Block the catalyst honeycomb structure for selective oxidation of ammonia to nitric oxide

 

The invention relates to the field of cooking block replacenode catalyst of the oxidation of ammonia production nitric acid and hydroxylamine. Described block catalyst honeycomb structure for selective oxidation of ammonia to nitrogen oxides, including oxides of iron, aluminum and promoter. As a promoter, the catalyst contains at least one compound of element of group: Co, Mn, Cr, V, Mo, Sn, Bi, or their mixture, and the precursor of aluminium oxide is a compound of aluminium of the formula Al₂About₃nH₂O, where 0.3n1,5, with layered x-ray amorphous structure. The precursor of aluminium oxide may contain at least one connection element from the group of Si, Mg, and CA in an amount of not more than 1.0 wt.% in terms of the oxide. The resulting catalyst has the following composition, wt.%: Fe₂About₃65-86, the promoter in terms of the oxide of 0.1-15, Al₂About₃the rest of it. Block the catalyst additionally contains titanium oxide in an amount of not more than 5 wt. % in order to increase its thermal stability. The proposed catalyst has high mechanical strength, thermal stability and has a high the tee cooking block replacenode catalyst of the oxidation of ammonia production nitric acid and hydroxylamine.

A widely used catalyst for the second stage of the oxidation of ammonia is gelatobaby catalyst KN-2 (Karavaev M. M. and other Catalytic oxidation of ammonia. M.: Chemistry, 1983, S. 155).

This catalyst is granular and can work effectively only when loading a contact apparatus low pressure.

For contact apparatus of high pressure, the most promising is the use of bulk catalysts of honeycomb structure. The block layer of the catalyst height 25-100 mm ensures required to complete additional oxidation of ammonia contact times, low resistance to gas flow at high linear speeds and a kind of protection against rupture of the platinum mesh in case of emergencies.

The complexity of technology for complex geometry of the cellular structure and strict requirements to the catalyst resistance to high operating temperature, oxidative environment, as well as rapid temperature changes, until recently, resisted the application of block catalyst in the contact apparatus oxidation of ammonia.

Known catalyst for the oxidation of ammonia to oxides of nitrogen (RF patent 2106908, IPC⁶B 01 J 23/78, 01 21/26, 1998), Kamennye on the monolithic carrier structure, made of heat-resistant material. The media has channels with a hydraulic diameter of 0.8-30.0 mm and a volume of voids 60-85% when the content of the catalytically active component 5-60% by weight of the catalyst.

The disadvantage of the catalyst is not sufficiently strong binding of the active component on the carrier, which reduces the service life of the catalyst.

The closest technical solution is the catalyst for the oxidation of ammonia (RF patent 2117528, IPC⁶B 01 J 23/83, 21/04, 1998) based on alpha-iron oxide and aluminum oxide, regular cell structure comprising the additional silicon oxide or silicon oxide and/or oxides of rare earth elements (REE) and zirconium and representing blocks of honeycomb structure.

However, the catalyst has a low activity, low mechanical strength and heat stability.

The objective of the invention is the development and preparation of the catalyst with high mechanical strength, thermal stability, while maintaining high catalytic activity and long life.

The problem is solved using block catalyst honeycomb structure for selective oxidation of ammonia to nitric oxide, on Obedinenie element from the group of Co, MP, CR, V, Mo, Sn, Bi or a mixture thereof in an amount of 0.1-15 wt.%. in terms of the oxide and the precursor of aluminium oxide is a compound of aluminium of the formula Al₂O₃nH₂O, where 0.3n1,5, with layered x-ray amorphous structure. The precursor of aluminium oxide may contain at least one connection element from the group of Si, Mg, Ca in an amount of not more than 1.0 wt.% in terms of the oxide. The resulting catalyst has the following composition, wt.%: Fe₂O₃- 65-86; the promoter is at least one compound of element of group: Co, Mn, CR, V, Mo, Sn, Bi or a mixture of 0.1 - 15; Al₂O₃- the rest.

