RU2372556C2 - Method of burning hydrocarbon fuels (versions) and catalysts to this end - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of burning hydrocarbon fuel involves passing initial fuel through several catalyst zones using a catalyst packet containing two catalystes: Pd-containing catalyst for initiating the combustion process of the fuel-air mixture and a catalyst for stable combustion of the fuel-air mixture. Burning takes place in two catalyst zones, which are distinguished by layer porosity, composition of catalysts and their activity in hydrocarbon oxidation reactions: the catalyst used in the 1^st zone has layer porosity between 0.45 and 0.60 and contains PdO and/or Pd, deposited on granular aluminium oxide, modified with oxides of rare-earth elements, particularly cerium and/or lanthanum, with palladium content between 0.5 and 2.5 wt %; the catalyst used in the 2^nd zone is a granular oxide catalyst with layer porosity between 0.4 and 0.53, containing active component in form of 3 to 20 wt % manganese oxide or 20 to 90 wt % manganese hexaaluminate, or an oxide catalyst, modified with PdO and/or Pd in amount of 0.1 to 2.5 wt %. Initiation of the combustion process of the fuel-air mixture, which contains 1.0 to 6.0 vol % methane, takes place on the catalyst in the 1^st zone at temperature between 250 and 530°C; stable combustion of the fuel-air mixture takes place on the catalyst in the 2^nd zone at input temperature between 450 and 800°C, wherein temperature of waste gases at the outlet of the catalyst packet is between 750 and 950°C. The height ratio of the 1^st and 2^nd catalyst zones in the packet is between 0.1/0.9 and 0.2/0.8. To control the burning of the hydrocarbon fuel, a layer of inert material is placed between the 1^st and 2^nd zones, where this material can be granular aluminium oxide or corundum. Height of the layer of inert material is 0.025 to 0.15 of the height of the entire packet.

EFFECT: provision for environmental safety of waste gases and stable combustion of natural gas.

17 cl

Description

The invention relates to catalytic technologies, namely to the catalytic combustion of natural gas, and can be used in the catalytic combustion chambers of gas turbine power plants of vehicles, gas turbine power plants, gas pumping units and other devices to ensure environmental safety of exhaust gases and stability of the natural gas combustion process . The invention provides high temperature catalysts for burning natural gas in catalytic combustion chambers of gas turbines. The proposed catalysts can also be used in other high-temperature combustion processes of natural hydrocarbon fuels.

The main advantage of the catalytic combustion process is the ability to control the combustion process and the temperature profile in the reaction zone of the catalytic combustion chambers of gas turbine power plants, which avoids the formation of nitrogen oxides formed during homogeneous combustion (above 1300 K). A number of patents (WO 9531675; US 5248251, B01J 23/44, F23C 13/00, 09/28/93; US 6015285, B01J 23/44, 01/18/2000; JP 07293833, etc.) describe methods of temperature control during the combustion of hydrocarbon fuels , mainly methane and natural gas, in the catalytic combustion chambers of gas turbines. Such methods are the use of a depleted fuel-air mixture, stepwise combustion, controlled combustion using one or more catalysts. Multi-stage (zone) combustion of fuel in catalytic combustion chambers has several advantages, since this method provides the temperature of the exhaust gases necessary for further supply to the gas turbine unit (750-1300 ° C), stable combustion of the fuel, the completeness of fuel combustion and the environmental cleanliness of the exhaust gases ( lack of CO, hydrocarbons and NO). The control of the temperature profile in multi-stage combustion of fuel, usually 2- or 3-stage, is carried out mainly by varying the activity of the catalyst in different zones of the catalytic combustion chamber. The process of staged combustion of hydrocarbon fuels on a catalyst in a combustion chamber of gas turbines can be implemented in several ways.

Burning on a block catalyst with inactive channels. American firms Catalytica (US 5248251, F23D 3/40, 09/28/1993; RU 2161755, F23D 1418, 01/10/2001) and Westinghouse Electric Corp. (US 4870824, F23R 3/40, 03.10.89) it is proposed to supply the air-fuel mixture to the block catalyst, which consists alternately of channels with and without an active component. If the surface reaction in the channel with the catalyst proceeds even in the diffusion mode, heating to adiabatic temperature of the flame does not occur, since heat is transferred to the inert channel of the block. The air-fuel mixture leaving the inert channels is burned at the outlet of the block catalyst.

Combustion using a diffusion layer. In the patent US 5248251, F23D 3/40, 09/28/1993 proposed to use a diffusion barrier to reduce the temperature on the catalyst, which is prepared by applying an inert coating on the surface of the catalyst. The coating reduces the diffusion of fuel to the surface of the catalyst and reduces the conversion of fuel on the catalyst, which prevents the catalyst from overheating.

Burning on a catalyst with different levels of activity. In patents US 5601426, F02M 27/02, 02/11/1997; US 5248251, F23D 3/40, 09/28/1993) proposed the use of a multi-section catalyst with different levels of activity, allowing the combustion process in a kinetically controlled mode. The catalytic activity is regulated by varying the concentration of the noble metal (mainly palladium) in the range from 5 to 20 wt.% Or the nature of the active component (noble metal, transition metal oxides).

The process of burning hydrocarbon fuel in the catalytic combustion chambers of gas turbine power and energy plants is carried out at 750-1300 ° C, a pressure of 1-20 atm and flow rates above 250,000 h ^-1 , therefore, it is of practical importance for high-temperature combustion processes in gas turbine plants, boilers, etc. P. have a low ignition temperature of the fuel-air mixture, high activity and thermal stability of the catalyst, low hydraulic resistance. The above requirements for high temperature combustion catalysts for natural fuels are met by Pd-containing catalysts and oxide catalysts with a hexaaluminate and perovskite structure.

The most widely used processes for burning natural gas in catalytic combustion chambers of gas turbines are Pd / PdO based catalysts supported on ceramic oxide supports, such as: Al ₂ O ₃ modified with REE and SCE oxides; ZrO ₂ ; SnO ₂ (US 5405260, B01D 53/86, B01J 23/38, 04/11/95; US 5259754, B01D 53/86, B01J 23/38, 11/09/93; US 5741467, B01D 53/94, B01J 23/63, 04/21/98; US 6620761, B01J 23/44, 09/16/2003; JP 8054121, F23R 3/40, B01D 53/86, 02/27/96). It is believed that the use of zirconium oxide as a carrier is preferable because it provides a low ignition temperature and long-term stability of the Pd-containing catalyst at elevated temperatures (US 5259754, US 5405260). However, the technology for producing zirconium oxide is expensive. The palladium content in the catalysts usually varies over a wide range of 2-25 wt.% (US 5248251, F23D 3/40, 09/28/1993). In most cases, the catalyst is prepared by depositing PdO or its precursor on a refractory carrier, followed by calcination, while high-temperature calcination at 960 ° C in an oxidizing atmosphere at a pressure of 2 atm (JP 08243391) provides a high and stable oxidative activity at 700-1000 ° C.

For example, in patents US 5741467, B01D 53/94, B01J 23/63, 04.21.98; JP 8054121, F23R 3/40, B01D53 / 86, 02/27/96 offer Pd catalysts containing Pd / PdO supported on alumina modified with CeO ₂ and / or La ₂ O ₃ in US 5750458, B01J 23/63 12.05.98 - a catalytic composition containing PdO and one or more REE oxides: Ce, La, Nd, Pr, and / or Sm supported on a refractory carrier. In the patent US 6284210, B01J 23/89, F23C 13/00, 09/04/2001 describes a highly active catalyst containing Ce (0.3-20 wt.%), Fe (0.01-3.5 wt.%) And Pt and / or Pd (12-20 g / l) deposited on a block carrier based on α, δ-, η-, γ-, κ-, χ-, ρ-, θ-Al ₂ O ₃ , SiO ₂ , aluminosilicates, TiO ₂ , ZrO ₂ and mixtures thereof.

In the group of patents US 5880059, B01D 53/86, B01J 23/34, 09.03.99; RU 2086298, B01J 27/70, 08/10/97; RU 2080920, B01J 23/745, 06/10/97; RU 2185238, B01J 23/34, 07/20/2002 and others for high-temperature combustion of natural gas, catalysts based on transition metal oxides, perovskites and hexaaluminates are proposed. Patents RU 2086298, 2080920 offer a catalyst based on period IV metal oxides, for example, Ni, Co, Fe Mn deposited on a porous ceramic carrier in the form of a multichannel monolith, the catalyst provides complete combustion of the fuel, high radiation temperature and durability. Patent RU 2185238 describes a method for modifying a manganese-aluminum oxide catalyst with the addition of Mg, La, Ce oxides or a mixture thereof to increase the thermal stability of the catalyst at temperatures of its use of 1100-1300 ° C while increasing the life of the catalyst. Patents JP 2078438, US 5830822, US 6015285, US 6060420 offer hexaaluminate catalysts, for example La _0.5 Sr _0.5 MnAl ₁₁ O ₁₉ and La _0.2 Sr _0.8 MnAl ₁₁ O ₁₉ . The catalysts have high activity and a long service life, however, in most cases, the catalyst must be activated in a reducing medium (hydrogen).

