RU2383389C1 - Catalyst head element, preparation method thereof (versions) and method of carrying out catalytic exothermal reactions - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: described is a catalyst head element containing a porous metal carrier and a catalyst, characterised by that granules of the ready catalyst and/or catalyst formed inside the porous carrier are paced in a shell made from porous metal carrier. Described is a method of making the catalyst head element involving putting the catalyst into pores of the metal carrier with pore volume of up to 95%. At the first stage a workpiece is formed by introducing into the volume of the carrier under vibration effect a suspension or a paste or a solution of the ready catalyst or components of the catalyst, and the workpiece is dried. At the second step the top and bottom part of the workpiece is covered by the porous metal carrier, the head element is pressed and calcined to obtain a catalyst head element in which granules of the ready catalyst and/or catalyst formed inside the porous carrier are inside a shell of porous metal carrier. Described is a method of making a catalyst head element in which between two surfaces of porous metal carrier granules of ready catalyst are placed, the workpiece is pressed and calcined to obtain a catalyst head element in which granules of the ready catalyst are inside the shell of porous metal carrier. Described is a method of carrying out exothermal catalytic reactions for combustion of fuel in a fluidised layer of dispersed particles of inert material in which catalyst heads made using the above described elements are used.

EFFECT: longer service life of catalyst heads when used in environmentally safe combustion of fuel in a fluidised layer of solid dispersed particles of inert material.

10 cl, 5 ex, 1 tbl

Description

The invention relates to the field of exothermic catalytic reactions, and in particular to methods of preparing elements of low-volume catalytic nozzles for reactions, for example, combustion of gaseous, liquid and solid fuels in an organized fluidized bed of dispersed particles of an inert material.

There is a method of exothermic catalytic reactions by feeding reagents into a bed of fluidized solid particles of an inert material - a coolant in the presence of a catalyst made in the form of an organizing low-volume nozzle (RU 2084761, F23C 11/02, 20.07.1997). The presence of a catalytic nozzle in a fluidized bed of an inert material allows the process of burning fuels at temperatures below 800 ° C while maintaining the advantages of burning fuels in a fluidized bed of a catalyst (SU 826798, 1983; RU 2057988, F23C 11/02, 10.04.96). The catalytic nozzle is made in the form of a fixed block, the elements of which are lattices, blocks, nozzles such as Raschig rings. The elements of the catalytic nozzle are catalysts for the deep oxidation of substances operating in the kinetic or intra-diffusion region. Therefore, along with high catalytic activity in relation to the combustion of fuels, the elements of the nozzles must have a sufficient specific surface area. Important additional requirements are the high mechanical strength of the nozzles to abrasion, as well as high thermal stability and thermal conductivity.

Known methods for the preparation of catalysts for the deep oxidation of hydrocarbons in catalytic fuel combustion units in the form of a monolithic block of foam or multichannel ceramics, on the surface of which a catalytically active material is formed from oxides or a mixture of oxides (RU 2055638, B01J 23/74, 04/10/1996; RU 2086298 , B01J 23/70, 08/10/1997). The use of such blocks for carrying out catalytic processes in a fluidized bed of an inert material is difficult due to the rather rapid detachment of the active component from the porous carrier and its subsequent removal from the composition of the carrier under the influence of significant mechanical and thermal loads in the fluidized bed.

A known method of preparing catalysts for burning fuel, including the manufacture of a porous support, the formation of a catalyst by impregnating the support with an aqueous solution of transition metal salts, followed by drying and calcination (RU 2039601, B01J 37/02, 07/20/1995). As transition metal salts, metal nitrates are used, which are selected from the group consisting of cobalt, nickel, chromium, and iron, and inorganic fibrous material, for example, silica, silica, kaolin, or basalt fiber, is used as a carrier. In this case, the carrier is impregnated in an aqueous solution of transition metal nitrate salts with the addition of urea and water-soluble polyhydric alcohol or carbohydrate in an amount of 0.25-1.5 wt.%. The resulting preform is dried in a stream of air at a temperature not exceeding 90-100 ° C to a residual moisture content of 5-10%, and then calcined by a traveling heat wave with a temperature of 500-600 ° C, using the heat of exothermic reaction. The disadvantage of this method is the low mechanical strength of the bond of the active component with the carrier and, as a consequence, the abrasion of the catalyst and loss of activity when used as a catalytic nozzle when burning fuels in a fluidized bed.

