RU2135279C1 - Catalyst for cleaning gases to remove hydrocarbons, nitrogen oxides, carbon monoxide and method of preparation thereof - Google Patents

Abstract

FIELD: gas treatment catalysts. SUBSTANCE: catalyst contains, wt %: one or several platinum group metals 0.05-2.0, sodium or potassium oxide 0.1-1.0, titanium oxide 0.6-30.0, aluminum oxide - the balance. Catalyst increases conversion of both individual components and their mixtures. EFFECT: reduced (in some cases) content of precious metal components with no loss in activity. 10 cl, 2 tbl, 14 ex

Description

 The invention relates to methods for producing oxide catalysts. The catalyst can be used to remove harmful organic impurities, carbon monoxide, nitrogen oxides, hydrogen, or in the purification of industrial gas emissions.

A known method of producing APK-2 ("Technology of catalysts" / Edited by Mukhlenov II, L .: Chemistry, 1979, S. 164-16 50), which is used to clean the tail gas production of diluted nitric acid from nitrogen oxides. The method includes impregnating alumina with a solution of palladium nitrate, followed by drying and calcination. The method consists in the following: tableted alumina is loaded into a device pre-filled 1/3 with demineralized water, where desulfurization is carried out. After loading the carrier, the reactor is completely filled with water, sharp steam is supplied to heat and mix the mass for 1 hour. In the same apparatus, the carrier is washed until there is no sulfur in the wash water, then it is dried in a dryer. A solution of Pd (NO ₃ ) _{2 is} obtained in the reactor by diluting palladium paste with demineralized water to a concentration of (86 ± 2) g / l (in terms of palladium). The amount of salt supplied is determined by the palladium content in the finished catalyst. The impregnated carrier is dried with hot air for 40 hours at 200-220 ^o C, then the catalyst is calcined in an oven at 380-400 ^o C in a nitrogen atmosphere. The catalyst mass provides gas purification from nitrogen oxides to a residual content not exceeding 0.005 vol.%.

 The disadvantage of this method is that the resulting catalyst does not have a sufficiently high activity.

Known three-functional catalyst (Patent EPO N 0637461, MKP ⁶ B 01 D 53/34, B 01 J 23/56, 1995) for cleaning the exhaust gases of cars and gases released in combustion plants with a specific surface area of 20-300 m ² / g. The catalyst also contains 0.1-3.0% of active metals, in particular Rh and Pd, in a ratio of 0.1: 1 to 0.5: 1 on a ZrO ₂ support stabilized with Y ₂ O ₃ , CaO, MgO and containing Al ₂ O ₃ or TiO ₂ . This catalyst can be used to purify gases from CO, NO _x and H ₂ .

 The disadvantage of the catalyst is a complex method for its preparation and, accordingly, the high cost of the catalyst.

Known three-layer catalyst (US Patent N 5021389, MCP B 01 J 21/04, B 01 J 21/06, 1991), which consists of a carrier based on Al ₂ O ₃ on which lanthanum oxide, palladium catalyst and discrete are sequentially distributed titanium oxide phase, palladium content is 0.05-10.0%, titanium oxide content 0.1-8.0%. A lanthanum coating is applied discretely to an aluminum-containing support, then impregnated with a Pd component to form a discrete phase and impregnated with a titanium component. The palladium component is a dilute solution of palladium nitrate with the addition of metallic palladium, the acidity of the solution is 3-5; after the carrier is impregnated, it is calcined in the temperature range 450-650 ^o C, the catalyst impregnated with an organotitanium compound is heated for 1-2 hours to 250-280 ^o C and for 5-10 hours to 400-600 ^o C. Initial Al ₂ O ₃ is treated with HNO ₃ to form a suspension, dried, the resulting granules undergo crumbling to obtain particles with sizes of 25-40 mesh. The catalyst for cleaning automobile emissions is highly active with respect to hydrocarbons at a temperature of 350 ^o C (60-400 ^o C); NO - at a temperature of 150 ^o C (80-500 ^o C).