The listed catalysts differ significantly in catalytic activity and can be used in different zones of the catalytic package, providing stage-by-stage burning of natural fuels in kinetic mode, the required completeness of combustion and the temperature of the exhaust gases required for supplying the gas turbine.

For example, JP 62041511, F23R 3/40, B01J 023/40, 02.23.1987, proposes a catalytic system for high-temperature combustion, with a small pressure loss and a long service life, in which a catalytic layer with active components Pd, Pt and NiO is located the front part, and another catalytic layer with the active component Pt is located in the rear part.

In the patents JP 7293833, F23D 14/18, B01J 35/02, 10.11.1995; JP 7293835, F23D 14/18, B01J 23/00, 11/10/1995 a 2-stage catalytic combustion process is described, the principle of which is based on the use of 2 different catalysts in the 1st and 2nd reactor zones. The first stage of combustion is carried out on PdO supported on a carrier comprising REM oxides and complex oxide Al, Si, Ti and Zr; the second on PdO and oxides selected from: MgO, ZrCh, REM oxides on a support including REM oxides and Al, Si, Ti, and Zr oxide. In the second stage, it is also possible to use a catalyst comprising an La-containing perovskite of the general formula La _1-x A _x Me _1-a O ₃ (0 <x <0.6).

A similar method for the catalytic combustion of gases containing mainly methane is proposed in the patent US 6015285, B01J8 / 02, 01/18/2000. In the 1st zone, part of the fuel is burned at a temperature not exceeding 800 ° C on a PdO catalyst supported on γ-Al ₂ O ₃ stabilized with La ₂ O ₃ , CeO ₂ or BaO; or on La ₂ O ₃ -hexaaluminate. The 1st combustion zone is limited by a diffusion layer of α-Al ₂ O ₃ or La ₂ O ₃ -11Al ₂ O ₃ hexaaluminate. Complete combustion of fuel takes place in the 2nd zone on a catalyst selected from the group La _0.5 Sr _0.5 MnAl ₁₁ O ₁₉ , PdO / La ₂ O ₃ -11Al ₂ O ₃ , La _0.2 Sr _0.8 MnAl ₁₁ O ₁₉ .

Gas turbines operate at high linear flow rates (> 250,000 h ^-1 ), therefore, to reduce the resistance of the catalytic layer, it is necessary to use highly permeable catalysts. As a result, the catalyst is applied to the surface of a permeable ceramic or metal carrier, and the use of metal blocks having high strength is preferable. For example, US Pat. No. 6,620,761, B01J 23/44, 09.16.2003, describes a suspension method for applying a Pd-Zi-O ₂ -containing composition to a metal foil, wherein the Pd-ZrO ₂ suspension is prepared by mixing Pd nitrate with a solution of alkyl ammonium hydroxide and hydroxide Zr. The suspension has a high activity and good adhesion to a metal surface, but is expensive. It should be noted that a multi-section catalytic package can be assembled from one block onto which several catalytic compositions of different activity are applied, or from several blocks onto which catalytic compositions of different activity are applied.

The closest in technical essence to the claimed and achieved result is a method of multi-stage combustion of natural gas, described in a series of patents of the company Catalytica (US 5326253, B01D 53/86, B01J 23/38, 07/07/94; RU 2161755, F23D 14/18, 10.01. 2001). The essence of the method is to separate the combustion process into 2-4 stages, so that the temperature of the catalyst and the average gas temperature are controlled by the choice of the composition and structure of the catalyst, including structures in which part of the combustible mixture is inhibited by contact with the catalytic material using a diffusion barrier or non-catalytic channels ( integral exchange surface). To initiate the combustion process, the catalyst is heated to a temperature of 325 ° C, at which a noticeable oxidation of methane in the fuel-air mixture begins and the gas temperature rises sharply. The composition and design of the catalyst for each catalytic zone of the reactor is selected so as to ensure the temperature of the exhaust gas at the outlet of the first zone is not more than 800 ° C, mainly 500-650 ° C, from the second zone - about 750-800 ° C, if there is 3- I have a catalytic zone (850-1050 ° C), and higher than the auto-ignition temperature, if a homogeneous combustion zone is desired.

In the first zone of the reactor, a palladium catalyst supported on a ceramic or metal block support (100 mesh / inch ² ) is used. The palladium content in the first zone ranges from 0.1 to 25 wt.%, Mainly 1.5-6.2 wt.%, Which is sufficient to ensure high activity at high volumetric gas flow rates, resistance to high temperatures and the reaction medium. Uncontrolled combustion is controlled by the transition of PdO to Pd or by adding a diffusion barrier layer based on oxides of aluminum, silicon, zirconium, or titanium to the surface of the catalyst. The second zone receives unburned gas from the first zone and provides further controlled combustion occurring in the presence of a catalytic structure with the ability to heat transfer and providing integral heat transfer. The catalyst preferably contains a Pd-containing composition, which is preferably applied on one side of the metal support, as a result of which some of the channels are not coated with a catalyst. The metal support is prepared from stainless steel or alloys containing aluminum, in the form of honeycombs, spiral rollers, corrugated sheet or other configurations having longitudinal channels. This design of the catalyst due to its high thermal conductivity provides good heat transfer, dissipating the heat of reaction to gas streams.

In the third zone, it is preferable to use thermostable catalysts at high temperatures, for example, a Pt-containing catalyst (20 wt.% Pt in the form of sulfide on Al ₂ O ₃ ) or a catalyst based on Group VIII metal oxides.

The homogeneous combustion zone provides the required temperature, about 1260 ° C. The gas residence time in it is 11-12 ms to ensure complete combustion (CO less than 10 ppm) and to achieve an adiabatic temperature.

The advantage of the method is the production of exhaust gases with a low concentration of CO (not more than 10 ppm) and NO _x at a temperature suitable for use in a gas turbine, steam boiler or furnace. The main disadvantage of this method is the high palladium content in the catalytic bag (up to 6.2 wt.% Pd), the complexity of preparing metal carriers and applying catalytic coatings on them, which leads to a significant increase in the cost of the method. In addition, metal supports are characterized by low thermal stability, accompanied by thermal corrosion, especially in the presence of water vapor, which leads to the destruction of the catalyst, entrainment of noble metals and, as a result, loss of catalytic activity, and shorten the life of the catalyst.

The problem solved by the invention: the development of an environmentally friendly method of burning hydrocarbon fuels, including natural gas, in the catalytic combustion chambers of gas turbine power plants of vehicles and gas turbine power plants using highly active and thermostable catalysts with a low content of noble metals.

This is achieved by creating in the catalytic combustion chamber two or more catalytic zones differing in porosity and catalytic activity in the oxidation reaction of hydrocarbon fuels, for example methane. The combination of several catalytic zones allows the process of burning hydrocarbon fuels in several stages and control the combustion process.

A method for burning hydrocarbon fuel (the first option) is proposed, which consists in passing the initial fuel through several catalytic zones using a catalytic package comprising two catalysts: a Pd-containing catalyst to initiate the combustion of the air-fuel mixture and a catalyst for the stable combustion of the air-fuel mixture, combustion is carried out in two catalytic zones, which differ in the porosity of the layer, the composition of the catalysts and their catalytic activity in oxidation reactions hydrocarbons: in the 1st zone, a catalyst is used that provides a porosity of 0.45-0.60 and containing PdO and / or Pd supported on granular alumina modified with rare earth oxides (REE), in particular cerium and / or lanthanum, with a palladium content of 0.5-2.5 wt.%; in the 2nd zone, a granular oxide catalyst with a porosity of 0.40-0.53, containing 3-20 wt.% manganese oxides or 20-90 wt.% manganese hexaaluminate, or an oxide catalyst modified with PdO and / or Pd in an amount of 0.1-2.5 wt.%.

The initiation of the combustion process of the fuel-air mixture containing 1.0-6.0 vol.% Methane is carried out on the catalyst of the 1st zone at a temperature of 250-530 ° C; stable combustion of the air-fuel mixture is carried out on the catalyst in the 2nd zone at an inlet temperature of 450-800 ° C, while the temperature of the exhaust gases at the outlet of the catalytic package is 750-950 ° C.

The ratio of the heights of the 1st and 2nd catalytic zones in the package is 0.1 / 0.9-0.2 / 0.8.

To control the process of burning hydrocarbon fuel between the 1st and 2nd zone, a layer of inert material is placed, which is used as granular alumina or corundum, while the height of the inert material layer is 0.025-0.15 of the height of the entire package.

A method is proposed for burning hydrocarbon fuel (second option), which consists in passing the initial fuel through several catalytic zones using a catalytic package comprising two catalysts: a Pd-containing catalyst for initiating the combustion of the air-fuel mixture and a catalyst for the stable combustion of the air-fuel mixture, combustion is carried out in three catalytic zones, which differ in the porosity of the layer, the composition of the catalysts and their catalytic activity in oxidation reactions hydrocarbons: in the 1st zone, a catalyst is used that provides a layer porosity of 0.45-0.60 and contains PdO and / or Pd supported on granular alumina modified with rare earth oxides, in particular cerium and / or lanthanum, containing palladium 0.5-2.5 wt.%; in the 2nd zone, a granular oxide catalyst with a porosity of 0.40-0.53, containing 3-20 wt.% manganese oxides or 20-90 wt.% manganese hexaaluminate, or an oxide catalyst modified with PdO and / or Pd in an amount of 0.1-2.5 wt.%, and at the exit of the catalytic package for burning off unburned hydrocarbons and ensuring the required temperature of the exhaust gases, a narrow layer of highly active catalyst with a porosity of 0.42-0.45 containing PdO and / or Pd on an alumina carrier, modified a rare earth oxide, or manganese-containing hexaaluminate modified PdO and / or Pd, Pd content is 0.5-1.5 wt.%.