A known method of preparing a catalyst for burning fuel containing iron and aluminum oxides, comprising mixing the catalytically active metal oxides with inorganic binders, grinding to obtain a homogeneous mixture, forming a workpiece of the desired shape and calcination. Iron-containing slurry wastes of galvanic production are used as catalytically active components, and a mixture of natural materials containing aluminum oxide: clay, kaolin, as well as inorganic additives: talc, wollastonite, or tremolite and pore-forming additive - charcoal are used as binder (RU 2058190, B01J 23/745, 04/20/1996). The method allows to prepare catalytic nozzles, which retain their activity for a long time when used when burning fuels in a fluidized bed, since during abrasion both the carrier and the active component are uniformly removed. However, the service life of the nozzles remains relatively short.

A known method of preparing a catalyst for burning fuel (RU 2275961, B01J 37/02, 05/10/2006), including the manufacture of a highly porous carrier with desired magnetic properties, using a temporary substrate of open-porous organic polymer material: porous polyurethane or polypropylene with a mesh size of 0.4- 1 mm and a pore volume of 95-97%, which is placed in an aqueous suspension of a metal powder selected from the group of transition metals: iron, cobalt, chromium, nickel or their alloys, or vanadium and organic glue as a binder for complete impregnation of the substrate. The ratio of the mass of the powder and the liquid in the suspension is selected so that the carrier preform impregnated after squeezing has a predetermined density. The pressed carrier blank is dried in air, then the temporary substrate is removed by burning it in a furnace in vacuum at a temperature of 750 ° C, after which the sintering process is carried out at a temperature of 900-1300 ° C. To increase the efficiency of the catalyst create a variable density of the porous structure of the carrier with a maximum density on the outer (one) side of the carrier by rolling. The rolling process is carried out using a rolling roller to a depth of 1-3 mm. Then carry out the process of formation on the carrier of a catalyst layer with a thickness of 50-80 microns in the form of oxides or spinels. To obtain a catalyst layer of a given thickness, the carrier is immersed in an aqueous solution of metal acetates or sulfates of transition groups: cobalt, chromium, vanadium, iron, nickel or their alloys, alternating with drying at room temperature and calcining in an oven to obtain a catalyst layer of 50-80 μm. In this case, the calcination is carried out by single or multiple heating at a temperature of from 400 to 1100 ° C in air or inert atmosphere for 30-120 min with or without activators. In another embodiment of this method of producing a gas-phase catalyst, the fabricated support is placed inside the furnace, where steam of a carbonyl metal selected from the group of transition metals is injected for 60-120 min, with simultaneous calcination, which is carried out by gradually raising the temperature in the furnace from room temperature to 850 ° C. The process is carried out until the catalyst layer is 50-80 microns thick. The disadvantages are the complexity and complexity of the preparation of the catalyst by this method. When used as an element of a catalytic nozzle in the combustion of fuels in a fluidized bed, the relatively low mechanical bond strength of the active component with the carrier leads to its detachment and its removal from the catalyst, which leads to a rapid loss of activity of the catalytic nozzle.

The closest in technical essence is the method of preparation of composite microchannel plates containing a catalyst and a metal carrier, including the introduction of the catalyst in the form of a suspension into the pores of a metal carrier (RU 2323047, B01J 37/02, 04/27/2008). In this case, the metal carrier placed in the catalyst suspension is subjected to ultrasonic treatment, drying and further pressing in a mold with a given channel pattern. The suspension consists of catalyst powder and various liquids, such as water, salt solutions, organic solvents, mixtures thereof, etc. The suspension contains 2-70 wt.% Of the catalyst and not more than 70 wt.% Of a binder, for example pseudoboehmite, gamma-alumina . Foam metals of various porosities, metal felt, metal wool made of nickel, copper, stainless steel, and various alloys having plasticity are used as a porous metal support.

The disadvantages of this method are the rapid precipitation of the catalyst from the volume of the pressed samples under the action of high temperatures and mechanical stresses in the fluidized bed and, as a result, the loss of catalytic activity.

The invention solves the problem of increasing the mechanical strength, thermal stability of the elements of the catalytic nozzles while maintaining their high catalytic activity.

The technical result of the invention is to increase the service life of the catalytic nozzles in the conditions of their operation with environmentally friendly burning of fuels in a fluidized bed of solid dispersed particles of inert material.

The problem is solved by the design of the element of the catalytic nozzle containing a porous metal carrier and a catalyst in which the granules of the finished catalyst, and / or the catalyst formed in the volume of the porous carrier, are placed in a shell of a porous metal carrier.