 The disadvantage of the catalyst is a complex method for its preparation.

 The closest solution is a three-way catalyst for controlling automobile emissions (US Patent N 5102853, MKP B 01 J 21/04, 21/06, 1992), characterized by a high degree of conversion of hydrocarbons, carbon monoxide and nitrogen oxides, including an alumina-based carrier, platinum subgroup metals 0.05-5.0 wt.% (mainly Pd) and the discontinuous phase of titanium oxide with a content of titanium dioxide in the amount of 0.2-8.0 wt.%.

 A method of producing such a catalyst includes impregnating the support with a noble metal salt, drying, impregnating with an organotitanium compound, followed by thermal decomposition of this compound and forming an intermittent phase of titanium dioxide on palladium oxide particles and about.

 The disadvantage of the method of producing the catalyst is the difficulty of its preparation and the formation of an intermittent phase of titanium dioxide.

 The problem solved by the present invention is to develop an effective catalyst for the purification of gases from hydrocarbons, nitrogen oxides, carbon oxides and obtained by simple technology.

The problem is solved on a catalyst for the purification of gases from hydrocarbons, nitrogen oxides, carbon monoxide containing titanium oxide, a compound of one or more platinum group metals on an alumina-based support, the catalyst additionally contains 0.1- sodium and / or potassium oxide 1.0% in terms of metal, the support is alumina with finely divided titanium oxide evenly distributed in it, and the catalyst has the following composition in terms of metal, wt.%:
One or more platinum group metals - 0.05-2.0
Na and / or K oxide - 0.1-1.0
Ti oxide - 0.6-30.0
Al Oxide - Else
The catalyst contains one or more metal oxides in terms of metal from the group of Mn, Cu, Cr, Fe, Ni in an amount of 0.1-7.0%.

The problem is also solved by the method of producing a catalyst for the purification of gases from hydrocarbons, nitrogen oxides, carbon monoxide containing titanium oxide, one or more platinum group metals, aluminum oxide, including the introduction of a titanium compound, the stage of impregnation of a solid support with a compound of one or more platinum metals groups, drying, calcining at a temperature of 200-600 ^o C, to obtain a catalyst carrier is used, which is an aluminum oxide having uniformly distributed therein of fine- ersnym titanium oxide carrier obtained by introducing the titanium compound into the charge to prepare a carrier comprising aluminum hydroxide, kneading, molding, drying and calcination at a temperature of 500-1250 ^o C, the resultant carrier was impregnated with a platinum group metal salt solution, wherein the sodium compound is further input and / or potassium is introduced into the mixture to prepare the carrier or simultaneously with the impregnation of a platinum group metal salt, and the catalyst has the following composition in terms of metal, wt.%:
One or more platinum group metals - 0.2-2.0
Na or K oxide - 0.1-1.0
Ti oxide - 0.6-30.0
Al Oxide - Else
Plasticization is carried out with nitric acid with M _to = 0.02-0.2.

Pore-forming additives are introduced into the charge for preparing the carrier:
wood flour, cellulose, carboxymethyl cellulose, carboxyethyl cellulose in an amount of 1-10 wt.%.

 In the mixture for the preparation of the carrier is introduced alumina, silica gel in an amount of 1-10 wt.%.

 The mixture of metals from the group of Mn, Cu, Cr, Fe, Ni in the amount of 0.1-7.0 wt.% Is introduced into the charge for preparing the carrier.

 The components of the mixture for the preparation of the media separately or jointly subjected to processing in a disintegrator to a particle size of 0.5-15 microns.

 Anatase titanium dioxide, metatitanic acid, are used as titanium compounds.

 When platinum is used as the metal of the platinum group, the calcination of the catalyst is carried out in a hydrogen-containing gas.

