Ammonia synthesis catalyst and a method of regeneration thereof

FIELD: inorganic synthesis catalysts.

SUBSTANCE: ammonia synthesis catalyst includes, as catalytically active metal, ruthenium deposited on magnesium oxide having specific surface area at least 40 m2/g, while concentration of ruthenium ranges between 3 and 20 wt % and content of promoter between 0.2 and 0.5 mole per 1 mole ruthenium, said promoter being selected from alkali metals, alkali-earth metals, lanthanides, and mixtures thereof. Regeneration of catalytic components from catalyst comprises following steps: (i) washing-out of promoters from catalyst thereby forming promoter-depleted catalyst and obtaining solution enriched with dissolved promoter hydroxides; (ii) dissolution of magnesium oxide from promoter-depleted catalyst in acidic solvent wherein ruthenium is insoluble and thereby obtaining residual ruthenium metal in solution enriched with dissolved magnesium compound; and (iii) regeneration of residual ruthenium metal from solution enriched with dissolved magnesium compound via liquid-solids separation to form indicated solution enriched with dissolved magnesium compound and ruthenium metal.

EFFECT: increased catalyst activity.

6 cl, 6 ex

 

The present invention relates to a process for the production of ammonia, especially the catalyst for ammonia synthesis and the method of regeneration.

Known catalyst for the synthesis of ammonia deposited on a refractory oxide, such as activated aluminum silicate, silica gel, titanium oxide, magnesium oxide, zirconium oxide and the like, the catalyst obtained by heating a composition containing at specified media, at least one salt selected from the group consisting of hexacyanocobaltate alkali metal, hexacyanocobaltate alkaline earth metal, hexacyanoruthenate alkali metal, hexacyanoruthenate alkaline earth metal, hexacyanocobaltate iron, hexacyanoruthenate iron, hexacyanocobaltate cobalt and hexacyanoruthenate cobalt at a temperature of from 325 to 430°C. the Catalyst may include a promoter (see U.S. patent 4309311, B 01 J 27/24, 5.1.1982).

The first objective of the invention is to provide a catalyst for ammonia synthesis, which includes a catalytically active metal ruthenium deposited on magnesium oxide, which guarantees a high catalytic activity and long working time.

The second object of the invention is a method for the regeneration of catalytic component of the catalyst according to the invention.

The first task of the invention dostigao is to be a catalyst for ammonia synthesis, including as a catalytically active metal ruthenium in a concentration of between 3 and 20 wt.%, deposited on magnesium oxide having a specific surface area of at least 40 m2/g and at least one promoter in amounts of between 0.2 and 0.5 moles per 1 mole of ruthenium, and the specified promoter is an alkali metals, alkaline earth metals, the lanthanides and their mixture. Preferred promoters are cesium and/or barium.

The second objective of the invention is achieved by the method of regeneration of the catalyst components of the catalyst for ammonia synthesis, comprising ruthenium as the catalytically active metal deposited on magnesium oxide and at least one promoter, the method includes the stage

(a) leaching the promoters of the main catalyst solvent, thus forming a depleted promoter catalyst and receiving the solution, enriched with dissolved hydroxides promoter;

b) dissolving magnesium oxide depleted promoter catalyst in an acid solvent, in which the ruthenium is insoluble, thereby obtaining a residual metal ruthenium in the solution, enriched with dissolved magnesium compound;

C) regeneration of the residual metal ruthenium from a solution enriched with dissolved magnesium compound, by separating the liquid and Tverdov the substance, thus obtaining the above solution enriched with dissolved magnesium compound, and metallic ruthenium.

It is preferable to use ammonia as a main solvent and nitric acid as the acid solvent. Metal ruthenium is preferably removed by filtration, centrifugation, sedimentation or flocculation.

It is generally accepted that there is a proportional relationship between the activity (moles obtained ammonia/g of catalyst) and the content in the catalyst of ruthenium in the group of ruthenium catalysts. According to the present invention the activity of the catalyst was increased 10-20 times, while the content of Ru was increased 1.5-8 times.

Thus, the invention provides a catalyst, active in the synthesis of ammonia, which has an improved activity.

In addition, we discovered that the activity of the catalyst according to the invention is improved in conditions where the concentration of ammonia is high and/or where the composition of the synthesis gas is reduced hydrogen content compared with the stoichiometry of the reaction scheme of the formation of ammonia.

In industrial applications, this increased activity has several advantages. A significant improvement in the activity of the catalyst allows the use of correspondingly reduced Converter synthesis or, alternatively,to use a lower pressure in the synthesis without lowering the rate of production of ammonia.

Example 1

Obtaining ruthenium catalyst.

Media MgO purchased from Johnson-Matthey (purity 99,9955%, specific surface 51,3 m2/g). Ruthenium impose on the media or application media EN3(CO)12in tetrahydrofuran or a chemical vapor deposition (HOP) EN3(CO)12. Otherwise, the ruthenium can be impregnated with the use of a suitable salt, such as RuCl3in the nonaqueous solvent. After drying the impregnated catalyst to remove solvent or directly after use HOP for deposition of Ru3(CO)12on MgO catalyst is activated by treatment with hydrogen. Activation is carried out at flow rate of 30,000 h-1and heated with a speed of 0.1°C/min until reaching 550°Since, at this temperature the catalyst was incubated for 12 hours and cooled to room temperature. The catalyst was slow to adjust to the ambient conditions (passivation)to minimize oxidation of small crystals of Ru. Activation can also be carried out in a nitrogen-hydrogen-ammonia mixtures. Suitable concentrations of Ru are in the range from 3 to 20 wt.% Eng.