The problem is solved by the method of preparing the elements of the catalytic nozzles for the implementation of exothermic catalytic reactions in a fluidized bed of particles of inert material, which includes at the first stage the formation of the workpiece by introducing into the pores a metal carrier with a bulk porosity of up to 95% under the action of vibration of a suspension, or paste, or a solution of the finished catalyst or catalyst components, drying the preform, then in the second stage, the preform is covered with a porous metal nose above and below itel, pressing and calcining the pressed catalytic nozzle element

The formation of the catalyst is carried out by introducing into the volume of the carrier blank under the action of vibration the pore-forming material in the form of plasticized aluminum hydroxide, or aluminosilicate, or silica gel, or clay mixed with catalyst components, or by introducing plasticized aluminum hydroxide mixed with powder into the volume of the carrier blank under vibration catalyst for the oxidation of substances, or by introducing into the bulk of the carrier blank under the action of vibration of an aqueous suspension of a catalyst powder substances and organic glue PVA polyvinyl acetate, or the formation of the catalyst is carried out by introducing into the bulk of the workpiece carrier under the influence of vibration of the powder of the catalyst for the oxidation of substances.

In another embodiment of this method of preparing the elements of the catalytic nozzles, granules of the catalyst for the complete oxidation of substances are placed between two metal-porous carrier blanks with a bulk porosity of up to 95% and the blanks are pressed by surface compression using a press or a rolling roller and calcined.

In both versions, foam metals of various porosities, metal felt, metal wool made of nickel, copper, stainless steel, and various alloys with ductility are used as a porous metal carrier.

The problem is also solved by a method of carrying out exothermic catalytic reactions in a fluidized bed of dispersed particles of an inert material, in which catalytic nozzles made from the elements described above are used.

The invention is illustrated by the following examples and table.

Example 1

The catalyst mass is prepared by mixing a solution of CuMgCr ₂ O ₇ in water with a concentration of 300 g / l of dichromate with a powder of aluminum hydroxide of a pseudoboehmite structure in the ratio of 110 g of hydroxide per 100 ml of solution. The mixture is stirred for 10-15 minutes to a pasty state. On the carrier blank in the form of a plate of porous nickel with a bulk porosity of 95%, 20 mm or 30 mm long, 20 mm or 10 mm wide and 5 mm thick, a uniform layer of plasticized catalyst mass is applied in a ratio of 1 cm ³ mass per 1 cm ³ plate. The plate with the catalyst mass is subjected to mechanical vibration for 5-10 minutes until the mass penetrates completely into the volume of the plate. The plate is placed in an oven and dried at 110 ° C. for 2 hours. The dried plate is placed between two porous nickel support plates with a bulk porosity of 95%. The plates are prepared with a length of 21 mm or 32 mm, a width of 21 mm or 12 mm and a thickness of 2-3 mm. Then, the obtained preform is pressed to a thickness of 4-6 mm and calcined in air at a temperature of 700 ° C for 2 hours. As a result, a catalytic element is obtained with the formation of a shell of a porous metal support.

Example 2

An aqueous suspension of aluminum hydroxide of a pseudoboehmite structure with a ratio of 100 g of hydroxide per 150 g of water is plasticized with a solution of nitric acid to a paste state. While stirring, hydroxide paste is added with a powder of a catalyst for deep oxidation of substances of the IR-12-73 brand (TU 6-68-102-89) of the composition CuMgCr ₂ O ₄ / γ-Al ₂ O ₃ in a ratio of 100 g of paste 60-80 g of catalyst powder . On the carrier blank in the form of a plate of porous nickel with a bulk porosity of 95%, 20 mm or 30 mm long, 20 mm or 10 mm wide and 5 mm thick, a uniform layer of plasticized catalyst mass is applied in a ratio of 1 cm ³ mass per 1 cm ³ plate. The plate with the catalyst mass is subjected to mechanical vibration for 5-10 minutes until the mass penetrates completely into the volume of the plate. The plate is placed in an oven and dried at 110 ° C. for 2 hours. The dried plate is placed between two porous nickel support plates with a bulk porosity of 95%. The plates are prepared with a length of 21 mm or 32 mm, a width of 21 mm or 12 mm and a thickness of 2-3 mm. Then, the obtained preform is pressed to a thickness of 4-6 mm and calcined in air at a temperature of 700 ° C for 2 hours. As a result, a catalytic element is obtained with the formation of a shell of a porous metal support.

