Catalyst and ammonia synthesis method

FIELD: inorganic synthesis catalysts.

SUBSTANCE: invention provides ammonia synthesis catalyst containing ruthenium as active ingredient supported by boron nitride and/or silicon nitride. Catalyst can be promoted by one ore more metals selected from alkali, alkali-earth metal, or rare-earth metals. Ammonia synthesis process in presence of claimed catalyst is also described.

EFFECT: increased temperature resistance of catalyst under industrial ammonia synthesis conditions.

4 cl, 6 ex

 

The present invention relates to a process for the synthesis of ammonia, in particular to a catalyst and method of producing ammonia.

Known catalyst to produce ammonia containing ruthenium as the active catalytic material supported on carbon, for example carbon-containing graphite. Additionally, the above-mentioned carbon media may include a promoter, such as alkali metal (see U.S. patent No. 4 600 571, C 01 C 1/04, 15.07.1986).

Obtaining ammonia is carried out by contacting the synthesis gas with the above catalyst in the conditions of formation of ammonia. Usually the ammonia synthesis is carried out under a pressure in the range 100-400 bar and at a temperature between 300°and 600°C.

A serious disadvantage of this known technical solution is that used carrier-based carbon is sensitive to hydrogenation in an industrial environment. Carbon media is slowly converted to methane, which leads to a gradual loss of the media and, ultimately, to difficulties in the work.

The object of the present invention is the provision of a ruthenium catalyst having a carrier which is stable in an industrial environment for the synthesis of ammonia.

The solution to this problem is achieved by the proposed catalyst to produce ammonia containing ruthenium as Akti the aqueous catalytic material, deposited on the boron nitride and/or silicon nitride.

BN or Si3N4can be obtained either from commercial sources or prepared according to methods known in the art. The surface area of the nitride of the carrier is preferably more than 25 m2/year nitride Alternative media can be obtained from Si and predecessor, which will be transformed in the nitride during treatment with ammonia.

And BN, and Si3N4can be formed into the required native methods known in the prior art.

Ruthenium is applied to the carrier by conventional means, for example by impregnation with a suitable compound containing ruthenium, such as chloride or acetate.

Ruthenium catalyst deposited on BN or Si3N4can also be promotional.

Before the promotion, the catalyst can be restored by the processing of regenerating gas, such as hydrogen or synthesis gas.

Promotion may be impregnated with salts of the promoter. The promoters are selected from known promoters of catalyst for ammonia synthesis, for example alkali or alkaline-earth metals or rare earth metals.

Promoters can be introduced sequentially or together.

Another object of the present invention is a method of producing ammonia from ntis gas for production of ammonia by contacting the synthesis gas with the above described catalyst under the conditions of formation of ammonia.

The invention is illustrated by the following examples.

Example 1

Obtaining catalysts

The carrier of boron nitride (hexagonal, the surface area of 85 m2/g, the size of the crystal, determined by powder x-ray diffraction, is 7.5 nm), soaked nitrogenatom ruthenium with obtaining the concentration of ruthenium 5 wt.%. The impregnated sample was dried at 80C and restore in a stream of hydrogen at 450C. This sample indicate 5RuBN.

Another sample get well, but with the content of ruthenium 7 wt.%. This sample indicate 7RuBN. The density of the catalyst is equal to approximately 1.5 g/ml

Example 2

Promotion catalysts caesium

5RuBN and 7RuBN impregnated with aqueous solutions of cesium nitrate to obtain the concentration of cesium 3 wt.%. These samples represent 3Cs5RuBN and 3Cs7RuBN respectively.

Example 3

Promotion catalysts barium

5RuBN and 7RuBN impregnated with aqueous solutions of barium nitrate with obtaining the concentration of barium 3 wt.%. These samples represent 3Ba5RuBN and 3Ba7RuBN respectively.

Example 4

The test catalysts

Catalysts check in isothermal reactor with piston flow when the operating mode 100 bar and a 400°C. the Incoming gas contains 4.5% of ammonia in a mixture of 3:1 hydrogen/nitrogen. Stream regulate to obtain 12% of ammonia at the outlet. Under these conditions, the catalysis of the Torah produce ammonia at different speeds, expressed in ml of ammonia obtained per gram of catalyst per hour:

The catalyst ml NN3/(g·h)

5RuBN 140

7RuBN 190

3Cs5RuBN 1150

3Cs7RuBN 1320

3Ba5RuBN 4600

3Ba7RuBN 4930

Example 5

thermal stability of the catalysts

To determine the stability of the catalysts 3Ba5RuBN and 3Ba7RuBN heated in the reactor at 550°C for 1000 hours Under these conditions, the concentration of ammonia at the outlet is approximately 7.0 percent. After this treatment the catalyst was again tested:

The catalyst ml NH3/(g·h)

3Ba5RuBN 4580

3Ba7RuBN 4960

Example 6

Passivation and regeneration

Determine whether the catalyst is regenerated after passivation. The catalyst from example 5 (3Ba5RuBN) treated with 1000 ppm oxygen in nitrogen for 10 hours and then exposed to the environment. Then again loaded into the reactor and check in identical conditions:

The catalyst ml NH3/(g·h)

3Ba5RuBN 4610

1. Catalyst to produce ammonia containing ruthenium as the active catalytic material supported on a carrier, characterized in that as the carrier contains boron nitride and/or silicon nitride.

2. The catalyst according to claim 1, characterized in that it promotional one or more metals selected from alkaline or alkaline-earth metals or rare earth metals.

<> 3. The method of producing ammonia from synthesis gas for production of ammonia by contacting the synthesis gas with a catalyst containing ruthenium as the active catalytic material supported on a carrier, in the conditions of formation of ammonia, characterized in that the catalyst used is a catalyst containing ruthenium as the active catalytic material supported on a carrier of boron nitride and/or silicon nitride.

4. The method according to claim 3, characterized in that the use of catalyst promoted with one or more metals selected from alkaline or alkaline-earth metals or rare earth metals.



 

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