The catalyst for purification of gases from nitrogen oxides and method thereof

 

(57) Abstract:

The invention relates to a catalyst for purification of gases from nitrogen oxides mainly in the presence of methane and oxygen, the conversion of natural gas and to a method thereof. The catalyst contains a compound of palladium, the modifier-aluminum oxide as a modifier is used as a compound of tin in the amount of 0.5 to 4.0 wt.% and the catalyst has the following composition in terms of metal, wt.%: palladium 0,01 - 2,2; tin 0,5 - 4,0; aluminium oxide - rest. A method of producing a catalyst for purification of gases from nitrogen oxides includes the introduction of the modifier in alumina carrier, heat treatment, impregnation of the modified alumina carrier with a solution of palladium nitrate and heat treatment, as a modifier is used as a compound of tin in the amount of 0.5 to 4.0 wt.% in terms of metal, type in its application of the compounds of tin at high temperature forms of alumina or their mixture containing or aluminum oxide to 20 wt.% or by mixing the modifier with the charge on the basis of aluminum hydroxide for the preparation of alumina carrier, a modified carrier is subjected to heat treatment at a temperature of 800 - 1300oC. T is the retention of high activity. 2 S. and 3 C.p. f-crystals, 1 table.

The invention relates to a catalyst for purification of gases from nitrogen oxides, mainly in the presence of methane and oxygen, the conversion of natural gas and how to obtain it.

It is known that the properties of the catalysts for purification from nitrogen oxides can be improved by modifying the various components /Catalysis, ed. Moscow state University, 1987/, such as rhenium, cerium, tin. The method of preparation of these catalysts may be different: mixing, impregnation, separate or joint application components. The cooking method is chosen individually for each process.

A known catalyst having a porous substrate structure MO2, where M is silicon, magnesium, manganese, zinc, cobalt, iron, titanium, and AlO2and PO2coated with the active material, for example, base metal and platinum group metal /EP 0396085 A2, 07.11.90). The disadvantage of this catalyst is not sufficiently high strength and activity.

The closest in composition is a catalyst that includes:

a) alkaline oxide or alkaline earth metal in wt.% 50-90;

b) a metal from the group consisting of Cu2O3, Cr2O, TiO2WO3, MoO3, SnO2and ZnO2wt.% 5-50;

C) a metal or metal oxide selected from the group consisting of Ru, Pd, Rh, Ag, Pt, Au, wt.% 0.01 to 10. Nitrogen oxides contained in the exhaust gas is brought into contact with the catalyst in the absence or in the presence of carbon monoxide as a reductant (US 5128305 A, 07.07.92).

The disadvantage of the catalyst is that the catalyst does not have a sufficiently high activity and a high ignition temperature.

Closest to the claimed method is a method of producing a catalyst containing palladium and as a modifier of manganese. The method is based on consistently pursued the impregnation of calcined to 1100oC aminoarabinose carrier with a solution of manganese salt. After drying conduct annealing at 700-1100oC, preferentially at 800-1000oC, and after cooling the impregnated to saturation with ammonia solution, in conclusion, are impregnated with a solution of palladium salt. After drying and annealing at 600-800oC the content of the modifier 1 to 5 wt.%, the palladium content of 0.01 - 0.5 wt.% (DE 2303695 AND 28.07.79).

The disadvantage of this method is the complexity of the technology and nedostatochna development of a catalyst purification from nitrogen oxides with low ignition temperature while maintaining high activity.

The problem is solved in the catalyst for purification of gases from nitrogen oxides, containing compounds of palladium modifier and aluminum oxide, and as a modifier is used as a compound of tin, and the catalyst has the following composition in terms of metal, wt.%:

Palladium - 0,01-2,2

Tin - 0,5-4,0

Alumina - rest

The problem is solved by the method of producing a catalyst for purification of gases from nitrogen oxides, including the introduction of the modifier in alumina carrier, heat treatment, impregnation of the modified alumina carrier with a solution of nitric acid, palladium and heat treatment, as a modifier is used as a compound of tin in the amount of 0.5 to 4.0 wt.% in terms of metal, type in its application of the compounds of tin at high temperature forms of alumina or their mixture containing or aluminum oxide to 20 wt.% or by mixing the modifier with the charge on the basis of aluminium hydroxide for the preparation of alumina carrier, a modified carrier is subjected to heat treatment at a temperature of 800 - 1300oC.