Example 3

With an aqueous solution of PVA glue, a powder of a catalyst for the complete oxidation of substances of the IR-12-73 (TU 6-68-102-89) composition of CuMgCr ₂ O ₄ / γ-Al ₂ O ₃ in a ratio of 2-3 wt.% Glue is added with stirring PVA, 40-50 wt.% Catalyst, the rest is water. On the carrier blank in the form of a plate of porous stainless steel with a bulk porosity of 95%, length 20 mm or 30 mm, width 20 or 10 mm and thickness 5 mm, a uniform suspension layer is applied in the ratio of 1 cm ^{3 of the} suspension to 1 cm ^{3 of the} plate. The plate with the suspension is subjected to mechanical vibration for 5-10 minutes until the mass penetrates completely into the volume of the plate. The plate is placed in an oven and dried at 110 ° C for 2 hours. The dried plate is placed between two carrier plates of porous stainless steel with a bulk porosity of 95%. The plates are prepared with a length of 21 or 32 mm, a width of 21 or 12 mm and a thickness of 2-3 mm. Then, the obtained preform is pressed to a thickness of 4-6 mm and calcined in air at a temperature of 700 ° C for 2 hours. As a result, a catalytic element is obtained with the formation of a shell of a porous metal support.

Example 4

Spherical catalyst pellets of Example 3 with an average diameter of 1 mm in a ratio of 0.2 cm are placed between two carrier blanks in the form of porous nickel plates with a 95% bulk porosity of 21 mm or 32 mm long, 21 mm or 12 mm wide and 5 mm thick. ³ catalysts per 1 cm ³ plate. Then, the obtained preform is pressed to a thickness of 4-5 mm and calcined in air at a temperature of 700 ° C for 2 hours. As a result, a catalytic element is obtained with the formation of a shell of a porous metal support.

Example 5 (prototype).

The carrier blank in the form of a plate of porous nickel with a bulk porosity of 95% 21 mm or 32 mm long, 21 mm or 12 mm wide and 5 mm thick is subjected to ultrasonic treatment in 30 wt.% Alcohol suspension of a powder of a deep oxidation catalyst IK-12-73 . Processing time 15 min. Next, the preform is dried at 200 ° C and pressed at a pressure of 180 atm.

A test of the activity and stability of the elements of the catalytic nozzles prepared according to the present invention is carried out in a laboratory setup simulating the combustion of fuels in a fluidized bed.

A catalytic nozzle consisting of three plates with dimensions of 21 × 21 × 4 mm and 14.6 cm ^{3 of} sand with a particle size of 1.0-1.5 mm is loaded into a reactor with an inner diameter of 23 mm. The plates in the nozzle are rotated 90 ° relative to each other. The volume fraction of the nozzle in the reactor is 30% of the reaction volume. The process of oxidation of liquid fuel (octane) is carried out in a vibro-fluidized layer of sand particles that occurs when the reactor vibrates at a frequency of 50 Hz with an amplitude of 1 mm. Air consumption is 30 l / h, fuel consumption is 0.8 g / h. The oxidation state of the fuel and the change in the weight of the elements of the catalytic nozzle depending on the operating time at a temperature of 700 ° C are given in the table.

Table. Activity and stability of nozzle elements in the process of octane oxidation. A is the degree of oxidation of octane to CO ₂ and H ₂ O in%, B is the change in the weight of the packing element with respect to the initial weight in%. Time h Example 1 Example 2 Example 3 Example 4 Example 5 BUT B BUT B BUT B BUT B BUT B 2 > 99.0 99.99 > 99.0 99.99 > 99.0 99.99 > 99.0 99.99 > 99.0 90.0 24 > 99.0 99.98 > 99.0 99.98 > 99.0 99.98 > 99.0 99.98 96.3 72.6 48 > 99.0 99.97 > 99.0 99.97 > 99.0 99.97 > 99.0 99.98 93.6 57.3 72 > 99.0 99.97 > 99.0 99.97 > 99.0 99.97 > 99.0 99.98 89.6 45.1

Testing the activity and stability of the elements of the catalytic nozzles prepared according to the present invention, is carried out on a bench installation with a fluidized bed of an inert dispersed material.

