RU2320411C1 - Method of preparing catalyst for middle-temperature steam-mediated conversion of carbon monoxide - Google Patents

Abstract

FIELD: carbon monoxide conversion catalysts.

SUBSTANCE: invention relates to a method of preparing catalysts for middle-temperature conversion of carbon monoxide, which can be used in industry when producing nitrogen-hydrogen mix for ammonia synthesis. Preparation of catalyst for middle-temperature conversion of carbon monoxide with water steam, comprising precipitation of iron hydroxide from iron nitrate solution with ammonia-containing solvent, washing of iron hydroxide with water to remove nitrate ions, mixing with calcium and copper ions, mechanical activation of components, molding, drying, and calcination of granules, is characterized by that, in the component mixing step, lanthanum oxide is supplementary added, in which case molar ratio of components is as follows: Fe₂O₃/CaO/CuO/La₂O₃ = 1:(0.8-0.9):(0.045-0.08):(0.005-0.01).

EFFECT: increased catalytic activity and more than thrice reduced content of by-products in condensate.

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Description

technical field

The invention relates to a method for the preparation of catalysts for medium-temperature conversion of carbon monoxide, which can be used in industry to obtain a nitrogen-hydrogen mixture for the synthesis of ammonia.

State of the art

A known method of preparing a catalyst for the conversion of carbon monoxide, comprising mixing a powder of iron oxide with a solution of chromic acid, extruding the resulting paste into granules, holding it in air, drying and calcining. According to this method, the mixing of iron oxide powder with chromic acid is carried out in two stages: first, 20-50% of iron oxide is crushed in the presence of chromic acid to achieve a degree of dissolution of iron oxide of 5.0-11.0%, and then the resulting suspension is mixed with the rest iron oxide powder to form a paste with a moisture content of 26.0-29.0% [A.S. SU 1235523 A1, B01J 37/04, 23/86, publ. in BI No. 21, 1986].

A significant disadvantage of this method is the use of a solution of ammonium carbonate as a precipitant, which complicates the process and causes undesirable foaming at the stage of obtaining iron carbonate. The resulting catalyst contains up to 0.3% sulfur compounds, which during operation are the deactivation of the low-temperature copper-containing catalyst for the conversion of CO.

A known method of preparing a catalyst for medium temperature conversion of carbon monoxide with water vapor, including the deposition of iron hydroxide from a solution of iron nitrate with an ammonia-containing precipitant, followed by obtaining the iron-containing component, the preparation of copper dichromate, mixing with the iron-containing component, drying, calcining, molding the catalyst mass. This method is characterized in that an ammonia-carbonate solution is used as a precipitant, the precipitate of iron hydroxide is separated and washed, dried, calcined at a temperature of 380-420 ° C, the obtained iron-containing component, which is iron oxide, is mixed with copper dichromate, the catalyst mass is moistened with water , molded, dried in air, dried and calcined with a gradual increase in temperature at a speed of 30-50 ° C [Patent RU, 2157731, B01J 37/04, publ. in BI No. 7, 2000].

The disadvantages of this method include the complexity and duration of the cooking process, insufficiently high mechanical strength and activity of the resulting catalyst, the use of scarce and toxic chromium compounds. In the process of preparing the catalyst, the stages of preparing a solution of chromic acid, copper chromate, drying and calcining iron hydroxide are quite laborious, lengthy and energy intensive.

The closest to the proposed invention by technical essence and the achieved result, that is, the prototype, is a method of preparing a catalyst for medium temperature conversion of carbon monoxide with water vapor, including the deposition of iron hydroxide from a solution of iron nitrate with an ammonia-containing precipitant, washing iron hydroxide with water from nitrate ions, mixing with a copper compound, molding, drying and calcining the granules, while iron hydroxide is mixed with copper and calcium oxides at a molar ratio of Fe ₂ O ₃ : CaO: CuO = 1: 1.0 ÷ 2.0: 0.03 ÷ 0.2, and then subjected to mechanical activation [Patent RU, 2254922 C1, B01J 37/04, 23/78, 23/72, 23/745, publ. 06/27/2005 in Byul. No. 18].

The disadvantages of the prototype include insufficiently high selectivity in the reaction of the conversion of carbon monoxide with water vapor, that is, the condensate contains a large number of by-products.

SUMMARY OF THE INVENTION

The objective of the invention is to provide a method for producing a catalyst for medium-temperature conversion of carbon monoxide with water vapor with high selectivity, while maintaining high catalytic activity.

The problem is solved in the proposed method for the preparation of a catalyst for medium-temperature conversion of carbon monoxide with water vapor, including the precipitation of iron hydroxide from a solution of iron nitrate with an ammonia-containing precipitant, washing iron hydroxide with water from nitrate ions, mixing with calcium and copper oxides, mechanical activation of the components, molding, drying and calcining the granules, while at the stage of mixing the components, lanthanum oxide is additionally introduced at a molar ratio of the components Fe ₂ O ₃ : CaO: CuO: La ₂ O ₃ = 1: 0.8-0.9: 0.045-0.08: 0.00 5-0.01.