The salient features of the catalyst are:
- the catalyst further comprises sodium and / or potassium oxide in an amount of 0.1-1.0 wt.% in terms of metal;
- the carrier is alumina with finely dispersed titanium oxide evenly distributed therein;
- the catalyst has the following composition in terms of metal, wt.%:
One or more platinum group metals - 0.05-2.0
Na and / or K oxide - 0.1-1.0
Ti oxide - 0.6-30.0
Al Oxide - Else
Salient features of the method of producing a catalyst for the purification of gases from hydrocarbons, nitrogen oxides, carbon monoxide are:
- to obtain a catalyst, a support is used, which is aluminum oxide with finely dispersed titanium oxide uniformly distributed in it;
- the carrier is obtained by introducing a titanium compound into the mixture to prepare the carrier, including aluminum hydroxide;
- plasticization;
- molding;
- drying;
- calcination at a temperature of 500-1250 ^o C;
- the resulting carrier is impregnated with a solution of a salt of a metal of the platinum group;
- additionally introduced into the catalyst compounds of sodium and / or potassium are introduced into the mixture to prepare the carrier or simultaneously with the impregnation of a platinum group metal salt;
- the catalyst has the following composition in terms of metal, wt.%:
One or more platinum group metals - 0.2-2.0
Na and / or K oxide - 0.1-1.0
Ti oxide - 0.6-30.0
Al Oxide - Else
The catalyst is prepared as follows.

Activated aluminum hydroxide obtained by hydration of a disintegrated aluminum oxide powder is mixed with nitric acid, mixed, pore-forming additives or aluminum oxide, silica gel, a titanium compound are added, mixed and formed, dried and calcined at 500-1250 ^o C. The resulting carrier has a surface of 7 up to 250 m ³ / g and pore volume from 0.2 to 0.7 cm ³ / g Then it is impregnated with metal salts of the platinum group. The compound of sodium and / or potassium is administered both at the stage of preparation of the carrier, and when the carrier is impregnated with the active component.

The resulting catalyst is tested in a flow reactor of titanium on catalyst fractions of 2-3 mm in the following range of process conditions:
Test conditions
Temperature, ^o C - 200-750
The concentration of the components in the initial mixture, vol.%:
Nitrogen oxides - 0.18
Methane - 1.48
Oxygen - 2.60
Argon - Else
The ratio of methane: oxygen - 0.57
Volumetric speed, h ^-1 - 20,000
These conditions correspond to the conditions of the industrial implementation of the process of purification of gases producing nitric acid.

The conclusion to the mode is carried out in a stream of nitrogen up to 200 ^o C, further heating is carried out in the stream of the reaction mixture at a speed of 100 ^o C / h Dosing and measuring the flows of methane, oxygen, argon, nitric oxide is carried out by automatic gas flow controllers, temperature control is performed by a high-precision temperature controller Proterm - 100. The initial mixture and the mixture after the reactor are analyzed by chromatographic methods (methane) and nitrogen oxides are determined using an infrared absorption spectrometer and CO (examples 1-10).

Testing of samples with particle sizes of 2-3 mm (examples 11-14) is carried out on the same installation at a space velocity of 40,000 h ^-1 and the content of components, vol.%:
2% CO; 2% O ₂ ; 0.05% C ₃ H ₈ , the rest is nitrogen.

 Data on the composition of the catalyst and its activity are shown in table 1, 2.

 The following examples illustrate the invention.

Example 1. To 3210 g of aluminum hydroxide pseudoboehmite structure with a sodium content of 0.1% and a moisture content of 25% add 30 g of wood flour, 750 ml of water and 190 ml of concentrated nitric acid at the rate of 0.1 mol per mol of Al ₂ O ₃ .

500 g of anatase titanium dioxide are added to the plasticized mass until a uniform distribution of finely dispersed titanium dioxide in aluminum hydroxide is obtained, formed, dried in air for 4 hours, dried at 110 ^° C for 4-6 hours, calcined at 1070 ^° C for 3 hours.