The initiation of the combustion process of the fuel-air mixture containing 1.0-6.0 vol.% Methane is carried out on the catalyst of the 1st zone at a temperature of 250-530 ° C; stable combustion of the air-fuel mixture is carried out on the catalyst in the 2nd zone at an inlet temperature of 450-900 ° C, afterburning of unburned hydrocarbons and products of incomplete oxidation of hydrocarbons is carried out on the catalyst of the 3rd zone, while the temperature of the exhaust gases at the outlet of the catalytic package is 800-950 ° C.

The ratio of the heights of the 1st, 2nd and 3rd catalytic zones in the package is 0.05 / 0.9 / 0.05-0.1 / 0.8 / 0.1.

To control the process of burning hydrocarbon fuel between the 1st and 2nd zone, a layer of inert material is placed, which is used as granular alumina or corundum, while the height of the inert material layer is 0.025-0.15 of the height of the entire package.

A catalyst is proposed for initiating the combustion process of a fuel-air mixture (first zone) containing PdO and / or Pd and rare-earth oxides supported on an alumina support. For the preparation of the catalyst, γ-alumina or a mixture of γ-Al ₂ O ₃ are used as a support. and χ-Al ₂ O ₃ , γ-Al ₂ O ₃ and δ-Al ₂ O ₃ , γ-Al ₂ O ₃ and θ-Al ₂ O ₃ ; the palladium content in the catalyst is 0.5-2.5 wt.%, rare earth oxide, mainly La and / or Ce, 0-15 wt.%, the rest is aluminum oxide, the catalyst is activated by heat treatment in an oxidizing or reducing environment at a temperature of 800 -1000 ° C.

The catalyst of the 1st zone may be in the form of rings with a diameter of 6-15 mm, a length of 6-15 mm and a hole diameter of 2-8 mm; or cylinders with a diameter of 3-8 and a length of 6-7 mm; or spheres with a diameter of 3-7 mm.

A catalyst is proposed for the stable combustion of a fuel-air mixture (second zone) containing manganese hexaaluminate. Granulated alumina is used to prepare the catalyst, the catalyst is prepared by impregnating the support with solutions of manganese and lanthanum salts, followed by calcination at a temperature of 900-1100 ° C, the content of manganese hexaaluminate in the catalyst is 20-90 wt.%, mainly 50-70 wt.%, the rest is aluminum oxide.

The catalyst of the 2nd zone may be in the form of rings with a diameter of 6-15 mm, a length of 6-15 mm and a hole diameter of 2-5 mm; or cylinders with a diameter of 3-5 and a length of 6-7 mm; or spheres with a diameter of 3-5 mm.

A catalyst is proposed for stable combustion of a fuel-air mixture (second zone) and afterburning of unburned hydrocarbons (third zone) containing manganese hexaaluminate and PdO and / or Pd. Granulated alumina is used to prepare the catalyst, the catalyst is prepared by impregnating the support with solutions of manganese salts, lanthanum and palladium, followed by calcination at a temperature of 900-1100 ° C, the content of manganese hexaaluminate in the catalyst is 20-90 wt.%, Pd 0.1-2.5 wt.%, the rest is aluminum oxide.

The catalyst may be in the form of rings with a diameter of 6-15 mm, a length of 6-15 mm and a hole diameter of 2-5 mm; or cylinders with a diameter of 3-5 and a length of 6-7 mm; or spheres with a diameter of 3-5 mm.

A catalyst for the stable combustion of a fuel-air mixture (second zone) containing manganese oxides is proposed. Granulated alumina having a phase composition of γ-Al ₂ O ₃ or a mixture of γ-Al ₂ O ₃ and χ-Al ₂ O ₃ is used to prepare the catalyst or a mixture of γ-Al ₂ O ₃ and θ-Al ₂ O ₃ , the catalyst is prepared by impregnating the carrier with solutions of manganese salts, followed by calcination at a temperature of 500-1100 ° C, the content of manganese oxides in the catalyst is 3-20 wt.%, mainly 5 -12 wt.%, The rest is aluminum oxide.

Manganese oxides are in the form of individual oxides MnO ₂ , Mn ₂ O ₃ , Mn ₃ O _4, or mixtures thereof, or as a solid solution of manganese cations in alumina.

In the first zone of the reactor, a highly active catalyst is used that provides a low ignition temperature of the fuel-air mixture (stage I of the combustion process) and initiates the combustion process in the second zone (by heating the fuel-air mixture as a result of heat generation during methane combustion). In the second zone of the reactor, a thermostable catalyst is used, which is resistant to high temperatures (up to 1100 ° C) and provides stable combustion and oxidation of hydrocarbon fuel unburned in the first zone and products of incomplete oxidation to harmless compounds - carbon dioxide and water (stage II combustion process). Varying the porosity of the catalytic layers and their catalytic activity allows us to provide the required temperature of the exhaust gases (750-1200 ° C) and the depth of combustion of hydrocarbon fuels (not more than 10 ppm СО). In addition, the use of granular catalysts of various geometry provides an increase in pressure in the chamber due to hydraulic resistance to gas flow. An increase in pressure leads to an increase in the temperature of the phase transition of PdO to Pd and a decrease in the temperature of homophase combustion of the fuel-air mixture, which allows for high activity of the Pd catalyst in a wider temperature zone. An increase in pressure can lead to an increase in the amount of CO in the products of the combustion process; in this case, it is recommended to organize the 3rd catalytic zone from a highly active catalyst that provides afterburning of products of incomplete oxidation of the fuel (stage III of the combustion process).

The proposed methods of two- and three-stage combustion of hydrocarbon fuels, designed for catalytic combustion chambers of gas turbine power and power plants, provide

- oxidation of fuel-air mixtures at an initial temperature of 250 ° C and not more than 530 ° C;

- the completeness of fuel combustion is not less than 99.9%;

- the concentration in the exhaust gases of carbon monoxide is not more than 10 ppm; hydrocarbons not more than 10 ppm; nitrogen oxides not more than 2-3 ppm;

- the temperature of the exhaust gases at the outlet of the combustion chamber is at least 750 ° C.

The proposed methods of two- and three-stage combustion of hydrocarbon fuels can significantly reduce the content of Pd in the catalytic package without reducing technological parameters. In addition, the proposed technology has high thermal stability and resistance to temperatures of at least 950 ° C.

The catalyst of the 1st zone provides the initiation of the combustion process of the fuel-air mixture at low temperature (250-530 ° C) and heating the gas mixture to temperatures of 450-800 ° C. The catalyst is characterized by a low content of Pd. An increase in activity is achieved by varying the Pd precursor compound and performing high temperature treatment in an air or reaction medium.

The catalyst of the 2nd zone provides stable combustion in the temperature range 450-800 ° C. To increase the catalytic activity, the oxide catalyst can be modified with the addition of palladium, while the regulation of the catalytic activity (therefore, the composition and temperature of the exhaust gases) is achieved by varying the concentration of Pd or its distribution over the granule. A uniform, “crust” or “intramole” palladium granule distribution is achieved by using various palladium precursors, for example palladium hydrochloric acid, palladium nitrate or acetate, tetraammonium palladium nitrate or chloride, and other palladium compounds.

If necessary, the catalytic package can be supplemented with a third zone in which the afterburning of unburned hydrocarbon fuel (methane) and products of its incomplete oxidation takes place, and the required temperature of the exhaust gases is also achieved. The catalyst of the 3rd zone has high thermal stability and activity, which is ensured by the synergistic effect in the catalytic activity of manganese hexaaluminate and palladium. An increase in activity is achieved by varying the Pd precursor compound and its content.

The following are examples of the preparation and testing of catalysts designed to burn natural fuels in various temperature zones (1st, 2nd and 3rd) of catalytic combustion chambers of gas turbine power and power plants.

The catalyst of the 1st zone. The preparation method, chemical composition and properties of the catalyst of the 1st zone are described in Examples 1-7 and are shown in table 1.

Example 1

For the preparation of a catalyst with the composition aPd / bCeO ₂ / Al ₂ O ₃ , where a and b are the mass content of Pd and CeO ₂ , varying in the range of 0.5-2.5 wt.% And 0-15 wt.%, Respectively, granules are used alumina carrier in the form of spherical granules, cylinders or rings having a specific surface area of 100-220 m ² / g, pore volume 0.3-0.6 cm ³ / g, phase composition: γ-Al ₂ O ₃ , or a mixture of γ- Al ₂ O ₃ and χ-Al ₂ O ₃ , or a mixture

γ-Al ₂ O ₃ and δ-Al ₂ O ₃ , or a mixture of γ-Al ₂ O ₃ and θ-Al ₂ O ₃ .