Block the catalyst additionally contains titanium oxide in an amount of not more than 5 wt.% to increase its thermostability.

In the proposed solution used for preparation of the catalyst layered x-ray amorphous compound of aluminium of the formula Al₂O₃nH₂O, where 0.3n1,5. The connection of Al₂O₃n H₂O, where 0.3n1,5, can be obtained by any known methods which sub>O₃nH₂O, where 0.3n1,5, x-ray amorphous layered structure is understood in this connection, x-ray analysis does not detect any lines, characteristic of any crystalline phase. In Fig. 1, 2 shows pictures of the particles of compound Al₂O₃nH₂O, where 0.3n1,5, at different magnification, where visible layered nature of its structure. This compound has high reactivity, which becomes possible intercalate compounds of the catalyst components in the interlayer space between alyumogidroksidnykh packages, accompanied by a shift alyumogidroksidnykh packages relative to each other.

Upon receipt of the catalyst is the formation of the active phase in the presence of compounds of the promoter group: Co, Mn, CR, V, Mo, Sn, Bi and aluminum compounds of the formula Al₂O₃nH₂O, where 0.3n1,5, layered, roentgena-isomorphous structure as rise in temperature to 350-950^oC. And slo 2O, where 0.3n1,5, facilitates production of the active component with high variance, which increases as the activity of the catalyst in the oxidation of ammonia and increase the mechanical strength of the catalyst due to the formation of stronger linkages particles of the active component with the surface of the aluminum oxide.

The catalyst is prepared as follows.

For the preparation of the catalyst is used as a compound of aluminum with the gross formula Al₂O₃nH₂O, where 0.3n1,5. This compound may contain at least one modifier compound of an element from the group of Si, Mg, and CA in an amount of 0.01 to 1.0 wt.%.

In the mixer load raw materials containing oxides of iron, chromium, add the connection of aluminum. Additional compounds of elements from the group of Si, Mg, Ca may be partially contained within the original connection of aluminum, the remainder more modifying compounds to be paid in connection aluminum impregnated his above-mentioned compounds. With stirring, add the plasticizer in the form of a mineral acid in the required quantity, move.

Composition and physico-chemical properties of the obtained catalyst is determined as follows: - the contents of Ni, Cr, K, Na, Si, Fe, Ca - the x-ray fluorescence method; - the crushing strength - on device MP-9S.

Testing the catalytic activity of the catalyst was carried out on pilot plant under the following conditions contact: - the content of ammonia in the initial reaction mixture of 10 vol.%; - temperature probe - 850-900^oC; - time contact - 0,08-0,1 sec.

thermal stability of the catalyst was determined by the number of thermoman, endured blocks until they fracture into two or more parts (fragment). One tablemenu considered to be the rapid heating unit in the muffle to 700^oC and cooled for 15 minutes outside the muffle at room temperature.

The catalytic activity was described as the conversion of ammonia into nitric oxide (II).

The invention is illustrated by the following examples.

Example 1. Getting gelatomaltitolo oxide catalyst. In a mixer with a capacity of 100 litres of load 65 kg of a mixture of powders of oxides of Fe₂About₃, Co₃About₄and TiO₂taken in the ratio of 80:15:5. Later in the mixer was downloaded 15 kg pepsirefresh hydroxide al is de n=0,65. From the obtained paste forming at a special press-snap-received blocks of honeycomb structure in the form of parallelepipeds or hexagonal prisms. Blocks cellular structures were provaljalis at room temperature for 6 hours and dried in running the dryer with purge through the channels of the honeycomb structure is heated to 350^oFrom the air. After drying, the blocks of the catalyst was progulivali at 950^oC.

The catalyst can withstand at least 27 of thermal cycles. One tablemenu taken one cycle of rapid heating unit of catalyst in the muffle to 700^oWith and cooling the outside of the muffle for 15 minutes.

The conversion of ammonia to NO was 86%.

