RU2024295C1 - Exhaust gas catalytic converter - Google Patents

Abstract

FIELD: gas cleaning. SUBSTANCE: catalytic converter intended for cleaning exhaust gases in industry and transport from carbon monoxide and/or nitrogen oxides and/or organic compounds has carrier made of porous material permeable for gas and catalytic active matter applied to carrier. Active matter has at least one metal of platinum group and/or at least one oxide of transition metal of fourth period of periodic system. Carrier has irregular cellular structure formed by doubling the structure of polymer open cellular material with metal, mean diameter of each cell being 0.5-5.0 mm and apparent density 0,1-1,0 g/cm³. EFFECT: enhanced reliability of gas cleaning. 1 tbl

Description

 The invention relates to means for cleaning gases from toxic components, and more specifically relates to catalysts for cleaning exhaust gases.

 A known catalyst for purification of exhaust gases of an internal combustion engine containing a carrier of a heat-resistant ceramic material with a cellular structure and a catalytic active coating deposited on it (1). Such catalysts do not have enough mechanical strength of the ceramic carrier in harsh operating conditions of vehicles, which leads to a decrease in the duration of its operation.

Also known is a catalyst containing, as an active material or its carrier, a ceramic foam material containing a network of irregular passages inside it with an average minimum size of 20-300 μm (2) IB. Due to the use of ceramic material in the catalyst, its mechanical strength under the conditions of operation of vehicles is insufficient. In addition, the pore sizes of this material are such that the catalyst layer creates a significant overpressure at high gas flow rates. Closest to the proposed solution is a cellular structure catalyst for the purification of diesel exhaust gases containing a carrier of a porous, breathable material that is heat resistant and has a regular cellular structure, the active coating is coated on its walls, which is active with respect to CO, HC and NO _x ( 3).

 The use of a carrier with a regular cell structure and parallel hollow channels leads to the passage of part of the exhaust gases without contact with the catalyst surface, which reduces the efficiency of emission cleaning.

 The basis of the invention is the creation of a catalyst for purification of exhaust gases, through the use of which would provide the most complete contact of the exhaust gases with its surface to increase the cleaning efficiency, which is achieved by changing the media.

This problem is solved in that in the catalyst for purification of exhaust gases of technological processes and vehicles from carbon monoxide and / or nitrogen oxides, and / or organic compounds, containing a carrier of porous gas-permeable material and a catalytically active substance supported on a carrier and including at least one metal from the platinum group and / or at least one transition metal oxide of the fourth period of the periodic system. According to the invention, the carrier has an irregular cellular structure obtained by duplicating the structure of the polymer open-cell material with a metal, with an average diameter of each cell of 0.5-5.0 mm and an apparent density of 0.1-1.0 g / cm ³ .

 The carrier may be made of nickel or copper, or an alloy of nickel with copper with a copper content of 50 wt.% Or an alloy of nickel with chromium with a chromium content of less than 30 wt. % or steel with a carbon content of less than 0.4 wt.% and alloyed with nickel and / or chromium.

 It is advisable that for cleaning the exhaust gases of vehicles, a carrier made of nickel or an alloy of nickel with chromium with a chromium content of less than 30 wt.% Or steel with a carbon content of less than 0.4 wt.% And alloyed with nickel and / or chromium would have an average diameter each cell is 1.5-3 mm.

 The catalyst for purification of exhaust gases of various technological processes or vehicles from carbon monoxide and / or nitrogen oxides and / or organic compounds contains a carrier and a catalytically active substance deposited on it.

 The carrier is made of porous gas-permeable material and has an unregulated cellular structure, which is obtained by duplicating the structure of the polymer open-cellular material with metal. Such a polymeric material may be, for example, polyurethane foam.

In the process of forming a cellular structure, cells are obtained having an average diameter of 0.5-5.0 mm and an apparent carrier density of 0.1-1.0 g / cm ³ . Such a carrier is a rigid three-dimensional metal frame, which provides it with high mechanical strength. The catalyst with this carrier has good gas permeability, which can be controlled by changing the average diameter of the cell. In this case, the use of a carrier with a cell diameter of less than 0.5 mm significantly increases the resistance of the catalyst layer to gas flow, which limits the use of the catalyst in processes with high volumetric gas flow rates. An increase in the average cell size of more than 5.0 mm leads to the passage of a significant part of the gas through the catalyst without contact with its surface, which also reduces the cleaning efficiency. The use of a carrier with an apparent density of less than 0.1 g / cm ³ reduces the life of the catalyst due to insufficient mechanical strength and corrosion resistance. The increase in apparent density of more than 1 g / cm ³ leads to a large consumption of metal without increasing the efficiency of the catalyst, which is not economically feasible.

 The carrier is made of copper or nickel, or of an alloy of nickel with copper with a copper content of less than 50 wt.%, Or of an alloy of nickel with chromium with a chromium content of less than 30 wt.%, Or of steel with a carbon content of less than 0.4 wt. %, and alloyed with nickel and / or chromium. Such alloys are widely known and all of the listed materials form a cellular structure when duplicating the structure of the polymer material, which is carried out in a known manner.