To modify cerium oxide, 100 g of granules of an alumina support are placed in an impregnation drum and, with stirring, impregnated with the required amount of cerium nitrate solution of a given concentration, for example, with a pore volume of 0.4 cm ³ / g, 40 ml of a solution with a concentration of 277 g Ce / l is required for application 12 wt.% CeO ₂ . The impregnated granules are dried in air at 70-120 ° C and calcined at 500 ° C for 4 hours. After calcination, the alumina support has a specific surface area of 100-220 m ² / g and a pore volume of 0.3-0.6 cm ² / g , characterized by the phase composition: γ-Al ₂ O ₃ , or a mixture of γ-Al ₂ O ₃ and χ (θ, δ) -Al ₂ O ₃ and highly dispersed CeO ₂ with a size of the coherent scattering region (CSR) of 8-12 nm.

Next, the granules of the alumina carrier modified with cerium oxide are placed in an impregnation drum and impregnated with a solution of palladium hydrochloric acid of a given concentration with stirring, for example, to impregnate 100 g of 12 wt.% CeO ₂ / Al ₂ O ₃ with a pore volume of 0.35 cm ³ / g, 35 ml of a solution with a concentration of 58.3 g Pd / L is required for applying 2 wt.% Pd. The impregnated granules are dried in air at 70-120 ° C and calcined at 1000 ° C for 4 hours to form the active component. The palladium content is determined from the data of atomic emission spectroscopy with inductively coupled plasma (AES-ICP).

Examples 2

The preparation is analogous to example 1. The difference is that the alumina carrier granules are impregnated with a solution of lanthanum nitrate of a given concentration, for example, with a pore volume of 0.4 cm ³ / g, 40 ml of a solution with a concentration of 185 g La / l is required for applying 8 wt.% La ₂ O ₃ .

Examples 3-5.

Similar to example 1. The difference is that for the application of palladium using a solution of palladium nitrate. The composition is shown in table 1.

Example 6

Similar to example 1. The difference is that the catalyst is activated in a methane-containing medium (1-5 vol.% In air) at 900 ° C for 4 hours

Example 7

Similar to example 3. The difference is that the catalyst is activated in a hydrogen-containing medium (5-15 vol.% In nitrogen) at 900 ° C for 4 hours

The catalyst of the 2nd zone containing manganese hexaaluminate has a gross composition of cMnLaAl ₁₁ O ₁₉ / Al ₂ O ₃ , where c is the mass content of manganese hexaaluminate, prepared by capillary impregnation. The preparation method, chemical composition and properties of the catalysts are described in Examples 8-10 and are shown in table 2.

Example 8

For the preparation of the catalyst, granules of an alumina support are used in the form of spherical granules, cuttings or rings having a specific surface area of 100-220 m ² / g, pore volume 0.3-0.6 cm ³ / g and phase composition: γ-Al ₂ O ₃ or a mixture of γ-Al ₂ O ₃ and χ-Al ₂ O ₃ , or a mixture of γ-Al ₂ O ₃ and θ-Al ₂ O ₃ .

First, lanthanum is applied in an amount of 6-18 wt.% Based on La ₂ O ₃ (mainly 8-15 wt.%), For which the carrier is placed in an impregnation drum and, with stirring, impregnated with the required amount of a lanthanum nitrate solution of a given concentration. The impregnated granules are dried in air at 70-120 ° C and calcined at 500 ° C for 4 hours

Then, manganese is applied in an amount of 2.2-8.0 wt.% Calculated on MnO (mainly 3.5-6.5 wt.%). For this, the granules of an alumina carrier modified with lanthanum oxide are placed in an impregnation drum and impregnated with a solution of manganese nitrate of a given concentration with stirring. The impregnated granules are dried in air at 70-120 ° C and calcined at 1000 ° C for 4 hours to form the phase of the active component.

The contents of manganese, lanthanum and aluminum are determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES), and the content of manganese hexaaluminate of 20-90 wt.% Is calculated from these data.

For example, per 100 g of alumina support with a pore volume of 0.45 cm ³ / g, 45 ml of a solution with a concentration of 275 g La / L and 48 ml of a solution with a concentration of 100 g Mn / L are required to obtain a catalyst with a mass ratio of components, wt.% , 12 La ₂ O ₃ , 5.2 MnO and aluminum oxide the rest, which corresponds to 58 wt.% Manganese hexaaluminate composition MnLaAl ₁₁ O ₁₉ .

Example 9

Similar to example 8, the difference is that the introduction of the active component is carried out from a joint solution of nitric acid salts of manganese and lanthanum with subsequent stages of drying in air at 70-120 ° C and calcination at 1000 ° C for 4 hours to form the phase of the active component.

For example, to obtain a catalyst with a mass ratio of components, wt.%, 14.3 La ₂ O ₃ , 6.3 MnO and alumina, the rest, which corresponds to 70 wt.% Manganese hexaaluminate composition MnLaAl ₁₁ O ₁₉ , take 100 g of alumina carrier with a pore volume of 0.55 cm ³ / g, placed in an impregnation drum and impregnated with 55 ml of a solution containing 140 g of La / L and 55.4 g of Mn / L. The impregnated granules are dried in air at 70-120 ° C and calcined at 400 ° C for 4 hours

The procedure of impregnation and drying is repeated and the catalyst is subjected to heat treatment at 1000 ° C for 4 hours.

Example 10

Similar to example 8, the difference lies in the fact that to control the catalytic properties (to reduce them and to ensure lower temperatures of the exhaust gases), the catalyst is calcined at a temperature of 1100 ° C for 4 hours

Depending on the content of the active component, the catalyst after calcination has a pore volume of 0.20-0.30 cm ³ / g, specific surface area 12-18 m ³ / g, contains, according to X-ray diffraction data, MnLaAl ₁₁ O ₁₉ and α-Al ₂ O ₃ and LaAlO ₃ (traces).

The catalyst of the 2nd zone may contain palladium and have the following composition dPd / cMnLaAl ₁₁ O ₁₉ / Al ₂ O ₃ , where d and c are the mass contents of palladium and manganese hexaaluminate, respectively. They are prepared by capillary impregnation in three stages. The preparation procedure, chemical composition and properties of the catalysts of the composition dPd / cMnLaAl ₁₁ O ₁₉ / Al ₂ O _{3 are} described in examples 11-19 and are shown in table 2.

Examples 11-13.

For the preparation of the catalyst, granules of an alumina support are used in the form of spherical granules, cuttings or rings having a specific surface area of 100-220 m ² / g, pore volume 0.3-0.6 cm ³ / g and phase composition: γ-Al ₂ O ₃ or a mixture of γ-Al ₂ O ₃ and χ-Al ₂ O ₃ , or a mixture of γ-Al ₂ O ₃ and θ-Al ₂ O ₃ .

Lanthanum is applied in an amount of 6-18 wt.% Based on La ₂ O ₃ , mainly 8-15 wt.%, For this, the carrier is placed in an impregnation drum and, with stirring, impregnated with the required amount of a solution of lanthanum nitrate of a given concentration. The impregnated granules are dried in air at 70-120 ° C and calcined at 500 ° C for 4 hours

Manganese is applied in an amount of 2.2-8.0 wt.% Calculated on MnO, mainly 3.5-6.5 wt.%. For this, the granules of an alumina carrier modified with lanthanum oxide are placed in an impregnation drum and impregnated with a solution of manganese nitrate of a given concentration with stirring. The impregnated granules are dried in air at 70-120 ° C and calcined at 500 ° C for 4 hours to decompose manganese and lanthanum nitrates to oxides.

The contents of manganese, lanthanum and aluminum are determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES), and the content of manganese hexaaluminate of 20-90 wt.% Is calculated from these data. For example, per 100 g of alumina support with a pore volume of 0.45 cm ³ / g, 45 ml of a solution with a concentration of 275 g La / L and 48 ml of a solution with a concentration of 100 g Mn / L are required to obtain a catalyst with a mass ratio of components, wt.% , 12 La ₂ O ₃ , 5.2 MnO and aluminum oxide the rest, which corresponds to 58 wt.% Manganese hexaaluminate composition MnLaAl ₁₁ O ₁₉ .

Then, palladium is applied in an amount of 0.1-2.5 wt.% Based on Pd, mainly 0.1-0.8 wt.%, For this, granules of an alumina carrier containing manganese and lanthanum oxides are loaded into an impregnation drum and while stirring, they impregnate with a predetermined amount of a solution of palladium-hydrochloric acid with the required concentration. The palladium content is determined by x-ray fluorescence spectral method.

For example, to apply 0.5 wt.% Pd per 100 g of alumina carrier containing 12 wt.% La ₂ O ₃ and 5.2 wt.% MnO and having a pore volume of 0.4 cm ³ / g, you need to take 40 ml a solution of H ₂ PdCl ₄ with a concentration of 12.5 g of Pd / L. The impregnated granules are dried in air at 70-120 ° C and calcined at 1000 ° C for 4 hours to form phases of the active component.

Depending on the content of manganese hexaaluminate, the catalyst after calcination has a pore volume of 0.25-0.35 cm ³ / g, a specific surface area of 40-55 m ² / g, and, according to the XRD data, contains PdO and / or Pd, a solid solution based on the γ structure -Al ₂ O ₃ and / or δ-Al ₂ O ₃ , MnLaAl ₁₁ O ₁₉ and LaAlO ₃ (traces). Palladium is mainly represented by a PdO phase with a particle size of 20-40 nm and has a uniform distribution over the catalyst granule. The composition and properties are shown in table 2.

