrodynamic heterogeneity and, consequently, to the emergence of technologically invalid when ammonia conversion phenomena "by pass". When the aspect ratio woven cell is less than the lower limit (less than 1.1) the positive effect of the transition to a rectangular cell, practically disappears.

Example 3. For the platinum wires with a diameter of 0.06 mm, used in the manufacture of catalytic nets, optimal s with a rectangular woven cell. The optimal grid structure, which is weaved by the wires with a diameter of 0.06 mm, answer the following geometrical parameters: 10-30 threads on one centimeter in one direction - duck basis, and 50-34 thread in another direction - based, duck.

Example 4. For the platinum wires with a diameter of 0.1 mm, used in the manufacture of catalytic nets, optimal characteristics of woven patterns required to manufacture the proposed type platinum catalysts with rectangular woven cell. The optimal grid structure, which is weaved by the wires with a diameter of 0.1 mm, answer the following geometrical parameters: 10-30 threads on one centimeter in one direction - duck basis, and 50-34 thread in another direction - based, duck.

Example 5. The study of specific contributions to the effectiveness of the platinum catalytic mesh up the threads oriented in two different directions (for "duck" and "basis"), showed that in the case of structures with rectangular woven cell contribution rarely recruited threads in the General conversion of ammonia is very low (5-15% for the aspect ratio of a cell 2-2,5). The reason for this effect to be found in the high density of the crosshairs on the threads of this series is ski inert wire from cheaper metals without significant damage to the overall catalytic efficiency of the grid. A direct test of this conclusion confirmed the hypothesis. Comparison of the catalytic efficiency of two grids with rectangular woven cell 4519 threads per 1 cm, one of which is woven entirely from the platinum wires (diameter 0,092 mm), and the other is woven from platinum filaments in the direction of 45 and from heat-resistant steel wires with a diameter of 0.1 mm in the direction 19, showed that both the platinum sample grids are characterized by almost the same efficiency, despite the fact that combined the platinum catalytic mesh contains platinum 30% less than in the platinum catalytic grid, entirely made of platinum.

Example 6. In their quest for an optimal structure of the catalytic package formed from layers stacked platinum catalytic grids with rectangular woven cell, it was found that the maximum efficiency of conversion of ammonia is achieved by this arrangement of grids, in which the direction of the "basics" of each next layer of the grid is oriented perpendicular to the direction of the "basics" of each previous layer of the grid.

Thus, we offer the platinum catalyst in the form of a wire is surrounding the flow chart of the catalytic conversion of ammonia, and in the same proportions to reduce the loss of platinum during operation compared to conventional platinum catalyst with a square woven cell, which is the prototype of the present invention.

Claims

1. The platinum catalyst in the form of woven wire mesh, woven wire with a diameter of 0.06 to 0.1 mm and containing alloys of platinum with rhodium, palladium, ruthenium, and other metals of the platinum group, characterized in that the woven cell has a rectangular shape with an aspect ratio of 1.1 to 5.

2. The catalyst p. 1, characterized in that the number of wires in the woven mesh on one centimeter is one of the directions of the woven structure on a duck or on the basis of 10-30 threads, and other area - based or on a duck - 50-34 thread.

3. Catalyst under item 1 or 2, characterized in that the woven structure of the grid in the direction with a smaller number of filaments formed by the wires of replacenode alloys, for example, of heat-resistant steels.

4. The catalyst according to any one of paragraphs. 1-3, characterized in that during Assembly of the grids in the catalytic batch reactor the direction of the fundamentals of each subsequent layer of the grid perpendicular to the direction of grounds for each of the previous

 

Same patents:

The invention relates to catalysts and methods of producing nitrous oxide (N2O) by oxidation of ammonia with oxygen or oxygen-containing gas
The invention relates to the catalytic elements of the regular cell structure for high-temperature heterogeneous reactions

The invention relates to the field of cooking block replacenode catalyst of the oxidation of ammonia production nitric acid and hydroxylamine
The invention relates to a method and apparatus for recovery of nitrous oxide, formed during the catalytic combustion of ammonia and oxygen to nitrogen oxides

The invention relates to a cellular replacenode oxide catalytic elements for the conversion of ammonia and can be used mainly in the production of nitrogen and hydrocyanic acid, and has synthesis, for example, as the catalyst of the second stage located behind the catalyst for the first stage (along the strip), made in the form of the platinum package nets
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

The invention relates to the field of technology for hydroxylamine sulfate production and can be used in the manufacture of caprolactam

The invention relates to catalysts and methods of producing nitrous oxide (N2O) by oxidation of ammonia with oxygen

The invention relates to the production of nitric acid, in particular to a method of conversion of ammonia using a two-stage catalytic system in aggregates UKL-0,716
The invention relates to the catalytic elements of the regular cell structure for high-temperature heterogeneous reactions

The invention relates to flow to the exhaust gas of the internal combustion engine catalytically active structure, especially to a cellular structure formed of at least one metal sheet having a catalytically active surface

Catalyst body // 2200624
The invention relates to the field of catalysis

The invention relates to the field of media catalyst for exhaust gas aftertreatment

The invention relates to a mobile element, which is used, for example, for catalytic conversion of exhaust gases of internal combustion engine

The invention relates to a cellular replacenode oxide catalytic elements for the conversion of ammonia and can be used mainly in the production of nitrogen and hydrocyanic acid, and has synthesis, for example, as the catalyst of the second stage located behind the catalyst for the first stage (along the strip), made in the form of the platinum package nets

The invention relates to a device for the implementation of heterogeneous catalytic reactions, particularly reactions of steam reforming of hydrocarbons

The invention relates to the preparation of catalysts for deep oxidation of organic compounds

The invention relates to a method of manufacturing a cell element, in particular housing-catalyst carrier, of several typed in at least one packet and at least partially structured metal sheets, as well as to a device for manufacturing such a cell element
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
Up!