Example 2

Promotion of the catalyst.

The catalyst of example 1, the received HOP EN3(CO)12on MgO with subsequent activation in hydrogen and passivation, promotirovat impregna is a Finance suitable salt of the promoter in non-aqueous solution. Suitable promoters are alkali metals, alkaline earth metals, lanthanides, and combinations thereof. Carbonates, hydroxides and nitrates are among the suitable counterions in the application of salts of the promoter. The counterions can be removed in the separation process with recovery, as described in example 1, or they can be directly introduced into the catalytic Converter. The optimum content of promoters depends on the concentration of Ru and dispersion, but lies in the range between 0.2 and 0.5 moles of promoter per mole of ruthenium.

Example 3

The catalyst test.

The applied catalyst Ru/MgO transferred to the installation used for the measurement of catalytic activity. The catalyst is heated to the desired test temperature, typically 400°and the pressure is increased until the desired test pressure, typically 100 bar (100×105PA). A known mixture of hydrogen, nitrogen, and possibly ammonia is passed over the catalyst bed at the desired flow rate, typically 30000 h-1determine the concentration of ammonia at the outlet. Systematic changes of temperature, pressure, flow rate and ammonia concentration at the inlet evaluate the effectiveness of a catalyst under appropriate conditions, i.e. at temperatures of 300-550°C, a pressure of between 10 and 140 bar (10-140×105PA)flow rate between 10000 and 10000 h -1and concentrations of ammonia at the inlet 0-20%vol.

Example 4

Regeneration of catalyst promoters, Ru and nitrate Mg of the used catalyst.

After the test the catalyst Passepartout as described in example 1. Then the catalyst is washed with a primary solvent consisting of a 1 M aqueous solution of ammonia. Possible quantitative (>97%) regeneration promoters without pollution ruthenium or magnesium. Wash water may be evaporated to dryness, to highlight the hydroxides of the promoter. The catalyst remaining after washing with ammonia, heated to 70°With acid in a solvent consisting of a solution of nitric acid with a concentration of more than 1 M in This way, the carrier of magnesium oxide into a solution of magnesium nitrate, which can be separated from the remaining metal ruthenium or by centrifugation, or filtration. This method can be regenerated more than 94% of Ru. Nitrate magnesium is very clean and can be used to produce other salts of magnesium or converted into oxide, for example, through carbonate.

Example 5.

Activity dinocerata promoted ruthenium catalyst.

The catalyst obtained in accordance with examples 1-3 containing 4.1 wt.% Ru and 6 wt.% base, 5 times harder than ordinary repeatedly promoted catalyst based on iron, KM1(commercially available from volume.

Example 6.

The activity of double-promoted ruthenium catalyst.

The catalyst obtained in accordance with examples 1-3 containing 3.8 wt.% EN, 5.8 wt.% VA and 4.1 wt.% Cs was tested in an isothermal furnace operating at a temperature of 400°and a pressure of 100 bar (100×105PA) in the synthesis gas for ammonia synthesis with respect to H2/N 3:1 and at a flow rate of approximately 30000 h-1. The catalyst is active in more than 5 times higher than normal repeatedly promoted catalyst based on iron, KM1, by volume.

1. The catalyst for ammonia synthesis, which includes a catalytically active metal ruthenium deposited on magnesium oxide, and a promoter, wherein the magnesium oxide has a specific surface area of at least 40 m2/g, the concentration of ruthenium is between 3 and 20 wt.% and the content of the promoter is between 0.2 and 0.5 moles per mole of the ruthenium and the promoter is an alkali metals, alkaline earth metals, lanthanides, and mixtures thereof.

2. The catalyst for ammonia synthesis according to claim 1, characterized in that as promoters include cesium and/or barium.

3. Method of regenerating the catalytic component of the catalyst for ammonia synthesis, comprising ruthenium as the catalytically active metal deposited on magnesium oxide, and, IU the greater extent, one promoter, characterized in that it includes a stage

(a) leaching the promoters of the main catalyst solvent, thus forming a depleted promoter catalyst and receiving the solution, enriched with dissolved hydroxides promoter;

b) dissolving magnesium oxide depleted promoter catalyst in an acid solvent, in which the ruthenium is not soluble, thereby obtaining a residual metal ruthenium in the solution, enriched with dissolved magnesium compound;

C) regeneration of the residual metal ruthenium from a solution enriched with dissolved magnesium compound by separation of liquid and solids, thus obtaining the above solution enriched with dissolved magnesium compound, and metallic ruthenium.

4. The method according to claim 3, characterized in that as the primary solvent used ammonia.

5. The method according to one of claim 3 or 4, characterized in that as the acid solvent, nitric acid.

6. The method according to one of p 5, characterized in that the metallic ruthenium is removed by filtration, centrifugation, sedimentation or flocculation.



 

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