Example 14-17.

Similar to example 11, the difference is that for the application of palladium using a solution of palladium nitrate. The composition is shown in table 2.

Depending on the content of manganese hexaaluminate, the catalyst after calcination has a pore volume of 0.25-0.35 cm ³ / g, a specific surface area of 40-55 m ² / g, and, according to the XRD data, contains PdO and / or Pd, a solid solution based on the γ structure -Al ₂ O ₃ and / or δ-Al ₂ O ₃ , MnLaAl ₁₁ O ₁₉ and LaAlO ₃ . Palladium is represented by highly dispersed phases of PdO and metallic palladium with a particle size of 20-40 nm, localized in the form of a “crust” in the surface layers of the catalyst (about 300-600 microns).

Examples 18.

Similar to example 11, the difference is that for the application of palladium use a solution of palladium acetic acid.

Depending on the content of manganese hexaaluminate, the catalyst after calcination has a pore volume of 0.25-0.35 cm ³ / g, a specific surface area of 40-55 m ² / g, and contains, according to XRD data, PdO, a solid solution based on the γ-Al ₂ O structure ₃ and / or δ-Al ₂ O ₃ , MnLaAl ₁₁ O ₁₉ and LaAlO ₃ . Palladium is represented by highly dispersed PdO particles with a size of 20-25 nm, distributed in the form of an “inner crust” with a thickness of 150-300 microns, recessed from the surface layers of the catalyst to a depth of about 150-200 microns.

Example 19

Similar to example 11, the difference is that for the application of palladium using a solution of tetraammonium palladium chloride, and the calcination of the catalyst is carried out at a temperature of 1100 ° C for 4 hours

Depending on the content of manganese hexaaluminate, the catalyst after calcination has a pore volume of 0.20-0.30 cm ³ / g, a specific surface area of 12-15 m ² / g, and contains, according to XRD data, Pd, MnLaAl ₁₁ O ₁₉ , LaAlO ₃ (traces) and α-Al ₂ O ₃ (traces). Palladium is represented by a coarse phase of metallic palladium with a particle size of more than 50 nm and has a uniform distribution over the catalyst granule.

The catalyst of the 2nd zone may also have the composition gPd-fMnO ₂ / Al ₂ O ₃ , where g and f are the mass contents of palladium and manganese oxides calculated on MnO _2, respectively. They are prepared by capillary impregnation followed by calcination at 500-1100 ° C. The preparation method, chemical composition and properties of the catalysts of the composition gPd-fMnO ₂ / Al ₂ O _{3 are} described in examples 20-23 and are shown in table 2.

Example 20

For the preparation of the catalyst, granules of an alumina support are used in the form of spherical granules, cuttings or rings having a specific surface area of 100-220 m ² / g, pore volume 0.3-0.6 cm ³ / g and phase composition: γ-Al ₂ O ₃ or a mixture of γ-Al ₂ O ₃ and χ-Al ₂ O ₃ or γ-Al ₂ O ₃ , and θ-Al ₂ O ₃ .

To apply manganese oxides in an amount of 3.0-20.0 wt.% Calculated on MnO ₂ , mainly 5.0-12.0 wt.%, The carrier is placed in an impregnation drum and, with stirring, impregnated with the required amount of manganese nitrate solution of a given concentration for example, to apply 3 wt.% MnO ₂ per 100 g of alumina support with a pore volume of 0.45 cm ³ / g, 45 ml of a solution with a concentration of 43 g Mn / L is required. The impregnated granules are dried in air at 70-120 ° C and calcined at 700 ° C for 4 hours to decompose manganese nitrate to oxides.

The manganese and aluminum contents are determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES), and the MnO ₂ content, which in this example was 3.1 MnO ₂ , was calculated from these data.

After calcination at 700 ° C, the catalyst has a pore volume of 0.35-0.5 cm ³ / g, specific surface area is 150 m ² / g, and according to the XRD data, it contains a solid solution based on the γ-Al ₂ O ₃ , MnO ₂ structure (traces ) and Mn ₂ O ₃ .

Example 21

Similar to example 20, the difference is that the catalyst is calcined at a temperature of 900 ° C, the manganese content is 11 wt.% MnO ₂ , the active component is a solid solution of manganese cations in the structure of γ-Al ₂ O ₃ and / or δ-Al ₂ O ₃ .

Example 22

Similar to example 20, the difference is that the catalyst is calcined at a temperature of 1050 ° C, the manganese content is 19.4 wt.% MnO ₂ , the active component is a mixture of Mn ₃ O ₄ and a solid solution of manganese cations in the structure of α-Al ₂ O ₃ .

Example 23

Similar to example 20, the difference is that after the deposition of manganese oxides, the catalyst is modified with the addition of palladium in an amount of 0.1-2.5 wt.% Based on Pd, mainly 0.1-0.8 wt.%. For this, granules of an alumina carrier containing manganese oxides are loaded into an impregnation drum and impregnated with a predetermined amount of a tetraammonium solution of palladium nitrate, Pd (NH ₃ ) ₄ (NO ₃ ) ₂ , with the required concentration. The palladium content is determined by x-ray fluorescence spectral method.

For example, to apply 0.3 wt.% Pd per 100 g of alumina support containing 9.5 wt.% MnO ₂ and having a pore volume of 0.4 cm ³ / g, you need to take 40 ml of a solution of Pd (NH ₃ ) ₄ (NO ₃ ) ₂ with a concentration of 7.5 g Pd / L. The impregnated granules are dried in air at 70-120 ° C and calcined at 950 ° C for 4 hours to form phases of the active component.

After calcination, the active component according to the XRD data is represented by a solid solution of manganese cations in the structure of δ-Al ₂ O ₃ and / or α-Al ₂ O ₃ and Mn ₃ O ₄ .

The distribution of palladium over the carrier granule is varied using palladium as a precursor compound: palladium hydrochloric acid, palladium nitrate or acetic acid, tetraammonium palladium nitrate or chloride, and other palladium compounds.

The activity and thermal stability of the catalysts in the oxidation of methane is determined by two tests.

1) A portion of the catalyst with a volume of 1 cm ³ with a fractional composition of 1-2 mm is placed in a flow reactor and fed to the reactor inlet at a speed of 400 cm ³ / min (24000 h ^-1 ) a reaction mixture containing 1 vol.% Methane in air ( O ₂ / CH ₄ = 20.8, an excess of O ₂ over stoichiometry, α, was 10.4). Every 20-50 ° С, starting from a temperature of 150 ° С, the composition of the gas mixture after the reactor is analyzed until stationary concentrations are established. Chromatographic analysis is carried out using an LHM-8MD chromatograph with a thermal conductivity detector. Columns filled with NaX (for separating O ₂ , N ₂ , CH ₄ ) and Poropak-T (for separating CO ₂ and H ₂ O) are used to separate the mixture, gas -carrier - helium. Activity is characterized by the temperature of reaching the 50% and 90% degrees of methane conversion.

2) Granules of the catalyst in an amount of 100 cm ³ are loaded into a metal tubular reactor with an inner diameter of 62 mm and a height of 200 mm, i.e. the height of the catalyst layer is 40 mm On a fresh catalyst, the ignition temperature, T _zh , is _determined , for which the minimum heating temperature of the catalyst layer is taken, at which the fuel inlet in the air stream leads to a noticeable increase in the temperature in the layer - heating of the catalyst. Then the catalyst is heated to a test temperature of 930 ° C. The heating is carried out partly due to the heating of the reactor by the furnace to 250 ° C and due to the heat of reaction during the combustion of natural gas. The tests are carried out at an input methane concentration of 5.2 vol.% (Α 1.8) and a gas flow rate of 4000 h ^-1 . The catalytic activity of the catalysts is evaluated by the “ignition” temperature (T _gas ) and by the completeness of combustion of a mixture of natural gas and air, by analyzing the reaction products with an accuracy of: total hydrocarbon C _x H _x (0.01%), carbon monoxide (1 ppm) and nitrogen oxides

NO _x (1 ppm).

The results of testing the catalytic activity of the catalysts of examples 1-23 are shown in tables 1 and 2. It is seen that the catalysts of the 1st zone containing PdO and / or Pd and rare earth oxides, Pd-CeO ₂ / Al ₂ O ₃ (table 1), They are highly active and thermostable. Examples 1-4 have a low ignition temperature (245-270 ° C), which does not change after 100 hours of operation at a temperature of 930 ° C, and provide a good methane burning depth (the concentration of CH and CO does not exceed 900 and 1 ppm, respectively ) It was shown that varying the precursor of the active component and the palladium content, as well as activating the Pd-containing catalyst in a methane or hydrogen-containing medium, makes it possible to control the catalytic activity of the catalysts proposed for use in the 1st zone of the catalytic package of the catalytic combustion chamber.

