RU2434678C1 - Method of producing catalyst for profound oxidation of co and hydrocarbons and catalyst obtained using said method - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to catalysts. Described is a method of producing a catalyst for profound oxidation of CO and hydrocarbons, involving preparation of an exothermic mixture of powdered starting components containing the following in wt %: nickel oxide - 10.4-23.0; iron oxide 12.7-25.2; cobalt oxide 4.2-4.7; manganese oxide 2.4-2.6; aluminium - the rest; putting the mixture into a heat-resistant mould whose inner surface is coated with a functional protective layer made from a ground, molten oxide phase based on corundum and organic binder, putting the mould with the mixture into a centrifuge, melting the mixture and carrying out synthesis in combustion mode with centrifugal acceleration of 40-80 g in an air atmosphere, separating the desired molten alloy from synthesis by-products, grinding the alloy, extracting fractions in form of granules with size from 0.5 to 4.5 mm, followed by leaching the obtained product with aqueous solution of an alkali metal hydroxide and washing the catalyst. Described also is a catalyst obtained using the described method, which is in form of granules of polymetallic alloys of aluminides of Ni, Fe, Co and Mn with a highly-grained, nano-structured, active surface, with the following ratio of elements in terms of said metals in wt %: Ni - 16-41; Fe - 18-44; Co - 6-8; Mn - 2-2.5; Al - the rest.

EFFECT: simple and highly efficient method of producing a catalyst, high catalytic activity and low cost of the catalyst.

2 cl, 2 tbl, 2 dwg, 1 ex

Description

The invention relates to the field of catalytic chemistry, in particular to catalysts based on polymetallic alloys (Rayney type) and methods for their preparation, which can be used for deep oxidation of CO and hydrocarbons, which are the basis for environmentally important processes for cleaning exhaust gases of internal combustion engines and exhaust gas flows of various industrial productions.

A known method of preparing a powdered Nickel catalyst (CT) for the hydrogenation of unsaturated compounds and steam reforming of methane, which includes mixing the original powders from 68.5-95.0% of Nickel and 5.0-31.5% of aluminum, processing the mixture in a high-energy grinding ball the apparatus-attritor, at a speed of rotation of the mixer-impeller of 160-180 rpm for 3-4 hours, followed by leaching of aluminum with an alkali solution and washing the finished catalyst with water (SU1294372 Al, B01J25 / 04, 03/07/1987). The method also describes a catalyst, which is a composite granule, the structure of which is alternating layers of nickel and aluminum with the presence in the obtained composite material of intermetallic compounds of the type NiAl and N ₃ A1 with a maximum specific surface area of 10.37 m ² / g. Testing the QD in the process of natural gas conversion shows that methane conversion is 41%, and the QD works in a wider temperature range (600-700 ° С).

There is a method of preparing a skeletal nickel catalyst for the hydrogenation of organic compounds. For this purpose, a nickel-aluminum alloy is prepared by machining in a grinding ball apparatus for 30-40 minutes nickel powders 20-60% and aluminum at a speed of the apparatus 5-7 m / s in the mode of constrained shock providing conditions for self-propagating high-temperature synthesis followed by leaching and washing of the catalyst (SU 15 99083 Al, B01J 25/02, 10/15/1990). The skeletal target catalyst is a composite material of intermetallic compounds such as NiAl and Ni ₃ Al, or NiAl ₃ and Ni ₂ A1 ₃ , or Ni ₂ Al ₃ . The catalyst during the hydrogenation of, for example, nitrobenzene provides high performance on the target product.

A known method for producing a Raney-type nickel catalyst by mechanochemical synthesis, including grinding the mixture of the initial nickel and aluminum powders in high-speed planetary mills at accelerations of 40 ... 60 g, in an inert atmosphere, followed by leaching of aluminum from the synthesis product (Fasman AB, Raney nickel catalysts from mechanochemical alloys Ni-Al. Izv. SB AN SSSR, chemical science, 1986, N 19, issue 6, p. 83-85).

The disadvantages of these methods are the complexity and energy consumption of the catalyst preparation process and their low activity relative to the deep oxidation of CO and hydrocarbons due to contamination during grinding.

A known method of producing a Raney-type nickel catalyst, comprising preparing an initial mixture of aluminum and nickel powders, heat treating it in an inert medium, followed by leaching the resulting product with an aqueous solution of sodium hydroxide, the initial mixture being taken in the following ratio, wt.%: Aluminum 52 ... 75; nickel 25 ... 48, and the heat treatment is carried out by local ignition of the mixture, followed by high-temperature reaction of the components in the combustion mode (RU 2050192, B01J 25/02, 20.12.1992).

The obtained alloy upon hydrogenation of hexene-1 shows a high degree of selectivity, but is inactive relative to the deep oxidation of CO and hydrocarbons.

The objective of the invention is to provide a high-performance method for producing a catalyst with a highly branched nanostructured active surface (Raney metals) for the deep oxidation of CO (carbon monoxide) and hydrocarbons with high catalytic activity due to the balanced chemical composition of the catalyst components.