 However, for use in a vehicle exhaust gas aftertreatment system, catalysts with a support made of corrosion-resistant materials — nickel, an alloy of nickel with chromium or stainless steel and having an average cell diameter of 1.5–3 mm are most effective, which allows a minimum reduction in engine power while maintaining sufficiently high efficiency of cleaning emissions.

 In addition, the proposed carrier materials containing copper or nickel or chromium have catalytic activity in the deep oxidation of carbon monoxide and organic compounds, which further increases the efficiency of the catalyst.

 Improving the efficiency of the catalyst compared to known catalysts is primarily achieved by increasing the turbulence of the gas stream when it passes through a system of irregularly oriented cells of the carrier frame, which provides the cleaned gas mixture with better contact with the catalyst surface.

 As a catalytically active substance deposited on a carrier, materials are used consisting of or including at least one transition metal oxide of the fourth period of the periodic system. For example, platinum, rhodium, palladium, ruthenium, copper oxide, cobalt oxide, chromium oxide, manganese oxide, vanadium oxide, iron oxide, nickel oxide and others are used.

 The catalytically active substance is applied to the carrier by chemical or electrochemical deposition, vacuum deposition, impregnation from solutions of thermally decomposable salts, or by any other known method.

 The coating of the catalytically active substance has such dimensions that it does not practically change the obtained geometry of the cellular structure of the carrier and the average diameter of the cells of this structure.

PRI me R 1. 100 g of nichrome powder (90% Ni: 10% Cr) with a particle size of 1-5 μm are mixed with 20 g of polyvinyl alcohol. The resulting slurry is impregnated with polyurethane foam with a cell diameter of 1.5 mm. The resulting sample is calcined in a hydrogen atmosphere at 1250 ° C. ^for 2 hours.

To apply the active phase, 7 g of PdCl ₂ and 10 g of HCl are dissolved in 1.5 l of distilled water. The solution was heated to 60-70 ^{° C,} the carrier was immersed for 2-3 min, the sample was then washed with cold water and dried. The amount of palladium deposited is controlled by the electrolyte composition. The resulting catalyst was tested in a flow apparatus at a catalytic 150-500 ^C. The composition of the reaction gas mixture, in weight%:. CO 2 n-Butane 0.5, NO _x 0.5, 2.5 O _2, balance nitrogen.

 Examples confirming the implementation of the invention and showing the achieved effect in its application are shown in the table.

The tests of the catalysts are carried out on a bench catalytic installation, including a car engine and temperature control system, flow rate and composition of the gas-air mixture, temperature control, flow rate and composition of the gas-air mixture. Technical and operational characteristics of the catalysts are given in the table. The degree of conversion of toxic components is shown at T = 350 ^{° C,} a flow rate of 50000 h ^-1, oxygen / oxidizing agent ratio of about 1.

As can be seen from the table, the use of the proposed catalyst for purification of exhaust gases, in particular from CO, HC, NO _x , allows to increase the degree of conversion of these gases in comparison with known catalysts that provide a degree of purification of not more than 91, 85 and 72%, respectively, for these gases , while the effect is achieved simultaneously for all components, or at least for one of them, which is significant under conditions of significant toxicity of gas emissions.

Thus, the application of the proposed solution will reduce the toxicity of gas emissions from industrial enterprises and vehicles with a high content of CO, NO _x or HC, increase the efficiency and service life of gas purification catalysts in comparison with known samples.

Claims (3)

 1. CATALYST FOR CLEANING GAS EXHAUST GASES of technological processes and vehicles from carbon monoxide and / or nitrogen oxides and / or organic compounds containing a carrier of a porous gas-permeable material and a catalytically active substance deposited on a carrier and comprising at least one platinum group metal and / or one transition metal oxide of the fourth period of the Periodic system with a total content of 0.1 to 10 wt.%, the rest is a carrier, characterized in that the catalyst contains a carrier having an unregulated bright cellular structure obtained by duplicating the structure of the polymer open-cell material with a metal, with an average diameter of each cell of 0.5 - 5.0 mm and an apparent density of 0.1 - 1.0 g / cm.  2. The catalyst according to claim 1, characterized in that the carrier is made of nickel or copper, or an alloy of nickel with copper with a copper content of less than 50 wt.%, Or an alloy of nickel with chromium with a chromium content of less than 30 wt.%, Or steel with carbon content less than 0.4 wt.% and alloyed with nickel and / or chromium.  3. The catalyst according to paragraphs. 1 and 2, characterized in that the carrier made of nickel or an alloy of nickel with chromium with a chromium content of less than 30 wt.% Or steel with a carbon content of less than 0.4 wt.% And alloyed with nickel and / or chromium has an average cell diameter 1.5 - 3 mm.

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