The compositions proposed in examples 8-23 have the catalytic properties necessary for use in the 2nd zone of the combustion chamber - average activity in the oxidation of methane and high thermal stability. Varying the composition and content of the active component, the precursor, and the calcination temperature make it possible to monitor the activity of the catalyst and, therefore, provide the required temperatures in the catalytic zone and exhaust gases, as well as provide the required depth of fuel combustion. Examples 8-10 and 20-22 are characterized by a high ignition temperature of the fuel-air mixture, equal to 365-390 ° C. Their activity and thermal stability does not change during 200 hours of operation at 930 ° C, ensuring the CO content in the exhaust gases at the level of 20-70 ppm. Modification of hexaaluminate (examples 11-18) and manganese aluminum oxide (example 23) palladium catalysts leads to an increase in the activity observed by lowering the ignition temperature (to 260-280 ° C) and the CO content in the exhaust gases (up to 1-20 ppm) . Changing the shape of the catalyst, and hence the porosity of the layer, allows you to vary the ignition temperature and the completeness of combustion of the fuel-air mixture (see examples 14, 16 and 17). The maximum completeness of combustion of the fuel-air mixture (99.6-99.8%) is observed for spherical granules (having a porosity of 0.42, example 16), the minimum ignition temperature (250 ° C) is observed for cylindrical granules (with porosity of the layer, close to 0.45, example 17).

To illustrate the proposed method of multi-stage combustion of hydrocarbon fuels, we give examples 24-36 of its implementation (table 3). For experiments, we used a model catalytic combustion chamber having a cylinder shape with a diameter of 80 mm and a height of 400 mm, in which catalysts differing in grain shape and composition (1, 2, 3 catalytic zones) were poured in layers. Varying the shape and geometric dimensions of the granules provided a difference in the porosity of the layer. Varying the composition of the catalyst provided a difference in catalytic activity. Evaluation of the catalytic properties of the catalytic package was carried out by increasing the temperature (dT) of the catalyst at different heights of the catalytic package compared to the inlet temperature, the completeness of fuel combustion and the heat resistance of the catalysts.

Example 24

The model catalytic combustion chamber has the shape of a cylinder with a diameter of 80 mm and a height of 400 mm, a volume of 2 liters.

The catalyst of Example 1 (Pd-CeO ₂ / Al ₂ O ₃ ), having the shape of rings with a diameter of 7.5 mm and a length of 7.5 mm, was placed in an amount of 0.4 L in a catalytic chamber, then a catalyst layer of Example 16 (Pd- MnLaAl ₁₁ O ₁₉ ) of a spherical shape with a diameter of 5 mm in an amount of 1.6 liters. Thus, 2 catalytic zones are obtained, the height of the 1st is 80 mm, the second is 320 mm; the porosity of the 1st and second zones is 0.53 and 0.42, respectively.

A mixture of natural gas with air (1.5 vol.% CH ₄ , α = 6.6) is fed into the catalytic chamber. Air consumption 4.5 g / s. The flow rate of 6250 h ^-1 . The reaction is initiated by heating the reactor to an inlet temperature. During the experiment, the temperature on various layers of the catalytic package and the completeness of fuel combustion in the reaction products at the exit of the combustion chamber are controlled.

At an inlet temperature of 450 ° C and α = 6.6, the temperature increase at the outlet of the catalytic package is 360 ° C. At an inlet temperature of 450 ° C, the content of CH in the exhaust gases is not more than 20 ppm, at 550 ° C - not more than 5 ppm. The content of CO does not exceed 10 ppm. at temperatures at 450 ° C and above 450 ° C.

Example 25 (comparative).

Similar to example 24, the difference is that the catalytic package is filled only with the catalyst from Example 1 (1st zone). Air consumption = 4.5 g / s.

At an inlet temperature of 510 ° C and a = 6.6, the temperature increase at the outlet of the catalytic package is 360 ° C. At an inlet temperature of 510 ° C, the content of CH in the exhaust gases is not more than 300 ppm, at 550 ° C - not more than 60 ppm, 565 ° C - 20-35 ppm. The СО content at 510 ° С did not exceed 45 ppm, at temperatures above 565 ° С - less than 20 ppm.

Example 26 (comparative).

Similar to example 24, the difference is that the catalytic package is filled only with the catalyst from Example 12 (1st zone). Air consumption = 4.5 g / s.

At an inlet temperature of 515 ° C and α = 6.6, the temperature increase at the outlet of the catalytic package is 360 ° C. At an inlet temperature of 515 ° C, the content of CH and CO in the exhaust gases was high, 1500 and 80 ppm, respectively. An increase in temperature leads to an increase in activity: no more than 100 ppm was observed at 550 ° C. CH, 565 ° C - 4-25 ppm CH The content of CO does not exceed 20 ppm at temperatures above 565 ° C.

Example 27

The model catalytic combustion chamber has the shape of a cylinder with a diameter of 50 mm and a height of 200 mm, a volume of 400 ml.

The catalyst of Example 3 (Re-CeO ₂ / Al ₂ O ₃ ), having the shape of rings with a diameter of 7.5 mm and a length of 7.5 mm, was placed in an amount of 40 ml in a catalytic chamber, then a catalyst layer of Example 16 (Pd-MnLaAl _{11 was} poured O ₁₉ ), having the form of spherical granules with a diameter of 5 mm, in an amount of 360 ml. An inert material 125 mm high (i.e. 245 ml) is placed in front of and behind the catalyst bed. Thus, 2 catalytic zones are obtained, the height of the 1st is 20 mm, the second is 180 mm; the porosity of the 1st and second zones is 0.53 and 0.42, respectively.

A mixture of natural gas with air (2.5 vol.% CH ₄ , α = 3.9) at room temperature is fed into the catalytic chamber. Air consumption 4.5 g / s. The flow rate is 6250 h ^-1 . The reaction is initiated by heating the reactor to a temperature of 400 ° C.

The results are shown in table 3. The temperature at the entrance to the 1st zone and exit from it is 200 and 480 ° C, respectively. The catalytic package provides an exhaust gas temperature of 820 ° C and a hydrocarbon content of 20 ppm, CO and NO in the exhaust gas is not fixed.

Example 28

Similar to example 27, the difference is that the catalyst of example 17 (Pd-MnLaAl ₁₁ O ₁₉ ), which is in the form of cylinders with a diameter of 4.5 mm and a length of 7 mm, in the amount of 360 ml, is poured into the second zone. The height and porosity of the 2nd zone are 180 mm and 0.45, respectively.

The temperature at the entrance to the 1st zone and exit from it is 200 and 480 ° C, respectively. The catalytic package provides an exhaust gas temperature of 850 ° C and a hydrocarbon content of 100 ppm. CO and NO are not recorded in the exhaust gas.

Example 29

Similar to example 27, the difference is that the catalyst of example 15 (Pd-MnLaAl ₁₁ O ₁₉ ), which has the shape of rings with a diameter of 7.5 mm and a length of 7.5 mm, in the amount of 360 ml, is poured into the second zone. The height and porosity of the 2nd zone are 180 mm and 0.53, respectively.

The temperature at the entrance to the 1st zone and exit from it is 200 and 480 ° C, respectively. The catalytic package provides an exhaust gas temperature of 750 ° C and a hydrocarbon content of 200 ppm. CO and NO are not recorded in the exhaust gas.

Example 30

Similar to example 27, the difference is that the catalyst of example 10 (MnLaAl ₁₁ O ₁₉ ), which has the shape of rings with a diameter of 7.5 mm and a length of 7.5 mm, in the amount of 360 ml, is poured into the second zone. The height and porosity of the 2nd zone are 180 mm and 0.53, respectively. The temperature at the entrance to the 1st zone and exit from it is 200 and 480 ° C, respectively. The catalytic package provides an exhaust gas temperature of 550 ° C and a hydrocarbon and CO content of 400 ppm. and 100, respectively. NO is not detected in the exhaust gas.

Example 31

Similar to example 27, the difference is that the catalyst of example 21 (MmO ₂ / Al ₂ O ₃ ), which has the shape of rings with a diameter of 7.5 mm and a length of 7.5 mm, in the amount of 360 ml, is poured into the second zone. The height and porosity of the 2nd zone are 180 mm and 0.53, respectively.

The temperature at the entrance to the 1st zone and exit from it is 200 and 480 ° C, respectively. The catalytic package provides an exhaust gas temperature of 600 ° C and a hydrocarbon and CO content of 350 ppm. and 100, respectively. NO is not detected in the exhaust gas.

Example 32

In the first zone is placed the catalyst of example 4, having a spherical shape with a diameter of 5 mm, in an amount of 20 ml; a layer of inert material is placed behind it, consisting of corundum and having the shape of rings with a diameter of 7.5 mm and a length of 7.5 mm, in an amount of 20 ml; then place the catalyst of example 17, having a spherical shape with a diameter of 5 mm, in an amount of 360 ml. Thus, 2 catalytic zones are organized, separated by a layer of inert material. The heights of the 1st, inert and 2nd zones are 10 mm / 10 mm / 180 mm, porosity 0.42 / 0.53 / 0.42.

Test conditions are similar to example 27.

The temperature at the entrance to the 1st zone and exit from it is 200 and 520 ° C, respectively. The temperature at the outlet of the inert material layer is 400 ° C. The catalytic package provides an exhaust gas temperature of 750 ° C and a hydrocarbon and CO content of 100 ppm. and 10, respectively. NO is not detected in the exhaust gas.