As a modifier use of tin dioxide. The catalyst was soaked in nitric acid, Pallady is more at this temperature at least 40 hours.

The catalyst has the following composition, wt.%:

Palladium - 0,01-2,2

Tin - 0,5-4,0

Alumina - Rest

The proposed catalyst was prepared in two ways. In the first method, the aluminum hydroxide calcined at a temperature of 750-1100oC, receive or modification of aluminum oxide with a content of up to 20% - or-aluminum oxide. The obtained aluminum oxide is applied compound modifier before the tin content in the finished catalyst of 0.5 to 4.0 wt.%. Dried at 80-100oC for 2 hours, calcined at a temperature of 800-1300oC. Then applied to the modified carrier solution of nitric acid, palladium based on the palladium content in the finished catalyst is from 0.01 to 2.2 wt.%. A sample of catalyst is dried at 200oC for 12 hours, then hold heat treatment at a temperature of 400-450oC.

In another method of preparation of the catalyst is injected modifier to the mixture to prepare alumina carrier of the calculation of the tin content in the finished catalyst is 0.5 to 4.0%. Dried at a temperature of 100oC, calcined at a temperature of 800 - 1300oC. Then applied to the modified carrier solution of nitric acid, palladium based on the palladium content in the finished catalyst 0.0 weave at a temperature of 400 450oC.

Thus, the essential distinctive features of the proposed catalyst is that the catalyst contains as a modifier compound of tin in the amount of 0.5 to 4.0 wt.% and the catalyst has the following composition in terms of metal, wt.%:

Palladium - 0,01-2,2

Tin - 0,5-4,0

Alumina - Rest

Salient features of the process of preparation of the catalyst is that as a modifier is used as a compound of tin in the amount of 0.5 to 4.0 wt.% in terms of metal, type in its application of the compounds of tin at high temperature forms of alumina or their mixture containing or aluminum oxide to 20 wt.% or by mixing the modifier with the charge on the basis of aluminium hydroxide for the preparation of alumina carrier, a modified carrier is subjected to heat treatment at a temperature of 800-1300oC.

Such a set of tools to achieve the goal you will get a positive effect, which consists in reducing the ignition temperature by maintaining high catalyst activity.

Physico-chemical properties of the resulting catalyst was determined in the following ways:

- soderzhanie">

the crushing strength was determined on the device MP - 9S.

Testing activity samples (5 cm3) was carried out in a flow reactor made of titanium on the fraction of the catalyst is of size 2 - 3 mm in the next interval of process conditions;

temperatureoWITH - 200-590

the concentration of components in the original mixture, vol.%:

Nitrogen oxides - 0,18

Methane is 1.48

Oxygen - 2,6

Argon or nitrogen - Rest

Space velocity, h-1- 20000

residual concentration:

Ox,% vol. no more than 0.005

CO, vol.% - not more than 0.3

the ratio of methane : oxygen - 0,5

The invention is illustrated by the following examples.

The data are summarized in the table (see the end of the description).

Example 1 (the prototype)

50 g of the carrier-modifications cause of 5.1 g of SnCl22H2O, dissolved in 11.3 ml of HNO3(56%) and then poured 20 ml of H2O. After impregnation, the sample is dried, then calcined at a temperature of 1000oC. the obtained modified media put a solution of nitric acid, palladium at the rate of 2% in the finished catalyst. Next, the catalyst was calcined at a temperature of 600oC.

Example 2

50 g of the carrier-modifying oxide luminova equal to 2.2%) and then poured 20 ml of H2O. After impregnation, the sample is dried, then calcined at a temperature of 1100oC for 2 hours. The obtained modified media put nitric acid palladium at the rate of 2% in the finished catalyst. The catalyst was dried in air for 4 hours, calcined, lifting up to 200oC temperature of 20oC per hour, maintained at 200oC for 12 hours, then raise the 20oC per hour up to 400oC and kept at this temperature for 40 - 60 hours. Calcination is conducted in a stream of air at a flow rate of 700 - 1000 h-1.