 An impregnating solution of palladium nitrate is prepared by diluting a concentrated solution of palladium nitrate to a palladium content of 60 g / l with the addition of nitric acid to a content of 140 g / l. The carrier in an amount of 1000 g is impregnated with a moisture capacity of 330 ml of a solution of palladium nitrate (60 g / l Pd).

The resulting catalyst is dried at a temperature of 80 - 120 ^o C for 4-6 hours, then calcined in air with increasing temperature from 100 to 440 ^o C at a rate of 20 ^o C / h After reaching 440 ^o C, the catalyst was kept at this temperature for another 3-4 hours.

 Example 2. The catalyst is prepared analogously to example 1, only the palladium content in the catalyst is 1.0%.

Example 3. The catalyst is prepared analogously to example 1, only TiO _{2 is} treated in a disintegrator to a particle size of 0.5 μm, and the palladium content is 0.5%, and the calcination temperature of the carrier is 1050 ^o C.

 Example 4. The catalyst is prepared analogously to example 1, only the palladium content in the catalyst is 0.1%, and manganese oxide is additionally introduced into the charge to the Mn content in the catalyst of 3.0%.

Example 5. The catalyst is prepared analogously to example 1, only the palladium content is 0.2%, TiO ₂ is 50% (30% Ti), potassium nitrate is introduced into the impregnation solution until the potassium content in the catalyst is 0.9 and 0.1% sodium, and add silica gel wt. %, and aluminum hydroxide is treated in a disintegrator to a particle size of 15 μm.

Example 6. The catalyst is prepared analogously to example 1, only the content of TiO ₂ is 1% (0.6% Ti).

 Example 7. The catalyst is prepared analogously to example 1, only the catalyst is different in the content of titanium dioxide, palladium, and the potassium compound is introduced into the impregnation solution, and copper is introduced into the charge to prepare the carrier.

 Example 8. The catalyst is prepared analogously to example 1, only its composition is different in the content of palladium, titanium dioxide, nickel and iron compounds, and aluminum oxide in an amount of 5.0% are added to the charge to prepare the carrier.

Example 9 (analog). α-Alumina is impregnated for one hour with a solution of palladium nitrate to a content of 2.0% in the catalyst. The impregnated carrier is dried for 3 hours at 120 - 130 ^o C, followed by calcination in an oven for 2 hours at 460 ^o C.

Example 10 (prototype). 10 g of aluminum oxide are impregnated with palladium nitrate to a palladium content of 1%, then dried at 100 ^° C, then 0.95 g of tetrabutoxytitanium in 15 ml of ethanol are added, dried at 95 ^° C until ethanol is evaporated, calcined at 280 ^° C for 1 hour and then at 600 ^o C for 6 hours and receive an intermittent phase of titanium dioxide.

 Example 11. The catalyst is prepared analogously to example 1, only the catalyst contains platinum and titanium dioxide in the amount of 10% (6% Ti) as the metal of the platinum group.

 Example 12. The catalyst is prepared analogously to example 11, only the catalyst additionally contains palladium.

 Example 13. The catalyst is prepared analogously to example 12, only the catalyst additionally contains rhodium and differs in the content of titanium dioxide.

 Example 14 (prototype). The catalyst is prepared analogously to example 10, only the content of titanium oxide is 9% (5.4% Ti).

 As follows from the above examples, the proposed composition of the catalyst allows to increase activity both in the conversion of individual components and in a mixture, which allows in specific processes to reduce the content of precious metals in the catalyst without reducing the efficiency of the process. So, for example, a catalyst with a palladium content of 1% is more active than the industrial catalyst APK-2 (Example 9), in which 2% of palladium.

 In the prototype, the discontinuous phase of titanium dioxide is located on or near the noble metal particles, which leads to increased stability of the catalyst and some increase in activity. An increase in titanium content over 20% leads to a decrease in activity. It is quite difficult to control the preparation and distribution of this phase and, in addition, there are large amounts of organic solvents of titanium compounds.

 The method of obtaining finely dispersed and uniformly distributed titanium dioxide in alumina with the addition of Na and / or K oxides allows the support and active component to be stabilized and leads to an increase in the activity of catalysts in the processes of complete oxidation of CO and organic compounds, reduction of nitrogen oxides.