The technical result of the invention is to simplify the production method, increase its productivity, increase the catalytic activity of a catalyst with a nanostructured active surface during the deep oxidation of CO and hydrocarbons, reduce the cost, increase the yield of the target product, increase the uniformity in chemical and structural composition.

The technical result is achieved by the fact that the method of producing a catalyst for the deep oxidation of CO and hydrocarbons involves the preparation of an exothermic mixture of powders of the starting components, containing, wt.%: Nickel oxide 10.4-23.0; iron oxide 12.7-25.2; cobalt oxide 4.2-4.7; manganese oxide 2.4-2.6; the rest is aluminum, placing the mixture in a refractory form, coated on the inner surface with a functional protective layer prepared from a crushed cast oxide phase based on corundum and an organic binder, placing the form with the mixture in a centrifuge, igniting the mixture and carrying out synthesis in the combustion mode under centrifugal acceleration 40- 80 g, in an atmosphere of air, by separating the target cast alloy from synthesis by-products, grinding the alloy, isolating a fraction in the form of granules with a size of 0.5 to 4.5 mm, followed by leaching to the floor chennogo product with an aqueous solution of alkali metal hydroxide and washing the catalyst. The catalyst for the deep oxidation of CO and hydrocarbons obtained by the proposed method is a granule of polymetallic alloys of aluminides of metals Ni, Fe, Co, and Mn with a highly branched, nanostructured, active surface, with the following ratio of elements in terms of these metals: wt.%: Ni 16-41; Fe 18-44; Co 6-8; Mn 2-2.5; Al the rest.

The essence of the method of producing a catalyst is to use the thermal energy released during exothermic reactions in the combustion wave after initiating a mixture of the starting reagents at a centrifugal acceleration of 40-80 g. As a result of the implementation of high temperatures directly in the combustion wave, the synthesis process is short-lived and takes several tens of seconds. The synthesis is carried out in an atmosphere of air in centrifugal units. A functional protective layer based on aluminum oxide deposited on the inner surface of the mold eliminates the contact of the melt of the target product with the mold material and reduces the cooling rate of the melt, acting as a heat-insulating layer. In general, the presence of a functional layer leads to an increase in the “life” time of the melt, which contributes to a more complete phase separation at overloads of 40-80 g, allows us to simplify the design of the centrifuge and carry out the synthesis on large masses of the initial mixtures. The thickness of the layer depends on the ratio of the initial components, the magnitude of gravity and the volume of the form.

After synthesis, the product is an ingot that consists of two layers: the lower is an intermetallic alloy based on aluminides Ni, Fe, Co and Mn, and the upper is a cast oxide material based on Al ₂ O ₃ (corundum), the layers are separated from each other and use as intended. Cast oxide material based on Al ₂ O _{3 is} used to make a suspension for coating the inner surface of the used molds from graphite material.

The lower intermetallic ingot of the alloy based on the aluminides Ni, Fe, Co, and Mn (Ni-Fe-Co-Mn-Al) is subjected to grinding and classification on standard equipment, the time takes from 20 to 60 minutes, after which the separated fractions of granules with size 0.5 to 4.5 mm is leached with an aqueous solution of alkali metal hydroxide for 20-40 minutes in stainless containers, followed by washing the catalyst to a neutral wash water reaction.

The catalyst obtained by the described method is a granule with a particle size of 0.5-4.5 mm, consisting of aluminides of metals Ni, Fe, Co and Mn with a nanostructured active surface (such as Raney metals). Such catalyst granules are used for the deep catalytic oxidation of CO and hydrocarbons, which are the basis for environmentally important processes for purification of exhaust gases from internal combustion engines and exhaust gas streams of various industrial plants.

Example 1

An exothermic reaction mixture of the starting components is prepared in the following ratio, wt.%: Nickel oxide -23.0; iron oxide -12.7; cobalt oxide -4.2; manganese oxide -2.4; aluminum - up to 100.

Previously, a suspension is prepared on the inner surface of the graphite form, prepared from a crushed cast oxide phase based on corundum (a by-product of the method) and an organic binder (alcohol polyvinyl butyral). The laminated form is dried at a temperature of 150 ° C for at least 1.5 hours. Then the finished mixture is poured into a mold and placed in a centrifugal installation. The centrifuge rotor is rotated and creates an overload of 40 g, after which the reaction mixture is ignited by an electric spiral. After completion of the combustion process, the synthesis product is cooled and removed from the reaction form. The synthesis product consists of two layers: the lower is an intermetallic alloy based on aluminides Ni-Fe-Co-Mn and the upper (by-product of the synthesis) is a cast oxide material Al ₂ O ₃ (corundum) with minor impurities of unstopped starting metal oxides. Layers are easily separated from each other. The aluminide-based alloy is subjected to grinding and classification on standard equipment for 60 minutes, after which the separated granule fractions with a size of 0.5 to 4.5 mm are leached with an aqueous alkali metal hydroxide solution for 20 minutes, followed by washing the catalyst to a neutral wash water reaction .

The content of elements in the target product is, wt.%: Ni-41; Fe-18; Co-6.0; Mn-2.0; Al is the rest.

Other examples of the method are presented in table 1.