It is known that complex lanthanum oxides with a perovskite structure are highly active in various oxidation reactions [L.A. Isupova et al. Oxygen forms and catalytic activity in deep oxidation reactions of oxides with a perovskite structure // Kinetics and Catalysis, 2004. V. 45, No. 3. S. 473-480]. However, lanthanum compounds have never been used to increase the selectivity of medium temperature carbon monoxide conversion catalysts with water vapor.

Information confirming the possibility of carrying out the invention

Example 1

To prepare the catalyst according to the proposed method, iron hydroxide Fe ₂ O ₃ · nH ₂ O · nH ₂ O is used, obtained by precipitation from a solution of iron nitrate with a concentration of 380 g / l at a temperature of 60 ° C, pH 7.8 and constant stirring with 25% aqueous NH ₃ solution. As a result of the interaction, a precipitate of Fe ₂ O ₃ · nH ₂ O is formed in a solution of ammonium nitrate. The precipitate is separated from the mother liquor, washed thoroughly with hot water to a residual content of nitrate ions of less than 0.5% and remove excess moisture. Upon receipt of 100 g of catalyst, 109 g of iron hydroxide containing 75 g of Fe ₂ O ₃ and 34 g of moisture, 20 g of calcium oxide, 3.5 g of copper oxide and 1.5 g of lanthanum oxide (molar) are loaded into the drum of a VM-4 vibration mill the ratio of Fe ₂ O ₃ : CaO: CuO: La ₂ O ₃ = 1: 0.8: 0.08: 0.01) and activate the mixture for 60 minutes. Then, 40 g of water is added to the resulting mass. The mass is thoroughly mixed for 30 minutes and formed into granules, which are dried at 100 ° C for 6 hours, and then calcined at 450 ° C for 6 hours. The composition of the obtained catalyst Fe ₂ O ₃ - 75%, CaO - 20%; CuO - 3.5%; La ₂ O ₃ - 1.5%.

Example 2

The catalyst is prepared analogously to example 1 with the difference that for the preparation of 100 g of catalyst take 109 g of iron hydroxide containing 75 g of Fe ₂ O ₃ and 34 g of moisture, 21.25 g of calcium oxide, 2.25 g of copper oxide and 1.5 g of lanthanum oxide (molar ratio of Fe ₂ O ₃ : CaO: CuO: La ₂ O ₃ = 1: 0.85: 0.06: 0.0075). The composition of the obtained catalyst Fe ₂ O ₃ - 75%; CaO - 21.25%; CuO - 2.25%; La ₂ O ₃ - 1.5%.

Example 3

The catalyst is prepared analogously to example 1 with the difference that for the preparation of 100 g of catalyst take 109 g of iron hydroxide containing 75 g of Fe ₂ O ₃ and 34 g of moisture, 22.5 g of calcium oxide, 1.75 g of copper oxide and 0.75 g of lanthanum oxide (molar ratio of Fe ₂ O ₃ : CaO: CuO: La ₂ O ₃ = 1: 0.9: 0.045: 0.005). The composition of the obtained catalyst Fe ₂ O ₃ - 75%; CaO - 22.5%; CuO - 1.75%; La ₂ O ₃ - 0.75%.

The activity of the catalyst samples was evaluated by the degree of conversion of CO in the reaction of carbon monoxide conversion with water vapor. Test conditions: temperature 350 ° С, steam: gas ratio = 0.6, space velocity 5000 h ^-1 , CO content at the inlet 12% vol. Chromatographic analysis of the condensate was carried out on a Crystal Lux gas chromatograph. The selectivity of the contacts was evaluated by the content of by-products in the condensate. The results of activity and selectivity are presented in the table.

Comparative characteristics of technical solutions

Example No. p / p Selectivity, (content of by-products, mg / l) Activity (CO conversion at t = 350 ° C),% Example 1 1,2 91.7 Example 2 1.4 91.4 Example 3 1.8 91.1 Prototype 4.18 91.2

The table shows that the use of the claimed invention reduces the content of by-products in the condensate by more than 3 times, while maintaining a sufficiently high catalytic activity of the catalyst.

Claims (1)

A method of preparing a catalyst for medium-temperature conversion of carbon monoxide with water vapor, including the precipitation of iron hydroxide from a solution of iron nitrate with an ammonia-containing precipitant, washing iron hydroxide with water from nitrate ions, mixing with calcium and copper oxides, mechanical activation of the components, molding, drying and calcination of granules, characterized the fact that at the stage of mixing the components additionally introduce lanthanum oxide at a molar ratio of the components Fe ₂ O ₃ : CaO: CuO: La ₂ O ₃ = 1: 0.8-0.9: 0.045-0.08: 0.005-0.01 .