Example 3

Similar to example 2, only the tin content in the finished catalyst is 1.7 wt. % and the temperature of calcination of the modified carrier 1200oC.

Example 4

Similar to example 2, only the tin content in the finished catalyst is 0.5. % and the temperature of calcination of the modified carrier 1200oC.

Example 5

Similar to example 2, only the tin content in the finished catalyst is 4% and the phase composition of aluminum oxide of the following: + 10% .

Example 6

Similar to example 2, only the palladium content in the finished catalyst is 1.5 wt.% and the temperature of calcination of the modified carrier 1100>
, plastificator solution of nitric acid to obtain a plastic mass is formed and thermoablative at a temperature of 1100oC for 4 hours.

Example 8

Similar to example 7, the temperature of the processing carrier impregnated with tin, equal 800oC (the content of tin is equal to 2.2%).

Example 9

Similar to example 7, the temperature of the processing carrier impregnated with tin 900oC.

Example 10

Similar to example 7, the temperature of the processing carrier impregnated with tin equal to 1300oC.

Example 11

Similar to example 7, only the composition of the carrier is as follows:

- Al2O3- 80%

- Al2O3- 20%

The temperature of calcination of the modified carrier 1200oC.

Example 12

Similar to example 7, only a different phase composition of the carrier and the content of palladium and tin.

As seen from the above examples, the proposed catalyst lowers the ignition temperature while maintaining high catalyst activity.

It is established that a preliminary application of tin dioxide on or aluminum oxide leads to the change of crystal structure for MF is HN tin occupy on the surface of the aluminum oxide predominantly cation vacancies. This increases the interaction of the active component (palladium) with modified carrier and accordingly increases the stable dispersion of the palladium crystallites.

Long exposure at a temperature of 200oC helps to reduce the acidity of the surface and increase the activity of the catalyst. Impurities up to 20 wt. % or alumina or modifications not have a material effect on the activity of the catalyst (example 2, 3, 5, 7, 8, 9, 11). The temperature of the heat treatment of the modified media significantly affects the ignition temperature and the activity of the catalyst. At lower temperature processing < 800oC ignition temperature increases and the activity of the catalyst falls (example 8). The temperature of the heat treatment of the modified media above 1300oC did not significantly affect the activity of the catalyst (example 10).

With the increasing content of tin > 4 wt.% in the catalyst is reduced catalyst activity, i.e., increases residual concentration of NOxin the cleaned gas.

At lower tin content < 0.5 wt.% the catalyst is the temperature of ignition (example 4).

The way watnogo influence on the activity and the ignition temperature of the catalyst (example 2, 7), but is the most technologically advanced method of making a modifier with the charge for preparation of the alumina carrier.

Thus, the proposed catalyst and method of its preparation allow to obtain a catalyst with a low ignition temperature, high catalytic activity and stability.

1. The catalyst for purification of gases from nitrogen oxides, containing a compound of palladium, the modifier-alumina, characterized in that the catalyst contains as a modifier compound of tin and has the following composition in terms of metal, wt.%:

Palladium - 0,01 - 2,2

Tin - 0,5 - 4,0

Alumina - Rest

2. A method of producing a catalyst for purification of gases from nitrogen oxides, including the introduction of the modifier in alumina carrier, heat treatment, impregnation of the modified alumina carrier with a solution of palladium nitrate and heat treatment, characterized in that the modifier is used as a compound of tin in the amount of 0.5 to 4.0 wt.% in terms of metal, type in its application of the compounds of tin at high temperature forms of alumina or their mixture containing or aluminum oxide to 20 wt. % or a mixture of p, the carrier is subjected to heat treatment at a temperature of 800 - 1300oC.

3. The method according to p. 2, characterized in that as a modifier use of tin dioxide.

4. The method according to p. 2, characterized in that the catalyst is impregnated with palladium nitrate, maintained at a temperature of 200oC for at least 12 hours, then raise the temperature to 400oC and kept at this temperature for at least 40 hours

5. The method according to p. 2, characterized in that the catalyst has the following composition, wt.%:

Palladium - 0,01 - 2,2

Tin - 0,5 - 4,0

Alumina - Rest

 

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