In a reactor with an internal diameter of 40 mm, a catalytic nozzle of plates with sizes of 32 × 12 × 4 mm, made in accordance with examples 1-4, is loaded. The number of plates in the nozzle is 132 pcs., The height of the nozzle is 924 mm. The plates in each row of the nozzle are arranged in pairs at a distance of 16 mm, the next row of plates is rotated 90 ° relative to the previous row of plates. The volume fraction of the catalytic nozzle in the reaction volume is 20%. Next, 600 cm ^{3 of} sand with a particle size of 0.63-1.25 mm are loaded into the reactor. Air is supplied to the lower part of the reactor through the gas distribution grid to fluidize sand particles and oxidize fuel 1.8 m ³ / h. Diesel fuel is fed through the nozzle to the bottom of the reactor in an amount of 100 g / h. The process of burning fuel is carried out at a temperature of 700 ° C. Excess heat is removed by a heat exchanger located in the upper part of the reactor. In the course of lengthy tests (at least 120 hours), the degree of oxidation of the fuel and the change in the weight of the elements of the catalytic nozzle are controlled. For nozzles from the elements prepared in accordance with examples 1-4, changes in the oxidation state of the fuel and weight loss of the elements of the nozzles were not detected.

Thus, the proposed method of preparing the elements of the catalytic nozzle for burning fuels in a fluidized bed of an inert dispersed material allows to obtain nozzles with high resistance to the effects of a fluidized bed of solid dispersed particles at high temperatures. The presence of a metal carrier in the nozzles makes it possible to efficiently remove the heat of the fuel oxidation reaction from the catalyst to the fluidized bed, preventing overheating of the nozzle elements. The preparation method allows you to use as the active component most of the catalysts for the deep oxidation of substances. The placement of the catalyst in a porous metal capsule does not prevent diffusion of the components of the reaction medium to the surface of the catalyst. The high catalytic activity of the nozzle is maintained for a long time and allows one to predict its service life comparable to the service life of the reactor vessel.

Claims (10)

1. The element of the catalytic nozzle containing a porous metal carrier and a catalyst, characterized in that the granules of the finished catalyst and / or the catalyst formed in the volume of the porous carrier are placed in a shell of a porous metal carrier. 2. A method of preparing a catalytic nozzle element, comprising introducing a catalyst into the pores of a metal support with a bulk porosity of up to 95%, characterized in that at the first stage, a workpiece is formed by introducing a suspension, or paste, or solution of the finished catalyst into the support volume, or catalyst components, drying the workpiece, then in the second stage, cover the workpiece from above and below with a porous metal carrier, pressing the nozzle element, calcining the element a supported catalytic nozzle, as a result of which a catalytic nozzle element is obtained in which granules of the finished catalyst and / or the catalyst formed in the volume of the porous support are housed in a shell of a porous metal support. 3. The method according to claim 2, characterized in that as a porous metal carrier, foam metals of various porosities, metal felt, metal wool made of nickel, copper, stainless steel, various alloys having ductility are used. 4. The method according to claim 2, characterized in that the formation of the catalyst is carried out by introducing into the volume of the carrier blank under the action of vibration of the pore-forming material in the form of plasticized aluminum hydroxide, or aluminosilicate, or silica gel, or clay mixed with catalyst components. 5. The method according to claim 2, characterized in that the formation of the catalyst is carried out by introducing into the bulk of the workpiece carrier under the action of vibration of plasticized aluminum hydroxide in a mixture with a powder of a catalyst for the oxidation of substances. 6. The method according to claim 2, characterized in that the formation of the catalyst is carried out by introducing into the bulk of the workpiece carrier under the action of vibration of an aqueous suspension of a powder of a catalyst for oxidation of substances and organic PVA polyvinyl acetate glue. 7. The method according to claim 2, characterized in that the formation of the catalyst is carried out by introducing into the bulk of the workpiece carrier under the influence of vibration of the powder of the catalyst for the oxidation of substances. 8. A method of preparing a catalytic nozzle element, characterized in that granules of the finished catalyst are placed between the two surfaces of the porous metal support, the workpiece is pressed and calcined, as a result of which a catalytic nozzle element is obtained in which the finished catalyst granules are placed in a shell of a porous metal carrier. 9. The method according to claim 8, characterized in that foam metals of various porosities, metal felt, metal wool made of nickel, copper, stainless steel, various alloys with ductility are used as a porous metal carrier. 10. A method of implementing exothermic catalytic reactions in a fluidized bed of dispersed particles of an inert material, characterized in that the use of catalytic nozzles made from elements according to claim 1.