The catalyst has the following composition, wt.%: Fe₂About₃- 65 Co₃O₄- 12,5 TiO₂- 4,0 Al₂About₃- Rest
Example 2. Getting ferromanganese oxide catalyst.

The initial charge is prepared from iron and manganese oxides, determining catalytic activity. Components of the charge Fe₂About₃, MnO₂were loaded into the mixer in the ratio of 80:20. Further, when mixing in the mixer to 65 kg of the mixture was added 15 kg pepsirefresh aluminum hydroxide-based layered x-ray amorphous aluminum compounds f the th catalyst honeycomb structure, having the following characteristics:
the number of thermal cycles - 25;
the conversion of ammonia to NO, % - 84.

the catalyst has the following composition, wt.%:
Fe₂O₃- 65
MnO₂- 8,5
Al₂About₃- Rest
Example 3. Getting zhelezohromovyh oxide catalyst.

The initial charge is prepared from oxides of iron and chromium. Components of the charge Fe₂About₃, CR₂About₃were loaded into the mixer in the ratio of 90:10. Further, when mixing in the mixer to 65 kg of the mixture was added 15 kg pepsirefresh aluminum hydroxide-based layered x-ray amorphous aluminum compounds of the formula Al₂O₃nH₂O, where n=0,85, containing in its composition SiO₂in the amount of 0.08 wt.%. Further, in the conditions of example 1 were received block catalyst honeycomb structure having the following characteristics:
the number of thermal cycles - 20;
the conversion of ammonia to NO, % - 85.

The catalyst has the following composition, wt.%:
Fe₂O₃- 73
CR₂O₃- 8,0
Al₂O₃- Rest
Example 4. Getting zhelezohromovyh oxide catalyst.

The initial charge is prepared from spent STK-1 catalyst containing, by weight. %: Fe₂O₃- 88, CR₂About2O₃nH₂O, where n=0,3. In the conditions of example 1 were received block catalyst honeycomb structure having the following characteristics:
the number of thermal cycles30;
the conversion of ammonia to NO, % - 81.

The catalyst has the following composition, wt.%:
Fe₂O₃- 78
CR₂O₃- 4,7
TiO₂- 5,0
Al₂About₃- Rest
Examples 5-6
Similar to example 1, only differ by the value of n, the promoters and the additional content of oxides of Si, Ca, Mg, and compounds of CA and Mg entered in the Al₂O₃0,75 H₂O, impregnation, and SiO₂there is the link of aluminum in the required quantity.

Example 7 (prototype)
80 g of iron oxide, 40 g of aluminum hydroxide and 2 g of aluminosilicate fibers are mixed in a mixer with 25 ml water, 8 ml of concentrated nitric acid and 2 ml of ethylene glycol for 1 h before formation of a plate of pasta, which is formed by extrusion in the form of blocks with a wall thickness of 1 mm Blocks provalivajut, then raise the temperature in a drying oven at 110^oC and maintained up to 24 h Dried blocks calcined at 900^oWith 4 hours the Catalyst withstands 5 cycles ub>2O₃13%, SIO, SIS₂2%.

From the presented examples and the table shows that the proposed catalyst has high mechanical strength, thermal stability and has a high catalytic activity.

Claims

1. Block the catalyst honeycomb structure for selective oxidation of ammonia to nitrogen oxides, including oxides of iron, aluminum and promoter, characterized in that the promoter contains at least one compound of element of group Co, MT, CR, V, Mo, Sn, Bi, or their mixture, and the precursor of aluminium oxide is a compound of aluminium of the formula Al₂About₃n H₂O, where 0.3n1,5, with layered x-ray amorphous structure, and the catalyst has the following composition, wt.%:
Fe₂About₃- 65-86
The promoter, in terms of oxide of 0.1-15
Al₂About₃- Rest
2. Block the catalyst p. 1, characterized in that the precursor of aluminium oxide further comprises at least one connection element from the group of Si, Mg, Ca in an amount of not more than 1.0 wt.% in terms of the oxide.

3. Block the catalyst p. 1, characterized in that more