Example 33

Similar to example 30, the difference is that the catalyst of example 10 (MnLaAl ₁₁ O ₁₉ ), which has the shape of rings with a diameter of 7.5 mm and a length of 7.5 mm, in the amount of 340 ml, is poured into the 2nd zone. In the bag, the 3rd zone is organized in which the catalyst of Example 4, which has the shape of spherical granules, is used in an amount of 20 ml. The heights of the 1st, 2nd and 3rd zones are 20 mm / 170 mm / 10 mm, porosity is 0.53 / 0.53 / 0.42.

The temperature at the entrance to the 1st zone and exit from it is 200 and 480 ° C, respectively. The temperature at the outlet of their 2nd zone is 550 ° C. The catalytic package provides an exhaust gas temperature of 850 ° C and a hydrocarbon content of 20 ppm, CO and NO in the exhaust gases were not recorded.

Example 34

Similar to example 33, the difference is that in the 3rd zone the catalyst of example 16 is operating, having the shape of spherical granules, in an amount of 20 ml. The heights of the 1st, 2nd and 3rd zones are 20 mm / 170 mm / 10 mm, porosity is 0.53 / 0.53 / 0.42.

The temperature at the entrance to the 1st zone and exit from it was 200 and 480 ° C, respectively. The temperature at the outlet of their 2nd zone is 550 ° C. The catalytic package provides an outlet temperature of exhaust gases of 850 ° C and a hydrocarbon content of 20 ppm, CO and NO in the exhaust gases were not recorded.

Example 35

Similar to example 34, the difference is that between the 1st and 2nd catalytic zone there is a layer of inert material based on granular alumina in the form of rings with a diameter and height of 7.5 mm in an amount of 0.01 l. Thus, the 1st (Example 4, 0.035 L), inert (AbO ₃ , 0.01 L), 2nd (Example 13, 0.34 L) and 3rd (Example 18, 0.015) are organized in the catalytic cartridge k) catalytic zones. The heights of the 1st, inert, 2nd and 3rd zones are 18 mm / 5 mm / 170 mm / 7 mm, porosity 0.42 / 0.53 / 0.45 / 0.42.

The temperature at the entrance to the 1st zone and exit from it was 200 and 480 ° C, respectively. The temperature at the outlet of their 2nd zone is 550 ° C. The catalytic package provides an outlet temperature of exhaust gases of 850 ° C and a hydrocarbon content of 20 ppm, CO and NO in the exhaust gases were not recorded.

Example 36

Similar to example 29, the difference is that the methane content in the mixture with air was 1.5 vol.% (Α = 6.6). Air consumption 4.5 g / s. The flow rate of 6250 h ^-1 . The reaction was initiated by heating the reactor to a temperature of 400 ° C.

The temperature at the entrance to the 1st zone and exit from it was 50 and 100 ° C, respectively. The catalytic package provides an exhaust gas temperature of 680 ° C and a hydrocarbon content of 300 ppm, CO and NO in the exhaust gas was not recorded.

Example 37

Similar to example 29, the difference is that the methane content in the mixture with air was 1.5 vol.% (Α = 6.6). Air consumption 9 g / s. The flow rate of 12500 h ^-1 . The reaction was initiated by heating the reactor to a temperature of 520 ° C.

The temperature at the entrance to the 1st zone and exit from it was 150 and 460 ° C, respectively. The catalytic package provides an exhaust gas temperature of 650 ° C and a hydrocarbon and CO content of 300 ppm. and 23 ppm respectively. NO was not detected in the exhaust gas.

According to the proposed scheme (examples 24, 27-37), a highly active catalyst with porosity ε = 0.53 and additives of noble metals is placed in the lower part of the combustion chamber reactor (ignition zone), initiates the oxidation of natural gas and provides a temperature of not less than 450 ° C, which is the initial for the combustion process in the next zone.

In the second zone, an oxide-type catalyst resistant to high temperatures or an oxide catalyst modified with palladium with a porosity of 0.42-0.53 is placed. The necessary porosity of the 2nd catalytic layer is selected from 2 conditions: 1) the temperature and composition of the exhaust gases coming from the 1st zone, 2) the completeness of combustion of the fuel-air mixture, which must be provided in the 2nd zone. In the case of low temperature of the exhaust gases entering their 1st zone, the recommended porosity of the 2nd layer is mainly 0.45-0.53. To increase the completeness of fuel combustion, the porosity of the 2nd catalytic layer should be 0.42-0.45. The content in the catalyst of 20-90 wt.%, Mainly 50-70 wt.%, Manganese hexaaluminate is sufficient to ensure high thermal stability of the catalyst, and the palladium content in an amount of not more than 2.5 wt.%, Mainly 0.1-0.8 wt.%, sufficient to ensure high completeness of combustion of natural gas. In the 2nd zone, stable combustion of the fuel-air mixture that has not burned in the 1st zone proceeds, the combustion depth of the fuel-air mixture is provided, and the required composition (CO content is not more than 10 ppm), and temperature (650-850 ° C) exhaust gases.

To improve the completeness of fuel combustion, a small layer of highly active catalyst with a porosity of 0.42-0.45 (examples 32-35) can be added to the upper part of the catalytic bag (afterburning zone). In this zone, it is proposed to use PdO and / or Pd catalysts supported on MnLaAl ₁₁ O ₁₉ or alumina modified with cerium oxide. The use of PdO and / or Pd supported on MnLaAl ₁₁ O ₁₉ is preferred. The recommended content of Pd in the catalyst is preferably 0.5-1.5 wt.%.

The proposed method for the combustion of hydrocarbon fuels is suitable for use in catalytic combustion chambers of gas turbine power plants of vehicles, gas turbine power plants of moderate power (up to 2 MW), in gas pumping units and other devices to ensure environmental safety of exhaust gases and the stability of the natural gas combustion process.

table 2
Physicochemical and catalytic properties of dPd / cMnLaAl ₁₁ O ₁₉ / Al ₂ O ₃ and dPd / fMnО ₂ / Al ₂ O ₃ catalysts, intended for use in the 2nd and 3rd zones, multi-stage combustion chambers. No. Chemical composition, wt.% Phase Composition Physicochemical properties The temperature of 50% (T _50% ) and 90% (T _90% ) of CH ₄ conversion (1 vol.% In air, α 9.9) at 24000 h ^-1 The ignition temperature ( _Tg ) and the residual content of CO, CH and NO at 5.2 vol.% CH ₄ in air, 4000 h ^-1 , α 1.8 Mn La c (f) d (g) Shape and size, mm ε,% S _yd , m ² / g V _Σ , cm ³ / g T _50% , ° C T _90% ; ° C T _zh , ° C CO, ppm CH, ppm NO ppm 8. 4.0 10.2 58 - MnLaAl ₁₁ O ₁₉ Ring 0.53 fifty 0.32 590 740 365 42 1000 one LaAlO ₃ , d ₁ 7.5 575 750 362 42 1000 0 γ-Al ₂ O ₃ d ₂ 3 1 7.5 9. ^* 4.8 12.2 70 - MnLaAl ₁₁ O ₁₉ Cuttings 0.45 38 0.28 575 700 360 10 900 one γ-Al ₂ O ₃ d 4.5 1 6-7 358 twenty 900 0 10 ^** 4.8 12.2 70 - MnLaAl ₁₁ O ₁₉ Sphere 0.42 eighteen 0.18 610 780 390 70 1100 four LaAlO ₃ , d 5-7 α-Al ₂ O ₃ eleven. 5.1 13.1 74 1.4 MnLaAl ₁₁ O ₁₉ Ring 0.53 40 0.33 525 670 380 21 900 0 γ * -Al ₂ O ₃ d ₁ 7.5 550 670 310 twenty 900 0 PdO (D <40 nm) d ₂ 3 1 7.5 12. 5.3 9.9 56 0.8 MnLaAl ₁₁ O ₁₉ - “-“ - “ 0.53 45 0.32 550 690 400 13 900 0 γ * -Al ₂ O ₃ PdO (D <40 nm) 550 660 320 19 900 0 13. 6.1 14.8 78 0.1 MnLaAl ₁₁ O ₁₉ Sphere 0.42 49 0.30 565 700 345 fifteen 1000 0 γ * -Al ₂ O ₃ d 5-7 fourteen. 7.3 9.7 55 0.65 MnLaAl ₁₁ O ₁₉ Ring 0.53 48 0.34 520 640 265 0 1000 one γ * -Al ₂ O ₃ d ₁ 7.5 585 660 265 3 1200 one PdO (D <40 nm) d ₂ 3 1 7.5 fifteen. 5.6 9.3 53 2.3 MnLaAl ₁₁ O ₁₉ - “-“ - “ 0.53 41 0.30 465 590 300 one 1000 0 δ * -Al ₂ O ₃ PdO (D <25 nm) 415 515 290 2 1200 0 Pd ⁰ (D <35 nm) 16. 5.8 10.0 58 0.52 MnLaAl ₁₁ O ₁₉ Sphere 0.42 70 0.33 525 625 350 0 200 0 y * -Al ₂ O ₃ d 5-7 490 625 265 one one hundred 0 PdO (D <20 nm) 17. 6.8 10.6 58 0.63 MnLaAl ₁₁ O ₁₉ Cuttings 0.45 84 0.49 450 590 265 0 900 0 γ * -Al ₂ O ₃ d 4.5 PdO (D <40 nm) 1 6-7 eighteen. 7.1 17.3 98 1.0 MnLaAl ₁₁ O ₁₉ Ring 0.53 54 0.28 465 580 275 3 1000 one γ * -Al ₂ O ₃ d ₁ 7.5 480 570 265 2 800 0 d ₂ 3 400 465 250 0 900 0 PdO (D <25 nm) 1 7.5 19. 5.1 13.1 75 1.5 MnLaAl ₁₁ O ₁₉ “-“ - “ 0.53 12 0.20 570 630 380 21 900 0 α-Al ₂ O ₃ Pd ⁰ (D - 50 nm) twenty. 1.9 - 3.1 - MnO ₂ , Mn ₂ O ₃ - “-“ - “ 0.53 150 0.45 470 560 420 95 1700 2 γ * -Al ₂ O ₃ 21. 7.0 - eleven - γ * -, δ * -Al ₂ O ₃ - “-“ - “ 0.53 67 0.40 470 580 350 60 1300 0 22. 12 - 19.5 - Mn ₃ O ₄ Cuttings 0.45 fifty 0.30 550 620 400 85 1400 one α * -Al ₂ O ₃ d 4.5 1 6-7 23. 6.0 - 9.5 0.3 Mn ₃ O ₄ Sphere 0.42 75 0.35 425 550 300 55 1200 0 δ * -, α * -Al ₂ O ₃ d 5-7 * - joint impregnation, ** - calcination temperature 1100 ° С