The composition and properties of the target material by examples are presented in table 2.

As can be seen from the data presented, the proposed method allows to obtain a polymetallic catalyst containing in its composition Ni, Fe, Mn, Co and Al with a content of not more than 0.6 wt.% Impurities. The yield of the target catalyst from the calculated values is 92-97% (depending on the conditions of gravity and the ratio of components). After grinding and chemical treatment of the catalyst granules, their specific surface area is at least 22.2 m ² / g. The catalyst is assigned the technological term InterKat-2-SVS-Ts.

X-ray phase analysis of the synthesized polymetallic catalyst revealed the presence of seven main intermetalide phases: NiAl ₃ , FeA1 ₃ , Ni ₂ Al ₃ , Mn ₄ Al ₁₁ , Mn ₅ Al ₈ , Mn ₆ Al and CoAl ₃ . In the process of leaching of the intermetallic alloy, aluminum is removed with a decrease in its content from 52 to 19 wt.% In the target catalyst.

Figure 1 presents the data of scanning electron microscopy of the microstructure of the surface of the granules (a. Fig. 1) of a polymetallic Ni-Fe-Co-Mn-Al catalyst, which indicate a strongly eroded nature of the relief of the catalyst particles. In photographs with a higher magnification (b, c), in certain sections of the samples, a layer of nanosized plates with a diameter of 1-2 microns and a thickness of 20-70 nm is noticeable. The catalyst compositions indicated in the table were used for the deep oxidation of CO and hydrocarbons in a model mixture of CO, propane, oxygen, and nitrogen. The dependence of the conversion of propane and CO on temperature for samples of the inventive catalyst Ni-Fe-Co-Mn-Al in accordance with the examples presented in figure 2, where it is seen that the temperature of 100% conversion of CO is 175 ° C. The conversion of 90% propane (C ₃ H ₈ ) is achieved at 250 ° C. These data indicate the possibility of efficient use of the obtained catalysts for purification of exhaust gases.

Thus, the combination of features claimed in the formula allows obtaining a polymetallic material based on aluminides Ni, Fe, Co, and Mn, which, after chemical treatment (leaching), is used as a catalyst for the deep oxidation of CO and hydrocarbons for purification of exhaust gases from internal combustion engines and exhaust gas streams various industrial productions.

The proposed method for producing catalytic material based on cast polymetallic alloys does not require large amounts of electricity, has high productivity, is environmentally friendly due to the absence of gaseous products in the synthesis products, and the catalytic material obtained after leaching has a high level of catalytic activity in the reactions of deep oxidation of CO and hydrocarbons.

Table 1 Example No. The composition of the reaction, exothermic mixture of components, wt.% Method Parameters Nickel oxide Iron oxide Cobalt oxide Manganese Oxide Aluminum Gravity conditions, g The time of alkaline etching, min one 23.0 12.7 4.2 2,4 rest 40 40 2 18.6 18.2 4.6 2.5 rest 60 thirty 3 10,4 25,2 4.7 2.6 rest 80 twenty

table 2 No. of Example The content of impurities (Al ₂ O ₃ ), wt.% The composition of the synthesized alloy before leaching,% wt. The composition of the granules of the catalyst after leaching,% wt. The specific surface of the granules after leaching, m ² / g one 04 Ni-20.6; Fe-12.5; Co-3.9; Mn-1.57; Al-Else Ni-41.0; Fe-18.0; Co-6.0; Mn-2.0; Al- The rest 22 2 2 0.5 Ni-18; Fe-18.5; Co-4.0; Mn-1.6; Al-Else Ni-36.0; Fe-30.0; Co-7.0; Mn2.2; Al-Else 25,4 3 0.6 Ni-ll; Fe-24.6; Co-4.2; Mn-1.65; Al-Else Ni-16.0; Fe-44.0; Co-8.0; Mn-2.5; Al-Else 27 7

Claims (2)

1. A method of producing a catalyst for the deep oxidation of CO and hydrocarbons, comprising preparing an exothermic mixture of powders of the starting components, containing, wt.%: Nickel oxide 10.4-23.0; iron oxide 12.7-25.2; cobalt oxide 4.2-4.7; manganese oxide 2.4-2.6; the rest is aluminum, placing the mixture in a refractory form, coated on the inner surface with a functional protective layer prepared from a crushed cast oxide phase based on corundum and an organic binder, placing the form with the mixture in a centrifuge, igniting the mixture and carrying out synthesis in the combustion mode under centrifugal acceleration 40- 80 g, in an atmosphere of air, by separating the target cast alloy from synthesis by-products, grinding the alloy, isolating a fraction in the form of granules with a size of 0.5 to 4.5 mm, followed by leaching to the floor chennogo product with an aqueous solution of alkali metal hydroxide and washing the catalyst. 2. The catalyst for the deep oxidation of CO and hydrocarbons obtained by the method of claim 1, which is a granule of polymetallic alloys of aluminides of metals Ni, Fe, Co and Mn with a highly branched, nanostructured, active surface, with the following ratio of elements in terms of these metals: .%:
Ni 16-41 Fe 18-44 With 6-8 Mn 2-2.5 Al Rest

Images