 The compound of sodium and / or potassium is introduced both in the charge for preparation is worn and in an impregnating solution of noble metals.

 Introduction to the charge for the preparation of a carrier of metal oxides from the group of manganese, copper, chromium, iron, nickel leads to stabilization of the noble metal on the surface of the carrier and increase activity in the cleaning process.

Varying the conditions for preparing the charge for the carrier (M _k , introducing pore-forming additives, aluminum oxide, silicon oxide, processing in a disintegrator, calcination temperature) allows one to obtain a carrier with the necessary characteristics for the operation of the catalyst.

 Thus, the method of obtaining the proposed catalyst is simple and lack of wastewater. The decrease in the number of stages in the preparation of the catalyst leads to a reduction in energy consumption and makes the method of preparation of the catalyst technological.

Claims (8)

1. The catalyst for the purification of gases from hydrocarbons, nitrogen oxides, carbon monoxide, containing titanium oxide, a compound of one or more platinum group metals on an alumina-based support, characterized in that the catalyst additionally contains 0 and 0 sodium, 1 - 1.0% in terms of metal, the support is alumina with finely divided titanium oxide evenly distributed in it and the catalyst has the following composition in terms of metal, wt.%:
One or more platinum group metals - 0.05 - 2.0
Na and / or K oxide - 0.1 - 1.0
Ti oxide - 0.6 - 30.0
Al Oxide - Else
2. The catalyst according to claim 1, characterized in that it contains one or more metal oxides in terms of metal from the group of Mn, Cu, Cr, Fe, Ni in an amount of 0.1 to 7.0 wt.%. 3. A method of producing a catalyst for the purification of gases from hydrocarbons, nitrogen oxides, carbon monoxide containing titanium oxide, one or more platinum group metals, alumina, including the introduction of a titanium compound, the stage of impregnation of a solid support with a compound of one or more platinum group metals, drying, calcination at 200 - 600 ^o C, characterized in that for the preparation of the catalyst, a support is used, which is alumina with finely divided titanium oxide uniformly distributed in it, which they are irradiated by introducing a titanium compound into a charge to prepare a carrier, including aluminum hydroxide, plasticizing, molding, drying and calcining at 500 - 1250 ^° C, the resulting carrier is impregnated with a solution of a platinum group metal salt, and sodium and / or potassium compounds added to the catalyst are additionally introduced into charge for the preparation of the carrier or simultaneously with the impregnation of a platinum group metal salt, and the catalyst has the following composition in terms of metal, wt.%:
One or more platinum group metals - 0.2 - 2.0
Na and / or K oxide - 0.1 - 1.0
Ti oxide - 0.6 - 30.0
Al Oxide - Else
4. The method according to claim 3, characterized in that the plasticization is carried out with nitric acid with M _k = 0.02 - 0.2.  5. The method according to claim 3, characterized in that pore-forming additives are introduced into the charge to prepare the carrier: wood flour, cellulose, carboxymethyl cellulose, carboxyethyl cellulose in an amount of 1-10 wt.%.  6. The method according to claim 3, characterized in that the alumina, silica gel in an amount of 1 to 10 wt.% Is introduced into the charge for the preparation of the carrier.  7. The method according to claim 3, characterized in that a mixture of metals from the group of Mn, Cu, Cr, Fe, Ni in an amount of 0.1 to 7.0 wt.% Is introduced into the charge for preparing the carrier.  8. The method according to claim 3, characterized in that the components of the mixture for the preparation of the carrier separately or jointly subjected to processing in a disintegrator to a particle size of 0.5 to 15.0 μm.  9. The method according to p. 3, characterized in that anatase titanium dioxide, metatitanic acid are used as titanium compounds.  10. The method according to claim 3, characterized in that when using the platinum group as a metal, the calcination of the catalyst is carried out in a hydrogen-containing gas.

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