Claims (17)

1. The method of burning hydrocarbon fuel, which consists in passing the initial fuel through several catalytic zones using a catalytic package comprising two catalysts: a Pd-containing catalyst for initiating the combustion process of the air-fuel mixture and a catalyst for the stable combustion of the air-fuel mixture, characterized in that combustion is carried out in two catalytic zones, which differ in the porosity of the layer, the composition of the catalysts and their catalytic activity in the oxidation reactions of carbon of hydrocarbons: in the 1st zone, a catalyst is used that provides a porosity of the layer 0.45-0.60 and contains PdO and / or Pd deposited on granular alumina modified with rare earth oxides of rare-earth elements, in particular cerium and / or lanthanum, with the content palladium 0.5-2.5 wt.%; in the 2nd zone, a granular oxide catalyst with a porosity of 0.40-0.53, containing 3-20 wt.% manganese oxides, or 20-90 wt.% manganese hexaaluminate, or an oxide catalyst modified with PdO, is used and / or Pd in an amount of 0.1-2.5 wt.%. 2. The method according to claim 1, characterized in that the initiation of the combustion process of the fuel-air mixture containing 1.0-6.0 vol.% Methane is carried out on the catalyst of the 1st zone at a temperature of 250-530 ° C; stable combustion of the air-fuel mixture is carried out on the catalyst in the 2nd zone at an inlet temperature of 450-800 ° C, while the temperature of the exhaust gases at the outlet of the catalytic package is 750-950 ° C. 3. The method according to claim 1, characterized in that the ratio of the heights of the 1st and 2nd catalytic zones in the package is 0.1 / 0.9-0.2 / 0.8. 4. The method according to claim 1, characterized in that to control the process of burning hydrocarbon fuel between the 1st and 2nd zone, a layer of inert material is placed, which is used as granular alumina or corundum, while the height of the layer of inert material is 0.025-0.15 of the height of the entire package. 5. A method of burning hydrocarbon fuel, which consists in passing the initial fuel through several catalytic zones using a catalytic package comprising two catalysts: a Pd-containing catalyst for initiating the combustion process of the air-fuel mixture and a catalyst for the stable combustion of the air-fuel mixture, characterized in that combustion is carried out in three catalytic zones, which differ in the porosity of the layer, the composition of the catalysts and their catalytic activity in the oxidation reactions of carbon of hydrocarbons: in the 1st zone, a catalyst is used that provides a porosity of the layer 0.45-0.60 and contains PdO and / or Pd deposited on granular alumina modified with rare earth oxides of rare-earth elements, in particular cerium and / or lanthanum, with the content palladium 0.5-2.5 wt.%; in the 2nd zone, a granular oxide catalyst with a porosity of 0.40-0.53, containing 3-20 wt.% manganese oxides, or 20-90 wt.% manganese hexaaluminate, or an oxide catalyst modified with PdO, is used and / or Pd in an amount of 0.1-2.5 wt.%, and at the outlet of the catalytic package for burning off unburned hydrocarbons and ensuring the required temperature of the exhaust gases, a narrow layer of highly active catalyst with a porosity of 0.42-0.45 containing PdO is placed and / or Pd on an alumina carrier, modified m oxide of rare-earth element REE, or containing manganese hexaaluminate, modified PdO and / or Pd, the palladium content is 0.5-1.5 wt.%. 6. The method according to claim 5, characterized in that the initiation of the combustion process of the fuel-air mixture containing 1.0-6.0 vol.% Methane is carried out on the catalyst of the 1st zone at a temperature of 250-530 ° C; stable combustion of the air-fuel mixture is carried out on the catalyst in the 2nd zone at an inlet temperature of 450-900 ° C, afterburning of unburned hydrocarbons and products of incomplete oxidation of hydrocarbons is carried out on the catalyst of the 3rd zone, while the temperature of the exhaust gases at the outlet of the catalytic package is 800-950 ° C. 7. The method according to claim 5, characterized in that the ratio of the heights of the 1st, 2nd and 3rd catalytic zones in the package is 0.05 / 0.9 / 0.05-0.1 / 0.8 / 0.1. 8. The method according to claim 5, characterized in that to control the process of burning hydrocarbon fuel between the 1st and 2nd zone, a layer of inert material is placed, which is used as granular alumina or corundum, while the height of the layer of inert material is 0.025-0.15 of the height of the entire package. 9. A catalyst for initiating the combustion process of a fuel-air mixture containing PdO and / or Pd and rare-earth element oxides of rare-earth elements supported on an alumina support, characterized in that γ-alumina or a mixture of γ-Al _{2 is} used as a support for the preparation of the catalyst O ₃ and χ-Al ₂ O ₃ , γ-Al ₂ O ₃ and δ-Al ₂ O ₃ , γ-Al ₂ O ₃ and θ-Al ₂ O ₃ , the palladium content in the catalyst is 0.5-2.5 wt.%, rare earth oxide REE, mainly La and / or Ce, 0-15 wt.%, alumina - the rest, the catalyst is activated by heat treatment in an oxide solid or reducing environment at a temperature of 800-1000 ° С. 10. The catalyst according to claim 9, characterized in that it has the shape of rings with a diameter of 6-15 mm, a length of 6-15 mm and a hole diameter of 2-8 mm; or cylinders with a diameter of 3-8 and a length of 6-7 mm; or spheres with a diameter of 3-7 mm. 11. A catalyst for the stable combustion of a fuel-air mixture containing manganese hexaaluminate, characterized in that granular alumina is used to prepare the catalyst, the catalyst is prepared by impregnating the support with solutions of manganese and lanthanum salts, followed by calcination at a temperature of 900-1100 ° С, hexaaluminate content Manganese in the catalyst is 20-90 wt.%, mainly 50-70 wt.%, aluminum oxide - the rest. 12. The catalyst according to claim 11, characterized in that it has the shape of rings with a diameter of 6-15 mm, a length of 6-15 mm and a hole diameter of 2-5 mm; or cylinders with a diameter of 3-5 and a length of 6-7 mm; or spheres with a diameter of 3-5 mm. 13. A catalyst for the stable combustion of a fuel-air mixture and afterburning of unburned hydrocarbons containing manganese hexaaluminate and PdO and / or Pd, characterized in that granular alumina is used to prepare the catalyst, the catalyst is prepared by impregnating the support with solutions of manganese, lanthanum and palladium salts with subsequent calcination at a temperature of 900-1100 ° C, the content of manganese hexaaluminate in the catalyst is 20-90 wt.%, Pd 0.1-2.5 wt.%, aluminum oxide - the rest. 14. The catalyst according to item 13, characterized in that it has the shape of rings with a diameter of 6-15 mm, a length of 6-15 mm and a hole diameter of 2-5 mm; or cylinders with a diameter of 3-5 and a length of 6-7 mm; or spheres with a diameter of 3-5 mm. 15. The catalyst for the stable combustion of the fuel-air mixture containing manganese oxides, characterized in that for the preparation of the catalyst using granular alumina having a phase composition of γ-Al ₂ O ₃ or a mixture of γ-Al ₂ O ₃ and χ-Al ₂ O ₃ or a mixture of γ-Al ₂ O ₃ and θ-Al ₂ O ₃ , the catalyst is prepared by impregnating the support with solutions of manganese salts, followed by calcination at a temperature of 500-1100 ° C, the content of manganese oxides in the catalyst is 3-20 wt.%, Mainly 5-12 wt.%, Aluminum oxide - the rest. 16. The catalyst according to clause 15, wherein the manganese oxides are in the form of individual oxides MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ or mixtures thereof, or in the form of a solid solution of manganese cations in alumina. 17. The catalyst according to clause 15, characterized in that it has the shape of rings with a diameter of 6-15 mm, a length of 6-15 mm and a hole diameter of 2-5 mm; or cylinders with a diameter of 3-5 and a length of 6-7 mm; or spheres with a diameter of 3-5 mm.